# Problems from the Omnibook

## EEC 503 SPRING 2010

HOMEWORK 5

Due Tuesday March 2

### Ch62: A1, A7, B13, C19

1. An impulse response test is performed on a continuous reactor. The following is measured.

a) Extrapolate the data back to the c axis to estimate the value of c at t = 0, and calculate the mean residence time in the reactor.

b) If the volumetric flow rate in this experiment was a 5 L/min, what is the reactor volume, and how much tracer was injected?

c) Suppose a first-order reaction A B, k = 0.625 min-1 is carried out in the reactor with the same volumetric flow rate used in the impulse response test. Use the results of part a) to choose and evaluate the parameters of an ideal reactor model, and calculate the fractional conversion of A which would be achieved based on such a model.

d) Use the tracer response directly to predict the exact conversion in the reactor.

2. A 45-liter mixed vessel is subjected to an impulse response test. The feed rate is 5 liters/second. The following response is obtained:

t (s)R (arbitrary units)

5 49.0

10 24.0

15 11.7

20 5.7

25 3.2

30 2.0

35 1.6

Use a semilog plot of the data to develop a two-region model for the tank. Determine the volume associated with each region.

3. A slug of radioactive tracer is used to determine the residence time density function (E-curve) in a reactor. The following data are obtained at the outlet:

a) Determine E (t) and (mean residence time) if you know that tracer half life is 5 min.

b) What error would you have made if you calculated directly from the above data without correction for radioactive decay.

4. Consider a reactor with the following E-curve:

where

A second order reaction takes place in the reactor at isothermal conditions. The rate of reactant A disappearance is:

Find the conversion of A when using this reactor for:

i)ii)

based on:

a)segregated flow model

b)maximum mixedness model

5. Consider the following reaction scheme for competitive reactions:

.

Both rates are given in (mol/L min).

The feed to the reactor is at .

The reactor has the following E-curve:

Consider for the above E-curve: i) N = 1, ii) N = 2, and iii) N = 10. (Note: Do not assume that you actually have tanks in series but that you only have the E-curve given by i), ii) or iii)).

Find and report the selectivity for:

a)the segregated flow model

b)the maximum mixedness model

for each of the three E-curves given by i), ii), and iii).