Abstract: This disclosure relates to a system for preheating scrap before charging in an electric furnace and for preventing the release of malodorous or noxious gas. The system includes a first duct leading from the furnace exhaust gas outlet to a chimney; a branching duct is connected in the first line for passing part of the gas to the chimney and for diverting the remainder of the gas to a scrap preheater. After preheating the scrap, the diverted gas is recirculated back to the first line at a junction which is adjacent the furnace outlet. The system further includes gas combustion means connected in the first line between the junction and the branching duct, and a heat equalizer-accumulator in the first line between the combustion means and the chimney. The system may further include a heat exchanger connected in the first line downstream of the branching duct and a second line for passing the diverted gas through the heat exchanger after it leaves the scrap preheater.

Abstract: Molten slag in a vessel or vessels is placed below heat absorbing tubes through which water is passed and converted into steam by the heat radiated by the slag of high temperature, the heat thus being recovered by utilizing the steam for heating purposes, or for driving a turbine or the like. A cover is placed over the tubes and the vessel or vessels to increase the heat transfer efficiency. Any cooled slag layer formed on the surface of the molten slag in the vessel is removed by skimming to promote the heat transfer and, after the temperature of the slag in the vessel has lowered to about 1,200.degree. C, the slag is agitated to further promote the heat transfer. Alternatively, the slag in the vessel or vessels is agitated from the beginning until its temperature has lowered to about 700.degree. C.