is available in practically unlimited amounts on earth. However, it is
present almost exclusively in chemical compounds such as hydrocarbons
(fossil fuels) and water. A large part (~40%) of today's hydrogen
production originates from chemical processes where it is a by-product (e.g.
chlorine-alkaline electrolysis or crude oil refining). In the case of
industrial production of hydrogen, steam reforming of natural gas is the
most widely applied method. Nevertheless, there are several different
types of production technology:
(light hydrocarbons) - partial oxidation (heavy hydrocarbons) -
(water or chlorine-alkaline) - Kvaerner Black process -
of light hydrocarbons
(e.g. methanol, methane or natural gas) to hydrogen can be done either by
steam or autothermal reforming techniques. Steam reforming involves two
steps, first a catalytic conversion of the fuel (here methane) at high
+ H2O 3 H2 + CO
is followed by a conversion of the resulting carbon monoxide and water to
hydrogen in a reaction, which is often called the shift reaction:
+ H2O H2 + CO2
oxidation of heavy hydrocarbons involves
addition of oxygen as well as steam to the process. The amounts of oxygen
and water are accurately controlled to adjust the oxidation rate of the
hydrocarbons. In principle, the reaction involves the components mentioned
+ H2O + O2
H2 + CO +CO2
applies both steam reforming and partial oxidation steps and can be used for
somewhat heavier hydrocarbons. After the reforming step, a gas purification
process is necessary to remove carbon dioxide, carbon monoxide and other
by-products not desired in the hydrogen rich product gas. The complexity of
the gas purification process depends on the reforming technique applied and
the intended application for the produced hydrogen. Small reformer systems
have also been developed for onboard production of hydrogen, for instance in
methane reformer (SMR) plant from Air Liquide.
is in principle a reversed fuel cell. From water and electricity we get
hydrogen and oxygen:
H2 + ½O2
as in fuel cells, reduction and oxidation take place on two spatially separated
electrodes. Hydrogen is produced on the cathode and oxygen on the anode. The
electrolyte is ion-conductive, usually either for protons (H+) or
hydroxyl ions (OH-). Most common is the alkaline (OH-)
process, which has been used since the beginning of the 20th century.
Other types are based on a solid polymer electrolyte or operated at elevated
pressures and/or temperatures. Water electrolysis accounts for about 2-3 % of
the global production of hydrogen.
electrolyser unit from Norsk Hydro.
The Kvaerner Black
is a way to produce hydrogen from hydrocarbons and electricity with only
solid carbon black as a by-product. At very high temperatures, the
hydrocarbon (e.g. methane) decomposes:
+ energy 2H2
pyrolysis process was developed by the Norwegian company Kvaerner in the
1980’s, and is especially interesting since it is CO2 free.
Carbon black is used in rubber production, for example.
is really an anaerobic digestion of biomass by bacteria, enzymes or other
small organisms. From this process, a gas containing methane is produced,
which can either be fed directly into high-temperature fuel cells or used
to produce hydrogen. By modifying the process, it is possible to increase
the hydrogen content of the product gas.
of hydrogen is also possible. Some micro-organisms (algae and bacteria)
are able to produce hydrogen primarily from water and light (photosynthesis).
Promising substances are selected and improved by genetic engineering.
described above, different kinds of hydrogen production technology are
already available today. However, the total annual amount produced,
corresponds only to the fuel consumed within a couple of days in the
transportation sector. Thus, a large industrial up-scale is necessary
before we can enter a hydrogen era.