Biomass Characteristics - Biomass Gasification, Pyrolysis and Torrefaction - page 84

The volume fraction of a gas can be found by noting that the volume that
1 kmol of any gas occupies at normal temperature and pressure (NTP) (at 0 C
and 1 atm)

is 22.4 m 3 . So,

taking the example of hydrogen, the volume of

1 kmol of hydrogen in the gas mixture is 22.4 nm 3 at NTP.
The total volume of the gas mixture is V summation of volumes of all con-

5

5 P ([number of moles (n i ) 22.4])/nm 3 stituting gases in the mixture 22.4n.

The volume fraction of hydrogen in the mixture is volume of hydrogen/total
volume of the mixture:

3 5

22 : 4n H n h

n 5 4 P n i 5

V H x H (iv)

5

22 :

Thus, we note that:

mole fraction
The partial pressure of a gas is the pressure it exerts if it occupies the entire
mixture volume V. Ideal gas law gives the partial pressure of a gas component,
i,as

Volume fraction 5

n i RT
V

P i 5 P a

The total pressure, P, of the gas mixture containing total moles, n,is

n RT
V

P

5

So we can write:

n i
n 5

p i
p 5

v i
V

x i (v)

5

Partial pressure as fraction of total pressure mole fraction volume fraction.

5 5

x H P.
The molecular weight of the mixture gas, MW m , is known from the mass
fraction and the molecular weight of individual gas species

The partial pressure of hydrogen is P H

5

X

MW m ½ x i MW i (vi)

5

where MW i is the molecular weight of gas component i with mole fraction x i .

SYMBOLS AND NOMENCLATURE

ASH weight percentage of ash (%)

C weight percentage of carbon (%)

C p

specific heat of biomass (J/g K)

specific heat of biomass at temperature θ C (J/g C) C p θ

C w specific heat of water (J/g K)

d pore pore diameter (m)

e rad emissivity in the pores ( )

FC weight percentage of fixed carbon (%)