Questions and Answers of Analysis Synthesis And Design Of Chemical Processes

The distillate stream from a distillation column (flowrate \(35 \mathrm{~m}^{3} / \mathrm{h}\), density of water) is recycled. The destination of the recycle stream is a point \(3 \mathrm{~m}\) below
Consider the system illustrated in Figure P22.25(a). The process is to be scaled up from a design flowrate of \(120 \mathrm{~m}^{3} / \mathrm{h}\). The fluid is a liquid, and it is to be fed to a
Consider the molten salt loop for removal of the heat of reaction in the production of phthalic anhydride described in Appendix C (on the CD) and illustrated in Figure C.5. It is necessary to scale
In the previous problem, it may be necessary to scale up or scale down by as much as \(50 \%\) from the original operating conditions. Prepare a performance curve similar to the one in Figure 21. 1
Consider Figure E17.6(a), in which the overall heat transfer coefficient \((U)\) is assumed to be 25 W/m2οC. It can be noted that in Figure E 17.6 (b) and E 17.6 (c)(b) the transients in
Modify the preceding problem to develop a flowsheet as shown in Figure P16.8. Replace the heat exchanger, E-2001, with a countercurrent heat exchanger between the feed to and product from the
Experimental solubility data of \(\mathrm{H}_{2} \mathrm{~S}\) in diglycolamine (DGA) have been provided by Martin et al. [17]. The DGA solution used in their experiment had \(60 \mathrm{wt} \%\)
Draw input/output diagrams for the following pieces of equipment:a. A fluidized bedb. A turbinec. A pumpd. A strippere. An adiabatic batch reactorf. A semibatch reactor with heat removal g. A heat
Write down the equipment-independent and equipment-dependent relationships for each piece of equipment listed in Problem 19. 1.Data from problem 19.1 Draw input/output diagrams for the following
Write down the equipment-independent and equipment-dependent relationships for a distillation column.
Draw input/output diagrams for the following processes. Pick any two adjacent pieces of equipment, and draw input/output diagrams for these, clearly showing how the output from one affects the input
It is known that for a certain second-order, elementary, gas-phase reaction, the rate of reaction doubles when the temperature goes from \(220^{\circ} \mathrm{C}\) to \(250^{\circ} \mathrm{C}\). If
A storage tank is connected to a pond (at atmospheric pressure!) by a length of 3-in pipe and two gate valves. From previous operating experience, it has been found that when the tank is at a
In a single-pass shell-and-tube heat exchanger, cooling water is used to condense an organic vapor. Under present operating conditions, the heat transfer coefficients are \(h_{o}=2000 \mathrm{~W} /
In a shell-and-tube heat exchanger, the overall and individual heat transfer coefficients are \(U=\)\(300 \mathrm{~W} / \mathrm{m}^{2} \mathrm{~K}, h_{i}=1000 \mathrm{~W} / \mathrm{m}^{2}
Derive the relationship, identical to Equation (20.9), for the situation described in Example 20.3.Equation 20.9Example 20.3 U 11/2 U h 0.8 (20.9)
You are considering two pipes to connect liquid leaving a pump to the entrance to a reactor. For a given mass flowrate of liquid, how much operating cost would you save (or lose) by using 2. 5in
For laminar flow of a Newtonian liquid in a pipe, determine the effect on flowrate of the following changes:a. The pressure drop triples (everything else remains constant).b. The pipe is changed from
Sketch \(T-Q\) diagrams for the following situations:a. The condenser on a distillation column; vapor condenses at \(160^{\circ} \mathrm{C}\) and is sub-cooled to \(130^{\circ} \mathrm{C}\), cooling
Air at approximately STP and \(15 \mathrm{~kg} / \mathrm{s}\) flows through \(100 \mathrm{~m}\) of 8-in commercial steel schedule40 pipe. Derive an expression for the system curve and sketch the
What is a pump curve? Sketch a typical pump curve, making sure that both axes are clearly labeled. On the same sketch, show a typical system curve. Indicate the typical region of good operating
Comment on the following statement: For a two-pump system, it is always best to run the two pumps in series rather than in parallel because greater scale-up will be possible.
Explain the meaning of the intersection of the two curves on the diagrams in Figure P21.3. P (a) Flowrate NPSH (b) Flowrate Figure P21.3. Diagrams for Problem 21.3
Comment on the following statement: The film heat transfer coefficient always increases with flowrate to the 0. 8 power.
