The following complex gas phase reactions follow elementary rate laws

(1) A + 2B → C ΔH_Rx1B = –15,000cal/mole B

(2) 2A + 3C → D ΔH_Rx2A = –10,000cal/mole A

and take place in a PFR. The feed is stoichiometric for reaction (1) in A and B with F_A0 = 5 mol/min. The reactor volume is 10 dm³ and the total entering concentration is C_T0 = 0.2 mol/dm³. The entering pressure is 100 atm and the entering temperature is 300 K. The coolant flow rate is 50 mol/min and the entering coolant fluid has a heat capacity of C_PCO = 10 cal/mol · K and enters at a temperature of 325 K.

Plot F_A, F_B, F_C, F_D, y, T, and T_a as a function of V for

a. Co-current heat exchange

b. Counter current heat exchange

c. Constant T_a

d. Adiabatic operation

P12-1_A

Read over the problems at the end of this chapter. Make up an original problem that uses the concepts presented in this chapter. To obtain a solution:

a. Make up your data and reaction.

b. Use a real reaction and real data. See Problem P4-1_A for guidelines.

c. Prepare a list of safety considerations for designing and operating chemical reactors. (See www.sache.org and www.siri.org/graphics.) The August 1985 issue of Chemical Engineering Progress may be useful for part (c).

P12-2_A

Load the following Polymath program from the DVD-ROM where appropriate:

a. Example 12-1. Safety. Suppose the value of the equilibrium constant and heat of reaction were measured incorrectly and were found to be K_C = 1,000 mol/dm³ at 330 K and ΔH_Rx = –20,000 kJ/mol. (1) Redo Example 12-1 using these values. (2) Suppose that a second highly exothermic reaction takes place beginning at 400 K. Can any of the heat exchange systems studied here prevent reaching this 400 K temperature? If not, what conditions should be changed to prevent the runaway explosion? (3) Let Q_g = r_AΔH_Rx and Q_r = Ua (T – T_a) and then plot Q_g and Q_r on the same figure as a function of V. (4) Vary the coolant flow rate (0 < < 2,000 kg/h) and the entering temperature 273 (K < T₀ < 315 K) and describe what you find. (5) Vary some of the other parameters and see if you can find unsafe operating conditions. (6) Plot Q_r and T_a as a function of V necessary to maintain isothermal operation.

b. Example 12-2. (1) Let Q_g = r_AΔH_Rx and Q_r = Ua (T – T_a) and then plot Q_g and Q_r on the same figure as a function of V. (2) Fix the reactor volume at 0.5 m³ and the entrance conditions at (T₀ = 1050 K, T_a0 = 1250 K) and then make a table, X_e, X, T_a, and T for each of the heat exchange cases, change the inlet conditions and determine which heat exchanger case gives the greatest differences in the conversion. (3) Repeat (2) for V = 5 m³. (4) Plot Q_g, Q_r, and –r_A versus V for all four cases on the same figure and describe what you find. (5) For each of the four heat exchanger cases, investigate the addition of an inert I with a heat capacity of 50 J/mol · K, keeping F_A0 constant, letting the other inlet conditions adjust accordingly (e.g., ε). (6) Vary the inert molar flow rate (i.e., Θ_I, 0.0 < Θ_I < 3.0 mol/s). Plot X and analyze versus Θ_I. (7) Finally, vary the heat exchange fluid temperature T_a0 (1,000°F < T_a0 < 1350°F). Write a paragraph describing what you find noting any interesting profiles or results.

c. Example 12-2. AspenTech Formulation. Repeat P12-2(b) using AspenTech.

d. Example 12-3. Describe how your answers would change if the molar flow rate of methanol were increased by a factor of 4.

e. Example 12-4. Other data show Btu/lb-mol and C_PA = 29 Btu/lb-mol/°F. How would these values change your results? Make a plot of conversion as a function of heat exchanger area. [0 < A < 200 ft²].

