Conversion Of Hydrogen Sulfide Research Articles

Supercritical carbon dioxide likely served as a prebiotic source of methanethiol in primordial ocean hydrothermal systems

Abiotic synthesis of methanethiol through CO2 reduction is a presumptive initiation reaction of protometabolism in primordial ocean hydrothermal systems. However, reported artificial means of methanethiol production indicate the necessity of gas-phase condition, rather than aqueous-phase setting, for this prebiotic reaction to occur. Here we show that, under supercritical CO2 with a geochemically feasible concentration of hydrogen, up to 7.9% conversion of hydrogen sulfide to methanethiol is attained through a 14-day reaction at 200 °C on molybdenum sulfide catalyst deposited in a carbonate-NaCl solution. On the present ocean floor, discharges of liquid/supercritical CO2 occasionally occur in close vicinity to hydrothermal vents. Geological records of ancient seafloor suggest prevalence of such CO2 fluxes associated with hydrothermal activities. Our experimental results link these facts with the protometabolism scenario, leading to the possibility that the generation and transportation of methanethiol through the subseafloor CO2 fluxes constituted the beginning step of protometabolism in primordial ocean hydrothermal systems. Thus, the supply of supercritical-CO2-derived materials likely assisted the chemical evolution of life in combination with the known geochemical processes at the vent-ocean interface.

Tungsten-needle intensifies microwave-sustained plasma accelerating direct H2S conversion to H2

Direct sustainable conversion of hydrogen sulfide (H2S) enables collaborative recovery of H and S resources via a metal-enhanced microwave plasma strategy, avoiding the hydrogen waste in the traditional Claus process. However, the metal size effect on microwave plasma property, the optimal process parameters, and the enhancement mechanism remain unclear in H2S conversion. Herein, the optimal tungsten needle (diameter: 1 mm, length: 60 mm, and tip angle: 10°) is experimentally proven for intensifying microwave discharge in multi-mode cavities. Theoretical calculations and plasma distribution reveal that the optimized tungsten needle achieves the ideal coupling with the microwave field, exhibiting extreme electric field augmentation around the needle tip. Tungsten-needle intensifies microwave-sustained plasma, realizing 40.2 % (90.1 %) conversion of 100 % (10 %) concentration H2S to H2 at a low microwave power of 300 W with a good stability of 30 hrs. Low power, large flow rate, and high H2S concentration are beneficial for improving energy efficiency. The excitation of microwave plasma is accompanied by a massive generation of highly energetic electrons. The direct high-energy electron-H2S collision contributes a lot to H2S splitting, especially for high-concentration H2S. In-situ optical emission spectroscopy confirms the vital S and H radicals in the plasma. The free radical reactions triggered by electron collisions are responsible for the production of H2 and S. This work opens an avenue to sustainable and low-carbon hydrogen production from the direct conversion and utilization of H2S.

Redox performance of trivalent iron iminodisuccinic acid in converting hydrogen sulfide to sulfur: A new complexed iron catalyst

A novel iron complex formed with tetrapotassium iminodisuccinate (IDSK4) was developed for catalytic conversion of hydrogen sulfide from industrial gases to monomeric sulfur, and a small-scale apparatus for the conversion of hydrogen sulfide in the laboratory was set up.The voltammetric curves of the system were generated with an electrochemical workstation, which indicated a quasireversible process. The catalytic capacity of the catalyst was saturated at 93.8% of the theoretical value for the trivalent iron complex.The open-circuit potential of the system was in the range −0.3 to −0.2 V, which provided full conversion of hydrogen sulfide, and after regeneration by air, it was restored to the initial potential.Full-cycle experiments showed that with increasing numbers of cycles, the open-circuit potential of the regenerated system was not fully restored to the initial value, thus requiring the design of a continuous absorption–regeneration system for industrial use. For safe treatment of hydrogen sulfide in industrial exhaust gases, a single-tower unit with absorption–regeneration cycles was used, and for safe treatment of hydrogen sulfide in combustible industrial gases, a double-tower unit with absorption–regeneration separation was used. The oxidation performance of the system was quickly monitored by measuring the open-circuit potential.

