Low-temperature Distillation Process Research Articles

Energy reduction and efficiency separation method of associated gas in oilfield based on EOR-CO2

Cryogenic distillation is considered to be the most promising technology for the treatment of CO2-EOR gases, but it is an energy-intensive process. Considerable scientific efforts are being made to reduce energy consumption in cryogenic distillation and to improve process efficiency. Therefore, this study proposes a unique low-temperature distillation process. The novelty of the designed distillation process lies in the fact that using a small amount of refluxed liquid CO2 mixed with untreated oilfield-associated gas into the distillation column reduces the process energy consumption and improves the rectification effect. The sensitivity analysis of different design key parameters of the system is carried out using ASPEN HYSYS, and the energy consumption is regarded as the key function of this cycle optimization. The simulation results show that the optimized low-temperature distillation process has lower energy consumption and better distillation results. Compared with the traditional process, the product purity of the optimized process increased from 94.01% to 94.82%, the product recovery increased from 95.87% to 98.46%, The energy consumption of the reboiler and condenser of the distillation column was reduced, and the total energy consumption was reduced from 1.147MJ/kg to 1.001 MJ/kg.

Rational Design of Mixed Matrix Membranes Modulated by Trisilver Complex for Efficient Propylene/Propane Separation.

The application of membrane-based separation processes for propylene/propane (C3 H6 /C3 H8 ) is extremely promising and attractive as it is poised to reduce the high operation cost of the established low temperature distillation process, but major challenges remain in achieving high gas selectivity/permeability and long-term membrane stability. Herein, a C3 H6 facilitated transport membrane using trisilver pyrazolate (Ag3 pz3 ) as a carrier filler is reported, which is uniformly dispersed in a polymer of intrinsic microporosity (PIM-1) matrix at the molecular level (≈15nm), verified by several analytical techniques, including 3D-reconstructedfocused ion beam scanning electron microscropy (FIB-SEM) tomography. The π-acidic Ag3 pz3 combines preferentially with π-basic C3 H6 , which is confirmed by density functional theory calculations showing that the silver ions in Ag3 pz3 form a reversible π complex with C3 H6 , endowing the membranes with superior C3 H6 affinity. The resulting membranes exhibit superior stability, C3 H6 /C3 H8 selectivity as high as ≈200 and excellent C3 H6 permeability of 306 Barrer, surpassing the upper bound selectivity/permeability performance line of polymeric membranes. This work provides a conceptually new approach of using coordinatively unsaturated 0D complexes as fillers in mixed matrix membranes, which can accomplish olefin/alkane separation with high performance.

Improving energy efficiency for a low-temperature CO2 separation process in natural gas processing

Conventional amine sweetening process is limited to treating gas with high content of CO2, due to significant energy demand for the regeneration of solvent and the compression of CO2 product for Enhanced Oil Recovery (EOR) or sequestration. Although distillation processes operating at sub-ambient conditions have been regarded as an economic and energy-efficient alternative to amine sweetening process, it is not straightforward to materialize the full benefits of the low temperature distillation process in practice because of complex design interactions existed. The distillation process for carbon dioxide separation operated at sub-ambient conditions are modeled with commercial simulator Aspen HYSYS®. A range of thermodynamic packages are screened for the selection of the most appropriate one to be used, while the validation of the process modeling is made with reference data. Understanding on the dependence of energy cost on the key design and operating variables is obtained with sensitivity studies, with which energy-efficient selection of column configurations and operating conditions throughout the process is made. Suggestion is also made for improving energy efficiency for the process without compromising separation process, by setting different operating pressure and introducing new configuration involving stream splitting and merging.

Natural gas sweetening using low temperature distillation: simulation and configuration

ABSTRACTHypothesis: Separation of CO2 from a stream of natural gas using low-temperature distillation process is complicated not only because of the existence of ethane (C2) and CO2 azeotrope but owing to the freezing of CO2. A modified process based on an existing Ryan–Holmes process in the form of a low-temperature distillation is presented here for the separation of sour gases. In addition, solvents were employed to prevent CO2 freezing and to avoid formation of the C2-CO2 azeotrope.Simulation: Simulation calculations were carried out using a natural gas stream containing CO2 and H2S. The process was designed and simulated using Aspen HYSYS 9.Findings: A low-temperature process for the separation of a feed stream containing up to 30 mole% CO2 and 2.5 mole% H2S was achieved, which lowered the levels of these gases to within 50 and 4 ppm, respectively. These values conform to liquefied natural gas specifications. The compositions of the product streams, the required solvent circulation flow rates, and the total energy requirements were estimated. The reported process successfully separated H2S and produced CO2 at a pressure of 25.0 bar and a temperature of −13°C, thereby ensuring its suitability for application in enhanced oil recovery. This described process also delivered the desired natural gas product at 35 bar and −90°C ready for liquefaction and further cooling.

