Brian,
My wife and I have an agreement where when we argue (well discuss would probably be a better word) about something and then one of us is proven to be right, the one who is wrong must say out OUT LOUD, "I was wrong, you were right.".
So, Brian, "I was wrong, you were right." :)
Before this morning I would have sworn in a court of law that you had written MONTREAL Protocol, not Kyoto Protocol. I have no idea how I could have read that wrong.
With regards to the technical information you wrote, I personally am well aware of this, being a fluorine chemist by training who was intimately involved in Nortel's CFC elimination program and am personally very interested in the whole global warming issue. I even have a 6 hour free "course" I gave at an APEX - to a room of less than 10 people. :(
But I am sure that many of our fellow Technetters are not aware of it. Thank you for sharing. My personal concern is why I originally wrote, "Then you have to decide if you can live with the answer."
Regards,
Bev
RIM
-----Original Message-----
From: Brian Ellis [mailto:[log in to unmask]]
Sent: Tuesday, May 13, 2008 3:55 AM
To: TechNet E-Mail Forum; Bev Christian
Subject: Re: [TN] Vapor phase
Bev
Absolutely 1000% certain!
I did not mention the Montreal Protocol, only the Kyoto Protocol.
Let us look at the GWP figures you mention and see what they mean. You
quote "2790 to 6230". As the HT fluids are in the higher range, for
convenience please allow me to take a hypothetical figure of 5000. This
means that, over a 100 year time frame, a given weight of emitted Galden
will have 5000 times the effect of the same weight of carbon dioxide.
IOW, if you lose 5 kg of Galden in a year (quite easy in a heavily used
machine, even the sophisticated types, because of vapour entrapment
under the components and even condensate entrapment under heavy
components like transformers), you will be emitting the equivalent of 25
tonnes of CO2 as a greenhouse gas.
Worse, the manufacturers do not mention the atmospheric residence time,
defined as the time for the residual quantity in the atmosphere to reach
1/e (about 37%) of the emitted quantity. This is typically 5,000-20,000
years. Why? Because the F-C bond is mighty strong and is not broken down
by hydrolysis in the troposphere or even by photolysis in the
stratosphere. I think it will break down by photolysis in the upper
mesosphere, but you can imagine the time needed for the molecules to
diffuse there, be destroyed and the by-products to homogenise through
the atmosphere. Actually, even this is largely theoretical; we do not
know the exact mechanisms and we cannot model them accurately. But what
it does mean is that the 25 t eq.CO2 is repeated over the next century
and the next century after that and the next century after that, for
many, many centuries, very slightly diminishing each time. You realise
that if your 5 kg emitted in 2008 has an ART of 10,000 years, on the
basis of 4 generations/century, in the 12008, your
97*great-grandchildren will be cursing you because they will still be
"benefitting" from the effects of 1.8 kg of Galden you emitted, still
equivalent to 9.2 tonnes of CO2.
I agree that these are approximations, because of our lack of precise
knowledge: we may find there are other decomposition mechanisms or
something else happens. With such long-lived substances we are playing
the sorcerer's apprentice. One thing I'm afraid of is if elemental
fluorine or weakly bonded fluorine diffuses back down from the
mesosphere into the stratosphere: it is possible that it could create
more ozone depletion, another gift (in German, as well as English!) for
your 97*great-grandchildren.
This is why perfluorocarbons, hydrofluorocarbons, their derivatives, and
sulfur hexafluoride are specifically mentioned as controlled substances
in the Kyoto Protocol. If you look at
http://upload.wikimedia.org/wikipedia/commons/b/bb/Radiative-forcings.svg,
you will see the radiative forcing of halocarbons (in yellow) is about
0.3 W/mē, against a total of ~1.6 W/mē of the anthropogenic component
derived from the positive and negative forcings. (Radiative forcing, in
the context of this chart, is the effect of increased energy reaching
the earth's surface since 150 years ago due to changes in the chemistry
of the atmosphere.) If we stopped emitting halocarbons, which are 99.99%
man-made, then our 97*great-grandchildren may curse us less. I should
mention that the ART of HFCs, as opposed to PFCs, is generally much
shorter, ~5 to ~150 decades. Most of that yellow area is due to PFCs and
HFCs, because other halogen-carbon bonds are weaker and there are more
rapid breakdown mechanisms with chlorine (photolysis in the ozone
layer), bromine (partially photolysis in the ozone layer, partially
hydrolysis in the troposphere) and iodine/astatine (mostly hydrolysis in
the troposphere). The photolytic breakdown is the cause of ozone
depletion. I would not like to see fluorocarbon emissions get any bigger.
