Gasification of Wood and Plastics in a Bubbling Fluidised Bed: The Crucial Role of the Process Modelling

Abstract

Gasification is a thermochemical process that aims to convert solid fuels into a synthetic gas that can be addressed to an end-use apparatus to produce electric energy and heat or can be further refined to be transformed in chemical valuable products. Many organic materials can be gasified under different operating conditions (pressure, temperature, reactants) in different kind of reactors. A technology widely utilized to gasify several solid materials is the bubbling fluidized bed reactor: this technology can ensure a very high heating rate but its performance is strongly affected by the material properties and its interaction with the bed during the process. This study aims to correlate the main process modeling outputs and experimental evidences obtained for the gasification of a commodity plastic waste, polyethylene, and a pinewood chip, to the hydrodynamics of a bubbling fluidized bed gasifier. To this end the rate controlling stage of the primary cracking stage has been determined in order to evaluate the reaction time for both the materials under typical gasification conditions and evaluate which is the characteristic time length of their primary cracking in the dense bed of the bubbling fluidized bed.