Miguel J. Bagajewicz

A review of recent design procedures for water networks in refineries and process plants

Abstract This paper presents a review of the procedures to design and retrofit water networks. Although the emphasis is in showing results for refineries, the methods are valid for any process plants. It is first shown that the problem has been decomposed into the design of two interacting subsystems. One problem is the freshwater and wastewater reuse allocation and the other is the wastewater treatment problem. It is also shown how the wastewater treatment problem was modeled as a distributed and decentralized treatment. The roadmap towards zero liquid discharge and energy integrated solutions is then discussed. Several solution approaches are briefly outlined emphasizing the main trend leaning towards the use of mathematical programming. The major claim made is that mathematical programming can produce globally optimal solutions and practically important sub-optimal solutions when conceptual insights are employed to build the models. Although the paper intends to be comprehensive, it emphasizes the authors recent work. Finally, a few of the existing challenges of the area are outlined.

On the optimality conditions of water utilization systems in process plants with single contaminants

This paper introduces necessary conditions of optimality for water-using networks in refineries and process plants. These necessary conditions correspond to the optimal water allocation planning (WAP) problem that considers wastewater reuse on the basis of a single contaminant and where the objective is to minimize the total water intake. The conditions under which degenerate solutions are possible are also identified. Examples are discussed.

On the Use of Linear Models for the Design of Water Utilization Systems in Process Plants with a Single Contaminant

This paper addresses the optimum design of water utilization systems when a single contaminant is present. The application of the necessary conditions of optimality allows an LP or MILP formulation depending on the objective function of choice. Several examples are presented to illustrate the proposed methodology and to point out that several alternative solutions are available.

Energy efficient water utilization systems in process plants

This paper introduces a new approach for the design of water utilization networks featuring minimum freshwater usage and minimum utility consumption in process plants. The procedure is confined to treat the single pollutant case, and it is based on a linear programming formulation that relies on necessary conditions of optimality and a heat transshipment model. An LP model is first solved to obtain minimum water usage and minimum heating utility target values. Once the energy and water targets have been identified, an MILP model is generated. This model, which accounts for non-isothermal mixing, provides the information needed to construct the water reuse structure as well as the corresponding heat exchanger network.

On zero water discharge solutions in the process industry

Abstract This paper presents a mathematical programming approach to analyze the feasibility of zero liquid discharge option in different industries. Mathematical programming methodologies are applied to four industrial cases—a tricresyl phosphate plant, an ethyl chloride plant, a paper mill and a refinery. In each case study various end of pipe and regeneration configurations using different treatment technologies are explored to determine the possibility of zero liquid discharge and its economical feasibility. The results show that the relationship between the cost of regeneration and the cost of freshwater as well as the discharge concentration of the treatment is the determining factor for the feasibility of zero liquid discharge.

Algorithmic procedure to design water utilization systems featuring a single contaminant in process plants

This paper introduces a non-iterative algorithmic procedure to design water utilization networks in refineries and process plants. The procedure is based on necessary and sufficient conditions of optimality that allow the construction of a global optimal solution without the need or a targeting procedure. In addition, the steps of this procedure are such that it can be implemented by hand and have no limitations on the problem size.

A robust method to obtain optimal and sub-optimal design and retrofit solutions of water utilization systems with multiple contaminants in process plants

In this paper, a simple new approach for the grassroots and retrofit design of water utilization systems with multiple contaminants is presented. This approach uses a combination of mathematical programming and necessary conditions of optimality to automatically generate the optimal solution featuring minimum capital and operating costs. This paper presents the only existing method to solve this problem that can guarantee global optimality.

Energy savings in the total site heat integration across many plants

In this paper, an extension of previous work performed for a system of two plants is presented. For a set of n plants, heat transfer leading effectively to energy savings occurs at temperature levels between the pinch points of supplying and receiving plants. In some cases, additional heat transfer in other regions is required to attain maximum savings. A systematic procedure, based on LP and MILP models, is used to identify energy-saving targets for the two forms of integration and find the location of the intermediate fluid circuits. Finally, the optimal location of these circuits allowing restricted operation is discussed. Alternative solutions exist, which allow flexibility for the subsequent design of the multipurpose heat exchanger network.

On the state space approach to mass/heat exchanger network design

In this paper, the conceptual framework and applications of the State Space Approach to Process Synthesis are presented. It is shown that the State Space Approach contains the concept of a Network Superstructure as a special case. Additionally, through various operators, it is shown to provide increased flexibility in formulating process network synthesis problems. As an example, it is demonstrated that an Assignment Operator can be used to facilitate the solution of large-scale problems. Pinch Operators are also employed in solving combined heat and mass exchange network synthesis problems. To demonstrate the usefulness of this new approach, two important problems are discussed. First, a one-step procedure is developed that minimizes the total annualized cost (TAC) of heat/mass exchange networks. Next, a novel problem, namely the pinch-based calculation of Minimum Utility Cost for a separable heat and mass exchange network, is solved.

Gross error modeling and detection in plant linear dynamic reconciliation

This paper presents a method to identify and estimate gross errors in plant linear dynamic data reconciliation. An integral dynamic data reconciliation method presented in a previous paper (Bagajewicz and Jiang, 1997) is extended to allow multiple gross error estimation. The dynamic integral measurement test is extended to identify hold-up measurements as suspects of gross error. A series of theorems are used to show the equivalencies of gross errors and to discuss the issue of exact identification. A serial approach for gross error identification and estimation is then presented. Gross errors are identified without the need for measurement elimination. The strategy is capable of effectively identifying a large number of gross errors.