Problem set # 3

# Problem set # 3 - F) to just exceed the flammability limit...

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CHBE 241 Material and Energy Balances Department of Chemical and Biological Engineering The University of British Columbia Problem Session #3 Tuesday, 10 October 2006, CHBE 101, 2–4pm 1. Complete a DOF analysis for the following process: Air (assumed to contain 79 mol% N 2 and 21 mol% O 2 ), is separated into two product streams. One product stream is 98 mol% O 2 , and it contains 80% of the oxygen in the air fed to the separator. The other product stream is mostly nitrogen. We want to produce 1 ton per day of the oxygen product. 2. Perform a DOF analysis and use 10 Easy Steps to solve the following problems: (a) Mixtures of hydrocarbon gases and air will burn only if the gas/air ratio is within the flamma- bility limit. For example, propane gas-air mixtures will not ignite, even if exposed to a flame, if the propane composition of the mixture is greater than 11.4 mol%. Calculate the pounds of propane (C 3 H 8 ) to mix with 100 L of air (at 1 atm pressure and 32
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Unformatted text preview: F) to just exceed the flammability limit and avoid ignition of the propane-air mixture. Air can be assumed to con-tain 79 mol% N 2 and 21 mol% O 2 . The density of air or propane gas can be calculated from the ideal gas law. (b) As a part of the process of producing sugar crystals from sugar cane, raw sugar cane juice is sent to a series of three evaporators to remove water. the sugar cane juice, which is 85 wt% water, is fed to the first evaporator at 10,000 lb/h. Equal amounts of water are removed in each evaporator. The concentrated juice out of the last evaporator is 40 wt% water. Calculate: i. The flow rate of the concentrated juice out of the last evaporator. ii. The amount of water removed in each evaporator. iii. The concentration of water in the juice fed to the second evaporator. Evaporator 1 Water Evaporator 2 Water Evaporator 3 Water Raw cane juice Concentrated sugar juice 1...
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## This note was uploaded on 04/05/2010 for the course CHEBE 241 taught by Professor Ali during the Spring '08 term at The University of British Columbia.

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