CN112725616B - Method for reducing emission of sintering flue gas pollutants by utilizing SCR (selective catalytic reduction) containing waste catalyst pellets - Google Patents

Abstract

The invention discloses a method for reducing emission of sintering flue gas pollutants by utilizing SCR (selective catalytic reduction) containing waste catalyst pellets,belongs to the technical field of pollutant emission reduction in the sintering process. In the preparation process of the sintering raw material, adding sintering pellets, wherein the sintering pellets are sequentially provided with an inner layer pellet, an outer layer pellet and a catalyst layer from inside to outside; the inner pellet comprises an ammonia inhibitor, and the ammonia inhibitor is decomposed by heating to release ammonia; the outer pellet comprises a pore-forming agent, and the pore-forming agent enables pores in the outer pellet to be formed in the sintering process; the catalyst layer comprises an SCR catalyst and vanadium-titanium blast furnace slag. The pore-forming agent in the sintered pellets is heated to decompose to form pores, thereby retarding the decomposition of ammonia inhibitors such as urea and NH ₃ Release of (2) to make it react with NO _X The emission window period of (2) is consistent, and NO is reduced _X Is discharged and breakthrough SO is realized under the action of the catalyst ₂ 、NO _X And the dioxin is cooperated to reduce emission.

Description

A method for reducing emissions of sintering flue gas pollutants by using spent catalyst pellets containing SCR

technical field

The invention relates to the technical field of pollutant emission reduction in the sintering process, and more specifically relates to a method for reducing emission of sintering flue gas pollutants by using SCR waste catalyst pellets.

Background technique

The sintering/pelletizing process is an important pollution link in the iron and steel industry. Existing flue gas pollutant emission reduction technologies generally adopt terminal treatment. Although the emission reduction effect is good, it requires a large investment, may cause secondary pollution, and is difficult Realize multi-pollutant coordinated emission reduction.

Long Hongming of Anhui University of Technology and others innovatively proposed adding urea in a specific material layer height interval in the sintering mixture, rationally utilizing the thermodynamic and kinetic conditions of the sintering process itself, and establishing the relationship between SO ₂ , NO _X and dioxins. Emission barrier, the reaction product neither enters the sinter ore nor enters the flue gas, but is concentrated and discharged with the dust at a specific position of the sintering machine. The urea method has good effects in removing SO ₂ and dioxins, and has a wide range of sources of ammonia additives, and the reaction products have no secondary pollution problems. It is one of the effective ways for iron and steel enterprises to reduce emissions in the future. However, the _NOx removal effect of this technology is not ideal, resulting in the _NOx emission in the sintering flue gas not meeting the existing national emission standards. A few enterprises use the SCR process or activated carbon method to treat _NOx . This process has a very significant control effect on flue gas _NOx , but the input cost and operating cost are huge, which increases the burden of emission reduction for enterprises. The SNCR process belongs to the non-catalyst injection process in the furnace, which is used in coal-fired boilers. The SNCR process does not need to add catalysts, and the reducing agents such as NH ₃ , ammonia water and urea are directly sprayed into the high temperature area of the furnace to react with NO _X. The denitrification rate of this method can generally reach 30-50%. The denitrification process of the SNCR process needs to control the temperature within the range of 850-1100°C, but the temperature of the sintering flue gas in actual production is generally below 200°C, which does not meet the reaction temperature requirements for ammonia injection denitrification. To sum up, it is urgent to find a suitable solution from the perspective of technology and economy to realize the synergistic emission reduction of SO ₂ , NO _X and dioxin in the sintering process, and achieve the goal of ultra-low emission and low-cost treatment.

After patent retrieval, some relevant technical solutions have been disclosed. For example: a method and system for synergistic emission reduction of SO ₂ and dioxins in the sintering process (CN104962732B), and a method for synergistic emission reduction of SO ₂ and dioxins in the sintering process based on the addition of solid inhibitors (CN105861816B). Related technical solutions for on-line SO ₂ emission reduction in the sintering process are disclosed: desulfurization method for iron ore sintering process based on adding inhibitors (CN201110022407.0), an online desulfurization method for sintering process (CN103834800B); Related technical solutions for oxin emission reduction are disclosed: method for reducing dioxin emission during iron ore sintering (CN102847419A), method and device for adding inhibitors to reduce dioxin generation during sintering (CN105316480B). The above-mentioned disclosed technical scheme proposes three adding schemes of ammonia inhibitors, (1) mixing all the ammonia inhibitors into the sintered material layer, (2) adding the ammonia inhibitors to a certain part of the sintered material layer (3) Spray the ammonia inhibitor on the sintering mixture layer. Although the above-mentioned technical solutions can realize the on-line reduction of SO ₂ and dioxin pollutants in the sintering process, they have no good suppression effect on NO _x emissions, and it is difficult to realize the synergistic reduction of SO ₂ , NO _x and dioxins.

