Monoethylene Glycol Regeneration Research Articles

Electrodialysis Membrane Technology applied to MEG reclamation – a case study

At Beach Energy’s Otway Gas Plant (OGP) the mono-ethylene glycol (MEG) system salt concentration increased significantly following the commissioning of new subsea horizontally completed wells. Therefore, to de-risk future developments, which are anticipated to include similar wells, a salt removal strategy was implemented. The use of MEG for gas hydrate suppression in wet-raw gas subsea or onshore production pipelines is common across the oil and gas industry, with the MEG recycled using well-proven regeneration and/or reclamation technologies. The MEG extracts water that can contain residual salt and minerals, which over time accumulate in the MEG and can lead to several operational issues, including severe fouling in the MEG regeneration plant, production line blockages and production pipeline integrity concerns, such as accelerated corrosion. MEG reclamation is used to minimise salt accumulation and to date, the dominant technologies employed have been vacuum distillation or flash vaporisation. However, since early 2022, electrodialysis (ED) membrane technology has been deployed at the OGP in an effort to find a more cost-effective solution. The technology is proving a viable alternative to a traditional vacuum distillation reclaiming–regeneration process with energy savings of 17–28% for a hybrid ED-Regeneration process with significantly lower capital cost. This paper details the technical and operational challenges overcome to implement the ED reclamation technology in an industry with more stringent regulatory requirements when compared to typical ED applications (e.g. within the water treatment, pharmaceutical, and food and beverage industries), as well as present the main system performance outcomes following 6 months of operation.

Influence of Injecting Some Chemicals on MEG Inhibition Performance for Less Recycled MEG

Monoethylene glycol (MEG) is often injected into submarine transportation pipelines, from offshore oil and gas platforms, to suppress hydrate formation. MEG can be recovered, for recycling, through a MEG regeneration plant, onshore. The costs related to hydrate inhibition operations are significant; thus, introducing new methods of reducing the volumes of MEG required by the system potentially will provide significant economic benefits for the operation. The objectives of this study were to evaluate the influence of ammonium hydroxide (NH4OH), sodium hydroxide (NaOH), potassium hydroxide (KOH), and methyl diethanolamine (MDEA) on inhibition performance when separately combined with a MEG 20 wt % solution in a methane gas system. The pH levels applied were 10.96, 10.84, 10.62, and 10.07 for NaOH, KOH, NH4OH, and MDEA, respectively. The results indicated that these compounds suppressed the hydrate dissociation temperatures, to different degrees, when compared with a normal MEG 20 wt % solution. The temperatures were reduced by an average, across the range of pressures, of 0.72, 0.78, and 0.94 °C in the case of MDEA, KOH, and NaOH, respectively. However, when combined with NH4OH, the reduction in dissociation temperature was even more significant, averaging 1.68 °C. An economical assessment of the benefits of reducing the inhibition temperature by this amount, through the combination with NH4OH, indicated an operational cost saving of about 17% within the MEG regeneration process. This level of cost reduction will be of significant interest to the offshore gas-producing industry.

Effect of electrolyte solubility and column inclination on the performance of monoethylene glycol regeneration process

AbstractIn this study, the solubilities of potassium‐chloride (KCl) in aqueous monoethylene glycol (MEG) solution and the vapour pressure of aqueous MEG solution containing KCl were investigated. A thermodynamic model was modified based on the data obtained to predict the solubilities of KCl, which was then applied to optimize the MEG regeneration process that is widely used in offshore gas fields. The solubility of KCl in the aqueous MEG solution decreased with an increase in MEG concentration and a decrease in temperature. The presence of KCl in aqueous MEG solution decreased the vapour pressure, thus increasing the boiling temperature at the corresponding pressure. A thermodynamic model based on the electrolyte non‐random two‐liquid (NRTL) coupled with the Redlich–Kwong (RK) equation of state was employed by modifying the binary interaction parameters using the experimental data. The modified model predicted the solubilities of KCl and the vapour pressure of aqueous MEG solutions, which were in good agreement with the experimental data. Moreover, the distillation column in pilot‐scale MEG regeneration was inclined to simulate the movement of the offshore platform, showing decreasing MEG concentration, possibly due to the distribution issues inside the column.

