Site-wide low-grade heat recovery with a new cogeneration targeting method

One of the key performance indicators for designing site utility systems is cogeneration potential for the site. A new method has been developed to estimate cogeneration potential of site utility systems by a combination of bottom-up and top-down procedures, which allows systematic optimization of steam levels in the design of site utility configurations. A case study is used to illustrate the usefulness of the new cogeneration targeting method and benefits of optimizing steam levels for reducing the overall energy consumptions for the site. Techno-economic analysis has been carried out to improve heat recovery of low-grade waste heat in process industries, by addressing a wide range of low-grade heat recovery technologies, including heat pumping, organic Rankine cycles, energy recovery from exhaust gases, absorption refrigeration and boiler feed water heating. Simulation models have been built for the evaluation of site-wide impact associated with the introduction of each design option in industrial energy systems in the context of process integration. Integration of heat upgrading technologies within the total site has been demonstrated with a case study for the retrofit scenario.     

A new targeting method for estimation of cogeneration potential and total annualized cost in process industries

One of the important tasks for optimal design and analyses of site utility systems is targeting total annualized cost and cogeneration potential. This paper introduced a new cogeneration and total annualized cost (TAC) targeting models that were developed to estimate the cogeneration potential of site utility systems and total annualized cost. The procedure which was proposed here provided a consistent, general procedure for determining mass flowrates and efficiencies of the applied turbines. This algorithm utilized the relationship of the entropy with the enthalpy and the isentropic efficiency. It is considered superior to previous works in that it was accurate, did not require any cumbersome simulation for initiation and could be easily traced,which enhance its programmability, considering full lifetime of the utility prices and it can estimate TAC and TASP with diffrent cost functions. Also, the developed model based on the trends of historical prices has been considered for estimation of utility costs.     

Targeting the optimal integration of steam networks: Mathematical tools and methodology

Targeting the integration of the utility system in an industrial site, introduces the problem of combined heat and power production and more specifically the optimal integration of the steam network. We present a mathematical tool that allows, using only the definition of the headers of the system, to target the integration of the steam network to satisfy the heat requirements at minimum cost while maximising the combined production of mechanical power. This tool allows to automatically adapt the steam flowrates when the hot utility is changed. It defines the optimal steam flowrates to be considered in the Heat Exchanger Network design of the processes or of the industrial site. Furthermore this technique may be used to compute the optimal configuration of power plants.     

考虑水需求的水电联产海水淡化系统的优化设计

水电联产不仅能缓解淡水资源不足的问题,而且可有效降低能耗和淡化成本。建立了水电联产系统数学模型,将优化设计描述为一个混合整数非线性规划(MINLP)问题,并采用混合编码的遗传算法进行求解,结果表明,以水定电模式下水电联产系统最优操作模式为发电、多级闪蒸(MSF)和反渗透(RO)三者的集成,且MSF和RO的产水比存在最优值,发电采用背压式蒸汽轮机。随着淡水需求量的增加,联产系统的淡水成本逐渐降低,MSF与RO的产水比呈现出逐渐降低的趋势。     

Techno-economic optimization of IGCC integrated with utility system for CO2 emissions reduction—Maximum power production in IGCC

Environmental legislation, with its increasing pressure on the energy sector to control greenhouse gases, is a driving force to reduce CO₂ emissions. In this paper, pre-combustion CO₂ capture through integration of a site utility system with an integrated gasification combined cycle (IGCC) is investigated as an option to provide a compressed CO₂-rich stream from a process site for sequestration. This work presents a two-step procedure for integration and optimization of a site utility system with an IGCC plant: (i) screening and optimization of IGCC plant performance parameters; (ii) integration and optimization of the utility system of the site with the IGCC plant. In the first step, an optimization approach applies the results of screening studies based on rigorous simulation of the IGCC. Having fixed the inlet fuel flow rate, the IGCC design parameters (including oxygen consumption, diluent flow rate and turbine exit pressure) are optimized for maximum power generation. Energy flows between the IGCC and CO₂ compression train are considered. In the second step, the economic and operating performance of the utility system integrated with the IGCC plant are modeled and optimized for minimum operating cost to find the most appropriate level of integration. In a case study illustrating the approach, 94% of the fuel is gasified; additional power generation offsets the operating costs of pre-combustion CO₂ capture.     