Contents of the invention

1. The problem to be solved

The present invention aims at the problem that the ammonia inhibitors in the prior art are mainly added to the sintered material through direct paving or direct mixing and granulation, and the problem of rapid decomposition due to the solid heat transfer between the ammonia inhibitors and the sintered material , will cause the NH ₃ produced by the decomposition of ammonia inhibitors to be inconsistent with the emission window period of SO ₂ , NO _X and dioxins produced by sintering, and the emission reduction efficiency will decrease; it provides a method to reduce sintering flue gas emission by using SCR waste catalyst pellets Pollutant method, by designing a porous structure pellet that can form an ammonia inhibitor at a specific temperature, so that the ammonia inhibitor slowly heats up, and the generated NH ₃ and SO ₂ , NO _X and dioxin emissions The window period is consistent to improve the efficiency of emission reduction.

2. Technical solution

In order to solve the above problems, the technical scheme adopted in the present invention is as follows:

A method for reducing emission of sintering flue gas pollutants by using SCR-containing waste catalyst pellets. During the preparation of sintered raw materials, sintered pellets are added, and the sintered pellets are sequentially arranged with inner layer pellets and outer layer pellets from the inside to the outside. and a catalyst layer; the inner layer of pellets includes ammonia inhibitors, which can release ammonia when heated and decomposed; the outer layer of pellets includes a pore-forming agent, and the pore-forming agent makes the outer layer during sintering Pores are formed in the pellets; the catalyst layer includes SCR catalyst and vanadium-titanium blast furnace slag.

Preferably, the specific steps are:

Step 1: Pour the prepared sintering raw materials and water into the cylinder mixer in turn for primary mixing, and then perform secondary mixing without adding water; after the granulation is completed, evenly add the prepared sintering pellets to the Among the raw materials, mix them to form a composite sintering raw material;

Step 2: Lay the bottom material layer on the lower part of the sintering cup device; then spread the mixed and granulated composite sintering raw materials and fill the sintering cup body; finally ignite and sinter;

Step 3: After ignition, carry out draft sintering, and conduct online measurement of NO _x , SO ₂ , NH ₃ and dioxin in the flue gas.

Preferably, the raw materials for sintering include domestic ore concentrate, king ore, Russian fine powder, Roy Hill ore, iron oxide scale, Pakistan mixed ore, blast furnace return ore, dust removal ash, internal return ore, and dolomite and quicklime as flux and coke powder as fuel.

Preferably, the SCR catalyst includes V2O5 and TiO2; the vanadium-titanium blast furnace slag includes CaO, SiO2, V elements, and Ti elements.

Preferably, the pelletizing material in the outer layer has a particle size of -0.149mm particle size ≥ 95% by mass; the pelletizing material in the inner layer has a particle size of -0.074mm particle size ≥ 95% by mass. The average particle size of the pelletizing material in the outer layer is larger than that of the pelletizing material in the inner layer, resulting in a larger gap between the mineral powder particles in the outer layer, which is conducive to the release of ammonium bicarbonate when heated.

Preferably, the particle diameter of the inner pellets is 3-5mm;

And/or the thickness of the outer pellets is 9-11mm;

And/or the particle size of the ammonia inhibitor and pore forming agent reaches -0.074mm particle size and the mass percentage content is ≥ 95%.

Preferably, the ammonia inhibitor is urea, wherein the N element content accounts for 0.02-0.15% of the mass of the inner pellet; the pore-forming agent is ammonium bicarbonate, and the molar ratio of urea and ammonium bicarbonate is ( 4:1)-(1:4).

Preferably, the moisture content of the sintered pellets is 8.0-8.5%, and the particle size is 14-18mm.

