Experimental Research Of Large Particle Coal Combustion Characteristic And Improvement Of Bed Combustion Model

There are huge amounts of coal-fired traveling grate boilers in China, which is next to the largest consumption of pulverized coal-fired plants. Compared with the pulverized boiler, the research about the traveling grate boiler is less because the complexity of bed combustion. The widely used traveling grate boilers are researched and discussed in the paper. Based on the experiment platform, the combustion of large particle coals in the bed combustion condition are researched here.In order to study the pyrolysis and combustion characters of large particle coals, a large coal particle combustion experimental bench was built. Main factors including coal rank, diameters, temperature are experimentally studied and compared. The results computed by unreacted shrinking reaction core model and the experimental results are compared. The comparison results proved that the unreacted shrinking reaction core model can be used to simulate the combustion of large particle coals. The XRD and TEM are used to analyze the char structure at different conditions. The fundamental reason of the large particle coals can’t be burned out is the ordering process of the coal crystal structure.A fixed-bed experimental furnace was built to simulate the coal bed burning on the moving grate. Some factors, i.e., coal type, bed height, diameter, excess air ratio and air supply, which influence the combustion on the grate are experimentally studied and compared. The experimental results were compared and analyzed to provide theoretical guidance for optimized operation of actual grate boiler.A typical coal-fired traveling grate boiler was tested. The optimized operation summarized in the lad-scale furnace was used to operate the actual boiler, and analyzed the reason why the optimized operation is better than the original operation. Based on the 2D bed combustion model, a 3D bed combustion model was developed to enrich the model. In order to verify the correctness of the improved model, a typical traveling grate boiler was computed, and the gas concentration at the coal bed was compared with the actual boiler. Model predicted results match well with the actual boiler.