Ratio Of H2S Research Articles

Development of a novel renewable energy-based integrated system coupling biomass and H2S sources for clean hydrogen production

The present work aims to develop a novel integrated energy system to produce clean hydrogen, power, and biochar. The Palmaria palmata, a type of seaweed, and hydrogen sulfide from the industrial gaseous waste streams are taken as potential feedstock. A combined thermochemical approach is employed for the processing of both feedstocks. For clean hydrogen production, the zinc sulfide thermochemical cycle is employed. Both stoichiometric and non-stoichiometric equilibrium-based models of the proposed plant design are developed in the Aspen Plus software, and a comprehensive thermodynamic analysis of the system is also performed by evaluating energy and exergy efficiencies. The study further explores and covers the modeling, simulation, and parametric analyses of various subsections to enhance the hydrogen and biochar production rate. The parametric analyses show that the first step of the thermochemical cycle (desulfurization reaction) follows a stoichiometric pathway and the optimal conversion is achieved at a ZnO/H2S ratio equal to 1. On the other hand, the second step of the thermochemical cycle (regeneration reaction) does not follow a stoichiometric pathway, and ZnS conversion of 12.87 % is achieved at a high temperature of 1400 °C. It is found that a hydrogen production rate of 0.71 mol/s is achieved with the introduction of 0.27 mol/s of H2S. The energy and exergy efficiencies of the zinc sulfide thermochemical cycle are found to be 65.23 % and 35.58 % respectively. A biochar production rate of 0.024 kg/s is obtained with the Palmaria palmata feed rate of 0.097 kg/s. The Palmaria to biochar energy and exergy efficiencies are found to be 55.43 % and 45.91 % respectively. The overall energy and exergy efficiencies of the proposed plant are determined to be 72.88 % and 50.03 % respectively.

Probing the Heights and Depths of Y Dwarf Atmospheres: A Retrieval Analysis of the JWST Spectral Energy Distribution of WISE J035934.06–540154.6

We present an atmospheric retrieval analysis of the Y0 brown dwarf WISE J035934.06−540154.6 using the low-resolution 0.96–12 μm James Webb Space Telescope (JWST) spectrum presented in Beiler et al. We obtain volume number mixing ratios of the major gas-phase absorbers (H2O, CH4, CO, CO2, PH3, and H2S) that are three to five times more precise than previous work that used Hubble Space Telescope (HST) spectra. We also find an order-of-magnitude improvement in the precision of the retrieved thermal profile, a direct result of the broad wavelength coverage of the JWST data. We used the retrieved thermal profile and surface gravity to generate a grid of chemical forward models with varying metallicity, (C/O)atm, and strengths of vertical mixing as encapsulated by the eddy diffusion coefficient K zz. Comparison of the retrieved abundances with this grid of models suggests that the deep atmosphere of WISE 0359−54 shows signs of vigorous vertical mixing with K zz = 109 [cm2 s−1]. To test the sensitivity of these results to our five-knot spline thermal profile model, we performed a second retrieval using the Madhusudhan & Seager thermal profile model. While the results of the two retrievals generally agree well, we do find differences between the retrieved values of mass and volume number mixing ratio of H2S with fractional differences of the median values of −0.64 and −0.10, respectively. In addition, the five-knot thermal profile is consistently warmer at pressure between 1 and 70 bar. Nevertheless, our results underscore the power that the broad-wavelength infrared spectra obtainable with the JWST have to characterize the atmospheres of cool brown dwarfs.

Thermodynamic Reaction Study of Conversion of H2S and CO2 and the Promoting Effect of Light on the Reaction

H2S and CO2 are common coexisted gases widely existing in natural gas resources, and they need to be treated harmlessly. The traditional Claus treatment process only focuses on H2S treatment but ignores CO2. This article systematically conducted theoretical thermodynamic research on the thermocatalytic conversion of H2S and CO2. It was found that increasing the reaction temperature and H2S ratio would have a positive impact on the reaction, while increasing the pressure would lead to a decrease in the conversion rate of reactants and product yield, and introducing COS into the feed gas could have a promoting effect on the reaction. Furthermore, 5%Mo/Al2O3 catalyst was used to preliminarily explore the thermal and photothermal catalysis for H2S and CO2 conversion. The results showed that the photothermal catalysis significantly promoted the production of syngas (H2 and CO), and suppressed COS production in contrast to thermal catalysis. This indicates that the introduction of light could effectively convert H2S and CO2 into high‐value product syngas, providing important reference value for further research on the conversion of H2S and CO2.

