The effect of fine particles on elutriation of coarse particles in a gas fluidized bed

Choi, Jeong-Hoo; Suh, Joon-Min; Chang, In-Yong; Shun, Dowon; Yi, Chang-Keun; Son, Jung Eek; Kim, Sang-Done

doi:10.1016/s0032-5910(01)00333-3

Cited by 37 publications

(29 citation statements)

References 6 publications

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“…The superficial velocity used in this study was 2U mf (0.12 m/s). For a particle to be carried out of the bed, the local gas velocity needs to exceed the particle's terminal velocity, which is the speed at which an object in free fall is no longer accelerating [21]. Therefore, one aim of this study was to keep the superficial velocity lower than the terminal velocity to avoid elutriation loss of bed material during experimental work.…”

Section: Gasification Proceduresmentioning

confidence: 99%

Kinetics and Performance of Raw and Torrefied Biomass in a Continuous Bubbling Fluidized Bed Gasifier

Al-Farraji

Marsh

Steer

et al. 2017

Waste Biomass Valor

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This paper is an experimental study of the kinetics of gasification of olive kernel by using a thermogravimetric fluidized bed reactor technique. Gasification of 'as received' and torrefied olive kernels were investigated in a lab-scale bubbling fluidized bed gasifier, operating at up to 3.2 kg/h. The effect of bed temperature between 550 and 750 °C in 50 °C increments on the gasification product gas at mass-based equivalence ratios of 0.15 and 0.2 was studied. To explore the potential of torrefied biomass, the gasification results were compared to that of the 'as received' biomass. The product gas from torrefied biomass produced higher H 2 , CO and CH 4 concentrations at identical oxidant flow rates in addition to higher cold gas efficiency and higher product gas heating value. The influence of equivalence ratio in gasification was also investigated at reactor temperatures of 750 °C and five equivalence ratios (0.15, 0.2, 0.25, 0.3, and 0.35). The results revealed that the torrefied biomass has the highest HHV at an equivalence ratio of 0.2 with a value of 6.09 MJ/Nm 3 , while 'as received' biomass 4.72 MJ/Nm 3 . Kinetic experiments under isothermal conditions were performed for the gasification of the materials in continuous mode. A mass balance model was successfully used to provide the capability of separately determining the rate constant of the reactions taking place. The kinetic parameters were calculated by a first order reaction model giving activation energies for 'as received' olive kernels of 84 kJ/mol and for torrefied olive kernels of 106 kJ/mol.

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Section: Gasification Proceduresmentioning

confidence: 99%

Kinetics and Performance of Raw and Torrefied Biomass in a Continuous Bubbling Fluidized Bed Gasifier

Al-Farraji

Marsh

Steer

et al. 2017

Waste Biomass Valor

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“…The weight variation in TGFBR during the pyrolysis process was recorded online with the weighing indicators at 1 s time intervals. According to Choi et al [29], bed particles should have terminal velocities larger than the superficial gas velocity to prevent elutriation loss of bed material. Therefore, during this study the superficial velocity was kept much lower than the terminal velocity (0.89 m/s) and accordingly no significant losses of bed material were measured (\0.1 %) with the load cell.…”

Section: Fluidised Bed Reactor Thermogravimetric Analysis (Tgfbr)mentioning

confidence: 99%

A Comparison of the Pyrolysis of Olive Kernel Biomass in Fluidised and Fixed Bed Conditions

Al-Farraji

Marsh

Steer

2016

Waste Biomass Valor

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The use of thermogravimetric analysis to describe biomass kinetics often uses bench top thermogravimetric analyser (TGA) analysers which are only capable of low heating rates. The aim of this research was to compare experimental fast pyrolysis of Olive kernels in a bespoke laboratory thermogravimetric fluidised bed reactor (TGFBR) characterised by rapid heating rates at high flow rates, compared to a smaller bench scale fixed bed TGA system. The pyrolysis in the TGFBR was analysed by using the isothermal kinetic approach and it was theorised that the pyrolysis decomposition reactions occurred by two mechanisms depending on the temperature, resulting in an activation energy of 67.4 kJ/mol at temperatures below \500°C and 60.8 kJ/mol at temperatures [500°C. For comparison, a bench scale TGA was used to look at the thermal behaviour in different fixed bed thermal conditions giving a higher activation energy of 74.4 kJ/mol due to the effect of external particle gas diffusion. The effect of biomass particle size (0.3-4.0 mm) on the conversion of biomass at different temperatures, was investigated between 300 and 660°C in the TGFBR. The results suggested inhibition of internal gas diffusion was more important at lower temperatures, but in comparison had no significant effect when measured in the fixed bed TGA at lower heating rates. Bench top TGA analysis of pyrolysis is a rapid and valuable method, but is limited by smaller sample sizes and lower heating rates. In comparison, the conditions encountered with the laboratory scale TGFBR are more likely to be relevant to larger scale systems where heat distribution, heat transfer and mass diffusion effects play major roles in the reactivity of biomass.

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“…Furthermore, the entire bed, especially the emulsion phase, expands due to the breakup of larger bubbles or voids into smaller ones. In addition, the fine particles can be entrained easily and the elutriation of coarse particles is enhanced by Ž the motion of fine particles Geldart and Pope, 1983;Choi et . al., 2001;Helland et al, 2001 .…”

confidence: 99%

Bed nonhomogeneity in turbulent gas‐solid fluidization

Warsito

Fan

2003

AIChE Journal

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The effect of fine particles on elutriation of coarse particles in a gas fluidized bed

Cited by 37 publications

References 6 publications

Kinetics and Performance of Raw and Torrefied Biomass in a Continuous Bubbling Fluidized Bed Gasifier

Kinetics and Performance of Raw and Torrefied Biomass in a Continuous Bubbling Fluidized Bed Gasifier

A Comparison of the Pyrolysis of Olive Kernel Biomass in Fluidised and Fixed Bed Conditions

Bed nonhomogeneity in turbulent gas‐solid fluidization

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