Preferably, the specific steps are:

Step 1: Pour the prepared sintering raw materials into the cylinder mixer one by one for mixing, add an appropriate amount of water into the air press, and then spray it into the mixer through the atomizer to mix with the sintering raw materials. The "first mixing" time is controlled at 6 minutes, and the second mixing is performed after the first mixing is completed. No water is added for the second mixing. The "second mixing" time is controlled at 3 minutes, and the moisture content of the mixture is controlled at 7.0%. The sintered pellets are evenly added to the sintered raw material, and then mixed for 30 seconds to form a composite sintered raw material;

Step two:

A) pave the bottom layer of 2kg at the bottom of the sintering cup device;

B) Directly spread the mixed and granulated compound sintering raw materials, fill the sintering cup body, and then lightly compact it with a special round cake, and put a little sintering raw material with finer particle size in the depression;

C) ignition and sintering. Start the exhaust fan below the sintering cup, rotate the ignition (device) cover to the top of the sintering cup body, control the negative pressure at 7kPa by adjusting the intake valve and the release valve, and carry out ignition, control the amount of air and gas opening, so that The ignition temperature is kept at about 1150°C, and the sintering begins to count. After 2 minutes of ignition, remove and close the ignition (device) cover, adjust the negative pressure to 14kPa, start the computer in the central control room to automatically collect the sintering temperature and exhaust negative pressure. When the temperature of the sintering flue gas reaches the highest value and begins to drop, it is the end point of sintering, and the timing time t is a complete sintering time. After sintering, adjust the suction negative pressure to 7kPa, and pour out the sintered ore when the exhaust gas temperature is cooled to 300°C;

Step 3: After ignition, carry out ventilation and sintering. During the ventilation and sintering process of the sintering machine, use an oil-free vacuum pump to take out the sintering flue gas from the sampling port. The gas pipeline takes gas in parallel, and sends the gas to the MCA 10m infrared flue gas analysis. In the instrument, online measurement of NO _X , SO ₂ , NH ₃ and dioxin in the flue gas.

Preferably, the size of the cylinder mixer is: Φ600×1200mm, power 8.5kw, charging capacity 120k;

And/or the specification of the operating platform of the sintering cup is: 4.0m×3.0m, the inner diameter of the sintering cup is Φ200, the effective height is 800mm, the cup body is cast from Cr-containing cast iron, and the charging capacity is 50kg.

3. Beneficial effect

Compared with the prior art, the beneficial effects of the present invention are:

(1) A method of the present invention for reducing emissions of sintering flue gas pollutants by using SCR-containing waste catalyst pellets. During the preparation of sintered raw materials, sintered pellets are added, and the sintered pellets are sequentially arranged with inner layer balls from the inside to the outside. group, outer layer pellets and catalyst layer; the inner layer of pellets includes ammonia inhibitors, which can release ammonia gas when heated and decomposed; the outer layer of pellets includes a pore-forming agent, and the pore-forming The agent makes holes in the outer layer pellets during sintering; the catalyst layer includes SCR catalyst and vanadium-titanium blast furnace slag. The pore-forming agent in the sintered pellets used in this emission reduction method produces pores after thermal decomposition, and the porous structure effectively delays the decomposition of ammonia inhibitors such as urea and the release of NH ₃ , making it It is consistent with the NO _X emission window period, reducing NO _X emissions; the activity of some V and Ti substances in the catalyst can promote the selective reduction of NO _X by urea, further improving the denitrification efficiency, and at the same time, the barrier effect of the catalyst layer can also delay The purpose of NH ₃ release is to make it consistent with the emission window period of SO ₂ , NO _X and dioxins in the flue gas, so as to achieve a breakthrough in synergistic emission reduction of SO ₂ , NO _X and dioxins, and ensure the sintering The normal production of the operation overcomes the technical drawback of the single pollutant terminal treatment in the existing technology, greatly reduces the cost of pollutant emission reduction in the sintering process, and reduces the emission reduction burden of iron and steel enterprises.

(2) According to a method of the present invention for reducing emission of sintering flue gas pollutants by using SCR waste catalyst pellets, the particle size of the ammonia inhibitor and the pore forming agent reaches -0.074mm particle size mass percentage content ≥ 95%. On the one hand, this is conducive to the full mixing of raw materials, so that the bonding effect can be fully exerted when dispersed in the pellets, and at the same time, it can reduce the adverse effect on the strength of the pellets after the pyrolysis of the decomposable substances in the binder bentonite To the minimum, to achieve the purpose of improving emission reduction efficiency.

(3) A method of the present invention that utilizes SCR-containing waste catalyst pellets to reduce emission of sintering flue gas pollutants uses urea and ammonium bicarbonate, two common and low-priced materials, as the main raw materials for pelletizing, and the source of raw materials for its preparation Wide range, low price, high flue gas emission reduction efficiency, reasonable technology, significant economic benefits, and broad application prospects.

