CO2 Capture Modeling, Energy Savings, and Heat Pump Integration

While chemical engineers have designed amine-based CO2 capture systems since 1927, concern over anthropomorphic climate change sparked renewed interest in the 1980s. Subsequent research has led to significant advances such as well-fit property and thermodynamic models, rigorous models for unit operations, and improved process designs. The aim of this work is to summarize proposed process improvements and energy-saving schemes, including absorber intercooling, stripper interheating, stripper condensate rerouting, distributed cross heat exchanger, flash stripper, multipressure stripper, and heat pump integration. We present simulation examples demonstrating that energy-saving schemes must be considered together because of strong and complex interactions. We report an optimal process design integrating all of these improvements in Aspen Plus V8.5, and then evolutionally simplify the design through simulation results. In particular, we propose an optimum energy-saving design that uses an absorption-driven heat pump together with a distributed cross heat exchanger and a stripper vapor condensate rerouting to reduce both the cooling and the heating utility consumptions. The resulting predicted solvent regeneration energy is an absorption-driven heat pump for waste heat recovery with a predicted solvent regeneration energy of 1.67 (GJt/tonne CO2 captured). To our knowledge, this is the lowest solvent regeneration energy yet reported in the literature or patents.