Baking-free silicon powder pellet as well as preparation method and application thereof

Abstract

The invention relates to the technical field of steel smelting, in particular to a baking-free silicon powder pellet and a preparation method and application thereof. The baking-free silicon powder pellets are mainly prepared from the following raw materials in parts by weight: 50-63 parts of silicon powder with the particle size of 0-1 mm, 40-50 parts of silicon powder with the particle size of 1-3 mm, 1-3 parts of bentonite with the particle size of 325 meshes, 0.6-1.2 parts of sodium metasilicate with the particle size of 325 meshes, 1-1.5 parts of a pellet binder with the particle size of 325 meshes and 5-8 parts of water. The sodium metasilicate is added to react with the silicon powder, heat is released to enable the pellets to generate heat to reduce moisture, the reaction time and temperature are controllable, the silicon powder and the sodium metasilicate after reaction have viscidity, the pellet strength can be enhanced, the baking process can be omitted, and the production cost is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of steel smelting, and in particular to a baking-free silicon powder pellet and a preparation method and application thereof. Background Art

[0002] At present, the main methods for heating solid (or liquid) metals are electric heating and chemical heating. Chemical heating is divided into the following two types: directly or indirectly spraying combustibles into (or outside) the container containing solid (or liquid) metal to make it burn and generate heat to heat the metal; secondly, adding a heating agent into the solid (or liquid) metal to utilize the oxidation heat release of the heating agent to heat the solid (or liquid) metal. There are many types of heat supplements for steelmaking converters. From the perspective of the application range of steelmaking, they can be divided into converter heating agents, electric furnace heating agents, ladle heating agents and tundish heating agents, etc., and from the main elements of the heating agent itself, they can be divided into carbon heating agents, silicon heating agents, aluminum heating agents and other metal or non-metal heating agents, etc. Different heating agents have different effects. Heat supplementers for steelmaking converters help to melt scrap steel, increase the input ratio of chemical energy in the electric furnace, and reduce electricity consumption. Heat supplementers for steelmaking converters can increase the scrap steel ratio of the converter, reduce the unit consumption of molten iron, and appropriately reduce blowing losses. Especially for converter steelmaking with insufficient molten iron supply, it is also a good way to increase output and reduce consumption.

[0003] The Chinese patent application number is CN2019111608916, and the patent document with the publication date of November 23, 2019 discloses a preparation process of a siliceous temperature raising agent, and its raw materials are: ferrosilicon alloy smelting slag or industrial silicon smelting slag, iron-containing fine particles, carbon powder, bentonite, and molding binder; the preparation process of the siliceous temperature raising agent also includes the following steps: step 1 dry mixing, step 2 wet mixing, step 3 cold pressing, step 4 initial screening, step 5 natural drying, step 6 baking and drying, step 7 final screening, and selecting the part with a particle size greater than 5mm to prepare industrial silicon powder pellets. The pellets produced by this invention solve the problem of secondary pollution in the industrial silicon industry, but the production cost is increased because it needs to be baked.

[0004] The Chinese patent application number is CN2018106852732, and the patent document with the publication date of May 31, 2019, discloses a method for preparing industrial silicon powder pellets and their uses. The components and mass percentages of the industrial silicon powder pellets described in the invention are: 50%-100% industrial silicon fine powder, 0-30% iron-containing fine particles, 0-50% ferrosilicon alloy powder, and the molding binder is 1%-8% of the total mass of the industrial silicon fine powder, ferrosilicon alloy powder and iron-containing fine particles; the preparation method of the industrial silicon powder pellets also includes: step 1 dry mixing, step 2 wet mixing, step 3 cold pressing, step 4 initial screening, step 5 natural drying, step 6 baking and drying, step 7 final screening, and preparing industrial silicon powder pellets. The amount of binder added is relatively high, and baking production costs are still required. Summary of the invention

[0005] The purpose of the present invention is to provide a baking-free silicon powder pellet and a preparation method and application thereof, which can solve the above-mentioned technical problems.

[0006] The invention provides a baking-free silicon powder pellet, which is mainly prepared from the following raw materials in parts by weight: 50-63 parts of silicon powder with a particle size of 0-1 mm (excluding 0), 40-50 parts of silicon powder with a particle size of 1-3 mm (excluding 1), 1-3 parts of bentonite with a particle size of 325 mesh, 0.6-1.2 parts of sodium metasilicate with a particle size of 325 mesh, 1-1.5 parts of a pellet binder with a particle size of 325 mesh and 5-8 parts of water.

[0007] Preferably, the silicon powder contains Si: 45%-51%, S≤0.15%, P≤0.1%, and C≤0.8% by weight.

[0008] Preferably, the bentonite contains SiO2 in an amount of 40% to 55% by weight.

[0009] Preferably, the sodium metasilicate is zero-water sodium metasilicate, which contains Na2SiO3≥99% by weight.

[0010] Preferably, the pellet binder is gelatinized starch, which is prepared by gelatinization process of corn or kudzu root starch, and the gelatinization degree reaches 50%.

