Integration of a Gas Fired Steam Power Plant with a Total Site Utility Using a New Cogeneration Targeting Procedure

A steam power plant can work as a dual purpose plant for simultaneous production of steam and elec-trical power. In this paper we seek the optimum integration of a steam power plant as a source and a site utility sys-tem as a sink of steam and power. Estimation for the cogeneration potential prior to the design of a central utility system for site utility systems is vital to the targets for site fuel demand as well as heat and power production. In this regard, a new cogeneration targeting procedure is proposed for integration of a steam power plant and a site utility consisting of a process plant. The new methodology seeks the optimal integration based on a new cogenera-tion targeting scheme. In addition, a modified site utility grand composite curve （SUGCC） diagram is proposed and compared to the original SUGCC. A gas fired steam power plant and a process site utility is considered in a case study. The applicability of the developed procedure is tested against other design methods （STAR？ and Thermoflex software） through a case study. The proposed method gives comparable results, and the targeting method is used for optimal integration of steam levels. Identifying optimal conditions of steam levels for integration is important in the design of utility systems, as the selection of steam levels in a steam power plant and site utility for integration greatly influences the potential for cogeneration and energy recovery. The integration of steam levels of the steam power plant and the site utility system in the case study demonstrates the usefulness of the method for reducing the overall energy consumption for the site.     

生物燃料工厂的能源与水资源的优化(英文)

In this paper we address the topic of energy and water optimization in the production of bioethanol from corn and switchgrass. We show that in order for these manufacturing processes to be attractive, there is a need to go beyond traditional heat integration and water recycling techniques. Thus, we propose a strategy based on mathematical programming techniques to model and optimize the structure of the processes, and perform heat integration including the use of multi-effect distillation columns and integrated water networks to show that the energy efficiency and water consumption in bioethanol plants can be significantly improved. Specifically, under some circumstances energy can even be produced and the water consumption can be reduced below the values required for the production of gasoline.     

考虑操作分解的热集成用水网络设计

This article deals with the design of energy efficient water utilization systems allowing operation split. Practical features such as operating flexibility and capital cost have made the number of sub operations an important parameter of the problem. By treating the direct and indirect heat transfers separately, target freshwater and energy consumption as well as the operation split conditions are first obtained. Subsequently, a mixed integer non-linear programming （MINLP） model is established for the design of water network and the heat exchanger network （HEN）. The proposed systematic approach is limited to a single contaminant. Example from literature is used to illustrate the applicability of the approach.     

Energy-efficient recovery of tetrahydrofuran and ethyl acetate by triple-column extractive distillation:entrainer design and process optimization

An energy-efficient triple-column extractive distillation process is developed for recovering tetrahydrofuran and ethyl acetate from industrial effluent.The process development follows a rigorous hierarchical design procedure that involves entrainer design,thermodynamic analysis,process design and optimization,and heat integration.The computer-aided molecular design method is firstly used to find promising entrainer candidates and the best one is determined via rigorous thermodynamic analysis.Subsequently,the direct and indirect triple-column extractive distillation processes are proposed in the conceptual design step.These two extractive distillation processes are then optimized by employing an improved genetic algorithm.Finally,heat integration is performed to further reduce the process energy consumption.The results indicate that the indirect extractive distillation process with heat integration shows the highest performance in terms of the process economics.     

通过数学规划方法设计具有混合结构的水回用网络

A new design method for a water-reusing network, with a hybrid structure, to reduce the complexity of the network and to minimize freshwater consumption, is proposed. The unique feature of the methodology proposed .in this article is to control the complexity of the water network by regulation of the control number in a water-reusing system. It combines the advantages of a conventional water-reusing network and a water-reusing net work with internal water mains. To illustrate the proposed method, a single contaminant system and a multiple contaminant system serve as examples of the problems.     

空气与水逆流直接接触热质交换过程模型计算及分析

Based on reasonable model hypotheses and the energy analysis of heat and mass transfer of air and water in a direct contact counter flow, a set of general equations that can describe the internal relationship between the state parameters of air and water and dimensionless parameters of transfer process are given. A method utilizing MATLAB to solve these general equations is also proposed. Calculations and analysis with the model of a cooling- dehumidifying process give a consistent result with that of previous experiment. A new method for designing equipment such as evaporating cooler and cooling tower, and for analyzing experiment data of heat and mass transfer of air and water in a direct contact counter flow can be derived from this study.     

CFD simulations of quenching process for partial oxidation of methane:Comparison of jet-in-cross-flow and impinging flow configurations

A new quenching process using the cold pyrolysis gas has been proposed for the partial oxidation (POX) of methane to recover the heat.The mixing of hot product gas and cold pyrolysis gas in milliseconds is critical to this new approach.Two most widely-used rapid mixing configurations,i.e.the jet-in-cross-flow (JICF) and impinging flow configurations,are compared in terms of mixing and quenching performances using computational fluid dynamics (CFD) coupled with detailed reaction mechanism Leeds 1.5.The mixedness,residence time distribution,temperature decreasing rate and loss ratio of acetylene during the quenching are systematically studied.The results show that the impinging flow has a more uniform mixing and narrower residence time distribution than the JICF.However,the temperature decreasing rate of the mainstream is faster in the JICF than in the impinging flow.The loss ratio of acetylene in the quenching process is 2.89％ for the JICF and 1.45％ for the impinging flow,showing that the impinging flow configuration is better and feasible for the quenching of POX of methane.     

