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engineering
chemical engineering
Questions and Answers of
Chemical Engineering
Air at 1 atm and 100°C flows across a thin, flat plate of naphthalene that is 1 m long, causing the plate to sublime. The Reynolds number at the trailing edge of the plate is at the upper limit for
Air at 1 atm and 100°C flows through a straight, 5-cm-diameter circular tube, cast from naphthalene, at a Reynolds number of 1,500. Air entering the tube has an established laminar-flow velocity
A spherical water drop is suspended from a fine thread in still, dry air. Show:(a) That the Sherwood number for mass transfer from the surface of the drop into the surroundings has a value of 2 if
Water at 25°C flows at 5 ft/s through a straight, cylindrical tube cast from benzoic acid, of 2-in. inside diameter. If the tube is 10 ft long, and fully developed, turbulent flow is assumed,
Air at 1 atm flows at a Reynolds number of 50,000 normal to a long, circular, 1-in.-diameter cylinder made of naphthalene. Using the physical properties of Example 3.14 for a temperature of 100oC,
For the conditions of Exercise 3.33, calculate the initial average rate of sublimation in kmols-m2 for a spherical particle of 1-in, initial diameter. Compare this result to that for a bed packed
Carbon dioxide is stripped from water by air in a wetted-wall tube. At a certain location, where the pressure is 10 atM and the temperature is 25oC, the mass-transfer flux of CO2 is 1.62 Ibmouh-ft2.
Water is used to remove CO2 from air by absorption in a column packed with Pall rings. At a certain region of the column where the partial pressure of CO2 at the interface is 150 psia and the
Determine the diffusivity of H2S in water, using the penetration theory, from the following data for the absorption of H2S into a laminar jet of water at 20?C. Jet diameter = 1 cm, Jet length = 7 cm,
In a test on the vaporization of H20 into air in a wetted-wall column, the following data were obtained: Tube diameter, 1.46 cm, Wetted-tube length, 82.7 cm Air rate to tube at 24oC and 1 atm, 720
The following data were obtained by Chamber and Sherwood on the absorption of ammonia from an ammonia-air system by a strong acid in a wetted wall column 0.575 in. in diameter and 32.5 in. long:The
Anew type of cooling-tower packing is being tested in a laboratory column. At two points in the column, 0.7 ft apart, the following data have been taken. Calculate the overall volumetric
Consider the equilibrium stage shown in. Conduct a degrees-of-freedom analysis by performing the following steps:(a) List and count the variables.(b) Write and count the equations relating the
Can the following problems be solved uniquely?(a) The feed streams to an adiabatic equilibrium stage consist of liquid and vapor streams of known composition, flow rate, temperature, and pressure.
Consider an adiabatic equilibrium flash. The variables are all as indicated in Figure. (a) Determine the number of variables. (b) Write all the independent equations that relate the variables. (c)
Determine the number of degrees of freedom for a nonadiabatic equilibrium flash for one liquid feed, one vapor stream product, and two immiscible liquid stream products as shown inFigure.
Consider the seven-phase equilibrium system shown in Figure. Assume that air consists of N2, O2, and argon. How many degrees of freedom are computed by the Gibbs phase rule? What variables might be
A liquid mixture containing 25 mol% benzene and 75 mol% ethyl alcohol, in which components are miscible in all proportions, is heated at a constant pressure of 1 atm (101.3 kPa, 760 tort) from a
Stearic acid is to be steam distilled at 200°C in a direct-fired still, heat-jacketed to prevent condensation. Steam is introduced into the molten acid in small bubbles, and the acid in the vapor
The relative volatility, a, of benzene to toluene at 1 atm is 2.5. Construct an x-y diagram for this system at 1 atm. Repeat the construction using vapor pressure data for benzene from Exercise 4.6
The vapor pressure of toluene is given in Exercise 4.8, and that of n-heptane is given in the accompanying table. (a) Plot an x-y equilibrium diagram for this system at 1 atm by using Raoult's and
Saturated-liquid feed, of F = 40 mollh, containing 50 mol% A and B is supplied continuously to the apparatus shown in Figure. The condensate from the condenser is split so that half of it is returned
It is required to design a fractionation tower to operate at 101.3 kPa to obtain a distillate consisting of 95 mol% acetone (A) and 5 mol% water, and a residue containing 1 mol% A. The liquid is at
Using vapor pressure data from Exercises 4.6 and 4.8 and the enthalpy data provided below: (a) Construct an h-x-y diagram for the benzene-toluene system at 1 atm (101.3 kPa) based on the use of
Vapor-liquid equilibrium data at 101.3 kPa are given for the chloroform-methanol system. From these data, prepare plots like Figures 4.6b and 4.6c. From the plots, determine the azeotropic
Vapor-liquid equilibrium data at 101.3 kPa are given for the water-formic acid system. From these data, prepare plots like Figures 4.7b and 4.7c. From the plots, determine the azeotropic composition
Vapor-liquid equilibrium data for mixtures of water and isopropanol at 1 atm (101.3 kPa, 760 torr) are given below. (a) Prepare T-x-y and x-y diagrams. (b) When a solution containing 40 mol %
Using the y-x and T-y-x diagrams in Figures 4.3 and 4.4, determine the temperature, amounts, and compositions of the equilibrium vapor and liquid phases at 101 kPa for the following conditions with a
For a binary mixture of components 1 and 2, show that the equilibrium phase compositions and amounts can be computed directly from the following reduced forms of Eqs. (5), (6), and (3) of Table 4.4
Consider the Rachford-Rice form of the flash equation,Under what conditions can this equation besatisfied?
