Page 177 - Fluid Catalytic Cracking Handbook

150 Fluid Catalytic Cracking Handbook

„ ,, , . N (13,817 moles/hrx 0.7901) iai _ , „
* Flue gas rate (dry basis)= = 13,145 moles/hr
J
0.8305
0.7901 and 0.8305 are concentrations of (nitrogen + argon) in atmospheric
dry air and flue gas (from analysis), respectively.

The flow rates of each component in the flue gas stream are:
« O 2 out = 0.015 x 13,145 moles/hr = 197 moles/hr
* CO 2 out = 0.154 x 13,145 moles/hr = 2,024 moles/hr
* SOj out = 0.0005 x 13,145 moles/hr = 7 moles/hr
* (N 2~ + Ar) out = 0.8305 x 13,145 moles/hr = 10,917 moles/hr
An oxygen balance can be used to calculate water formed by the combus-
tion of coke:
* O 2 out = 197 + 2,024 +7 = 2,228 moles/hr
* 1)3 in = 0.2095 x 13,817 moles/hr = 2,895 moles/hr
* O 2 used for combustion of hydrogen = 2,895 - 2,228 = 667 raoles/hr
Since for each mole of O 2, two moles of water are formed, the amount of
water is:

* H 2O formed = 667 x 2 = 1,334 moles/hr
Components of coke are carbon, hydrogen, and sulfur. Their rates are calcu-
lated as follows:
* Carbon = 2,024 moles/hr x 12 Ibs/mole = 24,288 Ibs/hr
* Hydrogen = 1,334 moles/hr x 2.02 Ibs/mole = 2,695 Ibs/hr
« Sulfur = 7 moles/hr x 32.1 Ibs/moles = 225 Ibs/hr
* Coke = 24,288 + 2,695 + 225 = 27,208 Ibs/hr

* H-, content of coke, wt% = — : — x 100 = 9.9
27,231 Ibs/hr
(The hydrogen content of coke indicates the amount of hydrocarbon vapors
carried through the stripper with the spent catalyst.

Conversion to Unit of Weight, Ibs/hr
The next step is to convert the flow rate of each stream in the
overall mass balance equation to the unit of weight (e.g., Ibs/hr).
Example 5-2 shows these conversions for gas and liquid streams.