Plasma arc gasification or Plasma Gasification Process abbreviated PGP is a waste treatment technology that uses electrical energy and the high temperatures created by an electric arc gasifier. This arc breaks down waste primarily into elemental gas and solid waste (slag), in a device called a plasma converter. The process has been intended to be a net generator of electricity, depending upon the composition of input wastes, and to reduce the volumes of waste being sent to landfill sites.
Relatively high voltage, high current electricity is passed between two electrodes, spaced apart, creating an electrical arc. Inert gas under pressure is passed through the arc into a sealed container of waste material, reaching temperatures as high as 25,000 °F (13,900 °C)[1] in the arc column. The temperature a few feet from the torch can be as high as 5000–8000 °F (2760–4427 °C).[1] At these temperatures, most types of waste are broken into basic elemental components in a gaseous form, and complex molecules are separated into individual atoms.
The reactor operates at a slightly negative pressure, meaning that the feed system is complemented by a gaseous removal system, and later a solid removal system. Depending on the input waste (plastics tend to be high in hydrogen and carbon), gas from the plasma containment can be removed as syngas, and may be refined into various fuels at a later stage or fired on site to provide power.
Syngas is produced exclusively from organic materials with a conversion rate of greater than 99% using plasma gasification.[2] Other inorganic materials in the waste stream that are not broken down but only go through a phase change (solid to liquid) add to the volume of slag with minimal energy recovery and increased cost for refining. For efficient operation of the plant, a portion of the syngas may be used to run on site turbines to power the plasma torches and feed system.[2]
The latest independent review of plasma technology providers was undertaken by Juniper Consulting in 2008,[3] as well as a separate independent review on Alter NRG /Westinghouse technology.[4]
PEAT International constructed a plasma arc waste disposal facility at National Cheng Kung University (NCKU) in Tainan City, Taiwan, which uses its proprietary Plasma Thermal Destruction Recovery method. The facility is able to handle 3–5 metric tons (3.3–5.5 short tons) of waste per day from a variety of waste streams, including incinerator fly ash, medical waste, organic industrial process waste and inorganic sludges. It can also process waste consumer batteries and other materials, including heavy metal sludges, and refinery catalysts (waste streams that would generate valuable metal alloys). The facility was constructed as part of a comprehensive resource recovery facility funded by the Taiwanese government, marking the first time the Government of Taiwan committed financial and technical resources to the utilization of plasma technology. It was commissioned in November 2004 and received its operating permit in January, 2005. PEAT has been an active participant in the operations and maintenance of the facility on behalf of NCKU for its research purposes.[5]
Three similar small plants are in operation in Japan — a 166-short-ton (151,000 kg) per day "pilot" plant in Yoshii, co-developed by Hitachi Metals Ltd. and Westinghouse Plasma, which was certified after a demonstration period in 1999–2000; a 165-short-ton (150,000 kg) per day plant in Utashinai City, completed in 2002; and a 28-short-ton (25,000 kg) per day plant commissioned by the twin cities of Mihama and Mikata in 2002.[6]
A new and different type of plasma arc waste conversion that uses plasma to refine gases produced during waste conversion, rather than to destroy waste by brute force as do other plasma systems, has yet to show itself to be successful on a full commercial scale. Plasco Energy Group completed a plasma-arc waste demonstration plant in Ottawa, Canada at the Trail Road Landfill, to process 85 metric tons (94 short tons) per day of municipal solid waste.[7] Unlike other plasma waste processing facilities, Plasco Energy Group's process does not use plasma to destroy waste, but rather to refine gases produced during waste conversion, in order to allow them to be used to run an internal combustion gas engine. On 24 October 2007, the Plasco Trail Road facility began delivering power to the grid.
The Plasco conversion system, which uses plasma to refine gases rather than expose them to extremely high temperatures, and whose liner is composed of refractory brick rather than metal, is not susceptible to premature attack of vessel liners. Plasco's internal studies claim that its emissions are also much lower than any other thermal waste processing system. By converting waste to CO2 and water, rather than to methane, the greenhouse gas emissions of the process might be much less than competing technologies such as landfills. Plasco Energy is proposing a scaled up residual waste plasma gasification facility for Los Angeles, California.
In an update to local area residents on 6 December 2008, Plasco president Rod Bryden said delays at its facility were caused by malfunctioning machinery, not problems with the waste-to-energy technology.[8]
In 2011, Plasco is seeking a commercial license for a permanent operation in the Ottawa area, claiming success for its three-year pilot project. The government is conducting public hearings.[9] The pilot plant was said to produce about 1 MWh of electricity from each tonne of waste.[10]
The heart of this technology, the Gasplasma process, forms the basis of APP’s Swindon Plant, the first Gasplasma facility in the world. Gasplasma is the sequential use of gasification, plasma gas treatment, syngas polishing and gas engine power generation.
