CN110721568A - A device and method for denitrification and desulfurization of flue gas from pellet roasting based on chain grate machine and rotary kiln - Google Patents

Abstract

The invention provides a device and method for denitrification and desulfurization of pellet roasting flue gas based on a chain grate-rotary kiln. The device includes a reaction system and a flue gas treatment system, and the reaction system includes a chain grate and a rotary kiln connected in sequence. The flue gas treatment system includes an SNCR unit, an SCR unit, an ozone oxidation unit, and a sulfur nitrate absorption unit. The flue gas outlet of the rotary kiln is connected to the gas inlet of the chain grate after passing through the SNCR unit, and the gas outlet of the chain grate is re-connected. Connect the SCR unit, the ozone oxidation unit and the sulfur nitrate absorption unit in sequence. The device of the invention combines the pellet production system and the flue gas treatment system, and utilizes the temperature and composition characteristics of the roasting flue gas as well as the heat exchange with the chain grate machine to perform denitrification and desulfurization treatment in sequence, so as to improve the removal of flue gas pollutants. In addition to efficiency; the device utilizes the temperature characteristics of different regions of the grate and the heat exchange of flue gas in different stages, so as to improve the utilization efficiency of heat and reduce energy consumption and operating costs.

Description

A kind of pellet roasting flue gas denitration and desulfurization device based on chain grate machine-rotary kiln and method

technical field

The invention belongs to the technical field of flue gas treatment, and relates to a pellet roasting flue gas denitration and desulfurization device and method, in particular to a pellet roasting flue gas denitration and desulfurization device and method based on a chain grate machine-rotary kiln.

Background technique

At present, in order to improve the technical and economic indicators of ironmaking, the main production enterprises in the iron and steel industry have adjusted the blast furnace structure, expanded the demand for pellets, and made the pellets develop well. Compared with sintered ore, pellets have uniform particle size, high iron content, good reducibility, and good low temperature strength. The use of pellets can generally increase production and reduce coke ratio.

The pellet production process mainly includes raw material preparation, batching, mixing, pelletizing, drying, roasting, cooling, finished product screening, etc. At present, the pellet roasting process mainly includes shaft furnace roasting process, belt roaster process, chain grate- Rotary kiln process. Among them, the shaft furnace has uneven roasting, poor product quality, and low productivity due to its own process limitations, and it is difficult to meet the production requirements of large blast furnaces; the belt roasting machine needs to be made of heat-resistant steel due to the high temperature operation of the trolley and the grating. The manufacturing cost is high, and the power consumption of the air supply system is high, the operating cost is large, and the application is less. Chain grate machine-rotary kiln has large production capacity, high heat utilization rate, low total energy consumption, uniform pellet quality and high strength, and is widely used in pellet production.

In the pellet production process, especially the pellet roasting process, the _NOx emission intensity is high. With the stricter air pollutant emission standards, it is imminent to control the pellet roasting flue gas. The _NOx produced by the rotary kiln process is efficiently treated. At present, the methods of treating nitrogen oxides mainly include selective catalytic reduction (SCR), selective non-catalytic reduction (SNCR) and ozone oxidation denitrification.

CN 108392984A discloses a chain grate rotary kiln denitrification system and a denitration method, the system includes a chain grate, a rotary kiln and a ring cooler connected in sequence, and the chain grate includes a blast drying section and a suction drying section connected in sequence , the first preheating section and the second preheating section, the denitration system also includes a denitration reactor located outside the grate machine, the second preheating section has a flue gas outlet, the exhaust drying section has a flue gas inlet, and the denitration reactor is connected A reducing agent injection device is also connected between the flue gas outlet of the second preheating section and the flue gas inlet of the extraction and drying section, and between the denitration reactor and the flue gas outlet of the second preheating section. The flue gas processed by this system is mainly the flue gas of the second preheating section in the chain grate machine. The temperature of this part of the flue gas is high, so it is difficult to directly carry out SCR denitration treatment, and the flue gas in the rotary kiln has not been treated. Incomplete processing.

CN 206168206U discloses a grate-rotary kiln denitrification system, comprising a first preheating section and a second preheating section for heating pellets, and a denitration device for removing nitrogen oxides in flue gas, The denitration device is arranged in the inner cavity of the second preheating section; the device only uses the temperature of the second preheating section to perform SNCR treatment on the flue gas, but the treatment time and efficiency of this stage are relatively low, and it is difficult to meet the emission requirements. And only denitration treatment is carried out, and sulfur oxides are not treated, so they cannot be directly discharged.

In summary, for the treatment of flue gas generated by the chain grate-rotary kiln process, it is necessary to take corresponding treatment measures in combination with the device structure, flue gas temperature and composition to achieve efficient purification of flue gas.

SUMMARY OF THE INVENTION

In view of the problems existing in the prior art, the purpose of the present invention is to provide a pellet roasting flue gas denitration and desulfurization device and method based on a chain grate-rotary kiln, which combines a pellet production system with a flue gas treatment system , using the temperature and composition characteristics of the roasting flue gas to carry out multi-stage denitration and desulfurization treatment in turn to improve the removal efficiency of flue gas pollutants, and at the same time use the temperature characteristics of different areas of the grate and the flue gas heat exchange in different stages to increase the heat efficiency and reduce energy consumption.

