fluidized bed membrane reactors
TRANSCRIPT
FLUIDIZED BED MEMBRANE REACTOR
Presented by
Vinesh S. Bagade
class-BE Roll-01
Content1. Introduction-• Definition
• Types of membrane reactor
• Fluidized bed membrane reactor
• Experimental set up
2.Pure hydrogen generation in fluidized bed membrane reactor
• Introduction
• Experimental studies
• Result and analysis
• Conclusion
• Advantages
• Disadvantages
• Referencess
Introduction
• A membrane reactor is a device for simultaneously performing a reaction
• The membrane not only plays the role of a separator, but also takes place in the reaction itself.
• A membrane-based separation in the same physical device
• Membrane can be defined essentially as a barrier which separates two phases and restricted transport various chemicals in a selected manner
Types of membrane reactor
Zeolite membrane reactor Fluidized bed membrane reactor Perovskite membrane reactors Hollow fiber membrane reactors Catalytic membrane reactors
Fluidized bed membrane reactor
Negligible pressure drop
no internal mass and heat transfer
Isothermal operation.
Flexibility in membrane and heat transfer surface area and arrangement of the membrane bundles.
Improved fluidization behavior
Reduced average bubble size due to enhanced bubble breakage, resulting in improved bubble to emulsion mass transfer.
Experimental set up
Partial oxidation of methanol
horizontal membranes inserted in the fluidized bed
it keeps the H2/CO ratio to an optimal value
“
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Pure hydrogen generation in fluidized bed membrane reactor
Introduction
• Hydrogen is currently an important commodity in several industrial processes
• proton exchange membrane (PEM) fuel
• hydrogen as a milestone to control global warming has grown
• Hydrogen may be produced by steam reforming of fossil fuels, gasification of coal/biomass, water electrolysis and high-temperature steam electrolysis
Experimental studies
Operation modes1. SMR with external heating-
• Methane steam reforming (R1): -
CH4+H2O↔CO+3H2 (Ho298=206.2kJmol−1)
• Water--gas shift (R2):-
CO+H2O↔CO2+H2 (H0298=−41.2kJmol−1)
• Methane overall steam reforming (R3):
CH4+2H2O↔CO2+4H2 (H0298=165kJmol−1)
2.ATR with addition of air or water-
• Methane combustion (R4):-
CH4+2O2 ↔CO2+2H2O (H0298=−802.7kJmol−1)
• Hydrogen combustion (R5):-
H2+ 1/2O2 ↔H2O (H0298=−242kJmol−1).
Experimental set up
Membranes for hydrogen removal
Transport of H2 molecules to the surface of the metallic membrane
Reversible chemisorption of H2 molecules on the metal surface
Reversible dissolution of atomic hydrogen at the membrane surface
Diffusion of atomic hydrogen through the metal lattice
Reassociation of atomic hydrogen at the surface of the downstream metal surface
Desorption of molecular hydrogen from the metal surface
H2 transport away from the outer surface of the membrane
Results Overall reactor performance:-
Components Mole fractions
Methane 0.955
Ethane 0.029
Nitrogen 0.007
Propane 0.005
Butane 0.001
Iso-butane 0.0005
Carbon dioxide 0.002
N-butane 0.0001
an overall carbon balance, as indicated by
,
𝑦𝑐𝑜2+ 𝑦𝑐𝑜(𝑦𝑐𝑜2+𝑦𝑐𝑜+ h𝑦𝑐 4 )
Influence of key operating parameters
Heat effects
Thermodynamic effect of reactor pressure
Membrane isothermality
Effect of membrane area
Effect of pressure driving force
Effect of air input (SMR vs ATR)
Effect of air split
Gas backmixing
Effect of feed rates
Conclusion
The performance of a novel fluidized-bed reactor containing internal vertical membrane panels was tested under steam methane reforming (SMR) and autothermal reforming (ATR) conditions, with and without active membranes.
Some reverse reaction was observed in the reactor free board,thus reducing overall methane conversion
Hydrogen permeate purities up to 99.995% and H2/CH4 yield of 2.07 were achieved with using only half of the full complement of membrane panels under SMR condition
The effects of reactor pressure, hydrogen permeate pressure, air top/bottom split, feed flowrate and membrane load were all investigated.
Advantages
Negligible pressure drop; no internal mass and heat transfer
small particle sizes that can be employed.
Isothermal operation.
Flexibility in membrane and heat transfer surface area and arrangement of the membrane
bundles.
Improved fluidization behavior
Disadvantages
Difficulties in reactor construction and membrane sealing at the wall.
Erosion of reactor internals and catalyst attrition
References Chen, Z., Grace, J.R., Lim, C.J., Li, A., 2007. Experimental studies of pure hydrogen
production in a commercialized fluidized-bed membrane reactor with SMR and ATR catalysts. International Journal of Hydrogen Energy 32 (13), 2359--2366.
M.E.E. Abashar, S.S.E.H. Elnashaie, Feeding of oxygen along the height of a circulating fast fluidized bed membrane reactor for efficient production of hydrogen, Chem. Eng. Res.Des., 85, 1529-1538 (2007).
Deshmukh, S.A.R.K., Van Sint Annaland, M., Kuipers, J.A.M., 2005c. Heat transfer in a membrane assisted fluidised bed with immersed horizontal tubes. Int. J. Chem. React. Eng., 3 A1
Carlucci, F., Van Sint Annaland M., Kuipers J. A. M., 2008a. Autothermal Reforming of Methane with Integrated CO2 Capture in a Novel Fluidized Bed Membrane Reactor. Part 1: Experimental Demonstration. Topics in Catalysis 51133-145
Adris, A.M., Lim, C.J., Grace, J.R., “The fluidized bed membrane reactor system: A pilot scale experimental study”, Chem. Eng. Sci., 49, 5833-5843 (1994).
Boyd, T., Grace, J.R., Lim, C.J., Adris, A.M, “H2 from an internally circulating fluidized bed membrane reactor”, Int. J. Chem. Reactor Eng., 3. A58, 2005.
Prasad, P., Elnashaie, S.S.E.H., “Novel circulating fluidized-bed membrane reformer using carbon dioxide sequestration”, Ind. Eng. Chem. Res., Vol. 43, 494-501 (2004).