Oxygen injection lance nozzle for improving steel scrap ratio of converter and blowing process

Abstract

The invention belongs to the technical field of ferrous metallurgy, and relates to a blowing oxygen lance nozzle for improving the steel scrap ratio of a converter and a blowing process. The main jet flow hole is formed in the bottom, the secondary combustion auxiliary holes are formed in the side wall, the secondary combustion auxiliary holes adopt the diverging pipe design mode, the secondary combustion oxygen flow outlet speed is reduced, interference to main oxygen jet flow caused by too high outlet speed is avoided, the secondary combustion efficiency is enhanced, meanwhile, the main oxygen jet flow is blown in through jetting gas in a rotational flow mode, and the secondary combustion efficiency is improved. The blowing stirring condition is improved, the stirring strength of the molten pool is enhanced, the heat and mass transfer process between the molten pool and the scrap steel is enhanced, the melting speed of the scrap steel is increased, and the uniform mixing time of the molten pool is shortened.

Description

Technical Field

[0001] The invention belongs to the technical field of iron and steel metallurgy, and in particular relates to an oxygen injection lance nozzle and a blowing process for improving the scrap steel ratio of a converter. Technical Background

[0002] my country has developed long-process steelmaking in converters. Therefore, increasing the use of scrap steel in the long-process steelmaking process can not only reduce carbon emissions, but also has important significance for improving the operating efficiency of enterprises. The difficulty of increasing the scrap steel ratio in the converter lies in the heat compensation in the converter. Domestic and foreign steel companies have done a lot of work in increasing the scrap steel ratio in the converter and reducing the molten iron consumption in converter steelmaking, such as using secondary combustion technology. The porous secondary combustion oxygen gun fully utilizes the chemical energy of CO gas produced by incomplete combustion for secondary combustion through oxygen-enriched operation, thereby accelerating the melting of scrap steel, increasing the scrap steel ratio in the furnace, and reducing the molten iron consumption. In order to overcome the problem that the secondary oxygen holes are radially arranged in the secondary combustion oxygen gun, which has limited effect on improving the degree of secondary combustion and is prone to radial erosion and erosion of the converter lining by high-temperature furnace gas, the patent named a self-rotating secondary combustion oxygen gun (CN105154617 A) provides a self-rotating secondary combustion oxygen gun, which expands the secondary combustion reaction area by forming a rotating secondary oxygen flow inside the converter, and makes the secondary combustion heat tend to be evenly distributed.

[0003] However, this type of secondary combustion oxygen lance has not been widely used. The reason is that the melting rate of scrap steel in molten steel is not only closely related to the temperature in the furnace, but also related to the mixing intensity of the scrap steel and the molten pool. Generally speaking, the better the stirring effect of the oxygen lance jet on the molten pool, the faster the melting of the scrap steel can be accelerated. The secondary combustion oxygen lance has unique advantages in heat compensation and increasing the temperature in the furnace. However, in order to ensure that carbon monoxide gas can burn above the furnace, the operating gun position of the secondary combustion oxygen lance is usually higher than that of the traditional oxygen lance blowing gun. The consequence is that the main oxygen jet is not strong enough to affect the slag formation speed and stirring of the molten pool. This deficiency and defect limits the further application of the secondary combustion oxygen lance.

[0004] It can be seen that the difficulty in increasing the scrap ratio of the converter lies in ensuring sufficient heat for melting the scrap steel in the converter, while not destroying the oxygen jet in the furnace and providing sufficient jet strength to strengthen the stirring of the molten pool. In order to solve the above problems, it is necessary to develop and design an oxygen lance nozzle and blowing process that can increase the scrap ratio of the converter, realize heat compensation in the converter, increase the temperature in the furnace, and improve the blowing and stirring conditions, thereby increasing the melting speed of the scrap steel and shortening the mixing time of the molten pool. Summary of the invention

[0005] In view of the above technical problems, the present invention provides a nozzle for oxygen lance blowing and a blowing process for improving the scrap steel ratio of a converter. The present invention realizes heat compensation in the converter by changing the oxygen jet of a conventional secondary combustion oxygen lance, thereby increasing the temperature in the furnace, and changes the blowing characteristics of the main jet swirl injection of the conventional secondary combustion oxygen lance. The main jet swirl injection method is innovatively adopted, and the oxygen jet state is changed through the optimized unique swirl angle design, the stirring capacity of the molten pool is improved, and various metallurgical reactions are promoted, thereby shortening the smelting time.

