Exercise 7

Exercise 7 Instructions 

Material Balance for FCC Regenerator

Problem

Burning the coke deposited on the catalyst particles generates all the heat necessary for catalytic cracking. Therefore, the coke burning rate is a critical parameter to control the rate of cracking. The composition of dry flue gas from the regenerator of an FCC unit is given in vol% as follows:

GasVolume %

N₂81.6

CO₂15.7

CO 1.5

O₂ 1.2

The dry air flow rate to the regenerator is given as 593 SCMM (standard cubic meters per minute). Considering that a significant portion of coke is carbon, you calculated in Exercise 6 the carbon burning rate in the regenerator as 52.6 kg/min.

For this exercise, calculate the coke burning rate in kg/min and the hydrogen content (wt%) of the coke burnt. Assume that the coke consists only of carbon and hydrogen.

Hint: Use an oxygen balance to determine the missing oxygen which was consumed to burn the hydrogen in coke. Water content of the flue gas is not given because only the dry gas analysis is reported.

Note: The assumption that “coke consists only of carbon and hydrogen” may be justified for gas oil feedstock that is virtually free of sulfur and other heteroatom species. For high sulfur feeds, sulfur content of the burnt coke can also calculated from the dry flue gas analysis.

Instructions for Submitting Response:

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