Review of Theoretical and Computational Studies of Bulk and Single Atom Catalysts for H2 S Catalytic Conversion.

Catalytic conversion of hydrogen sulfide (H2 S) plays a vital role in environmental protection and safety production. In this review, recent theoretical advances for catalytic conversion of H2 S are systemically summarized. Firstly, different mechanisms of catalytic conversion of H2 S are elucidated. Secondly, theoretical studies of catalytic conversion of H2 S on surfaces of metals, metal compounds, and single-atom catalysts (SACs) are systematically reviewed. In the meantime, various strategies which have been adopted to improve the catalytic performance of catalysts in the catalytic conversion of H2 S are also reviewed, mainly including facet morphology control, doped heteroatoms, metal deposition, and defective engineering. Finally, new directions of catalytic conversion of H2 S are proposed and potential strategies to further promote conversion of H2 S are also suggested: including SACs, double atom catalysts (DACs), single cluster catalysts (SCCs), frustrated Lewis pairs (FLPs), etc. The present comprehensive review can provide an insight for the future development of new catalysts for the catalytic conversion of H2 S.

INCREASING THE EXTRACTION OF VACUUM GAS OIL AT THE ELOU-AVT UNIT

The ELOU-AVT unit is part of a large oil refining complex. This unit is designed for primary processing of oils from various fields, as well as their mixtures. Refining is carried out in order to separate oil into separate fractions (gasoline, kerosene, diesel fuel, fuel oil), which are used as raw materials for secondary oil refining at other units. On the territory of modern refineries, in order to increase the depth of processing of petroleum feedstock, in most cases the following technological units are used: – The isomerization unit is designed for the production of low-boiling high-octane isomerizate used as a component of unleaded motor gasolines. For the production of a low-boiling high-octane component, the plant uses the process of low-temperature isomerization of C5-C6 normal paraffins. – The distillate hydrotreating unit is designed to produce high-quality diesel fuel with low sulfur and nitrogen content, high cetane number, and improved low-temperature properties. – The sulfur production unit is designed to produce solid commercial sulfur by the oxidative conversion of hydrogen sulfide into elemental sulfur. The delayed coking unit is designed to process heavy oil residues (straight-run tar) into lighter gaseous, liquid products and petroleum coke. The process of thermal cracking is the basis for the processing of tar. – The catalytic reformer with preliminary hydrotreatment is designed for the processing of gasoline fractions of oil in order to obtain high-quality gasolines and aromatic hydrocarbons, as well as hydrogen-containing gas (HCG), which is widely used both in petrochemistry and in such oil refining processes as: hydrotreating, hydrocracking, isomerization, etc. Oil refining is a multi-stage process of physical and chemical processing of crude oil, which results in the production of a complex of petroleum products. Industrial primary distillation units are divided into atmospheric (AT), vacuum (VT) and combined (for example, AVT, CDU-AVT, etc.). It is impossible to obtain a single marketable oil product from crude oil directly by one process (with the exception of gases), all of them are obtained by sequential processing at several installations. Keywords: ELOU-AVT machine, distillate hydrotreating unit, Oil refining, multi-stage process, primary distillation units

Controllable creating mesoporous coordination unsaturated sites in UiO-66 single crystals for efficient conversion of hydrogen sulfide into polysulphur

