Environmental characteristics of thermochemical conversion of agricultural residues

Abstract

The main purpose of this study was to find optimal methods and conditions for the processing of plant biomass in regard to the energy parameters of the obtained combustible gases as well as to determine environmental indicators during the subsequent combustion of these gases. In the numerical assessment of biomass processing, a non-stoichiometric model was used. It was assumed that a chemically reacting multicomponent mixture is in a state of thermodynamic and chemical equilibrium. This state of the mixture corresponds to the minimum value of the isobaric-isothermal potential. Pyrolysis processes had low efficiency of the thermochemical conversion of biomass processing into a mixture of combustible gases. These processes are of practical importance in obtaining such target products, as tar, biocoal and ash. In addition to pyrolysis, two types of biomass gasification were studied: (A) gasification with internal heating of the reaction volume due to partial biomass combustion; and (B) gasification with the supply of water vapor and external heating of the reaction volume due to the combustion of a part of the generated gas. The energy and environmental characteristics of the synthetic gas obtained through the steam gasification (B) were significantly better than those of the gas obtained through the gasification type (A).