However in the later part of the blow, when N2 absorption can create a problem, Ar gas is used for stirring. In LBE process, N2 gas is typically used almost exclusively for the majority of the blow in the range of 3 normal cubic meter per minute (N cum/min) to 11 N cum/min. The combined blowing aspect is achieved by a set of porous elements installed in the bottom of the converter through which argon (Ar) or nitrogen (N2) is blown. This process is much more closely related to the BOF process in that all the O2 is supplied from the top lance. The first combined blowing practice to be commercially accepted was the LBE (Lance Bubbling Equilibrium) process developed by ARBED-IRSID.
However, since inert gas purging provides generally higher control of wear, lifetime of the purging elements and the bottom, the majority of the converters are equipped with the bottom stirring with gas purging plugs. In rare cases, O2 is also injected from the bottom with concentric double tube tuyeres together with shrouding gases to control the temperature at the tuyere outlet and the wear of the bottom. In the combined blowing converter, the agitating and the mixing of the bath are forced by the top blown O2 jets and the bottom inert gas streams, which can achieve a high mixing efficiency for the bath. Presently, the top and bottom combined blown converter is commonly used in primary steel making plants. Fig 1 shows top blowing and combined blowing steelmaking processes.įig 1 Top blowing and combined blowing steelmaking processes Hence, proper functionality of the stirring has to be ensured over the entire campaign of the basic oxygen converter (BOF). The need of the bottom stirring system is necessary for the production of a range of high-quality demanding steel grades and is essential for the process to be economical. These range from fully cooled tuyeres, to uncooled tuyeres, to permeable elements. The configurational differences in mixed blowing lie principally in the bottom tuyeres or purging elements. The combined blowing process also known as the top and bottom blowing or mixed blowing process is characterized by both a top blowing lance and a method of achieving stirring from the bottom. The necessity to improve the steelmaking process in the top blown converter has led to the development of the combined blowing process. There is a relatively dead zone directly under the jet cavity in the converter. Inhomogeneities in chemical composition and temperature are created in the liquid steel during the oxygen (O2) blow in the top blown converters because of the lack of mixing in the liquid steel bath. argon, bottom blowing, LBE process, nitrogen, porous plug, top lance, tubular element ,.Combined Blowing Process in Converter Steelmaking
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