ch07 - Exercise 7.1 Subject Comparison of absorption...

Info iconThis preview shows pages 1–4. Sign up to view the full content.

View Full Document Right Arrow Icon
Exercise 7.1 Subject: Comparison of absorption, distillation, and stripping Find: Differences between absorption and distillation, and stripping and distillation Analysis: Absorption Stripping Distillation Feed is gas Feed is liquid Feed is liquid, vapor or a mixture of the two Second phase (absorbent) is added Second phase (stripping agent) is added Second phase is created by heat transfer Operation can be adiabatic Operation can be adiabatic Must have heat transfer at the top and bottom stages Single-section cascade Single-section cascade Two-section cascade Can be almost isothermal Can be almost isothermal Can have a large temperature range Can not separate a close- boiling mixture Can not separate a close- boiling mixture Can separate a close-boiling mixture Tray efficiency can be low Tray efficiency can be moderate Tray efficiency can be high Exercise 7.2 Subject: Emergence of packing to replace trays. Find: Reasons why some existing trayed towers are being retofitted with packing, and some large-diameter columns are being designed for packing. Analysis: New random packings and structured packings have been introduced with higher capacity, lower pressure drop, and higher efficiency than trays. Also for packed columns, liquid distributors have been greatly improved. Channeling of liquid in packed columns is now much less of a problem.
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Exercise 7.3 Subject: Condenser coolant for distillation of a methane-ethane mixture. Find: Appropriate coolant. Analysis: Assume that the distillate is nearly pure methane, the most volatile of the two components. To use cooling water, the distillate temperature would be approximately 120 o F. But the critical temperature of methane is -115 o F. Therefore could not condense it. The critical pressure of methane is 673 psia. Using Fig. 7.16, could consider operation at 415 psia because that is safely below the critical pressure ( P/P c = 0.62 and could operate as high as a P/P c = 0.8). From Perry's Handbook (p. 3-203, 6th edition), at P = 415 psia (28.6 bar), the saturation temperature of methane is 176 K or -143 o F. To condense at just below this temperature, could use a partial condenser with refrigerant R-14 (carbon tetrafluoride ), which from Perry's Handbook (p. 12-26, 6th edition) has a saturation pressure of 70 psia at -150 o F. Exercise 7.4 Subject: Operating pressure for distillation of an ethylene-ethane mixture Find: Suitable operating pressure. Analysis: Assume that the distillate is nearly pure ethylene, the most volatile of the two components. To use cooling water, the distillate temperature would be approximately 120 o F. But the critical temperature of ethylene is 9.7 o C or 49.4 o F . Therefore could not condense it. The critical pressure of ethylene is 50.5 atm or 742 psia. Using Fig. 7.16, could consider operation at 415 psia because that is safely below the critical pressure ( P/P c = 0.56 and could operate as high as a P/P c = 0.8). From Perry's Handbook (p. 3-203, 6th edition), at P = 415 psia (28.6 bar), the saturation temperature of ethylene is 258 K or 4.7 o F. To condense at just below this temperature could use a partial condenser with refrigerant R-1270 (propylene), which from Perry's Handbook (p. 12-26, 6th edition) has a saturation pressure of 35 psia at 0 o F.
Background image of page 2
Exercise 7.5
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Image of page 4
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

Page1 / 180

ch07 - Exercise 7.1 Subject Comparison of absorption...

This preview shows document pages 1 - 4. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online