Optimization of integrated cogeneration power plant and desalination plant systems for a range of power and water supply requirements

Comparative economic analysis is presented which shows necessity of integrated power and desalination plants optimization rather than separate optimization of power generating and desalination units. This paper introduces:- Calculational procedure and resulting curves for cogeneration plant selection for a range of power and steam demands.- Conceptual procedure for integrated power plant and desalination plant system optimization.- Results of comparative economic analysis of integrated power/ desalination plant optimization as compared with separate power plant and desalination plant optimization.     

A superstructure-based framework for simultaneous process synthesis,heat integration,and utility plant design

We propose a superstructure optimization framework for process synthesis with simultaneous heat integration and utility plant design. Processing units in the chemical plant can be modeled using rigorous unit models or surrogate models generated from experimental results or off-line calculations. The utility plant subsystem includes multiple steam types with variable temperature and pressure. For the heat integration subsystem, we consider variable heat loads of process streams as well as variable intervals for the utilities. To enhance the solution of the resulting mixed-integer nonlinear programming models, we develop (1) new methods for the calculation of steam properties, (2) algorithms for variable bound calculation, and (3) systematic methods for the generation of redundant constraints. The applicability of our framework is illustrated through a biofuel case study which includes a novel non-enzymatic hydrolysis technology and new separation technologies, both of which are modeled based on experimental results.     

Indirect heat integration across plants using hot water circles☆

Total site heat integration (TSHI) provides more opportunities for energy saving in industry clusters. Some design methods including direct integration using process streams and indirect integration using intermediate-fluid cir-cuits, i.e., steam, dowtherms and hot water, have been proposed during last few decades. Indirect heat integration is preferred when the heat sources and sinks are separated in independent plants with rather long distance. This improves energy efficiency by adaption of intermediate fluid circle which acts as a utility provider for plants in a symbiotic network. However, there are some significant factors ignored in conventional TSHI, i.e. the investment of pipeline, cost of pumping and heat loss. These factors simultaneously determine the possibility and perfor-mance of heat integration. This work presents a new methodology for indirect heat integration in low tempera-ture range using hot water circuit as intermediate-fluid medium. The new methodology enables the targeting of indirect heat integration across plants considering the factors mentioned earlier. An MINLP model with economic objective is established and solved. The optimization results give the mass flow rate of intermediate-fluid, diam-eter of pipeline, the temperature of the circuits and the matches of heat exchanger networks (HENS) automati-cally. Finally, the application of this proposed methodology is il ustrated with a case study.     

New emissions targeting strategy for site utility of process industries

A new procedure for environmental targeting of co-generation system is presented. The proposed method is based on the concepts of pinch technology for total site targeting of fuel, power, steam, environmental impacts and total annualized cost with considering emissions taxes. This approach provides a consistent, general procedure for determining mass flow rates and efficiencies of the applied turbines. This algorithm utilizes the relationship of entropy with enthalpy and isentropic efficiency. Also, the life cycle assessment (LCA) as a well-known tool for analyzing environmental impacts on a wide perspective with reference to a product system and the related environmental and economic impacts have been applied. In this regard, a damage-oriented impact analysis method based on Eco-indicator 99 and footprints analysis was considered. In addition, the present work demonstrates the effect of including both sensible and latent heating of steam in the extended Site Utility Grand Composite Curve (ESUGCC). It is shown that including sensible heating allows for better thermal matching between the processes. Furthermore, the other representation YSUGCC as the other form of Site Utility Grand Composite has been proposed. Two case studies were used to illustrate the usefulness of the new environmental targeting method.     

