Begell House Inc.
High Temperature Material Processes: An International Quarterly of High-Technology Plasma Processes
HTM
1093-3611
11
2
2007
INFLUENCE OF VOLTAGE FLUCTUATIONS RELATED TO PLASMA TORCH WORKING CONDITIONS ON ZIRCONIA PARTICLE THERMAL TREATMENT
161-174
10.1615/HighTempMatProc.v11.i2.10
E.
Nogues
SPCTS Laboratory, University of Limoges, 123 av A. Thomas, 87060 Limoges Cedex; and BOC Edwards, 224 bd J. Kennedy, 91105 Corbeil-Essonnes Cedex, France
Michel
Vardelle
LMCTS-URA 320, University of Limoges, 123 Avenue Albert Thomas -87060 Limoges Cedex - France
Pierre
Fauchais
Laboratoire Sciences des Procedes Ceramiques et de Traitements de Surface UMR CNRS 6638 University of Limoges 123 avenue Albert Thomas, 87060 LIMOGES - France
P.
Granger
BOC Edwards, 224 bd J. Kennedy, 91105 Corbeil-Essonnes Cedex, France
The microstructure of plasma sprayed coatings is strongly linked to particle trajectories depending among other parameters on arc root fluctuations. The latters depend on the torch anode-nozzle shape and internal diameter, the plasma forming gas composition and flow rate, and the anode erosion.
Experiments were performed with yttria partially stabilized zirconia (8 wt% yttria) particles with a size distribution between 5 to 25 μm and either a PTF4 or a 3MB GE Sulzer-Metco torch. The PTF4 torch was fed with an Ar-Mb mixture and an arc current of 600 A, while the 3MB torch was fed with N2-H2 mixture with an arc current of 500 A. Particle mean temperatures and mean velocities were measured to evaluate the influence of voltage fluctuations on the treatment.
This study shows that the torch working parameters, except the arc current, have nearly the same effects on the arc voltage fluctuations for the both torches. The 3MB torch voltage fluctuations are more important than those for a PTF4 torch, but they are less affected by the variations of spray parameters. Furthermore, the fluctuations of particle temperatures and velocities versus the voltage fluctuations are not the same.
OSCILLATIONS IN DC PLASMA JET AT REDUCED PRESSURES
175-180
10.1615/HighTempMatProc.v11.i2.20
Vladimir
Kopecky
Thermal Plasma Department, Institute of Plasma Physics AS CR, Za Slovankou 3, 18200, Praha 8, Czech Republic
Milan
Hrabovsky
Institute of Plasma Physics, Academy of Sciences Za Slovankou 3, 182 00, Prague
The oscillations of dc plasma jet generated by the hybrid water/argon plasma torch with external anode were studied at different ambient pressures. Fluctuations of plasma radiation from jet were recorded using system of photo-diodes with high frequency response. The frequency and the phase velocity of plasma flow oscillations were determined for various arc currents and argon flows and various ambient pressures. Two main types of oscillations were observed. The first type of perturbations is connected with a movement of an anode attachment and the second type of oscillations arises from plasma boundary instability. Frequencies of this two types oscillations approach each other when the pressure is reduced and the expansion zone was formed. In this case frequencies of these oscillations were equal to 200−350 kHz and their phase velocities were close to thousand meters per second.
INTERACTION OF HOT GAS MIXTURE FREE JET WITH SURROUNDING AIR
181-190
10.1615/HighTempMatProc.v11.i2.30
J.
Gregor
Faculty of Electrical Engineering and Communication, Brno University of Technology, Purkynova 118, 61200 Brno, Czech Republic
I.
Jakubova
Faculty of Electrical Engineering and Communication, Brno University of Technology, Purkynova 118, 61200 Brno, Czech Republic
T.
Mendl
Faculty of Electrical Engineering and Communication, Brno University of Technology, Purkynova 118, 61200 Brno, Czech Republic
J.
Senk
Faculty of Electrical Engineering and Communication, Brno University of Technology, Purkynova 118, 61200 Brno, Czech Republic
M.
