| Nearly 5%～10% of generated energy is consumed by its own auxiliary equipments during the energy generation in the power plant. The great portion of energy is consumed by the coal powder preparation system.The coarse coal powder separator as the major equipment of the intermediate storehouse type coal powder preparation system in the power plant, its structural design and working performance have great influence on the performances of the total power plant, such as the life-span of coal mill, the consumed electric power, and the burning of the coal powder in the boiler furnace, etc. Therefore, the quality of the coarse power separator directly affects the security and economy of the power plant operation. An ideal coarse coal power separator should have two unique characteristics as follows: on the one hand, the acceptable fine coal powder can be exported fully with the air flow; on the other hand, the over-sized coal powder can be returned fully to the coal mill to mill again. In the condition of the over-signed coal powder is not allowed to supply into the boiler furnace with the acceptable fine coal powder, the burning efficiency and stability in the furnace will be assured. In the recent years, many coarse coal powder separators used in China power plants, such as the original coarse coal powder separator in No.3 and No.4 boilers in Hunjiang power plant of Jilin province, were derived from the radial-type separator commonly in the former Soviet Union in 1950s~1960s of the 20 century. The separator structure is characterized by internal and external double coal powder retrieving pipelines. The gravitational separation of the air-coal powder mixture occurs between the internal and external cylinders of the separator at first, and the most coarse coal powder returns into the external retrieving pipeline. At the top of the separator there is a ring of radial spiral barriers, which make the air-coal powder mixture rotate around the vertical axis, thus the finer but still unacceptable coal powder falls into the internal retrieving pipeline under the action of the centrifugal force. The main disadvantages of this type of separator are low working efficiency and high flow resistance. Besides, the internal coal powder retrieving pipeline is prone to clog and difficult to clean, resulting in further deterioration of separator performance.In this dissertation, around the topic of the improvement of coarse coal powder separator, following tasks has been accomplished:Modification of separator structure Based on domestic and foreign literatures and the operation experience at the power plants in our province, technical modification was made to the original radial type coarse coal powder separator to form the novel combinational coarse powder separator. The swirling barriers of the separator change from the radial mount on the top to the axial mount between the internal and external cylinders. The axial swirling barriers enhance the rotational movement of the air, coal powder mixture and at the same time exert relatively little resistance on the mixture flow. Two rings of inertia barriers are added in the lower part of separator on the internal cylinder. The internal coal powder-retrieving pipeline is removed and the external retrieving pipeline around the inlet of flow retrieves the all of the over-sized coal powder. The expanding mouth pipeline replaces the original simple straight entry pipeline. The flow of air with coal powder passes through the entry and performs the gravitational separation of the most coarse coal powder in the expanded space between the internal and external cylinders. The air-coal powder mixture flow rises from the bottom to the top of the separator. When the mixture flow strikes on the inertia barriers, a part of the coarse coal powder is separated further by the particle inertia. As the mixture flow rises further and passes through the top axial swirling barriers of the separator, a strong helical rotating ascending mixture flow forms. After the mixture flow enters...
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