How does the recirculator work?

[cjf12]

Anyone interested in explaining to me how a recirculation on an RO works. Pros n cons.
I have a home built 4x40 and it's great to have especially with the lower sugar content this year but I would love to speed up the RO if possible.
Its nuts n bolts. Feed pump to 2x20 filter to high pressure pump (to small for another membrane I believe) psi gauge after prefilter and one after needle valve. I currently run at 250psi and average around 1 gpm of permeate and about 5ish gpm of concentrate.
Looking to speed up permeate to get us by for a year or two in hopes of getting something bigger in the future.

[western mainer]

Do you have a valve on the concentrate side of your line? If so, if you close it up slowly you will get more permeate and less concentrate.
Brian

[cjf12]

Yes I do. A needle valve which I typically run at 250 when concentrating. I turn it all the way back when rinsing.

I normally run enough to fill my head tank which is 275 gallon. Then just keep recirculating the head tank to about 1/2 then add more raw sap. Repeat. Run it till I'm done boiling.

[Urban Sugarmaker]

I have 4x40 RO (home-built) and I use a recirculation line. The concentrate line tees after the outlet of the membrane and then to two needle valves. One goes to the concentrate flow meter, the other back to the inlet of the Procon pump. I close down the valves to get to my flows I want. First I start closing the recirc, then the concentrate valve. Once the flows are close I make fine adjustments to both of them. A 4x40 membrane can do 75% water removal on one pass with recirculation and no recirc pump. But, the concentrate flow is only about 13GPH. At 50/50 flows with a good membrane my permeate is 0.8 and concentrate 0.85 give or take. Definitely worth the extra valve and plumbing.

[jrgagne99]

I have 4x40 RO (home-built) and I use a recirculation line. The concentrate line tees after the outlet of the membrane and then to two needle valves. One goes to the concentrate flow meter, the other back to the inlet of the Procon pump.

I’m thinking of adding recirculation to my Waterguys single-post 4x40 RO. I thought that in this context, recirculating “within the RO” meant to feed the concentrate back to the membrane inlet while still under high pressure, i.e. split it off upstream from the main needle valve and re-introduce it between the pressure pump and the membrane (still at high pressure).

If you re-introduce the concentrate to the flow before the pressure pump , as Urban Sugarmaker states, isn't that the same as recirculating it back to the raw sap tank and running the RO until you reach the desired concentration?