Increase In Sulfur Content Research Articles

Delaying cyclization of polyacrylonitrile by boric acid for sulfurized poly(acrylonitrile) cathode materials

Sulfurized poly(acrylonitrile) (SPAN) has become one of the most promising cathode materials in rechargeable Lithium-Sulfur (Li-S) batteries due to their inhibited polysulfide dissolution, high sulfur utilization and excellent electrochemical performance via unique solid–solid conversion mechanism. However, the sulfur content of SPAN (<50 %) is still one of the significant reasons that restrict the electrochemical performance and practical applicability. In this paper, a small amount of boric acid (HBO) was introduced into the precursor of SPAN cathode materials easily before heat-treating, to increase the sulfur content and improve the electrochemical performance. Meanwhile, the results of first principles calculation suggested that the increase of sulfur content of SPAN was derived from the delayed cyclization of polyacrylonitrile (PAN) by HBO. We also discovered when the additive amount of HBO was 1.5 % of PAN mass, the SPAN cathode material possessed high sulfur content up to 54.24 wt%, and delivered prominent reversible electrochemical performances of 714 mAh/g at 0.2C and 734 mAh/g at 0.1C with high Coulombic efficiency. In summary, we proposed a simple and easy method to improve sulfur content and introduced a new strategy for the design of high-sulfur content and high-performance SPAN cathode materials.

Modulation of shape memory properties of trans-polyisoprene by sulfur

Abstract In this paper, TPI/S composites were prepared by a simple physical melt blending method, and the composites were hot-pressed and molded using a vulcanization system. The effect of cross-linking on the vulcanization properties, mechanical properties, crystalline properties, and shape memory properties of trans-1-4 polyisoprene (TPI) was investigated by varying the amount of sulfur (S). It was shown that with the increase of sulfur dosage, both TPI scorch time and orthoclave time were shortened and the mechanical properties decreased; The melting peak area and melting temperature of the crystalline region of TPI decreased with the increase of sulfur content, and the cross-linking density increased while the crystallinity tended to decrease and the heat resistance deteriorated; In addition, with the increase of sulfur content, the shape return rate of TPI/S composites was increasing and the shape fixation rate was decreasing. When the TPI/S composites were used as shape memory materials, the sulfur dosage of 1 phr had the best shape memory performance, at which time the shape fixation rate of the composites reached 96.9% and the shape recovery rate reached 86.2%. When the sulfur content was elevated to 2 phr, the shape memory fixation rate was significantly decreased, indicating that the shape memory properties were severely compromised. This study reveals that the quantity of sulfur exerts a significant influence on the application of TPI/S composites. An appropriate amount of sulfur can facilitate the preparation of thermoplastic elastomers for utilization in shape memory materials. Nevertheless, an excessive amount of sulfur will substantially enhance the internal cross-linked structure of the composite and deteriorate the shape memory performance.&amp;#xD;&amp;#xD;

Rapid CO2 catalytic activation of binary cementing system of CSA and Portland cement

This study presents a novel approach to activating a binary cementing system composed of calcium sulfoaluminate (CSA) cement and ordinary Portland cement (OPC) using an instant CO2 catalysis. The activation led to significant and rapid strength enhancement, with the binary cement achieving a strength of 15.42 MPa immediately after activation, all within 1 min. The rapid CO2 activation catalyzed a notable heat release, accelerating the hydration of ye'elimite to form ettringite, which is a crucial component capable of bridging gaps and imparting high initial strength. Simultaneously, the CO2 activation catalyzed the increase in sulfur concentration, which in turn, also facilitated the formation of ettringite at an early age. Subsequent strength development was attributed to belite hydration. Apart from the rapid strength gain, employing CO2 activation facilitated control over the pH value of the pore solution, thus enabling the manipulation of ettringite's crystal morphology to strategically enhance the microstructure. Samples with lower pH values exhibited needle-like ettringite formations, whereas samples with higher pH values yielded rod-like and column-like ettringite crystal structures. Comprehensive analytical investigations were analyzed using XRD, FTIR, TGA, 27Al NMR, MIP, SEM, and ICP-OES. The present study provides a new perspective on the potential application of CSA-based cement, such as precast concrete element, instant concrete product delivery, and urgent reconstruction.

