A method for strengthening iron concentrate sintering based on concentrate pretreatment

Abstract

The application discloses a kind of based on concentrate pretreatment's reinforced iron concentrate sintering method, by the differentiation pretreatment of fine iron concentrate and coarse iron concentrate, and control the particle size gradient distribution of raw material when preparing precast pellet, by iron concentrate coupling quicklime and OG mud is pre-digested, and it is supplemented with strong mixing, improve the granulating performance of iron concentrate, improve the sintering material layer permeability, provide sufficient heat and CaO for iron concentrate sintering, alleviate the problem that the high temperature characteristic of iron concentrate is poor, to improve the utilization coefficient of concentrate sintering and sinter quality.

Description

Technical Field

[0001] This invention belongs to the field of sinter preparation technology, specifically relating to a method for strengthening iron concentrate sintering based on concentrate pretreatment. Background Technology

[0002] In recent years, although the proportion of pellets in blast furnace burdens in my country has shown an increasing trend, compared with foreign companies such as Mittal and United Steel (80% pellets + 20% sinter) and Swiss Steel and Dowfarkes (100% pellets), sinter will remain the main raw material in my country's blast furnace burdens for a considerable period, supplemented by pellets and lump ore. Affected by fluctuations in steel and iron ore prices, most steel companies have had to increasingly use domestically produced iron concentrate in order to reduce ironmaking costs and alleviate my country's steel industry's dependence on imported iron ore. This has increased the difficulty of controlling the sintering process and sinter quality indicators. China's iron ore resources are characterized by "abundant low-grade ore, fine-grained iron minerals, and numerous associated minerals." Iron concentrates produced through magnetic separation, flotation, and gravity separation are characterized by high iron content, fine particle size, and poor granulation performance. When iron concentrates are used in sintering production, there are many problems such as poor granulation effect, slow sintering speed, low sintering productivity, poor mechanical strength of sintered ore, and high energy consumption in the process. If the technical bottleneck of concentrate powder can be effectively overcome and its adverse effects on the sintering process can be reduced, it will be of great strategic significance to the safe and sustainable healthy development of my country's iron and steel industry.

[0003] Chinese patent CN 111041195 A discloses a high-intensity mixing-granulation method for enhancing the sintering of high-proportion fine-grained raw materials. The specific method is as follows: Material I, including iron concentrate, iron ore powder, and fine-grained return ore, is mixed in a cylindrical mixer to obtain a first-stage mixture; the first-stage mixture is then mixed with iron-containing dust material II, treated with a binder solution, in a high-intensity mixer to obtain a second-stage mixture; the second-stage mixture is then granulated with humidified coarse-grained return ore material III in a cylindrical mixer. This method controls the moisture content ratio in the three-stage mixing and granulation stages, as well as the particle size range of the sprayed water droplets, to increase the adhesion between fine-grained materials and their surfaces with other materials, effectively improving the granulation effect and enhancing the sintering of high-proportion fine-grained materials. However, this patent's method of uniformly dispersing quicklime on or around the iron ore surface through strong mixing does not improve the granulation performance of the fine-grained raw materials themselves, has limited improvement on the granulation effect of the mixture, and results in poor mechanical strength of the sintered ore.

[0004] Chinese patent CN 103484660 A discloses a method for enhancing the sintering of high-proportion iron concentrate. The method involves dividing the sintering raw materials into two parts for granulation. The first part consists of iron concentrate, quicklime, and coke powder separated from the sintering raw materials and undergoes a first-stage granulation. This first part is then combined with the second part of the raw materials for a second-stage granulation. The second part includes iron concentrate, quicklime, coke powder, as well as fine ore, limestone, dolomite, and recycled ore. By rationally distributing the concentrate, quicklime, and coke powder in the two parts, the method achieves enhanced granulation and sintering. The granulation effect of the first part of the raw materials in this patent primarily depends on the granulation performance of the iron concentrate itself. For iron concentrate with poor granulation performance, using this patented technology will result in a poor granulation effect in the first part, directly affecting the granulation effect of the second part and even the yield and quality of the sintered ore. Furthermore, the quicklime and coke powder in the first part are unsuitable as "nuclei." Summary of the Invention