Determination of the pressure and composition of wet gas fluid inclusions: An in situ Raman spectroscopic approach

Carbonaceous fluid within mineral-hosted inclusions provides important information for carbon cycle in deep Earth. In addition to CH4 and CO2, heavy hydrocarbons (e.g., C2H6 and C3H8) are frequently observed in carbonaceous fluid inclusions (i.e, wet gas inclusions with C1/∑Ci < 0.95). However, determination of the composition of such complex volatiles is difficult based on traditional microthermometric measurements. Here we carried out experimental calibrations on Raman spectroscopic measurements of the pressure (P) and composition of the CH4 ± C2H6 ± C3H8 ± H2S system at room temperature and 0.1–130 MPa. We confirmed that the C–H symmetric stretching vibration band of CH4 [ν1(CH4), ∼2917 cm−1] shifted to lower wavenumber with rising pressure, thus the P-ν1(CH4) relationship could be applied to calculate the pressure of wet gas. It should be noted that the presence of C2+ and/or H2S will shift the [ν1(CH4)] to lower wavenumber at constant pressure (with the order of C3H8 ≥ H2S > C2H6). Obviously, the P-ν1(CH4) relationship derived from pure CH4 system could not be simply applied to wet gas inclusion, otherwise the pressure would be overestimated. To avoid the overlap of the C–H vibrations of CH4, C2H6 and C3H8, the peak areas and peak heights of the overtone vibration of CH4 [2ν4(CH4), ∼2580 cm−1], C–C symmetric stretching vibrations of C2H6 [ν3(C2H6), ∼995 cm−1] and C3H8 [ν8(C3H8), ∼868 cm−1], and S–H symmetric stretching vibration of H2S [ν1(H2S), ∼2612 cm−1] were fitted using Gaussian + Lorentz functions. The obtained peak areas and peak heights were then used to calculate the Raman quantification factors (F factor and G factor, respectively) of C2H6, C3H8 and H2S relative to CH4, respectively. Both the F factor and G factor increased with rising pressure, whereas the FC2H6, FC3H8 and GH2S kept nearly constant at ∼5.69, 6.39 and 153.8, respectively in high pressure gas mixtures (e.g., >30 MPa). Therefore, for inclusions with higher internal pressure, the molar ratio of CH4, C2H6, C3H8 and H2S could be determined by the aforementioned F and G factors. This method was applied to the calcite-hosted single-phase gas inclusions in the Upper Permian Changxing Formation carbonate reservoir from the eastern Sichuan Basin (South China). Our results indicated that the trapping pressure would be obviously overestimated if the presence of heavy hydrocarbons was not taken into account.

Miniaturized Capsule System Toward Real-Time Electrochemical Detection of H2 S in the Gastrointestinal Tract.

Hydrogen sulfide (H2 S) is a gaseous inflammatory mediator and important signaling molecule for maintaining gastrointestinal (GI) homeostasis. Excess intraluminal H2 S in the GI tract has been implicated in inflammatory bowel disease and neurodegenerative disorders; however, the role of H2 S in disease pathogenesis and progression is unclear. Herein, an electrochemical gas-sensing ingestible capsule is developed to enable real-time, wireless amperometric measurement of H2 S in GI conditions. A gold (Au) three-electrode sensor is modified with a Nafion solid-polymer electrolyte (Nafion-Au) to enhance selectivity toward H2 S in humid environments. The Nafion-Au sensor-integrated capsule shows a linear current response in H2 S concentration ranging from 0.21 to 4.5ppm (R2 = 0.954) with a normalized sensitivity of 12.4% ppm-1 when evaluated in a benchtop setting. The sensor proves highly selective toward H2 S in the presence of known interferent gases, such as hydrogen (H2 ), with a selectivity ratio of H2 S:H2 = 1340, as well as toward methane (CH4 ) and carbon dioxide (CO2 ). The packaged capsule demonstrates reliable wireless communication through abdominal tissue analogues, comparable to GI dielectric properties. Also, an assessment of sensor drift and threshold-based notification is investigated, showing potential for in vivo application. Thus, the developed H2 S capsule platform provides an analytical tool to uncover the complex biology-modulating effects of intraluminal H2 S.

