Homework 14

Homework 14 - o F. (a) Based on the following data,...

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ChE 150B Problem Set 14 Due December 4, 2009 Problem 1. (30 Points) The following data were obtained in a BET apparatus for adsorption equilibrium of nitrogen on silica gel (SG) at -195.8 o C. Estimate the specific surface area in m 2 /g of silica gel. How does your value compare with that in Seader Table 15.2 (hint: silica gels can have vastly different properties depending on synthesis method)? N 2 Partial Pressure, torr Volume of N 2 Adsorbed in cm 3 (0 o C, 1 atm) per Gram SG 6.0 6.1 24.8 12.7 140.3 17.0 230.3 19.7 285.1 21.5 320.3 23.0 430 27.7 505 33.5 [Hint: The vapor pressure of N2 at -195.8 o C is 760 mm Hg. Also, your answer may depart largely from that in Table 15.2.] Problem 2. (35 Points) Air at a flow rate of 12,000 scfm (60 o F, 1 atm) and containing 0.5 mol% ethyl acetate (EA, Molecular weight 88.1 g/mol) and no water vapor is to be treated with activated carbon (C) (ρ b =30 lb/ft 3 ) with an equivalent particle diameter of 0.011 ft in a fixed-bed adsorber to remove the ethyl acetate, which will be subsequently stripped from the carbon by steam at 230
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Unformatted text preview: o F. (a) Based on the following data, determine the diameter and height of the carbon bed, assuming adsorption at 100 o F and 1 atm and a time-to-breakthrough of 8 hr with a superficial gas velocity of 60 ft/min. (b) Is the bed height-to-diameter ratio approximately 1.0? If not, would you increase or decrease the breakthrough time make the bed height-to-diameter approximately 1.0? Adsorption isotherm data (100 o F) for EA: p EA , atm q, lb EA / lb C p EA , atm q, lb EA / lb C 0.0002 0.125 0.0020 0.227 0.0005 0.164 0.0050 0.270 0.0010 0.195 0.0100 0.304 Breakthrough data at 100 o F and 1 atm for EA in air at a gas superficial velocity of 60 ft/min in a 2-ft dry bed: Mol Fraction EA in Effluent Time, min Mol Fraction EA in Effluent Time, min 0.00005 60 0.00100 95 0.00010 66 0.00250 120 0.00025 75 0.00475 160 0.00050 84 [Hint: Molecular weight of ethyl acetate is 88.1. Also, you may assume plug flow to estimate a bed diameter based on the superficial gas velocity.]...
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Homework 14 - o F. (a) Based on the following data,...

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