CN213335588U

CN213335588U - Pelletizing flue gas treatment system based on rotary kiln primary circulation air inlet

Info

Publication number: CN213335588U
Application number: CN202021622572.0U
Authority: CN
Inventors: 胡兵; 叶恒棣
Original assignee: Zhongye Changtian International Engineering Co Ltd
Current assignee: Zhongye Changtian International Engineering Co Ltd
Priority date: 2020-08-07
Filing date: 2020-08-07
Publication date: 2021-06-01
Anticipated expiration: 2030-08-07

Abstract

The utility model discloses a pelletizing flue gas processing system based on rotary kiln primary circulation air inlet circulates through the specific flue gas with the chain grate machine transition preheating section, carries out non-SCR denitration treatment of heating simultaneously to the waste gas that the preheating section came out. And a control method of an SNCR-SCR coupling denitration mathematical model is also established, and the pellet flue gas is treated by adding a composite additive into the SNCR denitration catalyst or providing a new SNCR composite ammonia agent. The utility model discloses optimized system hot air circulation mechanism, established the ultralow NOx emission technique of best coupling simultaneously, can effectively guarantee denitration efficiency under the prerequisite that reduces the SNCR ammonia consumption, can also prolong SCR denitration catalyst life simultaneously, obvious reduction system denitration running cost and investment cost. Under the condition of ensuring the product quality index, the waste gas treatment capacity is reduced, the fuel consumption is reduced, and the ultralow emission of smoke pollutants is realized.

Description

Pelletizing flue gas treatment system based on rotary kiln primary circulation air inlet

Technical Field

The utility model relates to a flue gas treatment engineering, concretely relates to pelletizing flue gas processing system based on rotary kiln once circulation air inlet belongs to chain grate-rotary kiln flue gas processing technology and energy saving and emission reduction field.

Background

The pellet ore is used as an important charging material for blast furnace iron making, has the advantages of high strength, good metallurgical performance and the like, and compared with a sintering process, the pellet process has lower energy consumption and pollution load, and the pellet ore is more suitable for the condition of iron ore resources mainly comprising concentrate in China, so the pellet ore is an iron ore agglomeration technology which encourages development. With the development of the steel industry, the yield of the pellet ore in China also tends to increase year by year.

The pellet process comprises three processes of a shaft furnace, a grate, a rotary kiln, a ring cooling machine and a belt type roasting machine, and compared with the other two pellet production processes, the grate, the rotary kiln and the ring cooling machine process has lower requirements on heat-resistant materials and fuel heat values and wider application range of raw materials, and because pellets roll uniformly in the roasting process of the rotary kiln, the quality of finished ore is relatively good, so the grate, the rotary kiln and the ring cooling machine pellet production process can still be the most main production process in pellet production in China within a considerable period of time. However, the amount of waste gas discharged in the pelletizing process of the grate-kiln-circular cooler is large, so that the treatment cost of the waste gas is high, and the waste heat utilization degree of the discharged hot waste gas is not enough, so that the energy waste is caused.

For the current grate-rotary kiln-circular cooler air flow system and waste gas treatment process in China, the discharged waste gas mainly comprises waste gas in an air blowing drying section, waste gas in an air suction drying section and waste gas in a transition preheating section. Wherein, the water vapor content in the discharged waste gas of the blast drying section is higher, and the pollutant content is lower. At present, hot waste gas in an air draft drying section and a transition preheating section is combined and is discharged after being purified. The temperature of the waste gas from the transition preheating section in the discharged waste gas is high, and the waste heat recovery value is achieved; the discharged exhaust gas has complex components and contains a large amount of pollutants such as NOx, SOx and the like, so that the hot exhaust gas at the section needs to be subjected to desulfurization, denitrification and other treatments. And directly denitrate the outer exhaust gas, it is big to have a waste gas handling capacity, and the waste gas temperature is low to need the heating to reach the temperature of SCR denitration, leads to with high costs, pollutant discharge degree of difficulty up to standard big.

The exhaust gas volume of the air draft drying section and the transition preheating section is large, the NOx treatment cost for treating the part of hot exhaust gas is higher and higher along with the implementation of an ultra-low emission policy, and meanwhile, because the temperature of the hot exhaust gas of the transition preheating section is higher, if the hot exhaust gas is not utilized, the exhaust gas is only treated, so that a large amount of energy is wasted. Therefore, there is a need to develop more efficient and economical ultra-low NOx emission control technologies.

The existing methods for removing nitrogen oxides in flue gas mainly adopt Selective Catalytic Reduction (SCR) technology and non-selective catalytic reduction (SNCR) technology. Wherein, the selectivity of the SCR denitration technology refers to NH under the action of a catalyst and in the presence of oxygen₃Preferentially reacts with NOx to generate N₂And H₂O, but does not react with oxygen in the flue gas. For SNCR denitration technology, the environmental temperature plays a leading role, and the temperature range is considered to be more appropriate to be 800-1100 ℃. When the temperature is too high, NH₃NO is generated through oxidation, the concentration of NO is increased, and the removal rate of NOx is reduced; when the temperature is too low, NH₃The reaction rate of (2) is decreased, the NOx removal rate is decreased, and NH is added₃The amount of escape of (a) will also increase. In the production process of the chain grate-rotary kiln, the temperature range of a preheating section (PH) is usually 850-1100 ℃, the conditions of the SNCR denitration technology are met, and the optimal emission reduction effect can be achieved only by optimizing control.

NOx is a main reason for forming photochemical smog, acid rain and dust haze weather, aggravating ozone layer damage and promoting greenhouse effect, and has great harm to the ecological environment. The NOx generation in the pellet production process mainly comes from two forms of fuel type and thermal type, and although the NOx generation amount in the grate-kiln pellet production process can be reduced by reducing the pellet yield, namely reducing the coal gas or coal powder injection amount, reducing the pellet strength requirement, namely reducing the rotary kiln temperature, and adopting measures of raw materials and fuels with lower NOx and the like, the NOx generation amount is difficult to meet the environment-friendly requirement of ultralow emission.

Although pellet enterprises do a lot of work in the aspect of environmental protection, dust removal and desulfurization are effectively controlled, and emission requirements can be met, the existing NOx removal process brings new challenges to the pellet industry due to high removal cost and complex process, and a part of enterprises have to reduce the production greatly due to the excessive NOx, and even face shutdown. From the production conditions of most pelletizing plants, the NOx emission concentration is generally 100-300 mg/m³And the oxygen content in the waste gas is 17% -19%, if the emission requirement can be met from the source and the process, the generation of NOx is reduced, the tail end denitration purification equipment can be omitted, the method has great significance for the production of the grate-rotary kiln pellets, and the vitality and the competitiveness of the pellet production can be further improved.

In order to meet the NOx emission requirement in the production process of the grate-rotary kiln pellets and respond to the national call on energy conservation and emission reduction, the production of the low-NOx pellets is realized on the premise of not adding tail end treatment equipment by starting from the process flow and utilizing the characteristics of the system. Therefore, a production system for pellet smoke ultra-low NOx emission is provided. According to the system, the SNCR NOx removal device is arranged at the preheating section of the chain grate machine, the content of NOx in pellet smoke is reduced, meanwhile, the SCR system is additionally arranged at the air outlet of the air box at the bottom of the preheating section, the content of NOx in the smoke is further reduced, and therefore ultralow emission of the pellet smoke NOx is achieved, the technical problems in the prior art are solved, and the system has the characteristics of energy conservation, emission reduction and ultralow NOx production. But the system control mechanism has yet to be optimized. So as to reduce the SNCR ammonia consumption and the service life of the SCR catalyst, and further reduce the denitration cost. In order to improve the denitration efficiency of the SNCR technology, researchers have proposed many technical solutions. For example, wu fai et al utility model "an additive for flue gas SNCR denitration and use thereof (No. CN 103252159B)": discloses an additive for SNCR (selective non-catalytic reduction) denitration of flue gas, which is prepared from cellulose ether and inorganic sodium salt, is mixed with a denitration reducing agent and then sprayed into the flue gas at 760-850 ℃ for denitration, and can adapt to different oxygen concentration changesReduction of by-product N₂And O is generated, the denitration efficiency is between 40 and 70 percent, the effective denitration temperature area is expanded, the range of the allowed oxygen is expanded, and the escape of ammonia is reduced. But at present, the research on the additives of the SNCR technology applied to the denitration of the oxidized pellet flue gas of the chain grate-rotary kiln (the flue gas temperature range is 850-1100 ℃) is less.

SUMMERY OF THE UTILITY MODEL

To the deficiency of the prior art, the utility model provides a pelletizing flue gas processing system based on rotary kiln once only circulates air inlet. Firstly, circulating the specific flue gas of the transition preheating section of the chain grate machine, and simultaneously carrying out non-heating SCR denitration on the waste gas from the preheating section to realize the ultralow emission of NOx in pellet flue gas. A plurality of air boxes which are not communicated with each other are arranged behind the transitional preheating section, the air boxes are divided into front-section air boxes and rear-section air boxes (according to the trend of materials), the division principle is that the air boxes are divided according to the content of NOx in the flue gas in the air boxes, namely the NOx content is sampled and detected one by one from the last air box of the transitional preheating section, and when the detected concentration of NOx in the flue gas in the air boxes is smaller than the average concentration of NOx in the flue gas of the transitional preheating section, the air boxes are divided into the front-section air boxes (the front-section air boxes correspond to the front-section air outlets of the transitional preheating section; similarly, when the detected concentration of NOx in the flue gas in the air box is greater than or equal to the average concentration of NOx in the flue gas in the transition preheating section, classifying the air box as a rear-section air box (the rear-section air box corresponds to a rear-section air outlet of the transition preheating section). According to the difference of the NOx content in the flue gas in different air boxes at the rear end of the transition preheating section, the rear section waste gas with high NOx content is circulated into the rotary kiln through the primary combustion-supporting air pipe, so that the temperature of the hot air entering the rotary kiln is increased, the waste heat of the transition preheating section can be fully utilized to reduce and balance the flame temperature of the rotary kiln, and the generation amount of thermal NOx is reduced. Meanwhile, the circulating hot waste gas of the rear-section air box of the transition preheating section is used as primary combustion-supporting air of the central burner of the rotary kiln, so that the oxygen content of primary mixed air is reduced (the oxygen content in normal air is about 21%, and the oxygen content in circulating hot waste gas is about 18%), the generation amount of NOx is reduced (namely, the generation amount of thermal NOx is reduced from the source), and then the NOx in the circulating hot waste gas can react with local CO formed in the central burner and is converted into nitrogen, so that the using amount of an amino reducing agent can be reduced. This scheme makes system heated air circulation more reasonable, is guaranteeing under the condition of product quality index promptly, reduces exhaust-gas treatment volume, has reduced fuel consumption, realizes flue gas pollutant's minimum emission.

Secondly, a control method of the SNCR-SCR coupled denitration system is adopted, a source, process and terminal control coupled denitration mathematical model is established by adopting a comprehensive weighting grading method of a multi-index test, and the matching relation between each technology (technological parameters, cost, technical and economic indexes and the like and the optimal denitration rate) is comprehensively considered, so that the pellet coupled denitration optimization control method is formed. By adopting the method, an optimal coupling ultra-low NOx emission technology can be formed, the denitration efficiency can be effectively ensured on the premise of reducing the SNCR ammonia consumption, the service life of the SCR denitration catalyst can be prolonged, and the denitration operation cost and the investment cost of a system can be obviously reduced.

Finally, a composite additive of the SNCR denitration catalyst is also provided, namely the composite additive is added into a flue gas denitration reducing agent (generally ammonia water) so as to improve the stability and the denitration rate when the SNCR technology is applied in the production process of the grate-rotary kiln pellets, improve the utilization efficiency of the flue gas denitration reducing agent and reduce NH₃The escaping amount. Or provides an SNCR composite catalyst (composite ammonia agent) for improving the utilization efficiency of the reducing agent for flue gas denitration and reducing NH₃The escaping amount.