Recovery of elemental sulfur direct from nonferrous flue gas by a low-temperature Claus process with H2S as the interim reducer

Direct reduction of high concentrations of SO2 from flue gases with oxygen to produce elemental sulfur (S8) is a promising pathway, that can realize sulfur resource recycling economically and storage avoiding the expensive SO2 pre-separation procedure. However, the process is significantly restricted by the O2 oxidation in flue gas and the traditional reducing gases can hardly work efficiently because of the excessive consumption by O2. In this study, we developed a low-temperature Claus process (LTCP) to reduce SO2 to S8 in the presence of O2 (5 vol%), and the interim production of H2S was employed as the reducer carrier, which can be efficiently re-produced by the reaction of S8 with H2 or CO thereafter. Results indicated that LTCP exhibited 97.2% S8 yield with the stoichiometric ratio at 150 °C and 5 vol% of oxygen content, which were both far higher than those for H2 or CO as the reducing gases at 350 °C. Further increasing the SO2 to H2S ratios to 1:1, almost 100% of H2S can be used to selectively reduce SO2 by Claus reaction at lower temperatures, and the slip H2S can be completely suppressed. As the catalyst and the temporary storage for S8 deposit, Al2O3 shows the best performance compared with other supported metal oxide and sulfide catalysts, and the sulfur capacity even achieves 432 mg(S)/g(Cat) with only 15% breakthrough. Meanwhile, LTCP also demonstrates excellent off-line temperature-swing regeneration performance, and part of the recovered S8 can be readily used to produce H2S. These promising results can officiously resolve the intractable problem of O2 oxidation and enable sulfur recovery directly from any nonferrous smelting and other flue gases with high concentrations of SO2.

Self-separation ionic liquid catalyst for the highly effective conversion of H2S by α,β-unsaturated carboxylate esters under mild conditions

The deep-processing utility of pure hydrogen sulfide (H2S) is a significant direction in natural gas chemical industry. Herein, a brand-new strategy of H2S conversion by α,β-unsaturated carboxylate esters into thiols or thioethers using task-specific carboxylate ionic liquids (ILs) as catalyst has been developed, firstly accomplishing the phase separation of product and catalyst without introducing the third component. It can be considered as a cascade reaction in which the product selectivity can be controlled by adjusting the molar ratio of H2S to α,β-unsaturated carboxylate esters. Also, the effects of ILs with different anions and cations, intermittent feeding operations, as well as pressure−time kinetic behaviors on cascade reaction were investigated. Furthermore, the proposed interaction mechanism of H2S conversion using butyl acrylate catalyzed by [Emim][Ac] was revealed by DFT-based theoretical calculation. The approach enables the self−phase separation promotion of catalyst and product and achieves 99% quantitative conversion under mild conditions in the absence of solvent, making the entire process ecologically benign. High-efficiency reaction activity can still be maintained after ten cycles of the catalyst. Therefore, the good results, combined with its simplicity of operation and the high recyclability of the catalyst, make this green method environmentally friendly and cost−effective. It is anticipated that this self-separation method mediated by task-specific ILs will provide a feasible strategy for H2S utilization, which will guide its application on an industrial scale.

Synthesis of 2,5-dimethylhexene by isobutene dimerization with H2S co-feeding.

This study investigates the effect of hydrogen sulfide (H2S) co-feeding on the synthesis of 2,5-dimethyl-1-hexene, 2,5-dimethyl-2-hexene, and 2,5-dimethylhexane (2,5-DMHs), useful compounds, using the dimerization of isobutene under mild pressure conditions. The dimerization of isobutene did not proceed in the absence of H2S, whereas the desired products of 2,5-DMHs were produced under H2S co-feeding conditions. The effect of reactor size on the dimerization reaction was then examined, and the optimal reactor was discussed. To enhance the yield of 2,5-DMHs, we changed the reaction conditions of the temperature, molar ratio of isobutene to H2S (iso-C4[double bond, length as m-dash]/H2S) in the feed gas, and the total feed pressure. The optimum reaction condition was at 375 °C and 2/1 of iso-C4[double bond, length as m-dash]/H2S. The product of 2,5-DMHs monotonously increased by an increment of total pressure from 1.0 to 3.0 atm with a fixed iso-C4[double bond, length as m-dash]/H2S ratio at 2/1.

