Plastic iron ore tailings-based pellet binder, its preparation and use

Abstract

The application belongs to the field of pellet binders, and particularly relates to a plastic iron ore tailing-based pellet binder, a preparation method thereof and application. The preparation method comprises the following steps: mixing and modifying raw materials of plastic iron ore tailing and a modifier to obtain the plastic iron ore tailing-based pellet binder. The modifier comprises at least one of component A and component B. The component A comprises a sodium humate component. The component B is a raw material for preparing the component A. The plastic iron ore tailing is mixed and modified by the component A and / or the component B, so that the binding performance of the prepared iron ore-based binder can be significantly optimized based on the physicochemical characteristics of the components, and good green ball and indurated pellet indexes can be obtained at a lower addition amount.

Description

Technical Field

[0001] This invention belongs to the field of mineral smelting, specifically relating to binders for mineral pelletizing. Background Technology

[0002] Pellet binders are used to bind finely ground mineral particles into pellets, improving the properties of wet pellets, dry pellets, and roasted pellets, thereby enhancing the smelting effect of the minerals. Pellet binders are mainly classified into three categories: inorganic binders, organic binders, and composite binders. Inorganic binders mainly include bentonite and hydrated lime; organic binders mainly include perlidone and modified starch; and composite binders are mainly a combination of inorganic and organic binders.

[0003] With increasing environmental awareness, the industry has begun to focus on research and attempts to utilize recycled mining waste to form binders. For example, Chinese patent document CN110724815A discloses a magnesium-based composite binder for pelletizing minerals and its preparation and application methods. The magnesium-based composite binder for pelletizing minerals is composed of the following components by dry weight percentage: 97%–99% calcined magnesite tailings, 0.5%–2.2% hydroxypropyl methylcellulose, and 0.5%–2.3% instant carboxymethyl cellulose sodium. This technical solution utilizes magnesite tailings as magnesium-containing raw material, which is calcined at medium temperature to obtain a composite of magnesium oxide and magnesium carbonate. Hydroxypropyl methylcellulose solution and instant carboxymethyl cellulose sodium solution that have not been dehydrated or dried are added, and the mixture is subjected to microwave heating and stirring for deep fusion reaction to obtain the magnesium-based composite binder for pelletizing minerals. For example, Chinese patent document CN104099468A discloses a bauxite tailings-based iron ore pellet binder, made from the following raw materials by weight percentage: 70-85% bauxite tailings, 10-20% accelerator, 3-5% polyferric chloride, and 2-5% Na2CO3. The preparation method of this binder includes the following steps: mixing the raw materials evenly and then activating them using a ball mill. Another example is Chinese patent document CN110004290A, which discloses a metallurgical pellet binder and its preparation method. The metallurgical pellet binder is made from the following components by weight percentage: 92-96% iron-containing tailings and 4-8% sodium carboxymethyl starch. The iron-containing tailings refer to iron ore tailings and iron-containing waste from aluminum plants.

[0004] In summary, although there are some attempts to use recycled mining waste to form binders, different mining wastes have different physicochemical characteristics, making it difficult to simply adapt existing technologies and predict their effects. Currently, there is no solution in the industry for preparing high-efficiency binders from plastic iron ore tailings with ultra-low expansion and extremely fine-grained montmorillonite aggregates. Summary of the Invention

[0005] To address the technological gap in the resource-based preparation of pellet binders from plastic iron ore tailings, this invention provides a method for preparing a plastic iron ore tailings-based pellet binder, aiming to obtain a high-performance pellet binder for the resource-based preparation of plastic iron ore tailings.

[0006] The second objective of this invention is to provide a plastic iron ore tailings-based pellet binder prepared by the aforementioned method and its application in pellet preparation.

[0007] A third objective of this invention is to provide green pellets and calcined pellets obtained by means of the aforementioned plastic iron ore tailings-based pellet binder.

[0008] The iron ore tailings are rich in secondary minerals, primarily kaolinite, a clay mineral, and have extremely fine particle size. However, due to their low expansion capacity, they exhibit poor bonding performance when used to prepare binders from resource-based resources. To address the problems encountered in preparing pellet binders from this plastic iron ore tailings, this invention, after in-depth research, provides the following solution:

[0009] A method for preparing a plastic iron ore tailings-based pellet binder involves mixing and modifying plastic iron ore tailings and a modifier as raw materials.

