Metal reclamation is the process by which metals are produced from scrap. These reclaimed metals are not distinguishable from the metals produced from primary processing of an ore of the metal. However, the process is slightly different and the exposure could be different. The engineering controls are basically the same. Metal reclamation is very important to the world economy because of the depletion of raw materials and the pollution of the environment created by scrap materials.
Aluminium, copper, lead and zinc comprise 95% of the production in the secondary non-ferrous metal industry. Magnesium, mercury, nickel, precious metals, cadmium, selenium, cobalt, tin and titanium are also reclaimed. (Iron and steel are discussed in the chapter Iron and steel industry. See also the article “Copper, lead and zinc smelting and refining” in this chapter.)
Control Strategies
Emission/exposure control principles
Metal reclamation involves exposures to dust, fumes, solvents, noise, heat, acid mists and other potential hazardous materials and risks. Some process and/or material handling modifications may be feasible to eliminate or reduce the generation of emissions: minimizing handling, lowering pot temperatures, decreasing dross formation and surface generation of dust, and modifying plant layout to reduce material handling or re-entrainment of settled dust.
Exposure can be reduced in some cases if machines are selected to perform high-exposure tasks so that employees may be removed from the area. This can also reduce ergonomic hazards due to materials handling.
To prevent cross contamination of clean areas in the plant, it is desirable to isolate processes generating significant emissions. A physical barrier will contain emissions and reduce their spread. Thus, fewer people are exposed, and the number of emission sources contributing to exposure in any one area will be reduced. This simplifies exposure evaluations and makes the identification and control of major sources easier. Reclaim operations are often isolated from other plant operations.
Occasionally, it is possible to enclose or isolate a specific emission source. Because enclosures are seldom air tight, a negative draught exhaust system is often applied to the enclosure. One of the most common ways to control emissions is to provide local exhaust ventilation at the point of emission generation. Capturing emissions at their source reduces the potential for emissions to disperse into the air. It also prevents secondary employee exposure created by the re-entrainment of settled contaminants.
The capture velocity of an exhaust hood must be great enough to prevent fumes or dust from escaping the air flow into the hood. The air flow should have enough velocity to carry fume and dust particles into the hood and to overcome the disrupting effects of cross drafts and other random air movements. The velocity required to accomplish this will vary from application to application. The use of recirculation heaters or personal cooling fans which can overcome local exhaust ventilation should be restricted.
All exhaust or dilution ventilation systems also require replacement air (known also as “make-up” air systems). If the replacement air system is well designed and integrated into natural and comfort ventilation systems, more effective control of exposures can be expected. For example, replacement air outlets should be placed so clean air flows from the outlet across the employees, towards the emission source and to the exhaust. This technique is often used with supplied-air islands and places the employee between clean incoming air and the emission source.
Clean areas are intended to be controlled through direct emission controls and housekeeping. These areas exhibit low ambient contaminant levels. Employees in contaminated areas can be protected by supplied-air service cabs, islands, stand-by pulpits and control rooms, supplemented by personal respiratory protection.
The average daily exposure of workers can be reduced by providing clean areas such as breakrooms and lunchrooms that are supplied with fresh filtered air. By spending time in a relatively contaminant-free area, the employees’ time-weighted average exposure to contaminants can be reduced. Another popular application of this principle is the supplied-air island, where fresh filtered air is supplied to the breathing zone of the employee at the workstation.
Sufficient space for hoods, duct work, control rooms, maintenance activities, cleaning and equipment storage should be provided.
Wheeled-vehicles are significant sources of secondary emissions. Where wheeled-vehicle transport is used, emissions can be reduced by paving all surfaces, keeping surfaces free of accumulated dusty materials, reducing vehicle travel distances and speed, and by re-directing vehicle exhaust and cooling fan discharge. Appropriate paving material such as concrete should be selected after considering factors such as load, use and care of surface. Coatings may be applied to some surfaces to facilitate wash down of roadways.
All exhaust, dilution and make-up air ventilation systems must be properly maintained in order to effectively control air contaminants. In addition to maintaining general ventilation systems, process equipment must be maintained to eliminate spillage of material and fugitive emissions.
Work practice programme implementation
Although standards emphasize engineering controls as a means of achieving compliance, work practice controls are essential to a successful control programme. Engineering controls can be defeated by poor work habits, inadequate maintenance and poor housekeeping or personal hygiene. Employees who operate the same equipment on different shifts can have significantly different airborne exposures because of differences in these factors between shifts.