Efficacy of H2O2 on the removal kinetics of H2S in saltwater aquaculture systems, and the role of O2 and NO3−

The occurrence of hydrogen sulfide (H2S) represents a challenge for recirculating aquaculture systems (RAS) under saline conditions. Even low concentrations of the toxic gas can result in sudden mass mortalities of fish, leading to large economic losses. There is an urgent need for efficient strategies to remove H2S, which can be applied effectively with a short response time, to prevent the risk of H2S-induced casualties. This study examines the kinetics of the two common oxidants applied to rearing water in a RAS facility; oxygen (O2) and hydrogen peroxide (H2O2) and evaluates their efficiency and applicability for the removal of H2S in an industrial RAS. Furthermore, we tested whether nitrate (NO3−) can be an oxygen donor in the chemical oxidation of H2S. The baseline oxidation rates of H2S by O2 were determined in air-equilibrated seawater (SW) and RAS water (RASW). The feasibility of using H2O2 as a practical treatment was evaluated by testing increasing H2O2 to H2S ratios in SW. In addition, RASW dilutions that yielded different concentrations of NO3− and total chemical oxygen demand (TCOD) were tested to identify their effects on H2S removal. The half-lives (t½) of H2S, derived from O2 oxidation rates, were considerably shorter in SW (118.5 ± 28.6 min) compared to RASW (168.0 ± 18.7 min). The addition of a 1:1 mole ratio of H2O2 to H2S, significantly increased the removal rate and decreased the half-life (t½) of H2S in SW to 29.5 ± 6.6 min. Further increasing H2O2:H2S ratios to 2:1 and 4:1, reduced t½ to 21.7 ± 5.2 and 17.4 ± 6.1 min, respectively. Similarly, a dosage of H2O2 at a ratio of 1:1 in RAS water resulted in a considerably shorter t½ of 86.1 ± 10.1 min. The influence of organic matter on the required H2O2 dose was demonstrated by the t½, which were reduced by 49% in RAS water and 75% in SW. NO3− was not found to be involved in the chemical removal of H2S. The results provide an improved understanding of the influence of RAS water chemistry and quality on H2S kinetics and the direct applicability of the kinetics for treating acute H2S levels in RAS to avoid mass mortalities. In conclusion, the addition of H2O2 is an efficient water treatment technology for H2S removal, and by adjusting H2O2 dosages accordingly to the concentrations of H2S and specific systems water parameters, a t½ <30 min can be achieved. Thus the technology is applicable in an industrial RAS, as a treatment process for acute levels of the hazardous gas H2S that is easily implemented, and safe for the fish.

Evolution and genesis of hydrothermal fluids for the Cretaceous Dongnan Cu deposit, Zijinshan ore district (SE China)

