CN109141028B - Chain grate machine-rotary kiln pellet low NOx production device and pellet production method - Google Patents

Abstract

Grate-rotary kiln pellet low NO_xThe mode production device comprises a chain grate (3), a rotary Kiln (Kiln) connected with the chain grate (3) and a ring cooling machine (C) connected with the rotary Kiln (Kiln), wherein a reducing agent injection device (1) is arranged on a transition section (2) between a second preheating section (PH) of the chain grate (3) and the tail end of the rotary Kiln (Kiln), reducing gas is injected in a reverse direction of the flue gas to fully mix and react with high-temperature flue gas after roasting of iron ore pellet materials, and therefore NO is achieved_xTo reduce NO in flue gas_xWhile the flue gas from the second preheating stage (PH) is partially recycled back to the first cooling stage (C1) of the ring cooler (Kiln) via the after-draft drying stage (DDD) to reduce the escape of reducing agent and further reduce NO_xThe amount of discharge of (c). The low NO of the grate-rotary kiln pellets is realized by the synergistic effect of the two technical means_xThe production is carried out in a mode.

Description

Chain grate machine-rotary kiln pellet low NOx production device and pellet production method

technical field

The invention relates to the technical field of engineering chain grate-rotary kiln pellets, in particular to a chain grate-rotary kiln pellet low _NOx (nitrogen oxide) production device and a production method for iron ore pellets.

Background technique

Pellets are the main iron-containing charge produced in blast furnace ironmaking in my country. In 2015, the output of pellets in my country was 128 million tons. Compared with sintered ore, because the pellet production process has low energy consumption, relatively friendly environment, and the product has the advantages of good strength, high grade and good metallurgical performance, the application in blast furnace smelting can increase production and save coke, and improve the technical economy of ironmaking. Therefore, the pellets have been well developed in my country.

The production of pellets in my country is mainly based on the chain grate-rotary kiln process, and its output accounts for more than 60% of the total output of pellets. The chain grate-rotary kiln process produces a certain amount of NO _x during the production of oxidized pellets. In recent years, with the increasing complexity of iron ore raw materials and fuels, the increase in the proportion of hematite (leading to an increase in roasting temperature), the large-scale utilization of low-quality fuels, and the application of nitrogen-containing coke oven gas in gas-based rotary kilns, etc. The NO _x emission concentration in the pellet production process of few enterprises _{is on} the rise; coupled with the increasingly stringent environmental protection requirements in China, NO _x emission has been included in the emission assessment system. The limit is 300mg/m ³ , which makes these enterprises need to add denitrification facilities to meet the national emission standards.

Although the pelletizing enterprises have done a lot of work in environmental protection, dust removal and desulfurization have been effectively controlled and can meet the emission requirements, but the current _NOx removal cost is high and the process is complicated. The group industry has brought new challenges. Some enterprises have to reduce production in large quantities due to excessive _NOx , or even face shutdown. Judging from the current production situation of most pellets, the emission of NO _x generally exceeds the standard by 30-100 mg/m ³ . If the source and process can be used to reduce the generation of NO _x , the emission requirements can be met, and the terminal denitration purification equipment can be omitted. , is of great significance to the production of chain grate-rotary kiln pellets, and is conducive to further improving the vitality and competitiveness of pellet production.

Existing methods for removing nitrogen oxides from flue gas mainly include selective catalytic reduction (SCR) and non-selective catalytic reduction (SNCR). Among them, temperature plays a leading role in SNCR denitration technology. It is generally considered that the temperature range of 800℃～1100℃ is suitable. When the temperature is too high, NH ₃ is oxidized to form NO, which may increase the concentration of NO and reduce the removal rate of NO _x ; when the temperature is too low, NH ₃ The reaction rate decreases, the _NOx removal rate also decreases, and the amount of _NH3 escape increases. Usually, the temperature range of the second preheating section, the transition section between the second preheating section and the rotary kiln is between 950°C and 1100°C, which meets the conditions of the SNCR denitration method.

The existing chain grate-rotary kiln pellet production process is shown in Figure 1. The chain grate is divided into a blast drying section, a suction drying section, a first preheating section and a second preheating section, and the ring cooler is divided into the first section. cooling section, second cooling section and third cooling section. Among them, the air in the first cooling section directly enters the rotary kiln to roast the pellets, and after heating the preheating balls in the second preheating section, they are blown into the exhaust air drying section for exhaust air drying, and then discharged to the outside through the exhaust air drying section. (the flue gas is purified before being discharged); the wind in the second cooling section enters the first preheating section to heat the green balls and then discharges to the outside; the wind in the third cooling section enters the blast drying section to blast and dry the green balls, thereby Realize the reasonable distribution of the air flow system of the chain grate-rotary kiln-ring cooler.

The publication number is CN 106268270 A, the publication date is January 4, 2017, and the patent document titled "a chain grate-rotary kiln denitration system" discloses a chain grate-rotary kiln denitration system. A denitrification device is added to the inner cavity of the second preheating section, and the injection direction of the nozzle is the same as the flow direction of the flue gas. Although this technology can reduce the amount of _NOx emissions to a certain extent, the reduction range _is limited, and the amount of reductant sprayed is difficult to control. Too much will cause NH ₃ to escape and pollute the environment. Require.

In the prior art, due to the lack of systematic research and reliable grate-rotary kiln pellet production process with low NO _x generation and control technology, the non-compliance of NO _x emission in the production process of the pellet plant has become the norm and the biggest problem faced by enterprises. one of the challenges. For this reason, enterprises can only reduce NO by reducing the output of pellets, thereby reducing the amount of gas or pulverized coal injected, reducing the requirements for the strength of pellets, thereby reducing the temperature of the rotary kiln and using raw materials and fuels with lower _NOx . Generation of _x . These methods not only affect the production of pellets in terms of output and quality, but also have high requirements on the quality of raw fuels, resulting in increased costs, and cannot fundamentally solve the problem of low- _NOx production of pellets. In addition, adding a denitrification device after the main exhaust fan, such as the use of selective catalytic reduction (SCR) and non-selective catalytic reduction (SNCR) technology, although it can meet the requirements of low _NOx emissions, but due to its investment cost High requirements, high equipment requirements, high energy consumption, high denitration cost and secondary pollution have not been popularized and applied in pelletizing enterprises. At present, the NO _x control method of pelletizing plants at home and abroad is mainly realized through process control.

In order to meet the requirements of NO _x emission in the production process of grate-rotary kiln pellets, and to respond to the national call for energy conservation and emission reduction, it is necessary to invent a more advanced air flow system from the process itself, and at the same time use the characteristics of the system itself to achieve low NO x _x pellet production.

