The harvested seeds were delivered to the processing facility
which is located in the Interuniversity Research Centre on Biomass
for Energy (CRIBE), 8 km SW of Pisa. The facility is meant to
represent the activity of a small scale farm dealing with bioenergy
and biofuels production. The facility includes a platform for oil
production and transesterification (Fig. 1).
Oil extraction occurs in a small pressing machine, consisting of
two screw extractors with a nominal processing capacity of
50 kg h
1
of seeds. The pressing machine is equipped with a
decantation drum which allow larger particles to settle and afilter
press forfinal purification.
The pressing machine can be controlled by an operator who has
to manually load the feeding hopper of the pressing machine.
The screw extractors are composed of two sections: in thefirst
one the seeds are crushed and most of the oil is released, in the
second one, the solid residue is extruded so as to increase pressure,
which allows collection of additional oil, and shape the press cake
into pellets.
Pressing is characterized by two parameters: extraction temperature, which can be adjusted by means of electrical resistors,
and press orifice, whose diameter can be adjusted in order to tune
the pressure achieved in the extrusion section. Both of these parameters influence the oil yield, oil and press cake qualities[32].
The size of the sunflower cake pellets will change accordingly to the
orifice diameter. Preliminary tests evidenced that a 10 mm orifice
and 60
C represent the optimal conditions for sunflower seeds oil
extraction.
In the present study seeds were sieved prior to pressing in a
vibrating sieve in order to remove dust, soil, leaves and other solid
contaminants. The loaded seeds as well as the extracted oil and the
residual cake were weighed in order to calculate the material balance. Nearly 300 kg of seeds of each variety were processed