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[SP500]

I am designing a fixed bed catalytic reactor. I want my reactor to behave like a fixed bed reactor ,but I need to check if my liquid reactant mixture will flow in such a velocity so as to make the bed act like a fluidized bed.

I know how to calculate this.

 

However, I've read in the majority of sources that this will happen only when the fluid , flows upwards rather than downwards and I dont understand this.  Doesn't fluidization occur if the fluid is flowing downwards? Is this because there are sieves preventing the catalyst from leaving?What if the catalyst is powdered rather than in pellet form? Can sieves be small enough to prevent powdered catalyst from leaving?

 

Also, in a fixed bed reactor what stops the catalyst from flowing away? Is it just the compacted packing in combination with the sieves at the end of reactor preventing this?

 

One last question , is mesh an actual unit?

 

So for example  is this unit conversion correct?

1 mesh=200 microns=0.2 mm

 

Also, I am guessing , in the case that the density of the solid catalyst is smaller than the density of the liquid fluid reactant it will float and therefore be fluidized irrespective of the velocity?

 

Thank you for your time.

Edited by SP500, 25 January 2017 - 08:45 AM.

[Francisco Angel]

SP500:

You generally assume that fluidization is due to a balance of the upwards force exerted by the fluidization media, and the downwards force due to gravity. So if the fluid goes downwards, there will be no other force to balance it, and the solid will accumulate at the bottom.

Regarding mesh size, there are generally a conversion, like this:

http://www.engineeri...ngs-d_1645.html

 

You must check if the mesh you are using conform to a standard, and which stadandard in particular.

Best regards.