Mixing technology

For over 30 years Nakkilan Metalli Oy has successfully designed and manufactured agitators for various industries. We can offer proven mixing solutions and manufacturing of agitators.

Have a look into our cutting-edge knowledge.

Tailor-made solutions

Every process is unique and each mixer is designed for its specific purpose.

Long-term practical experience

With our extensive process and equipment know-how we can guarantee not only the mechanical function but also the result of the mixing process.

Turn-key projects

We can also deliver turn-key projects from design to installation.




Agitator design and manufacturing

Our mixing solutions and manufacturing expertise have been proven by satisfied customers throughout the world. We have delivered agitators for example to

  • Mining / hydrometallurgy industry
  • Pulp & Paper industry
  • Chemical industry and Biochemistry


  • Analysis of mixing processes
  • Optimized agitator designs
  • Process assessments
  • CFD simulations (Computational Fluid Dynamics)
  • Stress calculations of vessels and internals
  • Protective coatings for stirrers
  • Process & equipment upgrades and modernizations
  • Spare parts

+358 (0)2 537 3748sales@nakkilanmetals.com

Mint F-L Cascade

“MultiInteractive Flow-Loop” (MInt F-L) Reactor technology

The MInt F-L reactor is an example of a stepwise, during several decades minted technology. The Driving force for this technological development has been the hydrometallurgical need for even larger reactors capable to an economical treatment of vast amounts of metal containing slurries, for example such dumped at both old and new mine sites.

A typical MInt F-L reactor is implemented as a cascade consisting of three to five separate flow loops, each divided into separate vertical and horizontal parts. Marine type high flow propellers are used to generate a master flow loop throughout each cascade, which are joined together by short overflow channels. The propellers arrangement allows a massive down flow in the vertical section, which in turn allows a design, according to which a diameter 2..6m flow enters the horizontal section at a speed of 1,0..2,0 m/s.

According to preferred design, the vertical flow is split into two horizontal parts using symmetrical steep profile bottom slopes in the middle of the horizontal loop section, the volume of which can exceed that of the vertical section by more than 50 percent. Preferably, a case specific “marine type propeller mixing” is used to enhance both the general processing performance as well as the flow speed of both the horizontal and the vertical cascade sections. A successful marine type propeller approach has in this case required some guiding flow arrangements for the propellers of both the vertical and the horizontal flow sections.

As the process economics of a MInt F-L plant, the very size of a reactor cascade greatly decreases the volume wise investment costs as well as the operating costs. The reactor cascade volume, typically 5000…15000m3, can be designed to exceed 20000m3. The main explanation for good process economics is an advanced use of high performance marine type propellers, a development, which has required several technical pilot installations based on serious flow laboratory test efforts.


  • Suitable for oxidative leaching treating large slurry flows
  • Increasing manageable flow capacities
  • Alternative for conventional autoclave treatment
  • Increasing manageable slurry densities
  • Autogenous heat generation when treating sulphide slurries facilitating energy recovery
  • Facilitating process economy improvements

Key benefits

  • Enables a major increase of slurry flows to be processed resulting in a good process economy
  • Retrieving of liberated energy possible
  • Represents a major improvements of present leaching technologies
  • Maintains a throughout well-mixed slurry state at low power costs
  • Allows a high gas hold-up
  • Creates new processing alternatives (Cleantech etc.)

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“HPNP” High Pure Neutralization Process

The main target of the HPNP process is a complete removal of heavy metals from dilute aqueous waste streams was the main target. Most waste has its origin in pickling, where the steel strip draws out liquid films from the pickling baths themselves. This is true both for electrolytic pickling and mixed acid pickling, which is require washing of the steel strip to remove any pickling solutions adhering to the steel surface. One proportion of this water is also formed, when some of the electrolytic bath electrolyte is replaced by fresh sodium sulphate solution. This action prevents a too heavy build-up of metal hydroxide sludge and of hexavalent chromium. All solutions from the electrolytic pickling are pre-treated in a separate sulphur dioxide aided reduction process for a total reduction of their content of hexavalent chromium. A separate description of the sulphur dioxide aided reduction part of the HPNP process will be given as contextual to this main neutralization presentation.

Main achieved environmental benefits

Clean aqueous effluents are obtained. The improved performance and reliability of the HPNP process result in reduced emissions of the heavy metals to discharged water streams. The neutralization sludge, to which the metals report as hydroxides, is conditioned to inhibit any later oxidation of chromium to a toxic hexavalent state.


Neutralization is included as a separate process step in most hydrometallurgical processes in addition to wastewater treatment processes including neutralization of dilute stainless steel pickling solutions and mine waters. The HPNP process is applicable in all cases both in new and existing plants.

Mint B-M

Flow intense stirrers (FIntS) for Multi Interactive Back-Mixing(MInt B-M), Unit process specific MInt B-M advantages and Precipitation/crystallization

  • Uniform mixing throughout whole reactor volume using mixing intensity according to product quality requirements
  • Mixing by interaction of a set of ordered sub-streams resulting in a master flow configuration covering the whole reactor volume
  • Mixing energy consuming swirling, especially by small turbulence eddies, is avoided, hence the good end product (precipitate or crystals) quality control
  • Low mixing power
  • High reactor product capacity
  • Flexible reactor design and a free choice of stirrers including all modified FIntS stirrers
  • Improved options to master critical crystal or precipitate grain size or morphology options

Mint L-M

Flow Intense Propellers (FIntP) for Multi Interactive Loop-Mixing (MInt L-M) and Leaching including oxidation or reduction

  • MInt L-M enables a major increase of slurry flows to be processed resulting in a good economy of scale
  • Retrieving of liberated energy possible
  • Represents a major improvements of present leaching technologies
  • Maintains a throughout well-mixed slurry state at low power costs
  • Allows a high gas hold-up
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