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Monoethanolamine solvent (MEA) is a common solvent used in biogas upgrading plant for carbon dioxide (CO2) and hydrogen sulfide (H2S) removal. However, it has some downsides such as corrosive, high toxicity, and promotes products degradation. Alternatively, amino acid-based solvents such as potassium lysinate (LysK) have been found to have good absorption performance. It is also claimed to be more environmentally friendly as it is less toxic and has a good biodegradability. However, its actual environmental impact for the application of biogas upgrading has not been quantified in a detailed manner. Therefore, in this study, the environmental impact of LysK solvent is quantified from gate to grave in terms of Global Warming Potential (GWP), Acidification Potential (AP) and Eutrophication Potential (EP) using life cycle assessment (LCA) approach. The process was simulated using process simulator, SuperPro Designer version 10 to obtain the input-output data. LysK solvent has a low heat of absorption, which could result in lower CO2 emissions during the biogas upgrading process. However, due to its energy-intensive nature, the incineration process significantly contributed to GWP, AP, and EP. There were also emissions of NOx and SO2 from the flue gas of the incinerator. The findings of this research provide some insight on the environmental impact of utilising LysK for biogas upgrading.

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).

Desalination using hydrates is a developing field, and initial research promises a commercially feasible approach. The current study proposes the natural amino acid, namely tryptophan, as a biodegradable gas hydrate promotor for desalination applications to speed up the hydrate formation process. Its kinetic behavior and separation capabilities with CO2 hydrates were investigated. The studies were carried out with varying concentrations (0.5, 1, and 2 wt.%) of tryptophan at different experimental temperatures (274.15, 275.15, 276.15, and 277.15 K) at 3.5 and 4.0 MPa pressure and 1 wt.% brine concentration. The induction time, initial formation rates, gas uptake, and water recovery are characterized and reported in this work. Overall finding demonstrated that tryptophan efficiently acted as a kinetic hydrate promotor (KHP), and increased tryptophan quantities further supported the hydrate formation for almost all the studied conditions. The formation kinetics also demonstrated that it shortens the hydrate induction time by 50.61% and increases the 144.5% initial formation rate of CO2 hydrates for 1 wt.% addition of tryptophan at 274 K temperature and 4.0 MPa pressure condition. The study also discovered that at similar experimental conditions, 1 wt.% tryptophan addition improved gas uptake by 124% and water recovery moles by 121%. Furthermore, the increased concentrations of tryptophan (0.5–2 wt.%) further enhance the formation kinetics of CO2 hydrates due to the hydrophobic nature of tryptophan. Findings also revealed a meaningful link between hydrate formation and operating pressure observed for the exact temperature settings. High pressures facilitate the hydrate formation by reduced induction times with relatively higher formation rates, highlighting the subcooling effect on hydrate formation conditions. Overall, it can be concluded that using tryptophan as a biodegradable kinetic promotor considerably enhances the hydrate-based desalination process, making it more sustainable and cost-effective.

The intimidating level of anthropogenic CO2 in the atmosphere responsible for global warming and erratic weather conditions needs to be addressed on a priority basis. Different kinds of materials were used to capture CO2 to curtail the alarming and drastic effects of global warming. An ionic liquid (IL) 1-butyl-3-methylimidazolium methanesulfonate [C4mim][CH3SO3] was chosen, owing to its unique and efficient characteristics required for CO2 capture. Thermos-physical characteristics such as sigma surface, sigma profile, and sigma potential are calculated from the COSMO-RS model independent of any kind of experimental or coefficient data as an input. The mandatory information required for the interaction of IL with CO2 was obtained from this model. The COSMO-RS model depends upon unimolecular quantum chemical analysis associated with statistical thermodynamics, molecular structure, and conformation. The structural confirmation of [C4mim][CH3SO3] IL was performed by FTIR, 1H NMR, and 13C NMR spectroscopic methods. Spectrochemical properties are calculated by FTIR, NMR, UV-visible, and fluorescence. Maximum CO2 solubility performed at room temperature (RT) and 45 bar was found to be ~2.7 mmol/g. The uptake of CO2 indicates the presence of sulphur-functionalized anions and bulky alkyl groups in IL’s significant affinity towards CO2. According to hysteresis-based classification, CO2 sorption and desorption follows type H3 classification, which indicates the presence of microporous and mesoporous in the IL sample. The effect of functionalized anions and alkyl groups on CO2 capture is highlighted in this study. The present study is aimed at providing a detailed overview related to theoretical and experimental study and application in terms of CO2 capture of IL.

