Although most powder mixing operations can be performed with relatively simple equipment, there is today a definite trend towards more complex mixing processes. In addition to blending components modern mixers also have to coat and granulate and more stringent standards are demanded by the market with regard to mixing quality. Products are frequently heat sensitive, high value and often not free flowing. With complex requirements come more complex buying decisions and when this is set against a drive for rapid results in increased throughput, or NPD and a desire for the fastest route into a competitive market the selection of the right equipment is even more crucial. Hosokawa Micron have a long heritage in applied mixing technology and are able to work with customers to advise on the most appropriate equipment and system integration.
Batch or Continuous Operation
Mixing can be carried out in single batches or continuously and this is one of the first decisions to be made prior to specifying equipment. Historically the batch route is the more frequently used and for product control, identification and traceability it has many advantages, in the pharmaceutical industry for example. However where large volumes are involved in the mineral, chemical and food industries then a continuous mixing system has advantages.
Working with a supplier who offers a full range of both batch and continuous mixing equipment for different applications and with the capability of more than single mixing processes has definite advantages for the customer. Demonstrated here is how you can ‘max your mixer’ by selecting the right option; saving you time, cost of additional equipment and leaving less risk potential in product transfer between process stages.
BATCH MIXING SYSTEMS
Mixing, Coating, Drying – Conical Mixer
The concept of a conical shaped vessel fitted with an orbital rotating screw was developed by the Dutch engineer, Nauta, many years ago and now these elegant conical blenders are often just called Nauta as a generic term. They are able to carry out complex processing tasks in addition to a blending operation, which uses mainly convective mixing to quickly achieve an homogeneous product. For example the addition of a small high speed rotating paddle (intensifier) in the vessel means that small quantities of liquids, waxes or chemicals can be efficiently blended into the main powder bulk; coated products can also be produced. Other additions include jacketed vessel walls for heating or cooling operations and designs where there is no bottom bearing for the orbital screw, which makes for easy cleaning and minimises cross contamination. Many design variations and sizes are available Application of vacuum to the vessel and slight changes to the design enables the conical mixer to become a vacuum dryer hence mixing and drying can be carried out in one processing vessel.
Fast, Intensive Mixing and Agglomeration Of Cohesive Or Heat Sensitive Products
High Shear Mixers
The mixing and agglomeration of cohesive or heat sensitive products can be achieved quickly using a variation of the conical blender using a smaller, highly efficient conical mixer. With a fast rotating set of paddles fitted to a central shaft an intensive high shear mixing action is generated in the small space between the paddle tip and vessel wall. Tip speeds up to 30m/s are typical .
The intensive, yet gentle, mixing action ensures homogeneous blending in short mixing times. These mixers are easy to clean and when fitted with a cooling jacket are highly suited to mixing heat sensitive products. Agglomeration of products can also be carried out within units such as the Cyclomix.
Intensive mixing without product deformation
An example would be the compactly designed Intensomix which operates at tip speeds from 1.0 to 10.0 m/s with the whole vessel mass in movement. It has been developed for processes where high shear leads to product deformation and low shear to inadequate mixing. Mixer sizes up to 10,000 litres are typical but can go up as high as 25,000 litres. The inclusion of two side wall fitted lump breakers ensures that efficient admixing of liquids can be carried out without the undesirable lump formation and the need for a separate de-lumping process.
In -Line Mixing And Delumping – In-Line Disintegrators
For manufacturers looking for effective transportation of liquid products between batch processes where sedimentation or settling may occur, the Hosokawa Rietz In-line Disintegrator offers effective mixing and de-lumping of thick suspensions or slurries and can readily be installed in pipe systems operating at up to 10barg.The efficiency of these unit are such that there is no need for additional strainers with their associated blocking and cleaning problems. They are designed for quick opening to facilitate rapid screen and hammer changeover and fast and easy cleaning for minimal downtime and due to their compact design have advantages where space is restricted.
CONTINUOUS MIXING SYSTEMS
Engineers designing continuous mixing systems which ensure mixing homogeneity need to pay close attention to the accuracy and control of the feed system for the powders , solids and liquids. This is particularly so where the residence time in the blender unit is very small. Time and money spent on an accurate and reliable feed system is well spent.
A Unique Solution to Mixing Pastes and Slurries
A unique solution to mixing pastes and slurries is found in the unique Schugi Flexomix mixer/agglomerator . Currently used in the production of instant products such as soups, beverages and sauces as well as chemical and pharmaceutical products the mixer achieves excellent product uniformity and avoids demixing due to the almost instantaneous blending of all ingredients. With a flexible and continuously flexing mixer wall product build up is avoided and small amounts of liquids or solids are efficiently disperse to a bulk carrier. Capable of handling from 250kgs/hr to over 40 tonnes/hr the Flexomix compact in size enabling it to be installed in small spaces. This is a typical example of the need for accurate feeding equipment as the material hold up in the machine at any one time is of the order of grams not tonnes.
Homogenous Mixing and Extrusion – Extruders
Low to medium pressure extruders , which can be used to generate very homogeneous pellets up to 5-6mm for example in the plastics industry can be used as mixer/extruders. The final product can be a paste, plastic mass or extrudate. These units can be supplied with a jacket for heating or cooling and the central shaft can also be made hollow to allow for additional heating/cooling.
Finding the right mixer for different applications can make the difference between achieving on-spec end product in the most cost effective way or off-spec product and the need to introduce additional processing stages and more equipment.
Hosokawa Micron is one of the world’s leading companies specialising in powder and solids processing having many industry standard brand names within its portfolio. The group specialises in being a single source for all powder processing needs and can offer advise on mixing options and complete system design and supply backed by substantial test facilities throughout the world.
Hosokawa Micron Ltd
Can be contacted on:
Tel: (01928) 755100
Fax: (01928) 714325
Hosokawa Micron Ltd
We offer a single source supply for the very best in proven processing machinery with associated technical expertise across process technologies and industries to deliver individual processing solutions to meet specific needs.