Sour Gas Research Articles

Potential toxic effects linked to taurine interactions with alkanolamines and diisopropylamine

Diisopropylamine (DIPA), aminomethyl propanol (AMP), amino ethoxy ethanol (AEE), diethanolamine (DEA), ethanolamine (EA), pyridine (PYR) and methyl diethanolamine (MDEA) are used for carbon capture and to sweeten sour gas, and are found in groundwater. They are also used in cosmetic products. Taurine is abundant in the body, with key biological functions linked to its charged SO groups. Interactions between SO and amines have not been studied, but can strongly affect the biological function of taurine. Fourier transform infrared spectroscopy indicates SO…HN hydrogen bonding between taurine and DIPA, AMP, AEE, DEA, EA and MDEA. These interactions induce the formation of hydrophobic amine-taurine clusters, thus decreasing amine miscibility in water, as revealed by light scattering. This effect is most marked for DIPA, leading to turbid mixtures indicative of micron-sized droplets. PYR and taurine likely interact via S…N bonding. This study offers insights regarding potential mechanisms of amine toxicity to humans.Graphical

Prediction of Solvent Composition for Absorption-Based Acid Gas Removal Unit on Gas Sweetening Process.

The gas sweetening process is essential for removing harmful acid gases, such as hydrogen sulfide (H2S) and carbon dioxide (CO2), from natural gas before delivery to end-users. Consequently, chemical absorption-based acid gas removal units (AGRUs) are widely implemented due to their high efficiency and reliability. The most common solvent used in AGRU is monodiethanolamine (MDEA), often mixed with piperazine (PZ) as an additive to accelerate acid gas capture. The absorption performance, however, is significantly influenced by the solvent mixture composition. Despite this, solvent composition is often determined through trial and error in experiments or simulations, with limited studies focusing on predictive methods for optimizing solvent mixtures. Therefore, this paper aims to develop a predictive technique for determining optimal solvent compositions under varying sour gas conditions. An ensemble algorithm, Extreme Gradient Boosting (XGBoost), is selected to develop two predictive models. The first model predicts H2S and CO2 concentrations, while the second model predicts the MDEA and PZ compositions. The results demonstrate that XGBoost outperforms other algorithms in both models. It achieves R2 values above 0.99 in most scenarios, and the lowest RMSE and MAE values of less than 1, indicating robust and consistent predictions. The predicted acid gas concentrations and solvent compositions were further analyzed to study the effects of solvent composition on acid gas absorption across different scenarios. The proposed models offer valuable insights for optimizing solvent compositions to enhance AGRU performance in industrial applications.

Predicting thermochemical sulfate reduction reaction process and H2S generation in carbonate reservoirs using comprehensive kinetics modeling

Thermochemical sulfate reduction (TSR) is a critical process controlling hydrogen sulfide (H2S) generation in carbonate reservoirs, posing significant economic and safety challenges for the oil and gas industry. This study develops a comprehensive model that integrates detailed thermal, burial, and hydrocarbon generation histories with key TSR kinetic parameters, such as reaction rate constants and activation energies, to predict TSR evolution and H2S generation accurately. A notable feature of the model is to separate and quantify the contributions of different hydrocarbon species (CH4, C2-5, C6-14, and C15+) to the overall TSR process, using the Arrhenius equation to simulate the temperature-dependent behavior of TSR for each hydrocarbon group. The model also accounts for the in-reservoir thermal cracking of heavier hydrocarbons into light hydrocarbons, ensuring predictions closely align with geological processes. Modeling results show that TSR reactions accelerate the depletion of oil and wet gas components. A large amount of CH4 is generated due to both kerogen thermal cracking and alteration of heavy hydrocarbon. Our modeling also allows for accurate prediction of TSR reactions as well as the timing and extent of H2S and CO2 generation over the history of a reservoir. Applications in the Puguang and Hetianhe gas fields validate the model's broad applicability and reliability, capturing extensive TSR activities and being consistent with the observed data. These results underscore the models' robustness in detailed predictions of TSR dynamics across diverse geological settings and its potential as a valuable tool for managing sour gas production, aiding in risk assessment and resource management.

