Multi-products oriented co-pyrolysis of papers, plastics, and textiles in MSW and the synergistic effects

Abstract

Plastics, papers, and textiles are the main dry waste components of municipal solid waste (MSW). Product-oriented pyrolysis of these wastes under proper blend ratio could be important not only for improving the quality of char, oil, or gas from MSW pyrolysis, but also for enhancing the recycle of plastics from MSW. In this study, the pyrolysis characteristics of papers (ivory board, coated duplex board with grey back, kraft paper and offset printing paper), plastics (polypropylene and polyethylene), and textiles (cotton and polyester) were studied using thermogravimetric-Fourier transform infrared (TG-FTIR) analysis, gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS) to obtain the optimum blend ratios for the desired products (gas, oil, volatile and char). The synergistic effects amongst different components during pyrolysis were investigated. Results showed that the co-pyrolysis of papers, plastics, and textiles under equal blend ratio promoted the production of aromatics, alkenes, water, alcohol, and phenol in volatile, but inhibited the production of CO2, CO, alkanes, and carbonyls. The optimum mass blend ratios were found to be paper: plastic: textile = 25 wt%: 50 wt%: 25 wt% and 12 wt%: 50 wt%: 38 wt%, respectively for obtaining the highest energy share in volatile and gas. While for producing char with higher surface area, higher paper ratio and lower plastics ratio is preferred. When the plastics percentage in mixture was increased from 12.5 wt% to 25 wt%, the oxygenates percentage in pyrolysis oil was reduced from 82 area% to 19 area%, further increase in plastics percentage, or, alterations of papers and textiles percentages did not show significant influence on oil composition, indicating that plastics can be recycled, without lowering the calorific values of pyrolysis oil or MSW for incineration, when their blend ratio in MSW exceeds 25 wt%.