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ABSTRACTRenewable energies have gained momentum in energy transition agenda based on the benefit of lower emissions of carbon and its compounds. Many technologies have been developed at different technology readiness levels addressing climate change impact with reduced emissions of greenhouse gases such as CO2. Herein the perspective article, we have reviewed CO2 capture technologies, such as absorption, adsorption, membrane separation, cryogenic separation and separation via hydrate formation, with further focus on the possibility of utilising ocean thermal energy conversion (OTEC) power to generate green hydrogen and produce low carbon fuels. The potential of OTEC generated hydrogen to produce methanol was explored using a simulation exercise utilising a scenario from a real-life offshore gas production facility. By varying the catalysts and reaction conditions, the findings showed encouraging results of CO2 conversion of ≥50% and product yield of ≥80%. Considering single path reaction with 90%, 95% and 99% of recycling, the highest prediction of methanol production coupled with CO2 hydrogenation process was 276.59 metric tonnes per day (MTPD). In addition, based on the assumption of 13.5 million standard cubic feet per day (MMSCFD) of CO2 produced, 204 MW of OTEC power is required to convert approximately 97.82 MTPD of hydrogen for methanol production making it potentially an industrially viable process.

Novel or unconventional technologies are critical to providing cost-competitive natural gas supplies to meet rising demands and provide more opportunities to develop low-quality gas fields with high contaminants, including high carbon dioxide (CO2) fields. High nitrogen concentrations that reduce the heating value of gaseous products are typically associated with high CO2 fields. Consequently, removing nitrogen is essential for meeting customers’ requirements. The intensification approach with a rotating packed bed (RPB) demonstrated considerable potential to remove nitrogen from natural gas under cryogenic conditions. Moreover, the process significantly reduces the equipment size compared to the conventional distillation column, thus making it more economical. The prediction model developed in this study employed artificial neural networks (ANN) based on data from in-house experiments due to a lack of available data. The ANN model is preferred as it offers easy processing of large amounts of data, even for more complex processes, compared to developing the first principal mathematical model, which requires numerous assumptions and might be associated with lumped components in the kinetic model. Backpropagation algorithms for ANN Lavenberg–Marquardt (LM), scaled conjugate gradient (SCG), and Bayesian regularisation (BR) were also utilised. Resultantly, the LM produced the best model for predicting nitrogen removal from natural gas compared to other ANN models with a layer size of nine, with a 99.56% regression (R2) and 0.0128 mean standard error (MSE).

Scarcity has made fresh water too economically and socially too valuable to be used by the processing industry without restriction. Wet evaporative cooling cycles offer competitive advantages in terms of CoP compared to other cooling cycles with relatively low cost but requiring extensive quantities of water. Dry cooling, on the other hand, requires large heat-transfer areas, in addition to high power requirements. In this study, a hybrid cycle is proposed for high-end cooling loads of 215 MW. The proposed cycle combines the benefits of phase change to make dry cycles competitive. Furthermore, the proposed cycle also diminishes the extensive use of various chemicals used in wet cooling cycles. The applicable dry bulb temperature range is 25–50 °C. Variations in cooling fluid cold temperature due to ambient conditions are curtailed to a maximum of 2 °C by the proposed cycle. A technoeconomic comparison of the proposed solution to wet evaporative cooling is presented, and the effects are summarized without providing extensive design calculations. ASPEN modules are used design and simulation.

Abstract Risk assessments of industrial facilities, especially offshore oil and gas companies, are required to consider safety, environmental, financial, and company reputation risks. Risk assessments of normally unmanned installation (NUI) facilities usually do not accommodate personnel or employees. Therefore, a risk value cannot be applied when there is a plan to deploy personnel at an NUI. Hence, this study aimed to determine the inherent risk value when security personnel are deployed at an NUI. The NUI to be assessed has two types of platforms with different conditions. Risk values were obtained using a semi-quantitative risk analysis method by determining the likelihood and consequence criteria, whose values ranged from 1 to 5 according to the 5 $$\times$$ × 5 risk-matrix scale used. The risk-assessment results demonstrate that NUI is at a “low risk” and is broadly acceptable.

