Chapter 5 Octave Solutions Manual

CHAPTER 5Solution’s for CHEMICAL REACTION ENGINEERING

BY-OCTAVE LVENSPIL

CHAPTER 5

Downloaded from – http://www.chemengineersworld.weebly.com/

DOWNLOADED FROM chemengineersworld.weebly.com1

Problem 5.1 (p. 113)

If the system is of constant density and residence time timespace are equal, but in this case the system is of variable densitybecause the flow rate varies during the reaction, since it is agaseous and varies the total number of moles.

Conclusion

No one can calculate the mean residence time of the fluid with the dataavailable

reaction 2 A →R + 2 S with kineticunknown. If required a space velocity of 1 min-1 to achieve90% conversion of A in a plug flow reactor, find the Consider the gas phaseSpace and time corresponding mean residence time of the fluidin the plug flow reactorsoln



In a batch reactor operated isothermally reached 70%conversion of liquid reagent in 13 min. What is space weatherrequired to perform this operation in a plug flow reactor andone complete mix?

Can not be calculated τ, or s for mixed reactor becausekinetics known.

because the system is constant density so you (is liquid)



An aqueous stream of monomer A (1 mol / L, 4 L / min) enters acomplete mixing reactor 2 where L is the radiated and polymerizesfollows

A→R→ S → T ........

In the output current CA = 0.01 mol / L and for a particular product Wmust be CW = 0.0002 mol / L. Find reaction rate of A andW

Solution

A→RR + A→SS + A→TT + A→UU + A→VV + A→W

Assuming that the reactions are elementary

-RA = k1CA + k2 + k3 CA CA CR CS CT + CA + k4 k5 + k6 CA CA CU CV

rW = CV + k6 k7 CA CA CW

There are 7 kinetic constants involved, so I require at least 8 pointsexperimental to calculate the numerical value of the constants.



It is planning to replace a mixed reactor with one thathas twice the volume. For the same feed rate and thesame aqueous feed (10 mol of A / L), find the new conversion. TheThe reaction kinetics are represented by

A→R CA1-rA = k, 5

The actual conversion is 70%.

Solution

6M

4

2

00.74

Calculated

Correct

0.76 0.78

Conversion

0.8 0.82



An aqueous feed A and B (400 L / min, 100 mmol / L of A, 200mmol / L of B) will be converted to product in a flow reactorpiston. The kinetics of the reaction is represented by:

A + B→R CA-CB rA = 200 mol / L min

Find reactor volume required to achieve 99.9%A product conversion in

Solution

Constant density liquid system

-



A plug flow reactor (2 m3) processes an aqueous feed (100L / min) containing a reagent A (CA0 = 100 mmol / L). This reaction isreversible and is represented by:

A R -RA = 0.04 min-1CA - 0.01 min-1 CR

Find first equilibrium constant and after the reactor the conversion

Solution

System fluid density is constant because



The gas coming out of a nuclear reactor containing a full range ofradioactive traces, the conflict being the Xe-133 (meanlife = 5.2 days) This gas flows continuously through a tank with ahigh retention, with residence time of 30 days, which may beassume that the contents are well mixed. Find activity fractionthat is removed in the tank

Solution

Assuming that the reaction is of constant density and that is firstorder can be calculated from the kinetic constant through timelife

For mixed reactor



A mixed reactor (2 m3) processes an aqueous feed(100 L / min) containing a reagent A (CA0 = 100 mmol / L). This reactionis reversible and is represented by:

A R -RA = 0.04 min-1CA - 0.01 min-1 CR

What is the equilibrium conversion and the actual conversion of the reactor?

Solution




A specific enzyme catalyzes the fermentation of A.Find the volume of the plug flow reactor required for 95% ofconversion of reactant A (CA0 = 2 mol / L) at a given concentration ofenzyme. Fermentation kinetics of this enzyme concentrationis given by:

enzyme

A� � � → R

Solution

CA-rA = 0.1 / (1 + 0.5 CA)

System constant density because 1 mol of A yields 1 mol of R


Problem 5.10 (p.114)

In a plug flow reactor a gaseous feed of pure (2mol / L, 100 mol / min) decomposes to give a variety of products.The kinetics of the reaction is represented by

