In our FCC (Deep Catalytic Cracking) Unit Spent catalyst slide valve(SCSV) DP suddenly decreased from 0.70 to 0.35 kg/cm2. All parameter such as aeration purge point pressure and flow, all types of steam flow, reactor and re-generator DP are normal. What is the reason for this?
Answers
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02/11/2016
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Peter Marsh, XBP Refining Consultants Ltd, peter.marsh@xbprefining.co.uk
If catalyst bed level and density are unchanged and standpipe aeration and other operating variables are normal, perhaps some erosion-resistant refractory has spalled off the orifice or slide gate such that the measured dP across the slide valve is smaller for the same valve opening?
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25/10/2016
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Ralph Ragsdale, Ragsdale Refining Courses, ralph.ragsdale@att.net
Conduct a complete pressure profile with a calibrated pressure gage from the MF OH receiver to the regenerator stack. Then, adjust the delta P setting if possible to improve the slide valve positions or delta P's. Something may have changed other than at the aeration locations. Also, compare the catalyst particle size distribution curve with a previous one for a possible explanation of aeration differences.
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24/10/2016
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William Miller, WorleyParsons, william.miller@worleyparsons.com
You lost 0.35 kg/cm2 pressure drop across the SCSV. Can you see where this went? If reactor-regen differerential pressure is steady did levels in reactor and/or regen change equivalent to 0.35 kg/cm2? I don't know your typical fluid densities in reactor / regen, but 0.35 kg/cm2 could be as much as a 30' change in level. If this is from reactor level dropping it is very serious as NS Murphy points out. You could be at higher risk of losing seal between reactor and regen.
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24/10/2016
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Bob Kalaria, KBR, bhavdip.kalaria@kbr.com
This may need a little more investigation. Has the spent catalyst standpipe pressure profile changed? Pressure survey from reactor top head to SCSV inlet may help identify where the higher pressure is. Has the E-CAT physical properties changed? Is the pressure drop now steady at 0.35 kg/cm2 or is it fluctuating? Is the slide valve opening steady or fluctuating? Has the catalyst circulation rate changed?
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24/10/2016
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NS Murthy, Suez, murthy.ns.ext@suez.com
In FCC or DCC, the differential pr across slide valves are very critical for plant safety. Of the spent and regenerated cat valves, the latter is even more super critical as typically one gets adequate pr drop in spent cat valve owing to reactor elevation and reactor cat level. If catalyst get lumps one can experience such phenomenon. You may check for any inadvertent ingress of water (moisture) in reactor stripping steam. Also, check whether the end point of oil got changed which can also result in momentary variation.
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