SUMMARY OF THE INVENTION

In view of the above-mentioned defects and problems in the prior art, the present invention, by optimizing the technological process of the chain grate-rotary kiln system, recycles part of the hot waste gas in the extraction and drying section, and extracts it back to the first cooling section of the ring cooler. Therefore, the exhaust gas temperature in the first cooling section is increased, the gas volume of the central burner is reduced, and the SNCR method for removing _NOx is added in the transition section between the second preheating section and the rotary kiln. The treatment can greatly reduce the _NOx emission in the production process of the grate-rotary kiln pellets, so as to solve the above-mentioned technical problems, and has the characteristics of "energy saving, emission reduction and low _NOx production".

According to the first embodiment provided by the present invention, a chain grate-rotary kiln (iron ore) pellet low _NOx production device is provided:

A chain grate machine-rotary kiln pellet low _NOx production device comprises a chain grate machine, a rotary kiln connected with the end of the chain grate machine, and an annular cooler located at the front end of the rotary kiln. Moreover, according to the process trend, the chain grate machine is sequentially provided with a blast drying section, a suction drying section, a first preheating section and a second preheating section; the ring cooler is sequentially provided with a first cooling section and a second cooling section. And the third cooling section, the tail end of the rotary kiln is connected to the second preheating section of the grate machine and the other end (ie the front end) is connected to the first cooling section of the ring cooler.

The air outlet of the second cooling section is connected to the air inlet of the first preheating section via the first pipeline. The air outlet of the third cooling section is connected to the air inlet of the bottom bellows of the blast drying section via a second duct and a first exhaust fan is provided on the second duct. The air outlet of the bottom bellows of the second preheating section is connected to the air inlet at the top of the extraction and drying section via a third duct, and a second exhaust fan is arranged in the third duct. The fourth duct drawn from the air outlet of the bottom bellows of the first preheating section is connected to the chimney and a third exhaust fan is arranged on the fourth duct. A fifth duct drawn from the air outlet at the top of the blast drying section is connected to the chimney and a fourth exhaust fan is provided on the fifth duct. The air outlet of the first blower is connected to the air inlet of the second cooling section through a sixth duct. The air outlet of the second blower is connected to the air inlet of the third cooling section through a seventh duct. The front end of the rotary kiln (Kiln) is equipped with a blower (rotary kiln blower or third blower) to supply combustion air to the central burner of the rotary kiln.

In the present invention, the production device further comprises a transition section arranged between the second preheating section and the rotary kiln, and a reducing agent injection device arranged in the transition section.

In the present invention, the reductant injection device includes a reductant storage tank, a pressure delivery pump, a mixing chamber, a gasifier, a gas distribution chamber and a reaction chamber within the transition section, which are connected in sequence. The reaction chamber is provided with a reducing agent conveying pipe, the reducing agent conveying pipe is communicated with the gas distribution chamber, and the reducing agent conveying pipe is provided with a nozzle.

Preferably, the reductant injection device comprises a reductant storage tank, a pressure delivery pump, a mixing chamber and a reaction chamber within the transition section, which are connected in sequence. The reaction chamber is provided with a gas distribution chamber and a reducing agent conveying pipe communicating with the gas distribution chamber, the reducing agent conveying pipe is provided with a nozzle, and the mixing chamber is connected to the gas distribution chamber in the reaction chamber through a pipeline.

Generally, the reducing agent is an aqueous solution of liquid ammonia, ammonia gas or ammonia water.

Preferably, the reducing agent injection device further includes a liquid flow regulating valve disposed between the pressure delivery pump and the mixing chamber.

Preferably, the reducing agent injection device further comprises a gas flow regulating valve arranged between the gasifier and the gas distribution chamber.

Preferably, the reducing agent injection device further comprises a gas (or air) supply pipe and a gas flow regulating valve arranged on the gas distribution chamber.

Generally, the air outlet of the bottom bellows of the extraction and drying section is also connected to the fourth duct, and then connected to the chimney. Preferably, the production device further comprises an eighth pipe drawn from the air outlet of the bottom bellows of the extraction and drying section, and the eighth pipe is connected to the air inlet of the first cooling section of the ring cooler, and the eighth pipe is provided with a fifth blower .

In the present invention, the suction drying section is further divided into a first suction drying section and a second suction drying section. The first exhaust drying section is connected with the blast drying section, and the second exhaust drying section is connected with the first preheating section. The eighth pipe drawn from the air outlet of the bottom bellows of the second air extraction and drying section is connected to the air inlet of the first cooling section of the ring cooler. Both the ninth duct drawn from the air outlet of the bottom bellows of the first extraction and drying section and the fourth duct drawn from the air outlet of the first preheating section are connected to the chimney after being merged or merged.

Preferably, the reducing agent conveying pipes are divided into 1-3 front and rear rows (for example, 2 rows), and the number of reducing agent conveying pipes in each row is 2-15, preferably 3-10.

Preferably, the number of nozzles on each reducing agent delivery pipe is 2-20, preferably 4-15, more preferably 6-12.

According to the second embodiment provided by the present invention, a production method of chain grate-rotary kiln pellets (low _NOx mode) is provided:

A chain grate-rotary kiln pellet production method or a method for producing pellets using the above-mentioned chain grate-rotary kiln pellet low- _NOx production device, the method comprising the following steps:

1) The raw balls of iron ore are dried in sequence through the blast drying section and the exhaust drying section of the chain grate machine, and then heated through the first preheating section and the second preheating section,

2) The heated iron ore green balls further pass through a transition section between the second preheating section and the rotary kiln provided with a reducing agent injection device, wherein in the transition section, the hot flue gas flowing through the transition section passes through the transition section. Reverse injection of reducing gas to make the reducing gas and the high temperature flue gas containing NO _x after roasting the iron ore pellets fully mixed and reacted for a long time, so as to realize the non-catalytic reduction of NO _x and reduce the smoke in the transition section the amount of _NOx in the gas, and

3) The iron ore green pellets output from the transition section enter the rotary kiln for roasting, and after roasting, the pellets are obtained through the cooling of the ring cooler;

Among them, the air in the upper space of the first cooling section of the ring cooler enters the rotary kiln directly from the front end of the rotary kiln to participate in the pellet roasting, and then flows through the second preheating section and then enters the exhaust drying section to exhaust and dry the green pellets. The hot exhaust gas in the lower part of the extraction and drying section is discharged to the chimney through the fourth pipe or circulated to the air inlet of the first cooling section through the eighth pipe; the air of the second cooling section enters the first preheating section to preheat the green balls and then flows outwards. Discharge to the chimney; the air in the third cooling section enters the blast drying section to blast and dry the green pellets and then discharges to the chimney; the air extracted from the bottom bellows of the second preheating section is transported to the exhaust drying section through the third pipe the air inlet at the top.

