Turning Up the Heat on Powder Processing
In response to increasing market demand for high temperature powder processing Hosokawa Micron B.V. has developed a range of new technologies that address the requirement for processing temperatures up to 325°C.
Gertjan Teekman, Drying specialist at Hosokawa Micron B.V. reviews the drivers fueling these developments, the engineering challenges associated with processing at high temperatures and the powder and particle engineering opportunities opened up by these advances – particularly in the production of high value materials.
High temperature processing allows chemical reactions that simply will not occur at lower temperatures. In enabling different chemical reactions material processors are able to impart different properties and altered characteristics leading to the development of customized powders. Turning up the process heat can also deliver time and cost efficiencies over more traditional processing models.
Multi-processing in a single vessel is increasingly important for those seeking contained processing for contamination free production and/or minimum handling and product transfer and we have incorporated this production advantage within our equipment and system designs.
Elevated temperatures are used to transform materials from one solid state to another state or for dehydration. Whilst drying is normally conducted at around 100°C, if other processes are involved, a higher temperature may be required. The challenges of engineering for high temperature processing are addressed by separating seals, bearings, drive mechanisms and valves from high temperature areas and by selecting appropriate, heat tolerant mechanical components and thermoplastic seals.
The diversity of demand in the market requires a flexible approach to high temperature processing solutions if both present and future opportunities are to be exploited and here Hosokawa Micron B.V. outline their most recent and on-going developments, over and above those on the renowned Nauta conical mixer/dryer which also offers successful high temperature processing of even the most sticky materials.
Conical Paddle Dryer (CPD)
Combines extremely fast drying rates with a compact design developed to enable vacuum, atmospheric and pressurized processing of a variety of materials such as powders, filter cakes, pastes, viscous slurries and especially brittle materials.
Capable of combining several processes in one vessel, the CPD has proved successful in a range of applications including:
· Chemical reactions: alkalization, solid-gas reactions
· Wet agglomeration and granulation of solids
· Sterilisation of products
Flash dryer Drymeister® (DMR-H)
This ultra-compact flash dryer combines drying, de-agglomeration/milling and classifying in one piece of equipment, drying temperature-sensitive products, safely, even under increased temperatures, in a matter of seconds! It delivers a lump free, defined particle size final product output.
With the capability to handle moisture content fluctuations from a few % up to more than 80% in suspensions, slurries, pastes, dough, filter cakes and wet powders it uses about 30-40% less energy per kilogram of evaporated water than conventional dryers.
The Hosokawa Disc Dryer is a compact, contact dryer that offers high heat transfer rates ranging from 85 to 300 W/m²K with high surface/volume ratios. The rotor consists of special, heated discs within a cylindrical jacketed housing. It is suitable for heating and cooling various types of product like filter cakes, powders, viscous materials and granules.
High Temperature Processes
Typically Hosokawa Micron B.V. heat treatments are applied following polymer reactor synthesis. The first step being for evaporation of water or still present monomers. The second step to physically alter material characteristics.
The advantage of this closed system is that both treatments occur in the same machine. The ability to accurately control the temperature and the process, prevent oxygen entering the system to inhibit burning of the mainly carbon based polymers, combined with the ability to add process flexibility by delivering different temperatures at different times, creates limitless opportunities for those wishing to exploit materials characteristics.
‘We have already supplied various 16m³ vacuum dryers for polymerisation processes and have current experience with a wide range of engineered polymers with special purpose applications in aerospace and Formula 1 where our ability to offer customers a route to producing a high quality, technically valuable end product is of paramount importance. This is enhanced by our lab to production capability across our range of equipment.’
The use of a DMR-H flash dryer, in carrier or support material preparation, offers significant advantages over traditional spray dryer systems that use excessive amounts of water incurring high vaporisation costs. Able to accept mechanically dewatered filter cakes or pastes as well as slurries the flash dryer offers an energy efficient approach to transforming carrier materials to the required consistency in petrochemical and other specialized applications.
The impregnation of active components, typically precious metals, onto carrier materials can be achieved efficiently utilising Nauta mixer/dryers with homogeneous distribution across the carrier before drying. The surface components can then be activated by additional heat treatments or the addition of oxygen to passivate the metals on the carrier.