Performance optimization of turboexpander-compressor applied for cryogenic carbon capture system

The cryogenic reverse Brayton refrigerator serves as a critical cold source for desublimation-based cryogenic carbon capture system. Recovering expansion work via a turboexpander-compressor (TEC) represents a key technique to enhance the efficiency of refrigerator and capture system. However, the multi-parameter coupling between the expander and coaxial compressor poses substantial challenges to the optimal design and high-performance operation of the TEC. In this paper, a co-design approach and an off-design model are developed for TEC. Thereafter, the characteristics of forward-bootstrap TEC (FBTEC) and reverse-bootstrap TEC (RBTEC) are evaluated. A comparative study shows that the capture system applied co-designed RBTEC achieves 4.4% higher capture rate and 17.9% higher capture quantity compared with the braking turboexpander process, with the lowest unit CO 2 capture energy consumption. The proposed design approach offers a deeper understanding of TEC coupling characteristics, facilitating the design and optimization of TEC in various systems.