Diagnostics of blast-furnace linings

Abstract

Hatch (Canada) has developed a system for the nondestructive monitoring of the residual lining thickness in blast furnaces and eletrofurnaces. This system, which is based on an acoustic-ultrasound echo signal (AU-E), supplements the traditional thermal simulation of the furnace lining by means of built-in thermocouples or on the basis of the thermal load on the cooling units in the blast furnace. By this means, the position of cracks and anomalies may be determined, and the boundary between the coating and the refractory may be identified. The constraints and sources of error in the AU-E method are analyzed, and an improved version is outlined. The improved method takes account of the influence of the following factors on the wave propagation: high temperatures; the furnace shape and size; and the difference in acoustic resistance of different layers in a multilayer refractory lining. The AU-E method permits reliable and nondestructive monitoring of the refractory lining in smelting furnaces. The hardware and software of the AU-E system have been significantly improved, so as to obtain measurements of satisfactory accuracy. Estimates of the method’s precision are confirmed by physical measurements on inoperative blast furnaces. Examples of the utilization of this diagnostic system at various Russian and non-Russian plants are presented. Some technological measures that extend the blast-furnace run are noted. As shown in the present study, the use of several successive measurements permits the determination of the lining’s wear rate and the time remaining before major repair. The AU-E method continues to operate well at more than 70 blast furnaces around the world, including those at the Novolipetsk, Cherepovets, Nizhny Tagil, Western Siberian, and Magnitogorsk steel works, as well as at electrofurnaces producing ferroalloys, copper, and platinum.