Minimum Air Fluidization Velocity Study of Specific 2-D Bubbling Fluidized Bed Reactor

Research on the thermodynamic behavior of sand beds was carried out using a commercial computational dynamic package. The work involved simulating, with the use of the Ergun equation, the air flow through a two-dimensional bubbling bed reactor to predict the bed character whilst considering the major effective function (particle size, particle density, bed height and reactor width). The Minimum Fluidization Velocity (Umf) values were then calculated before the optimum value of Umfneeded to ensure a workable Bubbling Fluidize Bed Combustor (BFBC) system. The effects of using different Umfvalues on the flow behavior were also investigated using the numerical approach at different times. The results from these investigations indicate that the bubbling region in the fluidized bed combustion can be correlated to the sand bed expansion with minimum errors and assist in enhancing the combustion efficiency by supplying the required volume of oxygen into the system.

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Three phase Eulerian-granular model applied on numerical simulation of non-conventional liquid fuels combustion in a bubbling fluidized bed

Thermal Science ◽

10.2298/tsci151025196n ◽

2016 ◽

Vol 20 (suppl. 1) ◽

pp. 133-149

Author(s):

Stevan Nemoda ◽

Milica Mladenovic ◽

Milijana Paprika ◽

Aleksandar Eric ◽

Borislav Grubor

Keyword(s):

Fluidized Bed ◽

Fluid Dynamic ◽

Numerical Procedure ◽

Combustion Efficiency ◽

Liquid Fuels ◽

Chemical Components ◽

Fluidized Bed Combustion ◽

Bubbling Fluidized Bed ◽

Energy Equations ◽

Kinetic Gas Theory

The paper presents a two-dimensional CFD model of liquid fuel combustion in bubbling fluidized bed. The numerical procedure is based on the two-fluid Euler-Euler approach, where the velocity field of the gas and particles are modeled in analogy to the kinetic gas theory. The model is taking into account also the third - liquid phase, as well as its interaction with the solid and gas phase. The proposed numerical model comprise energy equations for all three phases, as well as the transport equations of chemical components with source terms originated from the component conversion. In the frame of the proposed model, user sub-models were developed for heterogenic fluidized bed combustion of liquid fuels, with or without water. The results of the calculation were compared with experiments on a pilot-facility (power up to 100 kW), combusting, among other fuels, oil. The temperature profiles along the combustion chamber were compared for the two basic cases: combustion with or without water. On the basis of numerical experiments, influence of the fluid-dynamic characteristics of the fluidized bed on the combustion efficiency was analyzed, as well as the influence of the fuel characteristics (reactivity, water content) on the intensive combustion zone.

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Effects of Different Granular Viscosity Models on the Bubbling Fluidized Bed - A Numerical Approach

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.393.857 ◽

2013 ◽

Vol 393 ◽

pp. 857-862

Author(s):

M.I. Hilmee ◽

Mohan Sinnathambi Chandra ◽

Saravanan Karuppanan ◽

M. Fadhil ◽

Mohd Rizal Lias

Keyword(s):

Pressure Drop ◽

Fluidized Bed ◽

Granular Flow ◽

Simulation Models ◽

Numerical Approach ◽

Ansys Fluent ◽

Viscosity Models ◽

Simulation Based ◽

Bubbling Fluidized Bed ◽

Bed Expansion

Kinetic Theory of Granular Flow (KTGF) has been successfully incorporated and widely implemented in the Eulerian simulation models in many multiphase cases. The KTGF theory involves many parameters and is applied in the multiphase simulation for the purpose of hydrodynamic properties modeling of the granular phase. This paper is focused on granular viscosity which is a parameter in the KTGF that incorporates three different viscosities arising from the inter-phase and intra phases interaction in a bubbling fluidized bed (BFB). The 2D BFB model of 0.2 m width and 0.8 m length having a 13-hole orifice plate has been modeled for this purpose. The model was constructed using Gambit software version 2.4.6 and then simulated using ANSYS Fluent version 14. Two models of granular viscosity, namely Syamlal-Obrien model and Gidaspow model, were compared based on its effect to the pressure drop and bed expansion of the BFB. The results depicted that the simulation based on Syamlal-Obrien model tends to produce larger bubbles and contributing to a higher pressure drop across the distributor plate as compared to the Gidaspow model.

