Sulfur Release Research Articles

Hydrothermal alteration and mineralization of Baiyun gold deposit in Liaodong Peninsula, North China Craton

Baiyun deposit is a large gold deposit in the Liaodong Peninsula (North China Craton), containing over 31.7 t of gold. Silicic alteration, K‐feldspar alteration, and pyritization are well developed and closely related with mineralization in Baiyun deposit. Based on field and optical microscopic observations, the alteration styles include quartz + K‐feldspar zone, pyrite + sericite +quartz zone, and chlorite zone from orebody outward. In this study, the quartz, K‐feldspar, and pyrite of pre‐ore, syn‐ore stages 1 and 2 were selected for LA‐ICP‐MS trace element analysis and electron probe microanalysis (EPMA) to reveal the alteration‐mineralization link. Results show that the albite was altered to mainly K‐feldspar and minor secondary quartz at syn‐ore stage 1. Fluid‐rock reaction of the silicic‐potassic alteration may have decreased the fluid oxygen fugacity (fO2), which triggered the gold precipitation. Most of invisible gold occurred in the form of solid solution. At syn‐ore stage 2, albite altered to mainly quartz and minor K‐feldspar. The syn‐ore stage 1 K‐feldspar also altered to minor secondary quartz at syn‐ore stage 2. In addition, the release of sulphur from the syn‐ore stage 1 pyrite was likely another trigger for the gold precipitation. Most of syn‐ore stage 2 invisible gold occurred as nano‐particles. The ore‐forming fluids consist mainly of primary magmatic fluids mixed with minor metamorphic fluids. The ore metals may have sourced mainly from the magmatic fluid and the sillimanite‐mica schist of the Gaixian Formation.

Systematic evaluation and kinetic modeling of low heating rate sulfur release in various atmospheres

In the present work, a systematic experimental and numerical study of sulfur release from coal in varying atmospheres at low heating rates (LHR) is presented. To this aim, two bituminous coals were investigated, Colombian hard coal (K1) with typical sulfur content, and American high-sulfur coal (U2), with elevated sulfur content. Mass loss and release of target volatile species - H2S, COS, SO2- were tracked using a TG-MS. The samples were heated at 10 Kmin−1under different atmospheres: argon, CO2, synthetic air (21 vol% O2/79 vol% Ar) and oxy-fuel (21 vol% O2/79 vol% CO2). The role of the different atmospheres in the sulfur release was elucidated as well as the fate of the volatile species in the gas-phase. The advantage of investigating the release at LHR is that heat and mass transfer effects can be neglected, as the experimental conditions allow the process to remain in the kinetic regime. The successive increase in atmosphere complexity allowed to individuate the chemical paths leading to the formation of SOXand its precursors in each of the conversion steps: devolatilization, char conversion as well as the coupling to gas-phase reactions. The experiments were further analyzed with a kinetic model for the solid-phase of coal conversion, coupled with a detailed gas-phase kinetic mechanism. The solid-phase kinetic model was modifiedaccounting for the particularities of the fuels, for the effects of oxy-fuel atmosphere. A small number of kinetic parameters was adjusted for improved predictions of the release rate and the yields of sulfur species.

Emissions of biogenic sulfur compounds and their regulation by nutrients during an Ulva prolifera bloom in the Yellow Sea

Three cruises were conducted during an Ulva prolifera bloom in 2018 off the Qingdao coast to observe early-, late-, and after-bloom characteristics. Spatio-temporal changes in dimethylsulfide (DMS), dimethylsulphoniopropionate (DMSP), and acrylic acid (AA) and their relationships with environmental parameters were examined. Mesocosm experiments tested the effect of nutrient on the release of biogenic sulfur compounds during the decline period. Biogenic sulfur concentrations contrasted with those in non-bloom regions and reached their highest values during the late-bloom period. The average sea-to-air DMS flux was about 5 times higher than those of non-bloom regions. The mean concentrations of DMS and DMSP in the enclosures were 3–5 times those of in-situ seawater. Biogenic sulfur release was promoted by the addition of high concentrations of nutrients as U. prolifera was declining. The contribution of the U. prolifera bloom to atmospheric DMS was estimated to be 125 kg S d−1.