Production of low-sulphur tailings by hydrocycloning

Acid mine drainage (AMD) is an environmental problem in gold mines containing sulphur minerals. The potential for acid drainage in tailings facilities must be considered when studying their dry closure. Therefore, controlling the sulphur content in the final layer of tailings deposition has the potential to prevent AMD after closure. In this context, the rougher flotation tailings were hydrocycloning in a pilot plant in a gold mining company to assess the potential for generating modified tailings with low-sulphur content. A total of 10 samples were composited over one hour of pilot plant operation. The hydrocyclone overflow showed an average reduction of 36.2% in sulphur content and an average metallurgical recovery of 20.0%. The underflow had an average increase in sulphur content of 16.8% and 80.0% metallurgical recovery. These results demonstrated the possibility of generating modified tailings with reduced sulphur content through hydrocycloning.

Investigation of Sulfur Influence on the Atomization of Stainless Steels

In this study, the alloying of stainless steels with various sulfur contents is investigated to obtain steel powders with significantly reduced mean diameters without changing the operational parameters of the atomizing unit. The steels are produced in a VIM12 furnace and atomized on a VIGA‐1B setup with high‐pressure argon. The desired reduction in the mean diameter is attributed to the decrease in surface tension with increasing sulfur content, which is in good agreement with previous findings. A transition from a positive to a negative thermal gradient of the surface tension is observed, along with a shift to higher temperatures with increasing sulphur concentration. In addition, the chemical assessment of the powders reveals a lower evaporation of manganese and a reduced increase in nitrogen content with increasing sulfur content. The sphericity and flowability are not affected by the addition of sulfur. Viscosity and density measurements are also conducted to characterize the steels thoroughly. Scanning electron microscopy reveals the presence of manganese sulfide, which was submicron in size and well distributed. Iron sulfides, mostly attributed to hot shortness, were not observed, which was also confirmed by thermodynamic modeling using Thermo‐Calc software.

Anatomy of a fumarole field: drone remote-sensing and petrological approaches reveal the degassing and alteration structure at La Fossa cone, Vulcano, Italy

Abstract. Hydrothermal alteration and mineralization processes can affect the physical and chemical properties of volcanic rocks. Aggressive acidic degassing and fluid flow often also lead to changes in the appearance of a rock, such as changes in surface coloration or intense bleaching. Although hydrothermal alteration can have far-reaching consequences for rock stability and permeability, limited knowledge exists on the detailed structures, extent, and dynamic changes that take place near the surface of hydrothermal venting systems. By integrating drone-based photogrammetry with mineralogical and chemical analyses of rock samples and surface gas flux, we investigate the structure of the evolving volcanic degassing and alteration system at the La Fossa cone on the island of Vulcano, Italy. Our image analysis combines principal component analysis (PCA) with image classification and thermal analysis through which we identify an area of approximately 70 000 m2 that outlines the maximum extent of hydrothermal alteration effects at the surface, represented by a shift in rock color from reddish to gray. Within this area, we identify distinct gradients of surface coloration and temperature that indicate a local variability in the degassing and alteration intensity and define several structural units within the fumarole field. At least seven such larger units of increased activity could be constrained. Through mineralogical and geochemical analysis of samples from the different alteration units, we define a relationship between surface appearance in drone imagery and the mineralogical and chemical composition. Gradients in surface color from reddish to gray correlate with a reduction in Fe2O3 from up to 3.2 % in the unaltered regime to 0.3 % in the altered regime, and the latter coincides with the area of increased diffuse acid gas flux. As the pixel brightness increases towards higher alteration gradients, we note a loss of the initial (igneous) mineral fraction and a change in the bulk chemical composition with a concomitant increase in sulfur content from close to 0 % in the unaltered samples to up to 60 % in samples from the altered domains. Using this approach of combined remote-sensing and in situ analyses, we define and spatially constrain several alteration units and compare them to the present-day thermally active surface and degassing pattern over the main crater area. The combined results permit us to present a detailed anatomy of the La Fossa fumarole field, including high-temperature fumaroles and seven larger units of increased alteration intensity, surface temperature, and variably intense surface degassing. Importantly, we also identify apparently sealed surface domains that prevent degassing, likely as a consequence of mineral precipitation from degassing and alteration processes. By assessing the thermal energy release of the identified spatial units quantitatively, we show that thermal radiation of high-temperature fumaroles accounts for &lt; 50 % of the total thermal energy release only and that the larger part is emitted by diffuse degassing units. The integrated use of methods presented here has proven to be a useful combination for a detailed characterization of alteration and activity patterns of volcanic degassing sites and has the potential for application in alteration research and for the monitoring of volcanic degassing systems.