A→2.5 products -RA = 10 min-1 CA

Find expected conversion reactor 22 L

Solution

System variable density varies because Ftotal, which causes the flowvolume varies


Problem 5.11 (p. 114)

The enzyme catalyzes the fermentation E substrate A (reactive),obtaining R. Find size required mixed reactorfor 95% conversion of a feed stream (25 L / min)reagent (2 mol / L) and enzyme. Fermentation kinetics at thisenzyme concentration is given by

enzyme

A� � � → R

Solution

CA-rA = 0.1 / (1 + 0.5 CA)

Constant density System



An aqueous solution (400 L / min, to 100 mmol / L, 200 mol of B / L) willbe converted to product in a mixed reactor. The kinetics ofthe reaction is represented by

A + B→R CA-CB rA = 200 mol / L min

Find reactor volume required to achieve 90% conversion

Solution



Problem 5.13 (p. 115)

At 650 ° C the vapor decomposes as follows PH3

4 PH3 →P4 (g) +6 H2 -RPH3 = 10 h-1 CPH3

What size of plug flow reactor operating at 649 ° C and 11.4 atmrequired to achieve 75% conversion of 10 mol / H PH3 having2/3 of PH3 y1 / 3 inert?

Solution

System variable density varies because it is gaseous and Ftotal, whichcauses the volumetric flow varies


Problem 5.14 (p. 115)

A gas stream of pure reagent A (CA0 = 660 mmol / L) enters aplug flow reactor at a rate FA0 = 540 mmol / min and polymerizedas follows

3A→R -RA = 54 mmol / L min

How big should the reactor to CAF = 330 mmol / L?

Solution

System variable density because it varies Ftotal gas and as the flowvolume also vary


Problem 5.15 (p. 115)

A gaseous feed of pure A (1 mol / L) enters reactorcomplete mixture (2 L) and reacts as follows:

2A→R CA2-rA = 0.05 mol / L s

Find feed rate (L / min) to give a concentration ofCAf output = 0.5 mol / L

Solution

System variable density as it is gaseous and Ftotal varies during During the reaction, the volumetric flow varies


Problem 5.16 (p. 115)

The gaseous reagent is decomposed as follows

A→3R -RA = 0.6 min-1 CA

Find A conversion is obtained in a complete mixing reactorof 1 m3 which is fed with a stream containing 50% A and 50%of inert (v0 = 180 L / min, CA0 = 300 mmol / L)

Solution

System variable density as it is gaseous and Ftotal varies duringDuring the reaction, the volumetric flow varies


Problem 5.17 (p. 115)

A mixture of ozone 20% - 80% air at 1.5 atm and 95 ° C passes at arate of 1 L / s through a plug flow reactor. Under theseconditions decomposes ozone by reaction homogeneous

2 O3 →3 O2

What sizedecomposition?

Solution

The rate of reaction is second order and the system of density Yavariable design equation and varies because Ftotal is gaseous.integrated in the text for this case.

-RA = k Coz2k = 0.05 L / mol s

reactor is requires for achieve 50 % of


Problem 5.18 (p. 116)

An aqueous feed containing A (1 mol / L) is processed in aplug flow reactor 2 L (2 A →R, CA2-rA = 0.05 mol / L s). Find theThe outlet concentration for a feed rate of 0.5L / min

Solution

The system is liquid, so it is of constant density and � εA =0


Problem 5.19 (p. 116)

Is fed to a complete mixing reactor 1 a gas stream LA pure approximately 3 atm and 30 ° C (120 mmol / L). There aredecomposed and the concentration of A in the output is measured for eachflow rate. From the data the following equation Findrepresents the decomposition rate of A. Suppose that onlyA concentration affects the rate of reaction

v0 (L / min)CA (mmol / L)

Solution

The system is of variable density varies because it is gaseous and F total

0.06 30

0.48 60

1.580

8.1105

A→3R



Problem 5.20 (p. 116)

You are using a mixed reactor to determine thereaction kinetics whose stoichiometry is A →R. For this differentflow of an aqueous solution containing 100 mmol / L of A arefed to a reactor of 1 L and for each run the concentration of Aoutput is recorded. Find the equation representing the speedfollowing. Assume that only the reagent A affects the speed ofreaction

v (L / min)CA (mmol / L)

Solution

The system is fluid density is constant because

4 620

2450



It is planning to operate a batch reactor to convert A into Rby reaction in liquid phase with the stoichiometry A →R, whosereaction rate is shown in the following table

CA(Mol / L)-RA(Mol / Lmin)

0.1

0.1

0.2

0.3

0.3

0.5

0.4

0.6

0.5

0.5

0.6

0.25

0.7

0.1

0.8

0.06

1.0

005

1.3

0.045

2.0

0.042

How long must react each tuned to the concentration fallsfrom CA0 = 1.3 mol / L to CAF = 0.3 mol / L?

