Simulation of an HPC-process in Aspen HYSYS

Sammanfattning

With climate change being one of the greatest challenges of our time, interest in carbon dioxide removal and mitigation has increased, as a way of minimizing emissions. As a result, carbon capture has become a key focus in the industry. One of the most common chemical absorption techniques is carbon capture using hot potassium carbonate (HPC). This process operates at an elevated absorber pressure, where CO2 from a flue gas stream is absorbed into a potassium carbonate enriched solvent. The pressure is then reduced in a stripper, which promotes the CO2 release from the solvent. This master's thesis investigates the design and performance of an HPC process model in Aspen HYSYS. A base case model was developed for a representative flue gas stream, with each process step described and motivated. The model's performance and robustness was then evaluated using two additional flue gas streams with varying CO2 concentrations. Lastly, a sensitivity analysis was also conducted to assess the impact of solvent flow rate and absorber operational pressure. The model successfully converged for all three gas streams. The base case design was deemed effective, as it exhibited lower reboiler duty compared to cases found in the literature. The feasibility of heat integration with district heating water between compression stages was explored, but the results indicated that further research is needed due to the large heat exchanger areas required. Validation using the two alternative gas streams showed that a streams with high CO2 concentrations improve energy efficiency. The results from the sensitivity analysis demonstrated that increasing the solvent flow rate reduced reboiler duty, while increasing absorber pressure also reduced the reboiler duty, at the expense of raised electrical power consumption. This highlights the adaptability of the HPC process based on site specific energy availability. Further studies of the model configurations is encouraged, to further optimize the performance. Areas for future investigation include optimizing absorber and stripper heights and packing materials, implementing a rich flash, and assessing economic feasibility of increased solvent flow rate.