Investigation of the segregation and mixing behavior of biomass in a bubbling fluidized bed reactor using a CPFD model

Jaiswal, Rajan; Furuvik, Nora Cecilie Ivarsdatter; Thapa, Rajan Kumar; Moldestad, Britt Margrethe Emilie

doi:10.3384/ecp20170164

Cited by 2 publications

(3 citation statements)

References 9 publications

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“…Furthermore, the lift force exerted by the gas bubbles that envelops the biomass during devolatilization transports the lower-density and larger-size biomass to the surface of the bed [8,9]. The segregation of biomass is more intense in the case of on-bed feed as the biomass tends to remain on the surface of the bed, increasing the residence time.…”

Section: Introductionmentioning

confidence: 99%

A CPFD model to investigate the influence of feeding positions in a gasification reactor

Jaiswal¹,

Furuvik²,

Thapa³

et al. 2020

Int. J. EQ

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The efficiency of a gasification process is directly related to the rate of biomass conversion into product gas. The rate of fuel conversion depends on the interaction of fuel with the bed material, the gasifying agent, and the residence time of fuel particles. The interactions and the residence time depend on the fuel feeding positions along the height of the reactor. Thus, the fuel feeding position in a gasification reactor is an important parameter that influences the efficiency of the gasification process; longer residence time of the fuel particles in the bed enables efficient carbon conversion and less tar formation. In this work, in-bed and on-bed feed positions of the fuel particles have been investigated using a computational particle fluid dynamics (CPFD) model. The model is developed and validated against experimental data obtained from a bubbling fluidized bed gasification reactor. Experiments were carried out in a 20 kW pilot scale bubbling fluidized bed gasification reactor. Wood pellets of 3-30 mm length and 5 mm diameter are fed into the reactor at a mass flow rate of 2.4 kg/h. The molar flow rate of the producer gas, which typically consists of CH 4 , CO, CO 2 , and H 2 for both the in-bed and on-bed cases, is calculated by the CPFD model. The results show that CO and CH 4 concentrations increase in the product gas when the biomass is fed at the location near to the bottom of the bed, while CO 2 and H 2 increase in the case of on-bed feed. The fuel particles segregate, followed by partial combustion of the smaller fuel particles on the bed surface in the case of on-bed feed. The total mass of the bed including unreacted char is higher for on-bed feed, indicating that the char is consumed slowly. The CPFD model can predict the product gas compositions, the fuel conversion, changes in the bed hydrodynamics, and the product gas yield at different feeding positions of the fuel particles. Thus, the model can be useful for design purposes.

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Section: Introductionmentioning

confidence: 99%

A CPFD model to investigate the influence of feeding positions in a gasification reactor

Jaiswal¹,

Furuvik²,

Thapa³

et al. 2020

Int. J. EQ

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“…The total heat content of the system increased with increased bed height. When the grass pellets are injected into the reactor at fluidizing conditions, the fuel particles first sink downwards in the bed and then tends to move upward due to densities differences (Jaiswal, 2019;Agu, 2019). The increase in bed height allows the fuel particles to interact with the heated bed material and the fluidizing gas for a longer time when the contact area is increased.…”

Section: Effect Of Static Bed Heightmentioning

confidence: 99%

“…Gasification using fluidized bed has been considered as an flexible technology that can use a wide range of fuels. Fluidized beds provide major advantages such as uniform mixing and heat transfer (Jaiswal, 2018;Jaiswal, 2019), which enables efficient conversion of carbonaceous solid into product gases. The feedstock to the gasifier has to be cheaper and more flexible in order to make the process economically sustainable.…”

Section: Introductionmentioning

confidence: 99%

Study of agricultural waste gasification in an air-blown bubbling fluidized bed using a CPFD model

Jaiswal¹,

Thapa²,

Moldestad³

2021

Linköping Electronic Conference Proceedings

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Gasification using a fluidized bed is a promising technology to convert agricultural residues into product gases. In this work, the syngas production potential from agricultural waste (grass pellets) is studied using a Computational Fluid Dynamic (CPFD) model. The CPFD model is developed in a simulation software Barracuda virtual reactor and validated against the experimental data. Experiments are carried out in a 20 kW bubbling fluidized bed gasification reactor that operates with air as fluidizing gas. Grass pellets of size 5mm-30 mm in length and diameter of 5mm are used as the feed. The CPFD model considers the hydrodynamics of the gas-solid phase and reaction kinetics involved. Influence of the static bed height, bed temperature, and air to fuel ratio on the product gas composition (4 , , 2 , 2) and char conversion efficiency are investigated. Initial bed heights of 200 mm and 300 mm are used for the analysis. Biomass is fed at 2.46 /ℎ while the air supplied is varied to obtain the air to fuel ratio at 0.4, 0.6, 0.8, 1, and 1.2. The result shows that the increase in bed height has a significant effect on the reactor temperature but very small effect on the product gas composition and char conversion rate. An increase in bed temperature from 600℃ to 800℃ improves the gasifier performance in terms of maximum product gases yield and enhanced char conversion rate. Increase in the air to fuel ratio from 0.4-1.2 reduces the 4 , , 2 fractions in the product gas and increases the 2 concentration. The results obtained from the CPFD model are in good agreement with the experimental results and literature data. Thus, the CPFD model developed in this work can be utilized to optimize the gasification reactor used in a lab and industrial scale.

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Investigation of the segregation and mixing behavior of biomass in a bubbling fluidized bed reactor using a CPFD model

Cited by 2 publications

References 9 publications

A CPFD model to investigate the influence of feeding positions in a gasification reactor

A CPFD model to investigate the influence of feeding positions in a gasification reactor

Study of agricultural waste gasification in an air-blown bubbling fluidized bed using a CPFD model

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