Convert wood fired evaporator to burn Used Veggie Oil
I've done it. Converted to burn pure, FREE, used vegetable oil. My heat is free. Easy to handle and burns clean. Read on if you are interested on the journey or want any ideas....I'm happy to share.
Hello everyone and Thank you all for the amazing information on this site. I finally had time to sit down and make myself a profile on MT after years of lurking and getting ideas. My biggest motivator for joining the site is the ability to reach out and ask members directly about some of their crazy inventions and share some off mine too.
It has come to my attention from a message by one of the nice moderators that some of the info that I posted on the welcome board would be best suited here. I have successfully converted my 2x8 D&G wood fired evaporator to burn either wood or Used Vegetable oil (UVO or WVO)
I am like most on here. Bought my dream property on the shores of a beautiful Northern Ontario lake that just happens to be filthy with sugar maples. Had to try it so bought myself 5 buckets and spigots and set my trap line. Boiled on the deck with a large turkey roaster and really enjoyed the whole process. But, my engineering mind knew I could do it better. That was 22 years ago. I've gone through every phase of my personal maple addiction journey and in 2016 bought a used, 80's vintage Dominion and Grimm 2x8 with 2007 welded pans. That was awesome but did it every chew through my wood!!!!
So last year we had a good year. 285 taps with 3/16 lines on natural sloped vacuum. Just shy of 300 litres (79 us gallons for my more southerly neighbours, (and yes thats how we spell "neighbour" up here)) of syrup in the bottles. Pump up the hill to the sugar shack, which is 40 feet from the house and 30 ft from the Garage. I have been considering an RO system to cut down on the wood consumption but held off for the last few years because of one major improvement to the rig. I converted my evaporator to run on pure, used vegetable oil. Thats right, used veggie oil. it has by far been the biggest and absolute most incredible cost saving, time saving and wood saving endeavour so far.
2017 was my last year of using pure wood. I was burning about a face cord a day and finishing between 6-8 gallons of syrup a day on a good day. It was hard work doing it mostly by myself. Kids help when they are not in school but it was stressful trying to keep up with the sap. It was full days of spitting my house heating wood down to 3-4 inch splits because thats how it burns the hottest. Loading the firebox every 7-10 minutes all day long. Stoke the right side, wait 7 minutes while splitting wood, stoke the left and repeat. There had to be a better way. I only had 150 taps that year.
So that year I started thinking. I had a 5 gallon jug of used veggie oil from various fish frys and doing a turkey. I started to research how to supplement my fire with the used veggie oil. Everything I tried failed. Drip into a stainless pan burner, dipping logs before stoking, mixing it with sawdust to make cakes. All failed.
My aha moment came in the depths of winter 2018 after returning from dropping off some scrap metal at the local recycling depot. They had one of the old, stainless steel fire extinguishers that had just been dropped off. It was about 3 gallons and designed to be pressurized with a standard valve stem and propel either water, foam or dry chemical. The guys at the depot gave it too me. Long story short, and after many many unsuccessful attempts to create a self sustaining and controllable flame, we finally got it.
In the simplest terms, the just gets filled with warm filtered oil. I plumbed the trigger mechanism to add compressed air into the tank to propel the oil and split the air intake off to rejoin the pressurized oil just before the spray nozzle. We used a needle valve for both the oil and air to make the mixture controllable. We made the nozzle into what we call a double Venturi ejector which basically mixes the oil/air mixture into a fine mist. We installed it into a 3 ft long, 2” pipe and ignighted it with a blow torch. It took many tries to get it to work. Eventually the flame lit and the pipe got hot enough to remove the blow torch and get the oil mixture flame to be self sustaining. Many adjustments to get the right spot for the ejector and the right mixture of oil and air. But it worked. By god did it work. It was so loud it sounded like a fleet of jets taking off. The Heat was so intense that it melted the nickel out of the galvanized pipe and it looked like a shiny coral when it hardened in the snow. So now I had to find a way to get this to work in the evaporator.
With a bit of playing, engineering and cursing, I modified the evaporator and got it to work. I had to put a double layer of firebricks in the burn chamber. Once I get the fire lit with my normal wood and get the stove hot, I can initiate the oil mixture. I have to start slowly and let the heat build to keep it balanced.
In 2018 I upped my taps to 200. I burned 70% less wood and my evaporation rate was 40% faster than with just wood. I went from stoking the fire every 7 minutes with finely split wood to adding normal home heating wood every hour and a quarter. Most importantly, my supply of used oil was free. The fire burns hot, clean, no soot, no smoke and burns to completion. There is no unburned oil leaking out the bottom. The exhaust does not smell like French fries and there is no off odour or taste to the syrup. Best part is, its biodegradable. If I happen to spill some on the ground, the dog is more than happy to come by and clean it up for me. I dump all the bits that I filter out of the oil in the garden and the chickens love to eat that up. The best part of the whole deal is that I get the oil for free. There are lots of people that use veggie oil in their diesels in the summer but can’t use it in the winter because it gels way to easy. The restaurants are happy to give it to me because it piles up on them in the winter.
2019 I changed the config of the burn chamber again and added some sort of a glow plug. It really just a metal structure with firebricks for a kind of plate that stays hot like a glow plug. I've found out that 1/2 inch plate steel burns out in a season so a 8x8" plate is a consumable part. I also upgraded to a pair of Cornelius pop canisters that many people use for brewing beer. So now I go out and light the fire in the morning like normal. Once the chamber is hot I introduce the oil/air mixture and away it goes. I get about 2.5 hours of burn time per tank. I Keep the second tank full and ready and warm. The changeover is just a matter of closing the compressed air valve, disconnecting the input and outlet couplers and swapping tanks. It takes less then a minute and away it goes again. The glow plate works so well that I have about a 15 minute window before It gets too cool to to light the oil. Im at the point where once I light my wood fire in the morning, I don’t have to add another stick of wood all day. All of last year I burned less than a face cord of wood for the whole season and made almost 80 gallons of beautiful syrup. I got so confident with the system that I can walk away for an hour at time and putter in my garage while the automatic sap feed and the continuous burn keep things going.
All my neighbours are fascinated by this system. A couple of my local hobby producers have come by to see it work and get some Ideas. I have been told to submit the design to either the Dragon’s Den show here in Canada or the copy cat version down in the states called the shark tank. Not really interested in that because it is to specific to each rig and there is no way I could get it certified for CSA compliance. So I am happy to share the Idea and design with my maple syrup fanatics and give back to the community as a whole.
This year alone I figure I saved 14 face cord of hardwood. Overall I think I have saved over 40 cord of wood since I converted to UVO.
Ive got some pics and videos on how its built and how to run it. I will have to figure out this forum first and get my kids to help me get the videos uploaded to youtube. The only thing I ask is please don’t get the oil from my restaurants. I burned 750 litres of used veggie oil last year.
Once again, thank you to everyone here on Maple Trader for the free flow of information and the amazing ideas that have been shared.
Justin.
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