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Biomass boiler simulations - Temperature of volatiles

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Old   May 5, 2016, 11:24
Default Biomass boiler simulations - Temperature of volatiles
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iam
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Dear all,

I am trying to simulate the combustion of biomass. I am using the wood-air model of fluent, but I need to insert as input data the temperature of my input volatiles. Could someone please help me to calculate this value?

Thanks a lot!!!!
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Old   May 5, 2016, 15:49
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Angel Penev
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Dear iam,
You could insert your temperature in the BC and choose from the material tap wood volaties. You can calculate the adiabatic temperature for the fuel. If you use species transport you have to read user guide and make balance species DPM model.
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Old   May 6, 2016, 03:31
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Dear gartz,

Thanks a lot for you reply. In order to simulate the combustion of biomass, I am using the wood-air species model of fluent, but I change some of the values to adjust to the biomass composition and power I have in the boiler. I am following the following approach:

- From the elemental composition of the biomass (C,H,N,O) I calculate the PCI of the fuel.

- From the elemental composition of the biomass (C,H,N,O), I calculate an imaginary element CxHyOzNiSj, and I determine the moelcular weight and heat of formation of the element.

- I determine the volumetric rate (Nm3/h) of the volatiles formed, assuming that everything goes to CO2 and H2O. Would that be correct? And then I assume that the fraction of volatiles will be everything but O2 and N2 in the mixture.

- AS you indicate, I need to give a temperature of the mixture as boundary condition. How could I calculate the adiabatic temperature of the mixture?

Thanks a lot for you help!

Itsaso
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Old   May 6, 2016, 04:09
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Angel Penev
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First of all, you've got the proximate analysis of fuel. If you don't have it and you want to see only the thermal field and velocity field. You could only put BC inlet , outlet and walls heat transfer and handle calculate adibatic temperature of the fuel from this link http://elearning.cerfacs.fr/combusti...ture/index.php.
If you have proximate analysis and you use species transport you have to add C(s) solid fuel for your DPM model. Then add 3 reactions:
(1) wood volatile(fuel) + O2 -> CO2 + H2O
(2) C(s) + O2 -> CO2
(3) H2O(l) -> H2O(g)
After that you have to make injection. For more details you could look the Species transport for biomass in the forum. If you use non-premixed combustion and you want to put your proximate analysis in the coal calculator you can see the LHV the Cp and molecular weight of the fuel. Then your DPM is on and you could make injection (surface or other). I'm not quite sure for all these things. I'm a beginner, but in the forum have very big experts which could give you some experiance from this area.
Regards.
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Old   May 6, 2016, 04:21
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iam
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In my case, since I do not have the cp of the imaginary volatile molecule (CxHyOjNiSz), how could I determine the adiabatic temperature of the gas mixture?
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