Pelleting Equipment

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Pelleting equipment transforms powdered, mashed, or grounded material into a denser cylindrical shape. Pellet processing compresses the fine material against a perforated die, where it will be shaped and cut. Although granulating and extrusion also produce pellet-like products, manufacturing pellets is a distinct process.

What are you making?

Two primary types of pellet processing equipment

The main element in the pellet machine is the die. Select the die according to the specific characteristics of your material and the manufacturing variables of your product. Preventive maintenance is another critical consideration for industrial pelleting machines. Regular upkeep prolongs the service life of the die and protects the quality of your process. Make sure to clean the die after each batch and change dies before the wear damages the machine.

There are two main categories of pellet mills or presses: the flat die and the ring die. You may also hear about screw press pellet machines, but the operating principle is closer to the extrusion process than the pelleting process.

Flat die pellet machines are easier to maintain

Flat die pellet machines have a perforated disk or plate, and rollers press the material through the disk holes. The vertical design of these industrial pelleting mills makes the process simpler and their cleaning more convenient.

Flat die machines fall into two groups: die-driven and roller-driven. Die-driven flat die pelletizers have stationary rollers and a rotating die, whereas, in the roller-driven type, the die is still, and the rollers rotate. The latter configuration exerts more compression power on the raw materials, so it is a better option for pelleting hard materials such as sawdust hardwoods. Meanwhile, it creates less stress on the die, prolonging its life.

Flat die presses are typically used to make biomass pellets from wood, manure, straw, alfalfa, or fodder. However, this technology is also suitable for small-scale animal feed production.

Let's make wood pellets

Ring die pellet manufacturing equipment is suitable for mash materials

As the name suggests, the die in a ring pellet processing mill is perforated onto a circular plate. This pellet machine can be horizontal or vertical, depending on its feed orientation.

The ring die in a horizontal pellet press is, ironically, placed vertically. The mill receives moisturized mashed and mixed ingredients into its interior chamber, where rollers compress them against the rotating die. The friction between the rollers and the die heats the material as it passes through the holes of the die. The blades cut the material into hot dense pellets at the set size. Horizontal ring die pelletizers are commonly used in the animal feed industry.

Vertical ring die systems generate centrifugal force

The ring die is placed horizontally in vertical pellet machines. But the name of vertical pellet is given because the hopper is above the ring die, letting the raw materials fall directly into the ring die. The plate and the rollers rotate in opposite directions and at different speeds, creating a centrifugal force. Such pellet mill equipment is frequently used for pellet manufacturing in the biomass industry.

Pelleting equipment often find applications in the feed and biomass industries. It is generally possible to produce feed pellets using a mill designed for biomass materials, but the opposite cannot be done. The technical reason is that biomass materials are not as soft and malleable as feed ingredients and thus require a more resistant die.

Pellet processing for feed

An industrial feed pelleting line involves a hammer mill, mixer, pre-conditioner, pellet mill, and cooler. Pellet presses are used to produce compound feed and feed concentrates, as well as specialized feed for poultry, swine, cattle, and other farm animals. Sinking pellets may also be made using a pelleting machine, but aquafeed products are typically produced with an extrusion line.

For farm production or small-scale production, there is a more basic pellet manufacturing process involving a flat die pellet. It is a vertical process, where the mixed ingredients are fed through a hopper on the top and descend into a turning roller that presses them against the die.

Mind the gap between the roller and die

Pellet processing appears simple, but the range of variables makes it complex. The operator handling pelleting equipment must set the distance between the die and the rollers, the length of the cut by the blades, control the steam in the pre-conditioner, and establish the rotating speed, heat, and flow rate. They also need to keep an eye on the electrical motor settings and the overall performance.

Automatic pellet mills self-adjust the gap distance between the roller and the die. But in manual pellet machines, you need to adjust the distance. If the roller is too close to the die, this will reduce the life of the die. On the other hand, if the distance is too great, it causes efficiency loss.

Raw materials determine process setting in biomass pellets

Pellet manufacturing lines for biomass or biofuel pellets comprise a cutter or chopper (in the case of wood), a hammer mill, a pellet mill, and a cooler. Fine particles from powdered biomass or sawdust are pressed into the holes of the die to produce solid and compact pellets.

Biomass is easier to handle than feed during the pellet production process. However, biomass pellets present more challenges because the mill settings change according to the raw material. At the same time, biomaterials turned into pellet fuel and fertilizer pellets are safer for the environment than unprocessed biomass.