液化天然气装置净化与液化工艺关键技术研究

LNG技术是一种将天然气以液态的形式储存技术,便于管道装置的储存以及运输工作。以某地区液化天然气工程为例,首先是对原料气组分进行分析,根据原料气成分与各项成分含量标准要求进行选择合适的脱除工艺,选取MDEA剂脱除酸性气体和分子筛脱水等净化工艺。在液化工艺方面,主要分析了阶式制冷液化工艺与复迭式制冷液化工艺,从能耗、投资、回收期、税前内部收益率、设备数量、处理复杂程度、操作方面以及技术成熟度方面对比,优选出复叠式制冷液化工艺,该液化工艺在达到理想液化率97.3%的情况下,综合指标优于阶式制冷液化工艺,而且目前该技术使用比较成熟,设备数量少,占地面积小,是一种操作简单、处理高效的液化工艺,建议采用MDEA剂脱除酸性气体+分子筛脱水+复迭式制冷液化工艺。     

高含氮天然气液化工艺的探讨

在不同气源中,含氮量较高的天然气热值低、集输过程中能耗大,为脱除天然气中过高含量的氮气,设计了深冷脱氮的天然气液化工艺。利用过程系统软件HYSYS模拟了深冷脱氮及液化天然气的过程,并分析了原料天然气特性、制冷剂特性及精馏塔操作条件对液化单元能耗的影响,对工艺条件进行了优化。结果表明,在制冷剂循环压力和温度为0.4MPaG和35℃,原料天然气压力和温度分别为2.6MPaG和20℃,精馏塔压力为0.6MPaG,氮气所占比例为0.5时,该液化单元的功耗最小,为0.527kW/Nm3,该工艺模拟和优化为高含氮气源进行液化利用提供了重要的参考。     

A 2D numerical study on the condensation characteristics of three non-azeotropic binary hydrocarbon vapor mixtures on a vertical plate

To improve the transportation efficiency and reduce the supply cost, the liquefaction becomes an important technology to store and transport the natural gas. During the liquefaction, the various components (e.g. propane, ethane, methane etc.) undergo fractional condensation phenomenon due to their different boiling points. This means that when one component condenses, others play a role of non-condensable gas (NCG). In order to reveal the influence mechanism of NCG on this condensation process, a numerical method was employed in this paper to study the condensation characteristics of three non-azeotropic binary hydrocarbon vapor mixtures, namely the propane/methane (80%–95%), ethane/methane (65%–85%) and methane/nitrogen (2%–13%) mixtures, on a vertical plate. The model was proposed based on the diffusion layer model, and the finite volume method was used to solve the governing equations. A user defined function was developed by cell iterative method to obtain the source terms in the condensation process. The numerical results show that the gas phase boundary layer formed by the NCG becomes the main resistance to the reduction of heat transfer coefficient. And for the above three mixtures, there is a negative correlation between the NCG concentration and the heat transfer coefficient. Meanwhile, the results show a good agreement with the experimental data, meaning that the proposed model is reliable. Three mixtures within same non-condensable mole fraction of 20% were also investigated, indicating that the mixtures with a higher binary hydrocarbon molecular ratio have a lower heat transfer coefficient. As a result, the presence of the lighter NCG contributes to a thicker boundary layer.     

Evaluation of the local composition model for VLE of binary mixtures of triethylene glycol with methane,water and benzene

This work evaluated the predictive accuracy of the local composition model (LCM) formulation developed by Li et al. (1986) for four binary, vapor-liquid equilibria (VLE) mixtures. The four components comprising these mixtures were benzene, triethylene glycol (TEG), water and methane, while the mixtures examined in this work were the benzene-TEG, water-TEG, methane-TEG and methane-benzene systems. The Khan-Chung-Lee-Starling (KCLS) equation of state developed by Chung et al. (1984) was used with the LCM to predict the VLE behavior of these systems. The accurate results obtained in this work may be applied to the design of natural gas dehydration processes.     

