CN103540711B - Method for simultaneously removing sulfur and phosphorus from semi-steel - Google Patents

Abstract

The invention provides a method for simultaneous desulfurization and dephosphorization of semi-steel. The method comprises the following steps carried out sequentially at the semi-steel desulfurization station: the semi-steel is sprayed in the first stage with a desulfurization oxygen lance, and the injection object is an auxiliary blowing powder with an inert gas as a carrier; The semi-steel is injected in the second stage, and the injection is a mixture of blowing aid powder and passivated magnesium powder with inert gas as the carrier; the semi-steel is injected in the third stage with a desulfurization oxygen gun, and the injection is Inert gas is used as a carrier blowing powder, wherein the semi-steel is molten iron obtained after vanadium-containing molten iron is extracted from a converter, and the blowing powder consists of 55-80 parts by weight of passivated lime, 5-15 parts of oxidized It is made of iron and 20-30 parts of sodium oxide. The advantages of the invention include: simultaneous pretreatment desulfurization and dephosphorization can be performed on semi-steel after vanadium extraction; corrosion of the furnace lining of the vanadium extraction converter can be avoided, and the sodium content in the vanadium slag can be reduced at the same time.

Description

A method for simultaneous desulfurization and dephosphorization of semi-steel

technical field

The invention belongs to the technical field of semi-steel smelting after vanadium extraction, and specifically relates to a method for simultaneously desulfurizing and dephosphorizing semi-steel obtained after vanadium-containing molten iron is treated after vanadium extraction.

Background technique

Generally, phosphorus and sulfur are harmful elements in most steel types. In recent years, with the rapid development of science and technology, low-temperature steel, marine steel, hydrogen-induced cracking-resistant steel and steel for some thick plates require both extremely low sulfur content and phosphorus content in steel <0.01% or 0.005 %. As we all know, the sulfur content directly affects the performance of steel. Excessive sulfur content in steel will lead to deterioration of the hot workability of steel, resulting in "hot embrittlement" of steel; cracks; the plasticity of steel also significantly deteriorates with the increase of sulfur content; in pure iron or silicon steel sheets, the high sulfur content increases the hysteresis loss. So desulfurization has become one of the main goals in iron and steel smelting.

Desulfurization of hot metal is considered to be the main method to reduce the metallurgical load of blast furnace and converter and improve technical and economic indicators, and it has also become an indispensable technical means for smelting low-sulfur clean steel. Since the 1980s, various treatment methods have been developed for the pre-dephosphorization of molten iron. The dephosphorization pretreatment of molten iron is carried out in the converter, and these two methods have been applied in industry. Dephosphorization of ladles or torpedo tanks mainly has problems such as large temperature drop, severe splashing during oxygen blowing to compensate for temperature drop, and long processing time of molten iron, which affects the smooth production, and the application situation is not ideal. However, converter pre-dephosphorization has been realized on an industrial scale in iron and steel enterprises in Japan and South Korea. When producing low-phosphorus steel, Baosteel and Wuhan Iron and Steel in China adopt double-furnace double-dephosphorization process for smelting, and the molten steel [P] can be reduced from 0.08% to 0.003%～0.008%, the effect is excellent.

The patent document with the publication number CN102796840A discloses a coolant for dephosphorization and vanadium extraction in a converter and a production method thereof, and a method for vanadium extraction in a converter. The production method of the coolant for dephosphorization and vanadium extraction in a converter comprises the following steps: Granules, iron oxide scale particles, bauxite fine powder and water are mixed to form a mixture; the mixture is pressed into pellets through a ball press machine; the pellets are baked to remove moisture, and the finished cold-set pellets are obtained. The advantages of the present invention include: the vanadium extraction and dephosphorization can be realized simultaneously in the process of vanadium extraction in the converter; the operation is simple; the influence on the existing vanadium extraction process and semi-steel quality is small; the dephosphorization efficiency is high, and the vanadium extraction converter can be guaranteed Productivity. In addition, the present invention can forward part of the dephosphorization task of the steelmaking converter to the vanadium extracting converter, realize semi-steel low-cost converter steelmaking, and facilitate the obtaining of molten steel with qualified composition and temperature.

Publication No. CN101215619A discloses a method for extracting vanadium and dephosphorization from vanadium-containing iron water and a steelmaking process using the method. The method for extracting vanadium and dephosphorization from vanadium-containing iron water includes: In the process of blowing molten iron with oxygen, a vanadium extracting and dephosphorizing agent and a coolant are added to the molten iron. The vanadium extracting and dephosphorizing agent is Na ₂ CO ₃ , and vanadium slag and low-phosphorus semi-steel are obtained after blowing. The method can dephosphorize while extracting vanadium, thereby not only ensuring the effective extraction of vanadium, but also effectively removing phosphorus in molten iron.

