What are the disadvantages of risers?
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During one competition, there was a question asking about the disadvantages of lift tube reactors. I am aware of many advantages of lift tube reactors, but I really don’t know anything about their disadvantages. Could those with more experience share their views?
Shortcomings of the riser technology: First, the reaction time is too long； Second, the catalyst has low activity and poor selectivity ； Third, the backmixing of raw materials is still quite severe ； Fourth, it has high energy consumption ；
First, the reaction time is too long； The conventional riser reaction time is indeed long, but many risers these days are not very long; the two-stage riser at East China University of Petroleum is only about 10 meters long, with a total reaction time of around 1.6 seconds. Second, the catalyst has low activity and poor selectivity ； Studies show that the activity of the catalyst at the outlet of the riser is only about 1/3 of its initial activity; after 1 second of reaction, its activity drops by around 50%. Therefore, in the latter part of the riser reactor, the catalyst’s performance is poor, and thermal reactions as well as secondary reactions occur, which have an adverse effect on the product distribution and operation. Therefore, the catalyst has low activity and poor selectivity, and this applies only to long risers; many risers do not have low activity, such as TSRMP and CRC-FCC. Third, the backmixing of raw materials is still quite severe ； I’m not very familiar with this aspect, but there is indeed raw material backmixing in the riser; however, I’m not sure how severe it is. Fourth, it has high energy consumption ； Now it’s all riser columns; I don’t know how to compare them.
Reply to dawei0718: I’m just writing down what I know for reference only; there’s no need to be too harsh, right?