A method for preparing high-purity ferrosilicon using one-to-two acid-base refining furnaces

Abstract

The present application provides a method for preparing high-purity ferrosilicon by using a one-to-two acid-alkali refining furnace, wherein microsilicon powder particles are placed in an acid refining furnace, and the temperature is raised to 1300°C to 1400°C in the acid refining furnace, and the mixture is fully stirred and smelted until C ≤ 0.008%, P ≤ 0.010%, and S ≤ 0.005% in the ferrosilicon melt; the smelted liquid smelted in the acid furnace is transferred to an alkaline refining furnace, the smelting temperature in the alkaline furnace is 1300°C to 1400°C, and an alkaline slag-forming agent is added, stirred and smelted, and the slag is separated, until the ferrosilicon content in the ferrosilicon melt is ≥ 99.5%; the smelting product smelted in the alkaline furnace is discharged from the furnace to obtain a high-purity ferrosilicon product. In the present invention, H3BO3, Na2SiO3 and the like in the lining of the acid refining furnace react preliminarily with impurities such as sulfur, phosphorus and carbon in the molten liquid to remove the impurities such as sulfur, phosphorus and carbon in the molten liquid, and then the molten liquid is transferred to the alkaline refining furnace to remove the metal impurities. Compared with the prior art of preparing high-purity ferrosilicon using an ordinary refining furnace, the present invention can significantly reduce the amount of slag-forming agent used.

Description

Technical Field

[0001] The present application relates to the technical field of preparing high-purity ferrosilicon with an alkali refining furnace, and is a method for preparing high-purity ferrosilicon with a one-to-two acid-alkali refining furnace. Background Art

[0002] The industry standard high-purity ferrosilicon (YB∕T 4460-2015) requires that in high-purity ferrosilicon GCFeSi75-A, Si 72.0%~80.0%, Al≤0.008%, Ti≤0.008%, C≤0.008%, P≤0.010%, S≤0.005%, Mn≤0.10%, Cr≤0.05%, Ca≤0.008%, Cu≤0.05%, V≤0.05%, Ni≤0.10%, B≤0.002%, Zr≤0.03%, Mg≤0.008%, Mo≤0.05%, that is, the ferrosilicon content needs to be ≥99.5%

[0003] Microsilicon powder is produced in the ferrosilicon production industry. The ferrosilicon produced and prepared will be crushed into ferrosilicon blocks or particles of different sizes / particle sizes before being sold according to different uses. In the crushing and screening process, there will be dust. The dust particles collected by the dust removal system are usually above 100 meshes. This type of microsilicon powder cannot be used again in steelmaking, cast iron / steel smelting environment due to its small powder particle size. Due to its small particle size, the poor air permeability of the charge after entering the furnace causes the consequences of the ore-fired furnace being turned off. Usually, the production enterprise sells this part of the microsilicon powder collected by the dust removal system to cement plants as dust removal ash or treats it as solid waste. Microsilicon powder is mainly ferrosilicon alloy, and the silicon content is related to the grade of ferrosilicon produced. The composition of microsilicon powder is Si: 70%~80%, Fe: 20%~30%, C≤0.2%, Ca≤1.5, Al≤2.5%, Mn≤0.6%, P≤0.045%, S≤0.02%.

[0004] At present, the method for preparing high-purity ferrosilicon generally adopts refining slag-forming agent to remove the impurity elements in ferrosilicon, but the problem with this method is that the consumption of slag-forming agent is relatively large. Summary of the invention

[0005] The purpose of the present invention is to solve the problem of large consumption of slag-making agent in the traditional preparation of high-purity ferrosilicon in the background technology.

[0006] In order to achieve the above-mentioned object, the present invention provides a one-to-two acid-base refining furnace, which is composed of an acid refining furnace and a basic refining furnace, wherein the lining material of the acid refining furnace has the following components by mass: 95 parts of SiO2, 2 parts of H3BO3, and 3 parts of Na2SiO3;

[0007] The composition of the lining material of the basic refining furnace by mass is: 90 parts of MgO, 4 parts of SiO2, 3 parts of CaO, and 3 parts of Al2O3.

[0008] Based on the above-mentioned one-to-two acid-alkali refining furnace, the present invention also provides a method for preparing high-purity ferrosilicon using the one-to-two acid-alkali refining furnace, which is used to prepare the ferrosilicon content in the high-purity ferrosilicon ≥ 99.5%, comprising:

[0009] Granulation: Mix the microsilica powder with the binder and press into balls to prepare particles with a size of not less than 5 cm, and then dry to obtain microsilica powder particles;

[0010] Acid furnace smelting: put the microsilica powder particles into the acid refining furnace, and heat it to 1300℃~1400℃ in the acid refining furnace, stir and smelt it fully until C≤0.008%, P≤0.010%, S≤0.005% in the ferrosilicon melt;

[0011] Alkaline furnace smelting: the smelting liquid from the acid furnace is transferred to the alkaline refining furnace. The temperature of the alkaline furnace smelting is 1300~1400℃, and an alkaline slag-making agent is added. The mixture is stirred and smelted, and the slag is separated until the ferrosilicon content in the ferrosilicon melt is ≥99.5%;

[0012] Out of furnace: The smelting products of the alkaline furnace are taken out of the furnace to obtain high-purity ferrosilicon products.

[0013] The composition of the microsilica powder is Si: 70% to 80%, Fe: 20% to 30%, C≤0.2%, Ca≤1.5, Al≤2.5%, Mn≤0.6%, P≤0.045%, and S≤0.02%.

[0014] The alkaline slag-forming agent is 30%CaO-30%MgO-30%Al2O3.

[0015] The amount of the alkaline slag-forming agent added is 5% to 10% of the smelting raw materials.

[0016] The alkaline slag-forming agent is added by powder spraying.

[0017] The technical effects of the present invention are:

[0018] 1. The present invention uses an acid refining furnace and an alkaline refining furnace to smelt microsilicon powder particles respectively. First, H3BO3, Na2SiO3, etc. in the acid refining furnace are used to react with impurities such as sulfur, phosphorus, and carbon in the molten liquid to remove impurities such as sulfur, phosphorus, and carbon in the molten liquid. Then, the molten liquid is transferred to the alkaline refining furnace, and after the furnace lining material is used to preliminarily remove certain metal impurities, an alkaline slag-forming agent is added to remove the remaining metal impurities. Compared with the prior art that uses an ordinary refining furnace to prepare high-purity ferrosilicon, the present invention can significantly reduce the amount of slag-forming agent used.

[0019] 2. In the present invention, in the acid refining furnace, the furnace lining material is 95 parts of SiO2, 2 parts of H3BO3, and 3 parts of Na2SiO3. P reacts with Na2SiO3 to generate Si and Na3PO4 (P + Na2SiO3 → Si + Na3PO4). The boiling point of Na3PO4 is only 158°C, which can be quickly gasified in the refining furnace, thereby achieving the removal of P in the ferrosilicon melt; sulfur reacts with H3BO3 to generate H2S gas and B2S3 (2 H3BO3 + 3 S → 3 H2S + B2S3 + 3 H2O), and B2S3 reacts with Na2SiO3 to generate H3BO3 and Na2S, SiO2 (B2S3 + 2 Na2SiO3 + 2 H2O → 2 Na2S + 2 H3BO3 + SiO2), and the boiling point of Na2S is 1304 ℃, can evaporate during the smelting process; Na2SiO3 reacts with C to generate Na2CO3, Si and CO2 (2Na2SiO3+ 5C→2Na2CO3+ 4Si+3CO2↑), Na2CO3 decomposes into Na2O and CO2 at high temperature (Na2CO3 → Na2O + CO2↑), and Na2O reacts with SiO2 to generate Na2SiO3. Thus, phosphorus, sulfur and carbon can be removed without consuming the furnace lining material.

[0020] When smelting in an alkaline refining furnace, a slag-forming agent of 30% CaO-30% MgO-30% Al2O3 is added, wherein CaO can slag away metal impurities such as Mn and Ca, Al2O3 can slag away metal impurities such as Al and Mn, and MgO can improve the fluidity of the slag, which is beneficial to the separation of the slag agent.

