Study On Non-catalytic Reduction Of Exhaust Gas Denitrification In Pulverized Coal Boiler

Power plant boilers are the main energy conversion equipment in China and in the world.It plays a vital role in the production of electricity and the development of the national economy,but the combustion of coal also brings serious environmental pollution problems.The air pollution caused by the nitrogen oxides produced during the combustion of pulverized coal seriously endangers the living environment and life health of human beings.Selective non-catalytic reduction technology(SNCR)has become one of the most important ways to solve the problem of NOx pollution,and it has been paid much attention by scientists and technicians,especially in the transformation of the old units,which has a great advantage.Taking ANSYS 14.5 as the calculation platform and 16.5%urea solution as reducing agent,the numerical calculation of SNCR process for a 10t/h boiler is carried out in this paper.First,the structural modeling and mesh generation of the boiler combustion chamber were carried out.The flow field and temperature field in the furnace were preliminarily studied.Based on the simulation results,a reasonable SNCR reaction area was determined.And then sprayed into the reducing agent to calculate the SNCR process.In order to get the best SNCR design,the effects of the position of the urea nozzle,the jet velocity,the droplet diameter,the mole ratio of ammonia and nitrogen and the number of the nozzle on the denitrification efficiency are analyzed,and compared the amount of ammonia leakage of furnace outlet under different working conditions.The results show that when the injection velocity is 25m/s,the droplet diameter,NH3/NO molar ratio and the number of nozzles are the same,and the nozzle is arranged at the height of 3.1m of the front wall of the furnace,The effect of denitrification in the furnace is better and the escape of ammonia is low.The simulation results of the injection velocity of 35m/s,45m/s and 55m/s show that the reduction rate of NO in the furnace can reach 29.8%with other conditions unchanged when the injection speed is 45m/s.The effect of denitrification in the furnace with the diameter of 0.1 mm,0.2mm and 0.3mm was compared and analyzed,The results showed that the NO reduction rate was the highest when the droplet diameter was 0.2mm.The removal efficiency of NO and ammonia leakage were calculated when the mole ratio of NH3/NO was 1.2,1.4,1.6,1.8 and 2 respectively.The results showed that when the NH3/NO molar ratio was 1.4,the denitration efficiency could reach 33.2%,and The amount of ammonia leakage was 12.21 μmol/mol.By comparing the diffusion of NH3 in the furnace,the reduction efficiency and the amount of ammonia leakage under various conditions,the results show that when the nozzle position is located in the front wall of fumace,height 3.1m,urea solution injection rate is 45m/s,the droplet diameter is 0.2mm,the molar ratio of NH3/NO is 1.4 and the nozzle number is 3,The reduction rate of NO in the furnace is 33.2%and the amount of ammonia leakage is 12.21μmol/mol,which is lower than the industrial emission standard.