Method of identifying an operating regime in a bubbling fluidized bed gasification reactor

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

doi:10.2495/eq-v5-n1-24-34

Cited by 6 publications

(5 citation statements)

References 8 publications

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“…Mixing of the fuel particles can be enhanced by increasing the superficial gas velocity. However, for maximum gasifier efficiency and provided air to fuel ratio, the increment of superficial gas velocity is limited to operate the gasifier in a specified operating regime [16].…”

Section: Bed Hydrodynamicsmentioning

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: Bed Hydrodynamicsmentioning

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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“…Figure 1 represents the generated grid of the cold flow lab scaled fluidized bed unit. consistency with experimental results (Jaiswal et al, 2020;, the Wen-Yu drag model has been chosen for the simulations of this study. The fluid drag force on the particle can be calculated by…”

Section: Procedures To Implement the Cpfd Modelmentioning

confidence: 97%

CPFD simulation of enhanced cement raw meal fluidization through mixing with coarse, inert particles

Samani¹,

Jayarathna²,

Tokheim³

2021

Linköping Electronic Conference Proceedings

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In the current work, computational particle and fluid dynamics (CPFD) simulations are used to study an electrically heated bubbling fluidized bed (BFB) used as a calciner in a cement manufacturing process, applying a binary-particle fluidization system. Owing to the fine particle size (0.2-180 µm) of the limestone used as a raw meal in the cement kiln process, a conventional bubbling fluidized bed may be difficult to apply due to particle cohesion causing poor fluidizability of the particles smaller than 30 µm. In the current study, to enhance the fluidization of the raw meal particles, they are mixed with coarse (550-800 µm), inert particles. The aggregation and clustering of the fine particles will decrease due to collisions with inert coarse particles, and hence a more homogeneous distribution of raw meal particles may be achieved. The inert particles will also provide a thermal energy reservoir through their heat capacity and thereby contribute to a very stable bed temperature, which is advantageous in the control of the process. After the raw meal particles have been calcined, they have to be separated from the coarse, inert particles. This can be done by increasing the velocity of the CO2 used for fluidization to a value sufficiently high to entrain the raw meal particles, but still sufficiently low that the coarse, inert particles are not entrained. The commercial CPFD software Barracuda was used for simulations to investigate suitable operational conditions at 1173 K, such as the particle size distribution of the inert particles and the fluidization gas velocity. The impact of gas velocity variation on the fluidization of the particle mixture was studied, and an appropriate range of velocities for the calcination and entrainment modes could be determined. The simulations revealed that mixing raw meal particles with inert coarse particles can enhance the flowability in the FB reactor indicating that it is possible to apply the concept in a full-scale calcination process.

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“…Several in-built drag models are available in the Barracuda package, and detailed information about different drag models with references are discussed in the Barracuda manual [5]. Previous results from CPFD simulations of bubbling fluidized bed gasifiers have shown a good agreement with experimental data when the Wen-Yu drag model was used [6][7][8]. Furthermore, simulations of CFB systems [4,9] have also shown better results with Wen-Yu/Ergun drag model, and therefore it was used in this study.…”

Section: Development Of a Cpfd Modelmentioning

confidence: 99%

Experimental and computational studies of circulating fluidized bed

Moradi¹,

Samani²,

Mojarrad³

et al. 2020

Int. J. EQ

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Biomass gasification represents an efficient process for the production of power, heat and biofuels. Different technologies are used for gasification and this article focuses on a circulating fluidized bed (CFB) system. Understanding the behaviour of particles is of primary importance and a cold flow CFB experimental unit was constructed and tested. The particle circulation rate is greatly affected by the loop seal performance, and therefore the loop seal should be properly optimized to maintain an uninterrupted operation. Smooth flow regimes were obtained for the CFB by varying the loop seal aeration rates. Particles with size 850-1000 µm and 1000-1180 µm were chosen for the experiments. The minimum flow rates of air into the riser for the two particle sizes were found to be 1.3 and 1.5 Sm 3 / min, respectively. To obtain a smooth flow regime, a velocity range for aeration in the loop seal was found for the two particle sizes. Based on the experimental results, combinations of flow rates were suggested for the simulations. A Computational Particle Fluid Dynamic (CPFD) model was developed using Barracuda VR, and the model was validated against experimental results. The simulated results for the system regarding the pressure and the height of the bed material in the standpipe agreed well with the experimental results. The deviation between the experimental and computational pressure was less than 0.5% at all the locations for both the particle sizes. The deviation in particle level was about 6% for the 850-1000 µm particles and 17% for the 1000-1150 µm particles. Both the experiments and the simulations predicted that a small fraction of the circulating sands are emitted from the top of the rig. The validated CPFD model was further used to predict the flow behaviour and the particle circulation rate in the CFB.

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Method of identifying an operating regime in a bubbling fluidized bed gasification reactor

Cited by 6 publications

References 8 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

CPFD simulation of enhanced cement raw meal fluidization through mixing with coarse, inert particles

Experimental and computational studies of circulating fluidized bed

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