need advice on oil tank/firebox design

[TC matt]

I was a first-timer last year and boiled over a turket deep fryer - me and kids loved the experience, but the LP bill was bit much.

So, got a 300 gal fuel oil tank for free and just designed what I thought would work. Below is a link to pictures of it so far. I'm having a SS pan made (for free :)) that will be 34x66x7 to fit on top. THEN, i found this site, looked at other homemades and small "pro" evaporators and realized I was missing the boat on the couple of items - 1. insulation; and 2. internal firebox design. I am now planning on having two 22x63 panels made of 3/16" steel with a 1" deep area behind it and wire mesh background into which a 22x63x1" mineral wool "blanket" will be sandwiched. These panels will be layed inside the box at about the angle of these slash marks "\ /" from the grate to the edge of the opening/pan. I figure this will a. insulate the box, b. direct heat up and not out and c. shrink the area in the firebox. Now after looking at other evaporators online, I noticed almost all of them have a smaller fire area in the front and then a horizontal pitch up to the exhaust flue. Why is this? Is that design more effective or as effective as a wide open/deep firebox? Less firewood, same effect? If the answer to this last question in true, then I was thinking of having my grate cut in half and then leaning it up onto the angle iron along the back side of my firebox (see pic of wooden stake laying on angle iron) then either having another steel blanket holder made to lay on top or use a blanket and fire bricks. Is this a good idea? to costly? What else am I missing? Any advice is greatly appreciated.

Also, right now when i take out the grate this is very portable, which is important. So, I need to be able to move this thing 2-3 times per season and that's why the steel blanket holders seemed to make sense.



http://s1004.photobucket.com/albums/af164/masamcd/

[ebourassa]

I dont know if this helps or not, but i built one 5 years ago, and i dry layed fire brick on the sides becaus i too needed it to be moved every so often, You should make your fire box about 3' long at the most, either build a brick wall at that point or put in some sort of steel baffle there, this is to push the heat upward towards the pan instead of straight back and out, the way you have it will work but i might work more effeicant with the baffle, the key is to keep as much heat under the pan. i like your idea with the mineral blanket i think it also called ceramic blanket, if so you should be fine, 1" ceramic blacket i believe is rated to 2300F, i wish i thought of that when i built mine, but all in all have fun with it and you will make several adjustment and improvments through out the season, i love trying to figure out different idea to improve boiling sap, some are failures but other are success, thats what great about building one yourself.
good luck
Erik

[TC matt]

After thinking about it, I'm worried that the steel side of the blanket holder will eventually warp.
I found a company just two hours drive south of my town that sells these refractory tiles that come 12"x24"x2 and 2.5" (see link below) - these tiles are cheaper than my blanket holders would be. I spoke with the owner and he said they're hard as brick. I would then attach the mineral wool/blanket to the non-fire side, rather use the steel mineral wool/blanket holders.
I can have these cut to 22" and stand three of these upright on each side of the front of the fire box, and then another three along the back to create the baffle. THe joints between the sides and back will be a little tricky, but since nothing but ash and hot air will come in contact, I suppose I could just "caulk" it with mineral wool. Any thoughts on that?

Eric, do you have any pics of your evap?

http://www.indfirebrick.com/sales.htm

here's my rig so far..
http://s1004.photobucket.com/albums/af164/masamcd/

[kytepc]

If it were me building this i would brick all the firebox to the pan and only make the burning area 2 feet deep from the door, weld in a baffle and brick it. I would weld in a baffle 8" from the pan to the rear stack increase the pipe to 12". Loose that grate because it will be flat to the bottom when the fire gets hot. Next get a muffler pipe 2 1/2 and make it 2 feet long in the fire box side smash and weld the end drill 1/4 holes on 10 degree v to supply air to the fire put sand around bottom of pipe, I had mine bent on a 90 outside the fire box and away from the heat i put a small fan on a restate to adjust the speed to the fire this will slow down the build up of coals and make a hotter fire. I used sand on my baffle under the pan and bricked the sides I have been involved with 3 of the same setups and they have all worked well.

[TC matt]

I'm definitely going to cut the grate and weld in a baffle (up and back) now. Question - since I'll be laying a ceramic blanket or mineral wool or some other refractory hi-temp insulation blanket down and bricking it, could I use expanded metal with angle iron support rather than solid steel. Theoretically, the blanket and brick will keep it from losing form. Thoughts?

Also, my pan length is 66". Any opinions on how deep the firebox area should be? 24" , 36", other?

The last poster recommended I elimate the grate in the firebox, any other opinions?

[kytepc]

I would forget about the wool or ceramic blanket not needed if you use 2' brick and fire cement. The heat will not transfer through the brick that hot to be a concern. I think they use wool in oil arch's I have never seen it in wood! Most wood fired use brick. Angle is good for support I would use 1/4 plate with angle
for baffles. The whole idea is to loose the heat on the pans and not have it go up the stack so you want a short fire box and baffle to keep the heat on the bottom of the pans. As for your floor grate made of mild steel will bend under the heat and weight of the wood, cast iron street grate works but will build up too many coals and that will not give you a good heat, air injection burns off the coals and gives you a hotter fire.

[Gary R]

Look through this thread. I have a lot of pictures on it.

http://mapletrader.com/community/showthread.php?t=3621

I like the blanket. I have seen some of my firebricks glow red hot. That heat would transfer out the sides if no insulation. Under the back of my pan I only have blanket. I would go with at least 24" deep fire box probably 30". My brick are dry stacked. I do move the sugar shack around. The bricks don't fall out. Check out the use of fire bricks for a grate. They work very well. Any mild steel will not hold up to the heat in the fire box

[Haynes Forest Products]

TC Matt I like the work you did nice job. Those 24x24 tile are a nice way to go I pulled a BIG gas pool heater apart that had the same tiles in it. You could build a rack to hold the tiles for the bottom of the fire box and lay them on the rack drill holes for the combustion air and then lay the steel grating you already have over the tiles for protection and that will protect it. Use fourced air to keep the coals to a minimum and LET ER RIP. As far as the baffels weld some crossing bars on the back and weld them in. SO WHAT if they warp a little. Pack the back side with insulation and get to making syrup. Do a test put as hot a flame to some of the baffel steel with regular insulation from your house and see what happens to it.

I see all these turkey friers and all the heat that is lost because they only get about 1/4 of the heat on the bottom of the pot. and now your going to burn wood and God forbid you should waste some heat.

[TC matt]

I'm pretty sure my wife thinks I started having an affair with someone on line this weekend, as much time as I'm spending looking at everyone's old posts and learning how to make my homemade rig better. It's become an obession.

a few more questions...
once I build up the back the of firebox, should I ramp the rest of the area back to my 8" stove pipe hole? or just have it a level 8" from the bottom of the pan? or should I even consider shrinking that area to, say, 6" from the bottom of the pan and block off the bottom 2" of my hole?

Gary, what is behind the brick and insulation at the back of your firebox and under your ramp? Steel? expanded steel and bracing? concrete blocks?

Okay, now here are two questions that prove that I am a true rookie...
1. why the pan dividers? My pan is being made right now and I didn't plan to have them put in, but it's not too late.
2. the gph (gallons per hour) that everyone references is that of finished syrup?

Thank you everyone for all your help!