Study On Preparation Of White Carbon Black By Sintering The High Silicon Slag

Fly ash is a kind of industrial solid waste discharged from coal-fired power plants.A large amount of fly ash not only occupies a lot of land resources,but also pollutes the surrounding ecological environment,and even threatens public health.However,fly ash is a secondary resource with high added value,which is rich in aluminum,silicon and rare elements.At present,most of the researches focus on the extraction of alumina from high alumina fly ash,but the high value utilization of high silicon slag produced in the acid process still needs further research.In this paper,the high silicon slag and sodium carbonate are used as raw materials to prepare white carbon black,and the sintering process,dissolution process,and carbonation decomposition process are studied.The high silicon slag is derived from the new process for extracting alumina from fly ash with ammonium bisulfate.In the process of mixed sintering of high silicon slag and sodium carbonate,the effects of sintering temperature,sintering time and excess rate of sodium carbonate on the dissolution rate of silicon dioxide were investigated.The response surface method was used to optimize the sintering process conditions.The optimum process conditions are as follows:sintering temperature is 1192.9K,sintering time is 120min,and sodium carbonate excess rate is 9.74%.Under these conditions,the dissolution rate of silicon dioxide can reach 87.50%.The sintering kinetic of high silicon slag and sodium carbonate show that the sintering process is controlled by internal diffusion through the product layer in the range of 1023～1123K,and the apparent activation energy is 141.13k J/mol.In the range of 1123～1223K,the sintering process is controlled by internal diffusion through the product layer,and the apparent activation energy is 33.44k J/mol.In the process of dissolution,the effects of process conditions on impurity removal were mainly investigated.The optimal process conditions are as follows:reaction time is 1h,calcium oxide dosage is 6g/L,and reaction temperature is 70℃.Under these conditions,the removal rates of aluminum and iron are 87.5%and 81.8%,respectively,and the loss rate of silicon dioxide is only 7.3%.In the process of carbonation decomposition,the effects of process conditions on the performance of white carbon black were investigated.The optimum process conditions are as follows:endpoint p H is 9,concentration of sodium silicate solution is 70g/L,reaction temperature is 70℃,ventilation rate of CO₂ is 20ml/min,and aging time is 3h.The surface area,DBP oil absorption value,particle size,pore volume and pore size of the obtained white carbon black are 222.36m²/g,3.11ml/g,1.32μm,0.72cm³/g,15.52nm,respectively.This product meets the requirements of class A products in HG/T3061-2009.