Process integration techniques for optimizing seawater cooling systems and biocide discharge

This work addresses the problem of using seawater for cooling and the associated environmental problems caused by the usage and discharge of biocides. The discharged biocide and its byproducts are toxic to aquatic lives and must be decreased below certain discharge limits on load prior to discharge. The conventional approach has been to add biocide removal units as an end-of-pipe treatment. This work introduces an integrated approach to reducing biocide discharge though a set of coordinated strategies for in-plant modifications and biocide removal. In particular, process integration tools are used to reduce heating and cooling requirements through the synthesis of a heat-exchange network. Heat integration among process hot and cold streams is pursued economically by reconciling cost reduction in utilities versus any additional capital investment of the heat exchangers. Other strategies include maximization of the temperature range for seawater through the process and optimization of biocide dosage. This new approach has the advantage of providing cost savings while reducing the usage and discharge of biocides. A case study is used to illustrate the usefulness of this new approach and the accompanying design techniques.     

电厂宽负荷运行下蒸汽喷射器对低温多效蒸馏系统的影响

淡水资源匮乏问题日益严重,火电厂耦合低温多效蒸馏（low-temperature multi-effect distillation,LT-MED）海水淡化技术因可有效降低制水成本而被广泛利用。利用Ebsilon软件对某电厂和低温多效蒸馏海水淡化耦合系统进行建模,分析了电厂宽负荷下蒸汽喷射器对水电联产系统热经济性的影响规律。研究结果表明：基于单级蒸汽喷射器的水电联产系统,以电厂75% THA工况设计下的蒸汽喷射器的性能最佳。对于带两级蒸汽喷射器的水电联产系统,当电厂负荷在75% THA工况时系统的制水电耗量相比单级蒸汽喷射器系统降低了13.65%,并且电厂负荷在50% THA工况以上时,带两级蒸汽喷射器系统的制水电耗量较单级蒸汽喷射器系统的低。     

海水淡化技术在沿海电厂的应用浅析

简要介绍了海水淡化技术及其应用现状,仔细分析了沿海电厂应用海水淡化技术的可行性、必要性和需要解决的主要问题,并给出了有关综合利用的建议。     

海水淡化微生物控制的运行优化

微生物污染是海水淡化系统反渗透膜污染的主要类型之一。2016年春季,红沿河核电厂海水淡化系统一级反渗透膜出现压差频繁快速升高、脱盐率不变、产水量下降的现象,反渗透膜解体解剖分析表明受到微生物污染。分析反渗透膜压差频繁升高、产水量下降的原因,是由于杀菌不彻底造成微生物滋生,从而导致压差升高。通过增加海水预处理杀菌剂次氯酸钠加药量,提高超滤水箱出口残余氯水平,以减少海水中微生物滋生,并在不同的季节,控制不同浓度的加药量。经过运行验证,该措施能够将反渗透系统进水的微生物控制在较低水平,降低反渗透膜压差升高的频率,提高了红沿河核电厂海水淡化系统设备运行可靠性,取得了很好的效果。     

A systems-integration approach to the optimization of macroscopic water desalination and distribution networks: a general framework applied to Qatar’s water resources

The objective of this article is to introduce an optimization-based approach for the integrated design and operation of macroscopic water networks. A structural representation approach is developed to embed all potential configurations of interest. This representation accounts for water resources, desalination plants, water users, wastewater treatment facilities, and storage. Water recycle/reuse is enhanced via the use of treated water. Water utilization is improved by minimizing the losses of discharged water resulting from the linkage of power plants and thermal desalination plants and the lack of integration between water production and consumption. Excess water is saved in storage systems or injected in aquifers for strategic (long-term) storage. The developed approach also accounts for the economic values of water uses and storage and for the cost of water production and allocation. An optimization formulation is developed and solved to determine the optimal operation of the infrastructure. The solution also determines the optimal monthly allocation and storage of water resources. A case study is solved for managing the water resources in the State of Qatar while accounting for desalination, distribution, and storage. The solution indicates that storage in tanks reaches its maximum capacity in less than a month while storage in aquifers continues throughout the year as a strategic step towards water security. The solution also illustrates the need to treat wastewater in addition to using desalination of seawater. The output water streams with different qualities are assigned to proper destinations.     

Application of waste heat powered absorption refrigeration system to the LNG recovery process

The recovery process of the liquefied natural gas requires low temperature cooling, which is typically provided by the vapor compression refrigeration systems. The usage of an absorption refrigeration system powered by waste heat from the electric power generating gas turbine could provide the necessary cooling at reduced overall energy consumption. In this study, a potential replacement of propane chillers with absorption refrigeration systems was theoretically analyzed. From the analysis, it was found that recovering waste heat from a 9 megawatts (MW) electricity generation process could provide 5.2 MW waste heat produced additional cooling to the LNG plant and save 1.9 MW of electricity consumption. Application of the integrated cooling, heating, and power is an excellent energy saving option for the oil and gas industry.     