Preferably, the extraction and drying section is further divided into a first extraction and drying section and a second extraction and drying section, the hot exhaust gas of the second extraction and drying section is circulated to the first cooling section through the eighth pipeline, and the hot exhaust gas of the first extraction and drying section is passed through the fourth The pipe discharges out to the chimney.

Preferably, the reducing agent (eg liquid ammonia) stored in the reducing agent storage tank is transported into the mixing chamber under the suction of the pressure delivery pump to be mixed with the diluent (eg water or air or nitrogen) fed into it, and then transported To the gasifier for gasification, the gasified reducing agent mixture enters into each reducing agent conveying pipe through the distribution of the gas distribution chamber outside the reaction chamber, and is sprayed into the transition section through the nozzle on the conveying pipe. In a reaction chamber within the reactor in which the reducing agent reacts with nitrogen oxides (NO _x ) contained in the hot exhaust gas flowing through the reaction chamber.

Or, as another solution, the reducing agent (such as liquid ammonia or ammonia water) stored in the reducing agent storage tank is transported into the mixing chamber under the suction of the pressure feed pump and the diluent (such as water or air) fed into it or nitrogen) for mixing, and then directly transported to the gas distribution chamber located in the reaction chamber, and then the reducing agent mixture enters each reducing agent delivery pipe and is sprayed into the reaction chamber in the transition section through the nozzle on the delivery pipe A body in which the reducing agent reacts with nitrogen oxides ( _NOx ) contained in the hot exhaust gas flowing through the reaction chamber, producing nitrogen gas.

In the present application, the diluent may use liquid and/or gaseous diluents, such as water or air or nitrogen.

Typically, compressed air is passed through the gas distribution chamber.

In the present invention, the suction drying section is further divided into a first suction drying section and a second suction drying section, wherein the first suction drying section and the second suction drying section have equal or unequal distances. The first exhaust drying section is connected with the blast drying section, and the second exhaust drying section is connected with the first preheating section. Since the moisture content of the hot exhaust gas in the first exhaust drying section is relatively high, only the second exhaust drying section is used for the drying section. Or all the hot exhaust gas is circulated to the first cooling section as the cooling air of the first cooling section. Compared with the cooling method of blowing cold air in the prior art, the circulating hot exhaust gas can appropriately increase the temperature of the hot exhaust gas in the first cooling section, thereby appropriately reducing the heat provided by the central burner of the rotary kiln, that is, the outlet of the central burner. The temperature of the flue gas is reduced, which is an effective measure to reduce thermal _NOx , and the fuel consumption is also reduced, so it is also an effective measure to reduce fuel-type _NOx .

In the present invention, the reducing agent injection device is a device for removing _NOx by SNCR method, and the reducing agent injection device includes a liquid flow regulating valve arranged between the pressure delivery pump and the mixing chamber. Production requires real-time regulation of the liquid flow of the reducing agent. The reducing agent injection device includes a gas flow regulating valve, and the setting of the gas flow regulating valve is beneficial to adjust the gas flow of the gasified reducing agent in real time according to production needs. The reducing agent injection device includes reducing agent conveying pipes, which are divided into 1-3 rows before and after, and the number of reducing agent conveying pipes in each row is not limited, generally 2-15, preferably 3-10. Each reducing agent conveying pipe is provided with nozzles, and the number of nozzles is not limited, generally 2-20, preferably 4-15, more preferably 6-12.

In actual production, a diluent (such as water or air or nitrogen) is usually added in the mixing chamber to dilute the reducing agent (such as liquid ammonia or ammonia gas) to improve the dispersibility of the reducing agent. Compress the air to ensure that the reducing gas is sprayed into the reaction chamber at a certain flow rate. Preferably, the gasification furnace is cancelled, the gas distribution chamber is placed in the reaction chamber, the diluted reducing agent directly enters the gas distribution chamber to realize gasification, and compressed air is introduced into the gas distribution chamber to ensure that the reducing gas is in accordance with a certain The flow rate is sprayed into the reaction chamber. Wherein, the injected reducing gas reacts as follows in the transition section:

4NO+4NH ₃ +O ₂ →4N ₂ +6H ₂ O

6NO+4NH ₃ →5N ₂ +6H ₂ O

2NO ₂ +4NH ₃ +O ₂ →3N ₂ +6H ₂ O

6NO ₂ +8NH ₃ →7N ₂ +12H ₂ O

Through the above reaction, NO _x (including NO, NO ₂ ) in the flue gas can be converted into N ₂ , which effectively reduces the emission of NO _x in the flue gas. In addition, the unreacted reducing agent can further undergo the above reaction in the fume hood and the material layer of the second preheating section, thereby improving the removal rate of NO _x and reducing the escape of NH ₃ as much as possible.

In this application, the burner direction of the rotary kiln is the front end or kiln head. The end of the incoming material is the kiln tail.

In this application, for the nozzle of the reducing agent, it is generally required to have wear resistance. In operation, the mixed gas injection pressure is required to be greater than the pressure of the return hot air to avoid dust and particles from clogging the nozzles.

In the present application, the length of the grate machine is generally 20-80 meters, preferably 30-70 meters, more preferably 40-60 meters. The length of the rotary kiln is generally 20-60 meters, preferably 25-50 meters, more preferably 30-45 meters, such as 35 or 40 meters.

Compared with the prior art, the present invention has the following beneficial effects:

1. Based on the process characteristics of chain grate-rotary kiln pellet production, the present invention creatively develops a low _NOx production process for pellets, which realizes high _NOx flue gas circulation while ensuring the quality of pellets. Utilize and make full use of the waste heat resources in the flue gas, which not only reduces the production of fuel-type and thermal-type _NOx , but also the high- _NOx flue gas is recycled to achieve the purpose of energy saving and emission reduction;

2. The present invention combines the SNCR method denitrification technology, and the SNCR method reducing agent injection device is added in the transition section between the second preheating section and the rotary kiln, which can treat the NO _x in the circulating flue gas and the NO generated in the production process. _x , in order to finally achieve the purpose of low NO _x production;

3. The present invention starts from the process flow and the decomposition mechanism of _NOx to reduce the _NOx emission in the production process of the grate-rotary kiln pelletizing process, the process is simple, the cost of removing _NOx is low, and the problem that the _NOx emission of the current pelletizing enterprise exceeds the standard is solved. Technical difficulties, with the characteristics of "energy saving, emission reduction and low _NOx production".

4. In particular, a transition section is added between the second preheating section of the grate machine and the front end of the rotary kiln, and a reducing agent injection device is provided on the transition section, and the reducing gas is injected in the opposite direction with the flue gas. It is fully mixed and reacted for a long time with the high temperature flue gas produced by the roasting of iron ore pellets, so as to realize the non-catalytic reduction of NO _x to reduce the content of NO _x in the flue gas. At the same time, as another technical means, the The reacted flue gas is partially circulated back to the first section of the ring cooler through the exhaust air drying section to reduce the escape of the reducing agent and further reduce the emission of _NOx . Through the synergy of these two technical means, the chain grate-rotary kiln pelletizing low _NOx production is realized.

