Expanding Evaporator

[Deano686]

I currently boil on a 24"x32" raised flue pan. The pan is on a 2'x3' firebox from an old wood furnace that has been modified with the top removed to except the pan. I would like to add an arch this winter to except a second pan in hopes of increasing capacity. My options are to add a 2'x4' pan or 2'x6' pan. My question is, would I get the full benefit of a 6' pan, or would it be too long for the heat to reach the rear of the pan. If it would be beneficial at all over the 4' pan, I would rather go bigger, as I have an over abundance of trees that I can tap. Way more than I can handle.......I know....There are worse problems to have. Thanks so much for any input on this.
Dean

[optionguru]

BIGGER, BIGGER, BIGGER!!! Sorry, couldn't help myself. I would think any exposure to the flue heat in the back of the pan will still help your evaporation rate. Are you planning on having drop or raised flue on the new larger pan?

[BreezyHill]

I would suggest a 2'x6'. With out a sap preheater there are reports of 20 gallons per hour boiling rates. Adding a steam hood and a preheater for your sap will get you to the mid 20's. Adding air under fire you can increase this to 24-28, by adding air over fire there are reports of mid thirties per hour.
Once you have a 2x6 then I would suggest an RO to increase production by boiling higher sugar content sap. My experience with big units, 5x18, was it had a huge appetite for wood. Running an RO seemed more rewarding and meant less time cutting wood.
Protecting the evap from drafts will also increase your boiling rate.
How many taps could you have? Under high vac the max flo rate is recorded as .2 gallons/hr per tap. Then figure the boiling rate you can achieve, then the hours you have to boil; and you can figure out how large an evap you need....or how many trees you can tap.

Good Luck!

Ben

[Deano686]

I guess I didnt quite explain myself. I failed to mention that I will add a 6' pan to my existing 32" pan. This would give me an overall evaporator just shy of 9'. I do plan on adding AUF to assist in pushing some flame. Not sure about a hood this year. I did make one for the small pan last year, and it did increase my rate enough to do it again. As I will be sinking some coin into this expansion, pockets will be a bit light for material for a full hood. Thanks so much for the input fellas. I'll be sure to get some pics up as the progress begins.
Dean

[BreezyHill]

Details are good. Some people need one liners. I prefer to have all the details; because one little difference or detail can totally change the answer.
I will make you a hell of a deal. I have a roll of SS flashing with about 400' of 24" wide. So If you want to make the trip out here we can unroll and cut some off for you. Sketch out a design and we can cut the lengths you need. IF you want to see mine first that's fine and we can cut to copy that. Just let me know.

Ben