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Dew Point Calculation in a Gas Mixture

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Dew Point Calculation in a Gas Mixture fac 03-19-2008
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Posted by Abby Normal on March 22, 2008, 12:09 am
I think you get low dewpoints with the sulfur, you get acid consensing
out not so much water condensing out

some acids need water, but some can be a liquid unto themselves

wrote:
>
>
> > Do you know if there is any standar to calculate this. The composition
> > will
> > not remain always the same, so the dew point should change
>
> You may want to start here;http://www.jehar.com/dewpnt.htm
>
> =A0 =A0This will calculate the fuel dewpoint based upon the sulfur content=
, and
> will very according to burner, fuel type and combustion air used.
> =A0 However, your numbers look more like sampling from a Kiln or Process
> Dryer. That involves variable moisture from the process interacting with
> burner
> firing rate. It can be VERY complicated to calculate in advance.
> You can monitor that in real time if you must, but why you would want
> to, I have no idea.
>
> Why DO you need this information?
>
> -zero


Posted by Abby Normal on March 22, 2008, 12:03 am
looks like the products of combustion with way too much excess air

try daltons law of partial pressures, work out the pressure of the
water vapour then go look in a staurated steam table for the
saturation temperature.

I just pulled that out of my ass but would probably work.

Otherwise tell then it is a 140F

> I have a heated mixture of:
> O2: =A012%
> H2O: 13%
> N2: 70%
> CO2: 5%
>
> Temperature: is around 200=BAC.
>
> Somebody is asking me about the dew point. I know how to calculate the dew=

> point if it were H2O in air (using psicometric ASHRAE diagrams) but I am n=
ot
> able to calculate it in this mixture.
>
> Does anybody knows any standar o procedure to calculate this?
>
> Thanks
>
15$sw3.3357@trnddc06...
>
>
>
> > I don't know what are you trying to get or do
> > water contents in gases are measured in parts per million
> > and the dew point temperature varies with temperature
> > of particulars gas/refrigerant lower the Temp. the lower the dew
> > point, example while 10 parts per million maybe ok for R-134A
> > it is not good for R-508B which it needs to be 7 parts per million
> > or lower, there for dew point will be much lower.
> > if you are looking for formulas sorry can't help you.
> > In another process you can dry air what you are breathing
> > to 100 below zero dew point or lower using chemical reactivation.
> > which I am sure you are not looking for that.
> > Tony
>
> > > Does anybody knows where to find information to calculate the Dew Poin=
t
> > > temperature of water in a gas mixture.
>
> > > In air it is stated in ASHRAE, but what happens with water in differen=
t
> > > gases (for example a mixture of H20, Ar, N2 .......)
>
> > > Thanks- Hide quoted text -
>
> - Show quoted text -


Posted by Abby Normal on March 22, 2008, 12:11 am
> I have a heated mixture of:
> O2: =A012%
> H2O: 13%
> N2: 70%
> CO2: 5%
>
> Temperature: is around 200=BAC.
>
> Somebody is asking me about the dew point. I know how to calculate the dew=

> point if it were H2O in air (using psicometric ASHRAE diagrams) but I am n=
ot
> able to calculate it in this mixture.
>
> Does anybody knows any standar o procedure to calculate this?
>
> Thanks
>
15$sw3.3357@trnddc06...
>
>
>
> > I don't know what are you trying to get or do
> > water contents in gases are measured in parts per million
> > and the dew point temperature varies with temperature
> > of particulars gas/refrigerant lower the Temp. the lower the dew
> > point, example while 10 parts per million maybe ok for R-134A
> > it is not good for R-508B which it needs to be 7 parts per million
> > or lower, there for dew point will be much lower.
> > if you are looking for formulas sorry can't help you.
> > In another process you can dry air what you are breathing
> > to 100 below zero dew point or lower using chemical reactivation.
> > which I am sure you are not looking for that.
actually work out your pounds of moisture per pounds of dry gas and
use a pyschrometric calculator


> > Tony
>
> > > Does anybody knows where to find information to calculate the Dew Poin=
t
> > > temperature of water in a gas mixture.
>
> > > In air it is stated in ASHRAE, but what happens with water in differen=
t
> > > gases (for example a mixture of H20, Ar, N2 .......)
>
> > > Thanks- Hide quoted text -
>
> - Show quoted text -


