natural gas evaportator

[Maple Ridge Tapper]

This is my first year making syrup. I'll have around 300 taps in this week. Currently have 100. So far I've just been using a un modified little wood stove to evaporate and as you know, they are very slow at evaporating. So I need to upgrade. I have ordered the parts to make a smaller RO system that can do up to around 150 gallons of sap per day.

I will be building a 2 x 6 evaporator. Not sure yet if I'm gonna get fancy with a flu pan etc or just start with a flat pan. But what I am considering is the possibility of making a natural gas burning evaporator instead of a wood one. With the use of the RO if I can reduce the volume of sap down to boil by around 75% then it may very well be economical to use natural gas instead of wood. I do have a fair bit of dead fall on our property that I can use for wood fuel for awhile but eventually I would have to buy or scrounge up free wood to burn once our own wood supply is depleted.

Is there anything really important to consider regarding safety/hazards etc when building a natural gas burning evaporator? I have friends who are fabricators/welders who have said they can help me make the evaporator no problem but I don't really have any close friends or associates that are experts with natural gas. The other good thing with using NG at our location is that the sugar shack is very close to the natural gas meter/source so running a line to the sugar shack will be very easy. Are there stock natural gas burners i could buy to use in the evaporator? Or is this something that would have to be custom fabricated with the burner tips installed etc. And how about gas flow regulators etc; is there a certain pressure the line should have that is feeding the burner? Is there a calculation formula to do to figure out how much pressure to use for how big of a burner is used?

My other thought is that with an arch evaporator and wood used for fuel, the flames are forced to travel up the arch to under the pan, but what about with natural gas? Would the burner have to be fab'd and welded in place directly under the whole dimensions of the pan in order to ensure all areas are heated?

Would be great if someone could direct me to any tutorial or forum thread that covers a home built natural gas evaporator that worked out well. I'm in the process of searching the forum for something like this at the moment.

[Urban Hillbilly]

I built a natural gas fired cinder block arch with a pair of 2x3 flat bottom pans. Don't know anything about NG safety. Had a HVAC company put a valve right off my gas meter. I run 1 inch black pipe to my evaporator with some flexible gas piping at the end. I bought four 32 tip jet burners and put them together with 3/4 inch black piping, elbows, nipples, Ts, universal joints and valves from Lowes. Easy as pie. The jet tip burners are available on line and they work great but are pricey. Look around the internet because prices vary dramatically.

I have the burners maybe 4-6 inches below the pans setting on cinder blocks turned on end. Make sure there is a lot of air flow. I even set the pans up an inch above the arch so the exhaust comes out from around the bottom of the pans. Before I did that I got a lot of soot build up. It is astounding how much pressure is lost over distance with NG going through piping. You can look up some tables on line. The point is that if the gas has to flow any distance, you have to run a decent sized line. I tested my burners on a gas line coming to the side of my house meant for a gas grill. It barely provided enough gas and pressure to light a flame. Remember that the burners on your kitchen stove are from maybe 5,000 to 20,000 BTU. A typical gas grill might have a total of 50,000 BTU. My 4 burners can generate 500,000 to 1,000,000 BTU with enough gas flow. I might be I evaporate at 10+ gallons an hour I guess.

The beauty of my rig is that I can simply turn it on and off at will and I don't have to tend it meticulously. I religiously set the time on my iPhone and pour 10 more gallons in every time it going off. I can go eat dinner, work on other projects or even be watching a movie while the steam is billowing outside. Just be maniacal about setting the timer. I've woke up in the middle of the night in a cold sweat thinking the rig was outside going to town melting my pans because I'm so worried about screwing up. My rig is completely outside in the driveway so there is no CO2 worry.

[mellondome]

I run a 2x6 raised flue converted to ng. Converted a traditional wood arch. Using 2 torch style burners. 7"wc of gas is what you need at the burner. But you may need more flow than your house regulator provides. I'm using about 700k btu.
You need to figure you your total btu load and verify with your supplier that your current meter and regulator will work. I have a dedicated meter for the sugarhouse. As urban stated... use big pipe to eliminate line pressure loss.
There are lots of different burners ou there ..conversions for oil burners to ng. Long tube style like in hot water boilers, I use a torpedo tube or torch style. Uban is using pot burners.

[Maple Ridge Tapper]

Thank you very much Urban Hillbilly and Mellondome. I bit the bullet today and ordered a 3 burner NG complete stand with all fittings to hook my line up to. Each burner is rated at 100,000 BTU's at full 10.5 water column pressure. I did have to call my gas supplier to make an apt for next week for them to upgrade my meter and gas pressure. They do it for free so that's great. Then I just have to get my HVAC guy to put a T at my meter and put two seperate regulators on it; one with lower pressure going to my house and the other one with higher pressure going to my sugar shack. They are raising the pressure to my meter up to 56 water column pressure so I will have tons of pressure for the evaporator. The burner supplier is sending me three different manifold orifices so I can play around with them to see which one works best for the max gas pressure for the burners. Now all I gotta do is make a stainless pan for it which is no biggy. I have a professional welder friend that is gonna help me with that. Can't wait to be boiling down on NG. Like you guys say, it's so much less to worry about. I do love chopping wood but I can still do that for our smaller needs around the property.
I also ordered all the parts to make a small 150 gallon per day RO system so I'm really looking forward to the next few boil downs with the new toys :)

[mellondome]

How did you make out last season with the ng rig?