S-containing Gases Research Articles

Enhancement of sulfur control by conditioners during sewage sludge pyrolysis: Focusing on screening and in-situ sulfur fixation mechanism based on model compounds

Utilizing conditioners is effective to reduce S-containing gases during sludge pyrolysis. Revealing the relationship between conditioners of different prices and multiple S control factors under similar conditions is key for efficient screening. However, a detailed performance comparison of conditioners remains unavailable. This study, for the first time, comprehensively compared the S control effect of six typical conditioners, and the model compounds of organic-S were used to reveal the in-situ S fixation mechanism of the conditioners. Results show that the total release of gas-S (especially H2S) decreased by 34.4∼54.2% after the addition of CaO, Fe2O3, and FeCl3. These conditioners (especially Fe2O3) can enhance the stepwise oxidation of easily decomposed organic-S (especially aliphatic-S) into stable sulfoxide-S and sulfone-S. Additionally, sulfide-S and sulfate-S can be generated via the capture of S-containing intermediates (i.e., ·SH) by conditioners (especially CaO). The presence of Cl can react with inorganic sulfide-S or organic-S via replacement, leading to the re-release of H2S. Among all conditioners, CaO, followed by Fe2O3 and FeCl3, showed the best comprehensive performance, especially in terms of price and effective H2S control temperature range. This work can guide the selection of conditioners for the synergistic control of S-containing gases in the integrated treatment of sludge.

Fates of heavy metals, S, and P during co-combustion of textile dyeing sludge and cattle manure

The co-combustion of textile dyeing sludge (TDS) and cattle manure (CM) may enhance circularity in terms of resource and pollution controls. However, the pollutant migrations and transformations of ashes and their characterization during the co-combustion are still unclear. This study aimed to quantify the transformation and migration behaviors of the co-combustion ashes, as well as the interactions involved via thermogravimetric experiments and thermodynamic simulations. The addition of TDS facilitated the conversions of Ni and Cr from the extractable form to the stable one, increasing their environmental safety. P dominated S for the reaction with Ca which promoted the generation of S-containing gas emission and apatite P. The reactions between the minerals in CM and Ca in TDS generated calcium silicate, decreasing the S-fixation ability of Ca, while increasing the emission of S-containing gases. Our findings provide insights into the interactions among the minerals, the heavy metals, and the specific elements and their impacts on pollutant emissions, thus enhancing pollution control strategies.

Optimizing co-combustion synergy of soil remediation biomass and pulverized coal toward energetic and gas-to-ash pollution controls

The co-combustion synergy of post-phytoremediation biomass may be optimized to cultivate a variety of benefits from reducing dependence on fossil fuels to stabilizing heavy metals in a small quantity of ash. This study characterized the thermo-kinetic parameters, gas-to-ash products, and energetically and environmentally optimal conditions for the co-combustions of aboveground (PG-A) and belowground (PG-B) biomass of Pfaffia glomerata (PG) with pulverized coal (PC). The mono-combustions of PG-A and PG-B involved the decompositions of cellulose and hemicellulose in the range of 162–400 °C and of lignin in the range of 400–600 °C. PG improved the combustion performance of PC, with the blends of 30 % PG-A and 70 % (PAC37) and 10 % PG-B and 90 % PC (PBC19) exhibiting the strongest synergy. Both PG-A and PG-B interacted with PC in the range of 160–440 °C, while PC positively affected PG in the range of 440–600 °C. PC decreased the apparent activation energy (Eα) of PG, with PBC19 having the lowest Eα value (107.85 kJ/mol). The reaction order models (Fn) best elucidated the co-combustion mechanisms of the main stages. Adding >50 % PC reduced the alkali metal content of PG, prevented the slagging and fouling depositions, and mitigated the Cd and Zn leaching toxicity. The functional groups, volatiles, and N- and S-containing gases fell with PAC37 and PBC19, while CO2 emission rose. Energetically and environmentally multiple objectives for the operational conditions were optimized via artificial neural networks. Our study presents controls over the co-circularity and co-combustion of the soil remediation plant and coal.

