Process for manufacturing shaped pellets and use of shaped pellets

Abstract

The application discloses a kind of special-shaped pellets manufacturing process, including steps: S1, pellet raw material batching;S2, pellet raw material is pressed into different size and shape special-shaped pellets;S3, drying special-shaped pellets.The special-shaped pellets manufacturing process of the application improves the shape factor of pellet, and after practical production and use, the rolling phenomenon of pellet to the column around is inhibited, the blast furnace charging system can be optimized, the material surface shape is improved, the central coke proportion is reduced, and the fuel ratio is reduced.

Description

Technical Field

[0001] This invention belongs to the field of iron ore pellet technology in the steel industry. Specifically, this invention relates to a process for manufacturing irregularly shaped pellets and the uses of irregularly shaped pellets. Background Technology

[0002] With the continuous development and improvement of ironmaking technology, sintered ore and pellets have gradually become the mainstream raw materials in the ironmaking field. Through artificial agglomeration technology, refined and enriched iron ore powder is processed into artificial iron ore, also known as "clinker." Experiments and actual production have shown that a high proportion of pellets fed into the blast furnace can significantly improve the overall grade of the ore entering the blast furnace, reduce fuel consumption and slag volume, and thus reduce CO2 and pollutant emissions during the ironmaking process. This is one of the important supporting technologies and key technological approaches to achieving low-carbon and green ironmaking.

[0003] Traditional pelletizing roller presses use one or two pairs of rollers with spherical (or elliptical) holes of the same size to compress the material into pellets of a certain size. With the increase in the proportion of pellets fed into the furnace, the metallurgical properties of the furnace charge and the process parameters have undergone significant changes. Sintered ore has a large particle size and uneven shape, while pellets have a smaller particle size, generally spherical in shape (8mm–16mm). The impact of a high proportion of pellets on the bulk zone is mainly due to the poor packing properties of pellets, making it difficult to control the charge surface, thus affecting the permeability of the bulk zone and the distribution of gas flow. Experimental simulations have shown that increasing the proportion of pellets in the furnace causes the smaller pellets to slide outwards, resulting in an overall shift and lowering of the charge surface. Simultaneously, the larger sintered ore concentrates on the outside of the charge surface, while the pellets concentrate on the inside, which is detrimental to the permeability of the charge column and the reduction of the bulk zone.

[0004] Chinese Patent Application No. 201510717729.5 discloses a method for preparing cold-pressed iron powder pellets, belonging to the field of metallurgical pelletizing technology. This preparation method involves applying a compounded binder to the pressing and molding of mixed iron powder; the ratio of the mixed iron powder is iron ore powder: iron oxide scale powder = 70:30; the material ratio during pressing and molding is mixed iron powder: compound binder: water = 100:3.5-3.6:6-8. This invention uses cold-pressing pelletizing technology to produce iron powder pellets that meet the requirements for use. The performance indicators of the pellets, such as green pellet strength, bursting temperature, and compressive strength of the finished pellets, all meet the quality requirements for pellets; it solves the long-standing technical problem of cold-pressing iron powder in steel enterprises. This invention can fully utilize existing iron-containing waste materials in steel enterprises, solve the problem of surplus iron-containing waste, and achieve the goal of rational resource utilization and reduced environmental pollution. It is applicable to industrial production and has good economic, social, and environmental benefits.

[0005] Chinese Patent Application No. 202110051393.9 discloses a method for preparing cold-pressed iron ore powder briquettes and their applications. The method involves cold-pressing coarse-grained iron ore powder, iron concentrate, and iron-containing solid waste from the plant to produce cold-pressed iron ore powder briquettes for use in blast furnaces or smelting reduction furnaces without generating pollutants. This achieves the recycling of iron-containing resources and reduces environmental pollution. Simultaneously, hydraulic materials such as hydrated lime, ordinary silicate cement, and slag cement are used as binders, reducing the amount of flux such as limestone and dolomite added during use, thereby reducing CO2 emissions from the ironmaking process. Ultimately, this achieves both reduced production costs and environmental, social, and economic benefits.