Solution


-RA is plotted vs CA to complete the data between CA = CA = 0.8 to 1.3mol / L. Axis is used to facilitate the representation semilog


Problem 5.22 (p. 116)

For the reaction of 5.21 problem, what size flow reactorthe piston is required for 80% conversion of a stream of 1000A mol / h with CA0 = 1.5 mol / L

Solution

The density is constant and CA0 CAF = (1 - XA) = 1.5 (1 -0.8) = 0.3 mol / L

Chart values are taken from problem 5.21. Reproduced extended thenecessary part of the graph

Concentration A

0.1

0

Reaction rate

0.5 1 1.5 2 2.5


Problem 5.23 (p. 117)

a) For the reaction of 5.21 problem, what size CSTR Full required to obtain 75% conversion of stream A 1000 mol / h with CA0 = 1.2 mol / Lb) Repeat part a) with the modification that the power is double, or A 2000 mol / h with CA0 = 1.2 mol / Lc) Repeat part a) with the modification that CA0 = 2.4 mol / L, 1000 mol treating A / h and CAF = 0.3 mol / L

Solution

b)Assuming that the volume is still 1500 L and that what varies is XA


calculated

XAF /-RAF never going to be 0.75,said physically with τnot occur as smallreaction

Assuming XA = 0.75 and the volume required varies

correct


Problem 5.24 (p. 117)

A gaseous hydrocarbon of high molecular weight is fed a continuously mixed reactor which is heated to high temperatures to cause thermal cracking (homogeneous reactiongaseous) materials of lower molecular weight, collectively calledR using approximate stoichiometry A →5 R. Changingfeed rate is obtained different extensions crackingas shown

FA0 (mmol / h)CAs (mmol / L)

30016

1000 30

3000 50

5000 60

The vacuum inside the reactor volume is 0.1 L and temperatureA feed concentration is CA0 = 100 mmol / L. Find the equationwhich represents the cracking reaction

Solution

System variable density varies because it is gaseous and Ftotal

Draw a graph of rate of reaction vs concentration of A


Problem 5.25 (p. 117)

The aqueous phase decomposition of A is studied in a reactorthorough mixing. The results in the table were obtained P.5.25steady state runs. What residence time required forobtain 75% conversion of reagent feeding with CA0 = 0.8mol / L

CAeCAs

� t (S)

2.000.65

300

2.000.92

240

2.001.00

250

1.000.56

110

1.000.37

360

0.480.42

24

0.480.28

200

0.480.20

560

Solution

The system density is constant, so

These values are plotted for values-rA vs CA necessary

Concentration A

Reaction rate

.


Problem 5.26

Repeat the previous problem, but for a completely mixed reactor

Solution

=


Problem 5.28 (p. 118)

In a batch reactor operating at constant volume and 100 ° C.The following data were obtained from the decomposition of gaseous reactant A

t (s)pA (atm)

01.00

200.80

400.68

600.56

800.45

1000.37

1400.25

2000.14

2600.08

3300.04

4200.02

The stoichiometry of the reaction is 2 to →R + SWhat size of plug flow reactor (in L) can operate at 1 atmA treat 100 mol / h in a stream containing 20% inerts into obtain 95% conversion of A

Solution

The system is of constant density, both in the batch reactor asin the plug flow because Ftotal = Ntotal = constant

n-rA =KC

If first-order

kt = - ln (1-X A )

PA/pA0 is plotted vs. t gives a straight line and if it means 1st order

1


Then the reaction is first order

For plug flow reactor using equation 5.23 (p. 103)


Problem 5.29 (p. 119)

Repeat the previous problem, but for a completely mixed reactor

Solution

FOR MORE SOLUTIONS VISIT http://www.chemengineersworld.weebly.com/



Documents

Chapter 5 Octave Solutions Manual