The extrusion dies for forming are without doubt exposed to the highest loads due to temperature, friction, compression and wear. Die design is often a critical variable as the die pattern influences the pellet physical quality. A new revolver die gives a smooth aquafeed surface and enhances pellet size uniformity, especially at high temperatures of extrudate in the die area.
Density control in aqua feed is another critical variable since it effects a set of factors including pellet buoyancy, floating and sinking characteristics, oil impregnation during the coating process and factory capacity. Pellets buoyancy is easily correlated with bulk density.
Final product bulk density ranges have been defined for each feed for the environment in which it is fed e.g. neutral buoyancy (salt water 3% bulk density 520-540 g/l). Incorrect pellet bulk density will reduce aquatic animal feed intake and the level of oil absorption.
Density and SME controllers can help make floating, slow sinking and sinking pellets. These devices reduce the need to change the screw configuration and provide control of shear stress, specific mechanical energy and extrusion pressure. The controllers can also be connected to the extruder control system to automatically adjusted and maintain the process conditions to its chosen set-point in order to make aquafeed with a wide range of bulk densities.
Dr. Cristian Atienza, Aqua Feed Technology Manager, Bühler, Switzerland
Cristian Atienza was appointed Aquafeed Technology Manager at Bühler in September 2013. Cristian has 10 years of experience within the aquafeed market at leading companies such as Ewos Norway and Biomar A/S. In his most recent position, Cristian managed operational best practices for Biomar Norway. In this role, he contributed to the establishment of factory optimization platforms for long term strategic planning, working with the Senior Operations Team and key managers.
His experience is enhanced by a Master in feed manufacturing and technology from the Norwegian University of Life Science and his Doctor (c) in Agriculture Science from the University of Hohenheim/Germany.
As Aquafeed Technology Manager, Cristian supports Bühler’s efforts in areas such as customer consulting, sales support and assistance for strategic development, internal training and the definition and specification of machine and process parameters.
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