Assessing the energy intensity of alternative chemical and cryogenic natural gas purification processes in LNG production

The production of Liquefied Natural Gas (LNG) from natural gas reservoirs with high content of acidic compounds is expected to be a strategic and crucial issue for the development of the natural gas market in future decades. Therefore, the identification of alternative suitable processes for the synergistic natural gas purification and LNG production, when the amount of CO2 in the raw gas feed is high, and their comparative thermodynamic assessment, is necessary to foster a cleaner and efficient production of LNG.In this paper, the energy intensity of the classical chemical absorption units using aqueous solutions of Methyldiethanolamine (MDEA) and the novel Dual Pressure Low-Temperature Distillation process (DPD) operating in different national contexts is assessed by means of the Net Equivalent Methane analysis and the Energy Life Cycle Assessment. These methods return respectively the equivalent methane and the embodied non-renewable energy invoked by the two alternative processes in one operating year. In general, the primary energy required by the construction phases of both the systems results negligible compared to the operation phase, and most of the latter is due to the consumption of energy utilities, which is strongly dependent by the considered national context. According to the results obtained by means of both the methodologies, the DPD process is generally less energy intensive compared to MDEA: the DPD process results to be an efficient and promising technique to perform the synergistic natural gas purification and LNG production.

Low-Temperature Distillation Process for CO2/CH4 Separation: A Study for Avoiding CO2 Freeze-Out

In published literature, only very limited studies were carried out for low-temperature biogas upgrading for CO2/CH4 mixture separation due to the freeze-out of CO2 under low temperature, which causes several operational problems. Therefore, the present study aims to provide in-depth analysis for a low-temperature distillation process of a typical model of biogas mixture (CH4 + CO2) to tackle the problem of freezing. The process has been optimized by means of varying distillation column feed pressure, temperature and CO2 concentration, reflux ratio, feed stage number, and produced methane purity to lower the risk of CO2 freezing in the column. The modeling results reveal a substantial feature of the low-temperature process that it can capture CO2 in liquid phase with a purity of 99.5 mol % as a valuable byproduct for transport. Additionally, it is found that increasing the column reflux ratio mitigates the risk of CO2 freeze-out allowing the column to reach higher CH4 purities (up to 97 mol %) without CO2 solidification. Moreover, the occurrence of CO2 freeze-out in the column is not affected within a relatively wide range of feed CO2 concentrations. The low-temperature technique can serve as a new promising approach for biogas upgrading overcoming the risk of CO2 frosting.

Biogas to liquefied biomethane via cryogenic upgrading technologies

Liquid biomethane (LBM), also referred to as liquid biogas (LBG), is a promising biofuel for transport that can be obtained from upgrading and liquefaction of biogas. With respect to fossil fuels, LBM is a renewable resource, it can be produced almost everywhere, and it is a carbon neutral fuel. LBM is 3 times more energy dense than compressed biomethane (CBM) and it allows longer vehicle autonomy. LBM has also a higher energy density than other transport biofuels, it is produced from wastes and recycled material without being in competition with food production, and it assures a high final energy/primary energy ratio. The low temperatures at which LBM is obtained strongly suggest the use of cryogenic/low-temperature technologies also for biogas upgrading. In this respect, since biogas can be considered as a “particular” natural gas with a high CO2 content, the results available in the literature on natural gas purification can be taken into account, which prove that cryogenic/low-temperature technologies and, in particular, low-temperature distillation are less energy consuming when compared with traditional technologies, such as amine washing, for CO2 removal from natural gas streams at high CO2 content. Low-temperature purification processes allow the direct production of a biomethane stream at high purity and at low temperature, suitable conditions for the direct synergistic integration with biogas cryogenic liquefaction processes, while CO2 is obtained in liquid phase and under pressure. In this way, it can be easily pumped for transportation, avoiding significant compression costs as for classical CO2 capture units (where carbon dioxide is discharged in gas phase and at atmospheric pressure). In this paper, three natural gas low-temperature purification technologies have been modelled and their performances have been evaluated through an energy consumption analysis and a comparison with the amine washing process in terms of the equivalent amount of methane required for the upgrading, proving the profitability of cryogenic/low-temperature technologies. Specifically, the Ryan-Holmes, the dual pressure low-temperature distillation process and the anti-sublimation process have been considered. It has been found that the dual pressure low-temperature distillation scheme reaches the highest thermodynamic performances, resulting in the lowest equivalent methane requirement with respect to the other configurations.

