One of Australia’s leading scientific research bodies is cooperating with a company in China to develop cleaner, more sustainable methods for the combined production of steel and cement.
The CSIRO has entered an agreement with the Beijing MCC Equipment Research & Design Corporation (MCCE) on the further development of a process called dry slag granulation (DSG), which uses the huge volume of waste material created by the steel manufacturing process to produce a greener form of cement.
The metal smelting process alone produces hundreds of millions of tonnes of molten slag each year, which is usually air-cooled in large pits before being employed for either landfill or road construction purposes.
DSG technology diverts this slag to a more productive end by converting it into a highly suitable feed ingredient for cement, generating fewer greenhouse gas emissions than conventional manufacturing processes.
The process entails the installation of a granulation chamber equipped with a spinning disc onto existing blast furnaces. This granulation chamber employs centrifugal force to separate the molten slag produced by the steel-making process into droplets.
The droplets are then exposed to air and solidified, resulting in the formation of a “glassy” granulated slag. This glassy slag can then be ground into a fine powder that is highly suited to cement production.
Combining the steel and cement manufacturing processes together in this fashion brings a raft of environmental benefits.
Chief amongst them is a marked reduction in greenhouse gas emissions related to the calcination process required for ordinary Portland cement.
The DSG process also generates large amounts of superheated air that can reach temperatures as high as 500 to 600 degrees Celsius, and be employed for other industrial processes onsite such as drying, heating and steam generation.
In addition to this, the dry nature of the process makes it cleaner and more efficient than water granulation, which by its very nature consumes large amount of water that creates a pollution hazard during its disposal.
DSG is also free of other disadvantages associated with water granulation, such as the formation of a hazardous acid mist and the need to dry the resulting granulated slag.
According to Jonathan Law, CSIRO director of the Minerals Down Under Flagship, the process could be a key game-changer for both steel and cement production, particularly in China, which accounts for 60 per cent of the world’s annual output of 300 million tonnes of iron blast furnace slag.
“The benefits from wide uptake of DSG technology on blast furnaces will be profound in helping the global industry to reduce water and energy use and greenhouse gas emissions while sustaining metal production,” he said.
Law estimates that full commercialization and adoption of DSG technology by the steel industry could save as much as 60 billion litres of water, 800 petajoules of heat energy and 60 million tonnes of greenhouse gas emissions each year.
The agreement with MCCE is potentially a huge step forward in fostering the commercial adoption of DSG technology. Under the agreement, the Chinese company is called upon to demonstrate the technology at an industrial scale, and deploy it commercially within China and potentially overseas.
The agreement follows over a decade of work on DSG Technology by the CSIRO in collaboration with industry partners such as BlueScope and Arrium, involving the development of prototype plants at both the small and large ends of the scale.