Again we consider the production of propylene glycol (C) in a CSTR with a heat exchanger. Initially there is only water at 75°F and 0.1 wt % H₂SO₄ in the 1420-gallon reactor. The feed stream consists of 400 lb mol/h of propylene oxide (A), 5000 lb mol/h of water (B) containing 0.1 wt % H₂SO₄ ,and 20 lb mol /h of methanol (M). Plot the temperature and concentration of propylene oxide as a function of time, and a concentration vs. temperature graph for different entering temperatures.

Solution

(CDE9-1.1)



(CDE9-1.2)



(CDE9-1.3)



(CDE9-1.4)

(CDE9-1.5)


(CDE9-1.6)



(CDE9-1.7)




(CDE9-1.8)

(CDE9-1.9)

From Equation (E8-8.10):

(CDE9-1.10)

Neglectingbecause it changes the heat of reaction insignificantly over the temperature range of the reaction, the heat of reaction is assumed constant at

The POLYMATH program is shown in Table CDE9-1.1. Figures CDE9-1.1 and CDE9-1.2 show the reactor temperature and concentration of propylene oxide as a function of time. One observes that both the concentration of A and the temperature oscillate around their steady-state values before coming to rest at these values. The corresponding phase-plane plot of concentration and temperature shows a spiral approach to the steady state (Figure CDE9-1.3).

Table CDE9-1.1

Figure CDE9-1.1
Temperature Time Trajectory

Figure CDE9-1.2
Concentration Time Trajectory

Figure CDE9-1.3
Concentration temperature phase plane Plot