Regeneration and Reclamation of Mono-Ethylene Glycol (MEG) Used as a Hydrate Inhibitor: A Review

The use of Mono-Ethylene Glycol (MEG) as a hydrate inhibitor in wet gas pipelines is increasingly becoming widespread, especially in deep-water long-tie back pipelines where the use of low dosage hydrate inhibitor (LDHI) is not practical. MEG is a commonly used thermodynamic hydrate inhibitor (THI), and it prevents hydrate formation by lowering hydrate formation temperature. One significant advantage of MEG over other THIs is that MEG can be regenerated and reused, which minimises the cost of chemicals as large volumes of THIs are usually required. Over the years, significant research advances have been made in MEG recovery and the MEG Recovery Unit (MRU) design. This paper presents a comprehensive review of the evolution of MEG regeneration systems over the years and introduces recent developments, particularly on energy conservation. The entire MEG recycle and regeneration process is reviewed as well as the various sections and their functions. The different MRU configuration are discussed and factors that affect the performance of the MRU as well as Corrosion and corrosion mitigation in the MRU. This review shows that there are a number of new improvements in the MRU application that are yet to be fully explored as well as some technical challenges that are yet to be fully understood.

Density and Electrical Conductivity for Aqueous Mixtures of Monoethylene Glycol and Sodium Chloride: Experimental Data and Data-Driven Modeling for Composition Determination

Monoethylene glycol (MEG) is a gas hydrate inhibitor widely applied for natural gas flow assurance. A series of density and electrical conductivity measurements of water + MEG + NaCl mixtures are reported, allowing the supervision of the MEG regeneration unit. Density (509 data points) and electrical conductivity (212 data points) measurements were performed in wide ranges of temperature, T = 278.15−363.15 K, and concentration of solvents and NaCl up to almost saturation. The theory of solutions was applied for density description using excess volume, which was correlated with the Redlich−Kister equation. The resulting absolute and relative mean deviations are 0.00127 g·cm−3 and 0.12%, indicating accurate representation. A semi- empirical correlation with 15 adjustable parameters was considered for electrical conductivity of water + MEG + NaCl mixtures. The obtained absolute and relative mean deviations are 1.49 mS·cm−1 and 5.70%. The properties functions presented an approximately orthogonal behavior to each other, allowing the determination of mixture composition from experimental density and electrical conductivity data. The Matlab environment was found to be robust in solving the nonlinear system of two equations with constraints. The proposed methodology was extensively tested, and deviations less than 0.0060 and 0.0011 in solvents and NaCl mass fractions were obtained, respectively, demonstrating the required accuracy for industrial application

Salt Solubility and Saturated Electrical Conductivity Data for Water + Monoethylene Glycol + NaCl in a Wide Temperature Range

Monoethylene glycol (MEG) is used to prevent hydrate formation in subsea pipelines of natural gas production. MEG is recovered at an offshore regeneration unit. Sodium chloride is the predominant salt in the water−MEG streams. Thus, knowledge of NaCl solubilities in the process conditions is relevant for the design and operation of a MEG regeneration unit. Six isotherms of NaCl solubility were measured (76 data points) from T = (293.15 to 403.15) K in the whole solvent concentration range. The analytical method for salt solubility was based on the reproducibility of the concentration of two successive samples. Density measurements were accurately applied for these analyses. The temperature dependence on NaCl solubility is relatively weak. A reverse behavior with increasing temperature was observed for MEG contents higher than 90 wt %. Salt solubilities were successfully correlated with Redlich−Kister expansion (AADwNaCl = 0.0006 and ΔwNaCl = 0.47%). Electrical conductivity of NaCl - saturated solutions were measured (44 data points) at T = (293.15 to 363.15) K and correlated with a semiempirical model. A large difference in electrical conductivity for the two solvents was observed. The correlation adequately represented the data set (AADκ = 5.67 mS·cm−1 and Δκ = 5.94%). NaCl solubilities and electrical conductivities were accurately determined and are useful for the MEG regeneration process

Performance Degradation of the Monoethylene Glycol Regeneration Process in the Presence of Electrolytes: Pilot-Scale Experiments and Dynamic Simulations

Safe production of natural gas from offshore gas fields would rely on the injection and regeneration of monoethylene glycol (MEG) to inhibit hydrate formation as well as corrosion and scale issues ...

