Non-destructive testing (NDT) and monitoring of refractory lining in operating furnaces

Abstract

The refractory lining in a smelting furnace is crucial to providing structural integrity to the furnace and protecting the furnace which is designed to withstand extreme mechanical, chemical and thermal stresses; however, soon after the start-up of a furnace, the refractory lining inevitably suffers from wear and deterioration. The measurement and evaluation of the refractory lining of smelting furnaces is crucial to continue operation. However, due to the nature of smelting furnaces, it is nearly impossible to drill into the lining while the furnace is in operation and directly evaluate the refractory thickness and condition. Due to this limitation and industry demand, several non-destructive sting (NDT) methods were developed. These NDT techniques can indirectly measure refractory lining thickness and can evaluate refractory quality by determining if any chemical changes, hydrations, cracking, oxidation or metal impregnation have occurred within the refractory. The accuracy of these indirect NDT methods relies largely on the quality and homogeneity of the refractory bricks in the lining. In this paper, the available furnace refractory lining NDT and monitoring techniques will be reviewed and discussed.