[Stoves] At what temperature are the bad gases from zinc created, vs harmless zinc oxide?

Art Donnelly art.donnelly at seachar.org
Fri Feb 1 17:41:47 CST 2013


Hey,
Having spenr many years doing Art casting and welding I had to learn about
this subject. Also I get asked about this frequently, because we have a
galvanized secondary-air shroud on the Estufa Finca.

The following is copied from a welders safety manual:

When zinc vapor mixes with the oxygen in the air, it reacts instantly to
become zinc oxide. This is the same white powder that you see on some noses
at the beach and the slopes. Zinc oxide is non-toxic and non carcinogenic.
Extensive research1 into the effects of zinc oxide fumes has been done, and
although breathing those fumes will cause welders to think that they have
the flu in a bad way, there are no long-term health effects. Zinc oxide
that is inhaled is simply absorbed and eliminated by the body without
complications or chronic effects. Current research2 on zinc oxide fumes is
concentrated in establishing the mechanism by which zinc oxide causes
"metal fume fever," how its effects are self-limiting and why zinc oxide
fume effects ameliorate after the first day of exposure even though the
welder may continue to be exposed to zinc during subsequent days
("Monday-morning fever"). Other research3 is being done using zinc oxide
fumes together with various drugs which results in a synergetic effect for
treatment of cancer and AIDS. Another area of research is use of zinc
compounds as the active ingredients in throat lozengers that are recognized
as significantly effective in reducing the duration and intensity of the
common cold.
Typical “metal fume fever” begins about 4 hours after exposure, and full
recovery occurs within 48 hours. The symptoms include fever, chills,
thirst, headache and nausea. All of these symptoms, pain and suffering, as
well as lost work (and play) time, can be avoided entirely by simply not
inhaling the zinc oxide fumes. This can easily be done using any of the
methods described later.
Unlike other heavy metals, such as copper, lead and mercury, zinc is an
essential micro nutrient. Zinc is essential to the proper growth of plants
and animals. Zinc forms part of the enzyme system that regulates biological
processes throughout the body. As shown on any multi-vitamin/mineral
bottle, the recommended minimum adult intake is 15 mg/day.

You still have to vaporize the zinc and I sorry but none of our stoves is
getting that hot.
saludos,
Art Donnelly

On Fri, Feb 1, 2013 at 2:00 PM, <stoves-request at lists.bioenergylists.org>wrote:

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>    1. Re: WBT (never ending) (Crispin Pemberton-Pigott)
>    2. Re: WBT (never ending) (Frank Shields)
>    3. At what temperature are the bad gases from zinc created, vs
>       harmless zinc oxide? (Paul Anderson)
>    4. Re: At what temperature are the bad gases from zinc created,
>       vs harmless zinc oxide? (Boston Nyer / BURN Design Lab)
>
>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Thu, 31 Jan 2013 15:19:48 -0500
> From: "Crispin Pemberton-Pigott" <crispinpigott at gmail.com>
> To: "'Discussion of biomass cooking stoves'"
>         <stoves at lists.bioenergylists.org>
> Subject: Re: [Stoves] WBT (never ending)
> Message-ID: <054a01cdfff0$55136220$ff3a2660$@gmail.com>
> Content-Type: text/plain; charset="utf-8"
>
> Dear Frank
>
>
>
> Crispin > Whatever is happening, the numbers are required in real time.
>
> Frank> Why? Don?t all we need is energy going in ? energy left to = energy
> used during the time of the test? Nice to have real time measurements to
> see how the stove performs but not needed for the WBT.
>
>
>
> The WBT is not a very helpful test. That is starting to penetrate the haze
> of confusion that surrounds the testing of stoves. A WBT (as presently
> contrived) is a mix of a task-based test and an engineering metrics test
> and does neither correctly.
>
>
>
> If we were to talk about task-based testing (TBT) we would use a
> begin-and-end- energy value to get an overall number that represents
> something well defined and well quantified. If we want engineering metrics
> like ?heat transfer efficiency we would not do a TBT. That is simply not a
> productive approach. Both are useful and both are possible, but it is not
> possible to do both simultaneously and get meaningful answers. You can an
> answer, but it is not a useful or  correct one. When applying these mixed
> WBT?s across different platforms the results are skewed against or in
> favour of a stove or fuel type resulting in unfair comparisons being made.
