Pellet production method and pellets

Abstract

The application discloses a pellet manufacturing method and a pellet, and relates to the technical field of metallurgy. The pellet manufacturing method provided by the application comprises the following steps: uniformly mixing raw materials to obtain a mixture, wherein the raw materials comprise dried magnetite concentrate and pelletizing concentrate, and the raw materials further comprise 2-5% of limonite tailings in terms of the total mass of the raw materials; using the mixture to manufacture green balls; drying and preheating the green balls; and roasting the green balls to obtain the pellet. Since 2-5% of the limonite tailings are added into the raw materials, the SiO2 content of the limonite tailings is relatively high, and therefore, the alkalinity of the finally manufactured pellet is relatively low, which is beneficial to reducing the cost of blast furnace ironmaking. The moisture contained in the limonite tailings can facilitate the green ball forming in the subsequent pelletizing process, and therefore, additional water is not needed in the pelletizing process, and therefore, the process cost of adding water is further reduced. The pellet provided by the application is manufactured by the above pellet manufacturing method.

Description

Technical Field

[0001] This application relates to the field of metallurgical technology, and more specifically, to a method for manufacturing pellets and pellets. Background Technology

[0002] Sinter and pellets are commonly used feedstocks in blast furnace ironmaking. Sinter offers the best cost-effectiveness, while pellets are relatively less so. From a cost perspective, increasing the proportion of sinter used helps reduce costs. Blast furnace feed often needs to maintain a suitable basicity to ensure ironmaking efficiency. However, the basicity of sinter remains consistently high. To balance the acid-base balance of the blast furnace slag, it is unavoidable to use a suitable amount of pellets (which have a relatively lower basicity than sinter) to maintain the appropriate basicity of the feedstock. With consistently high basicity of sinter, it is difficult to reduce the proportion of pellets used, thus hindering the reduction of ironmaking raw material costs.

[0003] Therefore, this application is hereby submitted. Summary of the Invention

[0004] The purpose of this application is to provide a method for manufacturing iron pellets and iron pellets that can reduce the raw material costs of ironmaking processes.

[0005] This application is implemented as follows:

[0006] In a first aspect, this application provides a method for manufacturing pellets, comprising:

[0007] The raw materials are mixed evenly to obtain a mixture, which includes dried magnetite concentrate and pelletizing concentrate, as well as limonite tailings accounting for 2-5% of the total mass of the raw materials.

[0008] Use a mixture to manufacture green balls;

[0009] Dry and preheat the green pellets;

[0010] The raw pellets are roasted to obtain ore pellets.

[0011] In an optional embodiment, the magnetite powder accounts for 30-35% of the total mass of the raw materials, and the pelletizing powder accounts for 60-65% of the total mass of the raw materials.

[0012] In an optional embodiment, bentonite, comprising 2-3% of the total mass of the raw materials, is added during the step of uniformly mixing the raw materials.

[0013] In an optional embodiment, the particle size of the mixture satisfies that the content of -200 mesh is not less than 80%.

[0014] In an optional embodiment, the moisture content of the dried magnetite powder and pelletizing powder is 7-9 wt%.

[0015] In an optional embodiment, the moisture content of the limonite tailings is 15-18 wt%, and the moisture content of the mixture is 9-10 wt%.

[0016] In an optional implementation, the step of manufacturing green balls using the mixture includes:

[0017] The mixture is added from the edge of the disc pelletizer, and green pellets with a particle size of 8-16 mm are formed using limonite tailings as the parent pellets.

[0018] In an optional embodiment, the steps of drying and preheating the green balls include:

[0019] The raw pellets are laid on the grate to form a material layer with a thickness of 140-160mm;

[0020] The grate bed carrying the green balls passes sequentially through the drying section and preheating section of the chain grate machine.

[0021] In an optional embodiment, the temperature of the fume hood in the drying section is 200–400°C, and the temperature of the air box in the drying section is 50–150°C.

[0022] In an optional implementation, the chain grate machine speed is 1.8 to 2.2 m / min.

[0023] In an optional embodiment, the step of roasting the green balls includes:

[0024] The green pellets are roasted in a rotary kiln at a temperature of 900–1000°C.

[0025] In an optional embodiment, the SiO2 content in the limonite tailings is 20–30 wt%.

[0026] Secondly, this application provides a pellet ore, which is obtained by the pellet ore manufacturing method of any of the foregoing embodiments.

