Self-segregation of high-volatile fuel particles during devolatilization in a fluidized bed reactor

Bruni, Giovanna; Solimene, Roberto; Marzocchella, Antonio; Yates, J.G.; Lettieri, Paola; Fiorentino, Maria

doi:10.1016/s0032-5910(02)00149-3

Cited by 95 publications

(70 citation statements)

References 10 publications

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“…In tum, the fluidization promotes gas-solid contact, resulting in good mixing, and high heat and mass transfer rates [3,4]. Unlike more traditional reactors for coal combustion or catalytic reactions [5), gasifying biomass poses formidable challenges due to their unique characteristics. Biomass feedstock does not readily fluidize and is subsequently injected in a second inert material, typically refractory sand, to improve the fluidization characteristics.…”

Section: Introductionmentioning

confidence: 99%

Approximating a Three-Dimensional Fluidized Bed With Two-Dimensional Simulations

Deza

Battaglia

Heindel

2008

Volume 10: Heat Transfer, Fluid Flows, and Thermal Systems, Parts A, B, and C

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Fluidized beds can be used to gasify biomass in the production of producer gas, a flammable gas that can replace natural gas in process heating. Modeling these reactors with computational fluid dynamics (CFD) simulations is advantageous when performing parametric studies for design and scale-up. From a computational resource point of view, two-dimensional simulations are easier to perform than threedimensional simulations, but they may not capture the proper physics. This paper will compare two-and three-dimensional simulations in a 10.2 cm diameter fluidized bed with side air injection to determine when two-dimensional simulations are adequate to capture the bed hydrodynamics. Simulations will be completed in a glass bead fluidized bed operating at 1.5Umf and 3Umf , where Umf is the minimum fluidization velocity. Side air injection is also simulated to model biomass injection for gasification applications. The simulations are compared to experimentally obtained time-averaged local gas holdup values using X-ray computed tomography. Results indicate that for the conditions of this study, two-dimensional simulations qualitatively predict the correct hydrodynamics and gas holdup trends that are observed experimentally for a limited range of fluidization conditions.

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Section: Introductionmentioning

confidence: 99%

Approximating a Three-Dimensional Fluidized Bed With Two-Dimensional Simulations

Deza

Battaglia

Heindel

2008

Volume 10: Heat Transfer, Fluid Flows, and Thermal Systems, Parts A, B, and C

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“…Such a result can be explained by the fuel particle behavior in the sepiolite bed. The jetsam behavior of the fuel particle ensured that the devolatilization occurred within the dense bed, and thus endogenous bubbles were produced, as explained in [13,14]. These bubbles affect the fluid-dynamic behavior of the entire bed increasing the effective flow rate, and thus, changing the CE distribution.…”

Section: Combustible Behavior: Jetsammentioning

confidence: 97%

“…Fuel particles may have higher densities than the dense phase, showing a jetsam behavior. This causes the formation of endogenous bubbles when devolatilization occurs, changing the properties of the fuel particles, and promoting their motion throughout the whole bed [12][13][14]. In contrast, flotsam fuel particles tend to remain at the top of the bed showing a low mixing degree with the bed particles [15,16].…”

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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“…Since 60 g Ni-based oxygen carrier provides enough oxygen for the complete conversion of gaseous products generated from 2 g sludge, the incomplete conversion of CO and H 2 is not because of the insufficiency of Ni-based oxygen carrier, but should be due to sludge particle segregation [5,37]. In general, fragmentation and segregation of sludge particles during devolatilization and char gasification play a key role in a fluidized bed reactor [37]. In particular, segregation of volatile matter is expected to cause the poor contact between bed materials and volatile matter, which results in incomplete conversion of CO and H 2 in CLC process.…”

Section: Effect Of Ni-based Oxygen Carrier On Sludge Conversionmentioning

confidence: 99%

Sewage sludge combustion in a CLC process using nickel-based oxygen carrier

Niu

Shen

et al. 2015

Chemical Engineering Journal

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Self-segregation of high-volatile fuel particles during devolatilization in a fluidized bed reactor

Cited by 95 publications

References 10 publications

Approximating a Three-Dimensional Fluidized Bed With Two-Dimensional Simulations

Approximating a Three-Dimensional Fluidized Bed With Two-Dimensional Simulations

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

Sewage sludge combustion in a CLC process using nickel-based oxygen carrier

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