> If they are unfair, they are not useful.
>
>
>
> Crispin>  I think you need to see the SETAR test method in operation. It
> is not nearly as difficult as you imagine and I am beginning to have more
> confidence that we can get the fuel analysis as it burns from the
> combustion products.
>
> Frank> So many combustion products in all forms of energy bonds that need
> to be looked at and assembled along with accurate flow measurement,
> possible leaks, calibration for gas flow and equipment etc.
>
>
>
> It is actually much simpler than that. For a start, don?t worry about
> having to capture literally everything. Suppose you had exotic constituents
> of smoke that accounted for 0.2% of the combustion. So what? You still have
> 99.8% of what you are looking for.
>
>
>
> Frank> The method to estimate energy left over that have been used are
> very inaccurate -agree. But we can use much better equipment (CHN analyzer)
> that will give us the values far more accurate than needed.
>
>
>
> That is a good point. There is an old American maxim which is, ?Do not put
> precision and accuracy where it is not needed.? There is no point weighing
> condensate from a boiling pot to 0.1 g and measuring the kerosene fuel used
> to 1g. It takes less than 0.1 g of kerosene to boil 1 g of water. It should
> be the other way round. Should be 0.1g for the fuel and 1.0 for the boiled
> water. You get my point? If you start with one element of the whole chain
> giving you numbers ?25% there is little point reducing something else from
> 1% to 0.1%.
>
>
>
>
>
> Frank> If burning liquid fuel why not just weight the fuel to Start ? fuel
> left over?
>
>
>
> Again a good point. That is fine unless the thermal efficiency changes
> with time (as the stove heats up) or perhaps the burner functions different
> at different temperatures (like a Panda which is quite variable). If you
> are testing a stove for certification, it is important to know these
> things. For example a stove in South Africa was tested and it passed the
> ?fuel heating test? which is to say, the temperature of the kerosene did
> not rise much after 1 hour. But the test was not well conceived. If the
> fuel was indeed heating at a rate that would have it over-heat (and
> evaporate without burning) then after perhaps 2 hours it would be very
> dangerous. One stove passed the test by increasing the storage volume so
> that absorbed heat couldn?t raise the (larger mass) fuel temperature within
> one hour. But it was still really dangerous after 2 hours.
>
>
>
> If you only measure end points you miss things like that. In another  case
> merely change the pot diameter tripled the CO output. It was legal with one
> pot size and illegal with another. If you specify the pot to be used (only)
> you miss dangerous situations which have already been shown to be real
> risks.
>
>
>
> Crispin> Here is an example: if you have a fuel you know is 50% carbon,
> and 10% is missing (based on what you expected, based on a change in mass)
> what does that tell you? Quite a bit. It means char is being produced
> somewhere inside or on the fuel and what is burning is hydrogen. That?s not
> hard.
>
>
>
> Frank> Much easier if you know the CHN of the starting material and the
> CHN of the final material and weight of both. Very exact measurements.
> Moisture at the start is easy. Only problem is moisture at the end and I
> think that can be dealt with. Then we have only the estimated calculations
> for bond energy to determine the energy used.
>
>
>
> I would love to have the real times measurements as accurately as
> possible. The problem is the moisture in the middle ? the end we can work
> out with patience. But if the boiling portion of a WBT is done using wood
> that dries out entirely and is half charred by the time boiling arrives,
> what is the energy applied? How do we know what the energy of the burning
> char/wood mix is during simmering? What are we really trying to find out?
> The mass of fuel consumed each time a new copy of the task is performed, or
> the heat transfer efficiency? Or the CO emitted per MJ at different power
> levels? You must decide up front what we are trying to measure then devise
> an experiment that determines it exactly. This is done routinely in
> academia and industry. There is nothing special about stoves that requires
> us to use vainly imagined metrics and methods. Just get on and do the job
> properly.
>
>
>
> Crispin> The big variable is water vapour and when the moisture left the
> fuel.
>
> Frank> ?When? the moisture left the fuel? We need this for the WBT? Or
> just total water vapor during the run?