[0005] The purpose of this invention is to provide an enhanced iron concentrate sintering method based on concentrate pretreatment. This method involves differentially pretreating fine and coarse iron concentrates, controlling the particle size gradient distribution of raw materials during pre-granulation preparation, pre-digesting the iron concentrate with quicklime and OG mud, and supplementing with vigorous mixing. This improves the granulation performance of the iron concentrate, enhances the permeability of the sintering bed, provides sufficient heat and CaO for iron concentrate sintering, alleviates the problem of poor high-temperature characteristics of iron concentrate, and thus improves the utilization coefficient and sinter quality of the concentrate.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A method for strengthening iron concentrate sintering based on concentrate pretreatment includes the following steps:

[0008] (1) After the fine iron concentrate and quicklime are mixed evenly, they are pre-treated by high-pressure roller mill to form a pre-treated material;

[0009] (2) Mix the pretreated material with crude iron concentrate, return ore, quicklime, OG mud and solid fuel evenly, and then perform disc pelletizing or cylinder pelletizing to form pre-granulated material;

[0010] (3) The sintering raw materials are mixed once, and then pre-made granules are added for a second mixing to obtain a sintering mixture. The sintering mixture is then distributed, ignited, sintered, cooled, and granulated to obtain the finished sintered ore.

[0011] Iron concentrate accounts for 8-50% of the weight of iron-containing material in sinter.

[0012] Quicklime accounts for 3-12% of the total weight of the pretreated material and 3-12% of the total weight of the pre-formed granules.

[0013] In step (1), the increase in specific surface area of ​​the fine iron concentrate after high-pressure roller mill pretreatment is not less than 500 cm². 2 / g.

[0014] In step (2), the particle size of the returned ore is 1-3 mm, and the 1-3 mm returned ore accounts for 5-15% of the total weight of the pre-made granules.

[0015] In step (2), solid fuel accounts for 3.5 to 4.5% of the total weight of the pre-formed pellets.

[0016] In step (2), the mass concentration of OG mud is controlled at 30-40%, and OG mud accounts for 1.0-4.0% of the total weight of the pre-formed granules.

[0017] In step (2), the solid fuel is any one or both of coke powder or coal powder.

[0018] In step (3), the sintering raw materials include iron ore powder, fuel, return ore and flux; the mass ratio of iron ore powder, fuel, return ore and flux is 100:5~9:35~60:15~30; the fuel is any one or two of coke powder or coal powder; the flux is any one or more of limestone, dolomite and quicklime.

[0019] In step (3), the pretreated raw materials, crude iron concentrate, 1-3mm return ore, quicklime, OG mud, and solid fuel are mixed evenly by a high-power mixer, and then granulated into 2-10mm balls by a cylindrical mixer, or into 3-15mm balls by a disc pelletizer.

[0020] The fine iron concentrate is a mixture of one or more iron concentrates, with a particle size of less than 0.074 mm content of more than 50%; the coarse iron concentrate is a mixture of one or more iron concentrates, with a particle size of less than 0.074 mm content of less than 50% and an average particle size of less than 1 mm.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] 1) This invention employs differentiated pretreatment based on the particle size of the iron concentrate: For fine iron concentrate, a static pressure-type material layer crushing principle of a high-pressure roller mill is used to pre-treat it together with quicklime, increasing the specific surface area of ​​the iron concentrate, changing the particle morphology, improving the surface activity of the iron concentrate, and enhancing its pelletizing performance; this makes the particle size distribution of quicklime tend to be fine, significantly reducing the content of coarse particles, which is more conducive to the full digestion of quicklime, and also eliminates the adverse effects of large quicklime particles acting as "nuclei"; while for coarse iron concentrate with a particle size of less than 0.074mm and an average particle size of less than 1mm, high-pressure roller mill pretreatment is not performed, which not only avoids the increase of "adhesive powder" in fine particles, but also saves the operating cost of the high-pressure roller mill.

