98
Water for Energy and Fuel Production
and quality of product gases are constant and uniform; (4) it is mechanically stable
and removed from any leakages to the groundwater; and (5) the process requires a
minimal or no underground work.
4.7.6 oTher novel ProCeSSeS
Sato and White [219] showed that using a physical mixture of powdered Texas
lignite and platinized titania, in the presence of water vapor and ultraviolet (UV)
light, a catalytic reaction to produce H 2 and CO 2 at 23°C can be achieved. Quantum
yields were very low, but improvements were thought to be possible. Belghit and El
Issami [220] developed a theoretical model of a moving bed chemical reactor for
gasifying coal with steam. The heat was supplied by a high-temperature nuclear
reactor. Cypres [221] discussed the metallurgical process for hydrogen production from coal and other carbonaceous materials, including coal gasification in a
molten iron bath. An argument was made to place such a gasifier in the vicinity of
steel manufacturing plant.
A steam–iron process is one of the oldest commercial methods for the production
of hydrogen from syngas [222–230]. Various types of oxides of iron were examined.
Neither chemical composition nor porosity of the ores was found to govern the
efficiency. Potassium salts enhanced the activity of both natural and synthetic
oxides. A number of recent studies have examined the classical steam–iron (sponge
iron) process for upgrading synthesis gas (mainly CO and H 2 ) to pure hydrogen for
use in FCs and other energy devices. Friedrich et al. [226] looked at this purification
of nitrogen containing “reduction” gas from biomass gasifier using wood and wood
wastes. The process involved two steps: (1) cleaning of gas from solid biomass, coal,
or methane, and (2) energy storage in sponge iron. This study investigated woody
biomass and commercially available sponge iron. The reactions are as follows:
Fe 3 O 4 + 4CO → 3Fe + 4CO 2 (coal, biomass, or natural gas)
(4.76)
3Fe + 4H 2 O → Fe 3 O 4 + 4H 2
(4.77)
This process was stated to have little risk. Jannach et al. [230] extended the sponge
iron process to FeO, as well as Fe as the oxidant. The sponge iron reaction was
further studied by Hacker et al. [228,229] and Jannach et al. [230] in TGA (thermogravimetric analysis) and tube furnace devices. Other types of reactors were
also examined by Fankhauser et al. [225] and Hacker et al. [227–229]. Biollaz et al.
[223] explored the iron redox process to produce clean hydrogen from biomass. In
the first step, iron oxide in the form of Fe 3 O 4 reacted with the reducing components of wood gas to produce FeO, CO 2 , and H 2 . The kinetics of the second step,
3FeO + H 2 O → H 2 + Fe 3 O 4 , could be improved by adding other transitional metal
oxides. The reduction of iron oxide with biosyngas to sponge iron and later oxidation
of sponge iron with steam offers the potential of shifting and purifying biosyngas,
and storing and transporting its energy. Bijetima and Tarman [222] described the
steam–iron process for hydrogen production operated in a large-scale pilot facility.
Economic advantages of the process were also presented.