World Grain - December 2007 - 34

FEATURE: INCREASE AQUAFEED PRODUCTION THROUGH PLANT OPTIMIZATION

Table 1: Global aquaculture
production by region
Global region

Seafood production
(million tons)
37.0
2.0
1.2
0.3

Asia
Europe
Americas
Africa

* extruder volumetric capacity;
* die open area;
* downtime;
* upstream/downstream unit operations.
PRECONDITIONING CAPACITY
The preconditioning step initiates the
heating process by the addition of steam
and water into the dry mash.
Uniform and complete moisture
penetration of the raw ingredients significantly improves the stability of the
extruder and enhances the final product
quality. Objectives of a preconditioning
step are to continuously hydrate, heat
and uniformly mix all of the additive
streams together with the dry recipe.
The preconditioning process is relatively simple. Raw material particles are
held in a warm, moist, mixing environment for a given time and then are continuously discharged into the extruder.

This process results in the raw material
particles being hydrated and heated by
the steam and water in the environment.
Dual shaft, intermeshing preconditioners have improved mixing in comparison
to the single shaft preconditioners and
have a longer average retention time of
up to 90 seconds for a similar throughput.
Dual shaft, intermeshing preconditioners
have beaters that can be changed in terms
of pitch and direction of conveying. This
feature of adjustable beaters is not found
on many conditioning devices.
Of all the preconditioners available
today, the differential diameter/differential speed preconditioners (DDC) are the
most sophisticated.
The DDC has the best mixing characteristics combined with the longest
average retention times of those available (see Figure 1, right).
DDC preconditioners offer retention
times of up to six minutes for given
throughputs comparable to the 15 to 45
seconds possible in single preconditioners or multiple-stacked single conditioners (sometimes referred to as dual conditioners). The two shafts of a DDC preconditioner are counter-rotating so that
material is continuously interchanged
between the two intermeshing chambers
for maximum mixing.

Priv�

Un-preconditioned raw materials are
generally crystalline or glassy amorphous materials, which are very abrasive until they are plasticized by heat
and moisture within the extruder barrel. Preconditioning prior to extrusion
will plasticize these materials with heat
and moisture by the addition of water and steam prior to their entry into
the extruder barrel. This reduces their
abrasiveness and results in a longer
useful life for the extruder barrel and
screw components.
Extruder capacity can be limited by
energy input capabilities, retention time
and volumetric conveying capacity.
While preconditioning cannot over-

Figure 1: DDC (Differential Diameter Cylinder)
Preconditioner

Store your grain with Privé

Privé silos help you to solve your grain storage problems, for example :

*
*
*
*
*

Length of time to build a silo.
Long-term investment.
Aeration.
Classification of grain.
Origin of stored grain.

*
*
*
*

Cost per ton of stored grain.
Cost of labour
Pest control (insects, rodents, birds).
Dust control.
* Explosion risk.
CASA GRAIN
CASABLANCA
Maroc.
26.000 tons in 8 bins
with a diameter 17,77m

ALGERIA

Phone/fax 213 21 63 63 50

GERMANY

Phone 49 60 03 91 110
Fax 49 60 03 514

ROMANIA

Phone/fax 40 247 31 98 56

POLAND

Phone/fax 48 22 84 72 168

SWEDEN

Phone 46 413 54 44 44
fax 46 413 54 44 40

PORTUGAL Phone 351 21 778 61 55
fax 351 21 778 34 74
MOROCCO Phone 212 22 24 04 81
fax 212 22 24 04 84
TUNISIA

Phone 216 71 354 366
fax 216 71 343 401

TURKEY

Phone 90 332 352 17 22
fax 90 332 352 42 99

98, avenue du Général Patton - BP 536
51010 CHALONS EN CHAMPAGNE Cedex France
Web site : www.prive.fr
E-mail : contact@prive.fr
Tél 33 3 26 68 66 66 - Fax 33 3 26 68 66 99
For more information, see Page 54.

December 2007 / World Grain / www.World-Grain.com

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World Grain - December 2007

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