This study was carried out to evaluate the effect of blending the rubbery and glassy polymer with an alkanolamine on the mechanical properties. Due to the intrinsic properties of glassy polysulfone (PSU) and rubbery polyvinyl acetate (PVAc), optimizing their properties by blending both polymers is expected to address the shortage. The enhanced polymeric blend membrane (EPBM) was developed by varying the composition of PVAc ranging from 5 to 20 wt. % with 95 to 80 wt. % base PSU in dimethyl- acetamide (DMAc) solvent. The DEA amine composition was added to the blend and kept at 10 wt. % over solvent. The tensile analysis technique is utilized to evaluate the mechanical behaviour of a polymeric material which comprises the deformation of the polymeric material underneath the effect of an applied force prior to failure. The mechanical analysis showed improvement in tensile strength, Young's modulus and elongation at break properties with the increase in PVAc/DEA composition in the enhanced polymeric blend membranes. The elongation at break property increased with an increase in the amine contents which indicated the flexibility of the EPBM. In addition, the mechanical analysis revealed remarkable enhancement in the mechanical properties of the EPBM which might be attributed to the robust interactions among the PSU blend with PVAc and DEA.

Polymeric blend mixed matrix membranes (PB3Ms) are synthesized with different blend compositions at a fixed content of carbon molecular sieve (CMS) inorganic filler. The resulting membranes are characterized by FESEM, TGA, DSC and FTIR analyses. Polyethersulfone (PES)/polyvinyl acetate (PVAc)/CMS polymeric blend mixed matrix membranes are prepared by solution casting method. A homogenous mixture of all these components is formed and cast on a clean glass plate. The produced PB3Ms show drastic enhancement in CO2 permeance and CO2/CH4 selectivity in both single and mixed gas permeation tests in comparison with pure PES membrane. Significant CO2 permeance of 132.47 GPU with CO2/CH4 selectivity of 75.27 at 6 bar is obtained for the PB3M having 80 wt%/20 wt% blend ratio of PES/PVAc and 20 wt% CMS loading. The synthesized polymeric blend mixed matrix membranes in this research study demonstrate competitive CO2/CH4 separation performance in comparison with the reported literature on PB3Ms for gas separation.

Cryogenic carbon dioxide (CO2) capture technologies showed promising results for the purification of highly sour natural gas reserves. However, quantitative experimental data for solid and liquid CO2 formation during cryogenic separation is not adequately examined in the previous studies. Moreover, an economical and efficient cryogenic CO2 capture technology with reduced energy and hydrocarbon losses is necessary to make it attractive for commercial use. A high-pressure cryogenic hybrid network comprised of the packed bed and the cryogenic separator was developed for the cryogenic experimental study on CO2 capture from binary CO2-CH4 mixture to focus these areas. Feed containing 30, 50 and 70 % CO2 content were used and the separation study was conducted in vapor-solid (V-S), vapor-liquid (V-L), and vapor-liquid-solid (V-L-S) regions of phase equilibria. The packed bed was used in the V-S operational domain to quantify CO2 solid up to 20 bar because of the operational limitations. Separation characteristics and V-L isothermal flash measurements at 20, 30, and 40 bar pressure and temperature ranges from -20 to −60 °C were carried out in the cryogenic separator. The operation in the setups was carried out at different compositions of the CH4-CO2 binary mixture to define the boundaries of the hybrid cryogenic network. Liquid formation at 40 bar for 70% CO2 feed was 0.15 kg at -55 °C as compared to 0.03 kg for 30 % CO2 feed. The simulation study was carried out using Aspen Plus along with the Peng Robinson Equation of State (EoS), and the results were compared with the experimental data, which showed good agreement. The hybrid cryogenic network showed an energy reduction of 37 % compared to the conventional cryogenic distillation network with 90.6 to 97.3 % CH4 purity and 2.65 to 12.39 % methane losses with different arrangements of the hybrid cryogenic network.