A New Distillation Process for the Upgrading of Acid Gas

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 183154, “The Potential of a New Distillation Process for the Upgrading of Acid Gas,” by L.A. Pellegrini, G. De Guido, S. Langé, and S. Moioli, Politecnico de Milano, and B. Picutti, P. Vergani, G. Franzoni, and F. Brignoli, Tecnimont, prepared for the 2016 Abu Dhabi International Petroleum Exhibition and Conference, Abu Dhabi, 7–10 November. The paper has not been peer reviewed. In this work, the potential of a new low-temperature distillation process for natural-gas sweetening has been investigated. The proposed technology consists of a dual pressure-distillation scheme designed to avoid the formation of a solid phase in all parts of the process while remaining able to fulfill the required natural-gas-purity specifications. The new process offers the competitive advantages of low-temperature technologies while avoiding carbon dioxide (CO2) solidification and solvent addition. Introduction The industry must find technologies that allow the profitable exploitation of low-quality and high-CO2-content gas reserves in order to meet increasing demand while still decreasing production costs. Low-temperature processes are preferred to traditional chemical or physical absorption for gas purification when the CO2 concentration in natural-gas streams is high. For this reason, attention on low-temperature processes for CO2 removal has increased in recent years. In this work, an analysis has been carried out to determine the trade-off between classical methyldiethanolamine (MDEA) gas-sweetening units, still representing the industry benchmark for acid- and sour-gas purification, and a low-temperature distillation process. The MDEA unit typically requires steam at the reboiler of the regeneration column, while the low-temperature distillation processes consume electric energy to drive the refrigeration cycle. In amine regeneration units, the steam consumption is a significant part of the total energy demand of the process and thus of the total operating costs. The complete paper defines a merit-index function to determine the trade-off between the two considered technologies. The Low-Temperature Process The new process for the low-temperature purification of natural gas is based on a dual-pressure (approximately 40/50 bar) low-temperature distillation operation, designed to bypass the solid/liquid/vapor (SLV) locus of the methane (CH4) and CO2 binary mixture through a proper thermodynamic pathway. In this work, an optimized process layout has been taken into account. The gas stream to be purified is fed to the high-pressure (HP) section at its dewpoint; in this first part of the distillation unit, the natural-gas feed is separated into two streams: a bottom one with a high CO2 content and a top product flow rich in CH4. The top product stream from the HP section is split into two streams: the first is heated and expanded to the low-pressure (LP) section; the second one is cooled so that after expansion it is at its bubblepoint at 40 bar. The superheated gas stream is fed at the bottom of the LP section, while the liquid feed enters the column a few theoretical trays above the bottom of the LP section. In the LP distillation section, a top product CH4 gas stream at commercial grade is obtained, while the bottom liquid stream rich in CH4 is pumped back to the HP section to provide the reflux. The condenser is a full-reflux condenser, and the top product stream is obtained as gas. The rationale of the process to avoid solid CO2 formation is the bypassing of the maximum of the SLV locus of the CH4-CO2 system.

Low temperature techniques for natural gas purification and LNG production: An energy and exergy analysis

Due to the rapid increase of the World’s primary energy demand of the last decades, low-temperature processes for the purification of natural gas streams with high carbon dioxide content has gained interest, since they allow to make profitable exploitation of low-quality gas reserves. Low temperature purification processes allow the direct production of a methane stream at high purity and at low-temperature, suitable conditions for the direct synergistic integration with natural gas cryogenic liquefaction processes, while CO2 is obtained in liquid phase and under pressure. In this way, it can be pumped for transportation, avoiding significant compression costs as for classical CO2 capture units (where carbon dioxide is discharged in gas phase and at atmospheric pressure), and further uses such as Enhanced Oil Recovery (EOR) or underground storage.In this paper, the three most common natural gas low-temperature purification techniques have been modelled and their performances have been evaluated through energy and exergy analyses. Specifically, the dual pressure low-temperature distillation process, the anti-sublimation process and a hybrid configuration have been considered. It is found that the dual pressure low-temperature distillation scheme reach the highest thermodynamic performances, resulting in the best values of exergy efficiency and equivalent methane requirements with respect to the other configurations. This is mainly due to the distributed temperature profile along a distillation column, resulting in a less irreversible heat exchanging process.

Energy Analysis of the New Dual-Pressure Low-Temperature Distillation Process for Natural Gas Purification Integrated with Natural Gas Liquids Recovery

The global natural gas demand is expected to rise continuously over the next decades, compelling industries to study and develop new natural gas purification processes, such as those using low-temperature, in order to allow the profitable exploitation of low-quality gas reserves (with high contents of CO2 and/or H2S) that up to some years ago were not considered suitable for their commercialization. When dealing with natural gas, not only are acidic gases present in the main stream but also hydrocarbons heavier than methane (ethane, propane, n-butane, etc.). These substances may have to be removed from the produced gas for the dew point control of the sales gas or to manage its BTU content. Moreover, they are widely used for petrochemical productions and their recovery can be profitable for natural gas producers. In this work, an energy analysis is carried out in order to assess the energy requirements for the recovery of Natural Gas Liquids (NGLs) during natural gas purification at low-temperatures. The ...

Energy and Economic Analysis of a New Low-Temperature Distillation Process for the Upgrading of High-CO2 Content Natural Gas Streams

An energy and economic analysis on a new distillation process for the upgrading of high-CO2 content natural gas streams has been carried out. The process has been optimized by means of a feed splitting technique to minimize the energy requirements. The performances of the process have been compared to the ones of a traditional MDEA scrubbing process in terms of energy expenses. The cost of energy has been quantified to build up a merit index function, which allows one to determine the trade-off between the two technologies as a function of the CO2 and H2S content in the feed gas and the geographic area where the gas reserve is located. The results have been discussed on the basis of the cost of energy in different geographic areas, showing the benefits (in terms of energy and operating costs savings) of a low-temperature distillation process when the CO2 content in the natural gas streams is high.

Low-temperature distillation processes in single- and dual-purpose plants

During the last decade, intensive research and development have been invested to improve further the advantages of the low-temperature process by increasing the unit's capacities and decreasing the energy consumption. This paper presents the advantages of the low-temperature distillation process, describes practical commercial application for steam driven multi-effect distillation plants in dual-purpose (electricity and water production) applications and the latest developments for single-purpose mechanical vapor compression plants.

Energy prices and requirements for commercial desalination processes; present state and future improvements

During the last decade, intensive research and development have been invested to improve further the advantages of the low-temperature process by increasing the unit's capacities and decreasing the energy consumption. This paper presents the advantages of the low-temperature distillation process, describes practical commercial application for steam driven multi-effect distillation plants in dual-purpose (electricity and water production) applications and the latest developments for single-purpose mechanical vapor compression plants.

The Preservation of Fishing Nets by Treatment with Copper Soaps and Other Substances. Part III

1. Frequent treatment with cutch is injurious, but Olie's method (cutch and ammoniacal copper sulphate) applied every four months preserved cotton netting for six years and eight months in Aquarium sea-water.2. Varieties of cutch tested showed differences which were quite insignificant in comparison with the improvement effected by adopting One's method, which was effective with all on cotton.3. A single treatment by Olie's method preserved trawl twines of Benares sann hemp, New Zealand Phormium fibre and of sisal (E. African) for 34, 34 and more than 48 months respectively under conditions such that the untreated twines perished in less than five months.4. Cotton treated with cutch alone is but little improved by a dip in crude phenols, but a neutral tar oil obtained from the “Coalite” low temperature distillation process was found useful.