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This wiki or knowledge database was developed as part of the Empyro project which is financially supported by the 7th Framework Programme of the European Commission (Grant number 239357). If you wish to contribute to this wiki please send your credentials to Patrick Reumerman of BTG Biomass Technology Group.
Biomass and other types of residues can be converted into more valuable material such as fuels or chemicals. The conversion processes are biochemical or thermochemical. The pyrolysis process is a thermochemical process. Pyrolysis is a process in which organic materials are heated in the absence of air. Under these conditions, organic vapors, permanent gases and charcoal are produced. The organic vapors can be condensed to form a liquid: Pyrolysis oil. Dependent on the reaction time, the reaction products can be directed at producing charcoal, a process called slow pyrolysis or carbonisation. If the reaction occurs fast - within a few seconds - it is called Fast Pyrolysis. This WikiPyro is mainly concerned with Fast Pyrolysis.
Fast pyrolysis technologies
In the fast pyrolysis process, biomass decomposed very quickly in the absence of oxygen. Vapours are produced and some charcoal and gases as well. After cooling and condesation, pyrolysis oils are formed. The essentail stepps of fast pyrolysis for the production of pyrolysis oils are:
- Very high heating rates and heat transfer rates at the biomass particles
- Controlling temperature at around 500 degrees centrigrade for optimal liquid yields
- Short residence time of about 2 seconds
- Rapid cooling of the vapors to form pyrolysis oil.
Several fast pyrolysis technologies are developed. All have their own thermal and time conditions. Besides this, also the technology itself differs. The four main technologies are:
In the past years several pyrolyis plants are constructed all over the world. These plants range from small capacity pilot plants to full scale large commercial pyrolysis plants. In the bullets below, a list with pyrolysis production units can be found.
Pyrolysis oilPyrolysis oil, or PO in short, is a dark-brown, free flowing viscous oil-like substance with several distinctive properties, such as a relatively high density compared to other oil types and a lower energy content.
De density of pyrolysis oil is very high 1.2 kg/l compare to crude oil of 0.85 kg/l. The heating value of pyrolysis oil is about 17 MJ/kg. It means that the liquid has 42% of the energy content of crude oil on a weight basis and 61% on a volumetric basis.
Pyrolysis oil contains a lot of water and is about 25% of the weight. The oil is highly acid with a pH of 2.5. The elemental analysis of pyrolysis oil on dry basis is C-56%, H-6%, O-38% and N-<0.1%.
Applications of pyrolysis
Pyrolysis oil is an energy carrier or feestock for platform chemicals. The applications for energy are:
- substite for natural gas in a boiler
- substite for fuel oil
- second generation diesel, jet fuel of gasoline.
Pyrolysis oil is also a feedstock for the biobased economy. Pyrolysis oil consists of pyrolytic sugars, pyrolytic lignocellulose and the water fraction. These three fractions are the basis for platform chemicals.
Almost all types of biomass are suitable for pyrolysis. Main requirements for the pyrolysis process is that the biomass is relatively dry (less than 10% moisture content) and a relatively small size (about 0.5 to 1 mm).
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