f. Example 12-5. How would your results change if there is (1) a pressure drop with α = 1.05 dm^–3? (2) Reaction (1) is reversible with K_C = 10 at 450 K? (3) How would the selectivity change if Ua is increased? Decreased?

g. Example 12-6. (1) Vary T₀ to make a plot of the reactor temperature, T, as a function of T₀. What are the extinction and ignition temperatures? (2) Vary τ between 0.1 min and 0.001 min and describe what you find. (3) Vary Ua between 4,000 and 400,000 J/min/K and describe what you find.

h. Example 12-7. (1) Safety. Plot Q_g and Q_r as a function of V. How can you keep the maximum temperature below 700 K? Would adding inerts help and if so what should the flow rate be if C_P1 = 10 cal/mol/K? (2) Look at the Figures. What happened to species D? What conditions would you suggest to make more species D? (3) Make a table of the temperature (e.g., maximum T, T_a) and molar flow rates at two or three volumes, comparing the different heat exchanger operations. (4) Why do you think the molar flow rate of C does not go through a maximum? Vary some of the parameters to learn if there are conditions where it goes through a maximum. Start by increasing F_A0 by a factor of 5. (5) Include pressure in this problem. Vary the pressure drop parameter (0 < αρ_b < 0.0999 dm^–3) and describe what you find.

i. DVD-ROM SO₂ Example PRS-R12.4-1. Load the SO₂ oxidation LEP R12-1. How would your results change if (1) the catalyst particle diameter were cut in half? (2) the pressure were doubled? At what particle size does pressure drop become important for the same catalyst weight, assuming the porosity doesn’t change? (3) you vary the initial temperature and the coolant temperature? Write a paragraph describing what you find.

j. SAChE. Go to the SAChE Web site, www.sache.org. On the left hand menu, select “SaChE Products.” Select “All” tab and go to the module entitled, “Safety, Health and the Environment” (S, H & E). The problems are for KINETICS (i.e., CRE). There are some example problems marked “K” and explanations in each of the above S, H & E selections. Solutions to the problems are in a different section of the site. Specifically look at: Loss of Cooling Water (K-1), Runaway Reactions (HT-1), Design of Relief Values (D-2), Temperature Control and Runaway (K-4), and (K-5), and Runaway and the Critical Temperature Region (K-7). Go through the K problems and write a paragraph on what you have learned. Your instructor or department chair should have the user name and password to enter the SAChE Web site in order to obtain the module with the problems.

P12-3_B

Load the Polymath LEP 12-T12-3 for Table T12-2 from the DVD-ROM for this exothermic reversible reaction with a variable coolant temperature. The elementary reaction

has the following parameter values for the base case.

Vary the following parameters in the ranges shown in Parts (a) through (i). Write a paragraph describing the trends you find for each parameter variation and why they look the way they do. Use the base case for parameters not varied. [Hint: See Selftests and Workbook in the Chapter 12 Summary Notes on the DVD-ROM.]

a. F_A0: 1 ≤ F_A0 ≤ 8 mol/s

b. Θ_I: 0.5 ≤ Θ_I ≤ 4

*Note: The program gives Θ_I = 1.0. Therefore, when you vary Θ_I, you will need to account for the corresponding increase or decrease of C_A0 because the total concentration, C_T0, is constant.

c.

d. T₀: 310 K ≤ T₀ ≤ 350 K

e. T_a: 300 K ≤ T_a ≤ 340 K

f.

g. Repeat (f) for counter current coolant flow.

h. Determine the conversion in a 5,000 kg fluidized CSTR where UA = 500 cal/s·K with T_a = 320 K and ρ_b =2 kg/m³.

i. Repeat (a), (b), and (d) if the reaction were endothermic with K_c = 0.01 at 303 K and .

P12-4_A

Load the Interactive Computer Games (ICG) from the DVD-ROM. Play the game, and then record your performance number for the module, which indicates your mastery of the material. Note: For simulation (b), only do the first three reactors, as Reactors 4 and above do not work.

a. ICG Heat Effects Basketball 1 Performance # ________________.

b. ICG Heat Effects Simulation 2 Performance # ________________.

