What is Reverse seal in an FCC Riser? How to maintain it at a certain value?
Answers
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26/02/2013
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A:
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Saugata Palit, KNPC, saugata.palit@gmail.com
Are you inquiring about the RCSP to riser bends which acts as a sort of seal to prevent feed reversal?
There are several types of bends (J, U ,Y) provided at the junction of RCSP and riser. Here the catalyst has to take a sharp turn to change its flowing path from descent in RCSP to ascent in the riser. For this to happen, the density variation, which aids the catalyst flow through the structure has to be maintained. Most Licensor provide steam at this bend, which actually pushes the catalyst up the riser. There are licensors who also provide another steam/ recycle nozzle below the feed nozzle to accelerate the flow of catalyst up the riser. These two steam/ steam-recycle combination help in catalyst transition from RCSP to Riser and up the riser. For smooth flowing catalyst up the riser, the chances of feed reversal is minimized.
The values of these steam/ recycles depend on your cat circulation and will be specified by the Licensor.
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