CN104419798B - Method for pre-desiliconizing molten iron by utilizing CAS-OB refining furnace - Google Patents

Abstract

The invention discloses a method for pre-desiliconization of hot metal in a CAS-OB refining furnace. The existing CAS-OB refining furnace in a steel plant is used to desiliconize molten iron to provide low-silicon hot metal for a converter or an electric furnace. The specific process is as follows: Use high-temperature resistant magnesia-carbon brick molten iron tank specially for desiliconization, firstly carry out slag removal treatment on the molten iron, use the spray gun above the impregnation cover of the refining furnace to blow in oxygen or air, the flow rate is controlled at 5-10Nm ³ /h∙t, when the slag When the layer reaches 30-80mm, stop the blowing of the top spray gun, open the bottom blowing gas valve to blow and stir, the gas flow rate: 80-100 Nm ³ /h. After the slag layer is discharged, the hood is lowered, and the spray gun above the dipping hood is used to blow in oxygen or the air flow rate is controlled at 5-10Nm ³ /h∙t, and the molten iron is transported to the slag removal position for slag removal treatment. The invention utilizes the factory's original refining furnace to desiliconize molten iron, which saves a lot of equipment investment costs and space occupation, and realizes high-efficiency and low-cost production of low-silicon molten iron.

Description

A method of pre-desilication of hot metal using CAS-OB refining furnace

technical field

The invention belongs to the technical field of pretreatment of molten iron, and in particular provides a method for producing low-silicon molten iron using a CAS-OB refining furnace.

Background technique

Desiliconization of hot metal is an important part of hot metal pretreatment. High silicon content in hot metal will bring adverse consequences to the normal operation of the converter and increase the cost of steelmaking. Reducing the silicon content in molten iron can reduce the smelting burden of the converter, reduce lime consumption, and realize steelmaking with less slag; promote the dephosphorization reaction in advance in the early stage of blowing, which will help improve the dephosphorization rate of the converter and create conditions for realizing efficient steelmaking . Practice has proved that when the silicon content of molten iron is removed from more than 0.6% to less than 0.2% by pre-desiliconization treatment of molten iron, the lime consumption in the steelmaking process can be reduced from 40-50kg/ton steel to 15-20kg/ton steel, and the consumption of refractory materials is reduced. 30-40%, it can be seen that the economic benefit is remarkable. The converter is smelted with low-silicon molten iron, which can bring a series of benefits to the converter operation, reduce the consumption of slagging materials, reduce the overflow and splashing of slag, reduce the erosion of the furnace lining by the slag, increase the service life of the furnace, and increase the yield of molten steel and molten steel The amount of residual manganese is reduced, the blowing time of the converter is shortened, the productivity and the quality of molten steel are improved; the discharge to nature is reduced, and the environmental quality is improved. Therefore, pre-desilication of molten iron has great economic and social significance.

There are several methods for desiliconization of hot metal: Document 1 ("Analysis and Research on Dephosphorization Process of Hot Metal", Zhang Feihu et al., Industrial Heating, Volume 41, No. 4, Pages 55-51), discloses a desiliconization of hot metal Methods, the article lists the domestic "Taiyuan Iron and Steel" has established a "three removal station" for molten iron, which can desiliconize, dephosphorize and desulfurize molten iron. Although the "three desiliconization stations" can realize the desiliconization of molten iron, its disadvantages are that it requires a lot of equipment, large investment, large floor area, complicated process and large heat loss. For example, document 2 ("Industrial Test of Desiliconization of Hot Metal by Slag Washing Method", Zhang Jiexin et al., Steelmaking, Volume 28, No. 2, Pages 44-47), discloses a method for desiliconization of hot metal by slag washing method. Desiliconization of molten iron can be achieved by adding desiliconization agent in the tapping process without additional equipment investment, but its disadvantage is that the desiliconization rate is low, and the desiliconization rate is only 52.69%; the consumption of desiliconization agent is high, and the desiliconization agent The consumption is more than 30kg/t; the desiliconization process is easy to produce foam slag, and the foam slag is easy to overflow if the control is not good. For example, Document 3 (“Current Status and Prospects of Hot Metal Pretreatment Technology Development”, Pan Xiulan et al., World Steel, No. 6, 2010, pages 34-36), discloses some methods for desiliconization of molten iron: , torpedo tanks and molten iron tanks are pre-desiliconized by spraying Fe ₂ O ₃ and a small amount of CaO flux for desiliconization of molten iron, which can achieve a certain desiliconization effect, but there are some problems. If the injection device needs to be used, It brings cost and space layout problems. In addition, the addition of desiliconizing agent will also bring about the problem of large temperature drop of molten iron, which will bring adverse consequences to the next process. Therefore, the above-mentioned desiliconization method still has corresponding problems, and can no longer meet the needs of high-efficiency and low-cost steelmaking, so a new method for desiliconization of molten iron remains to be studied.

