The reuse of high pressure flue gas from the top of the blast furnace is reducing ArcelorMittal’s carbon footprint – and our energy bill!
Over the past few years, ArcelorMittal has been perfecting the installation of Top Recovery Turbines (TRTs) to generate energy. TRT technology utilises the high-pressure gases (known as flue gases) which collect at the top of the blast furnace to drive very efficient electricity generators. Installed at just four sites so far, the TRT technology is already reducing ArcelorMittal Flat Carbon Europe’s (FCE) energy bills by more than 3% a year. Implementation of TRT is part of ArcelorMittal’s ongoing commitment to research and develop improvements to our processes in order to ensure our technological superiority in the use of energy and raw materials, reduce manufacturing costs, improve quality and minimise our environmental impact.
While the economic benefits of installing TRT are considerable, the environmental advantages are also an important consideration. ArcelorMittal’s current production of energy from TRT reduces CO2-equivalent emissions by around 176,000 tonnes/year. That equates to removing more than 35,000 cars from the road. TRT is also very sustainable as there are zero emissions from the process of producing electricity using this technology.
The TRT turbine generates energy by exploiting a known property of all gases – that they expand as their pressure drops. Dry and wet scrubbing is used to remove fine particulates from the flue gas as it leaves the blast furnace. At this point the pressure is between 1.6 and 2.5 bar. During the scrubbing process the gas cools, and its pressure drops about 0.3 bar. That needs to be reduced to 0.1 bar for the gas pipe network. The most energy efficient way to do this is to lead the gas through the turbine where it drives a generator to produce electricity.
There is no influence on the operation of the blast furnace and the flue gas is not consumed. As blast furnace gas is very combustible, it is normally utilised in other parts of the plant to generate heat or energy for other processes. With the TRT system installed, the flue gas effectively generates energy twice – once in the turbine and again when it is burnt for its usual purpose. For more detail on how flue gases are utilised in ArcelorMittal’s Gent mill, see ‘Energizing steelmaking!’ in the ay 2012 edition of Update.
TRT is a proven technology and there is little risk in its installation or operation. If he TRT system fails for any reason, the expanding gas is accommodated in the existing scrubber. This is normal in blast furnaces which do not have a TRT system installed.
Each TRT has the same capacity as three to four land-based wind turbines. To date TRT systems have been installed in six blast furnaces at four of our sites and are generating more than 482 Gigawatt hours
(GWh) of electricity each year.
ArcelorMittal FCE’s energy bill has dropped as a result. TRT also provides ArcelorMittal with security over the sustainability of our long-term energy supply, and reduces our exposure to rising energy prices.
ArcelorMittal is actively looking for energy partners to help us increase the amount of electricity we produce from TRT. An additional eight blast furnaces in Europe have been identified as being suitable for conversion. Together they have the potential to produce another 475 GWh/year using existing TRT technology.
ArcelorMittal hopes that the TRT technology can be rolled out to its blast
furnaces across the world. While Europe is leading in the introduction of TRT, significant efforts are already underway at our plants in Brazil and South Africa. With wider implementation of the TRT technology, ArcelorMittal will be able to sustainably secure even more of our energy
TRT is very sustainable as there are zeo emissions from the process of producing electricity using this technology. The process is 100% green.
We are still actively looking for energy partners to help us increase the amount of electricity we produce from Top Recovery Turbines.