Question about membrane performance

[Offgrid Canadian]

Hi everybody, syrup newbie here. No maples here in central British Columbia, just lots of pine, spruce, aspen and some birch. We started making birch syrup for the first time last winter, just on a whim. It was lots of fun and quite successful. Got my wife hooked, and that's half the battle right there!
I'm assembling the parts for a small RO system and have settled on using a Dow Filmtec XLE 2521 with a 100gph Procon Pump. For this year I'll just recirculate back to the sap tank; eventually I'll add a recirc pump with flow gauges, the whole deal.
There's a wealth of wisdom on this site, and I've spent many hours reading posts related to RO. But I have one question: Why don't manufacturers, like Dow, publish performance curves for their RO membranes? I'm thinking about the curves available for water pumps, which show output gpm at all heads. If an XLE 2521 can produce 365gpd at 100psi, what about at all other presures, like 150, 175, 200, 225, and 250psi? And for that matter, all the way up to the maximum 600psi? Just wondering.....Paul

[Offgrid Canadian]

No-one has any idea? I was sure someone must have thought about this. I'm a numbers nerd; maybe I'll do it myself for the Filmtec XLE when I'm all set up. Paul

[mellondome]

Actual performance is dependant on what you run through the ro.. ( water, sap, brine...) temperature, pressure, discharge %, surface flow rate, % solids ( dissolved and other ).


The published numbers on the membranes used in maple, are actually numbers for water.. at specific temp, pressure, and max flow rates with a defined tds limit.

[bowhunter]

I've done a lot of research on RO membrane performance and the only curves I've seen were published by Dow. http://msdssearch.dow.com/PublishedLiteratureDOWCOM/dh_060e/0901b8038060e609.pdf?filepath=liquidseps/pdfs/noreg/609-00382.pdf&fromPage=GetDoc
I've built a spreadsheet model for my own system which works ok, but the membrane system is fairly complex depending on sugar content, other compounds in the sap, temperature, pressure, etc. I made my system using a 25 x 40 nanaofiltration membrane and as an example I get about 50% of the permeate flow that the membrane is rated for on water at 77 F and 70 PSi. So if you using a membrane rated at 600 GPD you may get 300 GPD on cold sap if you're able to run up near 200 psi and keep the membrane fairly clean.