4.0 Mass Balance

 

Assumptions:

1) Conservation of matter 

2) No accumulation in the system 

3) Total mass of products initially in the gas phase (including non-condensable syngas and condensable vapours) is given by the feed mass less the char mass

4) Moisture present in the feed will not be distinguishable from pyrolytic water in the product mixture and must be taken into account in the calculation

 

D – dry mass of feed 

M – mass of moisture in feed 

C – char mass yield 

G – syngas mass yield 

L – liquid mass yield 

Gs – syngas sample mass 

Ls – liquid sample mass 

S – total sample mass 

x – unknown fraction sampled of total gas phase mixture

 

 

Mass balance :

 

D = C + G + L

 

Mass balance (including moisture):

 

D + M = C + G +L + M

 

(The sample taken is an unknown fraction, x, of total gas phase mixture, including vaporised feed moisture)

 

S = x( G + L + M) = x(D – C + M)

 

Rearrange:

 

S = xG + x(L + M)

or

S = Gs+Ls

 

xG represent gaseous fractions of the sample

x(L+M) represent  condensed fractions of the sample

 

Gs = xG , G=Gs/x 

 

Ls=x(L+M), L+M=Ls/x 

 

x=(Gs+Ls)/(D-C+M)

 

Equations for syngas and pyrolysis liquid mass yields:

 

G=Gs/x=(Gs(D-C+M))/(Gs+Ls)

 

L=Ls/x-M=Ls(D-C+M)/(Gs+Ls)-M

 

 

 

 

 

 

 

 

 

 

 

 

 

 

MASS BALANCE CALCULATION:

 

By using the experimental data from the table above, for slow pyrolysis

 

100% dry feed = 59.89 % char + 27.91% bio-oil + 10.26% syngas

D = C + G + L

 

Xe = (mass of wet feed-mass of dry feed)/(mass of dry feed)

w = mass of dry feed

 

0.1=(300kg-w)/w

w=272.73kg

 

 

Conversion, X=0.9806

 

Assuming 10wt% moisture feed (300kg),

              

Mass of char:                                             272.73kg×59.89%= 160.6 kg char

Mass of bio-oil:                                          272.73kg×27.91%= 76.12 kg bio oil

Mass of syngas:                                        272.73kg×10.26%= 27.98 kg syngas

 

 

270kg dry feed→160.6 kg char+76.12 kg bio oil+ 27.98 kg syngas