Defoaming

[DrTimPerkins]

A blast from the past (2009). https://www.youtube.com/watch?v=rldEWuCeGcE Video of is a prototype evaporator spray defoamer built and tested at UVM Proctor Maple Research Center for a few years. It recirculated sap and sprayed it through a series of nozzles into the backpan as a way to mechanically cut down on foaming and reduce the amount of defoamer used. We went through a couple of different iterations of it, including a UVM Engineering Student group final test product made entirely of SS.

The biggest issue was that the liquid being drawn off and pumped was so close to the boiling point that the small amount of negative pressure caused by the pump sucking sap in would result in spontaneous cavitation (bubbles forming in the liquid) inside the pump itself, which reduced the pump effectiveness and the spray dropped off. Kind of happened in cycles. Spray worked well for a little while, then dropped off, then pressure built again. The cost for a non-cavitating pump was too high to justify, so the project was eventually dropped. We did pass on the info to a few equipment companies though in case they wanted to work on it. Fun project.

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LMK if there are any questions.

[berkshires]

Neat idea! Is the volume of sap being sprayed too high to use cooler sap? Like, what if you used 180 degree sap coming from a pre-heater? Would there be too much volume, and it would kill the boil and/or lower the sugar percent in the syrup pan?

Gabe

[bill m]

Very interesting concept. I have a few questions. Besides acting as a defoamer would any of the following happen?
1) Increased evaporation rate because the sap is being sprayed. Less surface tension and smaller droplet size.
2) Could the spraying of the hot sap lead to lighter colored syrup because of air being introduced in the flue pan.
3) less niter buildup?

[DrTimPerkins]

Neat idea! Is the volume of sap being sprayed too high to use cooler sap? Like, what if you used 180 degree sap coming from a pre-heater? Would there be too much volume, and it would kill the boil and/or lower the sugar percent in the syrup pan?

Unless the evaporator is very large and has been running in a stable manner for a while, the inflow rate of sap from the line or preheater is variable, so foam could develop during those periods. With smaller evaporators, the inflow rate is not stable at all, so that approach wouldn't work well.

[DrTimPerkins]

Very interesting concept. I have a few questions. Besides acting as a defoamer would any of the following happen?
1) Increased evaporation rate because the sap is being sprayed. Less surface tension and smaller droplet size.
2) Could the spraying of the hot sap lead to lighter colored syrup because of air being introduced in the flue pan.
3) less niter buildup?

1. Yes.
2. Yes.
3. Possibly.

In addition, the spray system is essentially a built-in cleaning method. Drain the sweet and circulate permeate through the spray system.

[jrgagne99]

Is the necessary spray flow rate small enough to just use a portion of the cold sap feeding the evaporator? Put another way, would say 10 GPH of cold spray be enough to keep the foam down on the 4-foot flue pan of a 2x6? Or are we talking something greater than 30 GPH is needed to keep the foam down for such a rig.

[DrTimPerkins]

Is the necessary spray flow rate small enough to just use a portion of the cold sap feeding the evaporator? Put another way, would say 10 GPH of cold spray be enough to keep the foam down on the 4-foot flue pan of a 2x6? Or are we talking something greater than 30 GPH is needed to keep the foam down for such a rig.

I haven't done the calculations for that size pan (our test bed pan was a 3' x 10' with a 6' flue pan I believe). Changing pan size also changes size, distribution, and number of nozzles. It would likely be enough for part of the time, but not at all times, which means foaming would be very excessive when cold sap input slowed too much. Fixing these issues just added cost to the system, which is one reason we dropped the project after a certain amount of time. Hot sap spray worked quite well assuming you had the proper (costly) pump that 1) could deal with the hot liquid and 2) would not cavitate under those conditions. Our hope was that some company would take the idea and run with it.

[bill m]

With these possible benefits I am surprised a manufacture did not take it on. Any idea on the cost of this system compared to a steam away, air injection and an in place cleaning system? Seems like this one system could replace those three.