液化天然气冷能的利用

介绍了液化天然气冷能的概念及其在燃气轮机联合循环,低温发电,空气分离等方面的应用,为节省能源,提高液化天然气接收站的经济效益提供了新的途径。     

LNG冷能发电技术研究进展

液化天然气是21世纪的主要能源之一。液化天然气中携带的大量冷能具有重要的回收利用价值。文中对LNG冷能发电技术的主要形式及改进优化途径进行分析,指出LNG冷能发电技术的发展方向和思路。     

液化空气储能基本循环的热力学分析

  目的  以新能源为主体的新型电力系统对储能的需求不断增加,液化空气储能是一种新兴的长时间、大容量物理储能方法,具有广泛的应用前景。文章旨在探究液化空气储能的热力学原理以及关键参数对储能效率的影响规律。  方法  建立了液化空气储能三种基本循环:分离式循环、冷能回收循环、冷能热能回收循环的热力学模型,分析了冷能回收、热能回收、高压压力、释能压力等关键参数对液化率和循环效率的影响。  结果  结果表明液化率与循环效率正相关。分离式循环的液化率与循环效率极低,冷能回收循环由于利用了液空复温过程中的冷量可以显著提升液化率与循环效率,冷能热能回收循环在此基础上利用了压缩热而进一步提升液化率与循环效率。液化率与循环效率随冷能回收量的增加而升高、随高压压力的升高而升高、随释能压力的升高而下降。  结论  冷能热能回收循环是液化空气储能的优选方案。高效蓄冷将对提升循环效率发挥重要作用。在液空复温过程中利用工业余热、废热有助于进一步提升循环效率。     

积极发展LNG冷能回收产业

LNG(液化天然气)是常温的天然气经过脱酸、脱水处理,通过冷冻工艺液化而成低温(-162℃)的液体,其密度大大增加(约600倍),有利于长距离运输。进口LNG运抵接收站后还需要加热至常温状态才能正常使用,在这个过程中,冷能可以被回收利用。LNG冷能回收可用于空气分离、冷能发电,干冰制造、低温粉碎和蓄冷业等。这不仅有效回收、利用了能源,而且减少了机械制冷造成的大量电能消耗,具有可观的经济效益、环境效益和社会效益。     

LNG冷能综合利用系统的设计模拟与分析

液化天然气（LNG）中蕴含大量的冷能,这部分冷能通常在汽化器中随海水或空气被舍弃,造成了能源的极大浪费。以热力学原理为理论基础,以工艺流程模拟软件Aspen Plus为操作方法,对液化天然气冷能综合利用系统进行流程设计与模拟计算,从而实现合理用能的目的。研究结果表明：以温度对口、梯级利用为原则,将空气分离、制取液态CO2和干冰、冷库、低温破碎进行梯级利用集成,按LNG冷能温度匹配,系统大大地提高了LNG的利用效率。     

燃气电厂LNG一体化冷能发电系统参数研究

在燃气电厂与LNG站一体化建设的基础上以丙烷作为循环工质构建低温Rankine循环,以余热锅炉废热作为热源,利用LNG气化冷能发电,进行了模拟计算。结果表明,余热锅炉的废热利用,可以有效地提高丙烷蒸发压力和蒸发温度。降低汽轮机排汽压力,循环的净发电量和冷能利用率均出现先增加后降低的趋势。分析和确定了该循环的最佳参数。     

LNG冷能在燃气蒸汽联合循环机组中的利用

对于使用液化天然气(LNG)为燃料的燃气轮机电站,LNG在气化过程中会释放大量的冷能,若能合理利用这部分冷能,实现电厂的热电冷联供,不仅可实现资源的循环利用并能提高燃气蒸汽联合循环发电机组的技术经济性。     

基于液化天然气(LNG)接收站冷量的空分流程模拟研究

通过流程模拟软件Aspen Plus对大连液化天然气(LNG)接收站冷能用于空气分离的流程进行模拟。模拟计算采用三元物系模型,使用P-R方程进行流程的气、液相平衡计算,得到系统中关键设备的热力参数和工艺参数。根据软件模拟结果对流程进行分析及改进,得到能效更高、LNG消耗量更少的空分流程,从而使LNG冷量得到更充分的利用,产生更多的经济效益和社会效益。     

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...     

