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Abstract Decarbonisation of most industrial processes is imperative to achieve climate neutrality. In oil and gas, carbon dioxide (CO2) and natural gas are being discovered together with increasingly higher quantities of hydrogen sulphide (H2S). The negative effects of acid gases (predominantly CO2 and H2S) in that industry mean they have to be separated before both natural gas and petroleum fuels can be classified as safe for transportation and usage. The separated acid gas, usually composed of a higher CO2 volume is stored and utilised in enhanced oil recovery (EOR) or geologically stored (geosequestered) in formations. There are increasingly instances in which higher volume of H2S acid gas mixtures are being discovered and explored. In this work, the effects of a higher mole percentage H2S in an acid gas mixture is investigated using molecular dynamics simulations. The analysis found that it was easier for higher CO2 acid mixtures to reach pressure convergence comparatively. It has also been discovered that higher H2S acid gas mixtures had lower interfacial tension, which makes them more hydrophilic and more miscible with the formation water. The higher H2S acid gas content mixtures also have wider water coverage widths and greater interfacial interactivity between the injected and formation fluids. From the density profiles, H2S gas in the higher H2S acid gas mixture is found to have more influence on the higher H2S acid gas/water injection/sequestration process compared to the effect of CO2 on the higher CO2 acid gas mixture/water. While H2S is slightly more polar than the nonpolar CO2, the carbon of CO2’s ability to form strong dipole–dipole interactions with the oxygen of water increases the CO2's polarity, and this is reflected in the assertion of the primacy of the $${\text{O}}_{{{\text{H}}_{{2}} {\text{O}}}} \cdots {\text{C}}_{{{\text{CO}}_{{2}} }}$$ O H 2 O ⋯ C CO 2 interaction over all other pairs from the radial distribution function in the water/acid gas mixture during geosequestration. This demonstrates also that a reduction in interfacial tension is possible even for hydrophobic phases.

The solubility of ethane and carbon dioxide in three triethanolamine solutions (2.0, 3.5, and 5.0 M) has been measured at 348 K at pressures up to 6980 kPa. [ABSTRACT FROM AUTHOR]

In this work, 0.15 mol/L CuCl2 solution was used to impregnate rice husk char. Experiments were conducted in a laboratory-scale fixed-bed reactor to investigate the oxidation mechanism of Hg0 by acidic gases. The effects of acid gases (SO2, HCl and NO) atmospheres on the mercury removal efficiency of the adsorbent were studied by FTIR, XPS and experiments. The FTIR results showed that the surface of the prepared rice husk char adsorbent contained a large amount of Cu2+ and chlorine-containing functional groups. The XPS results showed that the Cu+ on the surface of the adsorbent increased after mercury adsorption. This work shows that the inhibitory effect of SO2 on Hg removal is reflected in the blockage of the pore structure on the adsorbent surface; the competitive adsorption of O2 needed for the generation of C-O*, the formation of an acid mist by SO2 hinders the contact of Hg0 with the active site. The promotion of HCl is due to the production of active chlorine substances (Cl*) to promote the oxidation of Hg0 to HgCl, HgCl2 and HgO. And introduction of NO will react with O2, while generation of NO2 is beneficial to the oxidation of Hg0 to HgO and Hg(NO3)2. The optimum mercury removal efficiency of the adsorbent is nearly 100% under certain conditions. [ABSTRACT FROM AUTHOR]

Decarbonisation of most industrial processes is imperative to achieve climate neutrality. In oil and gas, carbon dioxide (CO2) and natural gas are being discovered together with increasingly higher quantities of hydrogen sulphide (H2S). The negative effects of acid gases (predominantly CO2 and H2S) in that industry mean they have to be separated before both natural gas and petroleum fuels can be classified as safe for transportation and usage. The separated acid gas, usually composed of a higher CO2 volume is stored and utilised in enhanced oil recovery (EOR) or geologically stored (geosequestered) in formations. There are increasingly instances in which higher volume of H2S acid gas mixtures are being discovered and explored. In this work, the effects of a higher mole percentage H2S in an acid gas mixture is investigated using molecular dynamics simulations. The analysis found that it was easier for higher CO2 acid mixtures to reach pressure convergence comparatively. It has also been discovered that higher H2S acid gas mixtures had lower interfacial tension, which makes them more hydrophilic and more miscible with the formation water. The higher H2S acid gas content mixtures also have wider water coverage widths and greater interfacial interactivity between the injected and formation fluids. From the density profiles, H2S gas in the higher H2S acid gas mixture is found to have more influence on the higher H2S acid gas/water injection/sequestration process compared to the effect of CO2 on the higher CO2 acid gas mixture/water. While H2S is slightly more polar than the nonpolar CO2, the carbon of CO2's ability to form strong dipole–dipole interactions with the oxygen of water increases the CO2's polarity, and this is reflected in the assertion of the primacy of the O H 2 O ⋯ C CO 2 interaction over all other pairs from the radial distribution function in the water/acid gas mixture during geosequestration. This demonstrates also that a reduction in interfacial tension is possible even for hydrophobic phases. [ABSTRACT FROM AUTHOR]

Membrane contactors using microporous membranes for acid gas removal have been extensively reviewed and discussed. The microporous membrane acts as a fixed interface between the gas and the liquid phase without dispersing one phase into another that offers a flexible modular and energy-efficient device. The gas absorption process can offer a high selectivity and a high driving force for transport even at low concentrations. Using hollow fiber, gas–liquid membrane contactors are a promising alternative to conventional gas absorption systems for acid gas capture from gas streams. Important aspects of membrane contactor as an efficient energy device for acid gas removal including liquid absorbents, membrane characteristics, combination of membrane and absorbent, mass transfer, membrane modules, model development, advantages and disadvantages were critically discussed. In addition, current status and future potential in research and development of gas–liquid membrane contactors for acid gas removal were also briefly discussed. The most essential factors of membrane contactors for CO2 absorption/stripping are also discussed, including the hydrophilicity and hydrophobicity of the absorption materials in the membranes, as well as other models published in the literature. The benefits and drawbacks of gas–liquid contactor membranes in CO2 absorption/stripping are also investigated, and the technique is compared to existing separation methods. The technology's present condition and potential directions are explored, as well as some recommendations for further study in order to commercialize. [ABSTRACT FROM AUTHOR]