>
>
>
> If you want to know what the heat transfer efficiency is during some power
> level of at a certain stage of a cooking cycle, you need to know what the
> heat generated is. If you dno?t know whether the fuel has dried out yet,
> you can?t make the calculation.
>
>
>
> Crispin> This needs to be measured directly in real time and the emissions
> summed to see what is hydrogen burning and what is fuel moisture
> evaporating. That is not nearly as difficult a calculation as FTIR requires.
>
> Frank> Seems this is all good info for researching the stove performance
> but overkill and introduces much more potential error for the WBT test. IMO
>
>
>
> The WBT is filled with potential for errors already. It is a complex test
> involving multiple sections. It is a valid way of getting a task-based
> measurement like total fuel consumption or time to complete. It is not a
> good way to get a specific energy consumption or time to boil. As soon as
> you see ?specific? in a WBT metric, you know it is probably not a valid
> metric from an engineering point of view. Many things ?reported? by the WBT
> 3 and 4 series are based on a ?per litre? calculation, but if you look into
> it, there is no theoretical basis for assuming that the measured item is
> dependent on the number of litres involved. A good one is simmering.
> Simmering is not dependent on the mass of water in the pot, only the pot
> hot gas contact area. Boiling water, on the other hand, is dependent on the
> mass of water in the pot and the pot area. Changing the pot to a smaller or
> larger one but leaving the mass of water the same changes the boiling rate.
> Once this is realised, then the value o
>  f the output number is?devalued!
>
>
>
> >I get the feeling people think this should be a quick test and cheap.
> Always nice if possible. But this is an important test ?very important if a
> stove producer wants to compare his/her stove to others for sale. And that
> warrants the most accurate and reproducible test we can do.
>
>
>
> The WBT? Heavens no. The reason Prof Lloyd does not use the WBT is because
> the results are ?irreproducible?. Now imagine if at one lab you cannot
> reproduce the results consistently, what happens when to try to get another
> lab to ?replicate? the test? Think about this. In order to have a lab
> replicate the testing of a first lab, you have to be able to say, ?These
> results are comparable within x% and therefore the result has been
> replicated.? To do that you have to know the precision and accuracy of the
> test itself and then work out if the other lab has results consistently
> within the error band. As the WBT?s do not have a known precision nor
> accuracy, how can any other lab ever claim to have replicated the results?
> People have been comparing averages of test results which is a completely
> improper way of showing that a method works precisely.
>
>
>
> It is both an inaccurate and irreproducible test for two sets of reasons:
> it has not been evaluated to know, say, what the 95% confidence index is
> and calculating the total precision will quickly show that it does not meet
> our current needs. That is what Jim Jetter and I were discussing. I said
> that the WBT was analysed by Penn Taylor and that he said it was about 50%.
> Jim challenged me about that statement. In fact the errors are individually
> shown in Penn?s thesis but not calculated so I was wrong. But Penn told me
> the total was about 50% if calculated together. That was before the days of
> TLUD char making stoves becoming tested frequently and there are serious
> additional errors encountered when applying the WBT to them. In addition,
> rice hull gasifiers, also popular, have an additional set of issues. I am
> comfortable saying the WBT has a precision of 50% so you can quote me
> instead of Penn. When it is properly calculated and that calculation is
> reviewed, we can change our opinions
>   (which is all it is at the moment).
>
>
>
> >Each test may take a week+ to dry, grind and prepare samples for CHN
> analyzer etc. That?s typical for this type of complexity. It should all
> boil down to fuel quality as being the biggest variable during testing or
> round-robin test programs ?not test procedure or test equipment.
>
>
>
> I am ok with that for fuel-remaining analysis. It is very valuable and
> after a while we will get ?typical? values for certain stoves or procedures
> and not have to do it again. Or just check occasionally. Prof Lodoysamba
> invented a machine he makes in Ulaanbaatar that will tell you the ash
> content of a fuel sample (burned or not) in a few seconds, like, 5 seconds.