[0021] 3. The present invention uses microsilicon powder particles to prepare high-purity ferrosilicon, which greatly reduces the cost of raw materials and does not require the addition of additional reducing agents. DETAILED DESCRIPTION

[0022] The embodiments of the technical solution of the present application will be described in detail below. The following embodiments are only used to more clearly illustrate the technical solution of the present application, and are therefore only used as examples, and cannot be used to limit the scope of protection of the present application. In addition, the technical features involved in each embodiment of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0023] In the following embodiments of the present invention, the one-to-two acid-base refining furnace used is composed of an acid refining furnace and a basic refining furnace, wherein the composition of the lining material of the acid refining furnace is as follows: 95 parts of SiO2, 2 parts of H3BO3, and 3 parts of Na2SiO3 by mass;

[0024] The composition of the lining material of the basic refining furnace by mass is: 8 parts of B2O3, 45 parts of CaO, 20 parts of MgO, 15 parts of Al2O3, and 15 parts of Fe2O3.

[0025] Example 1

[0026] Granulation: Mix the microsilica powder with water and press into balls to prepare particles with a particle size of 5 cm to 8 cm. After drying, microsilica powder particles are obtained;

[0027] Acid furnace smelting: put the microsilica powder particles into the acid refining furnace, heat it to 1350℃ in the acid refining furnace, stir it thoroughly, and smelt it for 30 minutes;

[0028] Alkaline furnace smelting: the smelting liquid in the acid furnace is transferred to the alkaline refining furnace. The temperature of the alkaline furnace smelting is 1350 ℃, and the alkaline slag-forming agent 30%CaO-30%MgO-30%Al2O3 is added by powder spraying. After smelting for 30 minutes, the slag is separated. Among them, the amount of alkaline slag-forming agent added is 5% of the total mass of the molten liquid;

[0029] Out of furnace: The smelting products of the alkaline furnace are taken out of the furnace to obtain high-purity ferrosilicon products.

[0030] Example 2

[0031] Granulation: Mix the microsilica powder with water and press into balls to prepare particles with a particle size of 5 cm to 8 cm. After drying, microsilica powder particles are obtained;

[0032] Acid furnace smelting: put the microsilica powder particles into the acid refining furnace, heat it to 1400℃ in the acid refining furnace, stir it thoroughly, and smelt it for 30 minutes;

[0033] Alkaline furnace smelting: the smelting liquid in the acid furnace is transferred to the alkaline refining furnace. The smelting temperature of the alkaline furnace is 1400 ℃, and the alkaline slag-forming agent 30%CaO-30%MgO-30%Al2O3 is added by powder spraying. After smelting for 30 minutes, the slag is separated. Among them, the amount of alkaline slag-forming agent added is 8% of the total mass of the molten liquid;

[0034] Out of furnace: The smelting products of the alkaline furnace are taken out of the furnace to obtain high-purity ferrosilicon products.

[0035] Example 3

[0036] Granulation: Mix the microsilica powder with water and press into balls to prepare particles with a particle size of 5 cm to 8 cm. After drying, microsilica powder particles are obtained;

[0037] Acid furnace smelting: put the microsilica powder particles into the acid refining furnace, heat it to 1300℃ in the acid refining furnace, stir it thoroughly, and smelt it for 30 minutes;

[0038] Alkaline furnace smelting: the smelting liquid after smelting in the acid furnace is transferred to the alkaline refining furnace. The temperature of the alkaline furnace smelting is 1300 ℃, and the alkaline slag-forming agent 30%CaO-30%MgO-30%Al2O3 is added by powder spraying. After smelting for 30 minutes, the slag is separated. Among them, the amount of alkaline slag-forming agent added is 10% of the total mass of the molten liquid;

[0039] Out of furnace: The smelting products of the alkaline furnace are taken out of the furnace to obtain high-purity ferrosilicon products.

[0040] Comparative Example 1

[0041] The difference between Comparative Example 1 and Example 1 is that, in Comparative Example 1, refining is performed only in an acid furnace, and an alkaline slag-forming agent is added in the acid furnace.

[0042] Granulation: Mix the microsilica powder with water and press into balls to prepare particles with a particle size of 5 cm to 8 cm. After drying, microsilica powder particles are obtained;

[0043] Acid furnace smelting: put the microsilica powder particles into the acid refining furnace, and heat it to 1350℃ in the acid refining furnace, stir it fully, smelt it for 30 minutes, and add the alkaline slag-forming agent 30%CaO-30%MgO-30%Al2O3 by powder spraying. After smelting for 30 minutes, separate the slag. The amount of alkaline slag-forming agent added is 5% of the total mass of the melt.

