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Technical Paper


WEAR & TEAR IN (L/R)-FCCU PART 2


Preface


by Ing. W.A.J. Kastelic W/mKastelic Refractories Services 7.1 Mechanism


Damages to erosion-resistant refractory linings in FCCU Regenerator & Reactor sections are a well-known and recurring phenomenon, especially in the reactor/stripper and cat. piping, i.e. in the ‘black’ section, due to spalling and to a lesser extent, erosion. Although refractory failure is in most of the cases not the prime reason for an intermediate shutdown, there is generally a considerable amount of damage observed when the equipment is opened for inspection.


In the first part of this article an introduction was given about the principles and types of wear as they appear regularly in these types of units with fluidised bed circulation of an abrasive medium, like sand or catalyst.


In the second part the effect of erosion on refractory linings is given followed by an overview of erosion-resistant refractory linings particularly for (L/R)-FCCU’s.


Figures, photographs and tables are shown for explanatory purpose and illustration only and shall not be used for (re)production or presentation outside the content of this article.


7 Effect of erosion on the layer-thickness of 'softer material' in high abrasion-resistant refractory linings


May 2019 Issue


In 1928, Honegger *) presented impingement erosion results in terms of “specific erosion“ (erosion rate) curves which generally exhibited a rising and then falling pattern. The tests were executed with water droplet jets on steel surfaces for the investigation of cavitation/erosion.


He postulated a geometric explanation:


“As long as the surface of the specimen is smooth, it offers an unfavourable surface for impinging water to attack; hence, the water flows off to either side. Erosion does not take place. As soon as any roughness is formed, however, the erosion proceeds rapidly as the droplet-jet impinges with great force in the unevenness. If, finally, the unevenness has attained a considerable depth, a layer of water adheres to the now completely roughened surface, which absorbs part of the impact of succeeding droplets of water so that the force of the jet is not so effective anymore. The specific erosion consequently decreases after a certain depth has been attained.“


7.2 Catalyst erosion behaviour on ceramic and refractory surfaces


On basis of the above observations for catalyst erosion on refractory and steel a similar explanation can be given as well, if surfaces with e.g. thin strips of Hexmesh (continuous), Speedcells (interrupted) or Y-studs (very


ENGINEER THE REFRACTORIES


17


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