| Circulating fluidized bed combustion technology is the best commercialization of clean coal combustion technology, and it was used in the power generation of atmospheric circulating fluidized bed combustion technology from the late 1970s. As an efficient, low-cost clean combustion technology, it has many advantages, such as, high combustion efficiency, fuel adaptability, boiler loading ratio width, convenient load regulation, less pollutant emissions, facilitate the comprehensive utilization of ash.Researchers have made an independent development and research work on CFB boiler in China for a long period, and formed a practice proven system of design theory and methods to make a positive contribution for the development of China's CFB boiler technology, while also promoting the development of circulating fluidized bed combustion technology in the world. However, we can only product a small capacity boiler unit in using domestic technology, and also the self-development requires a lot of time and investment, in order to bring manufacture technology of China's CFB boiler to large-scale, we began the introduction of CFB boiler technology from abroad. Due to the introduction involves many confidential work of key technologies, in order to absorb the imported technology and integrate into the existing of the design and operation practices in China, and also to adapt China's national conditions and characteristics of chinese coal, economic situation and the user's requirements, localization of overseas technology completely is need, so as to provide reference for CFB boiler design in China. And make a consultation and cooperation with Pu Hua members (the major domestic boiler factory, the relevant universities and research departments), whom do an on-site researching on some already running CFB boilers of 200MW~300MW units.In this article I will make a necessary research for the furnace thermal calculation of CFB boiler. First, the heat transfer mechanism is based on the characteristics of gas-solid flow in furnace of the CFB boiler, and I make a summarizing and simply analysing on the furnace flow characteristics of CFB boiler which are currently accepted by general people. Secondly, I make an explaining and analysing on the furnace heat transfer mechanism and some heat transfer models. Third, through the understanding of gas-flow characteristics and heat transfer mechanisms, and combined with the survey information, this article summarized and established a completely heat transfer coefficient calculation model of CFB boiler's furnace. Using this model to analyse the effect factors which affecting the heat transfer coefficient of CFB boiler furnace. The effect factors include structure and size of the heated surface, bed-side temperature Tb, working fluid temperature Tf, heat transfer coefficient of working fluid sideαf and wall surface blacknessεw. Calculations showed that the model can reasonably reflect the trends of corresponding influence factors on heat transfer coefficient. Through analyse the field data and summarize the previous experience of operation, this article also provides a reference range of some performance parameters. At the end of chapter three of this article, I have made a simulation check thermodynamic calculation for a real 200MWCFB boiler in a power plant.Although the CFB boiler has many significant advantages, there are also a lot of problems in the field operation. Among them, the significant problem is operation problem of the slag cooler. As one of the key auxiliary equipment of the CFB boiler, slag cooler operating conditions have a direct bearing on security and stability of the boiler unit whether can run continuously. This will also become a difficult problem which restricted the development of CFB boiler technology. The main reason of the operating problem is the coal particle size too large, causing the inside of the Water Combined Ash Cooler over-temperature, scorification, congestion, wear and dishing problems, users are urging to solve the problems. As things stand, the majority of domestic power plants are using drum-type slag cooler, but the drum-type slag cooler can only meet the cooling requirements of the boiler's bottom ash, which can not be fully effective use of the bottom ash's physical heat. Given this situation, the Shanghai Boiler Works Co., Ltd. put forward a new CFB boiler bottom ash cooling method. In this method the high-temperature section of the bottom ash with a serpentine tube arrangement of heating surface which as part of the economizer is called the mobile-bed slag cooler, whose is direct recycling the physical heat of bottom ash. In the low temperature section of the bottom ash, it is a conventional drum-type slag cooler.In this article I do a cold-state experimental of flow and heat transfer characteristics on the mobile-bed slag cooler. By the experimental situation can see, the overall flow sitation of the bottom ash is good in the experimental device, and doesn't appear building a bridge phenomenon, just because the contraction paragraph at the bottom of the mobile-bed is flat which lead to a triangle flow stagnation region on both sides of the mobile-bed. Through the cold test calculation of bottom ash heat transfer experimental condition we can know that the heat transfer coefficient between the bottom ash and the heating surface is in the range of 25~30 W/ (m2·K). It's meet the requirements of heat transfer.
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