Combustion reactivity and morphological change in coal chars: Effect of pyrolysis temperature, heating rate and pressure

Cai, Hongfei; Güell, A.J.; Chatzakis, Ioannis; Lim, J.-Y.; Dugwell, D. R.; Kandiyoti, R.

doi:10.1016/0016-2361(94)00192-8

Cited by 187 publications

(118 citation statements)

References 18 publications

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“…To further increase coal injection rate, it is important to seek alternative approaches to enhance char combustion. It has been found that the combustion reactivity of chars prepared while using varying coals and conditions could be significantly different, [10][11][12][13][14][15][16] which provides opportunities to obtain more reactive char through coal selection and process optimization.…”

Section: Introductionmentioning

confidence: 99%

“…[17][18][19][20][21] Since char is formed during coal pyrolysis, the pyrolysis conditions are expected to affect char structure. By using 13 C-NMR (Nuclear Magnetic Resonance) spectroscopy and FTIR (Fourier Transform Infrared) spectroscopy, the chemical structure of fresh chars was investigated. [22][23][24][25] Fletcher et al 24) also compared the chemical structure of chars from five coals of different ranks.…”

Section: Introductionmentioning

confidence: 99%

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Chemical Structure of Chars Prepared under Conditions Prevailing in the Blast Furnace PCI Operation.

et al. 2002

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Using a drop tube furnace, char samples were prepared from coals of different ranks, under conditions similar to those prevailing during pulverized coal injection into the blast furnace. The chemical structure of resultant chars was determined by quantitative X-ray diffraction analysis (QXRDA) and high-resolution transmission electron microscopy (HRTEM), and investigated as a function of pyrolysis temperature, heating rate and coal type. Among the parameters examined, pyrolysis temperature was the key factor influencing char chemical structure. Char obtained at higher temperature is generally more ordered, with the distinctive peaks becoming sharper and the background intensity becoming lower. Heating rate is another important factor affecting char chemical structure. Char is more ordered at lower heating rate due to the longer residence time. Although considerable differences were still observed in the chemical structure of chars prepared from coals of different ranks, it is clear that such differences are reduced after coal pyrolysis. Char structural evolution during post-pyrolysis and combustion was also investigated. The importance and potential applications of this work to the blast furnace PCI operation have been outlined. KEY WORDS: pulverized coal injection; coal pyrolysis; char combustion; char reactivity; char chemical structure. different ranks. However little systematic investigation has been reported on the influence of pyrolysis conditions on char chemical structure. As part of an overall study on char structure and char reactivity, this paper is focused on the effect of pyrolysis conditions on char chemical structure. A subsequent paper will discuss char physical structure. Char structure formed as a result of pyrolysis serves as the starting point of combustion during PCI operation. These wellcharacterized chars have been subsequently used to establish an understanding of the effect of char structure on char combustion reactivity. Experimental Char PreparationA drop tube furnace (DTF) was used in this investigation to prepare chars under conditions similar to those prevailing in the raceway region of a blast furnace. Details regarding the drop tube furnace can be found elsewhere, 8) and only a brief account is given here. It consists of a coal feeding system, a sampling probe, a gas distribution system and an electrically heated furnace. The composition of gaseous reactants, position of the sampling probe as well as feeding rate of coal particles are adjustable depending on experimental conditions. To prepare char, a metered stream of coal particles was entrained into the iso-thermal zone of the furnace by a preheated gas flow (99 vol% N 2 ϩ1 vol% O 2 ), and a char sample was collected using a water-cooled probe after a residence time of about 1 second. A slightly oxidizing atmosphere was used to burn off the volatiles released during coal pyrolysis. This was considered necessary to avoid contamination of char samples with soot and condensed tar. Three size-graded Australian black coals of differ...

