8" ro build

[mountain man maple]

I'm looking at building a 8" single post machine.I was going to use a xle membrane does anyone know maximum flows for this membrane? I was going to use a 18 GPM pump that will do about 200 psi. Is this enough pump to be worthwhile using a 8" membrane? I hear people talk about permeate flow compared to pressure or feed rate in GPM but cannot find any charts that tell this info.

[maple flats]

Every pressure I've heard about in RO has been in the 300PSI and up, except the Leader Hero which I believe has no pump. 200 may work but will be far less than ideal. You should try to match the pump to the membrane vessel rating, a vessel using half clamps is generally 300 psi while better clamps go higher. I think a full clamp will be rated at 500 PSI.

[bowhunter]

Mountain Man,

This isn't a good match. Your pump is probably better suited for a 4"x 40" . They have a maximum flow of around 14-16 GPM. You might want to consider Nano filtration elements such as a NF 90. They're designed to operate at a little lower pressures. I've attached a couple of links from Dow's RO design site which might help you select a membrane. With your pump and a 4X40 membrane set up to recycle back to the pump you should be able to process 85 GPH of sap and reduce the volume by 70-75%.
http://msdssearch.dow.com/PublishedLiteratureDOWCOM/dh_08ca/0901b803808caf76.pdf?filepath=liquidseps/pdfs/noreg/609-02054.pdf&fromPage=GetDoc
http://msdssearch.dow.com/PublishedLiteratureDOWCOM/dh_0071/0901b803800710df.pdf?filepath=liquidseps/pdfs/noreg/609-02008.pdf&fromPage=GetDoc

[mountain man maple]

Right now I am running 2-4"x40" with a 10 gpm hp pump and running around 150 psi I'm removing 3 gpm of permeate with raw sap. I also looked at a pump that maxes out at 33 gpm and 249 psi would this be better fitted to a 8" membrane I can find pumps that go up to 500 psi but they are piston pumps and flow much less water all less than 10 gpm. Would recirculation be worth putting on this ro. RIght now my 4" 2 post machine doesn't recirculate I just run the water through more passes at a higher flow rate. I cant find minimum flow rates for the 8" membrane I would think 18 gpm would be plenty. The problem with nanofiltration is I want to get above 12 brix and that's all the higher my nf 270 will go to now. I was told xle will handle higher brix and also very low pressures. I thought people with 4" xle were running around 150 psi but maybe an 8 " requires more pressure to work. My original plan was to build a 6 post 4" machine but a 8" single membrane has about the same surface area and for less money than 6- 4" memrbranes.

[bowhunter]

The brix is limited by the pressure of your pump. At 150 psi you're probably not going to get above 12 brix with any membrane. At 150 PSI the maximum you can achieve is about 12.8% if you recycle forever. I assume you're getting to that level by recirculating back to sap tank? With your existing set up you are at or below the minimum recommended concentrate flow on a 4" membrane. The minimum is about 3-5 gpm of concentrate each and you're running about 3.5 gpm. If you used the 18 GPM pump with the two 4 X 40 at higher pressure and on recycle you could get much better performance. The capacity of that set up is 120 GPH once through with 75% volume reduction and about 30 GPH of concentrate. If you want to get to 14 brix you probably have to use two membranes in series. One membrane is generally limited to about 75% water removal.

You can go with one 8 inch membrane, but you need more flow. I couldn't find any minimum flow data on the 8 inch membrane either, but it's designed to do about 14,000 GPD of permeate so I'm pretty sure the feed flow was designed to be ~95,000 GPD or 65 GPM.

[Buffalo Creek Sugar Camp]

I really think you want recirc if you want high concentrate. I also think you want a pump that is capable of 400 psi even if you don't run it that high. I don't see the machine having good flow rates if you have anything less.