Variation of char reactivity during simultaneous devolatilization and combustion of coals in a drop-tube reactor

El-Samed, Abd; Hampartsoumian, E.; Farag, T.M.; Williams, Alan

doi:10.1016/0016-2361(90)90015-i

Cited by 27 publications

(10 citation statements)

References 8 publications

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“…Therefore, the char fractional burnoff (u) was B. Change in Char Physical Structure during calculated by the ash tracer method, [13] which was based on Combustion the chemical analysis of fresh and partly burnt chars.…”

Section: B Char Reactivity Measurementsmentioning

confidence: 99%

Coal char reactivity and structural evolution during combustion—Factors influencing blast furnace pulverized coal injection operation

Lü

Sahajwalla

Harris

2001

Metall Mater Trans B

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A fresh char was prepared and reacted with oxygen under conditions similar to those prevailing in the raceway region of the blast furnace (BF) during pulverized coal injection (PCI), using a wellcharacterized drop-tube furnace (DTF). Char combustion under the present conditions was found to be controlled by the combination of pore diffusion and chemical reaction. Both the char density and size gradually decrease with burnoff, while the char surface area increases up to a burnoff of 40 to 50 pct due to the formation of a large amount of meso-and micropores, which were observed by highresolution field-emission scanning electron microscopy (FESEM) and gas adsorption measurements. Despite the obvious increase in surface area, the char combustion reactivity decreases with burnoff. This is due to the loss of the intrinsic reactivity of char during combustion, as confirmed by fixedbed (FB) measurements of fresh char and chars partly burnt in a DTF. The structural characterization by quantitative X-ray diffraction analysis (QXRDA) shows that the amorphous concentration ( f am ) of the char decreases during combustion, while the aromaticity ( f ar ) and the average crystallite size (L 002 ) of the char increase. The char becomes more ordered during combustion, which is in accordance with the observations made using high-resolution transmission electron microscopy (HRTEM). The char structural ordering observed was found to be responsible for the loss of char intrinsic reactivity during combustion. Based on the QXRDA, a char structure model has also been suggested to explain the char structural evolution observed during combustion. The implications of char structural evolution for char combustion during a PCI operation are also discussed.

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Section: B Char Reactivity Measurementsmentioning

confidence: 99%

Coal char reactivity and structural evolution during combustion—Factors influencing blast furnace pulverized coal injection operation

Lü

Sahajwalla

Harris

2001

Metall Mater Trans B

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“…The ash content of the char samples was estimated using a muffle furnace available at UNSW laboratory. The combustion efficiency was calculated using the ash tracer method 26) often used for this purpose. [27][28][29] The notion of the ash tracer method is that the amount of the ash from the solid fuels and their derived chars is conserved (Eq.…”

Section: Drop Tube Furnace (Dtf)mentioning

confidence: 99%

Structural Transformation of Agricultural Waste/Coke Blends and Their Implications during High Temperature Processes

et al. 2011

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With a sharp increase in demand and production, palm oil wastes, (i.e. empty fruit bunches, fibre and shells) are generated, out of which a large amount ends up in landfill. In such a context, alternative solutions are needed to reduce the impact of these agricultural wastes on the environment. The present paper investigates the effect of addition of agricultural waste materials on the combustion behavior of its blends with metallurgical coke (MC). Two types of agricultural waste materials, palm shell and coconut shell, were mixed in different proportion with MC, while the gas phase reactions were studied at 1 200°C in a drop tube furnace (DTF). In the tested conditions, the blends containing agricultural waste materials indicated higher combustion efficiencies compared to MC alone. Carbon structure analysis were performed through 13 CP/MAS NMR spectroscopy showing various groups of carbons present in the agricultural waste samples ranging from aliphatic to aromatic carbons. The morphology of the samples was studied through Scanning Electron Microscope (SEM). SEM provided a qualitative description of the pore structure in the raw samples as well as the changes occurring following the gas phase reactions in the DTF. It was found that the particles derived from the wastes became increasingly deformed and lost their cell lumen. Surface area measurements were found to be in good agreement with the SEM images, supporting the higher combustion efficiency of the blends in comparison to coke alone. The present study suggests that agricultural waste materials have the potential to partially replace MC, as an auxiliary fuel in metallurgical processes.

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“…[5], often used for estimating high-rank coals, under the assumption that total ash is conserved. [19,24] [5]…”

Section: Dtf Measurementsmentioning

confidence: 99%

“…[1,12] Due to its importance, solid char combustion has been extensively studied in the past. [13][14][15][16][17][18][19][20][21][22][23][24][25][26][27] Char reactivity is controlled by the chemical reaction between char and oxygen and/or pore diffusion of gases in and out of char particle. [15] During combustion, oxygen from the reacting gases is transferred to the outer surface of char and also into the internal pores, followed by adsorption, and initiation of carbon oxidation, and subsequent transportation of product gases away from char.…”

Section: Introductionmentioning

confidence: 99%

Influence of carbon structure and mineral association of coals on their combustion characteristics for pulverized coal injection (PCI) application

Gupta

Sahajwalla

Al-Omari

et al. 2006

Metall Mater Trans B

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The influence of carbon structure and mineral matter of three pulverized coals on their char characteristics including reactivity was studied under a range of combustion conditions in a drop tube furnace (DTF) and thermogravimetric (TGA) furnace for PCI application. Physical and chemical properties of coals and their combustion derivatives were characterized by automated reflectogram, X-ray diffraction, scanning electron microscope, and BET N 2 adsorption. The QEMSCAN* technique was used *QEMSCAN is a trademark

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Variation of char reactivity during simultaneous devolatilization and combustion of coals in a drop-tube reactor

Cited by 27 publications

References 8 publications

Coal char reactivity and structural evolution during combustion—Factors influencing blast furnace pulverized coal injection operation

Coal char reactivity and structural evolution during combustion—Factors influencing blast furnace pulverized coal injection operation

Structural Transformation of Agricultural Waste/Coke Blends and Their Implications during High Temperature Processes

Influence of carbon structure and mineral association of coals on their combustion characteristics for pulverized coal injection (PCI) application

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