Batch evap two batch pans vs "preheater" to finishing pan?

[jrm]

I made my barrel evaporator with 2 pans, the large (steam table pan) runs parallel to the barrel and starts at the front, directly over the fire box. The second pan (half-size steam table pan) runs perpendicular to the barrel and sits at the back over the fire brick ramp and next to the stack.

In each of my prior years, and so far this year, I have treated the small pan as a preheater... Adding sap into both at the beginning, getting to a boil, add new not-preheated sap to the back pan, and as the large pan evaporates adding heated sap from the small pan to it. Typically the rear pan drops some in temp, but comes back to its boil.

i use a 32oz SS handled pot to transfer the sap. At some point this year, I decided to rest the filled pot on my pan lip to act as a preheater before adding it to the rear pan. I know I would increase my gph if I do a better preheat.

I know that the larger pan evaporates faster which is why I set up as I did originally. However, using this technique made me wonder if my method is most efficient, or if I should treat both pans as independent batches and let them evaporate and add more warmed sap to each.

Thanks for your thoughts.

[happy thoughts]

I don't think one way is more efficient than the other. It's still going to take the same amount of work and btus to boil both pans off. I think the advantage of doing it the way you do now is having a large pan that is more concentrated and closer to finishing off which I'll assume you don't do on your arch. That frees up the big pan sooner so you can boil more sap on your arch. Anyway, that's my 2 cents :)

[Big_Eddy]

I'd be tempted to switch them around. Use the smaller pan at the front for a syrup pan, and the larger pan at the back as a sap pan. Then set up a controlled pipe with a steady drip into the back pan to keep the level where you want it.

The advantage of using the smaller pan for a syrup pan is that you can then take smaller batches all (or almost all) the way to syrup in the smaller pan on your wood fire without having to boil FOREVER on the kitchen stove or propane, and without running out of sap.

The front of your arch, even though it is over the firebox, will typically be a little cooler than the middle is, as the hot gasses "cut the corner" in their rush to the flue pipe. By the very back of the arch, they are starting to cool off, so the boil is softest there. By having your syrup pan at the front, you have a hot but manageable boil for the syrup pan.

You're right to try to keep the back pan boiling, but a slow steady drip into the pan is more effective than a scoop every few minutes.

Either way around, the overall evaporation rate will be the same, but you're better to transfer sap from one pan to the next as it gets more concentrated. Makes it easier to manage your boils and batches regardless of how much sap is available.

[happy thoughts]

I like big eddy's thinking. That said, on my short block arch set up with two full size steam pans sitting crossways, the rear pan comes to boil the quickest and boils the hardest because of the short firebox. I'm not sure why you say your front pan evaporates faster but I imagine a barrel arch would suffer the same as mine with it's short length and cooler front pan. What I'm trying to get at is maybe you should double check with a thermometer which pan comes to boiling temp first and use the other one for syrup. I'm assuming they aren't the same length and width and you can't physically switch the pans themselves because of the way the barrel was cut out???

And ditto what was said about a slow steady drip. If you can't manage that, smaller but more frequent additions/transfers should work better than what it sounds like you're doing now. Not a quart at a time but maybe a ladle or half ladle full.

[maplestudent]

If you can't move the pans (meaning the barrel is cut specifically for each size) then I'd put the fresh sap supply in whichever pan boiled harder, and do like Big Eddy said - try to rig something up so you add sap by the trickle instead of by the pan full.

Questions for you:

how tall is your stack?
do you run it with the door open or closed?
do you have a grate in it, and can air get in under the grate?

I started with a barrel setup about 5 years ago (2 large steam table pans) and at different times sometimes the front pan boiled harder, and sometime the back one did. More info about your setup would help with offering suggestions. A couple years ago I expanded mine to a 6-pan setup (4 half pans and 2 full pans). I've done a lot of tweaking and this year, once I get it going, can get about 10 gph for hours on end, and that is with adding cool sap (not ice cold, but it's not warm either) at a very small stream rate.

[jrm]

Thanks for all the ideas...

I'm running a 6" stack coming out the back of the barrel, approximately 7' (3 sections plus height of elbow and straight connector. The fire is raised is on a grate and I generally run with the door partially open, as well as the air flow grate underneath open, but no added blower.

I like the idea of being able use the smaller pan to get closer to finishing as big_eddy suggests, but, alas, my cut holes are specific to the pan (the sawzall work wasn't pretty.) I think between all the ideas here, I really do need to tweak the sap delivery to me a slow even keel, but in the meantime, I can definitely ladle in smaller quantities.

I've typically kept a thermometer in each pan, though I ended one this last boil as it got sticky steamed out. But, I can't say clearly at this point which has come to the harder/faster boil first for two reasons. One, the smaller pan ha almost always been filled deeper since I am using that to heat and more forwarded, and I have figured in order to keep up with moving forward to the syrup pan that I needed more in it. Second, it's temperature fluctuates because of adding the cool, sometimes cold, and more recently slightly warmed, sap into it. I don't completely lose the boil, but it definitely drops that recovers pretty quickly. I figure the latter will be handled by changing how I handle the sap additions.

The front pan does seem to evaporate faster, but I'm sure that is at least partially attributed to the greater surface area as well as a shallower depth. I originally made my pan (size) and sap/syrup choices as I did Trader reading to get started it seemed that the hottest would be at the front.

