Design Of Water Allocation Networks Research Articles

Optimal Design of Heat-Integrated Water Allocation Networks

Industrial operations consume energy and water in large quantities without accounting for potential economic and environmental burdens on future generations. Consumption of energy (mainly in the form of high pressure steam) and water (in the form of process water and cooling water) are essential to all processes and are strongly correlated, which requires development of systematic methodologies to address their interconnectivity. To this end, the subject of heat-integrated water allocation network design has received considerable attention within the research community in recent decades while further growth is expected due to imposed national and global regulations within the context of sustainable development. The overall mathematical model of these networks has a mixed-integer nonlinear programming formulation. As discussed in this work, proposed models in the literature have two main difficulties dealing with heat–water specificities, which result in complex formulations. These difficulties are addressed in this work through proposition of a novel nonlinear hyperstructure and a sequential solution strategy. The solution strategy is to solve three sub-problems sequentially and iteratively generate a set of potential solutions through the implementation of integer cut constraints. The novel mathematical approach also lends itself to an additional innovation for proposing multiple solutions balancing various performance indicators. This is exemplified with both a literature test case and an industrial-scale problem. The proposed solutions address a variety of performance indicators which guides decision-makers toward selecting the most appropriate configuration(s) among a large number of potential possibilities. Results exhibit that despite having a sequential solution strategy, better performance can be reached compared to previous approaches with the additional benefit of providing many potential solutions for further consideration by decision-makers to select the best case-specific solution.

Water Allocation Network Design Concerning Process Disturbance

Water system integration can effectively reduce freshwater consumption and minimize wastewater discharge of a water-using system, but integration makes the resultant water network structurally more integrated among process units. Therefore, to design a flexible water allocation network that is easy to control becomes highly desirable. In this Article, a methodology is presented for water allocation network design with process disturbance taken into account. For a new design, the synthesized network structure can guarantee that the water system consumes minimum freshwater under both normal and disturbance conditions and with minimum number of control streams under disturbance. At the same time, the information needed to adjust flow rate under disturbance will be obtained. For an existing water system, an adjustment scheme under disturbance with minimum freshwater consumption for the existing structure will be obtained. The water network designed by the new methodology has the feature of minimum freshwater ...

Energy conservation in water allocation networks with negligible contaminant effects

A methodology to target the minimum energy requirement in water allocation networks where impurity concentrations do not play any significant role is proposed in this paper. The proposed methodology is mathematically rigorous and targets the minimum utility requirement satisfying the minimum approach temperature prior to the detailed design of both the water allocation network as well as the heat exchanger network. The proposed algorithm is presented through a tableau-based calculation procedure. A water allocation network design algorithm is proposed that guarantees the minimum energy targets obtained through the proposed energy recovery algorithm. The proposed methodology is also applied to inter-process heat integration between various water allocation networks.

State−Time−Space Superstructure-Based MINLP Formulation for Batch Water-Allocation Network Design

The mathematical technique presented in this work deals with one step design of single- and multicontaminant batch water-allocation network (WAN), where batch production, water-reuse subsystems, and wastewater-treatment subsystems are all taken into account. In the first place, a flexible schedule model combining the merits of discrete and continuous time formulations is introduced to integrate batch production and WAN. Then, two novel state−time−space (STS) superstructures incorporating all basic elements (i.e., states, tasks, equipment, and time) are adopted to capture all production schemes and batch WAN configurations. Specifically, by adding novel components in the original superstructure, a series of optimal network structures with multistage splitting and mixing options which have never been contained within previous superstructure can be easily generated. Finally, a reliable optimization strategy, where deterministic and stochastic searching techniques are combined, is suggested to deal with the resulting mixed integer nonlinear programming (MINLP) model. Two illustrative examples are presented to demonstrate the effectiveness of the proposed approach.

Integrating water-use networks in a paper mill

The pulp and paper industry is under regulatory pressure to reduce the volume of its water usage and wastewater discharge. To provide more efficient use of water resources and to minimise wastewater discharge, the design of water allocation networks has recently received increasing attention. Water system integration is often applied in the petroleum and chemical industry but much less so in the pulp and paper industry. We proposed a general methodology, nonlinear programming (NLP), for the design of optimal water use networks in a paper mill. The NLP requires specification of the lower and upper bounds on the contaminant concentrations flowing in and out of each process unit. This method can be effectively used to optimize the water network and minimise fresh water consumption and wastewater discharge in a paper mill. The minimised wastewater flows into a bio-treatment system where it is regenerated and can be reused for papermaking. We successfully achieved zero discharge of wastewater without affecting production and paper quality. Water consumption decreased from 90–110 m3 to 1.6 m3 per ton paper produced.

Design of Optimal Water-Using Networks with Internal Water Mains

To provide more efficient usage of water resources and to minimize wastewater discharge, the design of water allocation networks has drawn increased attention over the past two decades. However, wa...