REFRACTORY DAMAGE IN TAPPING HOLE OF COREX MELTER-GASIFIER

摘要

In order to investigate the wear of Al_2O_3-SiO_2 system refractories around the tapping hole of a COREX C-2000 melter gasifier, 3 wear mechanisms have been examined and they are ⅰ) mechanical wear (abrasion) due to friction loss by tapping hot metal and slag, ⅱ) thermal shock due to a sudden change in temperature, ⅲ) chemical wear (corrosion) due to dissolution of refractory into slag and chemical reactions between slag and refractory. In the last mechanism, the effects of refractory composition, temperature, slag basicity, and FeO content in slag have also been studied. The following results are obtained from the present study: ⅰ) A theoretical calculation shows that the frictional force by tapping hot metal 1.5 times higher than that by tapping slag, and the friction loss in the wall of tapping hole is higher than that due to sudden contraction in the entrance. This evaluation, however, is incompatible with actual observation. Therefore, it can be concluded that the mechanical wear by itself can not be the main mechanism of wear of the refractory around the tapping hole of a COREX C-2000 melter gasifier. ⅱ) Flexural strength increases with an increase in Al_2O_3 content in Al_2O_3-SiO_2 system refractories, but the refractories shows a sudden decrease in flexural strength with thermal shock of sudden temperature change higher than 400 □ regardless of Al_2O_3 content in the refractories. Therefore, in the operation of COREX C-2000 melter gasifier, the work which can cause a sudden temperature change higher than 400 □ should be avoided. ⅲ) The refractory consisting of mullite and corundum shows higher resistance against corrosion than that of mullite and tridymite. The cooling of refractory, as well as high Al_2O_3 content, is found to be one of the most important factors to increase the refractory life. The effects, however, of slag basicity and FeO content in slag are not clearly shown in this test of motionless slag and this can be ascribed to the formation of a liquid (melt) of high viscosity 10-100 times higher than slag and to an increase in the thickness of liquid film around refractory surface. Because the slag in COREX C-2000 melter gasifier is not motionless, it is expected that the slag basicity and the FeO content in slag might have some effect on the life of refractories around tapping hole.