For this purpose, the present invention adopts the following technical solutions:

In one aspect, the present invention provides a pellet roasting flue gas denitration and desulfurization device based on a grate machine-rotary kiln, the device includes a reaction system and a flue gas treatment system, the reaction system includes a chain grate machine and a flue gas treatment system connected in sequence. A rotary kiln, the flue gas treatment system includes an SNCR unit, an SCR unit, an ozone oxidation unit and a sulfur nitrate absorption unit, and the flue gas outlet of the rotary kiln is connected to the gas inlet of the chain grate after passing through the SNCR unit, and the chain grate The gas outlet of the machine is then connected to the SCR unit, the ozone oxidation unit and the sulfur nitrate absorption unit in sequence.

In the present invention, the roasting flue gas is processed on the basis of the chain grate-rotary kiln system used in the production of pellets, and the heat of the flue gas is fully utilized to dry and preheat the pellet material. After SNCR treatment, when passing through the chain grate machine, it preheats the material and takes away the generated flue gas, and further conducts SCR denitration treatment and ozone oxidation treatment in sequence, and then carries out sulfur and nitrate absorption treatment to fully remove the pollutants in the flue gas; In the process of flue gas treatment, the heat exchange between different areas of the grate machine can also greatly improve the heat utilization efficiency and reduce the energy consumption and operating cost of the device.

The following are the preferred technical solutions of the present invention, but not as limitations of the technical solutions provided by the present invention. Through the following technical solutions, the technical purpose and beneficial effects of the present invention can be better achieved and realized.

As a preferred technical solution of the present invention, the chain grate machine is sequentially divided into a first drying section, a second drying section, a first preheating section and a second preheating section along the pellet feeding direction.

In the present invention, the temperature in the grate machine is gradually increased along the conveying direction of the pelletized material, and the drying and preheating of the material are completed in turn; , the latter is dried by exhaust air.

Preferably, one end of the rotary kiln close to the chain grate is provided with a pellet inlet and a flue gas outlet, and the other end is provided with a pellet outlet and a fuel inlet, and the pellet material and the fuel are in reverse contact in the rotary kiln.

Preferably, the reaction system further includes a ring cooler, and the pellet outlet of the rotary kiln is connected to the ring cooler.

Preferably, the ring cooler includes a first cooling section, a second cooling section and a third cooling section in sequence along the pellet conveying direction.

As a preferred technical solution of the present invention, the flue gas outlet of the rotary kiln is connected to the second preheating section of the chain grate machine through a flue gas return line.

Preferably, the SNCR unit is arranged at the top of the second preheating section.

Preferably, the gas outlet of the second preheating section is connected to the gas inlet of the SCR unit, the gas outlet of the SCR unit is connected to the gas inlet of the second drying section, and the gas outlet of the second drying section is sequentially connected to the ozone oxidation unit and the sulfur Nitrate absorption unit.

In the present invention, after the flue gas passes through the second preheating section, SCR treatment is carried out according to the temperature conditions at this time. If the flue gas is directly reduced by ozone denitration treatment, the temperature is still high, so it first passes through the second drying section that matches its temperature. Heat exchange can also take away a small amount of flue gas in this section. At this time, the content of nitrogen oxides is low, and the amount of ozone required is small. The oxidized nitrogen oxides are absorbed with SO ₂ in the sulfur nitrate absorption treatment.

Preferably, the SCR unit comprises an SCR reactor.

Preferably, the ozone oxidation unit includes an ozone generating device, and the outlet of the ozone generating device is connected to the flue gas pipeline.

In the present invention, the ozone denitration treatment can be completed by mixing with ozone during the movement of the flue gas, no special reaction device is required, and only an ozone generating device is required.

Preferably, the sulfur nitrate absorption unit includes a semi-dry desulfurization device.

In the present invention, the flue gas desulfurization adopts a semi-dry method, mainly uses calcium-based desulfurizers, and does not produce waste water. In addition to the main desulfurization, it also has a good absorption effect on the acid gases HF, HCl and heavy metals in the flue gas. Hg, etc., High-efficiency synergistic purification of multiple pollutants can be achieved.

As a preferred technical solution of the present invention, the flue gas treatment system includes a dust removal unit, and the dust removal unit includes at least a first-stage dust collector.

Preferably, the dedusting unit includes a first dedusting device, a second dedusting device and a third dedusting device, the first dedusting device is arranged between the gas outlet of the second preheating section and the SCR unit, and the second dedusting device The filter is arranged between the gas outlet of the second drying section and the ozone oxidation unit, and the third dust collector is arranged after the sulfur nitrate absorption unit.

In the present invention, in addition to gas pollutants such as NO _x and SO ₂ , the flue gas also contains dust particles, which need to be dedusted. According to the treatment path of the flue gas, the flue gas passes through the grate and before being discharged. Dust removal is required.