Energy need is predicted to increase by 47% in the next 30 years. Global warming resulting from the continuously increasing atmospheric Carbon dioxide concentration is becoming a serious and pressing issue that needs to be controlled. Carbon dioxide capture and storage/use (CCS/CCU) provide a promising route to mitigate the environmental consequences of Carbon dioxide emission from fossil fuel combustion. In recent years, hollow fiber membrane contactors are regarded as an advanced technique with several competitive advantages over conventional technologies such as easy scale-up, independent control of flow rates, more operational flexibility, absence of flooding and foaming as well as high interfacial area per unit volume. However, many factors such as the membrane material selection, proper choice of solvent, and membrane module design are critical to success. In this regard, this paper aims at covering all areas related to hollow fiber membranes, including membrane material, membrane modification, membrane surface modification, shape, solvent characterization, operating parameters and costs, hybrid process, hydrophilicity and hydrophobicity of the absorption materials in the membranes, Advantages and Disadvantages of Membrane Contact Technology, membrane lifetime, and energy consumption as well as commercially available systems. Current progress, future potential, and development of pilot-scale applications and thermal fluid of this strategy are also assessed carefully. Furthermore, pore wetting as the main technical challenge in membrane contactor industrial implementation for post- and pre-combustion Carbon dioxide capture processes is investigated in detail. [ABSTRACT FROM AUTHOR]

The natural gases produced from underground reserves may contain sour gases such as H2S and CO2. If the amount of these gases is greater than the standard level, it will be harmful to humans and the environment. Hence, it appears important to accurately determine the concentration of H2S and CO2 in various equipment/units of a natural gas sweetening plant. In this study, a new connectionist approach is introduced to obtain the concentration of outlet acid gases of the sweetening tower of the South Pars gas refinery (in Iran), by utilizing a conventional connectionist tool optimized by an imperialist competitive algorithm (ICA). This ICA strategy is applied to optimize the weights, biases, and number of neurons of the artificial neural network (ANN) model. The input parameters in this modelling strategy include time, the amount of H2S in the output amine, the flow rate of input sour gas, the temperature of sea water for cooling, the mass flow rate of low‐pressure steam to the amine–amine heat exchanger, and the flow rate of input amine. The performance of the hybrid deterministic tool, ANN‐ICA, is compared with the ANN‐back propagation (BP) method. The coefficient of determination and mean squared error to forecast the concentration of output H2S are 0.8931 and 0.0125 for the ANN‐BP algorithm and 0.9057 and 0.0104 for the ANN‐ICA algorithm, respectively. These statistical values are 0.8428 and 0.0001 for the ANN‐BP model and 0.9307 and 0.000 05 for the ANN‐ICA model, respectively, while predicting output CO2 concentration. The results confirm that the ANN‐ICA is a more reliable approach, compared to ANN‐BP, to forecast the concentration of acidic gases leaving the absorption tower. [ABSTRACT FROM AUTHOR]

Despite the heterogeneous reaction of sulfur dioxide (SO 2) on mineral dust particles significantly affects the atmospheric environment, the effect of acidic gases on the formation of sulfite and sulfate from this reaction is not particularly clear. In this work, using the in-situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) technique, we employed a mineral dust particle model (CaCO 3) combined with NO 2 and acetic acid to investigate their effects on the heterogeneous reaction of SO 2 on CaCO 3 particles. It was found that water vapor can promote the formation of sulfite and simulated radiation can facilitate the oxidation of sulfite to sulfate. The addition of NO 2 or acetic acid to the reaction system altered the production of sulfate and sulfite accordingly. There was a synergistic effect between NO 2 and SO 2 that promoted the oxidation of sulfite to sulfate, and a competitive effect between acetic acid and SO 2 that inhibited the formation of sulfite. Moreover, light and water vapor can also affect the heterogeneous reaction of SO 2 with the coexistence of multiple gases. These findings improve our understanding of the effects of organic and inorganic gases and environmental factors on the formation of sulfite and sulfate in heterogeneous reactions. [Display omitted] [ABSTRACT FROM AUTHOR]

The GMOS (Global Mercury Observation System) project has the overall goal to develop a coordinated observing system to monitor mercury on a global scale. Here we present the long-term (2011–2020) air mercury monitoring data obtained at the Listvyanka station located at a shore of Lake Baikal, Siberia. The long-term monitoring shows obvious seasonal variation of the background mercury concentration in air, which increases in the cold and decreases in the warm season. The short-term anomalies are associated with the wind carrying the air from the industrial areas where several big coal-fired power plants are located. A positive correlation between the mercury, SO2 and NO2 concentrations is observed both in the short-term variations and in the monthly average concentrations. The analysis of forward and backward trajectories obtained with the HYSPLIT model demonstrates revealing of the mercury emissions sources. During the cruise of 2018, the continuous air mercury survey over Lake Baikal covered 1800 km. The average mercury concentration over Baikal is notably less in comparison with the average value obtained at the onshore Listvyanka station during the same days of the cruise. That can lead to the conclusion that Baikal is a significant sink of the atmospheric mercury.

