Syngas Generation From Landfills Derived Torrefied Refuse Fuel Using a Downdraft Gasifier

Abstract

Landfill reclamation is a good solution to utilize the wasted land occupied by municipal solid waste dumpsites or landfill sites. This also offers a good means to recover valuable materials and form environmentally benign green refuse-derived fuel (RDF) for use in power production. However, due to the heterogenous composition of the wastes, it is crucial to homogenize and upgrade the waste hydrocarbon fuel properties. Torrefaction is a thermochemical process that utilizes low temperature and inert environment to drive off the moisture and volatile fractions present in wastes to form valuable fuel. This upgraded RDF from reclaimed landfills offer high energy density and favorable hydrophobicity for use as a fuel feedstock in gasification to produce syngas for power generation. The objectives of this study are to first upgrading the reclaimed landfill wastes to RDF using torrefaction followed by its conversion to form clean syngas in a downdraft gasifier. This study examines the effect of air ratio on syngas heating value and cold gas efficiency. A comparison is made on the syngas produced from gasification using reclaimed landfill wastes and torrefied RDF. Experiments were conducted using a 10 kg/h lab-scale downdraft gasifier. The air ratios examined were 0.22, 0.27, and 0.32. The results showed an optimum air ratio of 0.27 operated with a gasifier using torrefied RDF. The results showed improved syngas quality, in terms of syngas composition, lower heating value, and cold gas efficiency. The lower heating value of 4.22 MJ/Nm3 and the cold gas efficiency of 65.84% were achieved. The results showed that landfill mining can provide ultimate solution to get rid of dumped wastes from landfills using torrefaction for high-quality fuel followed by the recovery of green and clean syngas energy using gasification.