Rational design of melamine-crosslinked poly(ethylene glycol) membranes for sour gas purification

Natural gas accounts for about a quarter of the world's energy consumption; however, most of the current natural gas reservoirs are sour. Sour natural gas containing significant amounts of hydrogen sulfide (H2S) along with carbon dioxide (CO2) must be purified to meet the strict requirements for transportation and storage in the industry. Sour natural gas purification involves two steps: acid gas removal (AGR) and acid gas enrichment (AGE), which currently use highly energy-intensive technologies. Membrane separation represents the most attractive technology to lower the operating cost and carbon footprint of these large processes. Guided by density functional theory (DFT) calculations, we rationally designed a crosslinked poly(ethylene glycol) (PEG) membrane for AGR and AGE applications. Specifically, PEG-bisazide monomers were crosslinked with a novel trialkyne-functionalized H2S-philic melamine via azide-alkyne cycloaddition click chemistry. The developed membranes were characterized and tested for (H2S + CO2)/CH4 and H2S/CO2 separations under realistic industrial conditions, targeting the AGR and AGE applications, respectively. These novel membranes achieved high H2S permeability while maintaining attractive H2S/CO2 selectivity.

Nomograph derivation for underwater sour gas releases in shallow waters based on computational fluid dynamics simulations

Ruptured underwater pipelines releasing sour gas (i.e., natural gas with high concentrations of H2S) pose significant threats to environmental safety due to their toxic and contaminative properties. This study suggests a transient Eulerian-Eulerian multiphase computational fluid dynamics (CFD) model for assessing the environmental impact of sour gas releases in shallow, ecologically sensitive waters. Employing the Realizable k-ε turbulence model and additional bubble plume mechanisms, the model was rigorously validated against well-documented experimental data, showing high levels of agreement across multiple metrics. Key environmental safety parameters—such as rise time and H2S surface gas concentration, indicative of toxic exposure risk to aquatic life and human health—were extracted for multiple release scenarios. To present generalized and easily accessible data, these parameters were nondimensionalized and incorporated into a nomograph, enabling environmental risk assessments to be conducted four orders of magnitude faster than with high-fidelity simulations. The study emphasizes the nomograph's utility in rapid, environmentally relevant risk assessment and emergency planning for mitigating the impact of sour gas spills. An error and sensitivity analysis revealed uncertainties of ±7 % for rise time and ±58 % for surface gas concentration, pinpointing avenues for future research.

Solubility of H2S-CH4 mixtures in calcium chloride solution: Insight from molecular dynamics simulations

This study uses equilibrium molecular dynamics (EMD) simulations to gain microstructural insight into and predict crucial properties of gas-brine mixtures affecting sour gas reservoir development. The effects of pressure, temperature, gas composition and salinity on the solubility and density of H2S-CH4 mixtures in pure water and CaCl2 brine were investigated at industrially relevant conditions (temperature range of 280 − 340 K, pressures up to 20 MPa, and a salinity range of 4.78 − 17.32 wt%). The force fields used in the MD simulations were validated using experimental data for pure H2S and CH4. The results showed that the solubility of pure H2S and CH4 in pure water increases with pressure, with the latter having a higher solubility. For H2S-CH4 mixtures, the solubility of H2S increased while that of CH4 fell with increasing H2S mole fraction, with the solubilities of the two gases intersecting at an H2S mole fraction of 0.28. Further, the solubility of H2S shows a greater pressure dependence than that of CH4, and H2S gas tends to reach saturation in pure water. In calcium chloride solution, the gas solubility decreases as the ions reduce the interaction between water and gas molecules. The solubility of H2S gas is a stronger function of the ion concentration compared with CH4, and increases 6-fold as the H2S mole fraction increases from 0.5 to 0.8. The overall solubility ranges were 0.45 to 3.48 mol/kg for H2S and 0.15 to 0.25 mol/kg for CH4.

