pyrolsis

Pyrolysis, sometimes spelled pyrolsis, is a thermochemical decomposition of organic material at elevated temperatures in the absence of oxygen. The process breaks large molecules into smaller, often more useful, compounds. Products typically include a solid char, a liquid condensate such as bio-oil or tar, and gaseous streams. The exact distribution of products depends on the feedstock, heating rate, temperature, residence time, and reactor design, as well as the presence of catalysts.

Pyrolysis is distinct from combustion, which requires oxygen, and from gasification, which operates with limited oxygen to produce a combustible syngas. It is conducted over a wide temperature range, commonly from about 300 to 900°C, with lower temperatures favoring char formation and higher temperatures favoring liquids and gases. Different processing regimes include slow pyrolysis (low heating rate, long residence time, higher char yield), fast pyrolysis (rapid heating, short residence time, high liquid yield), and flash pyrolysis (very rapid heating with extremely short residence time).

Feedstocks for pyrolysis include biomass residues (such as wood chips and agricultural waste), plastics, tires, and coal. The process is used for energy production in the form of bio-oil and syngas, for material production such as activated carbon, and for waste management through conversion of refuse into usable products. Biochar produced from biomass is used as a soil amendment and carbon sink, while bio-oil and syngas can be upgraded for fuels or chemical feedstocks.

Common reactor types encompass fixed-bed retorts, moving-bed and screw pyrolyzers, rotary kilns, and fluidized-bed systems. Environmental and safety considerations include managing tar and particulate emissions, ensuring oxygen exclusion to prevent combustion, and optimizing energy balance.