Questions and Answers of Separation Process Principles Chemical

A mixture of benzene and dichloroethane is used to obtain HETP data for a packed column that contains 10 ft of packing and operates adiabatically at atmospheric pressure. The liquid is charged to the
Why are triangular diagrams useful for ternary liquid–liquid equilibrium calculations? On such a diagram, what are the miscibility boundary, plait point, and tie lines?
For the specifications of Example 7.1, design a packed column using 50-mm metal Hiflow rings and operating at 70% of flooding by calculating for each section: (a) Liquid holdup, (b) Column
Figure 7.37 is an enthalpy-concentration diagram for n-hexane (H), and n-octane (O) at 101 kPa. Use this diagram to determine the: (a) Mole-fraction composition of the vapor when a liquid
Using the enthalpy-concentration diagram of Figure 7.37, determine the following for a mixture of n-hexane (H) and n-octane (O) at 1 atm: (a) Temperature and compositions of equilibrium liquid
When liquid–liquid extraction is used, are other separation operations needed? Why?
Explain why it is preferable to separate a dilute mixture of benzoic acid in water by solvent extraction rather than by distillation.
Under what conditions is extraction preferred to distillation?
What are the important characteristics of a good solvent?
Can a mixer-settler unit be designed to closely approach phase equilibrium?
Under what conditions is mechanically assisted agitation necessary in an extraction column?
What are the advantages and disadvantages of mixer-settler extractors?
What are the advantages and disadvantages of continuous, counterflow, mechanically assisted extractors?
What is the difference between a Type I and a Type II ternary system? Can a system transition from one type to the other by changing the temperature? Why?
What is meant by the mixing point? For a multistage extractor, is the mixing point on a triangular diagram the same for the feeds and the products?
For extracting acetic acid (A) from a dilute water solution (C) into ethyl acetate (S) at 25οC, estimate or obtain data for (KA)D, (KC)D, (KS)D, and βAC. Does this system exhibit: (a) High
Zirconium, which is used in nuclear reactors, is associated with hafnium, which has a high neutron-absorption cross section and must be removed. Refer to Figure 8.48 for a proposed liquid–liquid
What happens if more than the maximum solvent rate is used? What happens if less than the minimum solvent rate is used?
At 45C, 5,000 kg/h of a mixture of 65 wt% docosane, 7 wt% furfural, and 28 wt% diphenylhexane is to be extracted with pure furfural to obtain a raffinate with 12 wt% diphenylhexane in a continuous,
What are extract and raffinate reflux? Which one is of little value? Why?
What is the typical range of residence time for approaching equilibrium in an agitated mixer when the liquid-phase viscosities are less than 5 cP?
When continuously bringing together two liquid phases in an agitated vessel, are the residence times of the two phases necessarily the same? If not, are there any conditions where they would be the
At 45C, 1,000 kg/h of a mixture of 0.80 mass fraction docosane and 0.20 mass fraction diphenylhexane is extracted with pure furfural to remove some diphenylhexane from the feed. Phaseequilibrium
Fifty wt% methylcyclohexane (MCH) in n-heptane is fed to a countercurrent, stage-type extractor at 25οC. Aniline is the solvent and reflux is used at both ends of the column. An extract containing
A liquid of 27 wt% acetone and 73 wt% water is to be separated at 25C into a raffinate and extract by multistage, countercurrent liquid– liquid extraction with a solvent of pure
Acetic acid is extracted from a 3 wt% dilute solution in water with a solvent of isopropyl ether in a mixer-settler unit. The flow rates of the feed and solvent are 12,400 and 24,000 lb/h,
For the conditions and results of Example 8.4, determine the following when using a six-flat-bladed turbine impeller in a closed vessel with baffles and with the extract phase dispersed, based on the
A cascade of six mixer-settler units is available, each unit consisting of a 10-ft-diameter by 10-ft-high mixing vessel equipped with a 20-hp agitator, and a 10-ft-diameter by 40-ft-long settling
A Karr column is to be sized to extract 99.95% of the methyl vanillin in water using o-xylene. The feed rate is 6 m3/hr with a vanillin concentration of 40 kg/m3. The average partition coefficient is
Of the penicillin at a concentration of 0.065 kg/L, 98.5% is to be extracted from 3,000 L/h of a clarified and pH-adjusted broth with n-butyl acetate. The partition coefficient is 15. Optimal data
Penicillin in 12 m3/h of fermentation broth is extracted using isoamylacetate in a POD. The distribution coefficient at pH = 2 is KD = 50. If the number of countercurrent equilibrium stages in the
Penicillin in 12 m3/h of fermentation broth is extracted using 1.2 m3 /h isoamylacetate in a POD. The distribution coefficient at pH = 2 is KD = 50. Estimate the number of countercurrent
Actinomycin D present at 260 mg/L in fermentation broth is to be extracted into butyl acetate. At pH 3.5, the distribution constant is 57. How many stages are required to recover 99% of the
Derive general expressions for (a) The partition coefficient, KoD, in an organic (1) aqueous–(2) LLE system for an un-ionized (neutral) form of a weak base given byand (b) The
A distillate of 45 wt% isopropyl alcohol, 50 wt% diisopropyl ether, and 5 wt% water is obtained from an isopropyl alcohol finishing unit. The ether is to be recovered by liquid–liquid extraction
Benzene and trimethylamine (TMA) are to be separated in a three-equilibrium-stage liquid–liquid extraction column using pure water as the solvent. If the solvent-free extract and raffinate products
Why is liquid–liquid mass transfer so complex in agitated systems?
