Halland Instruments AS

Zinc production: Why use accurate and reliable pH analyzers in a zinc plant?

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]

Why use accurate and reliable pH analyzers in a zinc plant?

Accurate, reliable high performance pH measurements is a tool to increase production without increasing the energy costs, to get higher zinc yield and to reduce the consumption of additives. Precise pH control is required to produce zinc sulphate solution of high quality. If the zinc plant does not have good control of the pH values ​​in all the process steps then the average quality of the purified solution will be lower then with good pH control.
Purified zinc sulphate solution with low quality gives low current efficiency and lower production in the cell house. High current efficiency does not only reduce the energy costs but increases also the production capacity.
Most zinc factories have problems with unwanted "mishaps" that causes the leaching process to produce zinc sulphate solution unsuitable for electrowinning. Then the quality of the solution is so bad that the current efficiency falls far below normal. It becomes very difficult to get the zinc off the cathodes (stripping) and automatic stripping stations do not work properly. "The mishap" can be triggered by a mechanical problem, for instance that a tank must be taken out of production.

Then a chain of new events and wrong decisions leads to degeneration and worsening of the situation. The cause of the erroneous decisions is often that the operators do not know which pH values are in the processes because the zinc plant does not have enough pH measurements or because the pH measurements are wrong. The result is that the process is executed with incorrect pH values with disastrous consequences. Such "mishaps" causes major production losses and it may take several days before production is back up to normal levels after the "mishap". Accurate, reliable high performance pH measurements can reduce the number of such “mishaps”. Such “mishaps” are very costly and the prevention of one episode might actually be more than enough to pay for the number of accurate, reliable high performance pH analyzers needed.

 By using accurate, reliable high performance pH measurements the zinc yield is increased and the consumption of additives such as for instance zinc dust is reduced. Good pH control gives good quality of the solution and high current efficiency in the electrolysis and this provides a corresponding increase in production capacity. The number of "mishaps" with production losses can be reduced and this also provides increased production capacity. It is not possible to quantify the improvements that can be achieved because no zinc plants are similar, but usually the annual production can be increased by several percent.

In the zinc industry, the temperatures are high, the solids content is high, the solutions are complex with high ionic strength, the pH is in the range of 0.5 to 7 and most processes are precipitation processes. It is very difficult to measure the pH continuously under such conditions. There are many types of pH analyzers on the market, including systems with retractable electrodes. The problem is that none of these systems provides the accuracy and stability necessary for effective zinc production.
That is why we have developed pH analyzers specifically for the hydrometallurgical zinc industry.

The following properties distinguish our analyzer from other known technology:
1. High short-term and long-term accuracy.
2. Most reliable, infrequent error with the analyzer or the electrodes.
3. Other systems require calibration daily or even several times daily to provide high accuracy. Our analyzers have high accuracy even with weeks’ interval between calibrations.
4. Very low price compared to other on-line analyzers.
5. Low operating costs, long electrode life, low-maintenance and relatively long intervals between calibrations gives low total operating expenses.