EFFECT OF ABNORMAL TREATMENT ON THE MECHANICAL STRENGTH OF IRON-BASEDHIGH-TEMPERATURE SHIFT CATALYST

The abnormal conditions encountered by an iran-based high-temperature water-gas shift catalyst in different processing stages and the effect of these conditions on the mechanical strength of the catalyst have b een investigated by experimental simulation and Weibull statistics. In the process of production, heating and reduction, the catalyst can of ten be over-heated. Over-heating or thermal treating of the powder bef ore pelleting as well as the pellets, and thermal shock in the reducti on lower the mean horizontal crushing strength and the Weibull modulus , and increase the probability of strength failure by 3 to 10 orders. Absorption of moisture and wetness by water of the pellets, and steam or water shock in the reduction increase this probability by several o rders. The mechanical treatment by dropping down the pellets on the fl oor also lowers the strength. The results in this paper show that prop erly pelleted and reduced samples possess a very high and reliable str ength, for instance, the best reduced sample has a Weibull modulus up to 12.8. The probability of failure of this sample at 10 kg/pellet is as low as 4.16 . 10(-11). These results show the potentiality in incre asing catalyst mechanical strength, and show that due to their brittle ness, the catalysts should be properly processed.