P12-5_C

Safety Problem The following is an excerpt from The Morning News, Wilmington, Delaware (August 3, 1977): “Investigators sift through the debris from blast in quest for the cause [that destroyed the new nitrous oxide plant]. A company spokesman said it appears more likely that the [fatal] blast was caused by another gas—ammonium nitrate—used to produce nitrous oxide.” An 83% (wt) ammonium nitrate and 17% water solution is fed at 200°F to the CSTR operated at a temperature of about 510°F. Molten ammonium nitrate decomposes directly to produce gaseous nitrous oxide and steam. It is believed that pressure fluctuations were observed in the system and, as a result, the molten ammonium nitrate feed to the reactor may have been shut off approximately 4 min prior to the explosion.

Assume that at the time the feed to the CSTR stopped, there was 500 lb_m of ammonium nitrate in the reactor. The conversion in the reactor is believed to be virtually complete at about 99.99%.

Additional information (approximate but close to the real case):

where M is the mass of ammonium nitrate in the CSTR (lb_m) and k is given by the relationship below.

The enthalpies of water and steam are

H_w (200°F) = 168 Btu/lb_m

H_g (500°F = 1202 Btu/lb_m

a. Can you explain the cause of the blast? [Hint: See Problem P13-3_B.]

b. If the feed rate to the reactor just before shutoff was 310 lb_m of solution per hour, what was the exact temperature in the reactor just prior to shutdown? [Hint: Plot Q_r and Q_g as a function of temperature on the same plot.]

c. How would you start up or shut down and control such a reaction?

d. Explore this problem and describe what you find. [For example, add a heat exchanger UA (T – T_a), choose values of UA and T_a, and then plot R(T) versus G(T)?]

e. Discuss what you believe to be the point of the problem. The idea for this problem originated from an article by Ben Horowitz.

P12-6_B

The endothermic liquid-phase elementary reaction

A + B → 2C

proceeds, substantially, to completion in a single steam-jacketed, continuous-stirred reactor (Table P12-6_B). From the following data, calculate the steady-state reactor temperature:

Reactor volume: 125 gal

Steam jacket area: 10 ft²

Jacket steam: 150 psig (365.9°F saturation temperature)

Overall heat-transfer coefficient of jacket, U: 150 Btu/h·ft²·°F

Agitator shaft horsepower: 25 hp

Heat of reaction, Btu/lb-mol of A (independent of temperature)

Table P12-6_B Feed Conditions and Properties

P12-7_A

Use the data in Problem P11-3_A for the following

Additional information

a. Calculate the conversion when the reaction is carried out adiabatically in one 500 dm³ CSTR and then compare the results with the two adiabatic 250 dm³ CSTRs in series.

The reversible reaction (Part (d) of P11-3_A) is now carried out in a PFR with a heat exchanger. Plot and then analyze X, X_e, T, T_a, Q_r, Q_g, and the rate, –r_A, for the following cases

b. Constant heat exchanger temperature T_a

c. Co-current heat exchanger T_a

d. Counter current heat exchanger T_a

e. Adiabatic operation

f. Make a table comparing all your results (e.g., X, X_e, T, T_a). Write a paragraph describing what you find.

g. Plot Q_r and T_a as a function of V necessary to maintain isothermal operation.

P12-8_A

For the reaction

A⇄B

and data in Problem P11-6_B carry out the following. Plot and then analyze X, X_e, T, T_a, and the rate (–r_A) profiles in a PFR for the following cases. In each case, explain why the curves look the way they do.

a. Co-current heat exchange

b. Counter current heat exchange

c. Constant heat exchanger temperature T_a

d. Compare and contrast each of the above results and the results for adiabatic operation (e.g., make a table of X and X_e obtained in each case).

e. Vary some of the parameters, e.g., (0 < Θ_I < 10) and describe what you find.

f. Plot Q_r and T_a as a function of V necessary to maintain isothermal operation.

