Recirculate Or 2nd Pass Which Is Quicker?

[RiverValleySugarhouse]

Hello since I have had my ro 4 yrs now I have only had a raw sap tank and I would just put my concentrate back in and recirculate it until it got to 8% or higher then send it to a head tank. I was think of setting up a second tank and doing a single pass into additional tank then running it threw a 2nd time to get it up to 8% or higher. Normally I would wait until I had 100-125 gals of permeate then check sugar content and send to head tank and start fire. The ro I have is a 300 gal. by the way. The problem I ran into last year is my raw sap tank is 580 gal and it would be full and recirculating and my truck tank would be full while sap is still running and I would have to wait to empty it after it was done recirculating and getting sent to head tank. Normally it would take and hr or so to get 400 or so gallons up 8% depending on sugar content. So in theory if I had a second tank and ran it threw once into the other I would technically have to wait an hr or so for it to empty my raw sap tank and then feed it threw to the head tank. So my question is what would be more productive/ and time efficient. Hope this makes sense to people. Thanks.

[maple flats]

I have never tried an extra tank, I recirculate and like it that way. My RO runs slightly faster than my evaporator and I RO until my head tank gets to a certain level, (I boil at the same time). When I reach that level, I just close one valve as I open another and I am recirculation without shutting down. Then, before the concentrate hits the RO I back off on the pressure to prevent tripping the high pressure shut off. Once the pressure stabilizes on concentrate I turn the pressure up to squeeze it more. In my case, with a Ray Gingerich RO, my initial pressure on sap is about 275. As soon as I switch to recirculate I back off to about 225, but then when the pressure stabilizes, I increase adjust the pressure to about 260-265. When recirculating the pressure gradually climbs a little faster that it might on straight sap so I check it every 2 or 3 refuelings on the arch and adjust as needed.
Then as my head tank gets low, I change the valves back and after a few minutes (when it is then getting raw sap) I again turn the pressure back to about 275 PSI. I just never saw a need to set up another tank. That method works well for me.

[Sunday Rock Maple]

The guys at the Leader RO seminar last spring recommended going from 2 to 4 during the day while the sap was running and then taking the 4 to 12 to feed the evaporator as this was a lot easier on the membrane than going from 2 to 12. I expect this would vary based on your machine but they seemed to be advocating 4 tanks (raw, permeate, 4ish and 12ish) or 3 tanks with the ability to swap quickly.

[BreezyHill]

Last season I ran a 4 tank system. It worked very well. I pulled from the main collection tank to fill the batch tank. When desired concentration level was reached. Sap would be sent to the head tank. If the membranes started to plug I could pull raw sap to flush them for a moment and continue. End of the day I would run raw sap through until the sugar level was down to raw sap level or run permeate through to the batch tank until it was running 0 sugar. This reduced the number of wash cycles on the membranes to prolong their life.

For me it was much more productive to run one pass to fill the batch tank with enough to get the evap up and going for an hour. Refill the batch tank to full and concentrate that to further fill the head tank. If the head tank gets low I open the valve and send some up.

Ben

[mellondome]

From experience:
With a homebuild, it is probably better to recirculate back to the supply tank as you dont have recirculation on your membrane. This will allow you to remove more water before fouling than going from 2-4 then from 4-8.
With a factory built with recirculation, you will be better off running 2 seperate passes.

[VT_K9]

We use three tanks in the sugar house. The first holds raw sap from the woods. The second is the first time through the RO. Later in the season I will let it recirculate when the sap sugar content is lower. Then the final tank is elevated for a good gravity fee to the evaporator.

The only concern with recirculate on is loosing track of time and getting too high a concentration.

Mike

[DrTimPerkins]

The only concern with recirculate on is loosing track of time and getting too high a concentration.

Another issue with recirculation is sap/concentrate temperature. Each time the sap passes through an RO, it heat up (due to the pumps).

Warmer sap/concentrate = more microbes = darker syrup

[bowhunter]

In general it is always more efficient to minimize number of steps and inventory. If I knew what size RO you had relative to your evaporator and whether or not you RO as internal recirculation the question would be easier to answer. I agree with Dr. Tim recycling to a tank causes the temperature of the tank to increase and with increasing sugar content you get accelerated microbial growth.

I really don't like to store concentrate unless it is absolutely necessary. I would be best if your RO has internal recycle capabilities to set it up to achieve 8-10% on the first pass and feed as much of that concentrate to the evaporator as possible. It sounds like from your description that the RO is much larger than the evaporator?

[RiverValleySugarhouse]

I have a 300 gal ro with three 4" membranes and I have a 2x6 evaporator. I try to get it to 8%. I usually dump my raw sap and start ro squeeze it a little up to 4ish that way my flow rate is good and not to slow. Then I work on things in sugarhouse cleaning and getting ready and within a hr or so check the % if its 8% I will send it to head tank and wait 15 mins to 25 mins or so to get some in head tank then fire the arch and boil while the ro is running. Usually the ro will shut off during boiling and I can do a wash cycle and by the wash is done I would be done boiling and shut things up for the night. If I set up another tank I will have to buy another tank plus fittings to plumb in I am just trying to make it quicker and more efficient but I'm not going to invest money if it's not going to make a difference. I was thinking if I had a 2 tank system I could fill my raw sap tank and make a first pass into another tank and that would free up my raw sap tank for more sap. While I do a second pass from the 1st concentrate tank to my head tank. I would like to do 4%-4.5% on first pass then maybe 8% to 9% on the second. I just didn't know if that would be quicker then recirculating it. Anyone with a ro knows how it is waiting on them:D Ps My ro doesn't have recirculating pump. Just a feed and a high pressure. Thanks