Konrad
TECOSIM Technische Simulation Gmbh Robert-Bosch-Str. 10, D-50769 Collogne, Germany; and Institute of Plasma Physics, Za Slovankou 3, 182 00, Praha 8, Czech Republic
The paper analyses an interaction of the hot gas mixture free jet generated by a hybrid water-argon arc heater with the surrounding air of atmospheric pressure. An entrainment of air into the jet is investigated as diffusion of original components of the jet into the ambient air. The calculation is based on the continuity and momentum equations of the plasma jet together with continuity equations describing diffusion of individual components of the hot gas mixture. The input data are arc heater's efficiency, temperature and velocity profiles measured along the jet and thermodynamic and transport properties of the gas mixture. First, the ratio of concentrations of water vapour and argon in the mixture, the flow rate and the momentum of hot mixture at the arc heater's output are determined. The model enables to calculate the distribution of mass fractions of individual species of the hot gas mixture and the radial component of velocity. The character of flowing can be estimated, and the axial dependencies of the velocity half-width, the turbulence coefficient, and the rate of laminar and turbulent viscosity coefficient can be obtained.
HEAT TRANSFER AND NON-EQUILIBRIUM PHASE CHANGE OF LAMELLAE UNDER PLASMA SPRAY CONDITIONS
191-204
10.1615/HighTempMatProc.v11.i2.40
Y.
Lahmar-Mebdoua
Centre de Développement des Technologies Avancées, Algiers, Algeria
Armelle
Vardelle
ENSIL, ESTER Technopole, 87068 Limoges - France
Pierre
Fauchais
Laboratoire Sciences des Procedes Ceramiques et de Traitements de Surface UMR CNRS 6638 University of Limoges 123 avenue Albert Thomas, 87060 LIMOGES - France
Dominique
Gobin
University Paris-Saclay
The properties of a plasma-sprayed coating are, to a great extent, controlled by the cooling and solidification of the droplets impinging on the part to be covered. Both processes condition the cooling rate, crystal growth and formation of the crystalline phases. This paper presents a one-dimensional heat transfer model that predicts the cooling and solidification of a liquid lamella deposited on a flat surface. It is based on the solution of the time-dependent heat equation in the splat and the substrate coupled by an interface thermal resistance and takes into account the melt undercooling and crystal nucleation. The calculations are performed for alumina lamellae on steel and alumina substrates.
PLASMA FURNACES FOR TOXIC WASTE PROCESSING
205-218
10.1615/HighTempMatProc.v11.i2.50
A. L.
Mosse
Plasma Physics and Chemistry Laboratory, A. V. Luikov Heat and Mass Transfer Institute, National Academy of Sciences of Belarus, P.Brovka str. 15, 220072, Minsk, Belarus
A. V.
Gorbunov
Plasma Physics and Chemistry Laboratory, A. V. Luikov Heat and Mass Transfer Institute, National Academy of Sciences of Belarus, Minsk, Belarus
Vasili
Sauchyn
A.V. Luikov Heat and Mass Transfer Institute, National Academy of Sciences
of Belarus, 15 P. Brovka Str., Minsk, 220072, Belarus
The increasing amount of toxic waste is a serious ecological hazard. Composition of waste is various. In most cases it contains toxic substances, contamination and viruses that need special utilization.
One of the most promising ways of solving this problem is plasma treatment of toxic materials. This process is characterized by a significant reduction of waste. Any complex organic and inorganic compounds can be intensively destructed in thermal plasmas thanks to high temperatures. Melting of ashes allows to obtain thermal, chemical and deactivated forms of glasses or ceramics. For vitrification of wastes (ashes) thermal plasma is generated by an electric-arc plasma torch with bulk temperatures up to 6000 K.