> If it could do MASCON that would be great! (moisture, ash, sulphur, carbon,
> oxygen, nitrogen)
>
>
>
> Regards
>
> Crispin
>
>
>
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> ------------------------------
>
> Message: 2
> Date: Thu, 31 Jan 2013 14:16:31 -0800
> From: "Frank Shields" <frank at compostlab.com>
> To: "'Discussion of biomass cooking stoves'"
>         <stoves at lists.bioenergylists.org>
> Subject: Re: [Stoves] WBT (never ending)
> Message-ID: <000901ce0000$9fada380$df08ea80$@compostlab.com>
> Content-Type: text/plain; charset="utf-8"
>
> Dear Crispin,
>
>
>
> It seems the WBT is now not just a WBT but also plans to include a lot of
> great info regarding the combustion process through the cycle. I go along
> with that but would separate them into two test packages and for now just
> concentrate on perfecting the WBT using all the bells and whistles us labs
> have. Remember we have been talking (in words) about just the fuel section
> and still have the water simmering and boiling measurement method to
> develop.  Then when we get to the point where the fuel quality (not
> quantity) is the limiting factor we can experiment with fine tuning the
> fuel for the stove (or other way around).
>
>
>
> Also;
>
> <big snip>
>
>
>
> Crispin:
>
> I would love to have the real times measurements as accurately as
> possible. The problem is the moisture in the middle ? the end we can work
> out with patience. But if the boiling portion of a WBT is done using wood
> that dries out entirely and is half charred by the time boiling arrives,
> what is the energy applied? How do we know what the energy of the burning
> char/wood mix is during simmering? What are we really trying to find out?
> The mass of fuel consumed each time a new copy of the task is performed, or
> the heat transfer efficiency? Or the CO emitted per MJ at different power
> levels? You must decide up front what we are trying to measure then devise
> an experiment that determines it exactly. This is done routinely in
> academia and industry. There is nothing special about stoves that requires
> us to use vainly imagined metrics and methods. Just get on and do the job
> properly.
>
>
>
> Frank:
>
> We need to have one purpose for the test (as you mention). For now it is
> develop a test method the gives us the info we need to compute ?energy from
> biomass per water task?. This is more than enough to work out now.  If this
> is the one purpose the moisture in the middle does not matter. The rate
> wood turns to char does not matter if we stipulate the type of fuel to use
> because it will be the same for all tests and labs. But with different
> quality of biomass as fuel it will matter and to be experimented with at a
> later time when we have such a test where fuel quality is the limiting
> factor. Not yet! We need to get the test working before going out looking
> at exotic measurements. When measuring just CO2 and CO in the out gas you
> are thinking that represents such a large percentage of the carbon from the
> wood (leakage, tars, soot are so small) that you can use those numbers?
> Perhaps, but I see with only slight adjustments (air flow, dilution etc.)
> as making big differences. And I think
>  a good gravimetric and CHN analysis to verify results is still needed as
> a standalone test or to verify the gas analysis.
>
>
>
>
>
> Thanks
>
>
>
> Frank
>
>
>
>
>
> Frank Shields
>
> Control Laboratories, Inc.
>
> 42 Hangar Way
>
> Watsonville, CA  95076
>
> (831) 724-5422 tel
>
> (831) 724-3188 fax
>
>  <http://www.biocharlab> www.biocharlab.com
>
>
>
>
>
>
>
>
>
>
>
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> ------------------------------
>
> Message: 3
> Date: Fri, 01 Feb 2013 13:38:41 -0600
> From: Paul Anderson <psanders at ilstu.edu>
> To: Discussion of biomass cooking stoves
>         <stoves at lists.bioenergylists.org>
> Subject: [Stoves] At what temperature are the bad gases from zinc
>         created, vs harmless zinc oxide?
> Message-ID: <510C19C1.3050807 at ilstu.edu>
> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
>
> Stovers,
>
> Galvanized metal in stoves gets mentioned occasionally.  Do we have a
> clear answer about what is the temperature at which the zinc makes
> poisonous gases (such as when welding) versus making zinc oxide (the
> white stuff that you can by in a tube to put on your nose to prevent
> sunburn)?   Is it bad if the temperature is at 400 C to 700 C?   Or does
> it need to get much higher?
