Pyrolysis is the chemical decomposition of organic materials by heating in the absence of oxygen or any other reagents, except possibly steam. Chemical decomposition or analysis is the separation of a Chemical compound into elements or smaller compounds An organic compound is any member of a large class of Chemical compounds whose Molecules contain Carbon. Oxygen (from the Greek roots ὀξύς (oxys (acid literally "sharp" from the taste of acids and -γενής (-genēs (producer literally begetteris the Uses A Steam engine uses the expansion of steam in order to drive a Piston or Turbine to perform Mechanical work.

It is used in chemical analysis to break down complex matter into simpler molecules for identification, for example by pyrolysis gas chromatography mass spectrometry. Analytical chemistry is the study of the Chemical composition of natural and artificial Materials. Pyrolysis gas chromatography mass spectrometry is a method of chemical analysis in which the sample is heated to decomposition to produce smaller molecules that are separated by Gas

In industry, it may be used to convert one single chemical; for example, ethylene dichloride is pyrolysed to vinyl chloride to make PVC. Vinyl chloride is the Organic compound with the formula CH2CHCl It may also be used to convert complex materials such as biomass or waste into substances that are either desirable or less harmful (e. Biomass refers to living and recently dead Biological material that can be used as fuel or for industrial production WASTE is a Peer-to-peer and Friend-to-friend protocol and software application developed by Justin Frankel at Nullsoft in 2003 that features g. - syngas). Syngas (from syn thesis gas) is the name given to a gas mixture that contains varying amounts of Carbon monoxide and Hydrogen.

Extreme pyrolysis, which leaves only carbon as the residue, is called carbonization. Carbon (kɑɹbən is a Chemical element with the symbol C and its Atomic number is 6 Carbonization or Carbonisation is the term for the conversion of an Organic substance into Carbon or a carbon-containing residue through Pyrolysis Pyrolysis is a special case of thermolysis. For the biological process see Decomposition. For chemical decomposition in general see Chemical decomposition.

Contents 1 Anhydrous pyrolysis 2 Hydrous pyrolysis 3 Vacuum pyrolysis 4 Processes for biomass pyrolysis 5 Industrial sources 6 Industrial products 7 Fire protection 8 See also 9 References 10 External links

Anhydrous pyrolysis

Some pyrolysis processes are anhydrous (without water). As a general term a substance is said to be anhydrous if it contains no Water.

This phenomenon commonly occurs whenever solid organic material is heated strongly in absence of oxygen, e. g. , when frying, roasting, baking, toasting. Frying is the Cooking of food in Oil or Fat, a technique that originated in ancient Egypt around 2500BC Baking is the technique of prolonged Cooking of Food by dry heat acting by conduction, and not by radiation, normally in an Oven, Even though such processes are carried out in a normal atmosphere, the outer layers of the material keep its interior oxygen-free (which is why the outer layer oxidizes (burns), but the inside does not).

The process also occurs when burning compact solid fuel, like wood. Combustion or burning is a complex sequence of Exothermic chemical reactions between a Fuel and an Oxidant accompanied by the production of In fact, the flames of a wood fire are due to combustion of gases released by pyrolysis, not combustion of the wood itself. Thus, the pyrolysis of common materials like wood, plastic, and clothing is extremely important for fire safety and fire-fighting. Fire safety refers to precautions that are taken to prevent or reduce the likelihood of a Fire that may result in death injury or property damage alert those in a structure Distinguish from a Firefight, which means a battle with firearms

An ancient industrial use of anhydrous pyrolysis is the production of charcoal through the pyrolysis of wood. Charcoal' is the blackish residue consisting of impure Carbon obtained by removing water and other volatile constituents from Animal and Vegetation Wood is hard fibrous lignified structural tissue produced as secondary Xylem in the stems of Woody plants notably trees but also shrubs In more recent times, pyrolysis has been used on a massive scale to turn coal into coke for metallurgy, especially steelmaking. Coke is a solid Carbonaceous material derived from Destructive distillation of low-ash low-sulfur Bituminous coal. Metallurgy is a domain of Materials science that studies the physical and chemical behavior of metallic elements, their intermetallic compounds, and their Steelmaking is the second step in producing Steel from Iron ore.

