Smelter Demolition and Decommissioning: Decontaminate First, Then Demolish

A smelter is the hardest kind of industrial demolition there is, because the hazards are in the materials rather than the structure. Aluminium potrooms carry spent pot lining, which is a listed hazardous waste. Lead and zinc smelters leave heavy metal dust in every cavity and the ground under them. Copper and nickel smelters leave arsenic and sulphur compounds in flues and baghouses. The steel is the easy part. The decontamination and the waste are the job.

This is the order we work in on smelter and metallurgical plant demolition, what will hurt you, and the mistakes that turn a scrap job into a decade of remediation.

What you are actually dealing with

• Potrooms and pot lines in an aluminium smelter: hundreds of steel shells lined with carbon and refractory that has absorbed fluoride and cyanide over its life. That spent pot lining is regulated waste in every state.
• Furnaces, converters and launders in copper, lead, zinc and nickel plants, with refractory brick contaminated by the metal they processed.
• Baghouses, electrostatic precipitators, flues and stacks holding fine metal rich dust, arsenic in copper and gold circuits, lead in lead and zinc circuits.
• Casthouses with molten metal handling plant, gas fired holding furnaces and their fuel systems.
• Rectifier yards and switchyards with transformers, PCB risk in older equipment, and very high current busbars.
• Asbestos in insulation, gaskets, potroom roofing and cladding on anything built before 1990, and refractory ceramic fibre in newer linings.
• Contaminated ground under the whole footprint, often with fluoride, metals and hydrocarbons together.

Step one: decide what the end state is

Smelter sites are rarely cleared for nothing. The end use decides how far the remediation goes and therefore how the demolition is sequenced. A site heading for industrial reuse keeps slabs and roads; a site heading for anything more sensitive loses them and the ground beneath. Agree this with the owner and the regulator before pricing, because the difference is measured in years as well as dollars.

Step two: characterise everything

Hazardous materials survey for asbestos, SMF, RCF and lead paint. Process residue sampling in every vessel, flue, duct and baghouse. Spent pot lining inventory by cell. Transformer oil testing for PCBs. Soil and groundwater investigation across the footprint. The waste classification that comes out of this drives the method, the disposal cost and the program. It is the most valuable money spent on the job.

Step three: isolate and make safe

Electrical isolation at the rectifier yard and every switchroom, with the busbars proven dead. Gas, fuel and compressed air isolated and purged. Molten metal plant confirmed cold and empty. Process water and effluent systems drained and the liquids classified. Only then does anyone open a vessel.

Step four: decontaminate before you demolish

This is where smelters differ from almost everything else. Flues, ducts, baghouses and precipitators are cleaned of dust under controlled conditions, with the dust captured and classified. Spent pot lining is removed cell by cell and stored or shipped under its waste licence. Refractory is stripped and classified by what it was exposed to. Asbestos and SMF come out under the asbestos licence. Lead paint is managed through controlled cutting. When the structure is finally clean, it is just steel and concrete.

Step five: take the structure down

Potrooms are long, repetitive steel buildings and come down efficiently with high reach excavators and shears once the pots are out. Furnaces and converters are heavy castings and plate, cut and craned in sections. Stacks are taken down by whichever of the methods suits the site: top down with remote controlled machines, high reach, or a controlled fell where there is room. Rectifier yards are dismantled with the transformers removed intact for proper disposal.

Step six: the ground

Under a smelter the ground carries the history of the plant. Fluoride and cyanide under potrooms, metals under baghouses and stockpiles, hydrocarbons under fuel and oil systems. Remediation is a project in itself, usually run as a staged excavate, classify, treat or dispose program with validation at the end. Planning it alongside the demolition saves a second mobilisation and lets clean concrete and steel be processed on site.

What not to do

• Do not let anyone cut a flue, duct or baghouse before the dust has been sampled and removed. That dust is the hazard.
• Do not treat spent pot lining as rubble. It is regulated hazardous waste with its own transport and disposal chain.
• Do not mix waste streams. One contaminated load reclassifies everything it touches.
• Do not start demolition before the remediation plan exists. The order of works depends on where the contamination is.
• Do not sell the steel to a scrap merchant to run the job. The steel is worth a fraction of the liability.

Approvals and notifications

Licensed demolition notification to the state regulator, licensed asbestos removal notification, hazardous waste tracking for every regulated load, EPA involvement for contaminated land and for on site treatment or containment, and usually a site specific environmental management plan agreed before works start. For a major smelter closure the regulator will expect a staged plan with hold points.

Who should be doing this

A contractor that holds the Class A asbestos licence, the demolition licence and the waste transport licence in its own name, owns its high reach and remote controlled plant, and runs remediation as a core service rather than a subcontract. Perfect Contracting carries out industrial demolition, plant decommissioning and soil remediation across Australia from its Sydney and Brisbane bases. Read more about industrial demolition, plant decommissioning and site remediation, or send us the details.