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Non-Thermal Plasma - Multi-pollutant ControlBackground Coal Combustion EmissionsBurning coal to generate electricity produces a number of pollutant species that are considered harmful to people, animals, and the environment in general [1], [2], [3], [4]. Pollutants of significant concern are oxides of nitrogen and sulphur (NO x and SO 2 , respectively), mercury (Hg), and particulate matter (PM). The harmful effects of these species are well documented, and these emissions are the subject of numerous and ever- stringent legislation s in many parts of the world. Current Pollutant Reduction TechnologiesCurrent technologies such as baghouses, wet scrubbers, and electrostatic precipitators are typically designed to control emissions of a single pollutant species. Controlling multiple pollutants with conventional technologies can require the installation of a suite of different devices. The capital and operating costs of retrofitting or upgrading non-compliant facilities are major concerns for electricity producers and consumers. Non-thermal Plasma Pollutant ControlNon-thermal plasma technology can be used to control multiple pollutants of interest, namely SO 2 , NO x , and Hg. Currently, most of the plasma technology being developed employs wire-cylinder discharge geometry and an ammonia (NH 3 ) reagent introduced into the flue gases. The reduction of SO 2 , NO x , and Hg pollutant species can be over 90%, and the electrical consumption of th e technology can be as high as 3% of the power plant's production capacity [5]. Plasma Corona Radical Shower (PCRS) is a newer technology which employs a different geometric configuration in the reaction chamber, along with better control of the NH 3 injection. In this process, ammonia is fed into the reaction chamber through hollow electrodes, resulting in higher NH 3 concentrations within the plasma corona.
Initial testing of PCRS shows promise of improved plasma performance with substantially reduced electricity consumption (<1% of production) [5]. Our GoalCETC aims to develop the lab-scale PCRS technology into robust and economically optimized industrial solutions for controlling SO 2 , NO x , and Hg emissions. Our focus is to obtain the most relevant data possible to address practical concerns of industrial users. We have built a fully-customized test facility to simulate industrial flue conditions as realistically as possible at an economical scale (coal combustion producing flue gas at a rate of 53 m 3 /h) . Our tests will investigate the effects of various parameters on the efficiency of PCRS technology, including:
CETC-Ottawa Non-Thermal Plasma FacilityThe facility includes the following components:
Three truly unique pieces of technology lie at the core of this system: the custom-designed pulverized coal furnace , the PCRS reactor, and the high-efficiency ESP.
Above: plasma corona being generated during PCRS commissioning (image rotated 90° clockwise). Below: the PCRS facility in building 7, with the coal furnace in foreground.
The furnace allows for testing industrial fuels at a laboratory scale, thereby providing operational andexperimental flexibility. The size of the facility makes it financially amenable to further customization, and testing modified components or even entirely different devices, either separately from or in tandem with the existing configurations. The plasma generating zone is designed to be configurable such that any number of electrodes can be positioned in a variety of ways with regard to the inlet, outlet, ground plate, or other electrodes. Downstream of the PCRS is a custom-designed, high-efficiency electrostatic precipitator (ESP) which will be capable of very high particulate removal rates for capturing solid products of ammonium solts formed from pollutants and ammoia under plasma action. The ESP also has configurable electrode geometry.
Scope of WorkThe PCRS test facility will be primarily used in the investigation of the effects of variations in the following parameters:
In the course of this project we have developed more efficient electrodes with star-shaped discharge elements. Preliminary result showed that over 98% of SO 2 could be removed from the flue gas. Non-thermal Plasma ConsortiumCETC is forming a consortium with industry, government, and academic partners to ensure that the resultant technology develops in a way that is optimized for industrial applications and maximum environmental benefit. Consortium members will have input into the testing process and design in order to address individual application issues. In this way, the consortium will enable members to share and benefit from considerable expertise across sectors. The consortium members will also have unlimited license to use the technology for their own purposes. References[1] EPA. 2005. Air trends: sulfur dioxide. [2] EPA. 2005. Air trends: nitrogen dioxide. [3] EPA. 1997. Mercury study report to congress. Volume ii: an inventory of anthropogenic mercury emissions in the United States. [4] EPA. 1997. Mercury study report to congress. Volume v: health effects of mercury and mercury compounds. [5] Chang, J. & Kim, S.J. 1998. SUENTP code simulations of scaleup and economic evaluation of non-thermal plasma technology for exhaust gas emission control of coal fired power plants. Proceedings ICESP VII, Sep. 25-28, 1998, Kyongju , Korea.
For further information, please contact: CANMET Energy Technology Centre
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