Torrefaction - Biomass Gasification, Pyrolysis and Torrefaction - page 145

Recycled
flue gas

X.W' g ,T go

W oil ,T'' o

Burner
with
dilution

W g ,T gi

W air ,T' o air

FIGURE 4A.2 Control volume of burner with gas mixing chamber.

where,

A

5 ð

W v C v 1 W vl C g Þ T g0 1 W t C d T t 2 W f C b T 0 1 W v L

Oil Burner: Control Volume of Oil Burner
We assume that X fraction of the flue gas leaving the torrefier is fed into the
burner along with fresh air W air . Since the recycled gas (XW 0 g ) contains
some unburnt volatiles (XW vl ), we assume this to supplement oil in the

burner. We assume fuel oil is preheated to temperature T v 0 .
Q vl 5 heat energy released from the combustion of volatile gases

5 XW vl LHV vl η

where is combustion efficiency.

From Figure 4A.2 , we write the energy balance as:

η

XW 0 g C g T g0 1 W air C a T 0 0 1 W g C g T gi 5 XW vl LHV vl η 1 W oil LHV η 1 W oil C oil T v 0

So, the mass fraction, X, of torrefier product gas recycled is

C a T 0 0 2 W g C g T gi αð A = F Þ W oil LHV η 2 W oil C oil T v 0

X (A.6)

5

W 0 g C g T g0 1 W vl LHV vl η

Substituting values from Eqs. (A.4) and (A.6) , we have

T 0 0 2

½ W g 2 W oil ðαð A = F Þ 1 1 Þ W g C g T gi 2 W oil αð A = F Þ C a : W oil LHV η 2 Woil C oil T v 0

5

W 0 g W 0 g C g T g0 1 W vl LHV vl η

Amount of oil consumed in the burner is calculated from here as:

1 W g

W 0 g

C g T gi
C g T g0 1

W oil 5

P 3

VL 0 fr LHV vl η 2

1 (A.7)

K

2

where,

5 αð

= Þ

C a : T 0 0 1

η 1 v 0

A F LHV C oil T

5 ðα

A = F 1 Þ W vl

W 0 g

1

and VL 0 fr 5 K P

;

W 0 g C g T g0 1 W 0 g W vl LHV vl η