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Lead: Secondary Lead Smelter


ACGIH - American Conference of Governmental Industrial Hygienists

Agglomerating furnace - A furnace used to melt into a solid mass flue dust that is collected from a baghouse

ANSI - American National Standards Institute

ASME - American Society of Mechanical Engineers

Action level - Exposure to a level of airborne contamination that requires an employer to implement some, but not all, of the surveillance and control activities of an OSHA standard. The action level is usually equal to one-half of the permissible exposure level. An exception is the action level for lead, which is 30 micrograms per cubic meter of air as compared to the permissible exposure limit of 50 micrograms per cubic meter of air.

Battery breaking area - The plant location at which lead-acid batteries are broken, crushed, or disassembled and separated into components.

Baghouse - The structure housing the bags of tubular or envelope shaped fabric filter, used for the high-efficiency collection of solid particulate (i.e., dust and fumes) from a contaminated air stream/gas stream.

Blast furnace - Blast furnaces are reduction furnaces that produce hard or antimonial lead containing about 10% antimony. Pretreated scrap metal, rerun slag, scrap iron coke, recycled dross, flue dust, and limestone are used as charge materials to the blast furnace. The process heat needed to melt the lead is produced by the reaction of the charged coke with blast air that is blown into the furnace near the bottom through tuyeres. Some of the coke combusts to melt the charge, while the remainder reduces lead oxides to elemental lead.

Charging location - The physical opening through which raw materials are introduced into a sinter machine or furnace.

Charge - Material introduced into a furnace to be smelted or refined.

Converter - Steel shells lined with magnesite brick. Converters are used to purify the matte after smelting.

Cupola furnace - A refractory-lined, vertical, cylindrical shaft furnace equipped with air ports (known as tuyeres) at the bottom. Air is supplied from a forced- draft blower. Melting is accomplished in the cupola by heat released from the combination of coke (the reaction between oxygen in the air and carbon in the fuel) that is in direct contact with the metallic portion of the charge and the fluxes. The molten metal is drawn off through a taphole.

Dross - A scum formed on the surface of molten metal. Dross refers to the lead oxides, copper, antimony, and other elements that float to the top of the molten lead.

Dryer - A chamber that is heated and that is used to remove moisture from lead-bearing materials before they are charged to a smelting furnace.

Enclosure hood - A hood that covers a process fugitive emission source on the top and on all sides, with openings only for access to introduce or remove materials to or from the source and through which an induced flow of air is ventilated.

Flux - Any of a variety of materials used to purify metals or prevent undue oxidation of molten metal surfaces. It is a substance used to aid in the extraction of a furnace charge because of its ability to fuse with undesired matter (impurities/contaminants) in forming a more liquid slag.

Fugitive dust source - A stationary source of hazardous air pollutant emissions at a secondary lead smelter resulting from the handling, storage, transfer, or other management of lead-bearing materials where the source is not associated with a specific process or process fugitive vent or stack. Fugitive dust sources include, but are not limited to, roadways, storage piles, and materials handling transfer points, materials transport areas.

Hammermill - A machine designed for the crushing of complete full lead acid storage batteries and for the classification of their components. It produces plastic, paste, grid metal. and waste organic fractions and avoids the hazardous, time consuming procedure of sawing and dumping prior to classification.

Ladle - A large vessel for receiving and handling molten metal and slag.

Matte - A valuable metal concentrate. It is an impure metallic sulfide mixture produced by smelting the sulfide ores of such metals as copper, lead, or nickel.

Pigging machine - A metal casting machine which pours molten metal into molds to form ingots.

Primary smelting - Pyrometallurgical processes that utilize high temperatures and are accompanied by chemical changes. Primary smelters process sulfide concentrates, sulfates, oxides, and metallic scrap.

Refining kettles - Top-access pots sunk into the refinery floor. Refining kettles can purify the metal taken from the smelting furnace, or scrap lead supplied in clean metallic form (e.g., sheet or pipe) to remelt and refine without having to undergo smelting.

Refractory - A term used to describe materials with a high melting point that will retain its shape and chemical identity when subjected to high temperatures, and is used in applications that require extreme resistance to heat, such as furnace linings. Brick and ceramic are examples of refractory materials.

Reverberatory furnace - A furnace, with a shallow hearth, operating by radiating heat from its burner flame, a roof, and walls onto the surface of the charge (material being heated). This type of furnace may be gas fired or oil fired, or a combination of both. Combustion of fuel occurs directly above the molten bath. The reverberatory furnace is used to separate lead from scrap metal as well as to reclaim lead from oxides and drosses.

Secondary lead smelting - Secondary smelting produces lead and lead alloys from lead-bearing scrap metal. Raw materials used in secondary lead smelting include scrap automobile batteries, wheel balance weights, pipe, solder, drosses, and lead sheathing.

Slag - A product resulting from the interaction of flux and impurities in the refining and smelting of metals. The fluxing agent aids in separating the molten lead from the impurities, and forms a slag which floats on top of the molten metal.

TWA - Time-weighted average.

Tapping - The process of opening the pouring of a melting furnace to remove molten metal and slag. The molten metal is poured into molds or ladles.

Tuyere - An opening in the shell and refractory lining of a furnace through which air is forced.

Tuyere Punching - The process of cleaning the tuyere. Tuyere punching is achieved by an operator or "puncher" driving and withdrawing a punch-bar through the tuyere with sufficient force to penetrate and dislodge the adhering frozen solids. Manual tuyere punching has generally been replaced by an automated punching machine which mimics and enhances the human action of tuyere punching.

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