Hi James, it's a very ...
Published by anthony matulick, Osmoflo Pty Ltd - Senior Process Engineer / Operation
Hi James, it's a very interesting thought. Unfortunately I have no input on the behavior of water molecules, nor the membrane in the conditions you describe. Gut feel is the membrane (and water) would behave the same - it's all about the pressure differential, moving the reference line up or down doesn't change that. The comment I wanted to make is the practicalities of such a method. Although applying vacuum on the permeate side of the membrane, will result in less pressure requirement in the feed - it is only a maximum of 1 bar reduction (compared to the ~60 bar feed). Therefore any effect can only be minor. Also the added complexity of plant operation, maintenace etc. Increased energy costs, due to 1) vacuum pumps are typically less efficient than multistage centrifical pumps, and 2) reduction in energy recovery. Not trying to be negative, excellent thinking - but I think the practical side of this will win out over any minor increases in system performance. But please keep us posted if you do pursue this. Hope this helps. Anthony
1 Comment
Anthony, Thank You very much for your wonderful answer. You did manage to let me know exactly what I was wondering about. Again, Thank You. What you have alluded to is that if the multistage feed pump were placed on the discharge side of a membrane, then an energy savings of about 1.5% might be possible. It took me a moment to realize this. And while 1.5% is a small number, on larger RO systems, 1.5% could be a significant cost savings. Myself, I have worked with feed pumps before and do know you are right about their being efficient. And if the work they did on the intake side increased, the discharge pressure would decrease. And the flow rate should be able to be maintained. It should only change how they perform work. Adding; if this is right, then with RO systems powered by petrol, 15 liters of every 1,000 liters might be saved. And a primer pump may be necessary to ensure air is out of the system and the membrane is properly saturated. Still, for long term cost savings, am hoping someone can look into it. Have posted this where I know one university student will see it. Maybe he will let his professor know about this.
Published by James Lindgaard