蒸汽动力系统设计与综合优化研究综述

蒸汽动力系统是过程工业企业的重要组成部分,其设计水平、运行和控制性能对过程工业的能量利用效率和经济性具有重要影响,在过去的30多年里,蒸汽动力系统的优化研究一直是国内外学者研究的热点。本文归纳了过程工业蒸汽动力系统设计与综合优化方面的研究内容;从优化内容、优化方法、优化准则目标等方面详细介绍了过程工业蒸汽动力系统研究工作进展;针对当前研究工作的局限展开了评论,对蒸汽动力系统设计与综合的深入研究重点和方向提出了展望。     

基于数学规划法的蒸汽动力系统优化运行研究

为满足石油化工行业实际生产中各单元、各工艺过程对不同等级蒸汽的需求,将不同蒸汽动力循环过程归纳综合为一种通用的过程,并利用数学规划的方法建立了数学模型。采用数学规划法对实际操作系统进行优化,得到最佳操作参数,并与人工调度方案进行了比较。结果表明:对于复杂蒸汽动力系统的优化,借助优化模型和求解软件可以方便地确定系统最优运行状态,使整个蒸汽动力系统的运行费用最低。该方法可为过程动力、热能、工艺蒸汽等的分配提供参考数据,对实际蒸汽动力系统的优化改造有着重要的指导意义。     

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。     

基于马尔可夫链的蒸汽动力系统两阶段随机规划

现有的解决蒸汽动力系统蒸汽需求不确定性的优化方法有随机规划和鲁棒优化,但二者不能同时兼顾稳定性和经济性。本文提出一种基于马尔可夫链的两阶段随机规划去解决这个问题。第一阶段基于空间距离表达划分不确定变量,通过聚类算法划分成不同工况。第二阶段基于状态切换概率构建马尔可夫链,通过场景生成和削减的方法预测蒸汽的需求值。以某煤制气企业蒸汽动力系统为实例建立相应的优化模型,将预测的蒸汽值带入优化模型求解,得出的最优操作方案与随机规划和鲁棒优化法进行对比和分析。结果表明,本优化方法综合了随机规划经济性高和鲁棒优化稳定性高的优点,稳定性和经济性都介于随机规划和鲁棒优化的中间,为解决蒸汽动力系统的不确定优化问题提供了新思路。     

蒸汽动力系统柔性设计和多目标优化研究进展

蒸汽动力系统(SPS)消耗一次能源(煤等),产生蒸汽、电、机械功与冷剂,在过程系统中起着至关重要的作用。设计与优化蒸汽动力系统不但要考虑柔性以应对来自工艺过程内部与外部的变动,而且要考虑系统的经济性,环保性等指标以适应可持续发展。蒸汽动力系统的柔性与多准则设计已成为过程集成研究的热点。本文首先总结了蒸汽动力系统设计的启发式方法(即经验法)、热力学目标法、数学规划法或将它们相互结合的组合方法的研究进展;进一步对确定条件和不确定条件下的蒸汽动力系统柔性设计的研究情况进行了分析;最后对近十年来考虑经济、环境、有效能等目标、考虑余热发电和可再生能源驱动蒸汽动力系统的多目标优化设计进行了重点综述。研究表明,多种能源驱动的、柔性的、多目标的蒸汽动力系统与工艺过程、换热网络的同步综合是今后研究的重点方向。     

基于线性规划法的通用蒸汽动力系统的优化

为解决实际化工生产中各生产单元、工艺过程对不同品级蒸汽的需求,本文把不同的蒸汽动力循环过程归纳综合成一种通用的过程,并利用混合整数线性规划（LP）的方法对实际操作系统进行优化,得到最佳的操作参数。使整个蒸汽动力系统运行费用最低,从而达到节能的目的。这种方法还可以为过程动力、热能、工艺蒸汽等的分配提供参考数据,对实际蒸汽动力系统的优化改造具有重要的指导意义。     

蒸汽动力系统设计与多周期运行同步优化

蒸汽动力系统(Steam power system,SPS)是炼油企业的重要组成部分,针对炼油企业蒸汽动力系统设计与运行方案上存在的不合理方面,通过对蒸汽动力系统建立混合整数线性优化模型(MILP),改善部分系统结构、调整系统多周期运行方案,从而降低蒸汽动力系统的运行费用实现系统的优化。以某炼油企业蒸汽动力系统实为背景,对企业蒸汽动力系统的设计与多周期生产调度方案进行优化,并验证优化策略的有效性。     

