A Gas with the Following Composition Is Burned with 40% Excess Air

Material and Energy balances, 313a

Assignment #3

Sept. 22, 2003, Due date: Sept. 29 2003

1. In a distillation train a liquid hydrocarbon containing 20 mole % ethane, 40 mole %

propane, and 40 mole % butane is to be fractionated into essentially pure component as shown in Figure below. If the feed rate to the first column is 100 moles per minute, calculate the exit streams flow rate and the composition of stream A.

2. A gas with the following composition is burned with 40% excess air. What is the composition of the flue gas?

H2 = 50.8%, O2 = 0.2%, N2 = 2.6%, CO = 40%, CO2 = 6.4 %

3. Isooctane (C8H18) is burned with 20% excess air. If 30% of carbon forms carbon monoxide what is the gas analysis of the burner exit stream?

4. A water solution contains 60% (wt) Na2S2O2 together with 1% (wt) soluble impurity. Upon cooling to 10 oC the solubility of Na2S2O2 decreases and Na2S2O2 crystallizes out as Na2S2O2 .5 H2O. The solubility of this hydrate is 1.4 kg Na2S2O2 .5 H2O / kg free water. The crystals removed carry as adhering solution 0.06 kg solution / kg crystals. These are dried to remove the remaining water (not the water of hydration). The final dry Na2S2O2 .5 H2O crystals must not contain more than 0.1% (wt) impurity. To meet this specification, the original solution, before cooling, is further diluted with water. On the basis of 100 kg of the original solution determine:

a)  the amount of water added before cooling.

b)  the percentage recovery of in the dried hydrated crystals.

5. A purification system with recycle is used to recover the solvent DMF from a waste gas containing 55% DMF in air. The product is to have only 10% DMF. Calculate the recycle fraction assuming that the purification unit van remove two third of the DMF in the combined feed to the unit. See Figure below.