A method for recycling and utilizing KR desulfurization slag in a converter

Abstract

The application discloses a method for recycling and utilizing KR desulfurization slag in a converter, and belongs to the technical field of comprehensive utilization of slag. The method comprises the following steps: S1: adding scrap steel and molten iron into the converter, and then performing oxygen blowing operation by means of a lance; S2: adding a composite oxidizing agent into the converter after the oxygen blowing is started, controlling the alkalinity and oxidizability of the converter in the early stage, and adding KR desulfurization slag into the converter after the oxygen blowing is performed for 1 minute. The composite oxidizing agent comprises the following components in percentage by mass: 80-90% 2Fe2O3.SiO2 and 10-20% MnCO3. Alternatively, the composite oxidizing agent is composed of the following components in percentage by mass: 80-90% 2Fe2O3.SiO2 and 10-20% MnCO3. According to the method, the process parameters of the converter in the early stage are optimized, so that the KR desulfurization slag can be used for converter smelting, the CaO and iron resources in the KR desulfurization slag are maximally utilized, and the purposes of simplifying the process and reducing the cost are achieved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of comprehensive utilization of slag, and more particularly to a method for recycling and utilizing KR desulfurization slag in a converter. BACKGROUND

[0002] KR desulfurization process is widely used by steel enterprises at home and abroad due to its simple operation and high desulfurization efficiency. Currently, the KR desulfurizer mainly uses lime, and the chemical composition and mineral phase composition of the desulfurization slag formed after KR desulfurization are CaO, Fe (in the form of oxide or other compounds of iron), CaF2, and CaS, etc. In the KR desulfurization of molten iron, the desulfurization product CaS will wrap on the surface of lime, hindering the internal lime from continuing to play a desulfurization role, so that the utilization efficiency of lime is less than 20%, resulting in a large amount of resource waste. In addition, after KR desulfurization, slag removal treatment is needed, and due to the poor slag-iron separation effect, the iron content in KR desulfurization slag exceeds 50%, causing waste of iron resources and rising of smelting cost.

[0003] The resource utilization of KR desulfurization slag has been one of the hotspots in the field of smelting. According to the search, the Chinese patent application with the publication number CN111250518A discloses a method for efficient resource utilization of KR desulfurization slag. The method first crushes the desulfurization slag to a specified particle size, then uses magnetic separation to obtain slag iron and tailings, and further grinds the tailings for sintering. Although the application can realize the step-by-step use of metallic iron and tailings in KR desulfurization slag to a certain extent, the process is complex and the processing cost is high.

[0004] For example, the Chinese patent application with the publication number CN1730674A discloses a method for using molten iron desulfurization slag for molten iron desulfurization. The application mainly uses the desulfurization slag and lime together for molten iron desulfurization, but can only reduce the discharge amount of KR desulfurization slag, and the recycling times are generally only one. In addition, the desulfurization efficiency of the desulfurization method is generally low.

[0005] The Chinese patent application with the publication number CN116855667A discloses a recycling method for molten iron pretreatment solid waste. The method mainly applies KR desulfurization slag to the smelting of sulfur-containing free-cutting steel, and adds KR desulfurization slag in the LF refining process to increase the sulfur content of molten steel by using slag-gold reaction. However, the application range of the application is limited.

[0006] The Chinese patent application with the publication number CN117965837A discloses a KR molten iron pretreatment slag hot-state recycling method, which mainly adds Fe2O3 and bauxite in the molten iron pretreatment slagging process. However, the following problems exist: (1) the melting point of directly added Fe2O3 is above 1500 DEG C, the melting speed is slow, which limits the reaction rate of Fe2O3 and KR desulfurization slag, thereby leading to low desulfurization efficiency; (2) the SO2 formed after desulfurization is easy to react with Ca in the KR desulfurization slag to form CaSO4, and the decomposition of CaSO4 under high temperature conditions will cause resulfurization, affecting the desulfurization effect.

[0007] Therefore, it is of great significance to develop a new KR desulfurization slag resource utilization method. SUMMARY

[0008] In view of the problems of relatively complex process or poor resource utilization effect of KR desulfurization slag resource utilization in the prior art, the present application provides a method for recycling and utilizing KR desulfurization slag in a converter. The method optimizes the process parameters of the early stage of converter smelting, so that the KR desulfurization slag can be used for converter smelting, and the CaO and iron resources therein are maximally utilized, thereby achieving the purposes of simplifying the process and reducing the cost.