For a given flowrate, it is known that the pump through which the process flows cavitates. The pump has a spare, and a temporary fix to run both pumps simultaneously has been suggested. The pumps can
A storage tank uses gravity flow to supply a liquid feed material to a holding tank. The pressures and levels in each tank can be considered to be constant. If the viscosity of the fluid is sensitive
Two columns operate in a chemical plant. The first column operates at a pressure of 10 bar, and the second at a temperature of 1 bar. For process reasons, the pressures in the two columns are both
Explain, using equations where appropriate, why a pump located even with the bottom of a pressurized tank containing a vapor-liquid mixture of a pure component will likely not ever cavitate
A storage tank is connected to a pond (at atmospheric pressure!) by a length of 4-in pipe and a gate valve. From previous operating experience, it has been found that when the tank is at a pressure
Consider the pump and system curves in Figure P21.11 for identical pumps arranged in parallel and series.Figure P21.11a. If the flowrate is increased from \(3 \mathrm{~L} / \mathrm{s}\) to \(4
Operating data taken from the plant shortly following the cleaning of the reboiler tubes show that\[T_{\text {in }}=325^{\circ} \mathrm{C}, T_{\text {out }}=293^{\circ} \mathrm{C}, \dot{m}_{s}=1650
This is a continuation of Problem 21. 12. Estimate the fouling resistance for the base case presented in Figure 21. 1(a).Figure 21.1 (a)Data from problem 21.12Operating data taken from the plant
This is a continuation of Problem 21. 12. Typical heat transfer coefficients given in Table 11. 11 are used to predict the ratio of heat transfer resistances between boiling water and light oil. This
a. Use the guideline from Tables 11. 11 and \(\underline{11.18}\) to establish "normal" limits on the amount of heat that could be exchanged.b. How do these limits explain the fouling of the heat
a. Estimate the relative increase in heat duty that would result from increasing the liquid level from the base case to cover the tubes completely. The input streams and vapor temperature remain the
For the system presented in Example 21. 3 you are asked to appraise the effects of adding a second pump and impeller set identical to the current pump in the system.a. Prepare a performance diagram,
Referring to Example 21. 3, it has been decided that the storage tank should be kept at 1 bar and the reactor pressure at 1. 2 bar. To provide the pressure head required, a pump is placed in line
A centrifugal pump produces head by accelerating fluid to a velocity approaching the tip velocity of the rotating impeller. The liquid leaving the pump is at a high velocity and is forced into the
Naphthalene is fed to a phthalic anhydride production process. The feed is available at \(208^{\circ} \mathrm{C}\) and \(79 \mathrm{kPa}\). The flowrate is \(18,500 \mathrm{~kg} / \mathrm{h}\) in 1.
Refer to Example 21. 8. There are additional methods other than the two presented for increasing the NPSH in order to avoid pump cavitation. For the following situations, sketch the
Refer to the compressor curves given in Figure 21. 11.Figure 21.11a. At a flowrate of \(125 \mathrm{Mg} / \mathrm{h}\), what is the exit pressure from the compressor operating at 3500 rpm if the
A packed scrubber with 20 transfer units has been designed to reduce the solute concentration in \(80 \mathrm{kmol} / \mathrm{h}\) of air from a mole fraction of 0. 01 to 0. 006 . The solute is
Prepare a set of performance curves similar to those in Example 21. 10 for a packed scrubber with 10 transfer units that removes solute from air from a mole fraction of 0. 02 to a mole fraction of 0.
Repeat Problem 21. 24 and Example 21. 10 with the following change: In each case, the gas flowrate remains constant at the original conditions. The parameter on the performance curve is now absorber
The scrubber in Problem 21. 23 has been running well for several years. It is now observed that the outlet solute mole fraction in air is 0. 002 . Suggest at least five reasons for this observation.
It is necessary to increase the capacity of an existing distillation column by \(25 \%\). As a consequence, the amount of liquid condensed in the condenser must increase by \(25 \%\). In this
Prepare a performance plot for vapor velocity as a function of feed composition with benzene recovery as a parameter.
Prepare a performance plot for boil-up rate as a function of feed composition with benzene recovery as a parameter.
Prepare a performance plot for reboiler duty as a function of feed composition with benzene recovery as a parameter.
