Abstract: A method and apparatus for limiting the passage of a gas such as air through an opening, particularly an opening through which solid material passes, by providing a sealing chamber in advance of the entrance to the low pressure chamber having a large plenum with a variable speed exhaust blower in its upper portion, and a grate situated in its lower portion for access of air to the plenum. The blower speed is responsive to differential pressure measurements taken in the low pressure chamber and immediately adjacent the exterior of the low pressure chamber. Upstream of the plenum are one or more mechanical seals or flexible baffles which contact the top of the solid charge material and ride over it as the solid material passes beneath the mechanical seal.

Abstract: A method and apparatus for reducing the production or emission of noxious gases while continuously preheating a mixture of iron-bearing scrap charge materials for an electric steelmaking furnace operation with off-gas from, the furnace, including provision for controlled combustion within the preheating chamber. Removed gases are then treated by thermal incineration of combustible residual matter before release into the atmosphere to insure that no noxious gases are emitted.