The limited performance of pure glassy and rubbery polymeric membranes for natural gas purification are due to their intrinsic properties. Optimizing their properties by blending both polymers are expected to address the shortage. The foremost objective of this research is to synthesis enhance polymer blend membranes (EPBM) using glassy polysulfone (PSU) and rubbery polyvinyl acetate (PVAc) with the addition of amine for carbon dioxide (CO2) removal from methane (CH4). The EPBM were developed by varying the composition of PVAc ranging from 5 to 20 wt. % with 95 to 80 wt. % base PSU in dimethylacetamide (DMAc) solvent. The amines composition was added to the blend and kept at 10 wt. % over solvent. The findings showed good miscibility between PSU and PVAc blends and the original functional groups of polymers and amines were shown by FTIR with very few spectral peak shifts. The synthesized EPBM were found to have homogenous surfaces and a packed bed sphere structure as shown by FESEM images. Increasing the composition of PVAc from 5 to 20 wt. % has significantly reduced the glass transition temperature (Tg) of PSU from 185.09oC to 155.75oC.

For flow assurance applications, various chemicals are used in the oil and gas industry in order to mitigate corrosion. Among corrosion suppressing compounds, quaternary ammonium salts (QASs) find an exceptional usage as these relatively long chain compounds adsorb onto the surface of the pipeline. The formation of protective layer by adsorbing on the surface prevents corrosion. In this work, tetramethylammonium acetate (TMAAc) which is QAS is evaluated as a corrosion controlling compound in saline environment using weight loss method. The weight loss experiments are performed with the solution concentrations of TMAAc at 0.01, 0.5, 1, 2, 5 and 10 wt%. Corrosion rate values are determined at these concentrations. It is observed that the corrosion with the increase in concentration of TMAAc, corrosion rate is also increased. Rate of metal corrosion varies from 0.068 mm/yr to 0.176 mm/yr in the range of 0.01–10 wt%. The minimum value of corrosion rate is found to be 0.068 mm/yr at the sample concentration of 100 ppm. It is concluded that at lower concentrations, TMAAc can find its application as a commercial corrosion inhibitor.

In this work, CO2 absorption from simulated biogas is investigated using different blends of a PZ + AMP solution in an absorption system at CO2 partial pressures ranging between 20 and 110 kPa. The collected data were presented as CO2 removal profiles along the packed column and were evaluated in terms of CO2 removal efficiency (%) and average overall volumetric mass transfer coefficient in the gas phase (KGav¯). An increased PZ concentration in the AMP solution was found to significantly increase the CO2 removal efficiency and KGav¯ values. It was observed that, when conducted at different CO2 partial pressures, gas and liquid flow rates, and chemical concentrations, the Lamine/GCO2 ratio strongly influenced the process behaviour in the packed column. Additionally, the optimal inlet liquid temperature was observed to be 35 ± 2 °C in this study.

The inherent safety level (ISL) assessment of a heat exchanger network plays a vital role in developing its inherently safer design. New essential safety indices, i.e., inherent safety index for shell and tube heat exchanger (ISISTHE) and overall safety index for heat exchanger network (OSIHEN), are introduced to overcome this potential gap. A prototype tool is proposed by integrating these indices to a process design simulator via object linking and embedded automation. The heat exchanger network of an ammonia synthesis process and a steam reforming unit are presented as a case study. In conclusion, this prototype tool was found to have the potential to figure out a dangerous heat exchanger in a network. © 2020 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

The objective of this study is to measure the physicochemical properties of 2-aminoethanoic acid (glycine, GLY) and N,N-dimethyl-1,3-diaminopropane (DMAPA) solution, which are important parameters ...

This paper presented the absorption removal efficiency for carbon dioxide (CO2) removal from natural gas using an environmental friendly solvent, potassium carbonate promoted with glycine. Recently, CO2 capture using this solvent (with precipitating) was studied by previous researchers. However, the precipitates of the solvent increase the potential of blockage in the packing and piping thus result failure in absorption processes. Therefore, this study focused to assess the CO2 removal efficiency of non-precipitating potassium carbonate promoted with glycine. This green solvent contains aqueous blend of 20 wt% potassium carbonate and 8 wt% glycine. The absorption performance of the solvent was obtained by demonstrated a few experimental works using a bench scale packed absorption column. The packing type was Sulzer metal gauze and the column consisted of six sampling point which located equidistance along the packing. The effect of liquid flow rate was assessed in term of its CO2 removal efficiency and concentration profile along the packing. The study shows the increasing trend of CO2 removal as liquid flow rate increases. Higher liquid/molar flow rate gas (L/G) offers a better absorption performance compared to lower L/G ratio. The results demonstrated the efficient absorption up to 77% using non-precipitating potassium carbonate promoted with glycine.