The system docosane–diphenylhexane (DPH)–furfural is representative of complex systems encountered in the solvent refining of lubricating oils. Five hundred kg/h of a 40 wt% mixture of DPH in
What are Marangoni effects? How do they influence mass transfer?
What information about mass transfer in liquid– liquid extraction does the linearized Maxwell–Stefan relation provide?
The three-stage extractor shown in Figure 8.46 is used to extract the amine from a fluid consisting of 40 wt% benzene (B) and 60 wt% trimethylamine (T). The solvent (water) flow to stage 3 is 5,185
How do effects of pH, salt composition, and solute valence on partitioning of bioproducts compare in organic-solvent and aqueous two-phase extraction?
Two feeds—F at 7,500 kg/h containing 50 wt% acetone and 50 wt% water, and F0 at 7,500 kg/h containing 25 wt% acetone and 75 wt% water—are to be extracted in a system with 5,000 kg/h of
What are relative advantages and disadvantages of organicsolvent, aqueous two-phase, and supercritical-fluid extraction for recovery of bioproducts?
For each ternary system in Figure 8.45, indicate whether: (a) Simple countercurrent extraction, (b) Countercurrent extraction with extract reflux, (c) Countercurrent extraction with
What is axial dispersion? What causes it, and should it be avoided?
The extraction process shown Figure 8.47 is conducted without extract or raffinate reflux. Feed F' is composed of solvent and solute, and is an extract-phase feed. Feed F'' is composed of unextracted
How do polymer and solute size, and affinity ligand, affect partitioning in aqueous two-phase extraction?
Using the thermal diffusion apparatus of Example 3.22 with two bulbs at 0οC and 123οC, respectively, estimate the mole-fraction difference in H2 at steady state from a mixture initially consisting
Although citric acid (C6H8O7) can be obtained by solvent extraction from fruits (e.g., lemons and limes) and vegetables, or synthesized from acetone, most commonly it is produced by submerged, batch,
What is the HETP? Does it have a theoretical basis? If not, why is it so widely used?
Why are there so many different kinds of mass-transfer coefficients? How can they be distinguished?
For the acetone absorber of Figure 6.1, assuming sieve trays with 10% hole area, 3 /16 -inch holes, and 18-inch tray spacing, estimate:(a) Column diameter for 0.85 foaming factor and 0.75 fraction
Air containing 1.6 vol% SO2 is scrubbed at 1 atm with pure water in a packed column of 1.5-m2 cross-sectional area and 3.5m height, packed with No. 2 plastic Super Intalox saddles. Total gas flow
What is the difference between the loading point and the flooding point in a packed column?
When the solute concentration is moderate to high instead of dilute, why are calculations for packed columns much more difficult?
Your company, for a carbon-credit exchange program, is considering a packed column to absorb CO2 from air into a dilute-caustic solution. The air contains 3 mol% CO2, and a 97% recovery of CO2 is
What equipment is included in a typical distillation operation?
What determines the operating pressure of a distillation column?
Under what conditions does a distillation column have to operate under vacuum?
A mixture of methane and ethane is subject to distillation. Why can’t water be used as a condenser coolant? What would you use?
Why are distillation columns arranged for countercurrent flow of liquid and vapor?
Why is the McCabe–Thiele graphical method useful in this era of more rigorous, computer-aided algebraic methods used in process simulators?
Under what conditions does the McCabe–Thiele assumption of constant molar overflow hold?
Explain the economic trade-off between trays and reflux.
Liquid air is fed to the top of a perforated-tray reboiled stripper operated at 1 atm. Sixty % of the oxygen in the feed is to be drawn off in the bottoms vapor product, which is to contain 0.2 mol%
In the McCabe–Thiele method, between which two lines is the staircase constructed?
What is meant by the reflux ratio? What is meant by the boilup ratio?
What is the q-line and how is it related to the feed condition?
What are the five possible feed conditions?
