Numerical Calculation Of Air Preheater And Study On Air Leakage

Rotary Air Preheater is one of the main auxiliaries in heavy-duty plant. It has a lot of advantages such as the structure of tight, outside dimension small, easy deployment, the temperature of the surface being high; the corrosion of the dust gas is lighter and so on. But owing to the air pre-heater has intrinsic characteristic in structure and the high pressure in air side, there always some air leak into the smoke sides. Thus the thermal efficiency of the hearth and wind volume supply is affected seriously. Too much air leaking into gas side, not only makes the use of the electricity increase in the blower and the air compressors, but also leads to the lack of air supplied for fuel. This makes the boiler run in low load, and affects security and economy seriously.This paper introduces the principle of air preheater and the common problems in the operation:the high rate of air leakage, low temperature corrosion and clogging. The real-time monitoring the temperature of the metal plate heat storage is the key. As the rotary air preheater rotor is constantly rotating, it is difficult to realize real-time monitoring of plate temperature. In this paper, a finite difference method is used. A procedure is to spread the rotor’s peripheral side in the rotor’s rotary velocity direction and set grids between the matrix element and the fluid based on the energy balance equation between the matrix element and the stream. In addition, by combining the air-leakage factor and using an improved Gauss-Sidel arithmetic for iteration, a program is developed to calculate the heat transfer performance of tri-sectional air-preheater.According to the metal and fluid temperature distribution, the results of the flow resistance in the the flow channel of rotor component, the seal gap of air preheater and the air leakage quantity was obtained. Radial leakage in the hot end accounts for the vast majority of the direct air leakage, which is much more than the carrying leakage. Radial leakage in the hot end is most because of its large seal gap. The paper also makes a comparison of results between single channel seal and double channel seal. The results showed that the air leakage with dual channel seal dropped by nearly 30% compared with the air leakage with the single channel seal.