Natural Gas Dehydration Research Articles

Effects of energy conversion under shock wave on the effective liquefaction efficiency in the nozzle during natural gas dehydration

Shock wave induces boundary layer separation when back pressure is set at the nozzle outlet. However, the effects of the complex flow characteristics on energy conversion mechanisms and the non-equilibrium phase transitions are not fully understood. This study developed a physical model for the homogeneous condensation of water vapour. The accuracy of the model was verified through flow and condensation experiments. The findings indicate that vortex clusters enhance energy transfer near the shear layer when the boundary layer separates. The separation point represents the region with the highest entropy generation. The peak entropy value near the wall with an increase of 7.07% as back pressure decreases from 0.75 to 0.1 MPa. The significant discovery that shock wave has minimal influence on droplet evaporation when the back pressure is 0.15 MPa, and the liquefaction efficiency at the outlet peaks at 79.42%. Moreover, over-expansion of the gas mixture at the back pressure of 0.15 MPa can lower the total pressure loss from 72.89% to 62.96% compared with the back pressure of 0.25 MPa. These findings provide an effective theoretical basis for determining optimal back pressures to reduce total pressure loss and enhance the liquefaction efficiency of the nozzle.

Effect of K/Na ratio on adsorption of sweetened gas in dehydration packed bed adsorber: A Monte Carlo simulation study of single and multicomponent gas mixture

The input feed of natural gas dehydration units often contains significant quantities of mercaptan. To effectively separate water from the sweet gas stream, it is crucial to select an appropriate molecular sieve. Mercaptan adsorption can cause issues in later stages of the process. In this research, the Grand Canonical Monte Carlo (GCMC) method was employed to investigate the adsorption behavior of methane, ethane, water, methyl mercaptan, and carbonyl sulfide as both single and multicomponent gas mixtures on LTA zeolite with varying K/Na ratios. The obtained data were modeled using the Langmuir and Sips models, with the Sips model exhibiting better agreement with the simulation results. Gas adsorption simulations were conducted across temperatures of 323 K, 313 K, 303 K, and 333 K, a pressure range of 1–70 bar. The findings indicate that increasing temperature diminishes adsorption on LTA zeolite, while increasing pressure has an incremental effect on adsorption. Adsorption studies were performed for both wet and dry gas mixtures. A rise in the number of potassium ions within the zeolite structure resulted in decreased component adsorption, potentially due to the reduction in zeolite cavity size. The results emphasize that the sodium-to-potassium ratio plays a crucial role in mercaptan adsorption or depletion within the packed bed tower. For a gas mixture, it is not recommended to utilize LTA zeolite with a potassium content lower than 55% for gas adsorption due to its propensity to adsorb mercaptan.

Use of a New Gas Ejector for a TEG/TREG Natural Gas Dehydration System

Glycol dehydration is the most common and economical water removal method from natural gas streams. However, dehydration of low-pressure natural gas requires the use of higher concentration TEG (Triethylene Glycol) or TREG (Tetraethylene Glycol). This article describes how the ejector can be used to create a vacuum in the glycol reboiler to achieve a higher concentration of L-TEG/L-TREG (Lean Triethylene Glycol/Lean Tetraethylene Glycol). Process simulations of the gas dehydration and glycol regeneration units were carried out in Chemcad software. Simulations were performed for decreasing values of gas working pressure and TEG/TREG regeneration pressures. Dehydration unit efficiency was tested for two values of glycol flow rates. Ejector performance simulations were executed for two positions in the process flow line. The influence of pressure reduction in the glycol reboiler on the concentration of L-TEG/L-TREG and the water dewpoint of natural gas has to be found significant. The increase in glycol flow rate has a greater impact on TREG than for TEG. Creating a vacuum with an ejector in a TEG/TREG reboiler has been shown to be an attractive way to improve the efficiency of natural gas dehydration. The position of the ejector at the end of the vapor flow line, downstream to the condensed water separator, allows for a significant reduction in motive gas consumption.

