Refractive index measurements for brown stock washing loss - mill investigations

摘要

The usability of the refractometer to measure washing loss in chemical pulping was studied under mill conditions. Our earlier study showed that measurement works very well under laboratory conditions. The focus of investigation was on brown stock washing before and after oxygen delignification at a Finnish pulp mill. The E-values for the system were calculated on the grounds of the sample lap. Also, an on-line calculation method for washing effectiveness was generated. In addition, washing filtrates and filtrates which were centrifuged from pulp were analysed and the measuring results of the refractometer, SFS-3008 standard, conductivity and COD-analysis were compared. The measuring results indicated that the refractometer is suitable for measuring the dissolved dry solids of outgoing filtrates and pulp suspensions on a single washer. Therefore it is suitable for monitoring washing loss levels in the brown stock washing and because of this real-time measuring of washing effectiveness is possible.