[0006] The aim is to provide an improved process for producing irregularly shaped pellets, particularly regarding improving the shape factor of the pellets, in order to alleviate the problems of difficulty in controlling the feed surface and feed surface segregation caused by a high proportion of pellets entering the furnace. Summary of the Invention

[0007] The present invention aims to at least solve one of the technical problems existing in the prior art. To this end, the present invention provides a process for manufacturing irregularly shaped pellets, with the aim of improving the shape factor of pellet ore.

[0008] To achieve the above objectives, the technical solution adopted by this invention is: a process for manufacturing irregularly shaped pellets, comprising the following steps:

[0009] S1, Pellet raw material preparation;

[0010] S2. The raw material is pressed into irregularly shaped pellets of different sizes and shapes;

[0011] S3. Dry irregularly shaped pellets.

[0012] In step S2, a briquetting machine is used to press the raw material into irregularly shaped briquettes of different sizes and shapes. The briquetting machine includes rollers, and the roller skins are provided with multiple concave holes of different sizes and shapes.

[0013] The volume of the concave hole is 1-30 cm³ 3 .

[0014] In step S2, the rollers work together in pairs to extrude the pellet raw material.

[0015] In step S1, the pellet raw material is a mixture of one or more of iron concentrate, iron-containing solid waste, and sintered pellet return powder, and the moisture content of the pellet raw material is controlled at 5-8%.

[0016] In step S1, a binder is added to the pellet raw material, and the binder is a composite binder.

[0017] In step S2, the pressing pressure is 10–20 MPa, and the pressing time is 0.5–1 s, so that the bulk density of the pellets reaches 5–10 g / cm³. 3 .

[0018] In step S3, the pressed irregularly shaped pellets are dried in a drying drum at a temperature controlled between 100 and 200°C.

[0019] The present invention also provides an application of the irregularly shaped pellets prepared by the aforementioned manufacturing process in blast furnace smelting.

[0020] The amount of the irregularly shaped pellets used is controlled between 10 and 30 wt%.

[0021] The irregular pellet manufacturing process of the present invention improves the shape factor of the pellets. After actual production and use, the phenomenon of the pellets rolling around the material column is suppressed, which can optimize the blast furnace charging system, improve the shape of the material surface, reduce the proportion of central coke, and reduce the fuel ratio. Attached Figure Description

[0022] This manual includes the following figures, which illustrate the following:

[0023] Figure 1 This is a flowchart of the irregularly shaped pellet manufacturing process of the present invention;

[0024] Figure 2 This is a schematic diagram of the roller structure;

[0025] Figure 3 This is a schematic diagram of the automatic control model for roller pressing;

[0026] Figure 4 This is a diagram showing the surface shape of existing round pellet ore.

[0027] Figure 5 This is a schematic diagram of the surface shape of irregularly shaped pellet ore. Detailed Implementation

[0028] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings, in order to help those skilled in the art to have a more complete, accurate and in-depth understanding of the inventive concept and technical solution of the present invention, and to facilitate its implementation.

[0029] Firstly, such as Figure 1 As shown, the present invention provides a process for manufacturing irregularly shaped pellets, comprising the following steps:

[0030] S1, Pellet raw material preparation;

[0031] S2. The raw material is pressed into irregularly shaped pellets of different sizes and shapes;

[0032] S3. Drying irregularly shaped pellets;

[0033] S4. Screening.

[0034] Specifically, in this invention, based on further improvements to the roller-pressed pellet production process and the realization of automatic control of the roller pressing process, the shape of the traditional pellets is changed to improve the problem of difficulty in controlling the material surface and material segregation caused by a high proportion of pellets entering the furnace; at the same time, irregularly shaped pellets of different sizes and shapes increase the overall porosity of the furnace charge and enhance the permeability of the blast furnace.

[0035] The innovative aspects of this invention are as follows:

[0036] 1) This invention changes the traditional spherical concave holes on the roller skin to polyhedral and non-spherical concave holes of different sizes, and presses them into irregularly shaped pellets of different sizes and shapes; at the same time, it adds a control system that automatically adjusts the roller pressure and the amount of binder added according to the pellet size and pelletization rate.

[0037] 2) The beneficial effects of using irregularly shaped pellets in large blast furnaces are reflected in their increased specific surface area and angle of repose, which reduces the difference with sinter, optimizes the blast furnace charging system, improves the shape of the material surface and the permeability inside the furnace, thereby reducing the proportion of central coke and the fuel ratio.

