Special-shaped pellet manufacturing process and application of special-shaped pellets

Abstract

The invention discloses a special-shaped pellet manufacturing process. The process comprises the steps that S1, pellet raw materials are prepared; s2, the pellet raw materials are pressed into special-shaped pellets of different sizes and shapes; and S3, the special-shaped pellets are dried. According to the manufacturing process of the special-shaped pellets, the shape factors of the pellets are improved, the phenomenon that the pellets roll to the periphery of a material column is inhibited after actual production and use, the feeding system of a blast furnace can be optimized, the shape of the material surface can be improved, the proportion of center coke can be reduced, and the fuel ratio can be reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of iron ore pellets in the steel industry, and in particular, relates to a process for producing special-shaped pellets and uses of the special-shaped pellets. Background Art

[0002] After the continuous development and improvement of ironmaking technology, sintered ore and pelletized ore have gradually become the mainstream raw materials in the ironmaking field. Through artificial agglomeration technology, the selected and enriched iron ore powder is processed into artificial iron ore, also known as "clinker". According to experiments and actual production, high proportion of pellets in smelting can significantly improve the comprehensive grade of ore entering the blast furnace, reduce fuel consumption and slag volume, and thus reduce CO2 in the ironmaking process. 2 and pollutant emissions, and is one of the important supporting technologies and key technical approaches to achieve low-carbon green ironmaking.

[0003] The traditional pelletizing roller pressing device is composed of one or two pairs of rollers, and the roller skin is provided with spherical (or elliptical) holes of the same size to press the material into pellets of a certain size. With the increase of the proportion of pellets entering the furnace, the metallurgical properties and process parameters of the charge have undergone tremendous changes. The sintered ore has large particle size and uneven shape, while the pellets have small particle size, generally 8mm to 16mm spherical. The influence of the high-proportion pelletizing charge structure on the block belt is mainly due to the poor stacking performance of the pellets, which makes the material surface difficult to control, thereby affecting the permeability of the block belt and the gas flow distribution. Some scholars have found through experimental simulation that after increasing the proportion of pellets entering the furnace, the pellets will slide outward due to their small volume, causing the overall surface of the material to move outward and become shorter. At the same time, the larger sintered ore is concentrated on the outside of the material surface, while the pellets are concentrated on the inside, which is not conducive to the permeability of the material column and the reduction of the block belt.

[0004] The Chinese patent application number 201510717729.5 discloses a method for preparing mixed iron powder cold-pressed pellets, which belongs to the field of metallurgical pellet smelting technology. This preparation method is to apply the compounded composite binder to the pressing and molding of the mixed iron powder; the ratio of the mixed iron powder is iron ore powder: iron oxide powder = 70:30; the material ratio in the pressing and molding is mixed iron powder: composite binder: water = 100:3.5-3.6:6-8. The present invention adopts the cold pressing ball forming process technology to prepare iron powder pellets that meet the use requirements, wherein the performance indicators of the green ball strength, burst temperature and finished ball compressive strength of the pellets meet the quality requirements of the pellets; and solves the technical problems that have long plagued iron powder cold pressing molding in steel enterprises. The present invention can make full use of the existing iron-containing waste in steel enterprises, solve the problem of excess iron-containing waste, and achieve the purpose of rationally utilizing resources and reducing environmental pollution. It can be applied to industrial production and has good economic, social and environmental benefits.

[0005] Chinese patent application number 202110051393.9 discloses a method for preparing cold-pressed iron ore powder agglomerates and uses of cold-pressed iron ore powder agglomerates. Coarse-grained iron ore powder, iron concentrate and iron-containing solid waste in the factory are cold-consolidated to prepare cold-pressed iron ore powder agglomerates for use in blast furnaces or smelting reduction furnaces in a manner that does not generate pollutants, thereby recycling iron-containing resources and reducing environmental pollution. At the same time, hydraulic materials such as slaked lime, ordinary Portland cement, and slag cement are used as binders. When used, the amount of flux such as limestone and dolomite can be reduced, thereby reducing the CO2 content of the ironmaking process. 2 Emissions, ultimately achieving the goal of reducing production costs while also having environmental, social and economic benefits.

