4 replies to this topic

[manchester]

Hi,
I'm designing Mole Sieve Bed to remove water from Natural Gas. I got something that bother my mind...Why are wet gas entering bed from top of bed (downward flow)? Why don't they entering from the bottom,considering it is a gas?

My pre-analysis is that downward flow purpose is to reduce wet gas velocity,so that recidence time in bed is higher, then gas outgoing from bed will be drier.
Is this right??

Thanks a lot

[theleftcoast]

I think downward flow is preferred to prevent fluidizing the bed. If the flow of wet natural gas was introduced at the bottom of the bed, high gas velocities could "entrain" the adsorbent (usually a granular solid) and damage the bed. I interned at a plant that used PSA system to purify hydrogen and most of the catalyst/sorbent beds in the plant had the flow introduced to the top of the vessel. Also, the equipment you need to install to ensure even flow distribution of the gas across a bed is easiest to install at the top of a vessel. The flow direction and distribution considerations were briefly explained to me by one of the engineers at the plant so I don't have any books or print resources to back that up. Hope that helps.

[rana680]

Down flow is preferred because up flow at high rates can cause fluidization of particles ,causing attrition and loss of fines.

Regards

Rahul

Edited by rana680, 01 February 2010 - 11:57 PM.

[manchester]

Down flow is preferred because up flow at high rates can cause fluidization of particles ,causing attrition and loss of fines.

Regards

Rahul

Thanks guys...you helped me very much

[fatimah]

hi there

just to add, ppl use up flow for back flushing. well, not sure whether it's a common practise.