Release of Sulfur and Nitrogen during Co-pyrolysis of Coal and Biomass under Inert Atmosphere.

Coal combustion is a major energy provider but also a serious pollutant emitter worldwide. Biomass has attracted increasing research attention due to its carbon neutral and other advantages during co-pyrolysis of coal. Therefore, pyrolysis of corn straw, lignite coal, and their mixed fuel was investigated using a horizontal tube furnace at a temperature range of 300–900 °C in this study by concentrating on emissions of nitrogen- and sulfur-bearing gases. Emissions of HCN, NH3, COS, and SO2 were monitored, and char yield was calculated during pyrolysis. Results showed that char yield decreases with increasing temperature due to the decomposition of heterocyclic aromatic hydrocarbon. Sulfur (42.45 wt %, 900 °C) and nitrogen (73.23 wt %, 600 °C) were released from the mixed fuel during pyrolysis. The synergistic effect between corn straw and coal was evaluated and their experimental and calculated values were compared. The synergistic effect on emissions was remarkable at a temperature range of 600–800 °C due to high biomass content and desynchronization of volatile matter emissions between the coal and biomass. Volatiles in the biomass, which are released before coal, stimulated the volatilization of coal. Several conventional gases, such as CH4 and C2H6, were also analyzed to investigate emission patterns at different temperatures.

Direct Reduction of Heavy Nonferrous Metals from Sulfide Compounds

The results of long-term work of the group of authors on the problem of the direct reduction of heavy nonferrous metals directly from sulfide compounds contained in concentrates (lead) and metallurgical products (copper, nickel)—white matte and copper and nickel concentrates—from the separation of a converter matte are summarized. The preparation of materials for the reduction and the reduction process itself include the conversion of metal sulfides into oxygen compounds (oxidizing and sintering roasting) with the reduction of metals with carbon-containing reagents (coal and СО), as well as the reduction of copper and, partly, lead from oxide melts with sulfides. Sulfides conversion and reduction operations are associated with the release of sulfur- and carbon-containing compounds (SO2, SO3, CO, and CO2) and, consequently, with the need to capture and utilize gaseous and solid products. A fundamentally new process of the direct reduction of metals from sulfides using their own sulfide sulfur as a reducing agent is proposed. The reducing process occurs through the possible formation of short-circuited electrode pairs in the 2Mez+–zS–2 system due to the donor–acceptor interactions, primarily π binding. The process can be successful occurrence upon the removal of the products (product) of the electrochemical reaction, in particular, S0. Caustic soda is proposed as a reagent. Using the example of the above production materials, the possibility of reducing the metals is shown at temperatures of 550–700°C with the achievement of their deep extraction (more than 99%). The product of sulfide sulfur oxidation, elemental sulfur, reacts with the melt of caustic soda and accumulates in the form of nonvolatile sodium compounds in it.

Sulfur and Nitrogen Release From Co-Pyrolysis of Coal and Biomass Under Oxidative and Non-Oxidative Conditions

Abstract This is an investigation on the effects of pyrolysis atmosphere on the conversion of biomass/coal blends to chars and volatile matter, and on the release of sulfur and nitrogen to the gas phase. Pulverized corn straw and lignite coal were co-pyrolyzed either in an inert carrier gas (N2) or in oxidative gases consisting of 3–7% O2 and 13–17% CO2 in a balance of 80% N2. The process occurred at temperatures in the range of 300–900 °C, under 1 atm, and lasted for 20 min. The results showed that the solid-phase conversion of coal/biomass blends ranged from 30 to 60%, increasing with increasing temperature. Increasing oxygen concentration under oxidative atmospheres promoted the solid-phase conversion at 500–900 °C, more than under the inert atmosphere, but had no discernible effect at lower temperatures (300–400 °C). Under the inert atmosphere, the co-pyrolysis of coal and biomass exhibited a synergistic effect, which promoted the transformation of solid feedstock into the gas phase or tar. To the contrary, under the oxidative atmospheres, the co-pyrolysis inhibited the evolution of volatile matter. Sulfur compounds, COS and SO2, were mainly released at temperatures in the range of 300–700 °C. Higher amounts of SO2 were released under the oxidative atmosphere, and the co-pyrolysis of coal and biomass promoted the release of COS. As for the transformation and release of nitrogen, NH3 and HCN were mainly released in the temperature range of 600–900 °C and more HCN was converted into NH3 under inert atmospheres. The effects of the oxygen content in the atmosphere on conventional gas species (CO, CH4, C2H6, and HCl) released from coal/biomass blends were also recorded.