In order to achieve the above object, the utility model discloses the technical scheme who adopts specifically as follows:

according to the utility model discloses a first embodiment provides pellet flue gas processing system based on rotary kiln primary circulation air inlet, and this system includes chain grate machine, rotary kiln and SCR denitrification facility. According to the trend of the materials, the chain grate machine is sequentially provided with a blast drying section, an air draft drying section, a transition preheating section and a preheating section. And a central burner is arranged on the rotary kiln. The central burner is communicated with the fuel pipeline. And a primary combustion-supporting air pipe is also arranged on the fuel pipeline. And an air outlet of the rotary kiln is communicated to an air inlet of the preheating section through a first pipeline. And the air outlet of the preheating section is communicated to the air inlet of the air draft drying section through a second pipeline. The air outlet of the transition preheating section is divided into a front section air outlet and a rear section air outlet. And the rear-section air outlet of the transition preheating section is communicated to the air inlet of the primary combustion-supporting air pipe through a third pipeline. And the air outlet of the front section of the transition preheating section is communicated to the outside through a fourth pipeline. And an air outlet of the air draft drying section is communicated to a fourth pipeline through a fifth pipeline. And the second pipeline is provided with an SCR denitration device.

Preferably, the bottom of the transition preheating section is provided with J wind boxes, and an air outlet of each wind box of the J wind boxes is simultaneously connected with the third pipeline and the fourth pipeline through a switching valve. And the air outlet of each air box is controlled to be communicated with the third pipeline or the fourth pipeline only by switching the valves.

Preferably, the number of J wind boxes in the transition preheating section TPH is 1, 2, 3, J in sequence according to the trend of the materials. Wherein, the 1 st to the jth bellows are taken as front segment bellows and are communicated with the fourth pipeline. And the (J +1) th to the J-th air boxes are used as rear-section air boxes and are communicated with a third pipeline. J is more than or equal to 1 and less than or equal to J.

Preferably, J is from 1 to 100, preferably from 2 to 80, more preferably from 2 to 50.

Preferably, the system further comprises a circulation cooler. And according to the trend of the materials, the ring cooling machine is sequentially provided with a ring cooling first section, a ring cooling second section and a ring cooling third section. And an air outlet of the annular cooling section is communicated to an air inlet of the rotary kiln through a sixth pipeline. And the air outlet of the annular cooling second section is communicated to the air inlet of the transition preheating section through a seventh pipeline. And the air outlet of the annular cooling three sections is communicated to the air inlet of the blast drying section through an eighth pipeline. And an air outlet of the blast drying section is communicated to a chimney through a ninth pipeline.

Preferably, the system further comprises an SNCR denitration device. The SNCR denitration device is arranged in the preheating section and/or the first pipeline.

Preferably, the system further includes NOx concentration detection means provided in the windbox. And NOx concentration detection devices are independently arranged in J air boxes at the bottom of the transition preheating section.

Preferably, the SNCR denitration device comprises a first spraying device and a high-pressure atomization mixing device. The first spraying device is arranged in the preheating section and is connected with the high-pressure atomization mixing device through a tenth pipeline.

Preferably, the SNCR denitration apparatus further includes a second spraying apparatus. The second spraying device is arranged in the first pipeline and is connected with the high-pressure atomizing and mixing device through an eleventh pipeline.

Preferably, the eleventh pipeline is a bypass pipeline branched from the tenth pipeline.

Preferably, a vanadium-titanium catalyst conveying pipe, an ammonia water conveying pipe, a urea conveying pipe, a soluble sodium salt conveying pipe, an ethanol conveying pipe and a nano zero-valent iron or SBA-15 conveying pipe are arranged on the high-pressure atomization mixing device.

Preferably, the system also comprises a blending device. And the blending device is provided with a vanadium-titanium catalyst conveying pipe, an ammonia water conveying pipe, a urea conveying pipe, a soluble sodium salt conveying pipe and a nano zero-valent iron or SBA-15 conveying pipeline. The blending device is communicated with the high-pressure atomization mixing device through a twelfth pipeline.

Preferably, the system further comprises a dust removal device which is arranged on the second pipeline and is positioned at the upstream of the SCR denitration device. Preferably, the fourth pipeline is also provided with a dust removal device.

Preferably, the system further comprises a desulfurization device. The desulfurization device is arranged on the fourth pipeline. Preferably, the fourth pipeline is also provided with a dust removal device, and the dust removal device is positioned at the upstream of the desulfurization device.

Preferably, a dust removing device is optionally arranged on each of the third pipeline and the ninth pipeline or not.

According to the utility model discloses a second embodiment provides a flue gas treatment process or uses first embodiment pellet flue gas processing system based on rotary kiln primary circulation air inlet carry out the process that the flue gas was handled, this process includes following step:

1) according to the trend of the materials, the green pellets enter a chain grate machine, sequentially pass through a blast drying section, a draft drying section, a transition preheating section and a preheating section on the chain grate machine, and are conveyed into a rotary kiln for oxidizing roasting.

2) According to the flow direction of the hot air, the hot air in the rotary kiln is conveyed into the preheating section through a first pipeline. The hot air exhausted from the preheating section is firstly subjected to dust removal treatment by a dust removal device, and then is subjected to SCR denitration treatment by an SCR denitration device and then is conveyed into the air draft drying section. The hot air exhausted by the wind boxes at the front sections of the air draft drying section and the transition preheating section is firstly subjected to dust removal treatment by a dust removal device and then is exhausted after being subjected to desulfurization treatment by a desulfurization device. And hot air exhausted from the air box at the rear section of the transition preheating section is dedusted by the dedusting device and then conveyed into the primary combustion-supporting air pipe.

Preferably, the process further comprises the steps of:

3) in the circular cooler, hot air discharged from the circular cooler section is conveyed into the rotary kiln through a sixth pipeline. And the hot air exhausted from the annular cooling section is conveyed into the transition preheating section through a seventh pipeline. And hot air exhausted from the ring cooling three sections is conveyed into the forced air drying section through an eighth pipeline.

4) And spraying an SNCR catalyst in the preheating section and/or a first pipeline connected between an air inlet of the preheating section and an air outlet of the rotary kiln, and carrying out SNCR denitration reaction on NOx in hot air in the preheating section and/or the first pipeline and the SNCR catalyst.

5) The hot air discharged from the forced air drying section is optionally discharged through a ninth duct with or without dust removal treatment.

Preferably, the division mode of the front-section air box and the rear-section air box of the transition preheating section is specifically as follows:

301) the concentration of NOx in the flue gas in the bellows is sequentially H through the real-time detection of J NOx concentration detection devices arranged in J bellows₁，H₂，…，H_J，mg/m³。

302) Calculating the average NOx concentration in J wind boxes in the transition preheating section: h_Average＝(H₁+H₂+…+H_J) and/J. Then sequentially judging J windNOx concentration and H in the tank_AverageThe size of (2).

303) When H is present_j＜H_AverageAnd H is_j+1≥H_AverageAnd in the meantime, the 1 st to the jth wind boxes are front-section wind boxes of the transition preheating section. The (J +1) th to the J-th windboxes are rear-section windboxes of the transition preheating section.

After the dispensing of the bellows is completed, return to step 301) to continue the detection.

Preferably, the process further comprises the steps of:

a) an SNCR denitration system is arranged in the preheating section and/or a first pipeline between the preheating section and the rotary kiln. And meanwhile, an SCR denitration system is arranged behind the air outlet of the preheating section. And establishing an SNCR-SCR coupling denitration mechanism.

b) Detecting and acquiring the initial concentration of NOx before SNCR denitration, the ammonia-nitrogen ratio of SNCR ammonia spraying, the window temperature of SNCR ammonia spraying, the concentration of NOx before SCR denitration, the ammonia-nitrogen ratio of SCR ammonia spraying and the parameter information of the number of SCR catalyst beds in real time.

c) And establishing an SNCR-SCR coupling denitration mathematical model according to the detected parameter information.

d) And calculating and adjusting the SNCR ammonia injection quantity to be minimum and enabling the NOx content in the flue gas to meet the emission condition according to the SNCR-SCR coupling denitration mathematical model.

Preferably, the SNCR-SCR coupling denitration mathematical model is as follows:

y＝A·y_x+B·y_m+C·y_t+D·y_z+E·y_n+F·y_c.., formula I.

In the formula I, y is the coupling denitration rate of SNCR-SCR. y is_xIs the denitration rate based on the initial concentration of NOx before SNCR denitration. y is_mIs the denitration rate based on the ammonia-nitrogen ratio of SNCR ammonia injection. y is_tIs the denitrification rate based on the window temperature of SNCR ammonia injection. y is_zThe denitration rate is based on the NOx concentration before SCR denitration. y is_nIs the denitration rate based on the ammonia-nitrogen ratio of SCR ammonia injection. y is_cThe denitration rate is based on the number of layers of the SCR catalyst bed. And A is the weight of the influence factor of the initial concentration x of the NOx before SNCR denitration. And B is the influence factor weight of the ammonia-nitrogen ratio m of the SNCR ammonia spraying. C is SNCR ammonia spraying windowThe weight of the influence factor of the temperature t. D is the weight of the influence factor of the NOx concentration z before SCR denitration. E is the weight of the influence factor of the ammonia-nitrogen ratio n of the SCR ammonia spraying. F is the weight of the influence factor of the SCR catalyst bed layer number c. And a + B + C + D + E + F is 1.

Preferably, A is from 0.02 to 0.4, preferably from 0.05 to 0.2. B is 0.1 to 0.8, preferably 0.2 to 0.5. C is 0.05-0.5. Preferably 0.1 to 0.3. D is 0.01 to 0.3, preferably 0.02 to 0.2. E is 0.05 to 0.4, preferably 0.1 to 0.3. F is 0.05 to 0.5, preferably 0.1 to 0.4.

Preferably, the denitration rate y based on the initial concentration of NOx before SNCR denitration is_xComprises the following steps:

in the formula II, x is the initial concentration of NOx before SNCR denitration, mg/m³. i is the power of x. I is more than or equal to 0 and less than or equal to N_x。N_xThe highest power of x. a is_xiIs the coefficient of the ith power of x.

Preferably, the denitration rate y of the ammonia-nitrogen ratio based on SNCR ammonia injection_mComprises the following steps:

in the formula III, m is the ammonia nitrogen ratio of SNCR ammonia spraying. Beta is the power of m. Beta is more than or equal to 0 and less than or equal to N_m。N_mIs the highest power of m. a is_mβIs the coefficient of the power of beta of m.

Preferably, the denitration rate y based on the window temperature of SNCR ammonia injection_tComprises the following steps:

in the formula IX, t is the window temperature of SNCR ammonia spraying at DEG C. δ is the power of t. Delta is more than or equal to 0 and less than or equal to N_t。N_tTo the highest power of t. a is_tδIs the system of the δ -th power of tAnd (4) counting.

Preferably, the denitration rate y based on the NOx concentration before SCR denitration_zComprises the following steps:

in the formula V, z is NOx concentration before SCR denitration, mg/m³. Gamma is the power of z. Gamma is more than or equal to 0 and less than or equal to N_z。N_zIs the highest power of z. a is_zγIs the coefficient of the y-th power of z.

Preferably, the denitration rate y based on the ammonia-nitrogen ratio of the SCR ammonia injection_nComprises the following steps:

in formula VI, n is the ammonia-nitrogen ratio of the SCR ammonia injection. λ is the power of n. Lambda is more than or equal to 0 and less than or equal to N_n。N_nIs the highest power of n. a is_nλIs the coefficient of the power of lambda of n.