This paper presents plasma furnaces that have been designed for waste treatment: a plasma shaft furnace with a waste processing capacity of 200 kg/h for centralized waste treatment facilities and small chamber furnaces with a 50 kg/h capacity that can be placed in any hospitals, clinics or scientific laboratories. In addition, a plasma “combination” furnace that is designed for Nuclear Power Station and toxic radioactive waste treatment is also presented. A design procedure based on thermal analysis has been developed to achieve the best performance of furnace operation.
ARC PLASMA DEVICES FOR TREATMENT OF DIFFERENT WASTES
219-230
10.1615/HighTempMatProc.v11.i2.60
A. S.
An'shakov
Kutateladze Institute of Thermophysics SB RAS, Russia
M. R.
Predtechensky
International Scientific Center on Thermal Physics and Energetics, Russia
V. S.
Cherednichenko
Novosibirsk Technical State University The Institute of Thermophysics SB RAS - 630090 Novosibirsk - Russia
O. M.
Tukhto
International Scientific Center on Thermal Physics and Energetics, Russia
E.K.
Urbakh
Kutateladze Institute of Thermophysics SB RAS, Russia
A. S.
Zhgun
Novosibirsk State Technical University, Lavrentiev ave. 1, Novosibirsk, 630090, Russia
V. A.
Faleev
Kutateladze Institute of Thermophysics SB RAS, Russia
A. E.
Urbakh
Kutateladze Institute of Thermophysics SB RAS, Russia
Investigation results on development of the arc plasma generators and connected plasma devices (electric furnaces, reactors) are presented. Development possibilities for plasma-chemical plasma torches purposed for technological treatment of domestic and industrial wastes are considered.
BIOFUEL AND HYDROGEN PRODUCTION FROM BIOMASS GASIFICATION BY USE OF THERMAL PLASMA
231-244
10.1615/HighTempMatProc.v11.i2.70
M.
Brothier
CEA, DEN, DTN, 13108, St Paul lès Durance Cedex
P.
Gramondi
CEA Cadarache / DTN - 13108 St Paul-les-Durance- France
C.
Poletiko
CEA Cadarache / DTN - 13108 St Paul-les-Durance- France
U.
Michon
EUROPLASMA - 6 rue Lajaunie, 33 100 Bordeaux - France
M.
Labrot
EUROPLASMA - 6 rue Lajaunie, 33 100 Bordeaux - France
A.
Hacala
EUROPLASMA - 6 rue Lajaunie, 33 100 Bordeaux - France
The use of renewable energy sources is becoming necessary to reduce greenhouse effect gases emissions and economic dependence on fossil fuels. Although the biomass is largely widespread in Europe, quantities are still limited compared to the energy demand. The main objective of the presented studies is to develop a specific industrial process able to reach a high yield of conversion in order to improve, as well as possible, the valorisation of available biomass stock. This process is based on a gasification whose the necessary level of temperature is ensured by electric power since the conversion is globally endothermic. The required temperature level is reached thanks to the addition of external electric power, since the conversion is globally endothermic. Biomass is converted into syngas at temperature levels close to 1400°C, to reach gas characteristics compatible with a downstream Fischer-Tropsch synthesis. Technologic tools able to heat an industrial gasifier with an external source are electric arc or plasma torch. With regard to the gases conversion/treatment, non-transferred plasma torches seem a mature technology with several industrial applications even if an optimisation is necessary to adapt the torch to a special plasmagen gas (that means gas which are ionised by the arc). The main technological objectives of the collaboration between CEA and EUROPLASMA are to adapt existing technologies to a new application, and more precisely to put together the plasma torch system and the high temperature reactor in an optimised way. The present paper deals with the first part of the program on going (ie. the theoretical approach) and presents first results.
CHLOROFORM DESTRUCTION BY INDUCTIVE PLASMA PROCESS
245-256
10.1615/HighTempMatProc.v11.i2.80
B.
