Questions and Answers of Analysis Synthesis And Design Of Chemical Processes

Consider the problem given in Example 23.10 and assume that the ejector rated for the design conditions given in Example 23.10 has been purchased and is operating. However, during operation it has
What is the purpose of a mist eliminator?
Does a mist eliminator capture equally drops of different sizes in the vapor?
For what process function is the use of a V-L separator most critical?
For an L-L separator, do liquid drops separate slower or faster than drops of liquid in a V-L separator? Explain your answer.
What is the main principle of operation for a parallel plate L-L separator?
Why are steam ejectors needed for systems that operate below atmospheric pressure?
What is the advantage of partially condensing the intermediate stream in a multistage steam ejector?
Do steam ejectors typically operate in the subsonic or supersonic region?
Give two sources of noncondensable gas that may contribute to the vent stream leaving the reflux drum on a distillation tower that operates at vacuum conditions.
Determine the mass of a pressure vessel made of 304 stainless steel (SS), with standard (ASME) dished heads. The dimensions of the vessel are a diameter of 2.4 m and a length of 8.5 m
Repeat Problem 23.21 but using 316 SS as the material of construction. If the relative costs of 316 to 304 SS are 1:1.29, and both materials are suitable for the service, which material do you
A V-L separator drum is to be designed downstream of a reactor. The stream leaving a partial condenser that is the feed to the knockout drum has the following properties:Answer the following
Estimate the mass of the vessel designed in Problem 23.24, assuming a corrosion allowance of 6.35 mm and a material of construction of SA515-70 carbon steel. Use 2:1 elliptical heads but do not
If the vessel in Problems 23.21 and 23.22 were to handle 50% nitric acid, what material of construction would you recommend, and why?Problems 23.22Repeat Problem 23.21 but using 316 SS as the
Estimate the diameter of a vertical V-L separator containing a 6 in (150 mm) thick stainless steel wire mesh mist eliminator. The properties of the gas and liquid areFor the stainless steel mist
Consider the horizontal V-L drum designed in Examples 23.4, 23.5, and 23.6. Based on the conditions at the operating design point (using NOL), determine the maximum size of gas bubble that would not
What is the equivalent value of k for the mist eliminator in Problem 23.26 that would give the same diameter for the vessel?Problem 23.26Estimate the diameter of a vertical V-L separator containing a
Repeat Problem 23.29 for the case when the liquid residence time is 5 min instead of 10 min for Examples 23.4, 23.5, and 23.6. You may assume that the heights of liquid in the drum are the
Determine the pressure drop in the mist eliminator designed in Problem 23.26. Using this result, determine the maximum size of droplet for which the capture rate is 99% in this device at the design
For Example 23.11, Part (b), rework the problem for the case when the stream leaving the first stage of the ejector is condensed using cooling water (in at 30°C and out at 40°C) with a 5°C
For Problem 23.32, determine whether it is more economical to use the two-stage ejector with intermediate condensation than the noncondensing option given in Example 23.11, Part (b). Use the
A liquid-liquid separator, with a parallel plate settler installed horizontally, is 1.4 m in length and has a separation distance of 30 mm between the plates. The densities of the two liquids to be
The overhead reflux drum for a vacuum column in an oil refinery operates at 25 mmHg. The overhead temperature is 120°F, and the composition and flowrate of the vapor in the vent gas (not including
It is desired to maintain a vacuum of 100 mmHg absolute pressure in a drum by removing accumulated vapors (average MW = 40 g/mol, flowrate 200 kg/h, temperature = 50°C) and discharging them to an
A single-stage steam ejector is designed to remove 50 kg/h of air from a reflux drum operating at 25 kPa and 50°C and discharge it to the atmosphere through a vent using a steam ejector with
In the preceding problem, the composition of the feed was assumed to be constant. However, the CO/H2 ratio in the feed can be manipulated as these streams are usually supplied from different sources.
