Measurement of pH of Leachate in Zinc Hydrometallurgy and Air Jet Cleaning to Prevent Scaling

Download (277 KB)


Electrolytic Zinc Manufacturing Process

Electrolytic Zinc Manufacturing Process

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 analyzer with air jet cleaning system provides continuous cleaning and therefore can reduce maintenance frequency to once every one or two months.

Expected Benefits

  • Ensures stable and continuous pH measurement
  • Reduces operating costs
  • Eliminates manual cleaning work by hand

Process Overview

4-wire pH Measurement System with Jet Cleaning SystemRoasted 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.




Solution Details


Measurement system

4-wire pH measurement system (with jet cleaning system)

PH450G 4-wire pH/ORP converter
Power supply: 90 to 264 V AC, 50/60 Hz
Power consumption: approx. 15 VA
Submersion holder
Air for jet cleaning  
Air pressure: 200 to 400 kPa
Consumption: 100 to 300 Nl/min


  • Continuous air jet cleaning
    Since the leachate is a strongly acid solution, its pH value is not affected by air cleaning. This allows measurement and cleaning simultaneously.
  • Other applications
    This cleaning system can be used for other smelting processes of copper, manganese, sadmium, etc.

Field Data

Process condition

Measurement point: Leachate in the dissolving tank
Temperature: 80°C
pH value: pH 1.5 ± 0.2
Zinc: Approx. 160 g/l
Sulfuric acid: 2 to 3 g/l
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.


Zugehörige Produkte & Lösungen

2-Leiter-Analysator FLXA202/21

Die Analysatoren der FLEXA-Serie werden für kontinuierliche Online-Messungen in industriellen Anlagen verwendet. Mit der Option für die Ein- oder Zwei-Sensor-Messung sind sie die flexibelsten 2-Leiter-Analysegeräte auf dem Markt.

2-Wire 24VDC Transmitter / Analyzer DO202

This loop-powered analzyer is designed for both ppm and ppb dissolved oxygen measurements, suitable for both Pharmaceutical and Power Generation applications. HART, Foundation Fieldbus, and Profibus versions are available.

4-Leiter-pH/ORP-Analysator PH450

Der pH- und ORP-Analysator PH450 ist ein multivariabler Analysator, der pH- mit Temperatur- und ORP (Redox)-Messung kombiniert. Diese Messungen können über verschiedene Ausgangsfunktionen genutzt werden: zwei Stromausgänge, vier unabhängige SPDT-Kontaktausgänge und HART. 

Digitaler SMART pH/ORP-Universalsensor FU20F

Digitaler SMART-Kombinationssensor für pH und ORP nach dem Motto „einfach ist am besten“ mit eingebauter Intelligenz und direkter digitaler Kommunikation. 

pH/ORP-Universalsensor der Serie FU20/FU24/PH20

Die Universalsensoren PH20, FU20 und FU24 für pH und ORP (Redox) zeigen, wie Yokogawa das Motto „einfach ist am besten“ auf Sensortechnologie anwendet.

pH- und ORP-Analysatoren

Sensoren und Analysatoren für pH und ORP (Redox) werden zur kontinuierlichen Überwachung von pH- und ORP-Werten im Prozess eingesetzt, z.B. um die Wasser- und Produktqualität sicherzustellen oder um Abflüsse, Batch-Neutralisierung, Zellstoffbestand, Gaswäscher, Kühltürme, chemische Aufbereitung, Wasser- und Abwasserbehandlung und viele andere Anwendungen zu überwachen.

pH- und ORP-Sensoren

pH-Elektroden und -Sensoren sind die detektierenden Elemente bei der Messung des pH-Werts. Die verschiedenen Installationsoptionen schließen u. a. Wechsel-, Durchfluss- und Eintaucharmaturen sowie den direkten Einbau ein. Die richtige Auswahl von pH-Elektroden und Sensoren ist für optimale Messergebnisse von entscheidender Bedeutung.


Have Questions?

Contact a Yokogawa Expert to learn how we can help you solve your challenges.