Central Mixer for Biogas Digesters

Central Mixer Agitator for Efficient Biogas Digestion

Verito’s Central Mixer Agitator is designed for installation at the center of biogas digester tanks to ensure uniform mixing, improved gas yield, and stable long-term operation.

The system enables complete homogenization of slurry, biomass, and organic substrates, ensuring optimal biological activity and energy production.

With CFD-optimized flow patterns and a heavy-duty design, it is ideal for large-scale digesters up to 10,000 m³ capacity.

 

 

 

Working Principle

 

  • Upper impellers break floating layers and crust
  • Middle impellers create bulk circulation
  • Bottom impellers prevent sedimentation
  • Creates complete vertical circulation loop
  • Ensures uniform digestion conditions
  • Improves overall gas production efficiency

 

 

Technical Specifications

 

Tank Volume 2,000 – 10,500 m³
Motor Rating 11 kW – 55 kW
Impeller Diameter Up to 5.0 m
Speed 10 – 30 RPM
Shaft Length Up to 20 m
Material Stainless Steel

 

 

Key Features

 

  • Suitable for high viscosity feedstock up to 17% dry matter
  • Hydrofoil impeller for efficient mixing
  • Gas-tight hydraulic shaft sealing system
  • Double taper roller bearing for durability
  • Freely suspended shaft design
  • Heavy-duty helical gearbox
  • Motor with frequency converter (optional)
  • PTC motor protection system
  • CE, ATEX, IECEx & PESO compliant

 

 

Operational Benefits

 

  • Maximizes biogas production
  • Ensures uniform mixing & digestion
  • Prevents sedimentation and crust formation
  • Energy-efficient operation
  • Low maintenance design
  • Long service life

 

 

CFD-Based Design & Flow Optimization

 

  • At Verito, the Central Mixer Agitator is designed using advanced Computational Fluid Dynamics (CFD) analysis to ensure optimal mixing performance inside the digester

 

 

CFD simulation enables visualization and validation of

 

  • Velocity distribution across the entire tank volume
  • Flow circulation patterns (top-to-bottom axial loops)
  • Dead zone elimination and complete volume coverage
  • Suspension capability for high solid concentration
  • Power optimization vs mixing efficiency
CFD in Mixing Technology
What is CFD ?

 

  • Computational Fluid Dynamics (CFD) represents an approved approach within the realm of fluid mechanics. Its widespread application is evident in industries such as automotive, aircraft, process, and mixing.
  • The primary objective of CFD is to address fluid flow-related inquiries by leveraging numerical techniques. The governing equations typically revolve around principles like Navier-Stokes, Euler, or potential-based equations.

 

Flow Simulation at Verito

 

  • Verito leverages cutting-edge Computational Fluid Dynamics (CFD) technology, alongside laboratory experiments and field trials, to design, scale-up, enhance, or modernize agitators and mixing systems.
  • Verito’s engineers utilize CFD technology to gain an in-depth understanding of velocity distribution, flow patterns, areas with low velocity (referred to as dead zones, as illustrated in Figures 1, 2 & 3), as well as regions with both low and high shear rates within various mixing system configurations.
  • This enables the testing of multiple system setups and tank agitator designs to achieve optimal performance. Additionally, CFD technology aids Verito in fine-tuning impeller blade designs to strike a balance between power requirements and pumping capacity.

 

Key Outcomes of CFD-Studies

 

  • In-depth Information of Flow pattern
  • Areas with the potential of low mixing intensity can be pinpointed and rectified.
  • Availability of crucial process parameters like shear and energy dissipation
  • Evaluation of different design options
  • Shortened project timelines for complex process mixing systems
  • Mitigation of project risks