Search

To improve the yield and quality of coal pyrolysis tar while using pyrolysis gas (PG), a Ni/MgO catalyst was introduced to catalyze the pyrolysis of bituminous coal under a PG atmosphere. The effects of pyrolysis temperature, gas flow rate, catalyst packing methods, and atmosphere composition on coal pyrolysis were investigated. The yield and quality of tar obtained from Shihezi (SHZ) bituminous coal pyrolysis under N2, PG, and PG over a Ni/MgO catalyst were found to vary with the increase of pyrolysis temperature. The catalyst packed in the upper layer results in higher tar yields, but mixing the catalyst and coal leads to an increase in the maltene yield. The components in PG improved the tar yield and tar quality. Finally, a higher tar yield can be obtained from SHZ coal pyrolysis under CO/H2, CO2/H2, and CO2/CH4 atmospheres using a Ni/MgO catalyst. [ABSTRACT FROM AUTHOR]

• ILs exhibited higher extraction yield than optimized organic solvent pyridine. • [Bmim]Cl showed selective extraction ability for sulfur-containing compounds. • More sulfur was released during pyrolysis process through IL pretreatment. • High carbon number components in tar decreased after IL pretreatment. • IL pretreatment could improve the product distribution and increase oil yield. Four different ionic liquids (ILs) were used to identify their extraction properties on high-sulfur bituminous coal. And the effect of ILs pretreatment on pyrolysis characteristic was investigated in a fixed-bed reactor. The imidazolium-based ILs used namely: 1-butyl-3-methyl-imidazolium chloride ([Bmim]Cl), 1-butyl-3-methyl-imidazolium bromide ([Bmim]Br), 1-butyl-3-methylimidazolium hydrogen sulfate ([Bmim]HSO 4), 1-butyl-3-methyl-imidazolium tetrafluoroborate ([Bmim]BF 4). All the selected ILs exhibited extraordinary extraction ability for oxygen-containing compounds, mainly furans and ethers. Among them, [Bmim]Cl got the highest extraction yields of 20.82% and performed selective extraction ability for sulfur-containing compounds with a relative content of 5.10% in light oils. Compared with pyridine pretreated coal (R-PY), the yields of CO and CO 2 in pyrolysis gas showed increase trend when coal pretreated by ILs (R-ILs). The relative contents of tricyclic and larger PAHs, sulfur-containing compounds, and oxygen-containing compounds in tar from pyrolysis of [Bmim]Cl and [Bmim] Br treated coal increased significantly than R-PY tar, while phenols got decreased. High carbon number components from R-ILs tar reduced dramatically compared with R-PY tar, which was conducive to the upgrading of tar, after pretreated with ILs, the sulfur content was reduced. The crosslinks between coal macromolecules structure were destroyed after pretreated by ILs, and the pyrolysis products distribution had evident change. The oil phase yield got a substantial increase while [Bmim]Cl obtained highest oil yield of 24.89%. [ABSTRACT FROM AUTHOR]

Co-pyrolysis of coal and seaweed can not only effectively decrease the carbon footprint but also improve the quality and output of coal pyrolysis products, however, the influence of seaweed on thermal releasing behaviors of mercury during co-pyrolysis process are still unclear. In this work, the chlorella and Guizhou bituminous coal were mixed and used to reveal the mercury release behavior during co-pyrolysis by the temperature programmed pyrolysis experiments, thermogravimetric and differential thermogravimetric analysis (TG-DTG) and thermogravimetry-mass spectrometry (TG-MS) methods, offering a sufficient explanation on the control technology of mercury pollutants in co-pyrolysis. The results exhibited that a large amount of reducing gases such as CO, H 2 and H 2 O were generated in chlorella at the temperature range of 100-500°C, which was favorable for the transformation from oxidized mercury to elemental mercury, thus remarkably increased the release of elemental mercury in the raw coal sample. The mixed chlorella also significantly lowered the decomposition temperature range (from 400-600 to 300-400°C) of pyrite-bound mercury and decreased the decomposition temperatures of the pyrite-bound mercury species. Additionally, in the co-pyrolysis about 91.82% of mercury was released into the gas phase below 400°C and was 13.77% higher than that of in individual pyrolysis of coal. [Display omitted] [ABSTRACT FROM AUTHOR]

