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...:confused:

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?

20494
20495
https://static1.squarespace.com/static/5a00bad08fd4d2f13938ea54/t/5d4b0e8a85a7dc00018f4de5/1565200018889/80150550+R1+CAN+4040-1+to+12+O+%26+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)

[bowhunter]

The target recovery is 15% per membrane maximum. You have two membranes in series so the overall system recovery is about 27%. That should give you a total flow through the first membrane of about 4.5 gpm.

[wmick]

The target recovery is 15% per membrane maximum. You have two membranes in series so the overall system recovery is about 27%. That should give you a total flow through the first membrane of about 4.5 gpm.

Ahh yes... Now that makes sense... Thanks again.

I am quite happy with this estimated outcome.... Will keep my fingers crossed, of course. But cutting my wood cutting and boiling time down to less than half will be a tremendous improvement. and it looks as though I might be able to concentrate a 275 gallon tote in about 3 hours or so... which I can do in an evening after work....

[SmellsLikeSyrupNH]

I now have all of these exact components and I am getting the complete opposite of this. I am getting perhaps 50 gallons of Permeate per hour and 125 gallons of concentrate that is coming no where close to 7% from 2% sap. IM SO FRUSTRATED!!! lol



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.

[wmick]

So I finally got my RO going this weekend.... Thought I'd give an update on how it performed, on the couple batches I did. And any advice would be appreciated..

I went with a pair of MES 4x40 membranes.
My added re-circulation pump idea did not work out.... Turns out that there is way too much restriction through the concentrate side of a membrane for a little grundfos circ pump to generate flow... Need something that can create some pressure... So I plumbed the recirc back in before the pressure pump... (typical setup)... As it turns out, recovery did not restrict me anyway. My membrane/pressure combination seemed to be my limiter...

The factory control system was erring out at startup... So rather than spend a lot of time figuring it out, I wired my motors direct and controlled the system with a circuit breaker.

My Gould pump performed well.... and I pushed it a bit beyond its pressure specifications...
Running at 210 psi, taking 2.5% sap at 3 degrees C to 10%, I was able to remove water at 45GPH, and 10% recovery.
Running at 210 psi, taking 2.5% sap at 8 degrees C to 10%, I was able to remove water at 55GPH, and11.5% recovery.

I am quite pleased with the results... Not only can I remove water at twice the speed of my evaporator (20gph at best).... It will save a ton of time and resources in firewood preparation etc..

I managed to do rinses and a wash without incident... Although my wash did not come up to the recommended 130 deg, with friction,,, It seemed to cap out at 100. I will need to think about adding a heater for the wash cycle.

Couple things I want to change asap. (before my next batch this weekend, if possible)

Downsize my flow meters from 5gpm Perm, 5gpm Conc and 15 gpm recycle... to 2gpm, 1gpm and 5gpm... this will give me more accurate readings.
Upsize the line between my prefilter and pressure pump. It seemed like there may have been a bit of cavitation there. (air bubbles coming from somewhere??).... (I had 60psi at the filter outlet)

And for next year.... Heated truck box to house the system... Process Heater for washing.... Chiller for sap storage... Get the control panel and safety switches working... Take care of my membranes for the off-season.

The downfall to playing around with this first time RO, is that I've neglected my boiling.... My concentrate is currently in a tote, literally under a snowbank.... Buried it in snow with the front end loader in hope of keeping it fresh till boiling later this week.:emb:

[Bainbrook Boiler]

Hello Wmick - You started this thread by asking how people's membranes perform. I am late getting to the party here but I hope my information helps you. I boil with three other guys here in NE Ohio. We had 99 taps this year and made a little over 22 gallons. We boil on an oil tank arch in one guy's back yard with a Leader half-pint pan. We built an RO two years ago by pretty much following Hodorskib's plans. We have four 150GPD membranes we got off of Ebay (manufacturer unknown). We have a prefilter that we run with a 1 micron filter element and we use an Aquatec 8842-J203 pump running at 120 PSI to push everything through. One check that I wrote down this year showed we were running 5.2 GPH of permeate and 2.7 GPH of concentrate. This doesn't keep up with the rate of boil in the pan but I run the RO in my garage the day before we boil to reduce my sap to anything between 5% and 7%, depending on how much time I have and how much sap I have. I let the RO run overnight and put the concentrate right back into the barrel so it just keeps recirculating. By doing this, I can take over 100 gallons of sap down to 20 or 30 or 40 gallons of concentrate which makes it much easier to transport to the other guy's house for boiling. When we boil, we run the RO and have the concentrate going right into our warming pan. We also take the concentrate that I produced the day before and feed it into the warming pan to supplement what the RO is generating. We are looking to make changes to the RO to get more out of it but really don't want to take the next big step and go to the larger membranes and pump (we are basically cheap). We might try running two 150's in parallel and have them feeding the other two in series and add a final 100GPD membrane at the end. The last one would be smaller because the flow across it is significantly less and a smaller membrane would help address the fouling problem you get with reduced flow across a membrane. I would welcome input on this. I hope this helps you with your initial inquiry.