Computational prediction of erosion of air heater elements by fly ash particles

The service life of regenerative air heaters in some coal-fired power stations operated by Eskom (South Africa's national power producer) is significantly reduced by erosion resulting from collisions between fly ash particles and the steel air heater elements. In the present study, the fly ash erosion model for steel plates previously developed by the authors [1] was integrated with the gas-particle flow field as modelled using commercial computational fluid dynamics (CFD) software. Three plate element geometries were used for CFD simulations of the erosion of air heater elements in Eskom power stations. The erosion rates predicted in this way were validated by being found to differ by not more than 25%, but in the majority of cases by not more than 10%, from the values measured by Crookes [2] using a large accelerated erosion test facility located at a power station. Seven different plate element profiles were used to investigate how erosion varies with the element geometry under the operational conditions for Matimba Power Station (as an example). Very low erosion rates (less than 0.5 mg of steel removed per kilogram of ash throughput) and long service lives were predicted for the elements with the flow channels between the plates running parallel to the direction of bulk gas flow. On the other hand, high erosion rates (2-5 mg/kg) and shorter service lives (15-35 years) were predicted for the elements with plates having corrugations that run at an angle to the direction of bulk gas flow. © 2006 Elsevier B.V. All rights reserved.