New Siemens electric arc furnace for steel-making cuts CO2 emissions by up to 30%; Tyasa incorporating first unit in new mill
Mexico-based steel-maker Tyasa is building a compact steel mill that incorporates a new electric arc furnace from Siemens that reduces CO2 emissions by up to 30% compared to conventional electric arc furnaces. The new system, which recovers energy from the hot exhaust gas, also reduces costs by around 20%. The Tyasa mill is scheduled to be completed by mid-2013.
|Rendering of the Simetal EAF Quantum furnace. Click to enlarge.|
Electric arc systems are particularly well suited for making steel from scrap iron. The electric arc heats the scrap metal to more than 1,500 degrees Celsius so that it melts. Besides scrap metal, other materials such as pig iron and direct reduced iron can also be used. However, the process consumes vast amounts of electricity, produces lots of carbon dioxide, and can lead to fluctuations in the stability of the power grid.
The new Simetal EAF Quantum furnace combines proven shaft furnace technology elements with new processes in order to reduce carbon dioxide emissions while at the same time saving energy and costs. Unlike a conventional electric arc furnace, it is not necessary to raise the roof and retract the electrodes in order to charge the furnace. The other benefit of charging via a shaft is that the scrap is preheated by the offgas of the melting process, which significantly reduces energy requirements.
Because the amount of scrap that is added is relatively low compared to the existing liquid steel, this process is referred to as flat-bath operation. It considerably reduces the strain on the furnace and lessens the repercussions for the power grid.
In combination with the automated offgas stream redirection system and a special hood to capture dust and offgases during charging, process emissions are considerably lower in the steel plant. This reduces the cost and size of the dedusting system and the canopy installation substantially.
In addition, the furnace has a new tilting concept for the lower shell as well as an optimized, patented tapping system. This enables the plant operator to achieve very short tap-to-tap times of around 36 minutes.
The new furnace has a tapping weight of 100 tons and a production capacity of around 1.2 million tons of different grades of steel per year.
Siemens has also developed another electric arc furnace specifically for use with direct reduced iron. Called the Simetal EAF FAST DRI, this furnace allows electricity to be used for heating the metal and makes it possible to feed direct reduced iron into the system during tapping. This shortens tap-to-tap times and reduces specific energy consumption. As a result, the productivity of a 150-ton furnace can be increased by around 15%.