Study Of Fouling Monitoring On Heattransfer Surface In Coal-fired Power Plant Boiler Based On Acoustic Pyrometry

In coal-fired utility boiler, fouling and slagging problem tortures the convection heat transfer surface a lot, so a reasonable arrangement of sootblowing now is crucial for power plant's safety and profit. Previous sootblowing mechanisms are dominated by designed fuel and load, and often follow a fixed schedule. However, insufficient cleaning will lower heat transfer efficiency; too much cleaning will not only waste energy, increase erosion, shorten tube's life but also add maintenance cost. The reason why a fixed schedule of sootblowing fails to competent its task lies in low ranking fuel, deviation from designed coal and some drawbacks of coal feeding and arranging system.The development of acoustic pyrometer implemented on a domestic 300MW boiler is based on research group's former work. Stability and reliability of the system have been proved by cold adjustment, warm experiment and persistent operation test. The specially designed K type shield thermalcouples has served as the control group to prove that inaccuracy between thermocouple and acoustic pyrometer is less than 2% .In addition, there is a perfect match between the curve of acoustic measurement and history load. acoustic pyrometer is able to work as a substitute of gas temperature probe in furnace and is a totally new creation.Analysis has been taken to make clear the relation between waterfall's thickness of slagging and temperature of slagging surface, then how isotherm curved surface distributed in the furnace has been displayed. A model, simulating how heat transferred in the furnace, has been developed. Illustrating slagging rate of furnace, has been decided by taking average furnace temperature as key factor. The temperature of slagging surface has been acquired by acoustic waves. Finally, a mechanism, suitable for practical engineering, of simulating furnace slagging has been presented.In order to demonstrate how fouling the heat transfer surface is, certain fouling coefficient has been decided; and a model to simulate convection heat transfer surface has been developed. Heat absorption has been acquired by calculating the real time value, offered by DAS, of steam inlet pressure, temperature, flow rate. An ANN model has been developed to solve the problem of multiple inputs and non-linear relationship. Coal feeding, air supply, and flow rate of steam, as well as high flue gas temperature acquired by acoustic pyromety, have been served as input parameters and trained in ANN. Finally, a test has been taken to validate its feasibility and reliability.A domestic 300MW utility is served as the research subject; and a acoustic pyromety based monitoring system has been developed. A successful hardware framework has been decided; with the help of Delphi6.0, visible online monitoring software could offer visible tips of sootblowing for operators. This intelligent system has contributed a lot for increasing profit, saving energy, lowering maintenance cost and cutting down pollutant emission.