Study of refractory wear in the tuyere region of a Peirce-Smith nickel convertor

Profiles of the composition variation with distance from the hot face were mapped out by SEM analysis of chrome-magnesite tuyere refractory bricks from a Peirce-Smith nickel converter. The presence of magnesium sulphate was confirmed by XRD, SEM and wet analysis. The work showed that periclase was highly susceptible to attack by sulphur dioxide and formed magnesium sulphate in the cooler regions of the refractory brick where the reaction was favourable. Thermal cycling caused the periclase to alternate between the sulphate and the oxide leading to increased pore formation and decreased brick strength. This combined with tuyere punching contributed to the enhanced loss of refractory at the tuyere line. The accretion layer had a high nickel ferrite content which agreed with the high oxygen potential expected at the tuyere region. An interface region between the accretion layer and the refractory showed that counterdiffusion of iron and magnesium assisted in removing periclase from the refractory. Nickel and nickel compounds were limited to the first two mm of the hot face and no infiltration was found. The chrome-spinel is more resistant to attack than the periclase. The pore structure in the refractory brick was identified as the key variable in resisting sulphate formation. An ability to close or fill the pores will reduce the possibility of sulphur dioxide diffusion into the cooler regions for magnesium sulphate formation. (C) 1998 Canadian Institute of Mining and Metallurgy. Published by Elsevier Science Ltd. All rights reserved.