Page 21 - Best of 2019 English

about 290 m3 of the gas is required for each annealing process. The extracted hydrogen is burned and heats the entire process. The heat is maintained for 6 to 35 hours, after which air and water cool the interior. After about 18 hours the hydrogen is replaced with nitrogen. This process has been in use since the 1960s. Originally the gas mixture comprised 5 to 8 % hydrogen; it is only since 1987 that almost 100 % pure hydrogen has been used.
After annealing, the sheets can be galvanized – and hydrogen has an important role to play here, too. Salzgitter Flachstahl operates two hot-dip gal- vanizing lines for this purpose. Hot-Dip Galvaniz- ing Line 2 is regarded as the most complex facility of all in the cold flat-rolled product segment. It is a huge, impressive facility that soars to a height of more than 50 meters. All processes run fully au- tomatically, with only a few employees controlling operations. At the start of the process the material is uncoiled, threaded and welded to the end of the previous coil. This creates an endless strip that is cut into pieces afterwards.
On Hot-Dip Galvanizing 2, the steel strip is first pre-cleaned in several stages and then annealed in the furnace at 690 to 890 °C, cooled, and heat-
ed back up to 450 °C before being immersed in the zinc bath at approx. 420 °C via a closed feed channel.
The housing of the feed channel is filled with
a mixture of nitrogen and hydrogen. A thin layer of iron oxide forms on the steel that has to be removed before galvanizing. “The hydrogen takes care of this. It reacts with the oxygen from the iron oxide to form water,” explains Dr. Frank Barcikow- ski, plant manager of Hot Dip Galvanizing 2. 1000 m3 of the gas mixture is required per hour, which on Hot-Dip Galvanizing 2 has a hydrogen content of 5 %.
Consequently, hydrogen has a key role to play shortly before the important moment of the actual galvanizing occurs, contributing significantly to the quality of the hot-dip galvanized sheet.
Alexander Georgiew, Production Manager Galvanized Thin Sheet, Dr. Frank Barcikowski, Plant Manager Hot-Dip Galvanizing 2, and Dr. Michael Brühl, Plant Manager Cold Flat-Rolled Flat-Rolled Business Unit (from left)
Hot-Dip Galvanizing Line 2 can be seen in the background
Mannesmann is
“H2ready”
Mannesmann Line Pipe produces special pipes for hydrogen
The special pipes substantially exceed the minimum Irequirements for hydrogen-compatible pipes
n future, not only pipelines will be needed for hydrogen but tanks, too. Their material will have to meet rigorous requirements. Steel is the perfect solution here, since it is technically and
economically superior to other materials such as plas- tic pipes – especially given the fact that hydrogen has to be transported in pipelines under high pressure, so its energy density is comparable to that of natural gas at the same volume.
Mannesmann Line Pipe is already able to offer products capable of meeting these requirements – “Mannesmann H2ready”. Their particular features include an alloy composition, a very smooth inner surface and the welding process used to make them. Mannesmann Line Pipe's carbon content also re- mains significantly below recommended guidelines, which optimizes the weldability of the pipe material. Mannesmann Line Pipe also opts for higher-strength material that allows for thinner pipe walls and lower material costs. As such, the special pipes offer an excellent solution in terms of expanding the hydrogen network infrastructure.
“Mannesmann H2ready”: The name of the special pipes made by Mannesmann Line Pipe that are capable of transporting hydrogen.
For further details, see www.mannesmann-innovations.com
HYDROGEN 21
Photos: Mannesmann Line Pipe