OKTOP® series

Decades of experimental, design and operational activities have resulted in a large numberof separate reactor solutions as well as proven design elements and principles, which have now been launched as the generally applicable OKTOP® Reactor Series.

In most cases, a proven reactor solution (OKTOP® Reactor Series 1000-5000) can be selected for a given processing task. In very demanding cases, however, we use more specific design approaches (OKTOP® Reactor Series 9000) based on fluid dynamical analysis, and develop the individual reactor solution to fulfill your process requirements.

OKTOP® Reactors have been successfully applied in treating solid-liquid, gas-liquid, gas-liquid-solid and liquid-liquid systems for leaching, precipitation, crystallization, oxidation, reduction and solvent extraction. Process requirements are met by configuring reactor design elements such as the agitator, tank design and baffles.

OKTOP 1000

OKTOP® 1000


  • Multipurpose agitator
  • Moderate agitation intensity
  • Good compromise between macro and micro agitation
  • Very wide application range due to high configurability and infallible functioning
  • Selected when process results are gained through moderate agitation
  • Number of references and secured functions economic drivers to customer

Case: Iron removal, Zhuzhou Smelter Group, China, 2008

Zhuzhou Zinc Smelter expanded its operations through direct leaching and solution purification processes designed by Outotec. A hydrometallurgical zinc process requires an iron outlet in order to control the iron concentration in the process solution. Zhuzhou iron removal is based on goethite precipitation.

The drivers for process optimization are iron content in the precipitate, oxygen efficiency and the total volume of the built reactor capacity. An optimization function was defined for each driver in laboratory tests. The flexibility of series 1000 allowed an impeller configuration that simultaneously obtained a clear maximum for each driver. Outotec provided the total solution, with both process and equipment guarantees.


OKTOP® 2000


  • OKTOP 2000Gas-liquid-solid agitator
  • High agitation intensity, especially in bottom region
  • Micro agitation generally higher than in 1000 series
  • High gas hold-up including increased gas retention time, excellent gas dispersion and dissolution, abrasive mixing
  • Selected when the gas dispersion rate is the limiting factor of the reaction rate
  • Smaller reactors possible due to high gas utilization rate
  • Process examples: iron oxidation, lean H2S precipitation, nickel matte leaching


Case: Nickel matte leaching, Norilsk Nickel Harjavalta, Finland, 1995

Following the expansion and refurbishment of the Harjavalta nickel plant, its leaching reactors were replaced with new technology. The initial reason for the replacement of old reactors was that they provided no control over the leaching rate or oxygen consumption. The new OKTOP® 2000 Reactors were designed to fulfill challenging dispersion duties in three-phase conditions – gas, liquid, and solid.

The new approach enabled the optimal adjustment of the leaching rate and oxygen consumption for different feed rates by gas flow rate and impeller rotation speed. A positive side effect of using a series 2000 reactor was the 50%reduction in the average nickel content of the leach residue. Another impressive improvement was achieved in iron removal efficiency, and the suppression of hydrogen gas liberation regarding the electric furnace matte.


OKTOP® 3000 

OKTOP 3000Benefits

  • Low shear agitator
  • Low agitation intensity
  • Micro agitation near blades and lower compared to 1000 series
  • Excellent low shear properties and selfsupporting, non-expensive structure
  • Selected when suspending solids is the critical design criterion
  • Lower operation costs due to lower energy requirement
  • Process examples: cobalt and nickel precipitation, lime milk preparation, pulping processes and large-scale effluent treatment

Case: Neutralization, Talvivaara Mining Company, Finland, 2008

The Talvivaara nickel mine handles high capacities of process effluent. The process applies a so-called high density slurry neutralization, in which optimal performance requires a certain precipitation reactor type. The high flow capacity required was beyond the range of the optimal agitator type usually used. Thus, a new type of agitator was developed by combining the energy distribution of series 4000 and the scalability of series 1000.

In bench marking tests, this new 3000 series reactor proved to have outstanding energy efficiency and mechanical stability compared to the original one. The new arrangement provided 50% savings in installed power.


OKTOP® 4000

  • OKTOP 4000Helical agitator
  • Low agitation intensity
  • Uniform micro agitation in reactor volume, micro agitation lower than for 1000 series
  • Efficient mixing, applicable to highly demanding viscous slurries, uniform energy distribution, enable effective control of process performance, suppress scaling
  • Low shear and low intensity agitation prevents the break-up of precipitated or flocculated particles
  • Selected when uniform and non-abrasive mixing is the critical design criteria
  • Better product recovery in terms of quantity and quality, lower OPEX due to lower consumption of flocculants and lower filtration costs
  • Process examples: high density slurry precipitation, gypsum precipitation, mixing-settling processes


Case: Effluent treatment, Outokumpu Tornio Works, Finland, 2000

Twenty years of process and equipment development during three expansions of the Tornio steelworks' pickling acid treatment facilities resulted in outstanding process solutions, including a new, very innovative helical agitator and precipitation reactor. Compared to an old lime neutralization line, the 4000 series reactors improve the lime neutralization process significantly. This is achieved through the outstanding solid separation capacity of the hydroxide sludge produced, and significantly reduced maintenance costs due to minimized gypsum scaling.

Uniform mixing prevents shear and energy intensity peaks, which minimizes the breakage of precipitated or flocculated particles and thus provides optimal particle size distribution, a high settling rate and good filtering properties in the disposed solids. Moreover, the high volume of the effective mixing region of the helical agitator restricts the reactor vessel-scaling layer to a few percent of the reactor diameter.


OKTOP® 5000

  • Vertical fluid flow agitatorOKTOP 5000
  • Extremely high agitation intensity
  • Micro higher than macro when compared to 1000 series
  • Maximal agitation power, excellent solids suspension properties
  • Selected when particle diffusion limits overall leaching rate
  • Lower operating costs due to lower grinding and filtration costs in easier applications, capable of enabling commercially viable
    leaching yields for severe applications
  • Process examples: chalcocite, chalcopyrite and HydroCopper® leachin


Case: Chalcocite leaching, Inmet Mining Cobre Las Cruces works, Spain, 2009

Thanks to the copper recovery ratio of the OKTOP® 5000 Reactors Cobre las Cruces S.A. selected Outotec to supply a new atmospheric direct leaching process. To ensure the high yields, low operating costs and the fl exibility Cobre Las Cruces required, Outotec built its very own miniature copper plant in the laboratory. This exceptional scale model proved the success of the new atmospheric leaching process beyond all doubt. The start-up year of Cobre Las Cruces plant is 2009.


OKTOP® 9000

OKTOP 9000The OKTOP® 9000 series reactors are tailor-made for special process requirements that cannot be met by the generally applied elements of the OKTOP® Reactor Series 1000–5000. An example of such a single-focused solution is the zinc concentrate leaching reactor, applying a double-duty agitator and draft tube. The oxygen mass transfer and leaching rate achieved in 900 m3 reactors make zinc concentrate leaching economically attractive in atmospheric conditions. The atmospheric zinc direct leaching process was first commercialized in the Kokkola zinc plant in 1998.


  • Single/special application agitator and/or tank
  • Specially designed for its application, novel approaches possible
  • Selected when no other options are viable
  • Agitation intensity, benefits and economic drivers to customer depend on application
  • Process examples: zinc concentrate direct leaching, cadmium precipitation