Preferably, the denitration rate y based on the number of SCR catalyst beds_cComprises the following steps:

in formula VII, c is the number of SCR catalyst bed layers. Theta is the power of c. Theta is more than or equal to 0 and less than or equal to N_c。N_cIs the highest power of c. a is_cθIs the coefficient of the theta power of c.

Preferably, formula II-VII is substituted into formula I to yield:

further transformation of formula VIII affords formula I.

Preferably, step d) is specifically:

d1) when x is·(1-y)≤50mg/m³Then (c) is performed. Reducing the ammonia nitrogen ratio of SNCR ammonia spraying, wherein m is m-STEP_m. Iterative calculation is carried out according to the formula VIII until x (1-y) > 50mg/m is just met³. Then the value of m at this time is executed.

d2) When x (1-y) > 50mg/m³Then (c) is performed. Increasing the ammonia nitrogen ratio of SNCR ammonia spraying, wherein m is m + STEP_m. Performing iterative calculation according to the formula VIII until x (1-y) is just less than or equal to 50mg/m³. Then the value of m' at this time is performed.

Wherein: and m is the currently calculated ammonia nitrogen ratio of the SNCR ammonia spraying. And m' is the ammonia nitrogen ratio of the SNCR ammonia spraying calculated in the next iteration. STEP_mThe value of (A) is 0.01-0.5. Preferably 0.03-0.3. More preferably 0.05 to 0.1.

Preferably, the SNCR catalyst is a SNCR catalyst containing a complex additive comprising or consisting of: urea, soluble sodium salt, ethanol, a vanadium-titanium catalyst and SBA-15. Or

The SNCR catalyst is a compound ammonia agent, and the compound ammonia agent comprises the following components or consists of the following components: ammonia water, urea, soluble sodium salt, ethanol, a vanadium-titanium catalyst and a nano zero-valent iron-kaolin material.

Preferably, the composite additive in the SNCR catalyst containing the composite additive comprises the following components:

40-70 parts of urea, preferably 45-65 parts of urea, and more preferably 50-60 parts of urea.

10 to 30 parts by weight of soluble sodium salt, preferably 12 to 25 parts by weight, more preferably 15 to 20 parts by weight.

8-28 parts of ethanol, preferably 10-25 parts of ethanol, and more preferably 12-22 parts of ethanol.

1-12 parts by weight of vanadium-titanium catalyst, preferably 2-10 parts by weight, more preferably 3-8 parts by weight.

SBA-150.1-5 parts by weight, preferably 0.3-4 parts by weight, more preferably 0.5-3 parts by weight.

Preferably, the compound ammonia agent comprises the following components:

the ammonia water is 60 to 90 parts by weight, preferably 65 to 85 parts by weight, and more preferably 70 to 80 parts by weight.

8-30 parts of urea, preferably 10-25 parts of urea, and more preferably 15-25 parts of urea.

The soluble sodium salt is 0.05 to 1 part by weight, preferably 0.1 to 0.8 part by weight, more preferably 0.15 to 0.5 part by weight.

0.05 to 1.2 parts by weight of ethanol, preferably 0.1 to 1 part by weight, and more preferably 0.15 to 0.8 part by weight.

0.01-0.1 part by weight of vanadium-titanium catalyst, preferably 0.02-0.08 part by weight, more preferably 0.03-0.05 part by weight.

0.5-10 parts by weight of nano zero-valent iron-kaolin material, preferably 0.8-8 parts by weight, and more preferably 1-6 parts by weight.

Preferably, in the step 4), the specific method for spraying the SNCR catalyst is as follows: adding 0.1-2.0 wt% (preferably 0.3-1.2 wt%, more preferably 0.5-1.0 wt%) of a composite additive to a denitration reducing agent (e.g. ammonia water with a concentration of 20-25%) based on the total addition amount of the denitration reducing agent. Stirring and mixing evenly. And then spraying the SNCR catalyst containing the composite additive after being uniformly mixed into the preheating section and/or a first pipeline connected between an air inlet of the preheating section and an air outlet of the rotary kiln.

Or the compound ammonia agent is directly sprayed in the preheating section and/or a first pipeline connected between an air inlet of the preheating section and an air outlet of the rotary kiln.

Preferably, the preparation method of the compound ammonia agent comprises the following steps: firstly, grinding urea, soluble sodium salt, vanadium-titanium catalyst and nano zero-valent iron-kaolin material into powder. And then uniformly stirring and mixing the powdered urea, the soluble sodium salt, the vanadium-titanium catalyst and the nano zero-valent iron-kaolin material according to the proportion to obtain a powder mixture. Finally, the ethanol is independently measured in proportion to obtain wet materials. And adding the wet material and the powder mixture into ammonia water, and uniformly mixing to obtain the composite ammonia agent.

Preferably, the vanadium-titanium catalyst is selected from any of V-TiO₂Is a catalyst. The particle size of the vanadium-titanium catalyst is-0.074 mm or more and 80%, preferably-0.074 mm or more and 90%.

Preferably, the soluble sodium salt is NaCl or Na₂CO₃。

Preferably, the desulfurization treatment is dry desulfurization, semi-dry desulfurization or wet desulfurization. Preferably, lime is used for desulfurization.

Preferably, the dust removal treatment is cloth bag dust removal treatment or electric dust removal treatment.

In the prior art, in the process for treating the flue gas of the pellet by using the three machines of the chain grate machine, the rotary kiln and the circular cooler, the discharged waste gas mainly comprises waste gas of an air blowing drying section, waste gas of an air exhausting drying section and waste gas of a transition preheating section. Wherein, the water vapor content in the discharged waste gas of the blast drying section is higher, and the pollutant content is lower. At present, hot waste gas in an air draft drying section and a transition preheating section is combined and is discharged after being purified. The temperature of the waste gas from the transition preheating section in the discharged waste gas is high, and the waste heat recovery value is achieved; the discharged exhaust gas has complex components and contains a large amount of pollutants such as NOx, SOx and the like, so that the hot exhaust gas at the section needs to be subjected to desulfurization, denitrification and other treatments. And directly denitrate the outer exhaust gas, it is big to have a waste gas handling capacity, and the waste gas temperature is low to need the heating to reach the temperature of SCR denitration, leads to with high costs, pollutant discharge degree of difficulty up to standard big. The exhaust gas volume of the air draft drying section and the transition preheating section is large, the NOx treatment cost for treating the part of hot exhaust gas is higher and higher along with the implementation of an ultra-low emission policy, and meanwhile, because the temperature of the hot exhaust gas of the transition preheating section is higher, if the hot exhaust gas is not utilized, the exhaust gas is only treated, so that a large amount of energy is wasted. Meanwhile, due to the fact that the adjacent air boxes of the preheating section and the transition preheating section have the air channeling phenomenon, the content of NOx in the air box at the rear section of the transition preheating section is high, and if the NOx is directly discharged, the requirement of ultralow emission cannot be met.

The utility model discloses in, through inciting somebody to action the air outlet of transition preheating section divide into anterior segment air outlet and back end air outlet. And hot air output by the rear-section air outlet of the transition preheating section is conveyed into the primary combustion-supporting air pipe through a third pipeline under the action of the circulating fan and then conveyed into the rotary kiln through the primary combustion-supporting air pipe. The rear section waste gas with high NOx content in the partial flue gas of the rear section of the transition preheating section is circulated into the rotary kiln through the primary combustion-supporting air pipe, so that the temperature of hot air entering the rotary kiln is increased, the waste heat of the transition preheating section can be fully utilized to reduce the flame temperature of the rotary kiln, the generation amount of thermal NOx is reduced, and meanwhile, the NOx in the partial flue gas can be circulated into the SNCR and/or SCR denitration device for denitration treatment again. Furthermore, the circulating hot waste gas of the rear-section bellows of the transition preheating section is used as the primary combustion-supporting air of the central burner of the rotary kiln, so that the oxygen content of the primary mixed air is reduced (the oxygen content in normal air is about 21%, and the oxygen content in the circulating hot waste gas is about 18%), the generation amount of NOx is further reduced (namely, the generation amount of thermal NOx is reduced from the source), and then the NOx in the circulating hot waste gas can react with local CO formed in the central burner, so that the NOx is converted into nitrogen, and the using amount of an amino reducing agent can be reduced. The scheme can enable the system hot air circulation to be more reasonable, namely, the waste gas treatment capacity is reduced, the fuel consumption is reduced, the ammonia escape is reduced under the condition of ensuring the product quality index, and therefore ultralow emission is achieved.

The utility model discloses in, be provided with J bellows, J through the bottom at the transition preheating section the air outlet of each bellows all is being connected third pipeline and fourth pipeline simultaneously through switching over the valve in the bellows. And the air outlet of any one air box is controlled to be communicated with the third pipeline or the fourth pipeline only by switching the valve. The number of J wind boxes in the transition preheating section is 1, 2, 3, … and J in sequence according to the trend of materials. Wherein, the 1 st to the jth bellows are taken as front segment bellows and are communicated with the fourth pipeline. And the (J +1) th to the J-th air boxes are used as rear-section air boxes and are communicated with a third pipeline. J is more than or equal to 1 and less than or equal to J. J is 1 to 100, preferably 2 to 80, more preferably 2 to 50. Furthermore, at least one NOx concentration detection device is arranged in each of the J wind boxes to detect the content (mg/m) of NOx in hot air in each wind box in real time³) And dividing the transition preheating section air boxes into a front section air box and a rear section air box according to the content of NOx in each air box. The division mode of transition preheating section anterior segment bellows and back end air bellow specifically is:

301) by passingIndependent NOx concentration detection devices arranged in the J air boxes detect the concentration of NOx in the smoke in the J air boxes sequentially to be H₁，H₂，…，H_J，mg/m³。

302) Calculating the average NOx concentration in J wind boxes in the transition preheating section: h_Average＝(H₁+H₂+…+H_J) and/J. Then gradually judging the concentration of NOx and H in the J smoke gas in the wind box_AverageThe size of (2).

It should be noted that, in general, the concentration of NOx in the flue gas in the windbox at the rear of the transition preheating section gradually increases according to the trend of the materials. (the preheating section blows air to the transition preheating section, so that the concentration of NOx in the flue gas in the rear-section air box is higher than that in the front-section air box)

In the utility model, in general, after the exhaust gas of the rear segment bellows of the transition preheating segment is dedusted by the multi-tube deduster, the circulating waste gas is circulated into the rotary kiln by a circulating fan, and the circulating waste gas is directly conveyed into the rotary kiln as primary combustion-supporting air, because the circulating exhaust gas has a certain temperature, the flame temperature in the rotary kiln can be reduced and equalized, the generation amount of thermal NOx (the generation of NOx in the process) is reduced, and on the other hand, because the waste gas of the transition preheating section also contains NOx with certain concentration, part of the waste gas is directly circulated into the rotary kiln, the denitration treatment of the subsequent procedures (SNCR and/or SCR) can be carried out again along with the hot gas generated in the rotary kiln, the removal efficiency of NOx is improved, meanwhile, the method can also avoid increasing the carrying amount of NOx in the pellets after the part of hot waste gas containing NOx is contacted with the pellets in the annular cooling section, and reduce the escape amount of NOx. Through the direct circulation of the hot waste gas of the back end section to the rotary kiln with the transition preheating section for system heated air circulation is more reasonable, is guaranteeing under the product quality index condition promptly, reduces the exhaust-gas treatment volume, has reduced fuel consumption, realizes flue gas pollutant's minimum emission. The waste gas circulation amount accounts for 30-50% of the volume of the waste gas in the transition preheating section. Meanwhile, after the flue gas in the transition preheating section is circulated, the air volume introduced in the ring cooling section is maintained to be converted into the air volume under the standard condition or the same air volume as before circulation, so that the air volume of the ring cooling section is increased by 3-10% in the ring cooling section, and the air volume of the ring cooling section is increased by 5-10% in the ring cooling section, thereby ensuring that the temperature of the pellets discharged from the ring cooling machine is lower than 150 ℃. Hot gas from the ring cooling section is introduced into the rotary kiln, hot gas from the ring cooling section is introduced into a transition preheating section of the chain grate machine, and hot gas from the ring cooling section is introduced into a blast drying section of the chain grate machine. Further, as the waste gas in the transition preheating section circulates into the rotary kiln, the hot gas led out from the annular cooling section is optionally discharged outside or not, when the hot gas is required to be discharged outside (the amount of the discharged hot gas is consistent with that of the waste gas circulated to the rotary kiln in the transition preheating section), the part of the discharged hot gas can be directly discharged, and can also be circulated into the grate blower drying section and/or the air draft drying section and/or the transition preheating section to realize the waste heat recycling of the hot gas.

