Reliability and flexibility at heart of mixer advances

Paul Boughton
As the latest developments show, reliability, flexibility, ease of use and safety are the watchwords for modern mixing systems. Sean Ottewell reports.

Uni tec is a newly developed, individually designed general-purpose mixer provided by MTI Mischtechnik for manually or fully automatically controlled preparation of bulk materials in the process industries.

Depending on its configuration, uses of the new mixer unit range from homogenising bulk stock of diverse material characteristics to performing complex processing cycles aimed at providing specific product properties.

The design criteria of the mixing vessel, mixing tool and optional chopper systems are variable over a very broad range.

As a result, the unit can be optimally adapted to specific application needs - from gentle homogenisation of the most sensitive starting materials to the pre-dispersion of, for example, cohesive pigments (Fig. 1).[Page Break]

Spraying systems for fluids

Further options - including spraying systems for fluids, a double jacket for temperature-controlled process management, and a vacuum-proof or pressure shock resistant design of the mixing vessel - are available to handle coating and granulating tasks with high accuracy and repeatability.

Thanks to the operator-friendly design of the new Uni tec universal mixer, it ensures convenient filling, evacuating and cleaning in every situation.

"The new Uni tec system combines high ease of use, maximum process reliability and safety, as well as application-focused configurability in one single unit. This standard-setting combination enables users to obtain high-quality mixing results with remarkably superior efficiencies compared to most conventional mixers. Needless to say, MTI's products conform to all applicable codes and regulations including ATEX requirements according to the raw material property specifications. The Uni tec control system and the safety technology employed meet all demands on advanced, flexible production equipment performing to the highest quality standards," said MTI ceo Christian Honemeyer.

Apart from the new Uni tec universal mixer, MTI's product range comprises an easy-to-clean horizontal mixer, the application-focused MTI Flex-line and MTI Eco-line heating-/cooling mixer combinations, and highly efficient dehumidification and aspiration systems.

In late 2010, the company launched its Cool tec mixer, pioneering direct cooling by means of a refrigerant rather than with cooling water. According to MTI, the technology has been widely acclaimed for its much enhanced cooling performance and concurrently reduced energy demand.[Page Break]

Conical blenders

The concept of a conical-shaped vessel fitted with an orbital rotating screw was developed by the Dutch company Nauta many years ago and now, as part of the Hosokawa Micron worldwide group, these blenders are able to carry out complex processing tasks in addition to a blending operation.

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.

Application of vacuum to the vessel and slight changes to the design enables the Vrieco Nauta mixer to become a vacuum dryer, hence mixing and drying can be carried out in one processing vessel.

This range of conical vacuum dryers, developed from the basic conical mixer, is now one of the most respected dryers in industry.

Based on the design of the conical mixer, Hosokawa Micron's Cyclomix is a smaller, highly efficient intensive mixer developed to handle cohesive powders. The mixing element is a fast rotating set of paddles fitted to a central shaft and the real 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 possible. The conical vessel shape ensures the material moves upwards and falls down again guided by the vessel cover down into the base for more processing.

This intensive, yet gentle, mixing action ensures homogeneous blending to very high standards in short mixing times. The mixers have been designed for ease of cleaning and rapid change round, something which is very desirable in the paint and pigment field.

In a recent application involving the mixing of chrome oxide and iron oxide for use in the ceramic industry a Hosokawa Micron Cyclomix replaced an existing two-stage mixing and milling operation. By replacing the existing ribbon mixer with a Cyclomix it was possible to apply increased energy to the product which because of the intensity of the mix and dispersion of the materials eliminated the need for an additional milling stage. Mixing the chrome oxide and iron oxide in batches of 1300kg or 1000 litres, the Cyclomix achieved a consistent mix in approximately 40 minutes.[Page Break]

From lab to dairy

The new Silverson AX5 is a pilot-scale laboratory mixer equipped with a powerful 1hp (0.75kW) motor. Suitable for batches of up to 50litres, the AX5 features an integral rise and fall bench stand and touch pad controls with infinitely variable speed control, tachometer, ammeter and programmable timer.

This instrumentation and control provides excellent repeatability when carrying out QA testing and other repetitive tasks. In addition to the functional advantages, the touch pad control offers increased cleanliness and reliability (Fig. 2).

A major food manufacturer that uses several production models of Silverson mixers for a wide range of applications has bought an AX5 for scale-up of sauces from the test kitchen to the production plant.

In many cases an intermediate pilot-scale mixer can assist with scale up - going from five litres in a small lab trial to around 50 litres with comparable results makes it much easier to then scale up to bulk production.

In this case the AX5 provided that step in the scale-up process and once again the control and instrumentation featured with the AX5 was a deciding factor in the decision to purchase.

Meanwhile SPX is currently working to fill three new dairy processing orders worth over EUR78m for facilities in Europe and Asia. The orders utilise a wide range of SPX's custom engineered dairy processing technologies for varying applications - including mixing.

"These new orders for large global customers are a true testament to our expertise in dairy processing systems, as well as our ability to deliver highly engineered, custom solutions in a market that is increasingly technology-driven," said Don Canterna, segment president, SPX Flow Technology. "As the world's population grows, and demand for liquid and powdered dairy products continues to rise, we are working with our customers to develop processes that have high production capacity, run efficiently and help preserve our environment."[Page Break]

One of the new orders is for a large food and dairy manufacturer in Europe and features multiple technologies from SPX that will enable the customer to meet rising demand for its popular dairy products.

The project also includes innovative, custom designed features that are fully aligned with the customer's strict sustainability goals.

Another order, for a customer in Asia, calls for a fully integrated system, complete with mixing, infusion, evaporation and drying, for processing of consumer nutrition products. The system will include multiple SPX Flow technologies and is characterised as being flexible and expandable, in order to meet the needs of future demand.

The third order, also for a milk powder processing facility, is for a system capable of operating 24 hours/day, seven days a week, and will feature an innovative design that helps curb emissions.

Once completed, the new facility will be one of the largest milk dryers ever installed in Europe.[Page Break]

New mixing tank for chemicals and dry products

Protectoplas has launched its new MT mixing tank line that handles batches from 76-30,000 litres. The tanks come in standard sizes, although custom-built options are available for larger or smaller batching requirements.

The mix tanks are constructed from high density polyethylene (HDPE) resin for its outstanding chemical resistance. The mixing tanks include an integral HDPE mixer support system that provides easy access along with a low profile to save vertical space.

The tanks are designed for indoor or outdoor use, and Protectoplas mixers feature crucial components from State Electric and Baldor motors.

Variable frequency drives (VFD) are standard with packaged mix tank systems, allowing full control of motor speed, and adjusting for varying viscosities. According to the company, this feature is proving very popular with customers.

All wetted mixer parts are T316 stainless steel, and Protectoplas offers several coating options for harsher chemicals. Gear reduction, totally enclosed, fan-cooled mixer motor options, and agitators are also offered. Mixer gear reduction is standard on tanks larger than 1900 litre capacity.

Standard agitators included with packaged systems cover viscosities from 0-300 Centipoise, but can be tailored to specific customer requirements.

Pre-engineered to handle a wide range of applications, robust industrial design, along with a quick and easy set up make the MT ideal for any company in today's market, says Protectoplas.

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