[0044] Out of furnace: The smelting products of the alkaline furnace are taken out of the furnace to obtain high-purity ferrosilicon products.

[0045] Comparative Example 2

[0046] The difference between Comparative Example 2 and Example 1 is that the refining in Comparative Example 2 is only carried out in a basic furnace.

[0047] Granulation: Mix the microsilica powder with water and press into balls to prepare particles with a particle size of 5 cm to 8 cm. After drying, microsilica powder particles are obtained;

[0048] Alkaline furnace smelting: put the microsilica powder particles into the alkaline refining furnace, and heat the alkaline refining furnace to 1350℃, and add the alkaline slag-forming agent 30%CaO-30%MgO-30%Al2O3 by powder spraying. After smelting for 30 minutes, separate the slag. The amount of alkaline slag-forming agent added is 5% of the total mass of the melt.

[0049] After being taken out of the furnace, the smelting products of the alkaline furnace are discharged into ferrosilicon tanks for casting into ingots to obtain high-purity ferrosilicon products.

[0050] Comparative Example 3

[0051] The difference between Comparative Example 3 and Example 1 is that the refining in Comparative Example 3 is only carried out in a basic furnace.

[0052] Granulation: Mix the microsilica powder with water and press into balls to prepare particles with a particle size of 5 cm to 8 cm. After drying, microsilica powder particles are obtained;

[0053] Alkaline furnace smelting: put the microsilica powder particles into the alkaline refining furnace, and heat the alkaline refining furnace to 1350℃, and add the alkaline slag-forming agent 30%CaO-30%MgO-30%Al2O3 by powder spraying. After smelting for 60 minutes, separate the slag. The amount of alkaline slag-forming agent added is 5% of the total mass of the melt;

[0054] Out of furnace: The smelting products of the alkaline furnace are taken out of the furnace to obtain high-purity ferrosilicon products.

[0055] Table 1 is a composition table of microsilicon powder used in various embodiments and comparative examples, Table 2 is a composition table of ferrosilicon melts obtained after smelting in an acid furnace in various embodiments and comparative examples, and Table 3 is a composition table of the final products obtained in various embodiments and comparative examples.

[0056] Table 1 Components of microsilica powder used in various examples and comparative examples

[0057] Si / % Fe / % Al / % Ca / % Mn / % C / % P / % S / % Example 1 72.1 23.2 2.1 1.2 0.5 0.15 0.041 0.018 Example 2 74.6 22.6 1.5 0.5 0.1 0.1 0.02 0.01 Example 3 77.2 20.1 1.3 0.6 0.1 0.1 0.03 0.01 Comparative Example 1 72.1 23.2 2.1 1.2 0.5 0.15 0.041 0.018 Comparative Example 2 72.1 23.2 2.1 1.2 0.5 0.15 0.041 0.018 Comparative Example 3 72.1 23.2 2.1 1.2 0.5 0.15 0.041 0.018

[0058] Table 2 Composition of ferrosilicon melts obtained from various embodiments and comparative examples after smelting in an acid furnace

[0059] Si / % Fe / % Al / % Ca / % Mn / % C / % P / % S / % Example 1 72.2 23.2 2.1 1.2 0.5 0.007 0.004 0.004 Example 2 74.7 22.6 1.5 0.5 0.1 0.006 0.008 0.003 Example 3 77.2 20.2 1.3 0.6 0.1 0.007 0.006 0.003 Comparative Example 1 74.6 24.7 0.008 0.01 0.06 0.06 0.02 0.006 Comparative Example 2 / / / / / / / / Comparative Example 3 / / / / / / / /

[0060] Table 3 Composition of the final products obtained in each embodiment and comparative example

[0061] Si / % Fe / % Al / % Ca / % Mn / % C / % P / % S / % Product yield% Example 1 74.7 24.9 0.005 0.005 0.06 0.005 0.005 0.003 94.32 Example 2 76.2 23.5 0.006 0.007 0.08 0.006 0.008 0.003 94.38 Example 3 78.2 21.4 0.007 0.006 0.008 0.007 0.008 0.004 94.43 Comparative Example 1 / / / / / / / / 87.26 Comparative Example 2 74.6 24.7 0.008 0.009 0.08 0.11 0.035 0.013 95.06 Comparative Example 3 74.5 24.8 0.008 0.008 0.07 0.11 0.032 0.012 94.93

[0062] It can be seen that the ferrosilicon content in the high-purity ferrosilicon obtained in Examples 1 to 3 is ≥99.5%.

