Plasma gasification

Plasma Arc 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 an extreme thermal process using plasma which converts organic matter into a syngas (synthesis gas) which is primarily made up of hydrogen and carbon monoxide. A plasma torch powered by an electric arc, is used to ionize gas and catalyze organic matter into syngas with slag[1][2][3] remaining as a byproduct. It is used commercially as a form of waste treatment and has been tested for the gasification of municipal solid waste, biomass, industrial waste, hazardous waste, and solid hydrocarbons, such as coal, oil sands, petcoke and oil shale.[2]

Process

Small plasma torches typically use an inert gas such as argon where larger torches require nitrogen. 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).[4] The temperature of the plasma reaction determines the structure of the plasma and forming gas.[5]

The waste is heated, melted and finally vaporized. Only at these extreme conditions can molecular dissociation occur by breaking apart molecular bonds. Complex molecules are separated into individual atoms. The resulting elemental components are in a gaseous phase (syngas). Molecular dissociation using plasma is referred to as "plasma pyrolysis."[6]

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[7]). 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.[7]

For improved processing steam is sometimes added into the plasma gasification process.

Yields

Pure highly calorific synthesis gas consists predominantly of carbon monoxide (CO) and hydrogen (H2).[8] Inorganic compounds in the waste stream are not broken down but melted, which includes glass, ceramics, and various metals.

The high temperature and lack of oxygen prevents the formation of many toxic compounds such as furans, dioxins, nitrogen oxides, or sulfur dioxide in the flame itself. However, dioxins are formed during cooling of the syngas.

Metals resulting from plasma pyrolysis can be recovered from the slag and eventually sold as a commodity. Inert slag produced from some processes is granulated and can be 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

Some plasma gasification reactors operate at negative pressure,[1] but all attempt to recover both[9] gaseous and solid resources.

Advantages

The main advantages of plasma torch technologies for waste treatment are:

  • Clean destruction of hazardous waste[10]
  • Preventing hazardous waste from reaching landfills[11][12]
  • 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[13]
  • Potential production of vitrified slag which could be used as construction material[14]
  • Processing of organic waste into combustible syngas for electric power and thermal energy[15]
  • Production of value-added products (metals) from slag[16]
  • Safe means to destroy both medical[17] and many hazardous wastes.[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 some incinerators.

Disadvantages

Main disadvantages of plasma torch technologies for waste treatment are:

  • Large initial investment costs relative to that of alternatives, including landfill[18] and incineration.
  • Operational costs are high relative to that of incineration.
  • Little or even negative net energy production.
  • Wet feed stock results in less syngas production and higher energy consumption.
  • Frequent maintenance and limited plant availability.
  • For some early technologies, the plasma torch plume reduced the diameter of the sampler orifice over time, necessitating frequent maintenance.[19]

Commercialization

Plasma torch gasification is used commercially for waste disposal[20][21][22][23][24][25][26][27][28][29][30] at a total of five sites worldwide representing to a combined design capacity of 200 tonnes waste per day, of which 100 tonnes per day is biomass waste.

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.[31]

See also

References

  1. 1 2 3 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. (Subscription required (help)).
  2. 1 2 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. (Subscription required (help)).
  3. ↑ Messerle, V. E.; Ustimenko, A. B. (2007). "Solid Fuel Plasma Gasification". In Syred, Nick; Khalatov, Artem. 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. (Subscription required (help)).
  4. ↑ "The Recovered Energy System: Discussion on Plasma Gasification". Retrieved 2008-10-20.
  5. ↑ Bratsev, A. N.; Popov, V. E.; Rutberg, A. F.; Shtengel’, S. V. (2006). "A Facility for Plasma Gasification of Waste of Various Types" (PDF). High temperature. 44 (6): 823–828. Retrieved 2013-03-12. (Subscription required (help)).
  6. ↑ 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.
  7. 1 2 "How Stuff Works- Plasma Converter". Retrieved 2012-09-09.
  8. 1 2 "Plasma Gasification". United States Department of Energy. Archived from the original on 2010-08-13. Retrieved 2010-08-07.
  9. ↑ , "Method for the Gasification of Carbonaceous Matter by Plasma Arc Pyrolysis"
  10. ↑ 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.
  11. ↑ , "Apparatus and Method for Treating Hazardous Waste"
  12. ↑ , "Arc Plasma-Melter Electro Conversion System for Waste Treatment and Resource ..."
  13. ↑ 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.
  14. ↑ 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.
  15. ↑ 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.
  16. ↑ 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.
  17. ↑ 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.
  18. ↑ Pourali, M. "Application of Plasma Gasification Technology in Waste to Energy #x2014;Challenges and Opportunities". IEEE Transactions on Sustainable Energy. 1 (3): 125–130. Bibcode:2010ITSE....1..125P. doi:10.1109/TSTE.2010.2061242. ISSN 1949-3029.
  19. ↑ 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.
  20. ↑ "National Cheng Kung University - Tainan, Taiwan". PEAT International. Retrieved 2009-04-09.
  21. ↑ 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.
  22. ↑ "About the Project". A Partnership for a Zero Waste Ottawa. Archived from the original on 2009-04-20. Retrieved 2009-04-10.
  23. ↑ Czekaj, Laura (2008-12-07). "Mechanical problems plague Plasco". Ottawa Sun.
  24. ↑ "AFSOC makes 'green' history while investing in future". US Air Force Special Operations Command. Archived from the original on 2011-05-09. Retrieved 2011-04-28.
  25. ↑ "INEOS Bio Commercializes bioenergy technology in Florida" (PDF). Biomass Program. 2011-11-21.
  26. ↑ "The Plasma Arc Waste Destruction System to Reduce Waste Aboard CVN-78, pg. 13". Seaframe - Carderock Division Publication. 2008.
  27. ↑ "Alter NRG Announces Commissioning of Biomass Gasifier at Waste To Liquids Facility in China" (Press release). Alter NRG. Archived from the original on 2013-03-07. Retrieved 2013-01-29.
  28. ↑ Messenger, Ben (12 April 2013). "Second Plasma Gasification Plant for Teesside Following Government Deal". Waste Management News.
  29. ↑ "Air Products Will Exit Energy-from-Waste Business" (Press release). 2016-04-04. Retrieved 2016-04-06.
  30. ↑ Air Products abandons plans for plasma-based energy from waste plants in Tees Valley, 2016-04-05, retrieved 2016-04-06
  31. ↑ The Plasma Arc Waste Destruction System to Reduce Waste Aboard CVN-78, pg. 13, Seaframe - Carderock Division Publication, 2008
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