Material Balances
Lecture on Chapters 14 - Part B
Problem Review
ENGR 150
1
Homework Solutions Chapters 14
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Problem 14.1
[Solving (a) for A =
2150-18.5 - B]
{0.05)(2131.5 - B) + 0.11B = 177.4 - 18.5
106.6 - 0.05 B + 0.11 B = 158.9
0.06 B = 52.3}
{2150 - 18.5 - 872}
ENGR 150
Instructor: Doug Rode
Homework Solutions Chapter 14
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Problem 14.3
ENGR 150
Instructor: Doug Rode
Homework Solutions Chapter 14
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Problem 14.10
(P = Vapor Products)
Diagram to show givens
& unknowns vital
(wastes = inerts +
H2O)
{(initial %)(2 t/h) =
(P)( unknown %) + (W)(final %)}
ENGR 150
Instructor: Doug Rode
Quick Review
◼
◼
◼
Defined the principle of the Conservation of
Mass)
Investigated the use system approach to
solve material balance problems
Reviewed procedures for solving Material
Balance problems
ENGR 150
Instructor: Doug Rode
Review Problem 14.2
At Grace Foods facility, a cereal product containing 53% water is
.
produced at a rate of 750 lb/hr A dried product containing 75% cereal is
desired. How much water must be removed in an 8 hr period and how
much dry product is produced?
ENGR 150
Instructor: Doug Rode
Problem 14.2 Rate Process
ENGR 150
Instructor: Doug Rode
Review Problem 14.5
Casein, a dairy product used in making cheese, contains 25% moisture when wet.
A dairy sells this product for $40 / 100 kg. If requested they will dry the casein to
12% moisture. The drying costs are $5.00 / 100 kg of water removed. What
Should the dairy sell the dried product in order to realize the same margin of profit?
ENGR 150
Instructor: Doug Rode
Problem 14.5
ENGR 150
Instructor: Doug Rode
Review Problem 14.7
Three brine solutions B1, B2, B3 are mixed. B1 is 50%of the total mixture.
Brine B1 is 2.5% salt, B2 is 4.5% salt, and B3 is 5.5% salt. To this mixture
Is added 35 lbm of dry salt while 280 lbm of water is evaporated leaving 3,200
lbm of 5.1% brine. Determine the initial amounts of B1, B2, B3.
ENGR 150
Instructor: Doug Rode
Problem 14.7
Given
inputs
ENGR 150
outputs
Instructor: Doug Rode
Review Problem 14.11
A freezing process takes in 1.5 t/h of saltwater ( 4% salt ) and produces
salt-free ice and a brine solution ( 8.5% salt ). How much ice is produced in
an 8 hour day?
ENGR 150
Instructor: Doug Rode
Problem 14.11
ENGR 150
Instructor: Doug Rode
Conclusions
1)
2)
3)
Understanding Material Balances is essential to process
analysis
Principle of the Conservation of Material is fundamental
Procedure for defining any systems includes:
a)
b)
c)
Write the specific equations for overall and constituent balance
Solve for unknowns using an independent set of mass balance
equations
Always check that all values balanced
ENGR 150
Instructor: Doug Rode
Homework
◼
Prep for Exam #2 on November 4th
Subjects
Flow Charts – Appendix E
Statistics – Chapters 10 & 11
Engineering Economics – Chapters 8 & 9
Material Balances – Chapter 14
Problems Types
True / False (20 pts)
Multiple Choice (20 pts)
Matching (20 pts)
2 Word Problems (20 pts each)
ENGR 150
Instructor: Doug Rode