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Emerson Process Management pH sensors have been implemented by Umicore Precious Metals Refining (UPMR) to monitor wastewater at its Hoboken plant near Antwerp, Belgium.

Emerson Rosemount Analytical PERpH-X 3400HTVP high-performance pH sensor and the Model 1056 liquid analyser are providing an accurate solution that enables the company to meet environmental regulations related to the pH of water being discharged.

UPMR recycles and refines precious metals and other non-ferrous metals from a range of complex industrial intermediate materials.

This includes precious metal bearing scrap from applications such as electronic, photographic and catalytic processes.

The company was experiencing problems with the existing equipment used to measure the pH levels of its wastewater produced during the recycling process.

The wastewater contains traces of sulphuric acid and chlorides and metal compounds, which fouled the glass and attacked the reference electrode in the pH sensor, resulting in incorrect measurements.

Sensors were typically lasting only two or three days in these harsh operating conditions and the costs associated with purchasing, installing and calibrating replacement units were significant.

It was also necessary to revert to manual checks during the downtime while sensors were replaced.

Whereas the pH sensor would be continuously monitoring the water, the manual checks were only carried out every two hours; this meant that operators were much slower to react to any out-of-range measurements.

This could result in lost revenue from precious metals that should have been recovered and added costs as a result of the need for water to be reprocessed.

Following a discussion with Emerson engineers, UPMR asked for a demonstration of the Rosemount Analytical PERpH-X 3400HTVP high-performance pH sensor.

This was supplied with a poisoning resistance kit, which is specifically designed to protect sensors in challenging poisoning applications.

Randy Verbeeck, maintenance and service engineer at UPMR, said: ‘The PERpH-X sensor was combined with a Model 1056 liquid analyser, which was very easy to use.

‘Following calibration, the sensor has been working continuously for more than five weeks now without a problem and it is expected to have a life of between two and three months.’ The PERpH-X 3400HTVP high-performance pH sensor features advanced technologies for performance in aggressive fouling applications.

Most pH measurements fail because of fouled or poisoned electrolytes and clogged reference junctions.

The PERpH-X sensor family features an enhanced double-junction electrode that is claimed to excel in harsh applications.

The specially designed porous Teflon liquid junction has a large surface area to maintain a steady reference signal in dirty and fouling applications.

Custom solution kits further optimise the performance of the PERpH-X sensors by protecting the porous Teflon reference from coating and the electrolyte from fouling.

These are available to address high temperatures, bio-film resistance, poisoning resistance, oil resistance, scaling resistance and metals resistance.

Each kit contains a treated porous Teflon reference junction and a specially formulated electrolyte to extend the life of the reference electrode in its targeted application.

The outer reference electrolyte can be recharged using a gel-filled syringe supplied in the various solution kits.

Replacing a clogged junction or recharging the electrolyte will rejuvenate most failed sensors.

Proper preventative maintenance can extend the life of the sensor by minimising the depletion or poisoning of the primary reference.

Following the successful results of this installation, a further PERpH-X sensor has been added to the secondary section of the wastewater treatment at the plant and UPMR is also considering using a PERpH-X sensor for a difficult application at its Heusden-Zolder plant.

Emerson Process Management

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