[0010] The modifier includes at least one of component A and component B;

[0011] Component A contains sodium humate;

[0012] Component B is a raw material for preparing component A.

[0013] To address the difficulty in preparing binders from plastic iron ore tailings due to their physicochemical characteristics, this invention innovatively uses component A and / or component B to mix and modify the plastic iron ore tailings. This significantly optimizes the bonding performance of the prepared iron ore-based binder based on the physicochemical characteristics of the components, enabling the production of good green pellets and roasted pellets with relatively low dosage.

[0014] In this invention, the plastic iron ore tailings has a kaolinite content of more than 25%, a particle size of more than 98% of -400 mesh, and a plasticity index (Ip) of 15-17.

[0015] In one optional embodiment of the present invention, the plastic iron ore tailings are, for example, Meishan iron ore tailings.

[0016] The component A is prepared by oxidative fermentation of raw material a1 and alkaline extraction of raw material a2.

[0017] The raw material a1 includes at least one of peat, weathered coal, and lignite;

[0018] The temperature for oxidative fermentation is 100–150℃; the fermentation time is 3–9 hours.

[0019] The raw material a2 is sodium hydroxide.

[0020] Raw material a2 is 20% to 30% of the mass of raw material a1.

[0021] The solvent used in the alkali extraction stage is water, and its amount is 3 to 6 times the weight of the raw material a1.

[0022] The temperature for alkali extraction is 80–100℃; the extraction time can be 1–5 hours.

[0023] Preferably, component B includes raw material a1 used in the synthesis of component A or raw material a1 after oxidative fermentation, and also includes raw material a2; further comprising the solvent.

[0024] This invention also shows that the innovative use of component B to modify plastic iron ore tailings helps to further improve the physicochemical compatibility of plastic iron ore tailings and helps to further enhance the performance of the obtained binder.

[0025] In this invention, the weight percentage of the modifier in the plastic iron ore tailings and modifier is 10-50%, more preferably 15-25%.

[0026] In this invention, the systems before, during, and after the mixing modification also contain polymers.

[0027] The present invention demonstrates that the combined modification by the modifier and polymer helps to further improve the physicochemical compatibility of plastic iron ore tailings and further enhance the performance of the obtained binder.

[0028] In this invention, the polymer includes at least one of polyacrylamide, sodium carboxymethyl cellulose, and sodium lignosulfonate.

[0029] In this invention, the polymer is 0.5 to 3 wt.% of the total weight of the plastic iron ore tailings and modifier, and may further be 1 to 2 wt.%.

[0030] In this invention, the modification refers to fermenting the mixed raw materials. The fermentation time can be more than 20 hours, and more specifically, 20 to 30 hours.

[0031] The present invention also provides a plastic iron ore tailings-based pellet binder prepared by the above preparation method.

[0032] The preparation method described in this invention can endow the prepared adhesive with special physicochemical properties, and the adhesive prepared by the method can achieve good bonding performance with low addition amount, which can realize the efficient resource utilization of solid waste.

[0033] The present invention also includes the application of the binder in the preparation of mineral green pellets and calcined pellets.

[0034] The present invention also provides a mineral pellet comprising a concentrate and a binder, wherein the binder comprises a plastic iron ore tailings-based pellet binder prepared by the preparation method described above.

[0035] Preferably, the binder content in the mineral green pellets is 0.5–2.5 wt.% (more preferably 1–2 wt.%), and the water content is 7–7.5 wt.%.

[0036] The mineral pellets described in this invention may contain iron concentrate.

[0037] In this invention, the mineral pellets can be prepared using conventional methods.

[0038] The present invention also provides a mineral roasted pellet, which is obtained by roasting the aforementioned mineral green pellet.

[0039] In this invention, the roasting process is a pre-roasting process at a temperature of 950–1050°C, and a roasting process at a temperature of 1200–1250°C.

[0040] The holding time for the pre-roasting and roasting processes can be 5 to 15 minutes.

