Tenova LOI Thermprocess Reports Success in Hydrogen-Fueled Annealing Trial

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 (NOx) 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 NOx 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.

Courtesy of Tenova.

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