Relationship between Gasification Reactivity of Straw Char and Water Soluble Compounds Present in this Material

Henriksen, Ulrik Birk; Jacobsen, Michael; Lyngbech, T.; Hansen, Martin

doi:10.1007/978-94-009-1559-6_70

Cited by 3 publications

(2 citation statements)

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“…This reaction is the slowest step in industrial combustion and gasification processes and, therefore, generally determines the total conversion of carbon in practical systems. For this reason there have been numerous studies on the reactivity of coal − and biomass chars. − These studies have shown char reactivity to depend on the physical and chemical properties of the char, which, in turn, depend on the inherent properties of the fuel as well as on the devolatilization conditions . Certain inorganic elements are known to have a significant impact on char reactivity.…”

Section: Introductionmentioning

confidence: 99%

“…There is strong consensus in the literature that the alkali metals, K and Na, catalyze char reactivity. The alkaline earth metals, Ca and Mg, are understood to catalyze char reactivity but to a lesser extent than the alkali metals. , Silicon has been reported to reduce char reactivity by forming inactive alkali silicates . The overall catalytic effect of the inorganic matter likely depends on the relative proportions of inorganic elements in the char.…”

Section: Introductionmentioning

confidence: 99%

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Effect of Hydrothermal Carbonization on the Combustion and Gasification Behavior of Agricultural Residues and Macroalgae: Devolatilization Characteristics and Char Reactivity

et al. 2017

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Hydrothermal carbonization (HTC) can potentially improve the fuel quality of low-value biomass resources that are otherwise unsuitable for use in industrial heat and power applications. The effect of HTC pretreatment on the combustion and gasification behavior of two agricultural residues (grape marc and sugar cane bagasse) and a freshwater species of macroalgae was investigated, with an emphasis on devolatilization behavior and char reactivity. HTC was carried out in a custom-built, laboratory-scale, batch reactor at three temperatures, 180, 220, and 260 °C, with a slurry density of 15% w/w dry biomass in water. The volatile release behavior of the collected products (hydrochars) and untreated biomass feedstocks were characterized by dynamic thermogravimetric analysis. Char reactivity was characterized by isothermal gasification of samples of the hydrochars and untreated biomass in a thermobalance in carbon dioxide, following fast pyrolysis of the samples in a separate fixed-bed batch reactor. Hydrochars were more energy-dense and contained lower concentrations of catalytic metals, particularly K and Na, than the untreated biomass feedstocks. HTC caused a significant reduction in the total release of volatiles and an increase in the yield of char during devolatilization. The bulk of the volatile matter was released at higher devolatilization temperatures for the hydrochars. These trends became more pronounced with increasing HTC temperature from 180 to 260 °C. The char components of grape marc and macroalgae became substantially less reactive following HTC. The char component of bagasse became more reactive following HTC at 180 °C but became less reactive following HTC at 220 and 260 °C. Activation energies for char gasification of HTC-treated (220 °C) grape marc, bagasse, and macroalgae in CO 2 , were 177, 247, and 282 kJ mol −1 , respectively. These values are 92%, 10%, and 52% greater than the values for the untreated biomass.

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