Torrefaction - Biomass Gasification, Pyrolysis and Torrefaction - page 143

APPENDIX
MASS AND ENERGY BALANCE OF TORREFIER
Assumptions
Torrefaction is mildly exothermic.
Torrefaction occurs at constant atmospheric pressure.
Negligible moisture in air.

A/F 5 Air fuel ratio for stoichiometric combustion 5 14.6 for diesel oil.

T g0 is chosen higher than 100 C to avoid condensation in drier (assume
105 C).

T gi is chosen less than 300 C to avoid combustion of torrefied wood
(assume 300 C).

Heating values of volatile is estimated to be 1.286 MJ/kg on dry basis.

MASS BALANCE
Torrefier
From Figure 4A.1:

W 0 g 5

W t 1 W f 1 W g

On rearranging, one gets:
W 0 g 5 W f 1 W g W t (A.1)

W 0 g 5 W v 1 W vl 1 W g
where W vl is the volatile in fluid product leaving torrefier.
Moisture in fuel W v 5 MW f (A.2)

where is the excess air coefficient used in oil burner.

Substituting W 0 g

α

from Eq. (A.1) , we get:

W f 1 W g W t 5 W v 1 W vl 1 W g

Substituting W v from Eq. (A.2) :
W vl 5 W f W t

MW f (A.3)

Oil Burner
From Figure 4A.2:

W g 5 W air 1 W oil 1 XW 0 g