Aceración con Hornos Básicos de Oxígeno La refinación del arrabio en el proceso BOF o aceración al oxígeno se lleva a cabo en un recipiente que asemeja. Horno Básico de OxígenoUNIDAD 6 Horno Siemens Martin. Convertidor de Soplado Nariz (N) Lanza de Oxigeno (L) Cintur. The basic oxygen furnace (BOF), whose profile is shown in the figure, is a tiltable vessel lined with refractories such as magnesia carbon brick. Auxiliary.
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Basic Oxygen Furnace Steelmaking. Primeramente se le agrega al convertidor la chatarra que se encuentra en cajas previamente pesadas. However, elsewhere its use is growing.
There exist several variations on the BOS process: This study will focus only on the top blowing variation. It oxidizes the carbon and silicon contained in the hot metal liberating great quantities of heat which melts the scrap. There are lesser energy contributions from the oxidation of iron, manganese, and phosphorus. The post combustion of carbon monoxide as it exits the vessel also transmits heat back to the bath.
From here it may undergo further refining in a secondary refining process or be sent directly to the continuous caster where it is solidified into semifinished shapes: Basic refers to the magnesia MgO refractory lining which wears through contact with hot, basic slags. These slags are required to remove phosphorus and sulfur from the molten charge. BOF heat sizes in the U. This rate of production made the process compatible with the continuous casting of slabs, which in turn had an enormous beneficial impact on yields from crude steel to shipped product, and on downstream flat-rolled quality.
BOS process replaced open hearth steelmaking. The process predated continuous casting. As a consequence, ladle sizes remained unchanged in the renovated open hearth shops and ingot pouring aisles were built in the new shops. Six-story buildings are needed to house the Basic Oxygen Furnace BOF vessels to accommodate the long oxygen lances that are lowered and raised from the BOF vessel and the elevated alloy and flux bins.
Since the BOS process increases productivity by almost an order of magnitude, generally only two BOFs were required to replace a dozen open hearth furnaces.
Some dimensions of a typical ton BOF vessel in the U. A control pulpit is usually located between the vessels. Unlike the open hearth, the BOF operation is conducted almost “in the dark” using mimics and screens to determine vessel inclination, additions, lance height, oxygen flow etc.
Once the hot metal temperature and chemical analaysis of the blast furnace hot metal are known, a computer charge models determine the optimum proportions of scrap and hot metal, flux additions, lance height and oxygen blowing time. The hot metal is immediately poured directly onto the scrap from a transfer ladle. Fumes and kish graphite flakes from the carbon saturated hot metal are emitted from the vessel’s mouth and collected by the pollution control system.
Charging takes a couple of minutes. The lance is water-cooled with a multi-hole copper tip. Through this lance, oxygen of greater than If the oxygen is lower in purity, nitrogen levels at tap become unacceptable. As blowing begins, an ear-piercing shriek is heard. This is soon muffled as silicon from the hot metal is oxidized forming silica, SiO 2which reacts with the basic fluxes to form a gassy molten slag that envelops the lance.
The gas is primarily carbon monoxide CO from the carbon in the hot metal. The rate of gas evolution is many times the volume of the vessel and it is common to see slag slopping over the lip of the vessel, especially if the slag is too viscous. Blowing continues for a predetermined time based on the metallic charge chemistry and the melt specification.
This is typically 15 to 20 minutes, and the lance is generally preprogrammed to move to different heights during the blowing period. The lance is then raised so that the vessel can be turned down towards the charging aisle for sampling and temperature tests.
Static charge models however do not ensure consistent turndown at the specified carbon and temperature because the hot metal analysis and metallic charge weights are not known precisely.
In the past, this meant delays for reblowing or adding coolants. Today, with more operating experience, better computer models, more attention to metallic input quality, and the availability of ladle furnaces that adjust for temperature, turndown control is more consistent.
In some shops, sublances provide a temperature-carbon check about two minutes before the scheduled end of the blow. This information permits an “in course” correction during the final two minutes and better turn-down performance.
However, operation of sublances is costly, and the required information is not always obtained due to malfunctioning of the sensors. Once the heat is ready for tapping and the preheated ladle is positioned in the ladle car under the furnace, the vessel is tilted towards the tapping aisle, and steel emerges from the taphole in the upper “cone” section of the vessel.
The taphole is generally plugged with material that prevents slag entering the ladle as the vessel turns down. Steel burns through the plug immediately. To minimize slag carryover into the ladle at the end of tapping, various “slag stoppers” have been designed.
