In the air pollution control requirements, the country set off a wave of transformation of ultra-low emissions. Among them, the application of desulfurization and denitrification process is particularly important. This article focuses on two coke oven desulfurization and denitrification technology: coke oven flue gas desulfurization and denitrification waste heat recovery integration technology and low temperature organic catalytic desulfurization denitration dust integration technology.

1 coke oven flue gas desulfurization and denitrification waste heat recovery integration technology

1.1 process

Coke oven flue gas first enters the dry desulfurization system, desulfurization agent to remove SO2, and then into the denitrification system, the role of reductant NH3 removal of NOx, the desulfurization and denitrification process coke oven flue gas temperature drop is very low. Purified flue gas recovered by the waste heat boiler, the last by the induced draft fan back to the original chimney discharge.

1.2 Engineering Applications

The technology has been successfully used in Inner Mongolia United Coking Co., Ltd., which owns four coke ovens, each with a capacity of 600,000 tons / year. Each two coke ovens share one chimney, each with a chimney discharge of 250,000 Nm3 / h The emission of flue gas contained SO2 content of 250mg / Nm3, NOx concentration of 1000mg / Nm3.

Each chimney to build a desulfurization and denitrification waste heat recovery integrated unit, respectively, in June 2016 and August completed and a successful test run, has been running smoothly for more than six months. The SO2 concentration in the treated flue gas is less than 30mg / Nm3 and the NOx concentration is less than 150mg / Nm3, which not only meets the environmental requirements of Wuhai Region, but also meets the special requirements in Table 6 of GB16171-2012 "Emission Standard of Pollutants for Coking Chemical Industry" Indicators required, and the hourly by-product 12t0.6MPa low pressure saturated steam.

1.3 technical characteristics

1) desulfurization and denitrification, and finally waste heat recovery, the SO2 content in flue gas after desulfurization is low, which is favorable for reducing the amount of denitrification catalyst filling and prolonging the life of the catalyst; the desulfurization products belong to the conventional solid waste and can be processed conveniently Resource utilization.

2) For the first time, dry desulphurization is adopted in practical engineering applications, the temperature drop is very small, much lower than the semi-dry desulphurization and wet desulphurization, and the entire device has no temperature drop except for heat dissipation, which can ensure the flue gas temperature during denitration and has Conducive to the final waste heat recovery;

3) Moving bed desulfurization technology, and developed a special desulfurization agent, desulfurization efficiency, pressure drop;

4) Moving bed desulfurization with high efficiency dust removal function, can greatly reduce the dust content in flue gas to meet the national standard requirements, do not have to set the dust removal device;

5) flue gas into the waste heat boiler has been purified to minimize the corrosion of the boiler, extending the boiler life;

6) The use of low-temperature denitration, the use of imported porous high-efficiency low-temperature denitrification catalyst, the same amount of denitration efficiency of about 2 times the normal denitration catalyst, denitrification catalyst filling less; life of up to 3-4 years. The CFD simulation was used to design the ammonia injection system to maximize the catalyst effectiveness and reduce the ammonia slip.

7) Waste heat recovery after the exhaust gas temperature is high, the flue gas treatment back to the original chimney, the original chimney always in a state of preparedness, but also to avoid a large number of white smoke emissions at low altitude;

8) set the underground original flue gate automatic power off system, to ensure the safety of coke oven under special conditions;

9) The whole set is only equipped with three main equipments of desulfurization tower, denitrification reactor and waste heat boiler. The equipment quantity is small and can be flexibly arranged to minimize the floor space and investment cost, so that no matter the new integration unit or the original waste heat Recovery of desulfurization and denitrification expansion have become feasible.

2 low temperature organic catalytic desulfurization denitrification and dust removal integration technology

2.1 process

The flue gas enters the reaction tower through the flue gas, and the flue gas is in reverse contact with the circulating slurry. The catalyst captures the reaction product and forms a stable complex. Under the action of the original flue gas oxygen (> 4%), the sulfoxide catalyst complex and oxygen The reaction generates sulfuric acid, nitric acid and sulfoxide catalyst, sulfuric acid, nitric acid and ammonia react to form ammonium sulfate, ammonium nitrate, sulfoxide catalyst to complete a cycle. After desulfurization and denitrification flue gas into the high efficiency dust defogger, capture the droplets into the multi-stage cyclone set a barrel, flue gas desulfurization and denitration after row.

2.2 Engineering Applications

The end of 2016, the technology used in a coking plant in Shanxi coke oven gas desulfurization and denitration project. The coke oven gas flow was 320000Nm3 / h, SO2 content of 100mg / Nm3, NOx content of 800mg / Nm3, the temperature is about 160 ℃, flue gas oxygen content of 12%. Design requirements to meet the GB16171-2012 "Coking Chemical Industry Pollutant Emission Standards" in Table 5 in the index requirements. The coke oven flue gas desulfurization and denitrification project in June 2017 formally run.

2.3 technical characteristics

1) At the same time in a tower to achieve desulfurization, denitration and secondary dust removal, small footprint, saving construction investment, low production and operation costs.

2) high desulphurization and denitrification efficiency, desulfurization rate can reach more than 99%, the denitration rate can reach 85% or more, can meet the GB16171-2012 "Coking Chemical Industry Pollutant Emission Standards" in Table 5 of the indicators, or even to Table 6 special Regional index requirements.

3) The produced ammonium sulfate and ammonium nitrate fertilizer directly enter the existing ammonium sulfate system of the coking plant, so there is no secondary pollution and no waste water is discharged, meanwhile, certain economic benefits can be produced.

4) does not require high temperature, more suitable for coke plant coke oven flue gas desulfurization and denitrification.

5) The unique catalyst used in this technology will form sulfite catalyst complex and nitrite catalyst complex with sulfite and nitrite to prevent the reverse decomposition of sulfite and nitrous acid. The generated sulfite and nitrite Under the action of oxygen to form sulfuric acid and nitric acid, sulfuric acid and nitric acid react with ammonia to produce ammonium sulfate and ammonium nitrate solution.

6) Set efficient cyclone dust defogger can effectively overcome the ammonia escape and ammonium sulfite, ammonium nitrite aerosol problem.

7) The desulfurization and denitrification process is mainly controlled by the media ammonia, ozone and fertilizer solutions, by adjusting the concentration of ozone, the bottom of the solution pH

Ultrafiltration Water Purifier

Suzhou Puretal Electric Co.,Ltd , https://www.puretal.com