Environmental Assessment of Post-Combustion Carbon Capture Process Retrofitting in Power Plant : Life Cycle Assessment

Abstract

Abstract : Carbon dioxide (CO2) emission from burning fossil fuels in power plants is a major contributor toward climate change. Carbon capture and storage (CCS) is a potential solution to reduce the emission while renewable energy sources are being developed. Among CCS technologies, post-combustion carbon capture (PCC) is a promising method for reducing CO2 from existing power plants. However, PCC has drawbacks, including high construction costs, high energy demand for solvent regeneration, and potential environmental impacts. A stepwise multi-linear regression based on the least squares method was used to identify significant variables in PCC to reduce solvent regeneration energy and to enhance efficiency. Seven independent variables were selected, including lean solvent temperature, solvent concentration, lean CO2 loading, and flue gas conditions. The analysis revealed that solvent concentration, inlet CO2 concentration, and lean CO2 loading affect solvent regeneration energy. The regression equations were validated and found reliable, with prediction errors of 0.78% for CO2 rich loading and 2.47% for solvent regeneration energy. A study-state rate-based model of PCC system using monoethanolamine (MEA) as a solvent was developed and validated in Aspen HYSYS using pilot plant data. The model predictions using HYSYS agreed with PCC pilot plant experimental data where the deviation between the model and experimental results did not exceed +8%. A new simulation of PCC process using combined solvent MDEA/PZ under different total concentration (40 wt% and 50 wt%) and different individual concentration for MDEA and PZ was simulated. The aim of the simulated PCC process using combined solvents was to investigate the synergistic effect of the selected solvents compared to MEA at 30 wt%. The simulation shows that 43 wt% MDEA and 7 wt% PZ is the optimum composition that requires the minimum energy for solvent regeneration of 2.53 MJ/kgco2 for 88.5% process efficiency compared to 4.003 MJ/kgco2 for 30 wt% MEA without the need for any process modifications. A cradle-to-gate life cycle assessment is used to investigate and evaluate the environmental impact of PCC once retrofitted to power plant using SimaPro. Three methods of life cycle assessment were used in this study including ReCiPe 2016 Midpoint (H), ReCiPe 2016 Endpoint (H), and IPCC 2013 GWP 500. The findings from LCA study show that power plant equipped with PCC demonstrated a tremendous reduction of global warming potential compared to power plant without PCC. However, the study found that power plants with or without PCC cause resource depletion due to the utilization of fossil fuel. Furthermore, several environmental issues impact specifically water resources reach the maximum once MEA is utilized for PCC compared with MDEA/PZ that required of water management system to manage the water utilization and damping during PCC process. Hence, the study shows the synergistic effect of MDEA and PZ to capture carbon dioxide using PCC process shows the ability to resolve the drawback of PCC process from technical and environmental view and could be selected as one of the mitigation solutions to reduce CO2 emissions. However, the study limited to the economic assessment for the system and the variation in the power plant process as well as the transportation and storage stages of carbon capture and utilization or storage process.