The utility model discloses in, the waste gas that comes out at preheating section carries out non-heating SCR denitration, through circulating the back with the flue gas of transition preheating section, reduces rotary kiln coal injection volume or gas volume about 3% ~ 10%, and then ensures gaseous O in the rotary kiln₂The content is not lower than 18%, and the temperature of the waste gas from the preheating section is 280-380 ℃. And then directly carrying out SCR denitration treatment on the waste gas of the preheating section pipeline, wherein the waste gas is not required to be heated, and the catalyst adopts a medium-temperature vanadium-based catalyst. Before SCR denitration, a multi-tube dust remover can be used for removing dust of the waste gas to reduce the dust content of the waste gas to 20mg/m³The following. By optimizing the operating parameters of the chain grate machine, the rotary kiln and the circular cooler, the pellet energy consumption is reduced, and the treatment capacity of waste gas in the subsequent purification process is reduced; meanwhile, the waste gas from the preheating section is subjected to non-heating SCR denitration treatment, so that NOx can be efficiently removed under the condition that the waste gas is not heated. The utility model discloses after adopting transition to preheat back end bellows exhaust-gas circulation, can reduce buggy or coal in the rotary kilnThe consumption of gas or solid fuel such as coal powder, and the volume reduction of coal gas is about 3-10%.

At the present stage, in order to meet the NOx emission requirement in the pellet production process of the chain grate-rotary kiln, namely the hourly mean emission concentration of NOx in the pellet roasting flue gas is not higher than 50mg/m under the condition that the reference oxygen content is 18 percent³. If the oxygen content is higher than 18%, the NOx concentration is evaluated as a value converted to the reference oxygen content. In order to achieve the purpose, the existing process starts from the process flow and simultaneously utilizes the characteristics of the system to achieve the production of the low-NOx pellets on the premise of not adding tail end treatment equipment. The preheating section of the system grate is provided with the device for removing NOx by the SNCR method, so that the content of NOx in pellet flue gas is reduced, and meanwhile, the SCR system is additionally arranged at the air outlet of the air box at the bottom of the preheating section, so that the content of NOx in the flue gas is further reduced, and the ultralow emission of the NOx in the pellet flue gas is realized. Although the SNCR-SCR combined process can realize the ultralow emission of NOx, the SNCR denitration mechanism and the SCR denitration mechanism cannot be perfectly combined due to the fact that a corresponding optimization control mechanism is not available at present, so that the SNCR ammonia consumption is large (the problem of increased ammonia escape amount is caused correspondingly) or the SCR denitration catalyst is short in service life, and the SNCR-SCR combined process needs to be frequently replaced to meet the denitration requirement, so that the problem of high production investment cost is caused. And if the ammonia injection amount is reduced or the catalyst is not replaced in time, the problem of excessive NOx emission is caused.

At present, in a chain grate-rotary kiln denitration system, when an SNCR technology is adopted in a PH section or a transition section (the transition section between the PH section and the rotary kiln, namely a first pipeline), the concentration of NOx entering an SCR technology is greatly reduced, the consumption of a catalyst is reduced, and the activity of the catalyst is prolonged. In general, it is required to maintain the catalyst activity at 60% or more. When denitration is achieved using SCR technology alone, catalyst activity can be maintained for about 3 years, and when SNCR + SCR systems are used, catalyst activity is extended to about 3.6 years. The service life of the catalyst in different denitration systems is detailed in the attached figure 3 of the specification. By adopting the SNCR + SCR system, the engineering investment can be reduced by about 1000 ten thousand yuan, and the catalyst replacement cost is reduced by about 20 ten thousand yuan/year. The comparison of the investment and maintenance costs of different denitration processes is shown in the attached figure 4 of the specification.

The utility model discloses in, through real-time supervision and the key parameter of gathering among the SNCR-SCR coupling deNOx systems, real-time detection promptly and gather NOx initial concentration before the SNCR denitration, SNCR spout the ammonia nitrogen ratio of ammonia, SNCR spout the window temperature of ammonia, NOx concentration before the SCR denitration, SCR spout the ammonia nitrogen ratio of ammonia, the parameter information of the SCR catalyst bed number of piles. Then carrying out reasonable weight distribution according to the influence of each key parameter on the denitration effect, establishing an SNCR-SCR coupling denitration mathematical model by adopting a comprehensive weighting grading method of a multi-index test based on experimental research and engineering application experience, establishing an optimization control mechanism through the mathematical model, and carrying out optimization control on different chain grate machine-rotary kiln SNCR-SCR coupling denitration systems so as to meet the requirement of ultralow NOx emission (not more than 50 mg/m)³) On the premise of ensuring that the system can meet the optimal combination mechanism that the service life of the SCR catalyst is longest while the SNCR ammonia spraying amount is minimum, thereby ensuring the denitration efficiency of a denitration system, reducing the investment cost and obtaining the optimal economic benefit.

The utility model discloses in, to chain grate machine-rotary kiln NCR-SCR coupling deNOx systems, the first step is: the method mainly considers the influence of the initial concentration (x) of NOx (nitrogen oxide) before SNCR denitration (a preheating section and/or a transition section between the preheating section and a rotary kiln), the ammonia-nitrogen ratio (m) of SNCR ammonia spraying and the window temperature (t) of the SNCR ammonia spraying on the denitration rate, and then determines an SNCR denitration efficiency mathematical model through data analysis and data curve fitting:

first, the denitration rate y based on the initial concentration of NOx before SNCR denitration_xComprises the following steps:

Secondly, aim atDenitration rate y of ammonia-nitrogen ratio based on SNCR ammonia injection_mComprises the following steps:

Finally, the denitration rate y for the window temperature based on SNCR ammonia injection_tComprises the following steps:

in the formula IX, t is the window temperature of SNCR ammonia spraying at DEG C. δ is the power of t. Delta is more than or equal to 0 and less than or equal to N_t。N_tTo the highest power of t. a is_tδIs the coefficient to the δ -th power of t.

Further, combining the weight distribution to obtain the SNCR denitration rate formula as follows:

y_SNCR＝A1·y_x+B1·y_m+C1·y_t...(1)。

equation (1) is further evolved as:

in the formula (2), y_SNCRThe SNCR denitration rate is; a1 is an influence weight factor only considering the key parameter x during SNCR denitration; b1 is an influence weight factor only considering the key parameter m during SNCR denitration; c1 is an influence weight factor considering only the key parameter t during SNCR denitration; a1+ B1+ C1 is 1 (the weight proportion of a1, B1 and C1 is determined to be reasonably adjusted and distributed according to actual working conditions); i. beta and delta are powers of key parameters x, m and t respectively. N is a radical of_x、N_m、N_tThe highest powers of the key parameters x, m and t. a is_xi、a_mβ、a_tδAre respectively offAnd coefficients corresponding to the power of the key parameters x, m and t.

When only SNCR denitration is considered, the influence of each key parameter (x, m and t) on the SNCR denitration rate is obtained by adopting a single variable form and a big data fitting method, and then an SNCR denitration mathematical model is established according to a comprehensive weighting and scoring method of a multi-index test.

The utility model discloses in, to chain grate machine-rotary kiln NCR-SCR coupling deNOx systems, the second step is: mainly considering the influence of NOx concentration (z) before SCR denitration after multitubular, ammonia-nitrogen ratio (n) of SCR ammonia spraying and SCR catalyst bed layer number (c) on the denitration rate, and then determining an SCR denitration efficiency mathematical model through data analysis and data curve fitting:

first, the denitration rate y based on the NOx concentration before SCR denitration_zComprises the following steps:

Secondly, denitration rate y for ammonia-nitrogen ratio based on SCR ammonia injection_nComprises the following steps:

Finally, the denitration rate y based on the number of SCR catalyst beds_cComprises the following steps:

Further, the formula of SCR denitration rate obtained by combining weight distribution is as follows:

y_SCR＝D1·y_z+E1·y_n+F1·y_c...(3)。

equation (3) is further evolved as:

in the formula (2), y_SCRThe SCR denitration rate is; d1 is an influence weight factor only considering the key parameter z during SCR denitration; e1 is an influence weight factor considering only the key parameter n during SCR denitration; f1 is an influence weight factor only considering the key parameter c during SCR denitration; d1+ E1+ F1 is 1 (the weight proportion of D1, E1 and F1 is determined to be reasonably adjusted and distributed according to actual working conditions); gamma, lambda and theta are powers of the key parameters z, n and c respectively. N is a radical of_z、N_n、N_cThe highest powers of the key parameters z, n and c. a is_zγ、a_nλ、a_cθThe coefficients corresponding to the power of the key parameters z, n and c are respectively.

When SCR denitration is only considered, the influence of each key parameter (z, n and c) on the SCR denitration rate is obtained by adopting a single variable form and a big data fitting method, and then the SCR denitration mathematical model is established according to a comprehensive weighting evaluation method of a multi-index test.

Further, based on experimental research and engineering application experience, a comprehensive weighting scoring method of a multi-index test is adopted to establish a process (SNCR technology) and terminal control (SCR technology) coupled denitration mathematical model, namely an SNCR-SCR coupled denitration mathematical model:

y＝A·y_x+B·y_m+C·y_t+D·y_z+E·y_n+F·y_c.., formula I.

Formula I is further evolved to:

in formula VIII, a is the weight of the influence factor of the initial NOx concentration x before SNCR denitration. And B is the influence factor weight of the ammonia-nitrogen ratio m of the SNCR ammonia spraying. C is the influence factor weight of the window temperature t of the SNCR ammonia spraying. D is the weight of the influence factor of the NOx concentration z before SCR denitration. E is the weight of the influence factor of the ammonia-nitrogen ratio n of the SCR ammonia spraying. F is the weight of the influence factor of the SCR catalyst bed layer number c. And a + B + C + D + E + F is 1. Wherein A is 0.02 to 0.4, preferably 0.05 to 0.2. B is 0.1 to 0.8, preferably 0.2 to 0.5. C is 0.05-0.5. Preferably 0.1 to 0.3. D is 0.01 to 0.3, preferably 0.02 to 0.2. E is 0.05 to 0.4, preferably 0.1 to 0.3. F is 0.05 to 0.5, preferably 0.1 to 0.4. x is the initial concentration of NOx before SNCR denitration, mg/m³. And m is the ammonia nitrogen ratio of SNCR ammonia spraying. t is the window temperature of SNCR ammonia spraying at DEG C. z is NOx concentration before SCR denitration, mg/m³. And n is the ammonia-nitrogen ratio of SCR ammonia spraying. And c is the number of SCR catalyst bed layers. i. Beta, delta, gamma, lambda and theta are powers of key denitration parameters x, m, t, z, n and c respectively. N is a radical of_xThe highest power of x. a is_xiIs the coefficient of the ith power of x. N is a radical of_mIs the highest power of m. a is_mβIs the coefficient of the power of beta of m. N is a radical of_tTo the highest power of t. a is_tδIs the coefficient to the δ -th power of t. N is a radical of_zIs the highest power of z. a is_zγIs the coefficient of the y-th power of z. N is a radical of_nIs the highest power of n. a is_nλIs the coefficient of the power of lambda of n. N is a radical of_cIs the highest power of c. a is_cθIs the coefficient of the theta power of c.