Description of drawings

Fig. 1 is a schematic flow sheet of a method for reducing emission of sintering flue gas pollutants by using SCR waste catalyst pellets according to the present invention;

Fig. 2 is the schematic diagram of the sintered pellet that contains inner layer pellet and outer layer pellet used in the present invention;

Fig. 3 is a schematic diagram of the sintered pellets used in the present invention including inner pellets, outer pellets and catalyst layer.

Explanation of the labels in the schematic diagram:

100, inner layer pellets; 200, outer layer pellets; 300, catalyst layer.

Detailed ways

The present invention will be further described below in conjunction with specific embodiments.

Example 1

As shown in Figure 1, a method for reducing emission of sintering flue gas pollutants by using SCR waste catalyst pellets in this embodiment, during the preparation of sintered raw materials, sintered pellets are added, and the sintered pellets are sequentially arranged from inside to outside An inner pellet 100, an outer pellet 200, and a catalyst layer 300 are set; the inner pellet 100 includes an ammonia inhibitor, and the ammonia inhibitor is decomposed by heat to release ammonia; in the outer pellet 200 Including a pore-forming agent, the pore-forming agent makes the outer layer pellets 200 to form holes during the sintering process; the catalyst layer 300 includes SCR catalyst and vanadium-titanium blast furnace slag, in this embodiment, the thickness of the catalyst layer 300 is 2mm, The SCR catalyst and vanadium-titanium blast furnace slag in the catalyst layer 300 have a mass ratio of 1:1; the SCR catalyst includes V2O5 and TiO2; the vanadium-titanium blast furnace slag includes CaO, SiO2, V elements, and Ti elements; The pellets include domestic concentrates, whose particle size reaches -0.149mm particle size mass percentage content ≥ 95%; the outer pelletizing material includes domestic concentrates, whose particle size reaches -0.074mm particle size mass percentage content ≥ 95%; The particle size of the inner layer pellets 100 is 3-5mm; the moisture content of the sintered pellets is 8.0-8.5%, and the particle size is 12-16mm;

In this embodiment, the ammonia inhibitor is urea, and the decomposition temperature of the pore-forming agent is lower than 160°C. Here, the ammonium bicarbonate whose decomposition temperature is 60-70°C is selected, and the urea and ammonium bicarbonate are The molar ratio is 3:2; in addition, the N element content in the urea accounts for 0.047% of the mass of the inner pellet 100, and the mass ratio converted into urea is 0.1%; in this embodiment, the inner pelletizing material and The outer layer of pelletizing material is prepared by mixing domestic concentrate and bentonite as a binder. The specific content ratio is as follows:

Table 1. List of ingredients for pelletizing

type Guojing Bentonite Amount added (g) 2940 60

In order to verify the advantages and disadvantages of the emission reduction method in the sintering process of this embodiment, the performance of the sintered pellets is analyzed by detecting the content changes of SO ₂ , NO _X and dioxin in the sintering flue gas. The specific implementation steps are as follows:

Step 1: Preparation of sintered pellets.

(A) Prepare raw materials: weigh the inner layer pelletizing material and the outer layer pelletizing material according to the weight percentage, add suitable water, control the water to 8.0%, and put it into the moistening mill together with 5kg steel balls after mixing evenly , set for 40min to carry out pre-treatment of moist grinding, after the completion of moist grinding, carry out particle size sieving; take appropriate amount of ammonia inhibitor and pore forming agent, grind to fine particle size; take appropriate amount of ammonia inhibitor and water, stir to make it Sufficiently dissolve to obtain ammonia inhibitor solution;

It should be noted that the particle size of the ammonia inhibitor and pore-forming agent in this embodiment reaches -0.074mm particle size mass percentage content ≥ 95%; When it is in the pellets, it can give full play to the bonding effect, and at the same time, it can minimize the adverse effect on the strength of the pellets after the pyrolysis of the decomposable substances in the binder bentonite, so as to achieve the purpose of improving the emission reduction efficiency;

(B) Preparing the inner layer pellets 100: adding the inner layer pelletizing material into the disc pelletizer, and adding an ammonia inhibitor solution for mixing and pelletizing to obtain the inner layer pellets 100;

