Tenova LOI Thermprocess’ HPH®-BAF for thyssenkrupp

thyssenkrupp Hohenlimburg achieved CO2-neutral heat treatment of precision strip in an Ultra Low NOx HPH®-flameless Bell-type Annealing Plant by Tenova LOI Thermprocess

Tenova LOI Thermprocess collaborated on a project with thyssenkrupp Hohenlimburg GmbH to prove that CO₂-neutral heat treatment can go together with low nitrogen oxide (NO_x) emissions.

Traditionally fueled by natural gas, bell-type annealing plants perform precipitation and spheroidizing annealing of steel coils to tailor mechanical properties for subsequent rolling processes or meet specific product requirements for end customers. At thyssenkrupp's Hagen-Hohenlimburg site, Tenova LOI Thermprocess has successfully employed its latest generation heating hoods featuring the patented Ultra Low NOx HPH®-flameless concept for approximately 12 years. The innovative technology, characterized by significantly increased air preheating temperatures of 600°C, has resulted in energy and CO₂ savings of up to 12%.

In a joint project aimed at decarbonizing steel production, a further significant milestone has been reached through a series of annealing cycles. Production trials involved the gradual transition of fuel gas supply for the heat treatment of hot-rolled narrow strip from natural gas to up to 100% hydrogen. Notably, 70 t of steel strip were heat treated in a bell-type annealing plant using Tenova LOI’s HPH®-flameless technology, marking the world's first locally CO₂-neutral process. Despite the higher combustion temperature and the associated potential for increased nitrogen oxide emissions compared to natural gas, the flameless concept demonstrated remarkably low NO_x emissions.

To facilitate the flexible delivery of natural gas/H₂ mixtures, a specially designed mobile natural gas/hydrogen mixing station was deployed during the annealing process. This allowed for an assessment of the impact of increased hydrogen admixtures on the overall system. A special trailer supplied the increased hydrogen needed for annealing cycles due to the lower calorific value, feeding it directly into the pipework systems of the bell-type annealing plant.

The success of this project affirms that Tenova LOI Thermprocess's Ultra Low NOx HPH®-flameless bell-type annealing plant is well-suited for use with hydrogen. The utilization of regeneratively produced hydrogen can result in savings of up to 2600 kg of CO₂ per annealing cycle, maintaining productivity and product properties.