低温下半导体热电材料发电性能的初步研究

为了对液化天然气(LNG)的冷能回收利用，对半导体热电材料在低温下的发电性能进行了实验研究，得到了这种热电材料的发电性能随冷端温度变化的关系，并发现在热端温度不变的情况下，冷端温度在特定温度下热电堆的输出电动势达到最大值。运用数值方法理论计算了该热电堆在实验所处条件下的输出电动势。并将计算值与实验值进行了对比。     

Design and Optimization of a Full-Generation System for Marine LNG Cold Energy Cascade Utilization

This paper took a 100,000 DWT LNG fuel powered ship as the research object.Based on the idea of"temperature matching,cascade utilization"and combined with the application conditions of the ship,a horizontal three-level nested Rankine cycle full-generation system which combined the high-temperature waste heat of the main engine flue gas with the low-temperature cold energy of LNG was proposed in this paper.Furthermore,based on the analysis and selection of the parameters which had high sensitivity to the system performance,the parameters of the proposed system were optimized by using the genetic algorithm.After optimization,the exergy efficiency of the marine LNG gasification cold energy cascade utilization power generation system can reach 48.06%,and the thermal efficiency can reach 35.56%.In addition,this paper took LNG net power generation as the performance index,and compared it with the typical LNG cold energy utilization power generation system in this field.The results showed that the unit mass flow LNG power generation of the system proposed in this paper was the largest,reaching 457.41 k W.     

一种基于低品位热源的LNG冷能回收低温动力系统

在分析LNG物理冷Yong的基础上，提出了一种基于低品位热源的LNG冷能回收低温动力系统，并对影响系统循环效率的相关参数进行了研究。结果表明，在较低的热源温度下，系统的热效率和烟效率可以达到30％以上；对影响循环的主要参数分析表明，二次冷煤的冷凝温度及膨胀机进口压力对循环的效率影响很大。随着冷凝温度的降低及膨胀机进口压力的提高，循环热效率、Yong效率都将有所提高。     

燃气-超临界CO2联合循环发电系统

  [目的]  燃气轮机排气温度高,可增加底循环,利用排气的余热发电,从而提高燃料总的能量利用率。鉴于超临界CO₂循环热效率高,并且具有系统简单、结构紧凑、运行灵活等潜在优势,可与燃气轮机组成新型的燃气-超临界CO₂联合循环。  [方法]  为了充分利用燃气轮机排气余热,提出在简单回热超临界CO₂循环的基础上,再嵌套一个简单回热循环的布置方式,并以PG9351(FA)型燃气轮机为例,对其热效率进行了计算分析。同时,在系统中增加余热利用装置,可将剩余热量用于供热、转换为冷量或发电。  [结果]  结果表明:对于选定的燃气轮机,超临界CO₂循环最高温度可达约600 ℃,循环发电效率约32%,获得余热温度为170 ℃以上,余热热量占燃气轮机排气热量9%,联合循环发电效率约54%。  [结论]  燃气-超临界CO₂联合循环发电系统具有较高的热效率,并且保留部分较高品位的余热,可进一步用于电厂运行。     

提高燃气轮机联合循环电站性能的优化方法

天然气联合循环机组因启停快、运行灵活性好、热效率高、排放清洁、建造周期短而倍受中国市场青睐.围绕如何通过燃气轮机进气系统、主机参数匹配、汽轮机冷端等参数优化来提高联合循环热效率是国内外学者研究的热点.以配有目前市场上最高性能等级燃气轮机的联合循环为研究对象,建立了以提高联合循环热效率为目标的热力计算和分析模型,提出了各段蒸汽压力及温度参数优化匹配方法,并进一步分析、讨论了燃料预热对联合循环热效率的影响.在综合考虑余热锅炉换热温差、汽轮机结构设计等制约因素下得到了一组蒸汽循环的优化参数配置.计算结果表明,相比直接沿用上一代蒸汽循环参数,使用该优化参数配置可大幅度提高联合循环效率,并且使用燃料预热可使循环性能得到进一步改善.     

