The optimal water system with regeneration recycling can minimize freshwater consumption and wastewater discharge to the largest extent

and thus it has drawn much attention in academic and industrial circles. After introducing the regeneration process in a water-using system

the limiting water supply line will be changed

causing the possible change of the location and number of pinch points. Based on prior approach to constructing the optimal water supply line in regeneration recycling water systems

the influence factors on the change of pinch point when introducing the regeneration process were analyzed

such as the position and concave degree of concave points on the limiting composite curve and the flowrate relationship of the stream with highest concentration and freshwater. The change of the position and number of pinch points could be obtained

providing theoretical guidance for analysis and design of water-using networks.