Novel eco-efficient reactive distillation process for dimethyl carbonate production by indirect alcoholysis of urea

Dimethyl carbonate is an eco-friendly essential chemical that can be sustainably produced from CO₂,which is available from carbon capture activities or can even be captured from the air.The rapid increase in dimethyl carbonate demand is driven by the fast growth of polycarbonates,solvent,pharmaceutical,and lithium-ion battery industries.Dimethyl carbonate can be produced from CO₂through various chemical pathways,but the most convenient route reported is the indirect alcoholysis of urea.Previous research used techniques such as heat integration and reactive distillation to reduce the energy use and costs,but the use of an excess of methanol in the trans-esterification step led to an energy intensive extractive distillation required to break the dimethyl carbonate-methanol azeotrope.This work shows that the production of dimethyl carbonate by indirect alcoholysis of urea can be improved by using an excess of propylene carbonate(instead of an excess of methanol),a neat feat that we showed it requires only 2.64 kW·h·kg^-1 dimethyl carbonate in a reaction-separation-recycle process,and a reactive distillation column that effectively replaces two conventional distillation columns and the reactor for dimethyl carbonate synthesis.Therefore,less equipment is required,the methanol-dimethyl carbonate azeotrope does not need to be recycled,and the overall savings are higher.Moreover,we propose the use of a reactive distillation column in a heat integrated process to obtain high purity dimethyl carbonate(>99.8 wt-%).The energy requirement is reduced by heat integration to just 1.25 kW·h·kg^-1 dimethyl carbonate,which is about 52%lower than the reaction-separation-recycle process.To benefit from the energy savings,the dynamics and control of the process are provided for
10%changes in the nominal rate of 32 ktpy dimethyl carbonate,and for uncertainties in reaction kinetics.     

过程工业中具有能量集成的用水网络优化设计

Effective utilization of water and energy is the key factor of sustainable development in process industries, and also an important science and technology problem to be solved in systems engineering. In this paper,two new methods of optimal design of water utilization network with energy integration in process industries are presented, that is, stepwise and simultaneous optimization methods. They are suitable for both single contaminant and multi-contaminant systems, and the integration of energy can be carried out in the whole process system, not only limited in water network, so that energy can be utilized effectively. The two methods are illustrated by case study.     

一个基于NRTL方程的液体混合物表面张力模型

A new equation for predicting surface tension is proposed based on the thermodynamic definition of surface tension and the expression of the Gibbs free energy of the system. Using the NRTL equation to represent the excess Gibbs free energy, a two-parameter surface tension equation is derived. The feasibility of the new equation has been tested in terms of 124 binary and 16 multicomponent systems(13-ternary and 3-quaternary) with absolute relative deviations of 0.59~0 and 1.55~0 respectively. This model is also predictive for the temperature dependence of surface tension of liquid mixtures. It is shown that, with good accuracy, this equation is simple and reliable for practical use.     

Design of mixed energy‐integrated batch process networks by Pseudo‐direct approach

In this article, a novel framework for the design of mixed (combined direct and indirect) integration for batch process systems is presented. The framework is based on the concept of pseudo‐direct energy integration (PDEI) which reformulates indirect integration as direct integration using pseudo‐process streams. Two algorithms are presented to achieve energy integration for batch processes operating cyclically (in a campaign mode). The first algorithm targets maximization of energy recovery and overcomes the limitations of some of the existing contributions for design of mixed integrated systems. The second algorithm provides a network reduction methodology to generate a cadre of integrated designs while exploring the trade‐off between capital (number of heat exchangers and storage units) and operating costs (utility consumption). The proposed framework is illustrated using a benchmark example of two hot and two cold streams. © 2017 American Institute of Chemical Engineers AIChE J, 63: 55–67, 2018     

考虑间接换热额外换热温差的间歇过程储热集成

间歇过程流股间换热有直接换热和间接换热两种方式,通过储热介质进行间接换热会产生额外的换热温差。现有的夹点分析方法考虑间接换热额外换热温差后,难以得到经济且可行的储热集成方案。本文在夹点分析的基础上,提出了一种考虑间接换热额外换热温差的间歇过程储热集成方法。该方法首先使用不同的直接换热和间接换热温差进行热级联分析,确定储热集成后的最小冷、热公用工程用量,识别储热位置和储热量,并依据热级联分析结果,建立时间段温焓图确定储热介质温度,得到储热方案。然后,将储热流股转化为放热时间段的冷流股和需热时间段的热流股,进行换热网络综合与优化,得到符合实际应用的储热集成方案。最后,通过经典实例证明了所提方法的可行性和有效性。     

A new methodology combining total site analysis with exergy analysis

Total site analysis allows determining the potential heat transfer between multiple plants to obtain further energy savings to the process integration in industrial plants. Exergy analysis offers a clear understanding of the integration of thermodynamic systems in process integration. A new methodology that combines total site analysis and exergy analysis is presented. The methodology allows for simultaneous use of both thermodynamic systems and heat transfer networks. The combination of the two types of utilities allows for better exploitation of the plants’ energy profile. In addition, the methodology allows specifying the networks’ and thermodynamic systems characteristics and number. The capacities of this methodology are tested on a case study where different combinations of systems are studied to determine their behavior with variable parameters.     

