Preparation method of green pellets and composite adhesive

Abstract

The preparation method comprises the following steps that sodium hydroxide is added into water to be stirred and dissolved, then the sodium hydroxide and starch are stirred to be uniform, pre-gelatinization treatment is conducted through puffing equipment, pre-gelatinized starch is obtained, and iron powder, magnesium oxide, the pre-gelatinized starch and magnesium chloride enter a stirrer to be mixed and stirred to be uniform; adding borax, cellulose and polyacrylamide, and continuously stirring uniformly; conveying the final mixture into a ball press machine; after being pressed into balls, conveying the balls into a negative-pressure air-drying bin through a conveying belt; after being taken out of the negative-pressure air drying bin, the materials enter a finished product warehouse through a roller screen; according to the method, the metallurgical properties such as soft melting and dripping required by the cold-bonded pellets used for the high furnace are achieved, the furnace charge structure of the high furnace is optimized, and the proportion of sintered ore is reduced, normal use of the cold-bonded pellets in the high furnace is guaranteed, no heat source participates in the preparation process of the green pellets, roasting is not needed, and green and energy-saving effects are achieved.

Description

Technical Field

[0001] The invention relates to the technical field of steel smelting, and in particular to a method for preparing green pellets and a composite adhesive. Background Art

[0002] How the steel industry can reduce the use of sintered ore and increase the proportion of high-performance, low-pollution alternative products such as pellets and lump ore is an important issue facing the industry. At present, the blast furnace charge structure of steel companies is usually high-alkali sintered ore with pellets. When adding pellets, there are characteristics such as low soft melting temperature and high expansion rate. Large-scale use will affect the permeability of the blast furnace. Some steel companies try to increase the magnesium content of the pellets to improve the metallurgical properties of the pellets, but when it exceeds a certain amount, there will be problems such as reduced strength and high fuel consumption ratio. If the magnesium content of the sintered ore is increased, it will also affect the strength and pulverization rate of the sintered ore. Therefore, the research and development of high-magnesium furnace charges and the optimization of the blast furnace raw material structure ratio, thereby significantly reducing the use of sintered ore, have become the key research and development direction of energy conservation and emission reduction in the steel industry.

[0003] While steel companies are continuously exploring vertical furnace high-magnesium pellet technology, cold-solidified pellets have also attracted attention and attempts in the industry due to their advantages such as small investment, short process, low cost and less pollution. From the initial use of cement, water glass, resin, bentonite to the current starch adhesive, it has undergone many changes and attempts, but is currently still limited to slag ash solid waste treatment and rotary hearth furnace process applications.

[0004] The ultimate reason why cold-solidified pellets cannot replace sintered ore in blast furnaces on a large scale is that there are still technical barriers in technology and adhesives, which leads to the metallurgical properties of pellets failing to meet the standards for blast furnace use, especially the key data such as soft melting temperature, droplet range, and pressure difference. Therefore, there is an urgent need for a high-quality cold-solidified pellet and adhesive production process to break through the technical barriers, give full play to the advantages of cold consolidation, and realize the large-scale application of cold-solidified pellets to replace sintered ore in blast furnaces, which will play a positive role in the development of the steel industry. Summary of the invention

[0005] 1. Technical issues

[0006] In order to solve the problems mentioned in the above background technology, the present invention provides a method for preparing green pellets and a composite adhesive, which solves the problem that the key performance of cold solidified pellets such as soft melting dripping cannot meet the requirements of blast furnace use, optimizes the blast furnace charge structure, and reduces the sintering ore ratio.

[0007] (II) Technical content

[0008] S1: A green pellet composite adhesive, comprising, by weight: 0.5-8 parts of magnesium oxide, 0.3-1 parts of magnesium chloride, 0.6-1.5 parts of pregelatinized starch, and 0.8-1.5 parts of a reinforcing agent;

[0009] S2: As a further embodiment, the method for preparing the pregelatinized starch comprises the following steps:

[0010] 0.05-0.1 parts by weight of sodium hydroxide is added to 18-22 parts by weight of water and stirred to dissolve, and then mixed with 78-82 parts by weight of starch, pre-gelatinized by puffing equipment, and then finely ground into 80-100 meshes to obtain pre-gelatinized starch, with a gelatinization temperature of 150-190 degrees;

[0011] S3: The reinforcing agent includes borax, cellulose and polyacrylamide;

[0012] S4: 90-96 parts by weight of iron powder, 0.5-8 parts by weight of magnesium oxide, 0.8-1.5 parts by weight of pregelatinized starch, and 0.3-1 parts by weight of magnesium chloride are put into a mixer and stirred evenly;

[0013] S5: adding 0.5-1 parts by weight of borax, 0.1-0.3 parts by weight of cellulose, and 0.2-0.5 parts by weight of polyacrylamide and continuing to stir evenly;

[0014] S6: conveying the final mixed material into a ball press for compaction;

[0015] S7: After being pressed into balls, they are sent to the negative pressure air drying chamber through a conveyor belt;

[0016] S8: After coming out of the negative pressure air drying warehouse, it passes through the roller screen and enters the finished product warehouse. The preparation of green pellets is completed.

