For a given feed quality and constant Reactor temperature,
Which of the following gives Optimum yields.
a) Higher feed preheat & Low Cat/oil ratio
or
b) Higher Cat to oil ratio & low feed preheat?
Answers
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16/08/2015
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Prabhat Choudhary , IOCL, prabhatchoudhary26@gmail.com
Option B is always favourable, but you see that feed preheat must not be lower than minimum required, say around 220-230 degC. Below th minimum allowed temp liquid phase cracking may predominate and may direct to coke formation. Optimise the conditions between options a and b.
What is your design CCR of FCC/RFCC?
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12/04/2014
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Virendra Kapoor, Petroleum Refining Consultants, vkkapoor9@yahoo.com
With higher cat to oil ratio and constant reactor reactor temperature, conversion is higher as more active sites are available for the reaction. The selectivity for the reactions are also affected are more favorable for gasoline. If a refiner is interested to produce more diesel, may be he has to optimize the unit to manage the cat to oil ratio more towards condition of a) rather than b). So the best option is choosen depending on demand from the plant.
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08/04/2014
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Bob Kalaria, KBR, bhavdip.kalaria@kbr.com
Higher feed preheat and low cat/oil ratio will reduce the conversion and coke yield.
Lower feed preheat and high cat/oil ratio will increase the conversion, coke yield and will lower the dry gas yield at constant reactor temperature. If unit is not cat circulation limited or air limited, this will provide better yields.
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04/04/2014
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Ralph Ragsdale, Ragsdale Refining Courses, ralph.ragsdale@att.net
Higher cat/oil ratio, as long as the regenerator temperature is within an optimal range for your feedstock properties. As you know, some FCC units have no fired feed heater. The heater found in some units is intended to control regenerator temperature. Once that is adjusted, the overall unit heat balance determines the cat/oil ratio. UOP’s design that allows for recycling semi-spent catalyst flow to the bottom of the riser is intended to increase the cat/oil ratio to achieve enhanced product distribution.
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04/04/2014
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Lefter Rinaldo, Netcodietsmann, dumitrurinaldo@yahoo.com
The answer is b
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