formation. Discuss these formation mechanisms, including a
discussion of thermal NO
x
formation by the Zeldovich
mechanism. What is the role of NO
x
in the formation of
ozone? What are some NO
x
reduction strategies? Write a
report including at least three references.
14.3D Using appropriate software, develop plots giving the
variation with equivalence ratio of the equilibrium products
of octane–air mixtures at 30 atm and selected temperatures
ranging from 1700 to 2800 K. Consider equivalence ratios in
the interval from 0.2 to 1.4 and equilibrium products including,
but not necessarily limited to, CO
2
, CO, H
2
O, O
2
, O, H
2
, N
2
,
NO, OH. Under what conditions is the formation of nitric
oxide (NO) and carbon monoxide (CO) most significant?
Write a report including at least three references.
14.4D The amount of sulfur dioxide (SO
2
) present in off gases
from industrial processes can be reduced by oxidizing the
SO
2
to SO
3
at an elevated temperature in a catalytic reactor.
The SO
3
can be reacted in turn with water to form sulfuric
acid that has economic value. For an off gas at 1 atm having
the molar analysis of 12% SO
2
, 8% O
2
, 80% N
2
, estimate the
range of temperatures at which a substantial conversion of
SO
2
to SO
3
might be realized. Report your findings in a
PowerPoint presentation suitable for your class. Additionally,
in an accompanying memorandum, discuss your modeling
assumptions and provide sample calculations.
14.5D A gaseous mixture of hydrogen (H
2
) and carbon
monoxide (CO) enters a catalytic reactor and a gaseous
mixture of methanol (CH
3
OH), hydrogen, and carbon
monoxide exits. At the preliminary process design stage,
plausible estimates are required of the inlet hydrogen mole
fraction,
H
2
, the temperature of the exiting mixture, T
e
, and
the pressure of the exiting mixture, p
e
, subject to the following
four constraints: (1) 0.5 # y
H
2
# 0.75, (2) 300 # T
e
# 400 K,
(3) 1 # p
e
# 10 atm, and (4) the exiting mixture contains at
least 75% methanol on a molar basis. In a memorandum,
provide your estimates together with a discussion of the
modeling employed and sample calculations.
14.6D When systems in thermal, mechanical, and chemical
equilibrium are perturbed, changes within the systems can
occur, leading to a new equilibrium state. The effects of
perturbing the system considered in developing Eqs. 14.32
and 14.33 can be determined by study of these equations.
For example, at fixed pressure and temperature it can be
concluded that an increase in the amount of the inert
component E would lead to increases in n
C
and n
D
when
¢v 5 1n
C
1 n
D
2 n
A
2 n
B
2 is positive, to decreases in n
C
and
n
D
when Dv is negative, and no change when Dv 5 0.
(a) For a system consisting of NH
3
, N
2
, and H
2
at fixed pressure
and temperature, subject to the reaction
2NH
3
1g2
S
d
N
2
1g21 3H
2
1g2
investigate the effects, in turn, of additions in the amounts
present of NH
3
, H
2
, and N
2
.
(b) For the general case of Eqs. 14.32 and 14.33, investigate
the effects, in turn, of additions of A, B, C, and D.
Present your findings, together with the modeling assumptions
used, in a PowerPoint presentation suitable for your class.
Design & Open-Ended Problems: Exploring Engineering Practice 887
14.7D With reference to the equilibrium constant data of Table
A-27:
(a) For each of the tabulated reactions plot 1og
10
K versus
1/T and determine the slope of the line of best fit. What is
the thermodynamic significance of the slope? Check your
conclusion about the slope using data from the JANAF
tables.
1
(b) A text book states that the magnitude of the equilibrium
constant often signals the importance of a reaction, and
offers this rule of thumb: When K , 10
23
, the extent of the
reaction is usually not significant, whereas when K . 10
3
the
reaction generally proceeds closely to equilibrium. Confirm
or deny this rule.
Present your findings and conclusions in a report including
at least three references.
14.8D (a) For an equilibrium ideal gas mixture of N
2
, H
2
, and
NH
3
, evaluate the equilibrium constant from an expression
you derive from the van’t Hoff equation that requires only
standard state enthalpy of formation and Gibbs function of
formation data together with suitable analytical expressions
in terms of temperature for the ideal gas specific heats of N
2
,
H
2
, NH
3
.
(b) For the synthesis of ammonia by
1
2
N
2
1
3
2
H
2
S NH
3
provide a recommendation for the ranges of temperature and
pressure for which the mole fraction of ammonia in the mixture
is at least 0.5.
Write a report including your derivation, recommendations for
the ranges of temperature and pressure, sample calculations, and
at least three references.
14.9D U.S. Patent 5,298,233 describes a means for converting
industrial wastes to carbon dioxide and water vapor. Hydrogen-
and carbon-containing feed, such as organic or inorganic
sludge, low-grade fuel oil, or municipal garbage, is introduced
into a molten bath consisting of two immiscible molten metal
phases. The carbon and hydrogen of the feed are converted,
respectively, to dissolved carbon and dissolved hydrogen. The
dissolved carbon is oxidized in the first molten metal phase
to carbon dioxide, which is released from the bath. The
dissolved hydrogen migrates to the second molten metal
phase, where it is oxidized to form water vapor, which is also
released from the bath. Critically evaluate this technology for
waste disposal. Is the technology promising commercially?
Compare with alternative waste management practices such as
pyrolysis and incineration. Write a report including at least
three references.
14.10D Figure P14.10D gives a table of data for a lithium
bromide–water absorption refrigeration cycle together with
the sketch of a property diagram showing the cycle. The
property diagram plots the vapor pressure versus the lithium
bromide concentration. Apply the phase rule to verify that the
numbered states are fixed by the property values provided.
What does the crystallization line on the equilibrium diagram
1
Stull, D. R., and H. Prophet, JANAF Thermochemical Tables, 2nd ed., NSRDS-
NBS 37, National Bureau of Standards, Washington, DC, June 1971.
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