The basic principle of the CAS-OB refining furnace is to complete the deoxidation, alloying and heating operations of the molten steel inside the dipping hood under the condition of stirring the molten steel by blowing hydrogen at the bottom of the ladle, which solves the problem of exposed molten steel and slag curling caused by traditional argon blowing and stirring The peroxidation of molten steel caused by this problem has unique advantages in heating molten steel, alloying and removing inclusions. However, due to the high carbon content of molten iron, the CAS-OB refining furnace does not use a set of special process flow for desiliconization by blowing oxygen, which is prone to splash accidents. Therefore, no one has used the CAS-OB refining furnace for desiliconization of molten iron so far. processing technology. In addition, ordinary hot metal tanks usually use refractory bricks with low refractoriness, and the high temperature generated during oxygen blowing desiliconization will severely corrode the refractory bricks, which is also a factor that limits the desiliconization of molten iron in the CAS-OB refining furnace.

Contents of the invention

The object of the present invention is to disclose a method for pre-desiliconization of molten iron using a CAS-OB refining furnace, and to use the CAS-OB refining furnace to perform desiliconization of molten iron, so as to overcome the problems existing in the current desiliconization method for molten iron. The desiliconization of molten iron can be achieved by avoiding the construction of additional auxiliary devices such as "three desalination stations" for molten iron. Bottom blowing gas slag removal, oxygen blowing or air desiliconization of molten iron after lowering the cover, since no additional desiliconization agent is needed, it can avoid the problem of temperature drop of molten iron and prevent the formation of foamy slag caused by splashing and slag overflow question. Therefore, a large amount of equipment investment costs can be saved and complicated process operations can be avoided, so as to realize high-efficiency and low-cost production of low-silicon molten iron.

The present invention is based on the conventional smelting process and has little impact on normal production. Without increasing equipment investment, the existing CAS-OB refining furnace in the steelmaking plant is used to desiliconize molten iron to provide low-silicon molten iron for converters or electric furnaces. .

The specific process is as follows:

1) Adopt high-temperature-resistant magnesia-carbon brick molten iron tank specially for desiliconization, transport the molten iron to the slag removal position, and firstly carry out slag removal treatment on the molten iron. After the slag removal is completed, the molten iron is taken for temperature measurement and sampling.

2) Transport the molten iron to the station of the CAS-OB refining furnace, use the spray gun above the impregnation hood of the CAS-OB refining furnace to blow in one of oxygen or air, and the gas flow rate is controlled at 5-10Nm ³ /h∙t.

3) A slag layer will be formed on the surface of the molten iron after the oxidation of silicon in the molten iron. When the slag layer reaches 30-80mm, stop blowing air from the top spray gun, and open the bottom blowing gas valve for blowing and stirring. Gas flow rate: 80-100 Nm ³ / h.

4) After the slag layer is discharged, lower the hood. At this time, there is no slag or little slag in the immersion hood. Continue to use the spray gun above the immersion hood to blow in oxygen or air, and the gas flow rate is controlled at 5-10Nm ³ /h∙t.

5) After the desiliconization treatment is completed, the dipping hood and spray gun are raised, and the molten iron is transported to the slag removal position, and the slag removal treatment is performed on the molten iron.

6) After the slag removal is completed, temperature measurement and sampling are carried out. If the amount of desiliconization meets the requirements, the qualified molten iron can be hoisted to the next process by a crane.

If the amount of desiliconization does not meet the requirements, steps 2-6 can be repeated to perform the desiliconization operation repeatedly.

The slag removal treatment in the above step 1 is to ensure that the oxygen or air blown into the spray gun can fully react with the silicon in the molten iron to improve the desiliconization efficiency.

In step 3, when the slag layer reaches 30-80mm, the air blowing of the spray gun is stopped to prevent splashing and slag overflow. The bottom blowing gas can be one of argon or nitrogen.

In step 4, the lowering of the cover is to ensure that oxygen or air reacts with silicon in the molten iron in a slag-free environment, which can not only ensure the desiliconization efficiency but also avoid splashing and slag overflow.

In step 5, the slag removal operation is carried out in order to prevent the desiliconization slag from being brought into the next process and bring adverse consequences to the next process.

Since the present invention adopts the CAS-OB refining furnace to desiliconize the molten iron, it can use the factory's original refining furnace to desiliconize the molten iron without increasing equipment investment, which saves a lot of equipment investment cost and site occupation. . Bottom-blowing gas slag removal, blowing oxygen or air to desiliconize the molten iron after lowering the cover, since no additional desiliconization agent is needed, it can avoid the problem of temperature drop of molten iron and prevent the formation of foamy slag caused by splashing and slag overflow problem, to achieve efficient and low-cost production of low-silicon hot metal.

detailed description:

The present invention will be described in detail below in conjunction with specific embodiments.

