Allgaier CD Dryer

The Allgaier CD Dryer, unveiled at ACHEMA 2018, combines proven contact drying technology into a revolutionary form factor that improves process performance and reduces operating costs. While the CD Dryer’s operating concept is simple, the cost savings are what are impressive.

 
 Allgaier CD Dryer at ACHEMA 2018 in Frankfurt am Main, Germany

Allgaier CD Dryer at ACHEMA 2018 in Frankfurt am Main, Germany

 

The CD Dryer is an indirectly heated contact dryer. Liquid is pumped from a reservoir at the bottom of the machine directly onto vertically oriented, double-walled disks. The disks are internally heated using saturated steam. The direct transfer of heat quickly evaporates moisture as the disk rotates towards the scraper blades which are located on each side of the disks. After one rotation, the scrapers remove the dried material (in the form of powder, films or flakes) and discharges the material to the next step in the process for transport or collection.


CASE STUDY

In mining, recycling, and even brewing, water conservation is an ever-present concern from both a capital and environmental perspective. The Allgaier CD Dryer addresses these issues by reducing capital expenditure and minimizing environmental impacts.

In one example, a company generated approximately 6,000 tpy of wastewater in its plating process which was being reduced down to 1,200 tpy utilizing a condensing apparatus. This operation resulted in approximately $300,000 USD of disposal costs. The company needed a method to further reduce this cost. A CD Dryer was installed immediately downstream of the existing condensing apparatus. This resulted in reducing the original 6,000 tpy of wastewater to only 25 tpy of dried waste, a reduction to only 0.4% of the original wastewater volume. Disposal costs dropped from $300,000 USD to $6,300, a savings of $293,700/year.

Unique and Efficient Design

The heart of the CD Dryer is the disk assembly. The hollow disks are heated from the inside using saturated steam at a pressure of up to 5 bar (g), or up to 152°C (306°F). This temperature provides efficient contact drying of the liquid products. The material and coating of the disks can be adapted specific to the application or product characteristics, including handling highly corrosive or even abrasive products. 

Throughput capacities are dependent on the diameter and number of disks selected. Disks are available in 900 mm (35.4 in.) or 1,300 mm (51.2 in.) diameters. Both disk diameters are available in three housing sizes. For up to 4, 8 or 12 disks (900 mm diameter) and for up to 8, 12 or 16 disks (1,300 mm diameter). If greater throughputs are required, it is easy to add additional CD Dryers thanks to the CD Dryer’s modular design. Disc scrapers are also available in different material versions depending on the application.

The disk bay cover is made of laminated safety glass and swings up, allowing the process to be easily monitored from the front while the system is in operation. When opened, it also allows convenient access to the process space for cleaning and adjusting the blades. Separate swinging doors open for maintenance access to internal motors and components. Each bay has viewing ports and an integrated work light for visual inspection. 

 CD Dryer Operating Flowsheet

CD Dryer Operating Flowsheet


A Wide Range of Applications

The CD Dryer achieves outstanding drying results in treating organic and inorganic industrial wastewater. A large portion of industrial wastewater comes from the food processing: meat processing, breweries, soft drink factories, distilleries and dairies produce large quantities of wastewater. 

Various plant and animal materials such as algae suspensions, brewer's yeast, distillation residues, fish wastewater or gelatins are prime applications for the CD Dryer. Examples of inorganic wastewater that can be concentrated or dried using the CD Dryer are include: landfill leachate, bentonite and china clay sludges, as well as wastewater loaded with tin and tungsten sludges. Materials that which can be pumped, do not caramelize, contain solid elements, or no not produce a great deal of foam can also be processed. 
 

 Typical materials processed in the CD Dryer

Typical materials processed in the CD Dryer

 CD Dryer Disks in Operation

CD Dryer Disks in Operation


Energy-efficient drying

Allagier’s CD Dryer provides compelling advantages compared to the use of contact drum dryers. The space required by the central disk assembly is considerably less than that for a drum dryer. For example, to achieve a heat-transfer surface of 24 m², a traditional drum dryer needs 7.7 m² of space. A CD Dryer only needs 3.0 m². 

In addition, the scraping process of the dried products in a contact drum dryer is comparatively complicated. The blades need to be very precisely adjusted over a length of several meters. Assembly and maintenance correspondingly cost a lot of time and money for conventional contact drying technologies. With the CD Dryer, several disks operate in parallel. Each disk has its own short scrapers that are self-adjusting, simple to install, and easy to maintain. 
 

 Allgaier CD Dryer with open access bays

Allgaier CD Dryer with open access bays

The CD Dryer also scores points in energy efficiency. The thin-walled, sturdy disks ensure ideal thermal conductivity. This provides a high specific evaporation power per m² of heated dryer surface while requiring a short heating phase of the system. Compared to convective drying methods in heated air operation or gas recirculation, the CD Dryer, being a pure contact dryer, does not require an air supply for heat input since heat is fed to the moist product in direct contact with the steam-heated disk surfaces. The direct contact of the fluids on the drying surfaces substantially reduces the energy consumed in the drying process. Additionally, the drying process of the CD Dryer creates very little (usually dust-free) exhaust air. The small quantity of vapor produced is removed as a high water vapor concentration resulting in relatively little heat loss in the dryer exhaust.

In comparison to convective drying systems, the amount of exhaust air is substantially less, thereby reducing operating costs. Downstream equipment, such as the cyclone separator, filter, washer and exhaust air fan, can be smaller in design due to the smaller amount of exhaust air as well. 

The Allgaier test center in Uhingen has a semi-industrial scale CD Dryer available for tests using real customer material so that Allgaier can engineer the best full-scale CD Dryer configuration for your application.

Contact Allgaier Process Technology, Inc. to discuss your specific application and how a CD Dryer and can improve your process.