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Guideline on plasma technologies for environmental protection · Plasma technologies for...
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Part- financed by the Euro- pean Union (European Re- gional Development Fund) 1 plasma for environment protecon Guideline on plasma technologies for environmental protection What is plasma? Plasma is the primary state of maer of the universe (99,9 %). Furthermore, it is called the fourth state of maer be- cause of its differences from solid, liquid and gas phase properes. Plasma is an ionised gas which is a quasi-neutral mixture of free posive ions and electrons. The basic classificaon of plasmas in technological applicaons is: Low-temperature (non-thermal) plasma, also called “cold” or electrical discharge plasma; • High-temperature, colloquially called “hot” plasma. • Usually, the low-temperature plasma is ionised gas with a high content of neutral parcles. This non-thermal plasma is used in various praccal applicaons such as coangs, for surface treatment, metalworkings and especially for environmental protecon. Plasma generaon For technical purposes, plasma is produced “arficially” by means of a wide range of equipment that is especially designed for this aim. Non-thermal plasmas in gas streams under atmospheric pressure can be generated in a few ways: By injecng a high energy electron beam (EBFGT - electron beam flue gas treatment); • By applying an electric field to a neutral gas (various types of gas discharges); • By using microwaves. • The plasma generaon process by using an electron beam is based on an interacon of high energy electrons with the gas. Energies of such electrons usually reach from a few hundred keV (kiloelectron volt) to even few MeV (megaelectron volt). The fast electrons slow down through collisions with parcles of the flue gas and the plasma is formed in the whole volume of this treated gas. Accelerators, they are the most important devices in the whole technology, are responsible for electron beam gen- eraon. Electrons from a cathode are accelerated in acceleraon tubes unl they have the required energy. Then they are emied to the gas through a scanning device, where the beam is deflected by electromagnec coils. The efficiency of energy conversion in these apparatus is 70% and greater. Gas discharge origin cold plasma is usually obtained in closed reactors with electrodes inside. Different types of
Transcript of Guideline on plasma technologies for environmental protection · Plasma technologies for...
Part- financed by the Euro-pean Union (European Re-gional Development Fund)
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plasma for environment protection
Guideline on plasma technologies for environmental protection
What is plasma?
Plasma is the primary state of matter of the universe (99,9 %). Furthermore, it is called the fourth state of matter be-cause of its differences from solid, liquid and gas phase properties. Plasma is an ionised gas which is a quasi-neutral mixture of free positive ions and electrons. The basic classification of plasmas in technological applications is:
Low-temperature (non-thermal) plasma, also called “cold” or electrical discharge plasma;• High-temperature, colloquially called “hot” plasma. •
Usually, the low-temperature plasma is ionised gas with a high content of neutral particles. This non-thermal plasma is used in various practical applications such as coatings, for surface treatment, metalworkings and especially for environmental protection.
Plasma generation
For technical purposes, plasma is produced “artificially” by means of a wide range of equipment that is especially designed for this aim. Non-thermal plasmas in gas streams under atmospheric pressure can be generated in a few ways:
By injecting a high energy electron beam (EBFGT - electron beam flue gas treatment);• By applying an electric field to a neutral gas (various types of gas discharges);• By using microwaves. •
The plasma generation process by using an electron beam is based on an interaction of high energy electrons with the gas. Energies of such electrons usually reach from a few hundred keV (kiloelectron volt) to even few MeV (megaelectron volt). The fast electrons slow down through collisions with particles of the flue gas and the plasma is formed in the whole volume of this treated gas.
Accelerators, they are the most important devices in the whole technology, are responsible for electron beam gen-eration. Electrons from a cathode are accelerated in acceleration tubes until they have the required energy. Then they are emitted to the gas through a scanning device, where the beam is deflected by electromagnetic coils. The efficiency of energy conversion in these apparatus is 70% and greater.
Gas discharge origin cold plasma is usually obtained in closed reactors with electrodes inside. Different types of
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discharge (corona discharge, glow discharge, arc discharge) can be obtained, depending on the applied voltage.