P12-9_A

Repeat Problem P11-7_B with the reaction

Plot X, X_e, T, T_a and –r_A down the length of the PFR for the following cases.

a. Co-current heat exchange

b. Counter current heat exchange

c. Constant Constant heat exchanger temperature T_a

d. Compare and contrast your results for (a), (b) and (c) along with those for adiabatic operation and write a paragraph describing what you find.

P12-10_B

Use the data and reaction in Problem P11-3_A for the following:

a. Plot and then analyze the conversion, Q_r, Q_g, and temperature profiles up to a PFR reactor volume of 10 dm³ for the case when the reaction is reversible with K_C = 10 m³/kmol at 450 K. Plot and then analyze the equilibrium conversion profile.

b. Repeat (a) when a heat exchanger is added, Ua = 20 cal/m³/s/K, and the coolant temperature is constant at T_a = 450 K.

c. Repeat (b) for both a co-current and a counter current heat exchanger. The coolant flow rate is 50 g/s, C_Pc = 1 cal/g · K, and the inlet coolant temperature is T_a0 = 450 K. Vary the coolant rate .

d. Plot Q_r and T_a as a function of V necessary to maintain isothermal operation.

e. Compare your answers to (a) through (d) and describe what you find. What generalizations can you make?

f. Repeat (c) and (d) when the reaction is irreversible but endothermic with . Choose T_a0 = 450 K.

P12-11_B

Use the data in Problem P11-4_A for the case when heat is removed by a heat exchanger jacketing the reactor. The flow rate of coolant through the jacket is sufficiently high that the ambient exchanger temperature is constant at T_a = 50°C.

a.

b. Repeat part (a) for co-current and counter current flow and adiabatic operation with , C_PC = 5,000 J/kg K and an entering coolant temperature of 50°C.

c. Find X and T for a “fluidized” CSTR [see margin] with 80 kg of catalyst.

d. Repeat parts (a) and (b) for W = 80.0 kg, assuming a reversible reaction with a reverse specific reaction rate of

Vary the entering temperature, T₀, and describe what you find.

e. Use or modify the data in this problem to suggest another question or calculation. Explain why your question requires either critical thinking or creative thinking. See Preface B.2, B.3 and http://www.engin.umich.edu/scps.

P12-12_C

Derive the energy balance for a packed bed membrane reactor. Apply the balance to the reaction in Problem P11-4_B for the case when it is reversible with K_C = 1.0 mol/dm³ at 300 K. Species C diffuses out of the membrane with k_C = 1.5 s^–1.

a. Plot and then analyze the concentration profiles for different values of K_C when the reaction is carried out adiabatically.

b. Repeat part (a) when the heat transfer coefficient is Ua = 30 J/s·kg cat·K with T_a = 50·C.

P12-13_C

The biomass reaction

is carried out in a 6 dm³ chemostat with a heat exchanger.

The volumetric flow rate is 1 dm³/h and the entering substrate concentration and temperature are 100 g/dm³ and 280 K, respectively. The temperature dependence of the growth rate follows that given by Aibe et al., Equation (9-63)

r_g = μC_c

and

P12-14.1

a. Plot G(T) and R(T) for both adiabatic and non-adiabatic operation assuming a very large coolant rate (i.e., with A = 1.1 m² and T_a = 290 K).

b. What is the heat exchanger area that should be used to maximize the exiting cell concentration for an entering temperature of 288 K? Cooling water is available at 290 K and up to a maximum flow rate of 1 kg/min.

c. Identify any multiple steady states and discuss them in light of what you learned in this chapter. [Hint: Plot T_s vs. T₀ from Part (a).]

d. Vary T_o, , and T_a and describe what you find.

