JPH0349963B

PURPOSE:To increase the utility rate of gas, grasping the gas flowing state in a blast furnace by enabling the measurement of the grain size distribution of the charge in the radial direction of the furnace top thereof to be achieved, using the sonde with double tube mechanism. CONSTITUTION:A monitor is composed of a tublar main sonde 3 and an auxiliary sonde provided capably of advancing and retreating above the charge 2 in a reducing shaft furnace and further the device for measuring the grain size distribution of the charge. Said auxiliary sonde is capable of moving in the longitudinal direction in the sonde 3, and the tip of the body 10 of said auxiliary sonde in the side into which the auxiliary sonde advances has a flexible tube with minimum curvature. On the tip of this tube, the sensor 5 composed of a fiberscope and a projector is provided. Said device for measuring grain size distribution defines the horizontal position and the vertical position of the sensor 5 by moving the main sonde 3 and the auxiliary sonde, and analyzes the image from the sensor 5. By above mentioned device, the grain size distribution of the charge is measured, and the gas flowing state in the blast furnace is grasped, thereby increasing the utility rate of the gas.