Description of drawings

1 is a schematic diagram of the prior art chain grate-rotary kiln pellet production process;

Fig. 2 is a kind of chain grate machine-rotary kiln pellet low _NOx production process schematic diagram of the present invention;

Fig. 3 is another kind of chain grate of the present invention - a schematic diagram of the low _NOx production process of rotary kiln pellets;

4 is a schematic structural diagram of the reducing agent injection device of the present invention;

FIG. 5 is a schematic structural diagram of another design of the reducing agent injection device of the present invention.

Reference numerals: 1: reducing agent injection device; 101: reducing agent storage tank; 102: pressure delivery pump; 103: liquid flow regulating valve; 104: mixing chamber; 105: gasifier; 106: gas flow regulating valve; 106a : air supply pipe or gas supply pipe; 107: gas distribution chamber; 108: reducing agent delivery pipe; 109: nozzle; 110: reaction chamber; 2: transition section; 3: chain grate machine; UDD: blast drying section; UDDa: the air inlet of the blast drying section; UDDb: the air outlet of the blast drying section; DDD: the exhaust drying section; DDDa: the air inlet of the exhaust drying section; DDDb: the air outlet of the exhaust drying section; DDD1: the first exhaust drying DDD1b: the air outlet of the first extraction and drying section; DDD2: the second extraction and drying section; DDD2b: the air outlet of the second extraction and drying section; TPH: the first preheating section; TPHa: the air inlet of the first preheating section ;TPHb: air outlet of the first preheating section; PH: second preheating section; PHb: air outlet of the second preheating section; Kiln: rotary kiln; C: ring cooler; C1: first cooling section; C1a : the air inlet of the first cooling section; C2: the second cooling section; C2a: the air inlet of the second cooling section; C2b: the air outlet of the second cooling section; C3: the third cooling section; C3a: the third cooling section Air inlet; C3b: Air outlet of the third cooling section; 4: Rotary kiln blower (or the third blower); 5: First exhaust fan; 6: Second exhaust fan; 7: Chimney; 8: Third exhaust air 9: fourth exhaust fan; 10: first blower; 11: second blower; 12: fifth blower; L1: first duct; L2: second duct; L3: third duct; L4: fourth duct ; L5: the fifth pipe; L6: the sixth pipe; L7: the seventh pipe; L8: the eighth pipe; L9: the ninth pipe.

Detailed ways

According to the first embodiment provided by the present invention, a chain grate-rotary kiln pellet low _NOx production device is provided:

A chain grate-rotary kiln pellet low _NOx production device comprises a chain grate 3, a rotary kiln Kiln connected to the end of the chain grate 3, and an annular cooler C located at the front end of the rotary kiln Kiln. Moreover, according to the process trend, the chain grate machine 3 is sequentially provided with a blast drying section UDD, a suction drying section DDD, a first preheating section TPH and a second preheating section PH; the ring cooler C is sequentially provided with a first cooling section. Section C1, second cooling section C2 and third cooling section C3, the front end of the rotary kiln Kiln is connected to the second preheating section PH and the other end (ie the front end) is connected to the first cooling section C1 of the ring cooler C.

The air outlet C2b of the second cooling section C2 is connected to the air inlet TPHa of the first preheating section TPH via the first pipeline L1. The air outlet C3b of the third cooling section C3 is connected to the air inlet UDDa of the bottom bellows of the blast drying section UDD via the second duct L2 and a first exhaust fan 5 is provided on the second duct L2. The air outlet PHb of the bottom bellows of the second preheating section PH is connected to the air inlet DDDa at the top of the suction drying section DDD via the third duct L3 and a second suction fan 6 is provided in the third duct L3. The fourth duct L4 drawn from the air outlet TPHb of the bottom bellows of the first preheating stage TPH is connected to the chimney 7 and a third exhaust fan 8 is provided on the fourth duct L4. A fifth duct L5 drawn from the air outlet UDDb at the top of the blow drying section UDD is connected to the chimney 7 and a fourth exhaust fan 9 is provided on the fifth duct L5. The air outlet of the first blower 10 is connected to the air inlet C2a of the second cooling section C2 through the sixth duct L6. The air outlet of the second blower 11 is connected to the air inlet C3a of the third cooling section C3 through the seventh duct L7. The front end of the rotary kiln (Kiln) is equipped with a rotary kiln blower 4 (or a third blower), which is used to deliver combustion-supporting air to the former central burner.

In the present invention, the production device further includes a transition section 2 arranged between the second preheating section PH and the rotary kiln Kiln, and a reducing agent injection device 1 arranged in the transition section 2 .

In the present invention, the reductant injection device 1 includes a reductant storage tank 101 , a pressure delivery pump 102 , a mixing chamber 104 , a gasifier 105 , a gas distribution chamber 107 and a reaction chamber in the transition section 2 , which are connected in sequence. 110. The reaction chamber 110 is provided with a reducing agent delivery pipe 108, the reducing agent delivery pipe 108 communicates with the gas distribution chamber 107, and a nozzle 109 is provided on the reducing agent delivery pipe 108.

Preferably, the reducing agent injection device 1 includes a reducing agent storage tank 101 , a pressure delivery pump 102 , a mixing chamber 104 and a reaction chamber 110 in the transition section 2 , which are connected in sequence. The reaction chamber 110 is provided with a gas distribution chamber 107 and a reducing agent delivery pipe 108 communicating with the gas distribution chamber 107 , the reducing agent delivery pipe 108 is provided with a nozzle 109 , and the mixing chamber 104 is connected to the reaction chamber 110 through a pipeline. The gas distribution chamber 107 (to which the compressed air and reducing agent mixture are generally supplied simultaneously).

Preferably, the reducing agent injection device 1 further includes a liquid flow regulating valve 103 disposed between the pressure delivery pump 102 and the mixing chamber 104 .

Preferably, the reducing agent injection device 1 further includes a gas flow regulating valve 106 disposed between the gasifier 105 and the gas distribution chamber 107 .

Preferably, the reducing agent injection device 1 further includes an air supply pipe 106a and a gas flow regulating valve 106 arranged on the gas distribution chamber 107 .

Preferably, the production device further includes an eighth pipe L8 drawn from the air outlet DDDb of the bottom bellows of the extraction and drying section DDD, and the eighth pipe L8 is connected to the air inlet C1a of the first cooling section C1 of the ring cooler C, and the eighth pipe L8 is A fifth blower 12 is provided on the duct L8.