In process industry, failure or rupture of pressurized vessel is very dangerous especially when there is an escape of flammable gaseous mixture that can cause potential fire or explosion. One of the scenarios that causes such accidents is the blowdown process. Therefore, it becomes crucial to control blowdown process to prevent such accidents. It is important to design optimally to make sure that blowdown valve is according to the requirements. For the safe use of a pressure relief system, some of the parameters are critical, for example, selection of construction material, sizing of relief valves, temperature, and pressure, etc. There is no literature currently available that discusses all the mathematical models or simulation tools for optimum design of the blowdown process. This subject matters because the available models or tools cover different aspects of blowdown process. A meticulous review is required to present the applications of these models and tools based on the accidental scenarios. Therefore, this paper critically reviews the models and tools that are developed purposely to calculate optimum blowdown parameters based on fluid and vessel conditions. Recommendations are given for the development of new simulation tool to simulate phase change conditions especially when solid formation is involved.

The selection of suitable hydrate formers and their respective gas composition for high hydrate formation, driving force is critical to achieve high water recovery and metal removal efficiency in the hydrate-based desalination process. This study presents a feasibility analysis on the possible driving force and subcooling temperatures for the binary and ternary mixtures of methane, carbon dioxide, and propane for hydrates-based desalination process. The driving force and subcooling for the gas systems was evaluated by predicting their hydrate formation phase boundary conditions in 2 wt % NaCl systems at pressure ranges from 2.0-4.0 MPa and temperatures of 1-4 °C using modified Peng-Robinson equation of state in the PVTSim software package. The results suggest that the driving force of CH

Natural gas demand has dramatically increased due to the emerging growth of the world economy and industry. Presently, CO

Hydrate-based technology has yet to find its way to commercial applications due to several issues, including formation conditions and slow kinetics. Several solid particles were introduced to speed up hydrate formation. However, these solid compounds have given contradictory results. This study investigated the effect of high thermal conductive metallic nanofluids of silver (Ag) and copper (Cu) on CH 4 and CO 2 hydrates. The solid particles were suspended in a 0.03 wt% SDS aqueous solution, and the results were compared with the 0.03 wt% SDS and deionized water samples. A stirred tank batch reactor was used to conduct the thermodynamic and kinetic experiments. The thermodynamic study revealed that 0.1 wt% of solid particles do not shift the equilibrium curve significantly. The kinetic evaluation, including induction time, the initial rate of gas consumption, half-completion time, t 50 and semi-completion time, t 95, gas uptake, and storage capacity, have been studied. The results show that the Ag and Cu promote CH 4 hydrates while they inhibit or do not significantly influence the CO 2 hydrates formation. A predictive correlation was introduced to get the apparent rate constant of hydrate formation in the presence of metal-based fluid at the concentrations range of 0.005–0.1 wt%.

High frequency ultrasonic-assisted absorption in a batch system has shown significant enhancement for CO2 removal. Nevertheless, its performance in continuous mode has yet to be studied. A novel continuous high frequency ultrasonic contactor system for CO2 capture has been developed to study the effect of gas flow rate (15–25 SLPM), liquid flow rate (0.1–0.5 SLPM), pressure (10–50 bar) and voltage (0–30 V) on the absorption performance. A validated quadratic model was developed, and the optimum condition was identified using central composite design coupled with response surface methodology. Based on the results, current system demonstrated better absorption performance as compared to other contactors.

Chemical process manufacturing is associated with risks, which cannot be eliminated. Anyhow, controlling or minimizing of risks is possible up to a certain extent through various process safety strategies. Among these strategies, the inherent approach offers a sustainable process design. This review aims to offer an extensive survey regarding the bibliometrics and the features of the state-of-the-art inherent assessment methods. For the bibliometric part, numerous trends like publication trend, authors and geographical cooperation and prominent keywords are presented using the VOSviewer software. For the second intention, the scope and features of inherent assessments methods for sustainable process design are discussed in addition to the historical development of these methods. The techniques are categorized among seven groups based on the method adopted for inherent assessment along with the benefits and detriments of each group. It is revealed that initially, the inherent assessment has focused on the comparison of various process routes, whereas, the modern methods intend to minimize the risk. Furthermore, it is recognized that the process equipment approach is not much explored yet, which may improve the sustainable process designing via the equipment characteristics. Finally, the limitations of present schemes and future research directions for inherent assessment implications in the sustainable process design are also highlighted, such that the objectives of economic, healthier, safer and environmental-friendly process plants can be materialized. © 2019 Elsevier Ltd

