Desulfurization Process Research Articles

Numerical simulation study on erosion characteristics of desulfurization slurry using shell-and-tube heat exchanger for low-grade waste heat utilization

The wet desulfurization yields slurry with a moderate temperature and stable supply and thus holds promise for waste heat utilization. However, the corrosive nature and solid particle content of desulfurization slurry from the wet desulfurization process pose potential erosion challenges in waste heat utilization heat exchangers, which is an aspect scarcely explored in the existing literature. The present study aimed to investigate the erosion characteristics in desulfurization slurry heat exchangers using numerical simulation approaches, which can offer crucial insights for practical application in low-grade energy recovery. The result identified slurry mass flow rate and composition as essential factors of erosion distribution. Higher mass flow rates enhance heat transfer efficiency. Still, paradoxically, lower flow rates lead to more pronounced erosion, with a slurry mass flow rate of 35 kg/s resulting in nearly double the erosion compared to the benchmark condition of 56 kg/s. This phenomenon is ascribed to lower fluid velocities in the heat tubes, where the influence of changed velocity diminishes, but slurry exhibits more stable flow at higher mass flow rates. Furthermore, it is also observed that both elevated solids content and particle size lead to an increase in erosion rates. The difference in erosion caused by solid particles with particle sizes in the range of 200–350 µm is marginal. The heat exchanger structure and arrangement also impact fluid flow and erosion. While the difference in fluid flow between vertically and horizontally arranged heat exchangers is negligible, the erosion was significantly reduced to 1/10 in the vertical arrangement. The no-tube-in-window heat exchangers, designed to minimize vibration, exhibit reduced heat transfer capacity alongside diminished and more uniform erosion. The augmentation of tube passes reduces overall erosion but focalizes severe erosion at the slurry inlet, which presents a potential design solution.

Study on the Role of Additives in Calcination Desulfurization Process of High Sulfur Petroleum Coke

Due to the high sulfur content of high sulfur petroleum coke, sulfur-containing gas will be produced in the production process, reducing product quality and other problems, resulting in increased production costs and equipment corrosion. How to reduce the sulfur content of high sulfur petroleum coke is of great significance to improve the utilization rate of high sulfur petroleum coke and the sustainable development of related industries. In this paper, the desulfurization of high sulfur petroleum coke was carried out by using the additive-assisted high-temperature calcination method. It was found that the desulfurization effect of different kinds of desulfurization additives was different, among which MO1, MC2, MC1 desulfurization effect was better, and the desulfurization rate could reach 68%, 58%, 56%. After compounding the three desulfurizers, the desulfurization rate can be up to 75%, and then the influence of calcination temperature and time on the desulfurization rate was investigated. Finally, the physicochemical properties of petroleum coke before and after desulfurization were analyzed by X RD, FT-IR.

Closed-Loop Shaping-Based Active Disturbance Rejection Control With Delay Robustness and Application to Wet Desulfurization Process

Closed-Loop Shaping-Based Active Disturbance Rejection Control With Delay Robustness and Application to Wet Desulfurization Process

Efficient and promising oxidative desulfurization of fuel using Fenton like deep eutectic solvent

Oxidative desulfurization (ODS) has emerged as a prominent technique for the removal of sulfur compounds from fuels, aiming to comply with stringent environmental regulations and minimize sulfur dioxide emissions. Herein, Fenton-like deep eutectic solvents (DESs) were synthesized as a catalyst and reaction medium and their application for the ODS process was investigated. The study encompassed the optimization of DES composition, reaction conditions, and the influence of different parameters on the desulfurization efficiency. The experimental findings demonstrated that the Fenton-like DES exhibited outstanding catalytic activity in the oxidative desulfurization of fuel. The optimized conditions involved conducting the reaction at room temperature for 2.5 h, using 200 mg of the prepared DES (HNFM-FeCl4) as both the extraction solvent and catalyst. An oxidant-to-sulfur (O/S) ratio of approximately 3:1 was maintained, with a 30 wt% H2O2 solution utilized as the oxidant. The analysis of the reaction products using GC–MS revealed a remarkable yield of 98% for dibenzothiophene sulfone. The DES provided a suitable medium for the reaction, enhancing the solubility and availability of sulfur compounds. The iron catalyst, in the presence of hydrogen peroxide, facilitated the oxidation of sulfur-containing compounds to their corresponding sulfones, which can be easily separated from the fuel phase. The DES catalysts exhibited stability and recyclability, making them suitable for practical applications in fuel desulfurization processes.