It should be noted that the method of adding the ammonia inhibitor solution in this step is to first place it in a special storage device for the ammonia inhibitor solution, and spray it in through the pipeline during the process of preparing the inner core, and the ammonia The inhibitor-like solution storage device includes a storage box, an aluminum pipe with a diameter of 15mm, and a 4-hole nozzle; spraying urea into the disc pelletizer in the form of a solution can effectively increase the amount of urea and the inner pelletizing material. The contact area between them improves the bonding strength of the inner layer pellets 100 itself, avoids damage during the subsequent granulation or sintering process, and achieves the purpose of improving the utilization rate of urea;

(C) Adhesive outer layer pellets 200: continue to add common pelletizing material and pore-forming agent to the disc pelletizer, add water to make it grow into pellets;

(D) Preparation of the catalyst layer 300: continue to add vanadium-titanium blast furnace slag and SCR catalyst to the disc pelletizer to make it grow, and finally obtain the sintered pellets.

Step 2: Pre-granulation.

Pour the prepared sintered material into the cylinder mixer in turn for one-time mixing, add an appropriate amount of water into the air press, and then spray it into the mixer through the atomizer to mix with the sintered material. "The time is controlled at 6 minutes. After the first mixing is completed, the second mixing is performed. No water is added for the second mixing. The "second mixing" time is controlled at 3 minutes, and the moisture content of the mixture is controlled at 7.0%. After the granulation is completed, the sintered pellets made in step 1 are evenly added to the sintered material, and then mixed for 30 seconds to form a composite sintered raw material.

The sintering materials used in this example include domestic ore concentrate, king ore, Russian fine powder, Roy Hill ore, iron oxide scale, Pakistan mixed ore, blast furnace return ore, dust removal ash and internal return ore, and the fluxes used include dolomite and Quicklime, solid fuel is coke powder, the chemical composition of each raw material is shown in Table 2, and the proportioning ratio of each component of the composite sintering raw material is shown in Table 3. It should be noted that all components of various raw materials are not listed in the table , the part whose composition does not add up to 100% is other impurities;

Table 2. Chemical composition of sintered material (%, ω)

Table 3, sintering raw material ratio/%

Step 3: Sinter the cloth

(A) pave the bottom of the sintering cup device with a 2kg bottom layer;

(B) Directly spread the mixed and granulated composite sintering raw materials, fill up the sintering cup, and then lightly compact it with a special round cake, and place a little mixed material with finer particle size in the depression;

(C) ignition and sintering. Start the exhaust fan below the sintering cup, rotate the ignition (device) cover to the top of the sintering cup body, control the negative pressure at 7kPa by adjusting the intake valve and the release valve, and carry out ignition, control the amount of air and gas opening, so that The ignition temperature is kept at about 1150°C, and the sintering begins to count. After 2 minutes of ignition, remove and close the ignition (device) cover, adjust the negative pressure to 14kPa, start the computer in the central control room to automatically collect the sintering temperature and exhaust negative pressure. When the temperature of the sintering flue gas reaches the highest value and begins to drop, it is the end point of sintering, and the timing time t is a complete sintering time. After sintering, adjust the negative pressure of the draft to 7kPa, and pour out the sintered ore when the exhaust gas temperature is cooled to 300°C.

Step 4: Smoke detection

After ignition, the exhaust sintering is carried out. During the exhaust sintering process of the sintering machine, the sintering flue gas is taken out from the sampling port by an oil-free vacuum pump, and the gas pipeline is connected in parallel to take gas, and the gas is sent to the MCA 10m infrared flue gas analyzer. On-line measurement of NO _X , SO ₂ , NH ₃ and dioxin in flue gas and calculation of emission reduction efficiency, the detection results are shown in Table 4.

Example 2

The sintered pellets and the sintering emission reduction method of this embodiment are basically the same as in Embodiment 1, the difference is that in this embodiment, the thickness of the catalyst layer 300 in Embodiment 1 is maintained at 1 mm, and SO ₂ , NO _X and dioxin are detected The concentration of dioxins is recorded in Table 4, and the desulfurization and denitrification rate and the emission reduction efficiency of dioxins are calculated.

Example 3

The sintered pellets and the sintering emission reduction method of this embodiment are basically the same as in Embodiment 1, the difference is that in this embodiment, the thickness of the catalyst layer 300 in Embodiment 1 is maintained at 3 mm, and SO ₂ , NO _X and dioxin are detected The concentration of dioxins is recorded in Table 4, and the desulfurization and denitrification rate and the emission reduction efficiency of dioxins are calculated.