In the present invention, the suction drying section DDD is further divided into a first suction drying section DDD1 and a second suction drying section DDD2. The first draft drying section DDD1 is connected with the blast drying section UDD, and the second draft drying section DDD2 is connected with the first preheating section TPH. The eighth pipe L8 drawn from the air outlet DDD2b of the bottom bellows of the second air extraction and drying section DDD2 is connected to the air inlet C1a of the first cooling section C1 of the ring cooler C. The ninth duct L9 drawn from the air outlet DDD1b of the bottom bellows of the first extraction and drying section DDD1 and the fourth duct L4 drawn from the air outlet TPHb of the first preheating section TPH are connected to the chimney 7 after being merged or merged.

Preferably, the reducing agent delivery pipes 108 are divided into 1-3 front and rear rows (for example, 2 rows), and the number of reducing agent delivery pipes 108 in each row is 2-15, preferably 3-10.

Preferably, the number of nozzles 109 on each reducing agent delivery pipe 108 is 2-20, preferably 4-15, more preferably 6-12, for example, 10.

According to the second embodiment provided by the present invention, there is provided a production method of grate-rotary kiln pellets (low _NOx mode).

A chain grate-rotary kiln pellet production method or a method for producing pellets using the above-mentioned chain grate-rotary kiln pellet low- _NOx production device, the method comprising the following steps:

1) The raw balls of iron ore are dried in sequence through the blast drying section UDD and the exhaust drying section DDD of the chain grate machine, and then heated through the first preheating section TPH and the second preheating section PH,

2) The heated iron ore pellets further pass through the transition section 2 provided with the reducing agent injection device 1 between the second preheating section PH and the rotary kiln Kiln, wherein in the transition section 2, the The hot flue gas in section 2 injects the reducing gas in reverse to make the reducing gas and the high-temperature flue gas containing NO _x above the iron ore pellet material after roasting to be fully mixed and react for a long time, so as to realize the non-catalytic NO _x . reduction to reduce the _NOx content in the flue gas of transition section 2, and

3) the iron ore green pellets outputted from the transition section 2 enter the rotary kiln Kiln and carry out roasting, and obtain pellets through the cooling of the ring cooler C after the roasting;

Among them, the air in the upper space of the first cooling section C1 of the ring cooler C directly enters the rotary kiln Kiln from the front end of the rotary kiln to participate in the roasting of green pellets, and then flows through the second preheating section PH to preheat the pellets and then enters the exhaust air drying. Section DDD carries out suction drying on the raw balls, and then the hot waste gas at the lower part of the suction drying section DDD is discharged to the chimney 7 through the fourth pipeline L4 or circulated to the air inlet of the first cooling section C1 through the eighth pipeline L8; the second cooling section The wind of C2 enters the first preheating section TPH to preheat the green balls and then discharges to the chimney 7; the wind of the third cooling section C3 enters the blast drying section UDD to blast and dry the green balls and then discharges to the chimney 7; The air drawn from the bottom wind box of the second preheating section PH is delivered to the air inlet DDDa at the top of the suction drying section DDD through the third duct L3.

Preferably, the extraction and drying section DDD is further divided into a first extraction and drying section DDD1 and a second extraction and drying section DDD2, the hot exhaust gas of the second extraction and drying section DDD2 is circulated to the first cooling section C1 through the eighth pipeline L8, and the first extraction and drying section DDD2 The hot exhaust gas of DDD1 is discharged to the chimney 7 through the fourth pipe L4.

Therefore, a transition section 2 is further provided between the second preheating section PH and the rotary kiln Kiln, and a reducing agent injection device 1 is provided in the transition section 2, by injecting the reducing gas backward into the flue gas containing NO _x in the transition section to reduce _NOx to produce nitrogen. The pellets discharged from the chain grate are conveyed via the transition section 2 into the rotary kiln.

Preferably, the reducing agent (such as liquid ammonia or ammonia water) stored in the reducing agent storage tank 101 is transported into the mixing chamber 104 under the suction of the pressure feeding pump 102 and the diluent (such as water or air or nitrogen) input therein After mixing, it is transported to the gasifier 105 for gasification. The gasified reducing agent mixture is distributed through the gas distribution chamber 107 located outside the reaction chamber 110 and enters into each reducing agent delivery pipe 108 and passes through the delivery pipe 108 The upper nozzle 109 is injected into the reaction chamber 110 in the transition section 2 where the reducing agent reacts with nitrogen oxides (NO _x ) contained in the hot exhaust gas flowing through the reaction chamber 110 .

Or, preferably, the reducing agent (such as liquid ammonia or ammonia water) stored in the reducing agent storage tank 101 is transported into the mixing chamber 104 under the suction of the pressure feeding pump 102 and the diluent (such as water or air or Nitrogen) for mixing, and then directly delivered to the gas distribution chamber 107 in the reaction chamber 110, and then into each reducing agent delivery pipe 108 and injected into the transition section 2 through the nozzle 109 on the delivery pipe 108 In the reaction chamber 110 of the reaction chamber 110 , the reducing agent reacts with nitrogen oxides (NO _x ) contained in the hot exhaust gas flowing through the reaction chamber 110 .

Preferably, the compressed air and the reducing agent mixture (in gaseous form) are fed simultaneously into the gas distribution chamber 107 .

Example 1

As shown in Figure 2, a chain grate-rotary kiln pellet low _NOx production device includes a chain grate 3, a rotary kiln Kiln connected to the end of the chain grate 3 and an annular cooler located at the front end of the rotary kiln Kiln C. Moreover, according to the process trend, the chain grate machine 3 is sequentially provided with a blast drying section UDD, a suction drying section DDD, a first preheating section TPH and a second preheating section PH. The ring cooler C is sequentially provided with a first cooling section C1, a second cooling section C2 and a third cooling section C3. The rear end of the rotary kiln Kiln is connected to the second preheating section PH and the front end is connected to the first cooling section of the ring cooler C. C1.

The air outlet C2b of the second cooling section C2 is connected to the air inlet TPHa of the first preheating section TPH via the first pipeline L1. The air outlet C3b of the third cooling section C3 is connected to the air inlet UDDa of the bottom bellows of the blast drying section UDD via the second duct L2 and a first exhaust fan 5 is provided on the second duct L2. The air outlet PHb of the bottom bellows of the second preheating section PH is connected to the air inlet DDDa at the top of the suction drying section DDD via the third duct L3 and a second suction fan 6 is provided in the third duct L3. The fourth duct L4 drawn from the air outlet TPHb of the bottom bellows of the first preheating stage TPH is connected to the chimney 7 and a third exhaust fan 8 is provided on the fourth duct L4. A fifth duct L5 drawn from the air outlet UDDb at the top of the blow drying section UDD is connected to the chimney 7 and a fourth exhaust fan 9 is provided on the fifth duct L5. The air outlet of the first blower 10 is connected to the air inlet C2a of the second cooling section C2 through the sixth duct L6. The air outlet of the second blower 11 is connected to the air inlet C3a of the third cooling section C3 through the seventh duct L7. The front end of the rotary kiln (Kiln) is equipped with a rotary kiln blower 4 (or a third blower), which is used to deliver combustion-supporting air to the former central burner.

