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).