Volatile light hydrocarbons as thermal and alteration indicators in oil and gas fields

Volatile light hydrocarbons (VLH) are an essential component of reservoir petroleum fluids. Understanding of their origin and fate is crucial not only in exploration but increasingly also in petroleum engineering, as this greatly impacts fluid typing, proper mapping, recoverability and economic value. Due to their sensitivity to subsurface thermal stress and geological alteration processes, their proper characterisation holds promise to understanding the thermal conditions under which petroleum fluids were generated and subsequent fluid modifications during migration and within the reservoir. To study the behaviour of these hydrocarbons under different geological conditions we selected oil and gas fields from two giant conventional petroleum systems in the Arabian Peninsula collectively spanning the entire petroleum spectrum from heavy oil to dry and sour gas. In situ representative bottomhole or recombined pressure–volume–temperature (PVT) fluid composition data were constrained with molecular and stable carbon isotope geochemistry in key wells. Systematic covariance among the slope factor (SF) of propane to pentane and the isomer ratios of butane and pentane with reservoir engineering and geochemical variables in well-constrained black oil to gas condensate petroleum systems allowed the derivation of three formulas to calculate thermal maturity in terms of vitrinite reflectance equivalent from VLH fluid composition: (1) %VRe(SF) = 0.38 SF + 0.41, (2) %VRe(i4) = 1.70 (iC4/nC4) + 0.61, and (3) %VRe(i5) = 0.89 (iC5/nC5) + 0.56. The slope factor, iC4/nC4, and iC5/nC5 ratios all increase monotonically with the thermal evolution of unaltered fluids, allowing for effective application of their derived %VRe formulas across the entire unaltered fluid spectrum, from heavy oil to dry gas. Deviations from indigenous-fluid trends do occur for fluids altered by phase separation, biodegradation, thermal cracking, and thermochemical sulfate reduction (TSR), but corrections can be made to minimize uncertainty in assessing true thermal maturity of altered fluids while respecting other reservoir fluid properties such as gas-to-oil ratio (GOR) and saturation pressure relationships. For instance, although a single charge that has been phase fractionated yields fluids with variable GORs, saturation pressures and slope factors, their butane and pentane isomer ratios remain reflective of the original fluid maturity. In contrast, biodegradation-induced overestimation of maturity based on the isomer ratios of butane and pentane can be corrected by the less affected SF-derived maturity parameter. Reversal to lower apparent SF-derived maturity in thermally and TSR cracked fluids can, on the other hand, be corrected by considering the less affected butane and pentane isomer ratios. Overall, maturities calculated using VLH composition correspond well with fluid type defined based on phase behaviour and source-rock kinetics, thereby putting forward new tools to quantify thermal maturity of reservoir fluids that may be applicable in other petroleum systems.

Influence of oxidation–reduction potential and pH on polysulfide concentrations and chain lengths in the biological desulfurization process under haloalkaline conditions

Biological desulfurization under haloalkaline conditions has been applied worldwide to remove hydrogen sulfide (H2S) from sour gas steams. The process relies on sulfide-oxidizing bacteria (SOB) to oxidize H2S to elemental sulfur (S8), which can then be recovered and reused. Recently, a dual-reactor biological desulfurization system was implemented where an anaerobic (sulfidic) bioreactor was incorporated as an addition to a micro-oxic bioreactor, allowing for higher S8 selectivity by limiting by-product formation. The highly sulfidic bioreactor environment enabled the SOB to remove (poly)sulfides (Sx2−) in the absence of oxygen, with Sx2− speculated as a main substrate in the removal pathway, thus making it vital to understand its role in the process. The SOB are influenced by the oxidation–reduction potential (ORP) set-point of the micro-oxic bioreactor as it is used to control the product of oxidation (S8 vs. SO42−), while the uptake of Sx2− by SOB has been qualitatively linked to pH. Therefore, to quantify these effects, this work determined the concentration and speciation of Sx2− in the biological desulfurization process under various pH values and ORP set-points. The total Sx2− concentrations in the sulfidic zone increased at elevated pH (8.9) compared to low pH (< 8.0), with on average 3.3 ± 1.0 mM-S more Sx2−. Chain lengths varied, with S72− only doubling in concentration while S52− increased 9 fold, which is in contrast with observations from abiotic systems. Changes to the ORP set-point of the micro-oxic reactor did not produce substantial changes in Sx2− concentration in the sulfidic zone. This illustrates that the reduction degree of the SOB in the micro-oxic bioreactor does not enhance their ability to interact with Sx2− in the sulfidic bioreactor. This increased understanding of how both pH and ORP affect changes in Sx2− concentration and chain length can lead to improved efficiency and design of the dual-reactor biological desulfurization process.

