Experimental study on the trommel screening performance of municipal solid waste

Abstract

Trommel screens are widely used for screening of landfilled municipal solid waste (MSW). Due to the heterogeneous composition of MSW, the particle-size-based screening efficiency of different waste fractions under limited screening time requires further investigation. This paper presents an experimental study on the trommel screening performance of MSW samples obtained by large diameter drilling at a landfill. After sieving tests, screening products were manually grouped according to density and particle size differences to explore the effects of moisture content ( ${\mathrm{\omega }}_w$ ), fine particle content ( ${\mathrm{\omega }}_f$ ) and rotational speed ( $n$ ) on the size-based separation efficiency of the light and heavy materials. Screening efficiencies of heavy material ( ${\mathrm{\eta }}_H$ ), light material ( ${\mathrm{\eta }}_L$ ) and content of light material in the undersized product ( ${\mathrm{\omega }}_{L,U}$ ) are proposed to evaluate the screening performance based on the quality and yield of undersized products. The results revealed that light materials generally exhibited lower screening percentage than heavy materials. When ${\mathrm{\omega }}_w$ was 20%, higher ${\mathrm{\omega }}_f$ improved ${\mathrm{\eta }}_H$ but reduced ${\mathrm{\eta }}_L$ and ${\mathrm{\omega }}_{L,U}$ . When ${\mathrm{\omega }}_w$ was 60%, with increasing ${\mathrm{\omega }}_f$ , ${\mathrm{\eta }}_H$ decreased slightly while ${\mathrm{\omega }}_{L,U}$ decreased first and then increased. As ${\mathrm{\omega }}_w$ increased from 20% to 60%, the optimal $n$ at which ${\mathrm{\eta }}_H$ reached its maximum rose from 15 to 25 r/min. At this point, ${\mathrm{\omega }}_{L,U}$ corresponding to the maximum ${\mathrm{\eta }}_H$ reached its peak. When $n$ was higher, screening efficiency of MSW could be improved by appropriately increasing the screen length. High ${\mathrm{\eta }}_H$ and low ${\mathrm{\omega }}_{L,U}$ cannot usually be realized simultaneously, the optimal parameters should be set according to specific requirements.