Bournonville
Commissariat à l'Energie Atomique, CEA Le Ripault BP 16,37 260 Monts; SIMAP Laboratory, BP 75, 38402 Saint Martin d'Heres
Erick
Meillot
CEA/DAM Le Ripault, BP 16 - 37260 Monts - France
Waste: all industrial productions generate wastes which must be eliminated unless degrading the environment. In order to reduce the waste volumes, CEA (the French Atomic Energy Agency) has developed and patented a new process based upon the use of inductive plasma torch. The process is specialized in degradation of liquid wastes, pure or in mixture, such as organic or organic-halogen one. The goal of this development was, to achieve a complete destruction of products but also to control the atomic recombination in order to reject only non-toxic off-gases. Demonstration of the relevance is presented here by chloroform destruction capability. After presentation of the process, experiments with chloroform are presented The global results are discussed showing the good destruction efficiency and correct off gases composition: the wastes have been completely destroyed, only CO2 and H2O have been formed without any toxic compound or soot formation while the chlorine is trapped by soda and transforms in mineral salt. The final aim of this study is to develop a clean process for treatment of radioactive organic halogen compounds. A small scale reactor is being studied to prove the capability of the process for radioactive organic halogen liquid waste destruction.
2D MODELING OF LOW PRESSURE AIR PLASMA REACTOR
257-267
10.1615/HighTempMatProc.v11.i2.90
C.
Guyon
Laboratoire de Génie des Procédés Plasmas et Traitement de Surfaces, Universite Pierre & Marie Curie, 11 rue Pierre et Marie Curie, 75231 Paris Cedex, France
P.
Miquel
Université Pierre et Marie Curie-Paris6, ENSCP, Laboratoire de Génie des Precédés Plasmas et Traitement de Surfaces, 11 rue Pierre et Marie Curie, 75231 Paris Cedex, France
S.
Cavadias
Laboratoire Genie Precedes Plasmas - ENSCP 11, rue Pierre et Marie Curie - 75005 Paris- France
Jacques
Amouroux
Laboratoire de Genie des Precedes Plasmas Universite P. et M. Curie, ENSCP 11 rue P. et M. Curie 75005 Paris France
To study the heat and mass transfer phenomena of atomic oxygen at the solid/gas interface of thermal protection system, we propose to model a low pressure plasma reactor and to qualify by a simulation the recombination and the energy transfer by accommodation of oxygen atoms to a target surface at stagnation point configuration. The flow is described by a system of conservation (momentum, mass and energy) equations and Maxwell-Gauss equation solved by using a Computational Fluid Dynamics code (CFD-ACE®). Model parameters are issued from experimental parameters (reactor volume and geometry, flow rate and composition...). The simulation of plasma phase was performed to compare two kinetic models giving the evolution of the main species (e-, ions, radicals, atoms...) occurring in the plasma. Two surface reactions have been added to these gas phase models. We have obtained the field velocity, temperature and the fluxes of atomic and molecular species (oxygen and nitrogen) in the reactor under similar conditions to experiments. The originality of this work is the capability to characterize the electric field of the plasma discharge along the reactor.
Energy interchange channels analysis and parameters of RF plasma torch calculations
269-282
10.1615/HighTempMatProc.v11.i2.100
S.
Nguen-Kuok
Department of Physics of Moscow Power Engineering Institute (Technical University), Krasnokazarmennaya St. 14, Moscow 111250, Russia
Jacques
Amouroux
Laboratoire de Genie des Precedes Plasmas Universite P. et M. Curie, ENSCP 11 rue P. et M. Curie 75005 Paris France
The presented paper describes continued research of non-equilibrium plasma in RF plasma torch based on the two-temperature model.
The research resulted in determining complete description of energy interchange in RF plasma, including: Fields of temperatures of electrons and heavy particles; Field of gas flow; Field of power of Joule heating σE2; Field of plasma radiation power Ur; Field of power of atom-ions heating by electrons in elastic impacts; Field of power of ionization and recombination (triple impact radiation); Field of power of electron gas heating; The current flow zone and electromagnetic field of RF plasma torch.
