Case History No. 16

Industry & Location:

A cement plant in the southeast

Problem:

Inadequate draft from kiln

Source of Detection:

Reduced clinker production

Cause of Problem:

This particular cement plant was equipped with two I.D. fans at the end of the draft system as shown in Figure 16.1. Although these two fans are operated in parallel, they also operate in series with another I.D. fan developing high static pressure to induced gases through the kiln and through the Allis Chalmers roller mill. For some reason, the designer of the plant specified two parallel operated I.D. fans which are designed to operate at a point on the far right hand side of the performance curve. In addition, increased capacity was required which meant that additional volumetric flow was needed through the draft system. This increase in flow displaced the operating point further to the right and to a point which resulted in even greater inefficiency.

I.D. Fans

Solution of Problem:

As is the case of most draft system improvement programs, the obvious and initial solution is the replacement of the I.D. fans. However, the replacement cost associated with I.D. fans of this size is in excess of $150,000. A more affordable approach is the replacement of the fan impellers to provide the needed performance. Reusing housings represents a significant cost savings measure. In this particular instance, it was decided to replace the fan impellers with wider wheels which would move the operating point a little farther to the left and at a slightly more optimum condition. Because of the improvement in efficiency, additional capacity did result but because the fans were initially so poorly selected, ultimate fan replacements will be required to increase capacity further.

Benefits:

Improved draft from the kiln and slightly improved clinker production.