Nano Build

[HowsItRunning]

I wouldn't belong on this forum if I wasn't already thinking about next year, so I'm thinking about building a small volume RO based on the nano design, but not the small footprint.

I help my neighbor who has a large >500 tap operation, so he takes my sap that's easy to get with buckets. He gives me syrup at the end of the year and I often make maple sugar out of some it, but I always feel guilty knowing all of the work that goes into making the syrup, to then just sloppily process it into sugar. I'm a syrup purist, no RO, wood-fired, no vacuum, but I was thinking, to make sugar, who cares, I doubt I'll be able to tell the taste difference in the sugar, especially since I just use it in cooking. I will be boiling with a turkey fryer, so I will likely RO the heck out of it, and process straight to sugar. For now i'll just start with a mini pipeline of a dozen trees or so, so it's not a lot of sap. I'm also thinking about a similar pipeline for birch syrup.

After all of my research on here and you tube, I've decided to use the basic architecture found in the nano RO. I'm thinking this will give me maximum water removal in an acceptable amount of time, given my small quantity of sap, with potential in increase in the future. I've attached an initial diagram of my plan, and would appreciate any comments or suggestions. Since size isn't an issue [I'll probably mount this to a ~2' x 3' sheet of plywood] I've added a few things. From my research, I have some concerns over the temperature increase in the sap during processing, especially with all of the re-circulation. To prove i'm a newbie, I have at least one dumb question. I'm an electrical engineer, so I know when you drop a voltage across a resistor, it creates heat, so my question is, does forcing the sap through the membranes create heat? Or is the only heat generated in the system from the pumps? The sap going in should be about 40-45F, and I've added a temperature gauge at the end to monitor any increase during processing. I also haven't seen anyone add a cooling stage at the end, so I'm wondering if this would be useful? I'm thinking it would be a 5 gallon bucket filled with ice water and ~10' of 1/4" copper tubing that would circulate the low pressure condensate before re-circulation or processing.

Thanks for all of the help from the many contributors on here and you tube...

[DRoseum]

What pump do you plan to use for recirc? It has to be able to handle over 100psi input pressure at the inlet if you do it inside the high pressure loop. Is this the pump?

https://www.amazon.com/Youwise-Elect...ps%2C69&sr=8-8

It is only rated to 87 PSI...so that will be a big problem for multiple reasons.

I will have to think about this a bit more.

Might want to think about using 2 typ 8900 pumps in parallel to increase flow rate and have more membranes in series with recirculation on the low pressure side (from after needle valve back to pump inlets).

My current set up is 5 of the 400 gpd membranes in series with 1 typ8900 pump with low pressure recirc. Works fantastic. I have a 2nd pump and more membranes and am considering building an entire 2nd unit or doing the parallel pump setup.

It sounds like you are trying to achieve very high brix output...which with these membranes I am not sure will be all that achievable, efficient, or good for the membranes.

[DrTimPerkins]

Passing through the membrane doesn't generate heat but passing through pumps can. It is typically pretty small and cooling isn't really necessary unless you're going to do several passes or recirculate continuously from your concentrate tank (erroneously labeled "condensate" on your figure).

Recirculation within the RO system is primarily for maintaining a high flow rate across the membrane to prevent fouling. At that stage, there is no additional heat generated. Heat is added each time the sap passes through a pump, but those aren't real high pressure, so not a lot of heat is likely to be added. Altogether you have way too many valves (not needed on permeate lines, before the membranes themselves, or on the recirculation loop, but you do need one on the concentrate output line...which actually is what controls the Brix level you attain), so this build could be simplified somewhat. You may or may not need both a feed pump (probably can gravity feed if you provide a little head from your feed tank) and a recirculation pump. What you have labeled as "Recirc Pump" is actually more commonly called your Pressure pump. Forget the temp gauge...just measure the temp of the concentrate and decide whether you want to do a cooling stage...that is extremely rare.

Lastly, while you refer to being a "purist", I think that inadvertently implies there is something inferior about RO, vacuum, oil-fired syrup (which is not at all the case). Pure maple syrup can be made in many ways either with or without technology. Perhaps a better term to use would be "traditionalist".

There are many others here who can give far better specific advice on these small RO builds, but in general, start out simple and add the bells and whistles later once you get the basic system working.

[carls47807]

Cool setup!

There is generally zero heat transferred to your sap from these little RO setups. The system uses less than 200 watts. Assuming ALL of that went to heat, and you processed ONLY 10 gallons of sap per hour, you would be talking about a fraction of a degree.

The recirculation pump you have won't work at the system operating pressure. A flaw in the NANO is that they use a domestic recirculation pump that was designed for a residential water system. Even at 100psi (which is the max rating on the nano, probably because of this recirc pump), the seals fail and the motors burn up. I tried using recirc pumps in my systems 4 years ago and quickly ditched the concept because it was just too expensive and left a lot of customers frustrated. You need to get to 150psi and keep your sap COLD if you want to maximize your brix. Osmotic pressure increases with increased temperature. Another option, if you are just making sugar, is to use a nanofiltration element. You can pass some ions to get the osmotic pressure down and maximize your sugar.