Targeting for CO2 emissions for Total Sites

This paper describes an approach based on the concepts of Pinch Technology for Total Site targeting for fuel and power. If specific CO₂ emissions for fuel and power are known, the approach will also target for CO₂ emissions for any given site in the industry. The approach takes account of the trade-offs between process fuel and steam, between steam, site fuel and cogeneration, and of fuel mix. A case study is described where an 18% reduction in global CO₂ emissions is possible through the correct use of these trade-offs.     

考虑不同水质输入的水电联产优化设计

结合已有的反渗透/多级闪蒸混产系统和发电-多级闪蒸联产系统,设计了一个新的包括热力发电系统、反渗透海水淡化系统和多级闪蒸海水淡化系统的水电联产超结构,对以不同盐度苦咸水、海水为原水的水电联产系统进行了优化设计,通过求解系统以年费用最小为目标函数的非线性数学模型,得到不同盐度下联产系统优化的生产结构. 结果表明,在低盐度(≤25000 mg/L)下采用冷凝式发电和一级反渗透产水,高盐度下采用抽汽冷凝式发电和热膜混合产水,可降低联产系统的年费用,获得较低成本的淡化水. 在本工作所定的生产规模下,优化联产方案的年费用可降低23%~36%.     

The effect of steam temperature on the economics of a cogeneration power plant

Using steady-state simulation, we have evaluated the effect of boiler superheat and reheat temperatures on the economics of the utility section of a Bayer Alumina Plant. These economics were compared with those of a steam plant which purchased power. Under this study's nominal economic conditions, producing steam and purchasing electricity was the cheaper option. A sensitivity analysis showed that the cogeneration plant became the better choice when the local cost of electricity rose above 10C/kWh. The plant economics improved monotonically with superheat temperature as did the thermo-dynamic efficiency. However, for reheat, the plant economics did not improve monotonically with temperature even though the thermodynamic eficiency did; thus improvement in the thermodynamic efficiency does not always yield improved economics.     

满足不同需求的水热电联产系统的模型和设计简

In order to improve the energy efficiency, reduce the CO2 emission and decrease the cost, a cogenera- tion system for desalination water, heat and power production was studied in this paper. The superstructure of the cogeneration system consisted of a coal-based thermal power plant （TPP）, a multi-stage flash desalination （MSF） module and reverse osmosis desalination （RO） module. For different demands of water, heat and power production, the corresponding optimal production structure was different. After reasonable simplification, the process model ot each unit was built. The economical model, including the unit investment, and operation and maintenance cost, was presented. By solving this non-linear programming （NLP） model, whose objective is to minimize the annual cost, an optimal cogeneration system can be obtained. Compared to separate production systems, the optimal system can reduce 16.1%-21.7% of the total annual cost. showing this design method was effective.     

化工能量系统集成

本文叙述了讨论由换热网络及蒸汽动力系统,冷却,冷冻等公用工程系统组成的能量系统的优化集成方法作者着重阐述了广泛应用于工程节能的夹点技术及其有关的各种先进软件,通过列举多个工厂的实例,展示了能量系统集成在化工企业节能降耗工作中的重要作用。     

A Thermodynamic Approach to the Integrated Design of a Combined Cycle Cogeneration Plant

A thermodynamically oriented approach for the integrated design of a combined cycle cogeneration plant (CCCP) meeting a given sites requirements for process steam and power has been developed. It has been shown that the most efficient plant, for a targeted stack temperature, is achieved when the gas turbine cycle is designed for maximum specific net work and the steam turbine cycle is designed for maximum cycle efficiency. Based on this approach a computer program for rigorous analysis has also been developed.     

400 kt/a硫磺制酸装置化工投料试车总结

介绍400kt／a硫磺制酸装置投料试车情况。72h性能考核表明,该装置工艺技术先进适用,设备选型合理,装置控制先进;主要工艺指标达到设计要求,总转化率达99．79％,吸收率达99．997％;三废排放控制较好;水、电、汽等公用工程消耗较低。     