A liquid containing 60 mol% toluene and 40 mol% benzene is continuously distilled in a single-equilibrium-stage unit at atmospheric pressure. What percent of benzene in the feed leaves in the vapor
Solve Exercise 4.19 by assuming an ideal solution and using vapor pressure data from Figure. Also determine the temperature.
A liquid mixture consisting of 100 kmol of 60 mol% benzene, 25 mol% toluene, and 15 mol% o-xylene is flashed at 1 atm and 100°C.(a) Compute the amounts of liquid and vapor products and their
A seven-component mixture is flashed at a specified temperature and pressure.(a) Using the K-values and feed composition given below, make a plot of the Rachford-Rice flash function at intervals of ?
One hundred kilomoles of a feed composed of 25 mol% n-butane, 40 mol% n-pentane, and 35 mol% n-hexane are flashed at steady-state conditions. If 80% of the hexane is to be recovered in the liquid at
An equimolar mixture of ethane, propane, n-butane, and n-pentane is subjected to a flash vaporization at 150?F and 205 psia. What are the expected amounts and compositions of the liquid and vapor
The system shown in Figure is used to cool the reactor effluent and separate the light gases from the heavier hydrocarbons. K-values for the components at 500 psia and 100?F are (a) Calculate the
The mixture shown in Figure is partially condensed and separated into two phases. Calculate the amounts and compositions of the equilibrium phases, V andL.
The following stream is at 200 psia and 200?F. Determine whether it is a subcooled liquid or a superheated vapor, or whether it is partially vaporized, without making a flashcalculation.
The overhead system for a distillation column is shown in Figure. The composition of the total distillates is indicated, with 10 mol% of it being taken as vapor. Determine the pressure in the reflux
Determine the phase condition of a stream having the following composition at 7.2oC and 2,620 kPa.Perform the calculations with a computer simulation program using at least three different options
Prove that the vapor leaving an equilibrium flash is at its dew point and that the liquid leaving an equilibrium flash is at its bubble point.
The following mixture is introduced into a distillation column as saturated liquid at 1.72MPa. Calculate the bubble-point temperature using the K-values of Figure.
An equimolar solution of benzene and toluene is totally evaporated at a constant temperature of 90°C. What are the pressures at the beginning and end of the vaporization process? Assume an ideal
The following equations are given for the liquid-phase activity coefficients of the water (W)-acetic acid (A) system.Find the dew point and bubble point of a mixture of composition xw = 0.5, xA = 0.5
Find the bubble-point and dew-point temperatures of a mixture of 0.4 mole fraction toluene (1) and 0.6 mole fraction n-butanol (2) at 101.3kPa. The K-values can be calculated from (2-72), the
(a) For a liquid solution having a molar composition of ethyl acetate (A) of 80% and ethyl alcohol (E) of 20%, calculate the bubble-point temperature at 101.3kPa and the composition of the
A binary solution at 107°C contains 50 mol% water (W) and 50 mol% formic acid (F). Using (2-72) with vapor pressure data and the van Laar equation of Table 2.9 with AWF = -0.2935 andAFW = -0.2757,
For a mixture consisting of 45 mol% n-hexane, 25 mol% n-heptane, and 30 mol% n-octane at 1 atm, use a simulation computer program to:(a) Find the bubble- and dew-point temperatures.(b) Find the flash
In Figure, 150 kmol/h of a saturated liquid, L1, at 758kPa, of molar composition, propane lo%, n-butane 40%, and n-pentane 50%, enters the reboiler from stage 1. What are the compositions and amounts
(a) Find the bubble-point temperature of the following mixture at 50 psia, using K-values from figure. (b) Find the temperature that results in 25% vaporization at this pressure. Determine the
As shown in Figure, a hydrocarbon mixture is heated and expanded before entering a distillation column. Calculate, using a simulation computer program, the mole percent vapor phase and vapor and
Streams entering stage F of a distillation column are shown in Figure. What is the temperature of stage F and the compositions and amounts of streams VF and LF if the pressure is 785kPa for all
Flash adiabatically, across a valve, a stream composed of the six hydrocarbons given below. The feed upstream of the valve is at 250?F and 500 psia. The pressure downstream of the valve is 300
Propose a detailed algorithm like Figure and Table 4.4 for a flash where the percent vaporized and the flash pressure are to be specified.
