Design Of Water-Using Network

Pollution and Scarcity of water is a life-and-death problem that human being is facing. The research of water-using-network is significant to the economy of water resource and the environment protection. It is worthy of investigation evolving water-using processes to reduce freshwater consumption and wastewater production. At present, the researches which include water reuse, regeneration reuse and regeneration recycling, focus on the single factory. There are mainly two kinds of methods available in the literature: water pinch analysis approaches and mathematical programming methods. Basing on the existing achievements (such as water pinch analysis and mathematical programming methods), the author makes the research further on the minimum freshwater consumption of water-using-network involving reuse and regeneration reuse, and develops a set of new methods. The main contents are listed as follows:Firstly, for water using networks with single contaminant involving reuse only, traditional methods often determine the pinch points and the freshwater target simultaneously. Therefore, all the streams should be considered in detail either graphically or numerically in the calculation of the targets. In this work, by incorporating the insights of water-pinch-analysis, we will propose a new approach to determine the pinch point before target calculation. As the processes below the pinch can use freshwater only and those above the pinch point can reuse the wastewater which discharged by other processes, we may consider the processes below the pinch in detail to obtain the minimum freshwater flowrate. This will simplify the calculation of the freshwater target.Secondly, for water-using networks of single contaminant with multiple resources involving reuse only, a new method is proposed to calculate the fresh resource targets with multiple resources. For this kind of network, the quality of the fresh resource should be considered during the design procedure. Generally speaking, the consumption of higher quality resource can be reduced in the cost of expensing the lower quality ones. The optimize results, the design and the flowsheet of the network have been obtained during the calculation of the target(s). The procedure of the work is simpler compared to the literature methods.Thirdly, for the water-using networks with single-contaminant or multi-contaminant involving regeneration, a new insight about design of the water-using networks involving regeneration is proposed: if the regenerated water stream is treated as an additional source of the original water-using network involving reuse only, the design procedure used for water-using network involving reuse only can be used to design water-using network involving regeneration reuse as well. The insight gained above converts the complex task of the design of water-using network involving regeneration reuse to a simple task to determine the flowrate and the concentrations of the regenerated stream. This simplifies the design procedure significantly compared to the literature method.