Research On The Mixing Characteristics Of Selective Non-catalytic Reduction

China’s coal resources are extremely rich, but it is also the largestcoal-consuming country in the world. One problem which cannot be inevitable is thatpulverized coal combustion will inevitably accompanied by a large number ofpollutants discharge, such as dust, SO₂, NO_x, etc. For NO_xemissions, the state alsohas formulated strict standards, thus control coal fired boiler NO_xemissions has theextremely vital significance. Flue gas denitration technology is a promising NO_xemission control technology. This technology contains selective catalytic reductiontechnology （SCR） and selective non-catalytic reduction technology （SNCR）. SCRtechnology has a high denitration efficiency and also a high cost. Relatively, SNCRhas superiority on low cost, and more easily to the transformation of old unit. And incomplete mixing conditions, SNCR can also reach more than80%of the denitrationrate.Therefore, the research on mixing characteristics of selective non-catalyticreduction denitration technology of the reducing agent and flue gas, is one of the keyto improve the technology denitration rate.The whole furnace was modeled by GAMBIT. To determine the temperaturewindow of the SNCR reaction, FLUENT was used to calculate the furnacetemperature. The results show that the region near the furnace arch. Meanwhile theformation of NO_xin the furnace is also calculated, primary zone has the most highestNO_xconcentration, exit concentration is264ppm.In order to get the best injection conditions, the influence of boiler load,reducing agent injection velocity, flow rate of reducing agent, droplet size andarrangement of spray guns are investigated. The relative standard deviation of ureaconcentration is used to evaluate the mixing degree.The power plant was transformed to experiment on SNCR process. Theexperiment was conducted to measure the effect of boiler load, urea flow andconcentration on denitration rate. The research results show that the lower boiler load,the higher urea flow and concentration, the better the denitration rate, which is in linewith the results of numerical simulation.Then CHEMKIN packet was used to simulate the SNCR process. Simulation analysized the decomposition of urea in the chamber, and factors which can affectthe denitration rate of SNCR, such as the flue gas temperature, residence time andammonia nitrogen ratio, finally analysized the ammonia escape quantity at differenttemperature. The result found that the ammonia escape could be lower than5ppm attime sufficient conditions.