Dielectric Barrier Discharge (DBD) is one of the most commonly used cold plasma technologies which is often carried out at atmospheric pressure. Alternating feeding voltage or pulse discharge and the presence of a dielectric barrier are necessary to occur this type of discharge. In a barrier discharge reactor, the dielectric is placed on a high-voltage electrode (rarely on both electrodes) or between them, thus creating one or more of the discharge gaps. Gas ionisation occurs in the whole volume of the reactor by presence of highly ionised channels filled with electrons and positive ions. Geometry of the electrodes of the reactor, the type of dielectric that is used in the system and the way of energy supply determine the parameters of the produced plasma and the possibilities of reactor applications.
A characteristic feature of plasma generating by using microwaves is its high frequency of the electric field (300 MHz - 10 GHz). It is directly associated with the wavelength which is comparable to the dimensions of the reactor. Microwave discharge, in contrast to other types of discharges, does not require any electrodes for plasma excita-tion in the discharge gap. Microwave plasma excitation in gas occurs as a result of absorption of microwave energy, which is concentrated and local in a specific volume of gas. Microwave magnetrons or klystrons are energy sources of the microwave radiation.
Applications of plasma in the field of environmental protection
Non-thermal plasma is used in the process of sterilisation and disinfection due to its numerous advantages (the most important one is the lack of side effects and waste products, relative environment friendly, ability of conduct plasma-chemical treatment at an atmospheric pressure and ambient temperatures).
Among the environmental applications, the most popular in practice is the drinking water treatment technology. Chlorine is environmentally harmful ,so it is replaced by ozone produced in barrier discharges (e.g. swimming pool water ozonation).
Other environmental applications of plasma (including indirect methods with use of ozone) are:Sterilisation of air, water, soil, surface etc.;• Removal of sulphur and nitrogen oxides (SO• x and NOx) as well as volatile organic compounds (VOCs) from ex-haust gases from the combustion of fossil fuels, waste incineration etc.;Removal of VOCs that generated in the process of painting, varnishing and other chemical processes;• Odours removal;• Water treatment and other…•
Filamented discharge plasma
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plasma for environment protection
Advantages of plasma technologies
Plasma technologies are among the most promising technologies for environmental protection. Application of them allow to avoid many problems connected with conventional technologies as generation of problematic wastes. Moreover the plasma technologies are easy to control and optimi, that makes them user friendly.
Advantages of plasma technologies are clearly visible in flue gas treatment processes. During many technological processes associated with combustion, various kinds of pollution are emitted into the atmosphere. The most im-portant among the pollutants are oxides of sulphur and nitrogen, especially during the combustion of fossil fuels in power generation and metallurgy. Remove of these impurities by conventional methods require the use of compli-cated installations combining various methods of removing impurities. All these technologies are complex chemical processes associated with a formation of waste (gypsum, wastewater, spent catalyst) as well as costly (the cost of raw materials, energy, service and location). Plasma technologies allows for the simultaneously removal of SO2, NOx in the same process, that can reduce investment and operating costs at a comparable level of exhaust gas purifica-tion. Possibility of agricultural use of by-product may solve the problem of waste. Others contaminants are also removed such as volatile organic compounds, dioxins, acid pollutants (HCl, HF, SO3) and others (it is an additional advantage).
Case studies
Plasma technologies for environmental protection are not only in research stage. Beneath, two examples of success-ful practical implementations of plasma technologies in environmental protection has been presented.
1. Aquanet, Poznan, Poland
In the waste water treatment plant (WWTP) of Aquanet in Poznan (ul. Serbska 3) plasma were applied for the odour control. To prove the ability of plasma for odour removal, the measurements of off-gas composition before and after treatment were performed. At the same time as the samples for the olfactometry were taken.
Three different types of diagnostic methods were used for the detection of the appearing species. For a general approach, the detection of the main species, the method of FTIR spectroscopy was used. For the detection of trace gases gas chromatography coupled with mass spectroscopy (GC/MS) was used. Therefore, adsorption tubes were rinsed with the exhaust gas before and after plasma section and analysed by GC/MS afterwards. The third method was the electrochemical sensoring of H2S by a handheld device.
