Melting process

A process for melting a light metal charge, surface contaminated with volatizable and combustible impurities comprising:

• introducing the charge through a charging port of a charging chamber of a dual chamber furnace having a molten bath moving therethrough, said bath substantially continuously circulating from a directly fired heating chamber to the charging chamber and back to the heating chamber, said chambers separated by a wall and in communication below the surface of the molten bath through at least one lower passageway through said wall, and in communication above the surface of the molten bath through at least one upper passageway through said wall;
• placing a cover over the charging port of the charging chamber;
• maintaining a negative pressure of -0.01 to -0.05 inch water column in the heating chamber with respect to the charging chamber, whereby hydrocarbon vapors emitted from the charge are drawn through the upper passageway and into the heating chamber;
• and
• combusting the hydrocarbon vapors in the heating chamber, whereby combustion heat is provided to the heating chamber and the molten metal circulating therethrough.

A process for melting aluminum charge, surface contaminated with volatizable and combustible impurities comprising:

• introducing salt flux comprising approximately 2 to 6 percent of total charge weight through a charge port of a charging chamber in a dual chamber furnace having a molten aluminum bath moving therethrough in an amount equal to approximately 15 to 20 times the total charge weight, substantially continuously circulating said bath from a directly fired heating chamber through a recirculating line into the charging chamber and back to the heating chamber, said chambers separated by a wall and in communication below the surface of molten aluminum through at least one lower passageway through said wall, and in communication above the surface of molten aluminum through at least one upper passageway through said wall;
• dispersing and melting the salt flux in the bath circulating through the charging chamber;
• introducing the contaminated aluminum charge onto the surface of the bath in the charging chamber through the charge port;
• covering the charge port;
• maintaining a negative pressure of from -0.01 to -0.02 inch water column in the heating chamber with respect to the charging chamber by inducing a draft through an exhaust stack provided in the heating chamber whereby hydrocarbon vapors emitted from the charge are drawn through the upper passageway and into the heating chamber;
• combusting the hydrocarbon vapors in the heating chamber maintained at a temperature of approximately 1500.degree. to 2500.degree. F in the lower regions of the heating chamber above the molten bath level, whereby additional combustion heat is provided to the heating chamber and the molten bath circulating therethrough;
• removing the majority of the skim from the surface of the molten bath in the charging chamber;
• and
• removing molten aluminum from the system in an amount substantially commensurate with the total charge weight.

A process for burning hydrocarbons in vapors emitted from contaminated metallic scrap comprising the steps of:

• charging the scrap into a charging chamber of a dual chamber furnace having a molten metal bath therein, the charging chamber separated from a heating chamber by a wall, said chambers in communication below the surface of a molten metal bath circulating therebetween through at least one lower passageway through the wall, and said chambers in communication above the surface of the molten metal bath through at least one upper passageway through the wall;
• maintaining a negative pressure in the heating chamber with respect to the charging chamber, whereby hydrocarbon vapors emitted from the scrap charged into the charging chamber are drawn through the connecting member into the heating chamber;
• and
• completing the combustion of hydrocarbons in the vapors in the heating chamber.