Download Advanced Process Analysis System - Minerals Processing Research

temperature between the water inlet (CW1) and stream 12 is 60o F and the pressure drop is 5 psia.
Thus, stream 12 is at 140o F and 230 psia.
The purification section consists of the distillation columns to separate the chemicals into
products and non-products. The absorption column (T-100) separates the gases and the liquids.
T-100 is a 10-stage reboiled absorber (no condenser) fed at the top stage. The pressure at the top
of the column is 220 psia, while the pressure at the bottom of the column is 222.5 psia. The light
key component of this column is ammonia, while the heavy key component is water. Theory
says that any component lighter than the light key will appear in the distillate. Therefore, all of
the hydrogen and nitrogen go to stream 13. Theory also suggests that any component heavier
than the heavy key will appear in the bottoms product. Thus, all of the phenol, aniline and
diphenylamine go to stream 18. As for the key components, 99.9% of the ammonia and 10% of
the water go to the distillate.
From the absorption column, stream 13 goes to a splitter. The splitter sends 98.9% of the
stream to stream 14, which is the ammonia recycle stream. Since the recycle stream is not at the
same pressure as stream 3, it is passed through a compressor. Stream 16 emerges at 170o F and
255 psia. The splitter also sends 1.1% of stream 13 to the gaseous purge, stream 17. The purge
is necessary to avoid any pressure build-up in the process. Stream 17 is a non-product stream,
but it is used as fuel for the heater. The bottoms stream (stream 18) is one of the feeds to the
next column.
The second column in the purification section is the drying column (T-101). The column
has 25 stages and is fed at the top stage by streams 18 and 23. The pressure at the top of the
column is 15 psia, and the pressure at the bottom of the column stage is 21.25 psia. The key
components are water and phenol. However, some aniline is lost in the distillate because aniline
is soluble in water. The distillate contains 99.99% of the water, 6% of the phenol and 5% of the
aniline fed to the column (streams 18 and 23). The distillate, stream 19, is cooled by E-103 to a
temperature of 110o F with a pressure of 10 psia. Stream 20 is then sent to a three-phase
separator (V-100) to separate the aqueous product and the liquid (organic) product. The organic
product (stream 21) is recycled to the column. Stream 21 consists of 7% of the ammonia, 3% of
the water, 30.5% of the phenol and 86% of the aniline in stream 20. Because stream 21 is below
the pressure of the top stage pressure, P-102 is used to bring the pressure in stream 23 up to 15
psia. The aqueous product (stream 24) from V-100 is a non-product output stream. This stream
will be sent through wastewater treatment and released off-site. The bottoms stream (stream 25)
is the feed to the next column.
The final column is the product column (T-102). It is a 75-stage column fed on stage 35.
The pressure at the top of the column is 2.707 psia, while the pressure at the bottom of the
column is 21.46 psia. This column also has a side draw on stage 50. Due to a high-boiling
azeotrope between phenol and aniline, the main component in the distillate (stream 26) is aniline.
Stream 26 contains all of the water, 19.5% of the phenol and 92.3% of the aniline from stream
25. Stream 26 must be at least 99 wt% aniline for industrial use. Because there is a 10 psia
pressure drop for liquids in coolers, stream 26 needs to be pumped up to a pressure of 12.71 psia
by P-104. The resulting stream (stream 27) is cooled by E-104. Stream 28, a product stream,
emerges from the cooler at 90o F and 2.707 psia. The azeotrope between phenol and aniline is
19