Oxygen Blowing Lance and its Role in Basic Oxygen Furnace Oct10

Oxygen Blowing Lance and its Role in Basic Oxygen Furnace...

Oxygen Blowing Lance and its Role in Basic Oxygen Furnace In the basic oxygen furnace (BOF) steel making a water-cooled lance is used for injecting a high velocity (super-sonic) stream of oxygen onto the liquid bath for its refining. The velocity or momentum of the oxygen jet results in the penetration of the liquid slag and metal to promote oxidation reactions over a relatively small area. The velocity of the oxygen jet and the penetration characteristics are functions of the nozzle (lance tip) design. The top-blowing lance oxygen jet of the BOF converter works as the source of feeding oxygen and energy for stirring of the liquid metal in the bath. Major in-furnace phenomena of a BOF converter that involve the top-blowing lance oxygen jet are formation of a cavity as a result of physical interaction between the oxygen jet and liquid metal, stirring of liquid metal, generation of spitting and dust, and post combustion of CO gas generated by decarburization and reaction with oxygen. For the optimization of BOF converter operation and control the above phenomena, different devices and improvements have been made and applied to the design and operation of top-blowing lance. Examples of these include the employment of Laval nozzles capable of converting pressure energy to jet kinetic energy with high efficiency in order to promote stirring of liquid metal, and the use of a multi-hole lance that enables high-speed oxygen feeding while suppressing generation of spitting and dust by dispersing of the oxygen jet. With the introduction of combined blowing in the BOF converters, the role of top-blowing lance jets as the source of energy for stirring liquid metal iron declined and flexibility in design and operation has been enhanced significantly. The main reason for blowing oxygen into the liquid...

Factors affecting Lining Life of a Basic Oxygen Converter Sep20

Factors affecting Lining Life of a Basic Oxygen Converter...

Factors affecting Lining Life of a Basic Oxygen Converter The life, reliability and costs of lining in a basic oxygen converter are vital for the smooth operations of the steel melting shop utilizing basic oxygen process for steel production.  Higher lining life results into improved availability of the converter which in turn improves its productivity. Three important factors for achieving higher lining life of the basic oxygen converter (Fig 1) are (i) qualities of refractories and their laying pattern in the converter, (ii) operating practices followed, and (iii) monitoring of the lining wear and practices for the maintenance of the refractory lining. Development of improved refractory materials in combination with improved process control and better maintenance during campaigns make it possible to increase the lining life of the basic oxygen converter. Fig 1 Factors affecting lining life of the basic oxygen converter These days without exception, basic oxygen converters are lined with magnesia – carbon (MgO-C) refractories because of their superior properties than other types of converter lining materials. However zoned refractory lining practices are followed by using MgO-C refractories of different qualities in different areas of the converter. The causes of wear of refractories in the basic oxygen converter are either due to chemical reasons or due to the physical reasons. Chemical causes for the wear of the converter lining are mainly due to gaseous materials (oxidizing gases, reducing gases, and water vapour), liquid materials (slag. hot metal, and liquid steel melt), and solid materials (fluxes, and carbon disintegration).  Physical causes for the wear of the converter lining are excessive temperatures (poor dissipation, and hot spots), static mechanical stresses (spalling, and expansion), and dynamic mechanical stresses (abrasion, impact, and vibrations). The key wear mechanisms of the refractory lining of basic oxygen converter can...

Role of Slag in Converter Steelmaking Aug01

Role of Slag in Converter Steelmaking...