Study on water and gas permeation characteristics with ZIF-8 mixed matrix membranes

Abstract The membrane separation process lacks intrinsic permeation characteristics to compete with other separation technologies like adsorption, sedimentation, coagulation, skimming, and distillation. A mixed matrix membrane (MMM) is one of the strategies to improve the separation characteristics with embedded nanofillers particles. Zeolite imidazolate framework (ZIF) has a new subclass of inorganic–organic hybrid materials that are being introduced as new fillers for incorporation into the polymer matrix for various applications such as oily wastewater separation, wastewater treatment, natural gas dehydration, landfill gas upgrading, and mixed gas separation. In this experimental work, a metal-organic framework called ZIF-8 was synthesized and used as a filler for modification of MMMs and characterized with FTIR and SEM. ZIF-8 nanoparticles up to 5 wt% loading were added to PSF casting solution then the permeation characteristics of MMMs showed an improved result like the pure water flux of the modified membrane at 2.5 bar was increased up to 456.38 L/m2h. In the case of pure gas separation, at 5 wt% ZIF-8 loading in PSF, the pure gas CO2 permeability at 9 bar pressure had increased to 10.54 barrer.

A simulation study of reducing carbon dioxide and hydrogen sulfide adsorption in dehydration beds

In natural gas dehydration units, a problem that may arise is the increased concentration of carbon dioxide and hydrogen sulfide in their feed. During the adsorption stage, these gases are adsorbed along with water by the dehydration bed. During the regeneration stage, these adsorbed gases are desorbed from the bed. Their presence along with water and high temperatures causes the equipment and pipes in the regeneration path to corrode. Therefore, minimizing the adsorption of these gases in dehydration beds is imperative. Based on simulations of Aspen Adsorption, three solutions have been described and investigated in this article. The first solution is using 3 A adsorbent which has a lower adsorption capacity for carbon dioxide and hydrogen sulfide than other adsorbents like 4 A. But this adsorbent also has a lower adsorption capacity for water, so the first solution needs more cycles for the gas dehydration process. This reduces the adsorbent lifetime. Increasing the duration of the adsorption stage is the second solution. This solution has little effect and cannot solve the problem. The third solution is layering the dehydration bed with different adsorbents. This solution can reduce carbon dioxide and hydrogen sulfide adsorption by 48.7% and 49.9%, respectively, when 3 m of 3 A adsorbents are used at the bottom and 3.5 m of 4 A adsorbents are used at the top of the bed.

The production of zeolite-containing adsorbents using various kaolins for efficient dehydration and cleaning of natural gas

The paper explores the possibility of using KZhV, MP KAH, KCh-2 and KR-2 kaolins produced in Russia as a temporary binder for the production of granulated zeolite NаX, which has high crystallinity and phase purity and a hierarchical pore structure. This zeolite serves as the adsorbent for efficient dehydration of natural and casing-head gases and their cleaning to remove H2S. It was found that KZhV and MP KAH kaolins do not require additional treatments for the production of the indicated adsorbent, whereas KCh-2 and KR-2 kaolins should be additionally dispersed.

Joule-Thomson effect and flow behavior for energy-efficient dehydration of high-pressure natural gas in supersonic separator

The supersonic separator liquefies and removes water vapor of natural gas by using the pressure energy and cold energy recycles. To analyze the energy efficiency of the supersonic separation process, a novel CFD model combined with the Eulerian-Lagrangian model and the Eulerian wall film model was established for high-pressure conditions with Redlich-Kwong real gas model. The accuracy of the present model was validated based on the existing experimental data. The Joule-Thomson effect, entropy generation, and flow behavior were studied coupling with processes of swirl and phase change. The results showed that inlet pressure influences flow characteristics, entropy generation, and optimum parameters of the foreign droplets. As the inlet pressure rises from 6 bar to 120 bar, the centrifugal acceleration increases by 27.8%, the temperature drop caused by the Joule-Thomson effect increases from −0.1 K to 28.5 K, and the entropy generation decreases by 14.69% from 615.5 J kg−1 K−1 to 525.1 J kg−1 K−1. For the heterogeneous condensation, the optimum diameter of inlet foreign droplets increases by 100% from 1.7 μm to 3.4 μm, and the concentration increases by 177.8% from 0.0009 kg s−1 to 0.0025 kg s−1, which can maximize the dehydration efficiency to 78.9%.

Topological Properties and Entropy Calculations of Aluminophosphates

Topological indices are invariant numerical quantities of a graph that give facts about the structure of graphs and are found to be very helpful in predicting the physical properties of aluminophosphates. The characteristics of aluminophosphates are similar to the characteristics of zeolites. Two examples of current applications are natural gas dehydration and humidity sensors. Researchers in chemistry and materials science are synthesizing new frameworks. There are many layers and holes in these substances. The technique used to predict natural behaviors among the physicochemical characteristics of chemical molecules in their basic network is known as topological indices. This study explains the vertex version of distance-based topological indices, the entropy of topological indices and their numerical analysis.

Synthesis of PET-Magnesium Oxide-Chitosan Nanocomposite Membranes for the Dehydration of Natural Gas

Flat thin-film magnesium oxide-chitosan nanocomposite membranes were synthesized with polyethylene terephthalate (PET) and employed for natural gas dehydration. The water vapor permeation was most pronounced with a nanocomposite membrane doped with 0.9 g MgO nanoparticles (NP) as a result of a significant upsurge in the permeability of water vapor in the membrane (0.87). With the increase in MgO NP, large macro-voids are created, substratum pore size, and thickness together with the water vapor permeation were upsurged. The dehydration of natural gas performance of magnesium oxide-chitosan nanocomposite membranes synthesized with PET was enhanced with the increase in MgO NP embedded in the membrane. Though water vapor permeation was restricted by the polyester non-woven material used as a support for the nano composite membranes, as the three membranes did not reach the permeation coefficient of 1. However, the permeation coefficient increased with an increased MgO NP, with three mambrane samples (M1, M2 and M3) having permeation coefficient of 0.763, 0.77 and 0.87 respectively. The gas reduced with an increase MgO NP, with M1, M2 and M3 having 3.46×10−2, 3.17×10−2 and 3.88×10−3 kg/m3 respectively. From the adsorption study, the discrepancy observed between CH4 and vapor with isotherm models was ascribed to the different adsorption behavior of CH4 and vapor on the membrane-active area. The cost of making the membrane cannot be considered as a terminal criterion because most of the cost-effective option is not always the optimum one. The membranes confirmed their suitability for the dehydration of natural gas.

Modeling and simulation of an industrial adsorption process of dehydration of natural gas in 4A molecular sieves: Effect of adsorbent aging

Adsorption in molecular sieves is the number one choice for the dehydration of natural gas in offshore platforms. Many phenomenological and mathematical approaches have been used to describe this unit operation. However, the effect of aging on the operation performance, and consequently the adequacy of these models to describe operational field conditions, has been seldom assessed. This work presents the simulation of an industrial unit of natural gas dehydration with 4A molecular sieves in different cycle numbers using a phenomenological model. First, the most adequate equilibrium isotherm to describe experimental data of pure compound adsorption (viz., the dual-site Langmuir isotherm) was determined. Second, momentum, mass, and energy transfer equations were implemented, and the modeling of literature adsorption data was used to verify the adequacy of the developed equations. Finally, an industrial dehydration unit was modeled using the same approach, and calculated breakthrough times were compared to field data. In conclusion, the premature aging of molecular sieves in industrial operation appears as a defining factor in equipment performance.

Electric field-facilitated dehumidification of natural gas through nanochannels

The existence of water in natural gas causes serious congestion and acid corrosion problems during exploitation and transport. Water must be removed. Here, we performed molecular dynamics simulations to investigate the effect of electric fields on natural gas dehydration through nanochannels. When the electric field is applied, only water molecules occupy the nanochannel in place of C1-C3 paraffins, acid gases and N2 molecules. The dominant mechanism is that the electric field and confinement of channels induce the ordered arrangements of water molecules, forming stable ice-like structures and restricting the entry of other components. Once removing the electric field, the water molecules will be released from the channel due to the relatively low water-channel interaction. Importantly, hydrophilic and hydrophobic channels both exhibit effective separation for water. The separation selectivity is not strictly dependent on channel diameters, avoiding the trade-off effect between adsorption capacity and selectivity based on the size sieving mechanism.

