mnmaple
04-29-2013, 12:02 PM
Just finished building my oil tank evaporator last week, and boiled our first batch of sap down on saturday. We boiled down about 80 gallons of sap. From a cold start to drawing off an almost finished product , with no preheater, the 80 gallons took us 8 hours to boil down. The first 2 hours, the evaporation rate was pretty slow, getting things up to temp, and figuring out the firing schedule but by hours 3-6 we were boiling down at a pretty good rate.
Description of the evaporator: Roughly 60" long x 26" wide. 4 steam pans dropped down inside. 11' tall stack out the back of the tank. I don't have any fire brick in it, just some concrete pavers and brick set inside with lots of gaps going to bare metal. Nothing is cut to fit, just whole paver and bricks, using what we had in the time we had to do it in. I would like to line it with ceramic blanket and fire brick to seal it all up, but that is for another year.
I have to place the wood, real close to the door to get the 1st pan boiling, the 2nd and 3rd pans boil hard, no matter what. The last pan, the 4th one, hardly boils at all. What is causing the last pan to not boil very hard, and what can I do to get a better boil on the last pan? I have a theory, no idea on the validity of it, that possibly the fire and hot gasses are just running out of the back so fast and up the pipe, that I am not getting optimal heat transfer. Can I place some bricks inside to make the fire and gas move around a few objects to keep it under the pans longer before it leaves out the stack? Or would that just reduce the draft and cause other problems.
Is the angle of my arch on the inside causing my problems? The firebox is about 20" long, then the arch angles back, then levels out for about 30" to the back of the evaporator with about 3 inches between the brick and the bottom of the pans. Should I have angled the entire arch as it works its way up the stack pipe instead bringing it to level and then running back? Would that have brought more heat directly to the back pan?
I don't have any pictures right now to help show what it looks like, but I would like any input through your experience in making the evaporator perform better, or your help in fixing a design/build flaw.
Thanks
Description of the evaporator: Roughly 60" long x 26" wide. 4 steam pans dropped down inside. 11' tall stack out the back of the tank. I don't have any fire brick in it, just some concrete pavers and brick set inside with lots of gaps going to bare metal. Nothing is cut to fit, just whole paver and bricks, using what we had in the time we had to do it in. I would like to line it with ceramic blanket and fire brick to seal it all up, but that is for another year.
I have to place the wood, real close to the door to get the 1st pan boiling, the 2nd and 3rd pans boil hard, no matter what. The last pan, the 4th one, hardly boils at all. What is causing the last pan to not boil very hard, and what can I do to get a better boil on the last pan? I have a theory, no idea on the validity of it, that possibly the fire and hot gasses are just running out of the back so fast and up the pipe, that I am not getting optimal heat transfer. Can I place some bricks inside to make the fire and gas move around a few objects to keep it under the pans longer before it leaves out the stack? Or would that just reduce the draft and cause other problems.
Is the angle of my arch on the inside causing my problems? The firebox is about 20" long, then the arch angles back, then levels out for about 30" to the back of the evaporator with about 3 inches between the brick and the bottom of the pans. Should I have angled the entire arch as it works its way up the stack pipe instead bringing it to level and then running back? Would that have brought more heat directly to the back pan?
I don't have any pictures right now to help show what it looks like, but I would like any input through your experience in making the evaporator perform better, or your help in fixing a design/build flaw.
Thanks