3-D MODELING OF ICP TORCHES
283-296
10.1615/HighTempMatProc.v11.i2.110
Vittorio
Colombo
Dipartimento di Ingegneria delle Costruzioni Meccaniche, Nucleari, Aeronautiche e di Metallurgia (D.I.E.M.) and C.I.R.A.M., Università degli Studi di Bologna, Via Saragozza 8, 40123 Bologna, Italy
Emanuele
Ghedini
Università degli Studi di Bologna, Dipartimento di Ingegneria delle Costruzioni Meccaniche, Nucleari, Aeronautiche e di Metallurgia (D.I.E.M.) and C.I.R.A.M., Via Saragozza 8, 40123 Bologna
A three-dimensional model for the simulation of inductively coupled plasma torches (ICPTs) working at atmospheric pressure has been developed, using customized CFD commercial code FLUENT© . The helicoidal coil is taken into account in its actual 3-D shape, showing its effects on the plasma discharge for various geometric, electric and operating conditions. The electromagnetic equations are solved in their vector potential form, while the steady flow and energy equations are solved for optically thin plasmas under the assumptions of LTE and laminar flow; some of the results that will be presented have been obtained by means of an improved turbulent version of the 3-D model. Simulations are performed over a network cluster of double processor calculators in order to use the full capabilities of the 3-D modelling to describe the gas injection section of an industrial TEKNA PL-35 plasma torch without geometry simplifications, in order to perform a more realistic simulation of the inlet region of the discharge. In order to evaluate the importance of various 3-D effects on calculated plasma temperature and flow fields, our new results have been tested against the ones obtainable from 2-D models and from improved 2-D model that includes 3-D coil effects. Three-dimensional results concerning different operating conditions are presented, together with simulations of the trajectory and heating history of powders injected in the torch through a carrier gas.
EFFECTS OF PLASMA PARAMETERS ON PASSIVATION OF POLYCRYSTALLINE SILICON IN INDUCTIVE LOW PRESSURE HYDROGEN PLASMA
297-308
10.1615/HighTempMatProc.v11.i2.120
M.
Nikravech
Laboratoire de Genie des Precedes Plasmas et Traitement de Surfaces, Universite P. et M. Curie, Ecole Nationale Superieure de Chimie de Paris, 11 rue Pierre et Marie Curie 75005 Paris, France
S.
Darwiche
Laboratoire de Genie des Procedes Plasmas et Traitement de Surface - Université Pierre et Mane Curie- ENSCP 11-13, rue Pierre et Marie Curie 75231 Paris Cedex 05 France
S.
Awamat
Laboratoire de Génie des Procédés Plasmas et Traitement de Surface − Université Pierre et Marie Curie − Paris 6 - ENSCP, 11, rue Pierre et Marie Curie, 75231 Paris Cedex 05, France
Daniel
Morvan
Laboratoire de Genie des Precedes Plasmas Universite P. et M. Curie, ENSCP 11 rue P. et M. Curie 75005 Paris France
Jacques
Amouroux
Laboratoire de Genie des Precedes Plasmas Universite P. et M. Curie, ENSCP 11 rue P. et M. Curie 75005 Paris France
D.
Ballutaud
Laboratoire de Physique des Solides et de Cristallogenese, CNRS, 1 place Aristide Briand, F-92195 Meudon CEDEX, France
Passivation of crystallographic defects by hydrogen is known to improve the transport properties and to enhance the photovoltaic yield of polycrystalline silicone (poly Si). However, it has been demonstrated that the efficiency of hydrogenation depends on the process used. The treatment of poly Si was performed in an inductive low pressure hydrogen plasma reactor. The aim of this work is to elucidate the relation between the plasma characteristics and the efficiency of hydrogen passivation on a poly Si surface. Optical emission spectroscopy permitted to determine the main excited states of monatomic hydrogen and molecular hydrogen in the plasma. The excitation temperature measured by Boltzmann's method ranged between 4500 and 8000K depending on the plasma gas composition, pressure and applied power. The effects of these parameters on the efficiency of hydrogenation were studied by SMS, EBIC, and hydrogen effusion.