Work practice programmes, although often neglected, represent good managerial practice as well as good common sense; they are cost effective but require a responsible and cooperative attitude on the part of employees and line supervisors. The attitude of senior management toward safety and health is reflected in the attitude of line supervisors. Likewise, if supervisors do not enforce these programmes, employees attitudes may suffer. Fostering good health and safety attitudes can be accomplished through:
Work practice programmes cannot be simply “installed”. Just as with a ventilation system, they must be maintained and continually checked to insure that they are functioning properly. These programmes are the responsibility of management and employees. Programmes should be established to teach, encourage and supervise “good” (i.e., low exposure) practices.
Personal protective equipment
Safety glasses with side shields, coveralls, safety shoes and work gloves should be routinely worn for all jobs. Those engaged in casting and melting, or in casting alloys, should wear aprons and hand protection made of leather or other suitable materials to protect against the splatter of molten metal.
In operations where engineering controls are not adequate to control dust or fume emissions, appropriate respiratory protection should be worn. If noise levels are excessive, and cannot be engineered out or noise sources cannot be isolated, hearing protection should be worn. There should also be a hearing conservation programme, including audiometric testing and training.
Processes
Aluminium
The secondary aluminium industry utilizes aluminium-bearing scrap to produce metallic aluminium and aluminium alloys. The processes used in this industry include scrap pre-treatment, remelting, alloying and casting. The raw material used by the secondary aluminium industry includes new and old scrap, sweated pig and some primary aluminium. New scrap consists of clippings, forging and other solids purchased from the aircraft industry, fabricators and other manufacturing plants. Borings and turnings are by-product of the machining of castings, rods and forging by the aircraft and automobile industry. Drosses, skimmings and slags are obtained from primary reduction plants, secondary smelting plants and foundries. Old scrap includes automobile parts, household items and airplane parts. The steps involved are as follows:
Table 1 lists exposure and controls for aluminium reclamation operations.
Table 1. Engineering/administrative controls for aluminium, by operation
Process equipment |
Exposure |
Engineering/administrative controls |
Sorting |
Torch desoldering—metal fumes such as lead and cadmium |
Local exhaust ventilation during desoldering; PPE—respiratory protection when desoldering |
Crushing/screening |
Non-specific dusts and aerosol, oil mists, metal particulates, and noise |
Local exhaust ventilation and general area ventilation, isolation of noise source; PPE—hearing protection |
Baling |
No known exposure |
No controls |
Burning/drying |
Non-specific particulate matter which may include metals, soot, and condensed heavy organics. Gases and vapours containing fluorides, sulphur dioxide, chlorides, carbon monoxide, hydrocarbons and aldehydes |
Local exhaust ventilation, general area ventilation, heat stress work/rest regimen, fluids, isolation of noise source; PPE—hearing protection |
Hot-dross processing |
Some fumes |
Local exhaust ventilation, general area ventilation |
Dry milling |
Dust |
Local exhaust ventilation, general area ventilation |
Roasting |
Dust |
Local exhaust ventilation, general area ventilation, heat stress work/rest regimen, fluids, isolation of noise source; PPE—hearing protection |
Sweating |
Metal fumes and particulates, non-specific gases and vapours, heat and noise |
Local exhaust ventilation, general area ventilation, heat stress work/rest regimen, fluids, isolation of noise source; PPE—hearing protection and respiratory protection |
Reverberatory (chlorine) smelting-refining |
Products of combustion, chlorine, hydrogen chlorides, metal chlorides, aluminium chlorides, heat and noise |
Local exhaust ventilation, general area ventilation, heat stress work/rest regimen, fluids, isolation of noise source; PPE—hearing protection and respiratory protection |
Reverberatory (fluorine) smelting-refining |
Products of combustion, fluorine, hydrogen flluorides, metal fluorides, aluminium fluorides, heat and noise |
Local exhaust ventilation, general area ventilation, heat stress work/rest regimen, fluids, isolation of noise source; PPE—hearing protection and respiratory protection |
Copper reclamation
The secondary copper industry utilizes copper-bearing scrap to produce metallic copper and copper based alloys. The raw materials used can be classified as new scrap produced in the fabrication of finished products or old scrap from obsolete worn out or salvaged articles. Old scrap sources include wire, plumbing fixtures, electrical equipment, automobiles and domestic appliances. Other materials with copper value include slags, drosses, foundry ashes and sweepings from smelters. The following steps are involved:
Table 2 lists exposures and controls for copper reclamation operations.