In the utility model, N_xThe value range of (A) is 0 to 5, preferably 1 to 3. N is a radical of_mThe value range of (A) is 0 to 5, preferably 1 to 3. N is a radical of_tThe value range of (A) is 0 to 5, preferably 1 to 3. N is a radical of_zThe value range of (A) is 0 to 5, preferably 1 to 3. N is a radical of_nThe value range of (A) is 0 to 5, preferably 1 to 3. N is a radical of_cThe value range of (A) is 0 to 5, preferably 1 to 3.

Further, the SNCR-SCR coupled denitration mathematical model can be obtained by further converting the formula VIII:

y＝A·y_x+B·y_m+C·y_t+D·y_z+E·y_n+F·y_c.., formula I.

The utility model discloses in, according to the national requirement pellet calcination flue gas under 18% condition of benchmark oxygen content, NOx hourly mean value emission concentration is not higher than 50mg/m³. If the oxygen content is higher than 18%, the NOx concentration is evaluated as a value converted to the reference oxygen content. Namely, x (1-y) is less than or equal to 50mg/m³The lower the cost of this condition, the better, the higher the economic value. The cost is reflected in two aspects, namely the amount of the SNCR ammonia spraying. Secondly, the SCR catalyst activity duration. Under the condition of ensuring the denitration requirement, the smaller the ammonia injection amount is, the more economical the ammonia injection amount is, and the longer the catalyst activity duration is, the better the catalyst activity duration is.

When x (1-y) is less than or equal to 50mg/m³Then (c) is performed. Reducing the value of m to calculate the STEP length of STEP_m. I.e. m-STEP is continuously executed on the formula VIII_mUntil x (1-y) > 50mg/m is just satisfied³(i.e. just not satisfying x · (1-y) ≦ 50mg/m³) I.e. the minimum critical point of ammonia injection, for safety, we perform m-m + STEP on the basis of the value of m at that time_m. To ensure that x (1-y) is less than or equal to 50mg/m³The condition is the most economical ammonia spraying amount. The point not only ensures that the SNCR ammonia injection amount is minimum, but also can prolong the activity duration of the SCR catalyst to the maximum extent, and simultaneously meets the condition of ultralow NOx emission, thereby being the most economical choice.

When x (1-y) > 50mg/m³Then (c) is performed. Increasing the value of m to calculate the STEP length of STEP_m. I.e. continuously executing m-m + STEP on the formula VIII_mUntil x (1-y) is just less than or equal to 50mg/m³. Then the value of m at this time is executed. To ensure that x (1-y) is less than or equal to 50mg/m³The condition is the most economical ammonia spraying amount. The point not only ensures that the SNCR ammonia injection amount is minimum, but also can prolong the activity duration of the SCR catalyst to the maximum extent, and simultaneously meets the condition of ultralow NOx emission, thereby being the most economical choice.

Wherein, the STEP size STEP_mThe value of (A) is 0.01-0.5. Preferably 0.03-0.3. More preferably 0.05 to 0.1. Can be reasonably adjusted and designed according to actual working conditions.

Generally, the SNCR denitration technique is considered to be preferably carried out at a temperature in the range of 800 ℃ to 1100 ℃. In the production process of the grate-rotary kiln pellets, an SNCR denitration technology is applied, and usually a reducing agent (ammonia water or urea) is sprayed into flue gas at a preheating section (the temperature is 850-1100 ℃) to carry out flue gas denitration, but the optimal emission reduction effect can be achieved only by optimizing control. However, the application effect of the SNCR technique is sensitive to factors such as temperature and the amount of reducing agent. NH when the production process fluctuates, e.g. the temperature is too high₃The oxidation to NO may cause the concentration of NO to increase, the removal rate of NOx is reduced, and when the temperature is too low, NH is generated₃The reaction rate of (2) is decreased, the NOx removal rate is also decreased, and NH is added₃The amount of escape of (a) will also increase.

The utility model discloses in, weigh, stir the mixing and obtain a mixture through urea, soluble sodium salt (for example sodium chloride or sodium carbonate), ethanol, vanadium titanium catalyst, SBA-15 or aqueous ammonia, urea, soluble sodium salt (for example sodium chloride or sodium carbonate), ethanol, vanadium titanium catalyst, nanometer zero-valent iron-kaolin material according to specific mass ratio, wherein the ethanol need weigh alone and place for subsequent use. And then carrying out high-pressure atomization mixing on the primary mixture and ethanol to obtain a composite additive (vanadium-titanium composite additive) or a composite ammonia agent (vanadium-titanium composite ammonia agent) which is sprayed into the high-NOx flue gas to carry out SNCR denitration reaction. Because the ethanol is a flammable, volatile, colorless and transparent liquid, the ethanol needs to be weighed and placed separately, and is mixed with other raw materials in the production process to form the vanadium-titanium composite ammonia agent for denitration.

Further, the main component of the SBA-15 mesoporous material is SiO₂Has a two-dimensional straight-channel hexagonal crystal structure, the thickness of the hole wall can reach 6.4nm, the thermal stability can reach 900 ℃, the specific surface area can reach 700-²Per g, pore volume 0.6-1.3cm²(ii) in terms of/g. Has good dispersibility in water and ethanol. The utility model discloses in, add SBA-15 mesoporous material and can improve compound ammonia agent and NOx's area of contact, provide a better reaction site for ammonia agent and NOx to catalytic reduction acceleratesThe reaction takes place.

Further, the concentration of the ammonia water is 15-35%, preferably 20-25%. The purity of the urea is more than or equal to 99 percent, and the preferred purity is more than or equal to 99.5 percent. The particle size of the urea is-0.074 mm or more and 90 percent, preferably-0.074 mm or more and 95 percent. The purity of the NaCl is more than or equal to 99 percent, and the preferred purity of the NaCl is more than or equal to 99.5 percent. The granularity of the NaCl is more than or equal to 90 percent when the granularity is-0.074 mm, and preferably more than or equal to 95 percent when the granularity is-0.074 mm. The vanadium-titanium catalyst is selected from any V-TiO₂Is a catalyst. The particle size of the vanadium-titanium catalyst is-0.074 mm or more and 80%, preferably-0.074 mm or more and 80%. The ethanol is absolute ethanol. The purity of the absolute ethyl alcohol is more than or equal to 99 percent, and the preferred purity is more than or equal to 99.7 percent.

Furthermore, the adsorption method adopting the nano zero-valent iron-kaolin composite material is simple to operate, flexible, low in energy consumption, wide in material source and low in price. The nanometer zero-valent iron has strong reducibility, and the iron oxide generated on the surface also has strong adsorbability. However, because the nano zero-valent iron is easy to agglomerate, the removal efficiency of the nano zero-valent iron is influenced, and the nano zero-valent iron is loaded on other solids, so that the agglomeration can be reduced, the dispersity of the nano zero-valent iron is improved, the surface area of the nano zero-valent iron can be increased, and the reaction efficiency is improved. The kaolin (kaolinite) is a product in the nature, cannot cause secondary pollution, has an environment buffering effect, is stable in property and has certain adsorbability, so that the kaolin is selected as a carrier of the nano zero-valent iron. Simultaneously in the utility model discloses in, nanometer zero-valent iron-kaolin combined material also can further improve ammonia agent and NOx's area of contact, provides a better reaction site for ammonia agent and NOx to catalytic reduction's emergence is accelerated.

In the present invention, the diameter of the first pipe is 0.5-5m, preferably 0.8-4m, and more preferably 1-3 m. The blending device is a box body, a sphere or a tank body, and the volume of the blending device is 0.5-5m³Preferably 0.8 to 4m³More preferably 1 to 3m³. The width of the windbox (in the direction of the material flow) is from 0.1 to 5m, preferably from 0.2 to 4m, more preferably from 0.3 to 3 m. The length of the transition preheating section is 1 to 30m, preferably 3 to 20m, more preferably 5 to 15 m. The above definitions are only preferred embodiments of the present invention, and are not intended to limit the present inventionCan be used as the basis for limiting the utility model.

In the utility model, the vanadium-titanium composite additive is formed by compounding urea, soluble sodium salt, ethanol, vanadium-titanium catalyst and SBA-15. Wherein the urea decomposes at high temperature to release ammonia in NH₃When the nitrogen oxide is reduced, the reducing agent can be slowly released and provided within a certain period of time, so that the denitration reduction reaction is continuously carried out, and the conversion rate of the nitrogen oxide is improved. The soluble sodium salt and the ethanol can generate a large amount of-H, -CH, -OH and other active groups through reaction or decomposition after entering the high-temperature flue gas, a denitration reaction chain is activated at a lower temperature, and the sensitivity of SNCR denitration to the reaction temperature is obviously reduced, so that the optimal reaction temperature zone of the SNCR is shifted downwards, the denitration reaction temperature window is expanded, and the flue gas denitration rate is improved. In addition, the vanadium-titanium catalyst in the composite additive has the function of promoting the flue gas denitration reaction, and can obviously promote the SNCR denitration reaction. Therefore, the vanadium-titanium composite additive greatly improves the high-temperature denitration efficiency of the oxidized pellet flue gas of the chain grate-rotary kiln under the synergistic effect of several components.

The utility model discloses in, compound ammonia agent is formed by aqueous ammonia, urea, soluble sodium salt, ethanol and vanadium titanium catalyst complex. Wherein the urea decomposes at high temperature to release ammonia in NH₃When the nitrogen oxide is reduced, the reducing agent can be slowly released and provided within a certain period of time, so that the denitration reduction reaction is continuously carried out, and the conversion rate of the nitrogen oxide is improved. The soluble sodium salt and the ethanol can generate a large amount of-H, -CH, -OH and other active groups through reaction or decomposition after entering the high-temperature flue gas, a denitration reaction chain is activated at a lower temperature, and the sensitivity of SNCR denitration to the reaction temperature is obviously reduced, so that the optimal reaction temperature zone of the SNCR is shifted downwards, the denitration reaction temperature window is expanded, and the flue gas denitration rate is improved. In addition, the vanadium-titanium catalyst in the composite ammonia agent has the function of promoting the flue gas denitration reaction, and can obviously promote the SNCR denitration reaction. Therefore, the composite ammonia agent greatly improves the high-temperature denitration efficiency of the grate-rotary kiln oxidized pellet flue gas under the synergistic effect of a plurality of components.

In the utility model, the vanadium-titanium composite ammonia agent is added under high pressure (0.1-2 MPa)Preferably 0.15-1.5MPa, more preferably 0.18-1MPa) into the high NOx flue gas and is fully mixed with the high NOx flue gas. Ensuring the reaction time (generally 0.1-1s) under the condition of high temperature (850-₃Effectively reacts with NOx and is converted into N₂And the like, and the non-NOx toxic substances can reduce the dosage of the ammonia agent reducing agent under the catalytic action of the soluble sodium salt, improve the denitration efficiency and reduce the ammonia escape. The denitration rate can be improved from about 40 percent of the ammonia agent reducing agent to 60 percent.

Further, the utility model discloses still test and adopted when having or not having soluble sodium salt to exist in the compound ammonia agent of vanadium titanium (here use NaCl as an example) the effect contrast after the system carries out flue gas denitration:

TABLE 1 influence of NaCl on denitration rate and Ammonia slip

In the utility model, the pellet is further utilized (the hematite pellet has poor effect, the magnetite pellet has high oxidation degree and better effect, because of the new Fe₂O₃Better phase activity) material layer, and the synergistic catalytic action of the carrier, the vanadium-titanium catalyst and the macromolecular ethanol, further converting the residual NOx into N₂And the denitration rate can exceed 80% due to the non-NOx toxic substances. Also adopted simultaneously the system test pellet and catalyst influence (high temperature) to flue gas denitration rate and ammonia escape:

TABLE 2 pellet and catalyst effects on denitration rate and ammonia slip (high temperature)

The utility model discloses in, not only utilize the characteristics of chain grate-rotary kiln oxidation pelletizing production system, the high temperature denitration agent is sprayed at the changeover portion between chain grate and rotary kiln and or the preheating section of chain grate, can realize the low NOx emission of pelletizing production, the denitration rate can reach more than 60-80%, dust pelletizing system has still been set gradually at the end simultaneously, desulfurization system and SCR deNOx systems, further remove dust to the flue gas after vanadium titanium compound ammonia agent denitration treatment, the desulfurization, denitration treatment, has apparent flue gas purification effect, reduce the ammonia agent quantity simultaneously, reduce the secondary pollution of ammonia escape to the environment.

