In-Depth Performance Evaluation of RDF from Landfill Reclamation for Green Electricity Generation in a Downdraft Gasifier

Abstract

Landfill reclamation is one of the possibilities to reclaim land resources and recover energy hidden in garbage into green and renewable energy. This study aims to conduct a feasibility study of using waste reclaimed from old landfill, called mined Municipal Solid Waste (mined MSW), for power generation in a 50 kW downdraft gasification system and to optimize its operating conditions. Waste reclaimed from dumpsite in Phuket municipality, southern part of Thailand, consists of mostly plastic fraction and has a higher heating value of 28.68 MJ/kg. In this study, waste reclaimed is first solar dried and cut into small size before using as loose-RDF in 10 kg/h downdraft gasification process to study the gasification process. Three experiments with different air flow rates of 12, 18, and 21 Nm3/h were carried out, and it was found that the heating value of producer gas from loose-RDF ranged from 0.89 to 2.71 MJ/Nm3 which was considered to be very low for further use in diesel engine for power generation. Hence, the densification of RDF was performed in order to improve the RDF properties. After densification process, three experiments of dense-RDF gasification with different air flow rates of 18, 21, and 24 Nm3/h were repeated again. The results indicated that by using dense-RDF, the heating value of producer gas increased to 2.46–2.99 MJ/Nm3 and the cold gas efficiency reached 43.26–56.22 %. At the air flow rate of 21 Nm3/h, the producer gas has the maximum heating value and maximum cold gas efficiency. Although dense-RDF can produce the higher heating value of producer gas and can achieve the higher cold gas efficiency, it consumed more energy in preparation process which was accounted for 0.12 kWh per dense-RDF 1 kg. For the experiments in a 50 kg/h prototype scale downdraft gasifier, dense-RDF was gasified with three different air flow rates of 73, 85, and 101 Nm3/h. It was found that the maximum heating value of producer gas of 3.12 MJ/Nm3 was achieved at the air flow rate of 101 Nm3/h. After passing through gas-cleaning process, the producer gas can be used to fuel a diesel engine in continuous mode for power production. The electrical energy and overall efficiency as well as the quality of lube oil and wear of engine part have been reported.