However, the methods in the above two patent documents all use sodium compounds as dephosphorization agents and carry out dephosphorization in the vanadium extraction converter. Although this can achieve a certain dephosphorization effect, the addition of sodium compounds into the converter The furnace lining is eroded greatly, which affects the life of the converter, and at the same time increases the sodium content in the vanadium slag, which is unfavorable for the subsequent production of vanadium products.

Contents of the invention

It is an object of the present invention to solve at least one of the above-mentioned problems of the prior art.

For example, one of the objectives of the present invention is to provide a method capable of simultaneous desulfurization and desulfurization of semi-steel after vanadium extraction.

The invention provides a method for simultaneous desulfurization and dephosphorization of semi-steel. The method comprises the following steps carried out sequentially at the semi-steel desulfurization station: the semi-steel is sprayed in the first stage with a desulfurization oxygen lance, and the injection object is an auxiliary blowing powder with an inert gas as a carrier; The semi-steel is injected in the second stage, and the injection is a mixture of blowing aid powder and passivated magnesium powder with inert gas as the carrier; the semi-steel is injected in the third stage with a desulfurization oxygen gun, and the injection is Inert gas is used as a carrier blowing powder, wherein the semi-steel is molten iron obtained after vanadium-containing molten iron is extracted by a converter, and the blowing powder is composed of 55-80 parts by weight of passivated lime, 5-15 parts It is made of iron oxide and 20-30 parts of sodium oxide.

Compared with the prior art, the beneficial effects of the present invention include: the simultaneous pretreatment desulfurization and dephosphorization of semi-steel after vanadium extraction; Consumption of auxiliary materials for converter steelmaking; it can avoid the erosion of the lining of the vanadium extracting converter, and at the same time reduce the sodium content in the vanadium slag.

Detailed ways

Hereinafter, the method for simultaneously desulfurizing and dephosphorizing semi-steel of the present invention will be described in detail with reference to exemplary embodiments.

Vanadium-containing iron ore (for example, vanadium-titanium magnetite) is smelted in a blast furnace to obtain vanadium-containing molten iron, which requires vanadium extraction smelting and molten iron pretreatment. The inventors found that after the vanadium-containing molten iron is subjected to vanadium extraction treatment (for example, vanadium extraction and smelting in a converter), the content of silicon, manganese, vanadium and other elements is less, while the content of phosphorus and sulfur is basically unchanged; Between 1400°C, just in the optimum temperature range for dephosphorization. Therefore, the inventor has proposed a method for simultaneously desulfurizing and dephosphorizing semi-steel at a semi-steel desulfurization station.

According to an exemplary embodiment of the present invention, the method for simultaneous desulfurization and dephosphorization of semi-steel comprises the following steps carried out sequentially at the semi-steel desulfurization station: the semi-steel is sprayed in the first stage with a desulfurization oxygen lance, and the injection object is Blowing powder with inert gas as the carrier; use a desulfurization oxygen gun to spray the semi-steel in the second stage, and the injection is a mixture of blowing powder and passivated magnesium powder with an inert gas as a carrier; use a desulfurization oxygen gun to spray The semi-steel is sprayed in the third stage, and the blowing object is the blowing aid powder with inert gas as the carrier, wherein the semi-steel is the molten iron obtained after the vanadium-containing molten iron is extracted from the converter, and the blowing aid is prepared by It is made by weight of 55-80 parts of passivated lime, 5-15 parts of iron oxide and 20-30 parts of sodium oxide. Here, the passivated magnesium powder is a desulfurizer, and the passivated lime (CaO) in the blowing aid powder can react with [S] in the semi-steel to generate CaS. For the method of the present invention, the injection amount of the blowing aid powder and the passivation magnesium powder can be determined according to the phosphorus and sulfur content in the semi-steel. In addition, preferably, the blowing aid powder may be made of 60-75 parts by weight of passivated lime, 7-13 parts of iron oxide and 22-28 parts of sodium oxide.

