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Plasma gasification

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Plasma gasification
Process typeChemical
Industrial sector(s)Waste management
Energy
Main technologies or sub-processesPlasma arc
Plasma electrolysis
FeedstockMunicipal 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]

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: CO2, N2, 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 recover both[10] gaseous and solid resources.

Advantages

The main advantages of plasma technologies for waste treatment are:

  • Clean destruction of hazardous waste,.[11]
  • Preventing hazardous waste from reaching landfills,[12][13]
  • Some processes are designed to recover fly ash, bottom ash, and most other particulates, for 95% or better diversion from landfills, and no harmful emissions of toxic waste,[14]
  • Production of vitrified slag which could be used as construction material,[15]
  • Processing of organic waste into combustible syngas for electric power and thermal energy,[16] and
  • Production of value-added products (metals) from slag.[17]
  • Plasma arc gasification is a safe means to destroy both medical[18] and other hazardous waste.[1]
  • Gasification with starved combustion and rapid quenching of syngas from elevated temperatures can avoid the production of dioxins and furans that are common to incinerators.
  • Air emissions can be cleaner than landfills and incinerators. Plasma gasification plants using IC engines to produce electricity do not require stacks, and can be integrated in small spaces inside the urban envelope.

Disadvantages

Main disadvantages of plasma technologies for waste treatment are:

  • Large initial investment costs relative to that of alternatives, including landfill[19] and incineration. As with all major waste treatment processes, plasma gasification is an infrastructure process.
  • Operational costs are high relative to that of incineration.
  • The industry has a history of exaggerated claims about performance in order to sell equipment and licenses before processes were proven. This has resulted in a number of very costly failures from gasifiers that were not properly integrated with feed systems, gas cleanup, and power production, or from gasifiers that were scaled up without operational data to support the scaleups.
  • Little or even negative net energy production. Processes that use plasma for catalysis and refinement of syngas to operate IC engines and/or gas turbines can theoretically be more efficient than incinerators of equal size, but this is yet to be demonstrated in practice.
  • Frequent maintenance and limited plant availability.
  • For some early technologies, the plasma flame reduces the diameter of the sampler orifice over time, necessitating frequent maintenance.[20]

Commercialization

Main article: Plasma gasification commercialization

Municipal-scale plasma gasification is used commercially for waste disposal[21][22][23][24][25][26][27][28] in five locations representing to a total design capacity of 250 tonnes waste per day worldwide.

In the Northeast of England in the United Kingdom plasma gasification technology was attempted implemented within the Northeast of England Process Industry Cluster(NEPIC) on Teesside by Air Products. Two large units were erected, designed to gasify societal waste to produce power with the synthesis gas produced.[29] By late 2015, Air Products halted construction on the second phase until it fixed issues encountered during commissioning of the first phase. On April 4, 2016, Air Products announced it was leaving the waste-to-energy business, and was taking a write-down of $0.9-$1.0B.[30] [31]

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.[32]