Tailoring hole density and nitriding in graphene membranes for enhanced gas separation and selectivity

Sour gas, containing acidic gases like hydrogen sulfide and carbon dioxide, has a characteristic odor, and toxic effects, and reduces the overall energy content of the gas. Moreover, the presence of these acid gases in water leads to the formation of highly corrosive acid compounds, increasing transportation costs. Membrane technology is widely used for gas separation due to its low energy consumption, ability to operate at ambient temperatures, lightweight and compact equipment, ease of access to all separated phases, and high process flexibility. Computer simulation bridges the gap between microscopic temporal and spatial scales and the macroscopic laboratory environment. Molecular dynamics is a technique for analyzing the physical motion of atoms and molecules. By simulating the interactions between atoms and molecules over time, insights into the dynamic evolution of the system can be obtained. This research investigates the CO2/CH4 separation performance of modified graphene membranes (C3N) using molecular dynamics simulations under various operating conditions. First, cavities with different geometrical shapes and edge atoms were created, and gas separation was examined at 300 K. A cavity with a diameter of 4.9 Å exhibited the highest selectivity (infinity) and a carbon dioxide flux of 365.65 mol/m2·s, while methane molecules were completely blocked. This cavity was selected as the optimal structure. Next, the effects of pressure, and hole density on gas separation were studied. The results showed that the flux is directly proportional to the feed pressure, reaching 503.7845 mol/m2·s at a pressure of 328.0424 atm while maintaining infinite selectivity. Finally, examining the impact of cavity density on the separation process revealed that drilling four holes in the membrane area was the optimal density, achieving infinite selectivity, zero methane flux, and a carbon dioxide flux of 292.601 mol/m2·s.

Process simulation, optimization, and cost analysis of a proposed sulfur recovery unit by applying modified Claus technology

Removing sour gas from any suitable gas sweetening technology in a cost-effective and environmentally responsible manner is a major challenge. This paper discusses how to safely and economically dispose of small amounts of acid gases resulting from the amine sweetening process. A two-stage Claus desulfurization unit was studied and simulated to treat acid gases resulting from natural gas sweetening operations in Ras Gharib oil fields (Egypt). These acid gases are used as feedstock for the proposed plant to produce a valuable product, such as elemental sulfur, which is used as a raw material in many industries. Although many sulfur recovery techniques are available for various conditions and applications, the Claus process is a critical and widely used method for recovering elemental sulfur from gaseous hydrogen sulfide. This work represents the potential benefits of treating acid gases with high hydrogen sulfide content. In addition, operational variables that could affect sulfur production and sulfur recovery efficiency of the studied Claus unit were studied and optimized. Aspen HYSYS simulation software (version 9) was used to evaluate the economic aspects and optimize the operational parameters of the unit for producing sulfur from acid background gases. The results showed that the maximum sulfur production was achieved at a catalytic converter reactor temperature of 270 °C and 210 °C for the first and second catalytic reactor, respectively, with an air flow rate of 933.3 kg mol/h. The economic study of the proposed desulfurization unit showed that the Claus unit would be economically acceptable with an expected return on investment of approximately 10% and an average payback period of 10 years. Moreover, the introduced plant has a positive impact on the environment by reducing the concentration of hydrogen sulfide in the gas from 69.58 to 0.16%.

Probe into Water Chemistry Effects on Internal Corrosion Risk for Sour Gas Pipelines

Probe into Water Chemistry Effects on Internal Corrosion Risk for Sour Gas Pipelines

