The Converter treats the output matte from the smelter. This specific type, is a top-blown furnace, with furnace matte, air, and oxygen being injected into the converter via a lance submerged in the slag.
During the converting process, air is blown into molten matte, in order to remove the iron and sulphur by oxidation. Silica sand is utilized as a fluxing agent, to flux the iron oxide that is formed by the oxidation of the iron, and to form an iron silicate slag. Some of the sulphur leaves the system in the gas phase as Sulphur dioxide (SO2). The oxidation reaction is sufficiently exothermic to maintain a temperature around 1250oC in the converter. The temperature is controlled by adding cold feed to the converter if it becomes too hot. The required degree of iron and sulphur removal during converting is dictated by the choice of the subsequent refining process.