Mixing is critical to process success

Paul Boughton
Mixing is a fundamental process operation, but how it is done has a critical effect on production - as the examples here highlight. Sean Ottewell reports.

Going from the laboratory to production scale has always been a challenge. With the new Silverson Verso it's become less of one. The Verso reproduces what we can do on a production scale.

David Rothman, director of Silverson Machines, explains: "It gives clients the ability to start scaling accurately with smaller volumes than they were able to previously."

A bench top in-line mixer, the Verso is ideal for pilot-scale or laboratory applications. Controlled from a digital operating touch pad, it offers excellent reproducibility when scaling up, and with a tachometer, ammeter and programmable timer, it provides an accurate and easy method of forecasting the performance of larger in-line mixers under full-scale conditions.[Page Break]

Scale-up process

The Verso complements Silverson's lab range of equipment, providing the next step in the scale-up process. The 1hp machine has a self-pumping flow rate of 6.5US gallons/min (24litres/min) - depending on product viscosity (Fig. 1).

"We developed the Verso as a direct response to customer requests. Our customers wanted an interim size machine that could allow them to streamline their scale-up process," says Rothman.

"Our production scale UHS Series In-Line Mixers can be used with single or multistage rotor/stator configurations, so we have included that option with the Verso as well."

A full range of interchangeable workheads is available for the Verso, allowing it to perform the widest range of mixing duties, including blending, emulsifying, homogenising, solubilising, suspending, dispersing, particle size reduction and reaction acceleration.

Another innovation from Silverson is its new Flashmix mixer.

"It is a simple, effective and economical solution for some of the most complex powder/liquid mixing applications in the processing industries," says Peter Matthews, technical manager, Silverson Machines.

"In the design, we were able to combine intense high shear, which gives us an agglomerate free mix, with a high rate of powder incorporation of up to 250 pounds/minute (130kg/min)."[Page Break]

High powder flow rate

Ergonomically designed, the Flashmix does not need a feed pump nor does it require adjustment during operation to maintain the high powder flow rate as viscosity increases. Powder incorporation is consistent, batch to batch. Its sanitary design incorporates an EHEDG and 3-A certified mixer that can be cleaned-in-place.

The Flashmix is also energy efficient, requiring 65 per cent less power than similar machines. It is available in two models, each with or without a stainless steel sack table: the FMX30 with a 10 hp motor, and the FMX45 with a15 hp motor.[Page Break]

Test drive

Buying a piece of production equipment is a long-term investment, so it stands to reason that customers may want to take it for a test drive, so to speak. Silverson understands this desire.

In response to industry needs, it has initiated a free, no-obligation, two-week trial programme that lets customers try out its mixing equipment prior to purchase.

"Customers want to be certain the mixing equipment they are buying is optimal for their production process, and rightfully so," says Matt Smith, vp of sales, Silverson Machines. "It's an important decision and no small investment."

From years of experience across a wide swath of industries, the high shear mixing experts at Silverson have learned that every mixing application is unique.

Because of this, Silverson tests its mixers under the most realistic conditions possible. Then it helps customers choose the right mixer or customises one for their particular application.[Page Break]

End product viscosity

Knowledge of variables such as raw material characteristics, end product viscosity, batch size and mixing temperature is used to determine the best mixer for each application.

In addition to its trial programme, Silverson maintains two dedicated test facilities - one in the United States and one in the United Kingdom - each equipped with a complete range of laboratory and production scale machines.

At either of these sites, customers can test their applications, try out new products and discuss specific applications with the technical staff.

"We are confident that once a customer tries our equipment, we'll be able to help them optimise their processing," says Smith. "Our high shear mixers can often reduce mixing times up to 90 per cent compared to conventional mixing equipment."

Improving efficiency and energy use

A JR Boone Delta Blade mixer has helped UK-based cementitious flooring manufacturer F Ball to improve its efficiency and cut energy usage.

The mixer is being used for high-speed production in F Ball's new powder mixing plant. This is designed to produce up to 30 t/h of blended material.

At any time there may be as many as six batches within the process. With this amount of work in process, mixing speed and efficiency are paramount - thoroughly blending the additives throughout the bulk materials before the bomb door opens and the mixed material is deposited into the underhopper.

A key objective of the plant was that it would have as small an environmental impact as possible and a vital part of that objective was to minimise the energy used, for example by the use of gravity-fed rather than mechanically conveyed processes and making every element of the process as energy efficient as it could be - including the mixer itself.

The Delta Blade is a plough-type mixer, with a precisely engineered blade shape that uses the principles of high agitator speeds to radially and axially accelerate the product formulation in a short criss-cross pattern within the mixer shell.

Higher levels of shear are produced with lower power consumption than more conventional mixers, meaning that batches are mixed quickly, thoroughly and homegenously using minimum energy and reducing the carbon footprint of the new installation.[Page Break]

Efficient mixing action

Since entering service a further benefit of the Delta Blade system has been noted due to its highly efficient mixing action: despite the nature of the materials in use, no wear parts have been replaced in over two years of operation.

The new MT industrial mixing tanks from Protectoplas include standard sizes covering batches from 30 to 8000 usable gallons (113-30 000 litres).

Protectoplas can also provide custom sizes for larger or smaller batching requirements.

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

Designed for indoor or outdoor use, the new Protectoplas mixers feature crucial components from State Electric and Baldor motors.

Variable frequency drives (VFDs) are included as standard with components of packaged mix tank systems, allowing users full control of motor speed, and adjusting for varying viscosities.

The company says that specification is generating extremely positive feedback from 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 500 gallon (1900 litre) capacity.

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

Mixing tank

After years of development and tracking customer feedback Protectoplas has announced the MT mixing tank line. Pre-engineered to handle a wide range of applications, robust industrial design, along with a quick and easy set up make the MT a suitable solution for most companies operating in in today's market.

Overall Protectoplas offers a wide range of products backed by years of field service and experience.

The company says its welded flanges, MT mixing tank line, DW double walled tank line, Bleach-Guard System, AG-TANK II, and custom fabrication abilities make Protectoplas an ideal source for local and global companies seeking chemical resistant parts.