天然气水合物资源勘探开发技术研究进展

天然气水合物储量巨大,是人类理想的潜在的替代能源。对世界天然气水合物资源基本特征和分布情况进行了介绍,对国内外天然气水合物勘探开发技术以及环境效应进行了阐述。     

一种焦炉煤气制液化天然气的工艺技术

分析了焦炉煤气与天然气的应用现状,总结了国内外焦炉煤气制液化天然气的技术特点,介绍了中冶焦耐的焦炉煤气制液化天然气工艺技术,指出目前焦炉煤气制LNG技术核心不在于甲烷化,而是深度净化过程。     

Nucleation curves of model natural gas hydrates on a quasi‐free water droplet

Heterogeneous nucleation probability distributions of gas hydrates on a water droplet that was supported by inert and immiscible perfluorocarbon oil, perfluorodecalin is studied. The guest gas used was a mixture of 90 mol % methane and 10 mol % propane. The probability distribution was measured using a high pressure automated lag time apparatus under the guest gas pressure range of 6.7–12.5 MPa and the cooling rate range of 0.002–0.02 K/s. Nucleation curves were derived for unit area of water surface. The nucleation rate per unit area of water surface that was contained in a glass sample cell, which differed significantly from that on a quasi‐free water droplet, is also derived. It is concluded that the nucleation curves in the presence of a solid wall should be normalized to the unit length of the three‐phase line at which water, guest gas, and the solid wall meet. © 2015 American Institute of Chemical Engineers AIChE J, 61: 2611–2617, 2015     

Thermodynamic design of a cascade refrigeration system of liquefied natural gas by applying mixed integer non-linear programming

Liquefied natural gas (LNG) is the most economical way of transporting natural gas (NG) over long distances. Liq-uefaction of NG using vapor compression refrigeration system requires high operating and capital cost. Due to lack of systematic design methods for multistage refrigeration cycles, conventional approaches to determine op-timal cycle are largely trial-and-error. In this paper a novel mixed integer non-linear programming (MINLP) model is introduced to select optimal synthesis of refrigeration systems to reduce both operating and capital costs of an LNG plant. Better conceptual understanding of design improvement is illustrated on composite curve (CC) and exergetic grand composite curve (EGCC) of pinch analysis diagrams. In this method a superstruc-ture representation of complex refrigeration system is developed to select and optimize key decision variables in refrigeration cycles (i.e. partition temperature, compression configuration, refrigeration features, refrigerant flow rate and economic trade-off). Based on this method a program (LNG-Pro) is developed which integrates VBA, Refprop and Excel MINLP Solver to automate the methodology. Design procedure is applied on a sample LNG plant to illustrate advantages of using this method which shows a 3.3% reduction in total shaft work consumption.     

液化天然气储罐预冷过程温度场数值模拟

建立了液化天然气(LNG)储罐喷淋预冷过程的流动传热与传质模型,对储罐内热物理场和储罐壁面温度的变化进行探讨。分析表明,喷淋进入储罐的LNG液滴并不能完全覆盖整个储罐,液滴进入储罐后,速度迅速衰减并转成垂直下落,同时液滴不断吸热汽化。预冷过程中,LNG的喷淋速度决定了储罐的冷却速度,温降最快的位置出现在储罐底部的中心区域,侧壁温降速度较慢。由于储罐的底部中心区域出现二次流动,阻碍了储罐底壁与内部低温气体的换热,同时由于混凝土对容器的导热,造成容器底部中心区域的温度不减反增的现象。     

煤炭地下气化制液化天然气技术经济性分析

为了核算煤炭地下气化制液化天然气(UCG-LNG)技术的经济可行性,在试验数据的基础上,以年产液化天然气2亿m3的UCG-LNG项目为例,计算了项目的总投资额,以及工程费用和天然气生产成本的构成及各项占比,并分析了项目的敏感性。结果表明,项目总投资约18.7亿元,总投资的88.3%为工程费用,而在工程费用中,空分设备、煤气净化设备以及天然气液化设备的总费用占比高达69.5%;在天然气销售价格为3.21元/m3时,整个项目的税前内部收益率(IRR)为10.90%,投资回收期为9.85 a(含3 a建设期),经济上可行,敏感性分析得出天然气销售价格对项目IRR的影响最大。     

