STRUCTURAL ASSESSMENT AND REDISIGN OF THE WATER CHAMBER IN A DOMESTIC GASIFICATION BOILER

Residential heating boilers burn fuels to heat water, which flows through a network of pipes and radiators to warm the house. One type of residential heating boiler characterized by its high efficiency is the gasification boiler. Gasification boilers operate with an efficiency of around 85% compared to a classic wood boiler with an efficiency of around 63%. The gasification boilers use a controlled amount of oxygen and precisely defined temperatures to transform the solid biomass into gas, which is later combusted to generate the needed heat. The technology behind gasification boilers is called biomass gasification – a thermochemical conversion of organic feedstock under hightemperature conditions, through which biomass is converted to syngas. Syngas composition varies, but it is mainly composed of CO, H2, N2, CO2, and some hydrocarbons (CH4, C2H4, C2H6, etc.). A variety of papers have investigated gasification boilers and attempted to optimize their operation and design. The IEA Bioenergy annual report analyzed the product spectrum (organics, char, gas, water) from fast pyrolysis of aspen poplar wood, depending on process temperature. It was shown that with an increase in temperature, the yield of gas also increases. Similar research was done by Raibhole and Sapali, namely, they investigated how the flow rate of oxygen influenced the syngas composition. They concluded that the optimal mass flow of oxygen is around 8 kilograms per hour, when the participation of H2 in syngas is the highest. Karmarković et al. investigated the combustion chamber of the gasification boiler to find its optimal design. Drosatos et al. described the computational fluid dynamics simulation of syngas combustion and the heat transfer in a domestic wood gasification boiler to further optimize its operation. Hopan et al. investigated emissions from 111 measurements on solid fuel household boilers, among which was a hefty number of gasification boilers. One of the conclusions was that emissions-wise, a significant improvement was observed when the gasification boiler was operated by a trained operator. Overall, regardless of the type of boiler, the heated water is kept in the boiler water wall, hereinafter referred to as the “water chamber” (Fig. 1). To the authors’ knowledge, the pressure of 3 bars is considered as critical pressure of the water in the water chamber, which triggers the activation of the safety valve. This paper investigates how the critical pressure of the water of 3 bars will influence the water chamber with a wall thickness of 5 millimeters, and the possibility of mitigating the displacements without increasing the thickness of the wall.