Kinetic Study of Pyrolysis of High Volatile Bituminous Coal

Wiser, W.H.; Hill, George R.; Kertamus, N.J.

doi:10.1021/i260021a023

Cited by 43 publications

(18 citation statements)

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“…9 coal studied by Shalabi et al (1979). As before, all other parameters were kept constant (Ta- For the other coals referred to in Table 2, the kinetic results were obtained either using only one solvent to classify the products (Wiser and Hill, 1967;Curran et al, 1967) or using chromatographic method (Mohan and Silla, 1981;Leonard and Silla, 1983) to classify the products. These investigators provide no data on the fractional yields of asphaltenes and OGW fractions obtained during liquefaction of their respective coals.…”

Section: Reaction Severity and Product Yieldsmentioning

confidence: 99%

Modeling of coal liquefaction kinetics based on reactions in continuous mixtures. Part II: Comparison with experiments on catalyzed and uncatalyzed liquefaction of coals of different rank

Prasad¹,

Agnew²,

Sridhar³

1986

AIChE Journal

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Experimental kinetic data for three Australian coals are compared with predictions from the mathematical model developed in Part I. For these coals, as well as data reported for North American coals, the model is found to show good agreement, using the characteristic molecular weight as the only parameter. The effects of reaction time and temperature are coupled via a severity index that arises in the model as a dimensionless reaction time. The model is also shown to be applicable when catalysts are present. The product distribution for a particular coal seems to be a function only of the conversion even in the presence of catalysts, as long as the chemical reaction controls the rate of liquefaction. SCOPEConventional coal liquefaction kinetic modeling is based on the grouping together of products into several "lumps," usually determined by the solubility properties of the various species present. The reaction networks for such a lumped-product system depend clearly on the particular coal and it is not possible to generalize such models. In Part I, a model based on the concept of reactions in a continuous mixture was proposed and a methodology of applying such a model was developed.In this paper, the product distributions obtained upon liquefaction of three Australian coals-a low-rank Victorian brown coal and two subbituminous coals-are examined and compared with model predictions using the model developed in Part I and the lumping functions proposed therein. The kinetic data were obtained from two different types of reactors, a tubular flow reactor and a batch microautoclave reactor. All experiments were conducted under conditions where there was excess availability of hydrogen from donor solvent (tetralin). In addition, other reported kinetic data for North American coals were examined. The effect of catalyst addition (mostly iron-based), is also examined and the applicability of the model is evaluated. CONCLUSIONS AND SIGNIFICANCEThe model proposed in Part I is found adequate in predicting the product distribution for all coals examined. The only parameter varied between different coals is the characteristic molecular weight for coal.The molecular weight for coal broadly depends upon the rank, and increases as the rank increases.The model provides a basis for coupling the effects of reaction time and temperature using the concept of severity index. The implication for liquefaction of coal is that there is no optimum temperature for maximizing Correspondence concerning this paper should be addressed to T. Sridhar. the yield of a particular product as long as the solvent is capable of supplying all the hydrogen requirements. J . 9. Agnew is presently at the Department of Chemical Engineering, University of Adelaide, Adelaide, 5001. Australia. 1288August 1986 Vol. 32, No. 8 AIChE JournalThe product distribution is uniquely determined by reaction severity. This implies that the activation energy is similar for all reactions in the network. The first-order rate constant for the formation of tetrahydrofuran (THF) s...

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Section: Reaction Severity and Product Yieldsmentioning

confidence: 99%

Modeling of coal liquefaction kinetics based on reactions in continuous mixtures. Part II: Comparison with experiments on catalyzed and uncatalyzed liquefaction of coals of different rank

Prasad¹,

Agnew²,

Sridhar³

1986

AIChE Journal

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“…Another common way is to correlate pyrolysis conditions with the formation of particular products, such as methane, hydrogen, solvent soluble fractions or sulfur compounds [5][6][7][8][9]. It was also demonstrated that the mass-change curve of volatiles during pyrolysis can be decoupled into or fitted by a set of sub-curves, each representing a simple first-order and irreversible reaction and activation energies of all these reactions distribute following a certain pattern, such as the distributed activation energy model (DAEM) [10][11][12][13][14][15][16]. Although these researches contributed significantly to advancement in kinetics of coal pyrolysis in various aspects all of them fails to correlate with or disclose the changes in chemical bonds in coal, which is the fundamental base of coal pyrolysis kinetics.…”

Section: Introductionmentioning

confidence: 99%

Pyrolysis behavior and bonding information of coal — A TGA study

Shi

Liu

Guo

et al. 2013

Fuel Processing Technology

392

165

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“…During pyrolysis free radicals may detach from the fuel macromolecules, and leave the particle as volatile matter if they have a sufficiently high vapor pressure [27,28]. However, most of them, being reactive, seek stabilization by reacting with reactive species near them [27].…”

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confidence: 99%

“…However, most of them, being reactive, seek stabilization by reacting with reactive species near them [27]. The stabilization of free radicals (cracking, condensing) results in the formation of char and tar from the larger fragments, manifested by the char fluidity decrease [29].…”

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Characterization of free radicals by electron spin resonance spectroscopy in biochars from pyrolysis at high heating rates and at high temperatures

Trubetskaya

Jensen

et al. 2016

Biomass and Bioenergy

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a b s t r a c tThe concentration and type of free radicals from the decay (termination stage) of pyrolysis at slow and fast heating rates and at high temperatures (above 1000 C) in biomass char have been studied. A roomtemperature electron spin resonance spectroscopy study was conducted on original wood, herbaceous biomass, holocelluloses, lignin and their chars, prepared at high temperatures in a wire mesh reactor, an entrained flow reactor, and a tubular reactor. The radical concentrations in the chars from the decay stage range up between 7$10 16 and 1.5$10 18 spins g À1. The results indicated that the biomass major constituents (cellulose, hemicellulose, lignin) had a minor effect on remaining radical concentrations compared to potassium and silica contents. The higher radical concentrations in the wheat straw chars from the decay stage of pyrolysis in the entrained flow reactor compared to the wood chars were related to the decreased mobility of potassium in the char matrix, leading to the less efficient catalytic effects of potassium on the bond-breaking and radical re-attachments. The high Si levels in the rice husk caused an increase in the char radical concentration compared to the wheat straw because the free radicals were trapped in a char consisting of a molten amorphous silica at heating rates of 10 3 e10 4 K s À1. The experimental electron spin resonance spectroscopy spectra were analyzed by fitting to simulated data in order to identify radical types, based on g-values and line widths. The results show that at high temperatures, mostly aliphatic radicals (g ¼ 2.0026e2.0028) and PAH radicals (g ¼ 2.0027e2.0031) were formed.

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Kinetic Study of Pyrolysis of High Volatile Bituminous Coal

Cited by 43 publications

References 4 publications

Modeling of coal liquefaction kinetics based on reactions in continuous mixtures. Part II: Comparison with experiments on catalyzed and uncatalyzed liquefaction of coals of different rank

Modeling of coal liquefaction kinetics based on reactions in continuous mixtures. Part II: Comparison with experiments on catalyzed and uncatalyzed liquefaction of coals of different rank

Pyrolysis behavior and bonding information of coal — A TGA study

Characterization of free radicals by electron spin resonance spectroscopy in biochars from pyrolysis at high heating rates and at high temperatures

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