Research on the heat transfer model of platen heating surface of 300 MW circulating fluidized bed boilers

The heat transfer of the platen heating surface of circulating fluidized bed (CFB) boilers is a complex process. Because of technical protection and difficult measurement, at present there is no public calculation method which can be applied to engineering. Three 300 MW CFB boilers in actual operation in different field sites were conducted, the parameters of temperature and pressure at the side of steam and flue gas were measured respectively. Based on the tests at different loads, the effects of solids suspension concentration and average temperature parameters etc. on the heat transfer were investigated, and then the heat transfer coefficient calculation model of platen heating surface at the flue gas side was established, which takes the effects of structure and dimension of platen heating surface, furnace temperature, steam temperature, heat transfer coefficient at the steam side, emissivity of tube wall and fluidization velocity etc. into consideration. The field test data obtained from another 300 MW CFB boiler were used to verify the model. After comparing the calculated results and the values from the actual field test, it is found that the error is lower than 5%, which is within the precision permission range of engineering application. It is indicated that the calculation results using this model agree well with the experimental results on the site, confirming the reliability of this heat transfer model, which means that it can be used to calculate the heat transfer of platen heating surface of 300 MW CFB boiler and can provide reference for design, commissioning, operation of 300 MW CFB boilers.

Fig. 1 The arrangement of platen heating surface of No. 1 and No. 2 boilers.Figure optionsDownload as PowerPoint slideHighlights
► A heat transfer model of platen heating surface at flue gas side is established.
► The data obtained from this model agree well with the experimental results.
► The HTCs of different 300 MW CFB boilers were analyzed at different loads.
► The radiation heat transfer share gradually decreases with the load increasing.