Supervisory Control of a Stock Prep Refiner

Thomas Storsjö ; thomas.storsjo@semcon.se

Master Thesis, Report UPTEC 97 027E, 85 pages, February 1997.

Abstract:

The possibility to control a stock prep refiner using a measuring device, called PQM Inline has been studied in this project. The refiner has two possible control variables, namely the disc clearence (gap) and the pulp concentration. One major part of the project was to investigate how these variables effect the pulp quality and specially the quality parameters that are measurable by the PQM. The expectations were to control more than one quality parameter. Unfortunately the studies showed that the concentration has an almost insignificant effect on the pulp. Therefore, the controller had to be constructed using only disc gap as control variable. In contrast to concentration, the gap has a very large effect on the pulp quality and especially on freeness. Freeness is also a very important parameter in pulp production and it needs to be within certain intervalls, otherwise there will be higher risk for paper machine failure.

Due to these facts a gap-freeness controller was constructed in this project. The controller was implemented as an ordinary PID algorithm in a regulator module from Eurotherm. The results from the short test period show that the controller has capacity to reduce the quality variations in the pulp. The trials were made at the Ortviken pulp and paper mill in Sundsvall, Sweden.

Company:

Sunds Defibrator

Thesis Advisor:

Mikael Sternad