[0027] This application has the following beneficial effects:

[0028] The pellet manufacturing method provided in this application includes uniformly mixing raw materials to obtain a mixture, the raw materials including dried magnetite concentrate and pelletizing concentrate, and 2-5% limonite tailings by weight of the raw materials; using the mixture to manufacture green pellets; drying and preheating the green pellets; and roasting the green pellets to obtain pellets. Because 2-5 wt% limonite tailings are added to the raw materials, and limonite tailings themselves are inexpensive and have a high SiO2 content (an acidic oxide), the resulting pellets have a low basicity. Therefore, when sinter and pellets are used in combination, the proportion of pellets used can be further reduced, thereby lowering the raw material cost of blast furnace ironmaking. Furthermore, before preparing the mixture, only the magnetite concentrate and pelletizing concentrate are dried, without drying the limonite tailings, reducing drying process costs. The moisture content of the limonite tailings facilitates green pellet formation in the subsequent pelletizing process, eliminating the need for additional water addition during pelletizing, thus further reducing water addition process costs. It is evident that the pellet manufacturing method provided in this application has low process cost and can produce pellets with low basicity, which is beneficial to reducing the raw material cost of subsequent ironmaking processes.

[0029] The pellets provided in this application embodiment are obtained by the above-described pellet manufacturing method. Attached Figure Description

[0030] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0031] Figure 1 This is a flowchart of a pellet manufacturing method in one embodiment of this application. Detailed Implementation

[0032] Sinter and pellets are commonly used raw materials in blast furnace ironmaking. Sinter is obtained by mixing and granulating ore powder, various fluxes, and fine coke, then adding it to a sintering machine via a feeding system for sintering. Pellets are made by mixing finely ground concentrate powder and additives, then forming green pellets in a pelletizing system, followed by drying, high-temperature roasting, and cooling. The different pelletizing processes and raw materials result in sinter having lower cost and higher basicity, while pellets have higher cost and lower basicity. Basicity refers to the ratio of basic oxides to acidic oxides in the ore, such as the ratio of CaO to SiO2 in binary basicity. Maintaining acid-base balance, i.e., a reasonable basicity, is crucial in blast furnace ironmaking, often requiring the combined use of sinter and pellets. For cost considerations, using more sinter and less pellets helps reduce costs, but excessive use of sinter disrupts the acid-base balance. Therefore, it is necessary to obtain pellets with lower basicity, i.e., pellets containing more SiO2.

[0033] Therefore, this application provides a method for manufacturing pellets, which uses limonite tailings with high SiO2 content as one of the raw materials to manufacture pellets, thereby obtaining pellets with high SiO2 content.

[0034] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0035] The features and performance of this application will be further described in detail below with reference to the embodiments.

[0036] Figure 1 This is a flowchart of a pellet manufacturing method according to one embodiment of this application. Figure 1 As shown, the pellet manufacturing method provided in this application includes:

[0037] Step S100: Mix the raw materials evenly to obtain a mixture. The raw materials include dried magnetite concentrate and pelletizing concentrate, as well as limonite tailings accounting for 2-5% of the total mass of the raw materials.

[0038] In the embodiments of this application, the magnetite concentrate and pelletizing concentrate have been dried before mixing, while the limonite tailings are not dried.

[0039] Optionally, the magnetite powder and pelletizing powder can be mixed according to the required pelletizing ratio and then dried in a drying drum. Optionally, the inlet hot air temperature of the drying drum is 350–370°C, such as any value or any two of 350°C, 355°C, 360°C, 365°C, and 370°C, and the outlet hot air temperature is 140–160°C, such as any value or any two of 140°C, 145°C, 150°C, 155°C, and 160°C. The drying time is 20–30 minutes. The moisture content of the resulting magnetite powder and pelletizing powder after drying is 7–9 wt%. In other optional embodiments, the magnetite powder and pelletizing powder can be dried separately and then mixed.

[0040] Compared to magnetite concentrate and pelletizing concentrate, limonite tailings have coarser particle size and higher moisture content. If the time required to reach the required moisture content in the drying drum is too long, it will not only consume excessive electricity but also affect the batching schedule. Therefore, limonite tailings are separated and not dried. Furthermore, the moisture in the limonite tailings can help form green pellets in the subsequent pelletizing process.

[0041] Optionally, the SiO2 content in the limonite tailings is 20–30 wt%. Optionally, the moisture content of the limonite tailings is 15–18 wt%, and the moisture content of the resulting mixture is 9–10 wt%.

[0042] Optionally, the magnetite concentrate accounts for 30-35% of the total mass of the raw materials, and its main component is iron(III) oxide; the pelletizing concentrate accounts for 60-65% of the total mass of the raw materials. Among them, the pelletizing concentrate can be composed of 20 wt% imported pelletizing concentrate and 40-45 wt% domestically produced pelletizing concentrate.

[0043] Optionally, 2-3% of bentonite by weight of the raw materials may be added during the step of mixing the raw materials evenly. The bentonite helps to form green pellets in the subsequent pelletizing process.

