When using catalyst particles in fluidized beds and circulating fluidized beds, particle attrition can be a major problem.
Alfa Chemistry Catalysts is committed to providing customers with comprehensive catalyst wear tests. The following are several commonly used catalyst wear test methods. We can recommend suitable catalyst wear test solutions for you according to customer needs.
Catalyst samples, each weighing 25 g, are packed in cylindrical metal tubes mounted on a disc-shaped frame. The frame rotates at 25 rpm for one hour. The contents of each tube are then recovered and screened. The aperture of the sieve must be 2/3 of the smallest particle size. This means that the size range of the fine powder thus obtained is larger than the size range of the ASTM test. The initial sample, residue and "fine powder" are all weighed, which allows the wear to be determined.
This test method includes the determination of the attrition resistance of the catalyst and the catalyst carriers. It is suitable for tablets, extrudates, spheres, and irregularly shaped particles larger than about 1.6 mm and less than about 19 mm. Then, the contents in the drum are sieved with ASTM N°20 sieve (aperture: 0.85 mm), and the fine powder produced by abrasion and abrasion in the process is recovered. The weighing of the residue and the initial sample allows the calculation of wear loss.
Figure 1. Schematic diagram of the drum used to determine attrition and abrasion.
The powdered catalyst wear and abrasion were measured by air jet. It is suitable for sizes between 10 and 180 µm, skeleton density between 2.4 and 3.0 g/cm3 and is insoluble in water. Particles smaller than 20 µm are considered fine powder.
Taber wear test specifically refers to a test that measures material wear caused by sliding contact. Examples of such contact are scratching, grinding, and friction. The characteristic friction and wear effect is caused by the sliding and rotating contact between the sample and the two grinding wheels. When the turntable rotates, the wheel is driven by the sample in the opposite direction around a horizontal axis that is tangential to the sample axis. One grinding wheel rubs the outer periphery of the sample outward, and the other rubs the sample inward, while the vacuum system removes loose debris during the test. The wheel runs a complete circle on the surface of the sample, showing the wear resistance at all angles relative to the weave or texture of the material.
The attrition tendency of used and fresh vanadium phosphorus oxide (VPO) catalysts to be mechanically stressed in gas cyclones and bubbling fluidized beds has been studied, with and without submerged gas jets. The results show that when subjected to mechanical stress in the gas cyclone and immersed gas jet fluidized bed, the studied VPO catalyst has a low abrasion tendency comparable to that of the FCC catalyst.
Figure 2. (a) SEM image of broken fresh VPO particles before abrasion test; (b) SEM image of broken used VPO particles after abrasion test.