Controllable Synthesis of Titanium Silicon Molecular Zeolite Nanosheet with Short b-Axis Thickness and Application in Oxidative Desulfurization.

Titanium silicon molecular zeolite (TS-1) plays an important role in catalytic reactions due to its unique nanostructure. The straight channel on TS-1 was parallel to the orientation of the short b-axis and directly exposed to the aperture of the 10-member ring with a diameter of 0.54 nm × 0.56 nm. This structure could effectively reduce the diffuse restriction of bulk organic compounds during the oxidative desulfurization process. As a kind of cationic polymer electrolyte, polydimethyldiallyl ammonium chloride (PDDA) contains continuous [C8H16N+Cl-] chain segments, in which the Cl- could function as an effective structure-directing agent in the synthesis of nanomaterials. The chain of PDDA could adequately interact with the [0 1 0] plane in the preparation process of zeolite, and then the TS-1 nanosheet with short b-axis thickness (6 nm) could be obtained. The pore structure of the TS-1 nanosheet is controlled by regulating the content of PDDA. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), N2 physical adsorption analysis, infrared absorption spectrum and ultraviolet-visible spectrum were used to determine the TS-1. The thinner nanosheets exhibit excellent catalytic performance in oxidative desulfurization of dibenzothiophene (DBT), in which the removal rate could remain at 100% after three recycles. Here, the TS-1 nanosheet with short b-axis thickness has a promising future in catalytic reactions.

Analysis and Assessment of H2S Sorption Capacity of the Selected Biofiltration Materials

Hydrogen sulfide known as one of the highly toxic chemical compounds existed in the raw biogas and needs to be eliminated before implementation at any industrial sector. Biofilter (a typical bioreactor) is a tool used to separate sulfide/sulfate from hydrogen by biofiltration method, which is known as the green technology. Packing material is the main component inside a laboratory-scale biofilter to undertake the desulfurization process of H2S. This study is dedicated to evaluating number of selected recyclable/waste organic, inorganic, and synthetic packing material’s rate of impact on amplifying purification progress of hydrogen sulfide from biogas, known as biofilters “removal efficiency (RE)”. Variable effective factors such as environmental and equipment conditions, consumed time (day), and inlet H2S concentration will be controlled throughout the measurements for all chosen packing materials. In the end, the best performed environment-friendly biofiltration material in terms of sorption capacity of H2S from the biogas will be announced.

Development of an electrochemical reactor with rotating anode for fast and ultra-deep catalytic desulfurization of diesel: experimental and modeling

A novel electrochemical reactor with a rotating anode attached to its end with four baskets as catalysts holders is proposed for deep desulfurization of diesel fuel. In this reactor two experimentally prepared catalysts of (5% manganese oxide (MnO2)/modified activated carbon (MAC) and 5% iron oxide (Fe2O3)/MAC) were used for an efficient desulfurization process. This design is characterized by conducting two functions at the same time, which are to agitate the reaction mixture and to move the catalyst over all areas of the reaction vessel. Several experiments were conducted at different operating conditions such as voltage, reaction time, and agitating speed. Results showed that the proposed basket reactor is excellent and highly effective in removing dibenzothiophene (DBT) in diesel. The removal efficiency of sulfur compounds is significantly improved by enhancing reaction times, stirring speed, and cell voltage up to 3 volts and drops at higher than 3 volts. At all operating conditions, the 5% Fe2O3/MAC catalyst showed higher performance than the 5% MnO2/MAC catalyst. This result can be attributed to the high reactivity of Fe2O3/MAC toward DBT removal and its magnetic activity which could enhance the oxidation reaction. Under the best operating conditions, the removal efficiencies reached 98.8%, and 93.1% for 5% Fe2O3/MAC and 5% MnO2/MAC, respectively. A model for the proposed reactor was also developed using an artificial neural network (ANN) software. The modeling data displayed an excellent agreement between the experimental and predicted data. This interactive model produced an accurately strong basis for the behavior of the new electrochemical desulfurization (ECDS) process.

