Raw material extruder

Technology and Working Principle of the Raw Material Extruder

The raw material extruder, also called a dry extruder, is used to extrude raw materials such as soybeans, corn and soybean meal. It can also be used in the oil industry to produce extruded feed and pre-process seeds.

A good-quality raw material extruder is suited to both dry and wet extrusion technology. In dry extrusion, raw materials need no conditioning, so no boiler or piping system is needed.

Advantages of wet extrusion include:

• Raw materials are cooked before entering the raw material extruder, which increases capacity and extends the life of the shaft and the screw barrel sleeve.

• The moisture of the extruded feed is easy to control and energy consumption is reduced.

• This type of extruder can extrude various products such as corn, soybeans and porous feed.

How the Raw Material Extruder Works

In general, raw materials containing a certain amount of starch enter the feeder through the inlet hopper, are fed evenly into the conditioner by the screw feeder, are exposed to steam and moisture, become moist and warm, then enter the raw material extruder and move forward through the barrel by the rotating screw. The extrusion force on the feed gradually increases, accompanied by intense breaking, mixing and friction.

Because of the high temperature and pressure, reactions such as starch gelatinisation and protein denaturation occur and harmful bacteria are destroyed. In effect, the temperature and pressure in this process reduce anti-nutritional factors and improve the digestibility of starch and protein.

The extruded feed leaves through the die at the end of the extruder barrel and is cut to set lengths by a cutter. Dies with different hole diameters are used to produce feed in different sizes.

The raw material extruder is multi-purpose: it is designed to produce different feeds, and soybeans, soybean meal and corn can be extruded by changing only a few parts.

Extrusion Process for Soybeans and Corn

Soybean extrusion process:

To extrude soybeans, before starting the machine pull out the discharge chamber and prepare the screw flights, sealing ring and protective housing. Add some soybeans to the extruder barrel and heat up to the fourth screw to 50 °C. Tighten the bolt behind the outer screw three to four turns; once material comes out of the outer die matrix, gradually increase the feed rate until the machine current is 85 to 90 percent of its rated value. Using dies with different hole diameters, extruded feed can be produced in different sizes and capacities.

When producing extruded soybean feed, adjust the axial position of the ring, the sealing and the gap between the inner surface of the matrix and the conical shaft so that the extruder barrel temperature stays between 120 and 140 °C. For cost-effective pulverised feed, material moisture should be between 10 and 14 percent.

Corn extrusion process:

Pull out the discharge chamber and prepare the screw flights, sealing ring, adjusting chamber, inner matrix and cutter. Start the cutter motor, main unit, force feeder, conditioner and feeder in that order, add a small amount of material and open the conditioner steam valve at the same time, keeping the raw material temperature between 80 and 90 °C and moisture at 18 to 20 percent. After some extruded feed has been produced, gradually increase the feed rate and steam until the machine current is 85 to 90 percent of its rated value.

If you like, you can listen in this episode Listen to our podcast to learn in more detail how the raw material extruder works.