Clean and efficient fluidized bed power generation technology Zheng Chunying, Sun Fu, Zhu Liubin (Heilongjiang Electric Power Research Institute, Harbin 150090, Heilongjiang) Fluidized bed power generation technology is one of the important technologies. Fluidized bed boilers are classified according to their development process, including a boiling furnace, a circulating fluidized bed boiler and a pressurized fluidized bed boiler. Atmospheric pressure circulating fluidized bed boilers are being promoted and applied in the world. In Japan alone, there are three methods: stone planting, Mitsubishi and Chuanzhong. In order to further improve combustion efficiency and power generation efficiency, the United States, Sweden, Spain, Germany, Japan and other countries are developing and constructing a combined circulating fluidized bed boiler combined cycle generator set, of which Japan has built the world's largest 360MWA unit. Practice has proved that fluidized bed power generation technology, especially combined with pressurized fluidized bed boiler combined cycle power generation technology, has the advantages of high efficiency, good environmental protection characteristics, miniaturization, etc. It is the development direction of thermal power in China, and fundamentally solves the thermal power plant to the atmosphere. Serious pollution to achieve sustainable development of electricity. 0 Foreword The proportion of coal in China's primary energy production and consumption is as high as 75%, which will not change greatly in the future. At present, the conversion utilization rate of coal in China is relatively low, and combustion emissions have become the main source of pollution in the atmospheric environment. The development of high-efficiency, low-pollution coal-fired power generation technology is an important strategic measure for China to implement the basic national policy of environmental protection and achieve sustainable development of the power industry. The leaders of the State Power Corporation pointed out at the on-site exchange meeting of circulating fluidized bed boilers held in April 1999: Through the introduction and digestion of circulating fluidized bed technology in China in the past few years, the circulating fluidized bed technology can achieve sustainable development of electricity and power structure adjustment. Want to be a computer professional, engineer. Seeking, can fundamentally solve the serious pollution of the thermal power plant in China. The investment in circulating fluidized bed boilers is less than that of conventional boilers plus flue gas desulfurization equipment, and China currently has a certain amount of technology and talent reserves. After the large-scale and localization, the margin of circulating fluidized bed to reduce investment is still very large. Large-scale circulating fluidized bed will become the development direction of thermal power in China. The State Power Corporation will include circulating fluidized bed (CFBC) technology, combined fluidized bed boiler (FBC-CC) power generation technology and integrated gasification combined cycle (IGCC) power generation. The clean coal power generation technology including technology is included in the “10th Five-Year Plan†for scientific and technological development and the 2015 plan. 1 Fluidized bed combustion technology improves unit power generation efficiency and reduces environmental pollution, which is the direction pursued by coal-fired units. The so-called clean coal power generation technology refers to the lowest cost coal power generation technology that can obtain the most convenience and the lowest environmental load. In other words, in the development of clean coal power generation technology, it is necessary to pursue both high technology and technologies that may be cheap to build and operate. One of them is circulating fluidized bed power generation technology. Fluidized bed combustion is now becoming the main combustion mode for coal-fired boilers in parallel with pulverized coal combustion. In particular, its low-NOx combustion, desulfurization and other low-pollution properties are more important, so it is widely used. Fluidized bed boilers are classified according to their development process, and there are the following three types. 1.1 The boiling furnace burns fuel in a low-speed fluidized bed, and the flowing particles move through the bubbles in the fluidized bed to maintain the boiling state in the bed. Compared with pulverized coal combustion, it has the following advantages: a. The flow particles have large heat capacity, strong mixing, good fuel adaptability, and combustible use of inferior fuel including coal gangue; The heat transfer rate between the heat transfer tube and the flowing particles in the bed is high, so the heat transfer area can be reduced, and the boiler can be miniaturized; c. Desulfurization agent such as limestone can be used to realize desulfurization in the furnace without separately providing a desulfurization device; Low temperature combustion can suppress the production of NOx; The coarse pulverization of coal can be done without the need for milling system equipment. 