石化企业蒸汽动力系统柔性设计

蒸汽动力系统的设计工作是一项复杂的、系统的工程,除了力求实现全周期内总费用最小的经济性目标外,还要保证实际运行过程中的各种工况下的操作柔性。针对石化企业蒸汽动力系统变工况的特点,提出了蒸汽动力系统柔性优化设计策略;将确定性变化需求转化成多周期问题,将不确定性变化需求转化成虚拟的多工况问题,并对连续不确定性和离散不确定性变化分别处理;以经济性和可操作性的最优综合为目标,建立蒸汽动力系统柔性优化设计的大型混合整数线性（MILP）模型,并采用广义Benders分解算法进行求解。采用本文提出的柔性优化设计模型和求解方法,对某炼油厂蒸汽动力系统进行了柔性优化设计,并与传统设计方案和经济性最优的设计方案进行对比。与经济性最优的方案对比结果表明,该优化设计方案总费用增加不多,但实现了在各种变化工况下的安全、稳定、柔性操作;而与传统设计方案对比结果表明,不但提高了各种工况下的操作柔性,而且节省了大量的投资和运行费用,即柔性设计方案具备可操作性和经济性的综合最优性。从而证明了本文提出的柔性设计建模和求解方法的合理性和实用性。     

Systems analysis of dual-purpose nuclear power and desalting plants Part I. Optimization

The optimal process design of a dual purpose plant for producing power and water is investigated. A nuclear reactor and steam turbine power generator for steam and power production is coupled with two water plants, a multi-stage flash plant and a reverse osmosis plant. The total system cost for producing given levels of power and water is minimized. Optimal designs are presented for several combinations of water and external power demands ranging from 25 mgd to 150 mgd and from 50 MWe to 200 MWe.     

大型吸收式热电联产机组性能分析与对比

燃煤热电联产机组在电能与热能的协调和转换中起到至关重要的作用,并且在未来一段时间内仍是我国北方冬季采暖的主力热源。本文构建了包含电厂侧和热力站侧两部分在内的一种热电联产系统方案,并研究了机组背压、供给热电比、汽水系统?效率、热网换热器?效率、机组发电量、热网水泵功率在变工况下和单独改变供热功率、供水温情况下的变化规律,开创了电热价比的方法对电热两种捆绑式生产的热电联产机组来衡量其整体经济收益,最后通过热网水质量流量、热电比、背压、抽凝比和发电煤耗率这些指标将新方案与传统热电联产方案进行了对比。结果表明：对于热电联产机组,系统热力学参数随工况、供热负荷和供水温度变化呈现不同规律;本文新提出的电热价比方法能为热电联产机组提供运行决策和收益预测规划;新方案可通过提升热网供回水温差可以显著提高系统供热能力和能源利用效率：使得发电煤耗率减小3.22～7.00g/(kW·h),机组背压降低了65.07%,热网水流量减少了33.33%。     

装置蒸汽动力系统与热电厂运行同步优化

石化企业装置蒸汽动力系统通常独立设计和操作,忽视了与热电厂蒸汽动力系统的联系。热电厂蒸汽动力系统通常在固定的蒸汽和电力需求下进行优化,忽视了与装置蒸汽动力系统的联系。为实现石化企业蒸汽动力系统的全局优化,本文提出了用于装置蒸汽动力系统与热电厂运行同步优化的方法。首先使用热电厂透平和锅炉的设计及运行数据回归得到设备模型系数,依照现有结构建立热电厂蒸汽动力系统约束。然后以装置蒸汽动力系统设计和操作灵活性为区分,将装置分为三类：第一类装置蒸汽和电力需求无法调节;第二类装置可以通过减温减压调节蒸汽需求;第三类装置既可以通过减温减压调节蒸汽需求,也可以通过驱动选择调节热电需求。装置透平模型参数采用文献值,通过采集各类装置蒸汽和电力需求等数据建立装置蒸汽动力系统约束,最后通过热电厂与装置蒸汽和电力的连接关系建立耦合模型。耦合模型以年度费用为目标函数,其中包括热电厂运行费用以及装置透平和电机的年度投资费用,通过优化求解得到热电厂设备负荷分配方案以及装置蒸汽动力系统设计方案。通过算例论证了同步优化方法的可行性,与独立优化相比,同步优化降低年度费用451万美元。