chemical engineering

1

1. a) Use the group contribution method to estimate the normal melting point and the standard heat of formation at 298°K (Hf) of 1,9 nonanediol. [3 points]

b) Find the normal melting point and the standard heat of formation at 298°K of 1,9-nonadiol in AspenPlus® using the NRTL equation of state. (1,9- Dihydroxynonane in the NISTV88 Database). [3 pts]

Quiz #1 (due at 6pm on 10/10)

2

2. Complete exercise 5.9(a) and (b) in the text. [8 pts]

For part (a): The objective is to calculate the mass of anhydrous salt and the mass of water that would be placed in the bag (before crystallization) for each of the four candidate salts. Assume that, upon the completion of crystallization at 40°C, each of the salts has the capacity to add 100g of water in addition to the equilibrium solubility of the salt (you will not need to use the supersaturation of 2 given in the problem statement) and that there is no heat lost during the process. (Hint: First calculate how much of each of the hydrated salts is required by energy balance. For that energy balance, the heat released from salt crystallization must equal the heat gained by the entire solution, i.e., the hydrated salt, the additional 100 g of water and the non-hydrated salt that dissolves into that 100 g of water. After you’ve determined the amount of hydrated salt required, you can then calculate the amount of each solid, non-hydrated, salt that you will need for the bag and the total amount of water.)

For part (b): To calculate the required dimensions, assume that the bag should be square in surface and fit a typical hand that is 8cm x 8cm. Assume densities are constant over the range of 20°C to 40°C (see Table). To calculate the amount of heat available, assume that the hand temperature is 32°C, so the available heat is that which is transferred from 32°C to 40°C.

Quiz #1

Material Density (g/cc)

NaC2H3O2 1.52

NaS2O3 1.67

Ca(NO3)2 2.50

Pb(C2H3O2)2 3.25

Water 1.00

3

3. a) Use Aspen Plus® to determine the flow rate of saturated vapor benzene at 176.2°F and 1 atm to be mixed with 100 lbmol/hr of liquid benzene to raise its temperature from 25°F to 50°F. For convergence, you will need a reasonable first guess at the flow rate (ΔHv=13200 BTU/lbmol and cp=0.42 BTU/lb°F). [4 pts]

b) Create a plot of vapor benzene flow rate (lb mol/hr) vs. mixer discharge temperature(°F). [3 pts]

4. a)Use Aspen Plus® to determine the heat required to vaporize 45 mol% of a liquid stream entering an evaporator (heater) at 150°F and 202 psia and containing:

Assume the evaporator product is at 200 psia. [4 pts] b)Generate a plot of heat input to the evaporator vs. exit quality (mol fraction

vapor between 0 and 1). [3 pts]

Use RK-Soave EOS for both of these problems

Quiz #1

lbmol/hr

Propane 250

n-Butane 400

n-Pentane 350

4

5. A simplified flowsheet for the “Cavett Problem” is shown below:

a) Use Aspen Plus® to determine the component flow rates and conditions for all streams in the process. [4 pts] b) At what temperature in the top stage will the n-butane flow in the overhead be less than 100 lb mol/hr? (all other conditions are as shown) [4 pts] b) Plot the pressure in the top stage (F1) from 280 to 1200 psia vs. the mole fractions of propane, isobutane and n-butane in the overhead. (temp=100°F)[4 pts]

Use RK-Soave EOS.

Quiz #1