A power plant for integrated waste energy recovery from liquid air energy storage and liquefied natural gas

Liquefied natural gas(LNG)is regarded as one of the cleanest fossil fuel and has experienced significant developments in recent years.The liquefaction process of natural gas is energy-intensive,while the regasification of LNG gives out a huge amount of waste energy since plenty of high grade cold energy(-160℃)from LNG is released to sea water directly in most cases,and also sometimes LNG is burned for regasification.On the other hand,liquid air energy storage(LAES)is an emerging energy storage tech-nology for applications such as peak load shifting of power grids,which generates 30％-40％of compres-sion heat(～200℃).Such heat could lead to energy waste if not recovered and used.The recovery of the compression heat is technically feasible but requires additional capital investment,which may not always be economically attractive.Therefore,we propose a power plant for recovering the waste cryo-genic energy from LNG regasification and compression heat from the LAES.The challenge for such a power plant is the wide working temperature range between the low-temperature exergy source(-160℃)and heat source(～200℃).Nitrogen and argon are proposed as the working fluids to address the challenge.Thermodynamic analyses are carried out and the results show that the power plant could achieve a thermal efficiency of 27％and 19％and an exergy efficiency of 40％and 28％for nitrogen and argon,respectively.Here,with the nitrogen as working fluid undergoes a complete Brayton Cycle,while the argon based power plant goes through a combined Brayton and Rankine Cycle.Besides,the economic analysis shows that the payback period of this proposed system is only 2.2 years,utilizing the excess heat from a 5 MW/40MWh LAES system.The findings suggest that the waste energy based power plant could be co-located with the LNG terminal and LAES plant,providing additional power output and reducing energy waste.     

Simulation of partial oxidation of natural gas to synthesis gas using ASPEN PLUS

Conversion of natural gas to liquid fuels is a challenging issue. In SMDS process natural gas is first partially oxidized with pure oxygen to synthesis gas (a mixture of H₂ and CO) which is then converted to high quality liquid transportation fuels by utilizing a modernized version of the Fischer-Tropsch reaction. This paper presents a computer simulation of the first stage of the process, i.e. the synthesis gas production from natural gas. ASPEN PLUS equipped with a combustion databank was used for calculations. Concentrations of over 30 combustion species and radicals expected in the synthesis gas have been calculated at equilibrium and several non-equilibrium conditions. Using a sensitivity analysis tool, the relative feed flow rates and reactor parameters have been varied searching to maximize the CO/O₂ yield as well as to minimize the undesired nitrogen compounds in the product stream. The optimum reactor temperature for maximizing the CO mole fraction in the synthesis gas was also calculated.     

Numerical study on effects of the cofferdam area in liquefied natural gas storage tank on the leakage and diffusion characteristics of natural gas

The leakage and diffusion characteristics of natural gas were investigated in the condition of the leakage of liquefied natural gas (LNG) in the storage tank. Fluent was adopted to simulate the process in a series of three-dimension unsteady state calculations. The effects of different heights of the cofferdam (1.0 m, 2.0 m and 3.0 m), wind directions, ambient temperature, leakage location, leakage volume on the diffusion process of natural gas were investigated. The diffusion characteristics of the natural gas clouds over cofferdam were found. Under windless condition, when the gas clouds met, the gas clouds rose due to the collision, which made them easier to cross the cofferdam and spread out. The higher the ambient temperature was, the higher the gas concentration around the cofferdam was, and the smaller the gas concentration difference was. When the leakage occurred, the higher cofferdam was more beneficial to delay the outward diffusion of gas clouds. However, when the leakage stopped, the higher cofferdam went against the dissipation of gas clouds. Under windy condition, the time to form stable leakage flow field was faster than that of windless, and the lower cofferdam further reduced this time. Therefore, considering the effect of barrier and dissipation, it was suggested that the rational height of cofferdam should be designed in the range of 1.0 m to 2.0 m. In case of emergency, the leakage of gas should be deduced reasonably by combining the measurement of gas concentration with the rolling of gas clouds. When windless, the leakage area should be entered between the overflows of gas clouds.     

