Increasing process efficiency while reducing maintenance costs in paper

Vortex flowmeter enables reliable and accurate flow measurement in paper mill, reducing downtime, lowering production costs and enhancing safety

BillerudKorsnäs has improved its pulp digester process efficiency and reduced maintenance costs at its paper mill in Gävle, Sweden by installing a Rosemount® 8800 Vortex flowmeter from Emerson Process Management. The accurate and reliable flow measurements provided by the new meter have reduced downtime and lowered production costs.

With over 1500 customers in 100 countries, BillerudKorsnäs is a world-leading manufacturer of strong primary fibre-based packaging material. The mill had previously used a magnetic flow meter to measure the flow of white liquor used in a pulp digester. This technology is frequently used for this type of application; however, it was unsuccessful in this case because the flowmeter was occasionally subjected to a significant vacuum that partially collapsed the liner. This caused the magmeter to read a higher flow rate, resulting in too little alkali input which reduced digester performance. As the process could not be stopped outside the scheduled shutdown period, it was not possible to replace the meter immediately.

"When the flow measurement was inaccurate, unreliable, or completely failed, the alkali-to-wood ratio could not be accurately controlled," said Peter Hallenberg, Project Leader Process Automation, BillerudKorsnäs. "Replacing the meter tied up our maintenance team and incurred a cost of about •3,400 per unit. We needed an accurate and reliable measurement device for this challenging application."

Since the pulp digester is a critical part of the production process, the company tried other technologies to overcome these issues including using an ultrasonic flowmeter. However, this trial proved to be unsuccessful as the solids and fibres in the liquor would build up on the meter walls, causing unpredictable flow readings.

The mill solved this flow measurement challenge by installing a Rosemount 8800 Vortex flowmeter, which is not affected by the high liquor temperature, vacuum, coating, or suspended solids in the flow.

Vortex flowmeters are not typically considered for this application, as the fluid contains solids and fibres that would clog the crevices and ports common to traditional vortex flowmeters, impacting the meter performance. However, the unique design of the Rosemount 8800 Vortex eliminates crevices and ports and thus eliminates the risk of clogging. In addition, the 8800 is balanced so it is not affected by vibrations in the pipes that are typical in mill applications. The resulting flow measurement is accurate, stable and reliable.

For BillerudKorsnäs, the more accurate flow measurements translated to more consistent pulp quality and a lower cost per tonne of pulp. The mill has also reduced maintenance costs by eliminating the need to remove and clean the failed flowmeter. 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 enabled BillerudKorsnäs to detect that a decrease in the flow reading was being caused by progressive plugging of the heat exchanger. Operators are now able to proactively take corrective action, increasing process efficiency.

"Emerson’s flowmeter has been working reliably for two years with no downtime for cleaning or repair," Hallenberg added. "The accurate and reliable flow measurements provided by the Rosemount 8800 Vortex flowmeter have improved pulp digester process efficiency. In addition, process availability has increased and maintenance costs reduced."