Homogenization
Homogenization of bulk materials means the uniform distribution of particle size, moisture, color and temperature of an existing mixture or bulk material.
Homogenizing silos have a vertical mixing screw in the center. This allows good-flowing, dry plastic granules to be homogenized.
Cone screw mixers and Gyraton mixers belong to the precision large mixers. Both have mixing tools that are moved orbitally. They work gently and with minimal energy consumption. They produce very high mixing qualities.
Pneumatic silo mixers operate without mixing tools. The mix is swirled by the inflowing gas. The mixing materials must be finely grained, fluidisable, dry and monodisperse. All components must have a very similar bulk density. In this way, for example, several hundred tons of cement can be homogenized. The supplied gas generates a lot of dust. Powerful filters clean the dust and discharge the gas from the silo.
Batch mixers are much smaller. They operate at higher speeds than large mixers. They can change the particle size of powders. They can desagglomerate lumps. They can distribute small amounts of liquid into the powder. They can agglomerate the finest particles. The specific energy input of batch mixers is significantly higher than that of large mixers.
Free fall mixer: Here, an asymmetrically designed container mixes by slowly rotating around a horizontal axis. The mixing goods undergo overthrowing and sliding in the mixer. There are often fixtures such as paddles and deflectors in the mixing chamber. Free fall mixers require longer mixing times. They usually mix gently. However, they can only be used for free-flowing and low-dust goods. Free fall mixers should not be used if the goods are adhesive or if the bulk densities/particle sizes of the components differ greatly.
In principle, the terms "homogenizing" and "mixing" share the same meaning in bulk solids technology. In practice, however, a distinction is often made: Mixing mostly refers to the precise distribution of small components in a larger component. The definition of homogenizing, on the other hand, refers to, among other things, the uniform distribution of particle sizes, moisture, color, and temperature of an already existing mixture or pile.
In contrast to deagglomerating mixing, homogenization is usually carried out gently with the lowest possible energy input. Ideally, the particle shape and size are retained. If a raw material is to be the subject of industrial-scale processing or modification, the starting material must be as homogeneous as possible. Homogenizing silos or alternatively Gyraton mixers or conical screw mixers can be used for homogenization.
Special areas of application are:
- Preparation of raw materials
- Spice preparations,
- Instant soup mixes
- Pharmacy and cosmetics
- Baking mixtures
- Food stabilizers
- Tablet masses for effervescent tablets
- Cappuccino mixtures
- Infant formula
- Dessert mixes
- Instant drink mixes
- Plant protection agents that would be dissolved in water
- Metal powder
- Advanced ceramics
- Nanostructured materials
- Nanostructured active ingredients
- Building material additives
- Oleochemical products
- Plastic stabilizers
- ......
Interesting processes have been developed to mix bulk materials economically and hygienically. In practice, the MultiPlane®, SinConvex®, SinConcave® and Gyraton® tools have become established.
Vertical batch mixer: A rotating helix mixing tool initiates the homogenization process in the vertical cylinder: Along the wall of the apparatus, the mix is first transported upward to flow down again at the top, in the center of the mixing chamber. This flow process is universal and largely independent of the flow properties of all components involved.
Horizontal batch mixer: A rotating ploughshare mixing tool rotates in a horizontal cylinder and swirls the mix in a similar way to a fluidized bed. Instead of ploughshares, Becker shovels, helix segments or paddles can also be used.
Example of a complex mixing process from everyday operations:
- In the first step, the basic ingredients such as cereal derivatives, dextrose, starch, salt, egg powder, stabilizers and flavorings are homogeneously mixed.
- In the second step, liquid ingredients such as oleoresins, lecithins, liquid seasonings, spice extracts are added. All liquid ingredients must be homogeneously distributed into the powder without agglomerates.
- The mixing tool is then stopped.
- In the fourth step, fragile components are added to the mixer. These include sight spices, onion rings, freeze-dried meat preparations, dried fruits, vegetables and coarse herbs.
- In the fifth stage, a short homogenization takes place. In the industry, this is referred to as "underlifting" with minimal energy input.
- In step six, the instant soup is discharged from the mixer and transported to the packaging line. The product must not be segregated in the process.
Ideally, the instant soup is ...
- ideally homogeneous
- dust free
- segregation-free
- free flowing.
- Coarse pieces such as noodles, potatoes, croutons, dried fruits, onion rings, sight spices appear natural, fresh and undamaged.
- The finished product remains cool. The mixer has not heated the product. This extends the shelf life.
- The finished product dissolves quickly and homogeneously on contact with hot water
- and tastes delicious.
Product and process development
In practice, the development of a new formulation must be carried out in constant coordination with process development. What works well on a 1 liter scale does not necessarily work just as well on batches of 100 liters or 3000 liters. Food technologists and process engineers for mixing technology often meet in the technical center of mixer manufacturers. Tests are carried out there. Mixing processes are optimized. The goal is a perfect end product and sustainable profitability. Another goal is to conserve resources and minimize the carbon footprint.
Precision mixers, vacuum mixer-dryers and synthesis reactors are used in a wide range of industries. Accordingly, they are designed and manufactured for the respective industries:
- Pharmacy,
- Synthesis chemistry,
- Powder metallurgy,
- Nanostructured ceramics,
- Food,
- Dietetics,
- Oleo and plastics industry