[0023] 2) In the pre-granulation step, 1-3mm return ore, coarse iron concentrate, and pre-treated material form a particle size gradient distribution combining coarse, medium, and fine particles. The coarse 1-3mm return ore and coarse iron concentrate act as "cores" and "skeleton" in pelletizing, while the pre-treated material obtained after pre-treatment of fine iron concentrate acts as "adhesive powder". This not only improves the granulation effect of iron concentrate, but also enhances the anti-dust strength of the granulated pellets.

[0024] 3) Compared with iron concentrate and quicklime pretreatment technologies, the moisture content of iron concentrate is only about 7-12%. Quicklime digestion significantly reduces gravitational water and even capillary water in the iron concentrate. The reduction of capillary water, which plays a major role in the granulation process, is detrimental to improving the granulation effect. This invention couples iron concentrate with quicklime and OG mud for premixing. It not only utilizes the high viscosity of OG mud but also the large amount of moisture (about 45%) in OG mud to fully digest the quicklime in advance, effectively extending the quicklime digestion time, improving the quicklime digestion effect, and eliminating the drawbacks of pretreatment with only iron concentrate and quicklime. At the same time, it promotes closer contact between iron concentrate and quicklime particles, which not only helps to enhance the granulation effect of quicklime and solve the problem of low sinter yield caused by poor permeability of the iron concentrate sintering mixture layer, but also creates a local high-alkalinity environment around the iron concentrate, promoting the formation of liquid phase and calcium ferrite during the sintering process, thereby alleviating the problem of poor high-temperature characteristics of iron concentrate.

[0025] 4) This invention uses a high-power mixer, which improves the uniformity of pre-mixed granules, so that moisture, 1-3mm return ore, quicklime, OG mud and solid fuel are evenly dispersed, which improves the granulation effect of iron concentrate and can also reduce the consumption of solid fuel.

[0026] 5) This invention increases the amount of iron concentrate used to replace imported mainstream high-priced ore, reduces the sintering process's dependence on imported mainstream iron ore, and lowers the cost of sintering ore blending. Detailed Implementation

[0027] The present invention will now be described in detail with reference to the embodiments.

[0028] In all embodiments and comparative examples, the solid fuel is a mixture of coke powder and coal powder, with a mass ratio of coke powder to coal powder of 7:3.

[0029] The sintering raw materials are iron ore powder, fuel, recycled ore, and flux; the mass ratio of iron ore powder, fuel, recycled ore, and flux is 100:6:45:18; the fuel is a mixture of coke powder and coal powder, with a mass ratio of coke powder to coal powder of 7:3; the flux is dolomite and quicklime, and the amount of dolomite and quicklime is designed according to the sinter basicity of 2.0 and MgO content of 1.8%.

[0030] The sintering conditions were as follows: ignition time of 3.5 min, ignition temperature of 1100℃, and sintering negative pressure of 15 kPa.

[0031] Example 1

[0032] A method for strengthening iron concentrate sintering based on concentrate pretreatment includes the following steps:

[0033] (1) The iron concentrate in the iron-containing material is 8% by weight. Fine concentrate (4% by weight of the iron-containing material) and quicklime (3% by weight of the total pre-treated material) are mixed evenly and then subjected to high-pressure roller mill pretreatment. After high-pressure roller mill pretreatment, the specific surface area of ​​the iron concentrate is reduced from 700 cm². 2 / g increased to 1200cm 2 / g, forming a pretreated material;

[0034] (2) The pretreated material is mixed evenly with 4% by weight of crude iron concentrate, 5% by weight of 1-3mm return ore, 3% quicklime, 1.0% by weight of 30% OG slurry, and 3.5% solid fuel in a high-power mixer, and then granulated in a cylinder to form 2-10mm small balls to obtain pre-granulated material.