Investigation of oxygen-enriched atmosphere combustion of oily sludge: Performance, mechanism, emission of the S/N-containing compound, and residue characteristics

It is an indispensable and important link to increasing the harmless treatment of oily sludge at the end of the petrochemical production stage to achieve the goal of clean production. This paper comprehensively investigates the thermal transformation behavior and the release of gaseous pollutants (VOCs, NOx, and S-containing gas) of petrochemical oily sludge. The results show that Petroleum hydrocarbons composed of C6–C35 can be effectively removed in the temperature range of 241–607 °C. It is worth noting that since low boiling point components such as benzene and toluene in the oily sludge may volatilize rapidly near the initial combustion temperature and generate toxic and harmful gases. For example, in this study, the toluene vapor signal could be observed before the initial combustion temperature and the toluene vapor signal appeared neatly around 350 °C and did not participate in the combustion reaction and the strong fluctuation of benzene vapor. Organic sulfur dominated by Sulfonate-S, Sulfoxide-S, and Aromatic-S could be released in the form of SO2 around 250 °C and 450 °C, while organic nitrogen dominated by Pyridinic-N, Protein-N, and Pyrrolic-N could be released in the form of NOx between 300 °C and 500 °C, which is mainly related to the thermal stability of sulfur-containing groups.

Effect of FeCl3 combined with biochar as dewatering conditioners on sludge pyrolysis products

Owing to the rapid development of cities, sewage treatment plants produce an abundance of sewage sludge (SS). As a new sludge treatment technology, pyrolysis has been widely popularized in the disposal of SS. Sludge must be dewatered before pyrolysis, and FeCl3 combined with biochar has been shown to effectively improve SS dewatering performance in previous studies; however, its influence on subsequent SS pyrolysis disposal has not been studied. Based on the sludge conditioning-dewatering-pyrolysis system process, the effect and mechanism of the SS dewatering process on subsequent sludge pyrolysis disposal were elucidated. In this study, the combined effects of FeCl3 and biochar (FB) on sludge pyrolysis products were investigated using thermogravimetric mass spectrometry (TG-MS) and pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS). Additionally, the mechanism by which FeCl3 and biochar functioned are separately explained. Results showed that FB reduced the release of C/H/O-containing gases to a certain extent, which was mainly related to the biochar conditioner, promoted the S-containing gases, and reduced the release of N- and Cl-containing gases. Thus, FB is beneficial for improving the calorific value and chemical stability of bio-oil, in which the FeCl3 conditioner played a dominant role. Additionally, FB also moderately reduced the formation of N/S/Cl-containing compounds, mainly through the synergistic action of FeCl3 and biochar. Particularly, FB has the catalytic ability to remove tar. Several reaction kinetics models fitted using the Coats−Redfern method showed that FB was beneficial for reducing the energy required during pyrolysis. The results have important guiding significance to SS pyrolysis for the selection of sludge dewatering conditioners.

Gas sensing behavior and adsorption mechanism on χ3 borophene surface

Following the demands to find high sensitivity sensors for pollutant gases with compact size, we investigate the adsorption mechanism and detecting capability of χ3 borophene, based on the density functional theory (DFT) calculations. Except for HCN, the overall structure of adsorbed molecules is maintained during the adsorption on the χ3 borophene surface. The obtained adsorption energies vary from −0.20 to −2.45 eV. While the CO2 molecule has a weak interaction with the surface, other molecules, notably CO, NO, NO2, SO, SO2, and SO3 adsorb strongly to the surface. The minimum-energy path and energy barrier for dissociation of the HCN molecule on the surface were studied in detail through the CI-NEB method. Plots of charge density difference and electron localization function demonstrated the covalent character of the formed bonds between N or S-containing gases and the surface. Our investigations of surface and adsorbate band alignments clearly justify the amount of charge transfer in the gap between the Fermi level of χ3 borophene and the LUMO of gas molecules. Furthermore, the surface sensitivity to adsorption was confirmed by analyzing the changes in the transmission coefficient, calculated with the non-equilibrium Green’s function approach. In terms of recovery time, SO, SO3, and NO2 molecules diminish the surface sensing performance, but the χ3 borophene surface is suitable for their removal from the environment. Accordingly, the thermal stability and adsorption capacity of these gases was investigated by Car-Parrinello molecular dynamics simulations. Our study not only clarifies the mechanism of the adsorption of various gas molecules on the χ3 borophene surface, but also reveals the benefit of χ3 in the sensing and removal of these gas species.

