Steel Degassing

Steel degassing processes require robust and reliable vacuum systems. Our vacuum equipment lets you build a sustainable steel degassing plant.

Vacuum solutions for steel degassing processes

A steel degassing plant is a facility used in the production of high-quality steels. It is designed to remove elements such as carbon, hydrogen, oxygen, and nitrogen from the molten steel by a process known as vacuum degassing

During vacuum degassing the liquid steel is treated under vacuum which is created with a vacuum pump system.

The steel degassing process can have very specific requirements depending on the facility design, metallurgy routes, and desired quality of the final product.

Types of steel degassing processes can be split into three main groups:

VD – Vacuum Degassing
VOD – Vacuum Oxygen Decarburization
RH - Ruhrstahl-Heraeus process

VD – Vacuum Degassing

Vacuum treatment of molten steel where a vacuum is applied in a special chamber - degasser with a ladle of molten steel inside. The typically targeted operation pressures range from 1.33 mbar (1 Torr) to 0,67 mbar (0.5 Torr)

VOD – Vacuum Oxygen Decarburization

Vacuum process where pure oxygen is blown onto the surface of the molten steel in a pressure range of 50-200 mbar. The carbon content of the steel is oxidized, converted towards a gaseous CO/CO₂mixture which is then evacuated via the vacuum system. Typically, after the rough vacuum VOD process step, a VD process at low pressure follows, combining these two steps inside the same degasser design

RH - Ruhrstahl-Heraeus process

High productivity steel degassing process. The steel circulates inside a degassing chamberwhich is immersed into the steel ladle. Vacuum is used to lift up the steel into the degassing chamber and ensures the degassing itself (as in VD). The high circulation speed of the molten steel is ensured by an Argon flow into one of the suction snorkels. A RH-degasser can also be used for carbon reduction by blowing pure oxygen onto the circulating melt during a rough vacuum step, this is then called a RH(O) process.

VD – Vacuum Degassing

VOD – Vacuum Oxygen Decarburization

RH - Ruhrstahl-Heraeus process

The vacuum system is a critical component for the steel degassing process as it enables the creation and maintenance of the required vacuum level in the chamber. There are two rivalling types of vacuum solutions in steel degassing plants. Historically steam ejector vacuum systems (often with liquid ring vacuum pumps) are used while today mechanical vacuum systems consisting out of combinations or Roots blowers supported by dry screw vacuum pumps became a cost-saving and environmental friendly alternative.

Leybold offers an optimal portfolio of components for a modern and efficient steel degassing facility:

Forevacuum pumps – Dry Screw Pump DRYVAC DV 1200 – DV 1600
State-of-the-art dry screw vacuum pump with unprecedented robustness and highest level of reliability. DRYVAC vacuum pumps are the proven solution for many very harsh applications, and therefore perfectly suitable for the demands of steel degassing applications
Forevacuum pumps – RUVAC WH 7000
High-performance booster - fully hermetically sealed, without wearing shaft-seals, FC driven. The Roots blowers ensure the required pumping speed in combination with the DRYVAC fore-vacuum pumps.
Vacuum pump station concept – Vacuum skids
Leybold combines the individual pumps into modular systems with a scalable concept. The modular design of the system gives full flexibility for the best configuration of the individual degasser requirement: Typically 3 stage or 4 stage skids are chosen and depending on the required pumping speed several skids are installed in parallel.
Power and control system
Our intelligent control system allows to precisely tune the operation of all pumps by their frequency drives. The system gives the possibility for the master PLC to control all pumps inside one system as one virtual pump. The system provides several operation modes for the degasser to obtain the required pumping speed and to avoid slag foaming, always ensuring safe operation of all components even for continuous operation.
Gas cooler
Depending on the temperature of gases coming from the degasser during VD/ VOD or RH processes, the gases need to be cooled down to avoid overheating of dust-filters or vacuum pumps. Temperature sensors enable the user to keep full overview about the gas-coolers operation status.
Dust filter
Dust filters are a core component to protect the vacuum system from the ingression of metal or metal oxide particles, as it effectively separates the particles out of the pumping stream. A big challenge for dust filters is the handling of the often pyrophoric dust. To avoid filter bag damages, a proper filter management including an inert gas cleaning process is of utmost importance.
Valves and piping
Especially the raw gas valve installed between degasser and filter must be designed properly to withstand the abrasive dust coming from the process. Pipework must be designed to prevent dust accumulations and must be cleanable during maintenance.
Exhaust gases analyzer
To eliminate exhausting of non-environmental-friendly degassed components, a gas analyzer communicating with the main control panel could monitor the off-gas composition. To deactivate such components, often a flare stack is built into the exhaust line of the vacuum system.
Cooling system
To reduce cooling water consumption of the vacuum pumps a closed cooling water loop including a chiller can be optionally installed.

Steel Degassing plants are mostly equipped with steam ejector pump systems. These have relative low CAPEX cost but require a massive amount of utilities like steam and water. Moreover, they create a huge amount of waste-water which need to be treated. The steam is mostly produced with a steam boiler powered by natural gas, which causes immense CO₂ emissions.

Today’s need for energy savings, green transition and a carbon-emission free economy challenges the metallurgical industry massively. Every steel factory needs to develop the right strategy to survive on the market. To retrofit steam ejector systems with a mechanical vacuum system provides a solid step for the metallurgical industry to become more energy efficient and to emit less CO₂.

Leybold can support this transition with our “full revamping” proposal, offering you advice such as:

Full and precise analysis of existing vacuum system
High level support for upgrade projects
Efficient, application proven and reliable pumps
Complete steam ejector revamping solutions
Calculation of return of investments, CO₂ reduction, pumping cycles time

Leybold is a market leader in providing vacuum systems for steel degassing. Our proven solutions can be integrated into the design of new Steel Degassing plants or retrofitted into existing degassers by our “full revamping” offering. We provide complete upgrade solutions for steel degassing plants to upgrade old-fashioned, energy inefficient steam ejector systems with modern, robust and efficient mechanical vacuum systems.