Numerical Simulation And Structural Optimization Of Coal Blends Efficient And Low NO_x Combustion In Calciner

With the contradiction between economic development and the efficient andclean utilization of energy growing up, the traditional cement industry productionwhich has high energy consumption and pollution is gradually replaced by NSPcement production technology based on calciner. The reduction of coal reservesmakes blended coal combustion to be inevitable. Compared with quality coal,blended coal combustion will present much more problems. The condition of charburnout ratio, main pollutant emissions of nitrogen oxides (NOx) etc. andslag formation are far more complicated while the coal blend is burning. Therefore itis very important to optimize the operating parameters and structure of the calcinerby using blended coal.The advantages of the Trinal-sprayed Calciner make itself to be the most popularin cement production. This paper takes the5000t/d TTF calicner as research object,studies the high efficiency and low NOxcombustion of blended coal in calciner bysimulation. The main contents and conclusions are as follows:(1) With the reasonable hypothesis, the suitable gas-solid two-phase flow model,combustion model, NOxformation model and the corresponding boundary conditionsin the furnace are selected. The numerical simulation about the basic condition ofcalciner is carried out, and the experimental validation is used to prove the correctnessof the model. The result shows that the numerical simulation is reliable.(2) Making the other structural parameters settled, the feeding angle of the rawmeal in the lower cylinder of the calciner and the ratio of the raw meal are changed tooptimize the gas-solid two phase flow of the calciner. Through analyzing thetrajectory and the staying time of raw meal and the pressure loss of the calicner, thebest raw material feeding angle is26°~35°, the best raw material proportioningrange of the first feeding port is15%~20%.(3) Making the other structural size settled, the optimal diameter of the throat inthe circular cone site of the calciner is2.8m by using numerical simulation. Based onthe optimal diameter of the throat the optimal injection angle of the coal-injectiontube is settled by65°. After determined the optimal value of the optimal diameterand the coal injection angle, staging combustion of the coal is simulated, whichincluded simulations by research of the installation position, the injection angle and the installation height of the adding denitration coal-nozzle in conical part. The resultsshow that when the denitration coal-nozzle is parallel with the revivification tertiaryair, the optimal coal injection angle is up to15degree and the optimal installationheight is2.5m. In this condition the distribution of temperature is suitable for thedecomposition of raw meal, and the distribution of carbon monoxide, oxygen, carbondioxide is reasonable while the char burnout rate and char burnout ratio are optimal.(4) By analyzing the effect of structure optimization on NOxproducing incalciner, the rising of calciner choke diameter and coal-injection duct feed coal angleboth make NOxconcentration increase first and then decrease. Based on the optimaldiameter of the throat in the circular cone site of the calciner and the optimal injectionangle of the coal-injection tube the denitration coal-nozzles are added, and theconcentration of NOxincreases with height increasing.The numerical simulation results provide an important theoretical basis for thestructural optimization of calciner using mixed coal.