Brian
Bev Christian wrote:
> Brian,
> Are you sure? From Solvay's own website:
>
> "Solvay Solexis offers the Galden(r) PFPE line of lower molecular weight
> (LMW) fluorinated fluids. Galden fluids are perfluoropolyethers and
> contain only carbon, fluorine, and oxygen."
>
> Last I heard the Montreal Protocol only dealt with chlorofluorocarbons,
> bromofluorocarbons and some chlorinated solvents. Or is there an
> addendum that I don't know about? Interesting that in the listed
> properties, of the two I looked at, there is no GWP value listed.
>
> If I Google Galden GWP I get:
> H Galden HFPEs have a global warming potential (GWP) that varies for the
> particular fraction, ranging from 2790 to 6230 for the fractions having
> the highest ...
> www.epa.gov/EPA-AIR/2003/January/Day-27/a1623.htm - 67k
>
> AND
>
> They are used as solvents and heat transfer fluids and have zero ODP and
> low GWP. H-Galden HFPE fluids are linear fluoropolyethers end-capped
> with a ...
> www.solvaysolexis.com/products/bybrand/brand/0,,16050-2-0,00.htm - 200k
> -
>
> HMMMM....
>
> Bev
> RIM
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Brian Ellis
> Sent: Monday, May 12, 2008 11:49 AM
> To: [log in to unmask]
> Subject: Re: [TN] Vapor phase
>
> Oh! OOOOH! BIG environmental concerns with Galden. GWP in the tens of
> thousands (CO2 = 1), pretty well on a par with SF6. These PFCs are
> controlled substances under the Kyoto Protocol.
>
> Brian
>
> Bill Kasprzak wrote:
>> Gosh, with all due respect, I'm sure the equipment is using the Galden
>
>> fluid for vapor and that drag out if any is minimal. No environmental
>> concerns as far as I can tell.
>>
>> I think vapor phase will be the comeback kid in the years to come
> because
>> of the even distribution of heat. (We do not have any lead-free
> soldering
>> issues here)
>>
>> What I'm really talking about out is how inconsequential our impact on
>
>> global warming compared to the enormous volcanic eruption in Chile.
> Some
>> of the photo's are incredible. Maybe Steve can post them. I think they
> are
>> available from the UK's Daily mail website.
>>
>> What's happening right now in Chile is a huge environmental disaster
> and
>> no one, no laws, no regulations can do anything about it. It just
> shows
>> how inconsequential we really are.
>>
>>
>>
>>
>> Bev Christian <[log in to unmask]>
>> Sent by: TechNet <[log in to unmask]>
>> 05/12/2008 09:26 AM
>> Please respond to
>> TechNet E-Mail Forum <[log in to unmask]>; Please respond to
>> Bev Christian <[log in to unmask]>
>>
>>
>> To
>> [log in to unmask]
>> cc
>>
>> Subject
>> Re: [TN] Vapor phase
>>
>>
>>
>>
>>
>>
>> Ioan,
>> Ask the supplier what is the global warming potential of the materials
>> they are proposing as the thermal transfer material. Then you have to
>> decide if you can live with the answer.
>>
>> Also, RF cans with small holes can be problematic.
>>
>> Bev
>> RIM
>>
>> -----Original Message-----
>> From: TechNet [mailto:[log in to unmask]] On Behalf Of Ioan Tempea
>> Sent: Monday, May 12, 2008 9:24 AM
>> To: [log in to unmask]
>> Subject: [TN] Vapor phase
>>
>> Dear Technos,
>>
>>
>>
>> I would like to get your expert opinion on the latest developments in
>> the vapour phase technology. The last time this topic has been
> discussed
>> here this was still an environmental hazard.
>>
>>
>>
>> Here's the latest sales pitch:
>>
>>
>>
>> Dear Convection Oven Users:
>>
>> With Energy Costs Skyrocketing, You have a cheaper, efficient, and a
>> better yield Alternative!!
>>
>> Low Operating Cost, 110 Volt Machine, Run Lead and Lead Free
>> Sequentially!!
>>
>> High Yield, Run your Lead Free Boards at 230 Degrees Uniform
> Temperature
>> Distribution, No Circuit Board Delamination, Uses Environmentally
>> Friendly Teflon 2 Liquid No Hazardous Florocarbons!
>>
>>
>>
>> The questions are:
>>
>> * Are the advantages real, should I prefer vapour phase over
>> convection in day by day reflow operations, from the technical point
> of
>> view?
>>
>> * Would the technology finally be environmentally friendly?
>>
>>
>>
>> Thanks,
>>
>>
>>
>> Ioan
>>
>>
>>
>>
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