For the distillation problem outlined in Section 21. 3.2,a. Determine the values of \(F, B\), and \(x_{B}\) required when the concentration of the feed becomes \(z_{F}\) \(=0.25\). Assume that the
The information given in Figure 21. 18 showed that the benzene recovery column was not operating at maximum benzene recovery.Figure 21.18a. Estimate the maximum value of benzene recovery for the base
For the same feed, distillate, and bottoms shown in Figure 21. 16, determine the following:Figure 21.16a. The boil-up, \(V_{N+1}\), and reflux, \(L_{0}\), required if the feed is now introduced at
Assume that the distillation column in Figure 21. 16 is to be operated at the same value of \(L_{0}, D\), and \(B\) and the same feed as the base case.Figure 21.16a. Calculate \(x_{D}, x_{B}\), and
A heat exchanger was put into service approximately one year ago. The design conditions are that process gas is cooled from \(100^{\circ} \mathrm{C}\) to \(50^{\circ} \mathrm{C}\), with cooling water
In a process that produces a temperature-sensitive product, the final step is to cool the product from \(70^{\circ} \mathrm{C}\) to \(35^{\circ} \mathrm{C}\) prior to sending it to storage. This
A desuperheater permits the temperature of saturated steam entering a heat exchanger to be controlled. This is accomplished by having a valve that changes the pressure of the source steam to a known
In the process to produce acetone from isopropyl alcohol (see process description on the CD), heat is supplied to the endothermic reaction using a Dowtherm A (or molten salt) loop and a fired heater.
In a distillation column, if the bottom pressure decreases, what is the effect on the bottom temperature, the top pressure, the top temperature, and the flooding situation? Assume that all flows,
It is possible to generate performance curves for the reactor in Section 22. 1. One type of performance curve would have the rate of cumene production \((\mathrm{kmol} / \mathrm{h})\) on the
Repeat Problem 22. 3 for varying reaction pressure at a constant temperature of \(350^{\circ} \mathrm{C}\). The pressure range is \(3000 \mathrm{kPa}\) to \(3300 \mathrm{kPa}\), in intervals of \(50
For the distillation performance problem in Section 22. 2, assume that scale-down occurs while maintaining constant boil-up rate. Determine the conditions in the reboiler, column, and condenser for
The benzene-toluene distillation column in Section 22. 2 must temporarily handle a \(25 \%\) increase in throughput while maintaining the same outlet concentrations. Determine the operating
Suggest alternative changes in process conditions or addition of new equipment in the distillation column in Section 22. 2 that would allow 50\% scale-down. Suggest as many alternatives as you can
Consider the Dowtherm A loop described in Section 22. 3. For the options involving multiple pumps either in series or parallel, determine the configuration that provides the maximum scaleup capacity.
Repeat the analysis in Section 22. 3 for the case when cooling water is used in the heat exchanger in place of boiler feed water. The cooling water enters at \(30^{\circ} \mathrm{C}\) and must exit
Repeat the analysis in Problem 22. 8 using cooling water as described in Problem 22. 9.Data from problem 22.8 Consider the Dowtherm A loop described in Section 22.3. For the options involving
Suggest alternative solutions, not involving increasing the Dowtherm A flowrate, to obtain the maximum scale-up possible in the Dowtherm A loop in Section 22. 3. Suggest as many alternatives as you
Consider the situation illustrated in Figure P22.13. Due to downstream considerations, \(P_{8}\) is always maintained at \(200 \mathrm{kPa}\). It is known that \(P_{1}=100 \mathrm{kPa}\) and
Refer to Figure P22.14 and the data provided with the figure. The compressor (C-101) exhausts to \(101 \mathrm{kPa}\). Tank TK-102 is controlled to be always \(101 \mathrm{kPa}\). Assume all flows
Consider a process in which a fluid is pumped from a storage tank through a heat exchanger, where it is heated and then pumped into another storage tank. The process flow diagram for this process is
During the retrofit of a chemical plant, it was decided to place valves and bypass lines around two exchangers placed in series. The flows through each of the bypass lines are controlled by the
The feed system for a distillation process is shown in Figure P22.17(a). The feed to be distilled is an organic liquid stored in V-301 under a nitrogen blanket at a constant pressure of \(21
In the production of acrylic acid, the final step is distillation of an acrylic acid/acetic acid mixture. The acrylic acid, which is the bottoms product, may not exceed \(90^{\circ} \mathrm{C}\) due
The distillate stream from a distillation column (flowrate \(35 \mathrm{~m}^{3} / \mathrm{h}\), density of water) is recycled. The destination of the recycle stream is at a location \(3 \mathrm{~m}\)
A process heat exchanger has a bypass around it that is normally closed, thus forcing all the process flow through the exchanger. The process fluid (vapor) flows through the shell side of an
You are trying to evaluate whether an existing, idle distillation column can be used for a separation for which it was not originally designed. Answer the following questions about this column:a. The
During the design of a new separation system, a reboiler using throttled and desuperheated lowpressure steam ( 5 barg, \(T_{\text {sat }}=160^{\circ} \mathrm{C}\) ) was specified. The details of this
The bottoms product from a distillation column is pumped through two heat exchangers to recover energy and is then sent to a storage tank, which is at atmospheric pressure. The system is shown in
Two heat exchangers of equal area have been designed to heat a certain process fluid from \(50^{\circ} \mathrm{C}\) to \(100^{\circ} \mathrm{C}\) using condensing saturated steam at \(150^{\circ}
Explain why very high conversions ( \(>99 \%\) ) are often difficult to achieve in practice, even for plug flow reactors and nonequilibrium constrained reactions.
