考虑温度约束的单杂质水网络优化

实际用水过程有温度的要求,在用水网络集成中考虑温度的约束,使水耗和能耗同时降低,具有重要的意义。此外,过程系统中还存在只有温度限制的与用水无关的过程流股,将水网络中的水流股与其同时考虑热集成,可以使能量得到更合理的分配利用。在全过程系统能量集成的背景下,建立了对应的水网络优化方法。首先使用现有的废水直接回用水网络LP模型求解初始水网络并提取流股数据,然后在4条非等温混合规则的判断下,依次比较水网络流股与背景夹点、全过程夹点的关系,以排除不合理的非等温混合,最后以年总费用最低为目标进行全过程系统的热集成。使用本文提出的方法对某案例进行优化,得到的年总费用减少了6.27%,证明了该方法的可行性。     

与换热网络热集成的精馏塔压优化

调整精馏塔的操作条件是节省塔能耗的有效途径之一，然而在对已有装置进行用能优化时，需同时考虑精馏塔操作条件对塔能耗和换热网络能耗的影响。基于装置所有流股的冷热复合曲线，针对跨夹点的精馏塔，同时考虑了精馏塔的再沸、冷凝以及过程流股，分析了塔压变化对装置公用工程消耗的影响，并对某连续重整装置汽提塔进行了案例分析。结果显示，塔压降低可使冷凝器能耗增加，再沸器能耗减小，而对于塔顶塔底出装置流股，塔压降低可节省冷却公用工程但增加加热公用工程。装置总体的节能效果为塔顶冷凝器、塔底再沸器和塔顶塔底出装置流股节能效果的综合作用。对某连续重整装置汽提塔分析表明，塔压降低200.0 kPa时，其加热公用工程用量将减少577.5 kW。     

综合考虑泵的设备及运行费用的换热网络优化

流体流经换热设备产生的压降是影响换热网络综合的重要因素,且压降会对整个换热网络系统的稳态运行造成影响。因此在进行换热网络综合时,泵的设备购置费、运行泵的能耗费用需同换热设备费用和公用工程费用同时进行考虑。本文基于有分流的非等温混合分级换热网络超结构模型,并且去除流股给热系数为常数的假设,将流股的给热系数作为流股流速的函数,以换热网络最低年总费用作为本文数学模型的目标函数,综合考虑泵的设备购置费用和泵运行时的能耗费用,建立了一个换热网络同步综合的MINLP数学模型。采用改进的拟并行的遗传/模拟退火算法对该数学模型进行求解,可获得最优的压降值及最优流股给热系数下的换热网络结构。最后,通过具体的算例证明了模型的有效性和可靠性,达到了既简化换热网络结构又降低了年总费用的目标。     

最小年度化费用换热网络综合的匹配规则研究

本文在分析换热器投资费用的基础上，指出在进行换热网络综合时应以壳程数作为一个综合目标，并通过与公用工程费用的权衡得到年度化费用的换热网络，提出了基于最小壳程数的换热网络综合方法的匹配规则，指出了为获得最小壳程数，冷热流股进行匹配的最大可能交叉程度以及流股间进行匹配的顺序，并提出了不可行匹配的基本准则，通过实例分析得到较好的效果。     

基于经验规则的数学规划法快速设计多杂质用水网络

综合了夹点规则、排序思路等经验,提出了基于经验规则的数学规划法来快速设计多杂质用水网络。由于获取准确的用水过程顺序是剔除一些不必要流股、简化用水网络数学模型的关键,因此,基于对用水过程极限数据的分析和对用水过程的理解,提出了用水过程供水和受水的排序方法,并设定必要的水夹点规则、序列和逼近规则、混合规则以剔除不必要的水网络结构,达到简化模型、降低网络结构维数的目的,最后在LINGO软件上编写程序进行求解。通过三实例分析得知,设定经验规则后能够有效地降低模型规模、减少模型的非线性变量数、缩短模型的求解时间,并能够得到最优的设计方案。     

