What advantages do vertical mixers offer over horizontal mixers for large batch sizes?
Vertical mixers offer several process engineering and economic advantages with large batch sizes. They are particularly advantageous where batch volumes are high, floor space is limited and there are demanding requirements for residual discharge and product integrity.
Because of their vertical construction, the usable volume is scaled primarily via the height rather than the length of the mixing vessel. This results in efficient use of the floor space (footprint). At batch volumes of several tonnes, vertical mixers therefore require considerably less floor area than horizontal mixers.
Lower specific energy consumption: since the mixing tools of a vertical mixer generally rotate at low speed, their specific energy consumption is lower.
Gentle material handling with sensitive products: vertical mixers typically work with lower shear forces and lower circumferential speeds of the mixing tools. This reduces the mechanical stress on the material being mixed. Vertical mixers are particularly suitable for break-sensitive granulates and pellets, fibrous or fragile materials and abrasive products, where high shear forces would lead to excessive wear.
The lower friction and shear stress also reduces the thermal heating of the material, which is an advantage with temperature-sensitive formulations.
High flexibility in fill level: vertical mixers with a conical mixing chamber can be operated at a fill level as low as 10 % and still deliver ideal mixing qualities. Horizontal mixers generally require minimum fill levels of around 30–40 % of the nominal volume.
Advantages in maintenance and plant engineering: in vertical mixers, the drive and bearings can usually be arranged above the product level. There is only one shaft passage and one shaft seal. This lowers the risk of leakage, simplifies maintenance and extends the service life of components.
Despite these advantages, vertical mixers are not ideal for every application. In continuous mixing processes with very short mixing times, heavy liquid input or intensive agglomeration, high-speed horizontal mixers are frequently the better choice. The decision between a vertical and a horizontal mixer should therefore always be matched to the specific material, the required process times and the plant periphery.
Vertical instead of horizontal mixers: the design arguments from amixon®
Fill level independence as a system advantage: mixing independently of the fill level, residual discharge of 99.997 % and better.
amixon® vertical mixers (vertical single-shaft mixers, vertical twin-shaft mixers, the KoneSlid® conical mixer, SpherHelics® and Gyraton®) achieve the highest mixing qualities across a wide range of fill levels. Fill levels can typically vary from around 10 to 100 %. The mixing quality achieved corresponds to an ideal distribution that cannot be improved upon in practice.
The SinConcave®/SinConvex® helical mixing tool conveys the product upwards at the periphery of the mixing chamber. In the centre of the mixing chamber the bulk material flows downwards under gravity. This total flow works independently of the fill level. Batch sizes within one mixer can therefore vary by an order of magnitude without homogeneity having to be revalidated.
As regards hygiene and maintenance: in horizontal mixers the shaft ends penetrate the product space on both sides. The seals are under pressure from the bulk material. This increases the risk of contamination and the maintenance effort.
In the amixon® vertical mixer, by contrast, the mixing tool is mounted and driven exclusively at the top. There is no product-contact lower shaft passage. The mixing chamber is welded free of crevices and ground smooth, and the discharge devices are of dead-space-free design. This forms the basis for EHEDG, FDA and 3-A conformity and for validatable cleaning.
Discharge and design
The lowest point of the conical vertical mixer lies at the centre. Free-flowing products are discharged there almost completely with the assistance of gravity. Conical designs achieve discharge rates of approximately 99.997 % and better. Flat-bottom mixers can also achieve such high residual discharge rates, provided they are equipped with ComDisc® tools.
Vertical mixers from amixon® are generally of relatively cubic construction. On request, however, the mixers can also be built particularly slim or particularly low. amixon® thus adapts to the customer's spatial conditions.
Thanks to their compact design they integrate well into existing buildings.
Product protection with short mixing times
amixon® vertical mixers work at low circumferential speeds, typically of approximately 0.8 to 3.5 m/s. There are no throwing or impact zones. The mixing process is gentle on particles. Particle structures are therefore largely preserved, and coatings and agglomerates are protected.
The HM vertical twin-shaft mixer and the KoneSlid® mixer often reach the target mixing quality in as little as a third of the usual mixing time.
amixon® carries out the direct comparison in the pilot plant – with the original product and a documented assessment of mixing quality and product protection.
Verification in the amixon® pilot plant
Proof in the pilot plant comes before the investment. At the headquarters in Paderborn, 35 test units in various sizes are available.
Further pilot plants are located in Japan, India, Thailand, China, South Korea and the USA. amixon® thereby underlines its trendsetting position among competitors in vertical powder mixing.
The trials run with original products, real fill levels and batch sizes and within the intended temperature and pressure range. Mixing quality, product protection, energy input, cleanability and reproducibility are assessed.
The results are evaluated and documented together with amixon® specialists. This produces a sound basis for the decision that reduces technical and economic risks before the investment.
Hygienic design as the basis
All the properties named rest on the amixon® hygienic design.
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 critical lower shaft passage is eliminated. Dead-space-free discharge devices and integrated washing lances permit validatable dry and wet cleaning. Programmable targeted-jet cleaners help to reduce water consumption. A great deal of time is also saved, because amixon® has a technology that allows cold water to be evaporated from the mixing chamber completely and quickly without any heat having to be supplied.
Large Clever-Cut® inspection doors with permanently dead-space-free OmgaSeal® seals provide ergonomic access to all product-contact surfaces.