Transformation and control of organic sulfur during pyrolysis of sludge under conditions relevant to smoldering combustion: Role of oxygen and CaO

This study focused on the effect of oxygen (0–15 %) and 5 % CaO addition on the organic-S control and transformation behavior during pyrolysis (400–600 °C) of sludge under the conditions relevant to smoldering combustion. The results show that oxygen inhibits the total emission of gaseous sulfur (decreased by 25.6–36.9 %). At low temperatures (<500 °C), oxygen enhances the oxidation of aliphatic-S, aromatic-S/thiophene-S, and sulfide-S, leading more sulfur retains in the form of sulfone-S and sulfate-S in char products, also migrates to water-soluble products (especially sulfone-S). At high temperatures (>500 °C), the formed sulfur species in char products mainly further decompose into water-soluble sulfone-S, and partially generate SO2. After the addition of CaO during oxidative pyrolysis, the synergistic promotion effect on the sulfur fixation in char products is found, mainly due to the generation of more amount of stable sulfone-S and sulfate-S in char products. This leads to a decrease in gaseous sulfur by 12.4–14.6 % and an increase in sulfur content of char products by 31.3–202.9 %.

Response of sulfate concentration to eutrophication on spatio-temporal scale in freshwater lakes

The dramatical increase of sulfur concentration in eutrophic lakes, especially sulfate (SO42−), has brought attention to the impact on the lake ecosystem; however, the mechanisms driving the intensification of eutrophication and the role of SO₄2− concentrations remain poorly understood. To assess the impact of eutrophication on SO42− dynamics in lakes, this study monitored SO42− concentrations in water and sediments across seven lakes with varying trophic statuses on a spatial scale, and in the eutrophic Lake Taihu over one year on a temporal scale, as well as a series of microcosms with different initial SO42− concentrations. Exogenous sulfur input is the primary driver of increased SO42− concentrations in lakes, the highest SO42− concentration in overlying water was 100 mg/L, as well as which reached 310.9 mg/L in sediment. The concurrent input of nutrients such as nitrogen and phosphorus exacerbated eutrophication, resulting in the destabilization of the sulfur cycle. Eutrophication promoted the SO42− concentration on the spatio-temporal scale, especially in sediment, and trophic lake index (TLI) showed a positive correlation with the SO42− in sediments (R2 = 0.99; 0.88). The SO42− concentration in water and TLI showed a nonlinear correlation on the temporal scale (R2 = 0.44), and showed a positive correlation on the spatial scale (R2 = 0.49). Microscopic experiments demonstrate that the anaerobic environment created by cyanobacteria decomposition induced sulfate reduction and significantly reduces SO42− concentrations. Concurrently, the anaerobic environment facilitates the coupling of iron reduction with sulfate reduction, leading to a substantial increase in Acid Volatile Sulfides (AVS) in the sediment. These findings reveal that eutrophication has a dual effect on the dynamic change of SO42− concentrations in overlying water, which is helpful to accurately evaluate and predict the change of SO42− concentrations in lakes.

