Study On On-line Fouling Monitoring And Optimizing Sootblowing System For Pulverized Power Plant Boilers

Ash deposition and slagging on boiler heat exchange surfaces is a common phenomenon in fossil fuel fired power plants. This thesis focuses on the building a suitable model of soot deposition status of heat surfaces, and constructs a on-line monitoring system for heat exchange surfaces based on the built model. All of the work is based on a 300MW boiler. First, the thesis introduces the endangerment of soot deposition on boiler heat exchange surfaces. In order to reduce the loss due to fouling of the heat exchange surfaces and improve economic efficiency of the boiler, it is necessary to monitor the fouling statues of heat exchange surfaces and predict its development, then sootblowers can be scheduled properly. Subsequently, the thesis makes a comparison of other fouling monitoring systems for boiler heat exchange surface. And the thesis introduces the software and hardware of common sootblowing systems, which are the fundament of sootblowing optimization. Based on the data from DAS of power plant and using heating balance theory, the thesis puts forwards fouling monitoring models for boiler heat exchange surfaces including superheaters, reheaters and economizer. Cleanliness factor (CF) is used to assess the fouling statues of each surface. Using pressure difference method, the fouling monitoring model for rotary-type air preheater is built, and then these models are tested. After analyzed the model shortage of using CF as solely monitoring parameter, the new fuzzy model of optimized sootblowing monitoring system is brought forward. The input parameters of the models are CF, wall temperature of each heating surface and load of plant. The output is the degree of confidence of sootblowing. At last, the model is used to simulate the ashing degree of economizer surface. The result shows the model improves the precision of fouling monitoring in utility boilers and is suitable for the fouling process of heating surface. Using the outlet gas temperature of furnace as parameter, the whole fouling monitoring of furnace is built. Two methods are discussed which are heating flux and temperature difference of the furnace water wall. Finally, the thesis summarizes the studies and puts forward problems for further studies.