You can get to 6 Brix fairly easily with a single TYP8900 and three 400gpd membranes. Run them in series to decrease your % recovery. If you want a recirculation loop, I would just run a 125gph procon with a 1/3hp motor and set the system to run around 150 psi. If you use a high quality RO housing and good fittings you will have a nice system. There is a fella on here from Canada that built a 5 membrane 400gpd RO with a procon. Maybe he will see this and chime in.

[HowsItRunning]

Thanks for the replies. It seems like the recirc pump is good for the membranes and i would guess increase life and/or reliability of them, and since they are the most expensive part of the system, it seemed to make sense for the price of another motor. After further research, i would agree that those residential booster pumps won't last. What made sense to me about these pumps is that it only boosted pressure by 10 psi or so, so the recirc pressure is similar to the main pump pressure [the two feeds to valve #1 seen below]. If i use two equal sized pumps, without feedback you would think each would run at about 50 psi to generate the total 100 psi, so if the feedback pressure is ~90 psi [does anyone know approximately how much pressure is lost across the filters?] and you sum that into the output of the first pump at 50psi it seems odd. However, sap needs to be added into the system or the pressure goes to zero, so with feedback, would the first pump have to operate at slightly higher psi than the feedback pressure in order to add sap into the system, so that would mean the second pump would only be operating at the pressure that is lost across the filters, so about 10psi? I think i just answered my own question, lol.

On a side note, I do have a lot of valves, even more in the corrected diagram below, but they are small and cheap. Valves 1,2,3,7 are used to bypass the recirc pump if desired. After cleaning and rinsing the system, valves 2,3,5,6 are used to trap water in the membranes to keep them wet when not in use. Valves 4a/b are used to bypass 1 or 2 membranes if they fail. They also make it easy to find a bad membrane.

I will also be replacing the temp gauge with a pressure gauge and move it to the output of the membranes to monitor the pressure loss in the membranes which should help tell me when they need flushing. I also see a neat pressure and temperature gauge in-one that i will probably just use for all three.

[DRoseum]

I'd be interested to hear Carls perspective, but i would recommend doing low pressure recirculation instead. Split the output after your needle valve and control how much goes into recirc vs true output with another needle valve on that line. Feed the recirc line back to a tee fitting just before it intake side of your main pump. I would not put a pump inside the high pressure loop. You have to be careful of max inlet pressure a pump can handle and I do not know what that is for the TYP8900. It doesn't seem to be published.

The setup i have described is what I run with 5 of the 400 gpd membranes in series and it works great for getting higher brix in 1 pass and keeping the recovery rates lower for each membrane.

A few things to consider
(1) pumps in series (like your drawing) are used to increase pressure at a given/fixed flowrate.
(2) pumps in parallel are used to increase flow rate for q given/fixed pressure. Pumps in parallel have to have same performance characteristics (pressure/flowrate).
(3) I cannot find the exact performance curve for the TYP8900 pump to tell you which configuration (series or parallel) would get the greatest flowrate at 120 psi. Diaphram pumps tend to exponentially decay their flowrate at higher pressures.
(4) the rate/speed of water rejection is determined by the effective membrane size and temp/sugar concentration. 1200 gpd total in your system will reject water at the same rate for a given pressure regardless of flowrate.
(5) higher flowrate across membranes is to keep recovery rate low and reduce fouling. So yes higher flowrates are better for membranes... and again...finding the "sweet spot" of pressure vs flow will optimize your water rejection while keeping your membranes inside the design parameters (lower recovery rate) for longer life.

Maybe it's time I did the experiment to determine the best configuration for max flow at 120psi with 2 of those pumps...

[carls47807]

My understanding of the new schematic is the 1st pump would set your system operating pressure and the second would only recirculate without boosting pressure anymore. You would need a second control/needle valve on the recirculation loop to utilize the second pump as an additional pressure boost pump.

Your best bet is to set the first pump pressure to around 65psi and let it run continuously. This will essentially be a feed pump. Your second pump, as DROSEUM suggested, should work as a booster and recirculation pump. Set that pump to 150psi (these pumps use differential pressure so you'll need to set it to 85psi on its own, or set it to 150psi when the other pump is running). T the recirc line off before the needle valve with it's own control needle valve. If you leave it open it will just dump pressure back to the inlet. Start system with recirc needle valve closed and then when you get to max pressure with the main control valve, continue to dial it down while opening the recirc valve to maintain 150psi.

I still think a single 125gph vane pump would probably be cheaper and easier to use than two small boosters. I heard back from the gentleman who I helped build a 5 400gpd membrane system with a 125gph vane pump. He was getting around .15gpm concentrate, .25gpm permeate, and .9gpm recirculation with his setup. You couldn't get those flows with two 8900 pumps. Running around 175psi.

You can get flow meters with built in control valve which are really helpful.

[HowsItRunning]

Thanks for all of the comments, I guess it makes sense to just use low pressure circulation, so that's what I'll do. I was wondering how to set the re-circ rate, so i guess in the previous example, you would want 0.25/(0.15+0.25+0.9) to be around 15% for the health of the membranes? Those flow meters seem nice, does anyone have a link to them? Don't bother if they cost more than the motor, lol.

[carls47807]

The flow meters are $30 each with the cheap plastic handle. The nicer ones with a solid metal handle are $50 each.