Pyrolysis is generally the heating of matter above its decomposition point in absence of oxygen. This leads to the breakage of chemical bonds and forming of small molecules. But it can combine and form residues of larger molecular mass. Pyrolysis temperature ranges from medium (300–800°C) to high temperatures (800–1300°C).
The materials do not combust due to a lack of oxygen in the pyrolysis process. For combustion, the material is in an oxygen-rich atmosphere, at a very high operating temperature, with heat as the targeted output.
In this technology different waste convert into energy, in the form of:
• Solid (Charcoal, Biochar)
• Non-condensable gases (H2, CH4, CnHm, CO, CO2 and N)
• Fuel Oil can be used as an alternative fuel source for renewable industries or
can be refined such as diesel.
• Bio-Char can be used for road construction, as a reinforcing agent or coloring
material, Enhance soil fertility and water retention capacity (great soil
amendment), solid fuel, Improves the overall farming productivity, Animal
feed or as a bio-based substitute for active carbon.
• Gas ensures the self-sustained operation of the plant or can be used for power
Feedstock Composition: Each of the major constituents of biomass and waste features different temperatures of thermal decomposition, which means they contribute to the results of the process in a different ways.
The temperature has a major influence on the treatment results. Higher temperatures of pyrolysis provide a greater quantity of non-condensable gases (syngas, synthetic gas), while lower temperatures favor the production of high-quality solid products (charcoal, bio-coal).
Residence Time of Material in the Pyrolysis Chamber: Influences the degree of thermal conversion of received solid product as well as the residence time of the vapors, which influences the composition of vapors (condensable / non-condensable phase).
Particle Size: Lower particle size materials are quicker affected by thermal decomposition, which can result in greater quantities of pyrolysis oil than in the case of larger particle size.
Slow Pyrolysis: Slow pyrolysis, also called carbonization, is a well-established technology that has historically been used to manufacture “charcoal.” The slow pyrolysis product distribution of liquid, char, and gas is roughly 30%, 35%, and 35% respectively. “char produced from pyrolysis of animal or vegetable matter in kilns for use in cooking or heating.” When char is produced for the purpose of applying it to the soil for agronomic improvements or environmental management, it is often called “biochar”
Fast Pyrolysis: Fast pyrolysis refers to the rapid heating of a feedstock in the absence of oxygen to produce char, vapors, and permanent or non-condensable gases. The vapors are quickly condensed to a dark brown liquid. The major product is bio-oil. Several terms have been used to describe the liquid product, including pyrolysis oil, bio-crude, liquid wood, wood oil, and bio-oil. The yields of the products are liquid condensates – 30-60%; gases (CO, H2, CH4, CO2, and light hydrocarbons) – 15-35%; and char – 10-15%.
Ultra-fast, or flash pyrolysis: This type is an extremely rapid thermal decomposition pyrolysis, with a high heating rate. The main products are gases and bio-oil. Heating rates can vary from 100-10,000° C/s and residence times are short in duration. The yields of the products are liquid condensate ~10-20%; gases – 60-80%; and char – 10-15%.