Preferably, the flue gas treatment system includes a chimney, and the gas outlet of the third dust collector is connected to the chimney.

Preferably, the first dust collector comprises a cyclone dust collector.

Preferably, the second precipitator comprises an electrostatic precipitator.

Preferably, the third dust collector comprises a bag filter.

In the present invention, the multi-stage dust collector can be used to classify the particles, and the particle size of the particles that can be separated is gradually reduced, that is, the precision of the used dust collector is gradually improved.

As a preferred technical solution of the present invention, a cold air device is connected to the bottom of the ring cooler, and the cold air device feeds a heat exchange medium to the ring cooler.

Preferably, the top outlets of the different cooling sections of the annular cooler are independently connected to the grate or the rotary kiln.

Preferably, the top outlet of the first cooling section is connected to the fuel inlet of the rotary kiln, the top outlet of the second cooling section is connected to the gas inlet of the first preheating section, and the top outlet of the third cooling section is connected to the gas inlet of the first preheating section. The gas inlet of the first drying section is connected.

In the present invention, the ring cooler cools the pelletized material, and the temperature of the medium after heat exchange in different cooling sections is different, so it can be used in different areas of the device according to its temperature, making full use of the heat it carries.

Preferably, a fourth dust collector is provided on the pipeline between the top outlet of the third cooling section and the gas inlet of the first drying section.

Preferably, the fourth dust collector comprises a cyclone dust collector.

Preferably, the gas outlet of the first preheating section is connected to the second dust collector, and the gas outlet of the first drying section is connected to the chimney.

On the other hand, the present invention provides a method for denitrification and desulfurization of flue gas from pellet roasting using the above device, the method comprising:

The flue gas produced by the roasting of pelletized material is first subjected to SNCR treatment, then enters the grate for heat exchange, and then undergoes SCR treatment, ozone oxidation treatment and sulfur nitrate absorption treatment in sequence to obtain purified flue gas.

As a preferred technical solution of the present invention, the pelletized material is dried and preheated by a chain grate machine, and then enters a rotary kiln for roasting.

Preferably, the concentration of NO _x in the roasting flue gas is 300-400 mg/Nm ³ , such as 300 mg/Nm ³ , 320 mg/Nm ³ , 340 mg/Nm ³ , 360 mg/Nm ³ , 380 mg/Nm ³ or 400 mg/Nm 3 . ³ , etc., but not limited to the listed numerical values, other unlisted numerical values within the numerical range are also applicable; the concentration of SO ₂ is 750-900 mg/Nm ³ , such as 750 mg/Nm ³ , 780 mg/Nm ³ , 800 mg/Nm 3 ³ , 820mg/Nm ³ , 850mg/Nm ³ , 880mg/Nm ³ or 900mg/Nm ³ , etc., but not limited to the listed values, other unlisted values within the range are also applicable; the concentration of particulate matter is 50～ 130mg/Nm ³ , such as 50mg/Nm ³ , 60mg/Nm ³ , 80mg/Nm ³ , 100mg/Nm ³ , 120mg/Nm ³ or 130mg/Nm ³ , etc., but not limited to the listed values, within the range of the values Other non-recited values also apply.

Preferably, the temperature at which the flue gas is subjected to SNCR treatment is 800-1100°C, such as 800°C, 850°C, 900°C, 950°C, 1000°C, 1050°C or 1100°C, etc., but not limited to the listed values, The same applies to other non-recited values within this numerical range.

Preferably, ammonia gas is injected into the flue gas during the SNCR treatment, wherein the source of the ammonia gas includes any one or a combination of at least two of ammonia water, urea or liquid ammonia. Typical but non-limiting examples of the combination include: : The combination of ammonia water and urea, the combination of urea and liquid ammonia, the combination of ammonia water, urea and liquid ammonia, etc.

Preferably, the molar ratio of the ammonia gas to _NOx in the roasting flue gas is (0.5-1.0):1, such as 0.5:1, 0.6:1, 0.7:1, 0.8:1, 0.9:1 or 1.0:1 etc., but are not limited to the recited numerical values, and other unrecited numerical values within the numerical range are equally applicable.

In the present invention, by utilizing the characteristics of high temperature of roasting flue gas and high concentration of _NOx , SNCR treatment is performed first, and the removal rate of _NOx can reach about 40%.

As a preferred technical solution of the present invention, after the roasting flue gas is treated by SNCR, it enters the second preheating section of the grate machine for heat exchange and cooling.

Preferably, the temperature of the SCR treatment is 300-400°C, such as 300°C, 320°C, 340°C, 360°C, 380°C or 400°C, etc., but not limited to the listed values, and other values within the range are not limited to The values listed also apply.

Preferably, the catalyst used in the SCR treatment includes a vanadium-tungsten-titanium-based catalyst or a vanadium-molybdenum-titanium-based catalyst, specifically V ₂ O ₅ -WO ₃ /TiO ₂ or V ₂ O ₅ -MoO ₃ /TiO ₂ .

