Four-way
To mass
Steam
valve
spectrometer
Ducts for feed
gases
Inlet for feed
gases
Steam
Four-way
valve
Double tube
for feed gas
preheating
Cylindrical
SiC housing
Coated honeycomb structure
Quartz windows
Sealing
N 2
H 2
N 2 (O 2 )
FIGURE 11.5 Monolithic dual-chamber solar receiver reactor for continuous hydrogen
production. (From Meier, A. and Sattler, C., “Solar fuels from concentrated sunlight,”
SolarPACES, Solar Power and Chemical Energy Systems, IEA report, 2009.)
Water-molecule “cage”
Gas molecule
(e.g., methane)
Methane + neohexane,
methane + cycloheptane, etc.
Propane, iso-butane,
natural gas, etc.
Methane, ethane,
carbon dioxide, etc.
Structure I
Structure II
Structure H
1
8
2
5
12
5
12
6
4
5
12
6
8
4
3
5
6
6
3
5
12
6
2
6
16
2
3
FIGURE 12.1 Various molecular structures of gas hydrate and clathrate depending on guest
molecules. (From “Methane hydrates,” A communication by Center for Gas Hydrate Research,
Heriot-Watt University, Edinburgh, The Hydrate forum Org., 2012. With permission.)
0
500
1000
Depth/meter
Geothermal
gradient
Hy
dra
te
sta
bil
ity
zo
ne
Seafloor
Zone of
gas hydrates
in sediments
The sediments are saturated with water.
1500
273
Zone of gas hydrates in subsea
sediments
283
293 Temperature (K)
Hydrothermal
gradient
Hydrate-phase
boundary
(a)
FIGURE 12.2 Gas hydrate stability fields for (a) nominal marine settings. (From Tohidi,
2013, pers. comm. With permission.)