These work in conjunction with melter’s eyeballs, which remain the dominant control device. Slag borno the ladle results in phosphorus reversion, retarded desulfurization, and possibly “dirty steel”.
Ladle additives are available to reduce the iron oxide level in the slag but bqsico can be done to alter the phosphorus. After tapping steel into the ladle, and turning the vessel upside down and tapping the remaining slag into the “slag pot”, the vessel is returned to the upright position. In many shops residual slag is blown with nitrogen to coat the barrel and trunion areas of the vessel.
This process is known as “slag splashing”. Near the end of a campaign, gunning with refractory materials in high wear areas may also be necessary. Once vessel maintenance is complete the vessel is ready to receive the next charge.
A heat size of tons is used as the basis for the following baskco.
This is close to the average heat size for the 50 BOFs which were operable in the U. The following charge chemistry is assumed: NTHM yorno short ton or pounds of hot metal. The actual percentage of hot metal in the charge is very sensitive vof the silicon content and temperature of the hot metal and obviously increases as these decrease. Oxygen consumption increases if end-point control is poor and reblows are necessary.
The metalloids and Mn are oxidized out of the hot metal, the scrap is often coated with Zn which volatilizes, and iron units obf lost bsico the slag, fume, and slopping. Hot metal is liquid iron from the blast furnace saturated with up to 4. It is transported to the BOF shop either in torpedo cars or ladles.
The hot metal chemistry depends on how the blast furnace is basioc and what burden iron-bearing materials are charged to it. The trend today is to run at high productivity with low slag volumes basic fuel rates, leading to lower silicon and higher sulfur levels in the hot metal.
The sulfur level from the blast furnace can be 0. The most common desulfurizing reagents, lime, calcium carbide and magnesium – used alone or in combination baslco are injected into the hot metal through a lance.
The sulfur containing compounds report to the slag; however, unless the sulfur-rich slag is skimmed before the hot metal is poured into the BOF, the sulfur actually charged will be well above the level expected from the metal analysis.
In autogenous BOS operation, scrap is by far the largest heat sink. Steel scrap is available in many forms. The major categories are “home scrap”, generated within the plant. With the advent of continuous casting, the quantity of home scrap has diminished and it is now necessary for integrated mills to buy scrap on the market.
Flat rolled scrap is generally of good quality and it’s impact on the chemistry of BOF operations can almost be ignored. It finds its way into the recycling stream very quickly.
Proceso de oxigeno básico by carlos diaz on Prezi
Many steel mills have agreements with manufacturers to buy their prompt scrap. Cans return to the market very quickly but autos have an average life of 12 years. Scrap also comes in many sizes, varying chemical analyses and a variety of prices. All of which makes the purchase and melting of scrap a very complex issue. Very large pieces of dde can be difficult to melt and may damage the vessel when charged. Some scrap may contain oil or surface oxidation.
Obsolete scrap may contain a variety of other objects which could be hazardous or explosive. Obviously the chemical analysis of obsolete scrap is imprecise. Scrap selection is further complicated by the wide variety of steel products. While other products allow this to range as high as 0.
Since these elements cannot be oxidized from the steel, their content in the final product can only be reduced by dilution with very high purity scrap or hot metal. Fluxes serve two important purposes. First they combine with SiO2 which is oxidized from the hot metal to form a “basic” slag that is fluid at steelmaking temperatures. This slag absorbs and retains sulfur and phosphorus from the hot metal. They are obtained by calcining the carbonate minerals, generally offsite in rotary kilns.
Two types, “soft” and “hard” burned lime, are available. A lump of soft burned lime dissolves quickly in a cup of water liberating heat.
Contratista EPC 5-150 t básica oxígeno industrial horno fusorio BOF
Hard burned material just sits there. Soft burned fluxes form slag more quickly than hard-burned, and in the short blowing cycle, this is critical for effective sulfur and phosphorus removal. The amount of lime charged depends on the Si content of the hot metal.
A rule oxigdno thumb is 6 X the weight of Si charged.
Edgar Saldaña –
This saturates the slag with MgO, thus reducing chemical erosion of the MgO vessel lining. Limestone, scrap, and sponge iron are all potential coolants bor can be added to a heat that has been overblown and is excessively hot. The economics and handling facilities dictate the selection at each shop. Bulk alloys are charged from overhead bins into the ladle.
The basis for most refractory bricks for oxygen steelmaking vessels in the U.