[0006] It is hoped to provide an improved process for producing special-shaped pellets, in particular to improve the shape factor of the pellets, so as to improve the problems of difficult to control the material surface and material surface segregation caused by a high proportion of pellets entering the furnace. Summary of the invention

[0007] The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, the present invention provides a process for making special-shaped pellets, the purpose of which is to improve the shape factor of the pellets.

[0008] In order to achieve the above object, the technical solution adopted by the present invention is: a process for making special-shaped pellets, comprising the steps of:

[0009] S1, pelletizing raw material ingredients;

[0010] S2, the pellet raw materials are pressed into special-shaped pellets of different sizes and shapes;

[0011] S3, drying the special-shaped pellets.

[0012] In step S2, a ball press is used to press the pellet raw materials into special-shaped pellets of different sizes and shapes. The ball press includes a roller, and a roller skin of the roller is provided with a plurality of concave holes of different sizes and shapes.

[0013] The concave hole volume is 1 to 30 cm 3 .

[0014] In the step S2, the rollers cooperate with each other to extrude the pellet raw materials.

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

[0016] In the 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, the pressing time is 0.5-1 s, and the pellet volume density reaches 5-10 g / cm 3 .

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

[0019] The present invention also provides use of the special-shaped pellets prepared by the production process in blast furnace smelting.

[0020] The amount of the special-shaped pellets is controlled to be 10-30wt%.

[0021] The special-shaped pellet manufacturing process of the present invention improves the shape factor of the pellets. After actual production and use, the rolling phenomenon of the pellets around the material column is suppressed, the blast furnace charging system can be optimized, the material surface shape can be improved, the central coke ratio can be reduced, and the fuel ratio can be reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] This specification includes the following drawings, which show the following contents:

[0023] Figure 1 It is a flow chart of the process for making special-shaped pellets of the present invention;

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

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

[0026] Figure 4 It is the existing circular pellet material surface shape diagram;

[0027] Figure 5 It is a schematic diagram of the surface shape of the special-shaped pellets. DETAILED DESCRIPTION

[0028] The specific implementation methods of the present invention are further explained in detail below by describing the embodiments with reference to the accompanying drawings, with the aim of helping 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 facilitating their implementation.

[0029] First, as Figure 1 As shown, the present invention provides a process for making special-shaped pellets, comprising the following steps:

[0030] S1, pelletizing raw material ingredients;

[0031] S2, the pellet raw materials are pressed into special-shaped pellets of different sizes and shapes;

[0032] S3, drying the special-shaped pellets;

[0033] S4. Screening.

[0034] Specifically, in the present invention, based on further improving the roller-pressed pellet production process and realizing automatic control of the roller-pressing process, the shape of traditional pellets is changed to improve the problems of difficult-to-control material surface and material surface segregation caused by high proportion of pellets entering the furnace; at the same time, special-shaped pellets of different sizes and shapes are used to increase the porosity of the overall charge and enhance the permeability of the blast furnace.

[0035] In the present invention, the innovative points are as follows:

[0036] 1) The present invention changes the traditional spherical concave holes on the roller skin into polyhedral and non-spherical concave holes of different sizes, which are pressed into special-shaped pellets of different sizes and shapes; at the same time, a control system is added to automatically adjust the roller pressure and the amount of adhesive added according to the pellet size and pelletization rate.

[0037] 2) The beneficial effect of using special-shaped pellets in large blast furnaces is reflected in the increase of their specific surface area and stacking angle, which narrows the difference with sintered ore, optimizes the blast furnace charging system, improves the shape of the material surface and the air permeability in the furnace, thereby reducing the proportion of central coke and the fuel ratio.

