How does the mixing time of a KoneSlid mixer compare to classic double-cone mixers?
For many powder mixing tasks, a KoneSlid® mixer achieves significantly shorter mixing times than a classic double-cone mixer. The two systems differ fundamentally in how they work. The classic double-cone mixer is a free-fall mixer made of two hoppers welded together, which rotate as a closed vessel about a horizontal axis. The product is repeatedly lifted, divided, relocated, and falls back under the effect of gravity. The KoneSlid® mixer, by contrast, works as a vertical single-shaft cone mixer with an actively driven mixing tool. Its mixing time is therefore generally considerably shorter, because the product movement is generated in a targeted way rather than arising solely from the passive falling and avalanching motion of a rotating bulk material.
In the double-cone mixer, mixing takes place through a combination of convection and diffusive mixing. With every rotation, portions of the bulk material are relocated, but the exchange between spatially distant product zones is limited. This principle is particularly suitable for free-flowing, largely agglomerate-free powders and granulates with sufficiently similar particle size, particle shape, bulk density and flow behaviour. For such products, a double-cone mixer can achieve gentle and adequate homogenisation. However, the required mixing time is often in the range of several minutes and can be considerably longer for more demanding formulations. It depends on the fill level, rotational speed, vessel geometry, formulation, target homogeneity, and the number of vessel rotations required.
The KoneSlid® mixer, by contrast, generates an active three-dimensional product flow. A rotating mixing tool conveys the product upward in a spiral near the wall. In the central region, it flows back down under gravity. A conical displacement body redirects the downward-flowing product stream back toward the outer mixing zone. This continuously reshuffles the entire mixed material and distributes it throughout the whole mixing chamber. The active convective flow considerably accelerates mass exchange. For the KoneSlid®, mixing times of approximately 20 to 120 seconds are cited depending on the product and task; the number of tool rotations required can be considerably lower than the number of vessel rotations of a free-fall mixer.
The shorter mixing time does not automatically mean stronger or product-damaging stress. The KoneSlid® can be operated at a comparatively low rotational speed. The mixing effect arises primarily from the targeted, three-dimensional convection rather than from high circumferential speeds or uncontrolled falling motion. This can be advantageous for sensitive particles, brittle agglomerates, or low-dust formulations. At the same time, mixing duration, rotational speed and, where necessary, the integration of additional intensive mixing tools can be adjusted to the cohesiveness, agglomerate formation and desired homogeneity.
For complex formulations with small minor components, pigments or additives, an active single-shaft mixer can be particularly advantageous. The same applies to mixtures with different bulk densities, different particle sizes, or limited flow behaviour. Nevertheless, no mixer type can generally guarantee that a specific coefficient of variation will always be achieved, regardless of the formulation and process conditions. Target values such as a CV below 5 percent must be demonstrated for the specific mixture via a suitable sampling plan and a validated analytical method. For very small dosing proportions, premixes, suitable addition sequences, or dosing aids are additionally required.
Besides the net mixing time, discharge and cleaning influence the total batch time. With the KoneSlid®, a central displacement body can be lowered once mixing is complete; this supports product discharge via the central outlet. For sufficiently free-flowing products, this can enable short and largely complete emptying. However, the actual discharge time, the residual quantity, and the risk of segregation during discharge always depend on cohesiveness, moisture, particle structure, discharge cross-section, and downstream conveying equipment.
The specific power draw of an active convective mixer can be higher than that of a free-fall system, because the mixing tool moves the product in a targeted way. Whether this results in a higher or lower overall energy requirement per batch cannot be stated in general terms. It depends on mixing duration, fill level, product resistance, drive efficiency, charging, discharge, and cleaning effort. A possible advantage of the KoneSlid® is that the mixing energy is introduced over a considerably shorter time, which can reduce the total batch time. However, a robust energy assessment should be based on measurements with the specific product.
The choice between KoneSlid® and double-cone mixer should therefore not be made on mixing time alone. A double-cone mixer can be an economical, gentle solution for simple, free-flowing, already deagglomerated, and less time-critical powder mixtures. A KoneSlid® mixer is particularly attractive where short batch times, precise homogenisation, the processing of cohesive or differently composed powders, liquid addition, or flexible adjustment of the mixing intensity are required. In every case, mixing time, mixing quality, discharge behaviour, and possible segregation after mixing should be investigated with the original product.
