The Experimental Research On The External Heat Exchanger For CFB & A Comprehensive Mathematical Model Of CFB Solid Waste Incinerators

An innovative circulating fluidized bed (CFB) technology with compact external heat exchanger (CEHE) was proposed in this thesis. When the technology is applied in solid waste incinerator, it can not only improve the superheated steam temperature but also prevent the superheater' s metal tube from being corroded by HCI, which are contained in the incineration gas. In order to prove the effectiveness of the new CEHE, experimental research on fluid dynamics and heat transfer characteristics of the CEHE was conducted. The new CEHE proved to solve the high-temperature corrosion effectively.It was applied to uitility boiler fired solid waste and coal in Chengdong Combined Heat And Power Plant in Zhejiang province. A CFB solid waste incinerator cofired with coal is designed and is capable of 75 ton superheated steam every hour. The boiler heat and energy balance indicates that the CFB boiler with CEHE can stably operate in the range from 70-110% load. When the load changes, the combustor temperature is stable through adjusting the absorbing heat in CEHE, which is available to the combustion and controlling the concentration ofincineration gas.Based on the existing model of coal-fueled CFB boiler, the new model of solid waste fueled CFB boiler is constructed. The model is one-dimensional steady state and the release profile of volatile in CFB combustor follows Weibull function. It is supposed that the volatile matter contains CO, CO2, H2, CxHy, N2 and SO2. Because of high volatile content and high moisture content, the location of release and combustion of the volatile matter is particularly important for the solid waste incineration. It effects not only the distribution of heat release of the boiler but also the distribution of combustion gases. So the volatile sub-model is emphasized in this thesis and the effects of model parameters of volatile distribution function on combustion are analyzed in detail. The effects of load, the primary air to second air ratio, coal to solid waste ratio, moisture content is predicted. It is shown that the results conform to the practice. The computer program provides the effective tools to the operation of solid waste incinerator and provide beneficial guidance to optimize some design parameters.