Corrosion of Zinc Cold Spray Coatings in a Wet Sweet and Sour Gas Environment

Internal corrosion is a problem for steel pipelines transporting natural gas or CO2 containing water and partial pressures of H2S higher than 0.3 kPa (0.05 psi). This work aims to mitigate internal corrosion in steel pipelines transporting natural gas containing H2S using cold spray coatings. Two types of the cold spray binary metallic coatings (zinc chromium [ZnCr]. zinc niobium [ZnNb]) were studied using electrochemical techniques: potentiodynamic polarization, linear polarization resistance, and electrochemical impedance spectroscopy. The corrosion resistance of cold spray coatings (ZnCr, ZnNb) was evaluated in an environment containing 4 bar CO2 pressure, simulating the partial pressures found in gas transmission lines over a solution of 3.5 wt% NaCl heated to 40°C. A concentration of 0.003 M Na2S2O3·5H2O, corresponding to H2S partial pressures around 0.079 bar (1.146 psi), was used to simulate sour conditions. Postcorrosion surface characterization was performed using a scanning electron microscope (SEM) equipped with an energy-dispersive x-ray spectroscope (EDS) and x-ray diffraction analysis. The data showed that the presence of 0.003 M Na2S2O3·5H2O shifted the corrosion potential to more anodic values and decreased the corrosion current density. Both coatings showed similar behavior after 1 h of exposure in the CO2/H2S environment, indicating that similar electrochemical reactions were occurring on ZnNb and ZnCr. SEM images and EDS surface analyses for specimens showed a significant change in the surface chemical composition of carbon steel coated with ZnNb and ZnCr after 24 h of immersion. In the presence of thiosulfate (under sour conditions), the formation of corrosion product layers (ZnCO3 and ZnS) on top of ZnNb and ZnCr coatings increased their corrosion resistance, which helped to reduce their corrosion by a factor of 2. Under a sweet environment, the corrosion rates for steel coated with cold spray coatings after 14 d of exposure are lower than that for galvanized steel by a factor of 5 due to the ZnCO3 layer formed on top of the coatings. The ZnCO3 layer formed on the steel surface acts as a physical barrier against corrosion by blocking the diffusion of corrosive species to the surface. No localized attack was observed. ZnCr Cold spray coating with defect showed promising corrosion protection against CO2 corrosion (sweet corrosion) after 14 d of exposure to a CO2 environment. The scratch on the coating simulated damage created in service, and it was deep enough to expose the substrate material (steel). The formation of zinc oxide (ZnO) and zinc carbonate (ZnCO3) on the scratch confirmed the cathodic protection of the steel by ZnCr and ZnNb coatings.

Simultaneous Enhancement of Strength and Sulfide Stress Cracking Resistance of Hot-Rolled Pressure Vessel Steel Q345 via a Quenching and Tempering Treatment.

Sulfide stress cracking (SSC) failure is a main concern for the pressure vessel steel Q345 used in harsh sour oil and gas environments containing hydrogen sulfide (H2S). Methods used to improve the strength of steel usually decrease their SSC resistance. In this work, a quenching and tempering (Q&T) processing method is proposed to provide higher strength combined with better SSC resistance for hot-rolled Q345 pressure vessel steel. Compared to the initial hot-rolled plates having a yield strength (YS) of ~372 MPa, the Q&T counterparts had a YS of ~463 MPa, achieving a remarkable improvement in the strength level. Meanwhile, there was a resulting SSC failure in the initial hot-rolled plates, which was not present in the Q&T counterparts. The SSC failure was not only determined by the strength. The carbon-rich zone, residual stress, and sensitive hardness in the banded structure largely determined the susceptibility to SSC failure. The mechanism of the property amelioration might be ascribed to microstructural modification by the Q&T processing. This work provides an approach to develop improved strength grades of SSC-resistant pressure vessel steels.

Thermodynamic modeling of sour gas mixture (CH4/C3H8/H2S) hydrate formation in the presence of thermodynamic inhibitors mono ethylene glycol, NaCl, and CaCl2 using the ion pair concept

Thermodynamic modeling of hydrate equilibrium conditions for sour gas mixture (CH4/C3H8/H2S) in the presence of pure water and thermodynamic inhibitor(s) (MEG, NaCl, and CaCl2) was investigated in this study. Hydrate and vapor phases were evaluated using the van der Waals and Plattueew model, and the Peng-Robinson EoS along with the classic van der Waals mixing rule, respectively. As a different approach, by combining non-synonymous salt ions and forming ion pairs, they can be considered as molecular species. So ion pair concept was used to investigate liquid phase and calculate water activity coefficient in this phase. For short-range and long-range forces, the NRTL molecular model and the Pitzer-Debye-Hückel equation was used, respectively. The results of experimental data in the previous work were compared with the results of the proposed model and PVTsim Nova 3.0 software, and it was discovered that they have an acceptable agreement together. The average deviation in pressure (AARDP %) related to the model is 0.36% to 4.34% and 3.41% to 5.68% related to the software.