Characterization and optimization of ultrasound assisted oxidative desulfurization of a model fuel using a novel magnetic deep eutectic solvent

ABSTRACT In various studies, researchers have utilised different solvents to extract sulfur compounds from the fuels. This paper introduces a novel magnetic deep eutectic solvent employed in the ultrasound-assisted oxidative desulfurisation of dibenzothiophene within a model fuel. The solvent, synthesised at 85°C by combining choline chloride, p-toluene sulfonic acid, and FeCl₃, underwent characterisation through Fourier transform-infrared, Vibrating-sample magnetometer, and Raman spectrometry. Exploration of the key parameters, including oxidant to model fuel volumetric fraction percentage (0.2–0.3), Iron (III) chloride to choline chloride mole fraction (0.1–0.3), and Magnetic deep eutectic solvent to model fuel volumetric fraction (0.2–0.3), was conducted to assess their impact on dibenzothiophene conversion rates. Employing response surface methodology based on central composite experimental design, optimal operational parameters for the ultrasound-assisted oxidative desulfurisation process were identified, resulting in a sulfur removal rate of 98.7%. The findings highlight the solvent sustained efficiency even at higher dibenzothiophene concentrations. Additionally, the solvent paramagnetic properties facilitated an expedited separation from the fuel, leading to the significantly reduced process times.

Extraction of Dibenzyl Disulfide from Transformer Oils by Acidic Ionic Liquid.

In recent years, dibenzyl disulfide (DBDS) in transformer oils has caused many transformer failures around the world, and its removal has attracted more attention. In this work, nine imidazolium-based ionic liquids (ILs) were applied as effective, green desulfurization extractants for DBDS-containing transformer oil for the first time. The results show that the desulfurization ability of the ILs for DBDS followed the order of [BMIM]FeCl4 > [BMIM]N(CN)2 > [BMIM]SCN > [BMIM](C4H9O)2PO2 > [BMIM]MeSO4 > [BMIM]NTf2 > [BMIM]OTf > [BMIM]PF6 > [BMIM]BF4. Especially, [BMIM]FeCl4 ionic liquid had excellent removal efficiency for DBDS, with its S partition coefficient KN (S) being up to 2642, which was much higher than the other eight imidazolium-based ILs. Moreover, the extractive performance of [BMIM]FeCl4 increased with an increasing molar ratio of FeCl3 to [BMIM]Cl, which was attributed to its Lewis acidity and fluidity. [BMIM]FeCl4 ionic liquid could also avail in the desulfurization of diphenyl sulfide (DPS) from model oils. The experimental results demonstrate that π-π action, π-complexation, and Lewis acid-base interaction played important roles in the desulfurization process. Finally, the ([BMIM]FeCl4) ionic liquid could be recycled five times without a significant decrease in extractive ability.

Influence of oxidation–reduction potential and pH on polysulfide concentrations and chain lengths in the biological desulfurization process under haloalkaline conditions

