Experimental study on the trommel screening performance of municipal solid waste

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 (<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mi>ω</mml:mi><mml:mi>w</mml:mi></mml:msub></mml:mrow></mml:math>), fine particle content (<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mi>ω</mml:mi><mml:mi>f</mml:mi></mml:msub></mml:mrow></mml:math>) and rotational speed (<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mi>n</mml:mi></mml:mrow></mml:math>) on the size-based separation efficiency of the light and heavy materials. Screening efficiencies of heavy material (<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mi>η</mml:mi><mml:mi>H</mml:mi></mml:msub></mml:mrow></mml:math>), light material (<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mi>η</mml:mi><mml:mi>L</mml:mi></mml:msub></mml:mrow></mml:math>) and content of light material in the undersized product (<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mi>ω</mml:mi><mml:mrow><mml:mi>L</mml:mi><mml:mo>,</mml:mo><mml:mi>U</mml:mi></mml:mrow></mml:msub></mml:mrow></mml:math>) 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 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mi>ω</mml:mi><mml:mi>w</mml:mi></mml:msub></mml:mrow></mml:math> was 20%, higher <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mi>ω</mml:mi><mml:mi>f</mml:mi></mml:msub></mml:mrow></mml:math> improved <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mi>η</mml:mi><mml:mi>H</mml:mi></mml:msub></mml:mrow></mml:math> but reduced <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mi>η</mml:mi><mml:mi>L</mml:mi></mml:msub></mml:mrow></mml:math> and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mi>ω</mml:mi><mml:mrow><mml:mi>L</mml:mi><mml:mo>,</mml:mo><mml:mi>U</mml:mi></mml:mrow></mml:msub></mml:mrow></mml:math>. When <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mi>ω</mml:mi><mml:mi>w</mml:mi></mml:msub></mml:mrow></mml:math> was 60%, with increasing <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mi>ω</mml:mi><mml:mi>f</mml:mi></mml:msub></mml:mrow></mml:math>, <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mi>η</mml:mi><mml:mi>H</mml:mi></mml:msub></mml:mrow></mml:math> decreased slightly while <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mi>ω</mml:mi><mml:mrow><mml:mi>L</mml:mi><mml:mo>,</mml:mo><mml:mi>U</mml:mi></mml:mrow></mml:msub></mml:mrow></mml:math> decreased first and then increased. As <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mi>ω</mml:mi><mml:mi>w</mml:mi></mml:msub></mml:mrow></mml:math> increased from 20% to 60%, the optimal <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mi>n</mml:mi></mml:mrow></mml:math> at which <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mi>η</mml:mi><mml:mi>H</mml:mi></mml:msub></mml:mrow></mml:math> reached its maximum rose from 15 to 25 r/min. At this point, <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mi>ω</mml:mi><mml:mrow><mml:mi>L</mml:mi><mml:mo>,</mml:mo><mml:mi>U</mml:mi></mml:mrow></mml:msub></mml:mrow></mml:math> corresponding to the maximum <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mi>η</mml:mi><mml:mi>H</mml:mi></mml:msub></mml:mrow></mml:math> reached its peak. When <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mi>n</mml:mi></mml:mrow></mml:math> was higher, screening efficiency of MSW could be improved by appropriately increasing the screen length. High <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mi>η</mml:mi><mml:mi>H</mml:mi></mml:msub></mml:mrow></mml:math> and low <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mi>ω</mml:mi><mml:mrow><mml:mi>L</mml:mi><mml:mo>,</mml:mo><mml:mi>U</mml:mi></mml:mrow></mml:msub></mml:mrow></mml:math> cannot usually be realized simultaneously, the optimal parameters should be set according to specific requirements.