Damage evaluation of carbon fiber reinforced composites under corrosion condition of sour gas well

AbstractThe paper focuses on the excellent chemical inertness characteristics of nonmetallic materials and evaluates the performance of three types of new carbon fiber‐reinforced resin‐based composites under various simulated corrosion conditions in wellbores. Through comprehensive analysis of macro and micromorphology, moisture absorption performance, strength performance, and molecular structure, the damage characteristics and applicability of carbon fiber composites in oil and gas wellbore conditions were clarified. T700/epoxy and T300/epoxy composites experienced damage dominated by physical effects such as moisture absorption and wet thermal stress, manifested as swelling, deformation, and cracking at the macro level, and pore formation and delamination cracking at the micro level. After continuous corrosion tests, the tensile strength of T700/bismaleimide composite (913 MPa) was higher than that of T700/epoxy composite (814 MPa) and T300/epoxy composite (636 MPa), with reductions of 12.4%, 14.3%, and 19.5% respectively. The research results showed T700 carbon fiber/bismaleimide resin composites had the best mechanical and chemical stability.

Evaluation of corrosion behaviour and susceptibility to hydrogen-induced cracking in high-strength low-alloy X70 steels under sour gas conditions

High-strength low-alloy (HSLA) steels find extensive usage in the oil industry for manufacturing pipes due to their requirement for materials with high mechanical and corrosion resistance. Among these steels, the HSLA X70 steels are particularly of great interest to the petroleum industry because of its high mechanical resistance, ductility and weldability. In this study, it was aimed to assess the corrosion behaviour of HSLA API X70 pipelines using electrochemical impedance spectroscopy (EIS) technique and evaluate its resistance to hydrogen-induced cracking (HIC). The analyses were conducted in non-sour and sour media, as per NACE TM0284 standard. Microstructural characterisations of polished and corroded samples were also conducted using scanning electron microscopy (SEM) and optical microscopy (OM). The results indicate that the resistance to HIC in API 5L X70 steel is compromised when exposed to surface corrosion in sour gas media. This susceptibility may be attributed to the presence of microconstituents MnS and M/A along the grain boundaries, which were found in the crack trajectory. The identified microstructural features are deemed to exert a significant influence on the propagation of cracks and the consequent susceptibility to HIC. Moreover, the EIS tests revealed the lowest corrosion resistance when exposed to H2S media, as MnS inclusions accelerate the active regions in the matrix, consequently leading to the formation of a plethora of corrosion products and the dissolution of iron.

Improving the prediction of elemental sulfur solubility in sour gas mixtures by modifying cubic equations of state

So far, several correlations have been developed to forecast the solubility of sulfur in various mixtures of acid gases with different concentrations of hydrogen sulfide. These correlations are correlative methods requiring experimental sulfur solubility data to tune their model parameters. Besides, correlative methods have many restrictions and are useable only for a limited range of operating conditions. Another approach for predicting sulfur solubility is applying equations of state. The predictive ability of equations of state has made them a powerful tool to more accurately perform the equilibrium phase calculations of acid gas mixtures in a vaster operating range. The major problem of the equations of state is the inaccurate characterization of their parameters for elemental sulfur due to its chemical complexity. In this study, the performance of three cubic equations of state is evaluated for forecasting the solubility of elemental sulfur in different acid gas mixtures. The main idea which is supposed to be put forward for rectifying defects of cubic equations of state is to model the trend of errors propagated in predicting the solubility of sulfur. Indeed, the effect of sulfur chemical reactions is ignored, and a generalized correction function is developed to compensate for deviations arising from the simplification assumptions. Subsequently, the results predicted by modified equations of state are compared to experimental sulfur solubility data and previously existing methods. Finally, a case study is performed on a sour gas reservoir sample to predict precipitation P-T curve and to calculate sulfur solubility changes with the pressure and temperature reduction throughout the gas well. Predicted results revealed the proposed correction function could significantly decrease the solubility calculations obtained from the modified equations of state under 5.6%, which is a good achievement compared to their original versions.