A 2D numerical study on the condensation characteristics of three non-azeotropic binary hydrocarbon vapor mixtures on a vertical plate

To improve the transportation efficiency and reduce the supply cost, the liquefaction becomes an important technology to store and transport the natural gas. During the liquefaction, the various components (e.g. propane, ethane, methane etc.) undergo fractional condensation phenomenon due to their different boiling points. This means that when one component condenses, others play a role of non-condensable gas (NCG). In order to reveal the influence mechanism of NCG on this condensation process, a numerical method was employed in this paper to study the condensation characteristics of three non-azeotropic binary hydrocarbon vapor mixtures, namely the propane/methane (80%-95%), ethane/methane (65%-85%) and methane/nitrogen (2%-13%) mixtures, on a vertical plate. The model was proposed based on the diffusion layer model, and the finite volume method was used to solve the governing equations. A user defined function was developed by cell iterative method to obtain the source terms in the condensation process. The numerical results show that the gas phase boundary layer formed by the NCG becomes the main resistance to the reduction of heat transfer coefficient. And for the above three mixtures, there is a negative correlation between the NCG concentration and the heat transfer coefficient. Meanwhile, the results show a good agreement with the experimental data, meaning that the proposed model is reliable. Three mixtures within same non-condensable mole fraction of 20% were also investigated, indicating that the mixtures with a higher binary hydrocarbon molecular ratio have a lower heat transfer coefficient. As a result, the presence of the lighter NCG contributes to a thicker boundary layer.     

合成氨废气综合利用制天然气工艺设计

以合成氨膜提氢尾气为原料,根据气体压力、成分条件,采用低温液化精馏技术,将膜提氢尾气中的绝大部分甲烷提取并加工为管道天然气产品,通过管道输送方式就近并入天然气管网,从而解决合成氨提氢尾气利用不充分的生产现状。     

高压管输天然气利用压力能液化技术

通过火用分析得出,高压管网输送的天然气在调压过程中释放巨大的压力能,在调压站利用膨胀机回收天然气的压力能,用于天然气液化,以增加管网运行的经济性。并介绍了国内外几种天然气液化流程,阐述和分析了其液化方法和特点。     

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。     

液化工艺及其控制方案的分析

以高含氮天然气液化为例,设计了两种深冷脱氮的天然气液化工艺路线及其控制方案。通过对这两种工艺路线中控制方案的分析和对比,得出了较优的控制系统。利用过程系统软件HYSYS模拟了较优的控制系统所对应的工艺过程,给出了主要的控制点数据和最终产品特性,工艺方案及产品规格均能满足要求。此文旨在为设计含不凝气天然气液化的工作者提供一些有价值的参考。     

一种基于浮式LNG的预处理和液化流程模拟

天然气的预处理和液化是海上天然气利用前的两个关键环节。选取变压吸附分离法(PSA)作为浮式LNG预处理流程的工艺方法,选择新型CO₂预冷空气膨胀液化流程作为浮式LNG天然气液化的工艺方法,并对以上预处理和液化流程进行了模拟计算与分析。结果表明,采用双层吸附剂变压吸附(PSA)预处理流程能耗低,全气体运行避免了液体吸收剂随波浪晃动的缺点,可以满足海上天然气预处理的要求;CO₂预冷空气膨胀液化流程在预冷剂及制冷剂循环过程中,没有液体的产生,安全性高;以上预处理和液化流程适应于海上晃动的LNG平台。     

Standard Reference Materials to support measurement of fatty acids

The National Institute of Standards and Technology offers a variety of natural‐matrix and solution‐based Standard Reference Materials (SRM) that are characterized for fatty acid composition. The natural‐matrix SRM are intended primarily for use as control materials, but other uses include method validation, the development of new analytical methods, and use as a component in achieving traceability of measurements. The use of complex‐matrix reference materials for instrument calibration is not recommended; solution calibrants are better suited to this task. In addition to calibration, solution SRM can be used as spiking solutions for fortification of samples, in studying extraction recoveries, for developing chromatographic separations, and as authentic standards for identifying constituents in more complex‐matrix extracts. The use of SRM to support the measurement of fatty acids is relevant to a broad spectrum of applications including compliance with and accuracy of nutritional labeling, food manufacturing tolerances (e. g., infant formulas), traceability of measurements for food exports, clinical nutritional measurements, and characterization of alternative energy sources (e. g., biodiesel). Currently, nearly 30 SRM are available with certified, reference, and information values reported for fatty acids. Additional SRM are under development that will complement these reference materials by providing fatty acid profiles in different types of matrices.     