Anhydrous pyrolysis has been assumed to take place during catagenesis, the conversion of kerogen to fossil fuels. See Catagenesis (biology for usage in the field of biology where it refers to retrogressive evolution Kerogen is a mixture of organic Chemical compounds that make up a portion of the organic matter in Sedimentary rocks It is insoluble in normal organic Fossil fuels or mineral fuels are fossil source Fuels that is Hydrocarbons found within the top layer of the Earth’s crust.

In many industrial applications, the process is done under pressure and at operating temperatures above 430 °C (806 °F). The Celsius Temperature scale was previously known as the centigrade scale. Fahrenheit is a temperature scale named after Daniel Gabriel Fahrenheit (1686–1736 a German Physicist who proposed it in 1724 Anhydrous pyrolysis can also be used to produce liquid fuel similar to diesel from solid biomass or plastics. Diesel or Diesel fuel (ˈdiːzəl in general is any Fuel used in Diesel engines The most common is a specific fractional distillate of petroleum Biomass refers to living and recently dead Biological material that can be used as fuel or for industrial production Plastic is the general common term for a wide range of synthetic or semisynthetic organic solid materials suitable for the manufacture of industrial products ^[1] The most common technique uses very low residence times (<2 seconds) and high heating rates using a temperature between 350 and 500 °C and is called either fast or flash pyrolysis.

Hydrous pyrolysis

Main article: Hydrous pyrolysis

The term pyrolysis is sometimes used to encompass thermolysis in the presence of water, such as steam cracking of oil, or more generally hydrous pyrolysis. Hydrous Pyrolysis refers to the thermal decomposition which takes place when organic compounds are heated to high temperatures in the presence of Water. In Petroleum geology and Chemistry, cracking is the process whereby complex organic Molecules such as Kerogens or heavy Hydrocarbons Hydrous Pyrolysis refers to the thermal decomposition which takes place when organic compounds are heated to high temperatures in the presence of Water. An example of the latter is thermal depolymerization of organic waste into light crude oil. Thermal depolymerization ( TDP) is a process using Hydrous pyrolysis for the reduction of complex Organic materials (usually Waste products of Petroleum ( L petroleum, from Greek πετρέλαιον, lit

Vacuum pyrolysis

In vacuum pyrolysis, organic material is heated in a vacuum in order to decrease boiling point and avoid adverse chemical reactions. This vacuum means "absence of matter" or "an empty area or space" for the cleaning appliance see Vacuum cleaner. The boiling point of a liquid is the temperature at which the Vapor pressure of the liquid equals the environmental pressure surrounding the liquid It is used in organic chemistry as a synthetic tool. Organic chemistry is a discipline within Chemistry which involves the scientific study of the structure properties composition reactions, and preparation In flash vacuum thermolysis or FVT, the residence time of the substrate at the working temperature is limited as much as possible, again in order to minimize secondary reactions.

Processes for biomass pyrolysis

Fast pyrolysis of biomass feedstocks is required to achieve high yields of liquids. It is characterized by rapid heating of the biomass particles and a short residence time of product vapors (0. 5 to 2 s). Rapid heating means that the biomass must be ground into fine particles and that the insulating char layer that forms at the surface of the reacting particles must be continuously removed.

Since pyrolysis is slightly endothermic,^[2] various methods have been proposed to provide heat to the reacting biomass particles:

• Partial combustion of the biomass products through air injection. In Thermodynamics, the word endothermic "within-heating" describes a process or reaction that absorbs Energy in the form of Heat. This results in poor-quality products.
• Direct heat transfer with a hot gas, ideally product gas that is reheated and recycled. The problem is to provide enough heat with reasonable gas flow-rates.
• Indirect heat transfer with exchange surfaces (wall, tubes). In thermal physics, heat transfer is the passage of Thermal energy from a hot to a colder body It is difficult to achieve good heat transfer on both sides of the heat exchange surface.
• Direct heat transfer with circulating solids: Solids transfer heat between a burner and a pyrolysis reactor. This is an effective but complex technology.

