Study On Coke Oven Flue Gas Denitrification Technology With Low Nitrogen Combustion

In order to meet the requirements of controlling the emission of flue gas NO_X in coking industry in the 150 mg/m³ range of the coking industry emission standard?2012?,on the basis of the existing NO_X control technology analysis of the existing coke oven flue gas at home and abroad,this paper takes the 2x72 hole 5.5 m tamping coke oven in Jinchang Xin Hua coking plant in Gansu as the research object.Research and engineering design of NO_X control scheme for coke oven gas.The results show that:?1?The flue gas circulating low nitrogen combustion system can reduce the NOX content of flue gas.After its operation,the smoke NO_X decreases obviously.The content of NO_X is reduced from 1200 mg/m³ before the system input to 350 mg/m³after the system is put into operation.It is beneficial to reduce the load of SCR device after combustion and reduce the transportation cost of SCR.?2?After the flue gas circulating low nitrogen combustion system is put into operation,the heating gas quantity can be saved by about 10%,which is reduced from 20010m³/h before the system input to 18000 m³/h after the system has been put into operation;the uniformity of high direction heating of the coke oven is improved;the flue gas temperature is raised to the 289?before the system input to 312?after the system is put into operation.It is not only beneficial to SCR denitration after combustion,but also improves the recovery efficiency of flue gas waste heat.?3?After burning,the SCR denitrification system can effectively remove NO_X from flue gas,which is beneficial to further reduce the NO_X to 150 mg/m³.The use temperature of the denitrification catalyst window is not less than 160 degrees C,and when the flue gas temperature rises from 289 to 310?,the activity of the SCR catalyst is increased,the denitrification efficiency is obviously improved,and the denitrification efficiency is 90%.?4?The test of SCR system shows that when the ammonia nitrogen ratio is adjusted to1.15 gradually from 0.8 to 1.15,the denitrification efficiency will rise first and then descend,and the increase of ammonia nitrogen ratio will cause the excess of NH₃.The excess NH₃ will react with the SO₂ to produce ammonium salt,blocking the active pore position of the catalyst surface and affecting the efficiency of NO_X removal,so the optimum ammonia nitrogen ratio of the SCR denitrification system is1.At this time,the denitrification efficiency is 90%.?5?The SCR system debugging shows that the denitrification efficiency increases first and then decreases when the airspeed increases from 5000 h^-1 to 8000 h^-1,and the denitrification efficiency is 90%when the airspeed is set to 5500 h^-1.When the air velocity is too high,the reduction reaction of NO_X is insufficient and the denitrification efficiency is reduced.When the air velocity is too low,the catalyst can catalyze the oxidation of SO₂ to form ammonium salt,blocking the active pore position on the surface of the catalyst and affecting the efficiency of the removal of NO_X.?6?The SCR system debugging shows that when the volume of oxygen in the flue gas increases from 4%to 10%,the denitrification efficiency increases first and then decreases.When the oxygen content is controlled at 5%,the denitrification efficiency is 95%,and when the concentration of O₂ is 5%,the NO_X and NH₃ will be adsorbed on the surface of the catalyst,and the high concentration will oxidize the SO₂.?7?The SCR system test showed that the denitrification efficiency showed a downward trend when the content of SO₂ increased in the flue gas.When the concentration of SO₂ was 800 ppm,the denitrification efficiency decreased to 85%;the high content of SO₂ would cause the catalyst poisoning and also easily oxidize to SO₃ and easily form the ammonium salt blocking catalyst active site.