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
Contact Drying of Sewage Sludge
Partial drying of sewage sludge for recycling in fluidized bed incineration plants.
- Water evaporation per dryer: 2 to 6 t/h
- Dewatered sludge throughput per dryer: 6 to 12 t/h *
- DR throughput capacity per dryer: 1.5 to 6.0 t/h *
- Heating medium: Saturated steam up to 10 bar(a)
* dependent on inlet and outlet DR
Thermal drying of sewage sludge is an indispensable process component to ensure the sewage sludge has the right dry residue. The subsequent mono-incineration of the sewage sludge achieves an enormous reduction in volume and mass and provides for the recovery of phosphorus.
HUBER Disc Dryer RotaDry®
HUBER Disc Dryer RotaDry®: Partial contact drying of sewage sludge for recycling in fluidized bed incineration plants
Installed Disc Dryers for a mono-incineration plant
Preparations for lifting a disc dryer
Lifting a Disc Dryer with a caterpillar crane
A disc dryer is lifted into place with the help of a heavy-duty crane
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 dry exactly to the required DR content and thus enable a selfsustaining combustion in the fluidized bed incinerator.
The HUBER RotaDry® is available in different sizes, so that a water evaporation of about two to six tons per hour and dryer can be achieved. By using different disc diameters and numbers of discs, the heating surface can be optimally adapted to the amount of generated sludge and the dryer can be operated in the ideal capacity range.
The heat requires for drying is provided and, depending on the size of the plant, electricity is also generated by means of steam turbine.
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 monoincineration plant.
All dryers are optionally available with jacket heating.
Vapour condensation
The overall dryer system always includes the condensation of the vapours produced by the disc dryer. Depending on the project-specific conditions, there are various possibilities here.
- Tube bundle condenser (indirect condenser)
Compact design to maximise 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 vapour condensate is sprayed in the head of the condenser to knock down the condensable vapours. Robust and universal design. - Multi-stage condensation system
Consisting, for example, of a sludge preheater (for energy optimization and polymer consumption reduction in the dewatering process) and an injection condenser as residual condenser.
Steam and condensate system
In order to operate the dryer as efficiently as possible, the use of saturated steam is essential. Depending on the concept in the water-steam cycle, steam cooling is therefore necessary in addition to steam pressure control. Due to the ideal configuration of the controlled system. Both pressure-loss-minimized operation at nominal load and reliable regulation to the required steam pressure can be achieved. Even after it has passed the dryer, the liquid steam condensate does not remain energetically unused and is returned to the water-steam system. It is advisable to utilise the flash steam.
Vapour condensate treatment
Due to the high contact temperatures of the disc surface and sewage sludge, a high load of ammonium as well as particulate and dissolved COD (Chemical Oxygen Demand) is produced in the vapour condensate, which does not allow for immediate indirect discharge into the municipal sewage network and requires separate treatment on request, HUBER SE can develop a project-speficic solution for the treatment of the vapour condensate.
The benefits of the HUBER Disc Dryer RotaDry®
- Compact design
The HUBER Disc Dryer RotaDry® convinces by its compact design, which allows the dryer to be installed even on a small footprint or to be integrated into existing plants. - Proven and durable 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, a high volume-specific water evaporation can be achieved. - Uniform and homogeneous drying
The sludge is mixed by the rotation of the rotor and blades mounted on the outer end of the discs.
- Heat recovery through use of condensation heat
The water evaporated from the sewage sludge can be precipitated again in the vapour condenser, whereby part of the energy used for thermal drying can be recovered. - Long service life
By using a special welded construction for the discs the, minimum permissible residual wall thickened can be reduced. The service life of the rotor is thus extended to a maximum. - Optimised dryer control through online DR measurement
The control of the disc dryer is dependent on the detected DR content at the inlet and outlet. This provides the possibility to react to fluctuating DR contents of the dewatered sludge.
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