Natural Gas Stove Top Evaporator

[HowardR]

I just finished my first season with the stovetop evaporator and it worked great. My only discontent was with the 1/2 inch stainless steel float valve that I bought cheap on Ebay. I may, eventually replace it with a more expensive float valve, perhaps one designed for 3/4 inch pipe, because there was variation of about an inch in the level of the boiling sap in the connected pots. So if you use a cheap float valve, don't try for a boiling level below 2 inches.

I recommend this system for people who like to just check how things are boiling every 90 minutes or so instead of having to be with the evaporator constantly while it is boiling. I'd check the RO and the evaporator at the same time and I'd adjust the concentrate flowing from the RO so that the two would keep pace with each other. I'd also adjust the outflow of the system based upon the temperature of the boiling sap in the last pot and I'd occasionally have to tap the float on the float valve when the level of the sap was getting low.

I'm building a second RO for next year, identical to my first. Each of my RO's will be able to put out 3.5 gallons of concentrate per hour while getting rid of about three times as much water. I'll try feeding the concentrate directly from the ROs to the feeder pot. Even though my evaporator is slow, the combination of my two ROs and my evaporator should be able to process 30 gallons of sap per hour during a big run. And I can continue to process sap day and night when necessary, just checking every 90 minutes or so to make sure everything is proceeding without problem. My other advantages are that I can easily scale everything down for a small batch and also that I don't have to have as much storage capacity because I can process sap as it flows in.

So for about $3,000 of investment ($1,000 each for my evaporator and two ROs), I'll be able to process about 30 gallons of sap per hour!

[jdircksen]

Can you describe your gas supply to the 4 stoves? I am going to try a cooktop connected to a 3/8" hose. I'll have 2 steam table pans and maybe a 5th burner as a pre-heater. I'll make a stand and drop in one like this...

35829492_959547927556427_2845721729760755712_n.jpg

[HowardR]

All of my gas pipes are iron screw in pipes. My gas supply gets reduced to a 3/4 inch pipe when it enters the garage. (I'm planning to change that some year and keep it up at 1" in the garage.) I tap into the 3/4 inch pipes separately for each stove, usually reducing in order to connect a flexible metal gas stove feeder line (the ones that you use to connect a gas stove in the kitchen). None of my pipes is as narrow as a 3/8" hose.

[HowardR]

This year I replaced the cheap Ebay float valve that I used last year with a Blichman AutoSparge purchased from a beer supply store. The Blichman float valve is the same 1/2" pipe size and it is definitely a better valve, but it didn't solve the problem. I still have to tap the float sometimes to get the sap to flow faster through the valve.

My problems don't occur when I am running the output of my ROs right into the feeder pot. Whenever I am doing that, the level in the feeder pot doesn't change much and the float valve works perfectly. My problems occur when I am filling the stove top evaporator without the ROs. At such times, I have to fill the feeder pot every 80 minutes or so to keep it from running out of sap. As a result the feeder pot goes from nearly empty to nearly full and gradually back to nearly empty. As a result, I often have to tap the float to get the feeder valve flowing faster right after I fill the feeder pot.

All of this means is that the level of the sap in the stove-top evaporator can vary by as much as 3/4". So when you plan your system, don't aim for a 1" height in your pans. That could be cutting it too close. Aim for a 2" height.

[HowardR]

Maple Flats wrote last year:

Just be careful for foaming. You may not want to let it go unattended that long. As the sap is boiled down the likely hood of it foaming up increases big time. If it starts to foam up, it could quickly ruin a pan and the sap that is left in it. An hour is a long time unless you set up a automatic defoamer, otherwise it's a sure recipe for disaster.

Now that I have has almost 2 seasons experience with the Stove Top Evaporator, I can definitely say that there is no danger of foaming below 218 degrees. I even let the temperature get up to 219 in the last pot one time by mistake, and yet there was no foaming.

Foaming is caused by a low sap-volume-to-heat-source ratio. You can prove this by finishing up a batch of syrup on your kitchen stove. When it starts to foam at about 217 or 218 degrees, turn down the flame and it will stop foaming while you gradually heat it up to 219. My Stove Top Evaporator has a much higher sap-volume-to-heat-source-ratio than a standard evaporator.

[DRoseum]

I built a natural gas evaporator and RO this year and it worked great. Details are here:

https://www.sugartree.run/2019/03/cu...vaporator.html

[jdircksen]

Thank you for sharing that. I’m hoping to build something similar this summer.

[DRoseum]

No problem. Let me know if you have any questions about items I used. The steam table pans work great, and I use them to draw off into, to preheat sap above main pan, and to finish boil over one of the U-burners. Had 35 taps this year and made 6.25 gallons so far.

[Cedar Eater]

This really makes me wish that I had natural gas to my house. Propane destroys the economics of doing this. Good job!

[HowardR]

D. Roseum,

Your evaporator looks beautiful and professional! How much did it cost you in parts to build it?