>
> Paul
>
> --
> Paul S. Anderson, PhD  aka "Dr TLUD"
> Email:  psanders at ilstu.edu   Skype: paultlud  Phone: +1-309-452-7072
> Website:  www.drtlud.com
>
>
>
>
> ------------------------------
>
> Message: 4
> Date: Fri, 1 Feb 2013 11:43:30 -0800
> From: "Boston Nyer / BURN Design Lab" <boston at burndesignlab.org>
> To: Discussion of biomass cooking stoves
>         <stoves at lists.bioenergylists.org>
> Subject: Re: [Stoves] At what temperature are the bad gases from zinc
>         created, vs harmless zinc oxide?
> Message-ID:
>         <CALEDrLzgia+JT2pf8rQ3hdGr3go=
> VDhXPP-1FZqkBaWuWtLXew at mail.gmail.com>
> Content-Type: text/plain; charset="iso-8859-1"
>
> Recommended maximum service temperature for galv. is approximately 390 F
> (200C).
>
> Source: American Galvanizers Association (
>
> http://www.galvanizeit.org/about-hot-dip-galvanizing/how-long-does-hdg-last/in-extreme-temperatures
> )
>
>
>
> On Fri, Feb 1, 2013 at 11:38 AM, Paul Anderson <psanders at ilstu.edu> wrote:
>
> > Stovers,
> >
> > Galvanized metal in stoves gets mentioned occasionally.  Do we have a
> > clear answer about what is the temperature at which the zinc makes
> > poisonous gases (such as when welding) versus making zinc oxide (the
> white
> > stuff that you can by in a tube to put on your nose to prevent sunburn)?
> > Is it bad if the temperature is at 400 C to 700 C?   Or does it need to
> get
> > much higher?
> >
> > Paul
> >
> > --
> > Paul S. Anderson, PhD  aka "Dr TLUD"
> > Email:  psanders at ilstu.edu   Skype: paultlud  Phone: +1-309-452-7072
> > Website:  www.drtlud.com
> >
> >
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> > for more Biomass Cooking Stoves,  News and Information see our web site:
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> >
> >
>
>
> --
> Boston Nyer
> Managing Director / BURN Design Lab
> www.burndesignlab.org
> Skype:  BostonNyer
> Cell:      585.503.3459
> Office:   331.444.BURN (2876)
> Fax:       810.815.5052
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> End of Stoves Digest, Vol 30, Issue 1
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>



-- 
Art Donnelly
President SeaChar.Org
US Director, The Farm Stove Project
Proyecto Estufa Finca
<http://email2.globalgiving.org/wf/click?c=1Oy%2FmZbgIyjS5WI580KXwShvfKBcF2eaJvtN7Pi6p7Jl%2FiR4938EMMCBwY%2FuYALeA%2BQYUWN4RpvnxBsBC7e2%2BGIHcONTozBmvsUU5LTL%2FTNk4Q3vxE%2BKdXTV2cxIsFplSPh%2F9nMG3bQMQf4bz9ZK9SHMy46Z8OPLAtMAnPG9SKkPuLCWvofBTLC%2BImqax%2BZTkkF2RvDri5UdgH19NHjHOBj5WMUrS4L62Z2xxUJbBsJdDUOfeifheNFXH546Xm0yul4P2stm%2FTUOJxYnI0nFjXEaYfzxDSc%2FwgqVkR1t0USDHk30%2Fgt9UpDpyzLj37HWtnNQ0q8Jh1gZCkB4Y1Fgbg394gYFkyNqFN4MchxO2Js%3D&rp=wrhiOr2wAxUyDMDlMSqbOkKa0FpPoiCSHffb%2ByfHGClRxIFjEIrUDwAF%2BFD%2BpAPuvam9BDwvSMcadhFv7aFwKoyAXYrFk00%2B92xPIeMHXaTDJ3x0VIj6ZYwjm1win65o&up=YDTqBOjidbCUo%2Far1oAtZjp5ji73zPEvmoO14mevuXzIDUdb6Ac9W13SPOXmzL5NflZkH0HxLp0v4dT9UwEHDV0wSZ1qusv09bIKkUliWs4%3D&u=LHuflw_1TAib_lgCu2JvQw%2Fh0>
"SeaChar.Org...positive tools for carbon negative living"
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