CO_2液化项目中液化压力及制冷剂的选择

随着CO2减排日益成为世界各国研究的焦点,在CO2液化项目中,实现节能降耗,同时兼顾节省投资、简化系统等,是具有重要的现实意义的。本文对采用制冷机直接液化CO2的方案进行了分析,探求最佳液化压力、分析适合选用的制冷剂,以期最大程度的降低能耗。通过计算,总结了液化总功耗随液化压力的变化规律:随着液化压力的提高,液化总功耗降低,但降低的幅度逐渐减小。在工程项目的实际应用中,应尽量提高液化压力;在采用较低的液化压力时,选用带经济器的制冷机是最佳选择。另外,对于CO2液化过程中采用不同制冷剂时的性能进行了比较,指出应优先选用氨或R507作为制冷剂。     

二氧化碳液化技术进展

为了应对气候变化,人们分别提出了碳捕集与封存(CCS)和碳捕集、利用与封存(CCUS)两种途径,但无论是二氧化碳的封存还是利用,一般首先都需要将捕集的二氧化碳进行液化。工业上实现二氧化碳液化主要分为低温低压液化和常温高压液化两种工艺过程。低温低压液化工艺是国内外普遍采用的二氧化碳液化工艺,其优点是液化压力小,一次性投资小,安全性高,生产能力高;缺点是需要专门的制冷机组,能耗大,运行成本高,不利于长距离输送,制冷工质不利于环保,系统较复杂。常温高压液化工艺是通过提高压力使气态二氧化碳在常温下转变为液态,其优点是储存温度为常温,无需专门的制冷机组,节能,运行费用低;缺点是对设备的耐压性能要求高,一次性投资高,安全性低,维修和维护成本高,运输成本高。不过随着高压容器制造技术的日臻成熟,高压液化工艺的安全性已可以得到充分保证。由于与低温液化工艺相比,高压液化工艺无需制冷机组且能耗较低,在节能和环保方面优势明显,因而该工艺的推广实施具有越来越强的迫切性,需要解决的问题是如何降低储运成本和设备成本。     

太阳能二氧化碳运输船的设计

为了降低油气田的二氧化碳排放,找到一种更加经济有效的二氧化碳处理方法,提出二氧化碳运输船的概念设计。海洋平台液化储存二氧化碳;二氧化碳运输船负责运输,且其装载有太阳能板,电能供给船舶和储罐再液化,做到绿色船舶;陆基二氧化碳装卸储存码头负责临时储存运回的二氧化碳。二氧化碳可实现再利用,相比单纯的封存更加经济,使二氧化碳的使用价值得到最大化,同时实现节能环保。     

英国将着手在燃煤发电厂测试二氧化碳回收技术

英国将着手在燃煤发电厂测试二氧化碳回收技术,这是为实现燃煤发电的无碳排放而迈出的重要一步。据英国广播公司2009年5月29日报道,科学家们将设法用胺对二氧化碳进行液化,然后将其填埋。这项即将历时三个月的测试主要是检验胺的液化效率。测试一旦获得通过,首座完全回收二氧化碳的工厂可望于2014年投入运作。     

二氧化碳气体余热的利用

哈尔滨车辆工厂工业公司二氧化碳车间的主要产品是生石灰和二氧化碳气体。1986年以前冬季要用两台4吨/时锅炉来维持生产,一台用于厂房采暖,另一台用于提纯二氧化碳气体。 二氧化碳气体在提纯过程中成为高温气体,而提纯过程完毕后又要在液化前降温到     

简化级联式天然气液化流程数值分析

利用低温制冷机分级制冷的原理,设计了一种结合低温制冷机和蒸气压缩系统的简化级联式天然气液化流程;应用Matlab软件调用NIST REFPROP数据库,对该新型天然气液化流程进行数值分析;研究了不同工况下系统总比功耗的变化和各级制冷系统在液化流程中承担的热负荷情况,并采用■分析对此流程进行了评估。     

从烟气中生产二氧化碳气体(CO_2)

机力机械制造联合企业在焊接生产中需要大量的二氧化碳气体。以前主要由专门生产二氧化碳气体的企业供给。气体经过液化,进行长途运输,需要花费大量资金。现在有些焊接生产企业已经能够顺利地从工业锅炉的排烟中生产二氧化碳气体。从1974年起塞兹兰汽机制造厂中有一个生产能     

海上天然气液化流程模拟和优化分析

本文针对海上伴生气源参数,分别利用双级氮膨胀、氮-甲烷膨胀和单级混合制冷剂液化循环进行模拟,分析和优化了液化流程参数对其功耗的影响,最后选定了利用混合制冷剂循环作为天然气液化的制冷循环.并根据海上天然气装置对混合制冷剂的来源、贮存的要求对混合制冷剂的配比进行了改进.模拟结果表明,通过调整混合制冷剂组成可以方便的在海上平...     

