| Circulating Fluidized Bed Combustion (CFBC) technology is a kind of new clean combustion technology. Since it can realize the combustion in comparatively lower temperature, the emission of SO2 and NOx is much less than that of the popular pulverized coal fired boiler when burning the same coal. Hence the technology can solve the pollutant problems of SO2 and NOx that other coal-fired boilers cannot solve. As a result, the CFBC technology is developing rapidly in the world, and it has been well put into use on some medium and small sized boilers.In this paper, the characteristics of CFBC technology is introduced and compared with pulverized coal fired boiler, which helps to indicate the advantages of CFBC boiler. In the mean time, the development trend of CFBC technology, home and abroad, is explained in detail and the inevitability and enlarged trend of CFBC boiler are analyzed.A plot 460t/h CFBC boiler is illuminated. The inner structure and interactive relations of each part and the mutual relations between working medium flow and flue gas flow are emphasized. The drum, water-cooling system, combustion type, heat system, combustion system, super-heater, re-heater, economizer, air pre-heater, separator, loop seal system, steel structure, ladders and platform, furnace wall and insulation, desulphurization, emission of NOx, measures of anti-wear, seal and low temperature corrosion, and so on are explained in detail also. In the paper, in order to be in accordance with the theoretical requirements, the heat transfers of water-cooling wall, panel heating surface, cyclone separator and back-end heating surface are calculated. In addition, some experienced design data in normal boiler design are cited also to keep close to practical conditions.The paper not only introduces the detail design of CFB boiler parts in words, but also lists a summary sheet of heat calculation, in which the following items are listed: fuel element content, theoretical air flow, theoretical flue gas flow, boiler heat balance calculation, coal consumption, excess air coefficient of each heating surface, tubediameter and wall thickness, inlet/outlet temperature and flow velocity of working medium, flow velocity of flue gas, heat-transfer temperature and pressure, heat-transfer coefficient, area and amount. Since the data listed in the above-mentioned summary sheet are exactly and carefully calculated, it has powerful theoretical bases and offers possibilities for practical boiler design and manufacture.In this paper, the furnace structure- one of the main parts of CFBC boiler is illuminated in detail. The distribution of combustion quotient, main structure of furnace, local area, arrangement of upper heating surface and openings in furnace are considered. The design of lower, middle and upper furnace and location and arrangement of secondary air are discoursed upon separately to explain consideration of each part during detail design. Water wall, re-heater panel and super-heater panel are discoursed upon separately to explain arrangement of upper heating surface. In addition, coal feeding ports, limestone feeding ports, slag-drip opening, circulating material inlets, observation holes, access doors and testing holes etc. are discussed separately to explain the openings of furnace.The cyclone separator is emphasized in detail, at which CFBC boiler differs the most with pulverized coal fired boiler. The types and main dimensions of domestic cyclone separators are depicted and listed in tables. In the design of cyclone separator, high temperature insulating cyclone separator, which is more popular currently, has being recommended, and the new type of water-cooled and/or steam-cooled cyclone separators are also compared with this type of separator. The advantages and feasibility of high temperature insulating cyclone separator are indicated. In addition, for the plot design, the concrete structure and specialty of the designed cyclone are introduced; the conduct heat transfer and the structure are calculated also. |
PDF Full Text Request