How fast are typical mixing times for homogeneous food ingredient blends at batch sizes above 2,000 litres?
With batch sizes of more than 2,000 litres, the typical mixing times for dry food ingredients usually lie between one and 15 minutes. The exact time depends on the mixing principle, the product properties and the required degree of homogeneity. For many standard applications, CV values of ≤ 5 % are generally achieved within 5 to 8 minutes.
High-performance precision mixers, such as twin-shaft mixers, ploughshare mixers or mechanically fluidising systems, generally work particularly quickly. Mixing times of approximately 1 to 3 minutes are possible here, with very good homogeneity even for micro components. Standard convective mixers, such as ribbon mixers, generally take longer. Typical here are 8 to 15 minutes. Cone and vertical screw mixers often lie in the range of 10 to 20 minutes. They are also suitable for sensitive products.
What is decisive is achieving ideally high mixing qualities that cannot be improved upon, and preserving the structure of the raw materials. The lower the energy input, the more natural the end product remains.
The dosing and post-mixing phase with liquid additions such as oils, fats or flavourings extends the mixing time. In well-designed plants, however, such tasks can usually be accomplished in five to ten minutes. What has to be taken into account, though, is not only the pure mixing time but also the total cycle time including filling, discharge and cleaning.
The actual mixing time should always be validated in a trial with the original product. Particle size, bulk density, flow behaviour, moisture and mixing ratio often influence the result more strongly than the batch size alone.
How amixon® achieves short mixing times with large batches through three-dimensional restratification
This is possible when the mixing tool controls the entire volume and not only partial zones. The SinConcave®/SinConvex® helical mixing tool of the amixon® mixers (VM, HM, AM; SpherHelics®, KoneSlid® and Gyraton® silo mixers) produces a three-dimensional total flow: upwards at the periphery and downwards in the centre. With the vertical twin-shaft mixer HM, two mixing flows are superimposed. Very short mixing times with a high mixing quality are thereby achieved. This series is available up to 20,000 litres in the standard size range; larger designs up to 50,000 litres are available on request.
With the KoneSlid® mixer KS, the entire volume is completely restratified after a few revolutions. With finely dispersed, powdery mixtures the ideal mixing quality is achieved after approximately 20 to 40 revolutions; with coarse mix particles – for example in muesli recipes – after just 10 to 30 revolutions. This takes place with a very low energy input.
Large batches without compromises in quality
The mixing quality is thereby maintained across a wide fill level range of approximately 10 to 100 per cent. Even with batches of more than 2,000 litres, a technically ideal random mixture arises in this way. For very large volumes, the Gyraton® GM completes the range. It processes batches of approximately 10 to 100 m³ precisely and gently. As required, it works at minimal power or with a higher mixing intensity.
Free of segregation right through to packaging
The time gained must not be lost at discharge. ComDisc® elements ensure a segregation-free, residue-free discharge. The KoneSlid® mixer empties within a few seconds, and does so without a cone of repose and without segregation. With DosiFlap®, filling can take place directly and dead-space-free. Generously dimensioned discharge fittings additionally help to avoid any tendency towards segregation.
Robust time data from the trial
The actual mixing time depends on the formulation, the differences in density and cohesion. amixon® determines these values in the pilot plant with the original product. This creates a robust basis for cycle time and capacity planning before the investment.
Product protection as a system property
amixon® mixers operate at low speed. The circumferential speed of the tools is adjustable between approximately 0.8 and 3.5 m/s. Mixing is performed by the SinConcave®/SinConvex® helical mixing tools. This takes place without throw, impact or crushing zones and without heat input. Sensitive structures, coatings and agglomerates are thereby preserved. Where targeted de-agglomeration is required, switchable cutting rotors act within a locally limited area.
Hygienic design as the constructional basis
All the properties described rest on the amixon® hygienic design. The target-jet cleaning nozzles are freely programmable. Mixing chamber and mixing tool are welded free of crevices and ground smooth. The mixing tool is mounted at the top only, so that the contamination-critical lower shaft passage is eliminated. Large Clever-Cut® inspection doors with dead-space-free OmgaSeal® seals provide access to all product-contact surfaces. Dead-space-free discharge devices and integrated washing lances permit validatable dry and wet cleaning.