We report herein a facile pyrolysis etching strategy for the fabrication of UiO-66-xs single crystals with tunable coordination unsaturated zirconium sites (Zr-CUS) as well as interconnected mesoporosity. The synthesis is realized by having pristine UiO-66-xs subjected to thermal treatment, which results in the selective decomposition of thermal-sensitive organic linkers and hence the creation of permanent mesoporosity, leaving abundant Zr-CUS with enhanced degree of exposure. The prepared hierarchically porous UiO-66-xs (HP-UiO-66-xs) were innovatively applied for mild oxidation of H2S into polysulphur, achieving near 100 % H2S conversion and polysulphur selectivity in a wide range of temperatures. The superior activities can be well maintained in a continuous test of over 50 h. The Zr-CUS of HP-UiO-66-xs effectively activate H2S and O2 via the “adsorption dissociation tandem hydrogen transfer” mechanism, and the abundant mesochannels ensure efficient transport of reactants and bulky products in and out HP-UiO-66-xs, leading to catalytic activities superior to those of traditional H2S selective oxidation catalysts.

Multifarious characteristics of sulfur-oxidizing bacteria residing in rice rhizosphere.

Sulfur-oxidizing bacteria (SOB) are versatile microorganisms known for their ability to oxidize various reduced sulfur compounds, namely, elemental sulfur (S0), hydrogen sulfide (H2S), tetrathionate (S4O62-), and trithionate (S3O62-) to sulfate (SO42-). In this study, out of twelve SOB isolates from rice rhizosphere, five were screened based on their sulfur oxidation potential, viz., SOB1, SOB2, SOB3, SOB4, and SOB5, and were identified as Ochrobactrum soli SOB1, Achromobacter xylosoxidans SOB2, Stenotrophomonas maltophilia SOB3, Brucella tritici SOB4, and Stenotrophomonas pavanii SOB5, respectively. All the isolates displayed chemolithotrophic nutritional mode by consuming thiosulfate and accumulating trithionate and tetrathionate in the growth medium which is ultimately oxidized to sulfate. The strains were authenticated with the production of thiosulfate oxidizing enzymes such as rhodanese and sulfite oxidase. Despite their tendency to oxidize reduced sulfur compounds, B. tritici SOB4 and S. pavanii SOB5 were also found to possess phosphate and zinc solubilization potential, acetic acid, and indole acetic acid (IAA) production and 1-aminocyclopropane-1-carboxylate (ACC) deaminase activity. The presence of sulfanyl (R-SH) groups was noticed in the A. xylosoxidans SOB2. Elemental sulfur conversion into sulfate was noted in the S. maltophilia SOB3, and hydrogen sulfide conversion into sulfate was observed in the Ochromobacter soli SOB1. Sulfur oxidation potential coupled with beneficial properties of the isolates widen the knowledge on SOB.

Process modeling and optimization of an eco-friendly process for acid gas conversion to hydrogen

Hydrogen sulfide conversion to hydrogen is an attractive alternative for addressing energy problems, waste management, global warming, and supplying hydrogen in petrochemical and refinery plants. This research is focused on the development of an environmentally friendly process for the decomposition of hydrogen sulfide into hydrogen and elemental sulfur. The developed process includes a thermal cracker to produce hydrogen from hydrogen sulfide and a catalytic isothermal reactor to minimize emissions of sulfur contaminants. In the first step, a process flowsheet is planned for hydrogen sulfide conversion considering a real feed case. In the next step, the planned process is modeled based on the governing equations considering the heat and mass transfer resistances in the steady state condition. Then, optimum operating conditions of the designed process are determined considering the maximum hydrogen productivity and minimum contaminant emissions as objective functions. The results show that the designed process is capable to produce 51.03 kmol h−1 hydrogen and 84.92 kmol h−1 sulfur as main products. In addition, the rate of CS2 and COS emission is negligible in the proposed process.

Metal chloride anion based ionic liquids: synthesis, characterization and evaluation of performance in hydrogen sulfide oxidative absorption.