基于遗传算法优化双燃料发动机LNG气化流程的研究

液化天然气(LNG)气化器是LNG发动机的关键部件,其流程优化涉及多变量非线性问题。我们从热力学角度对ME-GI型发动机的LNG气化流程进行研究,用HYSYS建立仿真模型,通过MATLAB嵌入遗传算法优化气化工质的流量、温度和热水流量,从而降低总的泵功耗。研究结果表明,遗传算法对LNG气化器流程优化快速而精准,优化后的比功耗较优化前低14.5%。     

增压富氧燃烧与捕集CO2电站的经济性分析

以300MW燃煤锅炉汽轮发电机组为研究对象,计算了其在6～8MPa压力下增压富氧燃烧的经济性,并与常压富氧燃烧下的经济性进行了对比分析．结果表明：由于系统压力的提高,烟气中水蒸气的凝结热得以回收,用于加热汽轮机低温凝结水,减少汽轮机抽汽,使汽轮机出力增加,电厂的毛输出功率接近320MW;增压富氧燃烧的空气深冷分离制氧（ASU）功耗大大增加,占毛输出功率的26％,而烟气压缩（CPU）的功耗大大降低,约为毛输出功率的0．2％;综合考虑电站其他辅机功耗后,6～8MPa下增压富氧燃烧的电厂净效率比常压富氧燃烧下提高了4．5％．与常压富氧燃烧发电机组相比,增压富氧燃烧在CO2的捕集、压缩液化与封存（CCS）技术中的经济性明显提高．     

Analysis of the liquefaction process of exhaust gases from an underwater engine

In operating underwater engines, such as in exploring submarines, the dumping of the exhaust gas out of the engine requires a large portion of the total power, frequently amounting to 25–30% of the power generated. This can be solved by liquefying the exhaust gas and storing it. In the present study, two liquefaction systems are simulated to enhance the overall efficiency; one is a closed cycle diesel cycle and the other is a closed cycle liquefied natural gas (LNG) engine. LNG was chosen as a fuel not only because it is economical but also because its cold energy can be utilized within the liquefaction system. Since a mixture of oxygen and carbon dioxide is used as an oxidizer, liquefying carbon dioxide is the major concern in this study. To further improve this system, the intercooling of the compressor is devised. The power consumed for the liquefaction system is examined in terms of the related properties, including pressure and temperature of the carbon dioxide vessel as a function of the mass fraction of the exhaust gas that enters the compressor. The present study shows that much gain in the power and reduction of the vessel pressure could be achieved in the case of the closed cycle LNG engine. The compression power was remarkably low, typically only 6.3% for the closed cycle diesel engine and 3.4% for the closed cycle LNG engine, respectively, of net engine power. For practically, a design–purpose map of the operating parameters of the liquefaction systems is also presented.     

Simulation methodology for hydrogen liquefaction process design considering hydrogen characteristics

One promising method to improve the storage capacity of hydrogen is to liquefy it, resulting in high energy density. However, liquefying hydrogen is a challenging task because hydrogen characteristics, such as a boiling point at a cryogenic temperature and changes in equilibrium compositions of spin isomers constituting hydrogen molecules, must be considered. For a design of a hydrogen liquefaction process, it is necessary to use an equation of state that can accurately calculate the properties of hydrogen, and to consider conversion reactions of the spin isomers. In this study, it is confirmed that the modified Benedict-Webb-Rubin equation is a suitable equation of state for simulating hydrogen liquefaction processes and that an equivalent model used in this study for the conversion reactions of the spin isomers shows reasonable results. Furthermore, the economic feasibility of the designed hydrogen liquefaction process is investigated based on energy optimization and economic analysis.     

高温流体温度变化对液-气引射器内部汽化影响特性研究

为了揭示液-气引射器在工作流体温度较高时存在汽化的问题,通过建立液-气引射器三维模型,对不同温度工作流体引射器内部的流动状态进行了数值模拟,得到了引射器内部汽化的时变规律,明确了不同工作流体温度对引射器内部汽化的影响。研究表明,工作流体的温度越高,汽化现象越明显。该研究将为高温工作流体的液-气引射器的设计和安全运行提供了指导和参考。     

A novel hydrogen liquefaction process configuration with combined mixed refrigerant systems

A novel large-scale plant for hydrogen liquefying is proposed and analyzed. The liquid hydrogen production rate of the proposed plant is 100 tons per day to provide the required LH₂ for a large urban area with 100,000–200,000 hydrogen vehicles supply. In the pre-cooling section of the process, a new mixed refrigerant (MR) refrigeration cycle, combined with a Joule–Brayton refrigeration cycle, precool gaseous hydrogen feed from 25 °C to the temperature ?198.2 °C. A new refrigeration system with six simple Linde–Hampson cascade cycles cools low-temperature gaseous hydrogen from ?198.2 °C to temperature ?252.2 °C. The process specific energy consumption (SEC) is $7.69{\text{kWh/kg}}_{L{H}_2}$ which minimum value is $2.89{\text{kWh/kg}}_{L{H}_2}$ in ideal conditions. The exergy efficiency of the system is 39.5%, which is considerably higher than the existing hydrogen liquefier plants around the world. However, assuming more efficiency values for the equipment can improve it. The energy analysis specifies that coefficient of performance (COP) of the process is 0.1710 which is a high quantity of its kind between other similar processes. Effect of various refrigerant components concentration, discharge pressure of the high pressure compressors of the pre-cooling section, and hydrogen feed pressure on the process COP, exergy efficiency, and SEC are investigated. After that, a new MR will be offered for the cryogenic section of the plant. The system improvements are considerable comparing to current hydrogen liquefying plants, therefore, the proposed conceptual system can be used for future hydrogen liquefaction plants design.     

