scholarly journals Hydrodynamics of a Novel Design Circulating Fluidized Bed Steam Reformer Operating in the Dense Suspension Upflow Regime

2014 ◽  
Vol 2014 ◽  
pp. 1-13 ◽  
Author(s):  
Moataz Bellah M. Mousa ◽  
Seif-Eddeen K. Fateen ◽  
Essam A. Ibrahim
Keyword(s):  
Fluidized Bed ◽  
Circulating Fluidized Bed ◽  
Flow Characteristics ◽  
Homogeneous Catalyst ◽  
Reactor Performance ◽  
Two Phase ◽  
Dense Suspension ◽  
Fluidization Regime ◽  
Computational Fluid Dynamics Cfd ◽  
Steam Reformers

Circulating fluidized bed steam reformers (CFBSR) represent an important alternative for hydrogen production, a promising energy carrier. Although the reactor hydrodynamics play crucial role, modeling efforts to date are limited to one-dimensional models, thus ignoring many of the flow characteristics of fluidized beds that have strong effects on the reactor efficiency. The flow inside the riser is inherently complex and requires at least two-dimensional modeling to capture its details. In the present work, the computational fluid dynamics (CFD) simulations of the hydrodynamics of the riser part of a novel CFBSR were carried out using two-phase Eulerian-Eulerian approach coupled with kinetic theory of granular flow and K-ε model. Cold flow simulations were carried under different fluidization regimes. It was found that catalyst of Geldart's type “A” particle is more efficient for flow inside the catalytic reactor and dense suspension upflow (DSU) fluidization regime yields the best homogeneous catalyst distribution in the riser and thus best reactor performance. The optimum range for catalyst flux was found to be higher than 1150 kg/m2·s for a gas flux of 6.78 kg/m2·s. It was also noted that the value of 500 Kg/m2·s for catalyst flux represents the critical value below which the riser will operate under pneumatic transport regime.

Hydrodynamic Characteristics of a Novel Circulating Fluidized Bed Steam Reformer Operating in the Fast Fluidization Regime

2011 ◽  
Vol 9 (1) ◽  
Author(s):  
Moataz Bellah M. Mousa ◽  
Seif-Eddeen K. Fateen ◽  
Essam A. Ibrahim
Keyword(s):  
Fluidized Bed ◽  
Circulating Fluidized Bed ◽  
Numerical Approach ◽  
Hydrodynamic Characteristics ◽  
Two Phase ◽  
Radial Segregation ◽  
Fluidization Regime ◽  
Computational Fluid Dynamics Cfd ◽  
Model Equations ◽  
Steam Reformers

Circulating Fluidized Bed Steam Reformers (CFBSRs) represent an important alternative for the production of syngas for the Fisher-Tropsch (FT) process and for hydrogen production. Most research regarding this novel CFBSRs did not consider its hydrodynamic characteristics. In this work, the riser Computational Fluid Dynamics (CFD) simulations were investigated using two phase Eulerian-Eulerian approach coupled with kinetic theory of granular flow with k-epsilon model to describe the turbulence of each phase. The model equations were solved via the commercial CFD package FLUENT, which uses the finite volume numerical approach. Cold flow simulations were carried out under the fast fluidization regime and results were validated qualitatively against available experimental data. The radial segregation of the catalyst, the velocity distribution of both phases and other characteristics of the flow were captured by the simulation. This work showed that for operation under high density and high flux conditions, solids flux should be higher than 300 kg/m2s and inlet void fraction lower than 85%.

The Local Heat Balance in a Stationary Fluidized-Bed Furnace Burning Biomass Fuels

2003 ◽  
Author(s):  
Fredrik Niklasson ◽  
Filip Johnsson
Keyword(s):  
Fluidized Bed ◽  
Combustion Rate ◽  
Heat Balance ◽  
Circulating Fluidized Bed ◽  
Local Heat ◽  
Splash Zone ◽  
Two Phase ◽  
Bed Temperature ◽  
Temperature Constant ◽  
The Vertical Distribution

This work investigates the influence of biomass fuel properties on the local heat balance in a commercial-scale fluidized bed furnace. Experiments with different wood based fuels were performed in the Chalmers 12 MWth circulating fluidized bed boiler, temporarily modified to run under stationary conditions. A two-phase flow model of the bed and splash zone is applied, where the combustion rate in the bed is estimated by global kinetic expressions, limited by gas exchange between oxygen-rich bubbles and a fuel-rich emulsion phase. The outflow of bubbles from the bed is treated as “ghost bubbles” in the splash zone, where the combustion rate is determined from turbulent properties. It is found that a large amount of heat is required for the fuel and air to reach the temperature of the bed, in which the heat from combustion is limited by a low char content of the fuel. This implies that a substantial fraction of the heat from combustion of volatiles in the splash zone has to be transferred back to the bed to keep the bed temperature constant. It is concluded that the moisture content of the fuel does not considerably alter the vertical distribution of heat emitted, as long as the bed temperature is kept constant by means of flue gas recycling.