Preferably, ammonia gas is injected into the flue gas during the SCR treatment, wherein the source of the ammonia gas includes any one or a combination of at least two of ammonia water, urea or liquid ammonia. Typical but non-limiting examples of the combination include: : The combination of ammonia water and urea, the combination of urea and liquid ammonia, the combination of ammonia water, urea and liquid ammonia, etc.

Preferably, the molar ratio of the ammonia gas to the remaining _NOx in the roasting flue gas is (0.8-1.2):1, such as 0.8:1, 0.9:1, 1.0:1, 1.1:1 or 1.2:1, etc., but Not limited to the recited values, other non-recited values within the range of values apply equally.

Preferably, the SCR-treated flue gas passes through the second drying section of the grate machine to dry the pelletized material.

As a preferred technical solution of the present invention, during the ozone oxidation treatment, ozone is introduced into the flue gas.

Preferably, the molar ratio of the ozone to the remaining _NOx in the roasting flue gas is (0.8-1.5):1, such as 0.8:1, 0.9:1, 1.0:1, 1.1:1, 1.2:1, 1.3:1 , 1.4:1 or 1.5:1, etc., but are not limited to the listed values, and other unlisted values within the numerical range are also applicable.

Preferably, the sulfur and nitrate absorption treatment adopts semi-dry desulfurization and denitrification.

Preferably, the semi-dry method includes any one of a circulating fluidized bed method, a rotary spray drying method or a dense phase coherent tower method.

In the present invention, the flue gas desulfurization adopts a semi-dry method, mainly uses calcium-based desulfurizers, and does not produce waste water. In addition to being mainly used for desulfurization, it can also absorb a small amount of nitrogen oxides generated in the ozone oxidation stage. Gases such as HF, HCl and heavy metal Hg also have a good absorption effect, which can achieve efficient synergistic purification of various pollutants.

Preferably, the flue gas is dedusted before the SCR treatment, before the ozone oxidation treatment and after the sulfur nitrate absorption treatment.

As a preferred technical solution of the present invention, the pellet material is subjected to three-stage cooling in a ring cooler after roasting.

Preferably, a heat exchange medium is passed into the ring cooler during the cooling process.

Preferably, the heat exchange medium includes air.

Preferably, the heat exchange medium after primary cooling enters the rotary kiln for roasting the pelletized material.

Preferably, the heat exchange medium after secondary cooling enters the first preheating section of the grate machine for preheating the pellet material, and is then mixed with the outlet flue gas of the second drying section.

Preferably, the heat exchange medium after tertiary cooling enters the first drying section of the chain grate for drying the pelletized material.

Preferably, the heat exchange medium after tertiary cooling is subjected to dedusting treatment before entering the first drying section.

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

(1) The device of the present invention combines the pellet production system with the flue gas treatment system, utilizes the temperature and composition characteristics of the roasting flue gas and the heat exchange with the chain grate machine to carry out denitration and desulfurization treatment in turn to improve flue gas pollution. The removal efficiency of the pollutants is reduced, the _NOx concentration in the purified flue gas is reduced to below 16mg/ ^Nm3 , the _SO2 concentration is reduced to below 20mg/ ^Nm3 , and the particulate matter concentration is reduced to below 10mg/ ^Nm3 ;

(2) The device of the present invention utilizes the temperature characteristics of different regions of the grate and the heat exchange of flue gas at different stages to improve the utilization efficiency of heat and reduce energy consumption and operating costs;

(3) The present invention does not need to reheat the exhausted flue gas, which simplifies the process and reduces the cost of investing in reheating equipment.

Description of drawings

Fig. 1 is the structural representation of the pellet roasting flue gas denitration and desulfurization device based on chain grate machine-rotary kiln provided in Example 1 of the present invention;

Among them, 1-first drying section, 2-second drying section, 3-first preheating section, 4-second preheating section, 5-rotary kiln, 6-first cooling section, 7-second cooling section , 8-the third cooling section, 9-cold air device, 10-SNCR unit, 11-first dust collector, 12-SCR unit, 13-second dust collector, 14-ozone oxidation unit, 15-sulfur absorption unit, 16- 3rd dust collector, 17- 4th dust collector, 18- chimney.

Detailed ways

In order to better illustrate the present invention and facilitate the understanding of the technical solutions of the present invention, the present invention will be described in further detail below, but the following embodiments are only simple examples of the present invention, and do not represent or limit the scope of protection of the present invention. The scope of protection of the invention is subject to the claims.

The specific embodiment of the present invention partially provides a grate-rotary kiln-based pellet roasting flue gas denitrification and desulfurization device and method. The device includes a reaction system and a flue gas treatment system, and the reaction system includes chains connected in sequence. Grate and rotary kiln 5, the flue gas treatment system includes SNCR unit 10, SCR unit 12, ozone oxidation unit 14 and sulfur nitrate absorption unit 15, the flue gas outlet of the rotary kiln 5 is connected to the chain after passing through the SNCR unit 10 The gas inlet of the grate machine and the gas outlet of the chain grate machine are connected to the SCR unit 12 , the ozone oxidation unit 14 and the sulfur nitrate absorption unit 15 in sequence.

