RH (Ruhrstahl Heraeus) degassers have been developed to fulfill the huge vacuum degassing capacity requirements of integrated steel plants. Having ladle sizes of 150-350 t tank degassers would have a huge volume which would slow down the productivity of a plant. Compared with this, the RH design allows frequent vacuum treatments in rapid sequences.
Next to this degassing and decarburisation is more effective than in tank degassers (VD/VOD), thanks to a more intensive use of argon and a much larger freeboard of the reaction vessel.
In a RH-system the lower end of the vacuum vessel bears two snorkels, which are immersed into the ladle bearing the steel bath. By evacuation of the vessel, the steel is lifted up into the treatment chamber.
The process challenges for the vacuum system are in genaral similar to VD / VOD. But, as tonnages are higher and as the protection of the oxygen lance requires huge amount of additional inert gas flow, the typical pumping speed demand at the degassing pressure (~0.67 mbar) can go up to >1,000,000 m³/h.
Dust filtration is required to trap the partly huge amounts of dust created during the process. As the dust particles are often pyrophoric, the filtration system must be designed accordingly. Successfully used filter designs therefore typically use "inert-gas blow-back cleaning" steps to clean the filter surface.
During the long time oxygen blowing operation at rough pressure, the gases leaving the tank degasser do also have a high density, which means that they store a lot of heat energy. To protect the dust-filter from overheating, during the oxygen blowing phase a gas-cooler must be installed in between filter and tank.