催化裂化余热锅炉系统火用分析

利用火用分析方法对催化裂化余热锅炉进行了综合火用效率分析,分析了余热锅炉系统在运行中的火用效率表达式;并且用此方法进行了实例计算与分析,得出了余热锅炉在实际运行中有效能利用情况,对余热锅炉火用效率的影响因素进行了定性分析,确定了火用损失的关键环节为排烟火用损失和温差传热火用损失;通过针对性的优化方案对余热锅炉进行改造,若使其排烟温度降至150℃时,余热锅炉系统火用效率将提高10.4%.     

炼化企业装置能耗分析方法研究进展

我国炼化企业能耗水平与国外先进水平差距较大,而炼化企业的装置能耗又是全厂能耗最重要的组成部分,因此对其进行有效的火用能水平分析以进行合理节能改造具有重要意义。为提供给石化企业装置火用能分析一定的参考,总结了几种主要的装置火用能分析方法的内容及特点,并提出了各方法的应用建议,提出将节能与经济效益相结合是未来火用能分析方法发展的方向。     

硫铵装置用能分析与优化改进

基于过程系统能量分析与火用分析(热力学第二定律分析)策略,对硫铵装置的二效蒸发过程的用能状况进行分析评价,指出过程用能的薄弱环节,并提出了相应的过程用能改进措施;基于流程模拟优化计算,通过相应的用能改进措施的技术经济评价,得到了经济可行的优化改进流程,优化结果表明能取得显著的系统节能降耗效果。     

NGL回收工艺模拟及适应性分析

本文以NGL回收工艺模拟为研究核心,以四川境内须家河气藏组某气田天然气为研究对象展开讨论。采用混合冷剂制冷技术加上直接换热工艺再次深度脱烃工艺,以提高NGL收率。为此,针对NGL回收低温分离法工艺,以简单、准确的PR方程为热力学计算基础模型,对回收过程进行工艺模拟。详细分析模拟结果,并针对模拟的工艺装置进行压力适应性分析,装置处理能力适应性分析及原料气组成适应性分析。     

甲醛生产装置用能分析和改进

本文介绍了甲醛银催化法生产的工艺流程和生产特点。基于三环节能量流结构模型,对某甲醛装置进行了各个环节的能量平衡分析和火用分析,找出过程用能的薄弱环节,并提出了相应的改进措施。减少配料蒸汽的加入和合理利用反应热多副产蒸汽是用能改进的主要方向。     

芳烃分离装置物流热能（火用）值计算

运用热能（火用）平衡理论于芳烃分离装置各物流热能（火用）值计算。计算结果表明：此芳烃分离装置的热能利用效率（实际）为61．65％、热（火用）利用效率（实际）为59．77％、热力学第一定律效率和热力学第二定律效率分别为23．93％和7．76％。     

基于(火用)分析的南堡联合站轻烃回收装置改造与优化

为解决南堡联合站轻烃回收装置能量利用率低、能耗高以及C₃⁺回收率低的问题,采用(火用)分析方法对轻烃回收装置进行分析与优化。通过建立系统与设备的(火用)计算模型,确定了轻烃回收装置(火用)能利用的薄弱环节,提出了改造措施,再以降低能耗与提高C₃⁺回收率为目标函数进行优化并得到关键优化参数,提高了装置C₃⁺的收率,降低了能耗。优化改造后的装置生产C₃⁺的比功耗降低了0.94%,装置总能耗降低了1.14%,C₃⁺回收率由原流程的95.96%提高至98.11%。     

乙烯分离与复叠制冷系统用能的综合优化

乙烯装置的分离过程要在低温下进行,由乙烯制冷系统提供所需冷量。乙烯制冷系统为封闭式循环,独立于分离单元之外。将乙烯分离单元与制冷系统同时优化,能有效提高装置用能效率。复叠式制冷级数是当前乙烯工业中使用最为广泛的制冷技术。本文针对乙烯分离过程和配套的复叠制冷系统,采用Aspen Hysys进行模拟并进行(火用)分析,发现系统主要的(火用)损失发生在换热与压缩两部分,其占总(火用)损失的83%,为节能的重点。进而通过夹点技术对冷剂配置进行分析,发现-56℃以上各温位的冷量配置不合理,远超过理论最小值,-56℃以下各温位的冷量基本达到理论最小值。提出了采用多股流换热器的换热网络理论设计方法,并对冷剂进行重新配置,该理论方案可以降低丙烯制冷压缩机约30%的功耗,并节约部分乙烯制冷压缩机功耗,显著降低了乙烯深冷分离能耗。     

低温甲醇洗过程(火用)分析

根据某化肥厂合成氨系统中的低温甲醇洗工段的工艺,建立了(火用)分析模型.对甲醇洗系统进行了(火用)分析,并且与能量分析进行了比较,分析系统用能的薄弱之处,提出相应的改进措施.     

