Minh T. Ho

Simulation of CO2 Removal by Potassium Taurate Solution

The removal of carbon dioxide from gaseous sources such as flue gases from power plants traditionally uses aqueous solutions of alkanolamines; with monoethanolamine (MEA) considered the benchmark solvent. However, in order to overcome some of the main disadvantages associated with MEA, such as high volatility and toxicity, and high thermal requirements for regeneration; in recent years alternative solvents have started to be studied for CO2 removal. Taurine is an amino acid which can be dissolved in aqueous solution with potassium hydroxide and can be used for absorption of carbon dioxide. Compared to MEA, this solvent is considered to be more environmentally friendly because of its lower toxicity, higher biodegradability, negligible volatility and good stability towards degradation. Reactions with carbon dioxide are less exothermic than with MEA, therefore a lower amount of heat is required to reverse them in the regeneration column. Moreover, during absorption the zwitterionic form of the amino acid may precipitate, thus increasing the absorption capacity of the salt solution at equilibrium. This work describes the development of a simulation of the potassium taurate solvent system for carbon dioxide removal using ASPEN Plus. New ionic species due to the dissolution of solid taurine in water and KOH and due to the reactions of the components in the liquid solution with carbon dioxide have been introduced into the simulation. Vapor-Liquid Equilibrium in the presence of precipitating salt has been described by means of the Electrolyte-NRTL method, for which appropriate parameters have been determined and a rate-based simulation of the columns involved in the process (absorption and regeneration) has been performed. The model has been validated by comparison with data of vapor-liquid-(solid) equilibrium from the literature and can be used for further assessment of this process in the future.