Micro-nano composite binder as well as preparation and application thereof

Abstract

The invention belongs to the technical field of pellet binders, and particularly relates to a preparation method of a micro-nano composite binder, which comprises the following steps: mixing raw materials containing an inorganic matrix material, an organic modifier, a composite polymer and an alkaline component with water, carrying out first-stage ball milling treatment in advance, then carrying out second-stage ball milling treatment, and then carrying out spray drying treatment to obtain the micro-nano composite binder. The micro-nano composite binder is prepared. The invention innovatively finds that the particle size of the prepared binder dispersed in the concentrate powder can reach a micro-nano level through control of raw material components and synergism of preparation modes, the agglomeration phenomenon of the binder in preparation and use can be effectively reduced, the particle size is far smaller than the micron level of a conventionally used binder, and the binder can be used for preparing the concentrate powder. The dispersity of the binder in concentrate can be improved, and the use amount of the binder is greatly reduced.

Description

Technical Field

[0001] This invention belongs to the field of iron and steel metallurgy technology, and specifically relates to pellet binders. Background Technology

[0002] Binders are an essential raw material in the production of iron ore pellets or briquettes. Currently, the vast majority of binders used in iron ore pellet or briquette production are inorganic binders, such as bentonite. However, these binders suffer from problems such as high proportions and residual aluminum and silicon in the pellets or briquettes, reducing iron grade and leading to high fuel consumption in blast furnace ironmaking. While organic binders burn during the pellet or briquette roasting process, their poor thermal performance and high production costs have limited successful industrial applications. Due to the limited availability of bentonite resources, sodium modification or organic modification is generally required to improve bentonite's performance, but in actual production, problems such as incomplete reaction and excessive binder dosage still exist. After surveying several steel companies, it was found that existing modified bentonite still has problems such as poor bonding performance and poor dispersion. This is because the current national standard only requires bentonite to have a particle size of less than 74μm of ≥95%. However, with the continuous development of mineral processing technology, the particle size of some difficult-to-process iron concentrates has reached ≥80% of the particle size of less than 45μm. The requirement of excessively coarse particle size of the binder is no longer applicable to the current particle size level of iron concentrate, which further limits the dispersion of the binder in the concentrate.

[0003] To address the problems of existing technologies, some composite binders have been disclosed in the prior art. For example, CN105087915A describes a method for preparing and applying a highly absorbent composite binder for iron ore pelletizing. Specifically, it describes preparing a highly absorbent composite binder by mixing natural calcium-based bentonite with sodium carboxymethyl cellulose, sodium humate, and acrylic acid in a specific ratio, forming a network polymer structure that increases the binder's water absorption capacity, enabling it to adapt to high-moisture raw materials. Furthermore, a stable organic-inorganic composite structure is generated through the action of initiators and crosslinking agents. Although the binder disclosed in this technology has good water absorption and pelletizing effects, the particle size requirement remains at the conventional 74μm level. In actual production, it has been found that the binder is prone to agglomeration after drying, making it difficult to disperse during use and preventing further reduction in binder dosage. Additionally, the preparation process is relatively complex, requiring the preparation of a slurry reaction followed by drying, which to some extent limits its low-cost, large-scale industrial application.

[0004] To address the problem of excessively coarse binder particles, long-term research has revealed that specific preparation methods are required to obtain micro- and nano-sized binders. Although micro- and nano-powders can be obtained directly through grinding, a large amount of agglomeration still occurs during drying and use. Ultimately, the particle size of the binder dispersed in the concentrate cannot be maintained in the micro- and nano-scale range, resulting in a significant reduction in the performance of the binder.

[0005] In summary, existing technologies still struggle to obtain composite binders with micro / nano structures in powder form. Summary of the Invention

[0006] To address the problems existing in the prior art, the primary objective of this invention is to provide a method for preparing a micro / nano composite adhesive, aiming to obtain a composite adhesive with micro / nano structural characteristics that can achieve excellent pellet performance with a relatively low amount of adhesive.

[0007] A second objective of this invention is to provide a micro / nano composite binder prepared by the aforementioned method.

[0008] A third objective of this invention is to provide the application of the aforementioned micro / nano composite binder in pellet preparation.

[0009] A fourth objective of the present invention is to provide pellets or lumps obtained by the preparation method.

[0010] Currently, the binder used in pellet or agglomerate production is mainly bentonite, which is added to the concentrate powder in powder form. The national standard only requires that the proportion of bentonite particles smaller than 74μm be ≥95%. However, with the continuous improvement of mineral processing technology in recent years, the particle size of iron concentrate is becoming increasingly fine. Overly coarse binder particles are not conducive to uniform dispersion in the concentrate, resulting in a large amount of binder added and reducing the grade of pellets or agglomerates. Furthermore, theoretically, refining the particle size of the binder helps to enhance its modification effect and improve its performance. However, practical research shows that conventional grinding and drying processes for binders are insufficient to obtain the desired fine-grained particles, let alone disperse them in the concentrate powder to obtain micro-nano-sized particles. This is mainly because bentonite, as a highly viscous particle that easily absorbs water, readily agglomerates during grinding and drying, forming large particles, making it difficult to achieve the desired micro-nano-scale effect. To address this problem, this invention, after in-depth research, provides the following improvement scheme:

[0011] A method for preparing a micro-nano composite binder involves mixing raw materials containing inorganic matrix materials, organic modifiers, structure regulators and alkaline components with water and pre-processing them through a first-stage ball milling process, followed by a second-stage ball milling process, and then spray drying to obtain the micro-nano composite binder.