Gas hydrate inhibitors have proven to be the most feasible approach to controlling hydrate formation in flow assurance operational facilities. Due to the unsatisfactory performance of the traditional inhibitors, novel effective inhibitors are needed to replace the existing ones for safe operations within constrained budgets. This work presents experimental and modeling studies on the effects of nonionic surfactants as kinetic hydrate inhibitors. The kinetic methane hydrate inhibition impact of Tween-20, Tween-40, Tween-80, Span-20, Span-40, and Span-80 solutions was tested in a 1:1 mixture of a water and oil multiphase system at a concentration of 1.0% (v/v) and 2.0% (v/v), using a high-pressure autoclave cell at 8.70 MPa and 274.15 K. The results showed that Tween-80 effectively delays the hydrate nucleation time at 2.5% (v/v) by 868.1% compared to the blank sample. Tween-80 is more effective than PVP (a commercial kinetic hydrate inhibitor) in delaying the hydrate nucleation time. The adopted models could predict the methane hydrate induction time and rate of hydrate formation in an acceptable range with an APE of less than 6%. The findings in this study are useful for safely transporting hydrocarbons in multiphase oil systems with fewer hydrate plug threats.

Natural gas demand has dramatically increased due to the emerging growth of the world economy and industry. Presently, CO2 and H2S content in gas fields accounts for up to 90% and 15%, respectively. Apart from fulfilling the market demand, CO2 and H2S removal from natural gas is critical due to their corrosive natures, the low heating value of natural gas and the greenhouse gas effect. To date, several gas fields have remained unexplored due to limited technologies to monetize the highly sour natural gas. A variety of conventional technologies have been implemented to purify natural gas such as absorption, adsorption and membrane and cryogenic separation. The application of these technologies in natural gas upgrading are also presented. Among these commercial technologies, cryogenic technology has advanced rapidly in gas separation and proven ideally suitable for bulk CO2 removal due to its independence from absorbents or adsorbents, which require a larger footprint, weight and energy. Present work comprehensively reviews the mechanisms and potential of the advanced nonconventional cryogenic separation technologies for processing of natural gas streams with high CO2 and H2S content. Moreover, the prospects of emerging cryogenic technologies for future commercialization exploitation are highlighted.

Ionic liquids (ILs) are chemical substances with good solubility and low vapor pressure because they are ionized and therefore charged. ILs may damage ecosystem due to their good water solubility. Toxicological studies for individual ILs. Major constraint in ILs ecotoxicology is that risk cannot be quantified by risk quotient methods because of unavailability of exposure assessment data. At present, only limited information is available about the impacts of ILs to aquatic ecosystems. The main objective of the current work is to use statistical methods to available literature on acute toxicity data of ILs to assess potential ecotoxicological risks when the ILs do come into industrial use. Probabilistic ecotoxicological risk assessment (PETRA) method was adopted by using Chemical Toxicity Distributions (CTDs) and Species Sensitivity Distributions (SSDs). SSDs has been used to derive threshold values below which the ecosystem and its biotic components could be protected from the adverse effect of ILs. CTDs has been used to estimate the probability of finding ILs with an effect below a calculated concentration which is considered to be safe environmental concentration. Acute toxicity data were collected from the literature on the acute toxicity of four bacterial pathogens Aeromonas hydrophila, Escherichia coli, Listeria monocytogenes and Staphylococcus aureus. CTD method was applied to assess the distribution of toxicities of group of IL to individual species. The SSD method was applied to estimate guideline values (GVs) to estimate different level of protection of bacterial species from ILs. Imidazolium chloride and bromide ILs were reported to pose more than 5 % risk towards bacteria. Out of the four bacterial strains, E coli was reported to be potentially at higher risk because of highest sensitivity when exposed towards ILs. The risk posed was five percent which is acceptable level of risk.

This study evaluates the kinetic hydrate inhibition (KHI) performance of four quaternary ammonium hydroxides (QAH) on mixed CH4 + CO2 hydrate systems. The studied QAHs are; tetraethylammonium hydroxide (TEAOH), tetrabutylammonium hydroxide (TBAOH), tetramethylammonium hydroxide (TMAOH), and tetrapropylammonium hydroxide (TPrAOH). The test was performed in a high-pressure hydrate reactor at temperatures of 274.0 K and 277.0 K, and a concentration of 1 wt.% using the isochoric cooling method. The kinetics results suggest that all the QAHs potentially delayed mixed CH4 + CO2 hydrates formation due to their steric hindrance abilities. The presence of QAHs reduced hydrate formation risk than the conventional hydrate inhibitor, PVP, at higher subcooling conditions. The findings indicate that increasing QAHs alkyl chain lengths increase their kinetic hydrate inhibition efficacies due to better surface adsorption abilities. QAHs with longer chain lengths have lesser amounts of solute particles to prevent hydrate formation. The outcomes of this study contribute significantly to current efforts to control gas hydrate formation in offshore petroleum pipelines.

