CFD Analysis of the Fluidised Bed Hydrodynamic Behaviour inside an Isothermal Gasifier with different Perforated Plate Distributors

Al-Akaishi, Ahmed; Valera‐Medina, Agustin; Chong, CT; Marsh, Richard

doi:10.1016/j.egypro.2017.12.134

Cited by 11 publications

(7 citation statements)

References 15 publications

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“…The holes had a triangular configuration with 6.28 mm pitch. Al-Akaishi et al [22] reported that distributor plates with triangular hole arrangement has a better performance than square arrangement because it allows better fluidization performance as a result of better flow distribution. A screen mesh of size 75 µm was used to prevent silting of the silica sand particles to the plenary chamber and retain the solid particles in the fluidized bed.…”

Section: Experimental Setup and Methodsmentioning

confidence: 99%

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Numerical and Experimental Investigation of Fluidized Bed Hydrodynamics at Elevated Temperatures

Njuguna

Ndiritu

Gathitu

et al. 2023

JERA

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Fluidized bed gasifiers operate at elevated temperatures, and experimental measurements for the hydrodynamic parameters at high temperatures are difficult and time consuming, making computational fluid dynamics simulation useful for such investigation. In this study, Opensource computational fluid dynamics code, OpenFOAM, was used to investigate temperature effect on the fluidized bed hydrodynamics on a 3D fluidized bed model using Eulerian-Eulerian approach. Silica sand of particle sizes of 500, 335 and 233 m was used as the bed materials under temperatures between 25 and 400 °C. To validate the simulation model, a laboratory scale fluidized bed unit was used to conduct experiments for the same range of temperature and sand particle sizes. The results revealed that the temperature of the bed materials greatly affect fluidized bed hydrodynamics. The minimum fluidization velocity increased with the sand particle diameter but decreased with the temperature. On the other hand, the bed porosity at the minimum fluidization point increased marginally with both the temperature and the particle size of the bed materials. Further analysis showed that the expanded bed height increased with the temperature for a specific superficial velocity while the bubbles grew in size with both the air flow rates and the temperature. The numerical model results were compared with the experimental results based on minimum fluidization velocity, bed porosity and pressure drop at the minimum fluidization point. The hydrodynamic results of the numerical model were in good agreement with the experimental results.

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Section: Experimental Setup and Methodsmentioning

confidence: 99%

“…Before the simulation was run, grid independence was studied to determine its effect on the simulation results. Three grid sizes were studied for the pressure along the bed height and the time averaged bed porosity, which are important fluidization parameters [22]. Fig.…”

Section: Simulation Model Boundary Conditions and Proceduresmentioning

confidence: 99%

Numerical and Experimental Investigation of Fluidized Bed Hydrodynamics at Elevated Temperatures

Njuguna

Ndiritu

Gathitu

et al. 2023

JERA

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show abstract

“…In a fluidized bed gasifier, to check the hydrodynamics of gas-solid mixtures and particles-gas and particleparticle contact mechanisms, four different perforated plate distributors with rectangular and triangular arrangements with different holes and pitches were studied. As a result of the bubble formation, pressure drop and superficial velocity, the type D distributor, i.e., triangular, was the best distributor among the other types [30].…”

Section: Introductionmentioning

confidence: 99%

Optimizing Design and Operational Parameters for Enhanced Mixing and Hydrodynamics in Bubbling Fluidized Bed Gasifiers: An Experimental and CFD-Based Approach

