Application of CFD in the design of a grit collection system for the coal-fired power generation industry

A series of Computational Fluid Dynamics (CFD) simulations have been performed to evaluate the performance of a potential grit collector arrangement so as to assist the design of a new grit collection unit at a black-coal fired Power Station. Coarse ash particles are separated from the flue gas as it passes through a 90° bend prior to the ash-laden gas entering air heaters. An arrangement of baffles at the bend is used to enhance gas-particle separation. A mechanical conveying system was previously used to carry some of the collected grit material out of the grit collection unit, but it was found that this system requires a large amount of maintenance and is intrinsically unreliable, which is costly to the operator. A general design principle, which can be readily applied to design or modify a grit collection system has been developed. The CFD simulations show the same collection efficiency could also be achieved with a gravity removal system which has fewer moving parts and internal baffles. A detailed description of the grit collector designs simulated and a comparison of their predicted grit collection efficiencies are presented.