[0009] The present application provides a method for reducing the amount of smoke dust in the early stage of blowing in the double-slag method smelting process of a converter, comprising:

[0010] S1: adding scrap steel and molten iron into the furnace, and then performing oxygen blowing operation by lowering the oxygen lance; S2: adding a composite oxidizing agent into the converter after the start of oxygen blowing, controlling the basicity and oxidizing property of the converter in the early stage, adding KR desulfurization slag into the converter after 1 min of oxygen blowing, and continuing to perform blowing; wherein the composite oxidizing agent comprises the following mass percentage of components: 80-90% 2Fe2O3·SiO2 and 10-20% MnCO3; or the composite oxidizing agent is composed of the following mass percentage of components: 80-90% 2Fe2O3·SiO2 and 10-20% MnCO3.

[0011] In the existing KR desulfurization slag, CaO is mainly wrapped by CaS, and the internal CaO cannot be directly used as a slagging agent. In the traditional converter smelting process, due to oxygen blowing, the main component in the slag is FeO with high oxidizing property, the sulfur distribution ratio between the slag and the metal is very low, and sulfur will spontaneously mass transfer to the molten iron, causing the sulfur content of the molten iron to increase. Therefore, if the KR desulfurization slag is directly recycled and used as a slagging agent in the converter adopting the existing smelting process, the sulfur element in the KR desulfurization slag will flow back to the molten iron in the converter, causing the sulfur content of the molten iron to increase. In addition, since the basicity needs to be controlled in the converter smelting process to remove phosphorus, the gasification desulfurization capacity in the early stage of smelting is limited.

[0012] The present application can realize the recycling resource utilization of KR desulfurization slag in the converter by controlling the process parameters of the early stage of converter smelting, especially the slag basicity and oxidizability of the early stage of converter. It should be noted that the selection of the composite oxidizing agent is particularly important. On the one hand, 2Fe2O3·SiO2 in the composite oxidizing agent is a pre-melted slag, and the melting point is about 1200℃, which is lower than the temperature of the molten iron, so that the pre-melted slag can be quickly melted, thereby improving the desulfurization reaction rate of the KR desulfurization slag. On the other hand, the traditional converter slag is mainly FeO, which cannot be used for gasification of S, and the composite oxidizing agent can provide Fe2O3 required for the sulfur oxidation reaction. Moreover, in the gasification desulfurization process, SiO2 in the composite deoxidizing agent reacts with Ca element to form silicate, which can avoid the reaction of SO2 and Ca to form CaSO4, thereby facilitating the escape of SO2 generated by oxidation. In addition, MnCO3 in the composite oxidizing agent will generate CO2 and MnO after decomposition, and the MnO formed by decomposition can reduce the melting point of the slag and promote the dissolution of lime in the KR desulfurization slag; at the same time, CO2 is an oxidizing atmosphere, which is conducive to promoting the desulfurization reaction.

[0013] Further, when the oxygen blowing operation is performed in S1, the oxygen blowing conditions include: the oxygen supply intensity of the oxygen lance is controlled to be 2.2-3.0 m 3 / t / min, the lance position is controlled to be 2-3 m above the molten iron liquid level, and the oxygen partial pressure is controlled to be 10 -5 -10 -3 Mpa. It should be noted that the parameter limitation of the oxygen blowing condition is particularly important. The oxygen lance oxygen supply intensity, lance position and oxygen partial pressure are controlled, and low oxygen supply intensity and high lance position operation are adopted for blowing, in order to improve the oxidizability of the slag, i.e. to increase the content of Fe2O3 / FeO in the slag, to provide favorable conditions for subsequent gasification dephosphorization; the purpose of controlling the oxygen partial pressure is to prevent C in the molten steel or CO in the furnace gas from reducing Fe2O3 in the slag, so that the content of Fe2O3 in the slag is high. Further, the specific conditions for adding molten iron in S1 are that the temperature of the molten iron is 1300-1500℃, and the sulfur content is 0.02-0.045%. The temperature of the molten iron entering the furnace is limited. When the temperature of the molten iron entering the furnace is too low, the sulfur distribution ratio between the slag and the gold will decrease, so that the sulfur element in the KR desulfurization slag migrates to the molten iron, which is not conducive to the gasification and removal of sulfur in the slag. On the contrary, when the temperature is too high, the C-O reaction will be advanced, which will reduce the oxidizability of the slag, and is also not conducive to the gasification and removal of sulfur. In addition, since the sulfur element can only be oxidized to SO2 in the slag, the sulfur content in the molten iron is controlled under certain sulfur distribution ratio conditions, so that the sulfur element in the KR desulfurization slag exists in the slag layer to the greatest extent, thereby preparing for the subsequent oxidation and removal of sulfur element.

