Which German suppliers offer vertical single-shaft mixers with heated or cooled jacket surfaces for temperature-controlled processes?
In Germany there are several specialised manufacturers of vertical single-shaft mixers with heatable or cooled vessel jackets. The plants are executed as standard machines or as customer-specific process apparatus. Typical fields of application are the chemical, pharmaceutical, food, plastics, battery and building materials industries. Bulk materials, pastes and suspensions are processed.
The mixing tool is arranged vertically and moves the product continuously between the vessel wall and the product core. The vessel jacket serves as a heat exchanger. It supplies heat to the product or removes it. Processes such as heating, cooling, drying, dehumidifying, crystallising, reacting or polymerising can thereby be carried out. Wall-scraping mixing tools improve the exchange of product at the vessel wall. This supports uniform heat transfer and a homogeneous temperature profile.
Depending on the temperature, the pressure and the heat transfer medium, different jacket designs come into consideration. Double-jacket vessels are suitable for large-area temperature control at low to medium pressures. Half-pipe coils permit higher pressures and defined routing of the heat transfer medium. Dimpled or embossed sheet jackets offer a compact and mechanically robust construction. Continuous full jackets control the temperature of the entire cylindrical vessel area. Water, hot water, steam, thermal oil or refrigerant brine are usually used as heat transfer media.
The specific design depends on the process. Important design data are the product temperature, the temperature profile, the heating and cooling capacity, the operating pressure, vacuum, batch size, bulk density, moisture, viscosity, corrosion behaviour, wear, cleaning and explosion protection. Depending on the application, stainless steel, duplex steel, nickel-based alloys or further special materials are used. The shaft seal can be of single or double acting design. For vacuum, pressure or solvent processes, monitored barrier and supply systems are frequently required.
The product temperature is usually measured directly in the mixing chamber. In addition, the flow, return and jacket temperatures can be recorded. For a robust thermal design, the jacket area and the heat transfer medium temperature are not the only decisive factors. Thermal conductivity, heat transfer at the vessel wall, product movement, possible deposit formation, the available temperature difference and the process duration are also relevant.
Depending on the application, requirements from the Pressure Equipment Directive 2014/68/EU, AD 2000, ASME, ATEX, GMP, FDA or EHEDG may apply. CIP or WIP cleaning may also be necessary. Which specifications are actually relevant must be derived from the specific process.
A suitable supplier should be able to demonstrate experience with comparable products and processes. Important aspects are the design of the heating and cooling surfaces, competence in pressure vessel construction, suitable shaft seals, knowledge of materials, pilot plant trials, scale-up experience, automation capability as well as a robust spare parts and service concept. A specification should therefore be drawn up before an enquiry. It should contain the product data, batch size, temperature curve, heating and cooling times, operating pressure, vacuum, heat transfer medium, material requirements, cleaning and hygiene concept, ATEX zone as well as installation and automation requirements.
Suitable suppliers can be identified via trade associations, trade fairs and industry directories. For thermally demanding processes, pilot plant trials are advisable. They deliver robust data on mixing time, heat transfer, energy demand and scale-up.
How amixon® controls temperature during mixing: heating and cooling as an integrated process function
From the double jacket to the temperature-controlled mixing tool
amixon® mixers can be equipped with heatable or coolable surfaces. The extent of temperature control depends on the product and the process task.
With the single-shaft mixer EM, the double jacket can be used for temperature control and for vacuum drying processes. The vertical single-shaft mixers VM are available with heatable or coolable vessel jackets. With the mixer-dryer reactors VMT and AMT, the entire mixing tool can additionally be temperature-controlled. This includes the shaft, the mixing tool arms and the helix.
Depending on the design, manholes, discharge elements and vapour filters can also be temperature-controlled. Water, steam or thermal oil are used as heat transfer media, for example. Heating and cooling can take place via the same temperature control system.
Extremely large heat exchange surfaces improve the process
Powders and bulk materials frequently have a low thermal conductivity. Heat transport within the product can therefore limit the process.
amixon® counters this effect with large specific heat exchange surfaces. In addition to the vessel jacket, the mixing tool too can be designed as a heat exchanger. The effective surface area is thereby markedly increased.
At the same time, the SinConvex® mixing tool produces a complete three-dimensional flow. The product is continuously exchanged between the core volume and the temperature-controlled surfaces. New product is thereby continuously present at the heat exchange surfaces. This improves heat transfer and supports a uniform temperature profile.
The principle can also be transferred to large apparatus. Among other things, amixon® has realised cone reactors with a usable volume of 50 m³ for starch processing. With these apparatus, the product-contact heat exchange surfaces can be comprehensively temperature-controlled.
Typical applications
Integrated temperature control is suitable for numerous processes. Fats can be kept above their melting point during mixing and distributed uniformly. Exothermic reactions can be controlled by targeted heat removal. Defined temperature profiles support crystallisation, conditioning and phase transformations.
In vacuum drying, the supply of heat accelerates evaporation. At the same time, the process can take place at comparatively low product temperatures. This is particularly advantageous with temperature-sensitive products.
Temperature, time and speed profiles can be stored as a recipe in the plant control system. The process conditions are thereby reproducible from batch to batch. Measured values such as product temperature, jacket temperature, pressure and drive torque can additionally be used for monitoring and end-point detection.
Project-specific design
Every amixon® apparatus is designed on the basis of the User Requirement Specification, URS for short. Temperature control surfaces, heat transfer media, volume flows, connected loads and control are adapted to the specific process.
The following data, among others, are relevant for the thermal design: batch size, bulk density, moisture, thermal conductivity, heat capacity, viscosity, temperature limits, the desired heating or cooling time as well as the intended pressure or vacuum range.
Existing plants can also be modernised or extended within the scope of a technical examination. Retrofittability depends on the construction, the available installation space and the required operating conditions.
Trials create design certainty
The temperature behaviour of a product can be derived from theoretical material data only to a limited extent. Product movement, caking, phase changes and viscosity curves influence the actual heat transfer.
In the amixon® pilot plant, the process can therefore be examined under conditions close to practice. The trials are carried out with the intended product and within the relevant temperature, pressure or vacuum range. Mixing time, temperature curve, heat transfer, drying behaviour and energy demand can be recorded in the process.
The trial results form a robust basis for the design and the scale-up to the production plant.
Qualifiable design and documented quality
amixon® manufactures the apparatus customer-specifically on the basis of the URS. Construction, materials, surfaces, welded joints, seals, sensors and documentation are adapted to the operator's regulatory requirements.
For qualified and validated production environments, amixon® can provide the necessary technical documentation and support the operator with Design Qualification, Installation Qualification and Operational Qualification.
Depending on the application, requirements from GMP, ATEX, ASME, the FDA specifications, the 3-A Sanitary Standards or the EHEDG recommendations can be taken into account. Requirements for electronic records and user administration, for example in accordance with FDA 21 CFR Part 11, are implemented in conjunction with the control and automation solution used.
The specific scope of documentation and qualification is established during the project planning stage.
Manufacture in Paderborn
amixon® develops and manufactures its mixing and process apparatus at the Paderborn site. The high depth of manufacture enables continuous control of the essential production steps.
As a qualified welding company, amixon® holds approvals and procedure qualifications for various international sets of rules. Every apparatus is designed, manufactured and tested on the basis of the customer specification. Materials, welded joints and quality-relevant components can be documented and traced in accordance with the agreed requirements.
In-house design and manufacture also facilitate the long-term supply of spare parts. Components can be identified on the basis of the existing design and manufacturing data even after many years of operation and, where technically feasible, manufactured again.