Modelling and Optimization of Natural Gas Dehydration System Using Triethylene Glycol

The problem with water vapour in natural gas stream, threaten the process facilities if the dew point temperature is not properly managed. Hydrate formation is inevitable at temperatures below the dew point. It becomes very important to reduce the water content in the gas stream to below or within the acceptable limit of 6-7lb/MMSCFD. There are many methods that can be used to reduce the water content in the natural gas stream of which adsorption and absorption are one of them, in this work absorption was employed. Natural gas composition analysis was carried out and Industrial data of a natural gas dehydrating plant was obtained and simulated using Aspen Hysys software. Process conditions of 72.6 barg and 38oC and gas flow rate of 10 lb/mmscfd, were inputted into the software and simulated. Different Triethylene Glycol (TEG) flow rates were used for the simulation. Results obtained show that for a TEG of 3.5m3/h (0.1480 kgmole/h), the water content in the dry gas was 6.6333 lb/MMSCF which is within the acceptable water limit and when the TEG flow rate was increased up to 15.7m3/h (0.6640kgmole/h) the water content in the dry gas was further reduced to 1.0930 lb/MMSCF from an initial value of 19.84lb/MMSCF. For the first simulation, a reboiled still column was used and 88% of TEG was recovered and 12% was lost with water vapour at the top of the still column but after the second simulation where a recovery separator, still column with reboiler and reflux condenser were used, 99.98% of the TEG was recovered which was compared with other methods in the industry. This implies that for a higher purity of TEG to be achieved, a recovery separator and a reflux still column needs to be used because increasing the reflux reduces glycol loss. The sum of the total capital cost and glycol loss per year is 3,873,590 USD for simulation 1, while there is a negligible TEG loss in simulation 2 so the total capital cost is 3,863,380 USD and the two simulations have the same energy consumption of 114,300KJ/h.

Impact of ethylene glycol on ions influencing corrosion in pores between iron oxide and calcium carbonate

ABSTRACT Injection wells for carbon capture and storage are made of iron casings supported by cement. Cement can transform into calcium carbonate and iron into iron oxide. Thus, these wells are subject to corrosion. Monoethylene glycol (MEG), used for hydrate prevention and natural gas dehydration, can adsorb both to calcium carbonate and iron oxide. As a first step towards an atomistic understanding of effects caused by adsorbed MEG, molecular dynamics simulations were applied to estimate free energy changes to hydronium and bicarbonate as MEG was adsorbed to the surface. We found that the global free energy minimum of both hydronium and bicarbonate was moved closer to the surfaces, due to adsorbed MEG, which may be caused by MEG replacing water molecules within the first water layers. This could have an effect on chemical reactions involving hydronium and bicarbonate. Minima in the free energy profiles other than the global one was found to originate from adsorbed water combined with interactions from the surfaces.

High sour natural gas dehydration treatment through low temperature technique: Process simulation, modeling and optimization

Among the various fossil fuels, natural gas is a clean fuel because it has a less adverse impact on the environment compared to other energy sources. Natural gas emits less hazardous gases and less CO2 upon burning. Water, CO2, N2, H2S, and other contaminants could be present in raw natural gas, depending on its geographic location. The main issue among these contaminants is CO2, which decreases the calorific value of natural gas and corrodes pipes and process equipment. Absorption, adsorption, membrane separation, and cryogenic separation are the four main CO2 separation technologies. Cryogenic technologies for natural gas purification are environmentally friendly because they involve physical separation, and no harmful chemicals are required. Although cryogenic is an attractive alternative, it has some process limitations. The water must be removed before cryogenic separation because it can create piping blockage due to ice formation. The main goal is to remove water from natural gas at optimized conditions. The absorption technique employing triethylene glycol (TEG) as a solvent is the most widely used technology for dehydrating natural gas. Water extracts from natural gas as it passes over TEG, which acts as a dehydrating agent. The harmful effects of TEG on the environment are this technology's principal drawback. The current work investigates the dehydration of natural gas utilizing a low-temperature packed bed which could be an attractive alternative due to the absence of harmful chemicals. A thorough simulation analysis was carried out to learn more about the impact of the process parameter on the separation. The results showed that the pressure increase from 1 to 5 bar resulted in water removal from 25.4 to 83.7%. The optimum temperature and pressure for maximal water removal from natural gas were also determined. The maximum water was removed at 34 bar and −7.3 °C.

A reduced order model for triethylene glycol natural gas dehydration system

In natural gas processing plants, glycol dehydration is commonly used to remove water from the gas streams, to avoid pipeline blockage and equipment breakdown due to hydrates formation. This paper proposed a reduced order model developed based on integrated simulation-optimization approach for the glycol dehydration system, with the aim to minimize its operating cost while satisfying pipeline quality specifications. Steady-state process simulation software was used to identify important operating parameters for the glycol dehydration process; these include reboiler temperature and flow ratio of the regeneration column, and solvent flowrate. The identified parameters are built into a non-linear programming model, which was developed as a reduced order model for ease of implementation in the plant. The studied parameters are reboiler duties, hot oil, condenser, and pump, as well as TEG make-up flow rate and CO2 equivalent (CO2-eq) emissions. The Pareto Front is developed to identify the minimum operating cost at different levels of water dew point specification. The work has resulted in the annual savings of more than 34.6%.