In this study, three mixtures of methylyltriphenylphosphonium bromide (MTPPB) as hydrogen bond acceptor (HBA) and N-methyl diethanolamine (MDEA) as hydrogen bond donor (HBD) component was used to prepare transition temperature mixtures (TTMs) into different mole ratios of 1:7, 1:10 and 1:16 HBA/HBD. Two important physicochemical properties of TTMs such as density and refractive index were investigated at the atmospheric pressure and temperature ranges of (293.15–353.15) K and (293.15–343.15) K, respectively. The experimental density data were used to derive the molar volume, molecular volume, lattice energy and isobaric thermal expansion coefficients. With the help of experimental refractive index data, the electronic polarization, molar refraction, and free volume were calculated at the whole temperatures. Several empirical equations were used to correlate refractive indices such as an empirical equation and one-parameter equations (Dale–Gladstone, Eykman, Lorentz–Lorenz, Newton, Arago–Biot, and Oster). Finally, the response surface methodology (RSM) was applied to evaluate the effects of two main factors such as temperature and mole ratio on the density and refractive index of TTMs. The results revealed that the molar ratio has almost a higher effect on the studied properties than temperature.

3-dimethylaminopropylamine (DMAPA) and glycine (GLY) mixture was studied as a potential absorbent for carbon dioxide (CO2) capture and utilization. The solubility of CO2 in aqueous GLY-DMAPA solutions within the range of 0.1–2.0 mol/L (M) were measured experimentally using pressure differential technique. Utilization of CO2 was also studied by mixing the CO2-saturated absorbent with ethanol. The final products obtained were characterized by using Fourier transform infrared (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS). The solubility study revealed that the CO2 loading capacity increased as pressure of CO2 increased. In contrast, the loading capacity decreased when concentration of the absorbent and temperature in equilibrium cell increased. However, the total moles of CO2 absorbed showed an opposite trend such that net CO2 absorbed increased as concentration of absorbent increased. The chemical interactions between CO2 and GLY-DMAPA molecules were studied by analyzing the changes of characteristic peaks observed form the FTIR spectra. For CO2 utilization, the addition of ethanol as a reagent into 0.1 M CO2-saturated GLY-DMAPA solution did not produced any precipitate. Nonetheless, as the concentration of GLY-DMAPA increased from 0.5 M to 2.0 M, white precipitates were produced, indicated that the conversion of CO2 into solid compounds occurred instantaneously after the CO2 capture. The optimum concentration of GLY-DMAPA for CO2 capture and utilization depends on the amount of solids generated and the CO2 loading capacity of the absorbent. At 5 bar, the optimum concentration was found to be 1.0 M with 45 mg/g of solids recovered and CO2 loading capacity of 1.6 mol CO2/mol absorbent. The final product was identified as carbamate salt based on the main characteristic peaks present on the FTIR and XPS spectra.

The increasing global energy demand has compelled the researchers to utilize the undeveloped contaminated natural gas (N.G) reservoirs. However, due to the emissions standards established by environmental regulatory authorities, N.G treatment has become more crucial. Amongst the established CO2 separation strategies, the cryogenic CO2 removal techniques are promising due to environmentally friendliness, high N.G purification, low footprint values, no chemical reaction involved and capable of handling N.G with high CO2 content. Design and operation of a cryogenic process require accurate thermodynamic knowledge along with the understanding of the phase behavior of CO2 with light alkanes to make the process cost–effective. Furthermore, the study of frosting and liquefaction behavior of CO2 or CO2–alkanes mixture is significant for the energy minimization and smooth operation of the cryogenic CO2 removal from N.G. This paper provides a critical review of the available experimental and predicted thermodynamic data for CO2–alkanes mixtures at different conditions. The significance of pressure–temperature (PT), pressure–composition (P–xy), and temperature–composition (T–xy) phase diagrams for CO2–alkane mixtures are discussed in this paper. This paper also describes the use of the equation of states (EoS) for predicting the thermodynamic phase behavior of the CO2 mixtures. This review will help the researchers in designing more efficient, economical, and sustainable cryogenic CO2 capture processes.