Example 4

The sintered pellets and the sintering emission reduction method of this embodiment are basically the same as in Embodiment 1, the difference is that in this embodiment, the thickness of the catalyst layer 300 in Embodiment 1 is maintained at 4 mm, and SO ₂ , NO _X and dioxin are detected The concentration of dioxins is recorded in Table 4, and the desulfurization and denitrification rate and the emission reduction efficiency of dioxins are calculated.

By comparing the emission reduction efficiencies of sintered pellets of catalyst layer 300 with different thicknesses, it can be found that the emission reduction efficiencies of SO ₂ and dioxins are basically unchanged between 1-3 mm, and when the thickness increases to 4 mm, SO ₂ , NO The emission reduction efficiency _{of X} and dioxins decreased significantly, which may be due to the excessive coating of the catalyst affecting the release of ammonia in urea. When the thickness of the catalyst layer 300 is 2 mm, the _NOx efficiency is the highest, and this thickness is the best from the viewpoint of high efficiency and economy.

Comparative example 1

This comparative example is used as a benchmark experiment. The sintering process of this comparative example is the same as that of Example 1. The difference is that no urea is added in this comparative example, and the mixed sintering material is directly added to the sintering device for sintering cup test. After the sintering started, measure the concentration of SO ₂ , NO _X and dioxin in the flue gas during the sintering process and calculate the emission reduction efficiency.

Comparative example 2

The sintering process of this comparative example is roughly the same as that of Example 1, the difference is that this comparative example adopts the method of adding urea in the traditional urea method: pave the mixture mixed with urea into a specific area in the sintered material layer , where a specific area refers to the distribution of the mixture in the sintered material at 70-200mm on the sintering trolley, and the rest of the mixture is used for the sintered cup test without adding urea. After the sintering starts, measure the concentration of SO ₂ , NO _X and dioxin in the flue gas during the sintering process and calculate the emission reduction efficiency. The records are shown in Table 4.

Through the experimental results of Comparative Example 1, Comparative Example 2 and Example 1, it can be found that in Example 1, urea/ammonium bicarbonate is layered into pellets, and then mixed with sintering raw materials and added to the sintering process, compared with that in Comparative Example 1 In the benchmark experiment without urea and in comparative example 2, urea was directly paved on a specific material layer for sintering test, and the emission reduction efficiency of SO ₂ , NO _X and dioxins were all improved;

It can be found that compared with Comparative Example 1, the sintering flue gas release amount of Comparative Example 1 without any addition is very large, and the pollution caused to the environment is also very large; while the sintered balls prepared by mixing urea and ammonium bicarbonate in Example 1 Under the action of sintering pellets, sintering flue gas SO ₂ , NO _X and dioxins have been effectively reduced, thus reflecting the superiority of the technical solution of using urea and ammonium bicarbonate to prepare sintering pellets in the present invention;

Compared with Comparative Example 2, after adding urea in a specific material layer, the NO _X emission in the sintering flue gas is basically unchanged, because the temperature of urea pyrolysis to release ammonia is 160°C, while the NO _X emission temperature is 850- At 1250°C, the ammonia gas cannot effectively contact with _NOx and leaves quickly with the flue gas, making it difficult to achieve efficient reduction of _NOx emissions; while the SO ₂ emission in the flue gas in Example 1 was reduced from 151155mg/ ^m3 to 98458mg/ ^m3 , the emission reduction efficiency reached 83.11%; the NO _X emission was reduced from 160428mg/m ³ to 115468mg/m ³ , and the emission reduction efficiency reached 28.73%; the dioxin emission was reduced from 422pg-TEQ/m ³ to 356pg-TEQ/m ^3. The emission reduction efficiency reached 81.07%. It made a breakthrough to realize the synergistic emission reduction of online SO ₂ , NO _X and dioxin in the sintering process, overcoming this major technical bottleneck.

This is because the outer layer of pellets 200 and the catalyst layer 300 can effectively slow down the release time of _NH3 , making it consistent with the emission window period of _NOx , reducing _NOx emissions, but the release of ammonia is not stable enough, further, due to the outer layer Ammonium bicarbonate particles decompose at 60°C to form porous spheres. The heat insulation effect of the porous spheres effectively reduces the rate at which urea releases NH ₃ , making it concentrated and stable at 600-800°C, while NO _X is emitted at 650°C , to reach agreement with the release temperature range of NH ₃ , thereby reacting with each other; at the same time, the formation of dioxins can be suppressed during the cooling process until the temperature of sintering flue gas is lowered below the synthesis temperature of dioxins, and the reduction of SO ₂ and dioxins can be improved. discharge efficiency.