In the present invention, "optionally" means performing or not performing, selecting or not selecting, setting or not setting.

Compared with the prior art, the utility model discloses following beneficial technological effect has:

1. the utility model discloses a waste gas of circulation transition preheating section back end bellows has utilized the waste heat in the waste gas to through the whole optimization to pellet production technology, under the prerequisite that does not influence pellet output, quality, improve heat utilization efficiency, reduced the energy resource consumption of pellet production technology, the energy consumption reduces and is about 3% ~ 5%. Meanwhile, the treatment capacity of the discharged waste gas is reduced, and the investment cost and the operation cost of waste gas treatment are reduced.

2. The utility model discloses with the hot waste gas of transition preheating section back end bellows direct cycle to the rotary kiln in as a combustion-supporting wind, on the one hand can make full use of flue gas waste heat, the heat that the reducible fuel burning needs to provide, flame temperature in the waste heat reduction rotary kiln of the hot waste gas of this part of still can make full use of simultaneously reduces heating power type NOx's production, realizes the in-process formation that reduces NOx. On the other hand, the oxygen content of the primary mixed air (the oxygen content in normal air is about 21%, and the oxygen content in the circulating hot exhaust gas is about 18%) can be reduced, so that the generation amount of NOx (namely, the generation amount of thermal NOx is reduced from the source) is reduced.

3. The utility model discloses a hot waste gas that circulation NOx content is high reduces the NOx content in outer row waste gas on the one hand, and on the other hand ensures that NOx in the waste gas can carry out SNCR and SCR denitration in the preheating section and carry out the desorption, reduces the NOx content in outer row waste gas once more, and reaches the outer row flue gas of "about advancing the suggestion of implementing the ultralow emission of steel industry" regulation chain grate machine-rotary kiln pelletizing production procedureThe concentration of medium NOx is lower than 50mg/m³The requirements of (1).

3. Establishing a process (SNCR technology) and terminal control (SCR technology) coupled denitration mathematical model; by applying the model, denitration technological parameters can be optimized, and the investment, operation and maintenance costs of denitration in a pellet plant are reduced.

4. The method can effectively control the chain grate machine-rotary kiln SNCR-SCR denitration system to reach the most economical ammonia spraying amount. The minimum ammonia spraying amount of SNCR is ensured, the activity duration of the SCR catalyst can be prolonged to the maximum extent, the ultralow NOx emission condition is met, the investment and maintenance cost is reduced, and the economic benefit is obviously improved.

5. Control method easy operation, the parameter source of establishing SNCR-SCR coupling denitration mathematical model is convenient, need not additionally add large-scale controlgear and a large amount of operating personnel, has fine spreading value.

6. The utility model discloses a composite additive uses urea, soluble sodium salt and ethanol as the main ingredient, cooperates a small amount of vanadium titanium catalyst, SBA-15 material to constitute composite additive during the use, can reduce ammonia agent reductant quantity, and improves denitration efficiency, reduces ammonia escape.

7. The utility model discloses a compound ammonia agent uses aqueous ammonia, urea, soluble sodium salt and ethanol as main raw materials, cooperates a small amount of vanadium titanium catalyst and nanometer zero-valent iron-kaolin material to constitute compound ammonia agent during the use, can effectively improve chain grate-rotary kiln oxidation pelletizing flue gas high temperature denitration efficiency, and flue gas denitration rate can reach 80%, greatly reduced follow-up flue gas treatment's the degree of difficulty and cost.

8. The utility model discloses a raw materials that add in composite additive or compound ammonia agent have effects such as ammonia composition slowly-releasing, catalytic reduction, can realize the denitration effect under the higher ammonia nitrogen ratio condition under the lower ammonia nitrogen ratio condition, the availability factor of aqueous ammonia when improving flue gas denitration reduces ammonia nitrogen ratio and ammonia escape, and ammonia escape concentration can reduce to < 2mg/m³Greatly reducing the secondary pollution.

9. The compound additive and the compound ammonia agent of the utility model are all from the market, have the advantages of wide raw material source, low cost, simple preparation process and the like, and are easy to realize large-scale production.

10. Process adopt process SNCR denitration mechanism to combine the process of terminal dust removal, desulfurization, SCR denitration mechanism for dust removal, desulfurization, the denitration of flue gas are effectual, ammonia escape volume is few, and process flow is simple, and the small investment is suitable for the popularization.

Drawings

Fig. 1 is the structure diagram of the flue gas treatment system of the utility model.

Fig. 2 is a block diagram of a prior art flue gas treatment system.

FIG. 3 is a graph showing the relationship between the activity and the service life of the denitration catalyst in different denitration systems.

FIG. 4 is a table comparing the investment and maintenance costs of different denitration processes.

Fig. 5 is a structure diagram of the flue gas treatment system with the ring cooling machine of the present invention.

FIG. 6 is a control flow chart of the transition preheating section bellows dividing method of the present invention.

FIG. 7 is a control flow chart of the SNCR-SCR coupling denitration mathematical model method of the utility model.

Fig. 8 is a diagram of the distribution structure of the transition preheating section bellows of the flue gas circulation coupling treatment system of the present invention.

Fig. 9 is a connection structure diagram of transition preheating section bellows of the flue gas circulation coupling processing system of the present invention.

Fig. 10 is the structure diagram of the flue gas treatment system with the SNCR denitration device of the present invention.

Fig. 11 is the structure diagram of the flue gas treatment system with the blending device of the present invention.

Reference numerals: 1: a chain grate machine; 2: a rotary kiln; 3: a circular cooler; 4: a dust removal device; 5: an SCR denitration device; 6: a desulfurization unit; 7: an air box; 8: an SNCR denitration device; 9: a blending device; UDD: a forced air drying section; DDD: an air draft drying section; TPH: a transition preheating section; pH: a preheating section; 701: switching valves; 801: a first spraying device; 802: a second spraying device; 803: a high-pressure atomization mixing device; c1: cooling in a ring for one section; c2: a ring cooling section; c3: ring cooling for three sections; l1: a first conduit; l2: a second conduit; l3: a third pipeline; l4: a fourth conduit; l5: a fifth pipeline; l6: a sixth pipeline; l7: a seventh pipe; l8: an eighth conduit; l9: a ninth conduit; l10: a tenth conduit; l11: an eleventh pipe; l12: a twelfth duct; h: a NOx concentration detection means; s1: a vanadium-titanium catalyst conveying pipe; s2: an ammonia water conveying pipe; s3: a urea delivery pipe; s4: a soluble sodium salt delivery pipe; s5: an ethanol conveying pipe; s6: a nano zero-valent iron or SBA-15 conveying pipeline; f1: a first fan; f2: a second fan; f3: a third fan; f4: and a fourth fan.

Detailed Description

The technical solution of the present invention is illustrated below, and the claimed invention includes but is not limited to the following embodiments.

A pellet flue gas treatment system based on primary circulating air inlet of a rotary kiln comprises a chain grate machine 1, a rotary kiln 2 and an SCR denitration device 5. According to the trend of the materials, the chain grate machine 1 is sequentially provided with a blast drying section UDD, an air draft drying section DDD, a transition preheating section TPH and a preheating section PH. An air outlet of the rotary kiln 2 is communicated to an air inlet of the preheating section PH through a first pipeline L1. The rotary kiln 2 is provided with a central burner 201. The central burner 201 is in communication with a fuel conduit 203. A primary combustion-supporting air pipe 202 is also arranged on the fuel pipeline 203. And the air outlet of the preheating section PH is communicated to the air inlet of the exhausting and drying section DDD through a second pipeline L2. The air outlet of the transition preheating section TPH is divided into a front section air outlet and a rear section air outlet. And the rear-section air outlet of the transition preheating section TPH is communicated to the air inlet of the primary combustion-supporting air pipe 202 through a third pipeline L3. And the air outlet of the front section of the transition preheating section TPH is communicated to the outside through a fourth pipeline L4. And an air outlet of the air draft drying section DDD is communicated to a fourth pipeline L4 through a fifth pipeline L5. The second pipeline L2 is provided with an SCR denitration device 5.

Preferably, J wind boxes 7 are provided at the bottom of the transition preheating section TPH, and the outlet of each wind box 7 of the J wind boxes 7 is simultaneously connected to the third pipeline L3 and the fourth pipeline L4 through a switching valve 701. The air outlet of each air box 7 is controlled to be communicated with only the third pipeline L3 or only the fourth pipeline L4 by switching the valve 701.

Preferably, J wind boxes 7 in the transition preheating section TPH are numbered 1, 2, 3, J in sequence according to the trend of the materials. Wherein, the 1 st to jth wind boxes 7 are taken as front segment wind boxes and are communicated with a fourth pipeline L4. The (J +1) th to J-th windboxes 7 serve as rear-stage windboxes and are each communicated with a third pipeline L3. J is more than or equal to 1 and less than or equal to J.

Preferably, the system also comprises a circulation cooler 3. According to the trend of the materials, the circular cooler 3 is sequentially provided with a circular cooling first section C1, a circular cooling second section C2 and a circular cooling third section C3. An air outlet of the annular cooling section C1 is communicated to an air inlet of the rotary kiln 2 through a sixth pipeline L6. An air outlet of the annular cooling section C2 is communicated to an air inlet of the transition preheating section TPH through a seventh pipeline L7. And an air outlet of the annular cooling three-section C3 is communicated to an air inlet of the forced air drying section UDD through an eighth pipeline L8. And an air outlet of the air blowing drying section UDD is communicated to a chimney through a ninth pipeline L9.

Preferably, the system further comprises an SNCR denitration device 8. The SNCR denitration device 8 is arranged in the preheating section PH and/or the first pipeline L1.

Preferably, the system further includes NOx concentration detection means H provided in the wind box 7. And NOx concentration detection devices H are independently arranged in J air boxes 7 at the bottom of the transition preheating section TPH.

Preferably, the SNCR denitration device 8 includes a first spraying device 801 and a high-pressure atomization mixing device 803. The first spraying device 801 is arranged in the preheating section PH and is connected with the high-pressure atomization mixing device 803 through a tenth pipeline L10.

Preferably, the SNCR denitration device 8 further includes a second spraying device 802. The second spraying device 802 is arranged in a first pipeline L1 and is connected with a high-pressure atomization mixing device 803 through an eleventh pipeline L11.

Preferably, the eleventh pipe L11 is a bypass pipe branched from the tenth pipe L10.

Preferably, the high-pressure atomization mixing device 803 is provided with a vanadium-titanium catalyst delivery pipe S1, an ammonia water delivery pipe S2, a urea delivery pipe S3, a soluble sodium salt delivery pipe S4, an ethanol delivery pipe S5 and a nano zero-valent iron or SBA-15 delivery pipe S6.

Preferably, the system also comprises a blending device 9. And a vanadium-titanium catalyst conveying pipe S1, an ammonia water conveying pipe S2, a urea conveying pipe S3, a soluble sodium salt conveying pipe S4 and a nano zero-valent iron or SBA-15 conveying pipe S6 are arranged on the blending device 9. The blending device 9 is communicated with the high-pressure atomization mixing device 803 through a twelfth pipeline L12.