The Dongnan Cu(-Mo) deposit is a newly discovered porphyry-epithermal system located between the Zijinshan high-sulfidation (HS) epithermal deposit and Luoboling porphyry deposit, within the Zijinshan ore district, a large porphyry-epithermal Cu-Au-Mo-Ag ore system in southeast China. The deposit offers a window to investigate the origins of hydrothermal fluids in a coupled porphyry-HS epithermal magmatic-hydrothermal system.Drill hole logging and alteration mineral mapping has identified four hydrothermal alteration and mineralization stages at the Dongnan deposit, namely: stage I porphyry-type alteration, which can be subdivided into stage IA potassic alteration and stage IB phyllic alteration, stage II HS mineralization and associated alteration which can be subdivided into stage IIA-1 pyrophyllite-dominated, stage IIA-2 illite and illite-montmorillonite and stage IIB dickite-dominated alteration, stage III late veins (i.e., calcite and fluorite) and stage IV supergene alteration. Chalcopyrite and molybdenite mineralization is associated with Stage I, whereas covellite and digenite mineralization formed during Stage II. Stage IB minerals (i.e., muscovite) were largely superimposed by minerals from stage II (i.e., dickite, kaolinite, pyrophyllite and alunite). Stage II epithermal alteration is located mainly in the western part of Zijinshan ore district, whereas the eastern part is dominated by porphyry-type mineralization and alteration. Microthermometry results show the average Th and salinity of each sample suite from stage IB ranging from 341 ± 22 to 442 ± 2 °C and 1.6 ± 1.6 to 19.2 ± 2.6 wt% NaCl equiv. By contrast, stage III fluid inclusions are liquid-dominated, with low temperature of homogenization and low salinity (156 ± 9 to 165 ± 4 °C and < 0.5 wt% NaCl equiv.). Thermodynamic modelling of stage II suggest that the fluid responsible for epithermal mineralization was characterized by high temperature (270 to 320 °C), high water to rock (w/r > 1) and high SO2 to H2S ratios (SO2/H2S > 1). Because stage IIA pyrophyllite alteration is overprinted by late stage IIB dickite alteration and relatively different forming condition for pyrophyllite (>270 °C) and kaolinite (<270 °C and w/r > 1), stage IIA and stage IIB may have resulted from two different fluids. The Dongnan porphyry-type mineralization formed mainly in response to the cooling and dilution, led by the mixing of acidic magmatic water with meteoric water, whereas stage II alteration was more likely related to volatile gas escaping, resulting in pH decrease and contributing to the formation of pyrophyllite, dickite and alunite.The distribution of alteration minerals and evolution of hydrothermal fluids all indicate that the hydrothermal fluids for the porphyry-type and HS epithermal-type alteration at Dongnan came separately from nearby Luoboling granodiorite porphyry and the Zijinshan HS epithermal Cu-Au deposit, which implies that Luoboling porphyry deposit and Zijinshan HS deposit formed from separate magmatic-hydrothermal events. It suggests that multiple magmatic centers exist in the Zijinshan ore district, a finding which will contribute to both understanding of ore genesis of this overprinted porphyry-epithermal deposit and further mineral exploration in the Zijinshan Ore district.

Synthesize and characterization of polysulfone membrane for the separation of hydrogen sulfide from natural gas

The existence of Hydrogen Sulfide in natural gas (N.G) can lead to corrosion in equipment, global warming and so on. So, the separation of Hydrogen Sulfide from N.G is essential. In this study, the Polysulfone (PS) membrane was synthesized with Dimethylacetamide (DMAC) and Dimethylformamide (DMF) as solvent. The SEM (scanning electronic microscopy) images were used to compare prepared membranes by DMF and DMAC. An experimental setup was established and the effect of solvents, PS concentration, temperature and pressure were explored on the separation of H2S from N.G. The best temperature was achieved at 25°C. The results showed that the DMAC solvent was more appropriate than DMF and the amount of selectivity of this kind of membrane was reduced with an increase in temperature and pressure. In M3 membranes (20% of PS, DMAC solvent), which was the best membrane, the permeated amount was increased from 11800 to 490000 Barrer with an increase in pressure from 2.5 to 20 Barg, still the selectivity ratio of H2S to N.G was increased with increase in pressure from 2.5 to 5 Barg at first and then reduced with enhance in pressure until 20 Barg. The maximum selectivity ratio of H2S to N.G was 1.56 for M3 membranes at 25°C and 5 barg, at this condition, the permeated amount of H2S was 119000 Barrer.

Hydrogen sulfide restores cardioprotective effects of remote ischemic preconditioning in aged rats via HIF-1α/Nrf2 signaling pathway

The present study explored the therapeutic potential of hydrogen sulfide (H2S) in restoring aging-induced loss of cardioprotective effect of remote ischemic preconditioning (RIPC) along with the involvement of signaling pathways. The left hind limb was subjected to four short cycles of ischemia and reperfusion (IR) in young and aged male rats to induce RIPC. The hearts were subjected to IR injury on the Langendorff apparatus after 24 h of RIPC. The measurement of lactate dehydrogenase, creatine kinase and cardiac troponin served to assess the myocardial injury. The levels of H2S, cystathionine β-synthase (CBS), cystathionine γ-lyase (CSE), nuclear factor erythroid 2-related factor 2 (Nrf2), and hypoxia-inducible factor (HIF-1α) were also measured. There was a decrease in cardioprotection in RIPC-subjected old rats in comparison to young rats along with a reduction in the myocardial levels of H2S, CBS, CSE, HIF-1α, and nuclear: cytoplasmic Nrf2 ratio. Supplementation with sodium hydrogen sulfide (NaHS, an H2S donor) and l-cysteine (H2S precursor) restored the cardioprotective actions of RIPC in old hearts. It increased the levels of H2S, HIF-1α, and Nrf2 ratio without affecting CBS and CSE. YC-1 (HIF-1α antagonist) abolished the effects of NaHS and l-cysteine in RIPC-subjected old rats by decreasing the Nrf2 ratio and HIF-1α levels, without altering H2S.The late phase of cardioprotection of RIPC involves an increase in the activity of H2S biosynthetic enzymes, which increases the levels of H2S to upregulate HIF-1α and Nrf2. H2S has the potential to restore aging-induced loss of cardioprotective effects of RIPC by upregulating HIF-1α/Nrf2 signaling.