Comparative example 3

The sintered pellets and the sintered emission reduction method of this comparative example are basically the same as in Example 1, the difference is that: the sintered pellets of this comparative example have no catalyst layer 300, and the concentration of SO ₂ , NO _X and dioxins is detected, The records are shown in Table 4, and the desulfurization and denitrification rate and dioxin emission reduction efficiency are calculated.

By comparing Example 1 and Comparative Example 3, it can be found that SO in the flue gas of Comparative Example 3 The emission reduction efficiency increases from 75.66% to 83.11%, the NO _X emission reduction efficiency increases from 17.45% to 28.73%, and the emission of dioxin The amount of emission reduction efficiency increased from 79.73% to 81.07%. This is because the catalyst layer 300 is wrapped outside the outer pellet 200, and the activity of some V and Ti substances in the catalyst is used to promote the selective reduction of NO _x by urea, further improving the denitrification efficiency; and the barrier effect of the catalyst layer 300 is the same It can achieve the purpose of delaying the release of NH ₃ , making it consistent with the emission window period of SO ₂ , NO _X and dioxins in the flue gas, thereby effectively improving the emission reduction efficiency; therefore, without the catalyst layer 300, The emission reduction efficiency of the sintered pellets of this comparative example will be greatly reduced.

Comparative example 4

The sintered pellets and sintering emission reduction method of this comparative example are basically the same as those of Example 1, the difference is that: the catalyst layer 300 of this comparative example does not add vanadium-titanium blast furnace slag, and detects the formation of SO ₂ , NO _X and dioxins The concentration is recorded in Table 4, and the desulfurization and denitrification rate and the emission reduction efficiency of dioxins are calculated.

By comparing Example 1 and Comparative Example 4, it can be found that in the flue gas of Comparative Example 4, the emission reduction efficiency of SO2, NO _X and dioxins are all reduced, which is due to the lack of vanadium and titanium in the catalyst layer 300 of this Comparative Example. The synergistic effect of slag and SCR catalyst, but compared with Comparative Example 3, the flue gas emission reduction efficiency in Comparative Example 4 is significantly improved, which shows that the presence of the catalyst can effectively improve the flue gas emission reduction efficiency.

Table 4. Concentration and emission reduction efficiency of SO ₂ , NO _X and dioxin in flue gas of sintering test

The present invention has been described in detail above with reference to specific exemplary embodiments. However, it should be understood that various modifications and changes can be made without departing from the scope of the present invention as defined in the appended claims. The detailed description and drawings are to be regarded as illustrative only and not restrictive, and any such modifications and variations, if any, are intended to fall within the scope of the invention as described herein. In addition, the background art is intended to illustrate the research and development status and significance of the present technology, and is not intended to limit the present invention or the application and the application field of the present invention.

More specifically, although exemplary embodiments of the present invention have been described herein, the present invention is not limited to these embodiments but includes modifications, omissions, Any and all embodiments of combinations, adaptations, and/or substitutions (eg, among the various embodiments), and combinations among the various embodiments of the present invention as required. The definitions in the claims are to be interpreted broadly according to the language used in the claims and not limited to the examples described in the foregoing detailed description or during the prosecution of this application, which examples should be considered non-exclusive. Any steps recited in any method or process claims may be performed in any order and are not limited to the order presented in the claims. Accordingly, the scope of the present invention should be determined only by the appended claims and their legal equivalents, rather than by the description and examples given above.

Claims (7)

