Page 202 - Elements of Chemical Reaction Engineering 3rd Edition

1 74 Isothermal Reactor Design Chap. 4

Integrating with limits P = Po when L = 0, and assuming thatfdoes not vary,
we have

Po
Neglecting the second term on the right-hand side gives

Rearranging, we obtain

(4-41)

where

For the flow conditions given in Example 4-4 in a 1000-ft length of 1;-in.
schedule 40 pipe (ap = 0.01 18), the pressure drop is less than 10%.

4.5 Synthesizing a Chemical Plant

Careful study of the various reactions, reactors, and molar flows of the reac-
tants and products used in the example problems in this chapter reveals that
Synthesizing a they can be arranged to form a chemical plant to produce 200 million pounds
chemica1 Plant of ethylene glycol from a feedstock of 402 million pounds per year of ethane.
The flowsheet for the arrangement of the reactors together with the molar flow
rates is shown in Figure 4-1 1. Here 0.425 lb molls of ethane is fed to 100 tubu-
lar plug-flow reactors connected in parallel; the total volume is 81 ft3 to pro-
duce 0.34 lb molls of ethylene (see Example 4-4). The reaction mixture is then
fed to a separation unit where 0.04 lb molls of ethylene is lost in the separation
process in the ethane and hydrogen streams that exit the separator. This pro-
cess provides a molar flow rate of ethylene of 0.3 lb moVs which enters the
packed-bed catalytic reactor together with 0.15 lb molls of O2 and 0.564 lb
moVs of N2. There are 0.18 Ib mol/s of ethylene oxide (see Example 4-6) pro-
duced in the 1000 pipes arranged in parallel and packed with silver-coated cat-
alyst pellets. There is 60% conversion achieved in each pipe and the total
Always
catalyst weight in all the pipes is 45,400 lb. The effluent Stream is passed to a
separator where 0.03 lb moVs of ethylene oxide is lost. The ethylene oxide
stream is then contacted with water in a gas absorber to produce a 1-lb mol/ft3
boundaries of the
solution of ethylene oxide in water. In the absorption process, 0.022 lb molls
of ethylene oxide is lost. The ethylene oxide solution is fed to a 197-ft3 CSTR
together with a stream of 0.9 wt % H2S04 solution to produce ethylene glycol