Evaluating the carbon footprint of sulphur recovery unit: A comprehensive analysis

Desulphurising of oil based fuels and industrial gases is a widespread practice. The combustion process in the sulphur recovery unit (SRU) involves the reaction of H2S with oxygen to produce SO2, which is then converted to elemental sulphur through a series of catalytic reactions. Oxygen enrichment is a technique used to enhance the performance and efficiency of the SRU. By introducing a higher concentration of oxygen into the combustion process, the overall combustion reaction can be optimised, resulting in an increased sulphur recovery from sour gas and reduced emissions of sulphur compounds. The present study analyses the gate-to-gate comparative environmental impact of air versus oxygen enriched air used for combustion to recover 1.0 ton sulphur using GaBi software (8.5.0.79 version). The primary data was collected from the literature. The GaBi Indian extension database is used for the secondary data source. The results are reported using midpoint impact assessment methods CML 2001. The global warming potential for oxygen-enriched SRU is 232 kg CO2 eq. compared to 276 kg CO2 eq. for air enriched SRU. Similarly, the potential for abiotic depletion (elements + fossil), acidification, eutrophication, human toxicity, freshwater aquatic ecotoxicity, marine aquatic ecotoxicity, photochemical ozone creation and terrestric ecotoxicity are higher for air based SRU than oxygen-enriched SRU. The analysis concludes that oxygen enrichment technology is a highly effective way to reduce the environmental impact of the SRU.

Corrosion behaviors of TA2 and TA36 titanium alloys in a high-sulfur environment

The mixed medium of sulfur, H2S, CO2, and generated water in the developed sour gas fields in Sichuan-Chongqing Gasfield seriously corrodes pipelines. The carbon steel gathering system is not suitable for transporting such a medium and titanium alloy has become a hotspot due to its high specific strength and excellent resistance to H2S corrosion. The corrosion of titanium and titanium alloys in the mixed media of H2S, CO2, and water has been extensively explored, but their electrochemical corrosion behaviors in the presence of elemental sulfur are not clear. In this study, the effects of temperature and sulfur on the corrosion behaviors and electrochemical behaviors of TA2 and TA36 in the simulated solution were studied with hanging tests and high-temperature and high-pressure electrochemical corrosion method and the corrosion morphology was observed with a scanning electron microscope. When the temperature increased from 60 °C to 90 °C, the self-corrosion current of TA36 alloy was decreased by one order of magnitude and the corrosion rate of TA36 decreased, indicating the improved corrosion resistance. At the same temperature, the self-corrosion current of TA36 alloy was 28.8 % of that of TA2 and the corrosion resistance of TA36 alloy was better than that of TA2. Sulfur deposition accelerated the pitting corrosion of TA2 and TA36.

Reduction in the transport of sour gases and hydrocarbons to underlying PE-RT through thin films of PVDF

Raised temperature polyethylene (PE-RT) is being studied for use in the conveyancing of sour hydrocarbon fluids in spoolable composite pipe at temperatures above 90 °C. This grade of polyethylene swells on exposure to all hydrocarbons but specifically aromatic hydrocarbons and so there is a requirement to reduce the flux of hydrocarbons and gases into the base PE-RT. A multi-material pipe wall is one solution to reduce these fluxes but new experimental methods are required for design and validation while saturated in sour hydrocarbon fluids.In this study the simultaneous transport of species such as CO2, H2S, CH4, water vapour and aromatic hydrocarbon vapours such as toluene, xylene, IRM902 and cyclohexane were measured in real time through single films of PVDF and PE-RT and multilayer walls of PVDF/tie layer(s)/PE-RT extracted from a built (co-extruded) pipe section. The permeation test facility contained specialized gas chromatographs modified for continuous quantification of all species. The experimental methods were designed to run at 93 °C with gas pressures of 104 barg or 250 barg. Experiments were run with gas only mixtures (dry tests) and also with gas cap above a mixture of liquid hydrocarbons and water (wet tests). When possible, transport properties such as diffusion and solubility coefficients were derived from the permeation traces. The volume flow rate of all species was higher through PE-RT compared to PVDF and the volume flow rate for CO2, H2S, and CH4, increased when the gas pressure was increased from 104 to 250 barg. The gas permeability was calculated for the base polymers and also the combined multilayer structure. The flow rates estimated for a multilayer specimen using the values measured on individual films were confirmed experimentally. A simple mathematical model was proposed to derive the apparent permeability of the multilayer system and the steady-state concentration profiles across the specimen wall. Specimens were inspected for damage after a final depressurization at 70 bargmin−1. Post exposure assessment of the laminates showed that the adhesion levels were improved and the failure mode was altered from adhesive to cohesive on ageing.