Experimental study of natural gas hydrates and a novel use of neural network to predict hydrate formation conditions

A novel high-pressure apparatus with various abilities in hydrate investigation fields has been designed, constructed and fully described in the present paper. In order to achieve an appropriate understanding of the gas hydrate behavior in formation and destabilization, series of laboratory experiments with six different gas mixtures were done and more than 130 hydrate equilibrium points in the pressure range of about 450–3000 psia were recorded. Different methods of hydrate formation prediction were discussed and finally the new promising neural networks method was used. Because of the previous works defects in accurate hydrate formation prediction via neural networks, a new use of neural networks was introduced. Testing and validation of the new neural networks method indicates that it is a reliable technique for the accurate prediction of hydrate formation conditions for generalized gas systems and can be used in future automatic inhibitor dosing devices.     

天然气脱硫装置的系统模拟与优化

针对陕北某天然气净化厂脱硫装置CO2体积分数偏高﹑生产设备和输送管线故障频繁这一问题,文中利用ChemCAD 6.0.1对脱硫系统进行了全流程模拟优化,并通过FRI-Tray Rating 1.0.7,HTRI Xchanger Suit 4.00等专业软件对关键设备进行了校核。结果表明:适当提高MDEA循环量可使产品气达到国标相关要求;此外,MDEA吸收塔的各项流体力学指标均满足新工艺条件的要求;MDEA贫富液换热器的换热能力不足,可在原有换热器基础上串联一台同型号换热器来满足换热负荷;提高酸气空冷器的表面翅化率可使其满足换热要求;将原有MDEA循环泵更换为大功率机泵以保证MDEA循环量达到系统指定要求。     

天然气甲基二乙醇胺法脱硫脱碳工艺过程模拟分析

为了提高某天然气净化厂甲基二乙醇胺(MDEA)脱硫脱碳净化装置运行效率,降低运行成本,利用现场收集到的装置运行参数,选择原料处理量、温度,贫液进吸收塔温度和循环量作为影响装置平稳运行的主要变量,用化工模拟软件Aspen Hysys通过参数修正,对该天然气净化装置进行了全流程模拟计算和比对,并利用建立的模型分析了该厂净化工艺的适应性。结果表明:建立的模拟流程收敛且计算结果与生产实际相吻合,在原料气CO2摩尔分数较高而H2S摩尔分数相对较低的情况下,制约装置达标的因素主要是原料气温度、贫液循环量和温度,且循环量变化对净化效果的影响大于温度的影响。     

天然气脱水系统模拟及主要设备优化

陕北某天然气净化厂由于新气源的并入,造成净化后商品气无法达到国家天然气相关标准,这是一个迫切需要解决的问题。通过ChemCAD 6.0.1软件对脱水系统进行模拟,研究分析TEG循环量、原料气进料温度及TEG贫液质量分数对脱水效果的影响,得到最佳的优化操作参数为:TEG循环量为5.5 m3/h,原料气进料温度为26℃,TEG贫液质量分数为99%。通过FRI,HTRI,Pipe Flow Expert等专业软件对TEG脱水塔、TEG贫液水冷器等关键设备进行核算,结果表明:TEG脱水塔的流体力学性能均符合要求,其工作点亦落在负荷性能图的适宜位置;TEG循环量提高导致TEG贫液水冷器负荷增大,需要更换管束,以达到换热效果。研究结果可为该净化装置的优化和改造提供可靠的理论依据,同时对同类型装置也具有一定的借鉴作用。     

浅析天然气管网建设的生态影响评价方法

分析了天然气管网建设生态影响评价的现状及存在的主要问题,阐述了生态影响评价工作的基本程序、主要方法和生态保护措施。结合天然气管网建设项目生态影响评价实际提出,应强化生态影响现场调查、构建生态影响评价指标体系和创新生态影响评价模式。     

移动床煤与天然气共气化制备合成气的工艺技术

煤与天然气共气化是基于天然气蒸汽转化和煤气化工艺耦合的一种新工艺.阐述了煤与天然气共气化制合成气的技术原理.实验研究表明合成气最佳出口温度为1000 ℃,氧气、水蒸气和天然气在同一位置进入反应器能有效降低火焰区温度;理论计算得到的合成气有效气体浓度（CO+H₂）大于95%.实验研究和理论计算结果都表明,煤与天然气共气化可以直接得到H₂/CO在1.0～1.5之间可以调节的合成气.     

