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Spin Flash Dryer Handles Challenging Drying Application

August 21, 2014

Through its Anhydro brand, SPX has vast experience of powder drying solutions. In striving for ongoing innovation and customer benefit, it developed and pioneered the spin flash dryer technology. These units provide continuous drying of high-viscosity products, pastes, and filter cakes.
    When a leading global supplier of catalysts required a drying process for a particularly challenging application they approached SPX to discuss the solution. The process feed used a filter cake for a product with low solid content and the inlet mixture presented conveying challenges. A consistent dryer feed was an important requirement for this application.
    In searching for the best equipment to achieve the desired results, the company looked at standard flash dryers, spray dryers, and other proprietary technologies available, along with the SPX Anhydro spin flash dryer. It had experience with standard flash dryers and spray dryers for similar applications, and had a spin flash dryer in use for a different process application.
    The catalyst manufacturer narrowed its selection to three options, two of which gave clearly superior results. Final testing showed requirements for modification to the two remaining units under trial to produce the consistent feed to the dryer, which was so critical to the operation. The level of service and clear understanding of the technology and process shown by SPX secured the order for the Anhydro spin flash dryer.
    The Anhydro spin flash dryer requires lower air flow and is therefore more energy efficient than spray dryer technology. It can handle higher inlet moisture content than a standard flash dryer, which, for this application, meant there was no need for the undesirable external recycling loop as used on other dryers to gain the product characteristics required. The Anhydro unit has now been in service for nearly two years and has proved easy to maintain and reliable during this time.
    For this application the key to a successful, high-quality end product is maintaining a constant rate of feed to the dryer. This is important as it directly relates to accurate control of the outlet temperature. After much experimentation to get a feed system to provide the desired consistency, the insight Anhydro provided delivered a dryer working with repeatability and reliability to the required specification.
    The SPX Anhydro spin flash dryer used for this application is one of the largest units currently made. Generally constructed from stainless steel, drying chambers are up to 2.5 m in diam, and can operate with inlet temperatures up to 600°C. The continuous process provides efficient drying with precision control. Cost savings and return on investment are realized with reduced energy requirements, no need for external recycling of the product to gain required specification, low maintenance, and high-quality end product. The unit has a relatively small footprint compared to alternate technologies, with minimum operator overhead and maintenance requirements.
    The spin flash dryer consists of a feed system with a vat and agitator for buffering and fragmenting feed product. The version installed for this particular process utilizes a feed screw, though some other installations have a pumped feed. The drying chamber has a rotor in its conical base, which creates an efficient drying air flow pattern. Hot air enters at a tangent into the chamber to create turbulent, whirling air flow to further assist with this efficiency. Once small enough, particles pass through a classifier at the top of the chamber and are finally collected in a bag filter. Air flow passes out at the top of the system drawn by an exhaust fan.
    The powder density of the outlet product is affected by drying temperature and air velocity. Good temperature control is critical for this application and is dependent on consistent feed control. The design of the dryer delivers this and ensures efficient, direct drying without feed pre-treatment, and flow patterns that quickly disintegrate wet lumps.
    The capability to work in partnership with a customer to engineer products to exact needs, understanding of industrial processes, and knowledge to apply latest, innovative technologies to work reliably in real-life applications made this project a success for SPX and its customer.
    For more information, contact SPX Corp. (Delavan, WI) at 262-728-4920 or www.spx.com.

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