The first step in pelleting is conveying of ingredients from bulk silos or godown to the batching bins. It is essential to remove oversize foreign materials and iron trash etc. which otherwise can affect functioning of slide gate, gravity screw feeder in batching or down stream.
Pre-cleaning machines generally include rotary sive, just remover, magnetic catchers etc. it is desired that system is designed to give continuous efficient cleaning at manimim flow of ingredients
In modem plants, automatic weighing of different Materials as per formulation to make
one batch is called batching or proportioning. In this any no. of silos of duitable capacity as per total capacity of plant. are incorporated and are having graviry or screw feeders for controlled discharging of material into weigh bin under neath it Generally two set of bin or silos arc installed - one for major ingredients, second for minor ingredients. The
discharge of both weighing bin come into common surge for further procesting. Bin
vibrator or shaking devices are installed on some or all of bins to make the material flow
incase ofjammrng of bin.
The weighing is done through an electronic controller working on PLC or SCADA based.
which can be operated through a Computer. The computer control and ercord all the detail
of a batch- over or under weighing of ingredients from set point, reporting on each batch.
shift, day ,weak, month basis. The generally desired features of a batching system are
It should give accurate weighing within specified time to meet output of plant
Though it should be highly refiable and work automatically, it should have manual control
also in case of auto failure.
After batching. next step is to reduce the material to the required degree of finenees to
have maxmimum Surface area for exposure to heat and moisture to accomplish gelatinisation in conditioners.
In pelleting process grinding and pelleting are two major energy consuming operations.
it we can perform fine grinding with minimum of energy. it will not only cut grinding
cost but also save on energy required in pelleting.
Efficient mixing of micro ingredients in whole batch is significant in making quality
feed. The designed features of a good mixing system are:
It should perform mixing to achieve minimum coefficient of variation in minimum time.
Mixer discharging mechanism should aim at no leakage of gates with minimum residue
in drum to avoid carryover to next batch.
Conditioning is done to add heat and moisture in mixed feed to achieve gelatinization
and making the product more pliable for pelleting. An Idcal conditioning system should
meet the following:
It should raise the temperature and moisture of product by direct or indirect heating
It should give desired retention time in conditioners.
After conditioning the product is possed through a die in pellel mill with the help of rollers and powdery material is converted into pellets. The quality and output of peller mill. is dependent on so many parameters. like
Quality of grinding. conditionimq.
Formulation of feed:- (precentage of oil, protein, fiber etc)
Die configuration:- Deciding working on product in pelleting
Hot pellets coming out of pellet mill are required to be cooled immediately to remove moisture and heat. Generally counter flow
cooler are used for the purpose. The desired feature of an efficient cooler are:
It should be capable to remove the unwanted heat and moisture from pellets to improve its shelf life.
The cooling should be uniform from all the sides.
Product coming out from pellet cooler, These are required to be screened to remove fines and over. Single deck screeners are used
to remove fines only while double deck screeners are used to remove both fine and overs.. The unbroken or the overs are returned
and fines return to pelleting line for repelleting.
A screener should have following features:
It should remove the desired percentage of fines from product.
Screens should not clog frequently.
Changing of screens of desired mesh should be easy and quickly.