[0044] Optionally, the particle size of the mixture must meet the requirement that the content of -200 mesh is not less than 80%, that is, the mass of particles passing through a 200-mesh sieve accounts for more than 80% of the total mass of the mixture. By controlling the particle size to meet the requirement that the content of -200 mesh is not less than 80%, the specific surface area of ​​the mixture is ensured to be large enough to meet the requirements of pelletizing ore.

[0045] Optionally, the various raw materials can be mixed using a high-powered mixer to obtain a mixture.

[0046] In this embodiment, the proportion of limonite tailings in the raw material is no higher than 5 wt%, because excessive use of limonite tailings can lead to a decrease in pellet quality or affect the process. For example, the compressive strength of the pellets may decrease, and excessive moisture may lead to excessive blast furnace fuel consumption. Excessive use of limonite tailings may also cause a decrease in green pellet bursting temperature, increased dust at the production site, a decrease in the speed of the chain grate, and a reduction in output. Optionally, the content of limonite tailings in the raw material can be any value among 2 wt%, 3 wt%, 4 wt%, and 5 wt%, or any value between any two of these values.

[0047] Step S200: Use the mixture to manufacture green balls.

[0048] Specifically, a disc pelletizer can be used to manufacture green pellets. Optionally, the mixture is added from the edge of the disc pelletizer, and during operation, green pellets with a particle size of 8–16 mm are formed using limonite tailings as the parent material. No water needs to be added during pelletizing because the limonite tailings contain a certain amount of moisture, which is sufficient to meet the pelletizing requirements and aid in green pellet formation. Therefore, this method eliminates the need for water addition, reducing processing costs.

[0049] Step S300: Dry and preheat the green pellets.

[0050] Optionally, step S300 may include: laying green balls on a grate to form a material layer with a thickness of 140-160 mm, for example, the material layer thickness may be any thickness value among 140 mm, 145 mm, 150 mm, 155 mm, and 160 mm or any value between two thickness values; then, controlling the grate carrying the green balls to pass through the drying section and preheating section of the chain grate machine in sequence, thereby completing the drying and preheating.

[0051] Optionally, the chain grate machine is divided into three sections: a drying section, a preheating section (section 1), and a preheating section (section 2). The drying section is responsible for drying the green balls, while the preheating sections (sections 1 and 2) are responsible for preheating the green balls. In one specific embodiment, the total area of ​​the chain grate machine is 152m². 2 The drying section is 60m long. 2 Preheat a 24m section 2 Preheating stage 2, 68m 2The temperature of the fume hood in the drying section can be controlled between 200 and 400℃, for example, at any point or between any two of 200℃, 250℃, 300℃, 350℃, and 400℃. The temperature of the air box in the drying section can be controlled between 50 and 150℃, for example, at any point or between any two of 50℃, 60℃, 70℃, 80℃, 90℃, 100℃, 110℃, 120℃, 130℃, 140℃, and 150℃. The inlet temperature of the heat-resistant fan is ≥220℃. The speed of the chain grate machine can be controlled between 1.8 and 2.2 m / min, for example, at any point or between any two of 1.8 m / min, 1.9 m / min, 2 m / min, 2.1 m / min, and 2.2 m / min.

[0052] Step S400: Roast the green pellets to obtain pellet ore.

[0053] Optionally, after the green pellets are preheated, a rotary kiln can be used to roast the preheated green pellets. The kiln head temperature of the rotary kiln can be selected as 900-1000℃, and further, the kiln head temperature can be controlled at 940-960℃. After roasting, pellets are obtained.

[0054] The pellet manufacturing method provided in this application replaces a portion of the pelletizing concentrate (typically with a lower SiO2 content, such as 6.5 wt%) with limonite tailings containing a high SiO2 content of 20-30%, by a substitution ratio of 2-5%, thereby increasing the SiO2 content in the final pellets by 0.4-0.9 percentage points. Furthermore, this method eliminates the drying step of the limonite tailings and the water addition step in the subsequent pelletizing process, resulting in lower process costs. Simultaneously, the cost of limonite tailings themselves is lower than that of pelletizing concentrate, thus this pellet manufacturing method is characterized by low cost. The resulting pellets, with lower basicity, can be further reduced in proportion when used in blast furnace ironmaking, thereby lowering the raw material costs for blast furnace ironmaking.

[0055] Example 1

[0056] In this embodiment, the chemical composition of the limonite tailings is shown in the table below, where the data is in wt%.

[0057] goethite tailings 44.11 24.83 0.095 0.078 0.034 0.053 0.089 15.99 60.81

[0058] 5 wt% limonite tailings, 30 wt% magnetite concentrate, and 65 wt% pelletizing concentrate were processed according to the above-mentioned pelletizing method, including drying, batching, mixing, pelletizing, spreading, drying preheating, and roasting, to obtain pellets. The pellets were tested, and the results are shown in the table below.