The production device also includes an eighth pipe L8 drawn from the air outlet DDDb of the bottom bellows of the extraction and drying section DDD, and the eighth pipe L8 is connected to the air inlet C1a of the first cooling section C1 of the ring cooler C, and the eighth pipe L8 A fifth blower 12 is provided thereon.

The production device also includes a transition section 2 arranged between the second preheating section PH and the rotary kiln Kiln, and a reducing agent injection device 1 arranged in the transition section 2 .

4, the reducing agent injection device 1 includes a reducing agent storage tank 101, a pressure delivery pump 102, a liquid flow regulating valve 103, a mixing chamber 104, a gasifier 105, a gas flow regulating valve 106, a gas distribution chamber 107 and The reaction chamber 110 in the transition section 2 . The reaction chamber 110 is provided with a reducing agent delivery pipe 108 , the reducing agent delivery pipe 108 communicates with the gas distribution chamber 107 and a nozzle 109 is provided on the reducing agent delivery pipe 108 . The number of reducing agent delivery pipes 108 is 6, and the number of nozzles 109 on each reducing agent delivery pipe 108 is 10.

Example 2

Example 1 is repeated, except that as shown in Figure 3, the suction drying section DDD of the device is further divided into a first suction drying section DDD1 and a second suction drying section DDD2. The first draft drying section DDD1 is connected with the blast drying section UDD, and the second draft drying section DDD2 is connected with the first preheating section TPH. The eighth pipe L8 drawn from the air outlet DDD2b of the bottom bellows of the second air extraction and drying section DDD2 is connected to the air inlet C1a of the first cooling section C1 of the ring cooler C. The ninth duct L9 drawn from the air outlet DDD1b of the bottom bellows of the first extraction and drying section DDD1 and the fourth duct L4 drawn from the air outlet TPHb of the first preheating section TPH are connected to the chimney 7 after being merged.

Example 3

Example 2 is repeated, except that as shown in FIG. 5 , the reducing agent injection device 1 of the device includes a reducing agent storage tank 101 , a pressure delivery pump 102 , a liquid flow regulating valve 103 , a mixing chamber 104 and a reaction in the transition section 2 , which are connected in sequence. cavity 110 . The reaction chamber 110 is provided with a gas distribution chamber 107 and a reducing agent delivery pipe 108 communicating with the gas distribution chamber 107 , and a nozzle 109 is provided on the reducing agent delivery pipe 108 . The reducing agent injection device 1 also includes a gas flow regulating valve 106 provided on the gas distribution chamber 107 . The mixing chamber 104 communicates via conduits to a gas distribution chamber 107 located within the reaction chamber 110, and the compressed air and reducing agent mixture are generally supplied to the gas distribution chamber 107 at the same time.

Example 4

A method for producing a chain grate-rotary kiln pellet in a low _NOx mode, using the device in Example 1, the method comprises the following steps:

1) The raw balls of iron ore are dried in sequence through the blast drying section UDD and the exhaust drying section DDD of the chain grate machine, and then heated through the first preheating section TPH and the second preheating section PH,

2) The heated iron ore pellets further pass through the transition section 2 provided with the reducing agent injection device 1 between the second preheating section PH and the rotary kiln Kiln, wherein in the transition section 2, the The hot flue gas in section 2 injects the reducing gas in reverse to make the reducing gas and the high-temperature flue gas containing NO _x produced by the roasting of the iron ore pellets fully mixed and reacted for a long time, so as to realize the non-catalytic NO _x reduction to reduce the _NOx content in the flue gas of transition section 2, and

3) the iron ore green pellets outputted from the transition section 2 enter the rotary kiln Kiln and carry out roasting, and obtain pellets through the cooling of the ring cooler C after the roasting;

Among them, the air in the upper space of the first cooling section C1 of the ring cooler C directly enters the rotary kiln Kiln from the front end of the rotary kiln to participate in the roasting of green pellets, and then flows through the second preheating section PH to preheat the pellets and then enters the exhaust air drying. Section DDD carries out suction drying on the raw balls, and then the hot waste gas at the lower part of the suction drying section DDD is discharged to the chimney 7 through the fourth pipeline L4 or circulated to the air inlet of the first cooling section C1 through the eighth pipeline L8; the second cooling section The wind of C2 enters the first preheating section TPH to preheat the green balls and then discharges to the chimney 7; the wind of the third cooling section C3 enters the blast drying section UDD to blast and dry the green balls and then discharges to the chimney 7; The air drawn from the bottom wind box of the second preheating section PH is delivered to the air inlet DDDa at the top of the suction drying section DDD through the third duct L3.

The reducing agent (such as liquid ammonia) stored in the reducing agent storage tank 101 is transported to the mixing chamber 104 under the suction of the pressure feeding pump 102 to be mixed with the diluent (such as water or air) input into it, and then It is transported to the gasifier 105 for gasification, and the gasified reducing agent mixture is distributed through the gas distribution chamber 107 located outside the reaction chamber 110 and enters each reducing agent delivery pipe 108 and passes through the nozzle 109 on the delivery pipe 108 It is injected into the reaction chamber 110 in the transition section 2 where the reducing agent reacts with nitrogen oxides (NO _x ) contained in the hot exhaust gas flowing through the reaction chamber 110 . The compressed air and the reducing agent mixture (in gaseous form) are simultaneously fed into the gas distribution chamber 107 .

Example 5

A kind of chain grate-rotary kiln pellet low _NOx production method, using the device in embodiment 2, the method comprises the following steps:

1) The raw balls of iron ore are dried in sequence through the blast drying section UDD and the exhaust drying section DDD of the chain grate machine, and then heated through the first preheating section TPH and the second preheating section PH,

2) The heated iron ore pellets further pass through the transition section 2 provided with the reducing agent injection device 1 between the second preheating section PH and the rotary kiln Kiln, wherein in the transition section 2, the The hot flue gas in section 2 injects the reducing gas in reverse to make the reducing gas and the high-temperature flue gas containing NO _x produced by the roasting of the iron ore pellets fully mixed and reacted for a long time, so as to realize the non-catalytic NO _x reduction to reduce the _NOx content in the flue gas of transition section 2, and

3) the iron ore green pellets outputted from the transition section 2 enter the rotary kiln Kiln and carry out roasting, and obtain pellets through the cooling of the ring cooler C after the roasting;

Among them, the air in the first cooling section C1 directly enters the rotary kiln Kiln from the front end of the rotary kiln Kiln to participate in the pellet roasting, and then flows through the second preheating section PH to preheat the pellets and then enters the draft drying section DDD for draft drying of the green pellets. The suction drying section DDD is further divided into the first suction drying section DDD1 and the second suction drying section DDD2, the hot waste gas of the second suction drying section DDD2 is circulated to the first cooling section C1 through the eighth pipeline L8, and the first suction drying section DDD1 The hot exhaust gas is discharged to the chimney 7 through the fourth pipe L4; the wind of the second cooling section C2 enters the first preheating section TPH to preheat the green balls and is discharged to the chimney 7; the wind of the third cooling section C3 enters the chimney 7. The air drying section UDD blows and dries the raw balls and then discharges them to the chimney 7; the air drawn from the bottom bellows of the second preheating section PH is transported to the air inlet DDDa at the top of the draft drying section DDD through the third duct L3.