The following technologies have been proposed for biomass pyrolysis:

• Fixed beds were used for the traditional production of charcoal. Poor, slow heat transfer resulted in very low liquid yields.
• Augers: This technology is adapted from a Lurgi process for coal gasification. An auger is a device for moving material or liquid (see Archimedes' screw) by means of a rotating Helical flighting Hot sand and biomass particles are fed at one end of a screw. The screw mixes the sand and biomass and conveys them along. It provides a good control of the biomass residence time. It does not dilute the pyrolysis products with a carrier or fluidizing gas. However, sand must be reheated in a separate vessel, and mechanical reliability is a concern. There is no large-scale commercial implementation.
• Ablative processes: Biomass particles are moved at high speed against a hot metal surface. Ablation is defined as the removal of material from the surface of an object by Vaporization, Chipping, or other erosive processes Ablation of any char forming at the particles surface maintains a high rate of heat transfer. This can be achieved by using a metal surface spinning at high speed within a bed of biomass particles, which may present mechanical reliability problems but prevents any dilution of the products. As an alternative, the particles may be suspended in a carrier gas and introduced at high speed through a cyclone whose wall is heated; the products are diluted with the carrier gas. Cyclonic separation is a method of removing Particulates from an air gas or water stream without the use of filters through Vortex separation ^[3] A problem shared with all ablative processes is that scale-up is made difficult since the ratio of the wall surface to the reactor volume decreases as the reactor size is increased. There is no large-scale commercial implementation.
• Rotating cone: Pre-heated hot sand and biomass particles are introduced into a rotating cone. Due to the rotation of the cone, the mixture of sand and biomass is transported across the cone surface by centrifugal force. Like other shallow transported-bed reactors relatively fine particles are required to obtain a good liquid yield. There is no large scale commercial implementation. ^[4]
• Fluidized beds: Biomass particles are introduced into a bed of hot sand fluidized by a gas, which is usually a recirculated product gas. Fluidization (or fluidisation) is a process similar to Liquefaction whereby a Granular material is converted from a static Solid -like state High heat transfer rates from fluidized sand result in rapid heating of biomass particles. There is some ablation by attrition with the sand particles, but it is not as effective as in the ablative processes. Heat is usually provided by heat exchanger tubes through which hot combustion gas flows. There is some dilution of the products, which makes it more difficult to condense and then remove the bio-oil mist from the gas exiting the condensers. This process can not be easily scaled up, it is not yet applied commercially . See Brigdwater: There are technical and economic challenges. Technical challenges lie in scaling up the endothermic pyrolysis reactor, particularly concerning heat transfer, and in improving the quality and consistency of the bio-oil.
• Circulating fluidized beds: Biomass particles are introduced into a circulating fluidized bed of hot sand. Gas, sand and biomass particles move together, with the transport gas usually being a recirculated product gas, although it may also be a combustion gas. High heat transfer rates from sand ensure rapid heating of biomass particles and ablation is stronger than with regular fluidized beds. A fast separator separates the product gases and vapors from the sand and char particles. The sand particles are reheated in fluidized burner vessel and recycled to the reactor. Although this process can be easily scaled up, it is rather complex and the products are much diluted, which greatly complicates the recovery of the liquid products.

