Coke oven flue gas desulfurization and denitrification purification device

Abstract

The utility model discloses a coke oven flue gas desulfurization and denitrification purification device which comprises a coke oven, a cold air valve, a desulfurizer supply mechanism, a desulfurization reaction tower, a heating furnace, a bag-type dust collector, a denitrification reaction tower, an induced draft fan and a chimney which are sequentially connected through a flue, a cold air supply pipe communicated with the coke oven and the desulfurization reaction tower is arranged on the flue between the coke oven and the desulfurization reaction tower, a cold air valve is arranged on the cold air supply pipe, and the desulfurizing agent supply mechanism is communicated with the flue between the cold air supply pipe and the desulfurization reaction tower. And the heating furnace is communicated with the flue between the desulfurization reaction tower and the bag-type dust collector and is used for heating the mixed denitration flue gas. Compared with the prior art, the desulfurization agent consumption can be reduced under the same desulfurization efficiency, the regeneration frequency of a low-temperature catalyst is reduced, the service life of the catalyst is prolonged, and ammonia escape is controlled.

Description

[Technical field]

[0001] The utility model relates to the technical field of flue gas desulfurization and denitrification, and in particular to a flue gas purification system of dry desulfurization + low-temperature denitrification. [Background technology]

[0002] Currently, the coking industry is carrying out large-scale ultra-low emission transformation across the country.

[0003] According to the latest draft of the "Emission Standard of Air Pollutants for Coking Chemical Industry" GB 16171, the hourly average concentration of coke oven flue gas pollutants must meet the following requirements:

[0004] SO2 emission concentration at flue gas outlet ≤30mg / Nm 3 ;

[0005] NOx emission concentration at flue gas outlet ≤150mg / Nm 3 ;

[0006] Dust emission concentration at flue gas outlet ≤10mg / Nm 3 ;

[0007] Ammonia escape ≤8mg / Nm 3 .

[0008] The parameters of coke oven flue gas vary greatly. There are many factors that affect coke oven flue gas, including coke oven production process, furnace type, heating fuel type, coke oven operation system, organic sulfur content of coking raw coal, coke oven leakage, etc. X , NOx, mercury, dioxins and other pollutants. It has the characteristics of low sulfur and high nitrogen oxides. According to different fuel proportions and characteristics, SO2 is generally between 80 and 300 mg / Nm 3 , up to 600mg / Nm 3 , and the NO content is 600mg / Nm 3 ~1200mg / Nm 3 Another characteristic is that the temperature of coke oven flue gas is relatively high, generally in the range of 180℃~300℃, and mostly in the range of 180℃~250℃.

[0009] At present, the mainstream ultra-low emission of coke oven flue gas generally adopts SDA rotary spray desulfurization + bag filter + low-temperature SCR denitrification, or SDS dry desulfurization + bag filter + low-temperature SCR denitrification process. The integrated denitrification and dust removal of ceramic cartridges and catalytic filter bag denitrification and dust removal processes applied to coke oven flue gas are essentially also in the category of low-temperature SCR denitrification.

[0010] Since the temperature of coke oven flue gas is relatively high, mostly between 180℃ and 250℃, but the SO2 concentration is relatively low, the SDS dry method or SDA semi-dry method desulfurization process can basically meet the outlet SO2≤30mg / Nm 3 emission standards.

[0011] As mentioned above, the SO2 concentration in coke oven flue gas is relatively low, generally between 60 and 300 mg / Nm 3 However, it varies with the coke oven type, production process, fuel type, etc., and can reach as high as 600 mg / Nm 3 . With the implementation of ultra-low emission of NOx in coke oven flue gas, the use of SDS dry desulfurization has gradually become a more mainstream process. This is because the SDS dry method only requires the spraying of desulfurizers into the flue gas, so the flue gas basically does not cool down, while SDA and other semi-dry or wet desulfurization require water spraying for cooling, which will result in a lower flue gas temperature after desulfurization. Denitrification requires a higher temperature increase, resulting in a complex configuration of the subsequent denitrification system and higher energy consumption. The use of SDA semi-dry process in new projects is gradually decreasing.

