Magnetically stabilized helium arc for scattering experiments

For verifying some theoretical predictions of light scattering from magnetized plasmas, a stable pulsed helium arc discharge in a magnetic field up to 5 Teslas has been built. The arc has been investigated at filling pressures of 2 to 5 torr and plasma currents between 1 and 5 kA. Plasma parameters were measured at a magnetic field of 4 Teslas and a pressure of 3 torr. At these values of the magnetic field and the filling pressure the arc is steady and approximately cylindrically symmetric up to a plasma current of 2.8 kA. Time dependence and radial distribution of the electron density and temperature have been determined from spectroscopic measurements, 1aser•interferometry, and laser scattering. The latter two techniques were used successfully for the first time on a magnetically stabilized arc to measure the electron density and temperature in the hot core of the arc. The axial electron density is 1.2 x 10¹⁶ cm⁻³ and is approximately constant over the arc cross-section in the high temperature region as predicted by theory. The axial temperature is 145,000°K. Thus the arc design and the plasma properties are suitable for scattering experiments. The arc behaviour is governed by dynamic processes which depend on the geometry of the apparatus. In order to show the problems of the design and operation of the apparatus, the theory of arc behaviour in a magnetic field is outlined.Science, Faculty ofPhysics and Astronomy, Department ofGraduat

Modelling of the coke calcining kiln

Modelling the rotary kilns used for the calcination of the coke is no simple undertaking, due to the manyinteracting physical phenomena governing the behavior of the solid bed and the freeboard gas. To date, a few attempts havebeen made, resulting in models that are either limited to a static global heat balance evaluation or affected by weaknessescaused by too many crude simplifying assumptions. As the main purpose is to control coke quality by controlling the calcination temperature and its rate ofincrease, the key issue is to control the temperature and location of the calcining zone, and in order to do so, it isimportant to introduce the effect of the many critical factors such as emissivities, volatiles and third air into the model. We have succeeded in doing so. Simulation results will be presented and discussed, clearly showing a possibility of optimizingthe operation of the kiln

Analyzing the heat transfer in a coke calcining kiln

This paper presents the heat transfer analysis in a coke calcining kiln based on a general three-dimensional model that has been developed for such systems. The overall model consists of four sub-models: freeboard energy, freeboard flow, coke bed energy and coke bed flow. These sub-models are linked using the parallel computation technique. All the phenomena involving heat transfer, fluid flow, turbulence and combustion are included in the model. The governing differential equations are solved by the CFD code PHOENICS. The six-flux method used in a previous version of the model was replaced by the zone method for the radiative heat transfer calculations. In this paper, the model is described in detail for the heat transfer analysis. It was used for the simulation of a pilot kiln for which experimental data are available. Results are presented for two cases. Model predictions compare favourably with the experimental data