[0059] 2583 31.30

[0060] As can be seen from the table above, the pellets produced by the pellet manufacturing method provided in this embodiment still maintain good compressive strength and have low solid fuel consumption. Compared with pellets without the addition of limonite tailings, there is no significant deterioration in performance, which can better meet the needs of blast furnace ironmaking.

[0061] Example 2

[0062] In this embodiment, the chemical composition of the limonite tailings is shown in the table below, where the data is in wt%.

[0063] goethite tailings 43.55 26.68 0.103 0.049 0.016 0.018 0.045 17.88 57.29

[0064] 3 wt% limonite tailings, 30 wt% magnetite concentrate, and 67 wt% pelletizing concentrate were processed according to the above-mentioned pelletizing method, including drying, batching, mixing, pelletizing, spreading, drying preheating, and roasting, to obtain pellets. The pellets were tested, and the results are shown in the table below.

[0065] 2617 30.81

[0066] As can be seen from the table above, the compressive strength of the pellets produced by the pellet manufacturing method provided in this embodiment can fully meet the needs of blast furnace production, and the solid fuel consumption is not much different from that of pellet production without adding limonite tailings.

[0067] In summary, the pellet manufacturing method provided in this application includes uniformly mixing raw materials to obtain a mixture, the raw materials including dried magnetite concentrate and pelletizing concentrate, and 2-5% limonite tailings by weight of the raw materials; using the mixture to manufacture green pellets; drying and preheating the green pellets; and roasting the green pellets to obtain pellets. Because 2-5 wt% limonite tailings are added to the raw materials, and limonite tailings themselves are inexpensive and have a high SiO2 content (an acidic oxide), the resulting pellets have a low basicity. Therefore, when sinter and pellets are used in combination, the proportion of pellets used can be further reduced, thereby lowering the raw material cost of blast furnace ironmaking. Furthermore, before preparing the mixture, only the magnetite concentrate and pelletizing concentrate are dried, without drying the limonite tailings, reducing drying process costs. The moisture content in the limonite tailings facilitates green pellet formation in the subsequent pelletizing process, eliminating the need for additional water addition during pelletizing, thus further reducing water addition process costs. It is evident that the pellet manufacturing method provided in this application has low process cost and can produce pellets with low basicity, which is beneficial to reducing the raw material cost of subsequent ironmaking processes.

[0068] The pellets provided in this application embodiment are obtained by the above-described pellet manufacturing method.

[0069] The above are merely preferred embodiments of this application and are not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for manufacturing pellets, characterized in that, include: The raw materials are mixed evenly to obtain a mixture, the raw materials including dried magnetite concentrate and pelletizing concentrate, and limonite tailings; wherein the magnetite concentrate accounts for 30-35% of the total mass of the raw materials, the pelletizing concentrate accounts for 60-65% of the total mass of the raw materials, and the limonite tailings account for 2-5% of the total mass of the raw materials; the moisture content of the limonite tailings is 15-18 wt%, and the SiO2 content in the limonite tailings is 20-30 wt%; the moisture content of the mixture is 9-10 wt%. In the step of mixing the raw materials evenly, bentonite, accounting for 2-3% of the total mass of the raw materials, is also added; The mixture is used to manufacture green balls; The green pellets are dried and preheated; The green pellets are roasted to obtain ore pellets.

2. The method for manufacturing pellets according to claim 1, characterized in that, The particle size of the mixture must meet the requirement that the content of -200 mesh is not less than 80%.

3. The method for manufacturing pellets according to claim 1, characterized in that, The moisture content of the dried magnetite powder and pelletizing powder is 7-9 wt%.

4. The method for manufacturing pellets according to claim 1, characterized in that, The steps of manufacturing green pellets using the mixture include: The mixture is added from the edge of the disc pelletizer, and the limonite tailings are used as the mother pellets to form green pellets with a particle size of 8-16 mm.

5. The method for manufacturing pellets according to claim 1, characterized in that, The steps of drying and preheating the green pellets include: The green balls are laid on the grate to form a material layer with a thickness of 140-160 mm; The grate carrying the green balls is controlled to pass sequentially through the drying section and preheating section of the chain grate machine.

6. The method for manufacturing pellets according to claim 5, characterized in that, The temperature of the fume hood in the drying section is 200–400°C, and the temperature of the air box in the drying section is 50–150°C.

7. The method for manufacturing pellets according to claim 5, characterized in that, The chain grate machine has a speed of 1.8~2.2m / min.

8. The method for manufacturing pellets according to claim 1, characterized in that, The step of roasting the raw balls includes: The green pellets are roasted in a rotary kiln at a kiln head temperature of 900-1000℃.

9. A type of pellet ore, characterized in that, It is prepared by the pellet manufacturing method according to any one of claims 1-8.

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