1. A method for reducing emissions of sintering flue gas pollutants by using SCR waste catalyst pellets, characterized in that, in the preparation process of sintered raw materials, sintered pellets are added, and the sintered pellets are arranged with inner layer balls from inside to outside A group (100), an outer layer of pellets (200) and a catalyst layer (300); the inner layer of pellets (100) includes an ammonia inhibitor, and the ammonia inhibitor can be decomposed by heat to release ammonia gas; the outer layer The pellet (200) includes a pore-forming agent, which makes the outer layer of the pellet (200) form pores during sintering; the catalyst layer (300) includes SCR catalyst and vanadium-titanium blast furnace slag, and the SCR catalyst Including V ₂ O ₅ and TiO ₂ ; the particle size of the outer pelletizing material reaches -0.149mm particle size mass percentage content ≥ 95%; the inner layer pelletizing material particle size reaches -0.074mm particle size mass percentage content ≥ 95% ; The particle size of the inner layer pellets (100) is 3-5 mm; The thickness of the outer pellets (200) is 9-11 mm; The particle size of the ammonia inhibitor and pore-forming agent reaches -0.074mm particle size mass percentage content ≥ 95%; The ammonia inhibitor is urea, wherein the N element content accounts for 0.02-0.15% of the mass of the inner pellet; the pore-forming agent is ammonium bicarbonate, and the molar ratio of urea to ammonium bicarbonate is (4:1 )-(1:4). 2. A method of utilizing waste catalyst pellets containing SCR to reduce emissions of sintering flue gas pollutants according to claim 1, wherein the specific steps are: Step 1: Pour the prepared sintering raw materials and water into the cylinder mixer in turn for primary mixing, and then perform secondary mixing without adding water; after the granulation is completed, evenly add the prepared sintering pellets to the Among the raw materials, mix them to form a composite sintering raw material; Step 2: Lay the bottom material layer on the lower part of the sintering cup device; then spread the mixed and granulated composite sintering raw materials and fill the sintering cup body; finally ignite and sinter; Step 3: After ignition, carry out draft sintering, and conduct online measurement of NO _x , SO ₂ , NH ₃ and dioxin in the flue gas. 3. A method for reducing emission of sintering flue gas pollutants by using SCR-containing waste catalyst pellets according to claim 2, characterized in that, the sintering raw materials include domestic concentrates, king ore, Russian fine powder, Roy Mountain ore, scale, mixed ore, blast furnace return ore, dust removal ash, internal return ore, as well as dolomite, quicklime as flux and coke powder as fuel. 4. A method for reducing emissions of sintering flue gas pollutants by using SCR-containing waste catalyst pellets according to claim 1, wherein the vanadium-titanium blast furnace slag includes CaO, SiO ₂ and V elements, Ti elements. 5. A method for reducing emissions of sintering flue gas pollutants by using SCR waste catalyst pellets according to claim 1, wherein the sintered pellets have a water content of 8.0-8.5% and a particle size of 14 -18mm. 6. A method for reducing emission of sintering flue gas pollutants by using SCR waste catalyst pellets according to any one of claims 1 to 5, characterized in that the specific steps are: Step 1: Pour the prepared sintering raw materials into the cylinder mixer one by one for mixing, add an appropriate amount of water into the air press, and then spray it into the mixer through the atomizer to mix with the sintering raw materials. The "first mixing" time is controlled at 6 minutes. After the first mixing is completed, the second mixing is performed. No water is added for the second mixing. The "second mixing" time is controlled at 3 minutes, and the moisture content of the mixture is controlled at 7.0%. The good sintered pellets are evenly added to the sintered raw materials, and then mixed for 30 seconds to form a composite sintered raw material; Step two: A) pave the bottom layer of 2kg at the bottom of the sintering cup device; B) Directly spread the mixed and granulated compound sintering raw materials, fill the sintering cup body, and then lightly compact it with a special round cake, and put a little sintering raw material with finer particle size in the depression; C) Ignition and sintering: Start the exhaust fan under the sintering cup, rotate the ignition cover to the top of the sintering cup, control the negative pressure at 7 kPa by adjusting the air intake valve and the release valve, and start the ignition, control the amount of air and gas opening ℃, keep the ignition temperature at 1150 °C, start timing for sintering, remove and close the ignition hood after 2 minutes of ignition, adjust the negative pressure to 14 kPa, start the computer in the central control room to automatically collect the sintering temperature and exhaust negative pressure, when the sintering flue gas After the temperature reaches the highest value, it begins to drop, which is the end point of sintering. The timing time t is a complete sintering time. After sintering, adjust the negative pressure of the exhaust to 7 kPa, and pour out the sintered ore when the temperature of the exhaust gas cools to 300 °C; Step 3: After ignition, carry out ventilation and sintering. During the ventilation and sintering process of the sintering machine, use an oil-free vacuum pump to take out the sintering flue gas from the sampling port. The gas pipeline takes gas in parallel, and sends the gas to the MCA 10m infrared flue gas analysis. In the instrument, online measurement of NO _X , SO ₂ , NH ₃ and dioxin in the flue gas. 7. A method for reducing emission of sintering flue gas pollutants by using SCR waste catalyst pellets according to claim 6, characterized in that the size of the cylinder mixer is: Φ600×1200mm, power 8.5kw , charging capacity 120kg; And/or the specification of the operating platform of the sintering cup is: 4.0m×3.0m, the inner diameter of the sintering cup is Φ200, the effective height is 800mm, the cup body is cast from Cr-containing cast iron, and the charging capacity is 50kg.

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