Isobaric Vapor–Liquid Equilibrium Measurements and Modeling of Water + Monoethylene Glycol + NaCl Mixtures

Vapor−liquid equilibrium (VLE) data for aqueous systems in the presence of electrolytes have many industrial applications. VLE data for water + monoethylene glycol (MEG) mixtures in the presence of sodium chloride at low pressures are important to describe the effects of composition, temperature, and pressure on a MEG (gas hydrate inhibitor) regeneration unit. A modified version of the Othmer ebulliometer was applied to measure reliable VLE data for water + MEG + NaCl at 101.325, 65, and 35 kPa. Binary systems (water + MEG and MEG + NaCl) were also experimentally studied. Vapor pressures for water and MEG were determined and compared with the selected literature data via Antoine correlation. The electrolyte nonrandom two-liquid and universal quasi-chemical activity coefficient models were successfully parameterized to describe the VLE behavior for water + MEG + NaCl systems. Thermodynamic consistence of the data sets was also checked. Interaction parameter estimation followed a systematic strategy: (1) water−MEG, (2) water−NaCl, and finally (3) MEG−NaCl with the experimental data of MEG + NaCl and ternary data. MEG + NaCl solutions presented an inverted colligative property, that is, the addition of salt decreases the boiling point. VLE data indicated that water separation is less efficient due to the addition of salt. The parameterized models allow an evaluation of the MEG regeneration process as a function of temperature, pressure, and composition

Low‐voltage and ion‐free‐reverse‐migration electrically regenerated mixed‐bed ion exchange for MEG desalination

AbstractAn improved electrical regeneration method of ion exchange was proposed to enhance the feasibility of applying ion exchange for mono‐ethylene glycol (MEG) desalination and simplify the existing MEG regeneration process in deepwater gas fields. Compared with the latest electrical regeneration process named membrane‐free electrodeionization (MFEDI), this method required lower voltage, did not consume high purity water, and eliminated ion backward migration in principle. These improvements were achieved by changing the electric field direction and the flow direction from parallel in MFEDI to perpendicular during ion exchange regeneration step. In this work, a pair of commercial ruthenium oxide‐coated titanium electrodes was installed on both sides of the cuboid experimental setup. The mixed resins consisting of strong‐base and weak‐acid resins were filled between the electrodes. In water flow and direct current electric field, the resins were regenerated successfully. The feasibility of efficient regeneration with high conductivity feed water (3–200 μS/cm) was verified. After regeneration of the resin bed for 1 h at a voltage lower than 73 V, 33.83% of NaCl in 5.16 bed volume (BV) simulated rich MEG liquid was removed. After 15 cycles of repeated operation, the performance of the resins remained stable. These results provide the possibility to reclaim MEG in deepwater gas fields through a simpler method.

Evaluation of reboiler temperature retention time on MEG degradation products at varying MEG concentrations

