The Effect of Biomass & Coal Co-firing on The Flue Gas Temperature Profile in a 350 MW Class Pulverized Coal-Fired Power Plant

Abstract

Direct biomass co-firing within pulverized coal-fired power plants involves the integration of biomass into the existing coal consumption process, enabling utilization by the power plant’s established equipment. Typically, biomass co-firing accounts for up to 5% of the total coal consumption. This paper examines the impact of co-firing fractions on the flue gas temperature, specifically focusing on the regenerative air preheater hot side outlet temperature. Among the various operational parameters requiring compliance with acceptable limits, maintaining the flue gas temperature above the sulfur dew point is critical to prevent sulfur dioxide condensation. Such condensation risks corrosion of the flue gas duct and other downstream components. Empirical studies reveal a linear reduction in flue gas temperature as power plant load decreases, with the temperature eventually reaching the sulfur dew point threshold. This study further explores the influence of biomass co-firing fractions on the part-load temperature profile of flue gas, demonstrating an additional decline in temperature with the inclusion of biomass in the combustion process. Findings indicate that through modest adjustments in operational management and logic control systems, sustainable operation of the flue gas pathway can be maintained. These modifications ensure operational flexibility remains close to the original design specifications. Additionally, an economic assessment of the fuel mixture comprising coal, biomass, and fuel oil across the operational range of the power plant is essential. Optimization of the fuel mix is required to identify the optimal operating range for coal-fired power plants (CFPPs) while simultaneously minimizing fuel costs.