A computational simulation study for techno-economic comparison of conventional and stripping gas methods for natural gas dehydration

In the present work, the conventional natural gas dehydration method (CDM) and stripping gas method (SGM) are technically and economically analyzed, utilizing Aspen HYSYS and Aspen Process Economic Analyzer (APEA), respectively. To optimize the CDM and SGM, the sensitivities of the water content of dry gas, reboiler duty and raw material loss are analyzed against solvent rate and stripping gas rate. The optimized processes are set to achieve a targeted value of water content in dry gas and analyzed at optimized point. The analysis shows that SGM gives 46% lower TEG feed rate, 42% lower reboiler duty and 99.97% pure regenerated TEG. Moreover, economic analysis reveals that SGM has 38% lower annual operating cost compared to CDM. According to results, from both technical and economic point of view, SGM is more feasible for natural gas dehydration compared to CDM.     

天然气脱汞吸附剂的制备及其性能评价

天然气中含汞会对天然气的开发及使用带来危害，实验采用固定床吸附法脱除天然气中的汞。实验以Al₂O₃和活性炭复合颗粒为载体，通过浸渍法负载S、CuS和CuS _x 多组分活性物，制备了天然气脱汞吸附剂，考察了制备工艺条件的影响。采用X射线衍射检测（XRD）与扫描电镜（SEM）对活性物负载情况进行了表征。结果表明，在载体上成功负载了CuS和S，其中CuS质量分数为12.80%，总S质量分数为8.32%。以含汞空气模拟含汞天然气，考察了进气口汞含量、停留时间对脱汞吸附剂脱汞效果的影响。结果表明，脱汞剂处理汞含量为300μg/m³的天然气，停留时间为1s时，出口汞含量为24.99μg/m³，已达到工业天然气要求。当停留时间为2s、进气口汞含量达到600μg/m³时，经脱汞剂脱汞后，出口汞含量为18.92μg/m³，达到小于28μg/m³要求。脱汞吸附剂的汞容量达到6.36%。     

天然气制乙烯技术进展及经济性分析

介绍了当前几种主要的天然气制乙烯技术新进展,包括天然气经甲醇制乙烯、费-托合成制乙烯、甲烷氧化偶联制乙烯技术进展及应用情况,并对这几种工艺进行了技术经济评价,结论认为:天然气制乙烯技术的大规模应用,主要取决于天然气原料供应的有效保障及其价格是否合理,在天然气供应充足、价格合理的条件下,天然气经甲醇制乙烯工艺将会得到较快发展,而费-托合成制乙烯、甲烷氧化偶联制乙烯技术目前尚未达到成熟应用阶段,需要持续加大研发力度,争取早日实现工业化应用。     

Comparative study of coal,natural gas,and coke-oven gas based methanol to olefins processes in China

Traditional olefins production mainly depends on oil. In view of the short supply of oil, feedstocks are expanded to coal, natural gas, coke-oven gas, and methanol in China. In this paper, a comparative study of alternative olefins production is conducted from aspects of techno-economic feasibility and environmental friendliness. Results show that coal-to-olefins has a significant cost advantage. However, it suffers from low energy efficiency and serious CO₂ emissions. To address these problems, this study proposes and analyses coal-to-olefins with CO₂ capture, coal and natural gas-to-olefins, and coal and coke-oven gas-to-olefins. The two co-feed systems ensure great reduction of CO₂ emissions and significant improving energy efficiency. They should be actively developed in regions with rich coal and gas. While in regions with rich coal and lean gas, coal-to-olefins with CO₂ capture should be developed in large scale. This paper also provides several suggestions on planning these olefins production routes in China.