(2gj) Simulation-Aided Energy and Economic Evaluation for Amine-Based CO2 Capture Matching Existing Power and Industrial Processes

Research Interests: carbon capture, utilization and storage; carbon recycling; process simulation; technology assessment; circular economy

Power and industrial sectors contribute significantly to CO₂ emissions, and prompt action is needed to reduce their impact. Carbon capture, utilization, and storage (CCUS) is expected to play a crucial role in meeting future emission targets, as it captures CO₂ from flue gases and the atmosphere. Amine-based post-combustion CO₂ capture is considered the most feasible option for existing combustion processes. CO₂ capture technologies largely determine the economic feasibility of CCUS systems since they are energy intensive.

Many previous studies focused on quantifying the cost and energy consumption of CO₂ capture technologies, with process simulations evaluating the impact of technology improvements on cost reduction. However, these studies did not consider characteristics of upstream processes such as fuel utilized, combustion systems, and heat recovery for the installation of CO₂ capture technologies.

This study aims to perform a process simulation-aided energy and techno-economic analysis for amine-based chemical absorption considering fuel and material inputs and types of combustion technologies in power and industrial sectors. The impact of differences in process configurations and solvent on heat duty for capturing CO₂ and CO₂ capture costs were investigated. Additionally, the variation of the fuel cost and the availability of the unutilized heat were not explored. This study allows for a more comprehensive understanding of the potential for heat recovery in CCUS processes and provide insights into further energy consumption reduction and CO₂ capture options.

Process simulations for amine-based CO₂ capture were performed with different process types retrofitted to existing combustion processes investigated in our previous study [1]. The conventional process configuration uses monoethanolamine (MEA) aqueous solvent, while the improved process configuration employs lean vapor compression (LVC) [2] and a blend of 2-Amino-2-methyl-1-propanol (AMP), piperazine (PZ), and MEA as the solvent [3]. The conventional process configuration is typically used in post-combustion CO₂ capture, with MEA solvent absorbing CO₂ from flue gas, and rich amine solvent being regenerated in a stripper. The solvent is then recycled back to the absorption step. In contrast, LVC process configuration reduces heat duty in the stripper's reboiler and lowers CO₂ capture costs. The blend amine solvent enhances reaction kinetics and absorption capacity, which can further reduce energy consumption and equipment size. With the consideration of the combinations of the process improvements, four simulation cases were investigated to examine the impact of process configurations and solvents on energy consumption and CO₂ capture costs.

The energy consumption for capturing CO₂ was divided into heat duty and electricity consumption. Heat duty was directly related to amine solvent regeneration, while electricity consumption was the sum of energy inputs for pumps and compressors. By calculating the amount of CO₂ captured per GJ of heat generation by fuel combustion from the carbon intensity for the heat generation, the heat loss due to the amine-based CO₂ capture was quantified using the different process types. A techno-economic analysis was performed to quantify CO₂ capture cost. CO₂ capture costs consist of fixed investment costs, variable and fixed operating costs, being calculated. This study assumed a project lifetime of 25 years and a discount rate of 8.5%. Capital costs were calculated with the cost data reported in the literature [4]. The variable operating cost encompasses fuel, electricity, water, and solvent make-up costs, while the fixed operating cost included labor, insurance, and plant overhead etc. based on the literature [4, 5].

By comparing the conventional process configuration with the improved LVC configuration and the use of blended amine solvents, this study provided the general insight into the effect of technology developments on heat loss and cost-effectiveness matching combustion characteristics in existing power and industrial processes. In addition, due to significant variations in the fuel costs and availability of the unutilized heat in combustion processes, the equal CO₂ capture cost curve was depicted at varying fuel cost and levels of the heat recovery for capturing CO₂.

This study clarified that heat duty and electricity consumption can be reduced through process modifications and replacement of the amine solvent, while the characteristics of combustion processes were found to have a minor impact on the energy intensity of amine-based CO₂ capture. However, CO₂ capture costs are significantly affected by types of combustion processes due to variation in fuel costs for steam generation and equipment size. In addition, the reduction potential of CO₂ capture cost by the heat recovery for capturing CO₂ significantly depends on fuel cost, while being restricted by the fixed investment cost.

In conclusion, process modification and solvent development for amine-based CO₂ capture are the key drivers in reducing energy consumption for capturing CO₂, which can enhance the economic feasibility of amine-based CO₂ capture. By exploring the availability of the unutilized heat in a combustion process, the economic feasibility of CCUS projects can increase and the heat recovery for capturing CO₂ synergistically enhance the effect of process modification and solvent development.

Reference

1. Yagihara, K., Ohno, H., Guzman-Urbina, A., Ni, J., Fukushima, Y. Analyzing flue gas properties emitted from power and industrial sectors toward heat-integrated carbon capture. Energy 250, 123775 (2022).
2. Yoro, K.O., Daramola, M.O., Sekoai, P.T., Armah, E.K., Wilson, U.N., Advances and emerging techniques for energy recovery during absorptive CO₂ capture: A review of process and non-process integration-based strategies. Renewable Sustainable Energy Rev. 147, 111241 (2021).
3. Nwaoha, C., Beaulieu, M., Tontiwachwuthikul, P., Gibson, D.M. Techno-economic analysis of CO₂ capture from a 1.2 million MTPA cement plant using AMP-PZ-MEA blend. J. Greenh. Gas Control 78, 400-412 (2018).
4. Towler, G., Sinnott, R., Chemical Engineering Design. Principles, practice and economics of plant and process design. Chemical Engineering (2012).
5. Turton, R. et al., Analysis, Synthesis, and Design of Chemical Processes 5^th Edition (2018).