Techno-economic analysis of potential natural gas liquid (NGL) recovery processes under variations of feed compositions

This paper presents the different process schemes used for known NGL recovery methods with respect to their economic performance. The original turbo-expander (ISS) was considered as base case plant. The GSP, CRR and RSV process schemes focus on improvement at the top of the demethanizer column. The IPSI-1 and IPSI-2 schemes focus on the bottom of the demethanizer column. All the process schemes were initially built using Aspen HYSYS with a common set of operating criteria. Numerous simulation runs were made by taking various typical feed compositions classified as lean and rich. The economic assessment for each process scheme was later made by considering the capital cost, operating cost and profitability analysis. Results showed that the IPSI-1 process scheme gives the best economic performance with lowest TAC and payback time compared to the other process schemes. On the other hand, the RSV process gives higher TAC and payback time compared to others.     

天然气轻烃回收装置工艺优化

本文以某套轻烃浅冷回收装置为研究对象,运用HYSIM烃类工艺模拟软件,对其进行了工艺参数的优化。同时,还考察了原料气的轻重程度不同对最优工艺参数的影响。结果表明:重原料组成时,装置的操作压力可适当降低;轻原料组成时,适当提高装置的操作压力可使轻烃的收率达到最大,实现以最小的能耗获得最大的C 组分收率这一优化目标。     

Recovery enhancement of liquid hydrocarbons in dew point control unit of natural gas processing plant

ABSTRACT

The low temperature absorption method is currently used in a gas-processing unit to control the natural gas dew point. The major problem of this unit is the simultaneous absorption of high amount of methane within heavier hydrocarbons, which leads to low purity of ethane and propane streams. Considering the operational conditions, the mentioned method used in second and third phases, will control the dew point at ?23° c at the best condition. This temperature is not proper for dew point and shows very high amount of hydrocarbons in product gas. In this study, a new process has been introduced in order to drop the gas liquid dew point (natural gas liquid) to ?85° c by self-refrigeration technology. Due to the advanced nature of absorption process, the problem of methane existence in the product of gas liquids is noticeably overcome. In this process, natural gas enters the turbo expander after passing through a refrigeration cycle at ?37° c and it is then expanded in an isotropic process to 2896 kPa pressure. Expander outlet with reflux and condensate produced from a cold separator are fed to an absorption tower with a reboiler and the separation will occur. The advantage of this method is controlling the concentration of methane in the product streams. Simulation results show that the process can daily produce 22,280 barrels of gas liquids with a concentration of 0.5 mole% of methane. In addition, the recovery efficiencies of propane and butane in the newly proposed method are 97.3% and 99.99%, respectively, which show a remarkable advantage over the current trend.     

天然气深冷分离装置的(火用)分析及用能改进建议

将天然气深冷分离装置划分为6个子系统,采用“三箱”分析方法,建立了NGL装置的火用分析模型,并给出了具体分析过程和评价指标。利用实测数据,对某一实际运行的NGL装置进行了分析计算,根据测算结果提出了改进建议。实际应用表明,对NGL装置进行火用分析,能更全面地反映装置的用能情况。     

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。     

硫磺回收装置过程气加热方式比较

介绍了国内硫磺回收工艺特点及过程气加热方式。分析比较高温热掺合法、在线加热炉加热法、蒸汽加热法、气-气换热法和电加热法等过程气加热方式的优缺点,并探讨了高温掺合阀的安装位置及选材、Claus尾气加热方式选择等。建议设计人员根据各企业热源的可靠性、装置规模、装置操作弹性、酸性气组成、装置平面布局及投资情况等综合考虑,选择最佳的过程气加热方式。     

多晶硅生产氯化氢回收工艺的模拟与优化

建立了多晶硅生产氯化氢回收工艺过程的热力学模型,考察了吸收塔进气的氯化氢摩尔分数、吸收塔的液气比、解吸塔回流比等因素对吸收尾气中氯化氢摩尔分数、回收氯化氢中氯化氢摩尔分数的影响,并考察了闪蒸脱氢的最优条件。最终得出CVD尾气的最优吸收液气比和解吸回流比分别为1.4和0.3;STC氢化尾气的最优吸收液气比和解吸回流比分别为2.0和0.3;闪蒸的最优条件是0.2 MPa、-40℃。     

Control structure synthesis for operational optimization of mixed refrigerant processes for liquefied natural gas plant