et al. 2023

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An experimental investigation of hydrodynamics of gas-solid flow is carried out by engaging different designs of air distributor plates. An analysis of three different plates, i.e., perforated, 45° slotted and novel hybrid plate, revealed the difference in pressure drop and minimum fluidization velocities (Umf) for varying input operational variables. Umf is found to be lowest for perforated and highest for 45° slotted plate, whereas pressure drop is found to be highest for 45° slotted plate and lowest for novel hybrid distributor plate. The bubbles rise velocity ratio (Umf,b/Umf,f) is noticed minimum for 45° slotted plate due to relatively larger bubbles originating from the bigger slot openings and maximum for perforated distributor plate owing to smaller bubbles with dominant axial rise. Furthermore, the bed height rise ratio (h/L) is observed as a minimum for perforated distributor and maximum for 45° slotted plate due to larger bubbles through 45° slots rupturing the bed surface, causing more bed expansion. Furthermore, CFD analysis is also carried out to observe the insight flow dynamics using the distributor plates. The simulations use a two-fluid model (TFM) and K-Epsilon turbulence models. CFD model shows promising results in agreement with the experimental results. CFD results revealed that the lower portion enhanced lateral dispersion/mixing of solid particles due to 45° angular openings of an air inlet. In contrast, the perforated plate exhibited a straight upward motion of small air bubbles, causing no radial/lateral mixing. CFD results for the hybrid plate show the mixed axial as well as lateral mixing of solids by revealing velocity distribution; therefore, the novel hybrid plate is found to be an optimum distributor plate due to its lowest pressure drop, adequate Umf, intermediary bed height rise ratio and moderate bubble rise velocity ratio across the bed.

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“…It was revealed that as the plenum volume decreased, the bubbling frequency for a single-orifice distributor increased. Al-Akaishi et al (2017) have incorporated a discrete phase model (DPM) with a multiphase particle in cell method (MPPIC) as a numerical approach. Four different perforated plate distributors were used to study the effect of configuration on the fluidized bed's hydrodynamics.…”

Section: Introductionmentioning

confidence: 99%

Computational Analysis of the Hydrodynamic Behavior for Different Air Distributor Designs of Fluidized Bed Gasifier

et al. 2021

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Fluidized bed gasification has proven to be an appropriate technique for converting various biomass feedstocks into helpful energy. Air distributor plate design is one of the critical factors affecting the thermochemical conversion performance of fluidized bed gasifiers. The present study is proposed to investigate the mixing pattern and pressure drop across different configurations of air distributors using a two-fluid model (TFM) of finite volume method-based solver ANSYS FLUENT. The pressure drop across the bed and mixing pattern have been investigated through qualitative and quantitative analysis of CFD results using three diverse distributor plate designs: perforated plate, 90° slotted plate, and 45° swirling slotted plate. The pressure drop by employing the perforated distributor plate reveals the highest pressure drop due to the smallest open area ratio. However, the pressure drop in the case of 90° slotted plate is found to be 7% and 4% lesser than perforated and 45° slotted plate respectively due to a smaller velocity head developed through the wider open area of the straight slotted plates. The distributor design configuration having a 45° slotted plate exhibits considerable pressure drop compared to the 90° slotted plate due to the longer path length of the slot. Numerical pressure drop results across the bed with different types of distributor plates prove reasonable agreement with the experimental results available in the literature. Mixing behavior in perforated distributor plates exhibits lower portion solid volume fraction of around 0.58. However, it falls rapidly as go up the riser (7.7% of column height); 90° slotted plate shows bottom region solid volume fraction of around 0.5. In addition, it exhibits an even broader range of sand volume fraction and column height (13.46% of column height). Finally, the 45° distributor plate reveals the highest range of volume fraction through the riser height (17.3% of column height), indicating the better mixing characteristics of the fluidized zone.

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CFD Analysis of the Fluidised Bed Hydrodynamic Behaviour inside an Isothermal Gasifier with different Perforated Plate Distributors

Cited by 11 publications

References 15 publications

Numerical and Experimental Investigation of Fluidized Bed Hydrodynamics at Elevated Temperatures

Numerical and Experimental Investigation of Fluidized Bed Hydrodynamics at Elevated Temperatures

Optimizing Design and Operational Parameters for Enhanced Mixing and Hydrodynamics in Bubbling Fluidized Bed Gasifiers: An Experimental and CFD-Based Approach

Computational Analysis of the Hydrodynamic Behavior for Different Air Distributor Designs of Fluidized Bed Gasifier

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