coal volatile composition
 

Hi all....

Could anyone please tell me how FLUENT calculates the volatile composition from proximate and ultimate analysis??.....
e.g. my coal analysis are:

Proximate(FLUENT input)[/B] (%)
FC-43.7
VM-45.6
Moisture-2.2
Ash-8.5

Ultimate(dry ash free basis)(FLUENT input)[/B] (%)
C-77.6
H-6
O-12.7
N-1.3
S-0.5
Ash-8.5

Proximate (Dry basis) (%)
FC-44.8
VM-46.7
Ash-8.5

Ultimate(Dry basis) [B] (%)
C-71
H-6
O-12.7
N-1.3
S-0.5
Ash-8.5


The volatile composition it shows in the coal calculator when I input these values is completely different what it comes out from hand calculation...

Hand calculation: (From dry basis of both)
wt%C in volatile = (71-44.8)/46.7 = 0.561 => moles = 0.561/12 = 0.04675
wt%H in volatile = (6.5)/46.7 = 0.128 => moles = 0.128/1 = 0.128
wt%O in volatile = (12.7)/46.7 = 0.272 => moles = 0.272/16 = 0.017
wt%N in volatile = (1.3)/46.7 = 0.028 => moles = 0.028/14 = 0.002
wt%S in volatile = (0.5)/46.7 = 0.011 => moles = 0.011/32 = 0.00034

So, Volatile = C0.04675 H0.128 O0.017 N 0.002 S0.00034

But FLUENT calculates (based on FLUENT input) :
C1.4 H3.78 O0.51 N0.0587 S0.0109

The FLUENT calculation is also not an exact multiple of hand calculation...could anyone please explain why is the discrepancy and how FLUENT calculates the volatile matter composition...

Thanks....

Hand Calculation
C0.04675 H0.128 O0.017 N 0.002 S0.00034

But FLUENT calculates (based on FLUENT input) :
C1.4 H3.78 O0.51 N0.0587 S0.0109

If you change the C ratio into 1, you will find the result quite similar

Hand Calculation
CH2.738 O0.364 N0.043 S0.007

But FLUENT calculates (based on FLUENT input) :
CH2.7 O0.364 N0.042 S0.008

adjusting the MW for the volatile
 

Include the molecular weight. It seems like for Fluent your MW for the volatile is around 30 kg/kmol.

Therefore, you should multiply the volatile MW value (kg/kgmol) to the mass fraction, before converting into mols.

So, for instance, if we take C for now

wt%C in volatile = (71-44.8)/46.7 = 0.561 * 30=16.83=> moles = 16.83/12 = 1.4025

This is applicable to the other elements in the volatile, which will give
C1.4 H3.78 O0.51 N0.0587 S0.0109