Page 199 - Biomass Gasification, Pyrolysis And Torrefaction Practical Design and Theory

176 Biomass Gasification, Pyrolysis and Torrefaction

110 14 350

300
100
12
Carbon recovery (% of initial °C) 90 10 pH 200 CEF (mmol c /kg) Surface area (m 2 /g)
250

80
8
150
6
70
100
60
4
50
0
50 2
0 200 400 600 800 1000
Temperature (°C)
Carbon recovery pH CEC Surface area

FIGURE 5.10 A qualitative diagram showing changes in properties of biochar with temperature
of its production. Source: Drawn after Lehman et al. (2007). Higher than 100% carbon recovery

below 200 C is likely to be an experimental error of the authors.

rise to 60% of the initial carbon, but it is less influenced above 600 C.

These suggests that pyrolysis at higher temperature is desirable from a bio-
char production standpoint.

SYMBOLS AND NOMENCLATURE
1
A preexponential factor (s )
E activation energy (J/mol)
1
k reaction rate (s )
m b mass of biomass at time t (kg)
m c mass of char residue (kg)
initial mass of biomass (kg)
m 0
R universal gas constant (J/mol K)
T temperature (K)
pyrolysis temperature (K)
T pyr
t time (s)
heating time (s)
t heating
reaction time (s)
t r
X fractional change in mass of biomass