Determination of mineral matter and elemental composition of individual macerals in coals from Highveld mines

Matjie, R.H.; Li, Z.; Ward, Colin R.; Bunt, John R.; Strydom, Christien A.

doi:10.17159/2411-9717/2016/v116n2a8

Cited by 27 publications

(30 citation statements)

References 42 publications

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“…coal with ash yield values of 14.7–28 (wt %, adb) and fixed carbon content values in the range >70 wt % (adb) may be utilized for gasification. Researchers − reported that the ash yield in feed coals entering South African commercial gasifiers ranged between 22 and 30%. They indicated that the ash yield in feedstock for utilization in South African commercial gasifiers must be less than 35%. − The liquefaction-derived residues thus show promise to be used as a feedstock for gasification.…”

Section: Resultsmentioning

confidence: 99%

Pyrolysis of Tetralin Liquefaction Derived Residues from Lighter Density Fractions of Waste Coals Taken from Waste Coal Disposal Sites in South Africa

Uwaoma¹,

Strydom²,

Matjie³

et al. 2019

Energy Fuels

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The lighter density (<1.5 g/cm3) fractions produced from two waste coals sampled from the waste coal disposal sites at thermochemical plants situated in South Africa were used as feed materials for liquefaction with tetralin. The liquefaction residues from the lighter density and untreated lighter density fractions were used in pyrolysis experiments. Pyrolysis of the lighter density fractions was carried out in a Fischer Assay oven at 750 and 920 °C under an argon atmosphere. Advanced analytical techniques (gas chromatography–mass spectrometry and nuclear magnetic resonance (NMR) spectroscopy) were employed to characterize the pyrolysis products. Also, the lighter density fractions, liquefaction residues, and their chars were examined using conventional and advanced analytical techniques. The pyrolysis char yields of the liquefaction residues ranged between 74% and 76%, and those of the coal float fractions ranged between 67.0 and 71.5%. Gas pyrolysis yields ranged between 16.0% and 20.0% for the residues and between 14.5% and 18.4% for the lighter density fractions, while the pyrolytic water and the tar products of the lighter density fractions were slightly higher than those of the liquefaction-derived residues. The proton NMR analysis of the tars from the residues shows marginally higher amounts of aromatic protons than those of the lighter density fractions. Chars which were generated after pyrolysis of the liquefaction-derived residues show higher porosity values than those from the pyrolysis of the lighter density fractions. The differences in the porosities are attributed to the opening of pores and extraction of some lower molecular mass aliphatic species from the coal matrix during liquefaction. The pyrolysis products distribution and characterization of the products showed that the residues (waste material) generated after tetralin liquefaction of the float fractions from the float–sink experiments of waste coals may be utilized for thermochemical processes (pyrolysis).

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Section: Resultsmentioning

confidence: 99%

Pyrolysis of Tetralin Liquefaction Derived Residues from Lighter Density Fractions of Waste Coals Taken from Waste Coal Disposal Sites in South Africa

Uwaoma¹,

Strydom²,

Matjie³

et al. 2019

Energy Fuels

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“…The mineral matter in coal is composed of CaCO 3 which can decompose to CaO and CO 2 ; MgCO 3 which decomposes to MgO and CO 2 ; Na 2 CO 3 which can decompose to Na 2 O and CO 2 ; SiO 2 , Al 2 O 3 , etc (Matjie et al, 2016). So, ash is residue that remains after complete decomposition with compounds like CaO, MgO, Na 2 O, SiO 2 , Al 2 O 3 , etc (Matjie et al, 2016). However, for biomass there is no such issues as mineral matter is negligible.…”

Section: Proximate Analysismentioning

confidence: 99%

“…C, H, N, and S are determined by chemical analysis and expressed on a moisture free basis. Ash is also determined as in proximate analysis and reported on moisture free basis (Nhuchhen and Basu, 2014;Matjie et al, 2016). Then O is then determined by the difference as:…”

Section: Ultimate Analysismentioning

confidence: 99%

“…Coal analysis reports Cl 2 in addition to CHNSO but this is not found in biomass unless it is waste biomass. In some biomasses, C is more than O whilst other biomasses have more O than C (Matjie et al, 2016). Some authors use the van Krevelen's diagram to represent ultimate analysis as it shows the change in H/C ratio on y-axis against O/C ratio on x-axis.…”

Section: Ultimate Analysismentioning

confidence: 99%

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Biomass torrefaction as an emerging technology to aid in energy production

Mamvura

Danha

2020

Heliyon

135

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Biomass torrefaction has gained widespread attention due to its benefits as a standalone process to improve biomass properties to be at par or similar to those for coal in electricity generation or as a pretreatment step before pyrolysis and gasification processes. It has also found application in other processes like steel production where it is aiming to replace coal or work alongside coal by co-firing the coal with biomass at certain proportions. There have been a lot of papers on biomass torrefaction review, but this paper tried to look at a different angle to show other aspects of torrefaction and how it links to other technologies as well as the chemistry behind it. Overall, the process has seen a big shift in the technology it utilizes, and the hope is that it will make the process more viable and applicable in future.The focus starts from the raw biomass, how it is analysed and the different analysis that are performed to determine relevant information about biomass properties. There are different reactors that are used but to date there is not a preferred one as they have their pros and cons. However, the focus mostly is the process not which reactor to use as they have all not shown any significant differences. The main product of the process, torrefied biomass determines the efficiency and how it can be applied to other technologies. To date, biomass torrefaction is for co-firing with coal for energy generation and as a pretreatment step for pyrolysis and gasification. Due to varying types of biomass in different countries, the technology has not yet reached its full potential, but the hope is it will with calls for use of renewable sources of energy.Other areas like modelling torrefaction of biomass have not been looked at in this review. However, the paper sets the foundations for such detailed reviews.

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“…The values are consistent with the ranks of the two samples and with other South African coals. 30 Ultimate analysis results, given in Table 3, indicate relatively low concentrations of total sulfur (1.6 and 1.9% daf) for coals A, B, and C.…”

Section: Results and Discussionmentioning

confidence: 99%

In Situ Capturing and Absorption of Sulfur Gases Formed during Thermal Treatment of South African Coals

et al. 2018

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The objective of this study, the first of its kind on these specific South African low-sulfur coals, was to capture H 2 S and SO 2 produced under inert and oxidizing conditions from sulfur compounds present in the coals. The capturing agents were calcium and magnesium oxides formed during the transformation of calcite and dolomite. The effectiveness of two different scrubbing solutions (0.15 M cadmium acetate and 1.1 M potassium hydroxide) for absorption of volatilized H 2 S and SO 2 was also investigated. The bituminous coal (coal A) contained dolomite, calcite, pyrite, and organic sulfur. Lignite (coal B) had a high organic sulfur content and contained gypsum, no or low dolomite and pyrite contents, and no calcite. A third sample (coal C) was prepared by adding 5 wt % potassium carbonate to coal A. Under oxidizing conditions and at elevated temperatures, FeS 2 produced Fe 2 O 3 , FeO, and SO 2 . It transformed to FeS and released H 2 S under inert conditions. Organic sulfur interacted with organically bound calcium and magnesium at 400 °C in an inert atmosphere to form calcium sulfate and oldhamite ((Ca,Mg)S). CaO, produced from calcite or dolomite, reacted with SO 2 and O 2 at 950 °C to form calcium sulfate. Treatment of lignite at 400–950 °C resulted in 96–98% evolution of sulfur as gases. Hydrogen sulfide formation increased with the increasing thermal treatment temperature under inert conditions for the three coals. Under oxidizing conditions, sulfur dioxide formation decreased with the increasing temperature when heating coals B and C. The lowest ratio (0.01) of H 2 S to SO 2 was achieved during thermal treatment of the blend of coal and potassium carbonate (coal C), implying that almost all of sulfur was retained in the coal C ash/char samples. In situ capturing of sulfur gases by CaO and MgO and by the added K 2 CO 3 in coal C to form calcium/magnesium/potassium sulfates and potassium/calcium/magnesium aluminosilicate glasses during utilization of these and similar coals could reduce the percentage of sulfur volatilized from the coals by 54–100%, thereby potentially decreasing their impact on the environment.

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Determination of mineral matter and elemental composition of individual macerals in coals from Highveld mines

Cited by 27 publications

References 42 publications

Pyrolysis of Tetralin Liquefaction Derived Residues from Lighter Density Fractions of Waste Coals Taken from Waste Coal Disposal Sites in South Africa

Pyrolysis of Tetralin Liquefaction Derived Residues from Lighter Density Fractions of Waste Coals Taken from Waste Coal Disposal Sites in South Africa

Biomass torrefaction as an emerging technology to aid in energy production

In Situ Capturing and Absorption of Sulfur Gases Formed during Thermal Treatment of South African Coals

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