Expert Opinion: Green hydrogen generation essential for decarbonising ironmaking

• China focussing on fossil-free hydrogen production
  
  
• Sustainability concerns driving innovation in industry
  
  
• Policy framework required to ensure cheap hydrogen availability
  
  

China, the world's top steel producing country, has already announced its carbon peak and carbon neutrality goals even as it seeks to find an alternative to metallurgical coal-based blast furnace ironmaking. Policymakers in that country believe that mass hydrogen production through renewable electricity and direct reduced iron (DRI) production through green hydrogen are absolutely essential to decarbonise ironmaking, said Praveen Chaturvedi, VP and Head, Sales Upstream India, Metals Division, Tenova, during a session held recently as part of SteelMint's ENGAGE 2.0 webinar series.

So, as China takes rapid steps towards hydrogen-based DRI, India needs to ponder how long it might take to switch over to greener methods of sponge iron production, the expert observed.

Hydrogen DRI

The world's top steel producer Baosteel is going ahead with its 1 million tonne (mnt) hydrogen-based DRI plant and has announced its target of achieving carbon neutrality by 2050 - 10 years ahead of China's zero-carbon target - based on technologies supplied by Tenova and Danieli.

HBIS, the world's third-largest steel producer, set up the first hydrogen-based DRI plant in China, with a capacity of 550,000 tonnes (t) per year. This shows that China is seriously considering hydrogen-based DRI as the safest and shortest route to sustainability. On its part, Tenova has implemented even 100% hydrogen-based DRI projects in Europe before the technology reached Chinese shores. Hydrogen is indeed the 'fuel of the future'.

Smart carbon & total avoidance

Green hydrogen obtained through splitting of water - electrolysis - can replace carbon monoxide as the reducing agent, the sole source of emissions in ironmaking. "The transition from 'smart carbon' use involving carbon capture, utilisation and storage to 'carbon direct avoidance' will necessarily involve an intermediate stage with natural gas or syngas or biogas as reductant, or even blue hydrogen, with embedded carbon capture," Chaturvedi observed.

Green hydrogen can be obtained from electrolysis and can be used to reduce the iron oxide in ironmaking. "The aim is to move from carbon to hydrogen and this is called decarbonisation, but it cannot be done in a single attempt; rather it requires various steps," the expert said.

Electrolysers

For carbon-free hydrogen generation there are different electrolyser technologies such as the Proton Exchange Membranes (PEM) and Atmospheric Alkaline Electrolysers (AAE), with units already in operation for high purity hydrogen (H2) and power consumption ranging from 4.8 to 3.8 kW/Nm3 of H2.

High Temperature Electrolysers (HTE), currently at a smaller scale, use steam and their power consumption is estimated at 3.6 kW/Nm3 of H2. Currently, larger PEM and AAE modules are in the range of 4,000 Nm3 of H2, sufficient for operation of a DR module of about 40,000 - 50,000 t/year, depending on the availability of alternate fuel.

Replication of available modules will be proportionally required for larger DR plants.

Towards green DRI

The steelmaking process based on conventional ironmaking route, DRI and EAF using natural gas can also adopt hydrogen, if available, which could replace methane. The main thrust should be on renewable energy whether wind or solar.

The transition to 'carbon direct avoidance' would necessarily mean working towards green DRI powered by hydrogen produced through renewable sources.

However, adopting hydrogen for a hard-to-abate sector such as steel would require policy enablers such as large-scale availability and cost reduction, easy transportation and storage facilities, policy formulation as regards a pan-India carbon emissions trading market and marked preference for fossil-free steel in government procurement.