Catalysis of coal char gasification by alkali metal salts

McKee, D.W.; Spiro, Clifford L.; Kosky, Philip; Lamby, E.J.

doi:10.1016/0016-2361(83)90202-8

Cited by 138 publications

(94 citation statements)

References 5 publications

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“…They also found that the catalytic effect of MBM minerals was not perceivable on lignite but was significant for anthracite. This is in accordance with McKee et al [97] and Srivastava et al [98] who demonstrated the increased catalytic activity of alkali metals on gasification with increasing coal rank. The reaction rates of a blend of waste birch wood and Daw Mill coal was significantly increased and the char yields were lower than a simple blending prediction in a pressurized fluidized bed oxygen atmosphere gasifier with temperatures varying from 973 K to 1173 K at a pressure of 0.4 MPa [67].…”

Section: Devolatilization/pyrolysissupporting

confidence: 92%

A Review of Thermal Co-Conversion of Coal and Biomass/Waste

2014

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Abstract:Biomass is relatively cleaner than coal and is the only renewable carbon resource that can be directly converted into fuel. Biomass can significantly contribute to the world's energy needs if harnessed sustainably. However, there are also problems associated with the thermal conversion of biomass. This paper investigates and discusses issues associated with the thermal conversion of coal and biomass as a blend. Most notable topics reviewed are slagging and fouling caused by the relatively reactive alkali and alkaline earth compounds (K 2 O, Na 2 O and CaO) found in biomass ash. The alkali and alkaline earth metals (AAEM) present and dispersed in biomass fuels induce catalytic activity during co-conversion with coal. The catalytic activity is most noticeable when blended with high rank coals. The synergy during co-conversion is still controversial although it has been theorized that biomass acts like a hydrogen donor in liquefaction. Published literature also shows that coal and biomass exhibit different mechanisms, depending on the operating conditions, for the formation of nitrogen (N) and sulfur species. Utilization aspects of fly ash from blending coal and biomass are discussed. Recommendations are made on pretreatment options to increase the energy density of biomass fuels through pelletization, torrefaction and flash pyrolysis to reduce transportation costs.

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Section: Devolatilization/pyrolysissupporting

confidence: 92%

A Review of Thermal Co-Conversion of Coal and Biomass/Waste

2014

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“…Alkali intermediates may also interact with the substrate to form free radical or possibly interaction compounds. For a given additive (Li 2 CO 3 , Na 2 CO 3 , K 2 CO 3 , Cs 2 CO 3 and Rb 2 CO 3 ), the magnitude of the catalytic effect increased with the rank of the parent coal [32]. A progressive loss in catalytic activity on thermal cycling during steam gasification was associated with reaction of the alkali salts with mineral matter in the chars.…”

Section: Mineral Substances or Ash In Coalmentioning

confidence: 91%

Catalytic Gasification of Coal Using Eutectic Salt Mixtures

Sheth¹,

Agrawal²,

Yeboah³

2001

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“…The contributions to the overall reaction rate of catalytic and noncatalytic steps are discussed. The extensive literature that exists on the subjects of kinetics and mechanisms in catalytic gasification has been reviewed by, among others, Walker et al (1966), Johnson (1976), Prasher (1979), Wen (1980), and McKee (1981McKee ( ,1983. It has been common to correlate the measured overall reaction rate with the total amount of added catalyst (Patrick and Shaw, 1975;Verra and Bell, 1978;Lang and Neavel, 1982;Walker et a]., 1983;Spiro et al, 1983;Huhn et al, 1983).…”

Section: Conclusion and Significancementioning

confidence: 96%

Porosity effects on catalytic char oxidation. Part I: A catalyst deposition model

Perlmutter

1985

AIChE Journal

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Six char samples generated from two coals were impregnated by solutions with different concentrations of NazC03 and/or KzCO3. The catalyst solution penetration was studied, the catalyst uptake was measured, and the effects of impregnation on the char pore structure were determined experimentally. The results indicate that the impregnated catalysts reside only on particle exteriors without significant penetration. The overall rate of reaction is therefore the combination of catalytic reaction on particle exteriors and noncatalytic reaction on the pore surfaces inside the particle. A kinetic model is presented that takes these findings into account. J. L. SU and D. D. PERLMUllER Department of Chemical EngineeringUniversity of Pennsylvania Philadelphia, PA 19104 SCOPESix char samples generated from two coals were impregnated by solutions containing different concentrations of NazC03 and/or KzCO3. The effects of catalyst impregnation on the char pore structure were examined by COz adsorption and mercury porosimetry. The catalyst uptakes were determined by atomic absorption. Pycnometry tests were also conducted to determine the degree of catalyst penetration during impregnation. Catalyzed and uncatalyzed samples were examined under a scanning electron microscope at both unreacted and partially reacted stages. The experimental results were used to formulate a kinetic model that accounts for the several findings. CONCLUSIONS AND SIGNIFICANCEThe experimental work of this study focused on the degree of catalyst solution penetration that occurs during impregnation of chars. The catalyst uptake was determined as well as the effects of impregnation on the char pore structure. The impregnating solution was found unable to penetrate into the interior pore structure of a char. The deposited catalysts resided mainly on particle exteriors without affecting the pore structure. As a consequence, rapid catalytic reaction occurs on a char's exterior surfaces, reducing particle size, while a slower noncatalytic reaction occurs simultaneously inside the pore structures. The observed reaction rate is then the combination of the contributions from catalytic and noncatalytic mechanisms.From such a physical picture a model was developed for reaction kinetics of catalytic gasification. The model produces an expectation that the enhanced reactivity would be more significant at low levels of conversion, and predicts that the overall rate would decrease to that of the noncatalytic reaction at high conversion. The contributions to the overall reaction rate of catalytic and noncatalytic steps are discussed.

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Catalysis of coal char gasification by alkali metal salts

Cited by 138 publications

References 5 publications

A Review of Thermal Co-Conversion of Coal and Biomass/Waste

A Review of Thermal Co-Conversion of Coal and Biomass/Waste

Catalytic Gasification of Coal Using Eutectic Salt Mixtures

Porosity effects on catalytic char oxidation. Part I: A catalyst deposition model

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