At present, U-tube catalytic cracking has been largely replaced by the riser type; what are the main disadvantages of the former?
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At present, U-tube catalytic cracking has been largely replaced by the riser type; what are the main disadvantages of the former?
To work in conjunction with highly active molecular sieve catalysts, it is considered that such catalysts require a shorter residence time due to their high activity; therefore, a lift tube is used
It has quite a few drawbacks. It seems there’s no place to produce the catalysts being used. We originally used the Type 4 catalytic cracking process; the catalyst had low activity, heavy feedstocks could not be used, and the plant achieved low yields with high energy consumption. Moreover, it is relatively cumbersome to operate, and its ability to resist accident risks is also poor.
Without U-tube catalysis, the U-tube is used to transport the catalyst; it’s what we now call an inclined tube. The riser is now a reactor; in the past, it was a bed reaction. It does not react in a U-tube.