Typical impact on the Riser wall from a FCCU, as result of the lift-steam nozzle
presence of quartz-sand in a limestone or in carbon, pyrites in brown coal, silicon-carbide grains in iron pellets.
6 Erosion Resistance testing
In Fluidised-bed Catalytic Crackers (FCCU) we are mainly interested in the abrasive action of catalyst. Early attempts in laboratories did not solve the problems altogether. Catalyst, already in various types on the market as well as spent-catalyst act differently with respect to their abrasive behaviour.
As forerunner to the current available abrasion test in ISO 16282 “Determination of resistance to abrasion at ambient temperature”, and almost identical other standardised tests, already earlier attempts were made to come up with an acceptable and practical test to measure abrasion in FCCU’s. i.e. particle impact abrasion in (gas-) fluid condition on abrasion-resistant refractory linings.
6.1 Ball hardness, Aggregate Corrected, Erosion Resistance Index (BACER)
Already in 1954 one laboratory was investigating the possibilities of expressing the erosion resistance in useful formulas or properties. It was also assumed that the aggregates used in these type of erosion-resistant materials were of sufficient hardness, such as dense-fired fireclay grog or preferably even harder types like, calcined alumina, calcined bauxite or (electro) corundum.
They developed a so-called BACER Index, which would allow roughly checking refractory qualities on short notice, based on and similar to the Brinell Hardness test, where:
Because there were no other equivalent standard tests available, laboratory’s tests were of course only valid internally for own use. When (still) prudently used as comparative test for the determination of the required materials and for as-built QAQC, the results would provide useful information.
Unfortunate, comparative data are no longer available.
6.3 ISO 16282 - EN 993-20 - ASTM C-704 In these almost identical tests a similar performance is executed as in the Erosion Performance test, though almost all parameters are being fixed or being determined in order to achieve a good repeatability. Standard silicon-carbide abrasive, with a specific particle size distribution, is used instead of catalyst and the test is executed in a pressurised test chamber and with a dedicated jet-nozzle configuration perpendicularly positioned to the specimen.
In these tests the erosion performance is measured as: Determination of the volume of material abraded from a flat surface of the
22 ENGINEER THE REFRACTORIES March 2019 Issue 6.2 Erosion Performance Index
The erosion resistance was determined on specimens measuring approx. 120 x 80 x 6 to 8 mm by spent-catalyst blasting at room temperature. Specimens were made, dried and fired according to specification prior to testing.
A specimen was placed on a rig in a blasting cabinet at an angle of 45° with respect to the stream of spent-catalyst from the nozzle (sieved through ASTM No.50). The distance between the surface of the panel and the nozzle outlet was 80 mm. The diameter of the tungsten carbide nozzle was 4.76 mm and the air pressure is 5.5 bar.
A panel was tested either until it had been penetrated or for maximum 15 minutes, whichever was reached first.
Results were measured weighing before and after testing, after they were freed from lose particles and dust by means of a pressured air-jet.
The erosion performance index was calculated from the loss in weight and apparent density and expressed as loss in volume in ml/15 min., but with a limit of maximum 2.5 ml per 15 min. blasting with spent-catalyst:
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