4. A big part of CO–CO 2 conversion is produced inside the reactor itself.
5. Emissions are reduced by about 34%–53% due to the use of concentrated
solar energy to obtain the process heat.
In this study, steam reforming of methane proceeded with the original module
having palladium membrane below the decomposition temperature of molten salt
(around 870 K). The SOLREF (solar reforming) process [211] and its various options
for solar reforming of natural gas by steam are also described by Moller [201]. A
review of hydrogen production technologies from solar energy is also given by
Suarez-Gonzalez et al. [212].
The above-described process can be easily adapted to solar gasification, but for
this case, heavy hydrocarbons are used as feedstock. These are transformed into
cleaner fuels for a combined cycle or in the process that can produce hydrogen. As
mentioned earlier, a solar gasification plant using petroleum coke has been tested in
the solar platform of Almería, Spain. The reactor has reached the hydrogen produc95
Steam Gasification and Reforming Technologies
tion efficiency of 60% working at 1500 K [192,199,202,211–213].
4.7.4 miCroWAve-ASSiSTed reForming
In the recent years, a significant interest in the use of microwave to carry out hightemperature operations such as steam reforming, pyrolysis, dry reforming, and cracking
has been reported [215–217]. Microwave heating is very different from conventional
heating in that it heats the materials from inside out unlike outside in heating that normally takes place in conventional heating. This means that all heat is generated and
absorbed by the materials and not the surroundings (like microwave cooking at home).
The microwave heating, however, requires materials with good dielectric properties
such that it not only absorbs microwave but also converts microwave energy into thermal energy. The use of porous, activated carbon for this purpose has been successfully
demonstrated [215–217]. Oxides of various materials can also be useful for this purpose.
Menendez et al. [215–217] have shown that microwave-assisted reforming can
give better results than the reforming carried out by conventional heating, particularly at lower temperatures. They studied both activated carbon and numerous catalysts deposited on the activated carbon. They also showed that microwave heating
is more energy efficient than conventional heating. This approach has a significant
potential. More research and development in this area is needed.
4.7.5 underground CoAl gASiFiCATion
When coal is imbedded underground in steep seams, it is very difficult to mine.
Often the energy from such steep coal seams is recovered by in situ underground
gasification. Just like conventional gasification, underground gasification is often
carried out with oxygen or with oxygen and steam mixture. Yang et al. [190,218]
studied the product distribution from underground coal in China. They found that
with pure oxygen gasification hydrogen volume percentage in product gas varied
from 23.63% to 30.24% and carbon monoxide volume percentage varied from
35.22% to 46.32%. When oxygen–steam mixture was used for the gasification, the
gas compositions virtually remained stable and CO + H 2 were basically between
5. Emissions are reduced by about 34%–53% due to the use of concentrated
solar energy to obtain the process heat.
In this study, steam reforming of methane proceeded with the original module
having palladium membrane below the decomposition temperature of molten salt
(around 870 K). The SOLREF (solar reforming) process [211] and its various options
for solar reforming of natural gas by steam are also described by Moller [201]. A
review of hydrogen production technologies from solar energy is also given by
Suarez-Gonzalez et al. [212].
The above-described process can be easily adapted to solar gasification, but for
this case, heavy hydrocarbons are used as feedstock. These are transformed into
cleaner fuels for a combined cycle or in the process that can produce hydrogen. As
mentioned earlier, a solar gasification plant using petroleum coke has been tested in
the solar platform of Almería, Spain. The reactor has reached the hydrogen produc95
Steam Gasification and Reforming Technologies
tion efficiency of 60% working at 1500 K [192,199,202,211–213].
4.7.4 miCroWAve-ASSiSTed reForming
In the recent years, a significant interest in the use of microwave to carry out hightemperature operations such as steam reforming, pyrolysis, dry reforming, and cracking
has been reported [215–217]. Microwave heating is very different from conventional
heating in that it heats the materials from inside out unlike outside in heating that normally takes place in conventional heating. This means that all heat is generated and
absorbed by the materials and not the surroundings (like microwave cooking at home).
The microwave heating, however, requires materials with good dielectric properties
such that it not only absorbs microwave but also converts microwave energy into thermal energy. The use of porous, activated carbon for this purpose has been successfully
demonstrated [215–217]. Oxides of various materials can also be useful for this purpose.
Menendez et al. [215–217] have shown that microwave-assisted reforming can
give better results than the reforming carried out by conventional heating, particularly at lower temperatures. They studied both activated carbon and numerous catalysts deposited on the activated carbon. They also showed that microwave heating
is more energy efficient than conventional heating. This approach has a significant
potential. More research and development in this area is needed.
4.7.5 underground CoAl gASiFiCATion
When coal is imbedded underground in steep seams, it is very difficult to mine.
Often the energy from such steep coal seams is recovered by in situ underground
gasification. Just like conventional gasification, underground gasification is often
carried out with oxygen or with oxygen and steam mixture. Yang et al. [190,218]
studied the product distribution from underground coal in China. They found that
with pure oxygen gasification hydrogen volume percentage in product gas varied
from 23.63% to 30.24% and carbon monoxide volume percentage varied from
35.22% to 46.32%. When oxygen–steam mixture was used for the gasification, the
gas compositions virtually remained stable and CO + H 2 were basically between