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Valmet Cooking Liquor measurement for continuous digester

Alkali meters in different circulations help operators to predict residual alkali and make necessary adjustment by white liquor additions

 

 

Clarified white liquor (Position 1)

Continuous white liquor alkali concentration is measured to adjust the amount of white liquor that is fed to the process. With continuous measurement it is possible to take into account possible changes in the liquor concentration to achieve uniform pulp quality. 

 

Correlation between AA in-line analyzer value and laboratory value. Click in the image to enlarge.

 

Transfer circulation (Position 2)

The quality of woodchips effect on how fast the alkali is used by the chips. To achieve stable Kappa it is important to have correct and stable amount of free alkali in the digester. Valmet cooking liquor meter is installed in the transfer circulation between impregnation and the digester. The measurement is used to control the white liquor dose to impregnation and transfer circulation. 

 

Correlation between laboratory sample analysis and analyzer in-line measurements.

 

Residual Alkali measurements (Positions 3 – 6)

Valmet cooking liquor meters are used to control the residual alkali in black liquor. If the alkali content is too low, lignin is re-absorbed back to cellulose fibers. Continuous measurement signal means superior pulp quality with minimum dead load in the process.

Valmet Cooking liquor meters are used to control the residual alkali of black liquor going to evaporation plant. Too low free alkali concentration can be a cause of blocking issues in the evaporation plant. Too large alkali dose increases the dead load in production.