Additional information

Y_C/S = 0.8 g cell/g substrate, C_C = C_S0 Y_C/S X

K_S = 5.0 g/dm³

μ_1max = 0.5h^–1 (note μ = μmax at 310 K)

C_Ps = Heat capacity of substrate solution including all cells = 5 J/g/K

m_s = Mass of substrate solution in chemostat = 6.0 kg

U = 50,000 J/h/K/m²

C_Pc = Heat capacity of cooling water 5 J/g/K

= coolant flow rate (up to 60,000 kg/h)

ρ_S = solution density = 1 kg / dm³

Note:

P12-14_A

The irreversible reaction

is carried out adiabatically in a CSTR. The “heat generated” [G(T)] and the “heat removed” [R(T)] curves are shown in Figure P12-14_A.

Figure . Figure P12-14_A Heat removed R(T) and heat “generated” G(T) curves.

a. What is the ΔH_Rx of the reaction?

b. What are the inlet ignition and extinction temperatures?

c. What are all the corresponding temperatures in the reactor corresponding to the inlet ignition and extinction temperature?

d. What are the conversions at the ignition and extinction temperatures?

P12-15_B

The first-order irreversible exothermic liquid-phase reaction

A → B

is to be carried out in a jacketed CSTR. Species A and an inert I are fed to the reactor in equimolar amounts. The molar feed rate of A is 80 mol/min.

Additional information

a. What is the reactor temperature for a feed temperature of 450 K?

b. Plot and then analyze the reactor temperature as a function of the feed temperature.

c. To what inlet temperature must the fluid be preheated for the reactor to operate at a high conversion? What are the corresponding temperature and conversion of the fluid in the CSTR at this inlet temperature?

d. Suppose that the fluid inlet temperature is now heated 5°C above the reactor temperature in part (c) and then cooled 20°C, where it remains. What will be the conversion?

e. What is the inlet extinction temperature for this reaction system? [Ans.: T₀ = 87°C.]

P12-16_B

The elementary reversible liquid-phase reaction

takes place in a CSTR with a heat exchanger. Pure A enters the reactor.

a. Derive an expression (or set of expressions) to calculate G(T) as a function of heat of reaction, equilibrium constant, temperature, and so on. Show a sample calculation for G(T) at T = 400 K.

b. What are the steady-state temperatures? [Ans.: 310, 377, 418 K.]

c. Which steady states are locally stable?

d. What is the conversion corresponding to the upper steady state?

e. Vary the ambient temperature T_a and make a plot of the reactor temperature as a function of T_a, identifying the ignition and extinction temperatures.

f. If the heat exchanger in the reactor suddenly fails (i.e., UA = 0), what would be the conversion and the reactor temperature when the new upper steady state is reached? [Ans.: 431 K.]

g. What heat exchanger product, UA, will give the maximum conversion?

h. Write a question that requires critical thinking and then explain why your question requires critical thinking. [Hint: See Preface Section B.2.]

i. What is the adiabatic blowout flow rate, υ₀?

j. Suppose that you want to operate at the lower steady state. What parameter values would you suggest to prevent runaway, e.g., the upper SS?

Additional information

P12-17_C

The first-order irreversible liquid-phase reaction

A → B

is to be carried out in a jacketed CSTR. Pure A is fed to the reactor at a rate of 0.5 g mol/min. The heat-generation curve for this reaction and reactor system,

is shown in Figure P12-17_C.

Figure . Figure P12-17_C G(T) curve.

a. To what inlet temperature must the fluid be preheated for the reactor to operate at a high conversion? [Ans.: T₀ ≥ 214°C.]

b. What is the corresponding temperature of the fluid in the CSTR at this inlet temperature? [Ans.: T_s = 164°C, 184°C.]

c. Suppose that the fluid is now heated 5°C above the temperature in part (a) and then cooled 10°C, where it remains. What will be the conversion? [Ans.: X = 0.9.]

d. What is the extinction temperature for this reaction system? [Ans.: T₀ = 190°C.]

e. Write a question that requires critical thinking and then explain why your question requires critical thinking. [Hint: See Preface Section B.2.]

