Process for Melting Scrap Metal

Abstract

Process for melting scrap metal in a furnace comprising the steps of feeding a charge of solid scrap metal to the furnace, supplying fuel and an oxygen-rich oxidant to the furnace and combusting the fuel with the oxidant to generate heat inside the furnace, melting the charge of solid scrap metal in the furnace by means of the heat, withdrawing the molten metal from the furnace. Following the step of feeding the charge of solid scrap metal to the furnace, the fuel is combusted with the oxidant so as to generate one or more visible flames in the furnace above the charge and before the step of withdrawing the molten metal from the furnace, the fuel is combusted with the oxidant so as to generate flameless combustion in the furnace above the molten metal.

1 - 15 . (canceled) 
     
     
         16 . A process for melting scrap metal in a furnace, comprising the steps of:
 feeding a charge of solid scrap metal to the furnace;   supplying fuel and an oxidant having an oxygen content of at least 60% vol to the furnace and combusting the fuel with the oxidant to generate heat inside the furnace;   melting the charge of solid scrap metal in the furnace by means of the heat so generated, thereby obtaining molten metal;   withdrawing the molten metal from the furnace, wherein said step of supplying and combusting the fuel and oxidant is performed such that:
 following said step of feeding the charge of solid scrap metal to the furnace, the fuel is combusted with the oxidant in a first combustion mode so as to generate one or more visible flames in the furnace above the charge, and 
 before said step of withdrawing the molten metal from the furnace, the fuel is combusted with the oxidant in a second combustion mode so as to generate flameless combustion in the furnace above the molten metal. 
   
     
     
         17 . The process of  claim 16 , wherein the one or more visible flames have a fixed orientation in the first combustion mode. 
     
     
         18 . The process of  claim 16 , wherein an orientation of at least one of said one or more visible flames is varied in the first combustion mode. 
     
     
         19 . The process of  claim 16 , wherein, in the first combustion mode, at least one of said one or more visible flames is directed towards the charge. 
     
     
         20 . The process of  claim 16 , wherein the furnace is a rotary furnace having a substantially cylindrical refractory wall, a first end wall at one end of the cylindrical refractory wall and a second end wall at an opposite end of the cylindrical refractory wall. 
     
     
         21 . The process of  claim 20 , wherein, during the first combustion mode, at least one of said one or more visible flames is directed towards the charge and/or towards the cylindrical refractory wall. 
     
     
         22 . The process of  claim 16 , wherein the furnace is a tilting furnace having a tilting pocket with a pouring and charging opening and a burner mounted in the pouring and charging opening. 
     
     
         23 . The process of  claim 16 , wherein a same burner generates said one or more visible flames during the first combustion mode and flameless combustion during the second combustion mode. 
     
     
         24 . The process of  claim 16 , further comprising a transitional combustion mode between the first combustion mode and the second combustion mode, whereby in the transitional combustion mode the fuel is combusted with the oxidant so as generate at least one visible flame and increase the temperature of the furnace atmosphere, in at least in an area of the furnace atmosphere where flameless combustion is to take place in the subsequent second combustion mode, to a temperature above a lower flammable limit of the fuel. 
     
     
         25 . The process of  claim 16 , wherein the scrap metal is selected from the group consisting of aluminium, copper, zinc, lead, cobalt, titanium, chromium, precious metals, and alloys thereof. 
     
     
         26 . The process of  claim 25 , wherein the scrap metal is aluminium or an aluminium alloy. 
     
     
         27 . The process of  claim 16 , wherein the fuel is a gaseous fuel. 
     
     
         28 . The process of  claim 27 , wherein the fuel is selected from the group consisting of natural gas, butane, propane, and mixtures thereof. 
     
     
         29 . The process of  claim 16 , wherein the oxidant has an oxygen content of at least 65% vol/vol. 
     
     
         30 . The process of  claim 16 , wherein the oxidant has an oxygen content of at least 80% vol/vol. 
     
     
         31 . The process of  claim 16 , wherein the oxidant has an oxygen content of at least 90% vol/vol. 
     
     
         32 . The process of  claim 16 , whereby the first combustion phase is terminated when substantially all of the solid scrap metal is melted.