Funded by PTJ and conducted in collaboration with WS Wärmeprozesstechnik GmbH, VDEh-Betriebsforschungsinstitut GmbH (BFI), and thyssenkrupp Steel Europe AG, the R&D project is developing hybrid radiant-tube heating for continuous annealing lines (CAL) and continuous galvanizing lines (CGL), where large gas-fired systems with multi-megawatt heating capacities remain widely used.

The project combines electric resistance heating with combustion heating in the same furnace architecture. Kanthal contributes the electric-heating technology and integration expertise, including high-temperature heater design, temperature monitoring, power control, and the interface between electric and combustion operation.Markus Mann, Business Development Manager, Kanthal.

The objective is to support higher levels of electrification by enabling the heating system to switch between energy sources within seconds. This gives operators the flexibility to use low-cost renewable electricity when available, while retaining fuel-fired operation when electricity prices or availability are less favorable.

“The key is that electric heating is not simply added as auxiliary power,” says Markus Mann, Business Development Manager at Kanthal. “The system can operate fully electrically, fully on fuel, or with both together. That gives operators a lot of flexibility and control.”

How can hybrid heating work in downstream steel processing?

SynErgie3 combines electric resistance heating, regenerative combustion, flameless combustion, and radiant-tube technology in a redesigned double-P radiant tube.

The system integrates 2x 63 kW electric resistance heaters with a 120-kW regenerative gas burner. Each heat source is independently controlled, enabling 100% electric, 100% fuel-fired, or combined operation. The burner is designed for natural gas, hydrogen, biogas, and other suitable renewable gaseous fuels.

“Integrating both technologies required changes to the radiant-tube geometry. The outer shanks are enlarged to accommodate the electric heaters while preserving the internal gas circulation required for combustion,” Mann explains.

A dedicated PLC-based control architecture coordinates thyristor-controlled electric heating, burner control, real-time temperature monitoring, plant communication interfaces, and automated safety and load management.

“You can switch between gas and electricity in seconds, which helps the heat source adjust quickly to changes in how it's used, the availability of electricity, and price signals,” he adds.

What are the advantages of hybrid heating for steel producers?

For steel producers, the hybrid approach addresses several operational and commercial priorities at the same time:

• Industrial decarbonization: reduce fossil-fuel consumption, CO₂ emissions, and exposure to carbon costs.
• Energy flexibility: select electricity, gas, or a combination of both according to energy availability, cost, and process requirements.
• A technology bridge: hydrogen, biogas, and other suitable renewable gases remain part of the transition.
• Electrical load management: an alternative when grid capacity or peak electrical demand constrains electric operation.
• Smart energy integration: rapid switching makes the process easier, smarter, and more versatile.
• Retrofit flexibility: the existing thermoprocessing plant can remain in place, with hybrid heating introduced selectively where it delivers the most value. 

How can existing steel furnaces be electrified without full replacement?

Retrofit capability is central to the SynErgie3 concept. Many continuous annealing and galvanizing lines still have substantial operating life, making complete furnace replacement difficult to justify purely to change the energy source.

The hybrid radiant-tube system therefore builds on an established furnace architecture, allowing electric heating while retaining substantial parts of the existing installation.

“For the steel industry, the installed base is critical,” says Mann. “You cannot assume that every decarbonization project starts with a new furnace. We wanted a concept that allows electric heating to be introduced into existing lines while retaining as much of the installed equipment as possible.”

“Operators can assess existing components for continued use, introduce electric heating where it delivers the greatest value, and plan modifications around the site's available electrical capacity,” he adds.

How is hybrid heating being validated under real production conditions?

SynErgie3 has progressed from full-scale pilot validation to industrial demonstration.

The demonstrator is now installed at thyssenkrupp Steel Europe’s continuous annealing line in Dortmund and integrated with the furnace infrastructure, plant control system and safety systems.

 “We have taken the technology through pilot testing into long-term testing under real production conditions, where we are evaluating controllability, interaction with the furnace system, switching performance, and durability. The objective is to build the operating data we need to assess long-term performance and economics before broader commercial application, Mann says.”

Is hybrid heating a practical path to full furnace electrification?

“Full electrification may be the long-term objective, but many sites will not get there in one step,” says Mann. “Hybrid heating provides flexibility during that transition. Direct use of green electricity is the more efficient option, while hydrogen can play a complementary role, for example by storing surplus renewable energy for later use. Because converting electricity to hydrogen and then back into heat comes with a significant efficiency and cost penalty, hydrogen combustion should be used where it adds value rather than as the default.”

Depending on the results in Dortmund, the potential application also extends beyond steel strip processing. Non-ferrous metals and other high-temperature thermoprocessing industries face many of the same challenges.

For Kanthal, SynErgie3 brings electric-heating expertise to a broader industrial transition that increasingly requires electrification, flexible thermal processing, renewable fuels, and intelligent energy control to work together.

For industry, the significance is the transition path itself: decarbonization does not have to wait any longer, and OPEX risk is almost zero. Steel plant operators can optimize their use of energy sources and have the option to become 100% carbon neutral – with green electricity or H2 combustion – whatever is the most economical operation every minute.