Differential Effect of Anaerobic Digestion on Gaseous Products from Sequential Pyrolysis of Three Organic Solid Wastes.

Studies have shown that anaerobic digestion (AD) has an effect on the liquid and solid product property of sequential pyrolysis, but its influence on the gaseous products is lacking. In this study, syngas produced by pyrolysis from three raw organic solid wastes and the corresponding digestates, i.e., food waste, vinasse, and cow manure were investigated. AD causes a decrease in the contents of volatile solid, fixed carbon, C, H, and N and an increase in the S content. The weight loss of the wastes mainly occurs at 200–550 °C during the pyrolysis and the loss of the food waste and vinasse is higher than that of cow manure. In the carbon (C)-containing gas, AD leads to a decrease in the CH4 content of the syngas, implying that the heat values of the digestates are lower than that of the raw substrates. After AD, the total amount of nitrogen (N)-containing gas from the vinasse increases by 40.1%, while that from cow manure decreases by 14.1%. On the contrary, the total amount of sulfur (S)-containing groups in the syngas from vinasse drop by 22.0%, while that from cow manure increases by 9.1%. In addition, slight changes in the C-, N-, and S-containing gases are found from food waste. The results indicate that AD has a different effect on the N- and S- containing gaseous groups from different organic solid wastes, and the mechanisms deserve further investigation. The findings supply a theoretical foundation for environmental-friendly application of syngas from the digestates.

Dynamic insights into combustion drivers and responses of water hyacinth: Evolved gas and ash analyses

Non-food biomass feedstocks owing to their advantages have come to the forefront as the efforts have been intensified to develop cleaner energy sources and technologies in the face of global climate change. This study aimed to dynamically characterize the combustion drivers and responses including the gas emission and ash deposition risks for roots (WHR) and stems and leaves (WHSL) of water hyacinth. Their combustion processes consisted of the four sequential stages of the water evaporation, the combustions of volatiles and fixed carbon, and the degradation of minerals. The WHR combustion had a higher total heat release (2140.6–4226.7 J/g) than did the WHSL combustion (1255.6–3110.6 J/g). In terms of the Flynn-Wall-Ozawa method, the average activation energy was estimated at 167.42 and 172.41 kJ/mol for WHR and WHSL, respectively. The reaction mechanisms of the volatiles and fixed carbon combustion stages were best elucidated by the F1 (f(α) = 1- α) and F3 (f(α) = (1- α)3) models for WHR and the F3 (f(α) = (1- α)3) and F1.5 (f(α) = (1- α)1.5) models for WHSL, respectively. CO2 was the main evolved gas for both WHR and WHSL and exhibited the fastest response to temperature. Evolved S-containing gases (SO2 and COS) (0.13% for WHR and 0.12% for WHSL) were extremely low. The WHSL ash had a higher risk of slagging and fouling than did the WHR ash. Our findings can provide insights into the cleaner and optimal production of the water hyacinth combustion.

Sensitivity enhancement of stanene towards toxic SO2 and H2S

Adsorption of S-containing gases on pristine, defective, and heteroatom doped stanene is studied for gas sensing applications by van der Waals corrected density functional theory. SO2 and H2S gas molecules are found to bind to pristine stanene too weakly to alter the electronic properties sufficiently for efficient gas sensing (binding energy of −0.20 and −0.33 eV, respectively). We demonstrate that vacancies and heteroatom doping can enhance the binding energy to −1.67 and −0.74 eV, respectively. It is found that presence of mono-vacancies, tri-vacancies, and In dopants at low concentrations in stanene results in considerable variations of the electronic properties in contact with S-containing gases, thus transforming stanene into an efficient sensing material.

