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

Lü, Liming; Sahajwalla, Veena; Harris, David

doi:10.1007/s11663-001-0068-9

Cited by 57 publications

(56 citation statements)

References 22 publications

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“…There has been evidence that the structural change of the char during char reaction reduces the char activity, 28) so that limiting burnout is expected. However, the char oxidation model does not take account of this reaction rate decrease or the petrographic constitution of the coal and the derived char morphotypes.…”

Section: Resultsmentioning

confidence: 99%

Three-dimensional Simulation of Flow and Combustion for Pulverised Coal Injection

Guo

Zulli²,

Rogers

et al. 2005

ISIJ Int.

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A three-dimensional numerical model of pulverised coal injection has been developed for simulating coal flow and combustion in the tuyere and raceway of a blast furnace. The model has been used to simulate previously reported combustion tests, which feature an inclined co-axial lance with an annular cooling gas. The predicted coal burnout agrees well with that measured for three coals with volatile contents and particle size ranging between 20.2-36.4 % and particle sizes 1-200 mm. Many important phenomena including flow asymmetry, recirculating flow and particle dispersion in the combustion chamber have been predicted. The current model can reproduce the experimental observations including the effects on burnout of coal flowrate and the introduction of methane for lance cooling.

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Section: Resultsmentioning

confidence: 99%

Three-dimensional Simulation of Flow and Combustion for Pulverised Coal Injection

Guo

Zulli²,

Rogers

et al. 2005

ISIJ Int.

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“…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.…”

Section: Char Preparationmentioning

confidence: 99%

“…Details regarding the fixed bed reactor can be found in the literature. 8) During experiment, a preheated and metered gaseous mixture of 70 vol% N 2 ϩ30 vol% O 2 (850 ml/min) passed through the char sample bed (about 0.25 g) and reacted with the char sample at about 673 K. The low temperature was selected to ensure that char combustion occurs in kinetic regime I, where the overall reaction is controlled by chemical reaction on the char pore surface. For each experiment, the off-gas composition was analyzed by an on-line infrared (IR) analyzer and recorded using a data acquisition system.…”

Section: Char Combustionmentioning

confidence: 99%

“…[1][2][3] However, some coalrelated technical difficulties remain, which could greatly limit the PCI rate. [4][5][6][7][8] One of the key practical issues being addressed is the unburnt char inside the stack of a blast furnace, which can cause severe operational problems, such as reduced permeability, undesirable gas/temperature distribution and cohesive zone shape, excessive coke erosion and significant char carryover. Therefore, keeping the amount of unburnt char in the BF stack under a reasonable level while increasing PCI rate is always an aim of PCI operation.…”

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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“…Among the various factors that define the success of this technology, the appropriate choice of the coal to be injected plays an important role [64][65][66] . The effects of coal type are shown in Figures 3.40 to 3.42.…”

Section: Effect Of Coal Typementioning

confidence: 99%

Computational Fluid Dynamics (CFD) Modeling for High Rate Pulverized Coal Injection (PCI) into the Blast Furnace

Zhou¹

2008

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

Cited by 57 publications

References 22 publications

Three-dimensional Simulation of Flow and Combustion for Pulverised Coal Injection

Three-dimensional Simulation of Flow and Combustion for Pulverised Coal Injection

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

Computational Fluid Dynamics (CFD) Modeling for High Rate Pulverized Coal Injection (PCI) into the Blast Furnace

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