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  • Quinn Giblin

Reverse Osmosis Rig



Purpose: The goal of this project is to filter water out of the maple sap collected during the maple sugaring process. Less water means less evaporation time and fuel needed to evaporate it. Our goal is to remove about half of the water this way, give or take, so the process of boiling can still be done but will not take as long.


Materials



For assembly:


  • Screw Driver (electric)

  • Screws (1-2 in)

  • Zip ties

  • Drill with drill bits


Build Process: the first part of the build process was research. I watched videos and read articles on Reverse Osmosis rigs and then created a design of my own, a first draft.



I then researched parts and created a part list. With the parts solidified, I created a final sketch.

















The next step was assembly. We got a wooden board and attached the pump with screws through the designated holes. For the pump adapter, filter, RO membranes, and gauge we drilled holes in the wood and attached the adapter, membranes, filter, and gauge with zip ties. The zip ties were not long enough on their own so we chained them by connecting one end to the other's beginning. We then used metal brackets to attach feet so the system could stand upright. At first, the board was slanted but we bent it back into place. Next, we connected the tubes. The pump was oriented the wrong way so we had to switch the input and output of that and then we test ran it. There were a few leaks. We had to tighten some of the quick-connect valves and add plumber tape to some of the connections. We also had to remove the needle valve at the end of the system and replace it with a plastic one because the needle valve wasn't restricting the flow. The final product looks like this:

How the system works: There are 2 outputs and one input. The tree sap, the input, is placed above the pump, on a table or other elevated surface, and a tube is placed in that bucket or container. The concentrated sap, the white tube at the end, is placed into a clean bucket, and the yellow tube, clean water, is placed into another bucket (this is a waste product so it does not matter if the bucket is clean). Then the pump is plugged in. There is no on-off switch to this system so once the system is plugged in it will start to run. This is important because you do not want to run the system dry, it might hurt the pump. To make sure you are getting water out of the system, you control the valve at the end of the white output pump, concentrated sap. The goal is to get both streams running at about the same speed so equal amounts of concentrated sap and water should be coming out. The pressure would be at about 100 psi.




Data: 


For the first test run, we only measured the brix before and after, not gallon amounts or yield data. For the initial test, the sap going in was at 2.3% brix and the sap coming out was about 7.5% brix. For the second test, we went from 6.5% Brix to 7.5% Brix. It seems that the system caps out at about 7.5% Brix.


As a second part of this data section, we were going to do a taste test. The idea was to boil the sap the rest of the way and see if the resulting syrup would differ in flavor from the syrup that was done completely in the evaporator. This was not a possibility though as circumstances made us wait to boil and the sap expired. 


Data Analysis: 


Using the first run, because that run was more productive and as such we will do one run in the future, water was taken out raising the saps brix by 5%. Using this information I calculated the amount of wood we would save per gallon of sap if it was run through the RO system. 1 gallon of water weighs about 3.79 Kg so we multiply that by 4180, the specific heat of water, and 162, the change in temperature in degrees Fahrenheit. Boiling, 212 F - room temperature, 50 F gets that tempo change of 162. This is added to the amount of energy needed to evaporate the 2.08 kg of water needed to make the sap into 57% brix syrup times the steam constant of 2.2 x 10^6. This results in 7.2 MJ of energy needed to turn a gallon of regular sap into syrup. This is 450 grams of dry wood at 8 MJ of energy per Kg.


When using the RO system, we start boiling with 3.6  kg of water and then only need to boil out 1.8 kg of water. The resulting energy usage is 6.4 Mega Jules. This saves a total of .72 MJ and 45 grams of wood. This may not sound like a lot but this calculation is per gallon of sap so it adds up. This year we had 287 gallons of sap so if we ran all of the sap we got through the system, we could have saved 13 Kg of wood.


Sources of Error: 

There were a few issues with the test. Firstly, in our setting, we did not measure the sap we put into our system for weight or volume. This means that we do not have numbers for our yield of sap compared to pure water. We did test the sugar condensation, Brix, but not the amount of water separated. The second issue was that we were unsure if we used the same bucket of sap for both test runs. The brix before and after would be valid as we tested that watch time, but this further complicates any calculation of the amount of water we filtered out. Lastly, it is hard to say if the second test was valid. The sap we used expired a few days after we ran it through the system and because of that, the sap would have been already starting to congeal. This means that it would have had a harder time running through the system. The main test we did, change in Birx, though, was valid to the best of my knowledge.


Conclusion: 

In conclusion, we did end up taking a substantial amount of water out from the sap. This number was 5%, far from the 50% I hypothesized but an amount that would save time and money that would go toward boiling. 


The future of this project is large. In the coming years there will likely be many improvements to the system, both functionally and ascetic, with the hopes that it could help reduce boiling time further. A few things that could be improved would be properly sealing all of the fittings to prevent any leakage. The 5-micron filter could be swapped for another. We still need the filer but one that works differently and doesn't create a backlog of sap that does not run through the system could improve our yield. The whole system could be put on a more well-designed back plate to make it easier to move and more aesthetically pleasing. Lastly, expanding the number of filters would allow for more water to be filtered out of the sap.

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