Container mixer for bulk goods
Two different designs and functional principles
If bulk solids are mixed in your plant and if your production logistics are based on intermediate bulk containers (IBC), then it makes sense to adapt your mixing technology accordingly. In this blog article, container mixers are reviewed in the context of precision mixing.
Precision mixers are equipped with at least one dynamically moved mixing tool. Precision mixers are capable of mixing heterogeneous mixtures (dry, moist powders, granulates with different flow properties and different bulk densities and particle sizes, and liquid components) with ideal accuracy.
Container mixers, which operate on the principle of free-fall mixing, move the mixing goods by rotating or shaking the closed bulk container. Free-fall mixers are also capable of achieving high mixing qualities if the components are dry and largely similar. These include, for example: comparable mass ratios, similarly good flow properties, similar particle sizes, similar bulk densities. In addition, it must be ensured that each particle is isolated and that no lumps form during free-fall mixing. Container mixers that operate on the principle of free-fall mixing are not included in the amixon® production portfolio and are not addressed in this article.
Two methods of precise powder mixing using bulk containers are discussed below:
- An amixon® cone mixer works with standard bulk goods containers, which can be round or polygonal.
- An amixon® mixing tool enters the container from above, performs the mixing work inside the container, and then exits the container. In this case, the container serves as both a storage vessel and as the mixing chamber.
Question from a customer: At first glance, the mixing systems shown above appear very similar. Both mixers have a conical mixing chamber. Nevertheless, they seem to be different concepts, because the containers differ significantly. Why does amixon® have two construction types?
Answer from amixon®: A standard container can look round or square. It is characterized by the fact that it has a filling nozzle on the top and a discharge nozzle at the bottom. In most cases, both sockets have the same dimensions. The lower nozzle contains a closure fitting. The upper nozzle can also be optionally locked with a closure fitting, but mostly only a lid is put on. The nozzle dimensions vary from DN 200 to DN 350 depending on the type of bulk goods and the size of the container.
A container looks completely different when it is part of a container mixer (b). Then it is completely open at the top. This situation can be problematic if the mixing goods are dusty, toxic or corrosive, or if they have a strong odor.
Question from a customer: Why is a classic container mixer COM less suitable for dusty products?
Answer from amixon®: If the container serves as a mixing vessel for a dynamically moving mixing tool, then it must be open at the top. In the case of dusty products, a certain amount of dust emission is unavoidable when the mixing tool enters the mixing goods and when it leaves the container after the mixing process has been completed. Due to the large open area of this type of container, it is difficult to completely extract the dust.
In our opinion, a classic container mixer should only be considered if both the raw materials and the finished mixtures are uncritical. By that we mean; the powders are:
- dust free,
- not corrosive and
- neutral smelling
However, if your goods are dusty, nuisance or hazardous, then we recommend the use of closed standard bulk containers as shown on the left. These types of standard containers (IBC = Intermediate Bulk Container) are manufactured in large quantities. In this respect, they are lighter and considerably less expensive than bulk containers, which serve as a mixing chamber for dynamic mixing tools.
The containers can be equipped with corresponding docking stations for filling and discharging. These can optionally include an discharge aid and a weighing device. Adequate docking stations can fill and empty almost dust-free. Advanced containment docking stations can even operate completely dust-free. They can comply with clean room requirements.
Question from a customer: What approach does amixon® recommend when a new blending facility should be established manufacturing dusty products and using standard bulk containers for in-house powder logistics?
Answer from amixon®: First of all, attention should be focused on the selection of the appropriate container. The individual components as well as the mixed products must flow out safely, without residues and free of segregation. This is linked to the following considerations:
- Container shape round or square, stackable
- Cone inclination steep enough to ensure that the powder discharge is segregation-free
- Type of closure fitting
- Valve to be operated automatically if necessary
- Diameter sufficient for safe powder discharge
- permanently dustproof even when it is moved
- if necessary, suitable for dosing powder discharge
- possibly the container is coupled with a vibration device for the purpose of powder discharge
- Filling nozzle of the bulk material container closed by fitting or by lid
- sometimes bulk containers have a filter nozzle for ventilation
- surface finish
- wet or dry cleanable
- possibly 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 are essential. This is the only way to find out if and when your powders flow out of the container completely. Surely your mixed goods should also flow into and out of the container segregation-free. We also recommend testing this with your product.
Round containers generally have better discharge properties than square containers. However, the latter are more compact and take up less vertical space. Many docking stations are equipped with vibration devices for improved powder discharge.
Question from a customer: When we have evaluated a suitable IBC, shouldn't we then look for a mixer that has similar good emptying properties as the container?
Answer from amixon®: This should be the goal. We recommend considering an amixon® precision mixer of conical design (as seen above) whose net volume (= maximum working volume) corresponds exactly to the net volume of the container.
We recommend that you carry out targeted mixing and discharging trials in our technical center. Appropriate cone mixers are available there. t is very likely that your tests at our site will be successful.
© Copyright by amixon GmbH