[0041] Beneficial effects

[0042] To address the difficulty in preparing binders from plastic iron ore tailings due to their physicochemical characteristics, this invention innovatively uses component A and / or component B to mix and modify the plastic iron ore tailings. This significantly optimizes the bonding performance of the prepared iron ore-based binder based on the physicochemical characteristics of the components, enabling the production of good green pellets and roasted pellets at relatively low dosages.

[0043] This invention also shows that modifying plastic iron ore tailings with component B and / or modifying them with polymers helps to further optimize the physicochemical characteristics of the binder and further enhance the bonding performance of the binder prepared from resources.

[0044] Compared to existing technologies, adding component B can organically modify component A through sodium modification, further enhancing its binding properties. Simultaneously, component B itself is also a binder, and its price is significantly lower than other common organic modifiers, thus reducing binder usage costs. During green pellet preparation, components A and B work synergistically to achieve efficient binding, reducing the amount of binder required in the green pellets. During pellet roasting, over 60% of component B volatilizes, reducing the residual binder in the roasted pellets by over 10%, thus improving the grade of the pellet ore. Furthermore, the resulting micropores facilitate mineral consolidation and liquid phase flow during roasting, enhancing the mechanical strength of the pellet ore. Attached Figure Description

[0045] Figure 1 This is the XRD pattern of the tailings from this invention;

[0046] Figure 2 This is a particle size distribution diagram of the tailings from the present invention;

[0047] Figure 3 The images are SEM images of the tailings of this invention, where (a) is 500x, (b) is 5000x, and (c) is 10000x.

[0048] Figure 4 The images shown are SEM images of the refined powder of this invention, where (a) is 500x, (b) is 2000x, and (c) is 5000x. Detailed Implementation

[0049] To enhance understanding of the present invention, the embodiments will be described in detail below with reference to the accompanying drawings.

[0050] I. Raw materials:

[0051] 1.1: Plastic iron ore tailings (hereinafter referred to as tailings)

[0052] The plastic iron ore tailings described in this invention are selected from Meishan high-plasticity iron ore tailings (hereinafter referred to as Meishan tailings), which are provided by Meishan Mining. Their chemical composition is tested by chemical analysis according to relevant national standards, and the chemical composition is shown in Table 1.

[0053] Table 1 Chemical composition of Meishan tailings mud (%)

[0054]

[0055] XRD of plastic iron ore tailings is shown in Figure 1 :

[0056] The main phases of the Meishan tailings mud consist of kaolinite [Al2Si2O5(OH)4] (27.6%), quartz [SiO2] (24.0%), siderite [FeCO3] (20.8%), hematite [Fe2O3] (14.4%), and calcite [CaCO3] (13.3%). The loss on ignition of 15.05% is mainly due to the presence of carbonate phases such as siderite and calcite.

[0057] In addition, other physicochemical characteristics of the Meishan tailings are shown in Table 2.

[0058] Table 2 Physicochemical Properties of Meishan Tailings

[0059]

[0060] Table 2 shows that the blue absorption capacity of the Meishan high-plasticity iron ore tailings is 11.80 g / 100 g. Based on the blue absorption capacity, the montmorillonite content is estimated at 26.70%, which is similar to the kaolinite content obtained from XRD semi-quantitative analysis. This component is the main binder in the iron ore tailings, and its content is significantly lower than that required for bentonite. The swelling capacity is 1.9 mL / g, the colloidal value is 38.8%, and the 2-hour water absorption rate is 174.2%.

[0061] Laser particle size distribution diagram of Meishan high-plasticity iron ore tailings is shown below. Figure 2 ;

[0062] Table 3 Laser particle size composition of Meishan tailings / %

[0063]

[0064] Depend on Figure 2 As shown in Table 3, the particle size distribution of Meishan tailings is extremely fine, with D(50) of 2.017 μm, D(90) of 16.590 μm, and D(99) of 36.866 μm. The extremely fine particles facilitate the full reaction between Meishan tailings and the modifier, and also promote the dispersion of Meishan tailings in iron concentrate, resulting in a good binding effect.

[0065] Microscopic morphology of Meishan tailings as follows Figure 3 As shown, (a), (b), and (c) are the microstructures magnified 500, 5000, and 10000 times, respectively.

