Coke oven gas enters dry desulfurization system first

2017-8-9 16:18:49

The flue gas of coke oven enters the dry desulfurization system firstly, then uses desulfurization agent to remove SO2, then enters the denitration system, and the NOx is removed under the action of reducing agent NH3, and the temperature drop of the flue gas of the coke oven is very low during the process of desulfurization and denitrification. After purification, the flue gas is recovered by the waste heat boiler, and finally sent back to the original chimney by the draft fan.

1.2 engineering application

This technique has been successfully applied to the Inner Mongolia Coking Co. Ltd., the company has four coke ovens, a coke production capacity of 600 thousand tons / year, per share two coke ovens in a chimney, a chimney flue gas emissions 250000Nm /h SO2 containing the fand, content in the flue gas from 250mg/Nm NOx concentration 1000mg/Nm fand fand.

Each chimney built a set of desulfurization and denitration waste heat recovery integration device, respectively, built in June 2016 and August, and a successful test, has been running smoothly for more than half a year. 30mg/Nm fand SO2 concentration was less than the flue gas after the treatment, the concentration of NOx is less than 150mg/Nm not only in Wuhai to fand, the requirements of environmental protection, but also reached GB16171-2012 "coke chemical industry pollutant emission standards" in Table 6 special area requirements, and each hour of by-product 12t0.6MPa saturated steam pressure.

1.3 technical features

1) desulfurization denitrification, finally recovery waste heat of the flue gas desulfurization, SO2 content is lower, is conducive to reducing the denitration catalyst filling quantity, prolong the life of catalyst; desulfurization products belong to conventional solid waste treatment is simple, also can realize resource utilization.

2) by dry desulfurization for the first time in the practical application, the temperature drop is very small, far less than the semi dry desulfurization and wet desulphurization, and the whole set of the device in addition to the heat without temperature drop, can ensure the denitration and temperature of flue gas waste heat recovery is conducive to the final;

3) using moving bed desulfurization process, and developed a special desulfurizer, high desulfurization efficiency, pressure reduction;

4) moving bed dry desulfurization has high efficiency dust removal function, which can greatly reduce dust content in flue gas, meet the requirements of the national standard, and do not need to set up dust removal device;

5) the flue gas in the waste heat boiler has been purified, which reduces the corrosion of the boiler to the greatest extent and prolongs the service life of the boiler;

6) by low temperature denitration, using imported porous efficient low-temperature denitration catalyst denitration efficiency, the same loading amount is about 2 times the average denitration catalyst, denitration catalyst filling quantity; the service life of up to 3-4 years. The ammonia injection system was designed by CFD simulation to maximize the catalyst effectiveness and reduce ammonia escape;

7) after the waste heat recovery, the exhaust gas temperature is high, the flue gas treatment back to the original chimney, so that the original chimney is always in the hot standby state, but also avoid a large number of white smoke emission at low altitude;

8) set the underground original flue gate gate power off self opening system, which can ensure the safety of the coke oven under special working conditions;

9) the whole device only desulfurization tower, denitration reactor, boiler three sets of main equipment, equipment number, flexible arrangement, to minimize the area and cost of investment, so that whether the new integrated device or in the original heat recovery under the condition of the expansion of desulfurization and denitrification are feasible.

2 low temperature organic catalytic desulfurization, denitrification and dust removal integrated technology

2.1 process flow

The flue gas through the flue into the reaction tower, flue gas and slurry circulation reverse contact catalyst capture reaction product and form a stable complex in the gas oxygen (>4%) under the action of sulfoxide catalyst complexes with oxygen to form sulfuric acid, nitric acid and sulfoxide catalyst, reaction of nitric acid and ammonia sulfate, ammonium sulfate, ammonium nitrate production. Sulfoxide catalyst to complete a cycle. After the flue gas desulfurization and denitrification into the high efficiency dust removal mist eliminator, the trapped droplets into a multi-stage cyclone set in a barrel, desulfurization and denitrification flue gas straight row.

2.2 engineering application

At the end of 2016, the technology was applied to the desulfurization and denitrification project of coke oven gas in a coking plant in Shanxi. The coke oven gas flow is 320000Nm /h SO2 100mg/Nm fand, the content of NOx was 800mg/Nm fand, fand, temperature is about 160, 12% of oxygen content in flue gas. Design requirements to meet the GB16171-2012 "coking chemical industry pollutant discharge standard" Table 5 in the index requirements. The coke oven flue gas desulfurization and denitration project has been formally operated in June 2017.

2.3 technical features

1) the desulfurization, denitration and two dust removal are realized in one tower at the same time. The area is small, the construction investment is saved, and the operation cost is low.

2) desulfurization denitration efficiency, desulfurization rate can reach above 99%, the denitrification rate can reach more than 85%, can reach GB16171-2012 "coke chemical industry pollutant emission standards" in Table 5 of the requirements, can even reach the requirements in Table 6 special area.

3) produced by ammonium sulfate and ammonium nitrate fertilizer directly into coking plant existing ammonium sulfate system, so no two pollution, no waste water discharge, also can bring certain economic benefits.

4) do not need high temperature section, more suitable for coking plant flue gas desulfurization and denitrification of low temperature coke oven.

5) the unique catalytic technology used in formation of sulfite and nitrite catalyst complex catalyst complexes with sulfite and nitrite in the reaction process, prevent sulfite and nitrite reverse decomposition, formation of sulfite and nitrite formation of sulfuric acid and nitric acid in the role of oxygen, sulfate and nitrate and ammonia sulfate reaction ammonium nitrate and ammonium solution.

6) the high efficiency cyclone dust eliminator can effectively overcome ammonia escape and ammonium sulfite and ammonium nitrite aerosol problems.

7) the main control medium of the desulfurization and denitrification process is ammonia water, ozone and chemical fertilizer solution, and the continuous and stable operation of the production can be realized by adjusting ozone concentration, pH value of tower bottom solution and concentration of chemical fertilizer solution