Abstract A furnace for melting solid ferrous pieces such as pig iron and steel scrap, features a combination of electric induction heating and flame heating of the pieces which are charged into the furnace hearth via a charging stack up through which the products of combustion flow from the furnace counter-current to the descending charged pieces moving downwardly through the stack. The flame heating is via burners supplied with hydrocarbon fluid fuel with oxygen proportioned for incomplete combustion, the products of combustion and unburned fuel ascending through the stack and preheating the descending charged pieces. Air is supplied to the stack to complete the combustion of the previously unburned fuel in and around the descending pieces, this being done at a level where the descending pieces have not yet reached temperatures sufficient to cause excessive oxidation of the pieces. Other details providing for effective utilization of these principles, are included in the disclosure.
A furnace for melting solid pieces of metal and comprising a horizontally elongated furnace enclosure having a length-to-width ratio of at least about 4:1, said enclosure having a bottom portion forming a hearth and a roof spaced above the hearth, a vertical stack down through which the pieces of metal are charged and positioned centrally through said roof and having a bottom positioned so the charged pieces form a column down to a melt in said hearth, electric induction means below said hearth for inductively stirring the melt to form interspaced ridges in the melt's top level and a valley between the ridges with the valley below the stack's said bottom, burner means for directing carbonaceous fuel and oxygen flames of low oxygen potential towards said hearth and melt and forming reducing gases leaving said furnace enclosure upwardly via said stack containing the metal pieces above said column, and injection means for injecting oxygen into said stack to cause complete combustion of said gases, the pieces in the stack gradually increasingly preheating downwardly in the stack to temperatures where they are combustible in the presence of oxygen, said injection means being positioned high enough in the stack to be above the level where the pieces have preheated to said temperatures.
Claim 2
Dependent Claim
210 words
A furnace for melting solid pieces of metal and comprising a horizontally elongated furnace enclosure having a length-to-width ratio of at least about 4:1, said enclosure having a bottom portion forming a hearth and a roof spaced above the hearth, a vertical stack down through which the pieces of metal are charged and positioned centrally through said roof and having a bottom positioned so the charged pieces form a column down to a melt in said hearth, electric induction means below said hearth for inductively stirring the melt to form interspaced ridges in the melt's top level and a valley between the ridges with the valley below the stack's said bottom, burner means for directing carbonaceous fuel and oxygen flames of low oxygen potential towards said hearth and melt and forming reducing gases leaving said furnace enclosure upwardly via said stack containing the metal pieces above said column, and injection means for injecting oxygen into said stack to cause complete combustion of said gases, the pieces in the stack gradually increasingly preheating downwardly in the stack to temperatures where they are combustible in the presence of oxygen, said injection means being positioned high enough in the stack to be above the level where the pieces have preheated to said temperatures.
Claim 3
Dependent Claim
22 words
The furnace of claim 1 in which said burner means directs said flames at downward angles in the direction of said column.
Claim 4
Dependent Claim
21 words
The furnace of claim 2 having means for introducing carbonaceous material to the sides of said ridges away from said valley.