Pyrolysis is a chemical reaction leading to decomposition of organic matters that requires heat and takes place without reagents, without oxygen or in oxygen-deficient atmosphere.
This transformation, distinct from combustion that involves an oxidant such as oxygen, creates new products following atomic or molecular rearrangements.
a carbonaceous solid,
and a gas.
It begins at a relatively low level of temperature (from 200 ° C) and continues until 1000 ° C. Depending on the temperature, the proportion of the three resulting compounds is different.
This reaction can be used to convert biomass into sources of more easily useable energy and to produce a soil amendment.
The major advantage of this technique is that those products are highly recyclable. The association, for example, of pyrolysis in a rotary furnace and gasification, provides a synthesis gas mixture of CO and H2, that can be used as raw material in a wide range of organic chemical synthesis.
Other gases resulting from pyrolysis can be used as fuel for heating the system, or produce steam for electricity generation.
The oily wastes are recoverable into high quality refinery products by hydrogenation. Coke is the main solid waste.
Charcoal or biochar: used as fuel (30 GJ / t), soil amendment, fertilizer, water retainer ...
Pyrolysis oil: can be used as liquid fuel or as intermediate for extracting biobased molecules
Syngas: used to produce heat for drying or converted into electricity
Biochar is an English neologism composed of the prefix bio and the word charcoal. It means: coal for agricultural use. The English word Biochar is sometimes replaced by the word Biocoal which is not really suitable (almost all coals, including fossil, have a biological origin).
Amendment for restoring or improving the soils.
Biochar is studied and recommended by a growing number of authors to improve and stabilize tropical soils, naturally acidic and poor and thus fragile, that have been severely degraded by agriculture and / or deforestation or are eroded or threatened by erosion.
Carbon sequestration in soils:
Biochar, as a carbon-rich product, stable and sustainable, also has a carbon sink function. This explains the growing interest it gives rise to on human global warming. It could be an immediate solution to the overall negative impact of agricultural activities.
Substitute for other uses of charcoal or activated charcoal:
For example, the introduction of biochar in soil improves the quality of water flowing through it (it plays a role of filter) and could thus increase watercourses and productivity of wetlands.
heavy metals in plants:
Biochar has recently been studied to assess its ability to bind the contaminants in the soil, to avoid contamination of trophic chains. The results are encouraging.
Pyrolysis oil is an advanced biofuel similar to crude oil. It can be directly burned to produce heat and energy, or refined to produce fuel for transport, such as gasoline, diesel and jet fuel.
The crude gases resulting from pyrolysis are condensed to form oil. The noncondensable gases, such as carbon monoxide, can be recycled to power the pyrolysis reactor.
Pyrolysis oil is extracted and can be burned as fuel for boilers and furnaces, or refined into molecules with the desired size to be used as a transportation fuel in other facilities.
"Pyrolysis oil is an excellent alternative to heavy fuel oil. It can be used in existing oil boilers with minimal modifications, which constitutes serious incentives for heat producers to turn to cleaner fuels . "
M. Joaquín Almunia,
Vice President of the Commission in charge of competition policy at the European Commission
Syngas or synthesis gas, once (early twentieth century) named "manufactured gas" then "town gas" is a combustible gas mixture produced by pyrolysis.
It comes from a complex chemical reaction. This reaction is characterized by a first step of gasification with pyrolysis of an organic material (wood or coal for example) in presence of an oxidizing agent deliberately introduced in sufficient quantity, enough so that there is combustion, but too little for it is complete.
This reaction produces "a gas formed of a mixture of condensable and noncondensable gas and a char, a kind of residual charcoal". The synthesis gas marketed is generated by a second thermal decomposition stage that is that of a part of the "char".
Synthesis gas contains mostly steam, hydrogen, methane, carbon monoxide and some carbon dioxide.
Formerly used as gaseous fuel, today, it is mostly transformed into liquid fuel for internal combustion engines.
Once cleaned, it can theoretically be used in cogeneration or trigeneration to produce movement, heat and / or electricity.
In the "Plastic to Fuel" system, the syngas may, for example, be used for operating the dryer, or power a turbine to produce electricity.