[0012] The core of SCR flue gas denitrification technology is the catalyst. The ideal temperature of conventional medium and high temperature catalysts is 300℃~420℃. If it is used in coke oven flue gas denitrification, it is necessary to configure a rotary flue gas heat exchanger or a plate heat exchanger, and set a heating furnace heating device behind the heat exchanger. For example, the Chinese patent document with patent publication number CN104923046A discloses an integrated method for coke oven flue gas desulfurization, denitrification and waste heat recovery. The flue gas from the coke oven first enters the rotary flue gas heat exchanger, then is heated to 300~420℃ by the heating furnace, and then enters the SCR denitrification device. Due to the large investment in this process, the complex system and the high fuel consumption, there are basically no actual engineering cases in operation.

[0013] Therefore, low-temperature SCR denitrification is generally used for coke oven flue gas denitrification.

[0014] Low-temperature SCR catalysts generally require a suitable flue gas temperature in the range of 200℃~250℃, at which time the catalyst will have a higher denitration efficiency and a longer service life, and can also ensure lower ammonia escape to avoid the problem of catalyst blockage caused by the formation of ammonium bisulfate. Since a large amount of desulfurizer needs to be added during the desulfurization of coke oven flue gas, a bag filter is required after desulfurization. This is to ensure that the outlet dust emission is less than 10mg / Nm 3On the other hand, the desulfurizer still has a good desulfurization effect on the surface of the filter bag to ensure that SO2 meets the emission standards. However, due to the air leakage of the bag filter body and the insulation effect of the shell, according to actual engineering experience, the temperature drop at the inlet and outlet of the bag is generally in the range of 10℃ to 20℃, which leads to a low flue gas temperature entering the subsequent SCR denitrification device, and even some projects will be lower than 160℃. At this time, the sprayed ammonia directly enters the surface of the low-temperature SCR catalyst. Since the temperature is not within the catalyst activity range, it is difficult to ensure the denitrification efficiency even if a large amount of ammonia is sprayed, and the ammonia consumption is greatly increased, resulting in a sharp increase in ammonia escape, causing the catalyst to be quickly blocked; so in general, we need to heat the coke oven flue gas to make its temperature reach above 200℃, which is more suitable for the temperature range of low-temperature catalyst operation, so the flue gas heating furnace heating device is an indispensable equipment in the coke oven denitrification process.

[0015] A Chinese patent document with the authorization announcement number CN 214809764 U discloses a coke oven flue gas desulfurization and denitrification device, which uses a catalytic method for desulfurization, and is provided with a set of rotary flue gas heat exchangers and flue burners, i.e., a heating furnace heating device, after desulfurization, to first perform gas-to-gas heat exchange and then use a burner to heat and heat the coke oven flue gas to raise the temperature to about 230°C, and then perform low-temperature denitrification; although this process can also improve the efficiency and life of the catalyst and appropriately reduce the flue gas outlet temperature, the equipment investment is too large, the system is complex and the operating power is high, so there are basically no actual engineering cases.

[0016] For example, the Chinese patent document with authorization announcement number CN 218871732 U discloses a low-temperature coke oven flue gas desulfurization, denitrification and waste heat utilization system, in which the burner, i.e., the heating furnace heating device, is arranged after the bag filter. After desulfurization and dust removal, the flue gas is heated to the 200°C to 240°C range, and then SCR low-temperature denitrification is performed.

[0017] For example, Chinese patent document No. CN 216726598 U discloses a system for collaboratively removing CO and other pollutants from coke oven flue gas. Similarly, the hot blast furnace is arranged after the bag filter. After dust removal, the flue gas is heated and then subjected to SCR denitrification and CO removal reactions.

[0018] In addition, as the Chinese patent document with authorization announcement number CN 215693077 U discloses a comprehensive purification system for coke oven flue gas using SDA semi-dry desulfurization, and the Chinese patent document with authorization announcement number CN 215782635 U discloses a comprehensive purification system for coke oven flue gas using SDS dry desulfurization. Both processes use ceramic catalytic filter tube bags for denitrification, but neither of the two patents involves a flue gas heating device, so it is unclear what temperature range the ceramic catalytic filter tube bags of the patent recommend for efficient denitrification. However, at present, when the flue gas temperature is less than 180°C, there are also problems such as low denitrification efficiency and large ammonia escape, and the influence of ammonium bisulfate on the ceramic catalytic filter tube bags also exists.

