Sugar Mill Demolition: Boilers, Bagasse and a Century of Asbestos

Queensland and northern NSW have been closing and consolidating sugar mills for a generation, and most of the ones still standing were built between the wars and extended ever since. A mill is a boiler house, a steam turbine hall, a crushing train, a process house full of vessels and a stack, all under one roof, with bagasse dust in every corner and a century of asbestos in the insulation. Demolishing one is industrial plant demolition with a biological fire risk on top.

This is how we approach sugar mill demolition, what will hurt you, and the mistakes that cost mill owners most.

What you are actually dealing with

• Boilers, often several generations side by side, with refractory, asbestos lagging on steam and condensate lines, and bagasse feed systems. Boiler stacks in brick, concrete or steel.
• Steam turbines and alternators, gearboxes and the high pressure steam range connecting them. Heavy, oil filled and sitting on deep foundations.
• The crushing train: shredders, mill rollers and the cane carriers feeding them, with hydraulics, gearboxes and drive motors. Mill rollers are large castings and worth money, but only once they are out.
• The process house: clarifiers, evaporators, vacuum pans, crystallisers, centrifugals and tanks, all in stainless, mild steel or copper, with the remains of juice, syrup and molasses in them.
• Bagasse. Dry bagasse dust is a fire and explosion risk in enclosed spaces and it is in the roof trusses, the boiler house and the conveyors.
• Molasses storage, fuel oil tanks for boiler light up, lime and chemical stores for juice treatment, and a cooling water system with its own tower or spray pond.
• Asbestos sheet roofing and cladding across a very large footprint, lead paint on structural steel, and in older mills asbestos in gaskets and valve packing throughout.
• The ground: hydrocarbons around fuel and oil systems, sugar affected soils that smell for years, and often a mill mud or ash dump nearby.

Step one: decide what is sold and what is scrapped

Mill rollers, turbines, centrifugals, pans and stainless vessels have a resale market in the sugar industry here and overseas. Whether they are being recovered intact or cut for scrap changes the sequence, the cranage and the price. Decide early, with the owner's salvage list in hand.

Step two: survey the lot

Hazardous materials survey across the whole footprint, with the boiler house and steam range given special attention because that is where the friable asbestos is. Residue sampling in process vessels and tanks. Transformer oil testing for PCBs in the old switchroom. Soil investigation around fuel, oil and molasses storage. Bagasse dust assessment in the roof structure and enclosed conveyors.

Step three: make it safe

Electrical isolation at the mill's incoming supply and every switchroom. Steam, fuel oil, compressed air and process lines isolated, drained and purged. Vessels emptied, washed and the washings disposed of under trade waste rules, because molasses washings have a very high oxygen demand and cannot go to a creek. Bagasse dust removed from enclosed areas before any hot work. Legionella treatment of the cooling system.

Step four: asbestos and lead first

Lagging on the steam range and boilers comes off under the asbestos licence, in enclosures where friable, before any demolition starts in those areas. Roofing and cladding are removed under Class B controls across the whole mill. Lead paint on steel is managed through controlled cutting rather than open flame.

Step five: salvage, then demolish

Salvage items are isolated, disconnected and craned out intact first. Then the process house, crushing train and turbine hall come down with excavators and shears, the boiler house follows once the boilers are cut and the refractory is classified, and the stack goes by whichever method the site allows, usually top down with remote controlled machines or high reach because mills are close to towns. Steel is graded and credited; stainless and copper are separated because they are worth several times mild steel.

Step six: the ground

Hydrocarbon affected soil around tanks and oil systems is excavated and classified. Sugar affected ground is assessed; it is a nuisance rather than a hazard but owners want it gone. Old mill mud and ash dumps need their own assessment before the site can be sold.

What not to do

• Do not start hot work in the boiler house or conveyors before the bagasse dust is removed. Mills burn.
• Do not cut the steam range before the lagging has been sampled and removed. That is where the friable asbestos is.
• Do not wash vessels to the drain. Molasses washings will kill a creek.
• Do not scrap the rollers and turbines before checking the resale market. They are worth more whole.
• Do not let a scrap merchant run the job. The steel is a fraction of the liability.

Approvals and notifications

Licensed demolition notification to Workplace Health and Safety Queensland or SafeWork NSW, licensed asbestos removal notification, council demolition consent, trade waste approval for vessel washings and basin water, EPA involvement for contaminated land, and heritage approval where the mill or its stack is listed, which in old sugar towns is common.

Who should be doing this

A contractor that holds the Class A asbestos licence and the demolition licence in both Queensland and NSW, owns its remote controlled and high reach plant, and can put a large crew into a regional town for months. Perfect Contracting carries out industrial plant demolition across Queensland and NSW from its Brisbane and Sydney bases and travels for the right project. Read more about our plant decommissioning and Queensland demolition work, or send us the details.