Nature-Derived Sulfur Carbons for Highly-Efficient Room Temperature Sodium-Sulfur Energy Storage

In recent years, a growing interest in “beyond-Li-ion“ batteries has caused a speedy development of alternative battery technologies based on other alkali metals. Room temperature sodium sulfur (RT Na-S) batteries are potential candidate for sustainable large-scale energy storage systems. They offer low cost, nontoxicity and natural abundance of both cathode and anode materials combined with high theoretical energy density. However, rapid capacity fading related to the irreversible shuttling of soluble polysulfides, poor reaction kinetics and low sulfur utilisation in the cathode materials significantly limit their practical application.In this work, a microporous sulfur-carbon complex is produced from sustainable natural precursors in a one-pot synthesis via stepwise thermally-induced inverse vulcanisation and condensation. The material exhibits a unique structure, with sulfur chains covalently anchored to the conductive carbon matrix and physically confined in ultra-micropores. An increase in sulfur content in the sulfur-copolymer alters the morphology and chemical composition of the final sulfur-carbon material, enhancing the amount of long-chain sulfur. The combination of optimal microstructure, good electrical conductivity and high content of electrochemically active sulfur translates to an unprecedented ~99% utilisation of sulfur and the highest reported capacity for a room temperature Na-S cathode, along with high rate capability, coulombic efficiency and long-term stability. This study offers an innovative approach towards the understanding of the key chemico-physical properties of the sulfur-carbon composite materials for the development of high-performance cathodes in RT Na-S batteries with an atom-efficient utilisation of sulfur.

Pitting Initiated by MnO·Cr2O3–MnS and MnS Inclusions in a Si‐/Mn‐Killed Stainless Steel

Two types of inclusions in the stainless steels are detected: MnO·Cr2O3–MnS dual‐phase ones and pure MnS ones. The increase of sulfur content can inhibit the formation of MnO–Cr2O3–MnS inclusions and reduce the harm of MnO·Cr2O3–MnS inclusions on the pitting corrosion of stainless steels. When the sulfur content increases from 26 to 70 ppm, the average pitting potential increases from 0.34 to 0.4 VSCE due to the decrease in the number density of MnO–Cr2O3–MnS inclusions. A Cr‐depletion zone exists in the steel matrix around MnO–Cr2O3–MnS inclusions. The size of pits induced by MnO·Cr2O3–MnS inclusions is larger, which poses a more serious threat to the pitting resistance of stainless steels.

Fabrication and Properties of Bi2S3 Nanowire Thin Film Solar Cells by Spin Coating with Varying Sulfur Concentrations in the Precursor

We conducted a simple solution-based method to fabricate Bi2S3 nanowire thin film solar cells by spin coating with varying sulfur-to-bismuth ratios. Spherical nanoparticles were observed in the thin film with low-concentration sulfur solution, with these nanoparticles gradually changing to nanorods. Finally, nanowires of Bi2S3 were observed in the thin film with a high sulfur concentration in solution. The band gap gradually decreased with the increase in sulfur concentration. The solar cell performance was significantly improved with the nanowire structure. During film fabrication, sulfur vacancy defects appeared primarily because of high annealing temperatures. These defects were somewhat reduced by the high concentration of sulfur in the solution, supported by the energy-dispersive x-ray spectroscopy (EDS) results. The elemental chemical composition of Bi2S3 material showed an increase in the sulfur-to-bismuth ratio, reaching saturation at almost 0.9. In this work, we systematically observed the effect on the optical properties, surface morphology, and photovoltaic properties by changing the concentration of sulfur in the precursor. The nanowire structure with a high concentration of sulfur in the solution is a promising way to improve the Bi2S3 thin film solar cell.