The KoneSlid® mixer KS: short mixing time, fast discharge
The amixon® KoneSlid® mixer KS is designed for particularly fast, and at the same time gentle, homogenisation of sensitive bulk materials. Typical applications are products from spray drying, fluid-bed granulation or belt drying, for example instant beverage powders, milk powder derivatives, instant soups, muesli, tea, or components for frozen products. Such products often consist of particles that vary in size, are sensitive, and are partly agglomerated. The aim is to achieve the required homogeneity without unnecessarily altering the particle structure, instantising properties, solubility, or low-dust characteristics.
The KoneSlid® mixer works with a central, actively driven mixing tool. This conveys the product upward near the wall, while it flows back down in the central region under gravity. A central displacement body redirects the downward-flowing product stream back into the outer mixing zone. This creates a three-dimensional, forced product circulation. After only around four tool rotations, the entire batch volume can have been reshuffled once. After approximately 20 to 40 rotations – depending on the formulation, fill level, target homogeneity and product properties – the technically ideal random mixture can be achieved. However, the specific number of rotations required and the mixing time must always be confirmed through trials with the original product.
By comparison, classic double-cone and V-mixers are free-fall or tumble mixers. The entire mixing vessel rotates while the product is lifted, divided, and returned by gravity. Homogenisation arises from repeated reshuffling and random motion of the bulk material. The method is gentle and suitable for free-flowing, largely agglomerate-free powders or granulates. Because product exchange is less targeted, double-cone mixers in many cases require more vessel rotations and longer mixing times than an actively working KoneSlid® mixer. However, the actual difference depends on the formulation, fill level, rotational speed, vessel geometry, and target homogeneity.
With pronounced differences in particle size or bulk density, the risk of segregation in the double-cone mixer can increase. Such risks also exist in particular during discharge, at fall sections, or during subsequent conveying. The KoneSlid® reduces this risk through its defined convective product guidance and through the short process time, but it does not fundamentally prevent segregation through its geometry alone. A claim of complete density insensitivity would therefore not be technically defensible. Whether the mixture remains stable through to filling must be checked for each formulation via mixing, discharge and conveying trials.
A further benefit of the KoneSlid® lies in its discharge concept. Once mixing is complete, the central closure system can lower and open a large discharge cross-section. For sufficiently free-flowing products, the batch can discharge within a few seconds. This can noticeably shorten the batch time and reduce product residue. However, figures such as a residual discharge of 99.98 percent or better must be related to the specific product, the actual fill level, and the specific apparatus configuration. Cohesive, moist, or adhesive products can show markedly different discharge behaviour.
Fast discharge can offer further advantages compared with solutions using a discharge screw or small outlet cross-sections. For a suitable product, it can reduce residence time in the discharge area, lower cleaning effort, and avoid potential zones of product build-up. However, statements such as “no bridging” or “no segregation” should not be made as blanket claims, since bridging and segregation always depend on cohesiveness, moisture, particle structure, air content, discharge geometry, and downstream conveying equipment.
The KS can be executed on a project-specific basis for hygienic and safety-relevant requirements. This includes an ATEX design for Zone 20, options for vacuum or inert operation, and hygiene concepts to EHEDG, FDA or 3-A Sanitary Standards. Specific conformity results, in each case, from the agreed configuration and the operator's requirements. Seam-free welded and ground-smooth product surfaces, a top-mounted mixing tool only, readily accessible CleverCut® inspection doors with OmgaSeal® seals, low-dead-space discharge elements, and integrated wash lances can support manual dry cleaning or a validatable wet-cleaning process.
Alongside the KS, amixon® offers different designs for various batch sizes and process tasks. Depending on the project, the vertical and cone mixers VM, HM and AM, as well as the mixing-dryer reactors VMT and AMT, can be executed up to approximately 50,000 litres. The Gyraton® GM covers large batches up to around 100 m³. For very small and development batches, the EM, in the range of approximately 5 to 200 litres, and the COM container mixer, in the range of approximately 100 to 4,000 litres, are available. Depending on the design, formulation and apparatus configuration, the possible fill-level range can be approximately 10 to 100 percent. Whether the technically ideal mixing quality is achieved across the entire range must be demonstrated on a product-specific basis.
amixon® can carry out the comparison between an existing double-cone mixer and the KoneSlid® at its pilot plant with the original product. This assesses not only mixing time and homogeneity, but also product protection, possible particle breakage, discharge time, residual discharge, dust behaviour, cleanability, and the stability of the mixture after discharge and conveying. The documented trial results provide a sound basis for deciding on the suitable mixing principle.