Study On Desilication And Dephosphorization Of Iron With KR Method Pre-Process In The Baotou Steel Company

Under the background of iron ore price rising continuously,the steel mills have to recycle the steel slag which rich in phosphorus and iron,which leads to the continuous increase of phosphorus content in molten iron and the increasing pressure of converter production.Take Baotou Steel Corporation for example,from 2010 to 2015,the phosphorus content in molten iron for converter production was about 0.12% on average,and from 2016,the phosphorus content in molten iron increased from 0.12% to 0.14% on average,the content of phosphorus in molten iron for general purpose is more than 0.15%.At present,most of the domestic steelmaking plants in Baotou Steel Corporation adopt KR pretreatment for desulphurization,converter for desiliconization and dephosphorization.If molten iron can be completely "Pre-treatment" or most of sulfur and a little of silicon and phosphorus can be removed in the KR process,it will make a great contribution to reducing the production cost and improving the quality of molten steel.In this study,some silicon and phosphorus in molten iron are removed in KR pretreatment process,the pressure of desiliconization and dephosphorization is reduced in converter,and the final hit rate and the quality of molten steel were improved,and improve the cleanliness of molten steel.At the same time,the reusable resources such as iron oxide scale ball and converter dust are used as oxidant to recover the iron resources and improve the utilization ratio of iron-rich wastes.The KR pretreatment desiliconization and dephosphorization process not only does not prolong the production time,but also removes part of silicon and phosphorus in molten iron without affecting the desulfurization,it has economic benefit not to be ignored.In this study,the influence factors of simultaneous pretreatment desiliconization and dephosphorization in KR desulfurization process were analyzed.The industrial performance of KR hot metal pretreatment was investigated,and it was found that desiliconization and dephosphorization could not be achieved in the conventional pretreatment process.Then a variety of desiliconization and dephosphorization agents were prepared in the laboratory,the physical and chemical characteristics of desiliconization and dephosphorization agents were analyzed,suitable desiliconization and dephosphorization agents were selected.Finally,the effects of physical and chemical characteristics of desiliconizing dephosphorization agent,hot metal conditions and KR hot metal pretreatment process on desiliconizing and dephosphorization were studied.The main conclusions are as follows: 0.05%-0.18% silicon and 0.003%-0.013%phosphorus can be removed by KR hot metal pretreatment;to realize the desiliconization and dephosphorization of KR hot metal pretreatment,the requirements of hot metal and pretreatment conditions are strict,the temperature of hot metal is 1290-1330?,the initial silicon content of hot metal is not more than 0.4%,the treatment time of KR pretreatment process was longer than the normal treatment time by more than 5 min,the kinetic condition was good,and a new stirring head was used.