One of the challenges for production of natural gas from very sour gas reservoirs with CO2 content up to 80 is the high cost of purification process. The hydrate-based gas separation (HBGS) process is gaining interest globally as a greener solution for separation of CO2 from gaseous streams including sour hydrocarbon mixtures. However, separation of large amounts of CO2 through gas hydrate formation typically leads to considerable loss of hydrocarbons. In this work, selective capturing of CH4 from high CO2 gas mixtures is investigated. Two water-soluble thermodynamic promoters, tetrahydrofuran (THF) and acetone, are used for this purpose. The results indicate that inclusion of these promoters dramatically increased CH4 uptake by sII hydrate formation. However, only THF exhibited a favorable selectivity of CH4. Moreover, this effect is pressure dependent, and the optimum pressure is around 4.5 MPa. Copyright © 2019 American Chemical Society.

The surface tension study is very crucial for the design of CO2 gas absorption contacting equipment. The significance of the surface tension has been increasing due to its consideration in various technological fields. This property influences the mass transfer and hydrodynamics of gas absorption systems, mainly multiphase systems, in which the interface between gas and liquid exists. Therefore, in this study, surface tension of aqueous solutions of sodium l -prolinate (SP) and piperazine (PZ) blends were measured at ten different temperatures from (298.15 to 343.15) K. The SP mass fractions were 0.10, 0.20, and 0.30; while the mass fractions of PZ were 0.02 and 0.05. The experimental results showed that the surface tension increase with increasing the mass fractions of SP and PZ in aqueous blends, and decrease linearly with rising temperature. The experimental data of surface tension were correlated by two empirical correlations as a function of temperature and mass fractions for estimating the predicted data using the optimized correlation coefficients. Moreover, the modeling of surface tension data was carried out using Artificial Neural Network (ANN) approach. The results obtianed from ANN modeling were compared with applied empirical correlation. It was found that the ANN approach outperformed the empirical correlation used in this study. Besides, a quantitative analysis of variation (ANOVA) was performed in order to determine the significance of data. The surface tension of aqueous SP and SP + PZ was also compared with various conventional solvents.

CO2 removal via absorption/stripping system using chemical solvents is a widely acknowledged technology for CO2 capture, either from natural gas or post-combustion processes. It offers higher capture efficiency. However, one of its main drawbacks is the high energy consumption in the regeneration step. Besides, for solvent-based absorption/stripping plant, the units feature nonlinearities as well as high process interactions. Hence, control strategies are crucial in the operational optimization of process set-point changes and disturbance rejections as well as reduction in the operational costs of such systems. Process control systems are key in processing plants as they direct production processes, minimise variations and regulate product consistency. In this paper, an overview on the related efforts that have been carried out in terms of basic and advanced process control strategies are reviewed to provide further understanding on the key features that are required to optimize the operation of the absorption/stripping system.

CO 2 capture using cryogenic packed beds with spherical glass packing material has great potential for applications in the natural gas industry. However, the influence of packing material on their performance has been rarely studied. In the present work, some novel packing materials, including Cellulose Acetate and CA/NH 2 −MIL−101(Al) were used to enhance the performance of the cryogenic packed bed. Pressure drop was determined as a function of specific surface area and module filling fraction experimentally. The CO 2 capture efficiency of the system, axial temperature profile study during cooling and CO 2 recovery steps for the spherical glass beads, CA hollow fibres and composite CA/NH 2 −MIL−101(Al) hollow fibres were also investigated. It was found that the hollow fibres reduce the pressure drop by a factor of 61 % and 33 % compared with the pressure drop caused by the spherical glass beads and monofilament fibres, respectively. The specific surface area provided by the hollow fibres was 230 % and 122 % more than that offered by the glass beads and monofilament fibres respectively. It was also observed that the CO 2 capture efficiency of composite hollow fibres was 141.9 % more than spherical glass beads and 9.5 % greater than the pure CA hollow fibres. The temperature profile study reveals that pure CA and the composite CA/NH 2 −MIL−101(Al) hollow fibres require less energy for cooling than glass beads and provides higher bed saturation time. It was concluded that the NH 2 −MIL−101(Al) hollow fibre reduces the pressure drop and capital cost along with increasing the CO 2 capture efficiency.

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.