Liraglutide restores late cardioprotective effects of remote preconditioning in diabetic rats via activation of hydrogen sulfide and nuclear factor erythroid 2-related factor 2 signaling pathway.

ABSTRACTPurposeThe present study explored the influence of liraglutide on remote preconditioning-mediated cardioprotection in diabetes mellitus along with the role of nuclear factor erythroid 2-related factor 2 (Nrf2), hypoxia inducible factor (HIF-1α) and hydrogen sulfide (H2S).MethodsStreptozotocin was given to rats to induce diabetes mellitus and rats were kept for eight weeks. Four cycles of ischemia and reperfusion were given to hind limb to induce remote preconditioning. After 24 h, hearts were isolated and subjected to 30 min of ischemia and 120 min of reperfusion on Langendorff system. Liraglutide was administered along with remote preconditioning. Cardiac injury was assessed by measuring the release of creatine kinase (CK-MB), cardiac troponin (cTnT) and development of left ventricular developed pressure. After ischemia-reperfusion, hearts were homogenized to measure the nuclear cytoplasmic ratio of Nrf2, H2S and HIF-1α levels.ResultsIn diabetic rats, there was more pronounced injury and the cardioprotective effects of remote preconditioning were not observed. Administration of liraglutide restored the cardioprotective effects of remote preconditioning in a dose-dependent manner. Moreover, liraglutide increased the Nrf2, H2S and HIF-1α levels in remote preconditioning-subjected diabetic rats.ConclusionsLiraglutide restores the lost cardioprotective effects of remote preconditioning in diabetes by increasing the expression of Nrf2, H2S and HIF-1α.

Elucidating the origin of selective dehydrogenation of propane on γ-alumina under H2S treatment and co-feed

A bulk γ-Al2O3 catalyst shows high selectivity for propane dehydrogenation upon pretreatment and co-feeding with H2S. The reaction kinetics, deactivation rates, and active sites for propane dehydrogenation on this catalyst were characterized using fixed bed conversion studies, NH3-TPD, O2-TPO, XPS, and density functional theory (DFT). Specifically, we observe that the selectivity to propylene was 94% at ca. 16% propane conversion at 560 °C for a C3H8:H2:H2S ratio of 1.1:1:0.1 on γ-Al2O3. Our results indicate that H2S can irreversibly modify the active sites of γ-Al2O3, postulated to be defect sites on the 110 facet comprised of a tri-coordinated Al atom, such that the modified site was more active and selective towards propylene and less inhibited by co-fed H2S. Along with XPS and O2-TPO, the dehydrogenation-regeneration experiments suggest the formation of sulfurous coke and strong adsorption of reaction products result in a less active catalyst. This study shows the potential of alumina/metal-sulfide as an earth-abundant and relatively benign class of catalysts for alkane activation, especially in the context of sour natural gas upgrading.

