Mass Exchange Networks Research Articles

Simultaneous optimization of integrated heat, mass and pressure exchange network using exergoeconomic method

Energy crisis becomes increasingly serious with the rapid industrial development. Apart from searching for the alternative energy sources, researchers are dedicated to increasing the efficiency of energy utilization in the industrial production process to alleviate the energy scarcity. The integration of heat, mass and pressure exchange networks is regarded as an effective way to reduce the energy consumption. This paper introduces exergoeconomic analysis to the integrated network optimization. The exergoeconomic analysis is performed by an overall analysis of energy and economic factors, which is very useful for industrial process design. The optimization turns out to be a mixed integer nonlinear programming (MINLP) problem due to the multi-objective and multi-constraint factors. A modified state space model is developed for the integrated network to handle all the parameters and possible network structures. Genetic algorithm is employed to get a globally optimal solution based on the developed state space model and MATLAB program. Case studies are carried out to demonstrate that exergoeconomic analysis is more suitable than the optimization of annual cost or raw material consumption. The results show that exergoeconomic analysis based on the proposed state space model performs well to solve the integrated network problems.

Systematic Synthesis of Mass Exchange Networks for Multicomponent Systems

The synthesis of mass exchange networks (MENs) is an important systematic tool for screening mass-separating agents (MSAs) and satisfying the mass transfer demands while considering process, enviro...

Supply-based superstructure synthesis of heat and mass exchange networks

A new simultaneous mixed integer non-linear programing (MINLP) approach to heat exchange network synthesis (HENS) and mass exchange network synthesis (MENS) is presented. This supply-based superstructure (SBS) approach uses the supply temperatures/compositions of all the streams (including utilities) present in the synthesis problem to define heat/mass exchange superstructure intervals. The intermediate temperatures/compositions are variables used in the optimization of the network total annual cost (TAC). The ability of each stream to exchange heat/mass in any interval in the SBS is subject to thermodynamic/mass transfer feasibility. The paper presents the mathematical formulations for optimizing the TAC for HENS and MENS. The SBS synthesis technique has been applied to nine literature problems involving both HENS and MENS. The solutions obtained are in the same range as those in the literature, with one solution being the lowest of all.

Hydrogen recovery from the purge stream of an HDA process using the concept of Mass Exchange Networks

In this paper we use the concept of Mass Exchange Networks to design the hydrogen recovery from the purge stream of an HDA Process by implementing a recently proposed counter current gas permeation equipment to exchange hydrogen between the purge and the toluene feed to the process. This design would correspond to the final design refinement step in the Douglas [1,2] hierarchical process design procedure, proposed by Fischer and Iribarren [3]. The goal of this design is recovering part of the hydrogen available in the purge stream, and results in a process alternative different from other flow sheet recently proposed by Bouton and Luyben [4], also resorting to gas permeation membrane units, but in a traditional arrangement. Two different types of available zeolite ceramic membranes were studied, of different permeability and selectivity. The here proposed mass exchange design recovers a similar amount of hydrogen as the process alternative proposed by Bouton and Luyben [4] who use a less expensive type of polymeric membrane, but need a compressor to recycle the permeate stream because they use transmembrane pressure as the driving force. The here proposed design at actual cost of zeolite membranes allows an 153.9% increase of the Net Annual Savings with respect to the pressure driven membrane system when using the less selective ceramic membrane, while this figure descents to a 32.61% when using the most selective (which is also the most expensive alternative).

Synthesis of Multi-component Mass-exchange Networks

This paper presents a superstructure-based formulation for the synthesis of mass-exchange networks (MENs) considering multiple components. The superstructure is simplified by directly using the mass separation agents (MSA) from their sources, and therefore the automatic synthesis of the multi-component system involved in the MENs can be achieved without choosing a ‘key-component’ either for the whole process or the mass exchangers. A mathematical model is proposed to carry out the optimization process. The concentrations, flow rates, matches and unit operation displayed in the obtained network constitute the exact representation of the mass exchange process in terms of all species in the system. An example is used to illustrate and demonstrate the application of the proposed method.

A systematic approach for synthesizing combined mass and heat exchange networks

Mass and heat are very important resources in the process industry. Numerous approaches have been proposed for the optimization of either mass or heat exchange networks. Since the process usage of mass and heat is typically intertwined, it is important to account for such interactions. The objective of this paper is to introduce a systematic method for the simultaneous synthesis of combined mass- and heat-exchange networks (CMAHENs). The proposed method is based on a novel approach that incorporates the mass pinch technology (MPT) for mass exchange networks (MENs) synthesis and the pseudo-T-H diagram approach (PTHDA) for the heat exchange networks (HENs) synthesis. New bypass streams are included in the structural representation of the problem to expand the search space. A combined optimization approach is applied to minimize the total annualized cost of the CMAHEN. Finally, two cases are solved to illustrate the application of the proposed method.

