Numerical investigations of the four-path separator
Wybrane pełne teksty z tego czasopisma
In the pneumatic conveying systems of large power boilers, the required separation of the dust-air mixture to particular burners has to be obtained. This problem is very important in consideration of limitation of losses connected with incomplete combustion, life of many elements of the furnace system and NOx emission. The realized design works on dust pipes are usually based on the assumption that dust concentration in the section is approximately the same and there is no segregation of dust particles. However, in many cases in the pneumatic conveying systems for coal dust, diversified concentration and out-of-control segregation of particles take place. Such segregation leads to diversification of propagation, disturbance in the combustion process and accelerated erosion of the installation elements. This paper presents numerical investigations on the air-coal dust mixture flow through the four-path separator system. Diversification of concentration and particle segregation behind the separator are determined by the elbow presence just before the inlet to the separator. The elbow presence causes diversification of concentration on the mixture silt to the four-path separator located directly over the elbow. It is a reason of the diversified silt of the dust on the boiler corners and the accelerated erosion of separators. The author tried to assess influence of configuration of the pipe delivering the medium to the separator on uniformity of dust separation behind the separator. Numerical investigations were performed for six positions of the inlet interval before the separator at different velocities and dimensions of the dust particles. In order to realize calculations for three-dimensional geometry, the Euler model was selected for description of the gaseous phase motion, and the Lagrange model was used for description of the particle motion. From analysis of the performed calculations it appears that the inlet configuration in relation to the separator strongly influences the proper dust separation to outlets. The best dust separation can be observed for the inlet location angle in the range 60÷90°.
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