(414c) CO2 Separation Using Mg(OH)2 Solutions – Dissolution Kinetics and Vapor-Liquid-Solid Equilibrium Studies of CO2- Mg(OH)2 System

Coal-fired power plants are responsible for a considerable amount of total anthropogenic CO₂ emissions throughout the world.  CO₂ from flue gases can be absorbed by Mg(OH)₂ slurry at 52 °C in a column followed by a regeneration step in a stripper operated at 65 °C.  

One of the most important steps in the CO₂ scrubbing process is the rate at which magnesium hydroxide dissolves from the solid part of the slurry and becomes available for reaction with absorbed CO₂.  The dissolution rate kinetics of Mg(OH)₂ was studied using a pH stat and the dissolution rate was determined based on acid consumption required to maintain a preset pH value.  The effects of pH, temperature, mixing and particle size on the dissolution rates of Mg(OH)₂  will be presented.  A dissolution rate kinetic expression obtained under different operating conditions will also be presented.

Knowledge of Vapor liquid solid equilibrium (VLSE) of CO₂ in Mg(OH)₂ is essential for the proper design and operation of absorption and desorption equipment.  The VLSE data for the Mg(OH)₂ – CO₂ system under various operating conditions of pressure, temperature, and concentration of Mg(OH)₂ will be presented.  A suitable model for fitting the VLSE data will also presented.