The natural gas amine sweetening process to remove acid impurities has been analyzed, the related problems have been considered, and ways of their solution have been proposed. Problems such as optimization of compositions of both the amine solution and the acid gases to be eliminated, contamination of amine solutions with different impurities, amine degradation, and high energy consumption for their regeneration, have been analyzed. Foaming in the absorber and means of its suppression have been considered, as well as the main issues of management and disposal of spent amines. [ABSTRACT FROM AUTHOR]

The development of new, efficient and cost-effective technologies for acid gases (CO2 and H2S) removal from natural gas is pertinent for cleaner energy productions. The removal of acid gases from natural gas can be carried out using different techniques (chemical, physical or hybrid). Although the widely employed techniques are generally effective, they have some ascribed drawbacks such as process efficiency and high-energy cost. Emerging techniques are being considered to reduce or eliminate these limitations but their deployment on an industrial scale may require that certain scientific and technological criteria, such as higher selectivity and gas separation kinetics, be met. Unprecedented and lacking in previous appraisals, this review has focused on the emerging and sustainable developments on acid gases removal from natural gas, but not without a critical evaluation of the existing technologies to provide a better background on the subject, ascertain the status-quo and identify gaps for further improvements. Efficiency of these emerging technologies are analysed with focus on ionic liquids and their blends, binding organic liquids, enzyme-based separation technologies and others. This review also features the brief contribution of the authors towards the development of low-cost materials for CO2/natural gas separation. This article is expected to serve as an in-depth requisite background for further research on carbon capture processes with respect to natural gas purification. [ABSTRACT FROM AUTHOR]

One way to support the development of new safety practices in testing and field failure situations of electric vehicles and their lithium-ion (Li-ion) traction batteries is to conduct studies simulating plausible incident scenarios. This paper focuses on risks and hazards associated with venting of gaseous species formed by thermal decomposition reactions of the electrolyte and electrode materials during thermal runaway of the cell. A test set-up for qualitative and quantitative measurements of both major and minor gas species in the vented emissions from Li-ion batteries is described. The objective of the study is to measure gas emissions in the absence of flames, since gassing can occur without subsequent fire. Test results regarding gas emission rates, total gas emission volumes, and amounts of hydrogen fluoride (HF) and CO2 formed in inert atmosphere when heating lithium iron phosphate (LFP) and lithium nickel-manganese-cobalt (NMC) dioxide/lithium manganese oxide (LMO) spinel cell stacks are presented and discussed. Important test findings include the large difference in total gas emissions from NMC/LMO cells compared to LFP, 780 L kg -1 battery cells, and 42 L kg-1 battery cells, respectively. However, there was no significant difference in the total amount of HF formed for both cell types, suggesting that LFP releases higher concentrations of HF than NMC/LMO cells. [ABSTRACT FROM AUTHOR]

Firefighters are exposed to a variety of combustion products during operational fires but also during live-fire training. As part of an on-going project investigating firefighter operational and training environments, this study measured the atmospheric concentrations of volatile organic compounds and acid gases outside and inside the structural firefighting ensembles worn by instructors during compartment fire behavior training using particleboard as a fuel. Atmospheric concentrations of benzene, formaldehyde, and hydrogen cyanide within the firefighting environment were observed to exceed Australian workplace exposure standards; although, the use of self-contained breathing apparatus throughout the training meant that atmospheric concentrations measured were not representative of firefighter inhalation exposures. Concentrations of air contaminants inside the structural firefighting ensembles during compartment fire behavior training were substantially lower than outside the ensembles, and much lower than those documented as potentially causing acute toxic effects in humans by dermal absorption from vapor. Although this study is focused on the generation of air contaminants in compartment fires, dermal absorption in these types of training environments may still constitute a potential route of low-level exposure to some combustion products. [ABSTRACT FROM AUTHOR]

Acid gases such as carbon dioxide and hydrogen sulfide are common contaminants in oil and gas operations, landfill gases, and exhaust stacks from power plants. While there are processes currently used to treat these effluents (e.g., amine absorption and adsorption using zeolite), many of these processes require high energy, space, and hazardous chemicals. Removal using biochar derived from the fast pyrolysis of forestry residues represents a more sustainable option. In this study, adsorption using CO2 as a surrogate for acid gases was investigated using various biochars produced from fast pyrolysis of sawmill residues. Response surface methodology was used to determine operating conditions for maximum adsorption and assess interaction of the adsorption parameters, i.e., temperature, inlet feed flow rate, and CO2 concentration, on biochar adsorption capacity. The Freundlich isotherm best represented the equilibrium adsorption, and the kinetic model was pseudo first-order. Thermodynamic analysis indicated the adsorption process was spontaneous and exothermic. The biochar had better adsorption capacity relative to commercial zeolite. Our results suggested that biochar could be used as a sustainable and cost-effective option for contaminant removal from acid gases produced in landfill gas treatment, fossil fuel extraction, and/or combustion. [ABSTRACT FROM AUTHOR]

Abstract A series of polyethyleneimine (PEI)-impregnated MIL-101(Cr, Mg) adsorbents with different PEI loadings was synthesized in the present work. Although the surface area and pore volume of MIL-101(Cr, Mg) decreased significantly as the PEI loading increased, all the resulting composites exhibited a dramatically enhanced CO 2 adsorption capacity at low pressures. Up to 20 wt% PEI loading, the CO 2 adsorption capacity reached a competitive value of about 3 mmol/g at 25 °C and 1 bar. The stability of these PEI-MIL-101(Cr, Mg) composites was analyzed by exposing them to humid air, SO x , and NO x for a period of six days. No noticeable changes could be discerned in the X-ray diffraction patterns of the exposed composites; however, the CO 2 adsorption capacity reduced by 30%–35% due to the formation of nitrate and sulfate compounds on the surfaces of the materials. Graphical abstract Image 1 Highlights • Polyethyleneimine (PEI) was impregnated to the bimetallic MIL-101(Cr, Mg) by a wet impregnation method. • As the PEI loading increases, the CO 2 capacity of the PEI-MIL-101(Cr, Mg) increased by 50%. • The optimum PEI loading was found to be 20 wt% showing the maximum adsorption capacity. • After the exposure to humid air and acid gases, samples showed decreased CO 2 capacities despite no changes in XRD. • CO 2 diffusivity analysis showed the decreasing behavior with PEI increase due to the steric hindrance. [ABSTRACT FROM AUTHOR]

