Supervisory Control of a Stock Prep Refiner
Thomas Storsjö ;
Report UPTEC 97 027E, 85 pages,
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.
- Sunds Defibrator
- Mikael Sternad