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| Industry | : Metals and Mining | | Product | : pH/ORP Meter |
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Measurement of pH of Leachate in Zinc Hydrometallurgy and Air Jet Cleaning to Prevent Scaling
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Most zinc are produced at hydrometallurgically, where a high-grade
zinc product can be obtained and valuable metals mixed
in the raw material can be recovered. In the hydrometallurgy, the
raw material of zinc concentrate is roasted and then dissolved in
sulfuric acid to remove impurities. The process called leaching
and pH control of the leachate is important. The leachate
contains gypsum and impurities that may cause scaling on
electrodes. As a result, it interfered with stable pH measurement
and required frequent cleaning at least once a week. A pH meter
with air jet cleaning system provides continuous cleaning and
therefore can reduce maintenance frequency to once every one
or two months.
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Ensures stable and continuous pH measurement |
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Reduces operating costs |
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Eliminates manual cleaning work by hand |
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Roasted concentrate sent from a roasting furnace, is dissolved in diluted sulfuric acid (spent electrolyte) in a dissolving tank.
ZnO + H2SO4 -> ZnSO4 + H2O
In addition, some iron and other material contained in the calcine are dissolved. Therefore, these impurities are removed by
precipitation by adding manganese, lime or other additives.
FeO + Additive -> Fe2O3 (precipitation)
pH control is important to allow zinc to dissolve fully and impurities to precipitate maximally. The leachate is filtered by a filter press to
remove impurities and the filtrate is fed to an electrolytic bath where zinc is electrolytically produced. |
| Measurement system |
| 4-wire pH measurement system |
| (with jet cleaning
system) |
| Sensor |
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KCl refillable pH sensor (Teflon liquid junction) |
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PH8EFP-☐☐-TN-TT1-N-T*A/TF |
| Holder |
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Submersion type holder with jet cleaning system |
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PH8HS-PP-☐☐-T-JT-JP*A/MS3 |
| Terminal box (when needed) |
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PH8TBG*A |
| 4-wire pH converter |
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PH400G-☐-EA*B |
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| PH400G 4-wire pH converter |
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Power supply: |
88 to 132/176 to 264 V AC, 50/60 Hz |
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Power consumption: |
approx. 8.5 VA |
| Submersion holder |
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Air for jet cleaning |
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Air pressure: |
200 to 400 kPa |
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Consumption: |
100 to 300 Nl/min |
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| Notes |
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Continuous air jet cleaning |
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Since the leachate is a strongly acid solution, its pH value is
not affected by air cleaning. This allows measurement and
cleaning simultaneously. |
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Other applications |
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This cleaning system can be used for other smelting
processes of copper, manganese, sadmium, etc. |
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Process condition
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Measurement point: |
Leachate in the dissolving tank |
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Temperature: |
80 °C |
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pH value: |
pH 1.5 ± 0.2 |
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Zinc: |
Approx. 160 g/l |
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Sulfuric acid: |
2 to 3 g/l |
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Lime: |
Saturated |
Before air jet cleaning system was introduced, the cleaning work
by hand had been required at least once a week. Continuous air jet
cleaning using the submersion holder with jet cleaning system, has
reduced the maintenance frequency to once a month or two months.
To ensure stable measurement, the pH sensor uses a Teflon liquid
junction, where the KCl outflow is higher than that of ceramic
junction. |
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Measurement of pH of Leachate |
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