Methanosarcina acetivorans contains a functional ISC system for iron-sulfur cluster biogenesis

BackgroundThe production of methane by methanogens is dependent on numerous iron-sulfur (Fe-S) cluster proteins; yet, the machinery involved in Fe-S cluster biogenesis in methanogens remains largely unknown. Methanogen genomes encode uncharacterized homologs of the core components of the ISC (IscS and IscU) and SUF (SufBC) Fe-S cluster biogenesis systems found in bacteria and eukaryotes. Methanosarcina acetivorans contains three iscSU and two sufCB gene clusters. Here, we report genetic and biochemical characterization of M. acetivorans iscSU2.ResultsPurified IscS2 exhibited pyridoxal 5′- phosphate-dependent release of sulfur from L-cysteine. Incubation of purified IscU2 with IscS2, cysteine, and iron (Fe2+) resulted in the formation of [4Fe-4S] clusters in IscU2. IscU2 transferred a [4Fe-4S] cluster to purified M. acetivorans apo-aconitase. IscU2 also restored the aconitase activity in air-exposed M. acetivorans cell lysate. These biochemical results demonstrate that IscS2 is a cysteine desulfurase and that IscU2 is a Fe-S cluster scaffold. M. acetivorans strain DJL60 deleted of iscSU2 was generated to ascertain the in vivo importance of IscSU2. Strain DJL60 had Fe-S cluster content and growth similar to the parent strain but lower cysteine desulfurase activity. Strain DJL60 also had lower intracellular persulfide content compared to the parent strain when cysteine was an exogenous sulfur source, linking IscSU2 to sulfur metabolism.ConclusionsThis study establishes that M. acetivorans contains functional IscS and IscU, the core components of the ISC Fe-S cluster biogenesis system and provides the first evidence that ISC operates in methanogens.

Release of nitrogen, sulfur and chlorine species from coal in carbon dioxide atmosphere

In oxyfuel combustion, the release of minority species, such as sulfur, nitrogen and chlorine compounds from the fuel plays an essential role, since significant corrosion and emission issues arise from these species. In the present study, the release of nitrogen, sulfur and chlorine species from a US-American bituminous coal with high sulfur content was studied in CO2 atmosphere in an entrained flow reactor. With the entrained flow reactor, particle heating rates comparable to those observed in a full-scale furnace can be achieved. The experiments were performed at different reactor temperatures in CO2 atmosphere. Gas samples were extracted from the reactor, and the concentration of various gas species, including NO, N2O, NH3, HCN, H2S, SO2, COS and HCl, was determined. It was found that the formation and release of the considered minority species changes with temperature and fuel residence time. A rapid decrease of the N2O concentration and an increase of the NO concentration was observed with increasing temperature. The release of NH3 from the fuel increased with increasing temperature, whereas the release of HCN decreased. Furthermore, compared to pyrolysis in nitrogen atmosphere, the release of sulfur and chlorine species increased significantly. Finally, COS was detected in significant amounts in CO2 atmosphere, but not in inert N2 atmosphere.

Experimental and modeling study of H2S formation and evolution in air staged combustion of pulverized coal

High-concentration H2S formed in the reduction zone of pulverized coal air-staged combustion can result into the high temperature corrosion of water wall tube of boiler, so it is of great importance to accurately predict H2S concentration for the safe operation of boilers and burners. H2S formation and evolution depends on two steps: the sulfur release from coal conversion and gas-phase reactions of sulfur species. In this study, the sulfur release characteristics from the pyrolysis of 17 coals, including 5 lignite, 9 bituminous coals and 3 anthracites, are investigated in a drop tube furnace (DTF). Sulfur release model is developed to describe the relationship between sulfur release and coal types. A global gas-phase reaction mechanism of sulfur species composed of ten reactions is used to calculate and predict the formation and evolution of H2S, COS and SO2 in the reduction zone of pulverized coal air-staged combustion. A wide range of air-staged combustion experiments of 17 coals are conducted in the DTF at different temperatures and stoichiometric ratios to validate the developed model. The results show that the prediction errors of sulfur species, including SO2, H2S and COS, are within ± 30%, which indicates that the developed prediction model of sulfur species is of great assistance for CFD modeling of actual engineering application.

