scholarly journals Wall-to-Bed Heat Transfer in Bubbling Fluidized Bed Reactors with an Immersed Heat Exchanger and Continuous Particle Exchange

2021 ◽  
Author(s):  
Christoph Eder ◽  
Gerhard Hofer ◽  
Tobias Pröll
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Fluidized Bed ◽  
Fluidized Bed Reactors ◽  
Bubbling Fluidized Bed ◽  
Particle Exchange ◽  
Continuous Particle

Particle mixing in bubbling fluidized bed reactors with continuous particle exchange

2019 ◽  
Vol 195 ◽  
pp. 585-597 ◽  
Author(s):  
G. Hofer ◽  
T. Märzinger ◽  
C. Eder ◽  
F. Pröll ◽  
T. Pröll
Keyword(s):  
Fluidized Bed ◽  
Fluidized Bed Reactors ◽  
Particle Mixing ◽  
Bubbling Fluidized Bed ◽  
Particle Exchange ◽  
Continuous Particle

Study on Heat Transfer from a Bubbling Fluidized Bed Combustor to a Membrane Wall

2012 ◽  
Vol 10 (1) ◽  
Author(s):  
Paula Neto ◽  
Albina M. Ribeiro ◽  
Carlos Pinho
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Fluidized Bed ◽  
Equivalence Ratio ◽  
Internal Diameter ◽  
Entrainment Rate ◽  
Particle Sizes ◽  
Temperature Range ◽  
Particle Entrainment ◽  
Bubbling Fluidized Bed

The importance of projection and splashing of bubbling bed particles on the heat transfer rate towards a membrane wall heat exchanger placed above the bed was studied.To characterize the heat transferred from a bubbling fluidized bed to a membrane wall heat exchanger placed above the freeboard, a laboratory scale fluidized bed reactor, heated by a 2 kW electric resistance, was used. The reactor, with an internal diameter of 54.5 mm, had two 0.83 m height double pipe heat exchangers placed one above the other. Only the heat exchanger close to the bed surface participated in the heat exchange process. Tests were done without and with combustion.For experiments without combustion the bed was fluidized with air at superficial velocities of 0.2 to 0.5 m/s in the 400-700 °C temperature range. For experiments with combustion, the fluidizing gas was obtained through propane combustion in the bed in 700-720 °C temperature range, for superficial velocities of 0.2 to 0.3 m/s. Five different bed particle sizes were considered: 107.5, 142.5, 180, 282.5 and 357.5 µm.Particle convective heat transfer coefficients were obtained in the range of 2 to 16 W/m²/K and a correlation for the corresponding Nusselt number as a function of the fluidization characteristics and the combustion equivalence ratio is proposed.For the three smaller bed particle sizes, the particle entrainment ratio had a strong influence on the heat transferred towards the membrane wall and the corresponding bed particle entrainment rate was determined and correlated with the fluidization characteristics and the combustion equivalence ratio.

CFD-DEM Modeling of CO2 Capture using Alkali Metal-Based Sorbents in a Bubbling Fluidized Bed

2014 ◽  
Vol 12 (1) ◽  
pp. 441-449 ◽  
Author(s):  
Zhonglin Zhang ◽  
Daoyin Liu ◽  
Yaming Zhuang ◽  
Qingmin Meng ◽  
Xiaoping Chen
Keyword(s):  
Fluidized Bed ◽  
Gas Flow ◽  
Fluidized Bed Reactors ◽  
Solid Sorbents ◽  
Bubbling Fluidized Bed ◽  
Shrinking Core ◽  
Simulation And Experiment ◽  
Kinetics Simulation ◽  
Reaction Processes ◽  
Back Mixing

Abstract This paper describes a CFD-DEM modeling of CO2 capture using K2CO3 solid sorbents in a bubbling fluidized bed, which takes into heat transfer, hydrodynamics, and chemical reactions. Shrinking core model is applied in reaction kinetics. Simulation and experiment results of bed pressure drop and CO2 concentration in the reactor exit agree well. Instantaneous dynamics as well as time-averaged profiles indicate detailed characteristics of gas flow, particle motion, and chemical reaction processes. The simulation results show an obvious core-annular flow and strong back-mixing flow pattern. CO2 concentration decreases gradually along the bed height, while regards on the lateral distribution CO2 concentration near the wall is lower than that in the middle zone where gas passes through faster. The effect of bubbles on CO2 reaction is two-sided: it can promote mixing which strengthens reaction, while it can be a short pass of gas which is not beneficial to reaction. The simulation is helpful for further understanding and optimal design of fluidized bed reactors of CO2 capture.

Experimental Study on Compact External Heat Exchanger for a 4 MWth Circulating Fluidized Bed Combustor

2013 ◽  
Vol 448-453 ◽  
pp. 3259-3269
Author(s):  
Zhi Wei Li ◽  
Hong Zhou He ◽  
Huang Huang Zhuang
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Fluidized Bed ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Cooling Water ◽  
External Heat ◽  
Circulating Ash ◽  
Fluidized Bed Combustor ◽  
External Heat Exchanger

The characteristics of the external heat exchanger (EHE) for a 4 MWth circulation fluidized bed combustor were studied in the present paper. The length, width and height of EHE were 1.5 m, 0.8 m and 9 m, respectively. The circulating ash flow passing the heating surface bed could be controlled by adjusting the fluidizing air flow and the heating transferred from the circulating ash to the cooling water. The ash flow rate passing through the heat transfer bed was from 0.4 to 2.2 kg/s. The ash average temperature was from 500 to 750 °C. And the heat transfer rate between the ash and the cooling water was between 150 and 300 W/(m2·°C). The relationships among the circulating ash temperature, the heat transfer, heat transfer rate, the heat transfer coefficient and the circulating ash flow passing through the heating exchange cell were also presented and could be used for further commercial EHE design.

scholarly journals Evaluation of Alternative Designs for a High Temperature Particle-to-sCO2 Heat Exchanger

2019 ◽  
Vol 141 (2) ◽  
Author(s):  
Clifford K. Ho ◽  
Matthew Carlson ◽  
Kevin J. Albrecht ◽  
Zhiwen Ma ◽  
Sheldon Jeter ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
High Temperature ◽  
Heat Exchanger ◽  
Transfer Coefficient ◽  
Fluidized Bed ◽  
Structural Reliability ◽  
Packed Bed ◽  
Heat Losses ◽  
Transient Operation

This paper presents an evaluation of alternative particle heat-exchanger designs, including moving packed-bed and fluidized-bed designs, for high-temperature heating of a solar-driven supercritical CO2 (sCO2) Brayton power cycle. The design requirements for high pressure (≥20 MPa) and high temperature (≥700 °C) operation associated with sCO2 posed several challenges requiring high-strength materials for piping and/or diffusion bonding for plates. Designs from several vendors for a 100 kW-thermal particle-to-sCO2 heat exchanger were evaluated as part of this project. Cost, heat-transfer coefficient, structural reliability, manufacturability, parasitics and heat losses, scalability, compatibility, erosion and corrosion, transient operation, and inspection ease were considered in the evaluation. An analytic hierarchy process was used to weight and compare the criteria for the different design options. The fluidized-bed design fared the best on heat transfer coefficient, structural reliability, scalability, and inspection ease, while the moving packed-bed designs fared the best on cost, parasitics and heat losses, manufacturability, compatibility, erosion and corrosion, and transient operation. A 100 kWt shell-and-plate design was ultimately selected for construction and integration with Sandia's falling particle receiver system.

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