The property, structure, and phase evolution of a binary cementitious material derived from sintering flue gas desulphurization ash and steel slag

The sintering flue gas desulphurization ash (DA) has emerged as the most significant solid waste, second only to granulated blast furnace slag and steel slag (SS), generated by steelmaking plants. However, its high CaSO3 content has rendered it challenging to recycle effectively. This study delves into the hydration characteristics of a low-carbon cementitious material composed of DA and SS, across different sulphur contents (3.14%, 6.28%, 9.42%, 12.56%) and water to binder (W/B) ratios (0.30, 0.35, 0.40, 0.45). The hydration products of the DASS composite cementitious material encompass C–S–H, C–A–S–H, Ca(OH)2, and K2Ca5(SO4)6·H2O. The setting time and fluidity exhibit a diminishing trend with increasing sulphur content. Notably, the hydration exothermic peak for pastes with 3.14% sulphur content emerges at 3 h, signifying a 2-h advancement compared to pure steel slag paste. The compressive strength of cured DASS paste gradually increases with sulphur content ranging from 3.14% to 9.42% over the initial 28 d, but experiences a decline with further sulphur content increases. A reduction in the W/B ratio significantly reduces setting time and achieves a two-fold increase in 28 d compressive strength. In DASS paste featuring a W/B ratio of 0.35 and a sulphur content of 9.42%, a substantial quantity of newly generated Ca(OH)2 is consumed through the pozzolanic reaction with steel slag after 60 d, leading to the production of more C–S–H to fill the interstitial voids between raw material particles. In conclusion, the recommended formulation for the DASS cementitious material should incorporate approximately 6%–9% sulphur supplied by DA, while greater mechanical properties can be attained by minimizing the W/B ratio. This innovative low-carbon cementitious material mitigates the impact of the massive amount of cement demand and promise an alternative to industrial waste management.

Synthesis of two-dimensional MoO2 nanoplatelets and its multistep sulfurization into MoS2

To control the growth of layered two-dimensional structures, such as transition metal dichalcogenide materials or heterostructures, understanding the growth mechanism is crucial. Here, we report the synthesis of ultra-thin MoO2 nanoplatelets through the sublimation of MoO3. Rhombus MoO2 nanoplatelets with the P21/c space group were characterized using various microscopic and spectroscopic techniques. Introducing sulfur sources into the chemical vapor deposition system also leads to the formation of monoclinic MoO2 nanoflakes due to the incomplete sulfurization of MoO3. With a gradual increase in the vapor concentration of sulfur, MoO3 undergoes stepwise reduction into MoS2/MoO2 and eventually into MoS2. Additionally, utilizing MoO2 as a precursor for Mo sources enables the formation of monolayer MoS2 single crystals. This work provides an effective approach for growing MoO2 nanoplatelets and elucidates the mechanism behind the stepwise sulfurization of MoO3.

Impact of impurities on the thermal properties of a Li2S–SiS2–LiPO3 glass

AbstractThe preparation of 0.58 Li2S + 0.315 SiS2 + 0.105 LiPO3 glass, and the impacts of polysulfide and P1P defect structure impurities on the glass transition temperature (Tg), crystallization temperature (Tc), working range (ΔT≡ Tc ‐ Tg), fragility index, and the Raman spectra were evaluated using statistical analysis. In this study, 33 samples of this glass composition were synthesized through melt‐quenching. Thermal analysis was conducted to determine the glass transition temperature, crystallization temperature, working range, and fragility index through differential scanning calorimetry. The quantity of the impurities described above was determined through Raman spectroscopy peak analysis. Elemental sulfur was doped into a glass to quantify the wt% sulfur content in the glasses. Linear regression analysis was conducted to determine the impact of polysulfide impurities and P1P defect impurities on the thermal properties. Polysulfide impurities were found to decrease the Tg at rate of nearly 12°C per 1 wt% increase in sulfur concentration. The sulfur concentration does not have a statistically significant impact on the other properties (α = 0.05). The P1P defect structure appears to decrease the resistance to crystallization of the glass by measurably decreasing the working range of the glasses, but further study is necessary to fully quantify and determine this.