Biological desulfurization under haloalkaline conditions has been applied worldwide to remove hydrogen sulfide (H2S) from sour gas steams. The process relies on sulfide-oxidizing bacteria (SOB) to oxidize H2S to elemental sulfur (S8), which can then be recovered and reused. Recently, a dual-reactor biological desulfurization system was implemented where an anaerobic (sulfidic) bioreactor was incorporated as an addition to a micro-oxic bioreactor, allowing for higher S8 selectivity by limiting by-product formation. The highly sulfidic bioreactor environment enabled the SOB to remove (poly)sulfides (Sx2−) in the absence of oxygen, with Sx2− speculated as a main substrate in the removal pathway, thus making it vital to understand its role in the process. The SOB are influenced by the oxidation–reduction potential (ORP) set-point of the micro-oxic bioreactor as it is used to control the product of oxidation (S8 vs. SO42−), while the uptake of Sx2− by SOB has been qualitatively linked to pH. Therefore, to quantify these effects, this work determined the concentration and speciation of Sx2− in the biological desulfurization process under various pH values and ORP set-points. The total Sx2− concentrations in the sulfidic zone increased at elevated pH (8.9) compared to low pH (< 8.0), with on average 3.3 ± 1.0 mM-S more Sx2−. Chain lengths varied, with S72− only doubling in concentration while S52− increased 9 fold, which is in contrast with observations from abiotic systems. Changes to the ORP set-point of the micro-oxic reactor did not produce substantial changes in Sx2− concentration in the sulfidic zone. This illustrates that the reduction degree of the SOB in the micro-oxic bioreactor does not enhance their ability to interact with Sx2− in the sulfidic bioreactor. This increased understanding of how both pH and ORP affect changes in Sx2− concentration and chain length can lead to improved efficiency and design of the dual-reactor biological desulfurization process.

Completely Inorganic Deep Eutectic Solvents for Efficient and Recyclable Liquid-Liquid Interface Catalysis.

Organic acid-based deep eutectic solvents (DESs) as catalysts always suffer from weak stability and low recyclability due to the accumulation of organic oxidative products in the DES phase. Herein, a completely inorganic deep eutectic solvent (IDES) ZnCl2/PA with zinc chloride (ZnCl2) and phosphoric acid (PA) as precursors is constructed to realize liquid-liquid interface catalysis for desulfurization of fuel and product self-separation for the first time. Owing to the inorganic nature, the organic oxidative products are accumulated at the interface between the IDES and fuel rather than the IDES phase. With this unique feature, the IDES can be reused for at least 15 times without any further treatment in oxidative desulfurization process, showing a state-of-the-art cycle-regeneration stability. Moreover, compared with the reported organic DESs, the IDES also reveals more attractive catalytic oxidative desulfurization performance. Experimental and theoretical studies indicate that the strong coordination Zn···O═P and the strong adsorption energy between IDES and sulfides enhance the activation of H2O2 to reactive oxygen species, leading to the superior catalytic performance in oxidative desulfurization of fuel.

Waste to wealth: Efficient wet desulfurization of electric arc furnace dust (EAFD) and recycling of desulfurization solid residue

In this study, we used calcined hazardous waste electric arc furnace dust (EAFD) as a desulfurizer for an effective wet desulfurization process. Testing for desulfurization efficacy revealed that the calcined EAFD, particularly when treated at 800 °C in an oxygen (O2) environment (termed EAFD-O2), achieved an unprecedented breakthrough sulfur capacity (BSC) of 3.71 gSO2·g−1 at 55 °C-the highest to date for EAFD applications in desulfurization efforts. Further investigation indicated that the calcination method expels certain volatile contaminants, thereby enhancing the crystallinity and lattice oxygen content of zinc oxide, the strong active phase of desulfurization in EAFD, which is principally responsible for the superior desulfurization results of EAFD-O2. Moreover, the observed reduction in the desulfurization slurry’s activity primarily stems from the depletion of the strong active phase of desulfurization (ZnO) and the resultant rise in the liquid phase’s sulfate concentration. Notably, the deactivated slurry’s solid residue predominantly consists of high-purity ZnFe2O4, a form of zinc ferrite utilized extensively for its proficiency in photocatalytic. Following straightforward processing, this substance displayed exceptional performance in photocatalytic-Fenton degradation tests on tetracycline (TC). In sum, the study not only turns hazardous EAFD into a powerful agent for removing SO2, a gaseous pollutant but also converts it into a value-added material, ZnFe2O4, thus proposing an integrated and efficient approach to solid waste management.

