Membrane: Varying pressure drop for flow rate

[ports394]

I'm working with a cross flow membrane at the moment.. what I've noticed is that at lower TMP's, the dP across the membrane is higher, to give me X gpm.

At higher TMP's the dP is lower to give me the same X gpm.

I have 2 flow meters in the line checking the flow, and the X gpm rate is correct. It's also been "bucket tested".

Any ideas?

 

[hprorelis]

Dear sir
Drop pressure (DP)is in relation with retentate flow and viscosity. Linear velocity along membrane drives DP.
Permeate flow is in relation with TMP but there is no crosslinking between these two parameters
Best regards

 

[membranedr]

Hey ports394 and herve
Depending on the type of membrane that you are using, a higher delta PTM can give either more or less permeate. In MF the max delta P I would stay under is 0.5-1.0 bar, in UF 1 - 10 bar and in RO it is really not very relevant.
In MF the crossflow should be very high, lower in UF and in RO balanced to prevent scaling. Hope this helps you abit.

 

[ports394]

membranedr, thank you. Eventually I've just chalked it up to gauge error. I was looking at a difference from 5 psi dP to 2 psi dP. For that module, I was running it to maintain a specific permeation rate, so the membrane conditions didn't matter too much as long as they were within spec.

 

[membranedr]

Herve:
How are you
let me know
greetings
membranedr