[0017] Furthermore, in step S4, the fineness of the magnesium oxide is higher than 200 meshes.

[0018] Furthermore, the starch is corn starch, and the viscosity after pregelatinization is greater than 500.

[0019] Furthermore, the total water content of the iron powder is 4-6, and if it is insufficient, water should be added during stirring.

[0020] Furthermore, the components of the adhesive are in the following proportions by weight: 0.8-1.5 parts of pregelatinized starch, 0.5-8 parts of magnesium oxide, 0.3-1 parts of magnesium chloride, and 0.8-1.5 parts of a reinforcing agent.

[0021] (III) Technical Effect

[0022] Compared with the prior art, the advantages of the present invention are as follows: the present invention solves the problems of soft melting dripping and other metallurgical properties required for cold-solidified pellets used in blast furnaces, and optimizes the blast furnace charge structure and reduces the sintering ore ratio. The pellets produced by the present invention have a cold strength of not less than 2500N, are water-resistant and high-temperature-resistant, have a powder rate of <2%, and have comprehensive properties such as softening start temperature T10, softening end temperature T40, pressure difference, dripping temperature, and S characteristic value that are better than those of pellets and sintered ore, thereby ensuring the normal use of cold-solidified pellets in blast furnaces. The green pellet preparation process does not involve a heat source, does not require roasting, and is green and energy-saving. DETAILED DESCRIPTION

[0023] The present invention is further described in detail below in conjunction with the embodiments.

[0024] Example 1

[0025] A method for preparing green pellets comprises the following steps:

[0026] S1: 81 parts by weight of corn starch, 0.1 parts of sodium hydroxide and 19 parts of water are mixed evenly, pre-gelatinized by equipment, and then crushed to a size of 80 mesh or more to obtain pre-gelatinized starch;

[0027] S2: 97 parts by weight of iron powder, 0.5 parts by weight of magnesium oxide, 0.3 parts by weight of magnesium chloride, and 1.2 parts by weight of pregelatinized starch are mixed and stirred uniformly;

[0028] S3: 0.5 parts by weight of borax, 0.3 parts by weight of cellulose and 0.2 parts by weight of polyacrylamide are added into a blender and stirred evenly;

[0029] S4: conveying the final mixed material into the pelletizing machine;

[0030] S6: After being pressed into balls, they are sent to negative pressure air drying chamber through conveyor belt;

[0031] S7: After leaving the negative pressure air drying warehouse, the products are screened and sent to the finished product warehouse.

[0032] A green pellet preparation method and a composite adhesive, comprising the following ingredients: iron powder, pregelatinized starch (sodium hydroxide, water, corn starch), magnesium oxide, borax, magnesium chloride, polyacrylamide, and cellulose.

[0033] Example 2

[0034] A method for preparing green pellets comprises the following steps:

[0035] S1: 0.1 parts by weight of sodium hydroxide, 22 parts by weight of water, and 78 parts by weight of corn starch are mixed and uniformly mixed, and the mixture is pre-gelatinized by a device and then finely ground into 90 meshes to obtain pre-gelatinized starch;

[0036] S2: 94 parts by weight of iron powder, 3 parts by weight of magnesium oxide, 0.5 parts of magnesium chloride, and 1.2 parts by weight of pregelatinized starch are mixed and stirred uniformly;

[0037] S3: 0.7 parts by weight of borax, 0.3 parts by weight of cellulose, and 0.3 parts by weight of polyacrylamide are placed in a blender and stirred evenly;

[0038] S4: conveying the final mixed material into the pelletizing machine;

[0039] S5: After being pressed into balls, they are sent to negative pressure air drying chamber through conveyor belt;

[0040] S6: After leaving the negative pressure air drying warehouse, the products are screened and sent to the finished product warehouse.