MIL-101(Cr, Mg) is a promising metal organic framework (MOF) considering its moisture, thermal, and chemical stabilities. Piperazine-loaded polyacrylonitrile (PAN)/MIL-101(Cr, Mg) fiber mats were fabricated with different percentages of piperazine (10%, 20%, and 30%) in the polymer solution using an electrospinning technique. The PAN/MIL-101 fiber mats exhibited improved adsorption capacity and selectivity when combined with piperazine because of the improved affinity of CO 2 molecules for the basic amine sites of piperazine. PAN/MIL-101–20% was selected as an optimum fiber mat owing to its high CO 2 adsorption capacity (2.48 mmol/g) and selectivity (38), which are 2.4 and 2.9 times higher than those of the fiber mat without piperazine, respectively. The stability of the PAN/MOF fiber mat in humid air and NO 2 gas and the results of ten adsorption-desorption experiments showed consistent CO 2 capture performance. [Display omitted] • PAN/MIL-101(Cr,Mg) fiber mats with piperazine were fabricated using electrospinning technique • With 20% piperazine, PAN/MIL-101(Cr,Mg) fiber mats showed 2.4 and 2.9 times increase in CO 2 capacity and CO 2 /N 2 selectivity. • PAN/MIL-101(Cr,Mg)-Pz-20% showed a strong stability to humid air and NOx. • Consistent performance observed in CO 2 adsorption (298 K)-desorption (393 K) cycles of PAN/MIL-101(Cr,Mg)-Pz-20%. [ABSTRACT FROM AUTHOR]

Gaseous and particulate emissions from the combustion of coal have been associated with adverse effects on human and environmental health, and have for that reason been subject to regulation by federal and state governments. Recent regulations by the United States Environmental Protection Agency have further restricted the emissions of acid gases from electricity generating facilities and other industrial facilities, and upcoming deadlines are forcing industry to consider both pre- and post-combustion controls to maintain compliance. As a result of these recent regulations, dry sorbent injection of trona to remove acid gas emissions (e.g. HCl, SO2, and NOx) from coal combustion, specifically 90% removal of HCl, was the focus of the current investigation. Along with the measurement of HCl, SO2, and NOx, measurements of particulate matter (PM), elemental (EC), and organic carbon (OC) were also accomplished on a pilot-scale coal-fired combustion facility. Gaseous and particulate emissions from a coal-fired combustor burning bituminous coal and using dry sorbent injection were the focus of the current study. From this investigation it was shown that high levels of trona were needed to achieve the goal of 90% HCl removal, but with this increased level of trona injection the ESP and BH were still able to achieve greater than 95% fine PM control. In addition to emissions reported, measurement of acid gases by standard EPA methods were compared to those of an infrared multi-component gas analyzer. This comparison revealed good correlation for emissions of HCl and SO2, but poor correlation in the measurement of NOx emissions.

Abstract An air quality monitoring campaign by passive sampling techniques was carried out, for the first time, between November 2016 and January 2017 on the Cape Verdean island of Fogo, whose volcanic mountain rises up to 2829 m. Levels of SO 2 and acid gases (HF, HCl, HNO 3 , H 2 SO 4 and H 3 PO 4) were, in most cases, below the detection limits. Alkylpentanes, hexane, cycloalkanes and toluene were the dominant volatile organic compounds. The m,p-xylene/ethylbenzene ratios revealed that air masses arriving at Cape Verde have been subjected to significant aging processes. High toluene/benzene ratios suggested extra sources of toluene in addition to vehicle emissions. Deposition rates of total settleable dust ranged from 23 to 155 mg/m2/day. On average, organic carbon accounted for 15.6% of the dust mass, whereas elemental carbon was generally undetected. Minerals comprised the dominant mass fraction. The dust levels were mostly affected by two main airflows: the westerlies and the Saharan Air Layer. These air masses contributed to the transport of mineral dust from desert regions, secondary inorganic constituents (SO 4 2−, NO 3 − and NH 4 +) and tracers of biomass burning emissions, such as potassium. Sea salt represented 12% of the mass of settleable dust. Scanning electron microscope observations of several particles with different compositions, shapes and sizes revealed high silica mass fractions in all samples, as well as variable contents of carbonates, sulphates, aluminosilicates, Fe, Ti, F and NaCl, suggesting that, in addition to the already mentioned sources, dust is likely linked to industrial emissions in the northern and north-western coast of the African continent. Although some atmospheric constituents presented higher concentrations near the crater, the small fumarolic activity still present after cessation of the eruption in February 2015 has a limited impact on air quality, which is most affected by long range transport and some local sources at specific locations. Highlights • Settleable dust rates and levels of SO 2 , acid gases and VOCs were monitored in Fogo. • The westerlies and the Saharan Air Layer highly affected the Cape Verdean Island. • Mineral dust was mixed with anthropogenic emissions from northern Africa and America. • Wildfires in Africa and marine air masses also influenced the dust composition. • Some local sources at specific locations were identified. [ABSTRACT FROM AUTHOR]

Metal Organic Frameworks (MOFs) have the potential to be used as adsorbents in industrial separations. Different ligand lengths can generate MOFs with similar topology but differing pore sizes. Molecular simulations were used in this work to assess the adsorption isotherms, heats of adsorption and selectivity of H 2 S and CH 4 in MOF UiO-66, UiO-67, and UiO-68. Detailed analysis of the distribution of molecules in the cages and the radial distribution functions suggest that the effect of the linker on the macroscopic properties is negligible at low pressures, but it becomes evident at high pressures, where adsorption far from the linker is observed in large pore materials. Based on the adsorption selection parameter, UiO-67 shows better performance in a wider range of conditions than the other materials. [ABSTRACT FROM AUTHOR]

