What are the potential problems if we have higher grid pressure drop than expected at conditions?
Answers
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22/08/2016
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Jhorman MartÃ_nez, PDVSA CRP, MARTINEZJMR@PDVSA.COM
Depending on how the plugged holes are distributed throughout the grid, is it possible that there are sections of the grid that are not receiving sufficient air to fluidize the bed?
In that case:
1) Any cyclone dipleg outlet that is submerged in a defluidized zone of the bed cannot properly discharge catalyst, resulting in filling of the dipleg, flooding of that cyclone, and high carryover of catalyst.
2) The total air flow will only pass through the well-fluidized zones of the bed (i.e., open grid holes). This can result in abnormally high velocities and high catalyst entrainment from those areas of the bed. Localized high catalyst loadings to some cyclones can then result in higher losses.
I mention this because we have high catalyst losses and we don´t have problem of attrition.
The PSD analyses are 0 vs 3% 0-40 microns fraction and 97 vs 83 microns average particle size.
We don't have catalyst fines. This loss rate continued after remove and replace the E-CAT.
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27/06/2016
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William Miller, WorleyParsons, william.miller@worleyparsons.com
High grid pressure drop with high grid hole velocity can increase generation of catalyst fines through attrition.
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16/06/2016
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Chayan Bhalla, Mangalore Refinery and Petrochemicals Ltd, chayan.bhalla@gmail.com
The higher than normal air grid pressure drop in regenerator is indicative of choking of ring nozzles. The extent of choking can be estimated by increment in the pressure drop. The potential problems are:
i) The air maldistribution/ channeling in the regenerator. This may lead to improper combustion and incomplete regeneration of catalyst, ultimately affecting the process conversion.
ii) The partial choked nozzles will have higher air velocity leading to higher catalyst attrition, fine generation and may also lead to higher catalyst losses.
The blockage of nozzles happens generally during sudden loss of blower air and resulting catalyst slumping into the ring. It can be prevented by lining-up blast air (stand-by plant air connection) immediately after loss of blower air.
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14/06/2016
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Snehamoy Halder, Bharat Petroleum Corporation Limited, sneha123moy@yahoo.co.in
Due to higher grid pressure drop following problems may occurs:
1. Lower air flow expected in Regenerator , subsequently FCC charge need to be reduce to same level of catalyst regeneration & circulation.
2. Grid pressure drop could be due to blockage of few air nozzle.
i) This results in maldistribution of air across the regenerator which could be cause of improper catalyst regeneration/uneven temperature distribution across the regenerator.
ii) Since few nozzles are blocked, to maintain same air flow other nozzle's air velocity could increase. Consequently, catalyst carry over to the regenerator cyclone might increase and also these nozzles would experience higher erosion.
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01/06/2016
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Ralph Ragsdale, Ragsdale Refining Courses, ralph.ragsdale@att.net
Please state process and which grid. Resid FCC regen air grid?
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31/05/2016
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Eric Vetters, ProCorr Consulting Services, ewvetters@yahoo.com
You are likely run out of control valve operating flexibility somewhere if the delta is enough. To maintain an acceptable DP between the reactor and regenerator you may have to drop the operating pressure of the main fractionator overhead system. If you do that you may run out of DP to for the suction throttling valve on the wet gas compressor. If you don't lower main frac overhead pressure, then the DP available for the riser temperature control slide valve will decrease, which could limit catalyst circulation. Higher DP may also back you up on the curve for your air blower, which would reduce air flow and limit coke burning capabilities. Depending on the measures taken to counteract, the result could be loss of feed rate and/or conversion.
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31/05/2016
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Eric Hennings, Technip Stone & Webster, EHennings@technip.com
Increased pressure drop can result in FCC constraints such as limitation in air (coke burning) or catalyst circulation (pressure balance).
Permanent damage can occur at low delta P, due to erosion from catalyst backflow.
Watch for “sudden” (and unexpected) decrease in delta P. This may indicate partial failure of distributor. Troubleshooting is based on cat attrition and process maldistribution.
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