1. Compared with the boiling furnace, the circulating fluidized bed boiler has stronger mixing of the flowing particles and the gas. The particles scatter with the gas, are collected by the cyclone separator and then returned to the combustion chamber, and the flowing particles are blown above the coal burning chamber in the furnace. A fluidized bed is formed. The characteristics are as follows: a. Maintaining a long residence time in the furnace through the particle circulation, the Ca/S molar ratio in the desulfurization reaction is small, and the desulfurizing agent is used in a small amount; the b particle circulation amount is equivalent to 40 to 100 times the coal supply amount; By controlling the amount of particle circulation, it can be adapted to low-load operation of the boiler. 1.3 The pressurized fluidized bed boiler 59~1.96MPa has the following advantages: a. The gas turbine can be driven by the residual pressure of the combustion gas and the residual heat to form a combined cycle to further improve the power generation efficiency; b. The ash can be well recycled and improved Combustion efficiency; The desulfurization rate in the furnace is higher and the NOx production rate is lower; d. The overall structure is very compact, reducing the construction cost and shortening the installation period. 2 Application of atmospheric pressure circulating fluidized bed boilers The atmospheric pressure circulating fluidized bed boilers are promoted and applied in the world. France put into operation 125MW units in 1990, and put 250MW units in 1992. The desulfurization efficiency is 99.7% of the S2 in the exhaust, below NOx, the dust is below 10mg/m3, and the boiler efficiency is 95.71%. It is planned to develop 600MW and 26.47MPa supercritical pressure units. The United States has built two 220MW units. There are currently 13 100~200t/h atmospheric circulating fluidized bed boilers in Korea. In 1998 and 1999, Korea Electric Power Company put into operation three self-developed 200MW units burning domestic anthracite with NOx emission concentration of 205mg/m3. Below, Thailand is constructing two 150MW cogeneration units, and the concentration of S2 in the exhaust gas is reduced by desulfurization in the furnace, below. Neijiang Power Plant Gaoba Power Plant is China's largest demonstration base for circulating fluidized bed boilers with an installed capacity of 100MW. It has introduced a 410t/h atmospheric circulating fluidized bed boiler from Austin, Finland. It has been stable since it was put into operation in 1996. run. Burning local anthracite and anthracite with high sulfur content, the desulfurization efficiency is more than 90%. In Japan, there are three ways to classify according to the manufacturing company: the whole system of circulating fluidized bed boiler with coal-fired coal as fuel, as shown. The circulating fluidized bed is formed from ash, limestone and bed material in the coal. The coal is pulverized into a coal piece of less than 10 mm by a pulverizer, and the primary air is supplied through a nozzle, and the secondary air is supplied from the two-stage combustion air passage provided in the upper part of the furnace. The circulating medium separated by the cyclone is recirculated into the furnace through an annular seal. The flue gas is removed from the air preheater and then removed by a bag filter. Practice has shown that the higher the fuel ratio, the less the NOx emission. When the fuel-fuel ratio is 6%, the NOx emission is about 51mg/m3, and the Ca and coal in the limestone. The S molar ratio is 2.0 sulfur ratio of about 80% Ca / S is 2.5, S2 emissions The fuel of the Mitsubishi type circulating fluidized bed boiler is a mixture of coal and papermaking sludge, the system is as shown. The furnace is surrounded by a water-cooled wall, and the combustion portion, the convective heat transfer portion in the rear flue, and the fluidized bed heat exchanger (FBHE) form an integrated structure, achieving miniaturization. A plurality of fluidizing air nozzles are arranged on the coal burning chamber and the FBHE sealed box sealing portion, and the water cooling wall and the superheater are usually arranged in the FBHE, and the convection heat transfer portion is provided with a primary superheater, a secondary superheater, an evaporator, and a province. Coal, air preheater. There is no heat transfer tube such as a superheater in the combustion chamber. Due to the low flow