A novel approach was examined by addition of amine-modified reduced graphene oxide (rGO) to amine solutions in order to enhance the CO 2 absorption capacity of amine solutions. Amine functionalized reduced graphene oxide (rGO)/methyl diethanolamine (MDEA) nanofluid was prepared for absorption of acid gases (CO 2 , H 2 S). GO was synthesized via a modified hummer method and functionalized through solvothermal method. As-synthesized NH 2 -rGO was characterized by XRD, BET, SEM, FTIR, EDX and XPS analysis to determine the structure. NH 2 -rGO was dispersed in MDEA and displayed excellent stability verified by zeta potential analysis. NH 2 -rGO/MDEA nanofluid showed high absorption capacity toward CO 2 and H 2 S. The absorption capacity of the solution for CO 2 and H 2 S was promoted up to 16.2% and 17.7%, respectively. Solubility results showed a reverse relationship with increasing temperature. Comparison of solubility data revealed that introducing 0.1 wt% NH 2 -rGO to 40 wt% had a greater enhancement relative to introducing 0.1 wt% GO to the same solution. [ABSTRACT FROM AUTHOR]

Chemical absorption with alkanolamines processes are commonly applied for natural gas purification. The knowledge of CO 2 , H 2 S, hydrocarbons and mercaptans solubilities in aqueous alkanolamine solutions is important in acid gas removal process simulation and design. In previous works, alkanes, aromatics and mercaptans solubilities in different aqueous alkanolamine solutions have been successfully represented by using the PR-CPA EoS. In this work, the PR-CPA EoS with a pseudo-chemical reaction approach is developed and applied to describe the solubility of acid gases in aqueous alkanolamines solutions. The results are in good agreement with a wide range of experimental data. Other relevant properties such as water content, electrolytes speciation and enthalpy of absorption are accurately predictd by PR-CPA EoS. [ABSTRACT FROM AUTHOR]

While kinetic hydrate inhibitors (KHIs) have seen increasing use in the hydrocarbon production industry as a cost effective hydrate mitigation strategy, there is still a lack of understanding concerning inhibition mechanisms and the underlying factors, which influence this. For example, little is known about the effect of gas composition even though this plays a major role, with lean acid gases presenting a particular challenge to KHIs. In this study, a Crystal Growth Inhibition (CGI) method previously developed in-house has been used to examine the effect of acidic gases on KHI performance. Using poly-n-vinylcaprolactam (PVCap) as the KHI, the effect of CO 2 and H 2 S on different gas mixtures has been measured in detail for pressures up to ∼14.0 MPa. In addition, the effect of a low pH resulting from hydrochloric, acetic and citric acids on PVCap methane hydrate inhibition has been investigated for comparison. Based on experimental results and thermodynamic modelling, it is concluded that hydrate growth from dissolved gas – a significant factor for water miscible H 2 S and CO 2 – does not appear to play a major role in KHI performance. Likewise, a pH reduction itself does not seem to have a notable influence. Instead, results point to changes in cage occupancy patterns/guest gas composition a function of pressure as having the greatest effect on KHI inhibition, potentially by changing the strength of polymer absorption on different hydrate crystal faces. [ABSTRACT FROM AUTHOR]

Thermodynamic modeling and molecular dynamic investigation of acid gases absorption in ionic liquids. [Display omitted] • Solubility of acid gases in different ionic liquids were thermodynamically modeled. • MPR2-LCVM-Wilson model indicated highest correlation with the experimental data. • Released absorption energies of acid gases in ILs were in tune with their solubility. • Sensitivity analysis results uncovered higher importance of pressure on solubility in ILs. • MD results showed that solute-solvent binding energy increases with increasing pressure. Ionic Liquids (ILs) have emerged as a promising generation of solvents for the absorption of acid gases (e.g., CO 2 and H 2 S) due to their unparalleled physiochemical properties. This study focuses on thermodynamic modeling and molecular dynamic simulation approaches to estimate the solubility and interaction energies of CO 2 and H 2 S gases in/with different frequently-used ILs. For thermodynamic modeling, the GE/EOS method was employed. This method allows for combining activity-coefficient models in the structure of the cubic equation of states. In the GE/EOS method, the modified Peng-Robinson equation of state (MPR2) together with the LCVM mixing rules was used. Excess Gibbs free energy models of Wilson, NRTL, and UNIQUAC were also applied for combination with the GE/EOS models. The prediction results of the combined models were compared with the experimental solubility data. The results demonstrated the capability of these models to predict the thermodynamic behavior of the acid gas-ILs systems. The results uncovered that the MPR2-LCVM-Wilson model can tabulate the highest correlation with the experimental data compared to the other model combinations. Results of the sensitivity analysis on the principal operational variables (temperature and pressure), showed superior effect of pressure on the gas solubility. In addition, the results of the molecular dynamic (MD) simulation disclosed an agreement between the trends of the solubility of acid gases in ILs with those of the released interaction energies of acid gases absorbed by the ILs. MD results also confirmed that the solubility of acid gases in ILs increases with an increase in the binding energy of the molecules with the ILs. [ABSTRACT FROM AUTHOR]

One way to support the development of new safety practices in testing and field failure situations of electric vehicles and their lithium-ion (Li-ion) traction batteries is to conduct studies simulating plausible incident scenarios. This paper focuses on risks and hazards associated with venting of gaseous species formed by thermal decomposition reactions of the electrolyte and electrode materials during thermal runaway of the cell. A test set-up for qualitative and quantitative measurements of both major and minor gas species in the vented emissions from Li-ion batteries is described. The objective of the study is to measure gas emissions in the absence of flames, since gassing can occur without subsequent fire. Test results regarding gas emission rates, total gas emission volumes, and amounts of hydrogen fluoride (HF) and CO2 formed in inert atmosphere when heating lithium iron phosphate (LFP) and lithium nickel-manganese-cobalt (NMC) dioxide/lithium manganese oxide (LMO) spinel cell stacks are presented and discussed. Important test findings include the large difference in total gas emissions from NMC/LMO cells compared to LFP, 780 L kg−1 battery cells, and 42 L kg−1 battery cells, respectively. However, there was no significant difference in the total amount of HF formed for both cell types, suggesting that LFP releases higher concentrations of HF than NMC/LMO cells.