[0038] The manufacturing process of this invention involves adding a certain proportion of binder to the raw material spheroids, and then pressing them into irregularly shaped spheroids of different sizes and shapes by a spheroidizing machine with multi-faceted non-spherical concave holes of varying sizes on the roller skin, under the control of a control system.

[0039] In step S1 above, the pellet raw material is a mixture of one or more of iron concentrate, iron-containing solid waste, and sintered pellet return powder, and the moisture content of the pellet raw material is controlled at 5-8%.

[0040] In step S2 above, a briquetting machine is used to press the raw material into irregularly shaped briquettes of different sizes and shapes. The briquetting machine includes rollers, such as... Figure 2 As shown, the roller is a cylinder and is rotatable. The roller skin has multiple recesses of different sizes and shapes. These recesses are non-spherical and have a polyhedral structure; they can be a combination of one or more types of holes, such as hexahedrons, octahedrons, or irregular shapes.

[0041] Preferably, the volume of the concave hole is 1–30 cm³. 3 Within this volume range, irregularly shaped pellets are available; smaller ones do not affect the permeability of the blast furnace, while larger ones do not affect drying, and their strength is guaranteed.

[0042] In step S2 above, the rollers work in pairs to extrude the pellet raw material. The axes of the two working rollers are parallel, and the two working rollers rotate in opposite directions.

[0043] In step S1 above, a binder is added to the pellet raw material using a binder adding device. The binder is a composite binder. The composite binder can simultaneously ensure the cold and hot strength of the irregularly shaped pellets, improve the pellet quality, and meet the needs of industrial production.

[0044] In step S2 above, the pressing pressure is 10–20 MPa, and the pressing time is 0.5–1 s, so that the bulk density of the pellets reaches 5–10 g / cm³. 3 Under these pressing parameters, the strength of irregularly shaped pellets is guaranteed, and the power consumption of the briquetting machine is reduced.

[0045] In step S3 above, the pressed irregularly shaped pellets are dried in a drying drum at a temperature controlled between 100 and 200°C. The moisture content of the dried pellets is no more than 1%. These drying parameters facilitate the drying of the irregularly shaped pellets and save on gas consumption.

[0046] In step S4 above, qualified irregularly shaped pellets are obtained after screening and can proceed to the next process.

[0047] like Figure 3 As shown, the binder addition equipment and briquetting machine are electrically connected to the control system, which in turn is electrically connected to the image recognition and analysis system. In step S2, the image recognition and analysis system acquires images of irregularly shaped briquettes at the outlet of the briquetting machine and analyzes and processes these images to detect the briquetting effect of the machine. The detection includes briquette particle size and briquetting rate. Based on the detection results, the pressure of the rollers and the amount of binder added are adjusted in real time, thereby achieving automatic control of the briquetting process and improving work efficiency.

[0048] Secondly, the present invention also provides the use of irregularly shaped pellets prepared by the manufacturing process described in the first aspect of the present invention in blast furnace smelting.

[0049] The amount of irregularly shaped pellets used should be controlled between 10 and 30 wt%.

[0050] The beneficial effects of using irregularly shaped pellets in large blast furnaces are mainly reflected in the fact that their specific surface area and angle of repose are increased and become close to those of sintered ore. This can optimize the blast furnace charging system, improve the shape of the charge surface, improve the permeability inside the furnace, thereby reducing the proportion of central coke and the fuel ratio.

[0051] Example

[0052] This embodiment provides a process for manufacturing irregularly shaped pellets, including the following steps:

[0053] S1. The raw materials for pelletizing are proportioned as follows: 50% iron concentrate and 50% sintered pellet return powder. The iron concentrate with a particle size of -200 mesh accounts for 90%, and the return powder with a particle size of 3mm or larger accounts for less than 20%. The total moisture content of the raw materials is controlled at 8%. 1.5% composite binder is added externally and mixed vigorously.

[0054] S2. The raw material is pressed into irregularly shaped pellets of different sizes and shapes using an irregularly shaped pelletizing machine. The pressing pressure is 20 MPa, and the pressing time is 1 second. The resulting irregularly shaped pellets have a bulk density of 8 g / cm³. 3 ;

[0055] S3. The pressed irregularly shaped pellets are dried in a drum dryer at 200℃ for 30 minutes. After drying, their moisture content is less than 1%.

