Flow chart of the extrusion line, drying and milling by oss17616

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									By Carlos Elwart


Flow chart of the extrusion line, drying and milling


                                        Flour loading




                                    Volumetric dosimetry




    Steam                                Conditioning       Water




Indirect heating                          Extrusion         Water




                                              Cut




                                            Drying         Warm air




                                           Cooling         Fresh air




                                            Milling




                                            Bulking




                                           Packing
By Carlos Elwart


Operation of the extrusion line, drying and milling

Flour loading:
The loading of raw flours is carried out in a platform opposed to a 300 kg grain feeder.
This grain feeder possesses a separating grid of thick particles such us bags,
cardboards, threads etc. At the bottom of the grain feeder, there is an elevating screw
that carries the flour up to the platform of the volumetric dosimeter.

Volumetric dosimeter:
The flour, coming from the loading feeder, falls into a stainless steel lung tank. At the
bottom of this lung tank, there are two parallel screws which turning speed is related
directly to the amount of flour being measured. This equipment has a speed shifter and
therefore its load can be varied into the following stage.

Conditioning:
This operation is carried out by a stainless steel, which possesses inside an axle with
transporting pallets. This equipment contains water and steam ingress. The water
entering into the equipment is perfectly known since its ingress is performed through a
Moyno bomb that defines accurately the coming-in volume of water. The steam
entering into the equipment is controlled by a modulating valve that is subject to the
temperature set required in a thermocouple which is attached to a side of the outlet of
the conditioning unit.
The conditioning unit has a cladding mouth and this implies the heating in the outlet
and in equipment attached to the conditioning unit. This equipment, that connects the
conditioning unit and the extruder, is called diverter. This stretch possesses a small
screw conveyor that allows the accurate introduction of conditioned flour within the
extruder.

Extrusion:
Iin this stage the wet and warmed flour is carried into the extruder. The flour fills in the
extruder screws, and in this way the screws have the function of mixing, warming,
cooking and changing the flour structure. These screws have a speed shifter and
therefore, the turning speed is a determining factor in the operation. The whole casing
of the extruder has cladding, through which steam circulates and it warms the extruder
barrels. It is possible to inject water into the extruder to wet the product, if necessary,
since the coming-in volume of water is perfectly known for being injected by a moyno
bomb with speed shifter. In the extruder extreme, there is a mould which is a plate with
60 wholes of 3 mm. As the product has high pressure, high temperature and low
humidity inside the extruder, when it goes out to the environment, it undergoes and
expansion and therefore its density varies.

Cut:
As the product goes out in a continuous way, it meets four shears turning at a very high
speed which allows the cutting of the product in a predetermined size and shape. The
size and shape are very important in the following stage of the drying. Once the
product has been dried, it is carried pneumatically into the drying machine; this carriage
is performed by a high pressure fan, which aspires from a cyclone that is located on top
of the drying machine, where the product undergoes a cyclonic effect and falls into a
canal which makes the extruded pellet enter within the drying machine. The humidity
of the product on the extruder outlet depends on the amount of water and steam that
has already entered into the conditioning machine and on the amount of water that has
already entered into the extruder. Generally, the humidity is 16-18%.
By Carlos Elwart

Drying:
The product enters the drying machine through a distributor, that consist on a stainless
steel oscillating bar, that allows the uniform outlet along the whole extension of the
transversal conveyor of the drying machine. The drying machine basically consists of a
horizontal stainless steel conveyor that carries the product. The drying is performed by
means of warm air that comes from a centripetal fan which takes the air from the
environment and drives it through a pipe. The air gets at a natural gas burner that
produces warming of the air. The air temperature can be controlled by a thermocouple,
which measurement is associated with the admission valve of the natural gas burner.
The warm air enters the low part of the conveyor and flows through the product layer;
the drying machine possesses two inlets in each side. In the final stretch of the drying
machine, there are two lateral injection cones, one in each side of air injection, aiming
at cooling the product. The wet and warm gases are removed from the drying machine
by a fan that aspires through a cyclonic divider in the following way: it eliminates these
gases out and the little carried particles are collected in the mouth of the cyclone. Once
the product has been dried, it falls from an elevator of oscilling buckets, that carries the
product into the following stage.

Milling:
Once the product is dried, it falls within a distributor that guides the product into the
milling chamber. The size of the product is reduced by the action of shears that turn at
a very high speed. The size will depend on the fabric sieve located it the mill, these
fabrics are exchangeable. Bear in mind that the turning direction of the mill must be
inverted each week as well as the clapped of the product admission into the mill.
The sizes of meshes that can be employed in the mill are 0.6mm and 0.9mm.
There is a mechanism by which it is possible to make a product by pass so as to avoid
its ingress into the mill and to pack a pellet in predetermined shape and size.
The carriage into the sleeve filter is performed from a high pressure fan. Once the size
of the product has been reduced, the pneumatic carriage takes it into a cyclone that
contains a sleeve filter. This filter prevents the product from escaping into the
atmosphere.

Bulking:
The product falls from the sleeve filter through pipes up to the bulking. This can be
carried out in bags of 25, 50 or large bags of 500 kg.

Packing:
This operation is carried out in the fractionation sector, in different formats: 125g,
250g, 350g, 400g, or in the format requested by the customer.

								
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