DEEP DESULFURIZATION PROCESS FOR PRODUCING ULTRA LOW SULFUR STEEL AT PT KRAKATAU STEEL

摘要

Recently, PT. Krakatau Steel has been producing ultra low sulfur steel grades for various specific end uses such as oil-gas -Line pipes, automotives, LPG bottles, pressure vessels etc. Such products need obviously deep desulfurization process to obtain extra low sulfur content to fulfill either required toughness or resistance on hydrogen embrittlement. Deep desulfurization necessary requires the optimum condition in thermodynamics and kinetics. Desulfurization degree will increase when sulfide capacity and sulfur partition ratio of slag are higher. In the other hand, desulfurization rate will accelerate when stirring energy is stronger. Slag composition may also determine desulfurization performance. PT.Krakatau Steel has been applying the deep desulfurization process at Slab Steel Plant (SSP). Desulfurization degree has reached 90,6 percent in average, whereas desulfurization rate has achieved 0,97 ppm sulfur per minute in average. The parameters are dominantly influenced by applying high stirring energy of 1650 Watt/m~2. Beside that, both of them has also applied specific process profile of desulfurization. Chemical composition of slag also determine to succeed the process in producing ultra low sulfur steel in which slag property is white colour. In this paper, the authors would like to describe the evaluation results of such desulfurization process to produce ultra low sulfur steel in Slab Steel Plant. Several metallurgical considerations are also written to support it.