Halland Instruments AS

Zinc production: pH analyzers for the neutral leaching process.

Applications in other industries:

[Zinc production]
[Nickel production, chlorine process]
[Fertilizer industry]
[Nickel production, HPAL process]
[Alumina production]
[Titanium dioxide pigment prod.]
[Wastewater treatment]
[Cobalt production]
[Electroplating industry]
[Froth flotation, ore benefication]

Process description:
Roasted zinc concentrate (calcine) is leached continuously in a string of five tanks.
The liquid flow into the first tank is a mixture of spent acid and overflow from the jarosite thickener. Oxygen is used for the oxidation of iron. This process is also a purification process. Accurate pH control is essential for a good result.
The first three tanks have screw feeders for adding calcine and the pH values are automatically controlled by three independent control loops.  The controller outputs goes to the variable frequency drives for the electric motors on the screw feeders.

pH range: 1 - 5 pH
Solid content: 30-50 g/l. Temperature: 75 -  85 C. Flow: 250 m/h. Tanks: 5 tanks each with a capacity of 200 m. Number of pH analyzers: 7

Neutral leach

NL-string, 5 tanks of 200 m, the analyzers are mounted in the container with the blue door.

Neutral leach seven analyzers

The seven pH analyzers are mounted indoors, in Norway we have cold winters with strong winds and heavy rain and snow.

Neutral leach feeder

Screw feeder with electric motor for adding calcine.

Trend picture:
7 pH analyzers, last 8 hours. The calcine is added in tank 2 and 3, not in tank 1.

Neutral leach trend picture

The analyzer faceplate on the Delta V process computer system at the Boliden Odda zinc plant.

Neutral leach faceplate