EB锭焊管用TA2冷轧钛带制备技术研究

TA2薄壁钛焊管具有比强度高、耐腐蚀、生产效率高、换热效果好等优点,被广泛应用于核电、化工、海水淡化等领域。本研究采用短流程、低成本电子束冷床熔炼炉EB扁锭制备焊管用TA2冷轧钛带卷,并对其组织性能进行分析。结果表明:采用EB锭制备的TA2冷轧钛带卷横向强度低、伸长率及表面硬度高,可有效避免焊管弯曲成型过程中表面划伤、磨痕等成型缺陷,满足薄壁焊管使用需求。      

Comparison of genetic and binary particle swarm optimization algorithms on system maintenance scheduling using prognostics information

Recent technical advances in condition-based maintenance technology have made it possible to not only diagnose existing failures, but also forecast future failures, which is called prognostics. A common method of maintenance scheduling in condition-based maintenance is to apply thresholds to prognostics information, which is not appropriate for systems consisting of multiple serially connected machinery. Maintenance scheduling is defined as a binary optimization problem and has been solved with a genetic algorithm. In this article, various binary particle swarm optimization methods are analysed and compared with each other and a genetic algorithm on a maintenance-scheduling problem for condition-based maintenance systems using prognostics information. The trade-off between maintenance and failure is quantified as the risk to be minimized. The forecasted failure probability of serially connected machinery is utilized in the analysis of the whole system. In addition to the comparison of a genetic algorithm and binary particle swarm optimization methods, a new binary particle swarm optimization that combines the good sides of two binary particle swarm optimizations is presented.     

Economical study for hydrogen production from seawater using renewable energy in Egypt

This study looks into the possibilities of hydrogen production in the north coast and red-sea Zone, Egypt, to conver renewable energy to hydrogen (power to gas). The main purpose is to estimate the power needed for each kg of hydrogen production from seawater using renewable energy and then the quantity of desalinated seawater needed to cover this cost. We will discuss different scenarios; the main two scenarios are photovoltaic (PV) solar with reverse osmosis (RO) desalination and concentrating solar power (CSP) with multi-effect desalination (MED).     

海水预处理一体化混凝-微滤工艺

针对渤海近岸海水浊度高、有机物和悬浮固体含量大等特点,开发了一体化混凝-微滤工艺对海水进行预处理.系统较长时间运行表明,出水水质好,能满足海水反渗透进水的要求.对污染的膜进行系统清洗后,膜通量基本可恢复至新膜水平;膜表面沉积物中Ca2 、Mg2 等的化合物含量较高;NaOCl溶液可有效洗脱膜表面UV254所代表的腐殖质类天然有机物.     

Using 0/1 mixed integer linear programming to solve a reliability-centered problem of power plant preventive maintenance scheduling

The problem of power plant preventive maintenance scheduling is studied in this paper. A reliability perspective is considered. This problem consists of ascertaining which generating units must halt production to be examined regularly for safety. It is very important because a failure in a power station may cause a general breakdown in an electric network. The main consequence is that the electricity demand of customers will not be satisfied in such cases. Therefore, reliability is the key point used in the methodology presented. The problem is approached under the operations research perspective as an optimization issue. 0/1 mixed integer linear programming is used to solve the model reached. An application study is included. The model is put to use in a real power plant setting, representative of the Spanish one. The result obtained is a schedule that allows the efficient organization of preventive maintenance over a specific time horizon.     

超滤用于海水淡化预处理的研究进展

良好的预处理是保证反渗透(RO)装置长期稳定运行的关键要素之一.与传统预处理技术相比,UF预处理能够有效降低海水的SDI、浊度和TOC等,为RO装置提供优良、稳定的进水,增强RO膜的可靠性.详细评述了近年来国内外采用UF技术作为RO淡化预处理过程的研究和应用进展.此外,对UF膜的污染和控制对策研究进展也作了评述.UF作为膜法海水预处理技术已成为该领域的发展趋势.     

提高制冷机效率的措施分析

当今很多空调使用的制冷机都存在严重的效率低的现象。制冷机设备效率(COP值)很低,一般在3.8左右,远低于额定值5.36。频繁对制冷机冷凝器进行化学清洗,对冷凝器管壁磨损又较严重。效率低的主要原因是换热器结垢、冷却塔脏、冷却水质较差。基于此,结合实例我们对制冷机效率提高的措施进行了研究分析。     

Augmented desalination with cooling integration

Humidification–dehumidification (HDH) desalination works based on a water cycle principle and involves air humidification and condensation (dehumidification). The cooling of humid air with chilled water increases the desalination and results in cold air suitable for air conditioning process. The merits of the proposed HDH desalination and cooling are not analyzed and compared in the literature. Therefore, the performance results of HDH with normal water (current technology) and HDH with chilled water (proposed idea) are compared to highlight the merit of this cycle. The combined cycle for desalination and cooling has been solved thermodynamically with psychrometric properties. The results are validated with a laboratory experimental setup. The examined operational process conditions are hot water inlet temperature, efficiency of humidifier, and vapor absorption refrigerator's (VAR's) evaporator exit temperature. The focused results are desalination, cooling and energy utilization factor (EUF). The comparative study recommends the use of chilled water in the final stage. The two stage desalination with dehumidification by normal water in the first stage and chilled water in combined two stages improves the cycle EUF from 0.18 to 0.33. Out of 300 W of cooling generation, 100 W is used for dehumidification and the remaining 200 W is available for air conditioning process at 15 N⋅m³ h⁻¹ of air.     

