Band heater vaporizer. - Page 47
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  1. #921

    Default Re: Band heater vaporizer.

    I have a concern about the temperatures that are involved in OA vaporization. I can't seem to get around the idea that one needs to be able to accurately control the temperature of the process otherwise it does not work correctly.

    OA Sublimates (Becomes gas directly from solid without transitioning to a liquid) at 315 F, but if it reaches 355 F it will begin to break down into carbon dioxide and formic acid, If it reaches 373 F it degrades into carbon dioxide, carbon monoxide and water. So there is a small temperature window for proper vaporization. (40 F and 58 F respectively). Most devices have no way to control the temperature. So how do we know if the vaporizer is actually delivering OA or if it is degrading some or all of the treatment? Once the temp gets to 373 F the OA will convert to CO2, CO, and H2O. Obviously we don't want to gas them with carbon monoxide.

    If the provap or any band heater is set to 230C(446F) this is well above the degradation temp of OA. Why is the set temp set so high and not within the Sublimation range for OA of 315f (157c) to 355f(179c) ??

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  3. #922
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    Default Re: Band heater vaporizer.

    When OA breaks down to Formic and Co2 there is not enough Formic to help and not enough co2 to hurt (if any is released at all because it is suspected that OA will only break down in laboratory conditions.) Those two are invisible gases. What you see coming out of the vaporizer is OA crystals (think baby powder).
    Last edited by snl; 10-27-2019 at 12:14 PM.
    http://OxaVap.com Your source for the ProVap 110
    OA Vaporizer. The fastest vaporizer on the market!

  4. #923
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    Alfred,
    Water boils at 212F.
    If you put a pan of water on the stove for a cup of tea do you set the burner at 212 degrees or do you turn the stove on 'high'?

    When the OA drops into the pre-heated band vaporizor the temp immediately drops dramatically. As it reheats the OA is vaporized.
    It's because of this temperature drop that you need the high pre-heat temp.

  5. #924

    Default Re: Band heater vaporizer.

    Yes this would hold for a tray device. But the band devices contain the OA more confined.

    No it is not really crystals any more that when you boil water that the steam is crystals. OA vapor is sublimated OA, OA in a gaseous state, No doubt it cools back to crystals quickly, but it is initially at least in a gaseous state. If it is then allowed to heat even more it degrades. If it degrades to the point that formic or even further to where CO is produced then it is no longer OA as it has DEGRADED into it's constituent compounds.

  6. #925
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    Default Re: Band heater vaporizer.

    Arnie, you beat me to it. That is exactly the same example I was going to use , except for the temp of the pan dropping. My ProVap will drop from 230C to as low as as 204 C when sublimating. Not a huge difference. They key is that the OAV itself is like the water and won't get over the sublimation temperature until it has all sublimated. At that point, if contained, I believe you could increase the temeratures and cause it to break down. Just like steam can be heated well above 212F if kept under pressure.

    Anyone that produces moonshine is well aware that the temperature of a solution will remain at the boiling point of a constituent of that solution until that constituent has boiled off completely no matter how much heat is applied.
    Last edited by JWPalmer; 10-27-2019 at 12:06 PM.
    Thankfully, the bees are smarter than I am. They are doing well, in spite of my efforts to help them.

  7. #926
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    Alfred,
    The OA is not confined in the EasyVap.
    The vaporized OA exits via the small outlet tube.
    But whatever. This discussion pops up from time to time and it seems the folks who like arguing the formic warnings are never convinced.
    Fine by me, I'll continue on my way.

  8. #927

    Default Re: Band heater vaporizer.

    If the OA is heated to 373 F the OA will convert to CO2, CO, and H2O. There is no OA left it has converted to CO2, CO and H2O.

    It may be that it escapes the chamber before it reaches 373 f....
    It could be that it then still reaches above 355 F in which case it degrades to Formic and CO2. Again there is no OA left as it has been converted away....

    Maybe it is that some of each has happened. Where some of the OA escapes the chamber before it reaches 355 f. Maybe even most of it does? But any that does not will be converted/degraded a process that does not leave any OA intact.

    So why are the temps not controlled within the Sublimation range?

    I ask because of my interest in DIY.

    It would not be a big deal except that the temp range window is only 40 degrees.

  9. #928
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    JWP, have you made honey moonshine?
    I have thought about trying to. Is there a recommended thread for that?
    I don't want to hijack this thread

  10. #929
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    Default Re: Band heater vaporizer.

    Arnie and JWP; you are not wrong!

    The higher set point of the evaporator is necessary to achieve an effective production rate to propel the plume into the hive in the band heater types where the charge is dumped in. The energy transfer necessary to effect the change of state will result in a temperature gradient such that the surface will quickly come to match the atmospheric pressure boiling of the charge whether it be water oxalic acid or your mash! A temperature gradient is the driver for energy transfer. That takes care of the need for the higher temp setting the makes many people nervous about the possibility of achieving disassociation breakdown temperatures.

