Study On Clean Utilization Of Gasification Slag And CO₂

With the high-speed development of coal chemical industry in China, entrained-flowcoal gasification technologies are widely applied in gasifiers; especially the coal waterslurry gasification technology: it is currently the most preferred technology in large-scalegasification plant for its high reliability and high efficiency.However, the large amount of gasification slag that can not be used effectively for along time has resulted in serious environmental problems as well as significant waste ofnatural resources; hence restraining the development of coal chemical industry. Therefore,the study on clean utilization of such slag and carbon dioxide reductions has significantmeanings for economy and environment.In this paper, a new process is proposed for targeting the clean utilization ofgasification slag and carbon dioxide, which is done by preparing white carbon black withthe slag from a GE coal water slurry gasifier and high levels of CO2from coal chemicalindustries.The experimental results indicated that the density of silicate vitreous particles wasmuch higher than residual carbon particles, so amorphous silicate vitreous particles withhigh content of calcium and residual carbon particles with net calorific value21.34MJ/Kgin dry basis could be separated by water disturbance and flushing. Leaching silicatevitreous particles with hydrochloric acid was the best way to obtain highly reactive SiO2.The influence of process conditions on the extraction rate of metal elements was decreasedin the order of hydrochloric acid concentration, reaction liquid-solid ratio, reactiontemperature and reaction time. SiO2extraction rate increased significantly as increasingtemperature in alkaline leaching experiment. In consideration of efficiency and economy,the optimum leaching conditions should be: hydrochloric acid concentration32%, reactionliquid-solid ratio3.5ml/g, reaction temperature85℃, reaction time60min for acid leachingand sodium hydroxide concentration13%, reaction liquid-solid ratio11ml/g, reactiontemperature90℃, and reaction time60min for alkaline leaching. More than90%of Fe and93%of SiO2could be extracted from the silicate vitreous material under the aboveconditions. The concentration and purity of sodium silicate solution had significant effecton the quality of white carbon black. The conversion of Na2SiO3and SiO2content of whitecarbon black decreased when the sodium silicate solution concentration increased;15g/l was the optimum condition of leaching solution considering absorption rate of CO2andquality of product. White carbon black with specific SiO2content, surface area and DBP,meeting the Chemical Industry Standards could be obtained by washing the precipitationwith acid. When disposed of1ton coarse slag under the optimum condition,0.17tonscarbon particles could be divided,0.43tons white carbon black could be prepared,0.38tons CO2could be absorbed and0.92tons coarse slag emissions could be reduced.Using this method, the pollution problems of gasification slag and CO2emission couldbe resolved effectively. By-product, such as carbon particles, white carbon black and acidused to prepare water purifier could be obtained: this realized the high-added value’sutilization of gasification slag and have broad prospects in application.