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Biomass Ash – Bed Material Interactions Leading to Agglomeration in FBC

17th International Conference on Fluidized Bed Combustion ◽

10.1115/fbc2003-150 ◽

2003 ◽

Cited By ~ 5

Author(s):

H. J. M. Visser ◽

S. C. van Lith ◽

J. H. A. Kiel

Keyword(s):

Coating Thickness ◽

Problem Area ◽

Critical Conditions ◽

Fluidized Bed Combustion ◽

Biomass Ash ◽

Fundamental Study ◽

Fluidization Velocity ◽

Bubbling Fluidized Bed ◽

Bed Agglomeration ◽

Bed Material

In (bubbling) fluidized-bed combustion and gasification of biomass, several potential problems are associated with the inorganic components of the fuel. A major problem area is de-fluidization due to bed agglomeration. The most common found process leading to de-fluidization in commercial-scale installations is “coating-induced” agglomeration. During reactor operation, a coating is formed on the surface of bed material grains and at certain critical conditions (e.g., coating thickness or temperature) sintering of the coatings initiates the agglomeration. In an experimental approach, this work describes a fundamental study on the mechanisms of de-fluidization. For the studied process of bed de-fluidization due to sintering of grain-coating layers, it was found that the onset of the process depends on: a) a critical coating thickness, b) on the fluidization velocity when it is below approx. four times the minimum fluidization velocity and c) on the viscosity (stickiness) of the outside of the grains (coating).

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Improved models for predicting bubble velocity, bubble frequency and bed expansion in a bubbling fluidized bed

Chemical Engineering Research and Design ◽

10.1016/j.cherd.2018.11.002 ◽

2019 ◽

Vol 141 ◽

pp. 361-371 ◽

Cited By ~ 12

Author(s):

Cornelius Emeka Agu ◽

Lars-Andre Tokheim ◽

Marianne Eikeland ◽

Britt M.E. Moldestad

Keyword(s):

Fluidized Bed ◽

Bubble Velocity ◽

Bubble Frequency ◽

Bubbling Fluidized Bed ◽

Bed Expansion

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Bubbling fluidized bed combustion of Syncrude coke

10.4095/304362 ◽

1987 ◽

Cited By ~ 2

Author(s):

E J Anthony ◽

H A Becker ◽

R K Code ◽

R W McCleave ◽

J R Stephenson

Keyword(s):

Fluidized Bed ◽

Fluidized Bed Combustion ◽

Bubbling Fluidized Bed

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Fate of bromine and chlorine in bubbling fluidized bed combustion – Formation of alkali halide aerosols

Fuel ◽

10.1016/j.fuel.2014.03.026 ◽

2014 ◽

Vol 128 ◽

pp. 390-395 ◽

Cited By ~ 6

Author(s):

Hao Wu ◽

Tor Laurén ◽

Patrik Yrjas ◽

Pasi Vainikka ◽

Mikko Hupa

Keyword(s):

Fluidized Bed ◽

Alkali Halide ◽

Fluidized Bed Combustion ◽

Bubbling Fluidized Bed

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Retrofitting 25T/h Pulverized Coal-Fired Boiler Into 35T/h Circulating Fluidized Bed Boiler for Burning Mixture of Coal and Bagasse

18th International Conference on Fluidized Bed Combustion ◽

10.1115/fbc2005-78041 ◽

2005 ◽

Author(s):

Han-Ping Chen ◽

Xian-Hua Wang ◽

Shi-Hong Zhang ◽

De-Chang Liu ◽

Yu-Hua Lai ◽

...

Keyword(s):

Fluidized Bed ◽

Circulating Fluidized Bed ◽

Combustion Efficiency ◽

Economic Benefits ◽

Pulverized Coal ◽

Industrial Wastes ◽

Pollutant Emission ◽

Fluidized Bed Combustion ◽

Circulating Fluidized Bed Boiler ◽

Combustion Technology

In China, there are a large number of pulverized coal-fired industrial boilers, whose steam capacities are usually relatively small. These boilers can burn only high-grade coal and have low combustion efficiency. Furthermore, the combustion emissions, such as SO2 and NOx, pollute the environment severely. Therefore it is very important and urgent to adopt economically efficient and environmentally friendly technologies to retrofit these boilers. At the same time, there are many industrial wastes, such as bagasse, wood waste, rubbish, petroleum coke and so on, need burning disposal in China. Fluidized bed combustion technology is a kind of clear combustion technology, which has many advantages, such as excellence fuel flexibility, high combustion efficiency, low pollutant emission and good turndown capability etc. So, adopting fluidized bed combustion technology, retrofitting pulverized coal-fired boiler into fluidized bed boiler can realize pure burning various wastes or co-firing with coal, which should have great economic benefits and social benefits. And the application prospect of the method is also extensive. The State Key Laboratory of Coal Combustion has successfully retrofitted a 25t/h pulverized coal-fired boiler into circulating fluidized bed boiler with in-bed tubes and downward exhaust cyclone. The retrofitted boiler can burn mixture of coal and bagasse and the steam capacity reaches 35t/h. This paper presents the retrofitting measures and the operation status of the boiler after retrofitting.

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