Theoretical And Experimental Researches On Fouling Monitoring Of Heat Transfer Surface And Sootblowing Optimization In Utility Boiler

Slagging and fouling on heat transfer surface is a familiar and unavoidable problem of power boiler, which is adverse to keep boiler running safely and economically. Blowing boiler heat transfer surface with high pressure and high temperature steam is one of the commonly effective methods to avoid severe ash deposits and slagging. Because it's very difficult for operating personnel to estimate the fouling degree of heat transfer surface directly by thermodynamic parameters, such as temperature, pressure of flue gas and steam, multiple soot-blowers are continuously initiated according to pre-defined sequence and a fixed schedule in all the power stations. But that's not very reasonable, so sometimes the soot-blowers are operated more frequently, sometimes far less frequently. Far less frequent blowing allows too much soot accumulation and hence decreases heat transfer efficiency, while more frequently operation of soot-blowers wastes steam, increases blower maintenance cost, and aggravates the tube erosion.Therefore, it is quite necessary to continuously monitor fouling degree on heat transfer surface during boiler operation and give advisory to initiate sootblowing under proper operational conditions. The basic requirement for optimal sootblowing is to maintain normal state of heating surface and reduce the steam consumption to practical minimum. Intelligent adjustment of the cleaning schedule according to the actual cleaning need becomes the means of achieving our primary goal, increased boiler efficiency and reduced opacity.The mechanism of fouling accumulation, characteristic of fouling increasing, fouling monitoring of radiant and convective surface, development of sootblowing optimization model are researched in theory or conducted in experiment, and the institution of sootblowing strategy is discussed. The main contents of the present paper include:The mechanism of fouling accumulation and the effects of fouling and slagging on boiler performance are analyzed. The model of fouling increasing is developed on the basis of sediment rate and denudation rate. The fouling monitoring models for boiler furnace and convective sections based on heat balance, the ones for air heater based on converted pressure difference are given. The implement results show that these models can reveal the cleanliness of boiler heat transfer surface. The disadvantages of the model for boiler furnace fouling and slagging monitoring based on heat balance are discussed, and the calculation of radiant heat flux is considered as the primary difficulty. A new fouling monitoring model based on artifical neural network is presented in this paper, including characteristic parameters selection and training data acquisition.A series of experimentations are carried out on a 300MW coal-fired boiler, including sootblowing by different pressure steam, sootblowing one-by-one soot-blower, etc. The experiment results show that: (1) One surface's being blown won't induce the fouling rate increase of the surface rapidly on downstream sections; (2) The fouling degree of different heat transfer sections and the cleaning effects of different soot-blowers are quite different, hence, those soot-blowers located in serious fouling area should be operated more often; (3) There exist be a reasonable steam pressure at which the fouling on surface could be eliminated effectively, and the sootblowing steam is saved farthest; (4) Keeping a surface not being blown for a limited long time, its fouling characteristic won't changed so much that the surface couldn't be blown to cleanliness by the same pressure steam.The model of sootblowing optimization is developed in order to improve boiler efficiency, reduce steam consumption, and help controlling steam temperature. The sootblowing optimization system for coal-fired power boiler is developed, which is constituted of original data pretreatment model, boiler efficiency calculation model, on line heat transfer surface fouling monitoring model, and sootblowing optimization model. The implement results on...