needs to understand recirculation

[sweet spot maple addict]

This year was my first with an homemade RO
A single 4x40 with a procon 330
I was told to run it so to get a 5:1 ratio to avoid fouling
It was finally easier to run than i tought , close the restriction valve on the concentrate untill
i get around 3,5 liter/min on the permeate and 19,5 liter/min on the concentrate which result
in about 150 pds pressure ( depending on temperature )
It was a big change since my 2x6 evaporates at about 110 liter/min ( about 22 gallons) the little osmosis "evaporates" faster than that !!
And for the fist time i enjoyed boiling sap with 3.5 and 5 % sugar !!!
But the other side of the coin is that the sap thank spoils faster , since i circulate in loop in it.
I have seen from some of you that plumbing a recirculation loop within the osmosis unit was possible , and that the rate of concentrate could match the evaporator.????
I would have to put a tee on the concentrate line, send one side to a valve and a flowmeter and to the concentrate head tank, and the other side to a valve and to the inlet of the procon ????
Then , how do you run the unit , i mean , if there is no flowmeter on the recirculation , you close the concentrate valve to get the flow you want ( about 20 gallons would match the evaporator) , and then close the recirculation valve to get the pressure ???? I guess thigtening one will affect the other ??? What should i be expected as flow and pressure and brix content?
Will the 5:1 ratio still be respected ?? Is fouling worst or better with recirculation??
Right now i have a 1-10 gallon flowmeter on the concentrate and .2 to 2 gallon per minute on permeate , but if i recirculate and get 20 gallon an hour of concentrate ( .3 gallon per minute ) i would have to switch flowmeters ????
When rincing and washing , do you close your recirculation loop ???

Feedback from your experience would be appreciated

Pierre
200 taps on 3/16
A wife that understand the basic of sugar making and the complexities of the sugarmakers !!!
And a good Shetland dog named Brix.

[jrgagne99]

See this thread:

http://mapletrader.com/community/showthread.php?35649-Recirculation-needle-valve-and-where-to-plumb-lower-end&p=384376#post384376

[sweet spot maple addict]

Thanks a lot
Many usefull infos there
I would like to match a 22 gallons evaporator , sending concentrate to a head tank.
With a single 4x40 by adding recirculation on it.
I understand that recirculation + concentrate will be the laminar flow , i mean the 5 to 1 ratio to avoid fouling ?????
I run actually about 50 gallons an hour permeate and 250 gallons an hour concentrate at 150 psi ( 330 procon)
If i want around 22 to 25 gallon an hour concentrate , how will that work , i close the concentrate valve to get 25 gallon and the close the recirculation valve to get about 150 psi which should give me 50 gallons of permeate ? What brix increase should i expect ???
i understand from your experience that keeping it at 8% , good rinces cycle are enough to maintain membrane flow.

Thanks again

[sweet spot maple addict]

Thanks a lot
Many usefull infos there
I would like to match a 22 gallons evaporator , sending concentrate to a head tank.
With a single 4x40 by adding recirculation on it.
I understand that recirculation + concentrate will be the laminar flow , i mean the 5 to 1 ratio to avoid fouling ?????
I run actually about 50 gallons an hour permeate and 250 gallons an hour concentrate at 150 psi ( 330 procon)
If i want around 22 to 25 gallon an hour concentrate , how will that work , i close the concentrate valve to get 25 gallon and the close the recirculation valve to get about 150 psi which should give me 50 gallons of permeate ? What brix increase should i expect ???
i understand from your experience that keeping it at 8% , good rinces cycle are enough to maintain membrane flow.

Thanks again

[DRoseum]

I've also been wondering how to keep the % sugar in the concentrate at a steady state while using recirc. In theory isn't the sap that is feeding back to the pump intake always increasing in % sugar and driving the output % sugar up higher and higher over time?

How are people dealing with that? Do you close recirc momentarily to purge the system with only raw sap?

[jrgagne99]

I have a single post 4x40 rig. I use my recirc valve mainly to set the membrane pressure. The original valve (i call it the main valve) basically becomes a concentrate bleed-off metering valve, which I use to set the concentrate flow rate. With my single post running at 225 psi (controlled mostly with the recirc valve), I set my concentrate flow to about 30 gph. Then re-adjust the recirc valve to re-establish 225 psi. I'm usually done adjusting right there, but it occasionally takes one more iteration, as there is a small amount of interplay between the two valves. On my unit at a membrane pressure of 225 psi , when i set the concentrate flow rate to 30 gph, the percentage is a steady 6-7%, which works great for me. I have no flow meter on the recirc line and my approach seems to work fine, 3 years running.

The concentration doesn't keep climbing higher and higher because you are always bleeding off some concentrate. Just like a continuous flow evaporator. Once you establish the gradient, you're all set. On an evap it can take a couple hours to get the gradient. On an RO, it is a few minutes.

[sweet spot maple addict]

Thanks again for sharing infos

What kind of pump on your RO, is it equivalent to my procon 330 gph ? Do you have another pump ?
Will my 330 be sufficient ?
What do you get as permeate flow ?
When you rince do you close the recirculation loop ?

THKS

[jrgagne99]

The pressure pump is a Gould deep well pump. Not sure of the number. The feed pump is a stainless sprinkler pump of some sort. Under the conditions I described in my last post, the permeate flow is about 1 gpm. Recirc flow is probably 5 gpm, but that's kind of a WAG since I don't have a flow meter on it. When I used to recirculate back into the truck tank, I think that's what it ran at. I'm not sure of the specs on your 330, but it seems like you probably need at least 5 gpm at 200 psi to run a single post. When I rinse, I leave the recirc loop just slightly cracked open to make sure it gets flushed out too.

[sweet spot maple addict]

The pump is procon 330 gph 250 psi
I have always, with no recirculation, process at around 150psi to 175psi.
And around 50 gph permeate, 260 gph concentrate.
I guess i could get somewhere around 25 gph of concentrate and 50 gph of permeate
which should meets the 15% recovery ( 330 ghp x 15% =50gph) to avoid excessive fouling.
So i would process about 80 gph 2% sap to 25gph 6% concentrate ( removing around 70% water)
The pump will be feed by 80gph fresh sap and 250gph recirculation
That would be a totally different game for me !!!!
I mean , sap is under 2% these last two years , and i love boiling ,
but boiling 240 gallons of 1,6% sap at 22gph is a little .....excessive behavior !!!

Thanks a lot

Pierre
Sweet spot sugar shack
200 taps on 3/16 ( 2017 )
single 4x40 RO (2021)
2x6 evaporator

[sweet spot maple addict]

Can i ask you what is the inline flowmeter you are using on the concentrate line to head tank
and the needle valve or valve on the recirculation ?

THKS

[Ghs57]

I'm definitely adding a recirc line on my RO rebuild. Almost all the parts are here.