Innovation and Practice of Hot Metal Pretreatment Technology

Shougang International Engineering Co., Ltd. has a number of patented technologies for molten iron dephosphorization and desulphurization and slagging, which can combine with the individual needs of customers to provide molten iron in various locations such as steelmaking plants, blast furnace iron ditch, molten iron transportation line, and molten iron inversion station. The pretreatment plan achieves the goal of smooth production process, reduction of equipment investment, energy saving and environmental protection. At present, these technologies have been successfully applied in projects such as Shougang, Chenggang, Shandong Hongda, Xuangang, Xinggang, Jiangsu Shente, Tangshan Jianlong, etc. The application effect is good, and the users have received unanimous praise.

　　Independent innovation of the “three-off process” for the injection of molten iron

The “three desulfurization” (desulfurization, desiliconization, and dephosphorization) technology of molten iron injection originated in Japan. This technology has been monopolized by Japanese companies. Shougang International Engineering Co., Ltd., through independent innovation and research, finally realized the localization of this technology and Successfully applied, it has become a superior technology independently developed by Shougang International Engineering Company. The investment in the same scale project is only 1/2-1/3 of the imported technology and equipment. The “three dephosphorization” effect is good, especially the dephosphorization effect has reached the international advanced level. The end point [P] is stable at <0.007%; this technology can also reduce the end point [Mn] of the molten iron to between 0.05% and 0.10% by adjusting the operation process, providing high-quality molten iron for the development of low-manganese steel grades.

　　Technical characteristics. Low-temperature molten iron dephosphorization process for low-headroom hot metal ladle; Adjustable throat valve is used to control the desulfurizing agent injection speed to achieve precise and continuous injection flow adjustment; Dynamic pressure difference injection control technology is used to achieve stable injection operation; Double spray guns are used The alternate process arrangement realizes the continuous operation of the injection station and meets the requirements of continuous production; the water-cooled low Mach oxygen lance is used to effectively ensure carbon preservation and soft oxygen blowing, and achieve the effect of controlling the temperature of the molten iron; set water-cooled coils and refractory materials The water tank type splash cover can effectively prevent the molten iron splash from damaging the equipment; by controlling the operating process parameters, the manganese removal from the molten iron can be controlled between 0.05% and 0.10%, and the molten iron manganese removal process can be realized.

　　 actual production effect

　　Shougang International Engineering Co., Ltd. independently developed the iron ladle injection three-removal process and equipment after it was successfully put into production in 2011. The equipment is operating normally, the three-removal effect is stable, and the dephosphorization effect has reached the international advanced level.

　　 Dephosphorization effect. Under the existing desiliconization and dephosphorization process conditions, the results of 63 hot metal dephosphorization in 2011 were calculated. The composition change of the molten iron is shown in Fig. 1, and the distribution of the end point P of the molten iron is shown in Fig. 2. It can be seen that the average P content of the molten iron treated by the dephosphorization station is 0.007%, which is far better than the design index ≤0.015%.

　　 The actual results of statistical production show that the average end point P of molten iron is 0.007%, the highest is 0.015%, and the lowest is 0.004%, which fully meets the requirements of all stainless steel molten iron de-P indicators and is better than the design indicators.

　　 Hot metal temperature control. This technology applies to the special supply of molten iron in steel mills. It needs to be transported backwards after tapping from the mixer in another workshop. Normally, the transport time is about 30 minutes. The temperature of the molten iron drops greatly during tapping and transporting. , The temperature of the molten iron at the station is basically between 1220-1250°C, while the requirements of AOD and EAF on the temperature of the molten iron must be greater than 1300°C, which brings certain challenges to the injection dephosphorization equipment. Shougang International Engineering Co., Ltd. adjusted and optimized the dephosphorization injection and top blowing oxygen process parameters according to the working conditions such as the low molten iron temperature. After the hot test, the adjusted dephosphorization process was fully adapted to the requirements of low temperature molten iron injection dephosphorization. .

　　Injection dephosphorization treatment cycle. The dephosphorization treatment cycle refers to the entire treatment time from entering the dephosphorization station to the dephosphorization station, including temperature measurement and sampling time, slag removal time, desiliconization time, and dephosphorization time. The factors that affect the treatment cycle have a great relationship with the proficiency of the operators and the matching of the previous and subsequent processes. Through the statistics of the dephosphorization records under the normal dephosphorization conditions during the commissioning period, a total of 63 dephosphorization tanks are counted, and only 1 furnace is greater than 75min, the pass rate of the dephosphorization cycle meets the design requirements.

　　 Dephosphorization agent consumption. The consumption of dephosphorization agent directly affects the production cost of stainless steel. The statistics of current dephosphorization agent consumption indicators show that the actual consumption indicators of various materials are better than foreign technical indicators. The comparison of the consumption of various dephosphorization agents is shown in Figure 3.

　　 Hot metal tank car online injection desulfurization new technology

　　 This process builds the desulfurization station on the molten iron transportation line between the blast furnace of the iron smelting plant and the steel smelting plant. It is a patented technology of an international engineering company and is a domestic initiative, and its various technical indicators have reached the leading domestic level in the same industry. This process can save floor space to the greatest extent, speed up the processing rhythm, reduce iron loss and temperature loss, and provide a unique desulfurization method for enterprises and old plants that have insufficient space in the existing steelmaking workshop and need construction. Has good economic and social benefits.

　　Technical characteristics

1) The desulfurization station is built on the molten iron transportation line between the blast furnace of the iron smelting plant and the steel smelting plant. The use of hot metal transport vehicles and blast furnace hot metal ladle desulfurization can save supporting large cranes, hot metal tanks, and hot metal tank cars, and solve the problem of molten iron transportation. It has the characteristics of low project investment.

2) Double-station process layout. Using the combination of a traverse car and a spray gun lifting device, through an innovative process arrangement, one spray gun traverse car corresponds to two injection desulfurization stations, which not only shortens the processing cycle, reduces the temperature drop of the molten iron, and saves equipment investment.

3) Using molten iron slag removal technology, and through the rotation function of the slag removal equipment, the process operation of one slag removal machine corresponding to two slag removal stations is realized. The slag conveyor is used to remove the iron slag generated in the desulfurization process, and there is no need to tip the iron ladle to remove the slag, which is suitable for the online desulfurization operation of the iron ladle truck. In addition, one slag conveyor corresponds to the process operation of two stations, which also saves equipment investment. Due to the application of the slag removal process, each ton of molten iron processed will reduce the loss of about 3.5 kg of molten iron, resulting in huge economic benefits, and at the same time, it has obvious benefits of energy saving and emission reduction.

4) The positioning device of the spray gun lifting and traversing vehicle is an independent innovation technology. In order to ensure the accurate alignment of the spray gun lifting and traversing vehicle, a set of locking mechanism has been independently developed and designed to enable the positioning of the spray gun traversing vehicle with a weight of dozens of tons. The accuracy reaches ±20mm, and it will be automatically locked after reaching the parking space, and will not deviate due to the vibration generated during the injection desulfurization process.

Shougang International Engineering Co., Ltd. takes advantage of its long-standing cooperation with the world’s advanced hot metal pretreatment technology companies, and relies on the advanced technology introduced by Shougang Group to develop a number of core technologies with independent intellectual property rights that are more suitable for the actual conditions of domestic steel companies, and through technology integration Innovation, occupying a certain domestic market in terms of hot metal pretreatment and technical services. Shougang International Engineering Company will continue to improve the hot metal pretreatment technology, and provide domestic and foreign steelmaking enterprises with products and services with advanced technology and equipment, reasonable engineering investment, and meeting individual requirements.

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