[0035] (3) The sintering raw materials are mixed once, and then the pre-made granules are added for a second mixing to obtain the sintering mixture. The sintering mixture is then distributed, ignited, and sintered to obtain the finished sintered ore. The weight ratio of the sintering raw materials to the pre-made granules is 18.6:1.

[0036] Example 2

[0037] A method for strengthening iron concentrate sintering based on concentrate pretreatment includes the following steps:

[0038] (1) The iron concentrate in the iron-containing material is 25% by weight. Fine concentrate (12% by weight of the iron-containing material) and quicklime (7% by weight of the total pre-treated material) are mixed evenly and then subjected to high-pressure roller mill pretreatment. After high-pressure roller mill pretreatment, the specific surface area of ​​the iron concentrate is reduced from 700 cm². 2 / g increased to 1300cm2 / g, forming a pretreated material;

[0039] (2) The pretreated material is mixed evenly with 13% of the weight of iron-containing material coarse concentrate, 8% of the total weight of pre-granulated material 1-3mm return ore, 7% quicklime, 2.0% of 40% OG slurry and 4.0% solid fuel in a high-power mixer, and then granulated in a cylinder to form 3-15mm small balls to obtain pre-granulated material;

[0040] (3) The sintering raw materials are mixed once, and then the pre-made granules are added for a second mixing to obtain the sintering mixture. The sintering mixture is then distributed, ignited, and sintered to obtain the finished sintered ore. The weight ratio of the sintering raw materials to the pre-made granules is 4.5:1.

[0041] Example 3

[0042] A method for strengthening iron concentrate sintering based on concentrate pretreatment includes the following steps:

[0043] (1) The iron concentrate in the iron-containing material is 50% by weight. After mixing fine concentrate accounting for 25% of the iron-containing material and quicklime accounting for 12% of the total weight of the pretreated material evenly, it is subjected to high-pressure roller mill pretreatment to form the pretreated material.

[0044] (2) The pretreated material is mixed evenly with 25% of the weight of iron-containing material coarse concentrate, 15% of the total weight of pre-granulated material 1-3mm return ore, 12% quicklime, 4.0% of 40% OG slurry and 4.5% solid fuel in a high-power mixer, and then granulated in a cylinder to form 3-15mm small balls to obtain pre-granulated material;

[0045] (3) The sintering raw materials are mixed once, and then the pre-made granules are added for a second mixing to obtain the sintering mixture. The sintering mixture is then distributed, ignited, and sintered to obtain the finished sintered ore. The weight ratio of the sintering raw materials to the pre-made granules is 1.2:1.

[0046] Comparative Example 1

[0047] A method for sintering iron concentrate includes the following steps: crude iron concentrate, fine iron concentrate, 1-3mm return ore, solid fuel, and sintering raw materials are mixed once and twice, respectively, and then the mixture is spread, ignited, and sintered to obtain the finished sintered ore. The amount of each raw material is the same as that in Example 1.

[0048] Unlike Examples 1 to 3, this method does not pre-treat the fine concentrate and quicklime, nor does it pre-granulate the coarse concentrate, quicklime, OG mud, and solid fuel. The iron concentrate is simply batched, mixed once, and mixed twice with other iron-containing materials, fuel, flux, and return ore.

[0049] Comparative Example 2

[0050] A method for sintering iron concentrate includes the following steps:

[0051] (1) The weight percentage of iron concentrate in the iron-containing material is 25%. Fine iron concentrate accounting for 12% of the weight percentage of the iron-containing material, crude iron concentrate accounting for 13% of the weight percentage of the iron-containing material, and quicklime accounting for 7% of the total weight of the pretreated material are mixed evenly and then subjected to high-pressure roller mill pretreatment to form pretreated material.

[0052] (2) The pretreated material is mixed evenly with 1-3mm return ore (8% of the total weight of the pre-granulated material), 2.0% of 40% OG slurry, and 4.0% of solid fuel in a high-power mixer, and then granulated in a cylinder to form small balls of 3-15mm to obtain the pre-granulated material.