Three metal chloride anion based ionic liquids (MCABILs) were synthesized and characterized for high conversion of hydrogen sulfide (H2S). The MCABILs were synthesized via metathesis reaction and characterized by chemical spectroscopy such as FTIR, UV-Vis and CHNS elemental analysis. Then, the performance of those ionic liquids in H2S conversion was evaluated at various temperatures and atmospheric pressure. The results indicated remarkable efficiency of metal chloride anion based ionic liquids in H2S conversion. MCABILs managed to reach over 90% conversion efficiency at temperature as low as 50 °C, despite operating at atmospheric pressure. This occurs due to their high oxidation capability. The regeneration experiment indicated that all MCABILs can be recycled easily. Taken together, the research findings highlight the synthesis, characterization and high efficiency of MCABILs in promoting faster H2S conversion as a catalyst.

Warm Plasma Application in Tar Conversion and Syngas Valorization: The Fate of Hydrogen Sulfide

Warm plasma techniques are considered a promising method of tar removal in biomass-derived syngas. The fate of another problematic syngas impurity—hydrogen sulfide—is studied in this work. It is revealed that processing simulated syngas with a microwave plasma results in hydrogen sulfide conversion. For different gas flow rates (20–40 NLPM) and hydrogen sulfide concentrations ranging from 250 ppm to 750 ppm, the conversion rate varies from ca. 26% to 45%. The main sulfur-containing products are carbon disulfide (ca. 30% of total sulfur) and carbonyl sulfide (ca. 8% of total sulfur). Besides them, significantly smaller quantities of sulfates and benzothiophene are also detected. The main components of syngas have a tremendous impact on the fate of hydrogen sulfide. While the presence of carbon monoxide, methane, carbon dioxide, and tar surrogate (toluene) leads to the formation of carbonyl sulfide, carbon disulfide, sulfur dioxide, and benzothiophene, respectively, the abundance of hydrogen results in the recreation of hydrogen sulfide. Consequently, the presence of hydrogen in the simulated syngas is the main factor that determines the low conversion rate of hydrogen sulfide. Conversion of hydrogen sulfide into various sulfur compounds might be problematic in the context of syngas purification and the application of the right technique for sulfur removal.

Thermodynamics of Claus conversion of reduced sulfur dioxide

To the sustainable economic development it is necessity to provide the total utilization every kind the waste including sulphurous off-gases of non-ferrous metallurgy. For the distant metallurgical works the most acceptable way for the utilization of the “strong” sulfurous gases of autogenous smelting that contain of over than 20% sulfur dioxide is elemental sulfur production because sulfur in elemental form is commercial product that the most tailored for transportation or long-time storage. To estimate of the potential resources of the sulfur recovery from the sulfurous off-gases autogeneous smelting, in the temperature range 250÷1350 oС, the thermodynamics of the reduction by methan of oxygen-beared sulfurous gases containing ~36 % by volume SO2 is analyzed at a total pressure of 1.0 and 1.3 bar. As it is show the thermodynamics calculation results excess of reducing agent strongly diminishing of the sulfur yield in last stage of the catalytic Claus processing of a real reducted sulfurous gas. According to the results of thermodynamic calculations at 3000 oC and under Claus ratio CR≡[H2S]/[SO2]=0,36÷1,98, it is find that equilibrium concentration of hydrogen sulfide in reducted gas is increase by the Claus ratio increasing. Comparing of the thermodynamic analysis results with the factual data of the reducted sulfurous gases conversion at the temperature 230÷260 oС in the catalytic reactor of the Elemental Sulfur Production Site at Copper Plant of Nornickel’ Polar Division is made. It is determine that in acid gases processing in Claus reactors the real values of the hydrogen sulfide conversion substantially exceed equilibrium conversion values, that may be because limits of the rate of the sulfur hydrolysis reaction inverse of the Claus reaction and make urgent to develop of the kinetic model of the Claus conversion. As it is found by the industrial experimental data analysis, the optimize temperature for the stage of the reducted sulfurous gas Claus conversion is temperature of the Claus reactor 230–250 oC.

