Comparative analysis of regenerative and air-extraction multi-stage humidification–dehumidification desalination system using pinch technology

To reduce energy consumption, the multi-stage type is a promising technology used in the humidification–dehumidification desalination system. Two types of multi-stage desalination system (regenerative and air-extraction multi-stage desalination) were proposed, and were studied and improved relatively separately. So, this paper comparatively investigated the two typical desalination systems based on the pinch technology. The pinch analysis models of regenerative and air-extraction multi-stage desalination were established and numerically analyzed. Subsequently, the effects of the pinch point temperature difference and the number of stage on the performance of the two desalination systems were comparatively analyzed. The result showed that the Gained Output Ratio (GOR) of regenerative multi-stage desalination was worse than that of air-extraction multi-stage desalination, while the Recovery Ratio (RR) of regenerative multi-stage desalination was better. Furthermore, when the single-stage system upgraded to two-stage system, the performance was significantly improved. But as the number of stage increases further, the enhancement effect is gradually weakened and even the performance becomes worse. The research content of this paper will help to select the device in the design of the desalination system.