Preferably, the system further comprises a dust removal device 4, wherein the dust removal device 4 is arranged on the second pipeline L2 and is positioned at the upstream of the SCR denitration device 5. Preferably, the fourth duct L4 is also provided with a dust removing device 4.

Preferably, the third pipeline L3 and the ninth pipeline L9 are each optionally provided with or without a dust removing device 4.

Preferably, the system further comprises a desulphurization unit 6. The desulfurization device 6 is disposed on the fourth conduit L4. Preferably, the fourth pipeline L4 is further provided with a dust removing device 4, and the dust removing device 4 is located upstream of the desulfurization device 6.

Example 1

As shown in fig. 1, the system for circulating and treating pellet flue gas of a chain grate-rotary kiln comprises a chain grate 1, a rotary kiln 2 and an SCR denitration device 5. According to the trend of the materials, the chain grate machine 1 is sequentially provided with a blast drying section UDD, an air draft drying section DDD, a transition preheating section TPH and a preheating section PH. The rotary kiln 2 is provided with a central burner 201. The central burner 201 is in communication with a fuel conduit 203. A primary combustion-supporting air pipe 202 is also arranged on the fuel pipeline 203. An air outlet of the rotary kiln 2 is communicated to an air inlet of the preheating section PH through a first pipeline L1. And the air outlet of the preheating section PH is communicated to the air inlet of the exhausting and drying section DDD through a second pipeline L2. The air outlet of the transition preheating section TPH is divided into a front section air outlet and a rear section air outlet. And the rear-section air outlet of the transition preheating section TPH is communicated to the air inlet of the primary combustion-supporting air pipe 202 through a third pipeline L3. And the air outlet of the front section of the transition preheating section TPH is communicated to the outside through a fourth pipeline L4. And an air outlet of the air draft drying section DDD is communicated to a fourth pipeline L4 through a fifth pipeline L5. The second pipeline L2 is provided with an SCR denitration device 5.

Example 2

In example 1, as shown in fig. 7 and 8, J wind boxes 7 are provided at the bottom of the transition preheating section TPH, and the outlet of each of the J wind boxes is simultaneously connected to the third line L3 and the fourth line L4 by switching the valves 701. The air outlet of each air box 7 is controlled to be communicated with only the third pipeline L3 or only the fourth pipeline L4 by switching the valve 701.

The J wind boxes 7 in the transition preheating section TPH are numbered 1, 2, 3, J in sequence according to the trend of the materials. Wherein, the 1 st to jth wind boxes 7 are taken as front segment wind boxes and are communicated with a fourth pipeline L4. The (J +1) th to J-th windboxes 7 serve as rear-stage windboxes and are each communicated with a third pipeline L3. J is more than or equal to 1 and less than or equal to J. J is 1-100.

Example 3

Example 2 is repeated except that the system also includes a circulator 3. According to the trend of the materials, the circular cooler 3 is sequentially provided with a circular cooling first section C1, a circular cooling second section C2 and a circular cooling third section C3. An air outlet of the annular cooling section C1 is communicated to an air inlet of the rotary kiln 2 through a sixth pipeline L6. An air outlet of the annular cooling section C2 is communicated to an air inlet of the transition preheating section TPH through a seventh pipeline L7. And an air outlet of the annular cooling three-section C3 is communicated to an air inlet of the forced air drying section UDD through an eighth pipeline L8. And an air outlet of the air blowing drying section UDD is communicated to a chimney through a ninth pipeline L9.

Example 4

Example 3 was repeated except that the system further included an SNCR denitration device 8. The SNCR denitration device 8 is arranged in the preheating section PH and the first pipeline L1.

Example 5

Example 4 was repeated except that the system further included a NOx concentration detection device H provided in the windbox 7. And J air boxes 7 are internally provided with NOx concentration detection devices H.

Example 6

Example 5 is repeated except that the SNCR denitration device 8 includes a first spraying device 801 and a high-pressure atomization mixing device 803. The first spraying device 801 is arranged in the preheating section PH and is connected with the high-pressure atomization mixing device 803 through a tenth pipeline L10.

The SNCR denitration device 8 further includes a second spraying device 802. The second spraying device 802 is arranged in a first pipeline L1 and is connected with a high-pressure atomization mixing device 803 through an eleventh pipeline L11.

The eleventh pipe L11 is a bypass pipe branched from the tenth pipe L10.

Example 7

Example 6 is repeated except that the high-pressure atomization mixing device 803 is provided with a vanadium-titanium catalyst delivery pipe S1, an ammonia water delivery pipe S2, a urea delivery pipe S3, a soluble sodium salt delivery pipe S4, an ethanol delivery pipe S5 and a nano zero-valent iron or SBA-15 delivery pipe S6.

Example 8

Example 7 was repeated except that the system further included a homogenizing apparatus 9. And a vanadium-titanium catalyst conveying pipe S1, an ammonia water conveying pipe S2, a urea conveying pipe S3, a soluble sodium salt conveying pipe S4 and a nano zero-valent iron or SBA-15 conveying pipe S6 are arranged on the blending device 9. The blending device 9 is communicated with the high-pressure atomization mixing device 803 through a twelfth pipeline L12.

Example 9

Example 8 was repeated except that the system further included a dust removing device 4, and the dust removing device 4 was disposed on the second pipe L2 and was located upstream of the SCR denitration device 5. The fourth line L4 is also provided with a dust removing device 4.

Example 10

Example 9 was repeated except that the dust removing device 4 was optionally provided or not provided on each of the third line L3 and the ninth line L9.

Example 11

Example 10 was repeated except that the system further included a desulfurization unit 6. The desulfurization device 6 is disposed on the fourth conduit L4. The fourth line L4 is also provided with a dust removing device 4, and the dust removing device 4 is located upstream of the desulfurizer 6.

Application example 1

Aiming at the pellet preparation process of a chain grate machine, a rotary kiln and a circular cooler, the adopted raw material is magnetite, SNCR denitration is adopted in a preheating section, an SNCR catalyst adopts a compound ammonia agent (the ammonia nitrogen molar ratio is 1.1:1, and the compound ammonia agent comprises 78 wt% of ammonia water, 20.45 wt% of urea and Na₂CO₃0.5 wt%, ethanol 1.0 wt%, vanadium-titanium catalyst 0.05 wt%); the average concentration of the NOx in the waste gas of the transition preheating section is 70ppm, the waste gas of a rear-section air box with the concentration of the NOx higher than 70ppm is used as primary combustion-supporting air to circulate to the rotary kiln, the waste gas of the rear-section air box accounts for 30% of the total amount of the waste gas of the transition preheating section, the average temperature of the circulating waste gas is 230 ℃, the circulating waste gas of the rear-section air box is dedusted by a plurality of pipes and is pumped into a primary combustion-supporting air pipe of a central burner by a circulating fan, the amount of air introduced by a cooling section (standard condition) is kept unchanged before circulation, and a part of hot air is discharged from a ring cooling section (the amount of the discharged hot air; the air quantity is increased by 3 percent in the second cooling section and 5 percent in the third cooling section, and the temperature of the pellets discharged from the circular cooler is 146 ℃; the flue gas of the air box at the rear section of the transition preheating section is circulated, so that the coal injection quantity of the rotary kiln is reduced by 3 percent, and the O content of the gas in the rotary kiln is reduced₂The content is 18 percent, and the temperature of the waste gas from the preheating section is 309 ℃; the waste gas of the preheating section pipeline is dedusted by a multi-pipe deduster, and the dust content of the waste gas is reduced to 15mg/m³Then, SCR denitration treatment is adopted, and the SCR catalyst adopts a medium-temperature vanadium-based catalyst. Adopt the utility model discloses the non-SCR denitration that heats of hot exhaust gas circulation coupling detects outer row exhaust gas NOx and discharges concentration and reduce to 34mg/Nm³And the ultra-low emission condition is achieved.

Application example 2

Aiming at the pellet preparation process of a chain grate machine, a rotary kiln and a circular cooler, 80 percent of magnetite and 20 percent of hematite are adopted as raw materials, the average concentration of NOx in waste gas of a transition preheating section is 76ppm, SNCR denitration is adopted in the preheating section, a composite ammonia agent (the ammonia nitrogen molar ratio is 1.1: 1; the composite ammonia agent group is adopted as an SNCR catalyst)The method comprises the following steps: 78 wt% of ammonia water, 20.45 wt% of urea and Na₂CO₃0.5 wt%, ethanol 1.0 wt%, vanadium-titanium catalyst 0.05 wt%); circulating the rear-section air box waste gas with the concentration of NOx in the transitional preheating section higher than 76ppm to the rotary kiln as primary combustion-supporting air, wherein the rear-section air box waste gas accounts for 40% of the total amount of the transition preheating section waste gas, the average temperature of the circulating waste gas is 220 ℃, the circulating waste gas of the rear-section air box is dedusted by a plurality of pipes and is pumped into a primary combustion-supporting air pipe of a central burner by a circulating fan, the amount of air introduced in the cooling section (standard condition) is kept unchanged before circulation, and a part of hot air is discharged from the hot air discharged in the ring cooling section (the amount of the discharged hot air is equal to the amount of the; the air quantity is increased by 5% in the second cooling section and 5% in the third cooling section, and the temperature of the pellets discharged from the circular cooler is 140 ℃; the flue gas of the air box at the rear section of the transition preheating section is circulated, so that the coal injection quantity of the rotary kiln is reduced by 4 percent, and the O content of the gas in the rotary kiln is reduced₂The content is 18.2 percent, and the temperature of the waste gas from the preheating section is 312 ℃; the waste gas of the preheating section pipeline is dedusted by a multi-pipe deduster, and the dust content of the waste gas is reduced to 15mg/m³Then, SCR denitration treatment is adopted, and the SCR catalyst adopts a medium-temperature vanadium-based catalyst. Adopt the utility model discloses the non-SCR denitration that heats of hot exhaust gas circulation coupling detects outer row exhaust gas NOx and discharges concentration and reduce to 32mg/Nm³And the ultra-low emission condition is achieved.

Application example 3

Aiming at a pellet preparation process of a chain grate machine-rotary kiln-circular cooler, 70% of magnetite and 30% of hematite are adopted as raw materials, the average concentration of NOx in waste gas of a transition preheating section is 81ppm, SNCR denitration is adopted in the preheating section, and an SNCR catalyst adopts a catalyst containing a composite additive (the ammonia nitrogen molar ratio is 1.1: 1; the composite additive comprises 52 wt% of urea, 20 wt% of NaCl, 20 wt% of ethanol and 8 wt% of a vanadium-titanium catalyst); circulating the rear-section air box waste gas with the concentration of NOx in the transitional preheating section higher than 81ppm to the rotary kiln as primary combustion-supporting air, wherein the rear-section air box waste gas accounts for 50 percent of the total amount of the transition preheating section waste gas, the average temperature of the circulating waste gas is 200 ℃, the circulating waste gas of the rear-section air box is pumped into a primary combustion-supporting air pipe of a central burner by a circulating fan after being dedusted by a plurality of pipes,keeping the air quantity (standard condition) introduced at the cooling section unchanged before circulation, and discharging a part of hot air out of hot air discharged at the ring cooling section (the discharged hot air quantity is equal to the circulating air quantity from the transition preheating section to the rotary kiln); the air quantity is increased by 5 percent in the second cooling section and 8 percent in the third cooling section, and the temperature of the pellets discharged from the circular cooler is 146 ℃; the flue gas of the air box at the rear section of the transition preheating section is circulated, so that the coal injection quantity of the rotary kiln is reduced by 5 percent, and the O content of the gas in the rotary kiln is reduced₂The content is 18.4 percent, and the temperature of the waste gas from the preheating section is 335 ℃; the waste gas of the preheating section pipeline is dedusted by a multi-pipe deduster, and the dust content of the waste gas is reduced to 15mg/m³Then, SCR denitration treatment is adopted, and the SCR catalyst adopts a medium-temperature vanadium-based catalyst. Adopt the utility model discloses the non-SCR denitration that heats of hot exhaust gas circulation coupling detects outer row exhaust gas NOx and discharges concentration and reduce to 31mg/Nm³And the ultra-low emission condition is achieved.