An alternative electron-donor and highly thermo-assisted strategy for solar-driven water splitting redox chemistry towards efficient hydrogen production plus effective wastewater treatment

An alternative technology has been sought for highly efficient and sustainable hydrogen production and wastewater treatment worldwide. This paper is focused on the intersection of solar energy, wastewater treatment and hydrogen production. The solar thermo-assisted and electron-donor alternative strategy was conducted for water-splitting redox chemistry to target highly efficient hydrogen production and effective wastewater treatment. The thermodynamic calculation displays that the solar thermal application and shuttle sulfide electron donor alternative are favorable for the hydrogen production and sulfide-to-sulfate oxidation by the falling trend in the potential (from 1.5V to 0.6V). The curves revealed that high current peaks in the low potential range were dominated by the thermal-assisted process and the alternative of the oxidation half-reaction. The experiments illustrated that solar thermal utilization and sulfide donors were dominant factors for the high efficiencies. Under the outdoor sunlight, the high hydrogen production rate and sulfide conversion efficiency were experimentally achieved at rates of 0.25 mL/h H2 and 93% sulfide-to-sulfate oxidation, reasonably more than that of the direct electrochemical water splitting to hydrogen (nearly no evolution) under the same applied bias (＜1.2V). The system realized that one sustainable technology conducts simultaneously both highly efficient hydrogen production and highly effective water treatment.

Thermodynamics and Kinetics of the Claus Conversion of Hydrogen Sulfide from Coke-Oven Gas

Thermodynamics and Kinetics of the Claus Conversion of Hydrogen Sulfide from Coke-Oven Gas

Kinetic Features of the Hydrogen Sulfide Sorption on the Ferro-Manganese Material

The kinetics of hydrogen sulfide sorption by the surface of a ferromanganese material containing in its composition a mixture of iron (II) and (III) oxides FeO × Fe2O3, takanelite (Mn, Ca) Mn4O9 × 3H2O and quartz SiO2, and which is samples of unrefined ferromanganese ore, was studied in this work. Sorption rate constant and activation energy constant values were calculated. The catalytic effect of iron (III) oxide was established, the presence of which in natural material contributes to a decrease in the H2S sorption activation energy. Based on the results of X-ray phase and chromatographic analysis methods, a chemical (redox) reaction of the conversion of hydrogen sulfide into elemental sulfur and H2O was revealed. The overall process rate is expressed in terms of the physical sorption stage and chemical transformation of the components; the influence of the rate of the third stage—reaction products desorption—on the overall rate of the process is taken into account. The limiting stage of the process is determined—a chemical reaction. The relation between the heat and the activation energy of the chemical transformation is used according to the Bronsted—Polanyi rule for catalytic processes. It was found that with an increase in the chemisorption heat, the activation energy of the chemisorption stage decreases and, as a consequence, its rate increases. The sorption process parameters were calculated—the Fe2O3 coverage degree with the initial substances and reaction products providing the maximum sorption rate, which can be a criterion for evaluating the catalytically active sites of the catalyst surface for carrying out catalytic reactions.

Screening of Metal Chloride Anion-based Ionic Liquids for Direct Conversion of Hydrogen Sulfide by COSMO-RS

In order to identify the best possible reaction media for performing H2S conversion, a total number of 300 different ILs from a combination of 20 cations and 15 anions were screened via COSMO-RS model simulations. By COSMO-RS method, thermodynamic and physicochemical properties of 300 ILs such as Henry’s law constants, activity coefficient, selectivity, capacity and performance index are obtained and analyzed. Thus, by comparing the performance of ILs via COSMO-RS, a series of TSILs containing cation of [P66614] with metal chloride anions such as Fe, Ga and Sn were chosen and selected for synthesis based on their performance predicted by COSMO-RS and their economic values. Consequently, the physiochemical properties such as density, viscosity, thermal properties, as well as H2S absorptive oxidation performances in those TSILs will be systematically investigated.