Intensification of biodiesel production via ultrasonic-assisted process: A critical review on fundamentals and recent development

Biodiesel is a good alternative fuel to petroleum diesel. It is produced through transesterification reaction between vegetable oil or animal fats and alcohol. The process faces various problems related to the immiscible nature of the reactants causing poor mass transfer rate. This drawback is responsible for long reaction time and low reaction rate leading to an energy intensive process. Process intensification through the use of active catalyst, pressure reactor, high temperature, high stirring rate or even non-conventional approaches such as supercritical method and Biox process often subjects to drawbacks with respect to energy consumption, product quality and reactants cost. This paper highlights recent development in the production of biodiesel under ultrasonic irradiation conditions. It handles the drawback of poor immiscibility between reactants as ultrasonic energy can emulsify the reactants to reduce the catalyst requirement, reaction time and reaction temperature. Ultrasonic energy also neglects the limitations in the use certain feed stocks. Fundamental aspects of the ultrasonic-assisted process using homogeneous and heterogeneous catalysts are reviewed. Recent achievement and future development in this technology in a batch and continuous process are also highlighted.     

Cavern integrity for underground hydrogen storage in the Brazilian pre-salt fields

Over the years, energy has depended on petroleum-based fuels. However, global warming and the energy crisis have drastically impacted the markets. It urges investing in renewable energy resources, such as hydrogen. Therefore, this work focuses on the hydrogen storage process in salt caverns, as these rocks have relevant properties, such as low permeability, relevant creep, and self-healing. A workflow for cavity integrity analysis is proposed. Hydrogen storage provokes variations in temperature and pressure inside the cavern. The gas thermodynamics is represented through a diabatic solution, which updates the gas pressure and temperature at each time step. The thermomechanical formulation is implemented into an in-house framework GeMA, which couples different physics. Four case studies are analyzed, and the discussions compared mechanical and thermomechanical models. Results demonstrate the importance of thermal effects, as temperature amplitudes may compromise rock integrity, for instance, inducing tensile stresses and affecting permeability.     

CO2双蒸发器压缩/喷射式跨临界制冷循环

为减小CO_2跨临界循环系统节流部分的膨胀功损失,提高系统性能,可在小型制冷系统中采用喷射器代替节流阀,部分回收工质从高压到低压过程的膨胀功。在对系统进行热力学分析的基础上,建立了CO_2跨临界压缩／喷射制冷循环的效率分析模型。计算结果表明：在合理的喷射器出口背压下,CO_2跨临界压缩／喷射制冷循环可以得到较高的循环性能。蒸发温度和气体冷却器出口温度两工况的变化对该系统性能的影响程度相对较大。在较低蒸发温度下,该系统可以明显降低压缩机出口温度,有利于系统稳定运行。     

低能耗机械镀锌技术及应用

机械镀锌是一种在常温常压下利用化学吸附和机械碰撞使金属锌粉沉积在工件表面形成镀层的工艺,与传统的热镀锌、电镀锌相比,具有生产过程能耗低、对环境污染小等优点,是一种清洁低耗镀锌技术。简要介绍机械镀锌工艺及设备,将机械镀锌、热镀锌和电镀锌的性能、特点、环境影响进行了对比,探讨了机械镀锌技术的发展及应用前景。     

氢存储技术

日益严峻的能源危机和环境污染，使得发展清洁的可再生能源成为各个国家的重要议题。氢能源以其可再生性和良好的环保效应成为未来最具发展潜力的能源载体。氢的储存是发展氢能技术的难点之一。文章介绍了高压、液化、金属氢化物和碳质吸附等储氢技术的研究现状，并对储氢技术的发展趋势进行了讨论。     

Performance analysis of an industrial waste heat‐based trigeneration system

The thermodynamic performance of an industrial waste heat recovery‐based trigeneration system is studied through energy and exergy efficiency parameters. The effects of exhaust gas inlet temperature, process heat pressure, and ambient temperature on both energy and exergy efficiencies, and electrical to thermal energy ratio of the system are investigated. The energy efficiency increases while electrical to thermal energy ratio and exergy efficiency decrease with increasing exhaust gas inlet temperature. On the other hand, with the increase in process heat pressure, energy efficiency decreases but exergy efficiency and electrical to thermal energy ratio increase. The effect of ambient temperature is also observed due to the fact that with an increase in ambient temperature, energy and exergy efficiencies, and electrical to thermal energy ratio decrease slightly. These results clearly show that performance evaluation of trigeneration system based on energy analysis is not adequate and hence more meaningful evaluation must include exergy analysis. The present analysis contributes to further information on the role of exhaust gas inlet temperature, process heat pressure, ambient temperature influence on the performance of waste heat recovery‐based trigeneration from a thermodynamic point of view. Copyright © 2009 John Wiley & Sons, Ltd.