Low-temperature Separation Research Articles

Carbon dioxide injection into the Achimov formations using reinjection technology by the example of Ach3-4 formation in the Novo-Urengoy area of the Urengoy field

The prerequisites for the study are the calculation results for the cycling process, where carbon dioxide is proposed as the injection agent into the Achimov formations instead of dry gas, with the goal of increasing the condensate recovery factor. The work is focused on the efficiency assessment of carbon dioxide reinjection technology and reducing carbon footprint at a late stage of field development. The research object is the Аch3-4 formation within the Novo-Urengoy license area of the Urengoy field. The leading method to identify this problem is the results of the full-scale composite dynamic model in the ECLIPSE 300 format. The model takes into account the history of field development on depletion. The articles deals with two schemes for injecting carbon dioxide into the formation. In the first scheme, pure carbon dioxide is injected in a closed-loop system, but carbon neutrality through storage is not achieved. In the second scheme, carbon dioxide is injected using reinjection technology. Once injection begins, gas production stops. Only the condensate separated from the formation gas during low-temperature separation is sold and sent for further processing. After allocation of the condensate, the mixture of natural gas and carbon dioxide, in a specific proportion, is sent to the compressor station for reinjection into the formation in a gaseous state. Injecting pure carbon dioxide achieves a condensate recovery factor similar to that of gas injection with a 30 % carbon dioxide mixture. However, this option is less economically viable compared to the base and other scenarios due to high capital costs for upgrading the existing gas processing equipment (requiring the construction of an amine treatment unit). With carbon dioxide injection using reinjection technology, in addition to recovering extra condensate that had condensed during natural depletion, a reduction in the carbon footprint is also achieved. To maximize the condensate recovery factor, the optimal concentration of carbon dioxide in the injection mixture has been determined. The optimal timing for the start of injection was identified to maximize gas recovery. Economic efficiency is expected from the additional recovery of condensate trapped in the reservoir and from achieving carbon neutrality through the monetization and storage of carbon dioxide.

The new phthalic acid-based deep eutectic solvent as a versatile catalyst for the synthesis of pyrimido[4,5-d]pyrimidines and pyrano[3,2-c]chromenes

A new DES (MTPPBr-PHTH-DES) was prepared from a mixture of methyltriphenyl-phosphonium bromide (MTPPBr) and phthalic acid (PHTH). The eutectic point phase diagram showed that a one-to-one molar ratio of MTPPBr to PHTH is the optimal molar ratio for the synthesis of new DES. Then, it was characterized with various techniques such as FT-IR, TGA/DTA, densitometer, eutectic point, and NMR and used as a novel acid catalyst in the synthesis of pyrimido[4,5-d]pyrimidines and pyrano[3,2-c]chromes in solvent-free condition. Short reaction time, low temperature, high efficiency, green condition, and easy recycling and separation of the DES catalyst are among the most important features of the presented method.

A spacer-based approach for localized Joule heating in membrane distillation

Membrane distillation (MD) is a versatile low-temperature separation process used for desalinating saline solutions with high salt rejection rates. Its current drawbacks include low flux and high energy demand. This study presents localized electrically induced heating using ceramic-coated metallic spacers to improve MD performance. We coated Ni-Cr spacers with MgO via electrolytic deposition and calcination, optimizing for a crack-free protective surface. Smaller wire diameter Ni-Cr exhibited superior heating. When a periodic current of 0.2 A cm−2 was applied, permeate flux increased by 15% although energy consumption only increased by 4%. Continuous supply of high-grade electrical energy added no further performance improvement as compared to periodic application. Our work highlights a spacer-based approach for localized Joule heating in MD systems without compromising membrane structure, while exploring coating systems to protect conductive spacers and optimizing schemes for electrically controlled performance.