In another exemplary embodiment of the present invention, the method for simultaneous desulfurization and dephosphorization of semi-steel, on the basis of the above exemplary embodiment, further includes the injection amount of the blowing aid powder in the first stage injection step, the second The injection amount of the blowing powder in the second stage injection step and the injection amount of the blowing powder in the third stage injection step are respectively controlled at 5% to 10% and 70% to 80% of the total injection amount of the blowing powder and 15% to 25%, and the sum of the injection volume of the blowing powder in the first stage injection step, the second stage injection step and the third stage injection step is the total injection volume of the blowing powder agent. In the method of the present invention, the first stage injection is mainly to remove the sulfur in the semi-steel, the sulfur content of this stage is high and the desulfurization kinetics conditions are good; the second stage adopts mixed injection, mainly to utilize the strong magnesium The desulfurization effect is desulfurized; the third stage is mainly to remove the phosphorus in the semi-steel. Preferably, in the second-stage injection step, the ratio of the injection amount of the blowing aid powder to the injection amount of the passivation magnesium powder is controlled to be 5:1˜7:1. This can make the condition of slag good and easy to remove, the phosphorus and sulfur capacity of the slag is high, and it is easy to control phosphorus and sulfur.

In addition, preferably, the distance between the desulfurization oxygen lance and the half-steel surface is controlled to be 50 cm to 100 cm, which can further improve the blowing effect of the desulfurization oxygen lance.

In another exemplary embodiment of the present invention, the method for simultaneous desulfurization and dephosphorization of semi-steel is implemented in the following manner.

After the converter vanadium extraction is completed, the non-desulfurized and dephosphorized semi-steel is transported to the desulfurization station. Before desulfurization, put the auxiliary blowing powder and passivated magnesium powder into different material tanks. The material tanks are sealed with dry nitrogen. Powder blowing agent, spraying speed is 30-55kg/min, spraying 0.5-2min; then, use blowing aid powder and passivated magnesium powder to spray at the same time for desulfurization and dephosphorization, when the injection volume of passivated magnesium powder meets the desulfurization requirements Finally, close the valve of the passivated magnesium powder silo. For example, the injection speed of the passivated magnesium powder in this stage can be 6-10kg/min, and the injection time can be 8-15min. The ratio of the injection amount of magnesium powder is controlled at 5:1~7:1; Next, continue to spray the blowing powder for 0.5~2min, the injection speed is 30~55kg/min, and then raise the spray gun until the spray gun leaves the semi-steel Stop spraying after the liquid level.

In an exemplary embodiment of the present invention, the mass percentage of CaO in the passivated lime can be more than 80%, preferably more than 85%, in order to achieve a better desulfurization effect, and the particle size of the passivated lime is preferably <1.5mm . The grade of passivated magnesium powder can be >90%, the density is usually 0.88-0.98g/cm ³ , and the particle size is preferably <2mm; more preferably, the weight of the part with a particle size greater than 1.2mm in the passivated magnesium powder does not exceed the weight of the passivated magnesium powder 2% of the total amount of passivated magnesium powder and the weight of the part whose particle size is less than 0.15mm is not more than 10% of the total amount of passivated magnesium powder. The grade of iron oxide (powder) can be >90%, and the particle size can be <0.5mm. Preferably, the weight of the iron oxide powder with a particle size of less than 0.075mm is not less than 80% of the total iron oxide powder and the particle size is less than 0.25mm The weight of the part should not be less than 98% of the total iron oxide powder. The grade of sodium oxide can be >95%, and the particle size can be <0.5mm. Preferably, the weight of the part of sodium oxide with a particle size of less than 0.075mm is not less than 80% of the total amount of sodium oxide and the weight of the part with a particle size of less than 0.25mm is not Less than 98% of the total amount of sodium oxide. This can further improve the dephosphorization and desulfurization effects. However, the present invention is not limited thereto. For example, when the particle size of passivated lime, passivated magnesium powder, iron oxide powder, and sodium oxide is not greater than 2 mm, good desulfurization and dephosphorization effects can be achieved.

In order to better understand the present invention, it will be further described below in conjunction with specific examples.

Example 1

Passivated lime, iron oxide powder, and sodium oxide are used as raw materials to produce blowing aids, of which 65% of passivated lime, 15% of iron oxide, and 20% of sodium oxide. Before desulfurization, put the blowing aid powder and passivated magnesium powder into different material tanks, and the material tanks are sealed with dry nitrogen.

After the vanadium extraction in the converter is completed, the non-desulfurized semi-steel obtained after the vanadium extraction converter treatment is transported to the desulfurization station. Among them, the C content of semi-steel is 3.61%, the P content is 0.068%, and the S content is 0.065%.