[0011] Preferably, the silicon powder pellets contain SiO2: 40%-50%, S≤0.15%, P≤0.1%, C≤0.8%, and H2O≤1.5% by weight.

[0012] The present invention also provides a method for preparing the baking-free silicon powder pellets, comprising the following steps performed in sequence: batching, adding water, stirring, pressing pellets and drying.

[0013] Preferably, a ball press is used in the ball pressing process, the silicon powder pellets are ellipsoids of 50mm×50mm×30mm, the pellet strength is greater than 800N, and the powder surface rate of ≤5mm is ≤5%.

[0014] Preferably, the drying time is 72 hours.

[0015] The present invention also provides an application of silicon powder pellets in increasing the temperature of molten steel. The baking-free silicon powder pellets are used in a converter and are added to increase the temperature of molten steel.

[0016] Beneficial effects:

[0017] The present invention adds sodium metasilicate to react with silicon powder, releases heat to make the pellets themselves generate heat and reduce moisture, and not only the reaction time and temperature are controllable, but also the silicon powder and sodium metasilicate after the reaction have viscosity to enhance the strength of the pellets, and the baking process can be avoided, thereby reducing production costs. DETAILED DESCRIPTION

[0018] It should be noted that the following detailed descriptions are illustrative and are intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present application belongs.

[0019] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form also includes the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this description, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0020] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0021] In order to avoid repetition, the raw materials involved in this specific embodiment are described as follows, and will not be repeated in the examples: the silicon powder contains Si: 45%-51% by weight, S≤0.15%, P≤0.1%, C≤0.8%. The bentonite contains SiO2≥40%-55% by weight. The sodium metasilicate contains Na2SiO3≥99% by weight. The gelatinized starch is prepared from corn and kudzu starch through gelatinization process, and the gelatinization degree reaches 50%.

[0022] The functions of the raw materials selected by the present invention are as follows: silicon powder is used as the main raw material, and its overall proportion reaches more than 90%, which increases the temperature raising ability of the product, and has the most suitable taste and high cost performance. The combination of silicon powder with a particle size of 0-1mm and silicon powder with a particle size of 1-3mm is to improve the balling rate and initial strength of the ball.

[0023] The purpose of using bentonite is to improve the viscosity of the pellets, and it can fill the gaps in the silica powder and increase the strength of the pellets. The best addition amount is 1%-3%. Too much will affect product indicators and increase costs. Too little addition will not work and the strength of the pellets will be reduced.

[0024] The purpose of using sodium metasilicate is to utilize silicon powder to react with it to generate heat. After natural stacking, the moisture content can be reduced to the target requirement. At the same time, sodium metasilicate itself has viscosity and can assist in balling. After the reaction, a network complex is generated in the pellets to increase the strength of the pellets in the later stage. The best addition amount is 0.6%-1.2%. Too much heat will generate too fast, the temperature will be high, the production rhythm will be difficult to control, and the production cost will be increased. If the addition amount is too low, the reaction temperature will be low and the moisture content will drop slowly.

[0025] Using gelatinized starch as a binder is not only low in price, but also has a higher viscosity and a higher cost-effectiveness ratio. The optimal addition amount is 1%-1.5%. Too much may cause the material to stick to belts, ball presses and other equipment, and increase costs; if the addition amount is too low, the powder rate of the pellets will increase and the ball formation rate of the product will be reduced.

[0026] The silicon powder pellets meet the following physical and chemical indicators (as shown in Table 1).

[0027] Table 1 Physical and chemical indicators of silicon powder pellets

[0028]

[0029] Example 1

[0030] 55 parts by weight of silicon powder with a particle size of 0-1mm, 41.2 parts by weight of silicon powder with a particle size of 1-3mm, 1.5 parts by weight of 325-mesh bentonite, 0.8 parts by weight of 325-mesh sodium metasilicate, and 1.5 parts by weight of 325-mesh gelatinized starch that have passed the inspection are sent to a planetary mixer for mixing and stirring. After mixing and stirring for 1 minute, 7.5 parts by weight of water are added and stirred for 3 minutes. The mixed material is put into a ball press through a belt. The pressed balls are dried for 3 days and passed the inspection, then marked and put into storage for standby. Samples are taken to test the physical and chemical indicators of the silicon powder balls (see Table 2 for the test results), and they are transported to a steel plant after passing the test. The units of the above weight parts are kilograms or tons or other weight units, which can be selected according to actual conditions.

[0031] Table 2 Physical and chemical testing indicators of silicon powder pellets in Example 1

[0032]

[0033]

[0034] This embodiment was sent to a steel mill, the steel grade produced was Q235B, and was added to the converter, the converter capacity was 220 tons, and the use effect was shown in Table 3.

[0035] Table 3 Experimental results of silicon powder pellets in Example 1

[0036]

[0037] The silicon powder pellets of the present invention have an average temperature increase of 6.1°C per 100Kg, have a good temperature increase effect, eliminate the baking step, reduce the amount of binder added, reduce the production cost, and have a good application prospect.