Oilfield Brine as a Source of Water and Valuable Raw Materials—Proof of Concept on a Laboratory Scale

Oilfield brine is the largest byproduct stream generated during the extraction of crude oil and natural gas and may be considered a resource for the production of potable water and valuable raw materials. The high salinity of such waters limits the application of typical membrane-based techniques. In most oilfields, waste cold energy from the process of the low-temperature separation of natural gas is available and may be used as a source of cold for the freezing desalination (FD) of brine. As a result of the FD process, two streams are obtained: partially desalinated water and concentrated brine. The partially desalinated water may be suitable for non-potable applications or as a feed for membrane desalination. The concentrated brine from the FD could be used as a feed for the recovery of selected chemicals. This paper focuses on verifying the above-described concept of the freezing desalination of oilfield brine on a laboratory scale. The brine from a Polish oilfield located in the Carpathian Foredeep was used as a feed. Four freezing–thawing stages were applied to obtain low-salinity water, which subsequently was treated by reverse osmosis. The obtained permeate meets the criteria recommended for irrigation and livestock watering. The concentrated brine enriched with iodine (48 mg/L) and lithium (14 mg/L) was subjected to recovery tests. Ion exchange resin Diaion NSA100 allowed us to recover 58% of iodine. Lithium recovery using Mn- and Ti-based sorbents varies from 52 to 93%.

Novel Study on Cryogenic Distillation Process and Application by Using CHEMCAD Simulation.

The purpose of this study was to examine the cryogenic separation process used in air separation plants with the CHEMCAD simulation program. A preliminary analysis was carried out with the literature about the operation of the process. In light of the technical information, the simulation of the cryogenic separation process was utilized with the program. While no changes were analyzed in the basic parts of the process, the filtration of the air and separation from moisture and carbon dioxide were not included in the simulation. The simulation showed the three basic components of air, nitrogen, oxygen, and argon obtained as a product of the desired purity rather than a one-to-one demonstration of the applications in the industry. In addition, the low-temperature separation process of an air separation unit was studied to obtain high-purity products (99.49-99.99%) achieving the expected separation efficiency. As a result, the production of all three substances in desired purity was achieved successfully.

CO2 Capture and Enhanced Hydrogen Production Enabled by Low-Temperature Separation of PSA Tail Gas: A Detailed Exergy Analysis

Hydrogen from natural gas reforming can be produced efficiently with a high CO2 capture rate. This can be achieved through oxygen-blown autothermal reforming as the core technology, combined with pressure-swing adsorption for hydrogen purification and refrigeration-based tail gas separation for CO2 capture and recirculation of residual hydrogen, carbon monoxide, and methane. The low-temperature tail gas separation section is presented in detail. The main objective of the paper is to study and quantify the exergy efficiency of this separation process in detail. To achieve this, a detailed exergy analysis is conducted. The irreversibilities in 42 different process components are quantified. In order to provide transparent verification of the consistency of exergy calculations, the total irreversibility rate is calculated by two independent approaches: Through the bottom-up approach, all individual irreversibilities are added to obtain the total irreversibility rate. Through the top-down approach, the total irreversibility rate is calculated solely by the exergy flows crossing the control volume boundaries. The consistency is verified as the comparison of results obtained by the two methods shows a relative deviation of 4·10−7. The exergy efficiency of the CO2 capture process is calculated, based on two different definitions. Both methods give a baseline exergy efficiency of 58.38%, which indicates a high degree of exergy utilisation in the process.

Selection of Natural Gas Dehydration Process for Offshore Floating Production Storage and Offloading

Based on the oil and gas component data of an offshore gas field in West Africa, the steady‐state models of the triethylene glycol (TEG) dehydration process and the low‐temperature separation dehydration process are established. The adaptability of two kinds of processes to the disturbance of pressure, temperature, and flow of imported natural gas source is studied, and the sensitivity analysis is carried out. In addition, the investment cost and operating cost of the two types of processes are compared. The low temperature separation dehydration process is more adaptable to the disturbance of inlet gas source than the TEG dehydration process. The former is more expensive to build than the latter, but less expensive to run. The low temperature separation dehydration is preferred as the natural gas dehydration process which is more suitable for floating production storage and offloading.

