Heat shield for high-temperature kiln

It is difficult to eliminate heat losses from a high-temperature (500-750 °F) rotary kiln since it is often not desirable to insulate the surface due to shell overheating problems. Often, the kiln bare shell is exposed to the ambient air to keep it under the critical temperature, and the large energy loss is evident. Installation of a simple concentric shield around the kiln not only cools the shell but also recovers 90% of the heat that otherwise would be lost. Furthermore, it acts as an effective air seal at the firing end of the kiln, reducing unwanted excess air into the system. The shield has been proved to save energy as well as to provide a safer and cooler environment. Fuel savings of $34 940 per year have been realized for use of such a shield over a 20-ft-long 8-ft-diameter kiln at 400 °F. This paper shows how to evaluate these heat savings and to design a shield for such a kiln.