A NEW IMPINGING JET TEST RIG USED TO IDENTIFY THE IMPORTANT PARAMETERS IN-SERVICE EROSION-CORROSION IN BAYER LIQUOR AND TO STUDY THE DAMAGEMORPHOLOGY

An impinging jet test rig (IJTR) was designed and constructed to study the mechanism of erosion-corrosion in high temperature caustic soluti ons and was used in a systematic program of experiments at the Bayer p lant site. Although there was a particulate loading in the liquor, no significant erosion-corrosion effect could be attributed to the presen ce of these particulates. Low damage rates were observed for all cases of a submerged liquid jet under controlled conditions of one-phase fl ow; for example, the damage rate was 0.04 mm year-1 at a jet velocity of 30 m s-1 at 150-degrees-C. Using liquor with a higher source temper ature, higher damage rates of 0.4-4 mm year-1 were measured. These hig her damage rates are tentatively attributed to the inevitable two-phas e flow at the start and end of these tests. There was a significant da mage rate of 40 mm year-1 in one test using liquor with a higher sourc e temperature. The damaged region showed flow-induced damage patterns with a facet type of surface morphology. Careful analysis of test cond itions led to hypotheses concerning conditions leading to high damage rates.