When the desulfurization spray gun is lowered to 50cm of the half-steel liquid level, nitrogen is used as the carrier to spray the blowing aid powder, the spray speed is 42kg/min, and the spray is 0.5min. Then, desulfurization and dephosphorization are carried out by simultaneously spraying the blowing aid powder and passivated magnesium powder. The injection speed of passivated magnesium powder is 8.5kg/min, and the injection time is 15min. The ratio of the injection amount of magnesium powder is controlled to be 5:1. Next, continue to spray the blowing aid powder for 1 minute, the spray speed is 44kg/min, then lift the spray gun, and stop spraying after the spray gun leaves the semi-steel liquid surface.

After testing, in the semi-steel after the above treatment, the phosphorus content is 0.039%, the dephosphorization rate reaches 43.28%, the sulfur content is 0.011%, and the desulfurization rate reaches 83.08%.

Example 2

Passivated lime, iron oxide powder, and sodium oxide are used as raw materials to produce blowing aids, of which 65% of passivated lime, 5% of iron oxide, and 30% of sodium oxide. Before desulfurization, put the blowing aid powder and passivated magnesium powder into different material tanks, and the material tanks are sealed with dry nitrogen.

After the vanadium extraction in the converter is completed, the non-desulfurized semi-steel obtained after the vanadium extraction converter treatment is transported to the desulfurization station. Among them, the C content of semi-steel is 3.84%, the P content is 0.070%, and the S content is 0.54%.

When the desulfurization spray gun is lowered to 100cm of the half-steel liquid level, nitrogen is used as the carrier to spray the blowing aid powder, the spray speed is 39kg/min, and the spray is 1min. Then, desulfurization and dephosphorization are carried out by spraying the blowing aid powder and passivated magnesium powder at the same time. The ratio of powder injection amount is controlled to be 7:1. Next, continue to spray the blowing aid powder for 2 minutes, the spray speed is 38kg/min, then lift the spray gun, and stop spraying after the spray gun leaves the semi-steel liquid surface.

After testing, in the semi-steel after the above treatment, the phosphorus content is 0.036%, the dephosphorization rate reaches 48.57%, the sulfur content is 0.009%, and the desulfurization rate reaches 83.33%.

The invention can simultaneously desulfurize and dephosphorize the semi-steel (for example, the dephosphorization rate can reach more than 40%, even more than 45%, and the desulfurization rate can reach more than 80%), thereby providing low-phosphorus-sulfur semi-steel for steelmaking converters. Steel, which reduces the dephosphorization task of the steelmaking converter when smelting molten steel, and creates conditions for smelting low-phosphorus steel and realizing less slag steelmaking. In addition, the present invention also has the advantages of simple operation, no additional construction of related facilities and equipment, no prolongation of process time, and a good effect on reducing the consumption of auxiliary materials for converter steelmaking. In addition, the invention can also avoid corrosion to the lining of the vanadium extracting converter, and can reduce the sodium content in the vanadium slag at the same time.

Although the invention has been described above in conjunction with exemplary embodiments, it will be apparent to those skilled in the art that various modifications may be made to the above embodiments without departing from the spirit and scope of the claims.

Claims (3)

1. a method for desulfurization and dephosphorization of semi-steel simultaneously, is characterized in that, described method comprises the following steps that carry out in semi-steel desulfurization station order: Use the desulfurization spray gun to spray the semi-steel in the first stage, and the sprayed object is the blowing aid powder with inert gas as the carrier; The semi-steel is sprayed in the second stage with a desulfurization spray gun, and the injection is a mixture of blowing aid powder and passivated magnesium powder with inert gas as the carrier; Use the desulfurization spray gun to spray the semi-steel in the third stage, and the sprayed material is the blowing aid powder with inert gas as the carrier. Wherein, the semi-steel is the molten iron obtained after vanadium-containing molten iron is extracted from the converter, and the blowing aid powder is composed of 55-80 parts by weight of passivated lime, 5-15 parts of iron oxide and 20-30 parts of made of sodium oxide, Wherein, in the step of the second-stage injection, the ratio of the injected amount of the blowing aid powder to the injected amount of the passivated magnesium powder is controlled to be 5:1-7:1. 2 . The method for simultaneous desulfurization and dephosphorization of semi-steel according to claim 1 , characterized in that, in the method, the distance between the desulfurization oxygen lance and the liquid surface of the semi-steel is 50 cm to 100 cm. 3. The method for simultaneous desulfurization and dephosphorization of semi-steel according to claim 1, characterized in that, the blowing aid consists of 60 to 75 parts by weight of passivated lime, 7 to 13 parts of iron oxide and 22 parts by weight. ~28 parts of sodium oxide.