HIsarna process

HIsarna process is a direct reduced iron process of iron making in which iron ore is converted almost directly into liquid iron. The name 'HIsarna' is a combination of the old Celtic word for iron, "Isarna" and the name of the vessel "HIsmelt". HIsarna process combines two process units: the Cyclone Converter Furnace (CCF) for ore melting and pre-reduction and a Smelting Reduction Vessel (SRV) where the final reduction of iron ore to liquid iron is carried out. The process eliminates iron ore agglomeration into pellets or sinter and the production of coke essential in a blast furnace process. The CCF part of the HIsarna process was developed by Tata Steel in IJmuiden and the melt reduction vessel, was originally developed by Rio Tinto.

Development

In 2004, a group of European steel companies, with the support of the European Union, started the Ultra-Low CO2 Steelmaking (ULCOS) project. The objective of the project was to identify technologies that will reduce CO₂ emissions per tonne of steel by 50% by 2050. In 2007, Tata Steel, Rio Tinto and ULCOS began actively collaborating to develop this coal-based smelting reduction process. The HIsarna pilot installation was built on the Tata Steel Netherlands site in 2010. Since the first trial campaigns in 2011, several tests have been carried out on the installation. In 2012, Tata Steel produced liquid pig iron using the technology in a stable process for a longer period of time. Later, in 2013, steel was made for the first time using this liquid pig iron. In 2016, the pilot plant was adapted for long-term tests in continuous operation. The process has been demonstrated to be stable and working successfully. In 2018, the installation was merged to became part of the main production line and the fifth pilot campaign was successfully concluded in 2019.

The Method

HIsarna process reactor (Source: IspatGuru)

HIsarna consists of a reactor maintained at a temperature above the melting point of iron throughout, nearly 1200 °C. A layer of liquid pig iron is then poured into the melting vessel to start the process. The injected iron ore immediately melts and is converted into liquid hot metal. The high temperature of the process gases in the melting vessel is further increased in a cyclone created at the top of the reactor by the addition of pure oxygen. The oxygen now reacts with the carbon monoxide present in the reactor. The turbulence in the cyclone helps the hot gas to melt the iron ore, as and when it is injected at the top of the vessel. The molten iron ore then drips to the bottom of the vessel, where powdered coal is injected The powdered coal reduces the iron ore, creating  liquid hot metal, which can then be drained off at the bottom of the vessel. The Tata Steel Ijmuiden pilot plant has a capacity to produce 8 tons of hot metal per hour (60,000 tons per year).

Advantages

HIsarna helps in reduction of energy consumption and CO₂ emissions by at least 20% and in the reduction of emission other gases like hydrogen, sulphur dioxide and nitrogen oxide. The process is relatively more efficient than current process, as it eliminates the need for pre-processing of iron ores into pellets and sinter and metallurgical coal to coke. This further reduces emissions, energy consumption, and cost of production. Finally, the HIsarna process can utilise much wider range of iron ore and coal grades. With this high quality steel can be produced from cheaper and easily accessible raw materials.

Future development

Further testing and development of the technology is being carried out in collaboration with ArcelorMittal, Thyssenkrupp, Voestalpine and technology supplier Paul Wurth. The next stage is to design, build and test an industrial-scale pilot plant, for demonstration of commercial viabillity of the technology. Tata Steel further plans to build a second larger test plant in India. Tata Steel aims to have a HIsarna factory on an industrial scale in IJmuiden by 2030.