The best control structures for the energy optimizing control of propane precooled mixed refrigerant (C₃MR) processes were examined. A first principles‐based rigorous dynamic model was developed to analyze the steady‐state and dynamic behaviors of the C₃MR process. The steady‐state optimality of the C₃MR process was then examined in a whole operation space for exploring the feasibility of the energy optimizing control for possible control structures. As a result, the temperature difference (TD) between the warm‐end inlet and outlet MR streams was exploited as a promising controlled variable to automatically keep the liquefaction process close to its optimum. The closed‐loop responses were finally evaluated for every possible control structure candidate. Based on the steady‐state optimality and the dynamic performance evaluation, several control structures with a TD loop were proposed to be most favorable for the energy optimizing control of the C₃MR process. The proposed optimality approach can be applied to any natural gas liquefaction process for determining a proper controlled variable for optimizing operation. © 2014 American Institute of Chemical Engineers AIChE J, 60: 2428–2441, 2014     

Natural gas conversion to liquid fuels in a zone reactor

A process for conversion of natural gas to liquid fuels is described. The process can be conducted in a “zone reactor” in which oxygen or air is first contacted with solid metal bromide, producing bromine and metal oxide. The bromine passes into a second zone, in which it reacts with natural gas, producing alkyl bromides and hydrogen bromide. The products of the second zone pass into a third zone, in which they react with metal oxide, producing metal bromide and liquid product. At the end of the cycle the oxygen feed and product streams are switched and the flow reversed. The advantages of the process including safety and capital cost reduction are presented and results discussed.     

Simulation and energy consumption analysis of a propane plus recovery plant from natural gas

This paper deals with the investigation of a cryogenic plant for the recovery of propane plus compounds from natural gas. The commercially available software ASPEN Plus® has been used to simulate the process, and to investigate the effect of the main operating variables on the efficiency of propane plus recovery and on the energy required by the various pieces of equipment of the plant. With respect to the base case considered, the optimized plant allows to reduce the heat required up to 25%; besides, the refrigeration required can be reduced up to 60%, without significantly affecting the propane plus recovery.     

A novel conceptual design by integrating NGL recovery and LNG regasification processes for maximum energy savings

Natural gas liquids (NGL) recovery from shale gas needs large amounts of cold energy for cooling, while liquefied natural gas (LNG) regasification requires tremendous hot energy for heating. Thus, recycling the cold energy from LNG regasification process at a receiving terminal to assist the NGL recovery process has great economic benefits on both energy saving and high‐value product recovery. A novel conceptual design by integrating NGL recovery from shale gas and LNG regasification at receiving terminals has been developed. It first generates a process superstructure. Then, a simulation‐assisted mixed‐integer linear programming (MILP) model is developed and solved for the optimal process synthesis. Next, heat exchange network (HEN) design and analysis are performed to accomplish the maximum energy‐saving target. Finally, rigorous plant‐wide simulations are conducted to validate the feasibility and capability of the entire conceptual design coupling of separation and heat integration. © 2013 American Institute of Chemical Engineers AIChE J, 59: 4673–4685, 2013     

Techno-economical and environmental optimization of natural gas network operation

In the present study, a multi-objective approach is proposed to find optimum operating condition of natural gas network. For this purpose, a thermodynamic modeling of natural gas through the main elements of the network i.e. pipelines and compressor stations (CSs) is performed. This study aims to find optimum values of three conflicting objective functions namely maximum gas delivery flow and line pack, and minimum operating cost (sum of fuel consumption and carbon dioxide emission costs), simultaneously. Here, fast and elitist non-dominated sorting genetic-algorithm (NSGA-II) is applied by considering fourteen decision variables: number of running turbo-compressors (TCs) and rotational speed of them in compressor stations as well as gas flow rate and pressure at injection points. The results of multi-objective optimization are obtained as a set of multiple optimum solutions, called ‘the Pareto optimal solutions’. Furthermore, a set of typical constraints, governing the pipeline operation, is subjected to obtain more practical solutions. To control the constraints satisfaction and to find better solutions in optimization process, the penalty functions are defined and applied. Sensitivity analysis of change in the objective functions, when the optimum decision variables vary, is also conducted and the degree of each parameter on conflicting objective functions is investigated.     

3种氯乙烯精馏尾气回收工艺的分析比较

介绍了聚氯乙烯树脂生产过程中氯乙烯精馏尾气产生的工艺,并对使用的3种氯乙烯精馏尾气回收工艺进行了分析比较.     

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.     