[0014] Further, the adding amount of the composite oxidizing agent in S2 is 22-40 kg / t of steel.

[0015] Further, the adding amount of the KR desulfurization slag in S2 is 5-30 kg / t of steel.

[0016] Further, the adding amount of the composite oxidizing agent in S2 is 22-40 kg / t of steel and the adding amount of the KR desulfurization slag is 5-30 kg / t of steel.

[0017] Further, after the oxygen blowing in S2 starts, lime is added at the same time as the composite oxidizing agent, and the adding amount of the lime is controlled to be 0-3 kg / t of steel.

[0018] Further, the basicity of the slag in the early stage of the converter is controlled to be 1.0-1.3, the sum of the mass of FeO and Fe2O3 accounts for 20-45%, and the mass ratio of Fe2O3 to FeO is greater than or equal to 4. If the basicity is too low in the early stage of the converter, the sulfur element in the slag will flow back into the molten iron, and on the contrary, if the basicity is too high, it is not conducive to the oxidation of the sulfur element in the slag. The main purpose of controlling the high content of Fe2O3 in the slag is that the oxidation reaction of sulfur mainly relies on Fe2O3, and in the traditional converter, the main component in the slag is FeO, which cannot gasify sulfur.

[0019] Further, after 3-4 min of blowing, lime and dolomite are continuously added into the converter in batches, wherein the adding amount of the lime is controlled to be 25-35 kg / t of steel, and the adding amount of the dolomite is controlled to be 10-20 kg / t of steel.

[0020] Further, the basicity of the final slag of the converter is controlled to be 4-5, and the temperature is 1630-1680 DEG C.

[0021] Further, the converter slag splashing operation is performed before the scrap steel and the molten iron are added into the furnace.

[0022] Compared with the prior art, the technical scheme provided by the present application has the following beneficial effects:

[0023] (1) The present application selects a composite oxidizing agent containing 2Fe2O3·SiO2 and MnCO3. On the one hand, the composite oxidizing agent oxidizes the sulfur element contained in the KR desulfurization slag to generate SO2, and makes the generated SO2 escape from the slag layer; on the other hand, the generated MnO can reduce the melting point of the slag, and the generated CO2 is conducive to promoting the desulfurization reaction, thereby preventing the sulfur element contained in the KR desulfurization slag from flowing back into the molten iron, saving the treatment processes such as crushing, magnetic separation and oxidation desulfurization, realizing the direct resource utilization of the KR desulfurization slag in the converter, and simplifying the process and reducing the cost.

[0024] (2) The present application further optimizes the oxygen supply condition, controls the oxygen supply intensity, the gun height and the oxygen partial pressure by a small flow, so as to improve the oxygen content in the furnace gas, control the Fe2O3 / FeO in the slag, and further improve the oxidation reaction of the sulfur in the KR desulfurization slag. In addition, by controlling the basicity of the converter in the early stage, the sulfur element in the slag is prevented from flowing back to the molten iron, and the oxidation reaction of the sulfur element in the slag is further promoted.

[0025] (3) The present application optimizes the composite oxidant, the basicity and the oxygen supply condition, better realizes the oxidation and removal of the sulfur element in the KR desulfurization slag, realizes the resource utilization of the KR desulfurization slag in the converter, so as to fully utilize the unreacted CaO and iron resources in the KR desulfurization slag, reduce the lime consumption and steel material consumption in the converter steelmaking, and save the production cost. In addition, the application of the KR desulfurization slag in the converter smelting can also appropriately improve the desulfurization capacity of the converter. DETAILED DESCRIPTION

[0026] In order to further understand the content of the present application, the present application will be described in detail in combination with specific embodiments.

