basic oxygen process
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What is the basic oxygen process in metallurgy?
The basic oxygen process (BOP) is a steelmaking method where pure oxygen is blown into molten blast-furnace iron and scrap. The oxygen starts heat-releasing reactions that oxidize impurities like carbon, silicon, phosphorus, and manganese. A typical top-blown basic oxygen furnace is a cylindrical vessel that can be tilted. It is charged with molten iron, scrap metal, and fluxes. An oxygen lance injects oxygen into the bath to reduce the carbon to the required level. The steel is tapped into a ladle, and ferroalloys and deoxidizers are added. Another oxygen steelmaking system is the bottom-blown Q-BOP, where oxygen is injected with lime through nozzles in the bottom of the vessel.
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Why is the basic oxygen process important in making steel?
The basic oxygen process (BOP) is important in steelmaking because it uses pure oxygen to refine molten blast-furnace iron and scrap into steel. Blowing pure oxygen into the mixture triggers exothermic reactions that oxidize impurities like carbon, silicon, phosphorus, and manganese.
The BOP offers commercial advantages such as high production rates, reduced labor needs, and steel with a low nitrogen content. The process's speed, with heats ranging from 30 to 360 tons produced in 30 to 45 minutes, makes it an efficient method. As a result, more than half of the world’s steel is produced using the BOP.
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What raw materials are used in the basic oxygen process?
The basic oxygen process (BOP) uses pure oxygen to convert a charge of liquid blast-furnace iron and scrap into steel. A typical charge consists of 70–75% molten blast-furnace iron (containing approximately 4 percent carbon), 25–30% scrap metal, and lime and other fluxes. The oxygen is blown into the furnace via a water-cooled lance, initiating heat-releasing reactions that oxidize impurities like carbon, silicon, phosphorus, and manganese. The duration of the oxygen blow is varied to reduce the carbon in the steel to the required level.
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How does blowing oxygen into molten iron help remove impurities?
In the basic oxygen process (BOP), blowing pure oxygen into molten iron facilitates the removal of impurities by oxidizing them. This process involves a series of exothermic reactions that significantly reduce elements such as carbon, silicon, phosphorus, and manganese. The oxygen reacts with these impurities to form oxides, which are then separated from the steel. This method's advantages, including high production rates and low nitrogen content in the steel, have made it a dominant steelmaking process.
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What are some major steps involved in the basic oxygen process?
The basic oxygen process (BOP) is a steelmaking method where pure oxygen is blown into molten blast-furnace iron and scrap to remove impurities.
Key steps:
1. The furnace is charged with molten iron, scrap metal, and fluxes like lime.
2. A water-cooled lance blows oxygen at supersonic speeds into the mixture, oxidizing impurities.
3. The oxygen flow rate and lance height are automatically controlled. Burnt lime is added to form slag.
4. A sublance checks the steel's temperature and composition, and results are fed to a computer that shuts off the oxygen when the required levels are reached.
5. The steel is tapped into a ladle, and ferroalloys are added to meet the steel composition requirements.
6. The converter is rotated to remove slag.2 Britannica SourcesCreated from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles. -
How has the basic oxygen process changed the steel industry compared to older methods?
The basic oxygen process (BOP) has revolutionized the steel industry by using pure oxygen to refine molten iron and scrap, which oxidizes impurities like carbon, silicon, phosphorus, and manganese. This method, first known as the Linz-Donawitz (LD) process, significantly boosts production rates, reduces labor needs, and lowers nitrogen content in steel.
Compared to older methods like the open-hearth and Bessemer processes, the BOP is much faster. It can produce a 200-ton batch of steel in about 60 minutes with up to 35% scrap metal, a process that used to take much longer. The charges of a basic oxygen furnace have grown to 400 tons and, with a low-silicon charge, blowing times can be reduced to 15 to 20 minutes. By 1987, the efficiency of the industry reached approximately 250 tons of steel produced per employee annually.
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basic oxygen process (BOP), a steelmaking method in which pure oxygen is blown into a bath of molten blast-furnace iron and scrap. The oxygen initiates a series of intensively exothermic (heat-releasing) reactions, including the oxidation of such impurities as carbon, silicon, phosphorus, and manganese.
The advantages of using pure oxygen instead of air in refining pig iron into steel were recognized as early as 1855 by Henry Bessemer, but the process could not be brought to commercial fruition until the 20th century, when large tonnages of cheap, high-purity oxygen became available. Commercial advantages include high production rates, less labour, and steel with a low nitrogen content. Development of the BOP was initiated in Switzerland by Robert Durrer in the late 1940s. After experimenting with a 2.5-ton pilot unit, Durrer worked with engineers at the Voest company at Linz, Austria, who set up a commercially operating 35-ton converter in 1952. A second unit began operation within a year at Donawitz, also in Austria. Consequently, the BOP was first known as the LD (Linz-Donawitz) process. Within 40 years, virtually all of the steel in Japan and more than half of the steel worldwide was produced by the BOP.
A typical top-blown basic oxygen furnace is a vertical cylindrical vessel with a closed bottom and an open upper cone through which a water-cooled oxygen lance can be raised and lowered. The vessel is lined with a refractory such as magnesite and is mounted on trunnions so that it can be tilted for charging and also for tapping liquid steel. A charge typically consisting of 70–75 percent molten blast-furnace iron (containing approximately 4 percent carbon), 25–30 percent scrap metal, and lime and other fluxes is fed into the furnace. The lance is lowered into the vessel, and oxygen is injected into the bath at supersonic velocities with flow rates that can exceed 800 cubic m (28,000 cubic feet) per minute. The duration of the oxygen “blow,” normally close to 20 minutes, is varied to reduce the carbon in the steel to the required level. The steel is then tapped into a ladle at temperatures close to 1,600° C (2,900° F), and appropriate ferroalloys and deoxidizers are added to meet the required steel composition. “Heats” of steel, ranging in size from 30 to 360 tons, can be produced in 30 to 45 minutes.
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Another, though less common, oxygen steelmaking system is a bottom-blown process known as the Q-BOP (quick-quiet BOP) in North America and the OBM (from the German, Oxygen bodenblasen Maxhuette, or “oxygen bottom-blowing furnace”) in Europe. In this system, oxygen is injected with lime through nozzles, or tuyeres, located in the bottom of the vessel. The tuyeres consist of two concentric tubes: oxygen and lime are introduced through the inner tube, and a hydrocarbon such as natural gas is injected through the outer annulus. The endothermic (heat-absorbing) decomposition of the hydrocarbon near the molten bath cools the tuyeres and protects the adjacent refractory. Yet another variation, which has found wide application in top-blown furnaces, is the injection of inert gases into the molten bath through permeable blocks in the bottom of the vessel for the purpose of enhancing chemical reactions.