Smelter Swelter

About 65% of North America’s aluminum is being recycled. Although aluminum is less than one per cent of the municipal solid waste stream, it remains one of the most valuable recyclable materials.

Used aluminum beverage cans remain the most recycled item in Canada and the U.S., but other types of aluminum, such as siding, gutters, storm window frames and lawn furniture, can also be recycled. Aluminum has a high market value and continues to provide an economic incentive to recycle.

Recycled materials such as aluminum also provide manufacturers with valuable feedstock. For example, recycled aluminum cans are used to make new cans. In fact, nearly 55% of a new aluminum can is made from recycled aluminum.

Here are some more facts about aluminum:

* Discovered in the 1820s, aluminum is the most abundant metal on earth.

* Twenty years ago it took 19 aluminum cans to weigh one pound, but today, aluminum beverage cans are lighter and it takes 29 cans to weigh a pound.

* Every minute of every day, an average of 123,097 aluminum cans are recycled. Today, the national average of aluminum can recycling is two out of every three cans.

* Tossing away an aluminum can wastes as much energy as pouring out half of a can’s volume of gasoline.

* Making new aluminum cans from used cans takes 95% less energy; 20 recycled cans can be made with the energy needed to produce one can using virgin ore.

* Recycling one aluminum can saves enough energy to keep a 100-watt bulb burning for almost four hours, or enough to run a television for three hours.

Safety concerns

As evidenced by the injury/illness statistics gathered by The Aluminum Association Inc., aluminum plants are relatively safe, healthy workplaces. However, the principal hazards encountered in the aluminum industry arise from the handling of molten metal.

The hazards of producing and handling of molten metal are well recognized and the industry has a number of programs to better understand and control the risks of burns and explosions.

Molten substances and water

Under certain conditions, contact between molten substances and water can result in an explosion. While millions of kilograms of molten aluminum are produced and handled every day without incident, explosions do occur. Because of the chemical reactivity of aluminum, an explosion, when it does occur, can be violent.

To address the explosion issue, safety procedures have been developed and implemented, guidelines and training aids prepared and distributed, and a number of international workshops and conferences held to provide pertinent information to those in need of it. These efforts are continuing and, while explosions have not been eliminated, the industry has made considerable progress in better protecting its employees.

Severe explosions could also take place when charging scrap into a remelt furnace. In particular, contamination of the charge was suspected in many of the explosions that have occurred from this activity.

Awareness of the potential hazards of scrap contamination is important. Guidelines for scrap receiving and inspection have been prepared, and a scrap rejection notification program should be implemented by every recycler.

Sow charging is the second leading cause of furnace explosions. A sow is an ingot weighing from 317 kg (700 lb) to more than 900 kg (2,000 lb) that has been cast in a steel mold. At times, solidification of the ingot leaves a shrinkage cavity below the surface. If water enters the cavity during storage and is not completely driven off by preheating and/or sectioning, an explosion can occur when the sow is charged into the furnace heel of molten metal. The violence is greatest when the sow explodes under molten metal.

In 1998, the Aluminun Association published guidelines for sow casting and charging, based on these efforts and company experience.

Protective clothing

Burns from a molten metal incident are often the result of employees’ clothing being set on fire from molten metal splash. While the aluminum industry has not eliminated the occurrence of molten metal explosions, it has made considerable progress in protecting its employees.

The Aluminum Association evaluated fabrics for exposure to molten metal and bath splashes. These fabrics resist ignition from molten metal without giving rise to discomfort or heat stress to the employees wearing them.

Since molten aluminum handling is a potentially explosive process, a Pre-Start Health and Safety Review, as mandated by Section 7 of Ontario Occupational Health and Safety Act, is required in Ontario. Under this regulation, a professional engineer specializing in this area must review the process and issue a report. This report must be given to the Joint Health and Safety Committee before a molten metal process becomes operational.

Simon Fridlyand, P.Eng., is president of S.A.F.E. Engineering, a Toronto-based company specializing in industrial health and safety issues and compliance. He can be reached simonf@safeengineering.ca. For more information, visit www.safeengineering.ca.