Flexible Operation of the Potassium Taurate Solvent Absorption Section for CO2 Removal in a Coal-Fired Power Plant

Abstract

To reduce global warming effects due to the increase of the carbon dioxide concentration in the atmosphere, CO2 can be removed from large emitting industrial sources as power production stations with several available technologies. Among these, the most common one is chemical absorption with aqueous amines. The benchmark solvent is MonoEthanolAmine (MEA), though presenting a few disadvantages such as being corrosive and toxic and requiring large amounts of energy for its regeneration. An aqueous solution of potassium taurate has the potential to replace MEA because of degradation resistance, low toxicity and low energy requirements. In addition, at specific conditions, it can enhance the chemical absorption of carbon dioxide by precipitating and forming a slurry with presence of solid taurine. The considered process scheme is similar to the one for the MEA system (basically composed of absorption column and stripping or distillation column), with the addition of a heat exchanger for the dissolution of any solid particle present in the system before being fed to the regeneration section. When applied to a power plant, CO2 removal decreases the revenues from the sale of electricity. Indeed, the requirement of thermal energy for running the reboiler of the regeneration section and of electrical energy for compressing the separated CO2 are some of the main drawbacks of the application of Carbon Capture and Storage (CCS) and may result in a significant decrease in the power output and profit. Operating the CO2 removal section in flexible mode significantly reduces effects on the profit and CO2 emissions. The research reported here focuses on determining the best operating conditions for the potassium taurate solvent absorption section with the aim of limiting the impact of the CO2 capture operation and maintaining a substantial reduction of CO2 emissions in a coal-fired power plant. The process of post-combustion scrubbing is well-suited for operation in flexible mode because it is located downstream of the power production system. For simulating the process, a tool previously developed and based on the commercial software ASPEN Plus® has been employed. The process simulator had been user customized for the representation of the chemical reacting system of carbon dioxide with potassium taurate, which is not present by default in the database. The Vapor-Liquid-Solid Equilibrium (VLSE) is considered in the thermodynamic model and rate-based simulations, also taking into account the kinetics, have been performed. An in-house tool, taking as input the data for electricity demand and price and the result of simulations in ASPEN Plus®, has been then used for analyzing the flexible operation of the plant. The study of a flexible solution for carbon dioxide removal has been carried out in this work, considering the amount of electricity sold during the day for which data are available from the Italian national service institution.