Consider Problem 16.22, but for the case when the unconverted reactants are recycled to the reactor, as shown in Figure P16.23. Consider the purge-stream flow to be 2% of the total flow of Stream 6,
In a process for producing methanol, synthesis gas composed of CO, CO1, H1, and H2O is sent through a heat exchanger, E- 2001, to a plug-flow reactor, R-2001, as shown in Figure P16.21. In addition
Consider Example 16.7. Make following modifications. For each modification, solve the optimization problems when the objective function is the operating cost and when the objective function is the
Formulate an optimization problem considering the flowsheet in Problem 16.16. One design block and two calculator blocks are active. Minimize the operating cost of this AGR unit:Assume the cost of
Experimental solubility data of H2S in diglycolamine (DGA) have been provided by Martin et al. The DGA solution used in their experiment had 60 wt% DGA, and the remainder was water. Equilibrium data,
n-Methyl-2-pyrrolidone (NMP) is a physical solvent that is widely used for acid gas removal. For improving the accuracy of the VLE calculation using an activity-coefficient model, it is desired that
Develop two dynamic models of the process heat exchanger shown in Figures E17.2(a)(a) and E17.2(a)(b), one with the simple option and another with the rigorous option. In this process heat exchanger,
What information about a process can be obtained from a dynamic simulation that is not possible to obtain from a steady-state simulation?
Steam is being condensed in a surface condenser of a steam turbine under vacuum using cooling water. The flowrate of the steam to the condenser is 50 kmol/h at a temperature and pressure of 55°C and
For obtaining a valid pressure-flow network, why should the pressure nodes be connected through flow devices?
Two flash vessels have the same length (L) but different diameters (D). Both vessels contain the same material and have the same operating pressure and temperature. In both vessels, the liquid level
Figure E17.3(a) shows the schematic of a jacketed flash vessel in which a mixture of CO and methanol is being separated. The inlet temperature of the heating medium stream is 90°C and its specific
In a process, it is desired to manipulate the refrigerant flowrate to a cooler to maintain the cooler outlet temperature. What heat transfer option would you choose for developing a dynamic model of
Synthesis gas composed of CO, CO2, H2, and H O is sent to a plug-flow reactor, R-1101, through a feed valve for producing methanol as shown in Figure E17.4(a). The following reactions take place [10,
In a cooler, cooling water is being used to cool a process stream. It is desired to maintain the proces stream outlet temperature. What will be the CV and MV of the controller? Due to the water
Consider Example 17.3, where a mixture of CO2 and methanol is separated in a jacketed flash vessel. The inlet temperature of the heating medium is 90°C, and its specific heat is similar to that of
In a reactor, it is known that a fast reaction takes place in the initial region combined with a slower reaction that occurs over the entire length of the reactor. What will be a computationally
When the fuel flow to a furnace is varied, in response the furnace outlet temperature changes after some time. The outlet temperature signal is noisy. Would you use a PID controller for this process?
Consider Example 17.5, where a mixture of CO and methanol is being separated in a jacketed flash vessel. The heat content in the bottom product from the flash vessel is now recovered in heat
Consider Example 17.4, in which methanol is produced in a PFR. After being cooled, the reactor effluent is now sent to a flash vessel, V-1103, as shown in Figure P17.9. The overhead gas stream from
Explain the concept of pressure head.