Biochar, a product of pyrolysis of biomass, represents an attractive alternative to non-renewable or unsustainably sourced biomass as an adsorbent material for treating gaseous effluents. Biomass from residues associated with agricultural and forestry operation, otherwise considered waste material or a storage issues, represents a potential sustainable source of adsorbent. There are several adsorbents for removal of contaminants from gases including carbon based, silica based, and metal oxide based adsorbents; however, availability of feedstock, low cost, and potential high adsorption capacity distinguish biochar from other adsorbents. This review includes common sorbents for removal of contaminants from gas, biochar production methods, and compares biochar with activated carbon as one of the most common commercial adsorbents. Adsorption isotherms, mechanisms, and process systems for removal of acid gases such as CO 2 and H 2 S by biochars have been comprehensively reviewed. The application of molecular modeling to describe adsorption by activated carbons and possible extension to biochar were studied. There is still a lack of published information in the molecular modeling of biochars, and using these models to understand the complex adsorbent mechanisms on the very heterogeneous surfaces of biochar (relative to commercial adsorbent materials such as activated carbons). Therefore, further research needs to fill these gaps to identify all potentials of this promising adsorbent. [ABSTRACT FROM AUTHOR]

The Perturbed Chain Statistical Association Fluid Theory (PC-SAFT) is used to investigate the solubility of carbon dioxide (CO 2 ) and hydrogen sulfide (H 2 S) in several methylimidazolium bis (trifluoromethylsulfonyl) imide ionic liquids (ILs) or [C n mim][NTf 2 ] where n =2, 4, 6, and 8. The pure component parameters of the ILs are estimated by fitting to experimental density data and binary solubility data of acid gases in ILs reported in literature. Two strategies are examined to model the ILs. In the first strategy, the ILs are treated as neutral molecules. In the second strategy, the ILs are modelled as two charged ions: imidazolium cation [C n mim] + and bis (trifluoromethylsulfonyl) imide anion [NTf 2 ] − . For each strategy, four different self association schemes are examined: non-associating, 2-site, 3-site, and 4-site schemes. The inclusion of self-association of the IL improves the calculated acid gas solubility. The 4-site association scheme with two donors and two acceptors provided the best results for almost all the investigated acid gases-IL binary systems, with an AARD of 2.76%–6.62% for H 2 S-ILs systems and 1.54%–4.98% for CO 2 -IL systems. Using these parameters, the solubility of ternary systems of CO 2 and H 2 S in C 8 mimNTf 2 IL is successfully represented, with an AARD of 6.24% for CO 2 and 7.99% for H 2 S, without the need for binary interaction parameters. The high pressure density of ILs and the binary solubility of CO 2 -ILs at high pressure is also represented with reasonable accuracy. The inclusion of the electrolyte term in the second strategy improves the high pressure density and solubility results as well as the predictive capability of the model by allowing for the examination of the effect of using different cation-anion combinations. [ABSTRACT FROM AUTHOR]

Arsenic emission from fuel combustion and metal smelting flue gas causes serious pollution. Addition of sorbents is a promising way for the arsenic capture from high temperature flue gas. However, it is difficult to remove arsenic from SO 2 /HCl-rich flue gas due to the competitive reaction of the sorbents with arsenic and these acid gases. To solve this problem, arsenic adsorption over γ-Al 2 O 3 was studied in this work to evaluate its adsorption mechanism, resistance to acid gases as well as regeneration behavior. The results show that γ-Al 2 O 3 had good resistance to acid gases and the arsenic adsorption by γ-Al 2 O 3 could be effectively carried out at a wide temperature range between 573 and 1023 K. Nevertheless, adsorption at higher-temperature (like 1173 K) leaded to the decrease of surface area and the rearrangement of crystal structure of γ-Al 2 O 3 , reducing the active sites for arsenic adsorption. The adsorption of arsenic was confirmed to occur at different active sites in γ-Al 2 O 3 by forming various adsorbed species. Increasing temperature facilitated arsenic transformation into more stable chemisorbed As 3+ and As 5+ which were difficult to remove through thermal treatment regeneration. Fortunately, the regeneration of spent γ-Al 2 O 3 could be well performed using NaOH solution. [ABSTRACT FROM AUTHOR]

Several types of air pollution control technologies about waste combustion system were developed on the last quarter century. If those new technologies have come into wide use, we ought to explain several new technology convincingly to customers or users. Therefore I will take a few examples of explanations about those new technologies. [ABSTRACT FROM AUTHOR]

The solubility of CO2 in the primary, secondary, tertiary and sterically hindered amine aqueous solutions at various conditions was studied. In the present work, the Modified Kent-Eisenberg (M-KE), the Extended Debye-Hückel (E-DH) and the Pitzer models were employed to study the solubility of CO2 in amine aqueous solutions. Two explicit equations are presented to evaluate the concentration of H+ as well as the equilibrium constants of protonation reactions for the tertiary and sterically hindered amine aqueous solutions. Using the M-KE model, the equilibrium constants ofprotonationreactionsof amines were correlated in termsoftemperature, CO2 partial pressure and amine concentration. Also the E-DH and Pitzer models were used to correlate the solubility of CO2 in MDEA aqueous solution. The binary interaction parameters for the models studied in this work as well as the parameters for the equilibrium constants of protonation reactions were obtained using the Davidon-Fletcher-Powell (DFP) minimization method. The results show that the M-KE, E-DH and the Pitzer models can accurately predict the corresponding experimental data. Although the solubility data for CO2 in amine aqueous solutions have been reported in the literature to a large extent, accurate data are required to model the CO2 absorption process. Therefore, two criteria for the tertiary and sterically hindered amines were presented using the M-KE model to screen the experimental data.

