How to decommission and demolish a cement plant safely in Australia

A cement works is one of the hardest industrial sites to demolish well. It is tall, it is heavy, it is full of fine alkaline dust, its silos hold material that has set like rock, and if it was built before the 1990s there is asbestos in more places than the survey will find on the first pass.

This is how we approach one. It is written for asset owners, plant managers and the consultants advising them, and it is deliberately blunt about the things that go wrong.

What is on a cement plant site

• Quarry crushing and raw material handling. Crushers, stackers, reclaimers and kilometres of conveyor.
• Raw mill and blending silos. The first of many silos.
• The preheater tower. Often the tallest structure on site, a concrete or steel frame carrying cyclones, ducts and platforms at heights most demolition crews never work at.
• The rotary kiln. A long steel shell lined with refractory brick, sitting on piers, with a burner, a cooler and a bypass system.
• Clinker storage and cement mills. More silos, more mills, and the heaviest single castings on the site.
• Dust collection. Baghouses and electrostatic precipitators on every process stream, full of fine dust.
• Coal or alternative fuel handling. Coal mills and storage carry a dust explosion risk that survives the shutdown.
• Packing plant, load out, workshops, laboratory, substations and offices.

Step one: settle the end state before anyone touches anything

Partial decommissioning of one line while the rest keeps producing is a completely different job from clearing the whole site for redevelopment. On a live site every isolation has to be proven against a plant that is still running next to it, and the sequence is driven by production, not by demolition logic. We have written about sequencing demolition inside a shutdown separately, and it applies here in full.

Step two: the investigation phase is longer than you think

Hazardous material survey, and then a second one. Older cement plants carry asbestos in gaskets, insulation, kiln seals, refractory backing, brake linings, switchboards, roof and wall sheeting, and in places that only become visible once demolition starts. Budget for a second survey during the works. Refractory brick from older kilns can contain chromium, and refractory ceramic fibre insulation has its own handling requirements.

Dust. Cement and kiln dust is fine and alkaline. It burns skin and eyes, it is a respiratory hazard, and bypass dust from the kiln system is a waste stream that has to be classified in its own right. Every baghouse, precipitator, duct and hopper is full of it.

Silos. Assume every silo has set material in it, on the walls, in the cone and bridged over the outlet. What looks like an empty silo from the top hatch is not. This is the single most dangerous thing on the site and it is dealt with from outside, never by sending a person in. Our note on silo cleaning without entry covers why.

Structure. Preheater towers and kiln piers were designed for the loads they carry in operation. Once the kiln shell is removed, or once a section of tower is cut, the load paths change. A structural engineer looks at the demolition sequence before it is priced, not after.

Ground. Fuel storage, workshops, oil stores and decades of dust fallout. A contamination assessment before the slabs come up.

Step three: isolate, then decontaminate

Isolation. Power to every drive, high voltage to the precipitators, gas and fuel to the burner, compressed air, water, and the coal handling system. Positive isolation, locked, tagged and proven. On a live site, tied into the plant's own permit to work system rather than run alongside it.

Dust removal comes before demolition, not after. Baghouses, precipitators, ductwork, hoppers and the kiln system are vacuumed out under controls, with the dust classified and removed as a waste stream. Knocking down a structure with the dust still in it turns the whole site and its neighbours into the exposure zone.

Refractory. Comes out of the kiln and preheater under respiratory controls, is classified, and goes to the right facility. We have covered refractory removal planning in detail.

Asbestos. Licensed removal, regulator notified before it starts, licensed supervisor on site for friable work, air monitoring and clearance before the area is released. Perfect Contracting holds a Class A friable asbestos licence.

Coal system. Cleared of all material and cleaned before any hot work happens anywhere near it. Coal dust does not care that the plant is shut.

Step four: the demolition sequence

• Height first. The preheater tower and the tall silos are the governing structures. Anything over fifteen metres is licensed demolition work in New South Wales, and Queensland has its own notification requirements. High reach machines, controlled cutting and staged lowering, never a pull over.
• The kiln shell. Heavy sections cut and lifted to a plan, with the piers and the cooler taken in an order the engineer has signed.
• Silos. Set material removed from outside first, then the shell brought down in a controlled sequence. A silo with material still hung up in it is a silo that can fail during demolition.
• Mills and castings. Some of the heaviest single items in Australian industry. Lift plans, not luck.
• Steel recovery. A cement works contains an enormous tonnage of structural steel and it is separated at the machine and recovered. That recovery is a significant part of what makes the job affordable.
• Concrete. Crushed on site and reused as fill or road base where it is clean.

We do not use explosives. On a site this close to dust, height and structural uncertainty, controlled mechanical demolition is the method.

Step five: the ground and the handover

Slabs, footings and the kiln piers come out. Contaminated ground around fuel stores, workshops and dust fallout areas is excavated, classified, removed and validated by sampling. If the site is heading for redevelopment, the validation report is the document the buyer's consultant reads first.

What not to do

• Do not send anyone into a silo. Not to clear it, not to inspect it, not on a harness. The material will move.
• Do not demolish with the dust still in the system. Vacuum first. Always.
• Do not trust one hazardous material survey on a plant built before the 1990s. There is more, and it is behind what the surveyor could not open.
• Do not cut the kiln or the tower without an engineer's sequence. The structure that stood for fifty years was carrying loads you are about to remove.
• Do not do hot work anywhere near the coal handling system until it has been cleared and cleaned.
• Do not let refractory, bypass dust or asbestos into a general waste load. The regulator holds the generator of the waste responsible, and the generator is the site owner.
• Do not price it from a site walk. The plant that is standing is not the plant you will be demolishing once the surveys come back.

Approvals

Local consent for demolition. Notification to the state regulator for licensed asbestos removal and for licensed demolition work. Environmental approvals where dust, noise and contaminated land are involved, and there will be a community around the plant that has lived with it for decades and will have a view. Start the approvals with the investigation, not after it.

Who should be doing this

A contractor with the asbestos licence, the demolition licence and the waste transport licence in their own name, their own high reach and remote demolition plant, and a track record on industrial process plant rather than buildings. The hard parts on a cement works are not the demolition. They are the silos, the dust, the asbestos and the sequence, and a contractor who subcontracts those out has subcontracted the job.

Perfect Contracting works on plant decommissioning and industrial demolition across New South Wales and Queensland and travels for the right project. If you have a cement works or a single line coming to the end of its life, call 02 8015 6345 or read more about our plant decommissioning work.