Research On Combustion Characteristics Of Blended Coals Under The Circumstance Of Precalciner In Cement Kiln

At present, mixing low-quality coal with high-quality coal have gradually beenutilized in the large and medium-sized cement enterprises in our country. If coals arechosen suitably, mixed equably, proportioned properly, and fired in good condition,blended coals will display respectively superiority of each single coal, and be able tobring good influences in security and efficiency of the combustion. Therefore, theresearch on combustion characteristics of blended coals would be significant in thestable combustion in precalciner. In this thesis, the research of ignition characteristics,dynamics, burnout characteristics and best ratio of blended coals had been carried on,which offer the theoretical foundation for blended coals using in new dry processkilns cement production.The rules of ignition and dynamics parameter of the blended coals wereresearched in the thermobalance and self-made coal combustion comprehensivemeasurement instrument. The relations between ignition characteristics and differentcoals, the ratios of the blend coals, equal volatile coal were discussed in differenttemperatures or surroundings. It is concluded that for the blended coals of bituminousand lean coal, blending a little bituminous to lean coal can obviously improve ignitioncharacteristics; for the blended coals of bituminous and anthracite, their ignitioncharacteristics of blended coals retained their own ignition characteristics; the ignitioncharacteristics of the blended coals were worse than the equal volatile coals'.Blending low volatile coals to bituminous could reduce the activation energy of theblended coals; the activation energy of blended coals is lower than the ratio averageof two single coal, and approach to the single coals of low ignition activation energy.The ignition activation energy would be different in different coals, or different mixedproportions.In this thesis, the burnout characteristics of blended coals were researched in thethermobalance and the test furnace for material suspension reaction at hightemperatures. It is concluded that the burnout characteristics of blended coals arebetween two single coals. The more bituminous blended in low volatile coal, thebetter the burnout characteristics would be. The burnout index proposed in this experiment could reflect the burnout characteristics of blended coals quantitatively. Inthe test of thermobalance, blending a little anthracite to bituminous can obviouslyimprove burnout characteristics; in the test furnace for material suspension reaction,the various mixing coals would retain their own burnout characteristics. The burnoutefficiency would be improved by making powdered coal smaller, or enhancing thefurnace temperature, or lengthening resident time and so on.According to analyze coal industry analysis, ignition and burnout characteristics,and activation energy, the synthesis appraisal method was proposed to compute bestratio of the blended coals. In this proportion, both the combustion characteristics andthe cost benefit are the best. In order to utilize blended coals properly, morebituminous were needed, when bituminous was blended in low volatile coal.