[0019] Based on the above cases, low-temperature SCR denitrification technology has the following main defects:

[0020] When a coke oven uses coal gas for coking, the SO2 produced varies with the type of coke oven, production process, fuel type, etc. Generally, the SO2 in the flue gas from the coke oven will reach 80-300 mg / Nm 3 , the highest even reaches 600mg / Nm 3 When the flue gas passes through the bag filter, due to the large temperature drop, if the coke oven flue gas temperature is originally low, the bag outlet flue gas temperature will be as low as 160℃~180℃. At this time, according to the above denitrification process, the flue gas must be heated. The burner or heating furnace heating device described in the above patent is used to heat the flue gas after the bag filter. The fuel can be one or more combinations of blast furnace gas, coke oven gas, and converter gas. The general temperature increase range is 30℃~50℃. It is assumed that the temperature increase range is conservatively considered to be 30℃, and the SO2 concentration in the high-temperature flue gas discharged into the flue after the heating furnace is heated is 200~300mg / Nm 3 Considering this, the SO2 concentration in the entire flue gas will increase to 3-5 mg / Nm 3 Therefore, in order to meet the SO2 emission standards, the SO2 concentration before the bag filter must be controlled to ≤25mg / Nm 3 Even lower, so it is necessary to greatly improve the desulfurization efficiency of the previous one, thereby increasing the consumption of desulfurizer in the whole system. Of course, when the SO2 concentration in the flue gas at the outlet of the heating furnace reaches 600mg / Nm 3 If so, the impact will be greater.

[0021] In addition, due to the increase in the temperature of coke oven flue gas, the SO2 concentration in the flue gas will increase by 3 to 5 mg / Nm 3 At the same time, the concentration of particulate matter in the flue gas will also increase, resulting in a greatly increased rate of generating ammonium bisulfate, which will increase the frequency of regeneration of the low-temperature catalyst, shorten its life, and greatly increase the operating cost. [Contents of the utility model]

[0022] The purpose of the utility model is to solve the problems in the prior art and to propose a coke oven flue gas desulfurization and denitrification purification device, which can reduce the desulfurization agent consumption at the same desulfurization efficiency, reduce the regeneration frequency of the low-temperature catalyst, increase the catalyst life, and control ammonia escape.

[0023] To achieve the above-mentioned purpose, the utility model proposes a coke oven flue gas desulfurization and denitrification purification device, comprising a coke oven, a cold air valve, a desulfurizer supply mechanism, a desulfurization reaction tower, a heating furnace, a bag dust collector, a denitrification reaction tower, an induced draft fan and a chimney, wherein the coke oven, the desulfurization reaction tower, the bag dust collector, the denitrification reaction tower, the induced draft fan and the chimney are connected in sequence through a flue, a cold air supply pipe connected to the flue between the coke oven and the desulfurization reaction tower is provided, a cold air supply pipe is provided on the cold air supply pipe, a cold air valve is provided on the cold air supply pipe, the desulfurizer supply mechanism is connected to the flue between the cold air supply pipe and the desulfurization reaction tower, the flue between the heating furnace and the desulfurization reaction tower and the bag dust collector is connected to heat the mixed denitrification flue gas, and the flue between the bag dust collector and the denitrification reaction tower is connected to the denitrification reducing agent supply pipe.

[0024] Preferably, the desulfurizer supply mechanism includes a desulfurizer silo, a desulfurizer preparation system and a conveying fan which are connected in sequence. The desulfurizer preparation system grinds or digests the desulfurizer, and uses the compressed air generated by the conveying fan as power to deliver the ground or digested desulfurizer into the flue at the entrance of the desulfurization reaction tower.

[0025] Preferably, a catalytic reaction layer is provided in the denitration reaction tower.

[0026] Preferably, the catalytic reaction layer uses a low-temperature catalyst at 180°C to 250°C.

[0027] Beneficial effects of the utility model: the utility model reduces the desulfurization agent consumption under the same desulfurization efficiency by changing the position of the heating furnace, reduces the regeneration frequency of the low-temperature catalyst, increases the catalyst life, and controls ammonia slip; and the process configuration is simple, and there is no need to set up a flue gas heat exchanger, saving investment costs and operating costs. Compared with the prior art, the utility model can reduce the desulfurization agent consumption under the same desulfurization efficiency, reduce the regeneration frequency of the low-temperature catalyst, increase the catalyst life, and control ammonia slip.

