Page 96 - Fluid Catalytic Cracking Handbook

FCC Feed Characterization 73

Step 2: 10%-90% slope

T(90%) - T(10%) 1080 - 652
Mope = =
80 80

Slope = 5.3°F/percent off

Step 3: From Appendix 2, corrections to VABP are approximately -34°F
for MeABP and -10°F for CABP.
Therefore:

MeABP = 851 - 34 = 817°F = 436°C

CABP = 851 - 10 = 841°F = 449.4°C
1 3
^ A K (817 + 460) /
Step 4: K w = = 11.88

0.913

Instead of using Appendix 2, the MeABP can be determined from the
equation below [11]:

( (T _T ) \
MeABP = VABP + 2 - ^ ^ +1.5 3
U 70+0.075 x VABP J

MeABP = 851 + 2-f I 080 " 852 +1.5
(170 + 0.075x851

MeABP = 816°F (435°C)

In the absence of full distillation data, the K factor can be estimated
using the 50% point in place of MeABP.

In summary, the K factor can provide information about the aromaticity
or paraffinicity of the feed. However, within the narrow range (K =
11.5-12.0), it cannot differentiate between ratio of paraffins, naphthenes,
and aromatics. To determine these ratios, other correlations, such as
TOTAL or n-d-M, should be employed.