Ted Raimi

The pyrolysis , is the decomposition of an organic compound by heat to obtain other products which it did not contain. By “organics”, one understands compounds of carbon except the Carbone itself (Graphite or Diamant), the Carbonic gas CO₂ and the Ion S Carbonate CO₃^2- like defined in the article Organic chemistry.

The complex organic compounds are indeed composed of molecules which form a chain Polymère (plastic, rubber, wood, paper, etc). Under the effect of heat, this chain breaks and one finds oneself with small organic molecules, of type Méthane CH₄.

One should not confuse this process with the Distillation, for which heat is just used to separate from the mixed bodies. To note however that before the invention of the word pyrolysis one spoke about “dry distillation”. In the case of pyrolysis, one destroys material. It is the same difference between separating the charts from a play (distillation), and cutting out the charts with scissors (pyrolysis). In the word “pyrolysis”, one finds the suffix besides - lysis which evokes the decomposition (analyzes, Hydrolyze…), from where the Greek root lusis and pure for fire.

When a solid body, like wood, burns, that is done often in the following way:

possible moisture is evaporated.
the heat of the flame breaks up the matter into light molecules.
the light Molecule S, of the methane type, burn with the Dioxygène of the air O₂.

One thus has makes of it a combination pyrolysis Combustion of a gas, combustion maintaining pyrolysis until disappearance the organic compound.

Most of the time, one speaks about pyrolysis for the decomposition without flame (for example decomposition of greases in the process of cleaning of a furnace called “to pyrolysis”).

Pyrolysis could have an interesting industrial future. Vis-a-vis the approach of the oil Peak and with the danger of the Greenhouse effect, the renewable energies are the subject of an increased interest, and pyrolysis could be an interesting process to develop certain forms of biomass currently used in a not very effective way or even simply burned in full field (straw, bagasse of cane with sugar, sheets, barks, chips of wood, etc).

If one pyrolysis this kind of biomass, one obtains solids - minerals (which can be useful in agriculture) and Charcoal an interesting fuel from an ecological point of view - and vapors.

Part of the vapors condenses with room temperature, giving a pyrolytic oil , which can be used as fuel, and can also provide some chemicals like phenol. The noncondensable part includes/understands a mixture of many gases (CO, CO₂, H₂, CH₄, etc) and can also be used as fuel. The proportion of the various products depends on the raw material but especially on the conditions of pyrolysis.

A long pyrolysis (several days) at moderate temperature (400°c), known as also carbonation will produce charcoal - technique employed since of the centuries. The modern work concerns a faster pyrolysis (a few minutes, even seconds), at temperatures from 500 to 800 degrees. The production of coal is then less, with the profit of the vapors.

Traditional pyrolysis is done in the dry air, but there exists also an alternative which is done in water, and is called thermal depolymerization. It makes it possible to convert biodéchets into solid carbons, gas, water, and especially hydrocarbons, providing a Syncrude good quality.

See too

Calcination

Simple: Pyrolysis

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