A new liquefaction method for natural gas by utilizing cold energy and separating power of swirl nozzle

A swirl nozzle with a central body was newly designed to make full use of the cold energy and separating power, and the coupling of swirling flow and condensation was realized based on a condensation model, a droplet surface tension model and a Reynolds stress model turbulence model. The flow and condensation characteristics of methane gas under supersonic swirling flow conditions were studied. The results show that the flow and condensation parameter distribution in the swirl nozzle are similar under varying swirling intensities, but the swirling performance improves with the increase in swirling intensity, and a tangential velocity is beneficial before the gas enters the nozzle. As the inlet temperature decreases or the inlet pressure increases, the liquefaction efficiency increases, and the gas condensation process can be promoted. With the advancement of the initial nucleation position and the increase in the droplet radius, the separation efficiency of the swirl nozzle increases.     

一种天然气液化和CO2捕集相结合的余热回收发电系统

针对余热回收和能源利用的问题,以液化天然气(LNG)作为冷源,稠油开采废气作为热源,提出了一种结合天然气液化和废气发电与CO₂捕集的余热回收利用系统。分析了关键热力学参数对系统热力学性能的影响。结果表明：对于有机朗肯循环和制冷循环,增加透平膨胀机的进口温度,降低其出口压力以及减少制冷循环压缩机进出口的压缩比,可获得最大净输出功为454.9 kW,余热回收效率为34.2%。对于天然气液化系统,采用C++进行非线性约束优化计算,以氮膨胀制冷循环压缩机总功耗为目标函数进行优化,得到压缩机最优总功耗为101.54 kW。降低天然气压缩机(K110)进口温度,氮气膨胀机(T3)出口压力以及氮气质量流量,可获得最大LNG调峰量为378.8 kg/h,反之,CO₂捕集量可提高28.6%。     

小型可移动式天然气液化装置研究进展

小型可移动式天然气液化装置以其独特优势在零散天然气源的液化集输、管输天然气的再分配及分布式调峰和车用LNG燃料站等场合有非常广泛的应用前景。概括对比分析了现有的天然气液化技术,指出占据国际LNG工业主流地位的混合制冷剂循环(MRC)液化流程也是适宜小型化的最佳技术之一。在简要介绍了小型天然气液化装置的近期进展后,重点介绍了本团队基于近20年的混合工质节流制冷技术方面的研究经验,研制成功系列规格小型混合工质撬装液化装置,同时提出并创建了以此为基础的"煤层气柔性液化中心和虚拟管网"集输方案的概念。已研制出的全风冷、制冷油润滑螺杆压缩机驱动的10000~30000 m³·d^-1"可移动式液化装置",其中30000 m³·d^-1液化装置生产中实测液化比功耗已经与国内1000000 m³·d^-1的集中液化工厂相当。目前在山西、内蒙古已有多套不同规模的装置运行,初步形成一定规模。     

一种发电和天然气再液化相结合的LNG冷能利用系统

针对冷能回收再利用问题,提出了一种结合LNG和燃煤废气发电与天然气再液化的冷能利用系统并对系统进行了改进。对原系统和系统改进部分进行了热力学计算,详细分析了蒸发压力、蒸发温度对系统热力性能的影响,分析了天然气液化率对系统净输出功的影响,确定了发电循环的最佳蒸发压力、蒸发温度及天然气液化率的范围。结果表明：以回收1000 kg·h^-1的LNG冷量（火用）计算,发电系统最大净输出功为69.6 kW·h,系统冷（火用）回收效率为41.43%;液化系统LNG液化率最大值为24%;系统改进后,发电系统净输出功和冷（火用）回收效率提高了17.85%,液化系统LNG液化率提高至28%。为日后LNG气化供气过程中的冷能利用提供一种新的思路。     