    If the chamber is pressurized the boiling point would be increased but that would perhaps raise the breakdown points as well. In any case that pressure is not achievable in either the wand type or the band heater type.

    What makes things interesting and has led to past discussions, is the very real abilty to raise the temperature of the escaping gas beyond the evaporating temperature. Here is what is necessary to achieve this condition which is so often stated as being an impossibility. If the escaping gas is directed to pass through an intensely heated space beyond where it is produced, it will of necessity have its temperature greatly increased as well as its volume. All this without needing to pressurize beyond atmospheric. It does take high temperatures and large surface areas. (Like in the tubes of a steam superheater boiler) This is one of the things Snl refers to as laboratory conditions. This whole paragraph is about conditions not applicable to the animals we are handling but perhaps a few will take something from it.

    I have worked on quite a few installations of steam superheater boilers to improve efficiency. Nasty laboratories indeed.

    Jwp; you can get your shine with less fuel and a lower temperature if you pull a vacuum on your condenser.
    Frank

  11. #930
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    Default Re: Band heater vaporizer.

    Quote Originally Posted by alfred westlake View Post
    If the provap or any band heater is set to 230C(446F) this is well above the degradation temp of OA. Why is the set temp set so high and not within the Sublimation range for OA of 315f (157c) to 355f(179c) ??
    I set and use mine on 400F and it works fine with no issues. You don't have to use higher temps if you do not want to.

  12. #931
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    Default Re: Band heater vaporizer.

    I suspect it is a matter of getting a bit quicker action. It would be interesting to see if an open air demonstration would show a bit more forceful discharge plume with the set temperature at the higher range. I haven't timed mine for a long while but from memory it was around 40 seconds. I have no thermostat on mine but I do have a dimmer switch control on the upper of the two bands
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    Frank

  13. #932
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    Default Re: Band heater vaporizer.

    Quote Originally Posted by Arnie View Post
    JWP, have you made honey moonshine?
    I have thought about trying to. Is there a recommended thread for that?
    I don't want to hijack this thread
    No, but I have 5 gallons of mead that I started last week. Might be interesting to try distilling some of it. I have a thread in the home brewing sub-forum you can follow if you wish. 80 proof mead, hmmm.
    Thankfully, the bees are smarter than I am. They are doing well, in spite of my efforts to help them.

  14. #933
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    Default Re: Band heater vaporizer.

    If you wish to turn 5 grams of water into steam you will require 1 calorie of heat to move each gram through 1 degree C until you hit 100 C thereafter you would require 400 calories of heat to turn each gram to steam, this 400 or 40 I cant remember now is called latent heat and is the heat required to change the state of water from liquid to vapor or gas. now if you set your vaporizer at 100 C you can boil the 5 grams of water away but only as the amount that the source of energy allows. Now if your set point is 200 C it will boil off the water in a much quicker time as you have a greater amount of energy already in the bowl however when you add the water the bowl temperature will drop to 100 C so you dont burn the Water LOL and boil it off much more quickly. The same goes with OA if the bowl is at 450F and the bottom is clean and free of the layer of oxide that normally forms when the OA hits the bottom of the bowl the temperature can fall down to 290 F and climbs untill all the OA has boiled off its water and the rest has sublimatedand what is more is that the OA is already crystalizing as it leaves the vaporizer outlet. Even the pan types where some treat fron just below the screened bottom board will find a coating of crystals on the mesh of the screen. So that high set point is just to give you a leg up on treating time. You could probably set the temperature even higher and I am sure it will still work OK however you will wear out your silicone cups and the wear and tear of the vaporizer will also be much greater and by the way you will boil off 5 grams of water in less than half the time it takes to sublimate 5 grams of OA which sot of points to the fact that OA takes more latent heat to sublimate than water to change its state

  15. #934

    Default Re: Band heater vaporizer.

    "If the escaping gas is directed to pass through an intensely heated space beyond where it is produced, it will of necessity have its temperature greatly increased as well as its volume."

    This is what happens in a standard insect fogger where the vapor is made to go through heated coils.

    But I hear that the consensus is that with a band heater the vapor escapes the heat before it can reach 375F(190c) even though the band heater is set to 446F(230c) and sublimation is at 315F(158c).

  16. #935
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    Default Re: Band heater vaporizer.

    Alfred this is not a consensus, it is a visible fact. You can see the temperature on the temperature controller drop to as low as 290 F from 450 F as soon as the OA hits the bottom of a clean hot bowl just as you will see the temperature drop to 212 F if you dump some water into the hot bowl, wear gloves and eye protection if you want to try that yourself.

  17. #936
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    Default Re: Band heater vaporizer.

    Quote Originally Posted by snl View Post
    if any is released at all because it is suspected that OA will only break down in laboratory conditions..

