The expert explains: «Pyrolysis is a thermal degradation, between 200 and 600ºC, of a substance in the absence of oxygen, which is why it decomposes by heat, without combustion reactions taking place ». The process, he adds, “gives rise to a gas, a liquid and a solid residue.” Rate: «Liquid and gaseous waste can be used by combustion through a steam cycle for the production of electrical energy. The solid can be used as fuel in industrial facilities, such as cement plants ”.
Gasification “is the partial oxidation of biomass using 25-30% of the oxygen for total combustion; that is to say, in the absence of oxygen ». Here «the temperatures are higher than those of the pyrolysis and it occurs in the presence of a gasifying agent, air, pure oxygen and / or water vapor ». It has several stages: drying (evaporation of moisture); pyrolysis (thermal decomposition in the absence of oxygen at 300-700 ° C); partial combustion (oxidation of part of the tar at 800-1100ºC) and gasification: (reaction of the tar with CO2, H2 and H2O. Andrea Brito underlines: «Syngas (synthesis gas) can be used to obtain electrical and thermal energy, as well as biofuels such as methanol ‘.
The generation of plasma, Brito argues, “is carried out by making an inert gas flow through an electric field between two electrodes. Working temperatures are very high, between 5,000 and 15,000 ° C. The thermal energy of the plasma itself is used as a heat source. He concludes: «A gas composed of carbon monoxide and hydrogen and a solid residue consisting of an inert, generally vitrified slag is obtained.
The professor summarizes: «In pyrolysis there is no combustion, since it occurs in absence of oxygen; there could be a marginal combustion due to the oxygen found in the matter subjected to the process. The same goes for plasma processes. In gasification one of its stages is combustion, but it always occurs in the absence of oxygen ». Final reflection: “In none of the cases does an incineration occur.”