[0066] 1.2: Iron concentrate

[0067] As an alternative, the iron concentrate can be sourced from Meishan concentrate, and its chemical composition is tested using chemical analysis methods in accordance with relevant national standards. The chemical composition is shown in Table 4.

[0068] Table 4. Main chemical components of Meishan concentrate (%)

[0069]

[0070] The main phases in Meishan concentrate are magnetite, hematite, and quartz. Meishan concentrate has a wide particle size distribution, with D(10) at 5.240 μm, D(50) at 62.040 μm, and D(90) at 288.192 μm. The -200 mesh content is only 55.85%, indicating a relatively coarse particle size, requiring further pretreatment before pelletizing. SEM images of the iron concentrate are shown below. Figure 4 The particle size of Meishan concentrate is relatively uneven, with large particles having smooth and flat surfaces and sharp edges, which is not conducive to improving the strength of green pellets.

[0071] 3. Bentonite

[0072] The bentonite described in this invention can be made from conventional components used in the industry. For example, bentonite has a high SiO2 content of 59.66%, a CaO content of about 4.60%, a K2O and Na2O content of 0.94% and 2.68% respectively, and a MgO content of 3.40%.

[0073] The bentonite contained 98.52% and 89.36% of particles with a diameter of -0.074 mm and -0.038 mm, respectively. The d (10%) particle size of the bentonite was 1.58 μm, the d (50%) particle size was 6.93 μm, and the d (90%) particle size was 41.26 μm.

[0074] The bentonite has a montmorillonite content of 54.3%, a 2-hour water absorption rate of 224.9%, an expansion capacity of 8.5 mL / g, and a colloidal value of 85.0%. Comparison of Tables 2-2 and 2-11 shows that all performance indicators of the bentonite are superior to those of the Meishan tailings mud.

[0075] 4. Polymers

[0076] As an optional solution, the polymer used can be polyacrylamide.

[0077] 5. Component A1: Sodium humate binder, which is prepared by alkaline extraction of low-rank coal after oxidative fermentation and sodium hydroxide. The low-rank coal includes at least one of peat, weathered coal, and lignite. The sodium hydroxide is 20% to 30% of the mass of the low-rank coal.

[0078] As a more specific factual approach, the preparation steps of component A1 are as follows: lignite with a humic acid content of 32-35 wt% is oxidized and fermented at 110-130℃ for 5-7 hours, and then alkali-extracted with 25% of its weight of sodium hydroxide and water (the oxidized and fermented lignite) at 90-95℃ for 2-4 hours; the amount of water used in the alkali extraction is 4 times the weight of the lignite.

[0079] 6. Component B1: consists of lignite, sodium hydroxide, and water after oxidative fermentation of component A1, with the proportions of the three components being the same as those of component A1.

[0080] Example 1

[0081] Mix the ingredients according to the formula in Table 5 and ferment at room temperature for 24–26 hours to obtain the modified binder.

[0082] The modified adhesives obtained were tested, and the results are shown in Table 5.

[0083] Table 5A1 and / or the physicochemical properties of polymer-modified adhesives

[0084]

[0085] *Note: Montmorillonite content is estimated based on the amount of blue absorbed.

[0086] Table 5 shows that adding component A1 to the tailings significantly increased the expansion capacity of the modified tailings; however, the increase in expansion capacity decreased with increasing component A1 proportion. When the mass proportion of component A1 in the tailings increased from 0% to 20%, the expansion capacity increased from 1.9 ml / g to 7.2 ml / g. The addition of polymers can increase the resin value of the modified tailings; adding 2% polymer to 100% tailings increases the resin value from 38.8% to 45%. Under the condition of a tailings-to-component A1 mass ratio of 8:2, adding 1% polymer increases the resin value of the modified tailings from 13% to 18.5%, but the expansion capacity decreases from 7.2 ml / g to 3.5 ml / g. Overall, the 2-hour water absorption rate of the modified tailings decreased, especially under the condition of adding only polymers; adding 2% polymer reduces the 2-hour water absorption rate of the tailings from 174.2% to 95.91%.

[0087] Example 2 - Modification scheme for component B1

[0088] Compared with Group B of Example 1, the only difference is that component A1 is replaced by component B1 in equal weight, while other operations and parameters are the same as in Example 1.