The method includes:

The flue gas produced by the roasting of pelletized material is first subjected to SNCR treatment, then enters the grate for heat exchange, and then undergoes SCR treatment, ozone oxidation treatment and sulfur nitrate absorption treatment in sequence to obtain purified flue gas.

The following are typical but non-limiting examples of the present invention:

Example 1:

This embodiment provides a pellet roasting flue gas denitration and desulfurization device based on a chain grate machine and a rotary kiln. The schematic structural diagram of the device is shown in FIG. 1 , including a reaction system and a flue gas treatment system. The reaction system includes The chain grate and the rotary kiln 5 are connected in sequence. The flue gas treatment system includes an SNCR unit 10, an SCR unit 12, an ozone oxidation unit 14 and a sulfur nitrate absorption unit 15. The flue gas outlet of the rotary kiln 5 passes through the SNCR unit 10. It is then connected to the gas inlet of the chain grate machine, and the gas outlet of the chain grate machine is connected to the SCR unit 12 , the ozone oxidation unit 14 and the sulfur nitrate absorption unit 15 in sequence.

The chain grate machine is divided into a first drying section 1, a second drying section 2, a first preheating section 3 and a second preheating section 4 in turn along the pellet feeding direction; the rotary kiln 5 is close to the chain grate machine. One end is provided with a pellet inlet and a flue gas outlet, and the other end is provided with a pellet outlet and a fuel inlet; the reaction system also includes a ring cooler, and the pellet outlet of the rotary kiln 5 is connected to the ring cooler, and the ring cooler The cooler includes a first cooling section 6 , a second cooling section 7 and a third cooling section 8 in sequence along the pellet conveying direction.

The flue gas outlet of the rotary kiln 5 is connected to the second preheating section 4 of the chain grate machine through the flue gas return line; the SNCR unit 10 is arranged on the top of the second preheating section 4 .

The gas outlet of the second preheating section 4 is connected to the gas inlet of the SCR unit 12, the gas outlet of the SCR unit 12 is connected to the gas inlet of the second drying section 2, and the gas outlet of the second drying section 2 is sequentially connected to ozone Oxidation unit 14 and sulfur nitrate absorption unit 15; the SCR unit 12 is an SCR reactor.

The ozone oxidation unit 14 includes an ozone generating device, and the outlet of the ozone generating device is connected to the flue gas pipeline; the sulfur nitrate absorption unit 15 includes a semi-dry desulfurization device, specifically a circulating fluidized bed.

The flue gas treatment system includes a dust removal unit, the dust removal unit includes a first dust collector 11 , a second dust collector 13 and a third dust collector 16 , and the first dust collector 11 is provided in the second preheating section 4 . Between the gas outlet and the SCR unit 12, a first fan is arranged behind the first dust collector 11, the second dust collector 13 is arranged between the gas outlet of the second drying section 2 and the ozone oxidation unit 14, the third The dust collector 16 is arranged after the sulfur nitrate absorption unit 15 .

The flue gas treatment system includes a chimney 18 , and the gas outlet of the third dust collector 16 is connected to the chimney 18 .

The first precipitator 11 is a cyclone precipitator, the second precipitator 13 is an electrostatic precipitator, and the third precipitator 16 is a bag filter.

The bottom of the ring cooler is connected with a cold air device 9, and the cold air device 9 feeds heat exchange medium to the ring cooler; the top outlet of the first cooling section 6 is connected to the fuel inlet of the rotary kiln 5, and the first cooling section 6 is connected to the fuel inlet of the rotary kiln 5. The top outlet of the second cooling section 7 is connected to the gas inlet of the first preheating section 3, the top outlet of the third cooling section 8 is connected to the gas inlet of the first drying section 1; the top outlet of the third cooling section 8 A fourth dust collector 17 is arranged on the pipeline between the gas inlet of the first drying section 1, and a second fan is arranged behind the fourth dust collector 17, and the fourth dust collector 17 is a cyclone dust collector.

The gas outlet of the first preheating section 3 is connected to the second dust collector 13 , and the gas outlet of the first drying section 1 is connected to the chimney 18 .

Example 2:

This embodiment provides a pellet roasting flue gas denitration and desulfurization device based on a chain grate-rotary kiln. The structure of the device refers to the structure in Embodiment 1, and the only difference is: the sulfur nitrate absorption unit 15 The semi-dry desulfurization device is a spray drying tower.

Example 3:

This embodiment provides a method for denitrification and desulfurization of flue gas from pellet roasting based on a chain grate-rotary kiln. The method is carried out using the device in Embodiment 1, and includes the following steps:

(1) The pelletized material is dried and preheated by the chain grate and then transported to the rotary kiln 5. The pelletized material and the gas fuel are in countercurrent contact and roasting. The concentration of NO _x in the roasting flue gas is 350 mg/Nm ³ , and the concentration of SO ₂ is 790mg/Nm ³ , the concentration of particulate matter is 100mg/Nm ³ , the flue gas is first subjected to SNCR treatment at a temperature of 1000°C, and ammonia gas is injected during the SNCR treatment process, and the molar ratio of the ammonia gas to the _NOx in the roasting flue gas is 1:1;

