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Abstract Our investigation revealed that alterations in sulphur (S) pools are predominantly governed by soil organic carbon (SOC), soil nitrogen (N), microbial biomass, and soil enzyme activities in sandy clay loam (Vertic Ustropept) soil. We employed ten sets of nutrient management techniques, ranging from suboptimal (50% RDF) to super-optimal doses (150% RDF), including NPK + Zn, NP, N alone, S-free NPK fertilizers, NPK + FYM, and control treatments, to examine the interrelation of S with SOC characteristics. Fourier-transform infrared (FT-IR) spectroscopy was utilized to analyze the functional groups present in SOC characterization across four treatments: 100% NPK, 150% NPK, NPK + FYM, and absolute control plots. Principal component analysis (PCA) was then applied to assess 29 minimal datasets, aiming to pinpoint specific soil characteristics influencing S transformation. In an Inceptisol, the application of fertilizers (100% RDF) in conjunction with 10 t ha−1 of FYM resulted in an increase of S pools from the surface to the subsurface stratum (OS > HSS > SO4 2−–S > WSS), along with an increase in soil N and SOC. FT-IR spectroscopy identified cellulose and thiocyanate functional groups in all four plots, with a pronounced presence of carbohydrate—protein polyphenol, sulfoxide (S=O), and nitrate groups specifically observed in the INM plot. The PCA findings indicated that the primary factors influencing soil quality and crop productivity (r2 of 0.69) are SOC, SMBC, SMBN, SMBS, and the enzyme activity of URE, DHA, and AS. According to the study, the combined application of fertilizer and FYM (10 t ha−1) together exert a positive impact on sulphur transformation, SOC accumulation, and maize yield in sandy clay loam soil.

Our investigation revealed that alterations in sulphur (S) pools are predominantly governed by soil organic carbon (SOC), soil nitrogen (N), microbial biomass, and soil enzyme activities in sandy clay loam (Vertic Ustropept) soil. We employed ten sets of nutrient management techniques, ranging from suboptimal (50% RDF) to super-optimal doses (150% RDF), including NPK + Zn, NP, N alone, S-free NPK fertilizers, NPK + FYM, and control treatments, to examine the interrelation of S with SOC characteristics. Fourier-transform infrared (FT-IR) spectroscopy was utilized to analyze the functional groups present in SOC characterization across four treatments: 100% NPK, 150% NPK, NPK + FYM, and absolute control plots. Principal component analysis (PCA) was then applied to assess 29 minimal datasets, aiming to pinpoint specific soil characteristics influencing S transformation. In an Inceptisol, the application of fertilizers (100% RDF) in conjunction with 10 t ha−1 of FYM resulted in an increase of S pools from the surface to the subsurface stratum (OS > HSS > SO42−–S > WSS), along with an increase in soil N and SOC. FT-IR spectroscopy identified cellulose and thiocyanate functional groups in all four plots, with a pronounced presence of carbohydrate—protein polyphenol, sulfoxide (S=O), and nitrate groups specifically observed in the INM plot. The PCA findings indicated that the primary factors influencing soil quality and crop productivity (r2 of 0.69) are SOC, SMBC, SMBN, SMBS, and the enzyme activity of URE, DHA, and AS. According to the study, the combined application of fertilizer and FYM (10 t ha−1) together exert a positive impact on sulphur transformation, SOC accumulation, and maize yield in sandy clay loam soil. [ABSTRACT FROM AUTHOR]

The transformation and fate of sulphur (S) in a spent tyre pyrolysis char during CO 2 gasification were studied by following the S species and contents using X-ray photoelectron spectroscopy (XPS). The spent tyre pyrolysis char (particle size fraction ≤150 µm), without and with 1 M HCl acid washing to remove inorganic S, were gasified in a fixed bed reactor. The effect of temperature (850, 950, 1050 °C), reaction time (1, 2, 3, 6 h) and CO 2 concentration (33.3, 50.0, 66.7 vol% in N 2) on the S species in the char samples were investigated. The main S species in the spent tyre pyrolysis char were ZnS and aliphatic sulphide. After CO 2 gasification, aliphatic sulphide, thiophene, sulphoxide and sulphone became the dominant organic S while ZnS and CaSO 4 were the main inorganic S. The percentage of total S increased with increasing gasification temperature, time and CO 2 concentration. The content of organic S increased with increasing gasification temperature and time, while, the content of inorganic S decreased. Increasing CO 2 concentration had negligible effect on the content of organic S but led to significant reduction in the content of inorganic S since ZnS reacted with CO 2 to produce ZnO and SO 2. Aliphatic sulphide, sulphoxide and sulphone were shown to have transformed to more stable thiophene. ZnS decomposed to release S X at > 900 °C while CaSO 4 reacted with CO and carbon to produce COS. Both S X and COS reacted with the organic matrix in the char to form sulphoxide and sulphone. [ABSTRACT FROM AUTHOR]