    The EMEA says that with the slow pan heater types 54% makes it in to the hive, 1% breaks down in to FA the rest Co2/water
    https://www.ema.europa.eu/documents/...roducts_en.pdf


    "This small electrical device can be inserted into the hive and allowsthe evaporation of oxalic acid in the closed hive55. During heating, approximately half ofthe oxalic acid disintegrates into harmless carbon dioxide, while the remainder forms anoxalic acid precipitate which settles on the bee,"https://www.researchgate.net/publica...f_the_Honeybee

    as you note your self
    Quote Originally Posted by snl View Post
    When heating, about half (46%) of OA decomposes into harmless carbon dioxide and water. Other half (54%) vaporizes and forms fine drops and dusts of OA that precipitates everywhere in hive. Because of this even distribution of fine particles, high and consistent efficacy against Varroa mites is possible [[/COLOR]http://www.mellifera.de/Engli2.pdf[COLOR=#333333] - Accessed 7/13/04].
    This realy shouldn't be any sort of suprize... Pure oxalic acid dehydrate is 71.42 wt % oxalic acid and 28.58 wt % water (Riemenschneider and Tanifuji 2011) and without it and more or less harmless "breakdown" we would get very little push out of band heater type systems

    while its "supected" that the high band heater types will have more break down do to their higher operation temps and speeds, there has been not much done on the subject... Randy oliver put pan and band head to head in a small trial and didn't see a mite reduction difference, and if there was most fokes would just add a bit more OAD
    If we look at Toufailia Et Al 2016 https://www.tandfonline.com/doi/full...9.2015.1106777
    tjar_a_1106777_f0002a_b.gif
    We see vapor is killing 81% at a low dose and not a huge gain as the does cranks up

  18. #937
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    A preliminary report from a study conducted at the OSU Bee Lab, presented at our state's beekeeping conference this past weekend, stated that that OA sublimation treatments showed little negative impact on eggs and open larvae. Good news that helps further validate its use against Varroa.

  19. #938
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    Default Re: Band heater vaporizer.

    Msl, I have no idea how the research on the OA dosage was carried out, or whether this would be effected in any way by actual field conditions and hive setups. I have always felt that the efficacy of the crystals was only as good as the internal coverage of the OA dust and if it did not get to every nook and cranny some mites could survive in those areas so by increasing the dose hopefully greater coverage is gained and as there appears to be no detrimental effect on the bees what is lost in the effort.

  20. #939
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    Default Re: Band heater vaporizer.

    Quote Originally Posted by alfred westlake View Post
    "If the escaping gas is directed to pass through an intensely heated space beyond where it is produced, it will of necessity have its temperature greatly increased as well as its volume."

    This is what happens in a standard insect fogger where the vapor is made to go through heated coils.

    But I hear that with a band heater the vapor escapes the heat before it can reach 375F(190c) even though the band heater is set to 446F(230c) and sublimation is at 315F(158c).
    It is not exactly a consensus yet but close examination of the results strongly supports it. What happens in the insect fogger is quite a different scenario and I think your take on that is correct. Often the oxalic acid is carried into the devices by being dissolved in alcohol which complicates the physics and chemistry issue.

    Here is a simple definition that is the core of understanding the mechanics of what the vaporizers are doing.


    "Latent Heat Transfer. At the point where one of the substances is ready to change state or phases (solid to liquid, liquid to gas, etc), heat is transferred from one substance in one state without a corresponding temperature shift in the substance in the other state".

    It is not an intuitive concept to get your head around. Oxalic acid also has an uncommon property of sublimating which is 2 changes of state without the intermediate one being evident.
    Frank

  21. #940
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    Default Re: Band heater vaporizer.

    One can also view the higher temperature as having the same effect as a heavy flywheel has, it basically stores kinetic energy, now to throw another wrench in the works water of crystalization in some chemicals forms the basis of a flame retardant as when the substance is heated to a certain temperature the water of crystalization is released thereby cooling down the materiel. Now to make it even more complicated all off the OA does not all heat up at the same time as there is a layering effect especially when the water starts to boil and this is the molten stuff folks talk about, water and oxalic acid mixed. I have also noticed that with the set point temp at 450 F the lower the temperature drops the quicker the treatment so the more the bowl is cleaned the quicker the treatment. I have now purchased a black and yellow stainless steel brush with bristles on the side and on the head and when stuck into the bowl and just twirled around the brush on the head takes off enough of the oxide film to really make a difference. Under normal operation the temperature drops to around 320 F when loaded and as the number of treatments increase that temperature slowly rises which means that the layer of oxide is providing some insulation to the OA and the sublimation time slowly increases. Once I started using the brush incidently from Ace Hardware after each treatment the temperature would drop into the 290 F range which would mean that the OA was absorbing more heat and so sublimed quicker. The temperatures were monitored with a very light thermocouple attached directly to the thin copper bottom of the bowl so the temperature readings change rapidly which might not be the case with a heavy bottom and heavy metal capped thermocouple.

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