Thermo-Chemical Conversion of Microwave Selectively Pre-Treated Biomass Blends

Abstract

Possibilities of more efficient use of regional lignocellulosic resources (wood, wheat straw, peat) of different origin for an environmentally friendly energy production using selectively MW pre-treated blends of commercial wood or wheat straw pellets with raw peat pellets are studied. A hypothesis is proposed and tested that selective MW pre-treatment of wood or wheat straw pellets at the frequency 2.45 GHz and blending of MW pre-treated pellets with raw peat pellets can be used to enhance and control the thermo-chemical conversion of biomass blends. To test this hypothesis, a combined experimental study and mathematical modelling of the processes were performed. The thermo-chemical conversion of selectively activated blends was experimentally studied using a batch-size pilot device, which consists of a biomass gasifier and a combustor. To evaluate the effect of selective MW pre-treatment of biomass pellets on the thermo-chemical conversion of pre-treated blends, measurements of the kinetics of weight loss, yield of combustible volatiles, flame temperature, heat output of the device, and composition of emissions were made at different MW pre-treatment regimes of wheat straw and wood pellets and different mass fractions of pre-treated pellets in biomass blends. The developed novel 2D numerical model of thermo-chemical conversion of MW pre-treated straw confirmed that the pre-treatment of wheat straw pellets increases the generated heat and significantly affects the temperature distribution in the flame/bed zones. It was confirmed that MW pre-treatment leads to a faster thermal decomposition of biomass pellets, synergistically activating the non-treated parts of blends. The overall improved yield of combustible volatiles and their complete combustion provide a surplus of heat production by limiting the formation of GHG emissions, which allows promoting MW pre-treated biomass of different origin as efficient regional bioenergy resources for energy production.

Co-firing and microwave pre-treatment of lignocellulosic pellets for control of thermochemical conversion of biomass mixtures and sustainable energy production

“…Mw-induced changes of the main characteristics and thermochemical conversion of pre-treated pellets suggest that additives of mw pre-treated pellets can be used to provide control of thermal and chemical interaction between raw and pre-treated pellets and thermochemical conversion of biomass mixtures. Such a conclusion follows from studies of thermal decomposition and combustion of selectively activated mixtures, which were carried out using a batch-size pilot device [13]. The results of these studies confirm that selective mw pre-treatment of the mixture components activates thermal decomposition of the mixture constituents resulting in faster and enhanced thermochemical conversion of the mixtures [13].…”

“…Such a conclusion follows from studies of thermal decomposition and combustion of selectively activated mixtures, which were carried out using a batch-size pilot device [13]. The results of these studies confirm that selective mw pre-treatment of the mixture components activates thermal decomposition of the mixture constituents resulting in faster and enhanced thermochemical conversion of the mixtures [13]. Therefore, results of the preliminary research suggest that selective pre-treatment of the components of biomass mixtures can be used for control of heat energy production and composition of products in heating devices with higher heat energy output.…”

“…Microwave (mw) pre-treatment of biomass pellets is suggested as an effective tool for modification and control of the thermochemical conversion of biomass mixtures, which can cause changes in their DOI: 10.22616/ERDev.2023.22.TF012 structure and chemical composition [11; 12]. Applicability of mw pre-treatment of pellets as a tool for control of thermochemical conversion of biomass mixtures is confirmed providing detailed experimental research and numerical simulation of thermal decomposition and combustion characteristics of selectively activated mixtures using a small-batch-size scale pilot device with heating power up to 5kW [13]. The main aim of the current study is to provide research of the processes developing during cofiring selectively activated mixtures of wood and wheat straw in a device using a biomass burner with continuous supply of the selectively activated mixture of biomass mixtures and heat output up to 20 kW with estimation of the main factors responsible for their ignition and thermochemical conversion.…”