adding evaporator pan dividers

[Maribel Orchard]

I wish to add dividers to may 18x28x6 flat bottom pan, which sits in a horizontal 55gal barrel (brick lined) homemade arch. I presently can boil down +4 gal. of sap/hr and finish off over propane seperately. I am contemplating adding two dividers. Question becomes does it mater if the pan is divided lenghtways or widthways ? Do the dividers need to be sealed (welded water tight) along the metal seams? I have read with interest postings to Ontario Guy concerning evaporator construction also.

[sweetwoodmaple]

Have you considered adding some sort of float box? If you do that, you will want channels (either length or width wise) to have a pass through at alternate ends with a draw off point on the last channel on the blind end. This would allow for a more of a continuous process and a better color grade of syrup.

If you are not doing a float box and just dumping sap in in batches, you would want water tight dividers (width wise) that have crossover valves on alternate sides. That way you could keep syrup of different densities separate and improve the color grade a little. This setup would allow you to dump fresh sap in the 1st divider (raising it's level above the others)with the valves closed, then open all the valves and draw off some syrup from the last divider until the whole pan comes back to the same level. If you didn't want to weld in the crossovers, you could always do siphons like the old Grimm evaporators. 8O :D

For what it's worth (just like the rest of this post :wink: )The stand alone 2 x 4 pans that I have seen have water tight dividers.

[Maribel Orchard]

Thank you sweetwoodmaple. To expand: I'm still learning about the finer point of boiling physics. I would like to insert the dividers widthwise to create three divisions such that preheated sap enters the pan near the rear of the arch and would gradiate to the front. The front division would act as the finishing chamber of sorts. This may not be practicle since the center of the pan seems to be the hotest spot while boiling, with the rear next hotest. I was thinking, if I installed two friction fitted dividers and experiment with various placements I might stumble on the solution. I have this plan in the back of my mind to make a preheater that draws heat off the smoke stack through a coiled copper pipe connected to a gravity feed sap container. At present I use a gravity drip pan mounted above the boiling sap. All said I may be tring to make a silk purse out of a sows ear.

[sweetwoodmaple]

Yes, even including my 2 x 6, have a tough time maintaining a perfect gradient due to uneven firing and mixing of sap due to boiling.

You can look at my website for some links. I'll try to post a few more sites besides the Maple Producers's manual that have information about evaporator design.

Though slightly date, the Maple Sirup Producer's Manual #134 from the USDA is a good reference. They are hard to find, but you can find a large local library and probably get copies.

http://www.nal.usda.gov/ref/USDApubs/aghandbk.htm

Personally, If I were to spend a lot of time configuring a pan, you might want to go bigger to make it worth your while. Though, on the other hand, you can experiment with a small set up first! :D

Brian

[WESTVIRGINIAMAPLER]

With the sections as you described them, I think that would work great. The further the syrup gets towards the front, the higher the sugar content and the harder the boil. The front section should probably boil nearly as hard as any other section or maybe harder due to having a higher sugar content. I think you have some great ideas and the ideas would work great.

I would recommend making a hole in the end of each section opposite from the hole in the adjacent section so the pan can maintain a constant level. With having the sections blocked off, if one section gets low really fast, you could get in trouble.

Great :idea: . Go for it!

[sweetwoodmaple]

Yes, at minimum you would need piping and valves between sections to keep the level and also push the denser syrup to the last partition.

After seeing Dave Y's setup, it might make sense if the partitions are running side to side, to put the draw off partition near the rear of the arch. That's always where the hottest fire seems to be vs. the very front of the evaporator.

Brian

[WF MASON]

With a pan that small ,18''x28'' theres only so much evaporation you can get out of it, Dividers in a pan are nice , but surface area gives you the evaporation , personally I'd rather have a little larger pan with no partitions and be able to evaporate faster. But thats just me, I know many people who have taken the top off an old box stove and slap a pan that size on it. They love to boil on that size , make their 4 gallons for the year and look forward to next season.
Would you see any difference in your evaporation or syrup by adding dividers to an evaporation pan this size ??? I'd say maybe. I'm sure others would say Absolutely.

[Johnny Cuervo]

Maribel Orchard

I have a pre heater made w/ copper using my stack. It works great.
Look at my photos, and I would be glad to answer any questions.


John

[sweetwoodmaple]

Johnny - how hot is the sap from your preheater? Do you remove it when not running sap through (i.e. starting or finishing)?

