Environmental Engineering Reference
In-Depth Information
Preferred technologies
and license(s)
Permits
Capital (investment)
Up-time/year
Production mode(s)
Oxygen carrier
Biomass
+ co-feed
Energy products
PROCESS
•
Which co-feed
•
Supply/year
•
Quality consistency
•
Supply dynamics
•
Price ranges
•
Suppliers
•
Which products
•
Demand/year
•
Quality
•
Demand dynamics
•
Price ranges
•
Customers
Design
speciications
Auxiliary chemicals
(solvents, catalysts, ...)
Process boundary
Waste (L/S), emissions (G)
Utility system
(water, steam, power, fuel)
FIGURE 7.7
Input-output diagram of a process as a basis for design.
the oxygen content by putting air through a cryogenic air separation unit with
partial or nearly complete removal of nitrogen. The cost of enriched air is signif-
icant but one saves much on investment cost by having a more compact process.
Thirdly, oxygen from the water molecules in steam can be used for conversion, as
is done for reforming reactions in the gas phase:
CH
x
O
y
+H
2
O
!
ð Þ
1
−
y
CO+
y
CO
2
+1+
x
ð
=
2
Þ
H
2
ð
0
≤
y
<1;0
≤
x
≤
4
Þ
ð
RX
:
7
:
1
Þ
Fourthly, in dry reforming, the oxygen atoms in carbon dioxide are exploited:
CO
2
!
CH
x
O
y
+1
ð Þ
−
y
ð Þ
2
−
y
CO+
x
ðÞ
=
2
H
2
ð
0
≤
y
<1;0
≤
x
≤
4
Þ
:
:
ð
RX
7
2
Þ
In all four situations, the reverse water
gas shift (WGS) reaction and the
methanation reaction play an additional role, turning carbon dioxide into
carbon monoxide and methane and so lowering the hydrogen-to-carbon
monoxide ratio:
-
CO
2
+H
2
!
CO+H
2
O
ð
RX
:
7
:
3
Þ
CO+ 3H
2
!
:
:
CH
4
+H
2
O
ð
RX
7
4
Þ
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