Pierre Proulx

Plasma-particle interaction effects in induction plasma modeling under dense loading conditions

Abstract The injection of powders into an inductively coupled plasma is modeled. Attention is given to the plasma-particle interaction and its effect on plasma fields. It is demonstrated that for most applications, such interactions must be considered in any model. For the calculations, copper and alumina powders are used. The plasma gas is argon at atmospheric pressure.

A two‐temperature model of the inductively coupled rf plasma

A two‐temperature model is proposed for the computation of the two‐dimensional flow and temperature fields in a rf inductively coupled plasma torch. The model is applicable to monatomic gases. The results obtained for an argon plasma indicate that, while at atmospheric conditions, deviations from local thermodynamic equilibrium (LTE) are relatively small, the situation is different under reduced pressure conditions, where substantial deviations from LTE have been noted, particularly in the energy addition region.

Heating of powders in an r.f. inductively coupled plasma under dense loading conditions

A study was carried out of the heating of powders in an r.f. inductively coupled plasma under dense loading conditions. The results obtained using a mathematical model taking into account plasma-particle interaction effects reveal an important cooling of the plasma caused by the presence of the particles. This, in turn, gave rise to a corresponding drop of the efficiency of the melting of the particles in the plasma. The effect is shown to depend strongly on the thermodynamic properties of the material of the powder.

Parametric study of the flow and temperature fields in an inductively coupled r. f. plasma torch

A theoretical investigation of the effect of different parameters on the flow and the temperature fields in a radiofrequency inductively coupled plasma is carried out. The parameters studied are: central injection gas flow rate, total gas flow rate, input power, and the type of plasma gas. The results obtained for argon and nitrogen plasmas at atmospheric pressure indicate that the flow and the temperature fields in the coil region, as well as the heat flux to the wall of the plasma confinement tube, are considerably altered by the changes in the torch operating conditions.

Mathematical modeling of a free‐burning arc in the presence of metal vapor

The transfer of energy between the plasma and the iron anode and the evaporation of metal were taken into account in modeling a short free‐burning arc in argon at atmospheric pressure. The presence of metal vapor in the plasma modifies the electrical conductivity and the radiated power and leads to arc cooling in the anode region. In return, the arc cooling modifies the rate of vaporization of the anode and thus the calculated concentration of iron vapor in the arc.

Plasma-refining process to provide solar-grade silicon

Abstract A new purification process has been developed to refine metallurgical silicon using a plasma torch blowing at the surface of the silicon to be purified. An inductive system has been designed to maintain the silicon in a liquid state, control the shape of its free surface and to provide a strong electromagnetic stirring, ensuring a rapid transfer of pollutants from the bulk liquid to its surface. A numerical model is used to control the design of the induction system and to look at its potential evolutions. It is shown that even with a reduced induction power, the stirring is sufficient to provide a very rapid mass transfer in the liquid, compared to the reaction rate at the surface (deduced from experiments). The effect of the power and frequency of the induction power is also discussed, showing that it gives the possibility to control the heating power and the shape of the surface, and even to push the liquid away from any contact with the crucible. The material provided by the refining process operating in such conditions was used to produce solar cells that reached a conversion efficiency of 12.7%

Turbulence phenomena in the radio frequency induction plasma torch

Abstract The mathematical modeling of the flow and temperature fields in an inductively coupled radio frequency (rf) plasma torch is carried out with the objective of elucidating the basic of turbulence phenomena met under such discharge conditions. Temperature and density fluctuations are included in the k–e turbulence model to investigate their effect on the plasma turbulence and energy transfer. Two distinct regions, one almost fully laminar and another significantly turbulent, are shown to coexist in the discharge. The effects of operation parameters on the plasma turbulence are discussed.

Modelling of the reactive synthesis of ultra-fine powders in a thermal plasma reactor

A two-dimensional, chemical kinetics and aerosol growth model is developed for the comprehensive simulation of the reactive synthesis of ultra-fine particles in a thermal plasma reactor. The model solves the velocity and temperature fields that are coupled to the equations describing the electromagnetic induction field. Conservation equations for the plasma species consider the multi-component diffusion and chemical reactions. For the condensable product, an additional term is introduced, due to the phase change. Particle growth occurs via homogeneous nucleation and surface condensation, and an evaporation term is considered for concentrations below saturation. The model is applied to the synthesis of silicon metal powders by the dissociation of . The effect of the input power and that of the radial quenching are investigated by comparison with a simulation base case.

Computer modeling of the emission patterns for a spectrochemical ICP

Abstract A computer model has been developed for the calculation of the two-dimensional emission pattern from a spectrochemical ICP. Assuming local thermodynamic equilibrium (LTE), the flow, temperature and the concentration fields are computed. These are used to estimate the population density of different species present in the discharge, and accordingly the emission pattern for different atomic and ionic lines. Typical results are given for Li, Ca, Ni, Cu and Fe for an ICP torch operated at 500 and 750 W.

A Mathematical Model for Ultrafine Iron Powder Growth in a Thermal Plasma

ABSTRACT A two-dimensional model is developed for the growth of ultrafine metal powders in a thermal plasma reactor. The model accounts for particle formation by nucleation, and growth by condensation and Brownian coagulation. Transport of particles occurs by convection, thermophoresis, and Brownian diffusion. The conservation equations for the moments of the particle size distribution are solved, coupled to the equation for the conservation of metal vapor. Elliptic conservation equations result from the consideration of both axial and radial diffusion of the particles. This allows for simulations in complex, recirculating flows, which are likely to occur for numerous reactor configurations and parameters. A progressive grid refining technique is used to accelerate convergence. The model is applied to the case of a typical thermal plasma reactor for the production of ultrafine iron powders. The fields of the macroscopic properties of the aerosol population and the contribution of the different mechanisms ...