中小型太阳能光合生物制氢系统的火用分析

利用热力学第二定律,采用白箱分析模型对实验室所研发的太阳能光合生物制氢系统进行了火用分析,得出该系统的产氢量较少,火用效率仅为24.4%。其中光能火用损最大,占耗散火用损的64.4%;并针对系统中用能的薄弱环节,即对火用损较大的光能火用损分析了影响光能转化的因素,并提出了相应的解决方法,为整个系统内部设备的改进提供方向,以提高系统有效能的利用,为推进光合生物制氢技术的工业化提供了科学参考。     

液化天然气冷能构成及其利用方式探讨

液化天然气(LNG)在汽化过程中会释放大量冷能,如果这部分冷能被成功回收利用,其节能效果和对系统效率的提高都十分显著。文中对LNG冷能从冷量和冷量的角度进行分析,把LNG冷能回收方式分为冷量回收与冷量回收,揭示了目前各种LNG冷能回收利用形式的能量利用实质:发电、空分中主要是利用LNG的冷量;冷藏、空调和制干冰利用了LNG的冷量。最后对不同的冷能回收系统提出指导性建议:动力回收系统中,应充分利用其在低温下的高品质能量;冷量回收系统中应减少跑冷。     

集成NGL回收的新型天然气液化系统AP-XTM的概念设计与模拟分析

为提高液化天然气能量集成与设备共用水平,提出了一种基于大型AP-X^TM液化流程，综合气体过冷技术（GSP）的集成NGL（天然气凝液）回收工艺的天然气液化系统的概念设计。基于化工流程模拟软件Aspen HYSYS进行模拟和分析，将集成工艺多流股换热器性能、全流程的单位功耗和乙烷回收率作为衡量系统性能的三项指标。模拟和分析的结果表明，集成NGL回收的AP-X^TM液化工艺单位功耗降低至0.45 kW·h·(kg LNG)^-1，较单产系统能耗降低了6%，同时乙烷回收率达到93%，实现了NGL的高效分离。通过热力学分析、?分析和经济性分析得出本设计流程具有较高的性能和经济价值，可为天然气液化工艺的集成设计和技术改造提供指导借鉴。     

空气分离与天然气液化组合循环

提出了利用空分系统冷量液化天然气的联合流程思想,并介绍了一种采用氮气膨胀循环的空气分离与天然气液化联合方案,在得到液化天然气（LNG）的同时,也生产氮气、氧气等多种产品。通过流程模拟计算并采用有效能分析原理,确定了高、低温膨胀量比对传热温差及有效能损失的影响规律,得到了不同液化量下的优化膨胀量之比。结果表明,基于热负荷总组合曲线的有效能分析原理能够方便、有效地研究整个传热过程的温差分布及有效能损失规律,对实际低温过程系统优化有重要意义。     

Exergy analysis of a combined RO, NF, andEDR desalination plant

A brackish water desalination plant in California that incorporates RO, NF, and EDR units was analyzedthermodynamically using actual plant operation data. Exergy flow rates were evaluated throughout the plant, and the exergy flow diagrams were prepared. The rates of exergy destruction and their percentage are indicated on the diagram so that the locations of highest exergy destruction can easily be identified. The analysis shows that most exergy destruction occurs in the pump/motor and the separation units. The fraction of exergy destruction in the pump/motor units is 39.7% for the RO unit, 23.6% for the NF unit, and 54.1 % for the EDR unit. Therefore, using high-efficiency pumps and motors equipped with VFD drives can reduce the cost of desalination significantly. The plant was determined to have a Second Law efficiency of 8.0% for the RO unit, 9.7% for the NF unit, and 6.3% for the EDR unit, which are very low. This indicates that there are major opportunities in the plant to improve thermodynamic: performance by reducing exergy destruction and thus the amount of electrical energy supplied, making the operation of the plant more cost effective.     

Efficiency enhancement of a commercial natural gas liquid recovery plant: A MINLP optimization analysis

ABSTRACT

This paper aims at modeling and optimizing a Middle East-based commercial natural gas liquid (NGL) recovery and fractionation plant, using a predictive process simulator. NGL units are known to be highly energy-intensive as steam-based heating and refrigeration-based cryogenic cooling are critical requirements for their operation. Indeed, these units govern the degree of profitability of gas plants especially during low natural gas price scenarios. As a result, this study explores the ways of improving the performance of NGL units through a deterministic optimization analysis. A steady state model of the plant is built using gPROMS process builder followed by validation using plant data to ensure the model accuracy. A mixed integer nonlinear programming optimization problem is formulated with the objective of maximizing the net revenue of the plants by means of manipulating various decision variables such as feed gas temperature, column operating pressure, feed stage location, reflux and boil up ratios subject to specific process constraints. Optimization problem is solved using outer approximation equality relaxation augmented penalty algorithm. It is determined that the process optimization yields an additional revenue of 4.1 MM USD annually due to ~22% increase in Liquefied Petroleum Gas (LPG) production, ~6% increase in Naphtha production, and ~16% reduction in steam consumption in the reboiler of the columns.     

