From our Ore to Your Door - Episode 17: Deadburned Magnesia Production

QMAG’s specially-designed vertical shaft kilns are an important part of our production process that leads to high-quality products.
Our kilns are used to convert reactive calcined magnesia to a significantly less reactive form of magnesia – dead burnedmagnesia (DBM). This name gives away the process – which involves heating the previously briquetted fine calcined magnesia to high temperatures (in excess of 2000ºC) where the reactivity is reduced.
The highly energy-efficient vertical shaft kilns used at QMAG are over 10m high. Green (unfired) briquettes are fed into the top of the kiln at a controlled rate. As the briquettes travel downwards through the kiln, their temperature increases thanks to 20 natural gas and air burners per kiln. These burners drive the sintering process.
During sintering, the small MgO crystals present in the calcined magnesia begin to coalesce, and large crystals of periclase (MgO) are formed. This is a physical process as well as a chemical one, and by the time each briquette reaches optimum density it will be almost half its original size.
As the briquettes reach the bottom of the kiln, they are met by large volumes of air in the product discharge area. This helps to cool them, while also providing additional air for combustion that’s still happening above.

WHAT MAKES OUR PROCESS DIFFERENT?

Our vertical shaft kilns are lined with multiple layers of different refractory materials to provide production consistency, long service life, and excellent energy efficiency. These layers are all contained within a steel shell, which has to be airtight due to the kiln’s pressurization.
We operate our kilns continuously, and they can produce product 24/7 for over nine months before they require scheduled maintenance.
To ensure extremely consistent density and periclase crystal sizes, our sintering process is tightly controlled. Our deadburned magnesia goes to refractory companies all over the world, and our DBM’s specific physical properties, like density and crystal size, are highly valued by the refractory industry.
Studies over the past 40 years have shown the clear relationships between refractory performance and high density, large crystal size and the correct chemical composition.
QMAG’s unique cryptocrystalline magnesite deposit is perfectly suited to the production of DBM as the small magnesite crystal structure is easier to sinter than many other magnesite deposits around the world. This means our DBM grades are highly consistent and are widely recognized to give the best performance.