| The experimental study on converters' big flow lance was carried out and succeeded in exploiting the optimum lance for PZH steel, properly solving the problem of deficient oxygen-supply and long melting time of converters, realizing rational match between LD and other equipments in steel-making process, hence meeting the requirement of increasingly quickened production pace, based on the investigation of the lance's design, process parameters and actual usage at home and aboard, the characteristics and difficulties of semi steel-making at PZH steel, as well as combining application of the lance's design principle and associated process condition. Since the LD of PZH steel was put into production in 1971, continuous scientific study and technical improvement on steel-making scheme of LD never stops. All of technic-economic indexes have been gradually increased. Especially, the annual production reached 3.7 million tons in 2002, far exceeding design ability of 180 million tons, which proves that the particular technology aiming at PZH's semi steel-making succeeded.But the technology of oxygen supply for converters in PZH steel developed slowly in the past years and has lagged behind other steelworks in China. Although the technic modification having been done for many times, oxygen-supply time of converters is still relativelylong due to lack of systematic and comprehensive study, i.e. the heats in which the oxygen-supply time exceeds 20 minutes account for about 50%. Theoretically, the oxygen-supply time of semi-steel making is less than that of hot iron steel-making, and generally, the oxygen-supply time in hot iron steel-making is about 15~16min in steelworks at home and board. Therefore, increasing oxygen-supply intensity and shortening oxygen- supply time are of the most significance in improving PZH steel's productivity.In this paper, it is introduced that the oxygen-supply system has been comprehensively and systematically redesigned and improved based on the design principle, advanced experience of lance design at home and aboard and production practice at PZH steel;that maximum oxygen-supply flow has been increased by means of making use of the current production equipments;that some problems were solved, that is, the problem of structure and parameters of spray heads and oxygen lance body, that of the ability of oxygen supply and other auxiliary equipments, and that of operation parameters of oxygen lance, etc. Eventually, steel-making production and oxygen-supply flow were raised synchronously. At present, LD steel-making production can reach more than 4 million tons annually and the steel-making process has been optimized and turned into a good cycle. In PZH Steel, the spray heads of oxygen lance in use are extrusiompress style and cast material, which are adjusted following the layout and parameters as below: laval lance jet, 5 spray holes are uniformly distributed along lance body, the diameter of oxygen lance is 245mm, that of throat opening is 35mm, that of exit was 46.4mm, the inclination angle of lance jet is 13°and 15°, mach number is 2.05, the flow of oxygen-supply is 24000Nm3/h, and the optimum oxygen operation pressure is 0.9MPa.Through two years of production practice, it proves that, oxygen-supply time of the new lance is shorten by 13.99% in comparison with the former one;melting time is reduced from 35.58min to 33.52min;steelmaking process is going smoothly;the rate of dephosphorization is increased from 75.53% to 77.79%;the oxygen activity in molten steel is reduced by 50><10"6~100xl0"6;the life of oxygen lance is raised from 460 heats to 640 heats;the erosion rate of furnace lining refractory is decreased;and the production security is ensured. The practice results have laid a foundation for further improving the technic-economic indexes oi converter at PZH steel. |
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