I.FLUID CATALYTIC CRACKING/A.PROCESS(Contd.)
Q-24:
When operating with one or more catalyst coolers on a regenerator,what control philosophy do you employ (e.g.constant heat duty,constant regenerator temperature,etc.)?.What are the advantages and disadvantages for each approach? How does operating in full or partial burn impact the control decision?
A-24:
The catalyst coolers are operated to minimize regenerator bed temperature to a limit,usually air or catalyst circulation.Catalyst cooler optimization is an advanced control application.The benefits for minimizing regenerator temperature include: maximize catalyst circulation,minimize dry gas production,minimize swings during feed changes,and reduce catalyst deactivation.
Q-25:
With the introduction of modern riser termination devices (RTD'S) ,what is your experience with the ash content of the main fractionator bottoms (MFB) product?Please describe the testing methodology utilized?
A-25:
Ash composition can vary greatly from one refinery to another.Though the primary ash components are inorganic(catalyst fines,metals,corrosion scale),heavier organic molecules can also be present which stabilize the ash in solution.Typical ash content data for various RTDs range from 0.005 to 0.2 wt% ash,with most in the 0.05 to 0.1 wt% range.The market price for saleable decant oil is strongly a function of ash content.Therefore ,refiners can realize significant economic benefit if the ash content of the slurry is below these specs
.
Testing of the ash content is done accordance with ASTM D-482.For units which are required to meet stringent ash content specifications,slurry settlers and filters have been uesd. All have been problematic and the filters require considerable maintenance.Filter plugging due to asphaltenes and waxes has been an issue at one location.The recycle stream generated by the backwash from these systems has caused feed system fouling and reactor coking.
One refiner is using settling aid to sell clarified slurry into the more lucrative "carbon black" market.
Q-24:
When operating with one or more catalyst coolers on a regenerator,what control philosophy do you employ (e.g.constant heat duty,constant regenerator temperature,etc.)?.What are the advantages and disadvantages for each approach? How does operating in full or partial burn impact the control decision?
A-24:
The catalyst coolers are operated to minimize regenerator bed temperature to a limit,usually air or catalyst circulation.Catalyst cooler optimization is an advanced control application.The benefits for minimizing regenerator temperature include: maximize catalyst circulation,minimize dry gas production,minimize swings during feed changes,and reduce catalyst deactivation.
Q-25:
With the introduction of modern riser termination devices (RTD'S) ,what is your experience with the ash content of the main fractionator bottoms (MFB) product?Please describe the testing methodology utilized?
A-25:
Ash composition can vary greatly from one refinery to another.Though the primary ash components are inorganic(catalyst fines,metals,corrosion scale),heavier organic molecules can also be present which stabilize the ash in solution.Typical ash content data for various RTDs range from 0.005 to 0.2 wt% ash,with most in the 0.05 to 0.1 wt% range.The market price for saleable decant oil is strongly a function of ash content.Therefore ,refiners can realize significant economic benefit if the ash content of the slurry is below these specs
.
Testing of the ash content is done accordance with ASTM D-482.For units which are required to meet stringent ash content specifications,slurry settlers and filters have been uesd. All have been problematic and the filters require considerable maintenance.Filter plugging due to asphaltenes and waxes has been an issue at one location.The recycle stream generated by the backwash from these systems has caused feed system fouling and reactor coking.
One refiner is using settling aid to sell clarified slurry into the more lucrative "carbon black" market.
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