Analysis of methods for modeling operating modes of compressor equipment that ensures the operation of field low-temperature separation units

Objective. A booster compressor station (BCS) is one of the key technological facilities necessary to ensure the effective operation of low-temperature separation technology for natural gas in field gas preparation systems for transportation. Ensuring promising operating modes of booster compressor stations with high efficiency is an urgent task. Method. One of the tools for solving this problem is mathematical modeling of the operating modes of centrifugal compressors (hereinafter - CPC), which are part of gas pumping units (GPU). The basis of the mathematical model is the gas dynamic characteristic (GDC) of the pulp and paper mill. The existing regulatory documentation presents simplified methods for modeling HDC, which are suitable for low-pressure pulp and paper mills with a pressure ratio of up to 1.5 and the number of compression stages of no more than three, but are not suitable for multi-stage high-pressure pulp and paper mills. Result. The results of a comparison of three methods of modeling the hydrodynamic characteristics (method of reduced characteristics, refined method of reduced characteristics, method of two-parameter approximation) of high-pressure pulp and paper mills are presented using the example of a pulp and paper mill with a pressure ratio of up to 2.0, intended for equipping a gas pumping unit as part of field booster compressor stations. An analysis and comparison of the obtained modeling results with actual data was carried out. Conclusion. When using the UMPH-2D modeling method, the smallest errors were obtained (no more than 2.0%), which, in turn, indicates its highest accuracy among the considered methods for recalculating the gas flow characteristics of high-pressure and multi-stage compressors.

Process optimization of osmotic membrane distillation for the extraction of valuable resources from water streams

The rising demand for sustainable wastewater management and high-value resource recovery is pressing industries involved in, e.g., textiles, metals, and food production, to adopt energy-efficient and flexible liquid separation methods. The current techniques often fall short in achieving zero liquid discharge and enhancing socio-economic growth sustainably. Osmotic membrane distillation (OMD) has emerged as a low-temperature separation process designed to concentrate valuable elements and substances in dilute feed streams. The efficacy of OMD hinges on the solvent’s migration from the feed to the draw stream through a hydrophobic membrane, driven by the vapor pressure difference induced by both temperature and concentration gradients. However, the intricate interplay of heat and mass processes steering this mechanism is not yet fully comprehended or accurately modeled. In this research, we conducted a combined theoretical and experimental study to explore the capabilities and thermodynamic limitations of OMD. Under diverse operating conditions, the experimental campaign aimed to corroborate our theoretical assertions. We derived a novel equation to govern water flux based on foundational principles and introduced a streamlined version for more straightforward application. Our findings spotlight complex transport-limiting and self-adjusting mechanisms linked with temperature and concentration polarization phenomena. Compared with traditional methods like membrane distillation and osmotic dilution, which are driven by solely temperature or concentration gradients, OMD may provide improved and flexible performance in target applications. For instance, we show that OMD—if properly optimized—can achieve water vapor fluxes 50% higher than osmotic dilution. Notably, OMD operation at reduced feed temperatures can lead to energy savings ranging between 5 and 95%, owing to the use of highly concentrated draw solutions. This study underscores the potential of OMD in real-world applications, such as concentrating lithium in wastewater streams. By enhancing our fundamental understanding of OMD’s potential and constraints, we aim to broaden its adoption as a pivotal liquid separation tool, with focus on sustainable resource recovery.

FEATURES OF NATURAL GAS DEMETHANIZATION PROCESS

Today, a significant part of the raw materials used in industry consists of natural gas. Thus, an important and urgent task for the further development of the industry is the development of more advanced processes aimed at natural gas treatment and processing of. Low temperature processes in gas processing are widespread due to the increasing demand for individual hydrocarbons and the growing demand for liquefied gases. Low temperature distillation remains the most important method for separating gas mixtures, especially when high throughput is required. The demethanization process is an industrially important example of such a process, which involves the interaction of separation, cooling and heat recovery systems.This article discusses a number of basic methods for low-temperature gas separation, such as condensation, rectification, absorption and separation, as well as the features of their application. Low-temperature separation is carried out in two stages in column-type apparatuses, the first of which demethanization is carried out with methane and C2+ fractions release. An overview of the demethanization process currently used for natural gas refining is given, and the key features of the demethanizer operation are described. The technological design of the process of low-temperature distillation, the design features of the installations are considered, a typical scheme of the demethanization process is given. Various technological schemes of demethanization proposed in patents are analyzed. A comparative analysis of the use of tray and packed contact devices and criteria for choosing a mass transfer column apparatus are given. The demethanization column arrangement is shown, the internal devices of the column, the feed input system, as well as the method of supplying heat to the demethanizer are described.

