The concept LESS – Low Energy Strategic Systems comprises three control concepts, TCtrl, CCtrl and QCtrl and one process optimization service which we call Energy optimization control ECtrl. This can be performed in automatic mode but most often the costumers prefer to optimize the process by tests according to the actual process situation. Therefore, to optimize refining processes we offer services as well.

In many situations the costumer wants to run the process at different operating conditions. Sometimes, new refining segments are tested which challenge the process stability, especially when running low energy segments which can require special attention. Other situations are related to feeding problems which can be related to malfunctioning plug screws etc.

When optimizing the process, the service ECtrl can sometimes help the costumer to reach the desired process conditions. This statement is best illustrated by an example:

When running e.g. CD refiners it is not always obvious how to operate the refiner to reach a maximized production. In this specific example, it was difficult to increase the production. The normal situation where the plate gap and dilution water to the conical (CD) zone are changed did not work without violating the pulp quality.

The operators requested more information about the process conditions in the flat zone (FZ) before changing the operating points in FZ and the CD zone. To overcome that problem it was proposed that the physical model should be used for temperature profile and consistency profile optimization before and after step changes in the plate gap, dilution water feed rate and production. Thereby, the operators got access to information about fiber residence times in each refining zone, as well as the motor load split in the refiner.

To solve the problem and thereby increase the production, the proposal was to open the plate gap in the CD zone at the same time as the plate gap was reduced in FZ while maintaining the consistency ratio between FZ and the CD zone as stable as possible. The motivation was to get a better refiner controllability.

Thanks to CCtrl the ratio between the consistency in FZ and the CD zone was maintained relatively constant which resulted in an increased production rate of 24 → 33 tonne/hr, see Figure 1 → Figure 4.

During the process optimization, the motor load was not affected so much when more work was applied to FZ, see Figure 4. This was initially a surprise and indicated that the motor load split can be used to optimize the process. In Figure 5, the concistencies are show together with the fiber residence time.

In short, the efforts led to a situation where the specific energy demand was reduced dramatically by about 40% see Figure 6, at the same time as two small refiners could be closed down without violating the pulp and handsheet property specification, see Figure 7.

For further reading, please download "CTMP Process Optimization Part I: Internal".