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Chemical Structure of Chars Prepared under Conditions Prevailing in the Blast Furnace PCI Operation.

et al. 2002

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“…Cai and coworkers [16] found that both Pitt #8 and Linby char combustion reactivities decreased with hydropyrolysis pressure from low to medium pressure(20-30 bar), then increased with hydropyrolysis pressure. Lee et al [21] found that Illinois char reactivity generally decreased with increasing char formation pressure, but that this decrease was not as significant for residence times longer than 1 s. Lee found no correlation between the micropore surface area (CO 2 ) of chars and reactivity.…”

Section: Intrinsic Combustion Reactivity Of Charsmentioning

confidence: 99%

“…burnout [8,14,16,17]. In the results presented here, the entire TGA reactivity curve as a function of burnout is presented.…”

Section: Intrinsic Combustion Reactivity Of Charsmentioning

confidence: 99%

Fundamental Investigation of Fuel Transformations in Pulverized Coal Combustion and Gasification Technologies

Hurt¹,

Calo²,

Fletcher³

et al. 2004

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“…As found experimentally [2][3][4][5][6][7], the pyrolysis temperature, the heating rate, and the pressure at the zone where volatile matter release and burning have an effect on the char reactivity and lead to changes in its structure. High-rank coals remain less sensitive to such a thermal activation/deactivation.A pyrolysis temperature increase and a decrease of the coal heating rate led to a decrease in the chemical reaction activity of char with reactant gases [2][3][4][5]. Senneca and Salatino [8] also noted a similar effect based on calculations performed with the use of bituminous coal sample; in this case, as the diameter of particles was increased, thermal deactivation came into play at a lower temperature and at a smaller degree of conversion of the sample.…”

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confidence: 93%

Effect of the rate of pulverized coal preheating on char reactivity

et al. 2017

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Abstract-The effect of the preheating rate of the char particles from Kuznetsk bituminous coal on their specific reaction rate was determined. The experiments were carried out with char samples with mean diameters of 0.15 and 0.35 mm heated to temperatures of 900-1000°C. It was found that the specific surface area of the initial coal, measured by CO 2 adsorption at 273 K, for rapid and slow heat treatments increased more that two times. According to the results of thermogravimetric analysis, it was established that rapid pyrolysis in a muffle furnace led to the production of char whose maximum specific reaction rate was higher than that of the samples after slow pyrolysis. DOI: 10.3103/S0361521917010037The efficient and environmentally appropriate use of coals for the generation of thermal and electrical power and the production of metallurgical coke is a problem of considerable current interest. A possible solution of this problem is the development of scientific fundamentals for a solid fuel preparation technology, which will make it possible to considerably increase the quality of fuel due to its partial gasification. The preliminary thermal preparation of fuel is one of such technologies [1]. On the thermal preparation of fuel, its partial gasification occurs in the burner volume, and a highly reactive mixture, which consists of combustible gases and coal char as the products of gasification, is formed at the inlet of the combustion chamber. As found experimentally [2][3][4][5][6][7], the pyrolysis temperature, the heating rate, and the pressure at the zone where volatile matter release and burning have an effect on the char reactivity and lead to changes in its structure. High-rank coals remain less sensitive to such a thermal activation/deactivation.A pyrolysis temperature increase and a decrease of the coal heating rate led to a decrease in the chemical reaction activity of char with reactant gases [2][3][4][5]. Senneca and Salatino [8] also noted a similar effect based on calculations performed with the use of bituminous coal sample; in this case, as the diameter of particles was increased, thermal deactivation came into play at a lower temperature and at a smaller degree of conversion of the sample.Data on changes in the properties of coals upon heating [9], on the dynamics of volatile matter release upon thermal destruction [10], and on changes in the porous structure of char during combustion [11] are widely available in the publications of Russian researchers; however, it is difficult to combine them for an integrated consideration of the effects on reactivity. As a successful example, Maistrenko et al. [12] reported in 1990 the results of an integrated study for anthracite concerning the effect of pyrolysis temperature on the subsequent rate of conversion in an atmosphere of CO 2 and O 2 .From a practical point of view, coal from the Kuznetsk Basin is of considerable current interest for the development of promising technologies with an integrated gasification combined cycle [13]. The conditions o...

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Combustion reactivity and morphological change in coal chars: Effect of pyrolysis temperature, heating rate and pressure

Cited by 187 publications

References 18 publications

Chemical Structure of Chars Prepared under Conditions Prevailing in the Blast Furnace PCI Operation.

Chemical Structure of Chars Prepared under Conditions Prevailing in the Blast Furnace PCI Operation.

Fundamental Investigation of Fuel Transformations in Pulverized Coal Combustion and Gasification Technologies

Effect of the rate of pulverized coal preheating on char reactivity

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