A novel method for layer separation in waste crystalline silicon PV modules via combined low-temperature and thermal treatment

With the significant growth in the production and installation of photovoltaic (PV) systems, the recycling of end-of-life PV modules has become a critical concern. Thermal treatment is a promising approach to decompose all the polymer and separate different layers rapidly. However, the combustion of the backsheet can lead to the release of hazardous fluorinated compounds. This paper proposes a novel method combining low-temperature and thermal treatment to separate different layers in PV modules. This method leverages the back metallization of solar cells for PV module separation, providing a fresh separation perspective. The focus lies on investigating a low-temperature separation process, and the separation interfaces are characterized using SEM and EDS, shedding light on the separation position and physical separation mechanisms. Subsequently, the effects of different freezing temperatures, freezing times, and different laminated parts were investigated, and the processing parameters were optimized. Compared to direct thermal treatment, the proposed process eliminates the generation of hazardous fluorides and mitigates mass losses caused by thermal treatment effectively. This research provides valuable insights into the green and sustainable resource recovery of waste PV modules.

Efficiency of gas preparation technology using a block drying plant

The object of research is the technology of gas drying using a mobile block installation. The task to ensure compliance of the composition of natural gas with the values of a number of basic characteristics before its supply to main pipelines has been solved. The results of a complex analysis of the gas preparation technology of the deposit, which is located in an agricultural area and is at a late stage of exploitation, are reported. It was established that in order to ensure the supply of conditioned gas to the system of main gas pipelines under the conditions of low gas pressures, the construction of gas treatment plants is required, first of all, for its drying. The method of ensuring gas quality considered in the current paper involves the use of a block-type gas drying installation as part of a low-temperature separation installation and a source of artificial cold. As the latter, it is envisaged to use a freon-refrigerating unit. The study shows that the proposed block gas drying units can be unified for different gas productivity and are characterized by relatively low capital and operating costs. The main advantages of the introduction of gas preparation block installations and the scheme of connecting the installation to the existing line are presented. Based on the results of the economic efficiency indicators, it was established that the use of a block gas drying unit is a profitable project with the value of the accumulated reduced free cash flow of almost 843 thousand conditional units; the investment payback period is 3 years. The results could be effectively used in the gas distribution sector, provided that the gas is extracted from a field close to exhaustion, which is characterized by low reservoir pressures

Modeling of a low-temperature gas treatment system

Objective. The main purpose of the work is: investigation of the effect of changes in technological parameters on the efficiency of the separation process and determination of optimal technological modes of operation of gas field X CNTS in the separation process.Method. The problem was solved in the KBC Petro-SIM computer program and the LTS model was built. To conduct the study, a model of the LTS was built in the KBC Petro-SIM computer program.Result. The results obtained with the help of it showed: with the current composition of the gas with a decrease in temperature for every 2oC, with other technological indicators being equal, the specific condensate yield increases in the range from 15 to 30%, and the lower the temperature, the higher this percentage. When the pressure on the throttle decreases by every 0.4 MPa, the condensate output increases, if the pressure drops below 1.8 MPa, the specific condensate output will begin to decrease, which is explained by the pressure drop below the maximum condensation line of the phase diagram. The change in gas flow within the design values did not affect the operation of low-temperature separation. At any available low temperature and high pressure at the inlet to the ILTS, the most optimal mode will be when the pressure after the throttle is maintained within 1.8 - 1.9 MPa. The maximum specific yield of gas condensate (48.21%) was obtained at a pressure at the inlet to the ILTS of 5.1 MPa, a temperature after the heat exchanger of minus 2oC and a pressure drop at the throttle of 3.05 MPa. As part of the numerical research, the following results were obtained: with an increase in the pressure at the inlet to the ILTC, the change in the specific output of the gas condensate is insignificant, but with this parameter it is possible to create a larger pressure drop on the throttle; with a decrease in the gas temperature at the outlet of the heat exchanger, the specific yield of the gas condensate will increase; with an increase in the pressure drop at the throttle, the specific output of the gas condensate increases until the pressure after the throttle reaches the range of values of 1.8 – 1.9 MPa. In this interval, the maximum specific condensate yield is achieved. With a further increase in the pressure drop on the throttle, the specific output of the gas condensate decreases. This is explained by the phenomenon of retrograde condensation, since the maximum condensation line is in the range of these pressures.Conclusion. Based on the results of the work, it was found that the developed software module can be used to solve the emerging series of problems. The results of the work show the suitability of the proposed method for practical purposes.

