Twinscrew extrusion -- flexibility with low costs
A high-capacity twinscrew extrusion system has been developed by Buhler in collaboration with some of its customers. ECOtwin is claimed to offer flexibility combined with good product quality and lower production costs.
ECOtwin comprises an extruder, a preconditioner, and peripheral equipment in a modular design. Its performance data is tailored to the specific needs of petfood and 'aquafeed' production.
High operational reliability is a feature of the equipment, as is ease of operation and cleaning.
Separate selection and online control of the cooking and the bulk density of the end products is provided, thanks to the patented specific mechanical energy (SME) and density control modules. The density control module also allows much of the thermal energy to be recovered and odour emissions to be reduced.
Traditionally, cooking is controlled by three techniques: by changing the moisture content; by adjusting the screw configuration; and by varying the extruder screw speed. However, these energy inefficient and costly techniques are eliminated with the SME module.
The density control module is based on an open extruder barrel. The opening is provided with a degassing socket and a hold-down mechanism, which prevents product particles from being discharged from the barrel along with the steam.
In general, three modes of operation are applied. In the positive-pressure mode, fresh steam is added, which raises the product temperature, increases product expansion at the outlet, and thereby leads to a lower bulk density. In the pressure-neutral mode, the steam discharged is returned straight to the preconditioner.
In the negative-pressure mode, the steam is discharged via a vacuum system, intensifying product cooling, reducing product expansion at the die, and thereby increasing the bulk density of the product. In this operating mode, too, the extracted energy is returned to the preconditioner in the form of hot water along with any odours generated, slashing the energy requirements and thereby cutting costs.
Contact: Buhler,
Tel: +41 71 955 37 97
