Articles & Case Studies

Emerson’s high performance pH sensors help reduce costs and achieve environmental compliance for Umicore, Belgium

Posted: Monday 7th December 2009

Emerson Process Management pH sensors have been implemented by Umicore Precious Metals Refining (UPMR), to monitor waste water at its Hoboken plant near Antwerp, Belgium. Emerson’s Rosemount Analytical PERpH-X 3400HTVP high performance pH sensor, together with the Model 1056 liquid analyser, are providing a highly accurate and reliable solution that enables the company to meet environmental regulations related to the pH of water being discharged.

Umicore Precious Metals Refining recycles and refines precious metals and other non-ferrous metals from a wide range of complex industrial intermediate materials. This includes precious metal bearing scrap from applications such as electronic, photographic and catalytic processes.

Umicore was experiencing problems with the existing equipment used to measure the pH levels of its waste water produced during the recycling process. The waste water 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 whilst 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 which should have been recovered and added costs due to the need for water to be reprocessed.

Umicore had tried alternative pH sensors from many different suppliers but each produced similar results. Following a discussion with Emerson engineers, Umicore 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.

“The Emerson demonstration was impressive,” said Randy Verbeeck, Maintenance & Service Engineer, Umicore. “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 over 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 superior performance in the most aggressive fouling applications. Most pH measurements fail due to fouled or poisoned electrolytes and clogged reference junctions. The PERpH-X sensor family features an enhanced double junction electrode that excels in harsh applications, and 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 dramatically extend the life of the sensor by minimising the depletion or poisoning of the primary reference.

“Emerson’s pH sensors have been installed for over five weeks,” added Ludo De Vogelaer, Maintenance & Service Engineer, Umicore. “During this time we haven’t needed to refill the sensor’s electrolyte, further reducing maintenance requirements and costs."

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

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