| In recent years, the circulating fluidized-bed combustion technology has been gradually developed. This caused the large-scale circulating fluidized-bed boiler (CFBB) to develop rapidly. But the boilers adopting the introduced technology and produced by Harbin, Shanghai and Dongfang Boiler Manufacturer existed various problems during running, such as tube explosion, wearing, fuel clogging, no slag discharge, exfoliate of refractory, deflection combustion in furnace, high combustible matter in fly ash and etc. They seriously influenced the reliable running of boilers. The continuous running time was only 80 days. Furthermore they seriously influenced the economic benefit of power plant. The writer analyses and researches the performance of 440t/h super-pressure and reheating CFBB developed by Jinan Boiler Group (JBG)1. Selection of Boiler TypeAt present, there are three types of large-scale CFBB: the one is that with single-furnace, double gas flue and high-temperature heat-insulating separator; the second is that with double-furnace, single gas flue and high-temperature heat-insulating separator; the third is that with double-furnace, double gas flue and steam cooled separator. Along with the increasing of requirements for the safety and reliability of large-scale CFBB, the requirements for boiler arrangement is also increasing. This article gives the analysis, selection, heat calculation and arrangement to different type of boiler.2. Design of Key PartsDue to the increase of boiler capacity, the key parts such as high-temperature separator, fuel returning device, air button and etc. shall be suitable to the requirements of large scale and high material circulation. Especially the high-temperature separator is the kernel part of boiler. It's diameter is 8 meters and therefore it is the pivot of design that how to ensure the separating efficiency of separator and the reliability of boiler. It gives out a new design idea after analyzing the factors that will influence the separating efficiency of separator and making a test on how the inserted depth and diameter of cyclone will influence the separating efficiency of separator.3. Wear-resisting of BoilerAmong the present running CFBB, the shutdown of boiler caused by wearing occupies a large proportion of boiler troubles. So it gives out a brief analysis on wear-resisting of boiler according to the requirements of wear-resistance and points out a new wear-resisting structure for the furnace transition zone, that is the three elbows structure. This is the original creation.4. Selection of Slag CondenserSlag discharge is the key process of normal running of large-scale CFBB and slag condenser is the key equipment for bottom slag condensing system. So the abnormal operation of condenser becomes the main reason causing the passive shutdown and trip-out of large-scale CFBB. It analyses the theory and structure of air and water cooled condenser and drum condenser according the requirements for slag discharge of boiler and furthermore points out the collocation requirements.5. Requirements for Boiler Economic and Safety PerformanceHow to assure the continuous, reliable and economic running of boiler is the chief problem of each CFBB power plant. So it gives out a general discussion on how to increase the boiler efficiency and reduce the combustibles in fly ash.The boiler was put into running in December, 2004. It's thermal efficiency and pollution emission has been tested. The testing results express that the boiler output, efficiency and emission index are all up to or higher than the design requirements, and prove that the design is successful. |
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