Page 110 - Analysis, Synthesis and Design of Chemical Processes, Third Edition

For a draining tank, the model is

(E3.1j)

where ρ is the density of the liquid in the tank, A is the cross-sectional area of the tank, H is the height of
t
liquid in the tank, A is the cross-sectional area of the exit pipe, and v is the velocity of liquid in the exit
p
p
1/2
pipe, which, from Bernoulli’s equation (turbulent flow), is (2gH) , where g is the gravitational
acceleration. Therefore, Equation (E3.1j) becomes

(E3.1k)

Integrating from H = 2.806 m at t = 0 to find the time when H = 0 yields

(E3.1l)

which gives Δt = 785 s = 13 min, which is rounded up to 30 minutes for this step. Note that this time can
be further reduced by pressurizing the vessel with an inert gas.

Step 4. Distillation of Reaction Products

A material balance on the reactor at the end of Step 2 yields the following:

Initially, the reaction mixture is heated to its boiling point of 115°C at the operating pressure. This is done
by condensing steam in a heat exchanger located in the still of the column. The time to heat the mixture
from 95°C (the temperature leaving the reactor, assuming no heat loss in the filter) to 115°C is given by
Equation (E3.1d) with the following variable values:
T = 120°C
s