rate and fine particles in the FBHE, the inner tube of the bed is less worn. The Chuanzhong method is a hybrid circulating fluidized bed boiler with both boiling and circulation characteristics, and the system is as shown. The coal powder with the particle size below 10mm merges with the circulating particles in the sealed box, and is sent to the fluidized bed for combustion. The combustion heat in the bed is recycled by the cyclone to heat the particles at a lower temperature of 400-500C to make the fluidized. The bed is often kept at 350 C. suitable for desulfurization and combustion. The recycled granules and small diameter pulverized coal particles are mixed with the secondary air in the suspension section to burn about 40% of the remaining coal. The particles cooled by the circulating evaporator tube, the superheater and the air-cooled wall tube, the circulating particles cool the suspension section to 800-900, and maintain sufficient residence time at this temperature, and the secondary air is appropriately fed to maintain a low level. The amount of NOx, S2, and CO generated. 3 Pressurized Fluidized Bed Boiler Combined Cycle (PFBC-CC) Power Generation Technology - CC Power Generation Technology Features The PBFC-CC unit is equipped with a fluidized bed boiler in a pressure vessel and burned under pressure to further improve combustion efficiency. At the same time, the conventional steam turbine power generation and the gas turbine power generation driven by the high-temperature high-pressure combustion gas of the fluidized bed boiler constitute a combined cycle power generation system. Its characteristics are as follows: high efficiency. The combined cycle system improves the power generation efficiency, uses the gas turbine air compressor, omits the blower; desulfurization in the furnace, omitting the desulfurization device, saving the plant electricity, and improving the efficiency of the power transmission end compared with the ordinary coal powder furnace thermal power generation The characteristics are good, the desulfurization in the furnace can be realized, the oxide reacts with the limestone to form gypsum, and is removed together with the coal ash by a dust removing device. Because the fluidized bed boiler utilizes high-pressure air, the fluidized bed has higher ventilation resistance and forms a high combustion bed, so that the residence time of the combustion substance in the bed is longer (about 4 s), so that higher desulfurization efficiency can be obtained. Since the combustion temperature in the combustion bed is lower than 860 ~ 870V, the NOx in the air can be suppressed, and the residence time of the fuel in the bed is long, and the fuel has a lot of contact with the reducing substance in the combustion process. Thereby a low NOx combustion is formed. The increase in power generation efficiency makes C2 production less than the ordinary pulverized coal furnace. In order to prevent gas turbine wear, a dust separator such as a cyclone separator and a ceramic filter is installed at the outlet of the boiler to make the dust concentration lower than the allowable concentration of the gas turbine. The low temperature part of the chimney entrance is equipped with an electric precipitator, which greatly improves the dust removal effect. c miniaturization. Since it is burned under positive pressure, the boiler can be miniaturized, the need for a flue gas desulfurization device is increased, the installation space is reduced, and the miniaturization of the entire power plant can be realized. PFBC-CC power generation technology application of pressurized fluidized bed combined power generation (PFBC developed by Europe as a new generation of coal-fired thermal power generation with low environmental impact under high efficiency, including the construction of the unit, the world It has the development performance of seven 70~80MW units. In 1969, the United States installed the first test equipment, and carried out tests on combustion characteristics, environmental characteristics, and corrosion characteristics of gas turbine blades. In the 1970s, the United States and Russia jointly invested in the construction of a 60MW test unit in the United Kingdom. In 1980, it was put into operation, obtained various design data, and conducted gas turbine material testing. As one of the US Department of Energy's plans to promote clean coal technology, the American Electric Power Company built a 73MW unit, which was put into operation in 1990 and completed its application test in 1995. In 1987, Stockholm Energy Company of Sweden built a cogeneration combined cycle unit consisting of two pressurized fluidized bed boilers, two gas turbines and one steam turbine. The output was 135MW/224MWth. It was put into operation in 1989 and entered commercial operation. The