Alternative regeneration of chemicals employed in mineral carbonation towards technology cost reduction

Abstract

Mineral carbonation (MC) using recyclable ammonium salts pH swing processes is considered among the most promising MC techniques to store CO2 permanently. However, the main key challenge to use this process at large scale is related to the energy consumption associated to the regeneration of the employed additives and in particular to the separation of the salt to be regenerated from the water solution.This work investigates the feasibility of a liquid-liquid extraction technique to replace the energy intensive salts/water separation step. Also, the CO2-balance of a 500MW coal-fired based power plant with an integrated pH swing MC facility was investigated. Different operating conditions were investigated, including temperature, reaction time, pressure, solid to liquid ratio (S/L), reagents concentration and stirring rate. An ammonium sulphate/water separation higher than 90% was achieved at 25°C, 10min, 1bar, 200g/lS/L ratio, 70% methanol and, 350rpm. The associated energy consumption was calculated, resulting in an energy saving of 35% in comparison to water evaporation. The process resulted carbon negative when water evaporation was replaced by extraction technique, with 33% of CO2 sequestered by using a S/L ratios of 300g/l.