Modeling Aerosol Growth for a Solvent Blend

Abstract

Management of aerosol in amine scrubbing requires the modeling of aerosol growth at the conditions of the absorber and water wash. If the amine aerosol grows well above 3 µm, it is collected through impaction on the packing and mist eliminator. Although aerosol models for single amine solvents have been developed, none have been reported for blended amine solvents. The presence of a second amine in the bulk liquid might affect the aerosol growth mechanism, composition, and size. Without a model for an amine blend, it is difficult to identify operating conditions that can grow the aerosol to larger sizes for mitigation. This work simulates aerosol growth for a proprietary solvent blend of amines AM1 and AM2. The model calculates the size and composition of a single aerosol drop traveling through the absorber and water wash. It tracks the water, CO2, AM1, and AM2 in the bulk gas phase and aerosol phase with mass transfer occurring at the bulk gas-drop interface and the bulk gas-solvent interface. The approach to modeling aerosol growth in the absorber and water wash involved two steps: (1) process modeling with ProTreat® and Aspen Plus® and (2) aerosol transport modeling with gPROMS®. The simulation was performed for two run conditions with 90% CO2 capture but different lean solvent and intercooling temperatures. The results show that the aerosol grows by picking up water, CO2, and AM1 in the absorber, and only water in the water wash. The aerosol grows to sizes well above 3 µm at the absorber mid-point, absorber outlet, and water wash outlet and will be easily collected. It grows fastest at cold zones in the absorber where the gas and aerosol are not in equilibrium. More packing and colder circulation water in the water wash were found to increase aerosol growth.

Keywords: Amine aerosol, solvent blend, gPROMS, CO2 capture