EXAMINATION OF PITTING CORROSION IN IRAQI MINERAL WATER

It was studied the pitting corrosion in low alloy steel samples by influence of various mining and geological factors of the Iraqi oil field. It is shown that the temperature and chloride content, the ratio of dissolved acid gases CO2 and H2S also affect the development and progress of this process. It was carried out the analysis of voltamperograms of a low alloy steel sample in the simulated reservoir water compositions typical of Iraqi deposits. The analysis of voltamperographs of the sample of low-alloy K55 steel in simulated reservoir compositions at different temperatures and ratios of aggressive CO2 and H2S gases characteristic of Iraqi deposits. It is established that in the presence of hydrogen sulfide in formation water, the potential of free corrosion shifts to the cathode region. Carbon dioxide activates general and pitting corrosion. An active experiment was conducted to study the depth of pitting for the selected steel sample and obtained the second-order regression equation for the dependence of the point corrosion depth on the selected impact factors. The mathematical model was obtained and analyzed for the dependence of the pitting corrosion depth on the selected factors by using the mathematical statistic. The regression model was analyzed, isocontours of influence for different pairs of factors on the depth of pitting corrosion were constructed. The analysis of the obtained model indicates the predominant influence of a factor that reflects the influence of the ratio of corrosive CO2 / H2S gases on the development of local corrosion in formation water. It is shown that there are certain areas with maximum values of the pitting corrosion depth Vp = 91m-6. In natural terms, this equates to a CO2 / H2S ratio of about 17.2.

Formation of active species for propane dehydrogenation with hydrogen sulfide co-feeding over transition metal catalyst

This study focuses on a novel route for propylene production using a transition metal (Fe, Co, Ni, Mn, Cu) catalyst via propane dehydrogenation (PDH) with co-feeding hydrogen sulfide (H2S). The SiO2-supported Fe (Fe/SiO2) catalyst was found to be highly active and selective for PDH with co-feeding H2S. The Fe/SiO2 catalyst displayed higher stability than the commercial CrOx/γ-Al2O3 catalyst. The durability of the Fe/SiO2 catalyst was tuned by changing the ratio of H2S to propane (H2S/C3) from 0.2 to 2.6: the most stable performance was obtained over the Fe/SiO2 catalyst with a H2S/C3 ratio of below 0.4 for 50 h. The structure of the active site on the Fe/SiO2 catalyst was investigated using XRD, XPS, and XAFS analyses. The co-supplying of H2S promoted formation of an iron sulfide species during the reaction, which was the active site for PDH. The thermodynamic calculations indicate that the iron sulfide active phase was non-stoichiometric, e.g., Fe1–xS. This structure was maintained by co-supplying H2S. DFT calculations of the dehydrogenation path suggest that PDH occurs on an iron sulfide active site via an intermediate of the propyl group combining with the surface sulfide ion.

In Situ Capturing and Absorption of Sulfur Gases Formed during Thermal Treatment of South African Coals

The objective of this study, the first of its kind on these specific South African low-sulfur coals, was to capture H2S and SO2 produced under inert and oxidizing conditions from sulfur compounds present in the coals. The capturing agents were calcium and magnesium oxides formed during the transformation of calcite and dolomite. The effectiveness of two different scrubbing solutions (0.15 M cadmium acetate and 1.1 M potassium hydroxide) for absorption of volatilized H2S and SO2 was also investigated. The bituminous coal (coal A) contained dolomite, calcite, pyrite, and organic sulfur. Lignite (coal B) had a high organic sulfur content and contained gypsum, no or low dolomite and pyrite contents, and no calcite. A third sample (coal C) was prepared by adding 5 wt % potassium carbonate to coal A. Under oxidizing conditions and at elevated temperatures, FeS2 produced Fe2O3, FeO, and SO2. It transformed to FeS and released H2S under inert conditions. Organic sulfur interacted with organically bound calcium and magnesium at 400 °C in an inert atmosphere to form calcium sulfate and oldhamite ((Ca,Mg)S). CaO, produced from calcite or dolomite, reacted with SO2 and O2 at 950 °C to form calcium sulfate. Treatment of lignite at 400–950 °C resulted in 96–98% evolution of sulfur as gases. Hydrogen sulfide formation increased with the increasing thermal treatment temperature under inert conditions for the three coals. Under oxidizing conditions, sulfur dioxide formation decreased with the increasing temperature when heating coals B and C. The lowest ratio (0.01) of H2S to SO2 was achieved during thermal treatment of the blend of coal and potassium carbonate (coal C), implying that almost all of sulfur was retained in the coal C ash/char samples. In situ capturing of sulfur gases by CaO and MgO and by the added K2CO3 in coal C to form calcium/magnesium/potassium sulfates and potassium/calcium/magnesium aluminosilicate glasses during utilization of these and similar coals could reduce the percentage of sulfur volatilized from the coals by 54–100%, thereby potentially decreasing their impact on the environment.