Determine algorithms for carrying out the following flash calculations, assuming that expressions for K-values and enthalpies areavailable.
A feed of 13,500 kgh consists of 8 wt% acetic acid (B) in water (A). The removal of the acetic acid is to be accomplished by liquid-liquid extraction at 25oC. The raffinate is to contain only 1 wt%
Forty-five kilograms of a solution containing 30 wt% ethylene glycol in water is to be extracted with furfural. Using Figures 4.14a and 4.14c, calculate:(a) The minimum quantity of solvent.(b) The
Prove that, in a triangular diagram, where each vertex represents a pure component, the composition of the system at any point inside the triangle is proportional to the length of the respective
A mixture of chloroform (CHC13) and acetic acid at 18oC and 1 atm (101.3 kPa) is to be extracted with water to recover the acid.(a) Forty-five kilograms of a mixture containing 35 wt% CHC13 and 65
Isopropyl ether (E) is used to separate acetic acid (A) from water (W). The liquid-liquid equilibrium data at 25oC and 1 atm(a) One hundred kilograms of a 30 wt% A-W solution is contacted with 120 kg
Diethylene glycol (DEG) is used as a solvent in the UDEX liquid-liquid extraction process to separate paraffins from aromatics. If 280 lbmol/h of 42.86 mol% n-hexane, 28.57 mol% n-heptane, 17.86 mol%
A feed of 110 lbmol/h includes 5, 3, and 2 lbmol/h, respectively, of formic acid, acetic acid, and propionic acid in water. If the acids are extracted in a single equilibrium stage with 100 lbmol/h
Repeat Example 4.9 for 200,000 kg/h of hexane.
Water is to be used in a single equilibrium stage to dissolve 1,350 kg/h of Na2CO3 from 3,750 kg/h of a solid, where the balance is an insoluble oxide. If 4,000 kg/h of water is used and the
Repeat Exercise 4.53 if the residence time is only sufficient to leach 80% of the carbonate.
A total of 6,000 lb/h of a liquid solution of 40 wt% benzene in naphthalene at 50?C is cooled to 15oC. Assuming that equilibrium is achieved, use Figure to determine the amount of crystals formed,
Repeat Example 4.10, except determine the temperature necessary to crystallize 80% of the naphthalene.
A total of 10,000 kg/h of a 10 wt% liquid solution of naphthalene in benzene is cooled from 30°C to 0°C. Assuming that equilibrium is achieved, determine the amount of crystals formed and the
Repeat Example 4.11, except let the original solution be 20 wt% Na2S04.
At 20?C. 1,000 kg of a mixture of 50 wt% Na2S04 . 10H2O and 50 wt% Na2S04 crystals exists. How many kilograms of water must be added to just completely dissolve the crystals if the temperature is
Repeat Example 4.12, except determine the grams of activated carbon to achieve:(a) 75% adsorption of phenol.(b) 90% adsorption of phenol.(c) 98% adsorption of phenol.
