Some good news about the environment from Graham Brown ~
Some good news at last! Our Commonwealth Scientific, Industrial and Research Organisation (CSIRO) has developed new technology for harvesting the waste from steel production and the process is being trialled for commercial use in China.
The process reduces water use and greenhouse gas emissions in the processing of blast furnace waste into material for use in cement.
Steel making is one of the largest industries in the world and over 300 million tonnes of blast furnace waste (slag) per year is a by-product of this. China produces over 60%.
One of the current methods of disposal of the slag is to dump it on the ground. This is wasteful because a gigajoule of heat is lost for every tonne and it can be used in cement manufacture. The slag must be converted to small granules, however. If it is attempted to convert it into a granulated form using water it requires 1000 litres per tonne of slag and this is a large environmental cost.
CSIRO’s method of “dry slag granulation” (click this link for more) which involves pouring molten slag onto a disc spinning at high speed atomises the slag into small granules which solidify as they travel through the air. These are collected in a receptacle surrounding the disc and are “quenched” and dried using air. This results in granules ideal for cement production. The heated air is extracted and can be used for on-site drying, preheating and team generation which is a huge saving of energy.
The benefits will be saving 60 billion litres of water, 800 PJ (Petajoules) of heat energy and 60 million tonnes of greenhouse gas emissions per year! These savings are equivalent to 14% of Australia’s energy use and 10% of our greenhouse gas emissions each year.
Source: Engineers Australia June 2015.