Investigation on desulfurization and ground granulated blast furnace slags reutilization for carbon dioxide sorption in a fluidized bed reactor

BackgroundThe atmospheric CO2 concentration is significantly increasing due to the utilization of fossil fuel in various activities. Implementation of steel slag is considered as a promising strategy for carbon capture MethodsIn this study, the slags from desulfurization (De-S) and ground granulated blast furnace (GGBS) processes in the steel company waste were applied as the sorbent in CO2 removal using a fluidized bed system. Various operating conditions were applied to determine the influence of operating parameters on sorbent performance. Moreover, examination on sorbent characteristic change and kinetics calculation were also carried out in this study. Significant findingOptimum operating temperature was reached by the application of 600 and 500 °C for De-S and GGBS slag, respectively. The higher CO2 concentration and 5 % water vapor improved the sorbent utilization. However, excessive water vapor and low fluidized velocity decreased the performance of sorbent. De-S slag performed better on overall CO2 capture process compared to GGBS slag. Therefore, upscaled study with 10 times greater size was further conducted with the 150–300 µm De-S slag for the CO2 capture from oxy-fuel and air combustion. The higher CO2 partial pressure in the flue gas of oxy-fuel combustion increased the capture process efficiency.

New design of eco-friendly Catalytic Electro - Photo Desulfurization process for real diesel fuel

Recently, due to the refineries processes considerations and environmental issues major limitations have been imposed on the sulfur compounds presented in petroleum distillates. Therefore, to reduce the sulfur compounds to minimum levels and to meet the global legislations, many of techniques were used, among them electro chemical photo desulfurization technique was used here. In this study, DBT was removed using electro chemical photo desulfurization over electrodes of titanium and stainless steel using Fe2O3/TiO2 as a catalyst under different temperatures (45, 60, 75 ℃), current density (10, 15, 20 A/m2), electrolyte concentration (25, 35, 45 wt%). The catalyst was characterized by different advanced surface techniques such as N2- adsorption-desorption, SEM-EDX, FTIR, and XRD. The reaction kinetic parameters (reaction order and activation energy) were estimated based on the experimental runs. According to the results obtained, this technique was revealed an efficient method with highest removal of 93.79% achieved using Fe2O3/TiO2 under the best of experimental operating conditions at 75 ℃, 20 A/m2 and 35 wt% of temperature, current density and electrolyte concentration respectively. It can be concluded that the electro chemical photo oxidative desulfurization reaction followed was pseudo 1st order and 41.67 kJ/mole activation energy over titanium dioxides catalyst.

Industrial Ecotechnological Assessment of Lime as a Sustainable Substitute for Desulfurization of Cast Iron

This study comprehensively assesses the ecotechnological consideration and perspective of implementing a lime-based desulfurization process in the cast iron industry to replace the utilization of magnesium partially. By adopting an injection process to introduce the lime powder into molten cast iron, this research elucidated that the new alternative concept can successfully be integrated with daily operations without any disparities in cast iron quality, as proved by the production of cast iron products with vermicular graphite. A mixture of lime powder and carbon was utilized, and it was substantiated that the aim of a sulfur content lower than 0.015% can be reliably achieved. Furthermore, an ecological analysis was also conducted to justify the possible environmental advantages. The results indicated that considering the cradle-to-gate approach, the maximum amount of CO2eq connected to the lime-based desulfurization is approximately 43 g for 1 kg of desulfurized cast iron. This amount of calculated emission is still expected to be lower than the minimum calculated emission associated with the magnesium-based process, which can reach an amount of 76 g for a similar functional unit.Graphical

Preparation of the MoO3- Fe3O4 nanocomposites for deep oxidative desulfurization of model fuel: Optimization and experimental design