[0006] In order to realize rapid combustion of converter atmosphere above the furnace, the present invention changes the structure of traditional straight tube injection and adopts a gradually expanding tube to reduce the outlet velocity, thereby avoiding the problem of secondary combustion oxygen jet interfering with the main oxygen jet due to excessive outlet velocity.

[0007] In order to achieve the above object, the present invention provides the following technical solutions.

[0008] An oxygen lance nozzle for increasing the scrap steel ratio of a converter comprises a first tube body 1; a second tube body 2 is sleeved on the outside of the first tube body 1, and a first annular gap is left between the first tube body 1 and the second tube body 2; a through hole 4 is opened at the center of the bottom of the second tube body 2; a third tube body 3 is sleeved on the outside of the second tube body 2, and a second annular gap is left between the second tube body 2 and the third tube body 3; the first tube body 1, the second tube body 2 and the third tube body 3 are all cylindrical tube bodies; A main jet hole 5 is provided at the bottom of the third tube body 3. The main jet hole 5 passes through the third tube body 3, the second tube body 2 and the bottom wall of the first tube body 1, and is connected with the interior of the first tube body 1. There are multiple main jet holes 5. A secondary combustion auxiliary hole 6 is arranged on the side wall of the third tube body 3 near the main jet hole 5. The secondary combustion auxiliary hole 6 passes through the side walls of the third tube body 3, the second tube body 2 and the first tube body 1, and is connected with the interior of the first tube body 1. There are multiple secondary combustion auxiliary holes 6, and the secondary combustion auxiliary holes 6 are evenly distributed along the circumference of the third tube body 3.

[0009] Furthermore, the secondary combustion auxiliary hole 6 is a single-channel secondary combustion oxygen lance nozzle, that is, the secondary combustion auxiliary hole 6 and the main jet hole 5 share an oxygen channel, and the oxygen flow is sprayed into the molten pool from the main jet hole 5 and the secondary combustion auxiliary hole 6 respectively.

[0010] Furthermore, the main jet hole 5 is a swirl jet hole, and a Lafayette structure nozzle is arranged in the main jet hole 5, and the throat diameter of the nozzle is d 2 , the outlet diameter is d e , d 2 / d e =0.3-0.8; the swirl angle of the nozzle is θ=6~10°, and the nozzle inclination angle is α=12~14°.

[0011] Furthermore, a gradually expanding tube is arranged in the secondary combustion auxiliary hole 6, and the angle between the central axis of the gradually expanding tube and the axial axis of the oxygen lance nozzle is β1, β1=25°~35°; the expansion angle of each side of the gradually expanding tube is β2, β2=3°~8°.

[0012] Furthermore, the outlet Ma of the main jet hole 5 is 2.0-2.1.

[0013] Furthermore, the applicable scope of the oxygen lance nozzle of the present invention is 100-200 ton converter, the number of the main jet holes 5 is 4 or 5, and the number of the secondary combustion auxiliary holes 6 is 8 or 10.

[0014] When the oxygen injection lance nozzle of the present invention is used, the slag lance position in the early stage of the blowing process is (40-50) d e , mid-term decarburization gun position is (35~45) d e , the position of the carbon pulling gun in the later stage is (30~35) d e .

