Technology & Steel Application - News

Salzgitter Flachstahl GmbH has awarded Tenova Metals Germany GmbH the contract for delivery of a new secondary metallurgical unit at their Salzgitter, Germany plant location. A new Duplex RH plant, used for the vacuum treatment of liquid steel with a nominal heat size of 220 tons, will be designed and supplied.

The LD steelmaking shop of Salzgitter Flachstahl GmbH produces about 4.7 million tons of slabs per year. With the installation of the new duplex RH plant, Salzgitter Flachstahl GmbH increases its production volume of vacuum treated steel by another 2 million tons per year. The main purpose for the installation of the new facilities is the production of automotive steel grades (Ultra Low Carbon IF Steel) as well as heavy plate grades.

For the execution of this project Tenova undertakes the complete engineering, supply of the entire mechanical and electrical equipment, hardware, software, installation and commissioning of the plant equipment. The start of production of the new plant is scheduled for spring 2017.

Plant concept and Project Details
Steel production is carried out in three LD converters, supplying liquid steel to the secondary metallurgical facilities. Therefore five lines (VPL1-5) with two twin ladle furnaces and one additional single ladle furnace completes the secondary metallurgical facilities as they are today. In three lines (VPL 1-3) VD (Vacuum Degassing) Plants are operated. Subsequently, the refined liquid steel will be casted by 4 slab casting machines.

The Duplex RH plant consists of two independent treatment stations, operated with a Hybrid Steam Jet Pump System. Ladle lifting is conducted by a winch system for each station. Each treatment station is also equipped with 2 ladle cars. After receiving the liquid steel in the converter bay the ladle will be transported to the RH treatment station by ladle car “north”.

After treatment, the ladle will be received by ladle car “south” and transported to the caster bay. Depending on the metallurgical requirements post vacuum treatment will be carried out in the ladle treatment station supplying metallurgical wires as well as insulation powder addition.

Snorkle and vessel maintenance
The snorkel maintenance is performed by three service cars operated in rectangular direction to the RH ladle car tracks. Two of these cars are equipped with snorkel deskulling devices, the third car is designed for making use of an automatic FF-snorkel gunning machine.
Exchange of the different RH vessel parts the ladle winch lifting system will be used as well. The respective vessel part of the split-type vessel is lowered to the ladle car “north” and transported by overhead crane to the taking over position of the maintenance area, where break out, relining and preheating takes place.

TOP Lance Systems
The RH treatment stations are equipped with a combined TECHNOMETAL? TOP lance. The TOP lance systems have metallurgical functions of oxygen blowing for decarburization and chemical heating as well as the burner function for keeping the refractory lining hot during the non-operating time of the RH Plants. The lance systems are equipped with the patented external TECHNOMETAL? ignition devices, which ensure reliable operation of the burner functions.

Alloys and dedusting
Both treatment stations will be connected to the alloy system of the existing ladle furnace. Furthermore, a new bunker group will be installed with an additional 18 weighing hoppers. The Vacuum Alloying Systems are designed with 2 vacuum locks as well as 2 direct feeding systems for the quick supply of aluminum and scrap. In order to collect the resulting dust loaded process gases resulting from the alloy system and ladle treatment stations a new dust filter system with a capacity of 90.000 m3/h will be provided. The new dust filter system ensures that emissions will not exceed 10 mg/m3.

Vacuum System and Water Treatment Plant
Operation of the RH treatment station will be executed with a moveable elbow device that can connect to either of the stations. The 4-stage Hybrid - Steam Jet Vacuum Pump System is equipped with liquid ring pumps as atmospheric stage. For the main working range of the vacuum system 3 parallel ejectors are installed in order to constantly maintain appropriate vacuum pressures for the required process steps, such as decarburization, oxygen blowing or degassing.

The condenser cooling water system of the vacuum pump has been designed for an economic operation mode: After having passed the first condensation stage the water is conveyed to the second condensation stage for reuse. By that operation the cooling water circulation compared to a conventional system can be reduced by about 30%.
After final condensation, the cooling water is conveyed to the new water treatment plant for filtering and sludge treatment. After cleaning, the cooling water will be pumped to the cooling towers and subsequently back to the vacuum pump system. Additionally, the existing machine cooling system will be extended in order to serve the new cooling equipment to be installed.