A colored substance (B) is to be removed from a mineral oil by adsorption with clay particles at 25oC. The original oil has a color index of 200 units/l00 kg oil, while the decolorized oil must have
Vapor-liquid equilibrium data in mole fractions for the system acetone-air-water at 1 atm (101.3 Pa) are as follows: (a) Plot the data as (1) a graph of moles acetone per mole air versus moles
It has been proposed that oxygen be separated from nitrogen by absorbing and desorbing air in water. Pressures from 101.3 to 10,130 kPa and temperatures between 0 and 100°C are to be used.(a) Devise
A vapor mixture having equal volumes of NH3 and N2 is to be contacted at 20?C and 1 atm (760 torr) with water to absorb a portion of the NH3. If 14 m3 of this mixture is brought into contact with 10
Repeat Example 4.15 for temperatures corresponding to the following vapor pressures for solid PA:(a) 0.7 torr(b) 0.4 torr(c) 0.1 torrPlot the percent recovery of PA versus the solid vapor pressure
Nitrogen at 760 torr and 300?C contains 10 mol% anthraquinone (A). If this gas is cooled to 200?C, calculate the percent desublimation of A. Vapor pressure data for solid A are as follows: These
At 25°C and 101 kPa, 2 mol of a gas containing 35 mol% propylene in propane is equilibrated with 0.1 kg of silica gel adsorbent. Using the equilibrium data of Figure, calculate the moles and
A gas containing 50 mol% propylene in propane is to be separated with silica gel having the equilibrium properties shown in Figure. The final products are to be 90 mol% propylene and 75 mol% propane.
Repeat Example 4.17 for 90% evaporation of the water.
A 5,000-kg/h aqueous solution of 20 wt% Na2SO4 is fed to an evaporative crystallizer operating at 60?C. Equilibrium data are given in Figure. If 80% of the Na2SO4 is to be crystallized,
Calculate the dew-point pressure, secondary dew-point pressure, and bubble-point pressure of the following mixtures at 50°C, assuming that the liquid aromatics and water are mutually insoluble:(a)
Repeat Exercise 4.71, except compute temperatures for a pressure if 2 atm.
A liquid containing 30 mol% toluene, 40 mol% ethylbenzene, and 30 mol% water is subjected to a continuous, flash distillation at a total pressure of 0.5 atm. Assuming that mixtures of ethylbenzene
As shown in Figure, water (W) and n-butanol (B) can form a three-phase system at 101 kPa. For a mixture of overall composition of 60 mol% W and 40 mol% B, use a simulation computer program and the
Repeat Example 4.19 for a temperature of 25oC. Are the changes significant?
Devise an interlinked cascade of the type shown in Figure e, but consisting of three columns for the separation of a four-component feed into fourproducts.
A liquid-liquid extraction process is conducted batchwise as shown in Figure. The process begins in vessel 1 (original),where 100 mg each of solutes A and B are dissolved in 100 ml of water. After
Nitrogen is to be removed from a gas mixture with methane by gas permeation (see Table 1.2) using a glassy polymer membrane that is selective for nitrogen. However, the desired degree of separation
In Example 4.9, 83.25% of the oil in soybeans is leached by benzene using a single equilibrium stage. Calculate the percent extraction of oil if:(a) Two countercurrent equilibrium stages are used to
For Example 5.1, involving the separation of sodium carbon-ate from an insoluble oxide, compute the minimum solvent feed rate in pounds per hour. What is the ratio of actual solvent rate to the
Aluminum sulfate, commonly called alum, is produced as a concentrated aqueous solution from bauxite ore by reaction with aqueous sulfuric acid, followed by a three-stage, countercurrent washing
(a) When rinsing clothes with a given amount of water, would one find it more efficient to divide the water and rinse several times; or should one use all the water in one rinse? Explain.(b) Devise a
An aqueous acetic-acid solution containing 6.0 moles of acid per liter is to be extracted in the laboratory with chloroform at 25oC to recover the acid (B) from chloroform-insoluble impurities
A 20 wt% solution of uranyl nitrate (UN) in water is to be treated with tributyl phosphate (TBP) to remove 90% of the uranyl nitrate. All operations are to be batchwise equilibrium contacts. Assuming
The uranyl nitrate (UN) in 2 kg of a 20 wt% aqueous solution is to be extracted with 500 g of tributyl phosphate. Using the equilibrium data in Exercise 5.9, calculate and compare the percentage
One thousand kilograms of a 30 wt% dioxane in water solution is to be treated with benzene at 25oC to remove 95% of the dioxane. The benzene is dioxane-free, and the equilibrium data of Example 5.2
Chloroform is to be used to extract benzoic acid from wastewater effluent. The benzoic acid is present at a concentration of 0.05 mol/liter in the effluent, which is discharged at a rate of 1,000
Repeat Example 5.2 with a solvent for which E = 0.90. Display your results in a plot like Figure. Does countercurrent flow still have a marked advantage over crosscurrent flow? Is it desirable to
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