Page 196 - Fluid Catalytic Cracking Handbook

161 Fluid Catalytic Cracking Handbook

III. Calculation of heat of reaction
Total heat out = total heat in
6
6
6
6
Total heat out = 878 x 10 + 512.6 x 10 + 15.2 x 10 + 6.1 x 1C) +
overall heat of reaction =
6
Total heat in = 1,499.6 x 10 Btu/hr
6
Overall endothermic heat of reaction = 84.5 x 10 Btu/hr or —» 128.2
Btu/lb of feed.
Analysis of Results

Once the material and heat balances are complete, a report must be
written. It will first present the data. It will then discuss factors
affecting product quality and any abnormal results. It will then discuss
the key findings and recommendations to improve unit operation.
In the previous examples, the feed characterizing correlations in
Chapter 2 are used to determine composition of the feedstock. The
results show that the feedstock is predominantly paraffinic (i.e., 61.6%
paraffins, 19.9% naphthenes, and 18.5% aromatics). Paraffinic feed-
stocks normally yield the most gasoline with the least octane. This
confirms the relatively high FCC gasoline yield and low octane
observed in the test run. This is the kind of information that should
be included in the report. Of course, the effects of other factors, such
as catalyst and operating parameters, will also affect the yield structure
and will be discussed.
The coke calculation showed the hydrogen content to be 9.9 wt%.
As discussed in Chapter 1, every effort should be made to minimize
the hydrogen content of the coke entering the regenerator. The hydro-
gen content of a well-stripped catalyst is in the range of 5 wt% to
6 wt%. A 9.9 wt% hydrogen in coke indicates either poor stripper
operation and/or erroneous flue gas analysis.

PRESSURE BALANCE

Pressure balance deals with the hydraulics of catalyst circulation in
the reactor/regenerator circuit. The pressure balance starts with the
static pressures and differential pressures that are measured. The
various pressure increases and decreases in the circuit are then cal-
culated. The object is to: