Lake Garda paper mill adds Emerson meter
30 Jun 2011
Lake Garda, Italy – Cartiere del Garda is using a density meter from Emerson Process Management to accurately measure the concentration of kaolin and other additives in the coating process at its paper mill on the banks of Lake Garda.
The Micro Motion 7845 density and concentration Meter was installed to provide more accurate density measurements under entrained gas conditions.
“The highly accurate measurement of the coating mixture concentration … means we have been able to discontinue the use of expensive additives,” said Fulvio Prati, instrument manager at Cartiere del Garda. “This has enabled significant annual savings and paper quality is improved.”
Cartiere del Garda operates one of the most modern paper mills in Italy, specialising in high quality coated papers.
For years, a Micro Motion Coriolis flowmeter was used to monitor the concentration of the paper coating mixture and this provided reliable and accurate results.
However, because the recirculation system on the feeding tank generated entrained air, it was necessary to add expensive additives to the coating mixture to prevent quality problems.
Removing the additives would reduce production costs but would cause up to 20% air to be entrained in the coating mixture. The existing Coriolis flowmeter was not designed to provide the same degree of density measurement accuracy under these conditions.
Cartiere del Garda needed an on-line, solids concentration measurement of the coating solution, made directly at the film coater machine feed. A minimum accuracy of +/-1% of solids was required to guarantee the high quality of the paper being produced and avoid off-spec batches.
In chosing the Micro Motion meter for the application, Cartiere del Garda specified the advanced electronics, entrained gas version, which is designed to accurately measure density in aerated liquids - providing a final accuracy of better than +/- 0.5%.
The 7845 provides a 4-20 mA signal to the control system, related to line density. Density is converted into percentage solids using a formula embedded into the control system.
The straight tube, liquid density meter uses a vibrating tube to measure density. As the liquid density changes, it affects the vibrating mass of the density meter. The change in vibrating mass then affects the resonant frequency, which is inversely proportional to the density of the process fluid.
By monitoring the resonant frequency and applying well-known conversions, the 7845 provides highly accurate in-line density data.