There is so much wasted heat going up the chimney, so I've run through many scenerios about using that heat. I even considered putting a coil on the inside of the chimney, but that didn't work out since that is hard to control (ended up with boiling sap inside the tubing)

Always seemed to be tough to get the right balance (having to do with flow rate, dia and length of tubing) between luke warm sap that grows bacterial and too hot where you get steam pressure and blow things apart.

Brian

[Johnny Cuervo]

Brian, it is tricky but if I keep my stack temp around 750 F the temp is about 160-170. Flow rate is about 1 quart every 70 seconds around 12 gal per hour. The valves are also adjustable; they are taps for refrigerator ice maker. Last year w/2x2 pan I used 5 horizontal runs this year the pan is 2x4 there is 11 runs. I use 3/8 tubing. The better direct contact to the stack the better heat. The springs you see release tension on the coils, you can adjust for temp with 1 or 2 or remove all too pull coil off when out of sap.
I made 14 gal this season so far. Yesterday it ran all day once set, only thing I had to do was load wood every 7 min.

John

[sweetwoodmaple]

John - I'm impressed with your thought process on this. I toyed around with many ideas in this area, sounds like you got one that worked.

With the amound of BTU's availible, you could gain lots of efficiency if you could make up some sort of boiler system that had tubes that went directly in the flames at the end of the arch before the heat went up the stack. Basically, the heat exchanger section of a wood fired steam boiler.

If you had stainless tubes that went through the stack with an open reservoir at either end, you could gain both higher inlet temps and some evap rate.

You would just have to make sure you sized the system so the incoming sap was hot so you would not fall victim to lower color grades of syrup due to high bacterial. (See some other posts on small Steamaway units and lower color grade syrup)

When you are all said and done, you are creating a home made wood fired steam boiler.

[brookledge]

One thing not mentioned in reguards to adding dividers is that if you did add dividers you should design it so you can reverse the flow. By reversing the flow it keeps the niter to a minimum
Keith

[Maple Flats]

One comment was that a harder boil would be where it was almost syrup, I think the other way around. Sap boils at 212 and syrup at 219 on a high air pressure day. Does it not follow that the syrup would boil less than the raw sap?
Concerning the dividers, I think they should be sealed so the flow must follow the long route and then you would get better grade syrup.

[WESTVIRGINIAMAPLER]

To think of it that way makes sense, but is backwards. The reason being is because of the sugar content is so much higher in syrup and the higher the sugar content, the harder the boil. For instance, watch the compartments in the front pan of you evaporator. The closer the compartment is to syrup, the harder it will boil. Normally the heat is fairly even across the front pan, so the sugar content is what triggers the harder boil. The reason it boils harder in the flue pan is because you have about 7 times the surface area as in the front pan. Where it boils up 3 or 4 inches in the flue pan, it would boil 15 to 30 inches in the syrup pan if it had 7" flues. 8O

[Maple Hill Sugarhouse]

Ask your self this ? and decide= When a hot bubble of sap reaches the top of the boiling surface of the liquid and pops it releases steam into the air. Now is it easier for a bubble to rise 1 to 1 1/2" to the top of the surface and release its steam or fight it way through 6" of liquid to release its steam. Maybe you'll want to see if your boiling rate pick up with defoamer or ask someone that has experienced the difference? Add defoamer to your flue pan and you can listen to it boil harder. Stand back and have someone drip a few drops of defoamer in your open flue pan and tell me if you see a difference?
I know on my rig if i keep on top of the defoamer i can up my GPH by approx. 25 gallons of sap per hour hands down. On the boilers at work we have conductivity meters that automatically regulate and do the blowdowns off the top few inches of the steam drums liquid to remove the scum so the steam bubble can release at the surface and not sub-surface and produce better steam.(In a sence it is removing the impurities from the water)

[Maple Flats]

Reply to westvirginiamapler, you may be right, you sure have more experience than I do. I can't check it out until I get sap again and I think it may be over for this year, hope not.

[WESTVIRGINIAMAPLER]

Dave,

If you ever make any candy, once it gets close to candy, just a little heat underneath a large kettle that is 12" deep and has 1" of syrup in it can make it boil completely out of the kettle. The same amount of heat would make raw sap barely boil. This is because the sugar content of the near candy syrup is close to 100%. :D