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cpp PROCESS ENGINEERING Pictures: Allgaier Process Technology The CD Dryer allows effective contact drying in a small space because the disc assembly is heated internally Indirectly heated contact dryer Fast evaporation on rotating discs The demand for energy-efficient devices in drying processes is rising steadily. At the same time, cost pressures and end-product quality requirements are increasing. Allgaier’s CD Dryer, a solution that satisfies the stringent demands of the industry, was specifically developed for drying solids dissolved or suspended in liquids. It is classed as an indirectly heated contact dryer. The drying process in the indirectly heated contact dryer (CD Dryer) is as follows: the liquid is applied by way of a pump and feed pipes directly to double-walled discs that rotate and are configured vertically as an assembly. These discs are heated internally using saturated steam. The direct transfer of heat to the liquid product evaporates the water very quickly, thus providing excellent efficiency because heat losses are mini - mised. After one disc rotation, scrapers making contact with the discs remove the dried solids and send the dry material to the next process step – in the form of pellets, films or flakes depending on the output product – via a product discharge. For example, the solid material portion of concentrated salt solutions can be obtained as a fine-grained powder. Thanks to the downstream conveyor unit, the product can be transported onward or collected directly in a silo or another container. The operating principle of the CD Dryer is fundamentally different from conventional disc dryers, where the discs are immersed in the moist material. These dryers are normally only used to reduce the water content of liquid, pasty or bulky products, for instance to save transport costs. The CD Dryer provides far more varied options for use, thus opening up considerable potential in a widely diversified application spectrum. One area where the CD Dryer achieves outstanding results is the treatment of organic or inorganic industrial and special waste water. In addition to this, the CD Dryer is capable of drying any material that can be pumped, does not caramelise, does not contain solid ingredients and does not produce a great deal of foam. As a result, it can be deployed in virtually every branch of process engineering in the chemical industry, from ceramics to waste management, wastewater treatment and breweries. Disc assembly is the heart The heart of the CD Dryer is the disc assembly. The hollow discs are heated from 30 cpp 03-2018
the inside using saturated steam at a pres - sure of up to 5 bar. This ensures efficient contact drying of the liquid products. Depending on the application or the product characteristics, the disc material and coating can be adapted for highly corrosive or even abrasive substances, for example. The diameter and number of discs depend on the desired throughput. There are two options available here, namely discs with a diameter of 900 or 1300 mm. Each disc diameter is offered in three housing sizes: for up to 4, 8 or 12 discs (900 mm diameter) or for up to 8, 12 or 16 discs (1300 mm diameter). If a higher throughput is required, it is easy to upgrade the CD Dryer with additional discs – up to the maximum possible number for each type – thanks to this platform design. The sturdy scrapers for extracting the dried substances from the heated discs can be manufactured from different materials and are automatically aligned to make optimum contact with the disc sides. The operator can see at a glance on the CD Dryer whether the production process is running as desired. The cover, which is made of laminated safety glass and opens up, allows easy monitoring of the process from the front while the system is in operation. When opened, it also provides convenient access to the process space for cleaning or for checking and adjusting the blades. The two technical spaces – the steam space on the left and the condensate space on the right – have viewing ports and an integrated work light for visual inspections. Separate swinging doors enable good accessibility to the technical spaces for maintenance work. The actual machine or process data can be retrieved or changed intuitively using a touch panel. PROCESS APP: The Allgaier Process App celebrated its world premiere at Achema 2018. Thanks to this new development, customers now have a digital twin of their machine conveniently in their pocket. The app is intuitive to use and is currently available for all newly delivered Allgaier tumbler screening machines. Each machine is supplied with its own QR code and can thus be uniquely identified immediately. A digital twin of the machine and an interactive drawing guide the app user quickly to the appropriate spare parts. A simple click is all it takes to select these and order them from Allgaier. Using a mobile device, customers can also view the documentation for a specific Small footprint The space required by the central disc assembly is considerably less than for a drum dryer, as the following example demonstrates: a traditional drum dryer needs 7.7 m 2 of space for a heat-transfer surface of 24 m 2 as compared to only 3.0 m 2 with a CD Dryer. This compact configuration also has another advantage. If necessary, the dryer can be moved to another location quickly and easily as a single unit. The fork shoes needed for transport are located beneath the process space. The control cabinet necessary for operation is moreover integrated into the machine frame. As a result, the CD Dryer provides maximum flexibility in production. In addition to this, scraping the dried products in a drum dryer is relatively complicated. The blades must be very precisely adjusted over a length of several metres. Installation and maintenance are correspondingly expensive and time-consuming. With the CD Dryer, several discs operate in parallel. Each disc has its own short scrapers that are self-adjusting, simple to install and easy to maintain. DIGITAL TWIN ON THE GO Thanks to the Process App, users have a digital twin of their machine conven - iently in their pocket machine directly at the production site. One-click contact with the Allgaier Service Department is possible, too, for scheduled maintenance or in the event of a malfunction. The app will gradually be expanded to become a digital platform for the Process Technology division’s entire range of products. Apart from benefits like easier ordering and improved system availability for tumbler screening machines, this will also create further potential for all Allgaier Process Technology customers and machines. The back end of the app, which is available in German, English and French, is hosted entirely in Germany. Energy efficient drying The rugged, thin-walled dryer discs ensure ideal thermal conductivity properties. This leads to a high specific evaporation power per square metre of heated dryer surface in combination with a short system heating phase. Compared to convective drying methods in air or using gas recirculation, the CD Dryer – being a purely contact dryer – does not need an air supply for heat input because heat is fed to the moist product in direct contact with the heated surfaces. The closeness of the dryer and the fluids substantially reduces energy consumption du - ring the drying process. At the same time, only a small amount of – usually dust-free – exhaust air is produced. The resulting small quantity of vapour is removed with a high water vapour concentration. The heat loss due to the dryer exhaust is therefore only minimal. The amount of exhaust air, which is significantly less than with convective drying systems, likewise has a positive effect on the acquisition and operating costs. Downstream equipment such as a cyclone separator, filter, washer and exhaust air fan can thus be downsized and operated in a much more cost-effective manner. The Allgaier Test Centre in Uhingen has a semi-industrial scale CD Dryer available for testing on real products – a valuable source of information when designing large-scale systems for customer projects. www.cpp-net.com Online search: cpp0318allgaier cpp 03-2018 31