[0063] It can be seen from Comparative Example 1 and Example 1 that the ferrosilicon content of the product obtained in Comparative Example 1 is 99.3. Since Comparative Example 1 is smelted in an acid furnace, when H3BO3, Na2SiO3, etc. react with impurities such as sulfur, phosphorus, and carbon in the molten liquid, some intermediate Na2O and substances generated have bonding properties, which adhere the slag-forming agent to the furnace wall. A large amount of slag formed by the slag-forming agent adheres to the furnace wall, which also results in a low yield of the ferrosilicon product finally obtained.

[0064] By comparing Comparative Example 2 and Comparative Example 3 with Example 1, the purity of ferrosilicon obtained in Comparative Example 2 and Comparative Example 3 is 99.3 and 99.4, respectively. However, the contents of C, P and S in the obtained ferrosilicon are significantly higher than the standard. The reason is that the use of 5% to 10% slag-forming agent cannot effectively remove non-metallic impurities such as C, P and S in the ferrosilicon melt.

[0065] In Examples 1 to 3, the microsilicon powder particles are melted in an acidic refining furnace and an alkaline refining furnace respectively. First, H3BO3, Na2SiO3, etc. in the acidic refining furnace are used to react with impurities such as sulfur, phosphorus, and carbon in the molten liquid to remove the impurities such as sulfur, phosphorus, and carbon in the molten liquid. Then, the molten liquid is transferred to the alkaline refining furnace, and after the furnace lining material is used to preliminarily remove certain metal impurities, an alkaline slag-forming agent is added to remove the remaining metal impurities. Compared with the prior art of preparing high-purity ferrosilicon using an ordinary refining furnace, the present invention can significantly reduce the amount of slag-forming agent.

[0066] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing high-purity ferrosilicon using a one-to-two acid-base refining furnace, characterized in that: A one-to-two acid-base refining furnace is used, wherein the one-to-two acid-base refining furnace is composed of an acid refining furnace and a basic refining furnace, wherein the composition of the lining material of the acid refining furnace is: 95 parts of SiO2, 2 parts of H3BO3, and 3 parts of Na2SiO3 by mass; The composition of the lining material of the basic refining furnace by mass is: 90 parts of MgO, 4 parts of SiO2, 3 parts of CaO, and 3 parts of Al2O3; The method is used to prepare high-purity ferrosilicon with a ferrosilicon content of ≥ 99.5%, comprising: Granulation: Mix the microsilica powder with the binder and press into balls to prepare particles with a size of not less than 5 cm, and then dry to obtain microsilica powder particles; Acid furnace smelting: put the microsilica powder particles into the acid refining furnace, and heat it to 1300℃~1400℃ in the acid refining furnace, stir and smelt it fully until C≤0.008%, P≤0.010%, S≤0.005% in the ferrosilicon melt; Alkaline furnace smelting: The smelting liquid from the acid furnace is transferred to the alkaline refining furnace. The temperature of the alkaline furnace smelting is 1300℃~1400℃, and an alkaline slag-making agent is added. The smelting is stirred and the slag is separated until the ferrosilicon content in the ferrosilicon melt is ≥99.5%; Out of furnace: The smelting products of the alkaline furnace are taken out of the furnace to obtain high-purity ferrosilicon products.

2. The method according to claim 1, characterized in that The composition of the microsilica powder is Si: 70% to 80%, Fe: 20% to 30%, C≤0.2%, Ca≤1.5, Al≤2.5%, Mn≤0.6%, P≤0.045%, and S≤0.02%.

3. The method according to claim 1, characterized in that The alkaline slag-forming agent is 30%CaO-30%MgO-30%Al2O3.

4. The method according to claim 3, characterized in that The amount of the alkaline slag-forming agent added is 5% to 10% of the smelting raw materials.

5. The method according to claim 3, characterized in that: The alkaline slag-forming agent is added by powder spraying.