Role of Slag in Converter Steelmaking The oxygen converter process is the primary steelmaking process for the production of carbon and low-alloy steels. The process is essentially an oxidizing process of refining of the high carbon hot metal (HM) to low carbon liquid steel. The oxidizing process is carried out by blowing oxygen in the converter. This causes liquid iron and the other metallic and non-metallic impurities present in the liquid melt in the converter bath to form oxides that are lighter than the liquid steel and they float to the surface of the bath. The generic name of these oxides is ‘slag’. Some oxides are acidic in nature which can react with the basic refractories of the converter and hence a basic slag using lime and calcined dolomite is usually made for protecting the converter refractories. The oxygen can also react with carbon to create a gas that provides bubbles for foaming the liquid slag and for providing chemical energy needed during steelmaking. In steelmaking process, the slag is predominantly a mixture of oxides with small amounts of sulphides and phosphides. The oxides are either acidic or basic in nature. Slag is formed during refining of hot metal in which Si oxidizes to SiO2, Mn to MnO, Fe to FeO, and P to P2O5 etc., and addition of oxides such as CaO (lime), MgO (calcined dolomite), iron oxide, and others. The addition of oxides is done to obtain desired physico-chemical properties of slag like melting point, basicity, viscosity etc. There are four primary sources for the slag during the steelmaking process in the converter. These are (i) oxidation of metallic elements in the liquid steel (e.g. silicon, manganese, aluminum, titanium, chromium, and vanadium etc.), (ii) due to presence of non-metallics in the liquid...

Refractory lining of a Basic Oxygen Furnace Mar28

Refractory lining of a Basic Oxygen Furnace...

Refractory lining of a Basic Oxygen Furnace The purpose of a refractory lining in a basic oxygen furnace is to provide maximum furnace availability during operation of the converter in order to meet production requirements and to ensure lowest possible specific refractory consumption. For this it is essential To optimize lining design To optimize lining maintenance practices To have good technological discipline during converter operation Typical refractory lining is shown in the converter cross section in Fig 1.               Fig 1 Refractory lining of a converter with removable bottom (Cross section) Lining design Wear of refractory lining is due to either the individual or the combined effect of the following agents. i)             Corrosion due to chemical attack of slag ii)            Temperature iii)          Oxidizing atmosphere iv)           Impact and Abrasion v)            Mechanical damage during deskulling Due to varying action of these agents there are many wear areas in the converter Theoretically the refractory lining of a converter is to be designed by the refractory type and different thicknesses so that no material is wasted at the end of the converter campaign. These   mean all the zones (Fig 2) of the converter lining is worn out to the stopping thickness at the same time. But in practice this does not happen and the refractories in some zones are worn out faster than the refractories in other zones. A balanced lining design is always aimed to improve lining life at the optimum refractory cost. A balanced lining is the lining where different qualities and thicknesses of refractories are used in different zone of the converter after careful study of the wear pattern of the refractories in the converter. This type of lining is also called zonal lining since in such type of...

Slag splashing technique in converter operation Mar24

Slag splashing technique in converter operation...

                     Slag splashing technique in converter operation  The erosion of refractory lining of a converter has a major contribution for the low lining life. Erosion occurs because of chemical erosion due to attack of slag and molten metal on the refractory of the converter at the high operating temperatures and because of thermal shocks as well as due to mechanical wear.  Slag splashing technique has been developed to counter this erosion and produce a freeze lining. Today slag splashing has become a powerful tool not only for increasing of the lining life of the converter but for increasing of the converter availability and maximizing of production besides reducing of the refractory and gunning costs. History Slag splashing technique was first developed in 1970 but was not put to large scale use. The Indiana Harbour plant of LTV steel was first to report success in 1992 with respect to improvement in the lining life by the use of this technique. Slowly this technique was used in the other steel melting shops of the world. Inland no. 4 BOF shop has reported a lining life of plus 60,000 heats. The process The slag splashing steps are as follows At the end of the previous heat the liquid steel is tapped in steel teeming ladle and molten slag remains in the converter. The converter operator visually inspects the slag condition to determine the quantity of slag conditioner to be added. The converter operator visually inspects the converter lining to determine if any specific area of the lining needs special attention. The molten slag is conditioned with respect to its temperature, FeO and MgO contents by the addition of a conditioner in required quantity. The converter is rocked for slag coating of the charge pad and tapping pad....