A full scale plant will treat 100,000 short tons (91,000 t) per annum of municipal waste and produce:
A full scale plant will be 150 metres (490 ft) long, 50 metres (160 ft) wide, and along most of its length only 11 metres (36 ft) high. Above the thermal plant, the roof height is about 14 metres (46 ft), and the single exhaust for the engines 10 metres (33 ft) higher, at only 34 metres (112 ft). The building is approximately the size of a supermarket store and operates under a light vacuum, meaning it contains all odors. The entire process occurs within the building.
On April 26, 2011, the Air Force Special Operations Command (AFSOC) held a ribbon-cutting ceremony to commemorate the official opening of its Transportable Plasma Waste to Energy System (TPWES) facility, located at Hurlburt Field, near Fort Walton Beach Florida, USA. The facility was designed, constructed and commissioned by Montreal-based PyroGenesis Canada Inc., and the unit deployed at the facility is based on the company’s Plasma Resource Recovery System (PRRS) technology. The plant is designed to process 10.5 metric tons per day of municipal solid waste, as well as hazardous and biomedical waste. The syngas generated by the process is fed to an internal combustion engine to produce electricity, while the inorganic fraction of the waste feed is converted into an inert, vitrified slag which can be used for building materials. The system is designed to be energy neutral and transportable to allow the Air Force the flexibility to potentially deploy it other bases around the world, including forward operating bases. [11]
Energy Park Peterborough - the UK’s First Green Energy Park, which is being managed by Peterborough Renewable Energy was granted consent by the Government Department for Energy and Climate Change (DECC) in November 2009. It will take in mixed waste and – through a combination of recycling, gasification and plasma-enhanced waste recovery – recycle and remanufacture it, producing reusable products and renewable energy in the process. Energy Park Peterborough alone will save 600,000 tonnes of CO2 per year, create over 100 green collar jobs in the local community and produce enough renewable energy to power 60,000 homes. Tetronics will Supply Plasma Hazardous Waste Treatment Technology. The technology will turn the Air Pollution Control (APC) residue generated from the Biomass Power Plant into bricks and tiles for the building industry, thereby; ensuring close to zero residues to be landfilled.
The first plasma-based waste disposal system in the USA was announced in 2006 in St. Lucie County, Florida. The county stated that it hopes to not only avoid further landfill, but completely empty its existing landfill — 4,300,000 short tons (3,900,000 t) of waste collected since 1978 — within 18 years.[12] The plant was originally scheduled to come into operation in 2009, but experienced several setbacks. Backers originally announced that the facility would produce 600 short tons (540,000 kg) of solid rubble from around 3,000 short tons (2,700,000 kg) of waste per day at 5,500 °C (9,900 °F), but uncertainties arose regarding the safety of such a facility. The public health and environmental threats from incinerators coupled with the uncertainty of the community's ability to produce such large quantities of waste on a consistent basis have led GeoPlasma to submit a new proposal for a much smaller facility that would convert 200 short tons (180 t) of waste per day. Current plans are to begin building the $120 million facility in 2011. [13]
INEOS Bio and New Planet Energy Florida are partnering to build a plant which will make about 8 million gallon of ethanol and 6 megawatts of electricity per year from the plasma arc waste disposal facility. The plant will use vegetative, yard, and municipal solid waste. More information on this project can be found at www.ineosbio.com. The project is targeted for completion and start-up in mid-2012. Utilizing a unique combination of gasification and fermentation processes, the facility will produce a synthesis gas that is cooled and cleaned before being fed to naturally occurring bacteria. These patented bacteria convert the synthesis gas into ethanol, which is purified for use as fuel in the transportation market. [14]
A proposed Plasma arc gasifier has been planned for the Metro Vancouver area. However residents of the area have protested. Metro Vancouver is currently conducting an RFP process to determine a long-term solution for waste management. Plasco is not proposing that Metro Vancouver discontinue the RFP process, but rather to establish an interim solution that can quickly address the shortfall in landfill capacity, while also providing a facility that will allow Metro Vancouver to closely scrutinize and evaluate this new technology as part of its long-term decision making process.
Utilizing technology licensed from Europlasma, the plasma arc facility proposed for lands in the vicinity of Wesleyville in Port Hope, Ontario (approximately 45 minutes east of Toronto) will handle 400 short tons (360 t) per day of Municipal Solid Waste (MSW) and Tire Derived Fuel (TDF). Sunbay Energy is currently obtaining the required approvals from Provincial authorities and intends to have the facility operational during the 4th Quarter of 2009.
