Home made 30" x 60" Evaporator - Have we reached our max efficiency?

[WoznicaSyrup]

We currently have a 30" x 30" drop flue pan, and a 30"x 30" finishing pan with 5 dividers on top of our evaporator. We also have a 20 gallon (30"x 12" x 16") pan resting over the back half of our flue pan to act as a preheater. Right now I'm getting a boiling rate of 22 - 25gph with a stack temperature of about 600 degrees - wood fired.

The way our chimney is set up is a bit funky - we have a 6" x 12" box that comes off of the back of our evaporator and then the chimney comes off the top with an elbow and goes out the side of our sugar shack at an angle. We mounted two steel plates on either side to create sort of that box to create a shelf over the chimney (where a lot of heat is moving through) however when moving the preheat pan back over that area rather than covering half of the flue pan with it I can't get my sap nearly as hot. When its over the flue pan it gets up to about 130 degrees, but over the chimney I can only get it to about 70.

My question is - is it better to cover half of my flue pan to get the sap hotter and risk condensation running back in, or to open the top completely and have cooler sap flow into the flue pan? Also, I'm looking for a way to use more of that heat going out of the chimney. Any suggestions? I can include pics when I get home if it would help anyone understand better. And also, I'm sure the recommendation of RO is the first thing to come to mind - we are working on that for next year.

[mol1jb]

Are you using a blower for forced air? That would definitely help.

For the preheater pan, if you put it over the flue pan that could result in condensation back into the pan. You could try to pitch the preheater pan toward the back to get any condensate to run off behind the flue pan.

Or you could build a hood and parallel flow copper preheater. I built my hood for about $50 in aluminum flashing and used a trim break to bend it up and assembled it using pop rivets and food grade silicone to keep the drip channels tight.

[motowbrowne]

Definitely get the "preheater" off the flue pan! Obviously I've never seen your setup, but that sounds like taking two steps forward and one stop step back. Unless you have a parallel flow preheater and a drip tray, I think you're shooting yourself in the foot trying to catch heat from the steam.

I think you should be able to get your stack temp higher, although it would depend based on how your measuring it (surface of the pipe or a probe). I'd focus on improving your draft (remove the elbows from your stovepipe and or add a blower).

[maple flats]

For efficiency a stack should not go thru an elbow and out thew wall. It loses a lot of draw going thru the elbow and more going horizontal or nearly horizontal. Add a blower for combustion.
The issue with putting your pre-heater pan on the flue pan is that a lot of the steam hitting the bottom is condensing and falling back into the flue pan to be boiled again. You will do far better making a hood for the flue pan with an inside drain channel around the perimeter and build a parallel preheater, put a drain tray under it and channel all of the condensate to the drain channel, then run a drain out of the hood to get it out of the re-boil loop. Look on this site for pre-heater designs. If you use the hood/pre-heater method, put a damper in the steam stack (SS or aluminum0. Under the stack make sure you catch the condensate from the stack too. When running the preheater close the damper until you get a little steam coming out the leaks in the hood fit, then barely open it a tiny bit, that will heat the sap the best.

[WoznicaSyrup]

We don't have AOF or AUF setup currently. We are talking about AUF for next year with a small blower. I agree on the stack - but the way our evaporator is setup in our sugar shack the Cupola would interfere with a chimney that went straight up. Our Cupola is set up towards one end of the shack rather than in the middle. We've talked about a preheat hood too, but I'm not sure if we want to get that crazy. Even though I have 6-700 degrees coming out of my stack for some reason there doesn't seem to be enough radiant heat to get our preheat pan much above 70 like I said. I use wrist sized wod 16 - 20" long and fire every 5 to 10 minutes and most of the time I do okay keeping up, its just times like right now where I have a backlog of 250 gallons of sap that I'd like to move things along a bit faster. Hope you all are having as good of a season as I am though - just made my first batch of golden delicate and I'm up to over 30 gallons of syrup off 75 taps!

[maple flats]

I use a timer, wood is wrist size and I fuel every 9 minutes, by using a timer. Don't let the times vary, use a timer and follow the routine. Maybe you might want to consider a small R.O. I had a back log the last year before I got my R.O, so that we were boiling 2 days in a row for 21 hrs each and at the same time I had to sell 1150 gal of sap. Then I bought my little 250 gph R.O. and ever since, I process all of my sap and also process on shares for others.

[maple flats]

If you are saying the the cupola would be forcing the stack a foot or 2 to get clearance, do it. Then shield the cupola from the heat of the stack and make the stack at least 2' above the peak of the cupola.

[mol1jb]

Auf should help quite a bit. If you add a blower then the elbow in your stack will not be an issue. Auf will also make your fire hotter and burn more even. Ask anyone who added forced air to their arch, no one ever goes back to natural draft.

[RileySugarbush]

A small blower into the area under the grate has the potential of over 50% improvement. And you would not need to change your stack, though it would be best if you did.
Messing around with the preheater might give you 10% improvement over no preheater. If there is any chance condensate is dripping off your preheater into your pan, get it off of there!

RO for next year if you want, hugh advantage in production but more to mess with.


Best first step- a simple blower.