Reliably and Consistently Measuring Green Liquor Density in the Paper Mill

Paper mill green liquor density measurement system
Paper mill green liquor
density measurement system.
Green liquor is the dissolved concentration of sodium sulfide, sodium carbonate, and other compounds from the recovery boiler in the paper making process. Measuring its density is a critical component for the quality of the paper production.

The difficult scaling associated with green liquor results in an optical coating on the refractometer sensing head. If this scaling can be controlled to allow an acceptable duration of on-line measurement, and then effectively removed when coating occurs, the accuracy of the refractometer can be fully utilized with minimal maintenance. The primary issue then becomes the maintenance required to keep the cleaning system operating effectively. 

Using inline refractometers with accompanying heated high-pressure water cleaning systems provides excellent results in effective removal of optical coatings by reducing thermal changes, minimizing maintenance, and allowing for a reliable measurement source for on-line automatic control.

The Electron Machine MPR EScan is used to measure the green liquor dissolved density, or TTA, at two stages in the process: after the green liquor dissolving tank and after the green liquor clarifier. The in-line measurement, with the refractometer sensing head installed directly in the main process lines, allows real-time control of green liquor dilution to meet target TTA set-points. The measurement is also used to indicate (and prevent) excessive green liquor density and the resulting dangerous impending crystallization within the dissolving tank.
Paper mill green liquor density measurement system MPR Escan
Electron Machine MPR Escan

Reducing the variation of green liquor solids by automatically controlling weak-wash dilution with the MPR E-Scan refractometer results in a reduction in scaling. Scaling issues are further reduced when pressurized water, heated to the process temperature, is used to effectively clean the refractometer optical components. The compound result is beneficial for both control and maintenance.

For more information, visit www.electronmachine.com or call 352-669-3101.

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