Biogastechnik Süd GmbH
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Service Digestate evaporator and Biogas - small plants

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paddle agitator RT-PRW

Varibull Paddle Agitator RT-PRW - proved and tested agitator for digesters, post-digesters and digestate storage tanks

The Varibull paddle agitator, type RT-PRW, is a proved and tested agitator for digesters, post-digesters and digestate storage tanks. The low-maintenance drive unit is installed on the outside of the pit and is therefore accessible at all times. A maintenance-free mechanical seal provides durable sealing of the wall penetration of the drive shaft. The agitator shaft inside the pit is equipped with a maintenance-free and durable plain bearing.
The RT-PRW is used exclusively for stirring viscous feedstocks such as slurry, manure and renewable raw materials (RRM) or similar in round reinforced concrete tanks (digesters). The four slanted paddles assure optimum mixing performance over a large vertical area within shortest time. This provides for ideal and energy-saving blending of the renewable raw materials, slurry or manure in the digester. The RT-PRW is suitable for operating in substrate with a dry matter content of up to 15 %, a pH value of 6-8 and a temperature of up to +55 °C. The drive of the RT-PRW is designed for an ambient temperature of up to +40 °C.

The original agitator developed by us has become the most widely used agitator among the slow-speed long-shaft agitators in biogas plants.

It was designed and built in accordance with the most stringent safety requirements and after careful selection of the applicable harmonised standards and other technical specifications. Thus, it meets the current state of the art and guarantees a maximum level of safety.

The RT-PRW has been designed according to the provisions of the 2006/42/EC Machinery Directive.
The RT-PRW is optionally deliverable in explosion-proof design.

Advantages of the Varibull paddle agitator

  • ideally suited for the anaerobic digestion of renewable raw materials, in particular also grass silage and manure as well as other substrates
  • energy efficient thanks to large-surface agitator paddles
  • thorough blending across the different substrate layers while being gentle on the bacteria
  • reliable operation also with high dry-matter content and long-fibred substrates
  • maintenance-free wall seal
  • maintenance-free, durable plain bearing inside the pit
  • no height adjustment inside digester
  • also manages varying fill levels
  • no additional mechanical parts, such as chains, ropes or other suspension gear
  • Simply install, start and stir - “That’s all!”

Components of the Varibull paddle agitator RT-PRW

Base model (1), inner support (2), paddle (3), sound protection hood (4) optional and digester (5) usually available.

Construction and installation of the paddle agitator Varibull

The RT-PRW is mounted to the wall and floor of the digester. The drive is screwed to the outside of the concrete wall so that the drive assembly is located on the outside and the agitator assembly (agitator shaft with blades) inside the digester. The height of the agitator shaft is determined by the pit height or the filling level of the digester. Ideally, the paddles should end with the fill level or protrude by up to 15 cm to guarantee thorough mixing. The RT-PRW is available in different sizes to suit different pit heights.

When using the RT-PRW in a digester with feeding system, the Varibull (RT-PRW) paddle agitator is ideally installed directly to the left or right of the feeding system. This assures that the freshly introduced substrate is instantly mixed in with the digester content. To optimally adjust the flow direction, the RT-PRW is available with two different senses of rotation, either left or right.

Our RT-PRW can be installed in digesters of different heights. The base model for digesters and post-digester is always the same.
Only the design of the inside supports and the length of the paddle arms are different.
Depending on the control type, the flow direction of the substrate can be changed. Left and right paddle sets are installed for different flow directions.

Control - Operated through an on-site control unit or the main biogas plant controller.

The RT-PRW is operated through an on-site control unit or the main biogas plant controller.
By default, the RT-PRW is delivered without a control unit.
It has to be installed on-site by a qualified electrician to be operated through a three-phase soft starter.

We optionally provide a ready-to-operate switching cabinet with the corresponding components.

Extensions of the paddle agitator Varibull

control cabinet and sound protection
control cabinet and sound protection
  • RT-PRW in explosion-proof design
  • sound protection hood for the drive of the RT-PRW to reduce the sound level
  • control cabinet to operate the RT-PRW

Technical data RT-PRW agitator

Agitator weight: approx. 1900 kg
Dimensions: length 7900 mm, width 4300 mm
height (depends on vessel height): 4600, 5420, 6420 or 7160 mm
Plant components
Drive: electric motor with three-stage planetary gear
Power rating: 15 kW
Output speed: 965 rpm
Agitator shaft speed: 10 rpm
Electrical connection: 400 – 690 V AC, 50 Hz

Technical data Digester

Substrate temperature: max. 55°
pH value of substrate: 6-8
Maximum dry matter content of substrate: 15 %
Min. fill level in digester: The agitator shaft must be fully immersed in the substrate
Max. fill level: 10-15 cm above the paddle
Ideal fill level with concrete roof: 40-60 cm below upper vessel edge
Ideal fill level with wooden roof: 60-80 cm below upper vessel edge

Technical data Operating unit (controller)

Electrical connection: 400 V AC, 50 Hz

Downloads for the paddle agitator Varibull

01 RT PRW DB 002 01 RT PRW Paddle agitator EN art 2020 03 30.pdf
101 003 03 BRO RT PRW EN KD.pdf
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