The reducing agent (such as liquid ammonia) stored in the reducing agent storage tank 101 is transported to the mixing chamber 104 under the suction of the pressure feeding pump 102 to be mixed with the diluent (such as water or air) input into it, and then It is transported to the gasifier 105 for gasification, and the gasified reducing agent mixture is distributed through the gas distribution chamber 107 located outside the reaction chamber 110 and enters each reducing agent delivery pipe 108 and passes through the nozzle 109 on the delivery pipe 108 It is injected into the reaction chamber 110 in the transition section 2 where the reducing agent reacts with nitrogen oxides (NO _x ) contained in the hot exhaust gas flowing through the reaction chamber 110 . The compressed air and the reducing agent mixture (in gaseous form) are simultaneously fed into the gas distribution chamber 107 .

Example 6

Example 5 is repeated, except: wherein the reducing agent (eg liquid ammonia) stored in the reducing agent storage tank 101 is transported into the mixing chamber 104 under the suction of the pressure delivery pump 102 and the diluent (eg water) input therein or air) for mixing, and then directly delivered to the gas distribution chamber 107 in the reaction chamber 110, and then into each reducing agent delivery pipe 108 and injected into the transition section 2 through the nozzle 109 on the delivery pipe 108 Inside the reaction chamber 110 , in which the reducing agent reacts with nitrogen oxides (NO _x ) contained in the hot exhaust gas flowing through the reaction chamber 110 . The compressed air and the reducing agent mixture (in gaseous form) are simultaneously fed into the gas distribution chamber 107 .

Claims (20)

1. Grate-rotary kiln pellet low NO_xThe production device comprises a chain grate (3), a rotary Kiln (Kiln) connected with the tail end of the chain grate (3) and a ring cooling machine (C) connected with the front end of the rotary Kiln (Kiln), wherein the chain grate (3) is sequentially provided with an air blowing drying section (UDD), an air blowing drying section (DDD), a first preheating section (TPH) and a second preheating section (PH) according to the process trend, the ring cooling machine (C) is sequentially provided with a first cooling section (C1), a second cooling section (C2) and a third cooling section (C3), and the tail end of the rotary Kiln (Kiln) is connected with the second preheating section (PH) of the chain grate (3) and the first cooling section (C1) of the ring cooling machine (C) at the other end;

wherein the air outlet (C2b) of the second cooling section (C2) is connected via a first conduit (L1) to the air inlet (TPHa) of the first preheating section (TPH), the air outlet (C3b) of the third cooling section (C3) is connected via a second conduit (L2) to the air inlet (UDDa) of the bottom windbox of the forced air drying section (UDD) and is provided with a first suction fan (5) on a second conduit (L2), the air outlet (PHb) of the bottom windbox of the second preheating section (PH) is connected via a third conduit (L3) to the air inlet (DDDa) at the top of the forced air drying section (DDD) and is provided with a second suction fan (6) on a third conduit (L3), a fourth conduit (L4) leading from the air outlet (TPHb) of the bottom windbox of the first preheating section (TPH) is connected to a chimney (7) and is provided with a third suction fan (8) on a fourth conduit (L4), the air outlet (TPHb) of the forced air drying section (TPH) is connected to a chimney (dhb) and is connected to a fifth conduit (dhl 5) at the top of the chimney (dh A fourth exhaust fan (9) is arranged on the passage (L5), an air outlet of the first air blower (10) is connected with an air inlet (C2a) of the second cooling section (C2) through a sixth pipeline (L6), and an air outlet of the second air blower (11) is connected with an air inlet (C3a) of the third cooling section (C3) through a seventh pipeline (L7);

the method is characterized in that: the production device also comprises a transition section (2) arranged between the second preheating section (PH) and the rotary Kiln (Kiln), and a reducing agent injection device (1) arranged on the transition section (2);

the production device also comprises an eighth pipeline (L8) led out from an air outlet (DDDb) of the bottom bellows of the air draft drying section (DDD), the eighth pipeline (L8) is connected to an air inlet (C1a) of the first cooling section (C1) of the ring cooling machine (C), and a fifth air blower (12) is arranged on the eighth pipeline (L8).

2. The apparatus of claim 1, wherein: the reducing agent injection device (1) comprises a reducing agent storage tank (101), a pressure delivery pump (102), a mixing chamber (104), a gasification furnace (105), a gas distribution chamber (107) and a reaction cavity (110) in a transition section (2), wherein the reaction cavity (110) is internally provided with a reducing agent delivery pipe (108), the reducing agent delivery pipe (108) is communicated with the gas distribution chamber (107), and the reducing agent delivery pipe (108) is provided with a nozzle (109).

3. The apparatus of claim 1, wherein: the reducing agent injection device (1) comprises a reducing agent storage tank (101), a pressure delivery pump (102), a mixing chamber (104) and a reaction cavity (110) located in a transition section (2), wherein the reaction cavity (110) is internally provided with a gas distribution chamber (107) and a reducing agent delivery pipe (108) communicated with the gas distribution chamber (107), the reducing agent delivery pipe (108) is provided with a nozzle (109), and the mixing chamber (104) is communicated to the gas distribution chamber (107) located in the reaction cavity (110) through a pipeline.

4. The apparatus of claim 2 or 3, wherein: the reducing agent injection device (1) further comprises a liquid flow regulating valve (103) arranged between the pressure delivery pump (102) and the mixing chamber (104).

5. The apparatus of claim 2, wherein: the reducing agent injection device (1) further comprises a gas flow regulating valve (106) arranged between the gasification furnace (105) and the gas distribution chamber (107).

6. The apparatus of claim 3, wherein: the reducing agent injection device (1) further includes an air supply pipe (106a) and a gas flow rate adjustment valve (106) provided on the gas distribution chamber (107).

