Carbon Capture and Storage in Biomass Combustion Process

Abstract

Biomass stores solar energy that man can convert into electricity, fuel or heat, resulting in cheap, clean energy with a negative carbon balance. The use of biomass from agricultural secondary production as a potential energy source can improve soil quality and reduce greenhouse gas emissions in a complementary, non-competing way. The paper presents a piece of combustion equipment performing the burning process by biomass gasification on the TLUD (Top-Lit UpDraft) principle, from which hot air and biochar are obtained. The main function of this type of gas generator set on the TLUD principle is to generate a syngas flame which can be used as a heat source. The biochar obtained as a by-product is a sterile, active carbon with a large adsorption surface which is used as a soil amendment in environments with limited capacity for carbon sequestration and in soils depleted of resources. Gasification on the TLUD principle occurs when the biomass layer is introduced into the reactor and rests on a grate through which the air flow for gasification passes from bottom to top. Priming of the gasification process is done by igniting the upper layer of biomass in the reactor. The oxidation front continuously descends consuming the biomass in the reactor. Due to the heat radiated by the oxidation front the biomass is heated, dried, and then it enters a fast pyrolysis process from which volatiles emerge and unconverted carbon remains there. When the combustion front reached the grate, all the volatiles in the biomass were gasified and some of the carbon fixed was reduced; about 10 - 20% of the initial mass in the form of sterile charcoal, called biochar, remains on the grill. Compared to wood direct combustion or gasification combustion processes, the TLUD gasification process is characterized by very low values of the superficial velocity of gas passing through the pyrolysis front. The slow process maintains superficial velocity of the generator gas produced at very low values, which ensures reduced carrying away of free ash of approximate size below PM2.5 and maxim values of 5 mg/MJbm when leaving the burner; such values are well below the target imposed in the EU in 2015 for biomass combustion processes, which is below 25 mg/MJ. The result of monitoring the gasification process can be used to automate and optimize the TLUD process in order to achieve green energy, for carbon sequestration in the obtained biochar and to reduce greenhouse gas emissions, thus contributing to achieving efficient protection of the environment and to ensuring sustainable energy development