Utilization of the cryogenic exergy of LNG by a mirror gas-turbine

In the course of worldwide efforts to suppress global warming, the saving of energy becomes more important. Recently, LNG (liquefied natural gas) terminals in our country have received more than 50 million tons of LNG per year. Therefore, the utilization of the cryogenic exergy in connection with the regasification of LNG gains more and more importance. The aim of this paper is the recovery of the energy consumed in liquefaction using the MGT (mirror gas-turbine), which is a new kind of combined cycle of a conventional gas-turbine worked as a topping cycle and TG (inverted Brayton cycle) as a bottoming cycle. The optimum characteristics have been calculated and it is shown that this cycle is superior to the current-use gasification systems in employing seawater heat in terms of thermal efficiency and specific output. In the present cycle, the cold LNG is used to cool the exhaust gas from a turbine of a TG, and then the exergy of the liquefied natural gas is transformed, with a very high efficiency, to electric energy. The main feature of this new concept is the removal of an evaporation system using seawater.     

A review of cryogenic power generation cycles with liquefied natural gas cold energy utilization

Liquefied natural gas (LNG), an increasingly widely applied clean fuel, releases a large number of cold energy in its regasification process. In the present paper, the existing power generation cycles utilizing LNG cold energy are introduced and summarized. The direction of cycle improvement can be divided into the key factors affecting basic power generation cycles and the structural enhancement of cycles utilizing LNG cold energy. The former includes the effects of LNG-side parameters, working fluids, and inlet and outlet thermodynamic parameters of equipment, while the latter is based on Rankine cycle, Brayton cycle, Kalina cycle and their compound cycles. In the present paper, the diversities of cryogenic power generation cycles utilizing LNG cold energy are discussed and analyzed. It is pointed out that further researches should focus on the selection and component matching of organic mixed working fluids and the combination of process simulation and experimental investigation, etc.     

Performance assessment and optimization of an integrated solid oxide fuel cell-gas turbine cogeneration system

The combined solid oxide fuel cells and gas turbine (SOFC/GT) system is known to be a potential alternative for distributed power generation. In this paper, a novel SOFC/GT based cogeneration system, which integrated a transcritical carbon dioxide cycle (TRCC) with a LNG cold energy utilization system is proposed. A mathematical (zero-dimensional) model is developed to analyze the co-generation system performance from the perspective of thermodynamic (energy and exergy) and economic costs. The main parameters of the system are chosen to analyze their effects on thermodynamic performance. The results show that the current system can achieve 64.40% thermal efficiency and 62.13% exergy efficiency under given conditions, and can further improve efficiency through parameter optimization. Finally, the multi-objective optimization program using NSGA-II (Non-dominated Sorting Genetic Algorithm II) is used to obtain the optimal value of the system design parameters. In the multi-objective analysis, the thermodynamic efficiency and economic cost of the system are considered as objective functions. The optimization results show that the final optimized design selected from the Pareto front can achieve 63.08% thermal efficiency and 61.10% exergy efficiency, respectively.     

Analysis and optimization of a cascading power cycle with liquefied natural gas (LNG) cold energy recovery

The effective utilization of the cryogenic energy associated with LNG vaporization is quite important. In this paper a cascading power cycle with LNG directly expanding consisting of a Rankine cycle with ammonia–water as working fluid and a power cycle of combustion gas is proposed to recover cryogenic energy of LNG. Energy equilibrium equations and exergy equilibrium equations of each equipment in the cascading power cycle are established. Taken some operating parameters as key parameters, influences of these parameters on thermal efficiency and exergy efficiency of the cascading power cycle were analyzed. Optimization of the cascading power cycle with maximum economic benefits as objective function together with optimum variables and constraint conditions was solved. The optimum objective and variables were achieved.     

微型燃气轮机外燃循环的分析

介绍了微型燃气轮机结构及其回热循环,阐述了微型燃气轮机的外燃循环的结构和特点,以及外燃循环在可再生能源利用方面的贡献,并采用MATLAB软件建立了以生物沼气为燃料的微型燃气轮机外燃循环的数学模型,对其在额定工况和变工况下进行了稳态分析,给出了各个运行参数对其性能的影响曲线和最佳运行曲线.结果表明:与采用天然气为燃料的回热循环相比,微型燃气轮机外燃循环具有较好的热经济性,在变工况下保持了较高的热效率,发电效率可达到30%左右,为可再生能源在热电联供中的应用提供了一种有前途、高效和廉价的供能方式.     

闭式注蒸汽燃气轮机循环热效率的估算方法

将实际循环在循环完善程度和设备完善程度方面与理论的卡诺循环进行对比,通过循环的特性参数估算出闭式注蒸汽燃气轮机循环的热效率,并在此基础上给出了中冷,再热和燃煤气的闭式注蒸汽循环热效率的估算公式,同时分析了循环系数和完善系数对循环热效率的影响。