Release and fate of pyritic sulfur in chemical looping combustion

Chemical-looping combustion (CLC) technology is an attractive solution for efficient fuel conversion with inherent separation of the greenhouse gas CO2. Sulfur is a major consideration in coal utilization, and pyrite is the major inorganic sulfur contaminant in most coals, therefore the release and fate of pyritic sulfur in the CLC process was investigated. A natural iron ore, and two synthetic materials (CuO/SiO2 and NiO/Al2O3) produced by the impregnation method were selected as oxygen carriers to investigate the effect of oxygen carrier on the sulfur distribution. Results showed that SO2 was the major sulfurous gas released, and a small amount of H2S and CS2 was escaped from the reactor in the reduction stage. The fractions of sulfur converted to gaseous substances in this stage were 90.38%, 82.22%, and 78.00% when using iron ore, CuO/SiO2, and NiO/Al2O3 respectively. Part of sulfur was stored in the oxygen carrier, and the presence of metal sulfides was confirmed by X-ray diffractometer (XRD). In the reoxidation stage, SO2 was produced by the oxidation of metal sulfides. The fraction of sulfur converted to gaseous species in this stage reached 2.26%, 11.84%, and 15.42% for iron ore, CuO/SiO2, and NiO/Al2O3 respectively. The accumulation of sulfur on the surfaces of three oxygen carriers was all detected by the Energy dispersive X-ray spectroscopy (EDX).

Metabolic Reprogramming of Sulfur in Hepatocellular Carcinoma and Sulfane Sulfur-Triggered Anti-Cancer Strategy.

Metabolic reprogramming is a cancer hallmark. Although the reprogramming of central carbon has been well documented, the role of sulfur metabolism has been largely overlooked. Additionally, the effects of sulfur are sometimes contradictory in tumorigenesis. In this study, we aimed to investigate the gene expression profile in hepatocellular carcinoma (HCC) and the effects of reactive sulfur species (RSS) on HCC tumor cells. Furthermore, the cell imaging technology was applied to discover some potential anti-cancer compounds. Gene Set Enrichment Analysis (GSEA) of Gene Expression Omnibus (GEO) dataset (GSE102083) revealed that sulfur amino acid-related metabolism and vitamin B6 binding activity in HCC tissues were downregulated. Calculation of the interaction network identified nine hub genes, among which eight were validated by differential expression and survival analysis in the TCGA_LIHC cohort, and two (CSE and CBS) had the highest enrichment degree. The metabolomics analysis suggested that the hub genes were associated with RSS metabolism including H2S, H2S2, cystine, cysteine, homocysteine, cystathionine, and methionine. The cell viability assay demonstrated that H2S2 had significant anti-cancer effects in HCC SNU398 tumor cells. The cell imaging assay showed that treatment with H2S2 remarkably increased intracellular sulfane sulfur content. On this basis, the anti-cancer activity of some other sulfane sulfur compounds, such as DATS and DADS, was further verified. Lastly, according to the fact that HCC tumor cells preferentially take in cystine due to high expression of SLC7A11 (a cystine/glutamate transporter), persulfided cysteine precursor (PSCP) was tested for its sulfane sulfur release capability and found to selectively inhibit HCC tumor cell viability. Collectively, this study uncovered sulfur metabolism in HCC was reprogrammed, and provided a potential therapeutic strategy for HCC by donating sulfane sulfur.

