WEAR MECHANISM OF Al_2O_3/SiC/GRAPHITE REFRACTORIES UNDER THE ACTION OF A DESSULFURIZING AGENT BASED ON A MIXTURE CONTAINING CaO AND POWDERED ALUMINUM DROSS

摘要

According to results obtained in this investigation, the use of 94wt percent CaO plus 6wt percent Aluminum dross top reject as a dessulfurizing agent, may carry on harmfull alkali compounds (such as Na_2O and K_2O) to the common Al_2O_3/SiC/Graphite torpedo laddle refractories. The wear mechanisms follow the sequence: a) Oxidation of SiC and Graphite phases due to the action of gaseous species typical to torpedo laddles in addition to the alkali vapors which come along the dessulfurizing agent. b) As a consequence of the mechanism in a, an increase in the brick's permeability results simultaneously to a silica deposition inside the pores which starts densifying the refractory matrix. c) As an end result, low melting point phases containing, CaO, SiO_2, Al_2O_3, K_2O and Na_2O are formed which accelerate the wear rate. The laboratory simulations of slag attack by means of the dynamic finger test, has offered a route to increase the refractory wear resistance by means of a combination of MgO and Spinel (MgAl_2O_4) in the matrix.