Inline Color Measurement in the Pulp

In paper production, pulp is the first place where information about color is available. While the readings are not the same as on finished paper, a color shift in the pulp is an indication that there will be a color shift in the wet paper. With this process, the OBA can also be controlled.


Pulp color measurement can be used for:

  • Early identification of disturbances
  • Blending two lines of raw material (e.g. dark and light) to a constant level
  • Monitoring the color addition in a batch process
  • Control the addition of waste, without significantly changing the color of the total pulp
  • To visualize the homogenity of the pulp after dye edition

The color sensor ERX40 is mounted in a stainless steel housing

  • Measures directly into the thick pulp (concentration: 3 % to 5 %) through a bypass system.
  • Option EG50R: Thin pulp (about 1 % concentration) flows through a bypass to the instrument. The instrument will measure the color of water and fibres and calculate the color like it is in wet paper. Small changes in concentration have no influence on the measurement.
  • The ER40WF is a “lite” unit which just can measure whiteness and brightness of the pulp with seperation of the OBA.

The ES15Win and ES18Win software control the instrument and display the data. The measurements can be connected to a DCS system. The measurements will be displayed as a trend diagram. Colored bars will show the deviation of the produced paper to the standard. At one glance the operators will see, if the paper is too light or too dark, too red or too green, too yellow or too blue (just ERX50) and the whiteness and brightness.


Our partner in Advanced Process Control: