Automated cement plant quality control: in-situ versus extractive sampling and instrumentation

Increasing production and quality demands in the cement industry have resulted in the need for improvement in the speed and accuracy of quality control results. This need has been addressed by many technological advances in quality control automation in recent years. Two distinct methods of sampling and analysis, in-situ and extractive, have gradually developed. In-situ analysis occurs in the field at the process equipment, with the results transmitted through a computer control system. Extractive sampling requires removing a sample from the process stream and transporting it to the laboratory for further preparation and analysis. Both approaches have distinct advantages and disadvantages. This paper discusses the characteristics and differences in analyzer and control technologies that utilize the two different methods of obtaining a result. The operation, accuracy, maintenance, troubleshooting, and relative costs associated with the two types of control are presented. Emphasis is placed on the criteria for primary selection of one technology over another at various points in the cement manufacturing process.