Help Maximizing Efficiency

[Dinorocks]

I have been collecting and boiling sap from about 70 maple trees in the woods about ¼ mile from my house for several years and have reached a “ceiling” in my boiling efficiency. I was hoping I could explain my procedures and possibly get some ideas from those more experienced to maximize my “backyard operation” this season.

I typically boil when I collect about 250 gallons of sap, and usually boil three times a season (the sap is stored in food-grade drums packed in ice). I boil sap in a 42” by 24” SS pan that is 8” deep, over a wood fire (split ash wood) lined with firebrick. The pan can hold 35 gallons (if filled to the top) and each inch of liquid is equal to 4.4 gallons. I use two 5-gallon SS surge milking containers to pre-heat sap which I then I use to feed the main pan as needed. The sugar content in my sap varies from about 1.5% to 3.5%, and I typically get 5 gallons of syrup from the 250 gallons of sap I boil (50:1). I start my boil with 20 gallons in the pan (4.5” of sap in pan) and use a ruler to monitor the depth to determine when to add additional sap. It takes me about 1 hour to evaporate 10 gallons of sap from my main pan at a level of 3” to 5”. I transfer one 5 gallons warming pots of boiling sap into the pan every ½ hour. Once I have boiled the 250 gallons of sap, I boil the nearup to 10 gallons (2.25” in main pan) before I remove the pan from the fire and filter/transfer back into the two 5-gallon SS surge milking containers to finish boil at the house where I can better control the final temperature. I would finish boil the 10 gallons of nearup to 5 gallons of syrup.

This year I will be using an RO bucket, capable of concentrating 10 gallons of sap per hour (I will get 25 gallons of concentrated sap from 50 gallons of unprocessed sap) and plan to only add concentrated sap to my boiling pan this season. Is it accurate to assume that I will still evaporate at the same rate I typically do as described above with concentrated sap as I did with unconcentrated sap?

And will the evaporation time increase/decrease with higher/lower volume of sap in the pan? That is, would I evaporate faster with 3” of sap in the pan compared to 6” in the pan? Its easier and less risky for me to maximize the amount of sap in the pan.

Thank you for reading the above and thank you in advance for any suggestions!

Dino
Western New York

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[lyford]

I would decrease the sap depth to 1.5-2 inches, many go lower. Also get your fire off the ground an on a grate. You will have a better fire and evap rate if you hve air moving throught the fire.

[wobbletop]

I've been told the lower the level of the pan, the quicker the evaporation. Of course this increases the risk.

Are you looking for time efficiency or resource efficiency? If time efficiency, I would look to adding air-under-fire to increase boiling rate, although it will probably increase your wood use.

[DRoseum]

Absolutely true that shallower sap levels will evaporate at faster rate. Reason is 2 fold... time & energy to heat the total volume of fluid is reduced and there is less heat loss from the sides. This means more of the heat is going into a smaller volume of sap, increasing evap rate. Not to mention bubbles cool and collapse as they rise in a fluid (helping heat the fluid). Shallower sap reduces that effect and maximizes the volume of steam released.

[ecolbeck]

Lots of good suggestions so far. I would add the following:

The use of the ROBucket will have no effect on your evaporation rate.
Make sure that your wood is as dry as possible. Any moisture in the wood is a waste of heat.
Split to wood wrist sized pieces to increase burn rate
Consider reengineering your arch design to incorporate a door and chimney. Any uncontrolled cold air entering the fire area will slow the evaporation rate.
Overall, I'd say that if you're getting 10gph out of that setup then you're doing pretty well!

[Dinorocks]

Thanks for the replies! I burnt my pan once when the level dropped and it worries me to have the volume below 2" but I'll try to keep the levels lower than I did in previous years. My fire gets extremely hot and the sap in the pan boils very hard, even at 4-5 inches. I do have a way for air to get in and out but will try to increase the air flow. Dumb question...can I boil the sap too hard? ...and another dumb question...if the sap is heated to temps above syrup level, can I save the batch by adding more sap...provided it hasn't burn?

Regarding efficiency, time efficiency is what I was looking for...I have a large supply of wood (although a balance between the two would be idea).

Again, thanks for your help!

[ecolbeck]

Sap cannot boil too hard as long as there is sap to boil.

Sap that is pushed beyond syrup can be brought back to syrup by using additional sap or water. I do this routinely during the season. It is easier to dilute slightly overconcentrated syrup than it is to reboil thin syrup at a later date. Why waste propane when I have a mountain of firewood? You have to have good instruments (thermometer and hygrometer) to make this work.

Pans can burn because a layer of niter has built up on the pan surface shielding it from the water. This causes the pan to overheat and burn. Cleaning the pan solves that issue.

[whity]

I would also wipe off any soot from the bottom of your pan. That will insulate the pan.

[maple flats]

RO'd concentrate will not likely affect the boil, but depth in the pan will. You need to realize that holding concentrate, if not kept cold enough will spoil much faster. The 10 gal Bucket RO, may not be your best choice, but if used properly it will be a big help In addition to the suggestions above I think you would do better if you make a hood for your pan, and 2 or 3 dividers to make it continuous flow would help too. That way, you can add new sap (but not in 5 gal slugs) while you draw either syrup or near syrup from the other end of the flow in the channels. That will increase your production and might result in slightly lighter syrup grade. However your finished product does look mighty fine.

[Dinorocks]

One again, I greatly appreciated the help!! Regarding a hood for my pan...I need to look into that as I’m not exactly sure what you mean (benefits).

Understood regarding keeping concentrate cold...as a follow up, how long before the concentrate spoils if kept cold (I.e., in a 55 gallon drum surrounded by ice. In my head I pretend sap/concentrate is milk and keep it comparatively cold. I would plan to run what I could run through my bucket RO the night before and run the rest through as I boil the next day.

Regarding soot on bottom of pan...reminds me of the thickness of a pan...I had a friend make a prototype pan for me and asked him to use the thickest SS he could get so it was “heavy duty”...after I got “smarter” the next pan had much thinner SS and I was able to get it hotter faster.

[maple flats]

The time it will last will be in direct relation to the sanitation in your system, the actual temperature of the sap/concentrate and the sugar %. I think Dr Tim might best shed light on that question. Another issue, do you have a source for enough ice when the outside temps get to 45 or more?

[Sugarmaker]

I think your doing fine! In fact we should all take turns coming to your place and making syrup! Great setup you have. I would suggest you boil more often, May be even more important now that you will have higher sugar content sap from the R.O bucket.
Regards,
Chris

[therealtreehugger]

I would consider boiling more often. You mentioned RO-ing and boiling the next day - good - make sure you don't go more than the day ahead. I would continue to RO while you are boiling. You can always run the sap through the RO more than once to get a higher sugar %. I believe someone also mentioned this, but even if you are preheating your sap, unless it is really hot, I would not dump it all in at once - all 5 or 10 gal of it. You should try to either set up a trickle system, or manually put in a little at a time. You don't want to reduce your boil.

I will also second the need for a stack/chimney on one end and a door on the other.

Other than that, you have a very cool looking set up! and 10 gal per hr is nothing to sneeze at!