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...

Blowing of Oxygen in Converter Steelmaking Sep14

Blowing of Oxygen in Converter Steelmaking...

 Blowing of Oxygen in Converter Steelmaking Oxygen (O2) is blown on the hot metal in the converter during steel making for removal of impurities such as carbon (C), silicon (Si), manganese (Mn), and phosphorus (P) etc.  A water cooled lance is used to inject oxygen at very high velocities onto a liquid bath to produce steel. In the 1950s when the top blown converter process was commercialized and the size of the converter was limited to 50 tons maximum then a lance with a single hole lance tip was being used for the blowing of O2 in the converter. With the passage of time the converter size went on increasing. This has necessitated increase of number of holes in the lance tip for better distribution of O2 over a larger surface of the bath in the converter. With the increasing demands to produce higher quality steels with lower impurity levels, O2 of very high purity is required for steelmaking in the converter. The O2 needed for steelmaking is to be at least 99.5 % pure, and ideally 99.7 % to 99.8 % pure. The remaining parts are 0.005 % to 0.01 % nitrogen (N2) and the rest is argon (Ar). In top-blown converters, the O2 is jetted at supersonic velocities with convergent divergent nozzles at the tip of the water cooled lance. A forceful gas jet penetrates the slag and impinges onto the surface of the liquid bath to refine the steel. Today most of the converters operate with lance tips containing 3 to 6 nozzles. Even 8 nozzles lance tips are under use. The axes of each of the nozzles in a lance with a multi hole lance tip are inclined with respect to the lance axes and equally spaced around the tip....