[0027] The early stage of the converter refers to the period from the addition of the composite oxidant to the addition of lime and dolomite again, that is, within 3-4 minutes after the beginning of blowing.

[0028] Example 1

[0029] This embodiment is carried out on a 180t converter, including the following steps:

[0030] (1) After the end of the converter slag splashing, scrap steel and molten iron are added into the furnace, and the composition and temperature of the molten iron are shown in Table 1. After the end of the molten iron addition, the oxygen lance is lowered to perform oxygen blowing;

[0031] (2) The oxygen supply intensity is controlled to be 2.5m 3 / t / min, the gun height is controlled to be 2.3m, and the oxygen partial pressure is controlled to be 10 -4.5 Mpa. 2kg / t of lime and 22kg / t of composite oxidant are added into the converter after the start of oxygen blowing, 12kg / t of KR desulfurization slag is added into the converter after 1min of oxygen blowing; the mass fraction of 2Fe2O3.SiO2 in the used composite oxidant is 90%, and the mass fraction of MnCO3 is 10%;

[0032] (3) After 3.5min of blowing, 31.4kg / t of lime and 16.7kg / t of dolomite are added in batches, the final point slag basicity is controlled to be 4.2, and the molten steel temperature is controlled to be 1656℃; the slag control condition and the converter smelting index are shown in Table 2.

[0033] The sulfur content of the molten iron at the end of the converter in this example was 0.028%, and compared with the sulfur content of the molten iron charged into the converter, no sulfur was returned at the end of the converter, the total lime consumption was 33.4 kg / t of steel, and the steel material consumption was 1071 kg / t.

[0034] Comparative Example 1

[0035] The composition and temperature of the molten iron charged into the converter in this comparative example are shown in Table 1, and the difference between this comparative example and Example 1 is that a composite oxidizing agent is not used, and iron oxide is used instead of the composite oxidizing agent, the addition amount of the iron oxide is 22 kg / t of steel, 2 kg / t of steel of lime is added into the converter after the start of oxygen blowing, after 3.5 min of blowing, 32.8 g / t of steel of lime and 16.7 kg / t of steel of dolomite are added in batches, and the rest of the operations are basically the same as those in Example 1.

[0036] The sulfur content of the molten iron at the end of the converter in this comparative example was 0.049%, and compared with the sulfur content of the molten iron charged into the converter, sulfur was returned at the end of the converter, the total lime consumption was 34.8 kg / t of steel, and the steel material consumption was 1069 kg / t of steel.

[0037] Comparative Example 2

[0038] The composition and temperature of the molten iron charged into the converter in this comparative example are shown in Table 1, and the difference between this comparative example and Example 1 is that the oxygen blowing conditions are different, the oxygen blowing conditions are as follows: the oxygen gun oxygen supply intensity is controlled at 3.1 m 3 / t / min, the oxygen gun position is controlled at 1.2 m above the molten iron liquid level, the oxygen partial pressure is controlled at 10 -6 Mpa, 2 kg / t of steel of lime is added into the converter after the start of oxygen blowing, after 3.5 min of blowing, 33.2 kg / t of steel of lime and 16.7 kg / t of steel of dolomite are added in batches, and the rest of the operations are basically the same as those in Example 1.

[0039] The sulfur content of the molten iron at the end of the converter in this comparative example was 0.050%, and compared with the sulfur content of the molten iron charged into the converter, sulfur was returned at the end of the converter, the total lime consumption was 35.2 kg / t of steel, and the steel material consumption was 1072 kg / t of steel.

[0040] Comparative Example 3

[0041] The composition and temperature of the molten iron charged into the converter in this comparative example are shown in Table 1, and the difference between this comparative example and Example 1 is that the temperature of the molten iron charged into the converter is 1260°C, 2 kg / t of steel of lime is added into the converter after the start of oxygen blowing, after 3.5 min of blowing, 32.7 kg / t of steel of lime and 16.7 kg / t of steel of dolomite are added in batches, and the rest of the operations are basically the same as those in Example 1.

[0042] The sulfur content of the converter end liquid iron in this comparative example is 0.046%, compared with the sulfur content of the liquid iron charged into the converter, sulfur is returned at the converter end, the total lime consumption is 34.7 kg / t of steel, and the steel material consumption is 1068 kg / t of steel.

[0043] Comparative Example 4

[0044] The composition and temperature of the liquid iron charged into the converter in this comparative example are shown in Table 1, and the existing converter smelting process is used in this comparative example, including the following steps:

[0045] (1) After the end of the converter slag splashing, scrap steel and liquid iron are added into the furnace, the composition and temperature of the liquid iron are shown in Table 1, and after the end of the liquid iron charging, the oxygen lance is lowered to perform oxygen blowing;

[0046] (2) The oxygen supply intensity is controlled to be 3.0 m 3 / t / min, the oxygen lance position is controlled to be 1.3 m, and the oxygen partial pressure is controlled to be 10 - 7 Mpa, and 6 kg / t of steel of lime is added into the converter after the start of oxygen blowing;

[0047] (3) After blowing for 0.5 min, 32.6 kg / t of steel of lime and 21.2 kg / t of steel of dolomite are added in batches, the final slag basicity is controlled to be 3.6, and the molten steel temperature is controlled to be 1658℃; the slag control conditions and the converter smelting indexes are shown in Table 2.

[0048] The sulfur content of the converter end liquid iron in this comparative example is 0.024%, compared with the sulfur content of the liquid iron charged into the converter, the sulfur content is not reduced, the total lime consumption is 38.6 kg / t of steel, and the steel material consumption is 1076 kg / t of steel.

[0049] Example 2

[0050] This example is carried out on a 180 t converter, including the following steps:

[0051] (1) After the end of the converter slag splashing, scrap steel and liquid iron are added into the furnace, the composition and temperature of the liquid iron are shown in Table 1, and after the end of the liquid iron charging, the oxygen lance is lowered to perform oxygen blowing;

[0052] (2) The oxygen supply intensity is controlled to be 2.2 m 3 / t / min, the oxygen lance position is controlled to be 2 m, and the oxygen partial pressure is controlled to be 10 -5 Mpa, 3 kg / t of steel of lime and 40 kg / t of steel of composite oxidizing agent are added into the converter after the start of oxygen blowing, and 25 kg / t of steel of KR desulfurization slag is added into the converter after blowing for 1 min; wherein the mass ratio of 2Fe2O3.SiO2 in the composite oxidizing agent is 80%, and the mass ratio of MnCO3 is 20%;

[0053] (3) After blowing for 3.7 minutes, start to add lime 27.9 kg / t steel and dolomite 13.4 kg / t steel in batches, control the final point slag basicity to be 5.0 and the molten steel temperature to be 1632℃; the slag control condition and the converter smelting indexes are shown in Table 2.

[0054] The molten iron sulfur content at the converter final point of this example is 0.023%, compared with the sulfur content of the molten iron charged into the converter, no sulfur back occurs at the converter final point, the total lime consumption is 30.9 kg / t, and the steel material consumption is 1063 kg / t.

[0055] Example 3

[0056] This example is carried out on a 180t converter, including the following steps:

[0057] (1) After the converter slag splashing is finished, add scrap steel and charge molten iron into the furnace, the molten iron composition and temperature are shown in Table 1, after the molten iron charging is finished, lower the oxygen lance to blow oxygen;

[0058] (2) Control the oxygen supply intensity to be 3.0 m 3 / t / min, control the oxygen lance position to be 3m, control the oxygen partial pressure to be 10 -3 Mpa, after the oxygen blowing starts, add composite oxidizing agent 34 kg / t steel into the converter, after blowing for 1 minute, add KR desulfurization slag 20 kg / t steel into the converter, wherein the mass ratio of 2Fe2O3.SiO2 in the composite oxidizing agent is 86%, and the mass ratio of MnCO3 is 14%;

[0059] (3) After blowing for 4 minutes, add lime 32.6 kg / t steel and dolomite 18.1 kg / t steel in batches, control the final point slag basicity to be 4.3 and the molten steel temperature to be 1675℃; the slag control condition and the converter smelting indexes are shown in Table 2.

[0060] The molten iron sulfur content at the converter final point of this example is 0.017%, compared with the sulfur content of the molten iron charged into the converter, no sulfur back occurs at the converter final point, the total lime consumption is 32.6 kg / t, and the steel material consumption is 1064 kg / t.