Effect of elevated pressure on gas-solid flow characteristics in a circulating fluidized bed

2020 ◽  
Vol 366 ◽  
pp. 470-476 ◽  
Author(s):  
Daoyin Liu ◽  
Jinding Hu ◽  
Jialong Song ◽  
Cai Liang ◽  
Chuanlong Xu ◽  
...  
Keyword(s):  
Fluidized Bed ◽  
Circulating Fluidized Bed ◽  
Flow Characteristics ◽  
Elevated Pressure ◽  
Solid Flow

Liquid-Solid Coupling Characteristics in the Fluidized Bed Evaporator for Tobacco Refined Liquid

2014 ◽  
Vol 686 ◽  
pp. 522-528
Author(s):  
Feng Lan Wang ◽  
Yuan Jun Yao ◽  
Fa Yun Gong ◽  
Fang Ping Ye ◽  
Wen Jie Qi
Keyword(s):  
Fluidized Bed ◽  
Flow Characteristics ◽  
Operating Conditions ◽  
Maximum Speed ◽  
Force Model ◽  
Liquid Density ◽  
Two Phase ◽  
Viscous Term ◽  
Inert Particles ◽  
Coupling Characteristics

Consider a two-phase liquid-solid coupling effect, using Euler - Euler two-fluid model is solved using standard viscous term with k-ε model and the velocity pressure coupling a simple algorithm to simulate liquid-solid two-phase flow characteristics of the fluid flow method bed, the applicability of the model to assess the drag. Different effects of a two-stage flow characteristics of fluidized bed flow characteristics, fluid and operating conditions affect the physical properties of the paper. We found from the simulation is the use of different drag coefficient models will greatly affect the results, which drag force model Syamlal - O'Brien is more suited to study the coupling characteristics of liquid flow in a fluidized bed of solid than Gidaspow. And velocity of the inert particles increase with the viscosity of the liquid increase. Further, the maximum speed of the inert particles in a fluidized bed by a central, which means the settling velocity in the fluidized bed of inert particles is the slowest; increasing liquid density and lead to increased speed of the inert particles; volume of the inert particles Score changes can also affect the speed of the particle velocity distribution, and there is no linear relationship.

Characteristics of Circulating Fluidized Bed Evaporator with Vapor-Liquid-Solid Three-Phase Flow

2012 ◽  
Vol 455-456 ◽  
pp. 1618-1626 ◽  
Author(s):  
Ji Tian Song ◽  
Jun Chi ◽  
Han Fei Zhang ◽  
Zhen Ying Liu
Keyword(s):  
Heat Transfer ◽  
Fluidized Bed ◽  
Circulating Fluidized Bed ◽  
Research Work ◽  
Correlation Equation ◽  
Evaporation Process ◽  
Two Phase ◽  
Heat Transfer Efficiency ◽  
Three Phase ◽  
Three Phase Flow

In this paper, pumpkin juice concentrations were carried out using a three-phase circulating fluidized bed evaporator. The flow and heat transfer characteristics of this evaporation process were investigated and parametric studies were conducted to identify the governing parameters in the process. It was found that compared with two-phase evaporation process, addition of inert particles improved the heat transfer efficiency by 35% and also inhibit forming and clean fouls during the pumpkin juice concentration. A correlation equation of boiling heat transfer coefficient was established for the three-phase circulating fluidized bed evaporator. This research work improves the understanding of the three-phase circulating fluidized bed evaporator and benefit to its wider application in foodstuff field.

scholarly journals Computational Fluid Dynamics of System Hydrodynamics and Erosion Behavior in Internally Circulating Fluidized Bed Reactor with Inserting Pipe

2020 ◽  
Vol 11 (11) ◽  
pp. 504-508
Author(s):  
D. Thiemsakul ◽  
◽  
R. Piemjaiswang ◽  
P. Piumsomboon ◽  
B. Chalermsinsuwan
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Fluidized Bed ◽  
Solid Particle ◽  
Circulating Fluidized Bed ◽  
Surface Region ◽  
Fluidized Bed Reactor ◽  
Erosion Behavior ◽  
Gas Leakage ◽  
Computational Fluid Dynamics Cfd