[0038] Example 2

[0039] 50 parts by weight of silicon powder with a particle size of 0-1mm, 40 parts by weight of silicon powder with a particle size of 1-3mm, 1 part by weight of 325-mesh bentonite, 0.6 parts by weight of 325-mesh sodium metasilicate, and 1 part by weight of 325-mesh gelatinized starch that have passed the inspection are sent to a planetary mixer for mixing and stirring. After mixing and stirring for 1 minute, 7.5 parts by weight of water are added and stirred for 3 minutes. The mixed material is put into a ball press through a belt. The pressed balls are dried for 3 days and passed the inspection, then marked and put into storage for standby. Samples are taken to test the physical and chemical indicators of the silicon powder balls (the test results are shown in Table 4), and they are transported to a steel plant after passing the test. The units of the above weight parts are kilograms or tons or other weight units, which can be selected according to actual conditions.

[0040] Table 4 Physical and chemical testing indicators of silicon powder pellets in Example 2

[0041]

[0042]

[0043] This embodiment was sent to a steel mill, the steel grade produced was Q235B, and was added to the converter, the converter capacity was 220 tons, and the use effect was shown in Table 5.

[0044] Table 5 Experimental results of silicon powder pellets in Example 2

[0045]

[0046] The silicon powder pellets of the present invention have an average temperature increase of 5.9°C per 100Kg, have a good temperature increase effect, eliminate the baking step, reduce the amount of binder added, reduce the production cost, and have a good application prospect.

[0047] Example 3

[0048] 63 parts by weight of silicon powder with a particle size of 0-1mm, 50 parts by weight of silicon powder with a particle size of 1-3mm, 3 parts by weight of bentonite with a size of 325 mesh, 1.2 parts by weight of sodium metasilicate with a size of 325 mesh, and 1.5 parts by weight of gelatinized starch with a size of 325 mesh that have passed the inspection are sent to a planetary mixer for mixing and stirring. After mixing and stirring for 1 minute, 8 parts by weight of water are added and stirred for 3 minutes. The mixed material is put into a ball press through a belt. The pressed balls are dried for 3 days and passed the inspection, then marked and put into storage for standby. Samples are taken to test the physical and chemical indicators of the silicon powder balls (the test results are shown in Table 6), and they are transported to a steel plant after passing the test. The units of the above weight parts are kilograms or tons or other weight units, which can be selected according to actual conditions.

[0049] Table 6 Physical and chemical testing indicators of silicon powder pellets in Example 3

[0050]

[0051]

[0052] This embodiment was sent to a steel mill, the steel grade produced was Q235B, and was added to the converter, the converter capacity was 220 tons, and the use effect was shown in Table 7.

[0053] Table 7 Experimental results of silicon powder pellets in Example 3

[0054]

[0055] The silicon powder pellets of the present invention have an average temperature increase of 6.0°C per 100Kg, have a good temperature increase effect, eliminate the baking step, reduce the amount of binder added, reduce the production cost, and have a good application prospect.

[0056] 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 baking-free silicon powder pellet, characterized in that: The invention is mainly prepared from the following raw materials in parts by weight: 50-63 parts of silicon powder with a particle size of 0-1 mm, 40-50 parts of silicon powder with a particle size of 1-3 mm, 1-3 parts of bentonite with a particle size of 325 mesh, 0.6-1.2 parts of sodium metasilicate with a particle size of 325 mesh, 1-1.5 parts of a pellet binder with a particle size of 325 mesh and 5-8 parts of water.

2. The baking-free silicon powder pellets according to claim 1, characterized in that: The silicon powder contains Si: 45%-51%, S≤0.15%, P≤0.1%, and C≤0.8% by weight.

3. The baking-free silicon powder pellets according to claim 1, characterized in that: The bentonite contains SiO2: 40%-55% by weight.

4. The baking-free silicon powder pellets according to claim 1, characterized in that: The sodium metasilicate is zero-water sodium metasilicate, which contains Na2SiO3≥99% by weight.

5. The baking-free silicon powder pellets according to claim 1, characterized in that: The pellet binder is gelatinized starch, which is prepared from corn and kudzu root starch through gelatinization process, and the gelatinization degree reaches 50%.

6. The baking-free silicon powder pellets according to claim 1, characterized in that: The silicon powder pellets contain SiO2: 40%-50%, S≤0.15%, P≤0.1%, C≤0.8%, and H2O≤1.5% by weight.

7. A method for preparing baking-free silicon powder pellets according to any one of claims 1 to 6, characterized in that: The method comprises the following steps which are performed in sequence: mixing ingredients, adding water, stirring, pressing balls and drying.

8. The method for preparing baking-free silicon powder pellets according to claim 7, characterized in that: A ball press is used in the ball pressing process, and the silicon powder pellets are ellipsoids of 50mm×50mm×30mm, with a pellet strength greater than 800N, wherein the powder surface rate of ≤5mm is ≤5%.

9. The method for preparing baking-free silicon powder pellets according to claim 7, characterized in that: The drying time is 72h.

10. Use of the silicon powder pellets according to any one of claims 1 to 6 in increasing the temperature of molten steel.

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