Fouling growth modeling of kraft recovery boiler fume ash deposits with dynamic meshes and a mechanistic sticking approach

The buildup of ash deposits represents a major challenge in the operation of industrial boilers since it entails significant losses in heat transfer performance. Therefore, the research of predictive tools is of great value in boiler operation. A CFD model for ash deposition and fouling growth prediction of industrial furnaces is presented. Considerations are taken regarding grid resolution and accuracy requirements available in literature. A 2D transversally-periodic bundle of four in-line tubes of a kraft recovery boiler bank is modeled with the gas laden with discrete solid fume ash particles. A sticking-rebound submodel determines whether to account the mass of a hitting particle for the deposit growth or to make it rebound, re-entraining it back into the flow. A dynamic mesh modifies periodically the model grid, simulating the expansion of deposits. 0.7 mu m diameter particles showed round and uniform deposits caused by thermophoresis. The deposit thickness grew up to about 3 mm after 100 min of fouling. 3.62 mu m particle showed more irregular distributions with some high local peaks, but lower deposition rates in average. For this particular case modeled, the constant particle sticking probability approach showed no major differences with respect to the particle sticking submodel. (C) 2016 Elsevier Ltd. All rights reserved.