(2) The flue gas treated by SNCR enters the second preheating section 4 of the chain grate machine for heat exchange and cooling, preheating the pellet material, and after the flue gas leaves, cyclone dust removal is performed first, and then SCR treatment is performed at a temperature of 350 ℃. The catalyst used is V ₂ O ₅ -WO ₃ /TiO ₂ , and ammonia gas is injected during the SCR treatment process, and the molar ratio of the ammonia gas to the remaining _NOx in the roasting flue gas is 1.2:1, and the flue gas after the SCR treatment enters the The second drying section 2 of the chain grate machine dries the material and discharges it;

(3) Step (1) After the pelletized material is roasted, it is transported to the ring cooler for tertiary cooling, air is introduced into the ring cooler during the cooling process, and the heat exchange medium after primary cooling enters the rotary kiln 5 for use in In the roasting of pelletized materials, the heat exchange medium after secondary cooling enters the first preheating section 3 of the chain grate machine for preheating of pelletized materials, and then discharged. The heat exchange medium after secondary cooling is cyclone dusted Enter the first drying section 1 of the chain grate machine, used for drying the pellet material, and then emptied through the chimney 18;

(4) After mixing the outlet flue gas of the second drying section 2 in the step (2) with the heat exchange medium discharged from the first preheating section 3 in the step (3), carry out electrostatic dust removal first, and then spray ozone into the pipeline to carry out ozone Oxidation, the molar ratio of ozone and residual _NOx in flue gas is 1.5:1, and then semi-dry sulfur nitrate absorption treatment is carried out in a circulating fluidized bed, and finally it is emptied after bag dust removal.

In this embodiment, the concentration of NO _x in the purified flue gas is reduced to 10 mg/Nm ³ , the concentration of SO ₂ is reduced to 15 mg/Nm ³ , and the concentration of particulate matter is reduced to 6 mg/Nm ³ , thus realizing the efficient removal of flue gas pollutants .

Example 4:

This embodiment provides a method for denitrification and desulfurization of flue gas from pellet roasting based on a chain grate-rotary kiln. The method is carried out using the device in Embodiment 1, and includes the following steps:

(1) The pelletized material is dried and preheated by the chain grate and then sent to the rotary kiln 5. The pelletized material and the natural gas fuel are in countercurrent contact roasting. The concentration of NO _x in the roasting flue gas is 300 mg/Nm ³ , and the concentration of SO ₂ is 750mg/Nm ³ , the concentration of particulate matter is 60mg/Nm ³ , the flue gas is first subjected to SNCR treatment, the temperature is 900 ° C, and ammonia gas is injected during the SNCR treatment process, and the molar ratio of the ammonia gas to the NO _x in the roasting flue gas is 0.8:1;

(2) The flue gas treated by SNCR enters the second preheating section 4 of the chain grate machine for heat exchange and cooling, preheating the pellet material, and after the flue gas leaves, cyclone dust removal is performed first, and then SCR treatment is performed at a temperature of 400 ℃. The catalyst used is V ₂ O ₅ -MoO ₃ /TiO ₂ , and ammonia gas is injected during the SCR treatment process, and the molar ratio of the ammonia gas to the remaining _NOx in the roasting flue gas is 1:1, and the flue gas after the SCR treatment enters the The second drying section 2 of the chain grate machine dries the material and discharges it;

(3) Step (1) After the pelletized material is roasted, it is transported to the ring cooler for tertiary cooling, air is introduced into the ring cooler during the cooling process, and the heat exchange medium after primary cooling enters the rotary kiln 5 for use in In the roasting of pelletized materials, the heat exchange medium after secondary cooling enters the first preheating section 3 of the chain grate machine for preheating of pelletized materials, and then discharged. The heat exchange medium after secondary cooling is cyclone dusted Enter the first drying section 1 of the chain grate machine, used for drying the pellet material, and then emptied through the chimney 18;

(4) After mixing the outlet flue gas of the second drying section 2 in the step (2) with the heat exchange medium discharged from the first preheating section 3 in the step (3), carry out electrostatic dust removal first, and then spray ozone into the pipeline to carry out ozone Oxidation, the molar ratio of ozone and residual _NOx in flue gas is 1.3:1, and then semi-dry sulfur nitrate absorption treatment is carried out in a circulating fluidized bed, and finally it is emptied after bag dust removal.

In this embodiment, the concentration of NO _x in the purified flue gas is reduced to 13 mg/Nm ³ , the concentration of SO ₂ is reduced to 17 mg/Nm ³ , and the concentration of particulate matter is reduced to 8 mg/Nm ³ , which realizes the efficient removal of flue gas pollutants .