大型天然气液化技术与装置建设现状与发展

国外天然气液化技术发展近百年,工业化应用也达半个多世纪,已发展成熟多种液化工艺及配套技术。我国涉足天然气液化技术较晚,正处于发展阶段。本文介绍了各种天然气液化工艺及其工业化应用情况,分析其工艺特点、装置规模、适用范围,为国内天然气液化技术开发提供指导。分析表明,混合冷剂制冷工艺（DMR和C3MR）与优化级联工艺是大型天然气液化装置所采用的主流工艺,应用实例多,地域范围广,装置规模不断扩大;近20年建成和目前正在筹建中的大型液化项目,主要为岸基且单线规模为（3.0～6.5）百万吨/年LNG;DMR技术新型高效灵活。此外,随着资源开发技术的发展,极地与深海资源的开发利用不断增加,适应极寒气候条件和海上浮式的液化技术将成为新的研究热点。     

Design and analysis of dual mixed refrigerant processes for high-ethane content natural gas liquefaction

Recovery and purification of ethane has a significant impact on economic benefit improvement of the high-ethane content natural gas. However, current LNG-NGL integrated processes mainly focus on conventional natural gas, which are not applicable to natural gas with high ethane content. To fill this gap, three dual mixed refrigerant processes are proposed for simulation study of high-ethane content natural gas liquefaction. The proposed processes are optimized by a combination method of sequence optimization and genetic algorithm. Comparatively analysis is conducted to evaluate the three processes from the energetic and exergetic points of view. The results show that the power consumption of Process 3 which compressing natural gas after distillation is the lowest. For safety or other considerations, some common compositions of the mixed refrigerant may need to be removed under certain circumstances. Considering this, case studies of mixed refrigerant involving six composition combinations are carried out to investigate the effects of refrigerant selection on the process performance.     

Synthesis of Mixed Refrigerant Cascade Cycles

This paper considers the synthesis of refrigeration systems with refrigerant mixtures as working fluids. The employed refrigeration topology encompasses features from industrial liquefaction of natural gas (LNG) systems. This configuration consists of a combination of horizontal and vertical cascades generalizing the vertical cascade of pure refrigerant systems. The key features of mixtures exploited here are their ability to evaporate/condense over a temperature range and their potential to generate streams with different compositions through partial condensation. The synthesis problem is formulated and solved as a nonlinear program. The proposed methodology is illustrated using an example of cooling a methane-rich stream.     

氢含量对含氢甲烷氮膨胀液化流程的影响

在以焦炉煤气或者煤制甲烷等含氢甲烷为原料生产液化天然气时,氢气含量会对液化流程产生较大影响。以氮气膨胀液化流程为考察对象,模拟了各种含氢量的含氢甲烷的液化流程。以单位功耗为第一优化目标优化流程,发现在回收率一定时,单位功耗随着含氢量的增加而增加;当含氢量一定时,随着回收率的提升,单位功耗显著增加。研究结果表明,仅采用液化而不采用精馏分离,可以从含氢天然气生产出高质量的LNG产品,流程的单位能耗和产品纯度均在可接受的范围。     

Synthesis of Mixed Refrigerant Cascade Cycles

This paper considers the synthesis of refrigeration systems with refrigerant mixtures as working fluids. The employed refrigeration topology encompasses features from industrial liquefaction of natural gas (LNG) systems. This configuration consists of a combination of horizontal and vertical cascades generalizing the vertical cascade of pure refrigerant systems. The key features of mixtures exploited here are their ability to evaporate/condense over a temperature range and their potential to generate streams with different compositions through partial condensation. The synthesis problem is formulated and solved as a nonlinear program. The proposed methodology is illustrated using an example of cooling a methane-rich stream.