Mono ethylene glycol (MEG) has been used as a thermodynamic hydrate inhibitor in the gas industry. Due to its high usage, recoverability and environmental impact, MEG is regenerated instead of releasing to the environment. During the regeneration (distillation) process, MEG is exposed to higher temperatures in the reboiler to remove surplus water. When exposed to high temperatures, MEG thermal degradation process can occur due to dissociation to organic acids including glycolic, acetic and formic acids. A batch distillation system was utilised in total reflux mode at different reboiler temperatures retention times for up to 18 h in a span of 3 h and MEG concentrations of 80.8, 70.3, 63.1, 51.0 and 40.2 vol percentage (vol %) with corresponding reboiler testing temperatures of 118.0, 113.2, 108.8, 104.2 and 102.5 °C, respectively. The objective of this experimental work focuses on determining the MEG degradation products i.e. organic acids, accumulation in the MEG regeneration system. The degradation products were analysed using Ion Chromatography (IC) technique at the Curtin Corrosion Centre (CCC) laboratory, Perth, Western Australia.The experimental results indicate that there is an increasing trend of the MEG degradation products at higher boiling point temperatures for higher MEG concentrations in comparison to the lower MEG concentrations. Moreover, organic acids accumulation in the reboiler was evident at longer reboiler retention time durations of 18 h. The findings of this study conclude that it is preferable to operate the reboiler at lower MEG concentrations levels of 40.2 vol % and at reboiler retention time of 3 h to decrease the likelihood of the MEG degradation products. The percentage increase of the total organic acids at 40.2 vol % was found to be 27.7% as compared to 32.6% at 80.8 vol %. This study is beneficial to the oil and gas industry as it proposes the percentage amount of MEG to be used for hydrate inhibition in order to minimize the production of organic acids. High levels of organic acids accumulation in the regenerated lean lowers the efficiency of MEG thermodynamic inhibition performance.

Исследование природы примесей в циркулирующем растворе гликоля на установке очистки газа от кислых компонентов

Natural gas contains a large amount of moisture, which causes a lot of problems in its transportation and processing. In order to extract this moisture, natural gas gets subjected to the dewatering process, thereby reducing the moisture content and preventing further formation of hydrates. This is achieved by cleaning the gas from hydrogen sulfide and mercaptans and cooling in heat exchangers with the participation of a solution of monoethylene glycol. Together with gas, impurities come in the form of hydrocarbons, brine water, mechanical impurities, corrosion inhibitors, various SASs, resinous substances, etc. As a result of deposition of unwanted impurities on the internal surfaces of devices, the efficiency of mass exchange and heat exchange processes is reduced, equipment wear is increased, so is the laborious process of cleaning equipment during planned repairs, the temperature of the glycol block is disrupted and, as a result, the reagent consumption increases in order to maintain the necessary dewatering temperature of natural gas, and the waste of the glycol from the regeneration apparatus increases. The object of the study was the regeneration block of the saturated solution of monoethylene glycol. During the planned repairs of the plant, there was revealed significant contamination of the devices and heat exchange equipment of the glycol regeneration unit with a large number of unwanted impurities and sediments, as well as significant corrosion of pipe beams of heat exchangers and internal cavity of devices. We found that the most effective ways to prevent sediment formation in the monoethylene glycol regeneration unit are to better control the level of amine in the 374 B09 devices, to control the consumption of the amount of monoethylene glycol injected into heat exchangers, and to reduce the amount of impurities in the circulating solution of monoethylene glycol. Also, to reduce sediments in the heat exchange apparatus of the gas dewatering section, we recommend increasing the separation rate by installing jack elements in the 374 B09 separator and installing an additional filter in accordance with the proposed scheme, with a cartridge of polyphenylsulfide or fiberglass.

Oxygen scavenging performance of carboxylic acids formed during the degradation of monoethylene glycol regeneration products

Previous studies have demonstrated that formic and glycolic acids could scavenge oxygen from aqueous solutions via complex radical mechanisms similar to that of erythorbic acid. Therefore, it is important to study the feasibility of using these common thermal degradation products obtained from the regeneration of monoethylene glycol (MEG). By replacing commercially used oxygen scavengers, such as sulfites, with these organic acids, the toxicity and subsequent environmental impact of oil and gas products could be easily reduced. Furthermore, these organic acids are rapid oxygen scavengers at low concentration, and they could be cost-effective; in addition, the chemical inventory could be reduced and project costs could be further optimized. The experimental results confirmed the potential of formic and glycolic acids to be used as oxygen scavengers downstream of the MEG regeneration process in the presence of manganese (II) ions as catalyst. Of the two commercial aqueous industrial oxygen scavengers tested, diethylhydroxylamine was an extremely rapid oxygen scavenger in salty aged lean MEG solutions under alkaline conditions, whereas methyl ethyl ketoxime exhibited extremely poor performance under similar conditions; therefore, it was ruled out as potential oxygen scavenger.