Navitus Plasma Inc. have proposed the installation of a system named "DEEP" "Dufferin Eco Energy Park" within East Luther Grand Valley located in the County of Dufferin (approximately 45 minutes north of Toronto) and plan to take all municipal garbage for the county to this facility. Residents have provided mixed support and the government has recently reduced the amount it was willing to pay for electricity from 12 cents per kilowatt hour to 8 cents. Construction is currently awaiting various environmental assessments, and government approvals but plans to be in operation by 2015. [15]
The city of Tallahassee, Florida has signed the largest plasma arc waste to energy contract (35 MW) to date with Green Power Systems to process 1,000 short tons (910 t) daily from the city and several surrounding counties. Completion of the project is scheduled for October 2010.
EnviroParks Limited[16] plan (31/9/07) a consortium to build an Organic Park in Tower Colliery at Hirwaun, South Wales. This includes a plasma gasification plant combined with advanced anaerobic digestion to divert municipal solid waste from the landfill. Enviroparks are currently collaborating with partner Europlasma of Bordeaux to provide the plasma gasification unit to the park.
As much as £60 million is being put into the project by EnviroParks Ltd and its partners, to establish organic waste and mixed waste treatment facilities next to the Tower Colliery at Hirwaun. The Hirwaun site itself is large enough for the processing of over 250,000 metric tons (280,000 short tons) of non-hazardous waste a year. Initially, though, an anaerobic digestion plant will be designed to handle 50,000 metric tons (55,000 short tons) of organic wastes a year.
PR Power Co. plans to open a plant south of Atlanta, near Jackson, Georgia, that will use a "plasma torch" to vaporize tires down to their natural elements — mainly hydrocarbons and scrap steel. The gases will be converted to electricity for sale to electric utilities and the scrap steel will be sold at an estimated $50 a ton.[17]
Plasco is preparing to start construction on a commercial-scale facility in Red Deer, Alberta in the Summer of 2009.[18] This facility, the company's first commercial plant, is expected to be completed by the end of 2010.[19]
SMS Infrastructures Limited (SMSIL), Central India’s largest civil engineering and infrastructure development company, constructed 68 tonne-per-day hazardous waste-to-energy plants, located in Pune, India, that will use Westinghouse Plasma Corporation’s (WPC) plasma technology and reactor vessel design. Each plant will provide comprehensive disposal services for a wide variety of hazardous waste, and will produce up to 1.6 MW (net) of electricity
Plasco announced in April 2010 that it is planning a joint venture with Beijing Environmental Sanitation Engineering Group Co. to construct a 200 tonne per day demonstration facility in Beijing. If successful, it is intended to construct a larger 1,000 tonne per day facility to help dispose of the city's 18,000 tonnes of municipal waste generated per day.[20]
In 2008, Northrop Grumman Newport News (now known as Huntington Ingalls - Newport News Shipbuilding), issued a contract to PyroGenesis Canada Inc. for the supply of a Plasma Arc Waste Destruction System (PAWDS) to be installed on board the Navy’s next generation aircraft carrier. This compact system will treat all combustible solid waste generated onboard the ship. After having completed factory acceptance testing in Montreal, the system is scheduled to be installed onboard the new ship in late 2011. Designs of PAWDS for commercial cruise lines also include the possibility of energy recovery and sludge oil processing.[21]
No municipal-scale waste disposal plasma arc facilities have as yet been constructed, so considerable technological and budgetary uncertainties remain.
Numerous municipal plasma arc gas plants (see above) are currently in development, including one for the city of Los Angeles. Practical (limited use of land space for landfills), technological (large-scale use of technology versus small-scale, e.g. plasma arc is currently favored as a means to destroy medical and hazardous waste), logistical (transportation infrastructure requirements) and budgetary considerations can affect the viability of individual projects.
An issue regarding plasma systems that rely on high temperatures for processing is in the life of their liners. The liner is an important aspect of separating the high interior temperatures of the plasma system from the [metal] shell of the plasma container. Liners are highly susceptible to both chlorine attack and to local variabilities in [high] temperatures, both of which would be found with typical municipal waste systems, and are not likely to last more than a year in service. One way to address this concern is by using the method demonstrated at the Trail Road Plant in Ottawa, Canada, which requires lower temperatures and a more robust material (fire brick) for a liner instead of the expensive and fragile metal.
The content and the consistency of the waste has a direct impact on performance of a plasma facility. Pre-sorting and recycling useful material before gasification provides a more consistent waste stream. A waste stream that is high in inorganic (metals and construction waste) materials increase slag production and decrease the more valuable syngas production. Secondly, shredding the waste before entering the main chamber creates an efficient transfer of energy ensuring all materials are broken down.