Water Sources Diagram in Multiple Contaminant Processes: Maximum Reuse

Water scarcity, rising energy costs, and stricter regulations on disposal of industrial effluents have forced a focus on the water usage in process plants. In this context, the development of methodologies to analyze the possibility of water reuse in industrial processes, considering the presence of multiple contaminants, has became an important issue for process engineers. There are a great variety of methods to deal with this problem, and they can be divided in two groups: algorithmic methods and mathematical programming methods. The problem with multiple contaminants becomes more complex, and the available algorithmic procedures are sometimes cumbersome; the methodologies based on mathematical programming present complex formulation and solving algorithms. This paper presents an extension of the algorithmic procedure water source diagram (WSD) to multiple contaminant processes. The proposed extended WSD procedure synthesizes water mass exchange networks for multiple contaminant processes, focusing on w...

Simultaneous Heat and Mass Exchanger Networks with Process Simulator

Simultaneous Heat and Mass Exchanger Networks with Process Simulator

Heat, mass, and work exchange networks

Heat (energy), water (mass), and work (pressure) are the most fundamental utilities for operation units in chemical plants. To reduce energy consumption and diminish environment hazards, various integration methods have been developed. The application of heat exchange networks (HENs), mass exchange networks (MENs), water allocation heat exchange networks (WAHENs) and work exchange networks (WENs) have resulted in the significant saving of energy and water. This review presents the main works related to each network. The similarities and differences of these networks are also discussed. Through comparing and discussing these different networks, this review inspires researchers to propose more efficient and convenient methods for the design of existing exchange networks and even new types of networks including multi-objective networks for the system integration in order to enhance the optimization and controllability of processes.

Hydrogen sulfide removal process embedded optimization of hydrogen network

Abstract Due to the trend in tighter environmental regulations on heavier crude oil processing, hydrogen has become an important strategic resource in modern refineries. Refiners have to improve the efficiency of hydrogen distribution networks to satisfy the increasing demand of hydrogen. Consequently, plenty of work has been focusing on optimizing hydrogen reuse and purification schemes, which is known as hydrogen network integration (HNI). In refineries, hydrogen purification techniques include hydrocarbon removal units and hydrogen sulfide (H 2 S) removal units. Hydrocarbon removal units such as membrane separation and pressure swing adsorption (PSA) are frequently employed in the HNI study. However, the possibility of integrating H 2 S removal units into HNI study has been overlooked until recently. H 2 S removal units are usually modeled as mass exchangers and independently studied as mass exchange networks (MEN). In the present work, an improved modeling and optimization approach has been developed to integrate H 2 S removal units into HNI. By introducing a desulfurization ratio, R d s p l , i ′ , simplified MEN is incorporated into hydrogen distribution network. Total annual cost (TAC) is employed as the optimizing object to investigate the tradeoffs between hydrogen distribution network cost and MEN cost. Pressure constraints and impurity concentrations are considered, and cost equations are established to determine the installation of new equipments in order to synthesis an economical network. A practical case study is used to illustrate the application and effectiveness of the proposed method.

DESIGN OF A CONTROL STRUCTURE FOR MASS EXCHANGER NETWORKS

This work aims to present a design for optimal operation of mass exchange networks (MENs) with minimum total annual cost (TAC) and optimal split-range control. The proposed strategy consists of five main steps. First, MENs are formulated as mixed-integer nonlinear programming (MINLP) with minimized TAC. Second, a network flexibility test is performed to ensure feasibility for a large number of uncertain parameters that are generated randomly within the operating ranges. Next, parametric programming is used to find the active constraint regions, and integer linear programming (ILP) is used to formulate an optimal split-range control structure. Then, the optimal operations of the control structure are verified with the preliminary dynamic behaviors. Finally, the common equipment design data are presented. The validation of the proposed method of designing an optimal split-range control structure for MEN is performed by three case studies from El-Halwagi and Manousiouthakis's work (1989, 1990). The results do not guarantee global optimization, but are checked through flexibility and dynamics tests. They demonstrate that the obtained control structures can keep all mass fraction targets at the desired values, even with the saturation of some manipulated variables when MENs are disturbed by reductions of 10, 20, and 30% of the mass fractions of rich streams and lean streams.