Experimental investigation and kinetic modeling of nanocrystal growth for scale reduction in mono-ethylene glycol regeneration unit

Scale formation is the major problem in mono-ethylene glycol regeneration units of gas refineries. In this study, the effect of adding different concentrations of silica nanoparticles on the growth rate of salt crystals in a rich mono-ethylene glycol solution is investigated, and the corresponding mathematical model is introduced. To obtain the crystallization kinetics, the particle size distribution was measured in continuous intervals of time and temperature using a dynamic light scattering. Measurements were taken at four temperature levels, in 20-min intervals, and 1, 3, 5, and 9 wt% of silica nanoparticles. Results showed that silica nanoparticles reduced the activation energy needed for nucleation and crystallization by more than 50%. However, increasing the concentration of nanoparticles did not result in a further reduction in the activation energy. Rather, it contributed to the formation of larger primary nuclei that form a larger crystal structure. An increase in temperature from 25 to 50 °C led to an increase of 8.8% in the initial crystal growth. On the other side, increasing the concentration of nanoparticles from 1 to 10 wt% at a constant temperature increased the crystallization growth rate by 3.4%. The proposed mathematical model predicts the kinetics of crystal growth with an acceptable accuracy with the mean relative error of 6.19% for the whole range of concentration and temperature.

Economic benefit of methane hydrate reformation management in transport pipeline by reducing thermodynamic hydrate inhibitor injection

Hydrate reformation is an inherent risk in a methane hydrate production system because dissociated water and methane flow through transport pipelines simultaneously. In this study, comprehensive experiments using high-pressure autoclaves are performed to investigate the effect of reducing the concentration of thermodynamic hydrate inhibitor on hydrate reformation characteristics. In order to simulate the production of methane hydrates, these are formed and dissociated in the preliminary stage; thereafter, the hydrates are reformed from dissociated water. Although dissociated water and fresh water are found to have similar formation rates, they have a major difference in relative torque, especially in the early stage of hydrate formation. The instant rise of the relative torque in the dissociated water is observed to be up to 2.5; thereafter, it remains approximately 3.0 until hydrate conversion reaches 28 vol%. This trend is different from that in fresh water, where a steady increase in relative torque with sudden spikes is observed. These results clearly show the high risk of hydrate blockage in the transport pipelines of a methane hydrate production system; hence, the injection of hydrate inhibitor is necessary. In this study, monoethylene glycol (MEG) is the selected thermodynamic hydrate inhibitor; its concentration is maintained below a specific value to completely avoid hydrate formation. Despite the occurrence of hydrate reformation, a stable relative torque is observed in a 20 wt% MEG concentration, where the conversion of water to hydrate approximately reaches 40 vol%. For a 10 wt% MEG concentration, a sudden increase in relative torque of up to 2.0 is observed in the early stage of hydrate formation; this suggests that the foregoing is less effective in sustaining flowability. Compared to fresh water, the addition of a 20 wt% MEG to dissociated water results in a more stable torque. Once the performance of the MEG concentration reduction is confirmed, the MEG regeneration process is designed accordingly by using both multiphase flow and process simulation models. A life cycle cost (LCC) analysis is conducted by estimating the capital expenditures (CAPEX) and operating expenditures (OPEX) of the MEG regeneration process. Considering both CAPEX and OPEX, the LCC for complete inhibition (35 wt%) is 90.15 MUSD (million United States dollars); however, for the 20 and 10 wt% MEG concentrations, the LCC values are reduced to 86.79 and 84.58 MUSD, respectively. The foregoing suggests the potential economic benefit of methane hydrate reformation management to avoid blockage.

