IGNITION OF WOODEN BIOMASS PARTICLES UNDER MICROWAVE EXPOSURE AT HIGH-TEMPERATURE RADIATION-CONVECTIVE HEATING

Abstract

Link for citation: Syrodoy S.V., Malyshev D.Yu., Kostoreva Zh.A., Kostoreva A.A., Omarov A.A. Ignition of wooden biomass particles under microwave exposure at high-temperature radiation-convective heating. Bulletin of the Tomsk Polytechnic University. Geo Аssets Engineering, 2023, vol. 334, no. 5, рр.159-167. In Rus. The relevance. Despite the active development of technologies for the production of electrical energy by means of wind power generators and solar batteries, by 2100, most of the energy will still be generated at thermal power plants that burn fossil fuels. As a rule, thermal power plants use coal as fuel (about 40 %). However, it should be noted that during the combustion of coal in the furnaces of steam and hot water boilers, toxic oxides of sulfur and nitrogen are intensively formed. In this regard, many scientists of the world working in the field of energy are working to create new innovative technologies for the eco- and energy-efficient production of heat and electricity. The latter include technologies for burning woody biomass in the furnaces of steam and hot water boilers of thermal power plants. The use of woody biomass can significantly reduce the environmental impact of thermal power plants on the atmosphere. However, no technology has yet been developed to burn wood with high energy efficiency. The latter is due to the high moisture saturation of woody biomass in its initial state. The main aim: experimental determination of the main stages and identification of a complex of physicochemical processes occurring together during the ignition of woody biomass particles under microwave exposure under high-temperature radiation-convective heating. Object: dry and moisture-saturated wood of two types (pine and cedar). The relative humidity of the wood from which the particles were made (with a characteristic size of 4 mm) varied from 6 (relatively dry biomass) to 42 % (moisture-saturated wood). Method. To establish the main characteristics of wood particle ignition under microwave exposure under high-temperature radiation-convective heating, a special experimental stand was developed, representing a reaction tube with heat-insulated radio-transparent walls through which a high-temperature oxidizer (air oxygen) was blown. The wood particle was mounted on the axis of the pipe so as to fall into the focus of the emitter. All processes were recorded by a high-speed video camera. Results. The paper introduces the results of experimental studies of ignition of dry and wet particles of woody biomass in the environment of air heated to high temperatures under conditions of radiation-convective and radiation-convective microwave heating. A significant influence of the type of wood on the ignition delay times (tign) was established. Rather significant effect of heating conditions on ignition is also shown, since microwave exposure leads to an acceleration of ignition of woody biomass particles. It was shown that during the ignition of wet wood particles, the effect of exposure to microwave radiation (acceleration of ignition) is more significant compared to ignition of dry wood particles. It was also found that the moisture content (φ) of woody biomass significantly affects the ignition delay times (increase in φ leads to growth in the tign value). The regularities established in the conducted experiments illustrate the prospects of using woody biomass (including moisture-saturated) in thermal power engineering as the main fuel.