Study On The Pyrolysis Properties Of Oil Shale Sludge

Oil shale sludge, which is mixture of oil, ash and water produced in the processof retorting reilnery in oil shale, will cause pollution to the environment to someextent.Oil shale sludge was pyrolyzcd to eliminate pollution and recovery shale oil,which will achieve harmless disposal of the resources. Based on the basic features ofoil shale sludge, pyrolysis characteristics and catalytic properties of oil shale sludgewere studied by thermogravimetric analysis and tubular electric furnace.Firstly, the basic physico-chemical experiments were conductcd to give theconclusion that the oil shale sludge from Wangqing and Huadian, had high oil content,low ash content. Then，the influences of heating rate、catalysts and other factors onpyrolysis characteristics of oil shale sludge were analyzed by thermogravimctricanalysis, and pyrolysis kinetics analysis was given by using the distribution activatedenergy model (I)AEM)，Flynn-Wall-Ozawa (F-W-O) method. At last, the releasingbehavior of non-condensed gas was also studied to understand pyrolysis mechanism.Three stages characterized the overall process of oil shale sludge pyrolysis. Moistureand lightweight components dissolved out in the ifrst stage(20?180°C); the secondstage(180-360"C)was that heavy quality components volatilize steadily, which wasresearch focus of the dynamics; in the third stage(360—600°C) semicoke carbonizedand mineral substances reduced in weight. Researches showed that K2CO3caneffectively reduce the temperature of oil slud’ges pyrolysis and improve productionrate of oil, however, AhOi had no obvious catalysis on the pyrolysis of oil shalesludge and even prevent it. The generating organic macromolccular degraded due toheat during processing, resulting in chain scission of carbon-carbon bond ofmacromolecules’ side chain and production of small molecules paraiffn andunsaturated hydrocarbon. In the condition of low pressure and high temperature, thechain scission tends to take place at the end of carbon chain, causing the number ofsmall molecule hydrocarbon to improve. Gatalytic pyrolysis of oil shale sludge was conducted by tubular electric furnaceto investigate the impact of three different kinds of catalysts (AI2O3、K2CO3andFe203> and ratioes (1:3、1:5and1:10) on destructive distillation, and pyrolysis oil’sdistillation range under various operating conditions was measured. The results showth’at the effect of oil shale sludges catalytic pyrolysis was good. Overall residue ratedropped, and oil yield was improved. The addition of K2CO3at1:5led to the increaseof the total oil yield up to44.08%. In the aspect of catalysts improving the quality ofshale oil, Fe2C>3appeared stronger catalytic role than other metal oxides. When themass fraction of Fe^Ch in oil shale sludge was10-20%，the yield of gasoline increasedsharply. Catalytic pyrolysis is abide by carbocations mechanism. Both the cracking ofheavy oil and polymerization of paraffin could improve the yield of gasolene.