[0015] According to the mechanical and geometric conditions that cause the gas flow rate to change, it can be known that: dP / P=-kMa 2 dc f / c f dA / A=(Ma 2 -1) dc f / c f In the above formula, P represents the pressure of the secondary combustion auxiliary hole, k represents the gas adiabatic coefficient, A represents the cross-sectional area of ​​the secondary combustion secondary hole, Ma represents the Mach number of the gas, c f Represents the gas flow rate in the pipeline; It can be seen from the above formula that, under the premise of unchanged mechanical conditions, the change of the outlet velocity can only rely on the change of the outlet area. The secondary combustion secondary hole adopts subsonic flow, so the use of a gradually expanding tube can theoretically reduce the outlet velocity.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows.

[0017] (1) The present invention fully utilizes the advantages of the secondary combustion auxiliary hole to compensate for the heat in the furnace, thereby increasing the temperature in the furnace.

[0018] (2) The position design of the secondary combustion auxiliary hole and the use of the gradually expanding tube in the present invention reduce the outlet velocity of the secondary combustion oxygen flow, avoid the interference of the excessive outlet velocity on the main oxygen jet, and enhance the efficiency of the secondary combustion. At the same time, the main oxygen jet adopts the method of blowing gas swirl to improve the blowing stirring conditions and enhance the stirring intensity of the molten pool. The heat and mass transfer process between the molten pool and the scrap steel is strengthened, the melting rate of the scrap steel is increased, and the mixing time of the molten pool is shortened. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be introduced below. Obviously, the drawings are only some embodiments recorded in the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0020] Figure 1 It is a front view of the oxygen lance nozzle of the present invention.

[0021] Figure 2 It is a schematic diagram of the structure of the oxygen lance nozzle of the present invention.

[0022] Figure 3 It is a top view of the oxygen lance nozzle of the present invention.

[0023] Figure 4 It is a bottom view of the oxygen lance nozzle of the present invention.

[0024] Figure 5 It is a front cross-sectional view of the oxygen lance nozzle of the present invention.

[0025] Figure 6 It is a cross-sectional stereoscopic view of the main oxygen lance nozzle of the present invention.

[0026] In the figure: 1, first tube body; 2, second tube body; 3, third tube body; 4, through hole; 5, main jet hole; 6, secondary combustion auxiliary hole. DETAILED DESCRIPTION

[0027] The embodiments of the technical solution of the present invention will be described in detail below in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention and are therefore only used as examples and cannot be used to limit the protection scope of the present invention.

[0028] Example

[0029] like Figure 1-Figure 6As shown, an embodiment of the present invention provides an oxygen lance nozzle for increasing the scrap steel ratio of a converter, comprising a first tube body 1; a second tube body 2 is sleeved on the outside of the first tube body 1, and a first annular gap is left between the first tube body 1 and the second tube body 2; a through hole 4 is opened at the center of the bottom of the second tube body 2; a third tube body 3 is sleeved on the outside of the second tube body 2, and a second annular gap is left between the second tube body 2 and the third tube body 3; the first tube body 1, the second tube body 2 and the third tube body 3 are all cylindrical tubes; a main jet hole 5 is provided at the bottom of the third tube body 3, and the main jet hole 5 passes through the third tube body 3, the second tube body 2 and the bottom wall of the first tube body 1, and is connected with the interior of the first tube body 1, and there are 5 main jet holes 5; the side wall of the third tube body 3 is provided with secondary combustion auxiliary holes 6 near the main jet holes 5, and the secondary combustion auxiliary holes 6 pass through the side walls of the third tube body 3, the second tube body 2 and the first tube body 1, and are connected with the interior of the first tube body 1, and there are 10 secondary combustion auxiliary holes 6, which are evenly distributed along the circumference of the third tube body 3, and the 10 secondary combustion auxiliary holes 6 are at the same height, and a gradually expanding tube is provided in the secondary combustion auxiliary hole 6.