Arsenic extraction from copper concentrate using controlled oxidative roasting and filtration process

For more efficient treatment of arsenic-bearing copper concentrates, arsenic can be extracted in two steps: high-temperature filtration of dust and low-temperature separation of condensed arsenic oxide. The oxygen content in the roasting environment has an important effect on the residual arsenic content in the concentrate. When the oxygen content is high, the arsenate formed remains in the concentrate. When the oxygen content is low, the formation of arsenic sulphide can clog the filter cake residue. Roasting at 700 °C with an oxygen content of 4 vol.% results in the lowest residual arsenic content in the concentrate, from 11.8 to 0.34 wt.%. In the pilot experiment, the oxygen content was indirectly controlled by controlling the feed rate. The residual arsenic content is reduced to 0.48 wt.% and the purity of the recovered As2O3 reaches 99.17 wt.%. Based on the study of the mechanism of arsenic change with different oxygen contents, a new process of oxygen-controlled roasting is proposed and successfully applied in the pilot test, so that the residual arsenic content in copper concentrates is lower than the standard of arsenic content in imported minerals from China (0.5 wt.%).

Room-Temperature CO2 Hydrogenation to Methanol over Air-Stable hcp-PdMo Intermetallic Catalyst.

CO2 hydrogenation to methanol is one of the most promising routes to CO2 utilization. However, difficulty in CO2 activation at low temperature, catalyst stability, catalyst preparation, and product separation are obstacles to the realization of a practical hydrogenation process under mild conditions. Here, we report a PdMo intermetallic catalyst for low-temperature CO2 hydrogenation. This catalyst can be synthesized by the facile ammonolysis of an oxide precursor and exhibits excellent stability in air and the reaction atmosphere and significantly enhances the catalytic activity for CO2 hydrogenation to methanol and CO compared with a Pd catalyst. A turnover frequency of 0.15 h-1 was achieved for methanol synthesis at 0.9 MPa and 25 °C, which is comparable to or higher than that of the state-of-the-art heterogeneous catalysts under higher-pressure conditions (4-5 MPa).

Performance evaluation and model of spacesuit cooling by hydrophobic hollow fiber-membrane based water evaporation through pores

A comprehensive mathematical model is presented that accurately estimates and predicts failure modes through the computations of heat rejection, temperature drop and lumen side pressure drop of the hollow fiber (HF) membrane-based NASA Spacesuit Water Membrane Evaporator (SWME). The model is based on mass and energy balances in terms of the physical properties of water and membrane transport properties. The mass flux of water vapor through the pores is calculated based on Knudsen diffusion with a membrane structure parameter that accounts for effective mean pore diameter, porosity, thickness, and tortuosity. Lumen-side convective heat transfer coefficients are calculated from laminar flow boundary layer theory using the Nusselt correlation. Lumen side pressure drop is estimated using the Hagen-Poiseuille equation. The coupled ordinary differential equations for mass flow rate, water temperature and lumen side pressure are solved simultaneously with the equations for mass flux and convective heat transfer to determine overall heat rejection, water temperature and lumen side pressure drop. A sensitivity analysis is performed to quantify the effect of input variability on SWME response and identify critical failure modes. The analysis includes the potential effect of organic and/or inorganic contaminants and foulants, partial pore entry due to hydrophilization, and other unexpected operational failures such as bursting or fiber damage. The model can be applied to other hollow fiber membrane-based applications such as low temperature separation and concentration of valuable biomolecules from solution.

