Application of an ammonia-based process with controlled solid formation for post-combustion CO2 capture

CO2 capture and storage is needed to reduce the carbon footprint related to industrial activities. Among the different available technologies, CO2 removal from power/cement plant’s flue gases is of particular interest due to its versatility and retrofit opportunities for existing plants. In this framework, the Chilled Ammonia Process (CAP) is a promising technology for post-combustion CO2 capture. Besides its competitive energetic performance compared to conventional amines, the use of aqueous NH3 as a solvent offers advantages concerning global availability, environmental footprint and cost compared to most amine processes. A new ammonia-based process for CO2 capture from flue gas has been developed, which found its origin in the Controlled Solid Formation - Chilled Ammonia Process (CSF-CAP). A controlled solid precipitation carried in a dedicated unit of the plant lead to a reduction of the energy penalty of the process without hindering its operability, since the mass flow rate sent to regeneration can be substantially reduced by means of CO2 concentration in the solid phase rather than the liquid phase. Differently from the original CSF-CAP, where ammonium bicarbonate has been exploited in the crystallization section, in this new process ammonium carbonate monohydrate is formed, which promises numerous advantages in terms of the overall energy efficiency of the process. Initially, the process synthesis has been performed, followed by a rigorous optimization and performance evaluation. The work have been carried out coupling Aspen Plus V8.6 and Matlab. The speciation model developed by Thomsen has been used for the calculations in the CO2-NH3-H2O system. Under the assumptions considered in this work, the new CSF-CAP has been found to require 0.84 MJ/kgCO2 of electrical energy, which corresponds to a reduction of 5\% of the overall energy duty of the plant, compared to the original CSF-CAP, which needs 0.89 MJ/kgCO2.