Thermodynamic Geometry 2
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Transcript of Thermodynamic Geometry 2
Distillation
• Sequence of K-stages• Min Exergy cost implies
constant distance stages
• Stages need heat input– diabatic column
L1
L2
L3
L4
L5
L6
L7
V7
V6
V5
V4
V3
V2
V1
L7
L6
V7
V6L5
L4
V5
L3
V4
V3 L2
V2 L1
V1
D, XD D, XD
F, Xf F, Xf
Additional
Heat Sinks
And
Heat Sources
QD QD
QB QB
B, XBB, XB
Adiabatic Diabatic
A False Stumbling Block
• Only a semi-metric– Scaling directions have zero length– Change of phase has zero length
-40
-30
-20
-10
0
10
20
30
40
0 10 20 30 40 50 60 70
Comparison of heat requirements
Plate number
Kilojoules of heat added
-2
-1.5
-1
-0.5
0
0.5
1
1.5
2
0 10 20 30 40 50 60 70
Equal thermodynamic distance heat demand (ends omitted)
Plate number
Heat (in Kilojoules)
Economic Realities
Investment $ vs. Operating $
More trays. Smaller reboiler
More heat exchangers. Smaller condenser
Same total area
More(?) heat pumps There exist clever heat pumps
Saves 75% of the exergy cost
ca. 200% of the capital cost
Political realities: Installation is gathering dust, within $200K of finished after $3M invested. Ricardo Rivero had a physical breakdown over it.