Dealing with dust
With dust chemistry varying between direct operation when the raw mill is out of action and indirect operation when the raw mill is running, finding a destination for baghouse dust while maintaining a homogenous kiln feed is a long-standing issue in cement production. By John Kline and Benjamin Kline, Kline Consulting LLC, USA.
Figure 1: a typical raw mill and kiln feed configuration
The simple question of what to do with baghouse dust when the raw mill is out of operation has plagued the cement industry since the invention of the rotary kiln. In wet kilns the dry dust was difficult to mix back in as it impacted the slurry characteristics. New inventions such as dust insufflation and mid-kiln dust scoops were developed to manage the problem. In long dry kilns dust was less of an issue. However, with the advent of the preheater the dust problem returned. The issue being that the dust chemistry varies between direct operation with the raw mill out of service and indirect operation when the raw mill is running. Solutions have usually varied between some combination of returning the dust to the homogenisation silo or directly back to the kiln feed system.