Consider Figure E17.6(a), in which the overall heat transfer coefficient (U) is assumed to be 25 W/m °C. It can be noted that in Figures E17.6(b) and E17.6(c)(b), the transients in exit temperature
Figure P17.12 shows the surge control loop of a compressor. The condensate in the feed and recycle stream is drained from V-1105. Then the feed gas is compressed to 25 bar in a compressor and sent to
Consider Problem 17.13. Now consider the overall heat transfer coefficient (U) to be 100 W/m2°C. Simulate the same changes as before. Did you notice any difference in the transient profiles in
Consider the benzene purification column, T-101, in Figure 1.5 for the toluene hydrodealkylation process. The column feed contains noncondensables, mainly methane and a small amount of hydrogen, that
Consider an alternative reactor configuration for the cumene reactor, R-801. The alternative is shown in Figure P18.1 and consists of a series of adiabatic catalytic packed beds through which the
It has been proposed that the feed toluene to the process shown in Figure 1.5 be vaporized prior to mixing with the hydrogen. It is believed that this scheme will allow more flexibility in the
In the DME process shown in Figure B.1.1, the reactor feed exchanges heat with the reactor effluent stream in exchanger E-202. From the diagram, it is evident that the temperature of the stream
For the benzene column (T-101) in Figure 1.5, do the following:1. Implement a control scheme that will regulate the purity of the benzene product (Stream 15). You may assume that the purity of this
Consider the feed section of the phthalic anhydride process in Appendix C, Figure C.5. A single control valve is used to control the flow of the combined vaporized naphthalene and air streams, Stream
Figure P18.8 shows a CSTR, R-901, carrying out a liquidphase exothermic reaction. The feed, Stream 1, comes from an upstream unit, and its flowrate is known to vary. The heat of reaction is removed
Describe which form of control strategy (feed-forward, feedback, cascade, or a combination of these) best describes how a responsible person drives an automobile. What would be the consequence of
In Example 18.10, there are two switches to start the pump. In addition, consider that the pump can be automatically started by a newly installed high-level switch as long as the stop switches are
In the feed section of the maleic anhydride process shown in Figure B.5.1, consider that the air flowrate must be regulated so that a desired ratio between benzene and air is maintained. However, as
Figure P18.9 shows a CSTR carrying out a liquid-phase, exothermic reaction. The heat released partially vaporizes the contents of the reactor. This vapor is condensed in an external condenser, and
Consider Problem 18.13. The control logic is now modified such that the pump can be automatically started by the highlevel switch even though the stop switches are pressed. Modify the ladder diagram
In the maleic anhydride process shown in Figure B.5.1, the temperature of Stream 6 at the outlet of the feed heater, H- 601, needs to be maintained. For this system, do the following:1. Devise a
In the distillation column shown in Figure 18.10, changes in the feed composition give rise to noncondensables in the tower overhead vapor. Devise a new control scheme for the tower top pressure. It
Two streams of crude oil (specific gravity of 0.887) mix as shown in Figure E19.1. The volumetric flowrate of Stream 1 is 0.006 m2/s, and its pipe diameter is 0.078 m. The volumetric flowrate of
Explain the physical meaning of each term in the mechanical energy balance.
luid flows from a larger-diameter pipe to a smaller-diameter pipe. How does the velocity change?
Water in an open (source or supply) tank is pumped to a second (destination) tank at a rate of 5 lb/sec with the water level in the destination tank 25 ft above the water level in the source tank,
For the toluene HDA process, using the data given in Tables 13.1 and 13.2, simulate the process and compare the results with those given in Chapter 1, Table 1.5. Remember that the number of actual
In Problem 13.7, you should have simulated the reactor as a stoichiometric reactor with 75% per pass conversion. In order to estimate the volume of the reactor, it is necessary to have kinetics
Using the results from Problem 13.7 and Tables 1.5 and 1.7, compare the results for the simulation of the benzene recovery column, T-101, using a shortcut method and a rigorous method. One way to do
Calculate the LLE for the ternary di-isopropylether/ acetic-acid/water using NRTL and the BIPs available for the three binary pairs in the simulator databank. Compare the prediction with ternary LLE
You are developing an equilibrium-stage model of a distillation column with fixed pressure drop in an electrolyte system. Is the model for surface tension important? Explain.
Develop the model of a sour-water stripper (SWS) as shown in Figure E13.7(a). Consider the following ionic reactions:For this system do the following:1. Simulate both an equilibrium-stage and a
Consider the DME Tower, T-201, in the DME process. Simulate this unit using a shortcut model with different liquid-state activity-coefficient models to determine the required number of stages for the
A model of biomass combustion in an industrial furnace is to be developed. Calculation of which thermodynamic property is the most important?