[0038] The production process of the present invention is to add a certain proportion of binder to the pellet raw material, and press it into special-shaped pellets of different sizes and shapes under the control of a control system by a roller pelletizing machine with polyhedral non-spherical concave holes of different sizes on the roller skin.

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

[0040] In the above step S2, a ball press is used to press the pellet raw materials into special-shaped pellets of different sizes and shapes. The ball press includes a roller, such as Figure 2 As shown, the roller is a cylinder, the roller is rotatable, and a plurality of concave holes of different sizes and shapes are arranged on the roller skin of the roller. The concave holes are non-spherical holes, the concave holes are polyhedral structures, and the concave holes can be a combination of one or more holes in hexahedron, octahedron, irregular body.

[0041] Preferably, the volume of the concave hole is 1 to 30 cm 3 The special-shaped pellets within this volume range, if small, will not affect the air permeability of the blast furnace, and if large, will not affect the drying, so the strength is guaranteed.

[0042] In the above step S2, the rollers cooperate with each other to extrude the pellet raw materials. The axes of the two rollers that cooperate with each other are parallel, and the rotation directions of the two rollers that cooperate with each other are opposite.

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

[0044] In the above step S2, the pressing pressure is 10-20 MPa, the pressing time is 0.5-1 s, and the pellet volume density reaches 5-10 g / cm 3 Under this pressing parameter, the strength of the special-shaped pellets is guaranteed and the power consumption of the pellet press is saved.

[0045] In the above step S3, the pressed irregularly shaped pellets are dried in a drying drum at a temperature of 100-200° C. The moisture content of the irregularly shaped pellets after drying is not more than 1%. Under this drying parameter, the irregularly shaped pellets are easy to dry and gas consumption is saved.

[0046] In the above step S4, qualified special-shaped pellets are obtained after screening and can enter the next process.

[0047] like Figure 3 As shown, the binder adding device and the ball press are electrically connected to the control system, and the control system is electrically connected to the image recognition and analysis system. In the above step S2, the image recognition and analysis system collects images of the irregularly shaped pellets at the discharge end of the ball press, and analyzes and processes the collected images to detect the pressing effect of the irregularly shaped pellets of the ball press, and the detection content includes the pellet size and the ball formation rate. According to the detection results, the pressure of the roller and the amount of binder added are adjusted in real time, and then the automatic control of the pellet rolling process can be realized, thereby improving work efficiency.

[0048] In a second aspect, the present invention further provides a use of the special-shaped pellets prepared by the production process described in the first aspect of the present invention in blast furnace smelting.

[0049] The dosage of the special-shaped pellets is controlled at 10-30wt%.

[0050] The beneficial effect of using special-shaped pellets in large blast furnaces is mainly reflected in the fact that their specific surface area and stacking angle are increased, which are close to those of sintered ore. This can optimize the blast furnace charging system, improve the shape of the material surface, and improve the air permeability in the furnace, thereby reducing the proportion of central coke and the fuel ratio.

[0051] Example

[0052] This embodiment provides a process for producing special-shaped pellets, comprising the following steps:

[0053] S1. The pellet raw materials are prepared according to 50% iron concentrate and 50% sintered pellet return powder, with the iron concentrate -200 mesh size accounting for 90% and the return powder size above 3mm accounting for less than 20%. The total moisture content of the raw materials is controlled at 8%. 1.5% composite binder is added externally for strong mixing;

[0054] S2. The pellet raw materials are pressed into pellets of different sizes and shapes by a pellet press. The pressing pressure is 20MPa and the pressing time is 1s. The volume density of the obtained pellets reaches 8g / cm 3 ;

[0055] S3, the pressed irregularly shaped pellets are dried in a drum dryer at 200°C for 30 minutes, and the moisture content after drying is less than 1%;

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

[0057] The prepared special-shaped pellets can be used in blast furnaces. The proportion of special-shaped pellets is 10-30wt%. The specific amount needs to be used according to the furnace conditions of the blast furnace. When used in a blast furnace, the same charging and distribution mode can be adopted. The surface shape of the traditional round pellets is as follows: Figure 4 The surface shape of the special-shaped pellets is as follows Figure 5 It can be seen that compared with the use of round pellets, the use of the special-shaped pellets of the present invention increases the center pile angle of the material surface by about 5°, the depth of the center funnel increases by 0.3m, and there is no obvious accumulation of pellets at the edge and center.