Additional information

The G(T) curve for this reaction is shown in Figure P12-17_B

Heat of reaction (constant): –100 cal/mol A

Heat capacity of A and B: 2 cal/mol°C

UA: 1 cal/min·°C, Ambient temperature, T_a: 100°C

P12-18_C

The reversible liquid phase reaction

A ⇄ B

is carried out in a 12 dm³ CSTR with heat exchange. Both the entering temperature, T₀, and the heat exchange fluid, T_a, are at 330°K. An equal molar mixture of inerts and A enter the reactor.

a. What product of the heat transfer coefficient and heat exchange area would give the maximum conversion?

b. What is the maximum conversion?

Additional information

C_PA = C_PB = 100 cal/mol/K, C_P1 = 150 cal/mol/K

F_A0 = 10 mol/h, C_A0 = 1 mol/dm³, υ₀ = 10 dm³/h

ΔH_Rx = –42,000 cal/mol

K = 0.001 h^–1 at 300K with E = 30,000 cal/mol

K_C = 5,000,000 at 300K

P12-19_C

The elementary gas phase reaction

2A ⇄ C

is carried out in a packed-bed reactor. Pure A enters the reactor at 450 K flow rate of 10 mol/s, and a concentration of 0.25 mol/dm³. The PBR contains 90 kg of catalyst and is surrounded by a heat exchanger for which cooling fluid is available at 500 K. Compare the conversion achieved for the four types of heat exchanger operation: adiabatic, constant T_a, co-current flow, and counter current flow.

Additional information

α = 0.019/kg cat.

Ua/ρ_b = 0.8 J/kg cat · s · K

C_PA = 40 J/mol · K

C_PC = 20 J/mol/K

F_A0 = 10 mol/h

C_A0 = 1 mol/dm³

υ₀ = 10 dm³/h

P12-20_C

A reaction is to be carried out in the packed-bed reactor shown in Figure P12-20_C.

Figure . Figure P12-20_C PFR with heat exchange.

The reactants enter in the annular space between an outer insulated tube and an inner tube containing the catalyst. No reaction takes place in the annular region. Heat transfer between the gas in this packed-bed reactor and the gas flowing counter currently in the annular space occurs along the length of the reactor. The overall heat-transfer coefficient is 5 W/m²·K. Plot the conversion and temperature as a function of reactor length for the data given in

a. Problem P11-3_A.

b. Problem P12-10_B(a).

P12-21_B

The irreversible liquid-phase reactions

are carried out in a PFR with heat exchange. The following temperature profiles were obtained for the reaction and the coolant stream.

Figure . Figure P12-21_B Reactant temperature T and coolant temperature T_a profiles.

The concentrations of A, B, C, and D were measured at the point down the reactor where the liquid temperature, T, reached a maximum, and they were found to be C_A = 0.1, C_B = 0.2, C_C = 0.5, and C_D = 1.5 all in mol/dm³. The product of the overall heat-transfer coefficient and the heat-exchanger area per unit volume, Ua, is 10 cal/s · dm³ · K. The feed is equal molar in A and B, and the entering molar flow rate of A is 10 mol/s.

Additional information

a. What is the activation energy for Reaction (1)?

P12-22_B

The elementary liquid phase reactions

are carried out adiabatically in a 10 dm³ PFR. After streams A and B mix, species A enters the reactor at a concentration of C_A0 = 2 mol/dm³ and species B at a concentration of 4 mol/dm³. The entering volumetric flow rate is 10 dm³/s.

Assuming you could vary the entering temperature between 300K and 600 K, what entering temperture would you recommend to maximize the concentration of species C exiting the reactor? (±25°K). Assume all species have the same density.

