天津大学传质期末试题

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9. Given feed line in distillation operation

10. Try to write the expression of Fick

(2 points each blank in the following questions)

11. At ambient pressure and 50 ℃

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学院专业班年级学号姓名A卷共5 页第2 页

II. (15 points)Draw diagrams

(1)Using McCabe-Thiele method to calculate the number of plates(5 points)

(2)Capacity chart of plate in plate column, including operating point and operating line(5

point)

(3)Using triangular diagram to solve the calculation of single-stage extraction process.

Assuming F,x F, S, y s,determine the composition of E, R, E'and R'(5 points)III．(20 points)In a countercurrent packed tower, pure solvent is used to absorb solute A from gas mixture. The gas mixture flow rate is 100 kmol/h, The inlet mixture gas contains 0.1 mole fraction solute A. Require 95% of solute content in the mixture is reduced during absorption. The internal diameter of the packed tower is 1 m. The volumetric overall mass transfer coefficient K Y a=0.1 kmol/(m3·s). The equilibrium relation under operation condition is Y =1.5X(X and Y are solute-free mole fraction of solute in liquid phase and gas phase). If the flow rate of pure solvent is L=1.2 L min, calculate

(1)The height of the packed section of the tower(m);

(2) The composition of liquid leaving the tower X1

IV．(20 points) A plate column is used to distillate a binary ideal mixture. The flow rate of the feed is 100 kmol/h. The composition of the feed is 0.5 (mole fraction of more volatile component, the same for all of the following compositions) and the feed entering the column at its bubble point. The composition of top product is 0.96. 96% more volatile component in the feed is recovered from top of the column. The ratio of actual reflux to minimum reflux R/R min is 2.0. The average relative volatility of the system is 1.5. A total condenser is used at the top of the column and the reflux temperature is at bubble point. Try to determine the operating lines for the rectifying section and the stripping section.

V．(20 points) To dry the wet solid in a countercurrent dryer with hot air. The mass flow rate of the wet solid is 1000 kg/h. The wet solid is dried from moisture content 2% to 0.2% (both on wet basis). The fresh air at 20℃, having the humidity 0.01 kg/kg dry gas, is heated to 115 ℃in a preheater, and then charged to a dryer. The dryer is an adiabatic dryer, and the temperature of hot air leaving the dryer is 50 ℃. Calculate:

(1)The consumption of dry air and the consumption of fresh air (kg/h);

(2) The thermal efficiency of the drying system.