Defluidisation of fluidised beds during gasification of biomass

Bio-syngas from gasification of sugarcane bagasse is one of the most promising sources for renewable energy. As an agriculture-based biomass, sugarcane bagasse has a high content of moisture (46-52%), fibrous (43-52%) and low bulk density (80-120 kg/m 3 ). This quality of bagasse will tend to initiate agglomeration and cause de-fluidization. It will disturb the gasification process and finally will decrease yield and quality of syn-gas. Its chracteristics in low quality can be improved by pretreatment, i.e., torrefaction process, addressed by slow heating of biomass on wet or dry conditions on atmosphere pressure for 1 hour before it is used as feedstock gasification.This preliminary work features an experimental investigation of torrefaction process of Indonesian sugarcane cane bagasse. Temperature of torrefaction varies from 150, 175, 200, 225, 250 and 300 °C. For bagasse gasification process, the optimum temperature of dry torrefaction is 150 °C. At this temperature, yield of syngas will higher than other torrefaction temperature. Temperature of dry torrefaction will give energy saving opportunities than that's of wet torrefaction (180 °C, 1 hr).Analysis ultimate and proximate also indicate that sugarcane bagasse with temperature torrefaction 150 °C give better result than other torrefaction's temperature in high content of hydrogen and low content of carbon.

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“…Stabilizers are usually used i.e. alkali metal oxides (group II) such as calcium and magnesium [24].…”

Section: Introductionmentioning

confidence: 99%

Torrefaction of Indonesian Sugar-cane Bagasse to Improve Bio-syngas Quality for Gasification Process

et al. 2015

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“…They can attach to the sticky bed particle surface and increase the sintering temperature of the eutectic composition. [18][19][20][21] Most of the aforementioned studies [8][9][10]14,[22][23][24][25] were carried out using silica sand as bed material.…”

Section: Introductionmentioning

confidence: 99%

High-Temperature Interactions between Molten Miscanthus Ashes and Bed Materials in a Fluidized-Bed Gasifier

et al. 2015

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One of the main concerns about biomass fluidized bed gasification and combustion is the risk of bed particle agglomeration due to ash melting. Although many studies have been conducted about the agglomeration mechanism using silica sand, olivine is mostly mentioned as an alternative bed material for tar decomposition, and its interaction with biomass ash has not been yet fully understood. The aim of this work is to investigate the agglomeration of miscanthus ashes, focusing on thermophysical and thermochemical aspects. Three different bed materials (silica sand (SiO 2 ), raw and calcined olivine ((Mg,Fe) 2 SiO 4 )) and an additive to prevent agglomeration (dolomite (CaMg(CO 3 ) 2 ) were tested. The effects of atmosphere and miscanthus harvest time were also investigated. It was found that the key parameter of agglomeration is the wettability of bed particles by molten ashes. In contact with ashes all three bed material showed good wetting tendencies, while dolomite had non-wetting properties. The adhesion between bed materials and molten ashes increases in the order of silica, olivine and calcined olivine. While in the case of silica sand only physical adhesion occurred, the diffusion of iron oxide into the molten ash was observed using olivine. Calcined olivine has a roughened surface which further increased the adhesion. The atmosphere did not influence the mechanism of ash/bed material interaction. On the other hand, miscanthus harvest time had a significant effect on ash reactivity and interaction with raw and calcined olivine.

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“…Limestone was used by Fernández et al [5], founding no sign of agglomeration due to the adsorption of alkali salts on the surface. Liliedahl et al [6] used magnesite and olivine as bed materials, obtaining a proper operation performance in both cases. Defluidization was avoided, although some clinkers from biomass ash were found inside the bed when using magnesite.…”

Section: Introductionmentioning

confidence: 98%

“…Bed sintering temperature is also an indicator of the bed agglomeration. Liliedahl et al [6] obtained an empirical equation for this parameter as a function of the feedstock, bed material, and operating conditions. Another possibility to reduce the agglomeration problems is the use a secondary fuel as Abelha et al [11], who employed bends of cardoon and eucalyptus to reduce this problem.…”

Section: Introductionmentioning

confidence: 99%

Agglomeration detection by pressure fluctuation analysis during Cynara cardunculus L. gasification in a fluidized bed

Gómez-Hernández

Serrano

Soria-Verdugo

et al. 2016

Chemical Engineering Journal

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h i g h l i g h t sJetsam and flotsam behavior of fuel particles was analyzed using pressure signals. Cynara cardunculus L. was gasified in a lab-scale FB using sepiolite and silica sand. Agglomeration mechanisms: cap-clinker formation and entire bed defluidization. Wide band energy and attractor comparison tool showed similar results. Wide band energy can identify and characterize each agglomeration mechanism. a b s t r a c tThe bed material and the fuel particles are the main actors in the agglomeration process in a bubbling fluidized bed reactor during a gasification conversion. The physical and chemical reactions between them determine whether the bed operates under a proper fluidization condition or the quality of the fluidization is deteriorated due to agglomerates appearance inside the bed. This work analyzes the pressure signals of a fluidized bed during Cynara cardunculus L. gasification in a reactor with an inner diameter of 52.8 mm. Jetsam and flotsam behavior of fuel particles is analyzed using sepiolite and silica sand as bed materials, respectively. The wide band energy and the attractor comparison tool are used to detect agglomeration, and, as a consequence, the defluidization of the bed. Similar defluidization times are obtained employing both methods. The wide band energy analysis shows that, for jetsam fuel particles, the endogenous bubbles produced by the fuel devolatilization inside the bed change the energy distribution, while for flotsam fuel particles, the cap-clinker agglomerate formed is detected by high frequencies in the power spectrum.

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Defluidisation of fluidised beds during gasification of biomass

Cited by 27 publications

References 9 publications

Torrefaction of Indonesian Sugar-cane Bagasse to Improve Bio-syngas Quality for Gasification Process

Torrefaction of Indonesian Sugar-cane Bagasse to Improve Bio-syngas Quality for Gasification Process

High-Temperature Interactions between Molten Miscanthus Ashes and Bed Materials in a Fluidized-Bed Gasifier

Agglomeration detection by pressure fluctuation analysis during Cynara cardunculus L. gasification in a fluidized bed

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