[Display omitted] • An acid–base electrochemical cell was established to harness chemical energy. • A chemical model was proposed to understand the energy harvesting process. • The system applies six acid gases with energy output of 0.78–133.3 kJ e /mol gas. • Valued added by-products were produced from the energy harvesting process. Treatment of toxic acid-gas pollutants are conventionally through acid–base chemical reaction which releases a significant amount of chemical energy, but these reaction energies are usually unused and their recovery is not being considered in current pollutant control technology. Here, we propose a new concept of acid–base electrochemical cell (ABEC) system that can convert the acid–base reaction energy into electrical energy by using the dual abilities of amine (or ammonia) to react with acid pollutants and coordinate with metal ions. By establishing copper/ammonia-based ABEC system, we experimentally demonstrated that ABEC is applicable to harvest the energy from the treatment of a wide range of acid-gas pollutants (SO 3 , HCl, CO 2 , SO 2 , H 2 S, NO 2) with the power density ranging from 0.48-546 W/m2 and energy density of 0.78–133.3 kJ e /mol gas dependent on their chemical reaction energy. This investigation provides the fundamentals and experimental evidence of electricity generation from acid gas treatment, holding the potential to develop energy-efficient emission control technology. [ABSTRACT FROM AUTHOR]

The properties of 1-ethyl-3-methylimidazolium glycinate ionic liquid mixed with CO 2 , SO 2 and H 2 O were studied using a computational chemistry approach considering classical molecular dynamics simulations and quantum chemistry calculations using density functional theory. Studies as a function of mixture composition, pressure and temperature allowed a detailed characterization at the nanoscopic level of the interaction between the acid gases and the ionic liquid as a model for the use of aminoacid-based ionic liquids for acid gas capture purposes. Likewise, the properties of aqueous mixtures were analysed considering the ubiquitous presence of water in acid gas capture industrial processes. Insights on the characteristics and strength of gas molecules – ionic liquid interactions were inferred from simulations, and thus, showing the arrangement and dynamics of gas molecules around the ions. [ABSTRACT FROM AUTHOR]

Our previously reported high pressure hollow fibers membrane (HFM) modules were specifically developed with aim to meet the operation requirements for the industrial sweetening of natural gas. The present work presents further characterization of CO 2 and H 2 S high pressure removal under different experimental conditions, which are in particular relevant to the ultimate intended industrial application. These include module packing density, feed gas/absorption liquid flow rate ratio, absorption liquid temperature as well as solvent loading. The operational stability of the HFM module, equipped with the PFA hollow fibers, was also investigated and reported. The presented results on the long-term operational stability of membrane modules based on hollow fibers, under industrially relevant conditions are believed to be the first report of its kind. The PFA-HFM modules showed excellent operational stability during the test period, i.e., ∼200 operation hours over a 7-week period using pressurized feed gas pressure (50 bar) and hot absorption solvent (100 °C). [ABSTRACT FROM AUTHOR]

The surface properties of 1-ethyl-3-methylimidazolium glycinate ionic liquid, as a model of amino acid-based compounds, in contact with a vacuum, CO 2 , SO 2 and flue gas phases are studied using molecular dynamics simulations. The orientation of ions at the interface and the characteristics of the adsorbed gas layers are inferred from the theoretical study. Densely adsorbed layers are obtained for CO 2 molecules at fast adsorption rates, with CO 2 interacting preferentially with imidazolium cations at the interface. SO 2 is adsorbed faster than CO 2 at the ionic liquid interface, showing large affinity for glycinate anions. The contact of the studied ionic liquid with a model flue gas leads to the fast development of an adsorbed layer of water molecules, with CO 2 molecules being adsorbed on top of this water layer. Therefore, the interface is initially blocked by the presence of water molecules, which would delay the adsorption and diffusion of CO 2 molecules across the ionic liquid interface. [ABSTRACT FROM AUTHOR]

Natural gas (NG) is a naturally gaseous hydrocarbon mixture that is formed under the earth’s surface. NG is considered to be the cleanest fossil fuel and is a safe source of energy when transported, stored and used. The primary constituent of NG is methane, it may also contain (C 2 + hydrocarbons, N 2 , CO 2 , He, H 2 S, and noble gases) according to its origin. Different gas processing technologies can be employed to remove constituents other than methane. Due to importance of NG as a fuel and the increasing global demand of it, this article reviews the fundamentals of NG origin, composition, and processing. [ABSTRACT FROM AUTHOR]

In this study, the physical solubilities of CO 2 in several amine solutions at different concentrations and pressures were determined using the nitrous oxide N 2 O analogy. The solubilities of N 2 O in four aqueous amine solutions, including Monoethanolamine (MEA), Diethanolamine (DEA), Diethylenetriamine (DETA), and Tetraethylenepentamine (TEPA) were determined experimentally at different concentrations and pressures ranging from 1 to 4 kmol/m 3 and 101.3–405.3 kPa, respectively. The solubility of N 2 O and CO 2 for a few amines were compared with data available in the literature. The experimental data agreed well with those published in the literature. The CO 2 solubility values obtained experimentally as well as other values from the literature were correlated to the concentrations of the amino groups in the amine. The physical solubility of CO 2 was found to be inversely proportional to the number of amino groups in the amine. The simple correlation can give reasonable predictions with an average error of less than 10% for CO 2 solubility at 298 K and 101.3 kPa. [ABSTRACT FROM AUTHOR]

Synergistically convert acid gases to valuable chemicals is meaningful. Herein, unsupported CoMo sulfide catalysts with abundant sulfur vacancies were fabricated to attain synergistical conversion of H 2 S and CO 2 to COS. Various metal sulfides were obtained, such as Co 3 S 4 , Co 9 S 8 and vacancy-defective MoS 2. Besides, simultaneous sulfidation of Mo with Co prompted formation of CoMoS phase, which enhanced catalytic performance. Among them, CoAlMo-S catalyst exhibited superior activity, allowing for equilibrium COS yield (6%, 300 ℃). DFT calculations indicate that chemisorbed H 2 S induced CO 2 activation via van der Waals interaction between C atom in CO 2 and S atom in H 2 S, contributed to efficient C–S bond formation. Sulfur vacancy significantly promoted dissociative adsorption of H 2 S while Co atom in CoMoS phase was beneficial for CO 2 adsorption and facilitated C–S bond construction. This work not only achieves H 2 S pollution control and carbon emission reduction, but also provides an alternative approach to synthesis COS. [Display omitted] • Synergistical conversion of acid gas to COS was attained on CoMo sulfide catalyst. • CoAlMo-S catalyst depicted superior activity allowing for equilibrium yield of COS. • Simultaneous sulfidation of Mo with Co prompted formation of special CoMoS phase. • The presence of Co was beneficial for CO 2 adsorption and favored formation of COS. [ABSTRACT FROM AUTHOR]

