As environmental regulations tighten, pulp and paper mills are striving to reduce fresh water consumption and environmental impact by increasingly closing the water system. Better process management and reduced variability also contribute to improved runnability while reducing the impact on the environment. Better control of the paper machine disc filters and presses reduces longterm variations in the process. Disc filter malfunctions and disturbances, causing MD ash variations, are among the most frequent sources of runnability problems.
Valmet LC – the new generation

Valmet LC is an optical consistency transmitter, in a new generation of transmitters from Valmet. It’s based on the measurement of light polarization and attenuation, and it replaces the famous smartLC. Compared to traditional optical consistency measurements, the biggest advantage is that this technique is independent of pulp color and brightness variations. Ash fluctuations have some impact on measurement accuracy, but even this effect is minimized with the polarization method compared with other optical singlesystem measurements. The measurement of light polarization is a well known, reliable technique that gives excellent accuracy. For screened pulps the method is suitable for consistencies from 0 to approx. 2.0 % Cs.

Headbox and white water application
Low consistency measurements are an essential element in the wet end process management concept. On slower paper machines where the stock contains no ash or the ash percentage is relatively stable, the Valmet LC can be used for total consistency measurement in the short circulation, both headbox and white water.

Disc filter

Reliable disc filter optimization requires accurate consistency and flow management. Valmet LC is the solution for the feed consistency control, as well as measurement of filtrate quality. Reliable measurements and accurate controls contribute to the stabilization of solid content of filtrates in the long circulation loop. This reduces basis weight variations in the machine direction and enables the increasing use of filtrate to replace fresh water in the process

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