Optimization of Excess Air and Flue Gas Temperature for Enhanced Efficiency in Circulating Fluidized Boiler Power Plant

Abstract

Enhancing the thermal efficiency of circulating fluidized bed (CFB) boilers is critical for reducing fuel consumption and mitigating emissions in coal-fired power generation. This study presents a practical and data-driven optimization strategy for a 100 MW CFB boiler unit in South Sulawesi, Indonesia, which focuses on regulating excess air and flue gas exit temperature. Using mass and energy balance calculations combined with sensitivity analysis, combustion efficiency curves were developed for two coal types with differing calorific values. The analysis supports a recommendation to reduce excess air from 43.5% to 31% to improve boiler performance and by reducing the flue gas temperature from 134.5 °C to 131 °C, yielding a 0.74% increase in boiler efficiency. Under these optimized conditions, the system demonstrated a measurable fuel saving of 350 ton of coal per month, savings equivalent to IDR 2.44 billion per year. Emission estimates based on stoichiometric combustion and ultimate analysis further indicated a potential reduction of 732.9 tons of CO₂/month. These findings underscore that optimizing excess air represents a cost-effective and operationally viable approach to improving CFB boiler performance, with direct applicability to utility-scale installations in similar contexts.