Hardibacker question

thomas rubino wrote:Hi Greg;
Yes,  Hardi board protected by firebrick splits will hold up fine for testing purposes, just not long-term.
Be sure to stick with the published dimensions for your J-Tube OR consider using an L-Tube.
Do not extend the burn tunnel on a J-tube  

Glenn Herbert wrote:I agree with Thomas. I would suggest an L-tube for evaporator use, which requires long intense fire. A 30-32" long burn tunnel with similar heat riser gives space for a lot of wood to keep the fire consistent. I would not use anything smaller than 8" x 8"; an 8" wide by 9" high burn tunnel is extremely easy to build with standard firebricks.

I have found that using mostly larger logs allows them to keep their shape until they are mostly burned up, so that air can get to all sides. Small wood quickly collapses into a mound of coals and chokes off air to the bottom, building up a heap of charcoal. I can run a 10 hour evaporator session and with attention to loading, never have to rake out ash/coals, and have just a couple inches of powdery mineral ash in the bottom after finishing.

thomas rubino wrote:Ha Ha, Well Greg you are talking to northern boys.
We know all about maple sap... and in my case virtually nothing about sugar cane.
Glenn is by far the more knowledgeable about this subject,  Montana has no natural Maple trees or any sugar cane at all.

As far as consulting goes you could continue to ask and receive answers right here at Permies.
I am always open to a scheduled phone call but my evaporator knowledge is limited. (No charge) you can contact me at dragontech@blackfoot.net

Thank you. That is very kind and I may take you up on the offer.

thomas rubino wrote:Hey Greg;
Well, you are boiling sap so it's going to be hot.
If I'm understanding correctly, the barrel is open top and there to help shield the heat.
I would consider using an insulated riser, it would concentrate the heat inside the riser giving the most out of the top under your pans.
Yes, I think a diverter to spread the high heat across all your pans is a good idea.
Consider, using a steel box as a stratification chamber that collects the heat, and then have your vent pipe leave from the lower part of the box.

For the workers, you could use 4x8 sheets of the rigid foil face insulation board standing on the edge to block quite a bit of the radiant heat.
Lots of fresh cold water, maybe misting fans, start before dawn and quit after lunch?

thomas rubino wrote:Ok;
You have a much smaller pan than I have seen in northern sugar shacks.

If it will fit over a barrel then that will work.

You may need to play with the diverter gap, it can't be too close.

For your "Work" force a 4x8 sheet of rigid insulation would work.

Be sure to use a good size exhaust stack.

Glenn Herbert wrote:That first one was a bit undersized for the 8 sf pan. I added a couple of bricks to the L-tube length and it seemed to work better, but I never got the chance to really test it. It would work great for a 4 sf pan like the OP's, and could be built entirely in/on a base of a dead kitchen stove.