Fate of sulfur in coal-direct chemical looping systems

The fate of sulfur in the coal-direct chemical looping system was investigated in the sub-pilot reactor system. The sulfur balance was successfully closed during the injection of high sulfur coal. More than 69% of the total amount of atomic sulfur in coal was released as SO2 and H2S from the reducer flue gas stream while less than 5% was emitted as SO2 from the combustor spent air. The remaining atomic sulfur was retained in coal ash as inorganic sulfur compounds. The finding suggests an acid gas removal system targeting both H2S and SO2 is required to meet the recommended quality of CO2 stream for sequestration and transportation. Using the determined ratio of SO2 and H2S, a properly designed Claus plant can enable the recovery of elemental sulfur as a value-added byproduct. The combustor spent air was found to comply with the US EPA sulfur emission regulation and can be released to the atmosphere without a costly acid removal system. The relationship between the sulfur and carbon capture efficiencies was established experimentally and was found to be proportional to each other throughout the experiment at a slope of 0.8 below 93% of carbon capture efficiency and near 1 above 93%. This was attributed to the delayed release of organic sulfur during incomplete char gasification in the reducer. The finding affirms the effectiveness of the counter-current moving bed design for minimizing the amount of carbon and sulfur emission in the combustor spent air with an average carbon and sulfur capture efficiency of 96.5 and 95%, respectively. Sulfur deposition on the iron based oxygen carriers did not affect the system performance, and complete removal of deposited sulfur was observed during oxidation in a thermogravimetric analyzer. Compared with chemical looping systems using circulating fluidized bed configuration, the use of a moving bed reducer has the additional benefit of minimizing slippage of char into the combustor due to the use of large oxygen carrier; resulting in lower sulfur emission in the combustor spent air. The findings demonstrate the robustness of the coal-direct chemical looping system to handle high sulfur coal without a complicated acid gas cleaning scheme or severe performance penalties.

Fluid dynamics and reaction assessment of diesel oil hydrotreating reactors via CFD

In this work, computational fluid dynamics (CFD) has been used to investigate diesel hydrotreating (Hydrodesulfurization (HDS) and Hydrodearomatization (HDA)) in a laboratory scale trickle bed reactor (TBR). In order to investigate these reactions, the 3D model was developed using a multi-phase Eulerian-Eulerian approach, an inter-phase interaction model, a porosity distribution model for the trilobe particles, mass transfer and chemical reactions model. Due to the small dimensions of the reactor, the simulations are carried out at isothermal and transient conditions and the catalyst bed is considered to be fully wetted. In this first phase of the work, a reaction model was used, which was later validated. Then, a counter-current reactor is simulated and the results are compared with a co-current reactor. The analyzed parameters are conversion, pressure drop and liquid holdup and a special attention was given in order to verify how operational changes on pressure, temperature, velocity and gas and liquid flows influence the reactor performance. The influence of porosity on fluid velocity and volume fraction of liquid is also investigated. Finally, the influence of the liquid hourly space velocity (LHSV), temperature, gas-liquid ratio and partial pressure of H2S are also discussed. The results for the two types of reactors are similar despite the fact that the counter-current arrangement has achieved lower conversions.

On the early fate of hydrothermal iron at deep‐sea vents: A reassessment after in situ filtration

AbstractDeep‐sea hydrothermal venting is now recognized as a major source of iron (Fe), an essential trace element that controls marine productivity. However, the reactions occurring during dispersal from buoyant plumes to neutrally buoyant hydrothermal plumes are still poorly constrained. Here we report for the first time on the dissolved‐particulate partition of Fe after in situ filtration at the early stage of mixing at different hydrothermal discharges, i.e., Lucky Strike (37°N), TAG (26°N), and Snakepit (23°N) on the Mid‐Atlantic Ridge. We found that hydrothermal iron is almost completely preserved (&gt;90%) in the dissolved fraction, arguing for low iron‐bearing sulfide precipitation of iron in basalt‐hosted systems with low Fe:H2S ratios. This result can only be explained by a kinetically limited formation of pyrite. The small part of Fe being precipitated as sulfides in the mixing gradient (&lt;10%) is restricted to the inclusion of Fe in minerals of high Cu and Zn content. We also show that secondary venting is a source of Fe‐depleted hydrothermal solutions. These results provide new constrains on Fe fluxes from hydrothermal venting.