用遗传算法进行多流股换热器网络综合的研究

建立了多流股换热器网络综合数学模型，该模型改进了文献中等温混合的不合理假设。多流股换热器网络综合问题本质上是一个混合整数非线性规划问题(MINLP)，这类问题的非凸非线性的特性使得目标函数存在多个局部最优解。传统的基于梯度的搜索方法在处理这类问题时由于计算规模庞大且极易陷于局部最优解而不再适用，而遗传算法却为解决这类问题提供了很有希望的一个方向。因而对遗传算法求解多流股换热器网络综合问题进行了研究，提出了可以自动产生可行的多流股换热器网络的方法策略，最后通过两个例题说明所提方法是可行的。     

考虑非等温混合的能量集成水网络设计方法

讨论了能量集成水网络中非等温混合对系统能量目标的影响,提出了分割温度的概念。对于同性混合,系统的公用工程需求量不会减少。对于异性混合,通过确定分割温度并比较分割温度以上区间混合流股的热量之和与低温区间所需的热量,可以准确确定系统公用工程会增加、减少或者保持不变。基于以上思想,得到了非等温混合规则。它能判断是否存在能量惩罚,以及如何通过设计混合温度来避免能量惩罚。结合改进的"分离系统"法,提出了一种系统化的能量集成水网络设计方法。     

多流股换热器网络综合方法在原油预热系统中的应用

以原油常减压蒸馏装置原油预热网络为研究对象,进行了多流股换热器网络的实例综合. 基于超结构物理模型建立了改进的多流股换热器网络综合数学模型,提出将该网络综合问题由混合整数非线性规划问题转化为简单的非线性规划问题的求解策略,并利用改进的遗传/模拟退火新算法进行了原油预热网络的综合. 与Hextran软件的综合结果以及现场换热网络的对比表明,本模型和求解策略可以应用于工业规模的多流股换热器网络综合,有可能取得较好的经济效益.     

低温精馏过程模拟及其分离特性分析(Ⅱ)带有侧线返回进料的低温精馏塔模拟

应用严格的热力学模型研究了带有侧线返回进料的氢同位素低温精馏塔的分离特性.根据氢同位素低温精馏体系的特点，以平衡级模型为基础建立了氢同位素低温精馏稳态模拟模型，确定了模型方程适宜的求解方法.塔的一股侧线出料流股经过一个平衡反应器完成平衡反应后，作为内部进料流股，与原外部进料混合后重新进入精馏塔内进行分离操作.通过对带有侧线返回进料的塔的计算模拟阐明了这一侧线流股对塔分离特性的影响.在平衡反应器内，HD部分分解为H₂和D₂，塔顶产品中H₂的浓度增加了8.635%，塔底D₂的浓度增加了11.327%.     

LNG系列板翅式换热器的研究与开发

介绍了一级制冷五股流板翅式换热器、二级制冷四股流板翅式换热器、三级制冷三股流板翅式换热器和混合制冷剂多股流板翅式主换热器的板束结构特征、制冷工艺与混合制冷剂制冷原理。展望了LNG系列板翅式换热器的重要研究方向以及需要进一步解决的关键科学问题。     

Thermodynamic analysis of non-isothermal mixing's influence on the energy target of water-using networks

In this paper, a thermodynamic analysis of non-isothermal mixing's influence on the energy target of water-using network is presented. Firstly, water streams in the network are divided into two categories, and then based on the classification all the non-isothermal mixing patterns between two streams are defined. Through thermodynamic analysis from energy composite curve of hot and cold water streams, the influences of non-isothermal mixing on the energy target of water-using network are explored and some mixing rules are obtained, which can be used to simplify the heat exchanger network of a given water-using system and improve the system's energy performance through identifying the beneficial non-isothermal mixings. The applicability of these rules is illustrated by an example in the paper and the result is very encouraging.     