Synthesis of mass integration networks: Integrated approach to optimization of stream matching for a metal pickling process

The purpose of this techno-economic feasibility study is to develop a procedure for the cost-effective synthesis and optimization of schemes to recover in-plant a valuable ingredient from waste streams and at the same time reduce the COD property. MILP and MINLP algorithms are used. The model minimizes the total annualized cost of the mass exchange network (MEN). The procedure involves a two-stage process: first, using the MILP, the pinch point location is identified along with the selection of an optimal set of mass separating agents (MSAs). At this stage the effect of each selected MSA on COD is scrutinized. In the second stage, the MINLP is applied to realize the optimal matching of waste and lean streams through the direct minimization of equipment capital cost. An example is presented to show the applicability and advantages of the proposed novel procedure. The project was found to be highly profitable.

A Systematic Approach for the Synthesis of Highly Controllable Mass Exchange Networks

It is known that the lack of controllability is the major cause of catastrophic events, energy inefficiency, and the generation of “off-spec” products to be treated as waste or to be recycled. This paper addresses the problem of synthesizing a mass exchanger network (MEN) that satisfies the control-related criteria “controllability”. In this work, four simple heuristic rules are introduced for MEN synthesis. Applying such simple rules in the matching step results in a highly controllable network, without requirement of sequential integration that would give rise to a time-consuming and tedious procedure requiring extensive iteration. Two alternative case studies are introduced to demonstrate the effectiveness of the proposed procedure.

Supply and target based superstructure synthesis of heat and mass exchanger networks

This paper presents new methods for the optimisation of superstructures involving heat exchanger networks (HENs) and mass exchanger networks (MENs). The techniques developed in this study explore the use of key variables (namely supply temperatures/compositions and target temperatures/compositions) in HENs and MENs to define the intervals of superstructures. Such superstructures are modeled as mixed integer non linear programmes (MINLP) with the objective of minimisation of the total annual cost (TAC) for each network. The superstructures presented in this paper are derivatives of the interval and supply based superstructures (IBMS and SBS) developed previously. Two different superstructures are developed in this paper: the first uses the supply temperature/composition of hot/rich streams and the target temperature/composition of cold/lean streams (denoted supply and target based superstructure, S&TBS), while the second superstructure uses the target temperature/composition of hot/rich streams and the supply temperature of cold/lean streams (denoted target and supply based superstructure, T&SBS). Five HEN examples and three MEN examples are presented. The results obtained compare well with those in the literature.

An integrated approach to the optimization of in-plant wastewater interception with mass and property constraints

This article addresses the problem of in-plant pollution prevention for processes with multiple streams, containing pollutants and environmentally undesirable properties through mass exchange networks (MEN). In-plant interception is used to adjust the concentrations and properties of the wastewater streams. A pinch-based disjunctive-optimization approach is adopted. The determination of the pinch point (being the most constrained thermodynamic and practical operating condition) is critical for determination of optimum design conditions. The selection of the appropriate mass separating agent(s) (MSAs) is based on thermodynamic and economic considerations. A screening procedure modeled through mathematical programming is developed with disjunctive constraints to screen alternatives and invoke the proper models when a certain technology is to be utilized. A case study is solved to illustrate the proposed approach.

What about industrial water sustainability?

Some have said that water will be in the 21st century what energy was in the 20th century, obviously referring to the issue of meeting adequate demand, availability, and safety issues of these resources for maintaining our living standards. It is true that the availability of fresh water is becoming increasingly a problem with time in many parts of the world, resulting from unsustainable withdrawals from surface and underground resources and from contamination making existing sources unfit. With respect to energy, however, the statement is indeed hyperbolic. If anything, concerns for energy availability will be even more enhanced, as evidenced by rapidly increasing demand and the rush to developing alternative sources of energy for both transportation and power needs all over the world. In the US about half of the water consumption is devoted to power generation, about a third for agriculture, and a relatively smaller amount, 5%, for industrial purposes. The bulk of the publicly or privately funded research on water technologies has been conducted to satisfy standards for municipal needs (11% of US water use), and the results of these studies are widely available publicly. The standards for municipal water are roughly similar everywhere. Industrial sectors, however, being many and of different types, technology needs are likewise varied. For instance the water quality needs of the textile dying industry are very different from those of the semiconductor processing industry. The effluents from these two sectors are also different, as are the technologies required to treat these effluents for reclamation purposes. Deficiency of overall water availability is already causing water scarcer for industrial needs, which is why industry will have to increasingly pay more attention to water sustainability. Thus industry will have to find ways of becoming less dependent on municipal sources. When there is a conflict between the two sectors for access to fresh water, municipal needs will garner higher priority from the governing bodies. This situation requires three actions: (1) minimizing water needs for industrial operations, (2) treating effluents to the standards for repeated recycling and reuse in the same industrial site, and (3) safely disposing the residuals or sludge from the treatment operations. Various modeling techniques have recently been developed and applied industrially, for instance, water pinch technologies and mass exchange network. There are no generic technologies for recycle/reuse, each application requiring means suitable to the specific needs. The advancement made in this regard is still in its infancy. Sludge disposal is a big problem, and techniques such as incineration, encapsulation/stabilization, compaction/drying, and land-filling and others are options to consider. In September 2010, a North Atlantic Treaty Organization (NATO) Advanced Research Workshop was held in Ankara, Turkey, on the sustainability issues of industrial water. Experts from more than 20 countries from North America, Western Europe, East Europe, and the Middle East gathered to share their research with one another. All the presentations are available in the website: http://www. epa.gov/nrmrl/events/event09162010.html.

