A 65-t/h oil shale-fired circulating fluidized bed (CFB) boiler of low circulation ratio, the earliest prototype operated in the world, was manually designed by our research group twelve years ago using our experience and published data available. On the basis of the long-term operation, it has been demonstrated that all expected performances, such as high combustion efficiency, low emission of NOx and SOx, stability of operation and flexibility of load change etc., have been reached. For evaluation and confirmation of the manual design, an Expert System (CFBCAD) developed by Greenfield Research Inc. was used to regenerate the boiler. The results from these two approaches were compared and validated, and a reasonable agreement was reached. Finally, the main parameters of the prototype were provided. Some design principles were given and a series of hot operation tests were carried out. The influence of load on the boiler performances such as temperature in the bed and the back pass, and heat loss were assessed and discussed. The properties of self-desulphurization and boiler start-up were also described.
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