Pelleting is a process in which mixed feed in powder form is converted into pellets by mechanical compression in combination with moisture and heat. Process is achieved by a set of rolls and die of suitable hole size and shape. As the die & roll rotates, the product passes through the nip of roll & die and pressed into the die holes to make pellets.
Today, the process is widely used because of both the physical and nutritional benefits of it.
We can count-improved ease in handling , reduced ingredients segregation , less feed wasage and increased bulk density.
Decreased feed wastage, reduced selective feeding , decreased ingredients segregation, less feed and energy expended on prehension, destruction of pathogenic organism ,thermal modification of starch and protein, improved palatability.
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 gates, gravity /screw feeder in batching or down stream.Pre-cleaning machines generally include rotary sieve, jute remover, magnetic catchers etc. In automatic plants, it is desired that system is designed to give continuous efficient cleaning at maximum flow of ingredients.
In modern 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 suitable capacity as per total capacity of plant, are incorporated and are having gravity or screw feeders for controlled discharging of material into weigh bin under neath it. Generally two set of bin or silos are installed - one for major ingredients, second for minor ingredients. The discharge of both weighing bin come into common surge for further processing. Bin vibrator or shaking devices are installed on some or all of bins to make the material flow incase of jamming of bin.
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 ideal 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 passed through a die in pellet mill with the help of rollers and powdery material is converted into pellets. The quality and output of pellet mill. is dependent on so many parameters like: Quality of grinding, conditioning. Formulation of feed: - (percentage 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.
Crumbling is a process in which pellet after cooling is broken into small pieces to make it suitable for small chicks. If not required it can be bye-passed and product escapes from side of crumbling rolls. A well designed crumbler should have following features: Should give uniform size of crumbs at the both ends of crumbling rolls. Should break the material without making much fines. Should have mechanism for equal gap adjustment on both sides
Product coming out of crumbler is either in pellets (if crumbler bye passed) or crumbs form. These are required to be screened to remove fines and overs. 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 to crumbler and fines return to pelleting line for repelleting.
After screener, the finished product is filled into bags. In small to medium plants, bagging can be carried out manually but for higher output it is better to go for electronic bagging machine. Electronic bagging machine can perform bagging with high accuracy and much faster rate.