[0089] The results are shown in Table 6:

[0090] Table 6B1 Modified Binder Physicochemical Properties

[0091]

[0092] As shown in Table 6, the expansion capacity can be increased to 18 ml / g by using component B1 for modification, which is 10.8 ml / g higher than the expansion capacity of directly adding component A1, thus achieving better modification performance.

[0093] Comparative Example 1

[0094] Compared with Example 1B, the only difference is that the following modifier is used to replace its component A1, and all other operations and parameters are the same as in Example 1.

[0095] The results are shown in Table 7:

[0096] Table 7 Physicochemical Properties of Bentonite-Modified Binders

[0097]

[0098] Example 3

[0099] The raw materials for pelletizing are first manually batched, with 1 kg of iron concentrate used each time. A binder is added as needed in a specific ratio. During manual mixing, a certain amount of water is added to ensure the raw material moisture content reaches the design moisture level for the experiment. The pelletizing experiment is conducted in a disc pelletizer, with the following main technical parameters: diameter Ф = 1000 mm, rotation speed 0–40 r / min (20 r / min was used in this experiment), side height h = 250 mm, and disc inclination angle 45°. The prepared green pellets are manually sieved, with 10–16 mm green pellets considered qualified. Samples of qualified green pellets are taken to determine their compressive strength, drop strength, bursting temperature, and moisture content. The remaining green pellets are dried and used as samples for the pellet calcination and consolidation test.

[0100] Iron concentrate and tailings-based binder prepared in Example 1 were subjected to high-pressure roller milling to form pellets. The high-pressure roller milling was performed once, and the pelleting time was 12 minutes. The moisture content of the pellet mixture was 7.0% to 7.5%, and the tailings-based binder was 1% of the weight of the iron concentrate. The results of the obtained pellets are shown in Table 8.

[0101] Table 8. Effects of Modifier Type on Green Pellet Quality

[0102]

[0103] Table 9. Effect of Bentonite Dosage on Green Pellet Quality

[0104]

[0105] Based on the above, the pretreatment method of the raw materials was fixed as one high-pressure roller milling, the pelletizing time was 12 min, the moisture content of the mixture was 7.0%–7.5%, and the tailings were used as the main component of the binder. The amount of binder was fixed at 1%, and the effect of the type of modifier on the quality of green pellets was investigated. The results are shown in Table 8. As can be seen from the table, when 100% tailings were used as the binder, the drop strength of the green pellets was 4.2 times (0.5 m), the compressive strength was 18.04 N / p, and the bursting temperature of the green pellets was 450℃. Under the same conditions, when bentonite was used as the binder (Table 9), the drop strength of the green pellets was 5.8 times (0.5 m), the compressive strength was 15.38 N / p, and the bursting temperature of the green pellets was >500℃. This indicates that under the same dosage conditions, the quality of green pellets prepared with bentonite is better than that prepared with unmodified tailings. When tailings were modified with component A1, the drop strength and burst temperature of green pellets were improved under the same binder dosage. When the mass ratio of tailings to component A1 was 8:2, with a binder dosage of 1%, the drop strength of the green pellets was 6.6 cycles per 0.5 m, the compressive strength was 15.90 N / p, and the burst temperature was >500℃, which is superior to the quality indicators of green pellets with 1.5% bentonite. Further analysis with the addition of polymers to the modified tailings showed that the addition of polymers reduced the burst temperature of the green pellets. This is because polymers are organic materials with poor thermal stability. When only 2% polymer was added to the tailings, the quality indicators of the green pellets were not improved. However, when the mass ratio of tailings to component A1 was 8:2, adding 1% polymer resulted in a drop strength of 6.9 times per 0.5m, a compressive strength of 16.07 N / p, and a bursting temperature of 480℃ for the green pellets. This can further improve the drop strength and compressive strength of the green pellets, but the bursting temperature is slightly reduced.

[0106] Example 4

[0107] Compared with Example 3, the only difference is that the adhesive used is the adhesive prepared in Example 2, while the other operations and parameters are the same as in Example 3.