Decomposition of hydrogen sulfide into elements in the cyclic chemisorption-catalytic regime

The research was devoted to experimental study of low-temperature cyclic chemisorption-catalytic process for H2S decomposition, including the identification of optimal chemisorbent-catalysts and quantitative investigation of process characteristics. The study involved sulfides of transient metals (Fe, Co and Ni) both in bulk and supported forms. The highest efficiency was achieved with bulk sulfides NiS, CoS and especially FeS. Sorption capacity of up to 10 % by weight is observed for these systems, while all the hydrogen sulfide is absorbed irreversibly. It was shown that at elevated temperatures (250−600 °C) the reaction can proceed in a quasi-stationary mode, in which the conversion of hydrogen sulfide and the yield of hydrogen are observed almost unchanged during rather long period of time. In this case, the conversion of H2S and the yield of H2 significantly exceed the equilibrium values for direct H2S decomposition reaction, thus indicating a noticeable contribution of chemisorption processes. In the optimal temperature range (350−400 °C), the hydrogen yield on these systems varies from 11 to 95 % with an average value of 26–34 % per cycle.

ПІДВИЩЕННЯ ЕФЕКТИВНОСТІ ТЕХНОЛОГІЇ ОТРИМАННЯ ВОДНЮ ШЛЯХОМ ВИКОРИСТАННЯ РЕГЕНЕРАЦІЙНОГО КОНТУРУ З РОТОРНО-ПОРШНЕВОЮ РОЗШИРЮВАЛЬНОЮ МАШИНОЮ

The article discusses a promising technology for the production and safe accumulation of hydrogen from the Black Sea hydrogen sulfide, which includes the following processes: production of hydrogen sulfide from the depths of the Black Sea; separation of hydrogen sulfide and seawater; destruction of hydrogen sulfide to produce a hydrogen-containing gas; separation of hydrogen from a hydrogen-containing gas; safe hydrogen storage; safe transportation of hydrogen. It is proposed to use the regeneration circuit to increase the efficiency of this technology, which includes: an expansion machine for high-pressure hydrogen sulfide, a seawater hydraulic turbine, and a heat pump installation. It is proposed to evaluate the efficiency of the application of the technology for the production and safe accumulation of hydrogen from the Black Sea hydrogen sulfide by effective capacity, which includes: thermal power of hydrogen, power of the regeneration circuit; the power needed to carry out hydrogen production processes. It is proposed to use the 20RPD-4.4/1.75 rotary piston engine as a hydrogen sulfide expansion machine that will satisfy all the requirements. Rational operating modes and limiting values of the efficiency of using the technology for obtaining and safe accumulation of hydrogen from the Black Sea hydrogen sulfide for daily hydrogen production of 200 kg/day were determined depending on the degree of hydrogen sulfide conversion during destruction, the gas content of hydrogen sulfide in seawater and the depth of immersion of the lifting pipeline using the regeneration circuit. The minimum permissible degrees of conversion at which the efficiency of using the technology for obtaining and safe accumulation of hydrogen from the Black Sea hydrogen sulfide for a gas content of hydrogen sulfide of 2.5 m3/m3 at a depth of immersion of the lifting pipeline of 250...1000 m is 0.427 ... 0.413, for 5 m3/m3 – 0.375...0.363, for 7.5 m3/m3 – 0.363...0.350, for 10 m3/m3 – 0.356...0.343. The use of the regeneration circuit allowed us to reduce the minimum permissible degrees of conversion for the gas content of hydrogen sulfide of 2.5...10 m3/m3 at a depth of immersion of the lifting pipeline of 250...1000 m by 0.136 ... 0.069.

