Abstract
From the total electricity generated in South Africa, about 85% is coal based. Coal powder is a solid fuel used in injectors for electricity production. The coal powder is extremely abrasive therefore it is important to maintain a minimum admissible flow speed. As the most severe pipe wall erosion takes place in bends, the most significant factor influencing wall erosion is the solid particle velocity. The aim of this research was to reduce the wall erosion through flow velocity control. Computational fluid dynamics (CFD) simulations, showed that for the same velocity, the erosion is dependent on flow direction change and the ratio between the radius of the bend and pipe diameter. The reduction of flow velocity was achieved by subtracting a spiral volume, from the inner volume of a horizontal pipe, just before an upward or downward bend. The modified volume geometry generated a vortex flow in the bend, achieving a more even distribution of maximum erosion points over the bend surface. The wall erosion, expressed in mm–wall thickness loss/hour, in the modified volume decreased by about 28,8 % while the installation life expectancy increased significantly. Furthermore the bend radius was proved to influence the erosion magnitude and location.
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