Linlin Liu

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.

Simultaneous Optimization of Synthesis and Scheduling of Cleaning in Flexible Heat Exchanger Networks

Abstract A novel methodology is presented for simultaneously optimizing synthesis and cleaning schedule of flexible heat exchanger network (HEN) by genetic/simulated annealing algorithms (GA/SA). Through taking into account the effect of fouling process on optimal network topology, a preliminary network structure possessing twofold oversynthesis is obtained by means of pseudo-temperature enthalpy ( T - H ) diagram approach prior to simultaneous optimization. Thus, the computational complexity of this problem classified as NP (Non-deterministic Polynomial)-complete can be significantly reduced. The promising matches resulting from preliminary synthesis stage are further optimized in parallel with their heat exchange areas and cleaning schedule. In addition, a novel continuous time representation is introduced to subdivide the given time horizon into several variable-size intervals according to operating periods of heat exchangers, and then flexible HEN synthesis can be implemented in dynamic manner. A numerical example is provided to demonstrate that the presented strategy is feasible to decrease the total annual cost (TAC) and further improve network flexibility, but even more important, it may be applied to solve large-scale flexible HEN synthesis problems.

Synthesis of Multi-component Mass-exchange Networks

Abstract 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.

Synthesis of water networks for industrial parks considering inter-plant allocation

Abstract Since an industrial park is a cluster of multiple company individuals, there is requirement to develop specific reuse strategies so as to improve the utilization of resources across plants. This article presents a ‘plant-based’ mode respecting to the water allocation problem within industrial parks. In the mode, mixers and splitters are involved to present the mixing, conveying and splitting operations for reusing streams across plants. Such that, the mixing possibilities can also be investigated and many redundant solutions can be avoided by considering the number limit of inter-plant stream connections at the building stage of network superstructures. On base of this mode, both direct and mixed (direct–indirect) integration scenarios are studied in this study. Superstructures are established and mathematically formulated aiming to minimum fresh water consumption as well as the total annualized cost. At last, three integration cases are explored based on an example from literature for illustration.

Heat-integrated water allocation network synthesis for industrial parks with sequential and simultaneous design

Abstract This paper presents a methodology for the synthesis of inter-plant heat-integrated water allocation network (IHIWAN) in industrial parks, to promote the overall level of resource conservation by exploiting the cooperative utilization among multiple plants. Based on superstructure, the proposed method introduces inter-plant integration strategies specific to industrial parks, involving the coupling scheme of water allocation and heat exchange. And a non-linear programming model (NLP) is formulated containing water allocation subsystem and heat integration subsystem. Accordingly, economically optimal IHIWAN is synthesized via two optimization routes respectively: sequential design and simultaneous design. Results of application examples indicate that inter-plant integration of the overall water-heat system in the scale of the park can bring about significant savings compared to the summation of integration within each stand-alone plant. In addition, simultaneous design presents preferable result with regard to overall economic performance, yet sequential design features more targeting flexibility and lower requirement on solution process.

A simultaneous synthesis method for combined heat and mass exchange networks

Abstract Mass-exchange operations are highly impacted by heating and cooling. Therefore, there is a natural coupling between the problems of synthesizing mass exchange networks (MENs) and heat exchange networks (HENs). The objective of this paper is to introduce a systematic method for the simultaneous synthesis of combined mass- and heat- exchange networks (CM&HEN). The proposed method is based on a novel approach that integrates the pseudo-T-H diagram approach (PTHDA) for HEN synthesis, with the mass pinch technology (MPT) for MEN synthesis. The applicability of the proposed approach is shown through an example problem, where a significant reduction in the total annual cost is obtained.

Multi-period water network management for industrial parks considering predictable variations

Abstract Designing processes in industrial parks by breaking plant boundaries will produce more resource and economic benefits than just focusing on every single plant. This article addresses the water management problem in industrial parks with considering two major points: (1) the water network synthesis problem towards park scenario in each time period, (2) the multi-period problem resulted from predictable development and adjustment variations of park. To achieve the optimal network configurations and water management plans for the operational scenarios in the future, an optimization mathematical model is formulated based on the proposed network superstructure including indirect water reuse and the planning strategies for multi-period concern. At last, three design cases are illustrated to demonstrate the application of the methodology.

Simultaneous Synthesis of WHEN Based on Superstructure Modelling Considering Thermodynamic and Economic Factors

Abstract To explicitly reveal the interaction mechanism between work and heat integration considering both thermodynamic and economic analysis, an improved superstructure, coupling of work exchange networks (WEN) and heat exchange networks (HEN), is proposed for simultaneous synthesis of work and heat exchange networks (WHEN) in this paper. The formulations based on exergy analysis are developed to determine the cold or hot identity of process streams. Afterwards, economic analysis is performed by formulating a cost-based mixed-integer nonlinear programming (MINLP) model to optimize the sequence of work and heat integration, aiming to minimize the total annual cost (TAC). Finally, an example study selected from the open literature is conducted to demonstrate the efficacy of the proposed methodology, where the solutions show a diminution of 40.4% in TAC of HEN prior to WEN, compared with that of WEN prior to HEN.

GC-COSMO based Reaction Solvent Design with New Kinetic Model using CAMD

Abstract Reaction solvents have been playing an important role in liquid-phase organic synthesis. To identify the optimal solvents for accelerating reaction rates, a GC-COSMO based computer-aided molecular design model is formulated, in which a new reaction kinetic model is proposed with the help of parameter reformulation strategy based on the conventional transition state theory. The high-performance solvent with the maximum reaction rate constant is generated using the proposed design model. This solvent design method can be applied to various reaction types. The validity of our method is demonstrated for the selected Menschutkin reaction.

Water networks synthesis for industrial parks respecting to unpredictable scenarios

Abstract Cooperative reuse of water resource across the plants placing in same industrial park would bring significant benefit to each participant plant, the park, and also the realization of resource-saving society. Different from designing water reusing networks merely subjecting to one or several pre-known operation scenarios, this study concentrates on solving the retrofit problem towards the unpredictable scenario which is upcoming yet unrealizable with current water allocation system. A hierarchical procedure is proposed, wherein by introducing series of specific constraints, the mixed integer non-linear programming model formulated for design purpose (Liu et al., 2017) is developed for achieving the optimal retrofit measures respecting to different retrofit specifications of decision-maker requires. At last, an industrial park example containing three retrofit cases at several typical scenarios is illustrated to show the application of the method.