The failure of Shell and Tube Heat Exchangers (STHE) is being extensively observed in the chemical process industries. This failure can cause enormous production loss and have a potential of dangerous consequences such as an explosion, fire and toxic release scenarios. There is an urgent need for assessing the explosion potential of shell and tube heat exchanger at the preliminary design stage. In current work, inherent safety index based approach is used to resolve the highlighted issue. Inherent Safety Index for Shell and Tube Heat Exchanger (ISISTHE) is a newly developed index for assessing the inherent safety level of a STHE at the preliminary design stage. This index is composed of preliminary design variables and integrated with the process design simulator (Aspen HYSYS). Process information can easily be transferred from process design simulator to MS Excel spreadsheet owing to this integration. This index could potentially facilitate the design engineer to analyse the worst heat exchanger in the heat exchanger network. Typical heat exchanger network of the steam reforming process is presented as a case study and the worst heat exchanger of this network has been identified. It is inferred from this analysis that shell and tube heat exchangers possess high operating pressure, corrected mean temperature difference (CMTD) and flammability and reactive potential needs to be critically analysed at the preliminary design stage.

Over the past three decades safety culture studies have bridged many gaps by developing specific existing culture models to workplace environment. But there is still no consensus over the core factors of safety culture, methods and improvement strategies. This conceptual work proposes a different approach by integrating the present general and workplace models to develop a new integrated framework of proactive assessment model for safety culture. In doing so, an summary of the current general and workplace literatures will be provided as well as their homogeneities and differences emphasized. This conceptual framework can be the basis for further research in order to provide a comprehensive picture of the safety culture assessment process. Lastly, implications for specific interventions to develop targeted Safety Culture assessment practices and work towards achieving sustainable safety culture will be discussed.

In this study, series of non-ionic surfactants from Span and Tween are evaluated for their ability to affect the viscosity profile of cyclopentane hydrate slurry. The surfactants; Span 20, Span 40, Span 80, Tween 20, Tween 40 and Tween 80 were selected and tested to provide different hydrophilic–hydrophobic balance values and allow evaluation their solubility impact on hydrate formation and growth time. The study was performed by using a HAAKE ViscotesterTM 500 at 2 °C and a surfactant concentration ranging from 0.1 wt%–1 wt%. The solubility characteristic of the non-ionic surfactants changed the hydrate slurry in different ways with surfactants type and varying concentration. The rheological measurement suggested that oil-soluble Span surfactants was generally inhibitive to hydrate formation by extending the hydrate induction time. However, an opposite effect was observed for the Tween surfactants. On the other hand, both Span and Tween demonstrated promoting effect to accelerate hydrate growth time of cyclopentane hydrate formation. The average hydrate crystallization growth time of the blank sample was reduced by 86% and 68% by Tween and Span surfactants at 1 wt%, respectively. The findings in this study are useful to understand the rheological behavior of surfactants in hydrate slurry.

Physical properties, such as density, refractive index and viscosity, of an aqueous sodium salt of (S)-2-amino-3-phenylpropionic acid (L-phenylalanine, Na-Phe) were investigated in this work. These properties were measured over a temperature range of 298.15-343.15 K at atmospheric pressure. The mass fractions (w) of Na-Phe were 0.05, 0.10, 0.15, 0.20, 0.25, 0.30, 0.35 and 0.40. The analysis of the experimental data showed that the values of density, refractive index and viscosity decreased with increasing temperature at any constant concentration of Na-Phe. However, these values increased with increasing concentration at any constant temperature. The density values were used to estimate the thermal expansion coefficient. The thermal expansion coefficient increased slightly with increasing temperature and concentration. The density and refractive index data were correlated using a modified Graber equation, while, the viscosity data were correlated using a modified Vogel--Tamman-Fulcher (VTF) equation. In all the cases, quantitative analyses of the influence of temperature and concentration were performed. [ABSTRACT FROM AUTHOR]

Removal of carbon dioxide (CO2) from natural gas is of importance because the existence of CO2in natural gas increases the cost of the sweetening process. In recent years, membrane technology has emerged as an attractive alternative in separating CO2from CH4due to its economical, efficient, and environmentally-friendly process. Here, we review the different types of membranes used in CO2/CH4gas separation. Zeolitic imidazolate frameworks (ZIFs) membranes are emphasized and ZIF-8 membranes are selected for further discussion due to their remarkable properties, including high chemical and thermal stability, facile and controllable pore apertures, and high CO2permeance. Different types of methods used for the synthesis of ZIF membranes and the challenges encountered in the growth of the membrane are summarized. Potential use of microwave technology in fabricating a continuous and low-defects ZIF membrane within a short period of time are discussed and highlighted. In conclusion, future direction and perspectives are indicated. [ABSTRACT FROM AUTHOR]