[0053] (3) Mix the remaining sintering raw materials once, and then add the pre-made granules for a second mixing to obtain the sintering mixture. The sintering mixture is then distributed, ignited, and sintered to obtain the finished sintered ore. The weight ratio of the remaining sintering raw materials to the pre-made granules is 4.5:1.

[0054] Comparative Example 2 differs from Examples 1 to 3 in that it does not differentiate between fine and coarse concentrates. Instead, the coarse and fine concentrates are pre-treated together with some quicklime using a high-pressure roller mill. The pre-treated raw materials are then mixed evenly with 1-3mm return ore, OG slurry, and solid fuel using a high-power mixer, followed by cylindrical granulation to form 3-15mm pellets. The remaining sintering raw materials are then mixed once, followed by a second mixing with the pre-formed pellets to obtain the sintering mixture. The sintering mixture is then distributed, ignited, and sintered.

[0055] Comparative Example 3

[0056] A method for sintering iron concentrate includes the following steps:

[0057] (1) The iron concentrate in the iron-containing material is 50% by weight. Fine concentrate accounting for 25% of the iron-containing material, coarse concentrate accounting for 25% of the iron-containing material, 1-3mm return ore, and quicklime are mixed evenly and then subjected to high-pressure roller mill pretreatment to form pretreated material. In the pretreated material, 1-3mm return ore and quicklime account for 15% and 12% of the total weight of the pretreated material, respectively.

[0058] (2) The pretreated material and solid fuel accounting for 4.5% of the total weight of the pre-granulated material are mixed evenly by a high-power mixer, and then the mixture is granulated in a cylinder to form small balls of 3-15 mm to obtain the pre-granulated material.

[0059] (3) Mix the remaining sintering raw materials once, and then add the pre-made granules for a second mixing to obtain the sintering mixture. The sintering mixture is then distributed, ignited, and sintered to obtain the finished sintered ore. The weight ratio of the remaining sintering raw materials to the pre-made granules is 1.2:1.

[0060] Comparative Example 3 differs from Examples 1 to 3 in that it does not differentiate between fine and coarse concentrates. Instead, coarse concentrate, fine concentrate, and 1-3mm return ore are pre-treated together with some quicklime using a high-pressure roller mill. The pre-treated raw materials are then mixed uniformly with solid fuel in a cylindrical mill, followed by cylindrical granulation to form 3-15mm pellets. The remaining sintering raw materials are mixed once, and then pre-granulated materials are added for a second mixing to obtain a sintering mixture. The sintering mixture is then distributed, ignited, and sintered.

[0061] The weight percentage of iron concentrate in the iron-containing materials and the composition of the pre-formed granules in each embodiment and comparative example are shown in Table 1.

[0062] Table 1

[0063]

[0064] The properties of the finished sintered ore prepared in each embodiment and comparative example are shown in Table 2.

[0065] Table 2

[0066]

[0067]

[0068] According to the data in Table 2:

[0069] Comparative Example 1: The iron concentrate was not pretreated by high-pressure roller milling and pre-granulation. Due to the poor granulation performance and poor high-temperature basic properties of the iron concentrate, the sintering utilization coefficient was only 1.532 t / m. 2 The sinter yield was 78.96%, and the drum strength was 67.60%. After implementing the strengthening measures in Example 1, the sinter utilization coefficient was 1.801 t / m. 2 .h, increased by 0.269t / m 2 The yield of sintered ore was 83.02%, an increase of 4.06%, and the drum strength was 67.60%, an increase of 3.93%.

[0070] Comparative Example 2 did not differentiate between fine and coarse concentrates. The coarse concentrate was also pre-treated with a high-pressure roller mill. While this improved the granulation performance of the coarse concentrate, it disrupted the trapezoidal particle size distribution of the pre-formed granules, directly affecting the granulation effect. The sintering utilization coefficient was 1.598 t / m³. 2The sinter yield was 79.12%, and the drum strength was 67.73%. In Example 2, after implementing the strengthening measures, the sinter utilization coefficient was 1.795 t / m. 2 .h, increased by 0.197t / m 2 The yield of sintered ore was 82.56%, an increase of 3.44%, and the drum strength was 70.86%, an increase of 3.13%.

