Page 341 - Distillation theory

P1: JPJ/FFX P2: FCH/FFX QC: FCH/FFX T1: FCH
0521820928c08 CB644-Petlyuk-v1 June 11, 2004 20:20

8.7 Petroleum Mixtures 315

the large interval of bubble temperatures of components: vacuum is necessary to
obtain heavy products at a permissible temperature, and light products cannot be
obtained under vacuum because of the low temperatures that would be required
for their condensation, which could not be ensured with the help of cheap cold
agents (air or water).
Therefore, the main succession of petroleum refining includes two main units:
that of atmospheric distillation and that of vacuum distillation. The lighter prod-
ucts are obtained in the first unit right up to mazut (bottom product of atmospheric
column with side strippings) and, in the second unit, the heavier products are ob-
tained right up to tar (bottom product of vacuum column with side strippings).
The first unit usually consists of one column with side strippings (one-column
flowsheet) (Fig. 8.32a) or of superatmospheric column of partial recovery of ben-
zine and of main column with side strippings (two-column flowsheet) (Fig. 8.32b).

a) D

st
M 1

st M 2

st M 3

F

st B

b) D 2

D 1
st
M 1
st M 2
F
st M 3

st B
Figure 8.32. Crude oil distillation: (a) in one column, and (b)
in two columns.