Example 5:

The present embodiment provides a method for denitrification and desulfurization of flue gas from pellet roasting based on a chain grate machine-rotary kiln. The method is carried out using the device in Embodiment 2, and includes the following steps:

(1) The pelletized material is dried and preheated by the chain grate and then transported to the rotary kiln 5. The pelletized material and the fuel coal are in countercurrent contact roasting. The concentration of NO _x in the roasting flue gas is 400 mg/Nm ³ and the concentration of SO ₂ is 850mg/Nm ³ , the concentration of particulate matter is 130mg/Nm ³ , the flue gas is first subjected to SNCR treatment at a temperature of 800°C, and ammonia gas is injected during the SNCR treatment process. The molar ratio of the ammonia gas to the nitrogen oxides in the roasting flue gas is 0.6:1;

(2) The flue gas treated by SNCR enters the second preheating section 4 of the chain grate machine for heat exchange and cooling, preheating the pellet material, and after the flue gas leaves, cyclone dust removal is performed first, and then SCR treatment is performed at a temperature of 300 ℃. The catalyst used is V ₂ O ₅ -WO ₃ /TiO ₂ , ammonia gas is injected during the SCR treatment process, and the molar ratio of the ammonia gas to the remaining _NOx in the roasting flue gas is 0.8:1, and the flue gas after the SCR treatment enters the The second drying section 2 of the chain grate machine dries the material and discharges it;

(3) Step (1) After the pelletized material is roasted, it is transported to the ring cooler for tertiary cooling, air is introduced into the ring cooler during the cooling process, and the heat exchange medium after primary cooling enters the rotary kiln 5 for use in In the roasting of pelletized materials, the heat exchange medium after secondary cooling enters the first preheating section 3 of the chain grate machine for preheating of pelletized materials, and then discharged. The heat exchange medium after secondary cooling is cyclone dusted Enter the first drying section 1 of the chain grate machine, used for drying the pellet material, and then emptied through the chimney 18;

(4) After mixing the outlet flue gas of the second drying section 2 in the step (2) with the heat exchange medium discharged from the first preheating section 3 in the step (3), carry out electrostatic dust removal first, and then spray ozone into the pipeline to carry out ozone Oxidation and denitrification, the molar ratio of ozone and residual _NOx in the flue gas is 0.9:1, and then the rotary spray drying method is used to absorb the sulfur and nitrate, and finally the bag is dedusted and then emptied.

In this embodiment, the concentration of NO _x in the purified flue gas is reduced to 16 mg/Nm ³ , the concentration of SO ₂ is reduced to 19 mg/Nm ³ , and the concentration of particulate matter is reduced to 9 mg/Nm ³ , which realizes the efficient removal of flue gas pollutants .

It can be seen from the above-mentioned embodiments that the device of the present invention combines the pellet production system with the flue gas treatment system, and utilizes the temperature and composition characteristics of the roasting flue gas as well as the heat exchange with the chain grate machine to perform denitration and desulfurization treatments in turn. , improve the removal efficiency of flue gas pollutants, the NO _x concentration in the purified flue gas is reduced to below 16mg/Nm ³ , the SO ₂ concentration is below 20mg/Nm ³ , and the particulate matter concentration is below 10mg/Nm ³ ; The device utilizes the temperature characteristics of different regions of the grate and the heat exchange of flue gas in different stages, so as to improve the utilization efficiency of heat and reduce energy consumption and operating costs.

The applicant declares that the present invention illustrates the detailed apparatus and method of the present invention through the above-mentioned embodiments, but the present invention is not limited to the above-mentioned detailed apparatus and method, which does not mean that the present invention must rely on the above-mentioned detailed apparatus and method to be implemented. Those skilled in the art should understand that any improvement to the present invention, the equivalent replacement of the device of the present invention, the addition of auxiliary devices, the selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims (10)

1. a pellet roasting flue gas denitration and desulfurization device based on chain grate-rotary kiln, is characterized in that, described device comprises reaction system and flue gas treatment system, and described reaction system comprises chain grate and rotary kiln connected successively kiln, the flue gas treatment system includes an SNCR unit, an SCR unit, an ozone oxidation unit and a sulfur nitrate absorption unit, and the flue gas outlet of the rotary kiln is connected to the gas inlet of the chain grate after passing through the SNCR unit, and the chain grate The gas outlet is connected to the SCR unit, the ozone oxidation unit and the sulfur nitrate absorption unit in sequence. 2. The device according to claim 1, wherein the grate machine is divided into a first drying section, a second drying section, a first preheating section and a second preheating section in turn along the pellet feeding direction ; Preferably, one end of the rotary kiln close to the chain grate is provided with a pellet inlet and a flue gas outlet, and the other end is provided with a pellet outlet and a fuel inlet; Preferably, the reaction system further comprises a ring cooler, and the pellet outlet of the rotary kiln is connected to the ring cooler; Preferably, the ring cooler includes a first cooling section, a second cooling section and a third cooling section in sequence along the pellet conveying direction. 3. The device according to claim 2, wherein the flue gas outlet of the rotary kiln is connected to the second preheating section of the chain grate through a flue gas return line; Preferably, the SNCR unit is arranged at the top of the second preheating section; Preferably, the gas outlet of the second preheating section is connected to the gas inlet of the SCR unit, the gas outlet of the SCR unit is connected to the gas inlet of the second drying section, and the gas outlet of the second drying section is sequentially connected to the ozone oxidation unit and the sulfur Nitrate absorption unit; Preferably, the SCR unit includes an SCR reactor; Preferably, the ozone oxidation unit includes an ozone generating device, and the outlet of the ozone generating device is connected to the flue gas pipeline; Preferably, the sulfur nitrate absorption unit includes a semi-dry desulfurization device. 4. The device according to any one of claims 1-3, wherein the flue gas treatment system comprises a dust removal unit, and the dust removal unit comprises at least one stage dust collector; Preferably, the dedusting unit includes a first dedusting device, a second dedusting device and a third dedusting device, the first dedusting device is arranged between the gas outlet of the second preheating section and the SCR unit, and the second dedusting device The filter is arranged between the gas outlet of the second drying section and the ozone oxidation unit, and the third dust collector is arranged after the sulfur nitrate absorption unit; Preferably, the flue gas treatment system includes a chimney, and the gas outlet of the third dust collector is connected to the chimney; Preferably, the first dust collector comprises a cyclone dust collector; Preferably, the second precipitator comprises an electrostatic precipitator; Preferably, the third dust collector comprises a bag filter. 5. The device according to any one of claims 2-4, characterized in that, a cold air device is connected to the bottom of the ring cooler, and the cold air device feeds a heat exchange medium to the ring cooler; Preferably, the top outlets of the different cooling sections of the annular cooler are independently connected to the grate or the rotary kiln; Preferably, the top outlet of the first cooling section is connected to the fuel inlet of the rotary kiln, the top outlet of the second cooling section is connected to the gas inlet of the first preheating section, and the top outlet of the third cooling section is connected to the gas inlet of the first preheating section. The gas inlets of the first drying section are connected; Preferably, a fourth dust collector is provided on the pipeline between the top outlet of the third cooling section and the gas inlet of the first drying section; Preferably, the fourth dust collector includes a cyclone dust collector; Preferably, the gas outlet of the first preheating section is connected to the second dust collector, and the gas outlet of the first drying section is connected to the chimney. 6. A method for carrying out denitration and desulfurization of flue gas from pellet roasting using the device according to any one of claims 1-5, wherein the method comprises: The flue gas produced by the roasting of pelletized material is first subjected to SNCR treatment, then enters the grate for heat exchange, and then undergoes SCR treatment, ozone oxidation treatment and sulfur nitrate absorption treatment in sequence to obtain purified flue gas. 7. The method according to claim 6, wherein the pelletized material is dried and preheated by a chain grate machine, and then enters a rotary kiln for roasting; Preferably, the fuel used in the roasting comprises any one or a combination of at least two of natural gas, coal gas, heavy oil or coal, preferably coal gas; Preferably, the concentration of NO _x in the roasting flue gas is 300-400 mg/Nm ³ , the concentration of SO ₂ is 750-900 mg/Nm ³ , and the concentration of particulate matter is 50-130 mg/Nm ³ ; Preferably, the temperature at which the flue gas is subjected to SNCR treatment is 800-1100°C; Preferably, ammonia gas is injected into the flue gas during the SNCR treatment; Preferably, the molar ratio of the ammonia gas to the _NOx in the roasting flue gas is (0.5-1.0):1. 8. The method according to claim 6 or 7, characterized in that, after the roasting flue gas is processed by SNCR, it enters the second preheating section of the grate for heat exchange and cooling; Preferably, the temperature of the SCR treatment is 300-400°C; Preferably, the catalyst used in the SCR treatment comprises a vanadium-tungsten-titanium-based catalyst or a vanadium-molybdenum-titanium-based catalyst; Preferably, ammonia gas is injected into the flue gas during the SCR treatment; Preferably, the molar ratio of the ammonia gas to the remaining _NOx in the roasting flue gas is (0.8-1.2):1; Preferably, the SCR-treated flue gas passes through the second drying section of the grate machine to dry the pelletized material. 9. The method according to any one of claims 6-8, wherein, during the ozone oxidation treatment, ozone is introduced into the flue gas; Preferably, the molar ratio of the ozone to the remaining _NOx in the roasting flue gas is (0.8-1.5):1; Preferably, the sulfur and nitrate absorption treatment adopts semi-dry desulfurization and denitrification; Preferably, the semi-dry method includes any one of a circulating fluidized bed method, a rotary spray drying method or a dense phase coherent tower method; Preferably, the flue gas is dedusted before the SCR treatment, before the ozone oxidation treatment and after the sulfur nitrate absorption treatment. 10. The method according to any one of claims 6-9, wherein after the pellet material is roasted, three-stage cooling is performed in a ring cooler; Preferably, a heat exchange medium is introduced into the ring cooler during the cooling process; Preferably, the heat exchange medium comprises air; Preferably, the heat exchange medium after primary cooling enters the rotary kiln for roasting the pellet material; Preferably, the heat exchange medium after secondary cooling enters the first preheating section of the grate machine for preheating the pellet material, and then mixes with the outlet flue gas of the second drying section; Preferably, the heat exchange medium after tertiary cooling enters the first drying section of the chain grate for drying the pelletized material; Preferably, the heat exchange medium after tertiary cooling is subjected to dedusting treatment before entering the first drying section.

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