Posted by Abby Normal on March 22, 2008, 12:24 am
> I have a heated mixture of:
> O2: =A012%
> H2O: 13%
> N2: 70%
> CO2: 5%
>
> Temperature: is around 200=BAC.
>
> Somebody is asking me about the dew point. I know how to calculate the dew=

> point if it were H2O in air (using psicometric ASHRAE diagrams) but I am n=
ot
> able to calculate it in this mixture.
>
> Does anybody knows any standar o procedure to calculate this?
>
> Thanks
>
15$sw3.3357@trnddc06...
>
>
>
> > I don't know what are you trying to get or do
> > water contents in gases are measured in parts per million
> > and the dew point temperature varies with temperature
> > of particulars gas/refrigerant lower the Temp. the lower the dew
> > point, example while 10 parts per million maybe ok for R-134A
> > it is not good for R-508B which it needs to be 7 parts per million
> > or lower, there for dew point will be much lower.
> > if you are looking for formulas sorry can't help you.
> > In another process you can dry air what you are breathing
> > to 100 below zero dew point or lower using chemical reactivation.
> > which I am sure you are not looking for that.
> > Tony
>
> > > Does anybody knows where to find information to calculate the Dew Poin=
t
> > > temperature of water in a gas mixture.
>
> > > In air it is stated in ASHRAE, but what happens with water in differen=
t
> > > gases (for example a mixture of H20, Ar, N2 .......)
>
> > > Thanks- Hide quoted text -
>
> - Show quoted text -

if all else fails then the ASHRAE HOF has a chapter on combustion, has
dewpoint charts to use

Posted by Abby Normal on March 27, 2008, 8:25 am
I think the Dalton's law approach would would work

the water vapour pressure will make up 13% of the pressure in the flue
gas. The total pressure in the flue should be close to atmospheric so
the vapour pressure of water, assuming sea level, would be 0.13 x
14.696 =3D 1.9 psia

So looking in a saturated steam table on hand here at home the
stauration temperature and therefore the dewpoint will be in between
120F (1.69 psia) and 130F (2.22 psia), maybe around 124F. This is low
for natural gas, but you have a lot of excess air which lowers the
'pounds moisture per pounds dry air' if you will.

Usually 140F is an assumed dewpoint for natural gas, I am rusty but it
is for lower excess air amounts maybe around 50%.

I used to work for a custom build OEM, on our modulating gas burners,
we used to ramp up the combustion air blowers on low fire to get the
dewpoint down and reduce the risk of condensation.

Some one mentioned sulfur in fuel oil, sulfuric acid will condenses
out at higher temperatures than water will.





> I have a heated mixture of:
> O2: =A012%
> H2O: 13%
> N2: 70%
> CO2: 5%
>
> Temperature: is around 200=BAC.
>
> Somebody is asking me about the dew point. I know how to calculate the dew=

> point if it were H2O in air (using psicometric ASHRAE diagrams) but I am n=
ot
> able to calculate it in this mixture.
>
> Does anybody knows any standar o procedure to calculate this?
>
> Thanks
>
15$sw3.3357@trnddc06...
>
>
>
> > I don't know what are you trying to get or do
> > water contents in gases are measured in parts per million
> > and the dew point temperature varies with temperature
> > of particulars gas/refrigerant lower the Temp. the lower the dew
> > point, example while 10 parts per million maybe ok for R-134A
> > it is not good for R-508B which it needs to be 7 parts per million
> > or lower, there for dew point will be much lower.
> > if you are looking for formulas sorry can't help you.
> > In another process you can dry air what you are breathing
> > to 100 below zero dew point or lower using chemical reactivation.
> > which I am sure you are not looking for that.
> > Tony
>
> > > Does anybody knows where to find information to calculate the Dew Poin=
t
> > > temperature of water in a gas mixture.
>
> > > In air it is stated in ASHRAE, but what happens with water in differen=
t
> > > gases (for example a mixture of H20, Ar, N2 .......)
>
> > > Thanks- Hide quoted text -
>
> - Show quoted text -


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