A flexible state-space approach for the modeling of metabolic networks I: Development of mathematical methods

We introduce a novel, flexible, optimization-based mathematical framework for the modeling of arbitrarily complex metabolic networks: topological metabolic analysis (TMA). The framework is adapted from state-space approaches used by Manousiouthakis and co-workers for the representation of complex heat- and mass-exchanger networks. We offer a thorough discussion of the mathematics and general theory underlying the framework, and discuss certain mathematical advantages of our modeling representation in comparison with other commonly used techniques (MFA and FBA). We employ a novel aggregate objective function for use with our basic constraint model, including a generalized least-squares term (for fitting available experimental measurements) and a linear design term (for representing biological or engineering goals). Using a case-study taken from recent literature ( McKinlay et al., 2007), we demonstrate (among other benefits) the ability of this objective to identify alternate distinct-yet-equally optimal solutions for a given modeling problem. We also show that these solutions, obtained using only external metabolite uptake and secretion measurements, provide useful biological insights and compare favorably with solutions obtained on the basis of 13C isotope-tracing data.

Simulation of mass exchange networks using modified genetic algorithms

The optimum water usage network leads to both a minimum of freshwater consumption and a minimum of generated wastewater. This work is to develop a mass-exchange networks (MENs) module for a minimum freshwater usage target. This module works as an interface to retrieve supplemental data of chemical processes from a process simulator and to communicate this to the genetic algorithm optimizer. A reuse system and a regeneration/recyclingsystem with a single contaminant are considered as approaches for freshwater minimization. In the formulated model, as mixed integer nonlinear programming (MINLP), all of the variables are divided into independent and dependent variables. The values of independent variables come from randomization, whereas the values of dependent variables come from simultaneous solutions of a set of equality constraints after assigning the values of independent variables. This method is applied to the steps of initialization, crossover and mutation. The MENs module is validated with a tricresylphosphate process consisting of five unit operations. Water is used to remove a fixed content of cresol. From the result, the module gives a reliable solution for freshwater minimization, which can satisfy mass balance and constraints. The results show that reuse and regeneration/recycling strategies can reduce freshwater consumption, including wastewater generated. Reuse cannot decrease the mass load of the contaminant, while regeneration/recycling can. In addition, regeneration requires less freshwater than the reuse process.

Review of Water Network Design Methods with Literature Annotations

The designing of heat exchanger networks (HENs), mass exchanger networks (MENs), and water networks (WNs) is a major topic of process system engineering. The WN problem is most recent, and although the seminal work was published in 1980, the real development should be dated from 1994. Increasing public concern on scarce water resources, together with stringent regulations on wastewater discharge, has caused a great number of publications in recent years. Despite noticeable achievements in the topic, there is still a need for robust flexible approaches that will find wider application in practice. This review provides the reader with literature annotations on the WN problem from the year 1980 and follows the format of an earlier HEN review paper [Furman, K. C.; Sahinidis, N. V. A critical revue and annotated bibliography for heat exchanger network synthesis in the 20th century. Ind. Eng. Chem. Res. 2002, 41, 2335−2370]. An analysis of the WN problem formulation also is given, together with an overview of solution techniques. Statistics and classifications of the literature annotations are provided. Finally, thoughts on the direction of future research are presented.

Hybrid optimization approach for water allocation and mass exchange network

This study deals with the synthesis problem of mass exchange networks (MENs) with treatment option for waste minimization and minimal fresh solvent usage by adopting a hybrid combined graphical and mathematical programming approach based on state-space representation. A simple strategy has been proposed for the synthesis water allocation and mass exchange network (WAMEN), aiming at total recycle of effluent thus subsidizing the fresh water consumption to zero. The network synthesis problem has been decomposed into two main steps: (1) synthesizing a network candidate with simpler graphical tools and presenting in state-space representation (2) considering the state-space representation as an initial guess, the available results are formulated as a MINLP problem and the entire network is optimized. Optimized wastewater network along with mass exchange network for an oil refinery process is generated, illustrating the effectiveness of the proposed methodology. This simple procedure will be a useful tool for process engineers to design self-sustained solvent using networks with zero effluent discharge.