3.5. Effect of lignosulfonate addition to poplar
When a 17mmcompression diewas used, no significant effect of the
addition of lignosulfonate to poplar was observed on the electric intensity
used by the pellet press and on the die temperature (Table 5) for the
same moisture content (15 wt.% w.b.). It could be explained because a
low additive dosage was used and this compression die is not enough
for poplar pelletization.Mediavilla et al. [7] observed that with addition
of additives the specific energy decreases but an increase in the additive
dosage does not have an important influence on the specific energy
(kWh/dry t). However, a slight decrease in the die temperature and in
the electric intensity used in the pellet press was observed after the
additive addition, when compression die of 19 mm was used.
The physical characteristics of the pellet produced with poplar and
two additive dosages are shown in Table 6. The moisture content at
the inlet of the pellet press was keep constant thorough the entire
test, 15 wt.%, to avoid any effect of this parameter on the pelletization
process.
According to the durability, the pellet from poplar obtained with
2wt.% d.b. reached themaximumquality for poplar (due to its chemical
and compositional properties), ENPlus B. Without any additive andwith