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What is pyrolysis?

Pyrolysis

The pyrolytic process or pyrolysis  as it is also known is that process in which the degradation of biomass occurs through the effect of heat without the need for the presence of oxygen , that is, it is a process that occurs in an atmosphere completely inert . The products formed following the pyrolysis can be both solid and liquid and gaseous, and correspond to products such as coal or char , the tars and finally, the product gas or pyroligneous steamas it is also known. This process can occur in nature individually or together in combustion or gasification processes.

What is pyrolysis?

Pyrolysis is a thermochemical treatment , which can be applied to any organic product that is carbon- based . The material is exposed to high temperatures and, in the absence of oxygen , undergoes chemical and physical separation into different molecules.

  • Definition
  • Types
  • Pyrolysis process
  • Importance
  • Examples

Definition

Pyrolysis is a form of thermolysis that can be defined as the thermal decomposition that a material undergoes when it is in the absence of oxygen or some type of reactant . The decomposition undergone can be produced by means of a rather complicated series of chemical reactions and processes of transfer of matter and heat . It can also be defined as the step that occurs prior to gasification and combustion .

When it is produced in extreme form leaving only carbon as a residue, it is known as carbonization . Through pyrolysis we can get to obtain different secondary products which are useful in the area of technology .

The pyrolysis products always produce solid gases such as coal, liquids and non-condensables such as H2, CH4, CnHm, CO, CO2 and N. As the liquid phase is extracted from the pyrolysis gas only during its cooling, in In some applications, these two streams can be used together when supplying hot syngas directly to the burner or oxidation chamber .

Types

There are two different types of pyrolysis depending on the physical conditions in which it is carried out:

  • Aqueous pyrolysis : this term is used when it is necessary to refer to the thermolysis that occurs in the presence of water , such as, for example, the steam cracking of oil or the thermal depolymerization of organic residues in heavy crude oil.
  • Pyrolysis vacuum : this type of pyrolysis to the vacuum means that the organic material is heated in vacuum to further reduce the point of boiling and avoid adverse chemical reactions.

Pyrolysis process

The process for pyrolysis to occur has three stages, which are the following:

  • The first stage is in which a slow decomposition occurs , producing at the same time small amounts of water , carbon oxides , hydrogen and methane . This decomposition occurs as a consequence of the breaking of bonds due to the high temperature of the process and as a consequence of the release of gases retained in the coal.
  • The second stage is known as the active thermal decomposition stage . The temperature in this stage increases and occurs fragmentation more profound of the molecule carbon forming hydrocarbons condensable and tars . This stage begins at 360 º C and ends when temperatures around 560 º C approximately have been reached.
  • The last stage occurs at temperatures above 600ºC , and is characterized by the gradual elimination of hydrogen and other heteroatoms.

Importance

Pyrolysis is very important because it is responsible for facilitating the control of pollution of the air with regard to incineration . It also helps to reduce the volume of garbage that enters and the production of sterile waste , which increases life and improves the quality of landfills in relation to untreated garbage. And finally, it is also a method that serves to convert a part of the waste into storable and transportable fuel .

Examples

  • Pyrolysis of biomass : this pyrolysis can reach obtain fuel from coffee grounds , compounds phenological antioxidants, polyphenols of sugar cane.
  • Pyrolysis of alkanes : this case is also known by the name of cracking or disintegration , which can be thermal, catalytic and through treatment with hydrogen .
  • Petroleum pyrolysis : in the case of petroleum, alkanes are subjected to high temperatures, producing hydrocarbons .
  • Pyrolysis of plastics : through this process in which heat helps to decompose materials into gas, it has been possible to decompose plastic into its basic elements . The gases obtained can be injected directly into engines for energy production, which generates a reduction in plastic pollution since they can be used as raw material for this process.
  • Pyrolysis of wood : it is the decomposition of wood by heating up to 450º C without air access, with the formation of gaseous and liquid products as well as solid residue, which is charcoal .

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