Billerudkorsnäs improves efficiency, cuts maintenance costs 19 April 2013

BillerudKorsnäs says it has improved pulp digester process efficiency and reduced maintenance costs at its paper mill in Gävle, Sweden, since installing a Rosemount 8800 vortex flowmeter.

Peter Hallenberg, project leader for process automation at BillerudKorsnäs, explains that the fibre-based packaging material manufacturer had been using a magnetic flowmeter to monitor white liquor.

Although often used for this type of application, it was unsuccessful, because the flowmeter was occasionally subjected to a significant vacuum that partially collapsed the liner. This caused the mag meter to read a higher flow rate, resulting in too little alkali input, which impacted digester performance.

"When the flow measurement was inaccurate, unreliable or completely failed, the alkali-to-wood ratio could not be accurately controlled," states Hallenberg.

"Replacing the meter tied up our maintenance team and incurred a cost of about SKR3,400 per unit. We needed an accurate and reliable measurement device for this challenging application," he adds.

Plant engineers tried other technologies, including an ultrasonic flowmeter. However, this trial again proved unsuccessful, as the solids and fibres in the liquor built up on the meter walls, causing unpredictable flow readings.

Howerver, installing Emerson's Rosemount 8800 Vortex flowmeter – which is not affected by the high liquor temperature, vacuum, coating, or suspended solids – solved the problem, even though these devices aren't recommended for such applications, because of entrained fibres that would clog crevices and ports common to traditional meters.

The Rosemount 8800 vortex meter only works here because it was designed to be crevice- and port-free, so there is no clogging risk. In addition, since the 8800 is balanced it is not affected by the pipe vibrations typical in mill applications.

For BillerudKorsnäs, the more accurate flow measurements have translated to more consistent pulp quality and a lower cost per tonne. The mill has also reduced maintenance costs by eliminating the need to remove and clean failed flowmeters.

This has also enhanced safety at the plant, because operators no longer need to maintain faulty equipment.

In addition, the reliability of the vortex flowmeter has already enabled BillerudKorsnäs to detect that a decrease in the flow reading was being caused by progressive plugging of its heat exchanger. Operators are now able to proactively take corrective action, so further increasing process efficiency.

"Emerson's flowmeter has been working reliably for two years with no downtime for cleaning or repair," enthuses Hallenberg.

"The accurate and reliable flow measurements have improved pulp digester process efficiency. In addition, process availability has increased and maintenance costs reduced."

Brian Tinham

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Emerson Process Management

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