Evaluation of required heat flux for magnesio-thermic reduction furnace

Production of uranium metal using Magnesio-thermic reduction is one of the standard methods all over the world. The reaction of Uranium Fluoride and Magnesium is quite exothermic in nature, very much capable of producing the products in molten state. Since the density difference of products is very high, molten state facilitates metal slag separation by the action of gravity. But it is necessary to preheat the charge to increase the bulk temperature to 175°C, otherwise, post reaction temperature does not exceed the melting point of the metal and slag. In that case, the separation will not be proper and lead to inefficient metal recovery, Therefore, the batch is always heated under a specific temperature schedule by maintaining constant skin temperature at the vessel surface. Another important point to be addressed is that by using high flux heating or high temperature heating from the very beginning, the temperature of the charge material closer to the vessel increases at a faster rate as compared to the bulk charge owing to poor conduction properties of the charge. This can cause pre-firing and hence poor yield of the U metal. An analytical study has been conducted using COMSOL multiphysics to arrive at suitable heating flux value so as to aid selection furnace of optimum capacity