For the reactor system shown in Figure P23.4, answer the following:a. Is the reaction exothermic or endothermic?b. Give two reasons why this reaction is being run at a high temperature.Figure 23.4 CW
For the hypothetical, endothermic, gas-phase reaction\[A+B=C\]sketch a plot similar to Figure E23.1. Discuss the relationship between equilibrium conversion, temperature, and pressure.Figure E23.1
For the situation in Example 23. 3, if all of the reactions take place, what conditions maximize the selectivity for \(P\)?Example 23.3 Consider the reaction scheme given in Equation (23.1) where P
Examine the reaction network and the reaction kinetics for drying oil production in Appendix B, Section B.4.2. What conditions will maximize the selectivity for drying oil? Sketch concentration
Examine the reaction network and the reaction kinetics for ethylene oxide production in Appendix B, Section B.6.2. What conditions will maximize the selectivity for ethylene oxide? Sketch
Investigate the effect of increasing reactor volume on toluene conversion. Plot the results.Problems 23. 12-23.16 investigate the performance of the reactor section for a noncatalytic process for the
Investigate the effect of a variation of hydrogen feed rate (all other parameters held constant at base-case values).Problems 23. 12-23.16 investigate the performance of the reactor section for a
Investigate a two-reactor system to replace the single adiabatic PFR in the base case. The tworeactor system consists of an adiabatic CSTR followed by an adiabatic PFR. For the base-case toluene
Investigate the effect of increasing the feed rate on reactor performance.a. Prepare a performance curve of the toluene conversion versus feed rate.b. Prepare a performance curve of benzene generated
Investigate the effect of feed temperature on reactor performance. Prepare a performance curve for toluene conversion versus feed temperature.Problems 23. 12-23.16 investigate the performance of the
a. Derive an equation for the ratio \(\eta=\) rate of cumene formation/rate of DIPB formation Rewrite the equation in the form \(\eta=A / B-1\).b. Present the equation for \(\eta\) given above in
Replace the current catalyst with the new catalyst (maintain the same feed rate and conditions) anda. Provide a flow table (similar to that in Figure 23. 6).b. Compare cumene production with the new
Evaluate the effectiveness of the new catalyst at \(350^{\circ} \mathrm{C}\) that results from increasing the reactor volume.a. Plot cumene production versus reactor volume.b. Plot selectivity
In Figures 23. 8 and 23. 9, the volumetric flowrate to the reactor was held constant at increased temperatures by reducing the hydrogen in the feed. This altered the feed concentration. Investigate
Reconfigure the heating system to operate in countercurrent fashion. Retain the same utility stream input and IPA conversion (90\%).a. Determine the change in process feed rate.b. Determine the
Increase the utility feed rate by \(50 \%\), and maintain the base-case process feed stream.a. Determine the conversion obtained.b. Determine the percent change in the acetone produced.Problems 23.
Increase the utility feed rate by \(50 \%\). Retain the IPA conversion of 0. 9 .a. Determine the process feed rate.b. Determine the percent change in acetone produced.Problems 23. 21-23.26
Increase the utility feed temperature by \(50^{\circ} \mathrm{C}\). Retain the IPA conversion at 0. 9 .a. Determine the process feed rate.b. Determine the percent change in acetone
Prepare a performance curve for the change in utility flowrate necessary to maintain an IPA conversion of 0. 9 at increased process feed rates.Problems 23. 21-23.26 investigate the performance of the
Assume the individual film coefficients change according to the relationship\[h_{i} \alpha \text { velocity }{ }^{0.8}\]a. Estimate the effect of process flow changes on the overall heat transfer

Showing 1 - 100 of 1013