[0028] The features and advantages of the present invention will be described in detail through embodiments in conjunction with the accompanying drawings.

Brief Description of the Drawings

[0029] Figure 1 The utility model is a structural schematic diagram of a coke oven flue gas desulfurization and denitrification purification device.

[0030] In the figure: 1-coke oven, 2-cold air valve, 3-desulfurizer supply mechanism, 4-desulfurization reaction tower, 5-heating furnace, 6-bag dust collector, 7-denitrification reaction tower, 8-induced draft fan, 9-chimney, 10-flue, 11-cold air supply pipe, 12-denitrification reducing agent supply pipe, 13-catalytic reaction layer, 31-desulfurizer silo, 32-desulfurizer preparation system, 33-conveying fan. [Specific implementation method]

[0031] See also Figure 1 The utility model discloses a coke oven flue gas desulfurization and denitration purification device, comprising a coke oven 1, a cold air valve 2, a desulfurizer supply mechanism 3, a desulfurization reaction tower 4, a heating furnace 5, a bag dust collector 6, a denitration reaction tower 7, an induced draft fan 8 and a chimney 9, wherein the coke oven 1, the desulfurization reaction tower 4, the bag dust collector 6, the denitration reaction tower 7, the induced draft fan 8 and the chimney 9 are sequentially connected through a flue 10, a cold air supply pipe 11 connected thereto is provided on the flue 10 between the coke oven 1 and the desulfurization reaction tower 4, a cold air valve 2 is provided on the cold air supply pipe 11, the desulfurizer supply mechanism 3 is connected to the flue 10 between the cold air supply pipe 11 and the desulfurization reaction tower 4, the heating furnace 5 is connected to the desulfurization reaction tower 4 and the bag dust collector 6 is connected to heat the mixed denitrification flue gas, the flue 10 between the bag filter 6 and the denitrification reaction tower 7 is connected to the denitrification reducing agent supply pipe 12, the desulfurization agent supply mechanism 3 includes a desulfurization agent silo 31, a desulfurization agent preparation system 32 and a conveying fan 33 which are connected in sequence, the desulfurization agent preparation system 32 grinds or digests the desulfurization agent, and uses the compressed air generated by the conveying fan 33 as power to send the ground or digested desulfurization agent into the flue 10 at the entrance of the desulfurization reaction tower 4, and a catalytic reaction layer 13 is provided in the denitrification reaction tower 7, and the catalytic reaction layer 13 adopts a low-temperature catalyst of 180°C to 250°C.

[0032] A process for using the above-mentioned coke oven flue gas desulfurization and denitrification purification device comprises the following steps: when the original flue gas comes out of the coke oven 1 and the temperature is higher than 250°C, the cold air valve 2 is opened, otherwise it is not opened, the flue gas is cooled by mixing with the cold air output by the cold air supply pipe 11, the desulfurizer output by the desulfurizer supply mechanism 3 is mixed with the cooled flue gas, in the desulfurization reaction tower 4, the desulfurizer reacts chemically with SO2 in the flue gas to achieve the purpose of removing SO2, the flue gas after desulfurization enters the bag filter 6, and continues to undergo desulfurization reaction on the surface of the filter bag, the desulfurization final product is removed and sent to the ash storage for subsequent treatment, when the flue gas temperature is low and the flue gas temperature at the inlet of the denitrification reaction tower 7 is less than 200°C, the heating furnace 5 is started to make the mixed flue gas temperature at the inlet of the bag filter between 220°C and 250°C, and then the flue gas enters the denitrification reaction tower after dust removal, and denitrification reaction occurs on the surface of the catalytic reaction layer 13, and the clean flue gas after denitrification is discharged into the atmosphere through the induced draft fan 8 and the chimney 9.

[0033] The desulfurization process adopts the SDS dry method, and the desulfurization agent is baking soda or a highly active calcium-based absorbent.

[0034] The reducing agent sprayed out of the denitration reducing agent supply pipe 12 is ammonia water or urea solution, which is sprayed out after being converted into ammonia gas through solution evaporation, urea hydrolysis or pyrolysis process.