Swine diets impact manure characteristics and gas emissions: Part I sulfur level

Sulfur is an essential nutrient for animal growth but is also associated with odor and morbidity of animals from swine operations. A study was conducted to determine the effects of increasing dietary S levels in swine diets on DM, pH, C, N, S, VFA, indole, and phenol concentrations in the manure, and on the emissions of C-, N-, and S-containing gases. A total of 24 gilts averaging 152 kg BW were fed diets containing 0.19, 0.30, 0.43, or 0.64% dietary S, as supplied by CaSO4, for 31 d, with an ADFI of 3.034 kg d−1. Feces and urine were collected after each feeding and added to manure storage containers. At the end of the study, manure slurries were monitored for gas emissions and chemical properties. Increasing dietary S lowered manure pH by 0.3 units and increased DM, N, and S by 10% for each 1.0 g S increase kg−1 feed intake. Increased dietary S increased NH3, sulfide, butanoic, and pentanoic acid concentrations in manure. Carbon and N emissions were not significantly impacted by dietary S, but S emissions in the form of hydrogen sulfide (H2S) increased by 8% for each 1.0 g S increase kg−1 feed intake. Odor increased by 2% for each 1.0 g increase of S consumed kg−1 feed intake. Phenolic compounds and H2S were the major odorants emitted from manure that increased with increasing dietary S.

Recent Advances in Electrochemical Sensors for Detecting Toxic Gases: NO₂, SO₂ and H₂S.

Toxic gases, such as NOx, SOx, H2S and other S-containing gases, cause numerous harmful effects on human health even at very low gas concentrations. Reliable detection of various gases in low concentration is mandatory in the fields such as industrial plants, environmental monitoring, air quality assurance, automotive technologies and so on. In this paper, the recent advances in electrochemical sensors for toxic gas detections were reviewed and summarized with a focus on NO2, SO2 and H2S gas sensors. The recent progress of the detection of each of these toxic gases was categorized by the highly explored sensing materials over the past few decades. The important sensing performance parameters like sensitivity/response, response and recovery times at certain gas concentration and operating temperature for different sensor materials and structures have been summarized and tabulated to provide a thorough performance comparison. A novel metric, sensitivity per ppm/response time ratio has been calculated for each sensor in order to compare the overall sensing performance on the same reference. It is found that hybrid materials-based sensors exhibit the highest average ratio for NO2 gas sensing, whereas GaN and metal-oxide based sensors possess the highest ratio for SO2 and H2S gas sensing, respectively. Recently, significant research efforts have been made exploring new sensor materials, such as graphene and its derivatives, transition metal dichalcogenides (TMDs), GaN, metal-metal oxide nanostructures, solid electrolytes and organic materials to detect the above-mentioned toxic gases. In addition, the contemporary progress in SO2 gas sensors based on zeolite and paper and H2S gas sensors based on colorimetric and metal-organic framework (MOF) structures have also been reviewed. Finally, this work reviewed the recent first principle studies on the interaction between gas molecules and novel promising materials like arsenene, borophene, blue phosphorene, GeSe monolayer and germanene. The goal is to understand the surface interaction mechanism.

