basic oxygen process
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| basic oxygen process | |
|---|---|
| Name | Basic oxygen process |
| Type | Steelmaking |
| Inventor | Sir Robert Hadfield; Carl Wilhelm Siemens |
| Origin | Austria-Hungary; United Kingdom |
| Introduced | 1950s |
| Industry | Metallurgy; Steel industry |
basic oxygen process The basic oxygen process is a primary steelmaking method that converts molten pig iron into steel by blowing high-purity oxygen into a refractory-lined vessel. Developed and industrialized in the mid-20th century, it transformed operations at major producers such as ThyssenKrupp, US Steel, ArcelorMittal, Nippon Steel, and Tata Steel by increasing throughput, reducing fuel consumption, and enabling more precise composition control. The process is integral to integrated steelworks alongside sintering plant, blast furnace, and continuous casting systems.
History
Early routes to modern oxygen steelmaking built on work at institutions like the Royal Society and laboratories associated with École Polytechnique and Technische Universität Berlin. Pioneering efforts by researchers linked to Krupp and innovators such as Sir Robert Hadfield and engineers influenced by Carl Wilhelm Siemens set foundations that were further advanced by teams at Acerinox and Voestalpine. The commercial breakthrough came with installations at firms including Klockner and Bergwerksgesellschaft in the 1950s, rapidly displacing open-hearth converters at plants owned by Bethlehem Steel and Kaiser Steel during the post‑war expansion associated with projects like the Marshall Plan.
Process Description
Molten iron tapped from a blast furnace or returned from a hot metal desulfurization stage is charged into a refractory-lined vessel known generically as a converter. A water-cooled lance injects high-purity oxygen from suppliers such as Air Liquide or Linde plc into the bath, producing exothermic oxidation reactions that lower carbon and adjust alloying elements. Fluxes derived from limestone and dolomite are charged to form a basic slag; electromagnetic stirring and secondary metallurgy in a ladle furnace or vacuum degassing unit refine composition prior to continuous casting into billets, blooms, or slabs destined for rolling mills at locations like POSCO and Nucor.
Equipment and Materials
Primary plant components include the oxygen lance assembly often supplied by firms like Danieli and Siemens VAI, refractory linings produced by manufacturers linked to RHI Magnesita, and vessel designs standardized by industry consortia including World Steel Association. Raw inputs encompass hot metal from Pechiney-era blast furnaces, scrap steel procured via traders associated with Metal Bulletin, and fluxes such as Carrara limestone and dolomite from quarry operators. Auxiliary systems involve gas cleaning and heat recovery units engineered by companies like ABB and Babcock & Wilcox.
Metallurgical Chemistry and Reactions
The process centers on oxidation reactions: dissolved carbon oxidizes to carbon monoxide and carbon dioxide; silicon oxidizes to form silica that reacts with added basic flux to produce silicate slag; manganese and phosphorus oxidize under controlled slag basicity conditions. Slag chemistry is managed to favor dephosphorization via high lime activity, a principle developed in studies tied to Max von Laue-era physical chemistry and later refined by metallurgists at Lehigh University and Colorado School of Mines. Oxygen solubility dynamics interact with temperature and thermodynamic equilibria described in texts from ASM International and standards from ISO committees.
Operational Parameters and Control
Key variables include lance oxygen purity (typically >99.5%) from providers like Air Products and Chemicals, lance height and angle, blow schedule phases (oxygen blow, tapping, and post‑combustion), and scrap ratio set according to plant mix proven at integrated producers such as ArcelorMittal and Severstal. Process control employs distributed control systems from vendors like Siemens and Honeywell integrating measurements from top‑sub‑bottom thermocouples, off‑gas analyzers, and real‑time models developed in collaboration with universities including Imperial College London and Massachusetts Institute of Technology.
Environmental and Safety Considerations
Emissions include CO and CO2 requiring off‑gas treatment systems and recovery units for energy integration, implemented in projects by E.ON and Enel. Dusts and particulates are captured by electrostatic precipitators and fabric filters supplied by firms like Donaldson Company; residue handling links to regulations enforced by agencies such as the Environmental Protection Agency and European Environment Agency. Safety protocols address high‑oxygen hazards, thermal risks, and molten metal handling with standards from organizations such as ISO and training programs developed in partnership with Occupational Safety and Health Administration and industrial unions like United Steelworkers.
Applications and Economic Aspects
The basic oxygen process supplies the majority of flat and long products used by manufacturers in automotive supply chains tied to Toyota, Volkswagen Group, General Motors, and Ford Motor Company, as well as construction projects undertaken by conglomerates like Vinci and Bechtel. Economically, oxygen steelmaking offers lower unit energy costs compared with open‑hearth furnaces, influencing capital investment decisions at conglomerates such as Mittal Steel Company and national champions like POSCO. Market dynamics are shaped by iron ore and scrap prices referenced by commodities exchanges including the London Metal Exchange and policy instruments like emissions trading schemes administered by the European Union.