Maplestudent... 10gph, fantastic! Done with my haul in 2-4 hours, that'd be amazing.m:)

I'll try some of these suggestions this weekend, then brainstorm further for next year.

[happy thoughts]

Just for spits and giggles why don't you run the pans with equal levels of water, fire it up and see which pan boils first? If it's your front pan then you're good to go using the small back pan for syrup. If not, all you've wasted is a little time and water.

[maplestudent]

Do you have any pics you can post? I'm curious how the pans are set in the barrel.

Also how much open space do you have under and on the sides of the small pan? (On the inside of the stove). You want to direct the flame to the pan if you can.

Is the stack connected to the back end as high as possible? The heat/flame will move to that hole.....if it is lower than the bottom of the pans I might try putting a brick on the ramp, an inch or 2 behind the small pan to force the heat up over and around the brick. I did that on mine (read about it somewhere here) and that has helped my back pan heat better.

I also think that withe the door slightly ajar, the front panel probably is not getting all the heat ito potentially could. Is there any other way you could get air under the grate so you can keep the door closed? That could really help the front panel boil and then use that for adding the fresh sap as mentioned before.

[jrm]

Not a bad experiment... but, since the sap is mostly water, I figure I could test this out when I start on Sunday...

But, I'm a bit confused, and last night I couldn't think about articulating it... I've assumed that I want my syrup pan to be maintaining the harder boil, if I am one pan that is hotter/faster than the other. It seems that you and maplestudent are suggesting that the sap pan should be over the first to boil, and therefore probably the hotter location. Big_Eddy was suggesting, if I can to reverse the pans in order to be able to get closer to finished with the smaller pan and also be able to remove batches sooner, and it maintains a "hot, but manageable" boil.

[maplestudent]

yup.....that is the dilemma. syrup in smaller pan and sap in the hotter pan.....it doesn't always work that way by chance. In my opinion if you could tweak things to get that result, that would be the best scenario, along with the trickle feed of fresh sap. But sometimes the tweaks can help both too. bottom line is to try to keep as much heat as possible under the full extent of the pans.

[jrm]

I intended to post pics yesterday, but was having trouble. I will need to take a few additional to show you the interior setup and will post those later. Most of the set-up are from last year, the two showing the individual boiling pans are from this year.

Yes, I'd say my stack was as high as I could go... or at least as high as I could cut confidently, but I will take a look when I get the other pics. I am using firebrick to build up at the back and they come to the bottom of the stack opening, right in front of the stack, and come up higher on either side of the stack to help force the hot air in. I also have firebrick lining the sides of the barrel, at the firebox insulating, protecting the sides, and drawing heat up not out. The front pan is directly over the firebox. The back pan is not. Also, the front pan is set into the barrel lower than the back pan, which is more limited due to the firebrick ramp. This year, I put a bit of sand under the grate just to help insulate, not enough to prevent air flow.

My first year, I always kept the door closed, but it seems that keeping it slightly ajar provides me with a better, hotter fire. To get airflow under, I'll need to acquire a blower, of some sort and utilize the air grate for that purpose -- 2017 is another year, right?

For now, at least I have a number of good ideas and thoughts for tweaking my design, or if I end up doing a rebuild I'll have different ideas -- which might include turning my steam pans perpendicular and using two full-size instead of my mixed sizes. But, I also appreciate the thoughts about using each pan as individual batches vs the manner in which I've been doing it, because that I can definitely affect on Sunday/..13717137181371913720

[maplestudent]

yeah....just keep trying to tweak things. looks like you have a pretty decent boil going in both pans.

by the way, one of those pictures has snow in it.....where did you get that?

[jrm]

Snow was from last year... I did have any sideways pics from my boils this year. Any snow I had this year has been long gone. My son and I pulled out taps yesterday afternoon. Pulled the sap from my freezer this morning, probably should have take a few of the containers our last night.

Tomorrow will be our final boil, 20.5 gallons to evaporate. I bought a sap hydrometer which arrived last week, our various collections samples ranged from 1.6 - 2.0. Looking forward to seeing what we finish. (I'm guessing we won't finish tomorrow.) Maybe enough to make some cream for the first time. Or maybe, we'll just make some maple ice cream... Weather is warm enough for that!

Thanks again for the thought and help.

[wbreitbarth]

I run a barrel setup very similar to this but I have 2 custom made pans. I use the front one to warm the sap back one to boil it This year I made 2 huge changes. 1st was able to barrow some 12 inch block and stacked all the way around the stove. "took about 30 block" and it made a huge difference. The 2nd thing I did was put a small squirrel cage blower in the front just to keep a little more air flow. When I use to start the stove on the 1st day it would take me almost an hour to get both pans and rolling boil. Now it takes about 15 minutes. I went from 2.5 to 3 gallons an hour boiling to well over 5 gallons an hour when I would really tend the fire and feed it. The front pan I would use to preheat the sap I found would never stop boiling. Even when I added to it the roiling boil would go away but come back in less then 5 minutes. The block are very cheap you should be able to get them about a $1.00 each and well worth the investment. They also help to protect it from the wind. I also use the block behind the stove pipe to warm my sap now. 13750