Partial oxidation (POX) is a type of
chemical reaction
A chemical reaction is a process that leads to the IUPAC nomenclature for organic transformations, chemical transformation of one set of chemical substances to another. Classically, chemical reactions encompass changes that only involve the pos ...
. It occurs when a
substoichiometric fuel-air mixture is partially
combusted in a reformer, creating a hydrogen-rich
syngas which can then be put to further use, for example in a
fuel cell. A distinction is made between ''thermal partial oxidation'' (TPOX) and ''catalytic partial oxidation'' (CPOX).
Principle
Partial oxidation is a technically mature process in which
natural gas
Natural gas (also called fossil gas or simply gas) is a naturally occurring mixture of gaseous hydrocarbons consisting primarily of methane in addition to various smaller amounts of other higher alkanes. Low levels of trace gases like carbo ...
or a heavy hydrocarbon fuel (
heating oil) is mixed with a limited amount of oxygen in an
exothermic process.
* General reaction:
+ \frac\mathit -> \mathit + \frac\mathitH2
* Idealized reaction for heating oil:
+ 6O2 -> + 12H2
* Idealized reaction for coal:
+ 12O2 -> + 6H2
The formulas given for coal and heating oil show only a typical representative of these complex fuels. Water may be added to lower the combustion temperature and reduce soot formation. Yields are below stoichiometric due to some fuel being fully combusted to carbon dioxide and water.
TPOX
TPOX (''thermal partial oxidation'') reaction temperatures are dependent on the
air-fuel ratio or oxygen-fuel ratio. Typical reaction temperatures are 1200
°C
The degree Celsius is the unit of temperature on the Celsius scale (originally known as the centigrade scale outside Sweden), one of two temperature scales used in the International System of Units (SI), the other being the Kelvin scale. The ...
and above.
CPOX
In
CPOX (''catalytic partial oxidation'') the use of a
catalyst
Catalysis () is the process of increasing the rate of a chemical reaction by adding a substance known as a catalyst (). Catalysts are not consumed in the reaction and remain unchanged after it. If the reaction is rapid and the catalyst recyc ...
reduces the required temperature to around 800°C – 900°C.
The choice of
reforming technique depends on the
sulfur content of the fuel being used. CPOX can be employed if the sulfur content is below 50
ppm. A higher sulfur content can poison the catalyst, so the TPOX procedure is used for such fuels. However, recent research shows that CPOX is possible with sulfur contents up to 400ppm.
[Electricity from wood through the combination of gasification and solid oxide fuel cells](_blank)
Ph.D. Thesis by Florian Nagel, Swiss Federal Institute of Technology Zurich, 2008
History
1926 – Vandeveer and Parr at the
University of Illinois
The University of Illinois Urbana-Champaign (U of I, Illinois, University of Illinois, or UIUC) is a public land-grant research university in Illinois in the twin cities of Champaign and Urbana. It is the flagship institution of the Univer ...
used oxygen to replace air.
''Industrial Gas Handbook'', Frank G. Kerry, p. 230
See also
*Hydrogen production
Hydrogen production is the family of industrial methods for generating hydrogen gas. As of 2020, the majority of hydrogen (∼95%) is produced from fossil fuels by steam reforming of natural gas and other light hydrocarbons, partial oxidation of ...
* Industrial gas
*PROX
PROX is an acronym for PReferential OXidation, and refers to the preferential oxidation of a carbon monoxide in a gas mixture by a catalyst. It is intended to remove trace amounts of CO from H2/CO/CO2 mixtures produced by steam reforming and wate ...
* Small stationary reformer
*Glossary of fuel cell terms
The Glossary of fuel cell terms lists the definitions of many terms used within the fuel cell industry. The terms in this fuel cell glossary may be used by fuel cell industry associations, in education material and fuel cell codes and standards t ...
*Timeline of hydrogen technologies
This is a timeline of the history of hydrogen technology.
Timeline
16th century
* c. 1520 – First recorded observation of hydrogen by Paracelsus through dissolution of metals (iron, zinc, and tin) in sulfuric acid.
17th century
* 1625 – F ...
References
{{reflist
Chemical reactions
Hydrogen production
Industrial gases
Redox