Partial oxidation (POX) is a type of

chemical reaction A chemical reaction is a process that leads to the chemical transformation of one set of chemical substances to another. Classically, chemical reactions encompass changes that only involve the positions of electrons in the forming and breaking ...

. It occurs when a substoichiometric fuel-air mixture is partially combusted in a reformer, creating a hydrogen-rich

syngas Syngas, or synthesis gas, is a mixture of hydrogen and carbon monoxide, in various ratios. The gas often contains some carbon dioxide and methane. It is principly used for producing ammonia or methanol. Syngas is combustible and can be used as ...

which can then be put to further use, for example in a

fuel cell A fuel cell is an electrochemical cell that converts the chemical energy of a fuel (often hydrogen fuel, hydrogen) and an oxidizing agent (often oxygen) into electricity through a pair of redox reactions. Fuel cells are different from most bat ...

. 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 carbon d ...

or a heavy hydrocarbon fuel (

heating oil Heating oil is any petroleum product or other oil used for heating; a fuel oil. Most commonly, it refers to low viscosity grades of fuel oil used for furnaces or boilers use for home heating and in other buildings. Home heating oil is often ...

) is mixed with a limited amount of oxygen in an

exothermic In thermodynamics, an exothermic process () is a thermodynamic process or reaction that releases energy from the system to its surroundings, usually in the form of heat, but also in a form of light (e.g. a spark, flame, or flash), electricity ...

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 Partial oxidation (POX) is a type of chemical reaction. 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 ...

(''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 d ...

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 Sulfur (or sulphur in British English) is a chemical element with the symbol S and atomic number 16. It is abundant, multivalent and nonmetallic. Under normal conditions, sulfur atoms form cyclic octatomic molecules with a chemical formul ...

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
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 Uni ...

used oxygen to replace air.''Industrial Gas Handbook'', Frank G. Kerry, p. 230

References

{{reflist Chemical reactions Hydrogen production Industrial gases Redox

Principle

TPOX

CPOX

History

See also

References