Internally circulating fluidized bed reactor (ICFB) is the system with combining the function of reactor, cyclones and loop seal of a conventional circulating fluidized bed reactor (CFB) into a single reactor column. In this type of reactor, the reactor column is separated into two sections (riser and downer) by baffles and is linked together via connecting ports. This system is then considered as compact operation when comparing with the conventional CFB reactor. However, the simplicity of the ICFB reactor is trade-off with a gas leakage which takes place between the two sections through the connecting ports. In addition, the solid particle movement inside the system can cause the erosion on the inserting pipes which are used for heating or cooling this ICFB reactor column. In this study, the system hydrodynamics and erosion behavior inside ICFB reactor with inserting pipe were investigated by computational fluid dynamics (CFD) using two-dimensional Eulerian-Eulerian model. The adjusted Gidaspow drag model was applied to compute the interaction between the gas and solid particle phases. Then, the system hydrodynamics was obtained and the wall shear stress was calculated in the existent of the erosion at the surface region of the inserting pipes. The results from this simulation were used to design the inserting pipe arrangement inside this ICFB reactor.

scholarly journals Design of a Fast Internal Circulating Fluidized-Bed Gasifier with a conical bed angle

2019 ◽  
Vol 23 (1) ◽  
pp. 33-45 ◽  
Author(s):  
Jernej Mele ◽  
Andrej Senegacnik
Keyword(s):  
Fluidized Bed ◽  
Circulating Fluidized Bed ◽  
Industrial Process ◽  
Calorific Value ◽  
Fluidization Regime ◽  
Entire Height ◽  
Proper Design ◽  
Industrial Unit ◽  
Fluidized Bed Gasifier ◽  
Set Up

The main purpose of a fast internal circulating fluidized bed gasifier is the steam reforming of solid organic matter, like biomass, to a nearly nitrogen-free syngas. The calorific value of this syngas is approximately three times higher than the gas from common air-driven gasifiers. This article deals with a study of the particle dynamics in a 1 MWt fast internal circulating fluidized bed plant and focuses on the design of the gasification reactor?s geometry. Superheated steam is used for the fluidization and gasification in the reactor. The gasification of solid fuels causes an increase in the volume flow of the fluidizing gas and at the same time also a change in the fluidization regime. Approaching a turbulent fluidization regime or even fast fluidization is not desirable. However, with the proper design of reactor, i. e., an appropriately conical bed angle, suitable gasification conditions in the form of a fluidizing regime can be achieved across the entire height of the bed. For the purposes of the experimental research, a semi-industrial unit was set-up. The process was designed and experimentally tested on a lab-scale, cold-flow model and scaled-up to a semi-industrial process. The guidelines for designing the geometry of the gasification reactor were set.

scholarly journals Systematic Study of Pressure Fluctuation in the Riser of a Dual Inter-Connected Circulating Fluidized Bed: Using Single and Binary Particle Species

Processes ◽  
2019 ◽  
Vol 7 (12) ◽  
pp. 890 ◽  
Author(s):  
Yusif A. Alghamdi ◽  
Zhengbiao Peng ◽  
Caimao Luo ◽  
Zeyad Almutairi ◽  
Behdad Moghtaderi ◽  
...  
Keyword(s):  
Fluidized Bed ◽  
Pressure Fluctuation ◽  
Circulating Fluidized Bed ◽  
Pressure Fluctuations ◽  
Single Species ◽  
Terminal Velocity ◽  
Operating Conditions ◽  
Cold Flow ◽  
Fluidization Regime ◽  
Spectrum Density

This study systematically investigates the pressure fluctuation in the riser of a dual interconnected circulating fluidized bed (CFB) representing a 10 kWth cold-flow model (CFM) of a chemical-looping combustion (CLC) system. Specifically, a single-species system (SSS) and a binary-mixtures system (BMS) of particles with different sizes and densities were utilized. The pressure fluctuation was analyzed using the fast Fourier transform (FFT) method. The effect of introducing a second particle, changing the inventory, composition (i.e., 5, 10 to 20 wt.%), particle size ratio, and fluidization velocity were investigated. For typical SSS experiments, the results were similar to those scarcely reported in the literature, where the pressure fluctuation intensity was influenced by varying the initial operating conditions. The pressure fluctuations of BMS were investigated in detail and compared with those obtained from SSS experiments. BMS exhibited different behaviour; it had intense pressure fluctuation in the air reactor and in the riser when compared to SSS experiments. The standard deviation (SD) of the pressure fluctuation was found to be influenced by the fluidization regime and initial operating conditions, while the power spectrum density (PSD) values were more sensitive to the presence of the particles with the higher terminal velocity in the binary mixture.

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