Design and Optimization of Carbon Dioxide Capture and Storage Process for Low-carbon Power Generation

Abstract

Carbon capture and storage (CCS) technologies have been considered a realistic option for mitigating the climate change. Post-combustion CO2 capture utilizes existing coal-fired power plants, and aqueous monoethanolamine (MEA) scrubbing is the most well proven capture technology. However, the heat and energy requirements of solvent regeneration and CO2 liquefaction cause a 30% decrease in net power output. This power de-rate is a major obstacle for implementing CCS. Herein, the energy efficient and economical carbon capture, compression, dehydration, liquefaction and injection process is proposed. Firstly, simulation-based parametric optimization is performed to minimize the power de-rate. Post-combustion CO2 capture with aqueous MEA scrubbing (85 %, 90 %, and 95 % removals) and CO2 liquefaction integrated with a 550 MWe supercritical coal-fired power plant is simulated. The liquid to gas ratio and stripper operating pressure of the CO2 capture process are the selected manipulated variables with steam extracted from the IP-LP crossover pipe and the first LP turbine as possible heat sources. The power de-rate was reduced to 17.7 % when operating at optimum conditions. In addition, the author propose a comprehensive optimal design of CO2 dehydration process using a superstructure-based optimization. The superstructure model development includes binary interaction parameter regression for NRTL-RK thermodynamic model, unit operation modeling, and identification of all connectivity of the unit operations in the superstructure. The superstructure imbeds 30,720 possible process alternatives, and the optimum process configuration with the least cost and its operating condition are simultaneously identified using Aspen Plus-MATLAB interface. The optimum process includes three-stage contactor, ten-stage still column, lean/rich solvent heat exchanger, and cold rich solvent split flow fed to the sixth-stage of still column. The total annualized cost of the optimum process is 5.67 M$/yr, and it corresponds to the specific annualized cost of 1.80 $/tonCO2. Sensitivity analysis using Monte Carlo simulation is also presented for the optimum process, and the refrigerant and steam are the most influential utility costs. Lastly, the small-scale topside CO2 injection process for offshore platform is designed from conceptual design to piping & instrument diagram level with the hazard and operability study is presented.