Solutions%20to%20Homework#8

# Solutions%20to%20Homework#8 - Assignment Solution 8...

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Assignment Solution 8 Chemical Engineering 2800 (Summer 2008) Fundamentals of Process Engineering University of Utah Dr.Mataz Alcoutlabi Problem 1 19.23, p. 587 Calculate the bubble point of a liquid mixture of 80 mole% n-hexane and 20 mole% n- pentane at 200 psia. Solution Find BP for n-hexane, n-pentane at 200 psia with x p = 0.20 Data: * * 10 log ( ) , , B p A p bar T K T C = - = = + A B C pentane 3.9892 1070.6 2 -40.454 Hexane 4.0026 6 1171.5 3 -48784 Total pressure by Raoults’ law is * * ( ) p h tot p h p h tot p h p p p x p x p p y y = + = + = + Or * * 1 p h p h i tot tot p p x x y p p = + = Solve using Goal Seek in Excel Total pressure is 200 1.01325 13.79 14.696 tot p x bar = = 447 345 BP T K F = = Extra credit: * 0.330, 1 0.670 p p p h p tot p y x y y p = = = - = Problem 2 19.26, p. 587 A liquid mixture of n-pentane and n-hexane containing 40 mole percent n-pentane is fed continuously to a flash separator operating at 250 ° F and 80 psia. Determine: a) The quantity of vapor and liquid obtained from the separator per mole of feed. b) The composition of both the vapor and the liquid leaving the separator. Solution Flash separator at T = 250 ° F, p tot = 80 psia

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Use p* from the previous problem Overall balance: F – V – L = 0 Balance on pentane: 0 Fp p p Fx Vy Lx - - = Assume ideal solution: * i i tot i y p x p = Then * * * h h tot p p p p x p p - = - and * p p p tot p y x p = And , 1 p Fp p p y x L V L F y x F F - = = - - No iteration is required. Calculation performed in Excel ) 0.645, 0.355 ) 0.466, 0.280 0.534, 0.720 p p h h V L a F F b y x y x = = = = = = Problem 3 19.30, p. 588 Late in the evening of 21 Aug1986 a large volume of toxic gas was released from beneath and with Lake Nyos in the Northwest Province of Cameroon. An aerosol of water mixed with toxic gases swept down the valleys to the north of Lake Nyos, leaving more than 1700 dead and dying people in its wake. The lake had a surface area of 1.48 km2 and a depth of 200-250 m. It took 4 days to refill the lake, hence it was estimated to have lost about 200000 tons of water during the gas emission. To the south of the lake and in the
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Solutions%20to%20Homework#8 - Assignment Solution 8...

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