Effect of wettability on particle settlement behavior within Mono-Ethylene Glycol regeneration pre-treatment systems

This study was undertaken to diagnose routine settling problems within a third-party oil and gas companies’ Mono-Ethylene Glycol (MEG) regeneration system. Two primary issues were identified including; a) low particle size (<40 μm) resulting in poor settlement within high viscosity MEG solution and b) exposure to hydrocarbon condensate causing modification of particle surface properties through oil-wetting of the particle surface. Analysis of oil-wetted quartz and iron carbonate (FeCO₃) settlement behavior found a greater tendency to remain suspended in the solution and be removed in the rich MEG effluent stream or to strongly float and accumulate at the liquid-vapor interface in comparison to naturally water-wetted particles.As such, exposure of particles including quartz and FeCO₃ to the condensate phase within natural gas transportation pipelines may ultimately cause poor settlement of suspended particles downstream within MEG regeneration systems, leading to increase filtration requirements. The effect of oil-wetting on particle settlement was successfully managed through application of a cationic surfactants, including cetrimonium bromide (CTAB), to transition the initially oil-wetted surface to water-wetted. Cationic surfactants were found to be most suitable due to the negative surface charge of mineral particles at pH levels typical of MEG regeneration system pre-treatment systems (pH > 8).

Evaluating chemical-scale-inhibitor performance in external magnetic fields using a dynamic scale loop

Monoethylene glycol (MEG) is extensively used in oil and gas pipelines to prevent the formation of gas hydrates. However, the injection of MEG may inadvertently contribute to mineral-ion precipitation through reduced solubility of ionic species and operation under alkaline conditions for corrosion control. As a result, the injection of chemical scale inhibitors (CSI) to manage scaling is often required. Non-chemical inhibitors, such as external magnetic fields (MFs) have also been shown to inhibit scaling in aqueous solutions. With this in mind, we investigated the combined application of CSIs and MF treatment to study the formation of scale under conditions representative of a MEG regeneration system's reboiler, a system under a high risk of scale formation. Two commercial CSIs were examined in the presence and absence of a 0.650-T external MF using a dynamic-scale-loop device. The CSIs were injected into ionic solutions containing 1656.9 ppm calcium ions and 2628 ppm carbonate ions in aqueous MEG (80 vol%), and experiments were performed at 130 °C and pH 9.5. Despite the presence of a CSI, the MF promoted scale formation and afforded a stable calcium carbonate phase morphology at high MEG concentrations. Moreover, the zeta potential under the applied MF was lower than that in the absence of the MF, which led to greater scaling, implying that the magnetic field had an ionic interfacial effect. These results provide significant insight into the effect of a MF on scale formation, irrespective of the use of a CSI, and help to interpret the effects of various treatments for scale removal or the prevention of scale formation during the MEG regeneration process.

Removal of Organic Acids during Monoethylene Glycol Distillation and Reclamation To Minimize Long-Term Accumulation

Monoethylene glycol (MEG) is often used in offshore multiphase hydrocarbon transportation pipelines to prevent the formation of natural gas hydrates. Post hydrate inhibition, MEG is separated alongside the water phase and regenerated through a series of chemical and physical processes to remove excess water and process contaminants including mineral salts, production chemicals, and organic acids. The level of organic acids within closed-loop MEG systems is often controlled via vacuum reclamation systems through the formation of nonvolatile salt products allowing their separation from the evaporated MEG/water phase. However, if a reclamation system is unavailable, or operated at low pH, organic acids will ultimately accumulate within the MEG loop. Likewise, removal of organic acids may be achieved during the distillation process by vaporization of the acids in their undissociated volatile form. Within both processes, the removal efficiency of an organic acid is ultimately dictated by the acid’s speciation behavior and system pH. The purpose of this study was to measure the removal efficiency of acetic acid during the regeneration and reclamation processes to identify key pH levels to minimize the long-term accumulation of acetic acid. Two equations have been proposed to estimate the removal efficiency of acetic acid during distillation and reclamation individually with an average error compared to reported experimental data of 0.38% and 2.6%, respectively. Combining the two proposed equations, the plant-wide removal of acetic acid can be predicted for a known rich glycol pH and pH rise across the regeneration system allowing practical application to industrial MEG regeneration systems.

