Experiments and computational particle fluid dynamics simulations of biomass gasification in an air-blown fluidized bed gasifier

Timsina, Ramesh; Thapa, Rajan Kumar; Moldestad, Britt Margrethe Emilie; Eikeland, Marianne Sørflaten

doi:10.2495/eq-v5-n2-102-114

Cited by 4 publications

(8 citation statements)

References 21 publications

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“…The studied BFB gasifier is based on the experimental study. 27 The height of the cylindrical fluidized bed reactor is 1000 mm, with a diameter of 100 mm. Biomass is laterally introduced into the reactor from a square inlet that measures a vertical distance from reactor bottom of 230 mm.…”

Section: Numerical Setupmentioning

confidence: 99%

“…For simplicity, the generation and cracking of tar are not considered, and this assumption is not expected to have a significant impact on the final results 26 . Through elemental and proximate analyses of biomass in the experiment, 27 the specific mass fractions of each gas component in the volatile fraction can be determined. The process and its reaction rates are outlined as follows.

DryBiomass \to a_{1} CO + a_{2} {italicCO}_{2} + a_{3} H_{2} + a_{4} {italicCH}_{4} + a_{5} Char + a_{6} Ash, {false\sum}_{i = 1}^{6} a_{i} = 1

R_{2} = 1.49 \times 10^{5} \exp (- 1340 / T_{s}) m_{volatile}

…”

Section: Numerical Modelmentioning

confidence: 99%

“…Part II: Validation of chemical reactionsThe current model is further validated toward chemical reactions via monitoring the yields of product gas species at the reactor outlet. By adjusting the feed rate of biomass feedstock, three sets of validations with experiment and simulation27 are obtained, shown in Figure2. The validation data for gas molar fraction is derived by averaging the entire cross-section of the gasifier outlet over the last 5 s. The results reveal that the current model can well predict mole fraction of product gas during biomass gasification.…”

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confidence: 99%

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Insights of rising bubble dynamics of air‐blown biomass gasification in bubbling fluidized bed gasifier

Sun,

Yang,

Bao

et al. 2024

AIChE Journal

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Understanding the complex dynamics and spatial distribution of rising bubbles in fluidized bed gasifiers is crucial for designing, optimizing, and scaling up of the reactor. However, existing studies on bubble dynamics mainly focused on cold flow investigations, failing to capture the behavior of bubbles under the influence of chemical reactions and intricate coupling of heat transfer. Therefore, a reactive Lagrangian model is established to explore intricate bubble behaviors during biomass air gasification. The model is well validated with experiment, and the impact of operating parameters including bed temperature and equivalence ratio (ER) on the bubble behaviors is studied. The growth, coalescence, break, and eruption of rising bubbles are studied. A lower ER is recommended for better gasification performance. With an increase in the ER from 0.12 to 0.3, both the lower heating value and combustible gas concentration experienced a decrease of approximately 38.5% and 38.3%, respectively. The lateral feeding of biomass leads to asymmetrical distribution of bed temperature and bubble properties. Near the biomass inlet, a larger bubble aspect ratio is observed, possibly attributed to the hindrance in the lateral bubble growth due to the lateral biomass feeding. The bubble coordinate number is introduced to characterize the degree of bubble distribution density in a specific region. It is found that increasing the operating temperature results in a reduction in the density and an increase in the volume of bubbles at the bottom, resulting in a denser distribution of bubbles in this region. Although this concentrated bubble distribution may impact local heat and mass transfer, the differences in bubble distribution under temperature dominance gradually decrease along the reactor height. The impact of the operating conditions on the thermal properties and spatial distribution of bubbles obtained in this work can provide valuable guidance for practical gasification operations.

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Section: Numerical Setupmentioning

confidence: 99%

DryBiomass \to a_{1} CO + a_{2} {italicCO}_{2} + a_{3} H_{2} + a_{4} {italicCH}_{4} + a_{5} Char + a_{6} Ash, {false\sum}_{i = 1}^{6} a_{i} = 1

R_{2} = 1.49 \times 10^{5} \exp (- 1340 / T_{s}) m_{volatile}

…”

Section: Numerical Modelmentioning

confidence: 99%

mentioning

confidence: 99%

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Insights of rising bubble dynamics of air‐blown biomass gasification in bubbling fluidized bed gasifier

Sun,

Yang,

Bao

et al. 2024

AIChE Journal

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“…Computational Particle Fluid Dynamics (CPFD) modeling is used to simulate the bubbling fluidized bed gasifier reactor at the University of South-Eastern Norway, with the goal of mesh sensitivity analysis to find the optimal number of grid cells to achieve accurate results. The CPFD hydrodynamic model has been validated against the results of Timsina's experiment for wood chips as biomass air gasification at 1000 K (Timsina et al, 2020) by A. Samani (A. Samani et al, 2022).…”

Section: Cpfd Simulation Set-upmentioning

confidence: 99%

“…The rest of the physical and operational conditions used in the simulations are represented in Tab. 2 (Timsina et al, 2020). In Barracuda, the Wen-Yu model takes into account the particle packing by including a dependence on the fluid volume fraction in addition to the single particle drag models upon which it is based.…”

Section: Cpfd Simulation Set-upmentioning

confidence: 99%

Eulerian-Lagrangian simulation of air-steam biomass gasification in a bubbling fluidized bed gasifier

Samani¹,

Eikeland²

2022

Linköping Electronic Conference Proceedings

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To numerically study biomass gasification in a three-dimensional bubbling fluidized bed, a CFD-DEM (computational fluid dynamics – discrete element method) model with heat transfer and homogeneous and heterogeneous chemical reactions is implemented. An ideal reactor model is used for the air-steam bubbling fluidized bed (BFB) gasification reactor assuming perfectly mixed solids and plug flow. A validated computational particle fluid dynamics (CPFD) model has been applied to investigate the sensitivity analysis of mesh grids as well as to find the optimum number of grids. The result shows that 7452 grid cells are the optimal number of cells for the existence BFB gasifier. The effects of key process operating parameters such as steam to biomass ratio (SB), as well as temperature shows that by enhancing the SB ratio or reactor temperature, gas yields increase. H2 and CO2 concentrations promote by increasing the steam to biomass ratio while CO and CH4 production drop. The optimal value of SB for the gasification process can be found in the range of 0.3 to 1.

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Computational particle fluid dynamics simulation of biomass gasification in an entrained flow gasifier

Timsina

Thapa

Moldestad

et al. 2021

Chemical Engineering Science: X

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Experiments and computational particle fluid dynamics simulations of biomass gasification in an air-blown fluidized bed gasifier

Cited by 4 publications

References 21 publications

Insights of rising bubble dynamics of air‐blown biomass gasification in bubbling fluidized bed gasifier

Insights of rising bubble dynamics of air‐blown biomass gasification in bubbling fluidized bed gasifier

Eulerian-Lagrangian simulation of air-steam biomass gasification in a bubbling fluidized bed gasifier

Computational particle fluid dynamics simulation of biomass gasification in an entrained flow gasifier

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