三元制冷系统分析

乙烯装置产品分离过程需要在低温下进行,为此需配置压缩制冷系统为深冷分离提供冷量。三元压缩制冷由于能提供温位连续的制冷曲线,与工艺物流降温曲线更好地匹配,相比传统的复叠制冷具有热力学效率高、制冷能耗低的特点。为了分析三元压缩制冷的节能潜力,本文对某乙烯装置的三元制冷系统进行了(火用)分析。从(火用)总复合曲线(EGCC)图的分析可以得出该系统三元冷剂配置是比较合理的,(火用)损失较小。将该制冷系统划分为换热器、压缩机、节流阀、闪蒸罐等子系统,并分别计算了各子系统的(火用)损失。三元制冷系统的(火用)损失总计为24238.1kW,90%(火用)损失集中在换热器和压缩机两个子系统。然后将(火用)损失分为可避免的和不可避免的(火用)损失两类,其中不可避免的(火用)损失为13539.9kW,可避免的(火用)损失为10698.2kW,最后指出节能重点应该放在降低可避免的(火用)损失。     

Exergy analysis of a seawater reverse osmosis plant

Exergy analysis is a powerful tool to determine how inefficiencies of the processes influence system performance. The exergy analysis of a seawater reverse osmosis desalination plant with 21,000 m³/d of nominal capacity located in Tenerife (Canary Islands, Spain) was studied. Once defined, the flow chart of the process, the exergy rate and exergy cost of flows were determined as well as the exergy destruction rate in equipment. The main results indicate that 80% of the exergy destruction is placed on core processes (high pressure pumping and valve regulation, reverse osmosis separation and energy recovery), 29% extra exergy is necessary to obtain the unit of feed exergy from previous stages (seawater pumping and pretreatment) and extra exergy of 1.06 kJ is needed to generate 1 kJ of final product exergy (exergy performance about 50%). In addition, the moderate fluctuations of seawater environmental conditions in the Santa Cruz de Tenerife metropolitan area (and Canary Islands as a whole) establish that environmental parameters present a less important influence on exergy analysis.     

利用LNG冷能的冷库工艺模拟及分析

LNG卫星站由于负荷波动较大等问题,其LNG的冷能大多未经过利用。针对这一问题,提出了适用于LNG卫星站的LNG冷能用于冷库的冷能利用工艺。通过与电压缩制冷工艺对比可知,对于制冷负荷为306.7kW的冷库,工艺每小时可节电约为193kW,具有较好的节电效果。同时,火用分析结果表明,工艺的能量利用效率远优于电压缩制冷工艺。随着我国LNG产业的发展,工艺将拥有广阔的应用前景。     

A new exergy method for process analysis and optimization

A two level idealization concept involving the definition of intrinsic and extrinsic exergy destruction is incorporated into exergy analysis, exergoeconomic analysis and exergoeconomic optimization. The intrinsic exergy destruction is caused by the configuration constraints, whereas the extrinsic exergy destruction is caused by the transport rate limitations. For exergy analysis, intrinsic and extrinsic exergy destructions can be quantified for each process operation. For exergoeconomic analysis, the monetary costs associated with these exergy destructions can be determined. For exergoeconomic optimization, the variables associated with process configuration and transport rate limitations can be optimized independently. Methods for analysis as well as optimization are described and demonstrated by two case studies, an ethylene product recovery and separation plant and a benzene-toluene distillation column. Improvements demonstrated from these case studies are significant.     

Energy and Exergy Evaluation of an Air Separation Facility: A Case Study

In this study, an air separation plant working according to the principle of separation of two columns and producing argon, nitrogen, and oxygen with a daily capacity of 250 tons was analyzed in detail with respect to the first and second laws of thermodynamics and the results were evaluated. The energy and exergy values for each point defined in the system were obtained. By using these values, thermodynamic evaluations for both the whole system and also its components were made. The efficiency values of energy and exergy, the values of energy losses and exergy destruction rates, the EIP (energetic improvement potential rate), ExIP (exergetic improvement potential rate), and the production of entropy values were found as 0.453, 0.79, 4368.475 kW, 10535.875 kW, 2391.535 kW, 3800.485 kW, and 35.347 kW/K, respectively. The energy and exergy efficiencies of the plant were found to be 45.3% and 13.1% respectively.