Complementary imaging of nanoclusters interacting with mitochondria via stimulated emission depletion and scanning transmission electron microscopy

The emerging stress caused by nanomaterials in the environment is of great concern because they can have toxic effects on organisms. However, thorough study of the interactions between cells and diverse nanoparticles (NPs) using a unified approach is challenging. Here, we present a novel approach combining stimulated emission depletion (STED) microscopy and scanning transmission electron microscopy (STEM) for quantitative assessment, real-time tracking, and in situ imaging of the intracellular behavior of gold–silver nanoclusters (AuAgNCs), based on their fluorescence and electron properties. The results revealed an aggregated state of AuAgNCs within the mitochondria and an increase in sulfur content in AuAgNCs, presumably owing to their reaction with thiol-containing molecules inside the mitochondria. Moreover, AuAgNCs (100 μg/mL) induced a 75% decline in mitochondrial membrane potential and a 12-fold increase of mitochondrial reactive oxygen species in comparison to control. This mitochondrial damage may be triggered by the reaction of AuAgNCs with thiol, which provides direct imaging evidence for uncovering the action mechanism of AuAgNCs on the mitochondria. The proposed dual-imaging strategy using STED and STEM is a potential tool to offer valuable insights into cytotoxicity between subcellular structures and diverse NPs, and can serve as a key strategy for nanomaterial biosafety assessment.

Experimental evaluation of the effect of sulfur content on the spontaneous combustion characteristics parameters of coal

The coal spontaneous combustion (CSC) is the main hazard threatening the coal safety production. In this work, the CSC characteristic, CSC tendency and limit parameters with different sulfur were measured and discussed using temperature-programmed experiment. The results show that the cross-point temperature (CPT) decreases first and then increases with the increasing sulfur content. The CSC tendency of coal with sulfur content in the range of 3.28–5.13 % is greater than that with sulfur content of 2.57 % and 7.59 %. When sulfur content is less than 5.13 %, sulfur and its unstable compounds in coal have strong reactivity and can promote oxidation reaction. When sulfur content is greater than 5.13 %, a large number of sulfur-containing substances reduce the contact area of coal oxygen molecules, which inhibits the oxidation reaction of coal. The sulfur content of coal sample has a significant effect on the limit parameters of coal spontaneous combustion.

3D Plotting of Gold Solubility and Gold Fineness: Quantitative Analysis of Ore-Forming Conditions in Hydrothermal Gold Deposits

Abstract The 3D plotting of gold solubility and gold fineness aims to illustrate how to quantify their correlations with ore-forming conditions in hydrothermal gold deposits. The thermodynamic calculation of the Au-Ag solid solutions in Mathematica and the 3D plotting in MATLAB are used to build isopleths of gold solubility and gold fineness at different temperatures (200℃, 400℃), pressures (0.1, 5 kbar), salinities (1, 40 wt% NaCl eq.), and sulfur concentrations (0.01, 0.5 mol/kg). The plot indicates that the ore-forming conditions have different correlations with gold solubility and gold fineness. Average rates of change for the correlations are quantified, showing distinct values in the four pH-logfO2 fields of (I) HSO4−, (II) SO42−, (III) H2S, and (IV) HS−, where dominant gold and silver complexes have different dependencies on the conditions. The quantification of the plots illustrates that a decrease in gold solubility by one order of magnitude is possibly caused by a decrease in temperature of ≥40℃, the salinity of ≥9.6 wt% NaCl eq. or sulfur concentration of ≥0.14 mol/kg, or an increase in pressure of ≥3 kbar, while a decrease in gold fineness by 100 units is possibly caused by a decrease in temperature of ≥14 ℃, pressure of ≥1.4 kbar, or salinity of ≥4 wt% NaCl eq., or an increase in sulfur concentration of ≥0.07 mol/kg. Quantification results suggest that a sharp decrease in temperature may result in large-scale gold mineralization and a great variation in gold fineness. In addition, the quantification reveals that the correlation between gold solubility and gold fineness can be expressed by a function, providing a rapid method for 3D plotting.