Table 2. Engineering/administrative controls for copper, by operation
Process equipment |
Exposures |
Engineering/administrative controls |
Stripping and sorting |
Air contaminants from material handling and desoldering or scrap cutting |
Local exhaust ventilation, general area ventilation |
Briquetting and crushing |
Non-specific dusts and aerosol, oil mists, metal particulates and noise |
Local exhaust ventilation and general area ventilation, isolation of noise source; PPE—hearing protection and respiratory protection |
Shredding |
Non-specific dusts, wire insulation material, metal particulates and noise |
Local exhaust ventilation and general area ventilation, isolation of noise source; PPE—hearing protection and respiratory protection |
Grinding and gravity separation |
Non-specific dusts, metal particulates from fluxes, slags and drosses, and noise |
Local exhaust ventilation and general area ventilation, isolation of noise source; PPE—hearing protection and respiratory protection |
Drying |
Non-specific particulate matter, which may include metals, soot and condensed heavy organics |
Local exhaust ventilation, general area ventilation, work/rest regimen, fluids, isolation of noise source; PPE—hearing protection and respiratory protection |
Insulation burning |
Non-specific particulate matter which may include smoke, clay |
Local exhaust ventilation, general area ventilation, work/rest regimen, fluids, isolation of noise source; PPE—respiratory protection |
Sweating |
Metal fumes and particulates, non-specific gases, vapours and particulates |
Local exhaust ventilation, general area ventilation, work/rest regimen, fluids, isolation of noise source; PPE—hearing protection and respiratory protection |
Ammonium carbonate leaching |
Ammonia |
Local exhaust ventilation, general area ventilation; PPE—respiratory protection |
Steam distillation |
Ammonia |
Local exhaust ventilation, general area ventilation; PPE—glasses with side shields |
Hydrothermal hydrogen reduction |
Ammonia |
Local exhaust ventilation, general area ventilation; PPE—respiratory protection |
Sulphuric acid leaching |
Sulphuric acid mists |
Local exhaust ventilation, general area ventilation |
Converter smelting |
Volatile metals, noise |
Local exhaust ventilation, general area ventilation; PPE—respiratory protection and hearing protection |
Electric crucible smelting |
Particulate, sulphur and nitrogen oxides, soot, carbon monoxide, noise |
Local exhaust ventilation, general area ventilation; PPE—hearing protection |
Fire refining |
Sulphur oxides, hydrocarbons, particulates |
Local exhaust ventilation, general area ventilation; PPE—hearing protection |
Electrolytic refining |
Sulphuric acid and metals from sludge |
Local exhaust ventilation, general area ventilation |
Lead reclamation
Raw materials purchased by secondary lead smelters may require processing prior to being charged into a smelting furnace. This section discusses the most common raw materials which are purchased by secondary lead smelters and feasible engineering controls and work practices to limit employee exposure to lead from raw materials processing operations. It should be noted that lead dust can generally be found throughout lead reclamation facilities and that any vehicular air is likely to stir up lead dust which can then be inhaled or adhere to shoes, clothing, skin and hair.
Automotive batteries
The most common raw material at a secondary lead smelter is junk automotive batteries. Approximately 50% of the weight of a junk automotive battery will be reclaimed as metallic lead in the smelting and refining process. Approximately 90% of the automotive batteries manufactured today utilize a polypropylene box or case. The polypropylene cases are reclaimed by almost all secondary lead smelters due to the high economic value of this material. Most of these processes can generate metal fumes, in particular lead and antimony.
In automotive battery breaking there is a potential for forming arsine or stibine due to the presence of arsenic or antimony used as hardening agents in grid metal and the potential for having nascent hydrogen present.
The four most common processes for breaking automotive batteries are:
The first three of these processes involve cutting the top off of the battery, then dumping the groups, or lead-bearing material. The fourth process involves crushing the entire battery in a hammer mill and separating the components by gravity separation.
Automotive battery separation takes place after automotive batteries have been broken in order that the lead-bearing material can be separated from the case material. Removing the case may generate acid mists. The most widely used techniques for accomplishing this task are:
Industrial batteries which were used to power mobile electric equipment or for other industrial uses are purchased periodically for raw material by most secondary smelters. Many of these batteries have steel cases which require removal by cutting the case open with a cutting torch or a hand-held gas powered saw.