ReaxFF simulations of petroleum coke sulfur removal mechanisms during pyrolysis and combustion

Green petroleum coke (petcoke) is used as a feedstock for raw carbon material or as a fuel. Petcoke with high sulfur (S) content (>4 wt%) is typically restricted to fuel use unless extensive S removal is successful. Here, the S removal mechanisms during both pyrolysis and combustion were explored using the Reactive Force Field (ReaxFF) MD approach. A structural representation (C1648H772O59N24S47) of a green Qingdao petcoke was generated coupling high-resolution transmission electron microscopy lattice fringe image analysis and analytical data. This structure was consistent with elemental, aromaticity (FT-IR), the pair correlation function (XRD), and functional group (S, O, and N from XPS) data. The ReaxFF pyrolysis simulation produced gas and tar yields of 44.7 and 11.0 wt% at 3000 K after 250 ps of simulation. The combustion simulation on the same initial structure was performed in an O2 environment. During the pyrolysis simulation, the first-step for S-removal was thiophenic sulfur conversion to C1–4S (mostly C2S), COS, or CNS. The heteroatom pyrolysis overlapped, for this structure, at these conditions. However, for the combustion simulation earlier conversion of thiophenic sulfur to COS was observed. No NS containing structures occurred in this O-rich environment, as pyrrolic and pyridinic N quickly oxidized into CON or NO compounds. The S transformation during combustion can be summarized by COS → CO2S → CO3S → CO4S. The H atoms reacted with S-containing gases like COS/C2S/CNS producing HS and H2S rather than with the coke-S.

Efficient Synthesis of Nitrogen‐ and Sulfur‐co‐Doped Ketjenblack with a Single‐Source Precursor for Enhancing Oxygen Reduction Reaction Activity

Promoting the oxygen reduction reaction (ORR) catalytic activities of cost-effective catalysts is of great significance for the development of various energy conversion and storage systems. Herein, we describe the preparation of a highly active N- and S-co-doped ketjenblack (Kb) by facile pyrolysis of a mixture of thiourea and Kb in the presence of FeCl3 ⋅6 H2 O followed by an acid-leaching process. This novel synthetic approach was rationally designed with the consideration that thiourea could easily introduce both N and S heteroatoms into the carbon matrix by a heat-treatment method by releasing plentiful reactive N- and S-containing gases, which could simultaneously optimize the porous structure of the resultant catalyst. Physical characterization revealed that N and S were homogeneously incorporated into the nanostructure of Kb and formed a hierarchical porous structure with a high specific surface area. The N/S-Kb catalyst showed impressive ORR activity, with an onset potential of 0.08 V at 0.1 mA cm-2 , which is 20 mV more positive than that of commercial 20 wt. % Pt/C catalyst. This was coupled with long-term durability and superior methanol tolerance in alkaline media. The improved ORR performance can be mainly ascribed to synergistic contributions of highly efficient active sites arising from high contents of thiophene S and pyridinic N along with the high specific surface area and the favorable mass-transport properties arising from the hierarchical porous structure. The remarkable ORR performance and facile preparation method make the N/S-Kb catalyst a promising substitute for Pt in electrochemical energy devices.

Integrated biomass gasification using the waste heat from hot slags: Control of syngas and polluting gas releases

In this study, the thermodynamics of a novel strategy, i.e., biomass/CO2 gasification integrated with heat recovery from hot slags in the steel industry, were systemically investigated. Both the target syngas yield and the polluting gas release were considered where the effect of gasifying conditions including temperature, pressure and CO2 reacted was analyzed and then the roles of hot slags were further clarified. The results indicated that there existed an optimum temperature for the maximization of H2 production. Compared to blast furnace slags, steel slags remarkably increased the CO yield at 600–1400 °C due to the existence of iron oxides and decreased the S-containing gas releases at 400–700 °C, indicating potential desulfurizing ability. The identification of biomass/CO2 gasification thermodynamics in presence of slags could thus provide important clues not only for the deep understanding of biomass gasification but also for the industrial application of this emerging strategy from the viewpoint of syngas optimization and pollution control.

