Scribd
Upload
125 views24 pages

Lecture 3

The document outlines chemical process calculations related to an experiment requiring humid air enriched with oxygen, detailing input streams and their flow rates. It includes methodologies for drawing flowcharts, writing balance equations, and performing degree-of-freedom analysis for various chemical processes. Additionally, it provides examples of calculations for distillation and condensation processes involving liquid mixtures and gas streams.

Uploaded by

Kairav Barua
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
Available Formats
Download as PDF, TXT or read online on Scribd
125 views24 pages

Lecture 3

The document outlines chemical process calculations related to an experiment requiring humid air enriched with oxygen, detailing input streams and their flow rates. It includes methodologies for drawing flowcharts, writing balance equations, and performing degree-of-freedom analysis for various chemical processes. Additionally, it provides examples of calculations for distillation and condensation processes involving liquid mixtures and gas streams.

Uploaded by

Kairav Barua
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
Available Formats
Download as PDF, TXT or read online on Scribd
You are on page 1/ 24

CHEMICAL PROCESS CALCULATIONS

(Introduction to engineering calculations)


Lecture #3: August 20, 2024
An experiment on the growth rate of certain organisms requires an environment
of humid air enriched in oxygen. Three input streams are fed into an
evaporation chamber to produce an output stream with the desired
composition.

A: Liquid water, fed at a rate of 20.0 cm3/min


B: Air (21 mole% O2, the balance N2)
C: Pure oxygen, with a molar flow rate one-fifth of the molar flow rate of stream B

The output gas is analyzed and is found to contain 1.5 mole% water. Draw and
label a flowchart of the process, and calculate all unknown stream variables.
Flowchart scaling
Writing balance equations
Writing balance equations
• For a nonreactive system:
• maximum number of independent equations = the number of
chemical species in the input and output streams

• Priority for the balance which has the fewest unknown


variables
Degree-of-Freedom Analysis
• Draw and completely label the flowchart

• Count the unknown variables

• Count the independent equations relating them

• Subtract the second number from the first


Degree-of-Freedom Analysis
A stream of humid air enters a condenser in which 95% of the water vapor in the air is
condensed. The flow rate of the condensate (the liquid leaving the condenser) is
measured and found to be 225 L/h. Dry air may be taken to contain 21 mole% oxygen,
with the balance nitrogen. Calculate the flow rate of the gas stream leaving the
condenser and the mole fractions of oxygen, nitrogen, and water in this stream.
Single-Unit Process Calculations
1. Choose a basis

2. Draw and label the flowchart

3. Write expressions for the quantities asked in the problem statement

4. Convert mixed units to one basis

5. Perform degree-of-freedom analysis

6. Write system equations and outline a solution procedure

7. Calculate the unknowns

8. Calculate additional quantities requested in the problem statement


A liquid mixture containing 45.0% benzene (B) and 55.0% toluene (T) by
mass is fed to a distillation column. A product stream leaving the top of the
column (the overhead product) contains 95.0 mole% B, and a bottom
product stream contains 8.0% of the benzene fed to the column (meaning
that 92% of the benzene leaves with the overhead product). The volumetric
flow rate of the feed stream is 2000 L/h and the specific gravity of the feed
mixture is 0.872. Determine the mass flow rate of the overhead product
stream and the mass flow rate and composition (mass fractions) of the
bottom product stream.
Multiple units calculations
Multiple units calculations
Multiple units calculations
Multiple units calculations
Multiple units calculations
Texts
• BASIC PRINCIPLES AND CALCULATIONS IN CHEMICAL ENGINEERING
• David M. Himmelblau and James B. Riggs
• Prentice Hall

• ELEMENTARY PRINCIPLES OF CHEMICAL PROCESSES


• Richard M. Felder and Ronald W. Rousseau
• John Wiley & Sons, Inc.

You might also like