Method for controlling flux concentration in guide tubes

Abstract

A method for controlling electromagnetic flux concentration in a discharge guide tube for a metal refining apparatus is provided. The discharge guide tube comprises a base plate, an extension, a central orifice that extends through the extension from a source of liquid metal to an outlet in the discharge guide tube for directing a stream of metal therethrough, and an interior discharge guide tube flux concentration configuration; an induction heater system that generates an electromagnetic field in the discharge guide tube, the induction heater system being disposed on the extension with a gap defined therebetween, the induction heater system and the discharge guide tube being capable of relative vertical movement and subsequent positions with respect to each other with the gap being essentially constant. The method for providing electromagnetic flux concentration comprises providing current to the induction heater system; generating an electromagnetic field resulting from the step of providing current; and directing an electromagnetic flux to the central orifice at locations defined by the interior discharge guide tube. The step of generating an electromagnetic flux also generates heat and the step of generating heat provides a control of the flow of the stream of metal in its liquidus condition. The electromagnetic field is applied at a substantially constant level regardless of the relative vertical movement and subsequent positions between the induction heater system and the discharge guide tube.