Volume 11 Issue 3 ( September 2024)

Biomass cofiring, a technique that involves combusting biomass alongside fossil fuels in power generation, presents a promising pathway toward achieving net-zero emissions. As an alternative solution, biomass co-firing is planned to be implemented to reduce emissions of the existing coal-fired power plant (CFPP) in Indonesia. This paper presents a numerical study using the computational fluid dynamics (CFD) approach. A Paiton 9’s power plant was selected as the object domain, and five cases related to fuel composition were prepared i.e., 100% coal, 100% biomass and three cases of mixture ratio of coal and biomass. Sawdust, a source of biomass, is mixed with coal and varies in ratios namely 5%, 10% and 15%. The combination of the species transport model, realizable k-ε turbulence model, combustion model and dual heat exchanger model was used to analyze combustion characteristics such as the average temperature profiles, velocity profiles and mass fractions of pollutants, including NO_x, CO₂, and HC_n. The results report the highest average furnace gas exit temperature is about 1300oC by using 100% coal. By increasing the ratio of sawdust in the coal, the furnace gas exit temperature reduces close to recommended optimum range of gas exit temperature. Furthermore, the NO_x and CO₂ emissions trend to decline due to effects of decreasing furnace temperature and low carbon levels in fuel. Hence, selecting an appropriate sawdust ratio in the coal and fuel composition is the key point to maintaining the stability of furnace exit gas temperature. Later, observations of co-firing combustion are required to ensure the accuracy of the model in this study.

Keywords: cofiring; biomass; emission; realizable k-ε turbulence model; computational fluid dynamics