• Mercury occurrence and thermal stability in high ash bituminous coal were determined. • The relations of Hg content with organic sulfur, sulfate and sulfide were obtained. • Mercury species in various density fractions were quite distinct. • The matrix-bound Hg, HCl soluble Hg, HgS and Hg(NO 3) 2 ·xH 2 O were thermally unstable and released before 400 °C. • The pyrite-bound Hg mainly enriched in density >2.0 g/cm3 fraction and released at 400–600 °C. The high-ash coals have gradually become essential energy resources due to their availability, and the occurrence of Hg in coals and its thermal stability could be significantly influenced by ash-forming minerals. In this work, a high-ash bituminous coal was divided into 4 density fractions using sink-float procedure. The sequential chemical extraction procedures, temperature-programmed pyrolysis and TG/DTG experiments were carried to investigate the Hg occurrence and thermal stability in different samples. The results showed that the Hg contents in samples has a positive relation with the ash, sulfate and sulfide contents, and the correlation coefficients were 0.868, 0.535 and 0.924, respectively. However, the negative value with correlation coefficient of 0.751 between the Hg and organic sulfur content was obtained. The Hg species in different samples were quite distinct, the organic matrix-bound Hg was the dominate form in SG1 with the content of 76.14%, the SG2 and SG3 were mainly composed of HCl soluble Hg and Hg(NO 3) 2 ·xH 2 O, and the Hg species occurred in SG4 were mainly HCl soluble Hg and pyrite-bound Hg. In the process of pyrolysis, the matrix-bound Hg, HCl soluble Hg, HgS and Hg(NO 3) 2 ·xH 2 O were thermally unstable and could be released into gas in the drying and desorption stage of 30–400 °C, while the pyrite-bound Hg mainly released with the decomposition of pyrite in the temperature range of 400–600 °C. There was only little Hg released in the temperature range of 600–850 °C, indicating the negligible relationship of Hg with carbonate and silicate minerals. [ABSTRACT FROM AUTHOR]

Abstract The multistep solvent extraction is an effective way for evaluating the original structure of coal, however, it is seldom used for studying the Hg distribution in coal and its release behavior during mild pyrolysis process. In this work, the Guizhou bituminous coal was divided into organic-rich class C 1 and minerals-rich class C 2 , the C 1 was further subdivided into 4 groups (EG 1 –EG 4) using multistep solvent extraction method. The Hg species in different samples and their fate during pyrolysis was investigated using sequential chemical leaching methods and temperature-programmed experiments. The results showed the dominant Hg forms in different samples are quite different, the HCl-soluble and HNO 3 -soluble Hg are the dominant forms in C 2 , while organic matrix combined Hg is the most abundant form in C 1 , EG 1 and EG 2 samples. The Hg contents in EG 1 to EG 4 groups are in the order of EG 4 < EG 3 < EG 2 < EG 1 , and have little correlation with the total sulfur contents. The thermal stability of different Hg species are quite distinct, the Hg in EG 1 sample is the most thermal unstable and almost released completely before 400 °C. The Hg release of GZB, C 1 , and C 2 are similar, >60% and 95% of Hg in the three samples can be released at 400 °C and 600 °C, respectively. The Hg-OM+ combined with aromatic clusters in EG 2 is difficult to decompose during pyrolysis process, it mainly released in the temperature range of 400–800 °C. Except the Hg-OM+ combined with aromatic clusters in EG 2 , >95% of Hg can be released before 600 °C for other samples. When the heating rate increased from 5 °C/min to 20 °C/min, the Hg releasing peaks ranged from 150 to 400 °C shifted gradually to higher temperature zones, but there was no obvious change in the positions of peaks ranged from 400 to 800 °C. Graphical abstract Unlabelled Image Highlights • The Hg distribution and releasing behavior in samples were investigated by using multistep solvent extraction method. • The Hg contents in EG 1 to EG 4 samples have little correlation with the total sulfur contents. • The Hg species and their thermal stability in different samples are quite distinct. • More than 95% of Hg in raw coal can be released before 600 °C. • The Hg-OM+ combined with aromatic clusters in EG 2 has higher releasing temperature than other Hg species. [ABSTRACT FROM AUTHOR]