Other purchased lead-bearing scrap
Secondary lead smelters purchase a variety of other scrap materials as raw materials for the smelting process. These materials include battery manufacturing plant scrap, drosses from lead refining, scrap metallic lead such as linotype and cable covering, and tetraethyl lead residues. These types of materials may be charged directly into smelting furnaces or mixed with other charge materials.
Raw material handling and transport
An essential part of the secondary lead smelting process is the handling, transportation and storage of raw material. Materials are transported by fork-lifts, front-end loaders or mechanical conveyors (screw, bucket elevator or belt). The primary method of material transporting in the secondary lead industry is mobile equipment.
Some common mechanical conveyance methods which are used by secondary lead smelters include: belt conveying systems that can be used to transport furnace feed material from storage areas to the furnace charring area; screw conveyors for transporting flue dust from the baghouse to an agglomeration furnace or a storage area or bucket elevators and drag chains/lines.
Smelting
The smelting operation at a secondary lead smelter involves the reduction of lead-bearing scrap into metallic lead in a blast furnace or reverberatory.
Blast furnaces are charged with lead-bearing material, coke (fuel) limestone and iron (flux). These materials are fed into the furnace at the top of the furnace shaft or through a charge door in the side of the shaft neat the top of the furnace. Some environmental hazards associated with blast furnace operations are metal fumes and particulates (especially lead and antimony), heat, noise and carbon monoxide. A variety of charge material conveying mechanisms are used in the secondary lead industry. The skip hoist is probably the most common. Other devices in use include vibratory hoppers, belt conveyors and bucket elevators.
Blast furnace tapping operations involve removing the molten lead and slag from the furnace into moulds or ladles. Some smelters tap metal directly into a holding kettle which keeps the metal molten for refining. The remaining smelters cast the furnace metal into blocks and allow the blocks to solidify.
Blast air for the combustion process enters the blast furnace through tuyères which occasionally begin to fill with accretions and must be physically punched, usually with a steel rod, to keep them from being obstructed. The conventional method to accomplish this task is to remove the cover of the tuyères and insert the steel rod. After the accretions have been punched, the cover is replaced.
Reverberatory furnaces are charged with lead-bearing raw material by a furnace charging mechanism. Reverberatory furnaces in the secondary lead industry typically have a sprung arch or hanging arch constructed of refractory brick. Many of the contaminants and physical hazards associated with reverberatory furnaces are similar to those of blast furnaces. Such mechanisms can be a hydraulic ram, a screw conveyor or other devices similar to those described for blast furnaces.
Reverberatory furnace tapping operations are very similar to blast-furnace tapping operations.
Refining
Lead refining in secondary lead smelters is conducted in indirect fired kettles or pots. Metal from the smelting furnaces is typically melted in the kettle, then the content of trace elements is adjusted to produce the desired alloy. Common products are soft (pure) lead and various alloys of hard (antimony) lead.
Virtually all secondary lead refining operations employ manual methods for adding alloying materials to the kettles and employ manual drossing methods. Dross is swept to the rim of the kettle and removed by shovel or large spoon into a container.
Table 3 lists exposures and controls for lead reclamation operations.
Table 3. Engineering/administrative controls for lead, by operation
Process equipment |
Exposures |
Engineering/administrative controls |
Vehicles |
Lead dust from roads and splashing water containing lead |
Water washdown and keeping areas wetted down. Operator training, prudent work practices and good housekeeping are key elements in minimizing lead emissions when operating mobile equipment. Enclose equipment and provide a positive pressure filtered air system. |
Conveyors |
Lead dust |
It is also preferable to equip belt conveyor systems with self-cleaning tail pulleys or belt wipes if they are used to transport furnace feed materials or flue dusts. |
Battery decasing |
Lead dust, acid mists |
Local exhaust ventilation, general area ventilation |
Charge preparation |
Lead dust |
Local exhaust ventilation, general area ventilation |
Blast furnace |
Metal fumes and particulates (lead, antimony), heat and noise, carbon monoxide |
Local exhaust ventilation, general area ventilation, work/rest regimen, fluids, isolation of noise source; PPE—respiratory protection and hearing protection |
Reverberatory furnace |
Metal fumes and particulates (lead, antimony), heat and noise |
Local exhaust ventilation, general area ventilation, work/rest regimen, fluids, isolation of noise source; PPE—respiratory protection and hearing protection |
Refining |
Lead particulates and possibly alloying metals and fluxing agents, noise |
Local exhaust ventilation, general area ventilation; PPE—hearing protection |
Casting |
Lead particulates and possibly alloying metals |
Local exhaust ventilation, general area ventilation |
Zinc reclamation
The secondary zinc industry utilizes new clippings, skimmings and ashes, die-cast skimmings, galvanizers’ dross, flue dust and chemical residue as sources of zinc. Most of the new scrap processed is zinc- and copper-based alloys from galvanizing and die-casting pots. Included in the old scrap category are old zinc engravers’ plates, die castings, and rod and die scrap. The processes are as follows:
Table 4 lists exposures and controls for zinc reclamation operations.