[0030] The present invention adopts the position of the secondary combustion auxiliary hole and the design of the gradual expansion tube to reduce the outlet velocity of the secondary combustion oxygen flow, avoid the interference of the excessive outlet velocity on the main oxygen jet, and enhance the efficiency of the secondary combustion. At the same time, the main oxygen jet adopts the method of blowing in the form of a swirl of injection gas, which improves the blowing and stirring conditions, enhances the stirring intensity of the molten pool, strengthens the heat and mass transfer process between the molten pool and the scrap steel, increases the melting speed of the scrap steel, and shortens the mixing time of the molten pool.

[0031] In the present invention, the main jet hole 5 is a swirl jet hole, and a Lafayette structure nozzle is arranged in the main jet hole 5, and the throat diameter of the nozzle is d 2 , the outlet diameter is d e , (39.5 / 51.8) d 2 / d e = 0.76; the swirl angle of the nozzle is θ=10°, the nozzle inclination angle is α=14°, and the outlet Ma of the main jet hole 5 is 2.02. Its structural feature is that the swirl angle is increased on the basis of the conventional oxygen gun, so that it can generate a large tangential component while generating axial and radial impulses, thereby improving the dynamic stirring of the molten pool.

[0032] In the present invention, the angle between the central axis of the gradually expanding tube of the secondary combustion auxiliary hole 6 and the axial axis of the oxygen lance nozzle is β1, β1=30°; the expansion angle of each side of the gradually expanding tube is β2, β2=15°.

[0033] In the present invention, the secondary combustion auxiliary hole 6 is a single-channel secondary combustion oxygen lance nozzle, that is, the secondary combustion auxiliary hole 6 and the main jet hole 5 share an oxygen channel, and the oxygen flow is sprayed into the molten pool from the main jet hole 5 and the secondary combustion auxiliary hole 6 respectively.

[0034] In order to further verify the obvious smelting effect of the oxygen lance and blowing process for improving the scrap steel ratio of the converter compared with the traditional oxygen lance and blowing process, so that the advantages and features of the present invention can be further understood by professional and technical personnel in this field, thereby making a clearer definition and understanding of the protection scope of the present invention, an industrial experimental comparison is carried out in combination with the embodiments below.

[0035] Taking a 120t converter used in a steel plant as an object, the oxygen lance nozzle of the present invention is adopted. The design parameters of the oxygen lance nozzle are shown in Table 1.

[0036] Table 1 Geometric dimensions of the oxygen lance nozzle of the embodiment and the conventional oxygen lance nozzle.

[0037] The specific blowing process is as follows: the slag lance position in the early stage is 2.1-2.6m; the decarburization lance position in the middle stage is 1.8-2.4m; the carbon pulling lance position in the late stage is 1.6-2.4m; the oxygen supply in the blowing process is 34600 Nm 3 / h~36200 Nm 3 / h, working oxygen pressure 0.9MPa~1.1MPa.

[0038] The composition of the molten iron used for blowing by the oxygen lance nozzle of the present invention and the composition of the molten iron used by the conventional 5-hole oxygen lance nozzle are shown in Table 2.

[0039] Table 2 Molten iron composition.

[0040] Taking the average value of the effective smelting index of 100 consecutive furnaces of the same steel grade as the object, the smelting index comparison results after using the oxygen lance nozzle of the present invention and the traditional 5-hole oxygen lance nozzle are shown in Table 3.

[0041] Table 3 Comparison of key smelting indicators.

[0042] After using the oxygen lance nozzle of the present invention, the composition of the steel produced is as shown in Table 3.

[0043] Table 4 Steel composition.

[0044] As shown in Table 3, compared with the blowing results of the traditional 5-hole oxygen lance nozzle, the 5-hole oxygen lance nozzle and blowing process for improving the scrap steel ratio of the converter of the present invention can shorten the average oxygen blowing time by 43 seconds, increase the scrap steel charging amount from 24.4t to 27.5t, an increase of 12.7%, and increase the scrap steel ratio from 14.0% of the traditional oxygen lance nozzle to 15.5%. With the increase of the scrap steel charging amount, the steel output increased from 162t to 171t, and the dephosphorization rate did not change significantly; as shown in Table 4, the steel composition is also relatively stable.