考虑非等温混合的能量集成用水网络综合

提出了考虑非等温混合的新的水网络模型,并结合线性规划（LP）转运模型同时优化水网络的水耗及公用工程目标。新的水网络模型引入非等温混合以改善用水网络的能耗特性及减少模型中参与集成换热网络的流股数,从而降低设计换热网络的复杂程度。在确定水网络的水耗及公用工程目标后,采用夹点法设计详细的换热网络结构。两个算例结果表明,新的水网络模型不仅能确定用水网络的最优水耗及公用工程目标,而且还能得到一个更加简单的换热网络。这对节省设备投资及减少操作费用具有重要意义。     

Retrofitting of the Heat Exchanger Network with Steam Generation in a Crude Oil Distillation Unit

Steam generation through hot streams has an important impact on the utility consumption of a crude oil distillation unit. Retrofitting of the heat exchanger network with steam generation in a crude oil distillation unit is studied with regard to efficient energy usage. The grand composite curve is employed to provide insights into the steam generation problem, and a mixed‐integer linear programming model, presented previously for heat integration through hot discharges/feeds and steam generation, is used to obtain the optimal parameters for steam generation. Three heuristic rules are then proposed to determine suitable hot streams for steam generation. Finally, the heat exchanger network is modified based on pinch technology. After the retrofit, the hot and cold utility decrease.     

Direct observation of channel-tee mixing of high-temperature and high-pressure water

Channel-tee mixing of flowing high-temperature and high-pressure water streams was observed by using a newly designed high-pressure optical cell and results were compared with mixing at room temperature. The characteristic feature of the cell is a three-piece window with the center window containing a mixing channel. The mixing between aqueous streams at high-temperatures and high-pressures greatly depended on the mixing direction and it was found that gravity played an important role, even for mixing between streams of small diameters (2 mm).     

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.     

Progress in pressure retarded osmosis (PRO) membranes for osmotic power generation

The rapid increases in global energy consumption and greenhouse gas emissions have stimulated the exploration of renewable energy sources as alternative fuels. Osmotic pressure gradient energy released from the mixing of water streams with different salinities is an unexploited resource of renewable energy. By employing a semipermeable membrane to control the mixing process, the osmotic pressure gradient energy can be harvested in terms of electrical power via pressure retarded osmosis (PRO) without causing adverse environmental impacts. The ideal of harvesting osmotic power via PRO was proposed in the early seventies; however, the absence of effective membranes with desirable structure and performance hindered further advancement of the PRO technology. During the last few years, a significant progress in PRO technology has been achieved. Novel flat-sheet and hollow fiber polymeric membranes with desired structure, mechanical robustness and permeation characteristics have been developed for PRO applications. Membranes with a target power density of 5 W/m² to produce commercially viable PRO processes have been achieved. At this point of time, a comprehensive review is imperative in order to summarize what we have accomplished and provide insights for the development of next generation PRO membranes. After a brief introduction of the PRO process and the early PRO development using the existing RO/NF and FO membranes, this review focuses primarily on novel and the state-of-the-art PRO membranes. Furthermore, the requirements for fabricating effective PRO membranes will be discussed and future perspectives will be presented.     

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     

Step-wise synthesis of work exchange networks involving heat integration based on the transshipment model

Due to the deterioration of serious energy dilemma, energy-conservation and emission–reduction have been the strategic target in the past decades, thus people have identified the vital importance of higher energy efficiency and the influence of lower carbon development. Since work exchange network is a significant part of energy re-covery system, its optima design wil have dramatically significant effect on energy consumption reduction in chemical process system. With an extension of the developed transshipment model in isothermal process, a novel step-wise methodology for synthesis of direct work exchange network (WEN) in adiabatic process involv-ing heat integration is first proposed in this paper, where a nonlinear programming (NLP) model is formulated by regarding the minimum utility consumption as objective function and optimizing the initial WEN in accordance with the presented matching rules to get the optimized WEN configuration at first. Furthermore, we focus on the work exchange network synthesis with heat integration to attain the minimal total annual cost (TAC) with the introduction of heat-exchange equipment that is achieved by the following strategies in sequence:introducing heat-exchange equipment directly, adjusting the work quantity of the adjacent utility compressors or expanders, and approximating upper/lower pressure limits consequently to obtain considerable cost savings of expanders or compressors and work utility. Finally, a case taken from the literature is studied to illustrate the feasibility and effectiveness of the proposed method.