Table 4. Engineering/administrative controls for zinc, by operation
Process equipment |
Exposures |
Engineering/administrative controls |
Reverberatory sweating |
Particulates containing zinc, aluminium, copper, iron, lead, cadmium, manganese and chromium, contaminants from fluxing agents, sulphur oxides, chlorides and fluorides |
Local exhaust ventilation, general area ventilation, heat stress–work/rest regimen, fluids |
Rotary sweating |
Particulates containing zinc, aluminium, copper, iron, lead, cadmium, manganese and chromium, contaminants from fluxing agents, sulphur oxides, chlorides and fluorides |
Local exhaust ventilation, general area ventilation, work/rest regimen, fluids |
Muffle sweating and kettle (pot) sweating |
Particulates containing zinc, aluminium, copper, iron, lead, cadmium, manganese and chromium, contaminants from fluxing agents, sulphur oxides, chlorides and fluorides |
Local exhaust ventilation, general area ventilation, work/rest regimen, fluids |
Crushing/screening |
Zinc oxide, minor amounts of heavy metals, chlorides |
Local exhaust ventilation, general area ventilation |
Sodium carbonate leaching |
Zinc oxide, sodium carbonate, zinc carbonate, zinc hydroxide, hydrogen chloride, zinc chloride |
Local exhaust ventilation, general area ventilation |
Kettle (pot) melting crucible, reverberatory, electric induction melting |
Zinc oxide fumes, ammonia, ammonia chloride, hydrogen chloride, zinc chloride |
Local exhaust ventilation, general area ventilation, work/rest regimen, fluids |
Alloying |
Particulates containing zinc, alloying metals, chlorides; non-specific gases and vapours; heat |
Local exhaust ventilation, general area ventilation, work/rest regimen, fluids |
Retort distillation, retort distillation/oxidation and muffle distillation |
Zinc oxide fumes, other metal particulates, oxides of sulphur |
Local exhaust ventilation, general area ventilation, work/rest regimen, fluids |
Graphite rod resistor distillation |
Zinc oxide fumes, other metal particulates, oxides of sulphur |
Local exhaust ventilation, general area ventilation, work/rest regimen, fluids |
Magnesium reclamation
Old scrap is obtained from sources such as scrap automobile and aircraft parts and old and obsolete lithographic plates, as well as some sludges from primary magnesium smelters. New scrap consists of clippings, turnings, borings, skimmings, slags, drosses and defective articles from sheet mills and fabrication plants. The greatest danger in handling magnesium is that of fire. Small fragments of the metal can readily be ignited by a spark or flame.
Table 5 lists exposures and controls for magnesium reclamation operations.
Table 5. Engineering/administrative controls for magnesium, by operation
Process equipment |
Exposures |
Engineering/administrative |
Scrap sorting |
Dust |
Water washdown |
Open pot melting |
Fumes and dust, a high potential for fires |
Local exhaust ventilation and general area ventilation and work practices |
Casting |
Dust and fumes, heat and a high potential for fires |
Local exhaust ventilation, general area ventilation, work/rest regimen, fluids |
Mercury reclamation
The major sources for mercury are dental amalgams, scrap mercury batteries, sludges from electrolytic processes that use mercury as a catalyst, mercury from dismantled chlor-alkali plants and mercury-containing instruments. Mercury vapour can contaminate each of these processes.
Table 6 lists exposures and controls for mercury reclamation operations.
