How does your membrane perform?

[wmick]

As I prepare to work on a home-build RO... I find myself perplexed, trying to right-size feeder and circ pumps etc....
This is because I have no experience and membrane manufacturers seem to spec their products with saltwater, warm temperatures, etc, etc...
Trolling through the forum, I know the information I need is all here, but is somewhat skewed by different systems, different re-circulation systems and recovery rates, etc...

I know I am probably over simplifying things, but what I would really like to know is how much water flows through your membrane at your pressure while de-sugaring sap?

How many membranes do you run? What membrane? What pressure do you run your concentrate at? and how much permeate do you expect to get over time...
Not looking for exact numbers because I know they change depending on incoming brix, temperature, hours of running, etc... but I would love a ball park idea of what you expect, on average for membrane flow...

For example:: "I have one XLE 4040 at about 250-275psi approximately 1 GPM of permeate".
or maybe "I run Two MES 4040 MS2 at about 125 psi which gives 70 GPH of permeate".

Hopefully some of you will take the time to oblige me.... I think this will give me a baseline, to help design/finish my system around...

Thanks to all !

[bowhunter]

Membranes are generally sized on water at 77 F. I'd be happy to send you some sizing information for sap but first I need to know what you want to do. I can recommend the membrane, pump and flow meter sizes. How many taps do you have or how much sap do you need to process per day? How much sap can you boil per hour? Do you want to run your evaporator and RO at the same time? If you know what your typical sap sugar content is, that would be helpful.

[WVKeith]

wmick:

For several years, I averaged 90 gph with MES 4x40 membranes at 275 psi

[30AcreWoods]

Hello Bowhunter...I have a couple of questions for you if you could clear some space in your email inbox. Thank you!

[bowhunter]

I just cleared out some old messages.

[wmick]

wmick:

For several years, I averaged 90 gph with MES 4x40 membranes at 275 psi

Thanks Kieth. Is this 2 membranes? or ?

[wmick]

Membranes are generally sized on water at 77 F. I'd be happy to send you some sizing information for sap but first I need to know what you want to do. I can recommend the membrane, pump and flow meter sizes. How many taps do you have or how much sap do you need to process per day? How much sap can you boil per hour? Do you want to run your evaporator and RO at the same time? If you know what your typical sap sugar content is, that would be helpful.

Thanks Bowhunter... I am going about things a little backwards, I know.. Designing around existing parts, rather than operational needs.
I have purchased a small industrial water purifying RO, and my intention is to build a system around this, for the best possible results I can muster.
I only tap about 100 trees right now... depending on how this RO thing works out, I may do more... My intent is to concentrate in batches of 250 gallons of raw sap, or less, at my home, and trailer the concentrate to my sugar shack where there is no electricity to run the RO. ... I would like to do my batches one pass. utilizing a re circulation pump to ensure good recovery rates. I need to estimate what my pressure pump and prospective membranes are capable of flowing, so I can confirm adequate feeder and circ pumps.

I have acquired a used small commercial RO system that was designed to purify water.... It has two 4x40 housings, flowmeters, adjustment valves, pressure switches etc...
It has a Goulds booster pump the 7GB that is only capable of flowing about 7 GPM at 175 PSI... (I know this is lower pressure than a lot of units, but I'm hoping I can make something work.) (Also - This performance curve was taken at zero inlet pressure.... I should be able to add 40-50 psi with a jet pump in series)
I've attached a copy of the RO schematic and the pump curve. and a link to the RO unit that I have... its the 4040-2 system.

So I need to figure out (I think?)... (assuming I do all my recovery needs using a circulation pump) What flow can I expect my Gould pump to push through a set of membranes at Cold Temperatures approx 35-44F ... and what specific membranes to buy?

RO Pump Curve.JPG
RO Factory Schematic.JPG
https://static1.squarespace.com/stat...+M+5-15-19.pdf


As always... I appreciate your time and advice...

[bowhunter]

To estimate your performance I assumed you're using Filmtec Tech membranes. These membranes work well and are commonly used in maple sap processing. A 4 inch MES membrane would probably give similar results. The operating pressure was set at 175 psi to match the pump. I ignored the feed pump in this analysis so this is the minimum performance I would expect. It will perform better with the higher pressure. I set the water removal at 75% in a single pass. I think you should be able to process 100 gallons per hour of 1.8% sap concentrating it up to 7% sugar in one pass. At these conditions the concentrate flow is 26 gallons/hr and permeate flow is 74 gallons per hour. The pump output is 7gpm at 175 psi assuming it follows the pump curve. The minimum flow required to keep the recovery below 15% is 4.5 gpm so the pump should be fine. You can operate above 175 psi, but I would not exceed 200 psi across the pump because you will back the pump up the curve too far reducing the flow below 5 gpm. This could result in lower recovery and faster membrane fouling and poor performance.

[WVKeith]

That is 90 gph of permeate through each membrane. This is a rough average, exact value varies with sugar %, temperature, etc

[wmick]

To estimate your performance I assumed you're using Filmtec Tech membranes. These membranes work well and are commonly used in maple sap processing. A 4 inch MES membrane would probably give similar results. The operating pressure was set at 175 psi to match the pump. I ignored the feed pump in this analysis so this is the minimum performance I would expect. It will perform better with the higher pressure. I set the water removal at 75% in a single pass. I think you should be able to process 100 gallons per hour of 1.8% sap concentrating it up to 7% sugar in one pass. At these conditions the concentrate flow is 26 gallons/hr and permeate flow is 74 gallons per hour. The pump output is 7gpm at 175 psi assuming it follows the pump curve. The minimum flow required to keep the recovery below 15% is 4.5 gpm so the pump should be fine. You can operate above 175 psi, but I would not exceed 200 psi across the pump because you will back the pump up the curve too far reducing the flow below 5 gpm. This could result in lower recovery and faster membrane fouling and poor performance.

Thanks Bowhunter.
I really appreciate you taking the time...
I have a question about your calculation, though... Regarding recovery rate. I think I'm missing something.
Is recovery rate not defined as Permeate flow as a percentage of total feed flow?
If permeate flow is 74 gph... and desired recovery is 15% .. Would total flow not need to be 493 gph? (8.2 gpm) (74 / 0.15)