炼油及石油化工企业的能源优化技术

总结了国内炼油及石油化工企业使用的系统能源优化技术与工具,包括能耗计算与评价、能源资源的综合优化利用、热集成方法、能量平衡与用能分析、蒸汽动力系统优化、低温余热的回收利用和各种计算机软件等,分析了存在的不足之处,提出了今后发展的建议。     

工艺蒸汽加热网络与蒸汽系统的集成优化

蒸汽动力系统作为过程工业的重要组成部分,由蒸汽系统、分配系统和蒸汽加热网络组成。文中提出对蒸汽系统、分配系统和蒸汽加热网络进行集成优化。首先通过夹点分析对工艺蒸汽加热网络进行优化匹配,得到各等级蒸汽需求量及凝结水回收参数;然后根据建立的蒸汽系统和分配系统的运行优化模型得到产汽及分配方案。通过对某化工厂的能量利用系统进行集成优化,得到的优化方案与传统设计方案相比,锅炉燃料消耗量减少16.38%,同时系统所需要的外界补给水量减少16.27%。提出的集成优化方法对蒸汽动力系统的设计优化具有一定的指导意义。     

煤制气蒸汽动力系统多周期模拟与优化

蒸汽动力系统是煤化工的重要组成部分,为工艺提供蒸汽和动力.针对煤制气动力系统存在的能源浪费和经济亏损的问题,建立了锅炉、汽轮机、减温减压器和除氧器等关键设备的数学模型,以此集成得到蒸汽动力系统的数学模型.以系统运行成本为目标函数,采用某煤制气企业多周期的实际数据建立了混合整数非线性规划(MINLP)优化模型.优化后的系...     

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.     

乙烯联合装置能耗分析和节能技术

在石油资源日益紧张的情况下,作为石化行业能耗大户——乙烯装置的能耗分析和节能技术的研究意义非凡。根据科技原创力理论和集成技术创新思路对乙烯联合装置能耗进行分析,指出影响乙烯综合能耗的因素依次为裂解原料、裂解技术、分离流程、配套设施(公用工程、外围工程)。采用裂解原料优化、裂解技术改进、分离流程进步和配套设施改造等一系列节能技术从而使乙烯联合装置综合能耗分别下降10.23%,4.91%,2.95%,0.98%,0.59%以上,合计降低19.66%综合能耗。     

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.     

Incorporation of Mass and Energy Integration in the Optimal Bioethanol Separation Process

A techno‐economic analysis for the separation process in bioethanol production is presented. Optimized azeotropic separation processes in conjunction with process integration (mass and energy) are considered to simultaneously enhance the results from economic and environmental points of view. Process integration improves significantly the separation process because it helps to reduce the overall energy required in the reboilers based on energy integration and additionally to diminish the amount of required solvent based on mass integration. The SYNHEAT optimization model was applied for energy integration whereas a direct recycle strategy was implemented for the mass integration process. The best separation processes obtained correspond to an integrated conventional separation sequence with energy integration to ethanol‐water mixture III and integrated optional separation sequences with energy integration to ethanol‐water mixture III, with significant savings in utility costs and possible recycling of nearly all solvent.     

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.     

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     

过程系统能量流结构模型及其应用

综述了过程系统能量综合优化的能量流结构研究与进展；重点介绍了过程系统三环节能量流结构模型，该模型基于对过程系统中能量演变共性规律的认识，定量地描述了过程系统能量流在转换、利用、回收过程中的平衡关系；概述了按照能量流结构进行过程能量综合优化策略和方法；指出了过程系统能量综合优化中能量流结构的进一步发展可以包容其他相关方面，如环境、安全等。     

过程系统综合集成优化法的研究进展

综述了目前国内外过程系统综合集成优化的主要方法：直观推断法、最优化法、夹点分析法和过程系统火用经济调优法．并分析了各自的优缺点,指出利用各种方法的优点,发展数学规划、人工智能方法、夹点分析和火用经济学集成的方法、开发节源型过程耦合技术、进行过程系统综合和环境保护的协同优化研究,将是过程系统综合集成优化法研究的重要课题。     

Wärme-Integration und Prozeßoptimierung

Thermal integration and process optimization . The Pinch method for optimization of thermal integration of chemical plant has been widely accepted in recent years. Serving initially only as an aid in the design of energetically optimized heat exchanger networks, the method was developed in the course of time with regard to the following questions: optimization of heating and cooling systems; simultaneous optimization of energy and investment costs; operability, start-up and shut-down behaviour; inclusion of heat engines; optimization of old plant; and process optimization. The fundamentals of the Pinch method are summarized and further developments concerning development of the method for simultaneous optimization of energy and capital costs are presented. Optimization of the BASF butadiene process and the mutual interaction of process and energy system are then presented as practical applications.     

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。