Industrial sources

• domestic refuse: Pyrolysis is used as a form of thermal treatment to reduce waste volumes
• waste film plastic: to produce a synthetic diesel fuel^[5]
• agricultural waste: temperature of 450 to 550 °C
• sawdust and waste wood

There is also the possibility of integrating with other processes such as mechanical biological treatment and anaerobic digestion. WASTE is a Peer-to-peer and Friend-to-friend protocol and software application developed by Justin Frankel at Nullsoft in 2003 that features Thermal treatment is a term given to any waste treatment technology that involves high temperatures in the processing of the waste feedstock A mechanical biological treatment system is a form of waste processing facility that combines a sorting facility with a form of biological treatment such as Composting or Anaerobic digestion is a series of processes in which Microorganisms break down Biodegradable material in the absence of Oxygen. ^[6]

Industrial products

• synthetic diesel fuel
• bio-oil: can be used as a fuel, after removal of valuable bio-chemicals that can be used as food additives or pharmaceuticals. The bio-oil cannot be used directly in most car engines.
• syngas (flammable mixture of carbon monoxide and hydrogen): can be produced in sufficient quantities to both provide the energy needed for pyrolysis and some excess production ^{[7] [8]}
• solid char that can either be burned for energy or recycled as a fertilizer, also known as biochar. Syngas (from syn thesis gas) is the name given to a gas mixture that contains varying amounts of Carbon monoxide and Hydrogen. Fertilizers ( also spelt fertiliser are chemical compounds given to Plants to promote growth they are usually applied either through the soil for uptake by plant Biochar is a Charcoal produced from Biomass that can store carbon
• carbon black

Carbon black is made from heavy oil fractions (mainly) and is an important material used in the rubber industry, where it significantly influences the properties of the final product (hardwearing tread black, soft flexible carcass black). Biochar used as fertilizer is very attractive since it ameliorates the soil texture and releases fertilizer slowly. Soil structure is determined by how individual soil Granules clump or bind together and aggregate and therefore the arrangement of soil pores between them When compared to chemical fertilizers, it contains oligoelements, such as selenium, which help achieve higher crop yields. When compared to other “natural” fertilizers such as manure or sewage, it is safer since it has been disinfected at high temperature and, being a solid, greatly reduces any risk of water table contamination (inhalation risks remain)^[9]. Manure is Organic matter used as Organic fertilizer in Agriculture. Sewage is the mainly liquid Waste containing some solids produced by humans which typically consists of washing water Feces, Urine, laundry waste and other The water table is the level at which the ground water pressure is equal to Atmospheric pressure. Pyrolytic char is thought to be a major component in the formation of ancient terra preta soils. Terra preta (“dark soil” in Portuguese) refers to expanses of very dark fertile Anthropogenic Soils found in the Amazon Basin. Efforts are underway to recreate these soils through the production of biochar, which is designed to promote nutrient retention and enhance soil ecology. Biochar is a Charcoal produced from Biomass that can store carbon Biochar is also being considered for carbon sequestration in the mitigation of global warming. Mitigation of global warming involves taking actions to reduce Greenhouse gas emissions and to enhance sinks aimed at reducing the extent of Global warming ^{[10] [7]}

Fire protection

Destructive fires in buildings will often burn with limited oxygen supply, resulting in pyrolysis reactions. Fire is the heat and light energy released during a Chemical reaction, in particular a combustion reaction. Thus, pyrolysis reaction mechanisms and the pyrolysis properties of materials are important in fire protection engineering for passive fire protection. Fire protection engineering (also known as fire engineering or fire safety engineering) is the application of science and engineering principles to protect people Passive fire protection (PFP is an integral component of the three components of structural Fire protection and fire safety in a Building. Pyrolytic carbon is also important to fire investigators as a tool for discovering origin and cause of fires. Carbon (kɑɹbən is a Chemical element with the symbol C and its Atomic number is 6

See also

• Cracking (chemistry)
• Destructive distillation
• Dry distillation
• Gasification
• Karrick process
• Pyrolytic coating
• Woodgas

References

External links

• Pyrolysis and Gasification Factsheet
• The Biomass Pyrolysis Network
• Homepage of the project "Pyrum Innovations"
• Agri-Therm
• Resource Transforms International

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