[0041] Example 3

[0042] A method for preparing green pellets comprises the following steps:

[0043] S1: 0.1 parts by weight of sodium hydroxide, 22 parts by weight of water, and 78 parts by weight of corn starch are stirred evenly, and the mixture is pre-gelatinized by the equipment and then crushed into 90 meshes to obtain pre-gelatinized starch;

[0044] S2: 93 parts by weight of iron powder, 6 parts by weight of magnesium oxide, 0.8 parts by weight of magnesium chloride, and 1.2 parts by weight of pregelatinized starch adhesive were mixed and stirred uniformly;

[0045] S3: 0.4 parts by weight of borax, 0.3 parts by weight of cellulose, and 0.3 parts by weight of polyacrylamide are placed in a blender and stirred evenly;

[0046] S4: conveying the final mixed material into the pelletizing machine;

[0047] S5: After being pressed into balls, they are sent to negative pressure air drying chamber through conveyor belt;

[0048] S6: After leaving the negative pressure air drying warehouse, the products are screened and sent to the finished product warehouse.

[0049] A method for preparing green pellets. The performance test results of the green pellets obtained in Example 1, Example 2 and Example 3 are as follows:

[0050]

[0051] The pellets produced by the preparation methods of Examples 1 to 3 of the present invention have significant beneficial effects. Their cold strength is not less than 2500N, they have good water and high temperature resistance, and the powder rate is less than 2%. The softening start temperature T10, softening end temperature T40, pressure difference, dripping temperature, S characteristic value and other properties all meet the requirements for entering the furnace, and the droplet temperature shows a gradual increase trend from Examples 1 to 3. Therefore, Example 1 can be used for hydrogen-based vertical furnaces and small blast furnaces, Example 2 can be used for large blast furnaces, and Example 3 can be used for blast furnaces to increase the magnesium content and adjust the charge structure. Thereby successfully solving the metallurgical performance problem required for cold-solidified pellets used in blast furnaces, as well as the problem of optimizing the charge structure of blast furnaces and reducing the proportion of sintered ore, ensuring the large-scale application of cold-solidified pellets in blast furnaces, and providing a better solution for the selection of charge in steel production.

[0052] The present invention and its embodiments are described above, and such description is not restrictive. What is shown in the embodiment is only one of the embodiments of the present invention, and the actual structure is not limited thereto. In short, if ordinary technicians in the field are inspired by it, without departing from the purpose of the invention, they can design a structure and embodiment similar to the technical solution without creativity, which should belong to the protection scope of the present invention.

Claims

1. A method for preparing green pellets, characterized in that: The following steps are involved: S1: adding 0.05-0.1 parts by weight of sodium hydroxide to 18-22 parts by weight of water and stirring to dissolve, then stirring evenly with 78-82 parts by weight of starch, pre-gelatinizing through a puffing device, and then crushing to 80-100 meshes to obtain pre-gelatinized starch, the gelatinization temperature is 150-190 degrees Celsius; S2: 90-96 parts by weight of iron powder, 0.5-8 parts by weight of magnesium oxide, 0.8-1.5 parts by weight of pregelatinized starch, and 0.3-1 parts by weight of magnesium chloride are put into a mixer and mixed and stirred evenly; S3: adding 0.5-1 parts by weight of borax, 0.1-0.3 parts by weight of cellulose, and 0.2-0.5 parts by weight of polyacrylamide and continuing to stir evenly; S4: conveying the final mixed material into the pelletizing machine; S5: After being pressed into balls, they are sent to negative pressure air drying chamber through conveyor belt; S6: After leaving the negative pressure air drying warehouse, the products pass through the roller screen and enter the finished product warehouse.

2. The method for preparing high-magnesium cold-solidified pellets according to claim 1, characterized in that: The fineness of the magnesium oxide in step S2 is higher than 200 mesh.

3. The method for preparing high-magnesium cold-solidified pellets according to claim 1, characterized in that: The starch is corn starch, and the viscosity after pre-gelatinization is greater than 500.

4. A composite adhesive for preparing green pellets, characterized in that: It includes the following ingredients: pregelatinized starch, magnesium oxide, magnesium chloride, and enhancer.

5. The composite adhesive for preparing green pellets according to claim 4, characterized in that: The components of the composite adhesive are as follows by weight: 0.8-1.5 parts of pregelatinized starch, 0.5-8 parts of magnesium oxide, 0.3-1 parts of magnesium chloride, and 0.8-1.5 parts of a reinforcing agent.

6. The composite adhesive for preparing green pellets according to claim 5, characterized in that: The reinforcing agent includes borax, cellulose and polyacrylamide.

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