[0045] This fully demonstrates that the present invention can make full use of the advantages of the secondary combustion oxygen gun to effectively compensate for the heat in the furnace and increase the temperature in the furnace. The secondary combustion auxiliary hole position design and the gradual expansion tube design can reduce the secondary combustion oxygen flow outlet speed and avoid the interference of excessive outlet speed on the main oxygen jet, thereby enhancing the efficiency of secondary combustion. The effective shortening of the blowing time also fully demonstrates that the main oxygen jet adopts the method of blowing gas swirl, which can effectively improve the blowing and stirring conditions, enhance the stirring intensity of the molten pool, strengthen the heat and mass transfer process between the molten pool and the scrap steel, and increase the melting rate of the scrap steel.

Claims

1. An oxygen lance nozzle for increasing the scrap ratio of a converter, characterized in that: The invention comprises a first tube body (1); a second tube body (2) is sleeved on the outside of the first tube body (1), and a first annular gap is left between the first tube body (1) and the second tube body (2); a through hole (4) is opened at the center of the bottom of the second tube body (2); a third tube body (3) is sleeved on the outside of the second tube body (2), and a second annular gap is left between the second tube body (2) and the third tube body (3); the first tube body (1), the second tube body (2) and the third tube body (3) are all cylindrical tube bodies; The bottom of the third tube body (3) is provided with a main jet hole (5), the main jet hole (5) passes through the third tube body (3), the second tube body (2) and the bottom wall of the first tube body (1), and is connected with the interior of the first tube body (1), and there are a plurality of main jet holes (5); A secondary combustion auxiliary hole (6) is provided on the side wall of the third tube body (3) near the main jet hole (5); the secondary combustion auxiliary hole (6) passes through the side walls of the third tube body (3), the second tube body (2) and the first tube body (1), and is connected to the interior of the first tube body (1); there are a plurality of secondary combustion auxiliary holes (6), and the secondary combustion auxiliary holes (6) are evenly distributed along the circumference of the third tube body (3).

2. The oxygen lance nozzle for increasing the scrap steel ratio of a converter according to claim 1, characterized in that: The secondary combustion auxiliary hole (6) and the main jet hole (5) share an oxygen channel.

3. The oxygen lance nozzle for increasing the scrap steel ratio of a converter according to claim 1, characterized in that: The main jet hole (5) is a swirl jet hole. A Lafayette structure nozzle is arranged in the main jet hole (5). The throat diameter of the nozzle is d 2 , the outlet diameter is d e , d 2 / d e = 0.3-0.8; the swirl angle of the nozzle is θ=6~10°, and the nozzle inclination angle is α=12~14°.

4. The oxygen lance nozzle for increasing the scrap steel ratio of a converter according to claim 1, characterized in that: A gradually expanding tube is arranged in the secondary combustion auxiliary hole (6), the central axis of the gradually expanding tube and the axis of the oxygen lance nozzle are at an angle of β1, β1=25°-35°; the expansion angle of each side of the gradually expanding tube is β2, β2=3°-8°.

5. The oxygen lance nozzle for increasing the scrap steel ratio of a converter according to claim 1, characterized in that: The outlet Ma of the main jet hole (5) is 2.0-2.

1.

6. The oxygen lance nozzle for increasing the scrap steel ratio of a converter according to claim 1, characterized in that: The number of the main jet holes (5) is 4 or 5, and the number of the secondary combustion auxiliary holes (6) is 8 or 10.

7. The oxygen lance nozzle for increasing the scrap ratio of a converter according to any one of claims 1 to 6, characterized in that: When using oxygen injection lance nozzles to increase the scrap ratio of converter, the slag lance position in the early stage of the blowing process is (40-50) d e , mid-term decarburization gun position is (35~45) d e , the position of the carbon pulling gun in the later stage is (30~35) d e .

Images