Environmental Engineering Reference
In-Depth Information
KEY CONCEPTS
Energy efficiency
Gas cleaning
Electrochemistry
Thermodynamics
Fuel utilization
Current density
Polarization losses
Reversible voltage or Nernst voltage
SHORT-ANSWER QUESTIONS
16.1
Explain the fate of the main gas components in biosyngas when the syngas is
allowed to pass through the anode of an SOFC producing current.
16.2
Compare the electrical and total thermal efficiencies of gasifier
-
SOFC
-
GT
systems with competing power production technologies.
16.3
What is the fate of tars in biosyngas for the following two cases?
a. Biosyngas containing tar is processed in an SOFC.
b. Biosyngas containing tar is processed in a reciprocating engine.
16.4
What are the advantages and disadvantages of high-temperature and near-
ambient-temperature gas cleaning systems in the context of gasifier
-
SOFC
systems?
16.5
What are the causes of carbon deposition in SOFCs?
PROBLEMS
16.1
An electrolyte-supported SOFC is operated at atmospheric pressure and 800
C
with the following mole fractions of the reactant and product species:
x
H
2
=
0.95 and
x
H
2
O
= 0.05 (anode) and
x
O
2
= 0.21 (cathode). At 800
C, the fuel cell
has
188.6 kJ.mol
−1
mol
−1
Δ
Δ
g
f
=
−
and
h
r
=
−
248.3 kJ
of H
2
, and the
m
−1
. The cell active area is 2 × 10
−4
m
2
,
and the electrolyte thickness is 100
Ω
−1
conductivity of the cell is 5
μ
m. If the cell is operated at 0.7 V, then
determine the following:
a. The inlet Nernst voltage
b. The rates at which hydrogen and oxygen are consumed
c. The electrical efficiency (fuel to electricity)
16.2
A clean syngas stream contains 20% H
2
, 16% CO, 1% CH
4
, 10% CO
2
, 15%
H
2
O, and 38% N
2
(by volume). An SOFC is operated with a fuel with this
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