coal combustion; Calculation of adiabatic flame temperature(s)

[Julius]

Dear Cantera Group,

my problem is that the calculations i do seem wrong to me, and i dont
understand why.

Here http://groups.google.com/group/cantera-users/browse_thread/thread/f24d7f228c525fda/9dbaf023feb52db9?lnk=gst&q=coal#9dbaf023feb52db9
its written that you can change the biomass compostion to the coal
composition. (Using the baratieri2008.cti )

I modified the Molefractionvektor for the Gas by adding N2 and O2
(air).
In a loop i let my programm calculate the adiabatic temperature
[ using equilibrate(gas,'HP'); t=temperature(gas) ].
I varied the Equivalence ratio from fuel rich to fuel lean combustion.

For fuel rich combustion the temperatures become extremly high and
normaly they are highest near the stochiometric composition, but in my
calculations the more fuel the higher the temperatures get.
Also in the fuel lean area the temperatures are to high.

If i should post the code please tell me.

Greetings Julius and thank you very much for your help :)

[Rodolfo Rodrigues]

Hi Julius!

How did you calculate the adiabatic flame temperature? Do you estimate the enthalpy of fuel + air and start by guessing final temperature values until initial and final enthalpies have equal values?

Regards,

Rodolfo

--
Rodolfo Rodrigues, MSc Eng

  PhD-student in Chem. Engineering, UFRGS

  Porto Alegre, Brazil

  Email:  rod...@enq.ufrgs.br
             rod...@chengineer.com
  Tel: +55 51 3308-4019

[Julius]

Hey Community,
has no one an DataSet or idea, how i can for example change the
"equil" file in the "/Cantera/demos/Matlab folder", to make it work
with coal. Would be really nice if you could help me.
I need this for my bachlor thesis and i don't find a solution my self.
As written above the baratieri2008.cti doesn't work when i include it
into the equil file.
Greetings Julius

[Julius]

Hey Rodolfo thank you for your answer!

Im calculating the adiabatic temperature by defining my mixture of
specieswith the right molemasses at my certain Equivalence ratio.
Then i use the function "set" to give the gas my initial conditions
(working with the function "mix = Mixture({gas, 1.0; graphite, 0.1})"
always makes my matlab crash), so i have to use a gas. I am not sure,
if that is right, but after pyrolisis and other mechanisms the coal
is a gas except for the carbonate.
The next step is to use the function "equilibrate(gas,'HP')" (like
shown in the tutorial and the demo file, it works totally fine with
methane air combustion)
In the end the function "temperature(gas)" does the rest :)
Matlab warns me that " Warning: Temperature (5261.55 K) outside valid
range of 300 K to 5000 K", even if i use for example the
gri30_highT.cti file i found on the internet.

Regards, Julius

On 26 Aug., 19:34, Rodolfo Rodrigues <rodolfo....@gmail.com> wrote:
> Hi Julius!
>
> How did you calculate the adiabatic flame temperature? Do you estimate the
> enthalpy of fuel + air and start by guessing final temperature values until
> initial and final enthalpies have equal values?
>
> Regards,
> Rodolfo
>
>
>
>
>
>
>
>
>
> On Wed, Aug 17, 2011 at 1:42 PM, Julius <becker.jul...@web.de> wrote:
> > Dear Cantera Group,
>
> > my problem is that the calculations i do seem wrong to me, and i dont
> > understand why.
>
> > Here

> >http://groups.google.com/group/cantera-users/browse_thread/thread/f24...

> > its written that you can change the biomass compostion to the coal
> > composition. (Using the   baratieri2008.cti )
>
> > I modified the Molefractionvektor for the Gas by adding N2 and O2
> > (air).
> > In a loop i let my programm calculate the adiabatic temperature
> > [ using  equilibrate(gas,'HP');  t=temperature(gas) ].
> > I varied the Equivalence ratio from fuel rich to fuel lean combustion.
>
> > For fuel rich combustion the temperatures become extremly high and
> > normaly they are highest near the stochiometric composition, but in my
> > calculations the more fuel the higher the temperatures get.
> > Also in the fuel lean area the temperatures are to high.
>
> > If i should post the code please tell me.
>
> > Greetings Julius and thank you very much for your help :)
>
> --
> Rodolfo Rodrigues, MSc Eng
>   PhD-student in Chem. Engineering, UFRGS
>   Porto Alegre, Brazil

>   Email:  rodo...@enq.ufrgs.br
>              rodo...@chengineer.com
>   Tel: +55 51 3308-4019

[Julius]

Hey Guys, something else. On this link http://www.stanford.edu/~cammat/cantera/xml/
i was able to download a gasification.xml file, but my problem is that
in the speciesarray "C H O N S" species are missing so my programm
doesn't work...
In this text at the end of page 1 (http://www.stanford.edu/~cammat/
cantera/CanteraStancanPrimer.pdf) its written that "It also includes
a data set suitable for coal gasification simulations". But how should
this work without those species? Greetings a bit desperate Julius :)

[Rodolfo Rodrigues]

Julius,

I made the pyrolysis sample using "baratieri2008.cti" data file.

It was a test to reproduce this article: http://dx.doi.org/10.1016/j.biortech.2008.01.006

For your sample, if you represent the coal as combinations of C, H, O, N, and S atoms you must also consider the enthalpy of formation of coal. So using Cantera 'HP' equilibrium method to calculation isn't totaly right. You should use the function equilibrate('TP') to find an equilibrium temperature as a result the enthalpy be equal to enthalpy of initial coal and air fraction.

Hope this helps you! =)

Regards,

Rodolfo

  Porto Alegre, Brazil

[Julius]

Ah i fixed the problem by H(mole)/[1+2*(1+79/21)], i accumulated the
enthalpy for more then 1 mole. But i still got the problem with coal,
i think that i perhaps have to use the lower Heating Value, but H_u is
for example (methane) defined as the difference of the standart
enthalpies H_u(molar)=h_CH4_0-1*h_CO2_0-2*h_H2O_0. But in my coal
there are so many other Spezies and many more Products (not only CO2,
also CO....)

I don't think that saying it is a gas in the beginning with a C H O N
S H2O and Ash composition is right. There is energy bound in the
strukture of the coal (as far as i think)
Regards, Julius