Page 98 - Fluid Catalytic Cracking Handbook

FCC Feed Characterization 75

446) - (0.052 x 0.48} - (0.872 - In (7.37))

H 2 = 12.23 wt%

Aromatic (C A) Content, wt%

C A = -814.136 + (635.192 x RI (20)) - (129.266 x (SG)) + (0.013

x (MW)) - (0.34 x (S)) + (0.872 x In (v))

C A = -814.136 + (635.192 x 1.5105) - (129.266 x 0.913) +

(0.013 x 446) - (0.34 x 0.48) + (0.872 x In 7.37)
C A = 19.19 wt%

Where:
SG = Specific gravity at 20°C
AP °C = Aniline Point, °C
VABP °C = Volumetric Average Boiling Point, °C
VABP °K = Volumetric Average Boiling Point, °K
S = Sulfur, wt%
V = Viscosity at 100°C

For FCC feeds, particularly the ones containing residue, the TOTAL
correlation is more accurate at predicting aromatic carbon content than
the n-d-M correlation. Table 2-9 illustrates this comparison. One option
is to calculate MW, RI (20)» C A, and H 2 from the TOTAL correlation,
and use either the n-d-M or API method to calculate the wt% naphthene
(C N) and wt% paraffin (C p).

n-d-M Method

The n-d-M correlation is an ASTM (D-3238) method that uses
refractive index (n), density (d), average molecular weight (MW), and
sulfur (S) to estimate the percentage of total carbon distribution in the
aromatic ring structure (% C A), naphthenic ring structure (C N), and
paraffin chains (% C p). Both refractive index and density are either
measured or estimated at 20°C (68°F). Appendix 4 shows formulas
used to calculate carbon distribution. Note that the n-d-M method
calculates, for example, the percent of carbon in the aromatic ring