Numerical simulation study on the mixed combustion of composite biomass

With the rapid development of renewable energy, biomass energy has received widespread attention as a clean and renewable energy source. However, while the design fuel of the boiler is straw, it is actually burned in a mixture of straw, rice husk, and wood chips during use, resulting in the furnace temperature failing to meet the design requirements. Currently, there is no numerical simulation research on mixed fuels for specific boiler models. Taking the Nongan 140t/h water-cooled vibrating grate boiler as the research object, fuel ratio calculations and numerical simulation research have been conducted to address the issue of low temperature during the mixed combustion of biomass fuels. First, based on the storage and arrival conditions of fuels at the power plant, a sampling plan was developed to collect representative fuels on site, and industrial and elemental analyses were conducted on the fuels. Based on these data, a mathematical model for fuel ratio was established, and with the design fuel and economic efficiency of the power plant as constraints, the mixed combustion ratio scheme was obtained through iterative calculations. Subsequently, with the aid of Fluent and Flic gassolid simulation software, a simulation study was conducted on the mixed combustion process. The influence of different ratios on the furnace temperature and component concentration distribution was deeply explored. By comparing the simulation results with the actual temperature and design temperature of the furnace, a mixed combustion ratio scheme was obtained. The research results show that: when two types of biomass are mixed, when straw and rice husk are burned at a mass ratio of 1:0.57 and 1:0.63, the maximum temperature in the furnace is 1540K, and the temperature at 15700mm above the furnace arch is 1210K, which is 117K higher than the actual combustion temperature of 1093K at this point; when straw and wood chips are burned at a mass ratio of 1:0.55, the temperature at 15700mm above the furnace arch is 1192K, which is 97K higher than the actual temperature of the furnace; the actual temperature at 14600mm in the furnace is 1010.9K, and the simulated temperature at this point is 1091K, which is 7.9% higher than the actual combustion temperature; the CH4 content in the furnace is the highest, indicating that the combustion is intense and good.