To promote the utilization efficiency of coal resources, and to assist with the control of sulphur during gasification and/or downstream processes, it is essential to gain basic knowledge of sulphur transformation associated with gasification performance. In this research we investigated the influence of O2/C molar ratio both on gasification performance and sulphur transformation of a low rank coal, and the sulphur transformation mechanism was also discussed. Experiments were performed in a circulating fluidized bed gasifier with O2/C molar ratio ranging from 0.39 to 0.78 mol/mol. The results showed that increasing the O2/C molar ratio from 0.39 to 0.78 mol/mol can increase carbon conversion from 57.65% to 91.92%, and increase sulphur release ratio from 29.66% to 63.11%. The increase of O2/C molar ratio favors the formation of H2S, and also favors the retained sulphur transforming to more stable forms. Due to the reducing conditions of coal gasification, H2S is the main form of the released sulphur, which could be formed by decomposition of pyrite and by secondary reactions. Bottom char shows lower sulphur content than fly ash, and mainly exist as sulphates. X-ray photoelectron spectroscopy (XPS) measurements also show that the intensity of pyrite declines and the intensity of sulphates increases for fly ash and bottom char, and the change is more obvious for bottom char. During CFB gasification process, bigger char particles circulate in the system and have longer residence time for further reaction, which favors the release of sulphur species and can enhance the retained sulphur transforming to more stable forms. [ABSTRACT FROM AUTHOR]

• Steam promoted the release of S to gas phase from char as temperature increased. • Organic S contents increased with increasing gasification temperature and time. • Aliphatic sulphide converted to more stable thiophene at high temperature. • Sulphone and sulphoxide converted into each other in reversible redox reactions. • S x and COS were transferred to sulphone and sulphoxide during steam gasification. The transformation of sulphur (S) during steam gasification of a spent tyre pyrolysis char (STPC) was investigated by tracing the evolution of S species and their mass fractions through X-ray photoelectron spectroscopy analysis. The raw pyrolysis char and demineralised char samples were respectively reacted with steam in a vertical fixed bed reactor over a range of temperature (850, 950, 1050 °C), steam concentration (33.3, 50.0, 66.7 vol% steam in N 2) and gasification time (0.5, 1, 2, 3, 4 h). The mass fraction of S in the partially gasified char increased with increasing time at 850 °C and 950 °C, but decreased at 1050 °C. However, the net amount of S retained in the gasified char relative to that in the raw STPC decreased with increasing mass loss ratio, implying that S loss was faster than carbon consumption. The dominant S species in the pyrolysis char were aliphatic sulphide and ZnS. After steam gasification, more than 80% S species in the gasified chars were in the form of organic S. The proportion of organic S increased while that of inorganic S decreased with increasing gasification time and temperature, regardless of steam concentration. Thiophene, aliphatic sulphide, sulphone and sulphoxide became the main organic S species while ZnS and sulphate were the dominant inorganic S species. Aliphatic sulphide, sulphone and sulphoxide were converted to more thermally stable thiophene. Sx released from ZnS or COS produced from CaSO 4 reacted with the carbon matrix to form sulphone and sulphoxide in the gasified char. [ABSTRACT FROM AUTHOR]

Abstract: Transformation of various sulphur forms, including inherent and added pyrite, sulphates (CaSO4 and FeSO4) and organic sulphur, during pyrolysis of an Australian lignite was studied using TGA, TGA-MS and a fixed bed reactor, supplemented by sulphur form analysis. It was shown that hydrogen sulphide (H2S) and a small quantity of sulphur dioxide (SO2) were released during the pyrolysis of the pyrite-lignite blend. However, only SO2 was detected during the pyrolysis of the lignite with high pyrite content. Inorganic matter was found to help retaining some of the inorganic sulphur, including pyrite, in the char. Inherent sulphates decomposed at much lower temperatures than the added sulphates, releasing SO2 rather than H2S. The inherent sulphates in the lignite were dominated by iron sulphates which started to decompose and release SO2 at around 500K and all sulphate had been decomposed at 1073K. The retention of organic sulphur in the high organic sulphur lignite was higher than in its acid washed lignite sample, due to the interaction between inherent inorganic matter with the organic sulphur retaining the organic sulphur in the solid phase. SO2 was the only sulphur gas produced during pyrolysis of acid washed lignite. A comprehensive mechanism of sulphur transformation during pyrolysis of lignite was proposed. [ABSTRACT FROM AUTHOR]

Abstract: The transformation of sulphate minerals during pyrolysis of an Australian lignite has been studied using pure sulphates (CaSO4, FeSO4 and Fe2(SO4)3), a high mineral (HM) lignite sample and a low mineral (LM) lignite sample collected from different locations of the same deposit, and samples of acid-washed LM doped with sulphates (CaSO4+LM and FeSO4+LM), respectively. Thermogravimetric analysis and fixed-bed reactor techniques were used for the pyrolysis experimentation and the lignite samples and their chars were analysed using FTIR and XRD. The TGA experiments showed that CaSO4 decomposes between 1400 and 1700K in nitrogen and a 50/50N2/CO2 mixture, while in air CaSO4 decomposes between 1500 and 1700K. Using a TGA–MS it was found that only a small fraction of CaSO4 in CaSO4+LM decomposed at 653K, releasing SO2. CaSO4 was still observed in the char recovered at 1073K as confirmed by the FTIR and XRD analysis. FeSO4·7H2O released the bound water below 543K and the remaining FeSO4 decomposed between 813 and 953K. FeSO4 in FeSO4+LM decomposed at 500K to release SO2. The inherent sulphates in HM were dominated by iron sulphates which started to decompose and release SO2 at around 500K and all sulphate had been decomposed at 1073K. It was observed that during the fixed-bed pyrolysis at 1073K in nitrogen, approximately 36% of the total sulphur in the CaSO4+LM decomposed, 88% of the total sulphur in the FeSO4+LM decomposed and around 76% of the total sulphur in HM decomposed. It was also confirmed that FeSO4+LM produced more volatile sulphur than CaSO4+LM during pyrolysis. [Copyright &y& Elsevier]