Numerical Simulation Of Combustion Process And Air Distribution Of Tangentially Pulverized Coal-fired Boiler

Boiler's hot tests and the amount of wind allocated proportion experiment are one of the most important experiments for a heat power plant. They are of importance for operators to know a boiler's operating characteristic accurately and duly, to keep fuel combusting high-powered and cleanly, to ensure the security of boiler and operators, to checkup the performance of new unit.However, the combustion process is very complex in the boiler. Hot test has some limitations, such as a great amount of workload, difficulty of function adjust, complexity of measure, which leads to many difficulties in obtaining the detail about boiler's parameters. With the fast development of computer technology, computation heat transfer theory, computation combustion study and the model of combustion theory as well as the commercial software's gradual enhancement of computation hydromechanics, the numerical simulation already became the effective method in researching the boiler internal combustion process.In the dissertation, according to FLUENT, CFD software, the flowing, transferring heat and burning process of the internal boiler in the original designing condition of CG-220/9.81-M tangential firing boiler in a certain power plant are analyzed and simulated. Based on the analyses, the rationality of the physical and mathematic model and the numerical method in this dissertation is validated. At the same time, the conditions in different air distribution mode, the different excess air coefficients, the different rich-lean ratio of pulverized coal air flow and load are numerical simulated.The results of the simulation indicate that: in the full load condition, Normal pagoda type distribution wind is the best in the Equal, Normal pagoda type and Waist drum type distribution wind. Because in this air distribution, the high temperature flame is in the middle of the burning area, the combustion of the tangential circle is in order, the flame cannot stick to the wall and the heat load of the average wall is higher.; Along with the increasing of the excess air coefficient, the whole temperature level in the boiler reduces a little and the diameter of tangential circle and the area of high temperature reduce gradually. The NOx creating of fuel type increases because of the oxygenous increasing; Along with the reducing of the load, the whole temperature level in the boiler, the average heat flow density of the wall, the average temperature and velocity in the outlet as well as the average NOx mass concentration all reduce; The change of rich-lean ratio of the pulverized coal air flow has very important influence to the temperature field in the boiler and NOx's creating. As a result choosing the appropriate rate cannot only get a better distribution of the temperature field in the boiler, but also can reduce the formation amount of NOx.The study of this dissertation, offer an assistant means of boilers'cool and hot test. Meanwhile, they also provide a significant reference basis of optimizing the air distribution of boiler, choosing the rich-lean ratio of the pulverized coal air flow, operating in different load conditions and forecasting the NOx.