Martin Désilets

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.

Modeling of multicomponent diffusion in high temperature flows

Abstract Three methods for computing diffusive mass transfer in non-reactive high temperature flows are compared. Results show that the widely used effective binary approximation may lead to large errors (up to 70%) in the evaluation of the mass fluxes, reflecting, therefore, on the solution of the species conservation equations. Two other approaches, the consistent effective binary diffusion due to Ramshaw, hereafter called the Ramshaws approximation, and the linearized method are shown to reproduce accurately the mass transfer obtained with the exact formulation for multicomponent high temperature flows in isotherm conditions. When temperature gradients are imposed, the linear approximation leads to important errors (up to 40%) on the mass flux calculation.

Prediction of a 2-D Solidification Front in High Temperature Furnaces by an Inverse Analysis

This study presents an inverse heat transfer method for predicting the two-dimensional time-varying shape of the phase change protective bank on the inside surface of a wall of a high temperature furnace filled with molten material. The method rests on the Levenberg-Marquardt least-square minimization technique and it relies on non-intrusive temperature measurements. Results indicate that under typical melting furnace operating conditions, the 2-D inverse methodology provides accurate predictions of the moving boundary. For these real time industrial applications however, a simpler yet accurate quasi-2-D inverse method that is nearly 10 times faster than the full 2-D inverse model is proposed.

Control of the ledge thickness in high-temperature metallurgical reactors using a virtual sensor

A non-intrusive inverse heat transfer procedure for predicting the time-varying thickness of the phase change ledge on the inside surface of the walls of a high-temperature metallurgical reactor is presented. A Kalman filter, based on a state-space representation of the reactor, is coupled with a recursive least-square estimator in order to estimate online the position of the phase front. The data are collected by a heat flux sensor located inside or outside of the reactor wall. The inverse method, used here as a virtual sensor, is coupled to a classic proportional–integral controller in order to control the ledge thickness by regulating the air cooling applied on the outside surface of the reactor wall. The virtual sensor and the control strategy are thoroughly tested for typical phase change conditions that prevail inside industrial facilities. Results show that a virtual sensor that relies on a heat flux sensor embedded inside the reactor wall provides more accurate and stable information, but at a price of a more complicated installation. In that case, it is shown that the discrepancy between the exact and the estimated ledge thicknesses remains smaller than 3% at all times, and that the control strategy ensures a null steady-state tracking error, a maximum tracking error less than 10%, no overshoot and no significant time lag.

Prediction of the Bank Formation in High Temperature Furnaces by a Sequential Inverse Analysis with Overlaps

This article presents a simple sequential inverse method for predicting time-varying thickness of the phase change protective bank found on the inside surface of a wall of a high temperature furnace. The main feature of the proposed overlapping procedure is its unique capability to increase the diagnostic frequency for phase change processes with large thermal inertia. The inverse method rests on the adjoint problem and the conjugate gradient method, and it relies on nonintrusive temperature measurements. Results also indicate that under typical melting furnace operating conditions, the proposed overlapping procedure doubles the allowable diagnostic frequency for predicting the time-varying bank thickness.

Advanced numerical simulation of the thermo-electro-chemo-mechanical behaviour of hall-héroult cells under electrical preheating

In today’s context, aluminum producers strive to improve their position regarding energy consumption and production costs. To do so, mathematical modeling offers a good way to study the behavior of the cell during its life. This paper deals with the numerical simulation of the electrical preheating of a Hall-Heroult cell using a quarter model of the cell. The fully coupled thermo-electro-mechanical model includes material non linearities and multiphysical behavior at interfaces allowing accurate evaluation of the stress distribution in the cathode blocks and surrounding components. The baking of the ramming paste as well as the evolution of its thermo-electro-mechanical properties are updated via the baking index computed using a kinetic of reaction. The model is initially calibrated with in situ measurements and then used to estimate the effect of preheating on the behavior of the cell including temperature, current, deformations as well as the contact conditions at critical interfaces.

Numerical analysis of the effect of structural and operational parameters on electric and concentration fields of a lithium electrolysis cell

A fully integrated mass transfer and electrochemical model of a lithium production cell solved using a finite element method is presented. The coupled effect of momentum and mass transfer, kinetics, and electric fields is taken all into account. The turbulent flow resulting from the bubbles generated at the anode is solved based on a k-

Is the performance of a virtual sensor employed for the prediction of the ledge thickness inside a metallurgical reactor affected by the thermal contact resistance

\epsilon