Bioremediation of acid mine drainage using Fischer-Tropsch waste water as a feedstock for dissimilatory sulfate reduction

The treatment of acid mine drainage (AMD) using dissimilatory sulfate reduction (DSR) utilises the ability of sulfate reducing bacteria (SRB) to reduce sulfate to sulfide using organic compounds as electron donors. Given that AMD contains relatively low levels of organic matter, the electron donors need to be supplied externally to facilitate the bioremediation process. In this research we recognise Fischer Tropsch waste water (FTWW) as a potential organic source because of its richness in organic acids and alcohols. The FTWW was combined with synthetic AMD at an initial COD/SO42− ratio of 1.8 and was maintained in batch mode for 800 h before being turned to a fed batch mode, with an aerobic reactor receiving the sulfide rich effluent from the sulfate reducing reactor. The purpose of the aerobic reactor was to remove hydrogen sulfide through biological oxidation. The influent oxygen was regulated to avoid complete conversion of hydrogen sulfide to sulfate. We obtained up to 92.63 % sulfate removal, and almost 100 % COD removal in the anaerobic sulfate reducing reactor. The pH in the anaerobic reactor was raised from approximately 2 to above neutral. The subsequent aerobic sulfur oxidising reactor was able to convert up to 96.82 % of the sulfide produced in the anaerobic sulfate reducing reactor to sulfur.

HYDROGEN SULFIDE AND ALKANTHIOLS IN NUCLEOPHILIC SUBSTITUTION REACTIONS OF HYDROXY GROUPS IN ALIPHATIC ALCOHOLS

Hydrogen sulfide and alkanethiols are toxic compounds containing in the production of wells in many oil and gas condensate fields. Because the policy of hydrocarbon processing enterprises aimed at the development of new fundamental research, processes and technologies in order to find rational use of raw materials, the conversion of hydrogen sulfide and alkanethiols into valuable compounds is one of the strategic goals of the oil and gas industry. The methods of "green" chemistry are perspective processes for converting hydrogen sulfide and alkantiols into valuable organic compounds, which allow working in environmentally friendly conditions with minimal energy and resource costs. The reactions of direct nucleophilic substitution of butanol-2, pentanol-1 and hexanol-1 to HS- and RS- group by single-electron reduction of hydrogen sulfide and alkanthiol in acetonitrile and ionic liquid at room temperature and atmospheric pressure with a single by-product - H2O were described. The possibility of conducting an experiment without electrolyte due to the intrinsic electrical conductivity of the ionic liquid allows not only lowering the consumption of reagents, but also facilitating the isolation of the target product. Due to the structuring and the matrix effect in ionic liquids, the duration of electrolysis in the reactions under consideration is 2-3 times less than in the case of aprotic solvents.

Metal sulfide-based process analysis for hydrogen generation from hydrogen sulfide conversion

Fossil fuel power plants often generate sulfur species such as hydrogen sulfide or sulfur dioxide due to the sulfur content of the raw feedstocks. To combat the associated environmental, processing, and corrosion issues, facilities commonly utilize a Claus process to convert hydrogen sulfide (H2S) to elemental sulfur. Unfortunately, the potential for H2 production from H2S is lost in the Claus process. In this study, two chemical looping process configurations utilizing metal sulfides as chemical intermediates for sulfur recovery are investigated: (1) sulfur recovery (SR) system for sulfur production; (2) sulfur and hydrogen (H2) recovery (SHR) system for sulfur and H2 and production utilizing staged H2 separation. Since, H2 yield and sulfur recovery in a single thermal decomposition reactor is limited by low H2S equilibrium conversion, a staged H2 separation approach is used to increase H2S conversion to H2 using the SHR system. Steady-state simulations and optimization of process conditions are conducted in Aspen Plus (v10) simulation software for the chemical looping process configurations and the Claus process. An energy and exergy analysis are done for the Claus and chemical looping processes to demonstrate the relative contribution to exergy destruction from different unit operations as well as overall exergy and energy efficiency. The two chemical looping process configurations are compared against the conventional Claus process for similar sulfur recovery in a 629 MWe integrated gasification combined cycle power plant. The SHR system is found to be the most efficient option due to a 97.11% exergy efficiency with 99.31% H2 recovery. The overall energy and exergy efficiencies of this chemical looping system are 14.74% and 21.54% points higher than the Claus process, respectively, suggesting more efficient use of total input energy.