Twin Screw Extruder Vs Single Screw Extruder
Twin Screw Extruder Vs Single Screw Extruder
Here we introduce more about the Types of extruders used in food industry.
I. Single screw extruder
The single screw extruder has a simple structure and lower cost.
During the processing, the driving force for the forward movement of the material mainly comes from the difference in friction between the material and the barrel, and the material and the screw.
Its disadvantage is: if the friction between the material and the inner wall of the barrel is too small, the material will hug the screw and rotate together, so the screw will not be able to push the material forward. Therefore, single-screw extruders are suitable for limited materials and formulations.
| Performance Name | Self Heated Single Screw Extruder | Externally Heated Single Screw Extruder |
| Heating Method and Structure | The simplest food extruder. There is no jacket for heating. The thermal energy required during the extrusion process is converted from the mechanical energy consumed by the transmission system. | The barrel is equipped with a cooling water circulation jacket. The diameter of the screw axis is designed in a ‘gradually increasing’ style, making it slight compression capacity. |
| Control Parameters | Temperature and pressure are not controlled | Temperature can be controlled freely |
| Application | Low price. Suitable for small businesses and single food processing. | Suitable for foods that require cooling during processing |
II. Twin screw extruder
Forced conveying capacity: For the intermeshing twin screw extruder, the two screws mesh with each other. So when the screw rotates, the material will not flow back or stagnate.
Self-cleaning: At the meshing point of the twin-screw extruder, there is a speed difference between the tooth top of one screw and the tooth root of the other screw (when the two screws rotate in reverse direction). Due to this speed difference during the rotation process, they can clean each other of the Material adhering to each screw. In co-rotating twin screw extruder, the movement directions at the meshing points are opposite, and the relative speed difference is larger, which makes it more effective to remove materials adhered to the screws.
Co-rotating Meshing Type Twin-Screw
III. Twin Screw Extruder Vs Single Screw Extruder
| Performance Name | Single Screw Extruder | Twin Screw Extruder |
| Conveying Performance | Relying on friction, there are risks of clog and leak | Relying on the meshing of two screws, it is forced to convey and NO flowback. |
| Self-Cleaning | None | Has better self-cleaning effect |
| Work Reliability | There are risks of clog and and burn | Smooth and reliable |
| Heating Method
|
Many are only self-heating types, and some are externally heated. | Most are externally heated; more electric heating; less steam heating |
| Cooling Method | Less adopted | None; with barrel cooling jacket; or screw shaft hollow cooling |
| Control Parameters | Difficult to control, with few controllable parameters | There are many controlled parameters and easy to control |
| Production Capacity | Small | Larger |
| Adaptability | Suitable for raw materials with low water content and certain granular shape like corn grits; not suitable for raw materials with high oil content | Wide adaptability, can be used with water or oil |
| Energy Consumption | 900-1500kJ/kg | 400-600kJ/kg |
| Seasoning | Can only be sprayed after finished product | You can add some seasoning before and during the extrusion process |
| Processed Products | Fewer varieties (applicable to pure starch raw materials) | Can process a variety of products |
Edited by Jana
