Adsorption-based organic carbon pump for industrial exhaust valorization: Concept, modeling, and efficiency

Recovering volatile organic compounds (VOCs) from industrial exhausts is crucial for the circular economy transition. However, this process is constrained by emission and phase-change limits, lacking a unified thermodynamic evaluation framework. By analogy with pumps, this study proposes a concept of organic carbon pump (OCP), modeling the recovery of dilute gaseous organic carbon into liquid solvents as a thermodynamically driven upgrading of VOC concentration potential. The concept and implementation pathway of OCP were defined, followed by baseline and enhanced system configurations. Thermodynamic, kinetic, and exergy efficiency models were established to quantify minimum separation work and phase-change work. The results show that when the inlet concentration increased from 50 ppm to 4000 ppm, the molar separation work decreased from 54.53 kJ/mol to 33.35 kJ/mol. In contrast, when the purification target was tightened to 1 ppm, the total minimum work increased by 62.6%. A graphical framework based on the Clapeyron diagram was further developed, which can determine state parameters from operating paths and reversely design feasible operating paths under target constraints. Compared with the baseline system, the enhanced OCP increased the working capacity by 20%, while reducing emission VOC partial pressure and residual adsorption load by 81.2% and 49.0%, respectively. Under the optimized condition, the exergy-to-energy ratio and exergy efficiency reached 40.4% and 17.04%, respectively, indicating promising thermodynamic feasibility. This study aims to provide a thermodynamic framework and evaluation method for VOC recovery and valorization, and to extend carbon capture to industrial organic carbon sources.