Research On Key Problems Of SNCR-SCR With Low-calorific Value Coal Combustion In Fluidized Bed

In order to conserve energy and actively respond to the sustainable development strategy for Chinese government,a large number of low-quality coal is used in circulating fluidized bed boilers.Circulating fluidized bed boiler is operating in a cleaner combustion technology to make use of high ash and high sulfur low-quality coal for the sake of reducing the emission of harmful pollutants such as nitrogen oxides and sulfides to realize the efficient utilization of resources and the protection of the environment.Circulating fluidized bed boilers mainly rely on low-temperature combustion technology and zone control to achieve staged combustion,as a result the NOx emission of most circulating fluidized bed boiler is below 200-300mg/m3,however for the purpose of meeting the increasingly rigorous NOx Emission standards,circulating fluidized bed boiler should be transformed and equipped with SNCR-SCR flue gas denitrification system.SNCR-SCR flue gas denitrification technology is a combination of both SNCR technology and SCR technology,fully using each advantages.Using SNCR technology to remove the most NOx in front denitrification process,using a small amount of SCR catalyst to make the flue gas NOx reach the emission standards.This method which has the advantages of high denitrification efficiency,low investment cost and long service life can reduce nearly all NOx.In this paper,the key problems of SNCR-SCR denitrification technology are studied,and the reaction kinetics of SNCR denitrification process is studied by software Chemkin.The effects of temperature,water,reducing agent concentration in denitration process of SNCR are simulated according to circulating fluidized bed cyclone operating conditions with ammonia and urea respectively.The N2 O generation in SNCR was studied by simulation and the mechanism of N2 O formation was analyzed through sensitivity analysis.A series of SCR denitrification catalysts were prepared and setting up the SCR denitrification performance experiments and the SCR catalyst effect on SO2 conversion rate.The SCR poisoning of the SCR catalyst and the solid catalyst of the SCR catalyst on SO2 were studied.And the influence of SO2 conversion rate experiment.