How to use recirculation?

[ADK_XJ]

I have a new 4x40 single post kit I put together and it includes a recirc line...I understand the principle, I think, but not the practice.

How should/would I most effectively use recirculation? I've tinkered with it and keep going back to 50:50 conc to perm.

[ecolbeck]

I would adjust the recirculation valve to increase the permeate to concentrate ratio while maintaining the pressure parameters of the system. Did your kit come with instructions?

[maple flats]

I think you are talking about the use on an RO. I had a very simple system, a Glen Goodrich 250 gph RO, with recirculation. It was set up so I normally ran thru the inlet filter, thru the 2 membranes each a 4x40, then out to concentrate and permeate hoses. Then for re-circulation, there was a small hose (I think it was likely 5/16) that ran from just before the needle valve to just before the high pressure pump inlet. MY system ran at 275-280 psi up to a max of 300. Without recirculation I could get 240-260 gph thru the pump depending on sap temperature. at that I was going from 2% sap to about 7.5-8% concentrate. However, when I opened the recirculate valve I did get higher, more like 9 or even 10% but at the cost of gph. As such I found I did better running with the recirculation valve closed, send the concentrate to my head tank and when I got high enough in the head tank I would run recirculation from the transfer line just inside the sugarhouse, back out and thru the RO again and back to the head tank. When I did that I had to back off the pressure on the RO, usually to about 220 psi instead of 275psi. I did that anytime I could, but I had to keep a close eye on head tank level, and pressure on the RO along with all of the things I had to watch on the evaporator, I was usually running solo.

[Rselleck91]

So when you talk about recirculation on a non hobby ro. Recirculation is the term used to speed the flow across the surface of the membrane. This is achieved by a pump Lapierre and cdl use motors on the bottom of there vessels and turn the housing into a self contained pump to re run the sap across the membrane surface and it also keeps the sugar from sticking on the membrane surface and slowing down what can pass the the membrane. D&G does it by using its high pressure pump mounted to the membrane housing. (Personally I think a less effective design) h2o and leader do it with an external multistage pump.

They do have a loop as what you are describing but it’s not defined as a recirc loop. They call it a pressure control loop. You set how many gph of concentrate you want flowing out of your machine into a tank with a flow meter. Then this pressure control loop you would use it to tune in your operating pressure. This would come right off the high pressure pump to a needle valve that would regulate the pressure side back to the intake side with a check valve to the suction side of the intake of the hp pump.