CE 326 Principles of Environmental Engineering
Problem Set 1 - Material Balance Calculations
Due Date: Sept. 9
1.
Solve Problem 1-9 on page 43
Each month the Speedy Dry Cleaning Company buys one barrel (0.16 m3) of carbon tetrachloride dry
cleaning fluid. Ninety percent of the fluid is lost to the atmosphere and 10 percent remains as residue to be
disposed of. The density of carbon tetrachloride is 1.5940 g/ml. Draw a mass balance diagram and
estimate the monthly mass emission rate to the atmosphere (kg/month).
2.
Solve Problem 1-10 on page 43
The Rappahannock River near Warrenton, VA has a flow rate of 3.0 m3/s. Tin Pot Run (a pristine stream)
discharges into the Rappahannock at a flow rate of 0.05 m3/s. To study mixing of the stream and river, a
conservative tracer is to be added to the stream. If the instruments that can measure the tracer can detect a
concentration of 1 mg/L, what minimum concentration must be achieved in the stream so that 1.0 mg/L of
tracer can be measured after the river and stream mix? Assume that the 1.0 mg/L of tracer is to be
measured after complete mixing of the stream and Rappahannock has been achieved and that no tracer is in
Tin Pot Run or the Rappahannock above the point where the two streams mix. What mass rate (kg/d) of
tracer must be added to the stream?
3.
Show that 1% by weight is equal to 10,000 ppm
4.
The label on the bottle of wine you have purchased indicates that the wine contains 12% by volume of
alcohol. Estimate the concentration of alcohol is terms of (i) parts per million by volume and (ii) parts per
million by mass if the density of alcohol is assumed to be 0.80 and the liquid other than the alcohol is 1.
5.
In 1988, the university put into operation a state-of-the-art circulating fluidized bed (CFB) boilers for its
Power Plant. Coal from Wyoming is used. Wyoming coal has a heat of combustion of about 30.9 kJ/g as
received, a moisture content of 3.6 percent, and the following analysis on a dry weight basis:
Wyoming
Constituent
(%)
C
74.5
H
5.3
N
1.2
O
12.5
S
1.0
Inert Material
5.5
Questions:
(a)
If negligible amounts of sulfur end up in the ash, how much sulfur in Mg would be discharged to
the stack from burning 1 Mg of Wyoming coal?
(b)
Based on your answer to the previous question, how much sulfur dioxide (SO 2) in Mg
would be discharged to the stack in burning of Wyoming coal? (set up a balanced equation for
conversion of S in the presence of O2 to SO2)
(c)
When coal is burned, CO, CO2, H2O, NO, NO2, SO2 and an inert ash material are formed as
products of combustion. Assume that negligible amounts of CO and NO are produced, estimate
how much oxygen in Mg must be supplied (on a stoichiometric basis) to burn 1 Mg of Wyoming
coal in addition to the oxygen contained in the coal? (set up balanced equations for C and CO 2,
etc.).
(d)
If the volume percentages of N2, O2, and Ar in air are about 78%, 21%, and 1% respectively,
estimate the amount of air in Mg that would be needed to burn 1 Mg of Wyoming coal? Assume
that N2 in air does not reaction with oxygen during the combustion process.
(e)
What would be the concentration of SO2 in ppm (mole/mole or vol/vol) in the combustion gas
when 1 Mg of Wyoming coal is burned?
(f)
In most combustion processes, excess air is used (in addition to the stoichiometric air needed).
Estimate the concentration of SO2 in ppm (vol/vol or mole/mole), when 10% excess air is used.
(g)
If the CFD units introduce limestone into the coal to capture the sulfur dioxide, estimate the
amount of SO2 emitted per year (in Mg) by the Power Plant if the removal efficiency of SO 2 is
95%. ISU burns 150,000 Mg of coal per month.