2x6 oil fired- efficiency

[mainebackswoodssyrup]

Experienced a very dramatic and unwelcome change in boiling efficiency on our 2x6 this past weekend and today. We boil raw sap. Went from boiling all season at around 50 gph per usual with a 700 degree stack temp to Friday night during a big run, it slowing right down and ran more like 38 gph. Drawoffs spread way out because temps after drawoff dropped 4 degrees, which is a full degree or more than usual and stack temp spiked to 900-940! I thought niter so after the boil we emptied both pans and ran them thru the press then put it back in the pans. Cleaned the syrup pan like we always do (including the underside) and did a hot water rinse in the flue pan. The flue pan had a small coating of some sugar in it that did not come off but not bad buildup.

There were a few other variables so hard for me to guess but we ruled out niter because it ran the same today. Other changes:
1) Filled the oil tank with #2 oil before the boil Friday. Had about a 75/25 mix of #2 to kerosene after that. Earlier this fall we accidentally received kerosene on delivery so we started the season with 25/75 mix of #2 to kerosene. So that’s one difference.
2) Sap was 2% which is average for us but was cloudy for the first time.

My thoughts are that it may be the fuel which I know nothing about, soot buildup on the flue pan or just lower quality sap that affected things. It’s like the heat was there but it was going up the stack. Played with the draft and got it as cool as we could but that’s where it is always set. The part that really has me stumped is why the stack got so high, a full 200+ degrees more than the rest of the season. And it happened pretty quick. Any ideas or thoughts appreciated. Thanks.

[Robert K]

I don’t burn oil in my evaporator, however I have noticed that kerosene burns differently than fuel oil. I believe it is a cleaner burn and possibly more efficient per weight (btu’s). Perhaps it burns better from the start, ie on entering the evaporator and therefore produces more heat closer to the frt, while oil might burn slower in relation and not fully burn till further back causing the increased heat up the stack and lower boil rate. I know during the Ice storm 20 years ago , some farmers received kerosene in there fuel tanks when diesel was limited. One farmer told me it was the best his tractors had ever ran.

[Brian]

There are less btu's in kerosene. Kerosene is designated as #1 diesel. There are about 135,000 BTU per gallon vs. 139,000 BTU for a gallon of #2. This is part of the reason kerosene burns drier, with less lubrication, than #2 diesel. That is why straight kerosene is hard on engines but runs smoother.

[mainebackswoodssyrup]

So is it safe to say that all else being equal (burner, nozzle, etc) that the flame from kerosene wouldn’t extend as far back in evaporator as with #2? Cause that’s what it is acting like.

[Brian]

The pressure didn't change, so the flame distance didn't change.

[Brian]

v8 vs v6, less power.

[mainebackswoodssyrup]

10-4, I did know that #2 had more btu’s. I figured that would be equal or better but guess not. We’ll finish out this year and put the v8 back in. Just confused why it’s all going up the stack. We got this evaporator used so I guess it was dialed in for kerosene. Thanks for the help.