Comparative example 1

Aiming at the process for preparing pellets by a chain grate machine, a rotary kiln and a ring cooling machine, the adopted raw material is magnetite, the average temperature of circulating waste gas is 230 ℃, the temperature of the circulating waste gas is maintained to be cooled for the first section, the temperature of the circulating waste gas is maintained to be cooled for the second section, the air volume of the cooling for the third section is unchanged (under the standard condition), and the temperature of the pellets discharged from the ring cooling machine is 143 ℃; directly circulating the waste gas of the preheating section pipeline to the air draft drying section, and then sequentially carrying out dust removal treatment, desulfurization treatment and SCR denitration treatment on the hot air output by the air draft drying section and the transition preheating section, wherein the catalyst is a medium-temperature vanadium-based catalyst. The dust concentration of the discharged waste gas is detected to be 15mg/m³NOx emission concentration of 61mg/Nm³。

Comparative example 2

Aiming at the process for preparing the pellets by the chain grate machine, the rotary kiln and the circular cooler, the average temperature of circulating waste gas of 70 percent of magnetite and 30 percent of hematite is 240 ℃, the average temperature of the circulating waste gas is maintained at a first cooling stage and a second cooling stage, the air volume of the third cooling stage is unchanged (under the standard condition), and the temperature of the pellets discharged from the circular cooler is 140 ℃; directly circulating the waste gas of the preheating section pipeline to an air draft drying section, and then sequentially performing dust removal treatment, desulfurization treatment and SCR denitration treatment on hot air output by the air draft drying section and a transition preheating section, wherein a catalyst adopts medium-temperature vanadium-based catalysisAn oxidizing agent. The dust concentration of the discharged waste gas is detected to be 17mg/m³NOx emission concentration 65mg/Nm³。

Claims

1. The utility model provides a pelletizing flue gas processing system based on rotary kiln once circulates air inlet which characterized in that: the system comprises a chain grate machine (1), a rotary kiln (2) and an SCR denitration device (5); according to the trend of materials, the chain grate machine (1) is sequentially provided with a blast drying section (UDD), an air draft drying section (DDD), a transition preheating section (TPH) and a preheating section (PH); a central burner (201) is arranged on the rotary kiln (2); the central burner (201) is communicated with a fuel pipeline (203); a primary combustion-supporting air pipe (202) is also arranged on the fuel pipeline (203); an air outlet of the rotary kiln (2) is communicated to an air inlet of the preheating section (PH) through a first pipeline (L1); an air outlet of the preheating section (PH) is communicated to an air inlet of the air draft drying section (DDD) through a second pipeline (L2); the air outlet of the transition preheating section (TPH) is divided into a front section air outlet and a rear section air outlet; the rear-section air outlet of the transition preheating section (TPH) is communicated to the air inlet of the primary combustion-supporting air pipe (202) through a third pipeline (L3); the air outlet of the front section of the transition preheating section (TPH) is communicated to the outside through a fourth pipeline (L4); an air outlet of the air draft drying section (DDD) is communicated to a fourth pipeline (L4) through a fifth pipeline (L5); an SCR denitration device (5) is arranged on the second pipeline (L2); the length of the transition preheating section (TPH) is 1-30 m.

2. The system of claim 1, wherein: the length of the transition preheating section (TPH) is 3-20 m.

3. The system of claim 2, wherein: the length of the transition preheating section (TPH) is 5-15 m.

4. The system according to any one of claims 1-3, wherein: j air boxes (7) are arranged at the bottom of the transition preheating section (TPH), and an air outlet of each air box (7) in the J air boxes (7) is simultaneously connected with a third pipeline (L3) and a fourth pipeline (L4) through a switching valve (701); the air outlet of each air box (7) is controlled to be communicated with the third pipeline (L3) only or communicated with the fourth pipeline (L4) only by switching the valve (701).

5. The system of claim 4, wherein: according to the trend of materials, the serial numbers of J wind boxes (7) in the transition preheating section (TPH) are 1, 2, 3, ·, J in sequence; wherein, the 1 st to the jth wind boxes (7) are taken as front segment wind boxes and are communicated with a fourth pipeline (L4); the (J +1) th to the J-th air boxes (7) are used as rear-section air boxes and are communicated with a third pipeline (L3); j is more than or equal to 1 and less than or equal to J.

6. The system of claim 5, wherein: j is 1-100.

7. The system of claim 6, wherein: j is 2-80.

8. The system of claim 7, wherein: j is 2-50.

9. The system of any one of claims 1-3, 5-8, wherein: the system also comprises a circular cooler (3); according to the trend of the materials, the ring cooling machine (3) is sequentially provided with a ring cooling first section (C1), a ring cooling second section (C2) and a ring cooling third section (C3); an air outlet of the annular cooling section (C1) is communicated to an air inlet of the rotary kiln (2) through a sixth pipeline (L6); an air outlet of the annular cooling section (C2) is communicated to an air inlet of the transition preheating section (TPH) through a seventh pipeline (L7); the air outlet of the annular cooling three-section (C3) is communicated to the air inlet of the blast drying section (UDD) through an eighth pipeline (L8); an air outlet of the forced air drying section (UDD) is communicated to a chimney through a ninth pipeline (L9).

10. The system of claim 4, wherein: the system also comprises a circular cooler (3); according to the trend of the materials, the ring cooling machine (3) is sequentially provided with a ring cooling first section (C1), a ring cooling second section (C2) and a ring cooling third section (C3); an air outlet of the annular cooling section (C1) is communicated to an air inlet of the rotary kiln (2) through a sixth pipeline (L6); an air outlet of the annular cooling section (C2) is communicated to an air inlet of the transition preheating section (TPH) through a seventh pipeline (L7); the air outlet of the annular cooling three-section (C3) is communicated to the air inlet of the blast drying section (UDD) through an eighth pipeline (L8); an air outlet of the forced air drying section (UDD) is communicated to a chimney through a ninth pipeline (L9).

11. The system of any one of claims 1-3, 5-8, 10, wherein: the system also comprises an SNCR denitration device (8); the SNCR denitration device (8) is arranged in a preheating section (PH) and/or a first pipeline (L1); and/or

The system also comprises a NOx concentration detection device (H), wherein the NOx concentration detection device (H) is arranged in the air box (7); and NOx concentration detection devices (H) are independently arranged in J air boxes (7) at the bottom of the transition preheating section (TPH).

12. The system of claim 4, wherein: the system also comprises an SNCR denitration device (8); the SNCR denitration device (8) is arranged in a preheating section (PH) and/or a first pipeline (L1); and/or

13. The system of claim 9, wherein: the system also comprises an SNCR denitration device (8); the SNCR denitration device (8) is arranged in a preheating section (PH) and/or a first pipeline (L1); and/or

14. The system of claim 11, wherein: the SNCR denitration device (8) comprises a first spraying device (801) and a high-pressure atomization mixing device (803); the first spraying device (801) is arranged in the preheating section (PH) and is connected with the high-pressure atomization mixing device (803) through a tenth pipeline (L10).

15. The system according to claim 12 or 13, characterized in that: the SNCR denitration device (8) comprises a first spraying device (801) and a high-pressure atomization mixing device (803); the first spraying device (801) is arranged in the preheating section (PH) and is connected with the high-pressure atomization mixing device (803) through a tenth pipeline (L10).

16. The system of claim 14, wherein: the SNCR denitration device (8) also comprises a second spraying device (802); the second spraying device (802) is arranged in the first pipeline (L1) and is connected with the high-pressure atomization mixing device (803) through an eleventh pipeline (L11).

17. The system of claim 15, wherein: the SNCR denitration device (8) also comprises a second spraying device (802); the second spraying device (802) is arranged in the first pipeline (L1) and is connected with the high-pressure atomization mixing device (803) through an eleventh pipeline (L11).

18. The system according to claim 16 or 17, wherein: the eleventh pipe (L11) is a bypass pipe branched from the tenth pipe (L10).

19. The system according to any one of claims 14, 16, 17, wherein: the high-pressure atomization mixing device (803) is provided with a vanadium-titanium catalyst conveying pipe (S1), an ammonia water conveying pipe (S2), a urea conveying pipe (S3), a soluble sodium salt conveying pipe (S4), an ethanol conveying pipe (S5) and a nano zero-valent iron or SBA-15 conveying pipe (S6).

20. The system of claim 15, wherein: the high-pressure atomization mixing device (803) is provided with a vanadium-titanium catalyst conveying pipe (S1), an ammonia water conveying pipe (S2), a urea conveying pipe (S3), a soluble sodium salt conveying pipe (S4), an ethanol conveying pipe (S5) and a nano zero-valent iron or SBA-15 conveying pipe (S6).

21. The system of claim 18, wherein: the high-pressure atomization mixing device (803) is provided with a vanadium-titanium catalyst conveying pipe (S1), an ammonia water conveying pipe (S2), a urea conveying pipe (S3), a soluble sodium salt conveying pipe (S4), an ethanol conveying pipe (S5) and a nano zero-valent iron or SBA-15 conveying pipe (S6).

22. The system of claim 19, wherein: the system also comprises a blending device (9); the blending device (9) is provided with a vanadium-titanium catalyst conveying pipe (S1), an ammonia water conveying pipe (S2), a urea conveying pipe (S3), a soluble sodium salt conveying pipe (S4) and a nano zero-valent iron or SBA-15 conveying pipe (S6); the blending device (9) is communicated with the high-pressure atomization mixing device (803) through a twelfth pipeline (L12).

23. The system according to claim 20 or 21, wherein: the system also comprises a blending device (9); the blending device (9) is provided with a vanadium-titanium catalyst conveying pipe (S1), an ammonia water conveying pipe (S2), a urea conveying pipe (S3), a soluble sodium salt conveying pipe (S4) and a nano zero-valent iron or SBA-15 conveying pipe (S6); the blending device (9) is communicated with the high-pressure atomization mixing device (803) through a twelfth pipeline (L12).

24. The system of any one of claims 10, 12-14, 16-17, 20-22, wherein: the system also comprises a dust removal device (4), wherein the dust removal device (4) is arranged on the second pipeline (L2) and is positioned at the upstream of the SCR denitration device (5).

25. The system of claim 11, wherein: the system also comprises a dust removal device (4), wherein the dust removal device (4) is arranged on the second pipeline (L2) and is positioned at the upstream of the SCR denitration device (5).

26. The system of claim 19, wherein: the system also comprises a dust removal device (4), wherein the dust removal device (4) is arranged on the second pipeline (L2) and is positioned at the upstream of the SCR denitration device (5).

27. The system of claim 24, wherein: a dust removal device (4) is also arranged on the fourth pipeline (L4); and/or

A dust removal device (4) is optionally arranged on each of the third pipeline (L3) and the ninth pipeline (L9).

28. The system according to claim 25 or 26, wherein: a dust removal device (4) is also arranged on the fourth pipeline (L4); and/or

29. The system of claim 24, wherein: the system also comprises a desulphurization device (6); the desulfurization device (6) is disposed on the fourth conduit (L4).

30. The system according to any one of claims 25-27, wherein: the system also comprises a desulphurization device (6); the desulfurization device (6) is disposed on the fourth conduit (L4).

31. The system of claim 29, wherein: the fourth pipeline (L4) is also provided with a dust removal device (4), and the dust removal device (4) is positioned at the upstream of the desulfurization device (6).

32. The system of claim 30, wherein: the fourth pipeline (L4) is also provided with a dust removal device (4), and the dust removal device (4) is positioned at the upstream of the desulfurization device (6).