Chemical Engineering License Review, Second Edition
This text contains 146 problems with detailed step-by-step solutions, and is an ideal study guide and the first truly practical, no-nonsense review for the difficult PE Exam.
TABLE OF CONTENTS Chemical Engineering License Review, Second Edition
Chapter 6: Absorption
Absorption is an important unit operation used in industry. Problems involving absorption are frequently given in the P.E. examination. The candidates are required to become familiar with the equilibrium solubility relationships; absorption theory, including the height of transfer unit; the numbers of transfer units, mass-transfer coefficients, etc.; and the determination of the diameter and height of the absorption column.
Generally, the solution of problems on absorption requires establishing a material balance equation, an equation of the operating line, and an equation or graphical presentation of the equilibrium solubility relationship. Occasionally the solvent flow rate is not specified, and the candidate is advised to use a multiple of the minimum solvent flow rate. One must carefully examine the units of various parameters given in the problem statement and use the appropriate equation.
Equilibrium Solubility Curves
Equilibrium solubility relationships are available in many forms. Some of them may be converted into equations of the type Y* = f( X) or y* = f( x) which can be readily used for the calculation of the transfer units by integration.
Figure 6-1 shows the operations of the countercurrent and cocurrent gas-absorption towers which may be any of the following types: packed, spray and bubble-cap, or sieve tray. The design of the packed absorption towers will be dealt with here. The solvent gas and solvent liquid flows are essentially unchanged in quantity as they pass through the tower, and it is convenient to express the material balances in terms...
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