Chemical-looping combustion of solid fuels in a 100 kW dual circulating fluidized bed system using iron ore as oxygen carrier

Chemical-looping combustion (CLC) is an innovative carbon-capture technology with potential to drastically reduce the cost of capture. By using a circulating bed material to transfer oxygen from the combustion air to the fuel, air and fuel are never mixed and the CO2 can be obtained as a separate flue gas stream, undiluted by N2. In other words, carbon capture is inherent to the CLC process. Here, we present findings from a 100kW chemical-looping combustor for solid fuels. The oxygen carrier used in the present tests was an iron ore from Tierga, Spain. In total, 26h of operation using bituminous coal and wood char as fuel was achieved. The highest gas conversion with bituminous coal was 87%, and the highest gas conversion using wood char as fuel was 93%. The carbon capture efficiency with bituminous coal was 94–98%, which is lower than what has been observed with ilmenite. For the wood char, the carbon capture was even lower. The fate of nitrogen and sulfur was investigated. It was found that 84wt% of the S-containing gas was SO2, and only 16wt% was H2S. The nitrogen analysis indicates that the fuel-N converted to gas was distributed as 10wt% NO, 37wt% NH3, and 53wt% N2. It was found that the oxygen-carrier particles retained their high reactivity throughout the operational period. Furthermore, the expected lifetime of the iron ore was found to be approximately 300h.

Material balances of carbon, sulfur, nitrogen and ilmenite in a 100 kW CLC reactor system

Chemical-looping combustion (CLC) is an unmixed combustion concept where fuel and combustion air are kept separate by means of an oxygen carrier, and the CO2 capture is inherently achieved. This work presents findings from a 100kW chemical-looping combustor, which was operated with Colombian bituminous coal for 12h, using ilmenite as oxygen carrier. The focus of the study is on a 4.7-h experiment with stable operating conditions, during which inbound and outbound gaseous, liquid, and solid flows of carbon, sulfur, nitrogen and ilmenite were carefully monitored and analyzed. The fuel power during this experiment was 71kW. The gas conversion reached 83%, the carbon capture efficiency was 98–99%, and the solid fuel conversion based on carbon was 65%. The carbon balance confirms that a large fraction of the fuel escapes the reactor system unconverted. It also demonstrates that essentially all in- and outbound flows of carbon have been accounted for. The sulfur balance shows that the conversion in the fuel reactor of inbound sulfur is around 72%. Furthermore, it is found that 75% of the S-containing gas is SO2, and only 25% is H2S. The nitrogen analysis indicates that 62% of the nitrogen fed with the coal is converted to gas, and that the nitrogen in this gas is distributed as 1wt-% HCN, 11wt-% NO, 26wt-% NH3, with the balance probably being N2. In addition, the present work includes a comprehensive study on the structural integrity of ilmenite in circulating fluidized beds. It is found that the expected lifetime of ilmenite is approximately 700–800h.

Dual role of conditioner CaO in product distributions and sulfur transformation during sewage sludge pyrolysis

Product distributions and sulfur transformation during sewage sludge pyrolysis are essential to subsequent thermal disposal process, both of which are strongly affected by calcium-based compounds. Considering that lime (CaO) is widely applied in sludge conditioning pre-treatment, this study investigated the dual role of conditioner CaO in sludge pyrolysis behavior and sulfur evolution at the temperature range of 873–1273K. Specific compositions in three phases, such as solid residual, tar and gas, were also determined to further clarify the mechanisms involved. According to the results, conditioner CaO increased the fraction of ash and more stable organics in sludge particles, which contributed to higher yield of char comprising lots of carbon and hydrogen. The ring-opening of aromatic hydrocarbons followed by addition reaction of H2O in solid phase facilitated H2 and CO generation, leaving a large number of COH and CO in char. Meanwhile, conditioner CaO catalyzed tar cracking, further increasing the productions of H2 and CO. More interestingly, residual calcium was still capable of fixing sulfur in solid product. Raw sludge matrix prevented sulfur releasing mainly through cyclization reactions, and the relative ratio of char-S only accounted for less than 50%. Correspondingly, most of SO2, CS2, C2H6S2, H2S, COS, and CH4S were emitted. In contrast, char-S yields reached up to 92.8% mainly through forming thermal stable sulfide and sulfate promoted by conditioner CaO, which drove down the final production of sulfurous gases. These indicate that reusing conditioner CaO is a promising strategy for increasing combustible gases and char yields efficiently and reducing the formation of polluting S-containing gases dramatically.