In the present study, the catalytic activity of the MoO3-Fe3O4 of molybdenum oxides prepared by the impregnation method was investigated in the extractive oxidative desulfurization (EODS) process. Structural characterization of the nanocomposite catalysts was studied by XRD, N2 adsorption–desorption isotherm, FT-IR, and VSM analyses. The EODS technology was applied to remove sulfur from a model fuel (dibenzothiophene in n-octane, DBT) using H2O2 as the oxidant, acetonitrile as the extracting solvent, and MoO3-Fe3O4 as the catalysts. Among the catalysts with various loadings of MoO3 on Fe3O4 nanoparticles (3, 6, 9, 12, and 15 wt%), the catalyst with 9 wt% MoO3 demonstrated the highest performance. Subsequently, the optimal design of the experiments using response surface methodology (RSM) based on Box-Behnken design (BBD) was applied to study the effects of the independent parameters such as O/S molar ratio, reaction temperature, and catalyst dosage on sulfur removal efficiency. Optimization studies were performed, and maximum sulfur removal efficiency of 98 % was achieved under the optimal conditions of 58 °C, O/S molar ratio: 5.9, and 0.116 g of 9 wt% MoO3-Fe3O4 as catalysts. The activity of the catalyst remained unchanged after six times recycling in the EODS process. Additionally, a catalytic reaction mechanism was proposed.

Evaluation of different operating parameters in the photocatalytic oxidative desulfurization process to degrade dibenzothiophene sulfur compound in the presence of BiOI/CeO2/NaY zeolite heterojunction

In this study, BiOI/CeO2/NaY zeolite composite was applied to remove sulfur compounds in gasoline model fuel to reduce environmental pollution and increase clean fuel production. First, the parent NaY zeolite was transformed into mesoporous zeolite during the sequential dealumination-desilication process. Then, the binary structures of BiOI/NaY zeolite and BiOI/Meso NaY zeolite were successfully synthesized by hydrothermal method. Next, in order to increase the photocatalytic performance in the desulfurization process, cerium ion was impregnated on the synthesized binary samples, so that the ternary combination of BiOI/CeO2/Meso NaY zeolite was investigated for the first time in the application of photocatalytic oxidative desulfurization in the presence of air as an oxidant. Furthermore, XRD, XPS, FT-IR, FE-SEM, EDS-MAP, TEM, BET, UV–vis DRS, PL and EIS analyzes were used to identify the structure, evaluate the compounds and determine the performance of the synthesized samples. In addition, the effect of operational parameters in the photocatalytic oxidative desulfurization process including photocatalyst dosage, model fuel concentration, reaction temperature, type of oxidant, type of extractant, the volume ratio of model fuel to extractant, different sulfur compounds, reusability and scavengers were assessed. The results showed that the BiOI/CeO2/Meso NaY zeolite ternary sample with an amount of 50 mg at the temperature of 25 ℃ and the concentration of 500 ppm of the sulfur compound was able to eliminate 98.8 % of the pollutant in 30 min. Moreover, the effect of the active species in the process was evaluated using various electron-removing agents to remove the sulfur compound from the fuel on an industrial scale.

Hierarchical Porous N-Doped Carbon Particles Derived from ZIF-8 as Highly Efficient H2S Selective Oxidation Catalysts.

In the selective oxidation of H2S, the catalytic activity over N-doped carbon-based catalysts is significantly influenced by the accessibility of active sites and the mass transfer rates of reactant molecules (e.g., H2S and O2) as well as generated sulfur monomers. Therefore, it is crucial for enhancing the initial performance via the controlled synthesis of carbon-based catalysts with highly exposed active sites and unique porous structures. Herein, we reported on an efficient strategy to synthesize nanosized N-doped carbon particles with hierarchical porous structures by directly pyrolyzing an oversaturated NaCl-encapsulated ZIF-8 precursor mixture. The introduction of NaCl not only serves as a pollution-free template to promote the formation of graphitic carbon layers but also acts as an intercalating agent to guide the derivation of hierarchical porous structures, as well as enhances the amount of active nitrogen species in the catalysts. As a result, the as-prepared H-NC800 catalyst shows excellent H2S selective oxidation performance (sulfur formation rate is 794 gsulfur·kgcat-1·h-1), good stability (>80 h), and antiwater vapor properties. The characterization results and DFT calculations indicate the crucial role of pyridinic N in the adsorbing and activating reactant molecules (H2S, O2). Furthermore, nanoscale N-doped carbon particles accelerated the rapid transport of generated sulfur monomers under a hierarchical porous structure. This investigation introduces a distinctive strategy for synthesizing ZIF-8-derived N-doped carbon nanosized with a hierarchical porous structure, while its efficient and stable H2S selective oxidation performance highlights significant potential for practical implementation in the industrial desulfurization process.

