Co-combustion of paper sludge in a 750 t/d waste incinerator and effect of sludge moisture content: A simulation study

Co-incineration with municipal solid waste (MSW) is an efficient method in disposal of paper sludge (PS). CFD technology was adopted to verify the possibility of different blending ratio of sludge to combust with MSW in a 750 t/d waste incinerator, and to predict the impact of different moisture content of sludge on co-combustion. In this paper, the reliability of the numerical model is verified by comparing predicted results with operating data; the sludge which contain 30%, 40%, 50%, 60% and 67% moisture content were blended with MSW by the mass proportion of 5% (wet basis, the same below), 10%, 15%, 20% and 25%. The simulation shows that mass residual on bed increases from 19.8% to 27.6% with the mass percentage of sludge rising from 5% to 25%; as the moisture content in sludge increased, the volatiles release and fixed carbon burning are both delayed. The solid gasification efficiency has a negative correlation with blending ratio of sludge and moisture content of sludge. The NO emission is observed to be positively correlated to the percentage of sludge and the highest is not higher than 162 mg/Nm3. Raw paper sludge with high content of water will aggravate coking and corrosion on rear flue wall because of local high temperature. The result indicates that co-combustion of 25 wt% sludge (up to 67% moisture) with MSW is feasible which maintains the furnace temperature, mass residual and several pollutants in allowable range. However, partially dried paper sludge is more proper for incinerator in the consideration of mitigating corrosion. The current work greatly help to understand the effect of paper sludge and its moisture content in large-scale waste incinerator.