[0035] Since the temperature resistance of current high-temperature filter materials, including chemical fiber filter materials and inorganic filter materials, is generally not greater than 250°C, and the price of metal fiber filter bags or ceramic filter cartridges is much higher than the above filter materials, materials that can withstand a temperature of 250°C and are resistant to acid and alkali are generally selected in coke oven flue gas denitrification, and a cold air valve 2 is set to ensure that the filter bag is not burned by high temperature under abnormal working conditions.

[0036] At the same time, in order to avoid the cold air valve 2 opening too wide, causing excessive temperature drop and affecting the denitrification efficiency, the cold air valve 2 needs to be equipped with a cooling air volume adjustment device, and the temperature of the cooled flue gas is detected by a temperature sensor to ensure that the temperature of the mixed flue gas before the bag dust collector after the cold air is added is in the range of 220-250℃.

[0037] When the flue gas temperature at the outlet of the coke oven 1 is too low, the flue gas temperature cannot meet the high-efficiency reaction of the low-temperature catalyst. At this time, the heating furnace 5 needs to be started to make the flue gas temperature at the inlet of the reaction tower denitration above 200 degrees to ensure that nitrogen oxides are efficiently removed. As mentioned above, assuming that the heating furnace 5 is arranged after the bag filter 6, the SO2 generated by the combustion of coal gas in the heating furnace 5 cannot be effectively removed, so this patent requires that the heating furnace 5 be arranged before the bag filter 6.

[0038] Due to the complex composition and high temperature of the coke oven flue gas, the coke oven flue gas contains pollutants such as dust, SO, NOx, mercury, dioxins, etc. Although the sulfur content is not high, the nitrogen oxides can even reach 1000-1200 mg / Nm 3 Therefore, the filter material of bag filter 6 is required to not only withstand a temperature of 250°C, but also have good acid and alkali resistance.

[0039] In addition, the reducing agent is ammonia water or urea solution, which is made into ammonia gas through solution evaporation, urea hydrolysis or pyrolysis process and then sprayed into the flue 10 at the outlet of the bag filter 6. Considering that the flue gas temperature at the inlet of the denitrification reaction tower is controlled in the range of 200-240°C, the low-temperature catalyst of this process uses a low-temperature catalyst of 180°C-250°C.

[0040] The above embodiments are intended to illustrate the present invention, not to limit the present invention. Any solution that is a simple transformation of the present invention falls within the protection scope of the present invention.

Claims

1. A coke oven flue gas desulfurization and denitrification purification device, characterized in that: The invention comprises a coke oven (1), a cold air valve (2), a desulfurizing agent supply mechanism (3), a desulfurizing reaction tower (4), a heating furnace (5), a bag filter (6), a denitrifying reaction tower (7), an induced draft fan (8) and a chimney (9), wherein the coke oven (1), the desulfurizing reaction tower (4), the bag filter (6), the denitrifying reaction tower (7), the induced draft fan (8) and the chimney (9) are sequentially connected via a flue (10), and a cold air valve (2) is provided on the flue (10) between the coke oven (1) and the desulfurizing reaction tower (4) and connected thereto. The cold air supply pipe (11) is provided with a cold air valve (2); the desulfurizing agent supply mechanism (3) is connected to the cold air supply pipe (11) and the flue (10) between the desulfurizing reaction tower (4); the heating furnace (5) is connected to the flue (10) between the desulfurizing reaction tower (4) and the bag filter (6) for heating the mixed denitrified flue gas; the flue (10) between the bag filter (6) and the denitrification reaction tower (7) is connected to the denitrification reducing agent supply pipe (12).

2. A coke oven flue gas desulfurization and denitrification purification device as claimed in claim 1, characterized in that: The desulfurizing agent supply mechanism (3) comprises a desulfurizing agent silo (31), a desulfurizing agent preparation system (32) and a conveying fan (33) which are connected in sequence. The desulfurizing agent preparation system (32) grinds or digests the desulfurizing agent, and uses the compressed air generated by the conveying fan (33) as power to deliver the ground or digested desulfurizing agent into the flue (10) at the entrance of the desulfurization reaction tower (4).

3. A coke oven flue gas desulfurization and denitrification purification device as claimed in claim 1, characterized in that: A catalytic reaction layer (13) is provided in the denitration reaction tower (7).

4. A coke oven flue gas desulfurization and denitrification purification device as claimed in claim 3, characterized in that: The catalytic reaction layer (13) uses a low-temperature catalyst at 180°C to 250°C.

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