Se-loss-induced CIS Thin Films in RTA Process after Co-sputtering Using CuSe2and InSe2Targets

Chalcopyrite CuInSe2 (CIS) thin films were prepared without Se- / S-containing gas by co-sputtering using CuSe2 and InSe2 selenide-targets and rapid thermal annealing. The grain size increased to a maximum of 54.68 nm with a predominant (112) plane. The tetragonal distortion parameter η decreased and the inter-planar spacing d(112) increased in the RTA-treated CIS thin films annealed at a 400°C, which indicates better crystal quality. The increased carrier concentration of RTA-treated p-type CIS thin films led to a decrease in resistivity due to an increase in Cu composition at annealing temperatures ≥ 350°C. The optical band gap energy (Eg) of CIS thin films decreased to 1.127 eV in RTA-treated CIS thin films annealed at 400°C due to the improved crystallinity, elevated carrier concentration and decreased In composition.

Transformation of sulfur during pyrolysis of inertinite-rich coals and correlation with their characteristics

Sulfur transformation of inertinite-rich coals, which were sampled from three Western China coal mines, Xinjiang Hami (HM), Ningxia Lingwu (LW) and Shendong (SD), during pyrolysis is studied through measuring the release of H2S and COS gases by gas chromatography with flame photometric detector and through analyzing the sulfur forms in raw coals and chars from pyrolysis by X-ray absorption spectroscopy (XAS). It is revealed that the transformation of sulfur during coal pyrolysis is closely linked with coal properties, such as the vitrinite/inertinite ratio, alkaline mineral contents (especially calcium compounds) and H/C atomic ratio for three inertinite-rich coals. Comparisons are performed with a coal sample taken from Pingsuo (PS) coal mine located in North China, of which the properties are significantly different. The maximal release temperature of sulfur-containing gases for the pyrolysis of inertinite-rich coal is higher than that of the PS coal. The release of the S-containing gases in inertinite-rich coals has a maximal temperature interval around 600°C and this is associated with the conversions of inorganic sulfur species, such as pyrite transforming to FeS observed by the XAS in chars of these coals. During the process of pyrolysis, the organic sulfur compounds in inertinite-rich coal can be oxidized to form sulfoxide-like species due to the decomposition of oxygen-containing function groups in the coal matrix, but the active sulfur in PS coal can react with fresh char to form relatively stable thiophene structures. The formation of COS during the pyrolysis of inertinite-rich coals is mainly due to secondary reactions between H2S with CO and/or CO2.

Sulfur Fertilization and Fungal Infections Affect the Exchange of H2S and COS from Agricultural Crops

The emission of gaseous sulfur (S) compounds by plants is related to several factors, such as the plant S status or fungal infection. Hydrogen sulfide (H(2)S) is either released or taken up by the plant depending on the ambient air concentration and the plant demand for S. On the contrary, carbonyl sulfide (COS) is normally taken up by plants. In a greenhouse experiment, the dependence of H(2)S and COS exchange with ambient air on the S status of oilseed rape (Brassica napus L.) and on fungal infection with Sclerotinia sclerotiorum was investigated. Thiol contents were determined to understand their influence on the exchange of gaseous S compounds. The experiment revealed that H(2)S emissions were closely related to pathogen infections as well as to S nutrition. S fertilization caused a change from H(2)S consumption by S-deficient oilseed rape plants to a H(2)S release of 41 pg g(-1) (dw) min(-1) after the addition of 250 mg of S per pot. Fungal infection caused an even stronger increase of H(2)S emissions with a maximum of 1842 pg g(-1) (dw) min(-1) 2 days after infection. Healthy oilseed rape plants acted as a sink for COS. Fungal infection caused a shift from COS uptake to COS releases. The release of S-containing gases thus seems to be part of the response to fungal infection. The roles the S-containing gases may play in this response are discussed.