For the isopropyl alcohol to acetone process flowsheet given in Appendix B, Figure B.10.1, list the minimum input information required to obtain mass and energy balances for this process. Using the
For the DME flowsheet given in Appendix B, Figure B.1.1, list the minimum input information required to obtain mass and energy balances for this process. Using the process simulator available to you,
p-Xylene is commercially separated from a mixture of xylenes in a crystallizer, because its freezing point is much higher than that of its other isomers. The feed is first cooled and then sent to a
The results provided for the toluene hydrodealkylation process are based on the SRK model for both enthalpy and phase equilibria. Determine the BIPs for this model used by the simulator available to
For the ethylbenzene flowsheet given in Figure B.2.1, list the minimum input information required to obtain mass and energy balances for this process. Using the process simulator available to you,
For the styrene flowsheet given in Appendix B, Figure B.3.1, list the minimum input information required to obtain mass and energy balances for this process. Using the process simulator available to
For the maleic anhydride flowsheet given in Appendix B, Figure B.5.1, list the minimum input information required to obtain mass and energy balances for this process. Using the process simulator
Determine what thermodynamic models were used for each of the processes. Explain why each was chosen, and give at least one other thermodynamic model that is reasonable and should be tried for each
For the ethylene oxide flowsheet given in Appendix B, Figure B.6.1, list the minimum input information required to obtain mass and energy balances for this process. Using the process simulator
For the system DME/methanol/water, determine the BIPs used in the simulator available to you for each of these thermodynamic models: NRTL, Wilson, and UNIQUAC. Simulate T-202 using a shortcut module
Find VLE data in the literature for the system methanol/water. Regress these data to determine the BIPs for the UNIQUAC model. Compare the results of these with the results obtained using the BIPs
Using the Henry’s Law model in the simulator available to you, determine the concentration of oxygen (ppm by mass) in water at 25°C and at 35°C if the water is in equilibrium with air. Compare
Using the help facility of the simulator available to you, determine how the simulator handles VLE calculations with supercritical components when an activity-coefficient model is specified.
For the formalin flowsheet given in Appendix B, Figure B.7.1, list the minimum input information required to obtain mass and energy balances for this process. Using the process simulator available to
Investigate the batch aspects of the simulator available to you. Remember that these could include reactor, separation, and scheduling modules as well as others.
Determine which thermodynamic models were used for each of the processes. Explain why each was chosen, and give at least one other thermodynamic model that is reasonable and should be tried for each
As noted in Section 13.5, the results provided for the toluene hydrodealkylation process are based on the SRK model for both enthalpy and phase equilibria. Simulate the benzene column (T-101) with
Figure P13.27 is the absorber in an acid-gas removal (AGR) plant.The solvent, Stream 2, in this plant is a chemical solvent, methyl diethanolamine (MDEA). It is fed to the top of the column. The acid
Consider the same problem as Problem 13.27, but now develop a nonequilibrium-stage model with 20 theoretical stages. The first two reactions shown in Problem 13.27, even though reversible, are
Using the Henry’s Law model in the simulator available to you, determine the concentration of oxygen (ppm by mass) in water at 10°C and 27°C if the water is in equilibrium with air. Compare the
Consider Problem 13.28. The solvent MDEA becomes rich in acid gases. To recycle this solvent, it is first heated to 90°C in exchanger E-2001 and then sent to the top stage of the stripper T-2002 as
Develop a model of a coal combustor fed with Illinois No. 6 coal, a bituminous coal, at 2 atm pressure. The atmospheric air for combustion is available at a temperature of 150°C. The flow of
A biomass stream, Stream 1 in Figure P13.31, is being dried in a direct dryer, V-2001, by a stream of hot N . Develop a model for this dryer. The composition of Stream 1 (wt%) isThe ash can be

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