Controlled gasification of different carbon materials and development of pore structure

Kühl, Helmut; Kashani-Motlagh, Mohammad Mehdi; Mühlen, H.-J.; Heek, K.H. van

doi:10.1016/0016-2361(92)90236-h

Cited by 31 publications

(15 citation statements)

References 6 publications

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“…In this sense, Tay et al already identified the drastic effect of steam on the structure and reactivity of char [23]. Kühl et al also observed different effects of CO 2 and steam on the pore structure and the specific surface area of different cokes [47]. Sekine et al [41] stated that the ash morphology had a more significant effect on the gasification rate than the changes in the carbonaceous structure.…”

Section: Resultsmentioning

confidence: 97%

Conversion of high-ash coal under steam and CO2 gasification conditions

Aranda

Grootjes

Meijden

et al. 2016

Fuel Processing Technology

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The use of domestic high-ash coal reserves contributes to the security of energy supply, and therefore high-ash coal is expected to remain as a key energy source in several countries (e.g., India, Turkey) for at least the next 30-40 years. However, the use of high-ash coals for energy production (currently performed mainly via combustion processes) poses a number of technical and economic challenges, e.g., low efficiency and environmental issues. Gasification is an attractive option, since it allows a more efficient, more environmentally friendly conversion of the coal. In particular, integrated gasification combined cycle (IGCC) offers high efficiency, reduced emissions and potential for the implementation of CO 2 capture. With the aim of optimising the design and operation of high-ash coal fluidised-bed gasification processes, this paper studies the effect of temperature and partial pressure on the conversion and reactivity of coke from an Indian high-ash coal under CO 2 and steam gasification conditions using thermogravimetric analysis. Moreover, additional steam gasification tests have been carried out in order to determine the conversion rate under realistic fluidised-bed gasification conditions (e.g., coal ash as bed material, coal particle size, heating rate, bed hydrodynamics, gasification atmosphere), thus taking into account the effect of mass and heat transfer phenomena. Results of isothermal TGA tests have shown that coke reactivity increases at higher temperatures and/or partial pressures of gasifying agent. The experimental data have been fitted to two conversion models (shrinking core and volumetric). The determination of kinetic parameters (reaction order b, pre-exponential factor A and activation energy E a) has been carried out at three conversion levels: X = 0.2, X = 0.5, and X = 0.8. In the case of CO 2 gasification, the reaction order b ranges between 0.2 and 0.8, although at temperatures of 850-900°C, the reaction order has a value around 0.6. In the case of steam gasification, the reaction order ranges between 0 and 1.1, and increases with reaction temperature. Fluidised-bed steam gasification tests have shown that approximately 23-27% of the carbon contained in the coal (~40-45% of the overall coal, considering also hydrogen and oxygen released in the gas) is quickly converted during the devolatilisation stage. Between 12 and 22% of the carbon contained in the remaining coke is converted to gas within the first 25 min of steam gasification. Finally, 55-80% of the carbon in the coke remaining after steam gasification is converted during the first 25 min of oxidation with air. Conversion of the high-ash coal is favoured at higher steam partial pressures and/or higher gasification temperatures. The conversion rate under fluidisedbed conditions is significantly lower than that obtained in TGA tests at similar temperature and steam partial pressure values. Differences in coal particle size, heating rate during devolatilisation, inhibition issues, and other fluid-dynamic effects influence the re...

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Section: Resultsmentioning

confidence: 97%

Conversion of high-ash coal under steam and CO2 gasification conditions

Aranda

Grootjes

Meijden

et al. 2016

Fuel Processing Technology

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“…Steam activation at higher temperatures gave better activation and enhanced widening of the narrow micro-pore network. The steam gasification of oxicoke char [7] produced carbon with less micro-porous structure when compared to CO 2 gasification. This implies that the pore structure and adsorption properties of activated carbon are strongly influenced by physicochemical nature of precursor materials and the thermal history during the manufacturing process.…”

Section: Introductionmentioning

confidence: 98%

“…Considerable amount of work using fluidized bed reactor (FBR) for the preparation of activated carbon by steam/CO 2 /N 2 from various sources has been carried out. Fossil materials like miike coal [2], Spanish HV bituminous coal char [3][4][5], semi anthracite char [6], coal and pitch coke [7], the shell-based agricultural wastes like coconut shell [8,9], palm shell [10,11], almond shell [12] and agricultural waste materials like olive seed waste residue [13,14], pine waste [15], pine wood [16] and wood char [17] have been used as a raw material. Steam activation at higher temperatures gave better activation and enhanced widening of the narrow micro-pore network.…”

Section: Introductionmentioning

confidence: 99%

Preparation of steam activated carbon from rubberwood sawdust (Hevea brasiliensis) and its adsorption kinetics

Kumar

Shivakamy

Miranda

et al. 2006

Journal of Hazardous Materials

116

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“…Value for CO 2 / Value for N 2 λ (thermal conductivity) Figure 3. Comparison of the ratio of different thermo-physical properties and non-dimensional groups for CO2 and N2 [9] B. Nitrogen Adsorption Isotherm Analysis N 2 (77K) adsorption/desorption isotherms were performed on ASAP2020M apparatus. It can be seen that low temperature nitrogen (77K) isotherms (Fig.4) of samples, obtained under 1200 o C at axial length 575mm from the injection point, are type II according to Brunauer, Deming, Deming, Teller (BDDT) classification, but the quantity of nitrogen adsorbed by oxy-fuel chars is always less than that adsorbed by chars obtained under air environments.…”

Section: A Coal Combustion Characteristic In Two Environmentsmentioning

confidence: 99%

Coal Combustion Characteristic and Its Structural Evolution under Oxy-Fuel and Air Environment

Zhao

2011

2011 Asia-Pacific Power and Energy Engineering Conference

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In this paper, two typical Chinese coals were selected to investigate the pulverized coal combustion characteristic and their pore structure evolution in oxy-fuel combustion and conventional air combustion environment with a drop tube furnace (DTF). Results show that the burn-off rate of pulverized coal in O 2 /CO 2 mixtures is lower than that in O 2 /N 2 environment with equivalent oxygen concentration. The Oxy-Fuel chars show smaller porosity parameters such as specific surface area (S BET ), specific pore volume (V BJH ) and average pore diameter (d Pore ) than those of chars obtained in O 2 /N 2 environment. Morphology analyses also present the same results and agree well with those determined by N 2 adsorption method. The present results might have important implications for further understanding the intrinsic kinetics of pulverized coal combustion in O 2 /CO 2 environment.

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Controlled gasification of different carbon materials and development of pore structure

Cited by 31 publications

References 6 publications

Conversion of high-ash coal under steam and CO2 gasification conditions

Conversion of high-ash coal under steam and CO2 gasification conditions

Preparation of steam activated carbon from rubberwood sawdust (Hevea brasiliensis) and its adsorption kinetics

Coal Combustion Characteristic and Its Structural Evolution under Oxy-Fuel and Air Environment

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