The RotaDry® disc dryer can be used in existing plants as well as for the new construction of a sewage sludge incineration plant. The sludge to be dried must comply with the HUBER sewage sludge specification for the disc dryer. Ideally, it should be well-stabilised municipal sewage sludge.
HUBER Disc Dryer RotaDry® Partial contact drying of sewage sludge for recycling in fluidized bed incineration plants

Design and Function

The HUBER Disc Dryer RotaDry® is designed for homogeneous partial drying of dewatered sewage sludge. Due to its compact design and high specific water evaporation, it is not only ideally suited for use in new sewage sludge mono-incineration plants, but also for capacity expansions of existing plants. The dryer can precisely achieve the required dry residue (DR) content, ensuring self-sustaining combustion in the fluidized bed incinerator.
The HUBER RotaDry® is available in various sizes, allowing for a water evaporation capacity of approximately two to six tons per hour per dryer. By selecting different disc diameters and numbers of discs, the heating surface can be optimally tailored to the amount of sludge generated, ensuring the dryer operates within its ideal capacity range.
The heat required for drying is supplied, and depending on the size of the plant, electricity is also generated through steam turbines.
A reliable condensate removal system, an innovative concept for moisture control, an optimized feed and a steam control line with minimized pressure loss characterize the HUBER Disc Dryer RotaDry® as the perfect sewage sludge dryer in combination with a mono-incineration plant.
All dryers are optionally available with jacket heating.
Vapor condensation
The complete dryer system always includes the condensation of the vapors produced by the disc dryer. Depending on the the specific project requirements, there are various options available for this process.
- Tube bundle condenser (indirect condenser)
Compact design to maximize the extraction steam for district heating, as heating water is raised to the required temperature level directly in the condenser. - Injection condenser (direct condenser)
Circulating and cooled vapor condensate is sprayed in the head of the condenser to knock down the condensable vapors. Robust and universal design. - Multi-stage condensation system
Options may include components such as a sludge preheater, which optimizes energy use and reduces polymer consumption during the dewatering process, and an injection condenser, serving as a residual condenser for further energy recovery.
Steam and condensate system
In order to operate the dryer as efficiently as possible, the use of saturated steam is essential. Depending on the design of the water-steam cycle, steam cooling is required in addition to steam pressure control. Thanks to the optimal configuration of the controlled system, both pressure-loss-minimized operation at nominal load and reliable regulation to the required steam pressure are ensured. Even after passing through the dryer, the liquid steam condensate is not left energetically unused; it is returned to the water-steam system. Utilizing the flash steam is recommended to further enhance energy efficiency.
Vapor condensate treatment
Due to the high contact temperatures between the disc surface and sewage sludge, the vapor condensate contains elevated levels of ammonium, as well as particulate and dissolved COD (Chemical Oxygen Demand). This makes immediate indirect discharge into the municipal sewage network unfeasible. Separate treatment is required, and upon request, HUBER Technology, Inc. can develop a project-specific solution for treating the vapor condensate.
Ease of maintenance disc dryer
Maximum reduction of the activities during walkarounds
- The main rotor bearings and the discharge screw bearings are supplied with automatic grease lubrication.
- Highly efficient direct drive with peripheral speed adjustment capability. Wear-optimized driving style and startup under load possible.
- Discharge screw is easily accessible and removable for replacing wear plates and screw spiral.
The Benefits of the HUBER Disc Dryer RotaDry®
- Compact design
The HUBER Disc Dryer RotaDry® stands out for its compact design, enabling it to be installed on a small footprint or seamlessly integrated into existing plants, maximizing space efficiency. - Proven and reliable technology
The many years of successful use of disc dryers in combination with sewage sludge incineration plants demonstrate the robust technology of the process. - High specific water evaporation capacity
By heating the rotor discs and optionally the jacket, the HUBER Disc Dryer RotaDry® achieves a high volume-specific water evaporation rate, enhancing the efficiency of the drying process. - Competent partner
Thanks to the cooperation between HUBER and OESTERGAARD, the customer is offered the best possible solution, both in terms of process and design.
- Maintenance-friendly dryer
Minimal effort for operating personnel thanks to automatic grease lubrication and low-maintenance direct drive. - Extended service life
By using a special welded construction for the discs, the minimum permissible residual wall thickness can be reduced. The service life of the rotor is thus extended to a maximum. - Control concept adapted to mono-incineration plants
In the event of fluctuating sludge quality, the DR measured online can be included in the control. - Secure condensate drainage
Reliable condensate drainage from the discs due to the omission of a syphon pipe.
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