The main species in the off gas are, next to not detectable N2 and O2, CO2 and H2O. The main trace components oc-curring in waste water treatment plant off-gases are sulphur containing compounds as dimethyl sulfide, dimethyl disulfide, carbon disulfide and toluene. Among low concentrated sulphur containing gases there shall be mentioned disulfide methyl 2-propenyl, dimethyl tetra-sulfide and methanthiol. H2S is present only in traces (only few ppm
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were observed), however it is responsible for most of the odour.
Plasma-catalytic process removes 66 % to 100 % of H2S, which is probably the main odour. CH4 emission is reduced as well but not completely. A by-product of the H2S removal is SO2 in small concentrations. Beside that, all sulphur containing compounds with the exception of CS2, decrease in concentration after plasma treatment. It can be con-cluded that the plasma-based treatment and the catalyst in use are a promising method for the odour reduction at the water plant.
2. Pomorzany Power Plant, Szczecin, Poland
The first electron beam flue gas treatment installation for simultaneous SO2 and NOx removal has been constructed at the Electro Power Station (EPS) Pomorzany in Szczecin, Poland. The plasma here is generated by four electron accelerators of 1.04 MW total beam power, that makes it also the biggest radiation facility in the world. The plant treats the flue gases which are emitted from two Benson boilers of 100 MWth each, with a maximum flow rate of 270 000 Nm3/h. The installation has been constructed in 2001 and is now in routine operation. The removal effi-ciencies reach 70% for NOx and 95% for SO2. The technol-ogy is wasteless - the only byproduct (ammonium salts mixture) is sold as a valuable component for NPK fertilisers.
EBFGT plant Pomorzany. Gas cooling tower.
The scheme of an industrial plant at EPS Pomorzany.
The main advantages of the technology are:Simultaneous removal of SO• 2, NOx in one step, moreover the process may be applied for VOC decomposition and other pollutants removal;High effectiveness of the process;• Dry process, lack of problematic waste waters;• No waste generation through the agricultural use of by-products;• Simplicity of the construction and operation of the facility, that makes • easy retrofitting possible.
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Links
Here you will find information about plasma technologies for environmental protection:www.plastep.e• u: The site of the project “Dissemination and fostering of plasma based technological innovation for environment protection in the Baltic Sea region (PlasTEP)” gives information about various plasma technolo-gies and their applications in the air and water protection.www.ichtj.waw.p• l: Website of the Institute of Nuclear Chemistry and Technology. The institute is involved in ap-plications of electron beam in industry, medicine and environmental protection.www.inp-greifswald.d• e: Site of the Leibniz Institute for Plasma Science and Technology, one of the leading sci-entific centres of plasma research.
Contacts Project PlasTEP
West Pomeranian University of TechnologySikorskiego 37 | 70-313 Szczecin | PolandProject Partner: Marcin HolubFon: +48 914 494 805Fax: +48 914 494 098E-mail: [email protected]
Institute of Nuclear Chemistry and TechnologyDorodna 16 | 03-195 Warszawa | PolandProject Partner: Prof. Andrzej G. ChmielewskiFon: +48 225 041 205Fax: +48 228 111 532E-mail: [email protected]
This picture shows the reaction chamber that is applied in the Pomor-zany EBFGT installation.
The EBFGT technology is one of the most promising multipollution control systems. New implementations of this technology in industry are under development.
Technology Centre Vorpommern Brandteichstr.20 | 17489 Greifswald | GermanyProject Manager: Alexander SchwockFon: +49 3834 550-102Fax: +49 3834 550-110E-mail: [email protected]
BalticNet-PlasmaTec Brandteichstr.20 | 17489 Greifswald | GermanyNetwork Manager: Alexander SchwockFon: +49 3834 550-102www.balticnet-plasmatec.orgE-mail: [email protected]
