With the wall structure of this furnace, the refractory lining is exposed to a high temperature. As a consequence of this, considerable wear of the refractory lining occurs and its service life is reduced. At the state of the art the reference temperature is kept low by cooling and attempts are made to keep the interior temperature low by using refractory materials with a high heat conductivity, such as graphite, semi-graphite or other refractory materials containing graphite. The means for cooling the refractory wall structure can consist of means on the outside of the steel wall, such as for example spray-cooling, air-cooling or cooling ducts for fluid coolants, or of other means on the inside of the steel wall such as for example water-cooled cooling elements such as stave coolers or cooling plates which are generally made from copper.