Spanish state-owned power company developed a pressurized fluidized bed boiler as a low-pollution technology that can effectively utilize domestically inferior lignite technology. In 1990, it put into operation a 79MW combined cycle unit. In order to strengthen environmental protection, Germany has put into operation 71MW combined heat and power combined pressurized fluidized bed combined cycle unit in 1998. Japan's power development company built Japan's first 71MWPFBC-CC unit, and completed the application test in December 1997; Hokkaido Electric Power Company commissioned the No. 3 85MW unit of Jidong Houzheng Power Plant in March 1998; Kyushu Electric Power Company invested in July 1999 The new No. 1 unit of the 360MW Putian Power Plant, the largest force in the world, has been shipped; China Power Corporation plans to build two 250MW units in the No. 1 series of Daqi Power Plant. 3.3 Putian Power Plant New No. 1 PFBC-CC Unit Putian Power Plant No. 1 PFBC-CC unit system, as shown. The pressurized circulating fluidized bed boiler adopts ABB's hybrid mode, which combines the functions of a boiling and circulating fluidized bed. It is a fluidized bed-through method designed with a new concept. The evaporation amount is 260t/h, the main steam pressure is 25.0MPa, the steam temperature is 570/595C, the combustion pressure is 1.4MPa, the combustion temperature is 870 C, and the first, second and second cyclone separators are used for the coal, limestone and water. Pressure-resistant equipment such as bed storage containers and ash coolers are installed in a vertical cylindrical pressure vessel made of steel plate and supported by the side plates of the pressure vessel to simplify the interior of the vessel. In order to miniaturize the pressure vessel, the furnace section is hexagonal, and the inner tube is arranged in an equal quadrilateral shape. Inner diameter 15.4m, height 44.6m, carcass thickness 89.4mm, liner thickness air temperature 350C air pressure 1.68MPa gas turbine adopts ABB's pressurized circulating fluidized bed boiler supporting open-cycle double-shaft gas turbine, suitable for combustion 2 A device with a high dust concentration of flue gas after dedusting of a cyclone separator. The output is 75MW, the inlet gas pressure is about 1.3MPa, the inlet gas temperature is about 850, the outlet is about 390°C, the rotation speed is 3600r/min under high pressure, and the low pressure is 1 250~3150r/min. The double-shaft gas turbine has good air flow control. Features to ensure good load tracking characteristics of the unit. The high-pressure shaft is directly connected to the generator and operates at the rated speed. The low-pressure shaft can adjust the air flow using the low-pressure gas turbine inlet guide vanes corresponding to the output to improve the efficiency during low-load operation. The steam turbine is a cascade reheating condensing steam type with an output of 290 MW. The main steam pressure is 24.1 MPa. The steam is large. The steam parameters of the large steam turbine of 500 MW or more are used. The main steam pressure is 24.1 MPa and the steam temperature is 566/593 C. In order to improve the turbine efficiency, The low pressure is not graded with 40 inch titanium blades. The new Unit 1 uses a multi-axis combined system consisting of a turbo generator and a gas turbine generator. The gas turbine generator adopts a horizontal cylindrical rotating magnetic field generator and a brushless excitation method, and the stator and the rotor are all air-cooled. The start-up uses a thyristor frequency converter (SFC) to use the generator as a synchronous machine. Turbine generators also use horizontal cylindrical rotating field generators and thyristor static excitation with excellent response characteristics. In order to improve the power generation efficiency, a high-efficiency fan is adopted in the rotor, and the cooling efficiency is improved by optimizing the design of the end ventilation of the core. Through the desulfurization in the furnace, the SOx concentration in the flue gas is reduced to below 217 mg/m3; the NOx is reduced to below 123 mg/m3 by the low temperature combustion of the fluidized bed and the treatment of the dry denitrification device; the dust is removed once by the two-stage cyclone separator. With the secondary dust removal of the electrostatic precipitator, the dust concentration is reduced to less than 30mg/m3. 4 Conclusion Fluidized bed combustion technology, especially pressurized circulating fluidized bed combustion technology, is an important clean coal power generation technology, and pressurized fluidized bed boiler combined power generation technology can not only achieve clean coal power generation but also improve power generation efficiency. 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