Biomass Fuel Quality Enhancement and Respiratory Quotient (RQ) for Ranking Fossil and Biomass Fuels Based on CO2 Emissions - Novel Combustion Concepts for Sustainable Energy Development - page 60

Fig. 9 Variation in heating
value and ECR with increase
in temperature. M Mesquite;
J Juniper; HHV r Heating
value ratio; ECR Energy
conversion ratio

1.3

0.9

1.25

0.8

1.2

0.7

1.15

0.6

1.1

M-HHV r
J-HHV r
M-ECR
J-ECR

0.5

1.05

0.4

200 220 240 260 280 300

Temperature ( o C)

determined. Figure 9 shows the variation of heating value and ECR with respect to
torrefaction temperatures.
As can be observed from Fig. 9 , heating value of the torre ed sample increases

with increase in torrefaction temperature as the hemicellulose and cellulose vola-
tilizes and the sample becomes rich in char and lignin which have higher heating
value. The ratio of the heating value of the torre

ed samples to the raw biomass

samples from the experiments at 240 C for a residence time of 60 min was 1.06

and 1.05 for mesquite and juniper, respectively. The ratio of the heating values
predicted by the model was lower. In the case of TCM, the composition of volatile
matter released from the sample is assumed to remain constant and it also includes
carbon and hydrogen along with oxygen. Hence, lower ratios were predicted by the
model when compared to that of experiments. The ECR of the torre

°

ed samples
decreases due to loss of combustible volatile matter. As the energy content of the
sample decreases with increase in temperature, ECR decreases. It is seen that ECR
decreases rapidly after about 260

°

C due to higher loss of cellulose. Thus, T torr must

°

be limited to T torr < 260 C. However, on a unit mass basis, heating value of the

torre ed sample is higher than the raw biomass. Hence, the three-component model

is a simple and powerful model to predict the mass loss from the biomass samples
undergoing torrefaction. Such a model can also be applied to the fibrous biomass
torrefaction. It should be noted here that the order of reaction for the volatilization
of the three components is assumed to be one.
The kinetics used in the TCM also in uences the amount of mass loss and

change in heating value of the sample. In order to compare the effect of kinetic
constants on the mass and energy yield, kinetics of pine wood components
extracted using error minimization technique (Wang et al. 2012b ) was used to
predict the mass loss and ECR. The results obtained were compared to the heating
value ratio determined using the kinetics presented in Table 4 . Figure 10 plots the

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