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Optimizing hydrodynamic forces for gypsum scale removal and analysis through modeling using COMSOL
Author :Shahid Z. Ansari a, Anjali A. Ingle b, Diwakar Z. Shende b and Aniruddha B. Pandit *a
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ABSTRACT
Metal salts deposition on the surfaces of heat transfer equipment is one of the critical problems faced in chemical industries. A slight change in operating parameters of the process fluid after coming in contact with a foreign surface or particle often results in equilibrium shift of the dissolved metal ions leading to scale deposition. This causes reduced thermal efficiency, high maintenance cost and increased pressure drop in the unit has been observed followed by plant shut down for maintenance.
The present work involves a systematic simulation and modelling of a Stirred Tank Reactor (STR) with different orientations of the impeller. The effect of the fluid flow and hydrodynamic condition on surface of the impellers was studied and compared with experimental values from literature to confirm its significance on gypsum scale deposition or removal from the metal surface. The system was modelled using multiphysics software COMSOL version 5 for understanding of the process. It was observed that on increasing Reynolds number (Re), linear tip velocity (V) and shear rate (s–1) of the fluid, the rate of scale deposition increased up to Re of 21,000, V of 3.5–4 m/s and s of 25–33 1/s respectively. However, beyond these values the rate of scale formation and deposition started reducing and further increase in these parameters leads to physical attrition of the metal surface.
KEYWORD
Gypsum scale, inhibition, COMSOL, erosion, Reynolds number