TG- MS study on in-situ sulfur retention during the co-combustion of reclaimed asphalt binder and wood sawdust

Reclaimed asphalt binder (RAB) releases large amounts ·of hazardous sulfur-containing gases during combustion. This study attempts to introduce wood sawdust (WS) as an in-situ inhibitor of sulfur release during the combustion of refuse-derived fuel (RDF) blended with RAB-WS. The combustion characteristics, gaseous sulfur-containing products, interactions and combustion kinetics of RDF were investigated through thermogravimetry and mass spectrometry (TG-MS), and the mechanisms on migration and distribution of sulfur were revealed. Results indicated that WS additive inhibits the volatilization of light components and promotes the degradation of macromolecular components. WS addition improved the combustibility, burnout performance and combustion stability of RAB. The sulfur release of RAB-based RDF was mainly derived from resins and asphaltenes. WS addition generally decreased all gaseous sulfur-containing compounds (CH3SH, COS, SO2, CS2 and thiophene). Interactions between RAB and WS restrained all sulfur-containing gas emissions, and the normalized sulfur inhibition ratio reached 40.99 %. The Sarink and DAEM models could well describe the kinetic process of the co-combustion of RAB and WS. WS addition led to a decrease in activation energy, namely, it lowered the reaction barrier. Sulfur could be retained in-situ into incineration residue through the formation of sulfate minerals during the co-combustion of RAB and WS.

Simulation Study of the Formation of Corrosive Gases in Coal Combustion in an Entrained Flow Reactor

Gaseous sulfur species play a major role in high temperature corrosion of pulverized coal fired furnaces. The prediction of sulfur species concentrations by 3D-Computational Fluid Dynamics (CFD) simulation allows the identification of furnace wall regions that are exposed to corrosive gases, so that countermeasures against corrosion can be applied. In the present work, a model for the release of sulfur and chlorine species during coal combustion is presented. The model is based on the mineral matter transformation of sulfur and chlorine bearing minerals under coal combustion conditions. The model is appended to a detailed reaction mechanism for gaseous sulfur and chlorine species and hydrocarbon related reactions, as well as a global three-step mechanism for coal devolatilization, char combustion, and char gasification. Experiments in an entrained flow were carried out to validate the developed model. Three-dimensional numerical simulations of an entrained flow reactor were performed by CFD using the developed model. Calculated concentrations of SO2, H2S, COS, and HCl showed good agreement with the measurements. Hence, the developed model can be regarded as a reliable method for the prediction of corrosive sulfur and chlorine species in coal fired furnaces. Further improvement is needed in the prediction of some minor trace species.

Experimental and modeling assessment of sulfur release from coal under low and high heating rates

Coal combustion releases elevated amounts of pollutants to the atmosphere including SOX. During the pyrolysis step, sulfur present in the coal is released to the gas phase as many different chemical species such as H2S, COS, SO2, CS2, thiols and larger tars, also called SOX precursors, as they form SOX during combustion. Understanding the sulfur release process is crucial to the development of reliable kinetic models, which support the design of improved reactors for cleaner coal conversion processes. Sulfur release from two bituminous coals, Colombian hard coal (K1) and American high sulfur coal (U2), were studied in the present work. Low heating rate (LHR) experiments were performed in a thermogravimetric analyzer coupled with mass spectrometry (TG-MS), allowing to track the mass loss and the evolution of many volatile species (CO, CO2, CH4, SO2, H2S, COS, HCl and H2O). High heating rate (HHR) experiments were performed in an entrained flow reactor (drop-tube reactor – DTR), coupled with MS and nondispersive infrared sensor (NDIR). HHR experiments were complemented with CFD simulation of the multidimentional reacting flow field. A kinetic model of coal pyrolysis is employed to reproduce the experiments allowing a comprehensive assessment of the process. The suitability of this model is confirmed for LHR. The combination of HHR experiments with CFD simulations and kinetic modeling revealed the complexity of sulfur chemistry in coal combustion and allowed to better understand of the individual phenomena resulting in the formation of the different SOX precursors. LHR and HHR operating conditions lead to different distribution of sulfur species released, highly-dependent on the gas-phase temperature and residence time. Higher retention of total sulfur in char is observed at LHR (63%) when compared to HHR (37–44%), at 1273 K. These data support the development of reliable models with improved predictability.

