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ECOtwin : New Extrusion System For Manufacturing Petfoods
ECOtwin : New Extrusion System For Manufacturing Petfoods
By Detlef Janssen
Mar 18, 2005, 16:52
Uzwil, Switzerland -- The new, high-capacity twinscrew extrusion system ECOtwin has been developed in collaboration with leading customers especially for petfood and aquafeed applications. The ECOtwin sets new standards in terms of flexibility, product quality, and production cost reduction.
Proud of “their” ECOtwin, the Extrusion Systems team.
The Buhler ECOtwin extrusion system is made up of the extruder, the preconditioner, and the peripheral equipment. Its performance data is tailored to the specific needs of petfood and aquafeed production. Its modular design ensures that users’ current and future requirements can be optimally satisfied.
High degree of sanitation
The system is distinguished by its high operating reliability and ease of operation. Its easy cleaning and access to all critical zones ensure a high degree of sanitation. The new ECOtwin allows separate selection and online control of the cooking degree and the bulk density of the end products. This is possible thanks to the patented SME and Density Control modules.
The Density Control module additionally allows much of the thermal energy to be recovered and odor emissions to be reduced. The SME module consists of a throttling device with two valve cylinders. In their open position, they map the contour of the inside of the extruder barrel, and when closed the contours of the screw diameter. Closing of the valve cylinders increases the retarding length of the material ahead of the throttle, causing the filling degree and retention time to increase. This, in turn, increases the specific mechanical energy (SME).
When the cylinders open, the opposite happens. The module can be installed at any point of the processing section and not only at the end of the extruder. This allows the process sections of cooking and forming to be separated.
Drawbacks eliminated
Traditionally, three possibilities exist to control the cooking degree: by changing the product moisture, by adjusting the screw configuration, and by varying the extruder screw speed. Controlling the SME via the product moisture is uneconomical, since any water added to the product must be extracted again in a subsequent drying stage, which requires additional energy.
Adjusting the screw configuration requires a conversion of the screw shafts. This is very costly, resulting not only in long downtimes, but also in higher consumption of raw materials. The variation of the screw speed will change the throughput. But as a rule, the maximum screw speed is used to maximize the throughput rate.
All these drawbacks have been eliminated by the SME module. The mechanical energy input can be selected quickly during ongoing production and be maintained constant within narrow tolerances.
Open extruder barrel
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 odors generated, slashing the energy requirements and thereby cutting costs.
Buhler is a global Technology Group and System Partner for plant and equipment and for process expertise in the fields of Food Processing, Chemical Engineering, and Die Casting, with a worldwide payroll of about 6,100.
For more information on the ECOtwin, please contact:
Christopher Rubin, Sales representative for the Extrusion Systems business unit at Buhler in Uzwil, T +41 71 955 37 97, F +41 71 955 24 81, E-mail es.buz@buhlergroup.com
Web site: http://www.buhlergroup.com/
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