Study of Particulate and Sulfur Dioxide Removal Efficiency in Wet Scrubbers for Flue Gas Desulphurization /

Abstract

Industrial emissions are becoming major source of air pollution. Different scrubbing technologies are used to overcome such emissions. Venturi scrubber is one of those technologies that assist in simultaneous removal of particulates and toxic gases. In this regard, the simulation is performed in ANSYS-CFX to study removal efficiencies of particulates and sulfur dioxide inside circular venturi scrubber. The venturi scrubber is designed in ANSYS design modular, comprise of three sections i.e. converging, throat and diverging section. The four concentric nozzles are placed on throat section for water injection, whereas gas is injected through converging segment. Eulerian-Lagrangian approach is employed in ANSYS-CFX to investigate particulate and sulfur dioxide removal efficiencies. RNG k-ε turbulence model is used to study turbulence characteristics of phases involved in the simulation. The chemical reaction between water and sulfur dioxide is studied by using transport equation in terms of defining sources for reactants and products. The droplet diameter is estimated by means of using Cascade Atomization Breakup (CAB) model. Throat gas velocity, required operational power, pressure drop, droplet size and water volume fraction are analyzed to estimate particulate collection efficiency. Response surface method is used to obtain optimized results for pressure drop. The parameters such as mass concentration of product i.e. sulfurous acid formation, sulfur dioxide mass concentration and distribution of water mass content within different sections of the venturi scrubber are inspected to determine sulfur dioxide removal efficiency. The affect of sulfur dioxide concentration on sulfur dioxide abatement effectiveness is also accounted. The liquid to gas ratio affect at specific throat gas velocities on particulates and sulfur dioxide removal efficiency are also considered in this research. The simulated particulate and sulfur dioxide removal efficiency is studied at different water and gas mass flow rates. The inlet boundary conditions of 0.093 kg/s, 0.279 kg/s and 0.35 kg/s air mass flow rates and water mass flow rates of 0.07 kg/s, 0.211 kg/s and 0.35 kg/s are used in the simulation. The results shows that the increase in particulates removal efficiency occurred by increasing gas mass flow rate and liquid to gas ratio at particular gas velocities. The decrease in droplet ii size is observed during accession in liquid to gas ratio. Particulate removal efficiency of 99 % can be achieved at higher gas mass flow rates due to high inertial impaction parameter. The distribution of water mass content in different segments of the venturi scrubber is greatly influenced by sulfur dioxide mass flow rates. The desulfurization efficiency depreciates with an increase in sulfur dioxide mass flow rate, whereas efficiency increases with accession in liquid to gas ratio. Maximum sulfur dioxide removal is observed at lower sulfur dioxide concentration comparatively to higher concentration of sulfur dioxide.