A New Sensor and a Novel Control Concept for Optimized Fiberline Operation

摘要

In kraft and sulfite pulp mills several consecutive process stages are used for the pulp production. A pulp mill can therefore be considered to be a rather complicated process industry but still usually only one key pulp parameter is used for process control and that is the lignin content in the fibers, typically expressed as Kappa number. However, to improve the process efficiency more key variables have to be monitored and therefore a new sensor has been developed including a new control concept. This sensor measures the dissolved lignin content in the pulp slurry using a unique principle based on optical measurements and it has the ability to perform the measurement of the dissolved lignin inline even at MC condition. The sensor has two major applications: (i) improving efficiency in washing stages, and (ii) optimizing chemical charges. Results from several mill trials have shown that the contribution from dissolved lignin in the filtrate portion of the pulp is up to 30% of the total bleach load, i.e. fiber and filtrate Kappa number combined into the bleach plant. Hence chemical savings can be achieved taking this component into account compared to only measuring the washed fiber Kappa number.