About rationale for the selection of the cooling capacity of the turbodetander unit in the process of gas preparation

In gas condensate fields, low-temperature separation process is mainly used for primary processing of gas. Cooling of well products in gas preparation systems is achieved by throttling them. As the reservoir pressure decrease, the amount of energy obtained decreases. This worsens the conditions for the preparation of gases. Therefore, raises a need to use additional energy sources. Analysis of the operating modes of gas treatment plants has shown that the energy obtained during the expansion of gas can be used rationally. Calculations have shown that the gas temperature at the outlet of turbodetander units during adiabatic expansion provides the required dew point for water and hydrocarbons. Keywords: gas; condensate; turbodetander; gas expansion; polytrophic; adiabatic; cold productivity; dew point.

A novel strategy for process optimization of a natural gas liquid recovery unit by replacing Joule–Thomson valve with supersonic separator

The natural gas liquid recovery is an important process in a gas plant to correct hydrocarbon dew point and earn profit. In this study, a natural gas liquid recovery unit operated based on the Joule–Thomson process was investigated and its performance was optimized. To improve the system performance, the plant configuration and intermediate pressure ratio were defined as the variables and maximization of the natural gas liquid recovery rate and maximization of exergy efficiency were defined as the objective functions. To improve the plant performance, the amount of natural gas liquid recovery rate should be increased. To achieve this goal, several scenarios for the intermediate pressure ratio and three new configurations were proposed for the investigated gas plant. In the proposed configurations, the supersonic separators with optimized structures were used instead of the Joule–Thomson process. It was observed that all three proposed configurations improved the natural gas liquid recovery rate compared to the existing configuration. For example, by installing two supersonic separators instead of second and third stage Joule–Thomson valve + low temperature separator, at the optimal operating condition, the natural gas liquid recovery rate increased about 390%. The influence of the intermediate pressure ratio on the phase envelope diagram, exergy efficiency, dew point depression and natural gas liquid recovery rate was also investigated. By comparing the influence of intermediate pressure ratio and modifying the plant configuration on the objective functions, it was observed that the system performance can be further improved by modifying the plant configuration.

Energy efficiencies and CO2 emissions associated with low-temperature separation technologies for the processing of formation fluid from the Achimov deposits

Three different technologies for the low-temperature separation (LTS) of gas condensate from the Achimov deposits in the Russian Urengoyskoe gas and condensate field were assessed using exergy analyses. The options examined included turbo-expansion and ejection. Thermomechanical exergy values were calculated for material streams and exergy losses and efficiencies were estimated for dedicated equipment used in the LTS. The lowest exergy loss of 4221.2 kW was obtained using turbo-expansion and electricity cogeneration. The carbon release associated with each scenario was calculated while considering different production rates, technological parameters and natural decreases in wellhead pressure. The integral carbon footprint after 40 years of LTS operation was estimated for all cases. A classical ejector-based LTS scheme was shown to produce 1200 t of CO2 emissions over 40 years of operation. This same scheme combined with a turboexpander and electricity generator produced 59% less CO2 in the same period. An expansion-cogeneration LTS scheme was found to be the most effective and ecologically friendly among the various options based on this analysis.

Features of Gas Flow in the Axial Stage of a Turbine with an Adjustable Nozzle Vane Assembly

The method of changing the gas flow rate through the turbine by adjusting (turning) the nozzle vanes has been known as the most economical one for more than 50 years. It is most widely used in transport gas turbines and internal combustion engine pressurization units. Recently, many articles have appeared in the technical literature on the advisability of using adjustable nozzle vane assemblies (ANVA) in advanced aircraft engines, power generating units, and in turbo-expander units of natural gas preparation and low-temperature separation systems. In all cases of using ANVAs, their developers are attracted by the possibility of economical and reliable provision of variable operating modes of installations. The article shows by calculation that a decrease in the stage efficiency due to the presence of end gaps in the ANVA, related to the flow-over the nozzle vane ends on the profile pressure side to the suction side and subsequent interaction with the main flow through the interblade channel, can be so significant, especially with low-height vanes, that it can lead to vanishing the advantages of this flowrate changing method. Design measures for tightening the gaps in the form of peripheral and root cylindrical bosses at the profile ends, which eliminate overflows in the vane end major part and partially screening the gap are proposed and studied. A favorable effect of the proposed measures on the losses in the ANVA and in the turbine stage has been confirmed.