Gaseous and particulate emissions from the combustion of coal have been associated with adverse effects on human and environmental health, and have for that reason been subject to regulation by federal and state governments. Recent regulations by the United States Environmental Protection Agency have further restricted the emissions of acid gases from electricity generating facilities and other industrial facilities, and upcoming deadlines are forcing industry to consider both pre- and postcombustion controls to maintain compliance. As a result of these recent regulations, dry sorbent injection of trona to remove acid gas emissions (e.g. HCl, SO2, and NOx) from coal combustion, specifically 90% removal of HCl, was the focus of the current investigation. Along with the measurement of HCl, SO2, and NOx, measurements of particulate matter (PM), elemental (EC), and organic carbon (OC) were also accomplished on a pilot-scale coal-fired combustion facility. Gaseous and particulate emissions from a coal-fired combustor burning bituminous coal and using dry sorbent injection were the focus of the current study. From this investigation it was shown that high levels of trona were needed to achieve the goal of 90% HCl removal, but with this increased level of trona injection the ESP and BH were still able to achieve greater than 95% fine PM control. In addition to emissions reported, measurement of acid gases by standard EPA methods were compared to those of an infrared multi-component gas analyzer. This comparison revealed good correlation for emissions of HCl and SO2, but poor correlation in the measurement of NOx emissions. [ABSTRACT FROM AUTHOR]

Air pollution caused by flue gas from municipal solid waste (MSW) incineration is becoming increasingly serious. There are many harmful products in flue gas, such as acid gases (SO 2 , NO x , and HCl, etc.), particulate matter (PM), heavy metals, and organic compounds. For controlling emission of toxic substances, the choice of the flue gas cleaning system plays an important role in the operation of an incinerator plant. In this study, a flue gas cleaning system of a power plant with circulating fluidized bed (CFB) incinerators of MSW located in Shandong Province (eastern China) was evaluated. The investigation included the removal of organic pollutants, PM, acid gases, and heavy metals. According to data of pollutants in the flue gas, the emission level of these items was under control and met the required domestic regulations. In order to comply with relevant international standards and the zero-release project, the selective non-catalytic reduction (SNCR), calcium magnesium acetate (ACM), catalytic filtration (CF), and secondary bag filter systems were suggested to optimize the existing flue gas cleaning system. The application of CFB incinerators with a semi-dry scrubber, activated carbon injection, and a bag filter to small and mid-sized cities in China serves as an example for developing countries in MSW management. [ABSTRACT FROM AUTHOR]

We present a new force field for H 2 S, based on an exponential-6 functional form for the repulsion–dispersion interactions and a charge distribution. This force field is used in a series of Expanded Wang–Landau (EWL) simulations, which allow to obtain an accurate estimate for the partition function and thus provides access to all thermodynamic properties of the system. The simulation results show that this new force field yields accurate values for the VLE properties of pure H 2 S. For binary mixtures of H 2 S with CH 4 , EWL results, obtained with this force field and the standard combining rules, are in excellent agreement with the experimental data. In line with previous work, no combining rules were found to perform well for the H 2 S–CO 2 binary mixture and parameters for the interactions between unlike sites were optimized to obtain an excellent agreement for this mixture. We finally extend the EWL simulation method to simulate phase equilibria for ternary mixtures of H 2 S with CH 4 and CO 2 and show that the parameters obtained in this work model accurately the vapor–liquid coexistence in these ternary mixtures. [ABSTRACT FROM AUTHOR]

Experimental results on the destruction of H 2 S and xylene mixtures in H 2 /O 2 –N 2 flames, at an equivalence ratio of three (Claus condition) are presented. The combustion generated products, including excited radical species were analyzed using flame emission spectroscopy and online gas chromatography (GC). The results showed the oxidation of H 2 S and H 2 that resulted in the formation of high mole fraction of SO 2 . The formed SO 2 further decomposed due to the formation of S 2 and CS 2 in the reactor. This reveals the possible interaction between sulfurous and hydrocarbon radicals. The examination of emission spectra of excited species between 280 nm and 490 nm showed C 2 ∗ and C 3 ∗ swan bands, CHO ∗ and CH ∗ bands and H ∗ (Balmer band series). The results also showed bands of SO, SH, S 2 ∗ , CS 2 ∗ and SO 2 ∗ . The continuum of SO 2 afterglow was also observed in the flame. These results provide insight on the reaction chemistry associated with the destruction of xylene and H 2 S. They are also of significant interest to operators and designers of sulfur plants, as well as related policy-makers. The results show the formation of value added chemicals, such as methane that can also be recovered from acid gases. [ABSTRACT FROM AUTHOR]

Firefighters may be exposed to toxic combustion products not only during fire fighting operations and training, but also afterwards as a result of contact with contaminated structural fire fighting ensembles. This study characterized the deposition of polycyclic aromatic hydrocarbons (PAHs) onto structural fire fighting ensembles and off-gassing of combustion products from ensembles after multiple exposures to hostile structural attack fire environments. A variety of PAHs were deposited onto the outer layer of structural fire fighting ensembles, with no variation in deposition flux between new ensembles and already contaminated ensembles. Contaminants released from ensembles after use included volatile organic compounds, carbonyl compounds, low molecular weight PAHs, and hydrogen cyanide. Air samples collected in a similar manner after laundering of ensembles according to manufacturer specifications indicated that laundering returns off-gassing concentrations of most of the investigated compounds to pre-exposure levels. These findings suggest that contamination of firefighter protective clothing increases with use, and that storage of unlaundered structural fire fighting ensembles in small, unventilated spaces immediately after use may create a source of future exposure to toxic combustion products for fire fighting personnel. [ABSTRACT FROM PUBLISHER]