Simple system using classical three-term PID controller for classifier speed

An Insitec system has been used for feedback control for the separator at this plant since the middle of June, 1999.

The separator speed has been controlled using the %<30 micron parameter, which provides the best correlation with the traditional plant control parameter of [% passing 325 mesh] (wet sieve). Despite the relatively small data set available at that time, the standard deviation (RMS) on fineness decreased by 34% from 1.5% to 1% of the indicated measurement.

The figure below shows a type change from type I to type V. The separator is under automatic control from the PID loop and can be seen to move to the lower speed quickly on 14 June at 14:20 hours. Even though two different % < 30µm set points are used, it is seen that the cement Blaine fineness is nearly the same. The type V cement, having a higher C₂S, is harder to grind. It can also be noted that the off-line Blaine measurement (input manually by the operator and shown in green), is insensitive to this type of change.

Graph showing type change from Type I to Type V