DLT-5500 Dissolved Lignin Transmitter

The Dissolved Lignin Transmitter DLT-5500 is a sensor which measures the dissolved lignin concentration in pulp suspensions or filtrates using a unique principle based on optical measurement. The sensor is pre-calibrated and requires only one measurement onsite for the final calibration. The results can be correlated to either a filtrate kappa or chemical oxygen demand (COD).

This sensor is ideal for determining black liquor carry-over into bleach plants and black liquor solids in brown stock washing and oxygen delignification.

Traditional application rate of ClO2 on the D0 stage is determined by measuring the lignin content of washed fibers via a kappa analyzer or laboratory test. The ClO2 is then applied based on the washed fiber kappa. While the lignin in the fiber consumes most of the ClO2, the traditional washed fiber kappa does not account for the dissolved lignin that enters the D0 stage from the brown stock washing area.

The lignin in the black liquor will rapidly consume the ClO2 leaving insufficient ClO2 to delignify the pulp. There are several other methods currently used to warn the operator of black liquor in the pulp.