Experimental study on co-combustion of low rank coal semicoke and oil sludge by TG-FTIR

Co-combustion was proposed as an effective and complementary means for the co-treatment of low rank coal semicoke (LRCS) and oil sludge. The combustion, kinetics and gaseous pollutants emission characteristics during co-combustion of LRCS and oil sludge were investigated by thermogravimetric analyzer coupled with Fourier transform infrared spectrometer (TG-FTIR). Results showed oil sludge had more complex weight loss characteristics than LRCS. Proper addition of oil sludge could effectively improve the ignition, burnout and comprehensive combustion performance of blends and 60% was a recommended oil sludge blend ratio. High heating rates could also enhance the combustion performance of blends. The activation energy determined by Coats-Redfern method gradually decreased with the increase of oil sludge blend ratio. DAEM kinetic analysis results showed the maximum activation energy of 113.4 kJ/mol was obtained when conversion rate was 0.4 due to the poor ignition performance of LRCS. All of the CO, CO2, NOx and SO2 emission gradually decreased with the increasing oil sludge blend ratio. LRCS had suppression effect on NOx emission during co-combustion while oil sludge was just the opposite. The low sulfur release rate of oil sludge resulted in the decreasing SO2 emission of blends although oil sludge had promotion effect on SO2 emission.

Beyond CO2 Reduction: Vistas on Electrochemical Reduction of Heavy Non-metal Oxides with Very Strong E-O Bonds (E = Si, P, S).

The carbon dioxide reduction reaction (CO2RR), in particular electrochemically, to produce carbonaceous fuels is considered as a viable approach to store energy and to enable a CO2-neutral carbon management. Besides CO2RR, there is an additional strong demand for benign electrochemical reduction of other important heavy non-metal oxo species (e.g., SiO2, phosphine oxides, SO2) with thermodynamically stable E-O bonds, which accrue in large quantities in industry. In this respect, the energy-intense deoxygenation of oxo compounds of silicon, phosphorus, and sulfur is of particular technological importance because they represent some of the main feedstocks to produce important molecules and functional materials. For example, the release of elemental silicon, phosphorus (P4), and sulfur (S8) from naturally occurring minerals (e.g., silicate, phosphate, sulfate) follows energy-intensive chemical routes. Thus, the established chemical reduction routes to deoxygenate such oxo precursors produce tons of reagent waste or, in the case of carbothermal treatment of minerals, afford a lot of CO2. On the contrary, electrochemical strategies developed for the selective deoxygenation of E-O compounds remain as a feasible alternative powered by renewable electricity instead of fossil energy. Moderate reaction conditions, a large scope in experiment design for selective reactions, easy product isolation, and zero reagent waste by applying electrochemical methods offer a promising solution to overcome the drawbacks of chemical reduction routes. This Perspective summarizes the emergence of electrochemical strategies developed for the reduction of selected examples of E-O/E═O compounds with E = silicon, phosphorus, and sulfur in the past few decades and highlights opportunities and future challenges.

Study on the performance of the purified CaSO4 oxygen carrier derived from wet flue gas desulphurization slag in coal chemical looping combustion

Flue gas desulphurized slag was collected as the raw material and purified using the multiple steps of sour purification procedures, which was further prepared as CaSO4 oxygen carrier (OC). Reaction characteristics of the purified desulphurized slag OC with the selected lignite as well as release of the different gaseous sulfur species from the CaSO4 side reactions were investigated in a lab-scale fixed bed reactor. Several main influencing factors, including reaction temperature, OC excess number ϕ and the cycle numbers, were focused. The experimental results indicated that the purified CaSO4 OC was of high reactivity and promising to be applied in the coal-fueled chemical looping combustion process as OC. Furthermore, according to the pros and cons of the three influencing factors on the carbon conversion versus the gaseous sulfur release, the optimized reaction conditions were determined as 900°C and the OC excess number around 1.0. Finally, under this optimized reaction condition, the effect of the cycle numbers was evaluated and found that the continuous release of gaseous sulfur from the CaSO4 side reactions deteriorated the reactivity of the purified CaSO4 OC and its reaction stability was diminished with the five cycles.

Mineralogy, physicochemical and oxidative thermal analyses of Cretaceous coals from the Benue Trough, Nigeria

The erratic supply of electricity in Nigeria has renewed interest in the utilisation of coal for energy self-sufficiency and diversification of the national energy mix. In this study, selected coal samples from three regions of the Benue Trough Basin were examined through pore water chemistry, X-ray diffraction (XRD), and thermosgravimetric analysis (TGA). The low pH observed for the Lower Benue Trough (LBT) coals indicates the release of sulphur and acids during oxidation. Mineralogical analyses reveal quartz, kaolinite, montmorillonite, albite, pyrite, gypsum and sodium chlorate in the coal samples. The genetic kaolinite species identified in Imeagha (IMG) coal are detrital kaolinite and the highly crystalline neomorphic kaolinite. Gypsum and jarosite minerals occurred in minor quantities in Garin Maiganga (GMG), whereas significant amount of pyrite was detected in Enugu (ENG) coal. Oxidative thermal degradation resulted in the residual mass (RM) ranging between 4.35% and 56.96% and mass losses (ML) between 43.04% and 95.65% due to the drying, devolatilization, and coke formation in the samples. The most reactive coal examined was GMG coal, whereas the least reactive was IMG coal. Lamja (LMZ), GMG, and OKB coals are suited for electricity generation, whereas ENG and IMG coals can be utilised for cement production.

Innovative Methodology for Sulfur Release from Copper Tailings by the Oxidation Roasting Process

To effectively prevent the accumulation of copper tailings from producing acid mine drainage (AMD) and maximize the comprehensive utilization of copper tailings, the process of oxidation roasting was adopted to release sulfur in the form of SO2 to achieve the purpose of sulfur recovery later. Based on the AMD risk assessment, thermogravimetric (TG) analysis, and differential scanning calorimeter (DSC) analysis, the influences of roasting temperature, residence time, and air flow in the roasting process were investigated. The thermal stability, reaction equilibrium, mineral transformation, and residual S content were characterized by TG-DSC, HSC chemical software 6.0, X-ray diffraction (XRD), and combustion neutralization, respectively. The optimum conditions for sulfur release in the roasting process were shown with a temperature of 1200°C, a residence time of 60 min, and an air flow of 0.8 L/min. Under these conditions, the sulfur release rate was 99.82%, and the residual S content was 0.05%. Subsequently, the process of sulfur release was proposed as four steps: oxidative decomposition of pyrrhotite, formation of ferric sulfate, decomposition of ferric sulfate, and formation of hematite. All of the findings could propose a theoretical and experimental reference for the recovery of the sulfur component from tailings rich in sulfide minerals.

Sulfur self-doped char with high specific capacitance derived from waste tire: Effects of pyrolysis temperature

Preparation of sulfur self-doped char derived from waste tire (WT) was realized via two successively processes of pyrolysis and activation treatment. WT was firstly pyrolyzed at 400 °C, 600 °C, 800 °C, and 1000 °C to collect waste tire chars (WTCs) and they were subsequently activated at 800 °C with potassium ferrate (K2FeO4). The specific capacitance of activated waste tire chars at different pyrolysis temperatures (AWTCs-x-800) decreased from 92.60 F/g to 54.05 F/g at 1 A/g with pyrolysis temperature rising from 400 °C to 1000 °C. As for AWTCs-x-800, higher pyrolysis temperature promoted pore-forming process before 800 °C, and higher pyrolysis temperature enlarged pores after 800 °C. Increase of pyrolysis temperature promoted decomposition of alkyl–aryl CC bonds, transformation of relative small to large aromatic ring system, ordered arrangement of carbon atoms. Besides, it was found that sulfur doping content dominated in specific capacitance performance before 800 °C while surface area dominated after 800 °C. The large surface area and high S 2p3/2 (-C-S-C-, sulphide bridge) content were beneficial for the larger specific capacitance while more S 2p5/2 (-C-SOx-C- (x = 2–4, sulphone bridge) had the negative effect. Pyrolysis mainly affected sulfur doping properties, lower pyrolysis temperature promoted sulfur enrichment and S 2p3/2 generation. Activation promoted surface area improvement and sulfur conversion, higher pyrolysis temperature promoted surface area improvement and sulfur release before 800 °C while the promotion effects weakened after 800 °C, and sulfur transformation of S 2p3/2 converting to S 2p5/2 strengthened at higher pyrolysis temperature.