See also

References

  1. ^ a b c d e Moustakasa, K.; Fattab, D.; Malamisa, S.; Haralambousa, K.; et al. (2005-08-31). "Demonstration plasma gasification/vitrification system for effective hazardous waste treatment". Journal of Hazardous Materials. 123 (1–3): 120–126. doi:10.1016/j.jhazmat.2005.03.038. Retrieved 2012-03-08. {{cite journal}}: Unknown parameter |subscription= ignored (|url-access= suggested) (help)
  2. ^ a b c "How Stuff Works- Plasma Converter". Retrieved 2012-09-09.
  3. ^ a b Kalinenko, R. A.; Kuznetsov, A. P.; Levitsky, A. A.; Messerle, V. E.; et al. (1993). "Pulverized coal plasma gasification". Plasma Chemistry and Plasma Processing. 13 (1): 141–167. doi:10.1007/BF01447176. Retrieved 2012-03-08. {{cite journal}}: Unknown parameter |subscription= ignored (|url-access= suggested) (help)
  4. ^ Messerle, V. E.; Ustimenko, A. B. (2007). "Solid Fuel Plasma Gasification". In Syred, Nick; Khalatov, Artem (eds.). Advanced Combustion and Aerothermal Technologies. Environmental Protection and Pollution Reductions. Springer Netherlands. pp. 141–156. doi:10.1007/978-1-4020-6515-6. ISBN 978-1-4020-6515-6. Retrieved 2012-03-08. {{cite book}}: Unknown parameter |subscription= ignored (|url-access= suggested) (help)
  5. ^ "The Recovered Energy System: Discussion on Plasma Gasification". Retrieved 2008-10-20.
  6. ^ Bratsev, A. N.; V. E. Popov; A. F. Rutberg; S. V. Shtengel’ (2006). "A Facility for Plasma Gasification of Waste of Various Types" (PDF). High temperature. 44 (6): 823–828. Retrieved 2013-03-12.
  7. ^ Huang, H.; Lan Tang; C. Z. Wu (2003). "Characterization of Gaseous and Solid Product from Thermal Plasma Pyrolysis of Waste Rubber". Environmental Science & Technology. 37 (19): 4463–4467. Bibcode:2003EnST...37.4463H. doi:10.1021/es034193c. Retrieved 2013-03-12.
  8. ^ a b "Plasma Gasification". United States Department of Energy. Retrieved 2010-08-07.
  9. ^ HTT Canada Plasma Treatment.Corporate Brochure. 2009-27-07. Retrieved on 2009-08-13.
  10. ^ [1], "Method for the Gasification of Carbonaceous Matter by Plasma Arc Pyrolysis" 
  11. ^ Tendler, Michael; Philip Rutberg; Guido van Oost (2005-05-01). "Plasma Based Waste Treatment and Energy Production". Plasma Physics and Controlled Fusion. 47 (5A): A219. Bibcode:2005PPCF...47A.219T. doi:10.1088/0741-3335/47/5A/016. ISSN 0741-3335. Retrieved 2013-03-19.
  12. ^ [2], "Apparatus and Method for Treating Hazardous Waste" 
  13. ^ [3], "Arc Plasma-Melter Electro Conversion System for Waste Treatment and Resource ..." 
  14. ^ Lemmens, Bert; Helmut Elslander; Ive Vanderreydt; Kurt Peys; et al. (2007). "Assessment of Plasma Gasification of High Caloric Waste Streams". Waste Management. 27 (11): 1562–1569. doi:10.1016/j.wasman.2006.07.027. ISSN 0956-053X. Retrieved 2013-03-20.
  15. ^ Mountouris, A.; E. Voutsas; D. Tassios (2008). "Plasma Gasification of Sewage Sludge: Process Development and Energy Optimization". Energy Conversion and Management. 49 (8): 2264–2271. doi:10.1016/j.enconman.2008.01.025. Retrieved 2013-03-20.
  16. ^ Leal-Quirós, Edbertho (2004). "Plasma Processing of Municipal Solid Waste". Brazilian Journal of Physics. 34 (4B): 1587–1593. Bibcode:2004BrJPh..34.1587L. doi:10.1590/S0103-97332004000800015. Retrieved 2013-03-20.
  17. ^ Jimbo, Hajime (1996). "Plasma Melting and Useful Application of Molten Slag". Waste management. 16 (5): 417–422. doi:10.1016/S0956-053X(96)00087-6. Retrieved 2013-03-20.
  18. ^ Huang, Haitao; Lan Tang (2007). "Treatment of Organic Waste Using Thermal Plasma Pyrolysis Technology". Energy Conversion and Management. 48 (4): 1331–1337. doi:10.1016/j.enconman.2006.08.013. Retrieved 2013-03-12.
  19. ^ Pourali, M. "Application of Plasma Gasification Technology in Waste to Energy #x2014;Challenges and Opportunities". IEEE Transactions on Sustainable Energy. 1 (3): 125–130. doi:10.1109/TSTE.2010.2061242. ISSN 1949-3029.
  20. ^ Leal-Quirós, Edbertho (December 2004). "Plasma Processing of Municipal Solid Waste". Brazilian Journal of Physics. 34 (4B): 1587–1593. Bibcode:2004BrJPh..34.1587L. doi:10.1590/S0103-97332004000800015. ISSN 0103-9733. Retrieved 2013-03-20.
  21. ^ "National Cheng Kung University - Tainan, Taiwan". PEAT International. Retrieved 2009-04-09.
  22. ^ Williams, R.B.; Jenkins, B.M.; Nguyen, D. (December 2003). Solid Waste Conversion: A review and database of current and emerging technologies (PDF) (Report). University of California, Davis, Department of Biological and Agricultural Engineering. p. 23. Archived from the original (PDF) on 2007-04-15.
  23. ^ "About the Project". A Partnership for a Zero Waste Ottawa. Retrieved 2009-04-10.
  24. ^ Czekaj, Laura (2008-12-07). "Mechanical problems plague Plasco". Ottawa Sun.
  25. ^ "AFSOC makes 'green' history while investing in future". US Air Force Special Operations Command. Retrieved 2011-04-28.
  26. ^ "INEOS Bio Commercializes bioenergy technology in Florida" (PDF). Biomass Program. 2011-11-21.
  27. ^ "The Plasma Arc Waste Destruction System to Reduce Waste Aboard CVN-78, pg. 13". Seaframe - Carderock Division Publication. 2008.
  28. ^ "Alter NRG Announces Commissioning of Biomass Gasifier at Waste To Liquids Facility in China" (Press release). Alter NRG. Retrieved 2013-01-29.
  29. ^ Messenger, Ben (12 April 2013). "Second Plasma Gasification Plant for Teesside Following Government Deal". Waste Management News.
  30. ^ "Air Products Will Exit Energy-from-Waste Business" (Press release). 2016-04-04. Retrieved 2016-04-06.
  31. ^ Air Products abandons plans for plasma-based energy from waste plants in Tees Valley, 2016-04-05, retrieved 2016-04-06
  32. ^ The Plasma Arc Waste Destruction System to Reduce Waste Aboard CVN-78, pg. 13, Seaframe - Carderock Division Publication, 2008
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