Parameter screening and optimized gaussian process for water dew point prediction of natural gas dehydration unit

Petrochemical equipment is characterized by continuity, large scale, complexity of processes, and critical operation conditions. Based on auto-collected monitoring parameters, online prediction of critical process parameters can be used to maintain high reliability of petrochemical equipment, which is generally unpractical due to interference parameters and the difficulty in establishing prediction models. In this paper, a process parameter online prediction method for petrochemical equipment is proposed. Firstly, sensitive parameters are selected applying gradient boosting decision tree (GBDT). Then optimized Gaussian process (GP) is utilized to develop a mapping model in order to inference process parameter from auto-collected parameters. Natural gas water dew point online prediction method for triethylene glycol (TEG) dehydration unit is investigated. The effectiveness of the proposed method is verified on production data of a natural gas dehydration station. The method proposed provides a promising solution for process parameter prediction for petrochemical processes as well as other similar scenarios.

Recovery of Methanol during Natural Gas Dehydration Using Polymeric Membranes: Modeling of the Process.

A significant proportion of natural gas (NG) is produced in cold climates, where conditions are relevant to the formation of gas hydrates in raw gas stream. Methanol is often used as an effective inhibitor of hydrate formation. Further conditioning of NG includes dehydration, and the most common process of water vapor removal from NG is absorption. Absorption also provides removal of methanol vapors, which allows it reuse. The membrane method of natural gas dehydration is considered as a promising alternative; however, the study of methanol recovery by the membrane method, simultaneously to the dehydration of NG, has not been carried out previously. In addition, data on methanol vapor transfer in gas separation polymer membranes are almost absent in the literature. This paper evaluates the permeability coefficients of methanol vapors for several polymer materials, which are applied to the production of industrial membranes (PPO, PSf, CA). Mathematical modeling of the membrane process of NG dehydration with simultaneous recovery of methanol was performed. The dependencies of membrane area, methanol recovery and energy consumption for methane recycling and recompression on the process parameters are calculated. Obtained data show that the recovery of methanol during membrane dehydration of NG varies in the range 57-95%. The lowest values of membrane area and specific energy consumption were found for PPO based membrane.

Investigation of natural gas dehydration process using triethylene glycol (TEG) based on statistical approach

Investigation of natural gas dehydration process using triethylene glycol (TEG) based on statistical approach

Multicomponent vapor-liquid equilibrium measurements and modeling of triethylene glycol, water, and natural gas mixtures at 6.0, 9.0 and 12.5 MPa

Triethylene glycol (TEG) is commonly used for natural gas dehydration, and with subsea processing facilities on the rise, an increasing interest is being shown in complex phase equilibria involving petroleum fluids and polar compounds. In this study, examples of such phase equilibria have been studied. New measurements for multicomponent vapor-liquid equilibrium (VLE) of TEG/Water/Natural Gas systems have been performed at pressures ranging from 6.0 MPa to 12.5 MPa and temperatures in the range 15 °C to 40 °C. Two types of natural gas, a Synthetic Gas (xCH4=0.62) and a Real Gas (xCH4=0.92), were mixed with an aqueous TEG solution, with TEG weight percentages ranging from 95 wt.% to 99 wt.%. Glycol in gas (y1), water in gas (y2), and gas solubility in liquid (xNG) were measured with relative experimental uncertainties below 32%. Since the systems are highly associating, the Cubic-Plus-Association (CPA) equation of state (EoS) was selected to model their phase behavior . Different association schemes (4C, 4F, 5F, 6F and 5C) were tested for TEG, and the classical 4C scheme is shown to perform best. The CPA EoS performed in general terms well, considering the number of components in the systems, the associated complexities, and high measurement uncertainty for such low concentrations (<1 ppm) in the gas phase. Furthermore, the content of N2, CO2, CH4 and ethane were modelled in the liquid phase at various conditions.

Multi-objective particle swarm optimization of industrial natural gas dehydration process

Multi-objective particle swarm optimization of industrial natural gas dehydration process