Degradation of castable refractory in a fluidized catalytic cracking unit of a Brazilian oil refinery: a case study

This paper reports the operational data of temperature and pressure obtained during six years of uninterrupted production of the converter assembly of the fluidized catalytic cracking unit of a Brazilian oil refinery, in particular the riser section of the separator vessel, up to the general maintenance stop of the unit, which took place in 2020. The catalytic cracking is responsible for breaking up the high molecular weight fractions of oil, producing more profitable light fractions. The converter is coated internally with castable refractory of the aluminosilicate type, resisting the high temperatures required in the cracking process, as well as the high displacement speeds of the mixture formed by the catalyst, water vapor and hydrocarbons, potential sources of erosion of the castable refractorys. The SEM micrographs of the degraded refractory indicated the presence of carbon elements in the interstitial sites of the refractory mass matrix and the occurrence of cracks. The degraded refractory showed a reduction of the specific mass (17%), of the linear dimension (0.21%) and of the abrasion resistance from 20.0 to 4.1 cm3. Impregnation of concrete by coke promoted an increase in the value of compressive strength from 10.0 to 12.25 MPa, that is, an increase of 18% in this property.