Outokumpu Oy

Timo T Koivunen

Launo L Lilja

Bror G Nyman

Valto J Makitalo

Sigmund P Fugleberg

Markku T Saarela

Hannu J Pouru

Seppo I Blomquist

Kaj-Henrik Lindroos

The residual acid mixture containing metals which has been produced in the steel pickling process is regenerated to become new HF/HNO.sub.3 pickling acid by applying H.sub.2 SO.sub.4 addition and evaporation. The metal sulphate salt produced in evaporation is converted into scarcely soluble iron jarosite Na[Fe.sub.3 (SO.sub.4).sub.2 (OH).sub.6 ] and chrome and nickel hydroxide, the last mentioned metal hydroxide being obtained as a separately utilizable precipitate. The metal sulphate salt is separated from 60% H.sub.2 SO.sub.4 solution, wherein the main part of the salt is also crystallized. For promoting the crystallization, part of the salt is crystallized in a side line where 80% H.sub.2 SO.sub.4 concentration is used. The acid slurry produced is carried back to the crystallizing stage in the main line.

Method for regenerating pickling acids

An immersion evaporator is disclosed having, connected to its evaporation vessel, a pipe for feeding a solution to be concentrated by evaporation into the evaporation vessel, a riser pipe for withdrawing the concentrated solution and any crystals from the evaporation vessel, a pipe for withdrawing flue gases and vapors from the evaporation vessel, and an immersion pipe extending vertically inside the evaporation vessel, the upper end of the immersion pipe being connected, by means of an angle joint piece to the outlet of the combustion chamber, there being at the opposite end of the combustion chamber, a burner for liquid or gaseous fuel, the burner having a cylindrical combustion gas turbulence chamber for an oxygen-bearing combustion gas, at one end of which there is a substantially tangential combustion gas inlet conduit and a fuel dispersion pipe extending coaxially into the turbulence chamber, the opposite end of the turbulence chamber being convergent. The tangential combustion gas inlet conduit is connected to a mantle which surrounds the burner and the combustion chamber, there being, at the opposite end of the mantle, a fuel inlet conduit for preheating the fuel, and the convergent end of the turbulence chamber continues into the combustion chamber as a cylindrical leveling conduit coaxial with the turbulence chamber, and the fuel dispersion pipe has at least such a length that it extends to the distance defined by the formula ##EQU1## from the inner end of the leveling conduit, in which formula H is the distance between the inlet end of the leveling conduit and the dispersion pipe, .alpha. is the andle of convergence of the opposite end of the turbulence chamber, d is the outer diameter of the dispersion pipe, and D is the inner diameter of the leveling conduit.

Immersion evaporator

Growing community of inventors

Ulvila, Finland

Timo T Koivunen