Abstract:
Zirconium metal is used in the alloy cladding of nuclear fuel rods. Necsa
produces ZrF4 by reacting ammonium bifluoride with desilicated plasmadissociated
zircon. The ZrF4 then undergoes a sublimation separation step
to reduce the Hf content to below 100 ppm Hf. The ZrF4 is converted into
ZrCl4 via its reaction with magnesium chloride. The ZrCl4 is then used in a
plasma process to produce Zr metal for use in the nuclear industry. The
aim of the research reported here is to obtain a first-order estimate of the
reaction kinetics for the chloridation reaction. This was done using the
data obtained from a dynamic thermogravimetric analysis experiment and
minimising the error between experimentally determined degrees of
conversion and predictions of a stepwise kinetic model predictions. The
reaction was found to take place only above the sublimation point of ZrCl4.
At a low enough heating rate it can be assumed the loss in mass is due to
sublimation of ZrCl4, the moment it is formed and the rate of mass loss is
equal to the reaction rate.
Description:
This paper
was first presented at the AMI Precious Metals
2017 Conference ‘The Precious Metals
Development Network’ 17–20 October 2017,
Protea Hotel Ranch Resort, Polokwane, South
Africa.