[0058] Furthermore, the experiment of the special-shaped pellets in this embodiment verifies that the advantage of adding coke to the center of the blast furnace is to reduce the pressure difference of the blast furnace and improve the permeability of the blast furnace, while the disadvantage is that the gas utilization rate is low and the fuel ratio is high. When the pellet ratio is 20%, the corresponding indicators of round pellets and special-shaped pellets are shown in Table 1. It can be seen that compared with the use of round pellets, the use of special-shaped pellets reduces the center coke ratio from 25% to 15%. Under the condition of similar blast furnace pressure difference and permeability, the gas utilization rate increases by 1.5 percentage points and the fuel ratio decreases by 6kg / t.

[0059] Table 1 Corresponding indicators of irregular shaped pellets and round pellets

[0060] type Center focus ratio, % Pressure difference, kPa Gas utilization rate, % Fuel ratio, kg / t Spherical Pellet Ore 25 172 46.5 510 Special-shaped pellets 15 173 48.0 504

[0061] The present invention is described above by way of example in conjunction with the accompanying drawings. Obviously, the specific implementation of the present invention is not limited to the above-mentioned methods. As long as various non-substantial improvements are made using the method concept and technical solution of the present invention; or the above concept and technical solution of the present invention are directly applied to other occasions without improvement, they are all within the protection scope of the present invention.

Claims

1. A process for producing special-shaped pellets, characterized in that: Includes steps: S1, pelletizing raw material ingredients; S2, the pellet raw materials are pressed into special-shaped pellets of different sizes and shapes; S3, drying the special-shaped pellets.

2. The process for producing special-shaped pellets according to claim 1, characterized in that: In step S2, a ball press is used to press the pellet raw materials into special-shaped pellets of different sizes and shapes. The ball press includes a roller, and a roller skin of the roller is provided with a plurality of concave holes of different sizes and shapes.

3. The process for producing special-shaped pellets according to claim 2, characterized in that: The concave hole volume is 1 to 30 cm 3 .

4. The process for producing special-shaped pellets according to claim 2, characterized in that: In the step S2, the rollers cooperate with each other to extrude the pellet raw materials.

5. The process for producing special-shaped pellets according to any one of claims 1 to 4, characterized in that: In the step S1, the pelletizing raw material is a mixture of one or more of iron ore concentrate, iron-containing solid waste, and sintered pellet return powder, and the water content of the pelletizing raw material is controlled at 5-8%.

6. The process for producing special-shaped pellets according to any one of claims 1 to 5, characterized in that: In the step S1, a binder is added to the pellet raw material, and the binder is a composite binder.

7. The process for producing special-shaped pellets according to any one of claims 1 to 6, characterized in that: In step S2, the pressing pressure is 10-20 MPa, the pressing time is 0.5-1 s, and the pellet volume density reaches 5-10 g / cm 3 .

8. The process for producing special-shaped pellets according to any one of claims 1 to 7, characterized in that: In step S3, the pressed irregularly shaped pellets are dried in a drying drum at a temperature controlled at 100-200°C.

9. Use of the special-shaped pellets prepared by the production process according to any one of claims 1 to 7 in blast furnace smelting.

10. The use of the special-shaped pellets according to claim 9, characterized in that: The amount of the special-shaped pellets is controlled to be 10-30wt%.

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