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Plasma gasification

From Wikipedia, the free encyclopedia
Plasma gasification
Process type Chemical
Industrial sector(s) Waste management
Energy
Main technologies or sub-processes Plasma arc
Plasma electrolysis
Feedstock Municipal and industrial waste
Biomass
Solid hydrocarbons
Product(s) Syngas
Slag
Separated metal scrap

Plasma gasification is a process which converts organic matter into synthetic gas,[1] electricity,[2] and slag[1] using plasma. A plasma torch powered by an electric arc is used to ionize gas and catalyze organic matter into synthetic gas and solid waste (slag).[1][3][4] It is used commercially as a form of waste treatment and has been tested for the gasification of biomass and solid hydrocarbons, such as coal, oil sands, and oil shale.[3]

Contents

Process

A plasma torch itself typically uses an inert gas such as argon. The electrodes vary from copper or tungsten to hafnium or zirconium, along with various other alloys. A strong electric current under high voltage passes between the two electrodes as an electric arc. Pressurized inert gas is ionized passing through the plasma created by the arc. The torch’s temperature ranges from 4,000 to 25,000 °F (2,200 to 13,900 °C).[5] The temperature of the plasma reaction determines the structure of the plasma and forming gas. This can be optimized to minimize ballast contents[6][clarification needed], composed of the byproducts of oxidation: CO
2
, N, H2O, etc..

The waste is heated, melted and finally vaporised. At these conditions molecular dissociation can occur by breaking down molecular bonds. Complex molecules are separated into individual atoms. The resulting elemental components are in a gaseous phase. Molecular dissociation using plasma is referred to as “plasma pyrolysis.”[7]

Feedstocks

The feedstock for plasma waste treatment is most often municipal solid waste, organic waste, or both. Feedstocks may also include biomedical waste and hazmat materials. Content and consistency of the waste directly impacts performance of a plasma facility. Pre-sorting and recycling useful material before gasification provides consistency. Too much inorganic material such as metal and construction waste increases slag production, which in turn decreases syngas production. However, a benefit is that the slag itself is chemically inert and safe to handle (certain materials may affect the content of the gas produced, however[2]). Shredding waste before entering the main chamber helps to increase syngas production. This creates an efficient transfer of energy which ensures more materials are broken down.[2]

For better processing, air and/or steam is added into plasma gasificator.

Yields

Pure highly calorific synthetic gas consists predominantly of Carbon monoxide (CO), H2, CH, among other components. The conversion rate of plasma gasification exceeds 99%.[8] Non-flammable inorganic components in the waste stream are not broken down. This includes various metals. A phase change from solid to liquid adds to the volume of slag.

Plasma processing of waste is ecologically clean. The lack of oxygen prevents the formation of many toxic materials. The high temperatures in a reactor also prevent the main components of the gas from forming toxic compounds such as furans, dioxins, nitrogen oxides, or sulfur dioxide. Water filtration removes ash and gaseous pollutants.

The production of ecologically clean synthetic gas is the standard goal. The gas product contains no phenols or complex hydrocarbons however circulating water from filtering systems is toxic. The water removes toxins (poisons) and the hazardous substances which must be cleaned.[9]

Metals resulting from plasma pyrolysis can be recovered from the slag and eventually sold as a commodity. Inert slag is granulated. This slag grain is used in construction. A portion of the syngas produced feeds on-site turbines, which power the plasma torches and thus support the feed system. This is self-sustaining electric power.[8]

Equipment

Gasification reactors operate at negative pressure[1] and recovers both[10] gaseous and solid resources.

Advantages

The main advantages of plasma technologies for waste treatment are:

Disadvantages

Main disadvantages of plasma technologies for waste treatment are:

  • Large initial investment costs relative to landfill[18] and
  • The plasma flame reduces the diameter of the sampler orifice over time, necessitating occasional maintenance.[19]

Commercialization

Municipal-scale plasma gasification is used commercially for waste disposal[20][21][22][23][24][25][26][27] in nine locations with five more projects in development. Sites for gasification facilities are often at landfills where recuperative landfill mining can return the landfills to their original states. Plasma arc gasification is a safe means to destroy both medical[28] and other hazardous waste.[1]

In the Northeast of England in the United Kingdom plasma gasification technology is being implemented within the Northeast of England Process Industry Cluster(NEPIC) on Teesside by Air Products. This company is building two units to gasify societal waste to produce energy with the synthesis gas produced.[29]

Military Use

The US Navy is employing Plasma Arc Waste Destruction System (PAWDS) on its latest generation Gerald R. Ford-class aircraft carrier. The compact system being used will treat all combustible solid waste generated on board the ship. After having completed factory acceptance testing in Montreal, the system is scheduled to be shipped to the Huntington Ingalls shipyard for installation on the carrier.[30]

See also

References

  1. The Plasma Arc Waste Destruction System to Reduce Waste Aboard CVN-78, pg. 13, Seaframe – Carderock Division Publication, 2008

External links

The team at Planet One Solutions is currently working directly with engineers and inventors of this amazing and very much needed Waste to Energy Plasma Technology. The current R.O.I. of Waste to Energy Plasma Tech is around 3.5 years max.

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