Pyrolysis is a process by which materials undergo thermal decomposition at elevated temperatures. It is a necessary step for the combustion of many solid fuels, but it also generates volatile chemicals that are toxic or contribute to air pollution if they are not completely burned.
Biomass (wood, sugarcane) pyrolysis is one potential technology for producing renewable energy from agricultural waste and other biomass feedstocks. It produces oil, gas and char by thermally breaking down the cell walls of cellulose, hemicellulose and lignin.
Characteristics
Pyrolysis is a process in which organic materials are thermally decomposed under elevated temperatures (often above 500°C) and in the absence of oxygen. It is a common practice in organic synthesis and pyrolysis can be used to convert biomass into fuels, chemicals, and other products.
The char obtained from pyrolysis of wood and other biomass is an important component of bio-fuels. The char chemical composition and properties are affected by the pyrolysis temperature, heating rate, and residence time in the reactor. Moreover, the reactivity of the char is also affected by these factors.
In this study, the char produced from pine (Pinus pinaster) and miscanthus (Miscanthus sinuatus) was synthesized at various pyrolysis temperatures, and the physical and chemical characteristics were characterized using analytical techniques such as Nuclear Magnetic Resonance (NMR) and Fourier Transform Infrared-Photoacoustic Spectroscopy (FTIR-PAS). The results showed that the char yield decreased with increasing pyrolysis temperature, from 5.5 to 3.9 wt.%, and the chars produced from low-temperature pretreatment had a better enrichment of the lightweight components of the bio-oil.
However, the chars synthesized at higher temperatures had lower adsorption capacities for CO2 (115-151%) compared with those produced at low temperatures. This was attributed to an increased pore volume and micro-surface area, especially at 600 and 700degC.
When analyzing the composition of the pyrolysis bio-oil, it was found that the acetyl content of the raw material had a positive influence on the acid concentration in the pyrolysis bio-oil. The acetyl content of the bagasse and corncob were higher than that of the spruce and pine, which resulted in higher acids in the pyrolysis bio-oil derived from these raw materials.
It is also interesting to note that the phenolic compounds in the pyrolysis bio-oil were also influenced by the pyrolysis temperature. In particular, a decrease of H-phenols and a rise of G-phenols were observed as pyrolysis temperature was increased.
The pyrolysis temperature is one of the most important variables that affects the yields of value-added compounds. In this study, the pyrolysis temperature of 480-580degC was found to be an effective parameter for maximizing small molecule aldehydes and acids and minimizing phenols. Furans, ketones, and anhydrosugars also showed a positive trend with temperature.
Synonyms
The term pyrolysium is derived from the Greek word pyro (fire), and lysis (separating). It is a chemical process in which materials are heated to elevated temperatures, often in an inert atmosphere. The heat causes the material to break down into different compounds.
It is used to produce a variety of useful products including gasoline, soap and wood gas. It also produces volatile by-products, such as benzene and pyridine.
Biomass pyrolysis is the thermal decomposition of biomass in an air-free environment at very high temperatures, usually above 500 degrees Celsius, without oxygen. The chemical compounds of the cellulose, hemicellulose and lignin that make up the biomass decompose to combustible gases and charcoal.
Pyrolysis can be performed on a wide range of carbon-based products, including organic waste, biowaste and sewage sludge. It is an effective way to transform these materials into value-added products, which can be further refined for use in industrial applications.
Typically, the rate at which the material is subjected to pyrolysis is controlled by a number of factors, such as temperature, residence time and particle size. Generally, lower particle size materials are faster affected by the pyrolysis process.
The amount of phenols that can be produced by the pyrolysis process depends on the temperature and the lignin content in the biomass. At low temperatures, the lignin mainly polymerizes to a p-vinylguaiacol, while at higher temperature a series of other aromatics can be produced.
Lignin is a complex, branched chain organic compound that has an average length of 125
In a variety of plant species, lignin is the primary component responsible for the strong bio-polymers and cell wall structures found in wood and other renewable natural resources. It binds with other plant components and can sequester carbon in the soil. It has been promoted as a potential nutrient-rich, organic soil amendment that can improve the fertility of a soil while increasing its capacity to promote and retain beneficial microorganisms.
Sources
Pyrolysis is the thermal decomposition of materials at elevated temperatures, often in an inert atmosphere. It is an important chemical process that changes the physical and chemical properties of materials. It is used to produce ethylene, many forms of carbon, and other chemicals, to produce coal coke, and to make hydrogen fuel from natural gas.
Bio-oil, a form of oil from pyrolyzed biomass (biological matter), has great potential as an alternative fuel for cars and other vehicles. The process can also be used to remove organic contaminants from sewage sludge and to create low-carbon liquid fuel from waste.
The first step in pyrolysis is to burn the material in an oxygen-free environment. The rate of pyrolysis increases as the temperature of the flame rises. It can also be carried out at lower temperatures for smaller-scale applications.
It is possible to pyrolyze a variety of materials, including wood, oil, rubber, plastics, and some metals. The resulting residues can be solid, such as biochar or noncondensable gases, or liquid, such as pyrolytic oil.
Another important application of pyrolysis is in producing semiconductors. For example, it can be used to form gallium arsenide. Other applications include the production of titanium dioxide, and in the synthesis of nanoparticles, such as zirconia and oxides, using ultrasonic spray pyrolysis.
In addition to its practical applications, pyrolysis has been shown to produce useful by-products and can help recycle other materials. For instance, pyrolyzing waste tires can turn them into gas and oil that can be used for fuel, and it can also remove PAHs and heavy metals from tires and other solid waste, making them inert and less harmful to the environment.
In addition, pyrolysis can be used to recycle other materials that would otherwise end up in landfills. For example, pyrolysis of rubber can turn it into fuel-grade fuel oils and carbon black, which can be used in rubber products and as fillers in new tires.
Applications
The pyrolysis process is used to convert a wide range of materials into usable fuels and chemicals. It is most commonly used to produce a variety of bio-fuels, but can also be applied to other types of waste products. The chemical reaction causes molecules in the material to break apart and separate into individual elements, such as carbon and hydrogen.
The use of pyrolysis as a fuel is particularly appealing because it allows a renewable source of energy to be generated from waste. It can also be used to convert toxic waste into safe substances for disposal.
Biomass pyrolysis is the heating of organic materials in the absence of oxygen to generate heat and combustible gases such as methane. It is a very efficient process and can be used to degrade biomass into char and sludge, which can then be recycled or burned.
Pyrolysis can also be used to convert sewage sludge into solid bio-fuel and a valuable fertilizer. It can remove organic contaminants, such as synthetic hormones, from sludge and make heavy metals such as lead inert.
Another use for pyrolysis is to convert rubbers into oil and gas for reuse by petrochemical industries. It can be done by boilers, autoclaves, rotary kilns, screw conveyors or fluidized beds.
In this process, the temperature of the feedstock is controlled so that a uniform thermal conversion occurs and the resulting product is consistent in quality. The degree of the thermal conversion is influenced by the residence time of the material in the chamber and the residence time of the vapours.
This can be achieved by changing the rotation speed of the screw conveyor. It is a fast and efficient method of producing high-quality pyrolysis oil from wood, sewage sludge and other materials. The resulting liquid oil contains a large number of aromatic, olefin and naphthalene compounds and has an energy value close to conventional diesel.
Moreover, the low or medium temperature pyrolysis of dry sewage sludge in a Biogreen(r) unit produces a sterilized product, odorless and easy to store. It is a good option for the management of waste sludge in sewage treatment plants, because it opens new routes to valorise this waste and avoid unnecessary transport costs.