Loughborough University STAGEWISE PROCESSES 16CGA002
Q1 Solute (A) should be extracted from the aqueous solution by the organic solvent (S). The organic solvent (S) and H_{2}O are insoluble in each other. The feed aqueous solution consists of 20 kg of solute (A) and 100 kg of H_{2}O. 100 kg of the organic solvent (S) is available for the extraction process. The equilibrium distribution for the solute (A) in organic solvent (S) and H_{2}O is given by:
Y = 2.5X
where Y = kg A/kg S and X = kg A/kg pure water
When answering each question, sketch the process, define all variables and label all inlet and outlet streams.
Q2 Bromine (Br_{2}) is to be extracted from water (H_{2}O) by the solvent carbon tetrachloride
(CCl_{4}). CCl_{4} and H_{2}O are insoluble in each other. The feed solution consists of 25 kg of Br_{2} and 100 kg of H_{2}O. 150 kg of CCl_{4} is available for the extraction process. The equilibrium distribution for Br_{2} between CCl_{4} and H_{2}O is given in the table below.
Equilibrium data for bromine distribution in water and CCl_{4}.
X |
0 |
0.025 |
0.05 |
0.1 |
0.15 |
0.20 |
0.25 |
0.30 |
Y |
0 |
0.154 |
0.204 |
0.269 |
0.316 |
0.355 |
0.388 |
0.417 |
where X ≡ kg Br_{2}/kg H_{2}O; Y ≡ kg Br_{2}/kg CCl_{4 }
When answering each question, sketch the process, define all variables and label all inlet and outlet streams.
(containing 0.3 kg h^{-1} of acetone) and the total inlet pure water flow to be used to absorb acetone is 90 kg h^{-1}. The process is to operate isothermally at 300 K and absolute pressure of 101.3 kPa. Consider the system to be dilute. The equilibrium distribution for the acetone (A) in the gas-liquid is given by:
Y_{A }= 2.53X_{A}
where X = kg A/kg H_{2}O; Y = kg A/kg air.
Determine the number of theoretical stages required for this separation and write down the compositions of the gas and liquid streams leaving each stage.
Use a graphical approach to obtain the solution. [12 marks]
Q3 A counter-current gas absorption tower with 4 equilibrium stages is used to absorb Br_{2} from air using pure water. The entering water flow rate is 70 kmol h^{-1} and the tower operates at an absolute pressure of 7 bar. The outlet gas flow rate is 5 kmol h^{-1} and the outlet gas contains 0.01 mole fraction of Br_{2}. For this problem, you may assume that water and air are mutually insoluble.
Hint: You will need to work on a solute-free basis.
The Henry’s Law constant for Br_{2}/H_{2}O is 46.6 bar per mole fraction Br_{2}.
Q4 A counter-current gas absorption tower is used to absorb hydrogen sulphide from air using pure mono-isopropyl amine (MIPA). The tower operates at 20°C and a total pressure of 10 bar. The inlet gas flow rate is 20 mol h^{-1} and the inlet gas contains 15% mol of hydrogen sulphide. The required outlet gas molar composition is 0.03 or less. For this problem, you may assume that MIPA and air are mutually insoluble. Hint: You will need to work on a solute-free basis.
The Henry’s Law constant for H_{2}S/MIPA is 12.2 bar per mole fraction of H_{2}S.
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