Table 6. Engineering/administrative controls for mercury, by operation
Process equipment |
Exposures |
Engineering/administrative controls |
Crushing |
Volatile mercury |
Local exhaust; PPE—respiratory protection |
Filtration |
Volatile mercury |
Local exhaust ventilation; PPE—respiratory protection |
Vacuum distillation |
Volatile mercury |
Local exhaust ventilation; PPE—respiratory protection |
Solution purification |
Volatile mercury, solvents, organics and acid mists |
Local exhaust ventilation, general area ventilation; PPE—respiratory protection |
Oxidation |
Volatile mercury |
Local exhaust ventilation; PPE—respiratory protection |
Retorting |
Volatile mercury |
Local exhaust ventilation; PPE—respiratory protection |
Nickel reclamation
The principal raw materials for nickel reclamation are nickel-, copper- and aluminium-vapour based alloys, which can be found as old or new scrap. Old scrap comprises alloys that are salvaged from machinery and airplane parts, while new scrap refers to sheet scrap, turnings and solids which are by-products of the manufacture of alloy products. The following steps are involved in nickel reclamation:
Exposures and control measures for nickel reclamation operations are listed in table 7.
Table 7. Engineering/administrative controls for nickel, by operation
Process equipment |
Exposures |
Engineering/administrative controls |
Sorting |
Dust |
Local exhaust and solvent substitution |
Degreasing |
Solvent |
Local exhaust ventilation and solvent substitution and/or recovery, general area ventilation |
Smelting |
Fumes, dust, noise, heat |
Local exhaust ventilation, work/rest regimen, fluids; PPE—respiratory protection and hearing protection |
Refining |
Fumes, dust, heat, noise |
Local exhaust ventilation, general area ventilation, work/rest regimen, fluids; PPE—respiratory protection and hearing protection |
Casting |
Heat, metal fumes |
Local exhaust ventilation, general area ventilation, work/rest regimen, fluids |
Precious metals reclamation
The raw materials for the precious metal industry consist of both old and new scrap. Old scrap includes electronic components from obsolete military and civilian equipment and scrap from the dental industry. New scrap is generated during the fabrication and manufacturing of precious metal products. The products are the elemental metals such as gold, silver, platinum and palladium. Precious metal processing includes the following steps:
Exposures and controls are listed, by operation, in table 8 (see also “Gold smelting and refining”).
Table 8. Engineering/administrative controls for precious metals, by operation
Process equipment |
Exposures |
Engineering/administrative controls |
Sorting and shredding |
Hammermill is a potential noise hazard |
Noise control material; PPE—hearing protection |
Incineration |
Organics, combustion gases and dust |
Local exhaust ventilation and general area ventilation |
Blast furnace smelting |
Dust, noise |
Local exhaust ventilation; PPE—hearing protection and respiratory protection |
Electrolytic refining |
Acid mists |
Local exhaust ventilation, general area ventilation |
Chemical refining |
Acid |
Local exhaust ventilation, general area ventilation; PPE—acid-resistant clothing, chemical goggles and face shield |
Cadmium reclamation
Old cadmium-bearing scrap includes cadmium-plated parts from junked vehicles and boats, household appliances, hardware and fasteners, cadmium batteries, cadmium contacts from switches and relays and other used cadmium alloys. New scrap is normally cadmium vapour bearing rejects and contaminated by-products from industries which handle the metals. The reclamation processes are:
Exposures in cadmium reclamation processes and the necessary controls are summarized in table 9.
Table 9. Engineering/administrative controls for cadmium, by operation
Process equipment |
Exposures |
Engineering/administrative controls |
Scrap degreasing |
Solvents and cadmium dust |
Local exhaust and solvent substitution |
Alloy smelting/refining |
Products of oil and gas combustion, zinc fumes, cadmium dust and fumes |
Local exhaust ventilation and general area ventilation; PPE—respiratory protection |
Retort distillation |
Cadmium fumes |
Local exhaust ventilation; PPE—respiratory protection |
Melting/dezincing |
Cadmium fumes and dust, zinc fumes and dust, zinc chloride, chlorine, hydrogen chloride, heat stress |
Local exhaust ventilation, general area ventilation, work/rest regimen, fluids; PPE—respiratory protection |
Casting |
Cadmium dust and fumes, heat |
Local exhaust ventilation, general area ventilation, work/rest regimen, fluids; PPE—respiratory protection |
Selenium reclamation
Raw materials for this segment are used xerographic copying cylinders and scrap generated during the manufacture of selenium rectifiers. Selenium dusts may be present throughout. Distillation and retort smelting can produce combustion gases and dust. Retort smelting is noisy. Sulphur dioxide mist and acid mist are present in refining. Metal dusts can be produced from casting operations (see table 10).