Study on Mechanical and Flow Properties of Cemented Sulfur Tailings Backfill Considering the Influence of Fiber Type, Fiber Content and Addition Method

Previous studies have confirmed that for cemented tailings backfill, mechanical properties are improved through the addition of fiber. However, for fiber-reinforced cemented sulfur tailings backfill (FRCSTB), physical and flow properties are still unknown. In this paper, the changes in fluidity, splitting tensile strength (STS) and uniaxial compressive strength (UCS) of cemented sulfur tailings backfill (CSTB) are analyzed in detail. Secondly, regarding the addition of glass fiber and polypropylene fiber, the changes in the fluidity, STS and UCS of the CSTB, resulting from the fiber length, fiber content and method of fiber addition used, were analyzed. Moreover, the relationship between the UCS and fiber content is established. Finally, the mechanism behind the influence of fiber and sulfur content on the mechanical properties of CSTB is revealed. The results indicate that with the increase in sulfur content, the fluidity of the tailings slurry exhibits exponential growth. During the process of increasing sulfur content, the UCS and STS of CSTB initially increase and then decrease, reaching maximum values at 12% sulfur content. Similarly, at a fiber content of 0.6%, the UCS and 28d STS of CSTB reach their maximum values. In terms of enhancing the mechanical properties of CSTB, the effectiveness of glass fibers surpasses that of polypropylene fibers. In addition, regarding the improvement of the UCS of CSTB, the mixed addition of fibers is obviously worse than that of fiber alone. However, in terms of enhancing the STS of CSTB, the mixed addition of fibers outperforms the single addition of polypropylene fiber. From a microscopic perspective, polypropylene and glass fiber are able to form strong cohesion with the cement–tailings matrix and effectively prevent the formation and expansion of pores and cracks.

Occurrence of characteristic defects of grinding balls from rejects of continuously cast billets of rail steel

On the basis of metallographic studies, the authors determined the characteristic defects of grinding balls rolled from the rejects of continuously cast billets of K76F rail steel. Relationship of the presence of internal defects of the balls with their impact resistance was established. Defects in the form of internal cracks with accumulations of non-metallic inclusions in the area of their localization and flocks have the greatest impact on the reduction of balls impact resistance. Such defects are the cause of balls destruction during impact resistance tests in 62 and 17 % of cases, respectively. The effect of internal cracks without significant accumulations of non-metallic inclusions and quenching microcracks located along the boundaries of the phase interface was estimated at 12 and 9 %. The regularities and mechanism of influence of the rejects chemical composition of K76F rail steel billets on the probability of destruction of the balls produced from them during impact resistance tests were established. An increase in sulfur content in the billets of the studied rail steel reduces impact resistance of the balls produced from them, as it contributes to formation of non-plastic sulfides that concentrate in the area of internal cracks. An increase in hydrogen content in rail steel naturally contributes to an increase in probability of formation of the flocks, which significantly reduce the balls stability to shock loads. An increase in carbon content in the initial billets affects the increase in probability of destruction of K76F steel balls during copra tests. It is explained by formation of cementite-type carbides when carbon content corresponding to the eutectoid steel is reached. In general, the relative degree of influence of the K76F rail steel chemical composition on impact resistance of grinding balls is 48 %.

On the Effect of the Reaction Medium on the HydroClaus Process: A Novel Sustainable H2S Valorization Strategy

Hydrogen sulfide (H2S) is becoming a critical issue to manage, due to the increasing sulfur content in the processed gas together with the stricter environmental regulations. Novel alternatives are being developed for the H2S abatement and conversion to valuable chemicals. Among them, the HydroClaus process, patented by Eni S.p.A., deserves attention. This technology aims at converting H2S and SO2 into a hydrophilic mixture of sulfur and sulfur-rich compounds, polythionates, to be used as a fertilizer. An improved configuration for an efficient water management is proposed in this work. The process operability has been demonstrated at the bench scale, through an ad hoc experimental campaign. For the technology scale-up, a flowsheet has been set up and its performances have been assessed in terms of heat and material balances and CO2 emissions. Results reveal that the modified HydroClaus process can be a valid solution for an effective H2S valorization, also considering that no direct CO2 emissions are released. Moreover, since only electric power is required, a further reduction of the indirect CO2 emissions is expected, if renewable sources can be exploited for this purpose.