Effect of Pretreatment Process on Scale Formation in the Re-Boiler Section of Monoethylene Glycol Regeneration Plant

Monoethylene glycol (MEG) regeneration plants often use pretreatment vessels to precipitate divalent cations, such as Fe2+, Ca2+, and Mg2+, in order to avoid or reduce fouling in downstream reboilers and heat exchangers. This pretreatment process operates under alkaline conditions and moderate temperatures (~ 80 °C) to accelerate the formation of low-solubility divalent salts. The objective of the present research was to determine whether the pretreatment process could be minimized, without negatively impacts on the MEG regeneration process from to the formation of scale on the heater bundle in the presence of low concentrations of divalent cations in the rich MEG stream. Scale formation was analyzed under MEG regeneration process conditions using a dynamic scale loop (DSL) test and verification experiments were performed in a MEG regeneration and reclamation pilot plant, both with and without pretreatment conditions. The scaling tendencies of several rich MEG–brine mixtures were evaluated at different pH pretreatment levels and dissolved CO2 concentrations. An evaluation temperature of 180 °C was chosen to match the skin temperature of the reboiler heater bundle during the MEG regeneration process. The experiments of pH 7.24 showed high amounts of precipitation scale within the reboiler due to high remaining concentrations of mineral ions. In addition, small concentrations of calcium and magnesium ions led to the precipitation of calcite, dolomite, and magnesium hydroxide on the reboiler bundle and within associated filtered outputs even when a pretreatment vessel was present. These results were confirmed by the differential pressure build-up and Scanning Electron Microscopy analyses for each experimental condition. Another interesting finding is that pH increased within the reboiler due to CO2 gas boiling off at high operating temperatures, thus contributing to increased alkalinity levels, which in turn promoted scale formation. These results indicate that pretreatment should not be reduced, even with divalent ion concentrations as low as ~ 5 ppm TDS, due to the harsh conditions within the reboiler heater bundle.

Absorption kinetics of mercury (II) chloride into mono-ethylene glycol (MEG) solution

Different mercury species have been found in the oil and gas reservoirs. Dynamic absorption of mercury (II) chloride (HgCl2) into solutions of mono-ethylene glycol (MEG) is reported in this work. It was observed that absorption of HgCl2 into MEG solutions was comparable to the absorption in pure water and the effect on MEG was not seen for MEG concentrations of 2–30 v/v%. The absorption flux was mainly affected by the absorption temperature and the concentration of HgCl2 in the gas phase. Utilisation of several mercury analysis techniques such as flow injection mercury spectroscopy (FIMS), inductively couple plasma-mass spectroscopy (ICP-MS), Fourier-transform infrared spectroscopy (FTIR) and Raman spectroscopy show that no interactions between HgCl2 and MEG were detected for the test parameters studied. The findings from this work helps to improve the knowledge on the behaviour of HgCl2 within natural gas processing facilities, especially during transportation in pipelines and the MEG regeneration process.

STRONTIUM CARBONATE SOLUBILITY DATA IN AQUEOUS MIXTURES OF MONOETHYLENEGLYCOL UNDER A CARBON DIOXIDE ATMOSPHERE

In order to inhibit natural gas hydrate formation, monoethyleneglycol (MEG) is usually injected into producing well heads. The MEG regeneration process is continuously performed at the platform. Scaling problems usually occur due to the presence of chlorides and carbonates. This work presents salt solubility data for the aqueous system with strontium carbonate, MEG and carbon dioxide. A specific analytical method was developed. Thus, experimental data for strontium carbonate (SrCO3) solubility at various carbon dioxide pressures are reported. Solubilities of SrCO3 in water were measured from 760 to 1610 mmHg at 278.15. 288.15. 298.15 and 323.15 K. For the mixed solvent (ms) conditions, solubilities were measured at 298.15 K and four isobars, i.e., 760, 1210, 1410 and 1520 mmHg. Experimental data were correlated and demonstrated to be accurate for thermodynamic modeling and process simulation