[0071] Comparative Example 3: Pre-treatment of coarse concentrate, 1-3mm return ore, and fine concentrate together using a high-pressure roller mill improved the granulation performance of the coarse concentrate and 1-3mm return ore, but significantly reduced the number of "spherical nuclei" in the pre-granulated material. Furthermore, the absence of OG mud also negatively impacted the granulation effect of the pre-granulated material, resulting in a sintering utilization coefficient of 1.528 t / m³. 2 The sinter yield was 78.87%, and the drum strength was 67.33%. After implementing the strengthening measures in Example 3, the sinter utilization coefficient was 1.787 t / m. 2 .h, increased by 0.259t / m 2 The yield of sintered ore was 82.02%, an increase of 3.15%, and the drum strength was 70.53%, an increase of 3.20%.

[0072] The above detailed description of a method for strengthening iron concentrate sintering based on concentrate pretreatment, with reference to the embodiments described above, is illustrative rather than limiting. Several embodiments may be listed within the defined scope. Therefore, variations and modifications that do not depart from the overall concept of the present invention should be within the protection scope of the present invention.

Claims

1. A method for enhanced iron concentrate sintering based on concentrate pre-treatment, characterized by, The method comprises the following steps: (1) mixing fine iron concentrate and quicklime uniformly and then performing high-pressure roller grinding pretreatment to form pretreated material; (2) mixing the pretreated material with coarse iron concentrate, return fines, quicklime, OG mud and solid fuel uniformly, and then performing disc balling or cylinder granulation to form preformed pellets; (3) mixing sintering raw materials once, then adding the preformed pellets to perform secondary mixing to obtain sintering mixture, and then performing distribution, ignition, sintering, cooling and granulation to obtain finished sinter; the fine iron concentrate is a mixture of one or more kinds of iron concentrate, and the content of the particle size less than 0.074 mm is higher than 50%; the coarse iron concentrate is a mixture of one or more kinds of iron concentrate, and the content of the particle size less than 0.074 mm is lower than 50% and the average particle size is less than 1 mm; the weight percentage of iron concentrate in the iron-containing material in the sinter is 8-50%; the content of quicklime in the pretreated material is 3-12% of the total weight of the pretreated material, and the content of quicklime in the preformed pellets is 3-12% of the total weight of the preformed pellets; in step (2), the particle size of the return fines is 1-3 mm, and the content of the 1-3 mm return fines in the preformed pellets is 5-15% of the total weight of the preformed pellets; in step (2), the content of solid fuel in the preformed pellets is 3.5-4.5% of the total weight of the preformed pellets; in step (2), the mass concentration of the OG mud is controlled to be 30-40%, and the content of the OG mud in the preformed pellets is 1.0-4.0% of the total weight of the preformed pellets.

2. The beneficiation pre-treatment based intensified iron concentrate sintering process according to claim 1, characterized in that, In step (1), the specific surface area of the fine iron ore concentrate after the high-pressure roller mill pretreatment is increased by not less than 500 cm 2 / g.

3. The beneficiation pre-treatment based intensified iron concentrate sintering process as claimed in claim 1, wherein, in step (3), the pretreated material, coarse iron concentrate, 1-3 mm return fines, quicklime, OG mud and solid fuel are mixed uniformly by a strong mixer, and then cylinder granulation is performed to form 2-10 mm pellets, or disc balling is performed to form 3-15 mm pellets.

4. The beneficiation pre-treatment based intensified iron concentrate sintering process as claimed in claim 1, wherein, in step (3), the sintering raw materials comprise iron ore fines, fuel, return fines and flux; and the mass ratio of the iron ore fines, fuel, return fines and flux is 100:5-9:35-60:15-30.

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