Additional information

P12-23_C

(Multiple reactions with heat effects) Xylene has three major isomers, m-xylene, o-xylene, and p-xylene. When o-xylene is passed over a Cryotite catalyst, the following elementary reactions are observed. The reaction to form p-xylene is irreversible:

The feed to the reactor is equal molar in both m-xylene and o-xylene (species A and B respectively). For a total feed rate of 2 mol/min and the reaction conditions below, plot the temperature and the molar flow rates of each species as a function of catalyst weight up to a weight of 100 kg.

a. Find the lowest concentration of o-xylene achieved in the reactor.

b. Find the highest concentration of m-xylene achieved in the reactor.

c. Find the maximum concentration of o-xylene in the reactor.

d. Repeat parts (a) to (c) for a pure feed of o-xylene.

e. Vary some of the system parameters and describe what you learn.

f. What do you believe to be the point of this problem?

Additional information⁸

All heat capacities are virtually the same at 100 J/mol · K.

P12-24_C

(Comprehensive Problem on multiple reactions with heat effects) Styrene can be produced from ethylbenzene by the following reaction:

1

However, several irreversible side reactions also occur:

2

3

[J. Snyder and B. Subramaniam, Chem. Eng. Sci., 49, 5585 (1994)]. Ethylbenzene is fed at a rate of 0.00344 kmol/s to a 10.0-m³ PFR (PBR), along with inert steam at a total pressure of 2.4 atm. The steam/ethylbenzene molar ratio is initially [i.e., parts (a) to (c)] 14.5:1 but can be varied.

Given the following data, find the exiting molar flow rates of styrene, benzene, and toluene along with for the following inlet temperatures when the reactor is operated adiabatically.

a. T₀ = 800 K

b. T₀ = 930 K

c. T₀ = 1100 K

d. Find the ideal inlet temperature for the production of styrene for a steam/ethylbenzene ratio of 58:1. [Hint: Plot the molar flow rate of styrene versus T₀. Explain why your curve looks the way it does.]

e. Find the ideal steam/ethylbenzene ratio for the production of styrene at 900 K. [Hint: See part (d).]

f. It is proposed to add a counter current heat exchanger with Ua = 100 kJ/m³/min/K where T_a is virtually constant at 1000 K. For an entering stream to ethylbenzene ratio of 20, what would you suggest as an entering temperature? Plot the molar flow rates and .

g. What do you believe to be the major points of this problem?

h. Ask another question or suggest another calculation that can be made for this problem.

Additional information

The kinetic rate laws for the formation of styrene (St), benzene (B), and toluene (T), respectively, are as follows (EB = ethylbenzene).

The temperature T is in Kelvin and P_i is in atm.

P12-25_B

The liquid phase dimer-quadmer series addition reaction

4A → 2A₂ → A₄

can be written as

and is carried out in a 10 dm³ PFR. The mass flow rate through the heat exchanger surrounding the reactor is sufficiently large so that the ambient temperature of the exchanger is constant at T_a = 315 K. The reactants enter at a temperature T₀, of 300 K. Pure A is fed to the rector at a volumetric flow rate of 50 dm³/s and a concentration of 2 mol/dm³.

a. Plot, compare, and analyze the profiles F_A, F_A2, and F_A4, down the length of the reactor up to 10 dm³.

b. The desired product is A₂ and it has been suggested that the current reactor may be too large. What reactor volume would you recommend to maximize F_A2?

c. What operating variables (e.g., T₀, T_a) would you change and how would you change to make the reactor volume as small as possible and still to maximize F_A2? Note any opposing factors in maximum production of A₂. The ambient temperature and the inlet temperature must be kept between 0°C and 177°C.

Additional information

Turn in your recommendation of reactor volume to maximize F_A2 and the molar flow rate at this maximum.

P12-26_B

The gas phase trimer-hexamer series addition reaction

6A → 2A₃ → A₆

can be written as

and is carried out in a 10 dm³ CSTR with heat exchanger. The mass flow rate through the heat exchange surrounding the reactor is sufficiently large. The ambient temperature of the exchanger is constant at T_a = 315 K and the entering temperature T₀ is 300K. Pure A is fed to the rector at a volumetric flow rate of 50 dm³/s and a concentration of 2 mol/dm³. Find F_A, F_A3, F_A6, and T exiting the reactor.

Additional information