Agriculture Reference
In-Depth Information
Hence, about 68% of raw juice must be converted into syrup for the factory to operate
during a year.
In order to save some energy and to concentrate stillage DM, stillage produced during
the harvest period is totally recycled at the extraction process. In addition, during the rest
of the year part of it is used to dilute the syrup. Hence, we suppose a distillation effluent
with a 10% DM content.
4.6.1.
Beet processing and juice extraction
Roots are washed, sliced and finally submitted to a counter-flow of water or stillage at 70
◦
C
to extract its sucrose.
According to D. Ballerini, using data provided by l'Union Nationale des Groupements
de Distillateurs d'Alcool UNGDA [2], the overall operation requires r
exct
= 22 kg
st
·
t
−
1
A
and 35
MJ
e
·
t
−
1
A 2000 Swiss study indicates a consumption of r
exct
= 64 kg
st
·
t
−
1
.
A
A
and 24
MJ
e
·
t
−
A
for a factory project based on Finnish processes [28].
By comparison in 2006 cane preparation and sugar extraction in a typical Brazilian
factory necessitate 141
kg
st
·
t
−
1
and 74
MJ
e
·
t
−
1
[31, 32]. On the other hand, it operates
A
A
at 100
◦
C.
The lowest requirement results probably from operating with modern equipment and
using waste heat available from other processes.
One
t
A
of beet yields 1.34 t of raw juice and 55
kg
DM
·
t
−
1
of pulp DM.
A
4.6.2.
Pulp treatment
Mechanical concentration of wet pulp DM
Pulp DM is first concentrated by mechanical
A mass 6.43
kg
w
·
kg
−
1
means from about 10% to 28%.
of water is thus removed, or
DM
w
pulpM ech
= 354 kg
w
·
t
−
1
A
. Nearly 200
kg
pulp
·
t
−
A
of concentrated pulp are produced.
We assume that the same process of centrifugation and decantation to concentrate stil-
lage DM from 12% to 30% in a wheat dry mill set up by the Maguin Interis Co. is used to
achieve the operation [2]. It consumes r
pulpM ech
= 52 kJ
e
·
kg
−
1
of electricity.
w
Drying of concentrated pulp
Pulp is then dried to reach a DM content of 89% [2, 29]. A
mass 2.5
kg
w
·
kg
−
1
DM
of water is thus evaporated, or w
pulpDry
= 135 kg
w
·
t
−
A
.
Thermal consumption is dominated by the water latent heat (2.25 MJ per
kg
w
). Residue
consistency makes difficult more efficient processes like the evaporator (see next Subsec-
tion). Some saving can be achieved by using part of the produced steam to finish pulp
drying [33]. Gas consumption is reduced from 2.9 to 2.1
MJ
HHV
·
kg
−
w
.
Electricity consumption to handle concentrated pulp (using conveyors, drum rotation...)
is considered equivalent to that for handling distillers grains in a wheat dry mill per unit of
their mass [2]. It amounts to r
pulpDry,e
= 115 kJ
e
·
kg
−
1
of electricity.
pulp
4.6.3. Juice concentration into syrup
Raw juice is concentrated from C
S
= 13
.
5%
to
61%
. A mass of 5.8
kg
w
·
kg
−
S
of water is
thus removed. Taking into account that
68%
of the raw juice, and so beet, are thus processed
over the year, the specific quantity of water amounts to w
Sconc
= 710 kg
w
·
t
−
1
.
A