煤气净化污水氨回收的流程进展及优化

煤气净化后,大量的氨进入煤气污水中,氨作为应用较为广泛的工业原料,这部分氨应加以回收,净化废水的同时获得无水液氨,创造经济效益。介绍了无水液氨工艺流程的优化过程。     

Theoretical analysis of natural gas recovery from marginal wells with a deep well reactor

Current natural gas harvesting technologies are only economically viable at high gas flow rates. Subsequently, a significant quantity of gas remains unused in abandoned wells. Methanotrophic organisms are under development to capitalize on this resource given their preference for ambient conditions, however capital and methane mass transfer costs must be minimized. We propose using the well as the bioreactor negating capital costs, and leveraging the gas pressure for mass transfer. We evaluate the Deep Well Reactor's feasibility by developing mathematical models to simulate mass transfer and explore how operating parameters impact ethanol production. The results show sufficient mass transfer for 100% conversion, despite minimal complexity. Current aerobic methanotrophs and inorganic catalysts provide sufficient reaction rates. Conversely, anaerobic methanotrophs rates must be improved by a factor of 1200. With an appropriate catalyst, this technology allows the recovery of methane at flow rates an order of magnitude lower than current technologies. © 2017 American Institute of Chemical Engineers AIChE J, 63: 3642–3650, 2017     

Plant-wide control for the economic operation of modified single mixed refrigerant process for an offshore natural gas liquefaction plant

The marine operation of floating liquefied natural gas (FLNG) demands process compactness, flexibility, simplicity of operation, safety, and higher efficiency. The modified single mixed refrigerant (MSMR) process satisfies the FLNG process requirements and is accepted as a suitable technology for FLNG operation. The aim of this study was to develop a plant-wide control structure or strategy that can sustain the economic efficiency of the MSMR process. The NGL recovery and liquefaction units were integrated in the MSMR process to provide a compact plant structure with an efficient operation. Steady-state optimality analysis was intensively conducted in a rigorous dynamic simulation environment to determine the correct variable to sustain the economic efficiency of MSMR process. The results showed that the flow rate ratio of heavy and light mixed refrigerant (HK/LK ratio) is a promising self-optimizing controlled variable. Controlling this variable can sustain the MSMR optimality, even when the process is operated under off-design operating conditions or in the presence of disturbances. Based on the control structure tests, the control configuration with the HK/LK ratio loop showed excellent performance, maintaining the process stability against a range of disturbances. The proposed approach can also be applied to any cryogenic liquefaction technology for determining a possible optimizing controlled variable.     

Discovery of novel zeolites for natural gas purification through combined material screening and process optimization

An efficient computational screening approach is proposed to select the most cost‐effective materials and adsorption process conditions for CH₄/CO₂ separation. The method identifies eight novel zeolites for removing CO₂ from natural gas, coalbed methane, shale gas, enhanced oil recovery gas, biogas, and landfill gas sources. The separation cost is minimized through hierarchical material screening combined with rigorous process modeling and optimization. Minimum purity and recovery constraints of 97 and 95%, respectively, are introduced to meet natural gas pipeline specifications and minimize losses. The top zeolite, WEI, can recover methane as economically as $0.15/MMBTU from natural gas with 5% CO₂ to $1.44/MMBTU from natural gas with 50% CO₂, showing the potential for developing natural gas reservoirs with higher CO₂ content. The necessity of a combined material selection and process optimization approach is demonstrated by the lack of clear correlation between cost and material‐centric metrics such as adsorption selectivity. © 2014 American Institute of Chemical Engineers AIChE J, 60: 1767–1785, 2014     

Flexibility and operability analysis of a HEN-integrated natural gas expander plant

In the heat-exchanger network (HEN) literature, synthesis, design, and flexibility analyses of HENs are done independently from processes to which HENs are integrated. Such analyses are made mostly based on nominal operating conditions at which the HEN's source- and target-stream properties are evaluated. However, terminal-stream properties of HENs depend upon temperatures, pressures, and compositions of the process connected to the HEN. In this work, flexibility and operability issues of a HEN are investigated with rigorous simulations using the process flowsheet simulator HYSYS for a HEN-integrated natural gas turbo-expander plant (TEP) operating under ethane-recovery mode. The contribution of this work is threefold. First, the HEN-plant interactions are exemplified via the process flowsheet simulator. Second, flexibility and operability issues are tackled using the optimization capability of the flowsheet simulator. Third, for highly energy-integrated complex plants like the TEP, the difficulties or impossibilities of automated HEN synthesis and flexibility analysis with process flowsheet simulators are demonstrated.     

Aspen Plus对Unipol工艺聚乙烯装置回收系统的优化

利用Aspen Plus软件对Unipol工艺聚乙烯装置回收系统进行优化。在受压缩机处理能力、冰机制冷能力和总的冷剂流量的限制条件下,合理分配高低压侧的冷剂流量,得到最大的回收凝液量。同时,提出向冷剂中加入缓蚀剂,减缓冷凝器的腐蚀,保证换热效率。