PROCESS FLOWSHEET DEVELOPMENT - Teach Yourself the Basics of Aspen Plus - page 180

TABLE 12.1 Process Feeds

Feed Recycle Gas Recycle

Component (lbmol/hr) (lbmol/hr) (lbmol/hr)

Hydrogen 2045.9

Methane 3020.8

Benzene 3.4 42.8

Toluene 274.2 82.5 5.3

Biphenyl 1.0

Temperature ( ◦ F) 75 250 121

Pressure (psi) 569 569 569

TABLE 12.2 Process Operating Conditions
Location Temperature ( ◦ F) Pressure (psi)

Furnace inlet 569 1000

Furnace outlet 494 1200

Reactor outlet 494 1268

Pump outlet 494

Heater outlet 480 180

Flash 480

An unavoidable side reaction that produces biphenyl is

2C 6 H 6 → C 12 H 10 + H 2

The conditions for the feed and two recycle streams are given in Table 12.1. The
specifications in Table 12.2 are the pressures and temperatures at various points in the
process.
The flow rate of the quench stream is to be such that the temperature of the com-
bination of reactor effluent and the quench stream should be 1150 ◦ F. Conversion of
toluene is 75%. Two percent of benzene present after the first reaction occurs is con-
verted to biphenyl. The overall heat transfer coefficient in the heat exchanger is 60
Btu/(hr-ft 2 - ◦ F). Develop an approximate material and energy balance for the process.

Workshop 12.2a Figure 12.12 shows a process to create a mixture suitable for use as
a natural gas and recover a light hydrocarbon liquid from the feed given in Table 12.3.
The feed is at 80 ◦ F and 237.7 psi. Develop a first estimate material and energy balance
for this process. The equipment is to be modeled simply. The specifications for the
processing equipment are as follows:

Chiller : outlet at − 40 ◦ F and 230 psi.
Gas/gas heat exchanger : modeled as two heaters with a heat stream used to pass
heat between them.
Cold-side heater : outlet at 160 psi. A 4 ◦ F approach at the cold-stream outlet of the
heat exchanger (i.e., the temperature of the inlet of the hot-side heater minus the
temperature of the outlet of the cold-side heater).