Method for Recycling Spent Reduction Gas in the Direct Reduction of Iron Ore Cleaner Ironmaking With Hydrogen and Recycled Gas

This patent describes a way to make direct reduced iron using a hydrogen-rich gas, then capture and recycle the spent gas leaving the furnace so it can be used again. It comes from Midrex Technologies, the company behind the most widely used direct reduction process in the world.

The Problem

Most steel still begins with a blast furnace that uses coke) and produces large amounts of carbon dioxide. Direct reduction is a cleaner alternative: instead of melting ore with coke, it strips the oxygen out of iron ore in a shaft furnace using a hot reducing gas, leaving a solid metallic iron that can be fed to a steelmaking furnace. Using hydrogen as the reducing agent can cut carbon emissions dramatically. But running such a process efficiently is hard. The gas leaving the top of the furnace still contains usable hydrogen along with steam, dust, and other components. Simply burning or venting that top gas wastes energy and valuable hydrogen, and heating fresh reducing gas to the high temperatures needed adds cost and emissions of its own.

What This Invention Does

The method produces direct reduced iron with a hydrogen-rich gas and heats that gas with a non-fired heater, such as an electric heater, rather than burning fuel to reach the temperatures needed for reduction. A shaft furnace reduces the iron oxide, and the gas leaving the top of the furnace is cleaned in a scrubber to remove steam and particulates. The scrubbed gas is then sent through gas separation units, such as a membrane and a pressure swing adsorption unit, which split it into a hydrogen-rich stream and a stream rich in methane and oxidants. The hydrogen-rich stream is recycled straight back into the furnace as reducing agent. Part of the methane-rich stream, blended with a hydrocarbon gas, is injected into a transition zone of the furnace to carburise the iron, meaning to add a controlled amount of carbon that is useful for downstream steelmaking. The overall effect is to reuse the gas, recover hydrogen, and lower the energy and emissions of the process.

Key Features

• Hydrogen-rich reduction. Iron ore is reduced with a hydrogen-rich gas in a shaft furnace.
• Non-fired heating. An electric or other non-fired heater raises the gas temperature instead of burning fuel.
• Top gas recycling. Spent furnace gas is scrubbed and separated so usable hydrogen is recovered and reused.
• Membrane and PSA separation. Gas separation units split the stream into hydrogen-rich and methane-rich fractions.
• Controlled carburising. Part of the methane-rich stream is injected to add carbon to the iron in a transition zone.

Who Is Behind It

The applicant is Midrex Technologies, Inc., headquartered in Charlotte, North Carolina. The MIDREX process has produced a large share of the world’s direct reduced iron since the 1980s, and the company is active in developing lower-carbon and hydrogen-based ironmaking. The named inventors are Haruyasu Michishita, Enrique Cintron, and Todd Astoria. This filing is a divisional application from an earlier related application.

Why It Matters

Steel is one of the largest industrial sources of carbon dioxide, so methods that cut emissions from ironmaking are central to decarbonising heavy industry. A process that uses hydrogen, heats gas without combustion, and recycles spent gas to recover hydrogen addresses both cost and emissions at once. Protecting the method in Australia is significant given the country’s major role as an iron ore exporter and its growing interest in green hydrogen and lower-carbon steel.

Related Concepts

• Direct reduced iron – the product and process at the heart of the patent.
• Hydrogen – the cleaner reducing agent used here.
• Pressure swing adsorption – one of the gas separation methods that recovers hydrogen.
• Blast furnace – the conventional, higher-emission route this technology competes with.
• Steelmaking – the downstream industry the iron feeds.

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AU 2026201938 was published in the Australian Official Journal of Patents on 9 April 2026 and is open for public inspection. Patent applications represent inventions that are sought to be protected and do not necessarily reflect commercially available products.