About an important problem in a melter-gasifier

Metallization degree of DRI（R;） reduces with rising oxidization degree of reduction gas（r;） and oxidization degree of reduction gas rises with falling metallization degree of DRI.This is a vicious circle exists in present operation of C3000.Fuel consumption（r;） in Corex increases with falling R;and decreases with rising r;. However,r;obviously increases with the integrated change of R;and r;.To increase R;and decrease r;,an analysis on energy consumption and its distribution was deployed in this paper.According to the results,proposal was tabled based on decreasing char bed height.

A brief consideration about PCI of COREX melter-gasifier

By analyzing the thermal and burden structure conditions inside the melter-gasifier of COREX process,the advantage and disadvantage of PCI into the melter-gasifier are clarified.The influence of PCI on the running condition inside the furnace is analyzed based on the information from production operation and mathematical and physical simulations,and measures to tackle with the problems arising from PCI are proposed.The main results are as follows.①Due to the unfavorable conditions for coking of coal in the melter-gasifier,coking of charged lumpy coal to get semicoke with good size and strength can hardly be expected.To maintain the permeability of the burden column,a packed bed similar to blast furnace is necessary.Therefore,a little more coke with PCI in place of most of the lumpy coal may improve the running of the reactor.This can also make the lumpy coal selection easier.②Overall heat balance analysis of the melter-gasifier shows that PCI has no effect on the thermal condition of the furnace as a whole.Local heat balance analysis,however,shows that the heath of the melter-gasifier is in a critical state of low heat supply.PCI into the hearth will deteriorate the thermal condition.To avoid the cooling of the hearth zone by PCI,more oxygen can be blown to the hearth zone,i.e.increase the oxygen supply to the hearth and decrease accordingly the oxygen supply to the freeboard.More oxygen supply to the hearth seems to bring out the issue of an increase in fuel rate and/or thereby the smelting intensity.Detailed analysis of the physical chemical processes concluded that PCI with more corresponding oxygen supply will not lead to the increase of fuel rate.③Comparing with blast furnace,the raceway volume of COREX melter-gasifier is about only 1/10～1/5 of that of corresponding-size blast furnace.This small raceway is not favorable for PCI.To enlarge the raceway to get more favorable condition for PCI,less tuyeres with more oxygen supply of each tuyere is proposed.④Comparing with lumpy coal feeding into the furnace top,PCI into the hearth will increase the heat consumption in the lower part and decrease the heat consumption in the upper part of the furnace,leading to an increase in freeboard temperature,as well as a heat insufficiency of the hearth zone.In addition to more oxygen supply to the hearth,a more active hearth for better heat transfer is thus also indispensible to maintain its thermal condition.This can be realized by greater raceway size and the consequent better central gas flow.⑤PCI from the primary tuyeres into the hearth can increase the gas volume from the raceway.It can also decrease the coal fines from the lumpy coal charged from the furnace top.These are all favorable to improve the central gas flow,and thereby improve the running of the furnace.⑥Comparing with blast furnace,COREX process is capable to easily control the direct reduction ratio of the overall reduction process,and thus,total fuel rate lower than blast furnace is attainable if the pursuance of coke-less operation is not overemphasized.

Analysis of the factors affecting the fuel rate in the COREX process and improvement measures

Increasing production capacity and operating rate, reducing fuel rates and costs of hot metal （HM） are the urgent tasks for the COREX process. In this study ,the various factors on the fuel consumption of COREX are researched from the theoretical analysis based on the calculations of material balances and heat balances. Combined with the production performances and practices of COREX-2000 （ Saldanha, India） and COREX-3000 （ Baosteel ）, the technical measures of reducing the fuel rate are analyzed and the way forward of technical innovation is addressed and discussed with the standpoint of the COREX process improvement.

COREX—learnings and innovations at JSW Steel Limited

Ultra pure ferritic stainless steel is a kind of new stainless steel grade with high quality developed in the mid-twentieth century,it is characterized by ultra low Carbon and Nitrogen content and micro-alloying with Ti, Nb,V,Cu etc.,so it overcomes a lot of use shortcomings of the ordinary ferritic stainless steel,such as intergranular corrosion sensitivity,low ductility and toughness under atmosphere temperature,crack inclining at the weld zone etc.,namely,it has better performance than the ordinary ferritic stainless steel in the aspect of corrosion resistance,toughness and weldability etc.Furthermore,a series of secondary refining equipments and technologies have been invented from the 1960s,low or ultra low Carbon and Nitrogen content in the molten stainless steel can be obtained during manufacturing production.Therefore,such steel has been applied in many fields,leading to the very rapid development over the past half century. This paper focuses on the secondary refining process which is the most important step of the whole steel-making process for the ultra pure ferritic stainless.Firstly,some difficulties of the secondary refining process are described,including the high purification in terms of both Carbon and Nitrogen contents,high efficient and stable control.Secondly,the development and progress of the secondary refining technology for ultra pure ferritic stainless is introduced in terms of the refining equipments,metallurgical process and assistant technologies.Some most famous secondary refining equipments and metallurgical technologies for ultra pure ferritic stainless steel had been invented mainly by Japan and European companies from 1960s to 1990s,such as VOD,SS-VOD,AOD-VCR, VOD-PB etc..During the same time of wide application of these secondary refining equipments and technologies,in order to strengthen the function and capacity of these refining equipments,some advanced assistant technologies were also introduced and applied,which consists of top lance,special raw materials,ladle refractory,process monitoring and mathematic model and so on.Finally,the prospect in the future was made for the development of secondary refining process for ultra pure ferritic stainless in terms of high efficiency,ultra purification,stable control with process model etc.