Table 10. Engineering/administrative controls for selenium, by operation
Process equipment |
Exposures |
Engineering/administrative controls |
Scrap pretreatment |
Dust |
Local exhaust |
Retort smelting |
Combustion gases and dust, noise |
Local exhaust ventilation and general area ventilation; PPE—hearing protection; control of burner noise |
Refining |
SO2, acid mist |
Local exhaust ventilation; PPE—chemical goggles |
Distillation |
Dust and combustion products |
Local exhaust ventilation, general area ventilation |
Quenching |
Metal dust |
Local exhaust ventilation, general area ventilation |
Casting |
Selenium fumes |
Local exhaust ventilation, general area ventilation |
The reclamation processes are as follows:
Cobalt reclamation
The sources of cobalt scrap are super alloy grindings and turnings, and obsolete or worn engine parts and turbine blades. The processes of reclamation are:
See table 11 for a summary of exposures and controls for cobalt reclamation.
Table 11. Engineering/administrative controls for cobalt, by operation
Process equipment |
Exposures |
Engineering/administrative controls |
Hand sorting |
Dust |
Water washdown |
Degreasing |
Solvents |
Solvent recovery, local exhaust and solvent substitution |
Blasting |
Dust—toxicity dependent upon the grit used |
Local exhaust ventilation; PPE for physical hazard and respiratory protection depending on grit used |
Pickling and chemical treatment process |
Acid mists |
Local exhaust ventilation, general area ventilation; PPE—respiratory protection |
Vacuum melting |
Heavy metals |
Local exhaust ventilation, general area ventilation |
Casting |
Heat |
Local exhaust ventilation, general area ventilation, work/rest regimen, fluids |
Tin reclamation
The major sources of raw materials are tin-plated steel trimmings, rejects from tin-can manufacturing companies, rejected plating coils from the steel industry, tin drosses and sludges, solder drosses and sludges, used bronze and bronze rejects and metal type scrap. Tin dust and acid mists can be found in many of the processes.
See table 12 for a summary of exposures and controls for tin reclamation.
Table 12. Engineering/administrative controls for tin, by operation
Process equipment |
Exposures |
Engineering/administrative controls |
Dealuminization |
Sodium hydroxide |
Local exhaust; PPE—chemical goggles and/or face shield |
Batch mixing |
Dust |
Local exhaust ventilation and general area ventilation |
Chemical detinning |
Caustic |
Local exhaust ventilation; PPE—chemical goggles and/or face shield |
Dross smelting |
Dust and heat |
Local exhaust ventilation, general area ventilation, work/rest regimen, fluids |
Dust leaching and filtration |
Dust |
Local exhaust ventilation, general area ventilation |
Settling and leaf filtration |
None identified |
None identified |
Evapocentrifugation |
None identified |
None identified |
Electrolytic refining |
Acid mist |
Local exhaust ventilation and general area ventilation; PPE—chemical goggles and/or face shield |
Acidification and filtration |
Acid mists |
Local exhaust ventilation and general area ventilation; PPE—chemical goggles and/or face shield |
Fire refining |
Heat |
Work/rest regimen, PPE |
Smelting |
Combustion gases, fumes and dust, heat |
Local exhaust ventilation and general area ventilation, work/rest regimen, PPE |
Calcining |
Dust, fumes, heat |
Local exhaust ventilation and general area ventilation work/rest regimen, PPE |
Kettle refining |
Dust, fumes, heat |
Local exhaust ventilation and general area ventilation, work/rest regimen, PPE |
Titanium reclamation
The two primary sources of titanium scrap are the home and titanium consumers. Home scrap which is generated by the milling and manufacturing of titanium products includes trim sheets, plank sheet, cuttings, turnings and borings. Consumer scrap consists of recycled titanium products. The reclamation operations include:
Controls for exposures in titanium reclamation procedures are listed in table 13.
Table 13. Engineering/administrative controls for titanium, by operation
Process equipment |
Exposures |
Engineering/administrative controls |
Solvent degreasing |
Solvent |
Local exhaust and solvent recovery |
Pickling |
Acids |
Face shields, aprons, long sleeves, safety glasses or goggles |
Electrorefining |
None known |
None known |
Smelting |
Volatile metals, noise |
Local exhaust ventilation and control of noise from burners; PPE—hearing protection |
Casting |
Heat |
PPE |
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