ANDRITZ pre-evaporator

In some kraft mill chemical recovery operations, it is necessary to process low-solids liquors or effluents prior to the main evaporation plant. ANDRITZ provides pre-evaporator systems for these situations.


When spent cooking liquors and mill effluents have such a low dry solids content that it would not be efficient to send them directly to the main evaporation plant, these liquors and effluents can be pre-evaporated to raise the solids to the correct level for evaporation.

Energy-efficient pre-evaporation

ANDRITZ pre-evaporators process these low-solids streams with minimal energy consumption while maximizing plant availability and condensate quality. Pre-evaporators use tested and proven lamella heating surfaces. This allows the use of multiple various heat sources, even inside the same unit, and enables the selection of the most energy-efficient process connection.

Non-foaming design

Low vapor velocities inside the evaporator, low shear rates, and the free flow falling film construction are advantages of the ANDRITZ design in minimizing foam creation. This is especially important in MVR evaporators, not only to maximize the production of clean condensate, but also for protection of the compressor or fan.

Non-plugging design

Uniform liquor distribution of the liquor over the lamellas, and the continuous redistribution of the liquor created by the dimpled shape of the lamella surface, ensure a completely wetted heating surface and eliminate local scaling or over-concentration of liquor. The lamella heating surface ensures that water-soluble scaling can be washed away by a simple dilution wash, eliminating the need for time-consuming and costly outages for cleaning.

Cleanest condensates

Highly efficient condensate segregation in the evaporator ducts and lamellas, plus the integrated stripping of foul condensate fractions, produce clean and re-usable water. Methanol in the liquor is separated from the condensate and recovered as an auxiliary fuel in an ANDRITZ methanol liquefaction system.


  • Maximum energy-efficiency
  • Ability to utilize existing secondary heat sources
  • Lowest steam and electricity consumption
  • Inherently non-plugging and non-foaming
  • Clean condensates

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