采用两种中间介质的工业园区厂际余热集成

发挥园区集群效应，借助中间介质回路将工业园区中各单厂内的余热于厂际间进一步回收利用，能够显著提高园区整体能源效率。其中，中间介质回路的设置与介质的选择将关系到整个余热回收系统的最优设计与节能效果。因此，不同于目前研究仅采用一种中间介质的集成策略，同时选用热水和导热油为介质开展厂际余热集成研究。提出耦合介质与厂内流股换热及介质流股在厂际间分配的换热器网络超结构，以年度总费用最小为目标建立MINLP热集成数学模型，优化获得包含介质回路结构与厂内换热器网络结构等内容的园区余热集成结果。最后，在一个包含3个厂的厂际余热集成案例中，分别研究了单种介质单回路、单种介质双回路及双种介质双回路3种情况，通过对比验证了所提方法的有效性。     

A game theory based method for inter-plant heat integration considering cost allocation

Inter-plant heat integration is an effective way for energy recovery in process industry. Although inter-plant heat integration can significantly reduce energy consumption, it is not widely applied in the multiple stakeholders' situation due to profit or cost distribution problems. Therefore, this work considers both the technique aspects of heat integration and its business aspects between stakeholders simultaneously. The new proposed methodology consists of three steps. Firstly the optimal matching of heat integration between plants is obtained through mathematical programming. Then the cost distribution is decided through game theory. Finally the cost distribution obtained previous is corrected by an ideal expert model. A case study is used to illustrate the effectiveness of the method in the end of the work.     

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.     

Studies on simultaneous energy and water minimisation—Part II: Systems with maximum re-use of water

A new systematic design methodology has been developed for the simultaneous management of energy and water systems that also feature maximum re-use of water. A two-dimensional grid diagram is proposed to exploit different options within water systems and also enable reduced complexity of the energy and water network. Isothermal and non-isothermal stream mixing between water streams are introduced to create separate systems between hot and cold water streams in the energy composite curves and provide a design basis for a better structure with fewer units for the heat exchanger network. In addition to allowing re-use of water, issues about heat losses inside unit operations have also been incorporated in the simultaneous management of water and energy.     

Optimal synthesis of multi-plant heat exchanger networks considering both direct and indirect methods

Heat exchanger networks (HENs) in separated plants can be simultaneously synthesized through process streams directly or intermediate fluids indirectly. However, the direct and indirect methods are studied separately in most existing researches. As the result, conventional designs are probably suboptimal, because optimal solutions may call for hybrid approach wherein direct and indirect integration methods are used synchronously. To circumvent this drawback aforementioned, we propose in this research a novel methodology to synthesize multi-plant HENs considering both direct and indirect approaches. The methodology employs a novel superstructure covering most potential topologies for both interplant and intra-plant heat integration. We also take into account multiple kinds of intermediate fluids for indirect integration and this has not been fully addressed in previous research. A mixed-integer nonlinear programming (MINLP) is formulated to optimize multi-plant HENs involving indirect and direct methods. One example from existing literature and one industrial problem are solved to demonstrate the methodology's capability.     

Simultaneous integration of water and energy in heat‐integrated water allocation networks

This article proposes a new methodology for simultaneous integration of water and energy in heat‐integrated water allocation networks (WAHEN). A novel disjunctive model is first developed to determine an optimal water allocation network (WAN) where water and energy are integrated in one step. Based on the optimal WAN, a detailed heat exchanger network (HEN) to satisfy the utility target is then synthesized. Although the final network structure is obtained through two steps, the targets of freshwater and utility are optimized simultaneously. The proposed method has specific advantages. First of all, it can capture a tradeoff among freshwater usage, utility consumption, and direct heat transfer by nonisothermal mixing. Second, it can greatly reduce the complexity of subsequent HEN design. Finally, it is effective for simultaneous water and energy integration in large‐scale WAHEN systems. The advantages and applicability of this new method are illustrated by three examples from literature. © 2015 American Institute of Chemical Engineers AIChE J, 61: 2202–2214, 2015     

Studies on simultaneous energy and water minimisation—Part I: Systems with no water re-use

This paper addresses the simultaneous management of energy and water. A new systematic methodology has been developed for targeting and design that simultaneously minimises the requirements of energy and water. Using this new approach, the design of a water system for maximum energy recovery can be achieved, taking into account the mixing opportunities offered by water networks, while maintaining the water quality to processes in terms of contamination. Direct and indirect energy recovery are analysed and a strategy developed to decrease the number of heat transfer units based on the generation of separate systems and non-isothermal stream mixing. Initially, the analysis is restricted to no water re-use.