A Burden Sensor with X-Band Microwave for Blast Furnaces

Abstract

New type of a burden sensor applied by 10GHz (X-band) microwave for measuring packing structure in a blast furnace is newly developed. This sensor is able to use at almost every part in the furnaces.
It was found that the attenuation of transmitted X-band wave in a burden layer differed between a coke layer and an ore layer, and the attenuation was kept constant regardless the change in the temperature of burdens. The change in a reflected power of X-band wave from the surface of burdens could be applied for the detection of particle size. Arranging the transmitted and reflected waves, a burden sensor was constructed. This sensor can measure the descending velocity, the thickness of burden layer and the particle size simultaneously.
A probe with an ellipsoidal cross section has three narrow slits set in a shell at the tip of it. One slit transmits an X-band wave and other two slits receive the wave scattered in a burden layer. Attaching two receiving slits above and below, boundaries of ore and coke can be detected with a certain delay of time. By using the signal corresponding to the boundaries and the delay time, the descending velocity and the thickness of layer can be obtained. The transmitted slit receives the reflected wave from the peripheral of the slit. Correcting the changing cycle of the reflected wave by the descending velicity, particle size can be obtained. An experiment at a laboratory showed that this sensor could measure these parameters within the accuracy of ±10%. Various types of microwave sonsor have been installed in a shaft, belly and bosh of several furnaces. The sensor shows stable signal for more than half a year.