In the McCabe–Thiele method, are the stages stepped off from the top down or the bottom up? In either case, when is it best, during the stepping, to switch from one operating line to the other? Why?
A column at 101 kPa is to separate 30 kg/h of a bubble-point solution of benzene and toluene containing 0.6 mass-fraction toluene into an overhead product of 0.97 mass-fraction benzene and a bottoms
Can a column be operated at total reflux? How?
How many stages are necessary for operation at minimum reflux ratio?
What is meant by a pinch point? Is it always located at the feed stage?
What is meant by subcooled reflux? How does it affect the amount of reflux inside the column?
Is it worthwhile to preheat the feed to a distillation column?
Fifty mol% methanol in water at 101 kPa is continuously distilled in a seven-plate, perforated-tray column, with a total condenser and a partial reboiler heated by steam. Normally, 100 kmol/h of feed
Why is the stage efficiency in distillation higher than that in absorption?
A fractionating column equipped with a steam-heated partial reboiler and total condenser (Figure 7.40) separates a mixture of 50 mol% A and 50 mol% B into an overhead product containing 90 mol% A and
A distillation unit consists of a partial reboiler, a column with seven equilibrium plates, and a total condenser. The feed is a 50 mol % mixture of benzene in toluene. It is desired to produce a
What kind of a small laboratory column is useful for obtaining plate efficiency data?
A saturated vapor of maleic anhydride and benzoic acid containing 10 mol% acid is a byproduct of the manufacture of phthalic anhydride. It is distilled at 13.3 kPa to give a product of 99.5 mol%
Methanol (M) is to be separated from water (W) by distillation, as shown in Figure 7.41. The feed is subcooled: q = 1.12. Determine the feed-stage location and the number of stages required. Vapor–
A bubble-point feed of 5 mol% A in B is to be distilled to give a distillate containing 35 mol% A and a bottoms containing 0.2 mol%. The column has a partial reboiler and a partial condenser. If a =
A 50 mol% mixture of acetone in isopropanol is to be distilled to produce a distillate of 80 mol% acetone and a bottoms of 25 mol%. The feed is a saturated liquid, the column is operated with a
A plant has 100 kmol of a liquid mixture of 20 mol% benzene and 80 mol% chlorobenzene, which is to be distilled at 1 atm to obtain bottoms of 0.1 mol% benzene. Assume a = 4.13. The plant has a column
A distillation unit consists of a partial reboiler, a bubble-cap column, and a total condenser. The overall plate efficiency is 65%. The feed is a bubble-point liquid of 50 mol% benzene in toluene,
A 10 mol% isopropanol-in-water mixture at its bubble point is to be distilled at 1 atm to produce a distillate containing 67.5 mol% isopropanol, with 98% recovery. At a reflux ratio L=D of 1.5 times
An aqueous solution of 10 mol% isopropanol at its bubble point is fed to the top of a stripping column, operated at 1 atm, to produce a vapor of 40 mol% isopropanol. Two schemes, both involving the
Solvent A is to be separated from water by distillation to produce a distillate containing 95 mol% A at a 95% recovery. The feed is available in two saturated-liquid streams, one containing 40 mol% A
Determine the optimal-stage location for each feed and the number of theoretical stages required for the distillation separation shown in Figure 7.42, using the following vapor–liquid data in mole
A distillation column to separate n-butane from n-pentane was recently put on line in a refinery. Apparently, there was a design error because the column did not make the desired separation, as shown
Determine the number of equilibrium stages and optimal-stage locations for the feed and liquid sidestreams of the distillation process in Figure 7.43, assuming that methanol (M) and ethanol (E) form
Chlorobenzene production by chlorination of benzene produces two close-boiling isomers, para-dichlorobenzene (P) and orthodichlorobenzene (O), which are separated by distillation. The feed to the
Performance data for a distillation tower separating a 50/50 by weight percent mixture of methanol and water are as follows:Feed rate = 45,438 lb/h; feed condition = bubble-point liquid at feed-tray
For the conditions of Exercise 7.41, a laboratory Oldershaw column measures an average Murphree vapor-point efficiency of 65%. Estimate EMV and Eo.Data From Exercise 41Performance data for a
Figure 7.47 depicts a propylene/propane distillation. Two sievetray columns in series are used because a 270-tray column poses structural problems. Determine column diameters, tray efficiency using
Ten thousand kg/h of a 10 wt% liquid solution of naphthalene in benzene is cooled from 30ο C to 0οC. Determine the amount of crystals and composition and flow rate of the mother liquor. Are
At 20οC, for 1,000 kg of a mixture of 50 wt% Na2SO4.10H2O and 50 wt% Na2SO4 crystals, how many kg of water must be added to completely dissolve the crystals if the temperature is kept at 20C

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