Absorption Chiller/Kalina Cycle Coupled System for Low-Grade Waste Heat Recovery in Hydrate-Based CO2 Capture Process: An Economic and Exergetic Study

Abstract

This study investigates a coupled system combined by a LiBr/H2O absorption refrigeration cycle and a Kalina cycle, to recover waste heat from a hydrate-based CO2 capture process. The optimal system operation has been obtained. Payback time, Return on investment, Net present value and Discounted cash flow rate of return are selected as the evaluation indicators for a comprehensive economic analysis. Cash flow patterns are obtained for different discounted interest rates and electricity prices. Exergy analysis is conducted and the exergy loss of each component is calculated. Results show that in comparison with the individual Kalina cycle, the net electricity generation is increased by around 45%. The highest thermal efficiency of this coupled system is 16.78%. Payment balance can be achieved with a payback time of 6 years. The purchase price of heat exchanger occupies the largest capital investment. Exergy efficiency of this system is obtained as 36.89%. Major system irreversibility occurs in heat transfer processes of heat exchangers and the largest exergy loss is found in generators of both subcycles. Reducing the heat transfer irreversibility and the size of heat exchangers are greatly encouraged in future efforts.