Closed-loop heat pump distillation system for ethanol solution separation: Experimental validation and operational characteristics analysis

This study experimentally validates a closed-loop heat pump (CLHP) distillation system for ethanol-water separation and investigates its operational characteristics under energy constraints. A pilot-scale platform is constructed, and a steady-state mathematical model is developed, incorporating the thermal integration degree ( ψ ) to quantify waste heat recovery efficiency. Full-lifecycle experimental data validate the model, achieving relative deviations of 8.5% for COP and 3.8% for ψ , respectively. Results show that the CLHP system successfully upgrades low-grade heat (60–66 °C) to a usable temperature level (90–105 °C), achieving stable energy circulation. Under full-load compressor operation, an adaptive “energy-material coupling” mechanism is revealed: the system prioritizes energy recovery over separation efficiency under varying operating conditions. When feed flow rate exceeds 1000 L/h, ethanol recovery decreases to 87–91% while ψ exceeds 0.98. Exergy efficiency reaches a peak of 53.9% at 900–1000 L/h, and the actual COP (5.01) surpasses the design value (4.87). The reflux ratio has a limited impact on heat pump performance but effectively regulates product purity. Compared with conventional distillation, the CLHP system reduces total annual cost (TAC) by 28.85% and CO₂ emissions by 64.8%. A dual-factor sensitivity analysis of electricity and steam prices establishes a clear economic decision boundary: electricity price <0.7 CNY/kWh or steam price >280 CNY/t favors CLHP. These findings provide theoretical and experimental support for the design, operation, and optimization of CLHP distillation systems in industrial applications.