Air Injection - Operating advice?

[johnallin]

Just finished plumbing in a new air injection system from H20 Innovations, and fired for the first time with it last night.

I'm looking for any tips or startup/shutdown procedures any of you have developed. The following in particular and anything else you can offer. Thanks in advance.

Amount of Air Injected
I don't know what the optimal amount of air to use may be. I have valves to control air to both sap and flue pans ...but had sap jumping out of the pan last night if I opened to much. Sounded really cool but temps went down per my probes, so I cracked it down a bit. What do you guys do?

Preventing Nitre build-up
I think I understand the principle as keeping nitre in suspension and off the bottom of the pans. Last night I realized that unless I drain the syrup pan off at the end of the boil, all of the "suspended" nitre is just going to settle to the bottom of the pan until I fire up again. That made no sense at all, so I drained off about 2 gallons and plan to pour back in tonight, hoping some of the junk stays in the bottom of my stainless pail.

Flue pan Vs Syrup pan
Is there a rule of thumb you use to gauge the amount of air to Syrup Pan vs the Flue Pan? I had the flue pan cranked up pretty hard, mostly because it's deeper and I didn't get soaked. The syrup pan was given much because to me the depth didn't need it and I don't like getting soaked in hot sap.

Thank you again for anything you can offer up - hopefully this thread will become a good reference for future air injection projects.. John

[Russell Lampron]

There is no rule of thumb for air adjustment. I set mine so that it's not splashing everywhere and run it there. Once you've figured out the setting that works for you, you don't have to touch it again.

The idea of keeping the nitre suspended is to keep it from burning in the flues or onto the bottom of the front pan. I run mine while the evaporator is cooling down and then just let it sit. When there's no more fire it's cool enough to keep the nitre from burning.

[johnallin]

Thanks Russ. Hadn’t considered the no burning part with the nitre. That makes perfect sense. I did notice that it was much lighter in color - more of an off white. Had one small draw last night and it was very light, so maybe this is working as it should.

I’ll keep playing with air volume.

[S.S.S]

We run our flue pan valve wide open and the syrup pan maybe only a quarter open.

[Bruce L]

How would you be able to get the airlines plumbed into the flue pan if you have hoods on,or even harder a steam away pan sitting on top of the flue pan?

[johnallin]

We run our flue pan valve wide open and the syrup pan maybe only a quarter open.

Thanks, that is what I have been doing...syrup pan was much less.

How would you be able to get the airlines plumbed into the flue pan if you have hoods on,or even harder a steam away pan sitting on top of the flue pan?

Bruce, I used sanitary pipe and clamps that allowed me to go through the hood and down to the flue pan. There is a tri-clamp connection inside the flue pan where air supply meets flue injector pipes, and another connection just out side of the hood (currently a fernco clamp).

To raise the hood; I reach in, disconnect the tri-clamp, then the fernco on the outside, hood can then be raised.

air injection finished 1.jpg air injection finished 2.jpg air injection finished 3.jpg

[DrTimPerkins]

Preventing Nitre build-up
I think I understand the principle as keeping nitre in suspension and off the bottom of the pans. Last night I realized that unless I drain the syrup pan off at the end of the boil, all of the "suspended" nitre is just going to settle to the bottom of the pan until I fire up again. That made no sense at all, so I drained off about 2 gallons and plan to pour back in tonight, hoping some of the junk stays in the bottom of my stainless pail.

Almost universally those who use air-injection make considerably lighter syrup. No question there.

In terms of niter build-up, the evidence is variable. Some producers notice less niter -- some don't. When we did research with it (a decade or so ago), I believe we found there was no difference in either the amount of niter that came out of the draw-off (so suspended and filterable) or the thickness of the scale deposited on the pan. What we definitely did notice was that the niter that was formed was WAY lighter in color. So when you looked into the pan after boiling, you'd definitely think...less niter. But when we actually measured the thickness at several locations throughout the front and back pans, we saw no difference between pans with and without air injection EXCEPT for directly below the holes where air was being injected. I suspect there is some variation in what is found depending upon the air injection device and pans used (style and placement) and how the air injection is operated (amount of air). There is also a real perception difference.

http://www.uvm.edu/~pmrc/air_injection.pdf

[Russell Lampron]

How would you be able to get the airlines plumbed into the flue pan if you have hoods on,or even harder a steam away pan sitting on top of the flue pan?

I ran my inlet pipe through a door in my steam hood. I can't close the door all of way but leaving it open the inch needed for the air pipe isn't an issue. There is enough of a draw from my steam stack to keep the steam in the hood. I'm not sure what you would have to do to make it work with a steamaway over the flue pan.

[Bruce L]

John,you only have a hood with preheater,correct? I don’t know if there’s a way I can run something down through the steam away to the flue pan

[johnallin]

John,you only have a hood with preheater,correct? I don’t know if there’s a way I can run something down through the steam away to the flue pan

Yes, I only have a steam hood with pre-heater. I had about 3-4" between the top of the hood's drip tray to the bottom of the pre-heater so I went through the side of the hood.

Looking at it, I'm pretty sure I could have gone through the side of the flue pan and still had room to make a connection to the air tubes. That would have eliminated all the elbows and disconnects needed at the steam hood. Once inside the flue pan; you can direct the pipes any where you need to and it all stays in place...