[0056] S4. After screening, irregularly shaped pellets with certain cold compressive strength and hot strength are obtained.

[0057] The aforementioned shaped pellets can be used in blast furnaces, with a proportion of 10-30 wt%. The specific dosage needs to be determined based on the blast furnace conditions. When used in a blast furnace, the same charging and distribution methods can be employed. The traditional round pellet surface shape is as follows: Figure 4 The shape of the irregularly shaped pellet ore surface is as follows Figure 5 As can be seen, compared with using round pellets, using the irregularly shaped pellets of this invention increases the center angle of the material surface by about 5°, increases the depth of the central funnel by 0.3m, and there is no obvious accumulation of pellets at the edges and center.

[0058] Furthermore, the shaped pellet test in this embodiment verifies that the advantages of adding coke to the center of the blast furnace are reducing the blast furnace pressure differential and improving blast furnace permeability, while the disadvantages are lower gas utilization and higher fuel ratio. Table 1 shows the corresponding indicators for using round and shaped pellets when the pellet proportion is 20%. It can be seen that compared with using round pellets, using shaped pellets reduces the proportion of coke added to the center from 25% to 15%. Under similar blast furnace pressure differential and permeability conditions, the gas utilization rate increases by 1.5 percentage points, and the fuel ratio decreases by 6 kg / t.

[0059] Table 1. Corresponding Indicators for Irregularly Shaped and Round Pellet Ore

[0060] Spherical pellets of ore 25 172 46.5 510 Irregular pellet ore 15 173 48.0 504

[0061] The present invention has been described above by way of example with reference to the accompanying drawings. Obviously, the specific implementation of the present invention is not limited to the above-described manner. Any non-substantial improvements made using the inventive concept and technical solution; or the direct application of the inventive concept and technical solution to other situations without modification, are all within the protection scope of the present invention.

Claims

1. A process for manufacturing irregularly shaped pellets, characterized in that, Including the following steps: S1, Pellet raw material preparation; S2. The raw material is pressed into irregularly shaped pellets of different sizes and shapes; S3. Drying irregularly shaped pellets; In step S2, a briquetting machine is used to press the raw material into irregularly shaped briquettes of different sizes and shapes. The briquetting machine includes a roller, which is cylindrical and rotatable. The roller skin has multiple concave holes of different sizes and shapes. The concave holes are non-spherical and have a polyhedral structure. In step S2, the rollers work together in pairs to extrude the pellet raw material; the axes of the two working rollers are parallel, and the rotation directions of the two working rollers are opposite.

2. The irregularly shaped pellet manufacturing process according to claim 1, characterized in that, The concave hole is a combination of one or more holes, such as hexahedron, octahedron, or irregular body.

3. The irregularly shaped pellet manufacturing process according to claim 2, characterized in that, The volume of the concave hole is 1-30 cm³ 3 .

4. The irregularly shaped pellet manufacturing process according to any one of claims 1 to 3, characterized in that, In step S1, the pellet raw material is a mixture of one or more of iron concentrate, iron-containing solid waste, and sintered pellet return powder, and the moisture content of the pellet raw material is controlled at 5-8%.

5. The irregularly shaped pellet manufacturing process according to any one of claims 1 to 3, characterized in that, In step S1, a binder is added to the pellet raw material, and the binder is a composite binder.

6. The irregularly shaped pellet manufacturing process according to any one of claims 1 to 3, characterized in that, In step S2, the pressing pressure is 10–20 MPa, and the pressing time is 0.5–1 s, so that the bulk density of the pellets reaches 5–10 g / cm³. 3 .

7. The irregularly shaped pellet manufacturing process according to any one of claims 1 to 3, characterized in that, In step S3, the pressed irregularly shaped pellets are dried in a drying drum at a temperature controlled between 100 and 200°C.

8. The use of irregularly shaped pellets prepared by the manufacturing process according to any one of claims 1 to 7 in blast furnace smelting.

9. The use of the irregularly shaped pellets according to claim 8, characterized in that, The amount of the irregularly shaped pellets used is controlled between 10 and 30 wt%.

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