[0108] Table 10 Effects of Modification Methods and Doses on Green Pellet Quality

[0109]

[0110] Example 5

[0111] Small-scale pellet calcination and consolidation tests were conducted in a dual-temperature zone horizontal tubular electric furnace, which consisted of a 50mm diameter iron-chromium-aluminum wire resistance furnace and a silicon carbide tube resistance furnace connected together. The former was used for preheating tests, and the latter for calcination tests. Qualified green pellets were first dried in an oven at 105℃. During the preheating and calcination tests, the green pellets were loaded into ceramic boats and preheated and calcined according to the set procedures. The strength of the preheated and calcined pellets was determined using a compression tester according to the national standard GB / T 14201-2018.

[0112] The green pellets of Example 4 (experimental group with 1% binder) were preheated at 950-1050°C. The parameters of the preheated pellets are shown in Table 11. Subsequently, the pellets were calcined at a predetermined temperature of 1050°C. The calcination temperature was 1200-1240°C. The results of the calcined pellets are shown in Table 12.

[0113] Table 11 Effect of preheating temperature on the performance indicators of preheated balls

[0114]

[0115] Table 12 Effect of calcination temperature on the performance indicators of calcined balls

[0116]

[0117] It should be noted that the above embodiments are not intended to limit the scope of protection of the present invention. Equivalent transformations or substitutions made based on the above technical solutions all fall within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing a plastic iron ore tailings-based pellet binder, characterized in that, It is obtained by mixing and modifying plastic iron ore tailings and modifier raw materials; The modifier includes at least one of component A and component B; Component A contains sodium humate. Component B is a raw material used to prepare component A.

2. The method for preparing the plastic iron ore tailings-based pellet binder as described in claim 1, characterized in that, The plastic iron ore tailings have a kaolinite content greater than 25%, a -400 mesh particle size greater than 98%, and a plasticity index (Ip) value of 15-17. The plastic iron ore tailings are iron tailings mud.

3. The preparation method of the plastic iron ore tailings-based pellet binder as described in claim 1, characterized in that, Component A is prepared by oxidative fermentation of raw material a1 and alkaline extraction of raw material a2; raw material a1 includes at least one of peat, weathered coal, and lignite. The temperature for oxidative fermentation is 100–150℃; the fermentation time is 3–9 hours. The raw material a2 is sodium hydroxide; Raw material a2 is 20% to 30% of the mass of raw material a1; The solvent used in the alkali extraction stage is water, and its amount is 3 to 6 times the weight of raw material a1. The temperature for alkali extraction is 80–100℃; the extraction time is 1–5 hours.

4. The method for preparing the plastic iron ore tailings-based pellet binder according to any one of claims 1 to 3, characterized in that, In plastic iron ore tailings and modifiers, the weight percentage of the modifier is 10-50%.

5. The method for preparing the plastic iron ore tailings-based pellet binder as described in claim 1, characterized in that, The system before, during, and after the mixing modification also contains polymers; The polymer includes at least one of polyacrylamide, sodium carboxymethyl cellulose, and sodium lignosulfonate.

6. The method for preparing the plastic iron ore tailings-based pellet binder as described in claim 5, characterized in that, The polymer is 0.5 to 3 wt.% of the total weight of plastic iron ore tailings and modifier.

7. A plastic iron ore tailings-based pellet binder prepared by the preparation method according to any one of claims 1 to 6.

8. The application of a plastic iron ore tailings-based pellet binder prepared by the preparation method according to any one of claims 1 to 6, characterized in that, It is used to prepare mineral pellets; Alternatively, mineral raw pellets can be roasted to obtain mineral roasted pellets.

9. A mineral pellet comprising a concentrate and a binder, characterized in that, The binder is a plastic iron ore tailings-based pellet binder prepared by the preparation method according to any one of claims 1 to 6; The mineral pellets contain 0.5–2.5 wt.% binder and 7–7.5 wt.% water.

10. A type of calcined mineral pellet, characterized in that, Obtained by roasting the mineral green pellets as described in claim 9; The roasting process described is a pre-roasting process at a temperature of 950–1050°C, and a roasting process at a temperature of 1200–1250°C. The holding time during the pre-roasting and roasting processes is 5 to 15 minutes.

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