Container mixer for bulk materials
This blog post explains terms such as container mixer, free-fall mixer and precision mixer.
If bulk materials are mixed in your operation and your production logistics are based on intermediate bulk containers (IBCs), it makes sense to adapt your mixing technology to this as well. This blog post looks at container mixers that act as precision mixers.
Precision mixers have at least one dynamically moved, space-controlling mixing tool that is capable of mixing the mix without dead space. Precision mixers are therefore able to mix heterogeneous mixtures (dry, moist powders, granulates with different flow properties, bulk densities and particle sizes as well as liquid components) in an ideal and precise manner.
Explanations on the subject of free-fall mixers
Container mixers that work according to the "free-fall mixing" principle move the mix by pouring it from the top to the bottom. This process is repeated several times. Such a pouring process takes place automatically when a suitable container is rotated. High mixing qualities can also be achieved with free-fall mixers if the mix components are dry, free-flowing and largely homogeneous. This includes e.g:
- comparable ratios,
- similar flow properties,
- similar grain sizes,
- similar bulk densities.
- Furthermore, it must be ensured that each particle is present individually.
- When mixing in free fall, no lumps should form.
- It is also particularly important that the filling level in the free-fall mixer is exactly right.
Container mixers whose mixing principle is based on rotating, swivelling, rolling or shaking the mixing container are not part of the amixon® production range. These called "free-fall mixers" will not be discussed further in this blog post.
Question from a customer: The mixing systems shown above look similar at first look. Both mixers have a conical mixing chamber and similar mixing tools. Nevertheless, they seem to be different concepts, as the handling is clearly different. Why are there two container mixer concepts at amixon®?
Answer from amixon®:
A standard container can look round or square. It is characterised by having a filler neck at the top and an outlet spout at the bottom. Both nozzles usually have the same dimensions. The lower spigot contains a shut-off valve. The upper spigot can also be optionally closed with a closure fitting, but usually only a lid is fitted. Depending on the type of bulk material and the container size, the column dimensions vary from DN 200 to DN 350.
A container looks completely different when it is part of an amixon® container mixer type COM. Then it is completely open at the top when the mixing tool dips into the container and when it moves out of the container. out of the container. This can be troublesome if the mix is dusty, toxic, corrosive or smelly.
Question from a customer: To what extent is a classic container mixer COM less suitable for dusty mixes?
Answer from amixon:
The bulk container must be open at the top if it serves as a mixing container for a dynamically moved mixing tool. With dusty mixes, a certain amount of dust emission is unavoidable when the mixing tool dips into the mix and moves out after the mixing work. Due to the large open area of this type of container, it is difficult to vacuum the dust completely.
In our opinion, a COM-type amixon® container mixer should only be considered if both the raw materials and the finished mixes are non-critical. By this we mean powders or granules with the following properties:
- not corrosive and
- neutral smelling
Are your goods dusty?
If your goods are dusty or hazardous, we recommend the use of closed standard bulk containers, such as those manufactured by AZO GmbH. Such standard containers (IBC = Intermediate Bulk Container) are produced in large quantities. They are therefore lighter and much cheaper than bulk containers, which serve as a mixing chamber for dynamic mixing tools.
So-called docking stations for filling and emptying can be provided to match the containers. These can optionally have an emptying aid and a weighing device. Suitable docking stations can fill and empty almost dust-free.
Further developed containment docking stations can even work completely dust-free and fulfil cleanroom conditions.
Question from a customer: What approach does amixon® recommend when a new mixing plant is to be set up that manufactures dusty products and whose in-house powder logistics are to be carried out using standard bulk containers?
Response from amixon®:
Attention should first be paid to the selection of the appropriate container. The individual components and also the mixed products must flow out safely, without residues and free of segregation. The following considerations are linked to this:
- Container shape round or square, stackable?
- Net volume versus gross volume: What gross volume must the container have, taking into account the angle of slope of the mixed material?
- Taper steep enough to ensure that the powder discharge is segregation-free?
- Type of closure fitting?
- Discharge fitting to be operated automatically if necessary?
- Diameter sufficient for safe powder discharge?
- Closure fitting also permanently dust-tight when the container is transported?
- Shut-off valve suitable for dosing powder discharge?
- The container may be coupled to a vibrating device for the purpose of powder discharge.
- Filling spout of the bulk material container closed by fitting or by lid
- Sometimes bulk containers have a filter nozzle for aeration and deaeration => nature of the filter?
- Stability; impact protection?
- Surface finish?
- Can be cleaned wet or dry?
- If applicable, suitable for a "washing-in-place" (wip) cleaning station?
- .... more details?
In order to evaluate the above questions, practical discharge tests with a wide variety of standard bulk containers cannot be dispensed with. This is the only way to find out if and when your powders flow out of the container completely. Your mixed goods should certainly flow into and out of the container free of segregation. We also recommend testing this with your mix.
Round containers usually have better discharge properties than square containers. However, the latter are more compact and require less vertical installation space. Many docking stations are equipped with vibrating devices for improved powder discharge.
Question from a customer: Once we have evaluated a suitable IBC, shouldn't we then look for a blender that has similar good residual emptying properties as the container?
Response from amixon®:
This is exactly what we should strive for. We recommend considering an amixon® precision conical mixer (as seen above) whose net volume (= maximum working volume) is exactly equal to the net volume of the container.
We recommend that you carry out target-oriented mixing and discharge tests in our technical centre. Corresponding conical mixers are available there. It is extremely likely that your attempts will be successful with us.
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