TMP - How can I calculate this? 1

[Shanzon]

Hi..

I have worked some cycles using a pilot plant with spiral wound membranes to concentrate fruit juices.
I have recorded the driven pressure (range 500-600 psi). I would like to know specific information about transmembrane pressure!!

a) What exactly is the Transmembrane pressure concecpt?
b) What are the variables required to run this calculation?
c) I have also recorded feed pressure values!!

Pilot plant Desal 4040 Recirc was the pilot plant used in this exploratory study.

 

[Jigneshpadia2002]

TMP can be calculated from the following equations

((Pinlet + Poutlet)/2)- Ppermeate)

cross flow and all these pressure controls the TMP. Higher the TMP higher the Flux but it will also foul the membrane faster

 

[FiltrationEngineer]

Answers to your questions:

A. TMP is quite simply the differential pressure across the membrane surface. It is a measure of how much force it takes to push the permeate through the membrane, so it can be used to tell you how fouled your membrane is so you can clean it.

B.To calculate the TMP you need to know the pressures on each side of the membrane surface, so it's really just (dirty side pressure - clean side pressure). Because you can't stick a pressure transducer on the dirty side of the membrane, and there is head loss across the membrane, to figure out the dirty side pressure, you measure pressure on each side of the dirty side (before and after the membrane) and average them. To get the clean side pressure, you just put a transducer on the permeate line.

So it is average on dirty side - clean side. For example if you have 600 psi on the driven pressure, 550 psi after the membrane and 75 psi on the permeate side, your TMP is 500 psi. (see calc in above thread)

If you trend you TMP you will see if you are running a stable operation. If your flux is too agressive, TMP will rise quickly because you are fouling the membrane. Good operation will show a slow rise in TMP between cleaning cycles.