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Abstract  

Differential thermal analysis (DTA) of low-rank coals of high lignite to subbituminous rank from coal mines of Pakistan is reported. The studies carried out in dynamic oxygen atmosphere indicate that the exothermic reactions occur between 300 and 650°C and that the samples undergo stepwise oxidation of the organic matter rather than a continuous process as indicated by the pattern of shoulders from 250 to 350°C accompanying the main peak around 450°C. The effect of heating rate, particle size and volatile content was also studied in relation to oxidation. The results show that the increase in heating rate from 10 to 80 deg min−1 results in a marked shift in all the events in the DTA curve towards higher temperatures. As for the effect of particle size, the DTA records of 100–75, 150–100, 250–150 μm and greater than 250 μm fractions show that the magnitude and position of shoulder peaks are more sensitive to changes in particle sizes compared to the main peak. The curves recorded to study the effect of changing volatile content of samples between 30–40% indicate a complex pattern of shoulders accompanying the main peak. In general, the number of shoulder peaks increases with increasing volatile content of samples but their positions do not follow any trend. The DTA curves recorded in nitrogen contain ill-de-fined oxothermic effects over the 300–750°C temperature range. These curves consist of an endothermic peak around 150°C, two exothermic shoulders in the temperature region 300–400°C and a large broad exothermic whip between 500 and 700°C. The heating rates have similar effects as in oxygen while the particle size do not influence the results. It has been concluded that the organic matter in the coals studied here is extremely heterogeneous with different burning characteristics; as a result it is very difficult to quantify energy changes associated with poorly resolved exothermic events along the DTA curve. The effects also dominate in N2 atmosphere thus making identification of mineral matter difficult. The overall pattern of DTA events in oxygen can be correlated with the heating rate, particle size and volatile content of samples.

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Thermogravimetric analysis on gasification reactivity of Hailar lignite

Influence of inherent mineral matters and external ash

Journal of Thermal Analysis and Calorimetry
Authors: Ao Hou, Ze Wang, Wenli Song, and Weigang Lin

in low rank coal gasification: 1. Gasification with carbon dioxide . Fuel 69 : 275 – 281 10.1016/0016-2361(90)90086-6 . 8. Köpsel , R , Zabawski , H 1990 Catalytic effects of ash

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Co-firing of biomass with coals

Part 2. Thermogravimetric kinetic analysis of co-combustion of fir (Abies bornmulleriana) wood with Beypazari lignite

Journal of Thermal Analysis and Calorimetry
Authors: Sinem Taş and Yuda Yürüm

was consistent with the activation energies that were reported for low rank coal [ 28 ]. Figure 4 shows ln[−ln(1 − α( T ))] versus ln(β) plot for the comparison of reaction orders. It was expected that n values depend on

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of the samples using kinetic approach for non-isothermal thermogravimetry. At the moment, low-rank coals are classified according to gross calorific value (GCV) on moist , mineral - matter - free ( mmf ) basis, and high-rank coals according to

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Journal of Thermal Analysis and Calorimetry
Authors: Hou-yin Zhao, Yan Cao, Song P. Sit, Quentin Lineberry, and Wei-ping Pan

reactions of hydrothermally and supercritically upgraded low-rank coal by using a new distributed activation energy model . Fuel Process Technol . 2001 ; 69 : 1 – 12 . 10.1016/S0378-3820(00)00113-2 . 8

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characteristics of an Indonesian Low-Rank Coal under O 2 /N 2 and O 2 /CO 2 conditions . Energy Fuels 24 : 160 – 164 10.1021/ef900533d . 10. Liu , H , Zailani , R , Gibbs , BM 2005

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Co-firing of biomass with coals

Part 1. Thermogravimetric kinetic analysis of combustion of fir (abies bornmulleriana) wood

Journal of Thermal Analysis and Calorimetry
Authors: Ahu Gümrah Dumanli, Sinem Taş, and Yuda Yürüm

, 54–92 kJ/mol, calculated by Kök [ 38 ] for some Turkish low rank coals using Coats and Redfern method [ 39 ], but lower than those calculated for the combustion of biomass using the Ozawa–Flynn–Wall kinetic method, 140 kJ/mol [ 18 ]. Otero et al. [ 40

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Low temperature reactivity in agglomerates containing iron oxide

Studies in the Ca(OH)2–C–Fe2O3 system

Journal of Thermal Analysis and Calorimetry
Authors: Ryan Robinson, Fabrice Patisson, and Bo Björkman

2004 43 : 6943 – 6947 10.1021/ie049907m . 12. Wang , J , Takarada , T . Role of calcium hydroxide in supercritical water gasification of low-rank coal . Energy Fuels 2001 15 : 356

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