Feasibility analysis of an OTEC plant as the bottom cycle of the third nuclear power plant

Abstract

A conceptual design, performance analysis, system optimization and simulation of an OTEC (Ocean Thermal Energy Conversion) power plant was carried out in the present study. The OTEC plant acts as the bottom cycle of the Third Nuclear Power Plant, utilizing the warm water discharged from the nuclear plant as the heat source and the cold deep seawater pumped from the nearby sea bottom as the heat sink. The nominal net power output from the OTEC plant is estimated to be 8.74 MWe. A plant simulation was further carried out to study the OTEC plant performance due to seasonal variation of the warm water temperature, which shows that the OTEC plant is able to deliver an electricity of 5.18×10⁷ kWH per year. The net power output in the winter season will be reduced to about one eighth of that in the summer season. The final discharged warm water temperature was shown to be below 29°C all year around, so that the current thermal pollution problem of the nuclear power plant can be eliminated. Additionally there is the side benefit of 8.74 MWe net power generation from ocean energy resource. This OTEC plant will become economically feasible if the installation cost is considered as a thermal pollution control investment.     

Power plant maintenance scheduling using ant colony optimization: an improved formulation

It is common practice in the hydropower industry to either shorten the maintenance duration or to postpone maintenance tasks in a hydropower system when there is expected unserved energy based on current water storage levels and forecast storage inflows. It is therefore essential that a maintenance scheduling optimizer can incorporate the options of shortening the maintenance duration and/or deferring maintenance tasks in the search for practical maintenance schedules. In this article, an improved ant colony optimization-power plant maintenance scheduling optimization (ACO-PPMSO) formulation that considers such options in the optimization process is introduced. As a result, both the optimum commencement time and the optimum outage duration are determined for each of the maintenance tasks that need to be scheduled. In addition, a local search strategy is presented in this article to boost the robustness of the algorithm. When tested on a five-station hydropower system problem, the improved formulation is shown to be capable of allowing shortening of maintenance duration in the event of expected demand shortfalls. In addition, the new local search strategy is also shown to have significantly improved the optimization ability of the ACO-PPMSO algorithm.     

横流板式间接蒸发热回收装置的优化研究

运用遗传算法对横流板式间接蒸发热回收装置的经济性进行分析,建立优化设计数学模型,并对新、排风风量均为540m^3／h的横流板式间接蒸发热回收装置进行优化求解,探讨其经济性随各结构参数的变化规律。研究结果表明：遗传算法可以很好地实现横流板式间接蒸发热回收装置的优化;得到横流板式间接蒸发热回收装置的优化结构;随各结构参数的变化,目标函数呈抛物线的变化规律。该研究对于横流板式间接蒸发热回收装置的设计有一定的参考价值。     

电厂锅炉优化改造试验分析

为进一步提高锅炉效率,减少锅炉污染物排放,以某电厂锅炉为研究对象,对锅炉的空预器密封装置、水平烟道吹灰系统以及高压省煤器进行等进行整体优化,对锅炉进行化学清洗和保温处理,通过试验对优化前后对锅炉热效率及污染物排放进行对比。结果表明：与改造前相比,不同负荷下锅炉效率平均提高2.3%,同时供电煤耗降低;锅炉排烟温度降低,干烟气热损失减少;未燃尽率碳热损失及空预器漏风率也大幅降低,锅炉排放NOx浓度达到排放要求。此次优化改造达到了预期效果。     

利用废旧膜元件实现电厂反渗透浓水的循环回用

本项目采用原系统中已经更换淘汰的反渗透膜元件材料,新建浓水回用反渗透系统,实现了废旧膜材料的循环回收利用。项目工艺流程采用了除垢过滤及反渗透膜除盐技术,以强磁过滤器、加药装置、反渗透装置、反渗透清洗／冲洗装置等构成主要材料设备单元。工业实际运行结果表明,经本工艺处理后的产水可回用于生产,既可以作为反渗透的进水,又可继续处理成适用于锅炉的补给水。     

间冷冰箱回风道的优化除霜设计

间冷冰箱蒸发器霜层分布对除霜加热器除霜热量分布的不一致性会导致除霜时间增加和除霜效率的降低,因此,本文提出一种间冷式冰箱回风道的优化除霜设计方法。首先通过实验测量除霜加热器表面温度分布,确定除霜加热器除霜热量分布,进而确定与除霜热量相匹配的蒸发器结霜分布;然后基于蒸发器结霜分布确定回风道出口的最优风量分布;最后基于最优的风量分布设计回风道,使蒸发器上霜层分布与除霜加热器除霜热量分布相一致,达到优化除霜的目的。通过某间冷冰箱回风道的优化设计案例表明,优化后的回风道可实现出口风量分布与除霜加热器除霜热量分布相匹配,除霜时间缩短了38.9%,同时使冰箱的制冷量增加了3.43%。