Submerged-jet tests

Figure 2. Time dependence of catalyst attrition in a submerged jet test (D, = 0.05 m, uor = 100 ms-1, dor = 2 mm, HA-HPV is a fresh catalyst whereas FCC is a spent cracking catalyst from a commercial unit. (From Werther and Xi, 1993.)...

Both devices described above were developed in order to test the friability of fluid-cracking catalysts. Nowadays the application of these or similar tests is a common procedure in the development of fluidized bed catalysts. Contractor et al. (1989), for example, used a submerged-jet test to compare the attrition resistance of newly developed VPO catalysts. In fact, such tests can be applied to any type of fluidized bed processes. Sometimes they have to be slightly modified to adapt them to the process under consideration. The drilled plate may, for example, be substituted by... 

Figure 10 Comparison of two different designs of a submerged jet test (a) after Forsythe and Hertwig (1949) (b) after Gwyn...

Figure 13 Influence of the static bed height on jet attrition of spent FCC catalyst in a submerged jet test facility D = 0.05m, Mqj = lOOm/s, = 2mm). (Werther and Xi, 1993.)...

Friability tests can be used for various purposes. They are widely used in quality control. Here, samples of produced material are subjected to a more or less arbitrary but well defined stress. The attrition extent is assessed by comparison with a standard value and a decision is reached whether the material meets the standard. Moreover, friability tests are often used for comparison of different materials to select the most attrition-resistant one. This is a usual procedure in the case of catalyst development. For example, Contractor et al. (1989) tested anew developed fluidized bed VPO-catalyst in a submerged-jet attrition test (described below). Furthermore, the specific attrition rate of a material in a certain process can be roughly estimated by friability tests. In this case the stress must be similar to that occurring in the process and the obtained degradation extent must be compared with those of other materials from which the process attrition rate is known. 

Friability tests are often used for a comparison of different types of materials to select the most attrition-resistant one (Vaux and Fellers, 1981 Davuluri and Knowlton, 1998). A field where friability tests are of particular importance is catalyst development (Dart, 1974). As an example, Contractor et al. (1989) used a submerged-jet attrition test (described below) in their development of a new generation of fluidized bed VPO-catalyst. 

Balch, L.R. (1913). Test of a jet pump. Engineering Series Bulletin 7(4) 1-15. Univ. Wisconsin. Balch, L.R. (1914). Investigation of flow through four-inch submerged orifices and tubes. 

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