Combustion Monitoring And Optimization Of Pulverized Coal Utility Boiler Based On Pre-numerical Calculation

The combustion monitoring and optimization of pulverized coal utility boiler aims to improve the combustion efficiency and reduce the emission of pollutions on the premise of guaranteeing the safe operation of the boiler by the methods of adjusting the boiler operating parameters. A 300MW tangential pulverized coal-fired boiler was taken as a study case. The contradiction between the unburned carbon in fly ash and emission of nitrogen oxide was analyzed. The pre-numerical calculation method was used to study the combustion monitoring and optimization. The application of numerical calculation, which was accurate but time consuming on the boiler real-time combustion monitoring and optimization, was discussed. The method offered an effective way for the combustion monitoring and optimization. Concrete research contents and main results were as follows:(1) The pre-numerical calculation was applied in the research of combustion characteristics in furnace. COALFIRE was used as an effective tool for numerical calculation of combustion and heat transfer of the tangentially pulverized coal-fired boiler. Total 28 operating conditions were calculated using COALFIRE. The influences of coal properties, pulverized coal size, boiler load and the distribution of secondary air to temperature, oxygen concentration and thermal load of radiation surfaces were discussed, with the emphasis on the variation of unburned carbon in fly ash and the released rule of nitrogen oxide. Compared with the actual operating data, the calculation result was accurate. Pre-numerical calculation offered the data base to the further work.(2) Taking the pre-numerical calculation results as the training samples, the predict model of combustion monitoring was established based on the Support Vector Machine. The Support Vector Machine has the characteristics of splitting the difference between the complexities and learning ability of model based on the limited sample information. Therefore, the model could obtain better popularizing ability. It adapted to solving the combustion problems because getting the operating samples was difficult. Compared with the calculated data and the actual operating data, the results indicated that the model responded the changes sensitively and the calculation results were reasonable, which met the request of the combustion monitoring. (3) The evaluation indexes of the combustion conditions were reduced using the factor analysis method. The security, economic and environmental factors were defined. The formula of each factors were deduced. After drawing the public factors, the combustion evaluation model was established by calculating the scores of different operating mode. The model was tested using the actual operating condition. The result showed that the model was reasonable. It can be used as a reference to direct the boiler combustion adjustment and optimization.(4) The combustion monitoring and optimization system based on pre-numerical calculation was developed using Visual Basic. The result of off-line running test indicated that it could realize the combustion monitoring and optimization. It offered a new way for the combustion monitoring and optimization on tangentially pulverized coal-fired boiler.