Integrated downdraft gasification with power generation system and gasification bottom ash reutilization for clean waste-to-energy and resource recovery system

Abstract

In this work, the small-scale downdraft gasification system was integrated with a set of internal combustion engine power generation and successfully used for converting biomass waste into energy in the forms of electricity and heat. The performance of integrated system was investigated by using redwood pellets with a lower heating value of 17 MJ/kg as a feedstock. Experimental results show that the maximum syngas yield of 33.6 Nm3/h can be achieved from the gasifier. From thermodynamics analysis, the maximum energy and exergy efficiencies of the whole integrated system were found to be 31.9% and 15.6%, respectively, considering both electricity and heat generated. Apart from syngas, gasification system also generates significant amount of bottom ash that can be harmful to the environment and public health if it is not treated properly. Therefore, this work also focused on the reutilization of bottom ash in order to reduce the environment and health concerns associated with its disposal, making the overall process more environmentally friendly. From elemental analysis, bottom ash produced from redwood pellets gasification contains significant amount of silica, making it become a highly potential source for synthesizing silica-containing compounds. In this work, alkali hydrothermal reaction has been successfully used to convert this bottom ash into zeolite (or aluminosilicate compound) which can be potentially used as an adsorbent material.