[0061] Example 4

[0062] This example is carried out on a 180t converter, including the following steps:

[0063] (1) After the converter slag splashing is finished, add scrap steel and charge molten iron into the furnace, the molten iron composition and temperature are shown in Table 1, after the molten iron charging is finished, lower the oxygen lance to blow oxygen;

[0064] (2) Control the oxygen supply intensity to be 2.6 m 3 / t / min, control the oxygen lance position to be 2.7m, control the oxygen partial pressure to be 10 - 3.5After the beginning of oxygen blowing, 2 kg / t steel of lime and 32 kg / t steel of composite oxidizing agent were added into the converter, 30 kg / t steel of KR desulfurization slag was added into the converter after 1 min of oxygen blowing, the mass ratio of 2Fe2O3.SiO2 in the composite oxidizing agent was 87%, and the mass ratio of MnCO3 was 13%;

[0065] (3) After 3.8 min of blowing, 27.5 kg / t steel of lime and 15.6 kg / t steel of dolomite were added in batches, the final point slag basicity was controlled to be 4.6 and the molten steel temperature was controlled to be 1667℃; the slag control condition and the converter smelting indexes are shown in Table 2.

[0066] The molten iron sulfur content at the end of the converter of the embodiment was 0.032%, compared with the sulfur content of the molten iron entering the furnace, there was no sulfur return at the end of the converter, the total lime consumption was 29.5 kg / t steel, and the steel material consumption was 1060 kg / t steel.

[0067] Table 1 Molten iron conditions and charging conditions

[0068]

[0069]

[0070] Table 2 Slag control condition and converter smelting index

[0071]

Claims

1. A method for the resource recycling of KR desulfurization slag in a converter, characterized in that, include: S1: Add scrap steel and molten iron into the furnace, then put the oxygen lance down for oxygen blowing. S2: After oxygen blowing begins, add composite oxidant into the converter to control the slag alkalinity and oxidizing properties in the early stage of the converter. After 1 minute of oxygen blowing, add KR desulfurization slag into the converter and continue the blowing process. The composite oxidant comprises the following components in the indicated mass percentages. Composition: 80~90% 2Fe2O3·SiO2, 10~20% MnCO3.

2. The method for resource recycling of KR desulfurization slag in a converter according to claim 1, characterized in that, When the lower oxygen lance in S1 is used for oxygen blowing, the oxygen blowing conditions include: the oxygen supply intensity of the oxygen lance is controlled at 2.2~3.0m. 3 / t / min, the oxygen lance position is controlled at 2~3m above the molten iron surface, and the oxygen partial pressure is controlled at 10. -5 -10 -3 MPa.

3. The method for resource recycling of KR desulfurization slag in a converter according to claim 1, characterized in that, The specific conditions for adding molten iron in S1 are that the temperature of the molten iron is 1300~1500℃, and the sulfur content is 0.02~0.045%.

4. The method for resource recycling of KR desulfurization slag in a converter according to claim 1, characterized in that, The amount of composite oxidant added in S2 is 22~40 kg / t steel; and / or the amount of KR desulfurization slag added is 5~30 kg / t steel.

5. The method for resource recycling of KR desulfurization slag in a converter according to claim 1, characterized in that, After oxygen blowing begins in S2, lime is added along with the composite oxidant, and the amount of lime added is controlled to be 0~3 kg / t steel.

6. The method for resource recycling of KR desulfurization slag in a converter according to any one of claims 1-5, characterized in that, In the early stage of converter operation, the slag basicity is controlled at 1.0~1.3, the total mass ratio of FeO and Fe2O3 is 20~45%, and the mass ratio of Fe2O3 to FeO is ≥4.

7. The method for resource recycling of KR desulfurization slag in a converter according to claim 6, characterized in that, After blowing for 3-4 minutes, lime and dolomite are added to the converter in batches. The amount of lime added is controlled at 25-35 kg / t steel, and the amount of dolomite added is controlled at 10-20 kg / t steel.

8. The method for resource recycling of KR desulfurization slag in a converter according to claim 7, characterized in that, The basicity of the converter slag is controlled at 4-5, and the temperature is 1630-1680℃.

9. The method for resource recycling of KR desulfurization slag in a converter according to any one of claims 1-5, characterized in that, The converter slag splashing operation is performed before adding scrap steel and molten iron into the furnace.

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