Numerical Simulation of Co-Firing Biomass in a 660 MW Coal-Fired Boiler

To address the challenges of combustion stability and pollutant control during biomass co-combustion in coal-fired boilers under deep peak regulation, a numerical simulation study was conducted on a 660 MW front-and-rear wall opposed-fired pulverized coal boiler using computational fluid dynamics (CFD) technology. First, the reliability of the numerical model was validated under the Boiler Maximum Continuous Rating (BMCR) condition by comparing the simulated results of furnace outlet temperature and NO concentration with on-site operational data, with relative errors of 1.2% and 1.9%, respectively, both within the acceptable range of 5%. Subsequently, the effects of different biomass co-combustion ratios (0%, 5%, 10%, 15%, 20%) and injection positions (primary air nozzles of lower, middle, and upper burners) on the in-furnace velocity field, temperature field, component distribution (O2, CO, CO2), and NO emissions were systematically analyzed. The results indicate that increasing the biomass co-combustion ratio does not alter the overall variation trend of flue gas components but significantly affects their concentrations: the O2 content at the furnace outlet decreases gradually, while the CO2 content increases, and the NO emission concentration decreases continuously. A 20% co-combustion ratio is identified as the optimal choice, balancing combustion efficiency and NO reduction. Regarding injection positions, biomass injected at the middle burner’s primary air nozzle achieves the best NO control effect, reducing NO emissions by 22% compared to pure coal combustion. This is attributed to the formation of a stable reducing atmosphere in the main combustion zone, which facilitates NOx reduction. The research findings provide valuable theoretical references and technical support for the parameter optimization and safe, low-emission operation of biomass co-combustion in large-scale coal-fired boilers.