Friday, February 20, 2015

20/02/2015: Innovation in aquafeed processing technology

by Clextral

First published in International Aquafeed, January - February 2015

World leading aquafeed technology expert Clextral has played a pioneering role in the innovation and development of twin-screw extrusion for aquafeed since the 1970s.  To respond to new challenges and increase the capacity of existing systems, Clextral is introducing two innovations this year: a new preconditioner and a new range of twin-screw extruders with advanced control.
In twin-screw extrusion of fish-feed pellets, preconditioners are recognised by industry experts for their production benefits. The new Clextral Preconditioner+ integrates two horizontal, intermeshing, counter-rotating shafts that provide tangible production benefits: improving the overall process and the quality of the finished food products and enabling energy savings, while providing greater flexibility and more precise control over the operating parameters, whatever the recipe.

The key innovation of Clextral’s Preconditioner that improves heat and mass transfer to the product is the Advanced Filling Control device (AFC) which interacts directly with the material inside the mixing chamber and enables the filling ratio to be adjusted. The AFC system uses an exclusive conveying screw inside the tank and adjusts the flow by enabling a partial and controlled recycling of the material being processed, from the outlet to the entry point, thus intensifying the specific preconditioning functions.

In addition to increasing the filling ratio, the AFC system also generates better product distribution, in particular in the first third of the mixing chamber which is the preferential zone for steam injection. The adjustable water and steam injection ports have been optimally positioned to enhance absorption and product exposure time during the mixing stage.

Extensive experimental trials have been carried out on the Preconditioner+ to verify the processing improvements generated by its AFC system on the twin-screw extrusion process. In this case a standard fish-feed recipe (basic salmon feed) was used, not to gauge optimal performance but to set an objective benchmark compared to traditional preconditioning systems.

The first significant observation was a lowering of the SME (Specific Mechanical Energy) required in the extruder – an average of 3 percent with equal extrusion parameters – mainly due to the increase in preconditioning time, and largely compensating for the additional consumption of the Preconditioner+. As mentioned previously, this efficient pre-cooking reduces the shear and the torque requirements in the extruder, which results in less wear of the screws and barrels.

By focusing exclusively on the Preconditioner+, the experiment also demonstrated that the new filling ratio (up to 75 percent) achieved with AFC made it possible to increase residence time by 60 percent for an equivalent fish-feed flow and therefore to exceed the average of three minutes. At the same time, the combination filling/steam distribution made it possible to increase the product temperature by 3-4°C at the outlet of the Preconditioner+, using comparable steam injection.

It is even possible to achieve a product temperature of over 96°C with optimised steam injection, while limiting energy loss due to the new design. Following the improvements on the pre-cooking stage, a significant increase in starch gelatinisation before product feed into the extruder was witnessed and measured.

Finally, on the finished product after extrusion, granulation and drying, these upstream modifications resulted in an increased hardness of the pellets of at least 10 to 15 percent, an essential quality criterion required for their use in fish farms.

Beyond the process benefits on product quality, it is important to note that this equipment is designed to facilitate industrial applications, in particular because of the increased flexibility provided by the AFC. This variable speed device enables adjustments of the residence time as required to adapt the equipment to different types of recipes and to respond to the needs of multi-product extrusion lines. Moreover, this convenient design allows the system to start up when fully charged, even after prolonged downtime with a full tank, thanks to the new kinematic feature.

In terms of hygiene and food safety, the Preconditioner+ is designed with minimal retention areas to facilitate cleaning. This feature is further enhanced by an integrated ‘quick recipe change-over’ function through the reversible AFC system, used here as a conveying screw that enables the entire tank to be emptied. These improvements in equipment cleaning capabilities and hygienic design are important advantages for food processing applications.
Finally, the intensification of Clextral’s Preconditioner + offers improvement in the overall process, energy savings and enhanced quality of finished products, as well as greater flexibility and better control of operating parameters, whatever the recipe.

A daily task of aquafeed processors is ensuring the perfectly stable quality of the finished product despite daily variation in the characteristics of the raw materials. Clextral’s new EVOLUM + twin-screw extruders offer advanced technology that gives processors new levels of throughput, flexibility, and control while ensuring maximum product quality and process stability.

A major innovation, the Advanced Thermal Control (ATC) is a self-learning, proprietary software solution to ensure absolute precision in temperature control. ATC continuously monitors production and adjusts to changes in parameters (characteristics of raw materials, recipes, throughput, etc.) to ensure process and product consistency. ATC is proven to enhance process stability up to 70 percent, with energy savings averaging 20 percent by eliminating excess heating/cooling to maintain process temperature set points in any circumstances.

The EVOLUM+ range has also been specifically built for more hygienic processing and food safety with ergonomic designs and open profiles that allow full machine access.

Clextral continues to innovate with twin-screw extrusion systems that produce aquatic feed with a precise balance of proteins, oils and carbohydrates, processed for optimum digestibility with reduced waste. Clextral’s systems process a wide selection of recipes and raw materials and accurately control pellet density for specific product attributes, such as sinking and floating properties. With these innovations in preconditioner and extruder technologies, Clextral is helping aquafeed processors meet the process challenges of today and the future.

Read the magazine HERE.

The Aquaculturists
This blog is maintained by The Aquaculturists staff and is supported by the
magazine International Aquafeed which is published by
Perendale Publishers Ltd

For additional daily news from aquaculture around the world: aquaculture-news

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