Example 1:

1) Use the special molten iron tank for desiliconization to transport the molten iron to the slag removal position, and firstly carry out the slag removal treatment on the molten iron. After the slag removal is completed, the molten iron is taken for temperature measurement and sampling. The measured molten iron temperature is 1313°C, and the silicon content is 0.67%.

2) Transport the molten iron to the station of the CAS-OB refining furnace, use the spray gun above the impregnation hood of the CAS-OB refining furnace to blow in oxygen, and control the gas flow rate at 6Nm ³ /h∙t.

3) When the slag layer reaches 40mm, stop the spray gun blowing, open the bottom blowing gas valve to blow nitrogen and stir, the gas flow rate: 90 Nm ³ /h.

4) After the slag layer is discharged, lower the hood, and continue to blow in oxygen with the spray gun above the immersion hood, and the gas flow rate is controlled at 5Nm ³ /h∙t.

5) After the desiliconization treatment is completed, the dipping hood and spray gun are raised, and the molten iron is transported to the slag removal position, and the slag removal treatment is performed on the molten iron.

6) After the slag removal is completed, temperature measurement and sampling are carried out. The measured temperature of the molten iron is 1346°C, and the silicon content is 0.19%. The amount of desiliconization meets the requirements, and the qualified molten iron is hoisted to the next process with a crane.

The results show that not only the desiliconization effect is obvious, but also the temperature of molten iron rises by 33°C instead of falling. While achieving desiliconization, the temperature loss of molten iron is avoided.

Example 2:

1) Use the special molten iron tank for desiliconization to transport the molten iron to the slag removal position, and firstly carry out the slag removal treatment on the molten iron. After the slag removal is completed, the molten iron is taken for temperature measurement and sampling. The measured molten iron temperature is 1345°C, and the silicon content is 0.64%.

2) Transport the molten iron to the CAS-OB refining furnace station, use the spray gun above the impregnation hood of the CAS-OB refining furnace to blow in air, and the gas flow rate is controlled at 8Nm ³ /h∙t.

3) When the slag layer reaches 50mm, stop the spray gun blowing, open the bottom blowing gas valve to blow argon and stir, the gas flow rate: 95 Nm ³ /h.

4) After the slag layer is discharged, the cover is lowered, and air is continuously blown in by the spray gun above the dipping cover, and the gas flow rate is controlled at 9Nm ³ /h∙t.

5) After the desiliconization treatment is completed, the dipping hood and spray gun are raised, and the molten iron is transported to the slag removal position, and the slag removal treatment is performed on the molten iron.

6) After the slag removal is completed, temperature measurement and sampling are carried out. The measured temperature of the molten iron is 1369°C, and the silicon content is 0.21%. The amount of desiliconization meets the requirements, and the qualified molten iron is hoisted to the next process with a crane.

The results show that not only the desiliconization effect is obvious, but also the temperature of molten iron rises by 24°C instead of falling. While achieving desiliconization, the temperature loss of molten iron is avoided.

Claims (1)

1. a method utilizing CAS-OB refining furnace molten iron pre-desiliconization, is characterized in that, adopts conventional smelting process, utilizes CAS-OB refining furnace to carry out desiliconization process to molten iron, and concrete process is as follows: 1) Use a high-temperature-resistant magnesia-carbon brick molten iron tank dedicated to desiliconization, transport the molten iron to the slag removal position, first perform slag removal treatment on the molten iron, and take temperature measurement and sampling of the molten iron; 2) Transport the molten iron to the CAS-OB refining furnace station, use the spray gun above the impregnation hood of the CAS-OB refining furnace to blow into one of oxygen or air, and control the gas flow at 5-10Nm ³ /h∙t; 3) When the slag layer reaches 30-80mm, stop the top spray gun blowing, open the bottom blowing gas valve to blow and stir, the bottom blowing gas is argon or nitrogen, the gas flow rate: 80-100 Nm ³ /h; 4) After the slag layer is discharged, lower the dipping hood, and continue to use the spray gun above the dipping hood to blow in one of oxygen or air, and the gas flow rate is controlled at 5-10Nm ³ /h∙t; 5) After the desiliconization treatment is completed, the dipping hood and spray gun are raised, and the molten iron is transported to the slag removal position, and the slag removal treatment is performed on the molten iron; 6) After the slag removal is completed, temperature measurement and sampling are carried out. If the amount of desiliconization meets the requirements, the qualified molten iron is hoisted to the next process by a crane; If the amount of desiliconization does not meet the requirements, repeat steps 2-6 to repeat the desiliconization operation.