7. The apparatus of any one of claims 1-3, 5-6, wherein: the air draft drying section (DDD) is further divided into a first air draft drying section (DDD1) and a second air draft drying section (DDD2), wherein the first air draft drying section (DDD1) is connected with the air blast drying section (UDD), the second air draft drying section (DDD2) is connected with the first preheating section (TPH), an eighth pipeline (L8) led out from an air outlet (DDD2b) of a bottom bellows of the second air draft drying section (DDD2) is connected to an air inlet (C1a) of a first cooling section (C1) of the ring cooling machine (C), and a ninth pipeline (L9) led out from an air outlet (DDD1b) of the bottom bellows of the first air draft drying section (DDD1) and a fourth pipeline (L4) led out from an air outlet (TPHb) of the first preheating section (TPH) are connected to a chimney (7) after being combined or joined.

8. The apparatus of claim 4, wherein: the air draft drying section (DDD) is further divided into a first air draft drying section (DDD1) and a second air draft drying section (DDD2), wherein the first air draft drying section (DDD1) is connected with the air blast drying section (UDD), the second air draft drying section (DDD2) is connected with the first preheating section (TPH), an eighth pipeline (L8) led out from an air outlet (DDD2b) of a bottom bellows of the second air draft drying section (DDD2) is connected to an air inlet (C1a) of a first cooling section (C1) of the ring cooling machine (C), and a ninth pipeline (L9) led out from an air outlet (DDD1b) of the bottom bellows of the first air draft drying section (DDD1) and a fourth pipeline (L4) led out from an air outlet (TPHb) of the first preheating section (TPH) are connected to a chimney (7) after being combined or joined.

9. The apparatus of any one of claims 2-3, 5-6, 8, wherein: the reducing agent delivery pipes (108) are divided into front and rear 1-3 rows, and the number of the reducing agent delivery pipes (108) in each row is 2-15.

10. The apparatus of claim 4, wherein: the reducing agent delivery pipes (108) are divided into front and rear 1-3 rows, and the number of the reducing agent delivery pipes (108) in each row is 2-15.

11. The apparatus of claim 9, wherein: the reducing agent delivery pipes (108) are divided into front and rear 1-3 rows, and the number of the reducing agent delivery pipes (108) in each row is 3-10.

12. The apparatus of claim 10, wherein: the reducing agent delivery pipes (108) are divided into front and rear 1-3 rows, and the number of the reducing agent delivery pipes (108) in each row is 3-10.

13. The apparatus of claim 9, wherein: the number of the nozzles (109) on each reducing agent delivery pipe (108) is 2-20.

14. The apparatus according to any one of claims 10-12, wherein: the number of the nozzles (109) on each reducing agent delivery pipe (108) is 2-20.

15. The apparatus of claim 13, wherein: the number of the nozzles (109) on each reducing agent delivery pipe (108) is 4-15.

16. The apparatus of claim 14, wherein: the number of the nozzles (109) on each reducing agent delivery pipe (108) is 4-15.

17. Grate-rotary kiln pellet low NO_xMethod of production or use of grate-kiln pellets according to any of claims 1-16 for low NO_xA method for producing pellets in a production facility, the method comprising the steps of:

1) the raw pellets of the iron ore are dried by a blast drying section (UDD) and a draft drying section (DDD) of a chain grate in sequence, and then heated by a first preheating section (TPH) and a second preheating section (PH),

2) the heated iron ore green pellets further pass through a transition section (2) which is arranged between a second preheating section (PH) and a rotary Kiln (Kiln) and is provided with a reducing agent injection device (1), wherein in the transition section (2), reducing gas and NO-containing gas above the roasted iron ore pellet materials are sprayed by the reducing gas in a reverse direction with hot flue gas flowing through the transition section (2)_xThe high-temperature flue gas is fully mixed and reacted for a longer time, thereby realizing NO_xTo reduce NO in the flue gas of the transition section (2)_xIn an amount of, and

3) the iron ore pellets output from the transition section (2) enter a rotary Kiln (Kiln) for roasting, and are cooled by a circular cooler (C) after roasting to obtain pellet products;

wherein, the air in the upper space of the first cooling section (C1) of the circular cooler (C) directly enters the rotary Kiln (Kiln) from the front end of the rotary Kiln (Kiln) to participate in pellet roasting, then flows through the second preheating section (PH) to preheat pellets, then enters the air draft drying section (DDD) to perform air draft drying on the pellets, and then the hot waste gas at the lower part of the air draft drying section (DDD) is discharged outwards to a chimney (7) through a fourth pipeline (L4) or circulates to the air inlet of the first cooling section (C1) through an eighth pipeline (L8); the wind of the second cooling section (C2) enters the first preheating section (TPH) to preheat green pellets and then is discharged to a chimney (7); air of the third cooling section (C3) enters a blast drying section (UDD) to blast dry the green pellets and then is discharged to a chimney (7); the air drawn out of the bottom windbox of the second preheating stage (PH) is conveyed via a third duct (L3) to an air inlet (DDDa) at the top of the updraft drying stage (DDD).

18. The method of claim 17, wherein the updraft drying section (DDD) is further divided into a first updraft drying section (DDD1) and a second updraft drying section (DDD2), hot exhaust gas of the second updraft drying section (DDD2) being recycled to the first cooling section (C1) via an eighth duct (L8), and hot exhaust gas of the first updraft drying section (DDD1) being discharged outwardly to the chimney (7) via a fourth duct (L4).

19. The method according to claim 17 or 18, characterized in that: the reducing agent stored in the reducing agent storage tank (101) is conveyed into a mixing chamber (104) under the suction of a pressure conveying pump (102) to be mixed with the diluent input into the mixing chamber, then conveyed into a gasification furnace (105) to be gasified, the gasified reducing agent mixture enters into each reducing agent conveying pipe (108) through the distribution of a gas distribution chamber (107) positioned outside a reaction cavity (110) and is sprayed into the reaction cavity (110) in a transition section (2) through a nozzle (109) on the conveying pipe (108), and the reducing agent and Nitrogen Oxides (NO) contained in hot waste gas flowing through the reaction cavity (110) are in the reducing agent storage tank and the Nitrogen Oxides (NO) contained in the hot waste gas flowing through the reaction cavity (110)_x) Carrying out reaction; or

The reducing agent stored in the reducing agent storage tank (101) is conveyed into a mixing chamber (104) under the suction of a pressure conveying pump (102) to be mixed with the diluent fed into the mixing chamber, then is directly conveyed into a gas distribution chamber (107) positioned in a reaction cavity (110), finally enters into each reducing agent conveying pipe (108) and is sprayed into the reaction cavity (110) in a transition section (2) through a nozzle (109) on the conveying pipe (108), wherein the reducing agent and Nitrogen Oxides (NO) contained in hot exhaust gas flowing through the reaction cavity (110)_x) The reaction is carried out.

20. The method of claim 19, wherein: compressed air is introduced into the gas distribution chamber (107).

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