An investigation of a process for selective biogas desulfurization and autotrophic denitrification in a membrane supported reactor

A lab-scale dense polydimethylsiloxane (PDMS) membrane bioscrubber (MBS) was used for selective removal of highly toxic H2S from biogas under autotrophic conditions for the first time. The performance of MBS was evaluated under the effects of sulfide loadings, pH, and hydraulic retention time (HRT). The results showed that gradual increase in sulfide loading rate from 131 to 316 g/m3.d boost S/N ratios 1.9–4.0, on average sulfide oxidation efficiencies higher than 95% were achieved. The S/N ratios were determinant on the formation of oxidation products, but not on the H2S gas removal efficiency. The transition of HRT significantly affected the denitrification rather than the sulfide oxidation, when HRT reduced from 24 to 12 h the nitrate removal efficiency suddenly dropped from 98% to 70%. Increasing the pH values from 7.0 to 9.0 also decreased the sulfide oxidation efficiency from 97±0.5–92±1.1%. Denitrification efficiency > 96% was observed between pH value of 7.0 and 8.0, whereas at pH 9.0 dropped rapidly to 82%. In the whole experiment time there was no membrane-induced problem that adversely affected the system performance. Over-all the developed anoxic dense MBS successfully employed for selective removal of 10,000 ppm H2S and nitrate concurrently with low chemical consumption, possibility for recovery of elemental sulfur, enhanced CH4 calorific value and eliminating the risks of explosion and dilution of biogas. The current work showed the PDMS MBS system is a promising alternative way in biological nitrogen removal and biogas desulfurization under anoxic conditions. Its application in real scale would have high economic importance.

Kinetic Investigation of the Deep Desulfurization of 5 wt% Si High-Silicon Austenitic Stainless Steel

Given the demand for extremely low sulfur content in 5 wt% Si high-silicon austenitic stainless steel (SS-5Si), smelting utilizes a slag composition of CaF2-CaO-Al2O3-MgO-SiO2 with a basicity of 1 to 3, Al2O3 content ranging from 2.04 to 9.61%, and CaF2 content between 20.8 and 31.62%. Experiments designed to investigate the sulfur content in molten steel at temperatures of 1773 K, 1823 K, and 1873 K over durations of 1, 5, 10, 15, and 30 min, under varying slag compositions, corroborated with a theoretically derived model hypothesizing a “rate-controlling” step in mass transfer, revealed that the mass transfer of sulfur within the molten steel was determined to be the rate-controlling step (RCS) in the (CaO) + [S] = (CaS) + [O] reaction kinetics, and the variability of the mass transfer coefficient of sulfur, kS,m, in the molten steel ranged from 1.04 × 10−5 m∙s−1 to 2.24 × 10−5 m∙s−1. Based on the temperature dependency of kS,m, the apparent activation energy for the desulfurization reaction was estimated to be 96.03 kJ/mol. Considering the slag components, the binary basicity, denoted as R, exerted an overriding influence on the process of desulfurization. At a basicity of 1, the sulfur content within the liquid steel was reduced, from 22 ppm to 11 ppm within a time span of 30 min. In contrast, an increase in the basicity to a value of 3 showed a significant consequence: over an identical temporal duration of 30 min, the sulfur content was drastically reduced to 2.2 ppm. By contrast, an initial surge in desulfurization rates is observed within the first five minutes, attributable to relatively lower concentrations of Al2O3 and higher levels of CaF2. Subsequently, these parameters exert no significant influence on the kinetics of the desulfurization process.