Food Unit Operations



Name: _______________________________________ Student ID ________________

Nickname: ______________________________________ Group: ________________

Prince of Songkla University

Faculty of Engineering

Exam: Mid-Term, Semester I Academic Year: 2003 – 2004

Date: July 31, 2003 Time: 1:30 – 4:30 PM

Subject: 230-391 Room: A401

Basic Chemical Engineering I ________________________________________________________________________

Instructions: There are a total of 4 problems and 5 pages (not including this page). Place your name and the student ID number on every page. Students are allowed to use only a pen or pencil and a calculator. They can also bring in 1 sheet of A4 front and back and also a Conversions Table. No exams are allowed to leave the room.

|Points Distribution (For Grader Only) |

|Problem |Points Value |Score |

|1 |20 | |

|2 |20 | |

|3 |30 | |

|4 |30 | |

|Total |100 | |

Exam prepared by

Ram Yamsaengsung

July 25, 2003

PLEASE CHECK TO MAKE SURE THAT

YOU HAVE ALL 4 PAGES OF THE EXAM BEFORE BEGINNING

(not including the cover sheet).

GOOD LUCK!

Prince of Songkla University

Faculty of Engineering

Exam: Mid-Term, Semester I Academic Year: 2003 – 2004

Date: July 31, 2003 Time: 1:30 – 4:30 PM

Subject: 230-391 Room: A401

Basic Chemical Engineering I ________________________________________________________________________

1. Convert the following to the given units: (20 Points)

0.085 g/(cm-s) to (Pa-s) (5 points)

a) 2.093 cal/(gmol K) to (psia)(ft3)/(lb-mol (R) (5 points)

b) 0.95 Btu/[(hr)(ft2)((F/ft)] to kJ/[(day)(m2)((C/cm)] (5 points)

c) If the thermal conductivity k is 25 Btu/[(hr)(ft2)((F/ft)], what is its value in cal/[(sec)(cm)(K)]? (5 points)

Constants: g = 32.2 ft/s2 = 9.81 m/s2 1lbm = 0.454 kg

gc = 32.174 ft-lbm /(lbf-s2) 1 ft = 0.3048 m

1 cp = 1 x 10-2 g/(cm-s) 1 m3 = 264.172 gal

1 psia = 1 lbf/in2 = 6.89476 kPa 1 Pa = 1 N/m2 = 1 kg/(m-s2)

1 K = 1.8(R 1(C = 1.8(F

(H2O = 62.4 lbm/ft3 = 1 g/cm3

Equations: Pressure = Force/Area

Static Pressure: P = (gh + Po

2. A centrifugal pump is to be used to pump water from the bottom of the PSU reservoir to a storage tank 120 feet above the surface of the reservoir. The pumping rate is 0.4 gal/s, and the water temperature is 20(C. The diameter of the reservoir is 200 m. (Neglect pipe friction kinetic energy effects, or factors involving the pump efficiency.) (20 Points)

What is the pressure in psig that the pump must develop in order to deliver a flow rate of 0.4 gal/s of water to the storage tank? (10 points)

a) What is the total force exerted on the bottom of reservoir in Newton? (10 points)

(Hint: Determine the total pressure at the bottom of the reservoir in Pa units.)

3. A mixture of 70% CH4, 25% C2H6, and 5% O2 is burned in a furnace with 75% excess air. If 70% of the CH4-C2H6 mixture is converted into CO2 and 25% in converted into CO, determine the following information: (30 points)

The moles of air entering the furnace (10 points)

The moles of water produced (5 points)

The moles of oxygen consumed (5 points)

The Orsat Analysis of the flue gas (10 points)

4. The process shown in the figure below is the dehydrogenation of propane (C3H8) to propylene (C3H6) according to the reaction.

[pic]

The conversion of propane to propylene based on the total propane feed into the reactor at F2 is 40%. The product flow rate F5 is 50 kg mol/hr. (30 points)

Calculate all the six flow rates F1 to F6 in kg mol/hr. (20 points)

What is the percent conversion of propane in the reactor based on the fresh propane fed to the process (F1)? (10 points)

-----------------------

Storage Tank

PSU Reservoir

120 ft

N2

O2

75% Excess Air

D = 200 m

CH4 0.70

C2H6 0.25

O2 0.05

Force (N)

20 ft

Po = 720 mm Hg

Furnace

P

F

W

100% H2O

Absorber

& Distillation Tower

Catalytic Reactor

F1

F2

F3

F4

F5

F6

Recycle

80% C3H8

20% C3H6

Fresh

C3H8 Feed

C3H6

H2

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