Experimental Study On Decomposition Characters Of Cement Raw Meal In O₂/CO₂in Precalciner

It is a strategic task of our country, and even our world, to reduce CO2emissionin cement industry, as the CO2emission in cement industry improves gradually, whichis only less than the power industry. O2/CO2combustion technology is promisinglyapplied to precalciner to reduce CO2emission in cement industry, as the concentrationof CO2emission from coal burning and cement raw meal decomposing in the cementproduction process is bigger than from the utility boiler. The O2/CO2combustiontechnology is that the coal and raw meal are burnt and in atmosphere of thecirculatory offgas with high concentration of CO2mixed with O2divided by air. Theoutlet flue gas contains high concentration of CO2, greater than95%, which can bedirectly used or sealed up. However, when N2is replaced by CO2, the atmospherewould be changed greatly in radiation, convection, specifit heat, and influencestemperature distribution in the furnace, combustion characters of coal, anddecomposition characters of raw meal.In the paper, the cement raw meal was heated with procedures inthermogravimetric analyzer in the atmosphere of O2/CO2. The results showed that thedecomposition characters of cement raw meal in the atmosphere of O2/CO2isobviously different with air. The decomposition curve of cement raw meal in theatmosphere of O2/CO2moved to the high temperature region compared with in the air.Moreover, the influences of the main ingredient of cement raw meal (CaCO3) bythe additives of cement raw meal (SiO2、Al2O3�'�Fe2O3) were studied. The resultsshowed that the decomposition of CaCO3was inhibited by SiO2, but the inbitingeffect in the atmosphere of O2/CO2was bigger than in the air. The decomposition ofCaCO3was weakly promoted by Al2O3in the air, but strongly inhibited by Al2O3inthe atmosphere of O2/CO2. The decomposition of CaCO3was weakly inhibited byFe2O3both in the air and in the atmosphere of O2/CO2.At last, the coupling of the combustion of coal and decomposition of cement rawmeal was preliminary studied. The coal was combusted in the thermogravimetric analyzer firstly. The results showed that the combustion characters of coal in theatmosphere of O2/CO2was worse than in the air. However, the combustion charactersof coal would be improved in the atmosphere of O2/CO2with the concentration of O2larger and larger. In the aspect of the coupling, the cement raw meal and the coal ofthe test were reacted in the different temperature range. The coal A and coal B wereimproved by cement raw meal A. However, the cement raw meal A was nothing withcoal A and coal B in addition to absorbing the heat from coal A and coal B.