[0012] The inorganic matrix material contains clay.

[0013] The organic modifier is a component containing mineral-derived humic acid;

[0014] The structure modifier is a polysaccharide or acrylamide oligomer chemically modified with a structural fragment of Formula 1;

[0015] Formula 1;

[0016] In Formula 1, R1 to R3 are individually C1 to C4 alkyl or allyl groups, or they may be cyclized together to form a four-membered ring or a five-membered ring;

[0017] The weight ratio of inorganic matrix material, organic modifier, structure regulator and alkaline component is 67~93:4~23:1~4:2~6.

[0018] The weight ratio of raw materials to water is 1:1.2~2;

[0019] In the first stage of ball milling, the size of the ball milling media is 1.5 to 5 times that of the ball milling media in the second stage; the ball milling speed is 0.1 to 0.9 times that of the ball milling speed in the second stage.

[0020] This invention innovatively combines inorganic matrix materials, organic modifiers, structure regulators, alkaline components, and water for co-reaction. Further optimization of the raw material composition ratio, the ratio of raw materials to water, and the combination of structure regulators, along with the aforementioned two-stage mechanical ball milling, achieves synergistic effects. This improves the interlayer spacing of the silicate structure in the inorganic matrix material, thereby enhancing the synergistic modification effect of the organic modifier and structure regulator on the surface and interlayer of the inorganic matrix material. It also facilitates the construction and maintenance of the formed inorganic matrix material-structure regulator-organic modifier micro / nano structure, reducing agglomeration of the micro / nano structure during drying and use, and significantly improving the quality stability and preparation stability of the pellets.

[0021] The inorganic matrix material includes natural clay minerals with layered or chain-like silicate structures and / or industrial solid waste rich in amorphous silica-alumina phases.

[0022] The natural clay mineral is selected from at least one of bentonite, montmorillonite, kaolinite, illite, and chlorite, and is more preferably bentonite;

[0023] The industrial solid waste includes at least one of iron ore tailings, titanium ore tailings, red mud, and boron mud.

[0024] Preferably, the inorganic matrix material contains not less than 50% SiO2+Al2O3. It can form a liquid-phase binder in the gaps between mineral powders at temperatures above 1200℃, providing good binding during the high-temperature stage of pellet or agglomerate calcination.

[0025] The organic modifier is a fossil-derived organic matter with thermal cross-linking properties, selected from at least one of lignite, weathered coal, asphalt, sulfonated asphalt, and fuel oil.

[0026] Preferably, the organic modifier is at least one of lignite and weathered coal containing mineral humic acid, comprising 35-75% alkali-soluble macromolecules and 25-65% alkali-insoluble macromolecules.

[0027] Preferably, the number average molecular weight of the alkali-soluble macromolecule is 500-4000 Da, and the polar functional group content is 1.5-5 mmol / g; the number average molecular weight of the alkali-insoluble macromolecule is 4000-20000 Da, and the polar functional group content is less than 1.5 mmol / g.

[0028] Preferably, the organic modifier undergoes condensation and carbonization in the range of 500~900℃, forming an intermediate phase with a binding effect during the low-temperature calcination stage of the pellets or lumps, and decomposes and burns above 900℃ without affecting the grade of the finished pellets or lumps.

[0029] Furthermore, the organic modifier is lignite and / or weathered coal with a humic acid content of 50-80%.

[0030] The structure modifier is at least one of structure modifier A and structure modifier B;

[0031] The structure modifier A is an oligomer of formula 1a chemically grafted with a polysaccharide;

[0032] Equation 1a;

[0033] In Formula 1, R1~R3 ​​are individually C1~C4 alkyl groups;

[0034] The polysaccharide is at least one of cellulose components and starch components.

[0035] Preferably, the cellulosic component includes at least one of lignin, hemicellulose, cellulose, and derivatives. For example, it may include at least one of lignin / hemicellulose extracted from wood products, modified lignin / hemicellulose salts (such as lignin sulfonates), lignin / hemicellulose-containing solid waste generated during wood product processing (such as papermaking sludge), cellulose extracted from plants, and modified cellulose salts (such as carboxymethyl modified cellulose salts, hydroxyethyl modified cellulose salts, etc.).

[0036] Preferably, the starch components include amylose / amylose extracted directly from corn or flour, and gelatinized starch obtained through processing.

[0037] Preferably, the molecular weight of the polysaccharide can be 200-300 Da, and more preferably 220-280 Da.

[0038] In structure regulator A, the weight ratio of formula 1a to polysaccharide is 1:0.3~0.7; more specifically, it can be 1:0.5~0.7.

[0039] The structure modifier B is an oligomer of formula 2;

[0040] Formula 2;

[0041] Where x is 1~10; y is 1~8; R4~R5 are C1~C4 alkyl groups; and A is a halide anion.

[0042] The structure modifier B is obtained by copolymerization of raw materials of formula 2a and formula 2b:

[0043] Equation 2a

[0044] Equation 2b

[0045] The molar ratio of the raw material of formula 2a to the raw material of formula 2b is 1:0.3~0.8; it can be further 1:0.65~0.75.

[0046] The number-average molecular weight of the oligomers of structure modifier B is 230~2200 Da.

[0047] The structure modifier described in this invention is a small organic molecule that can enhance the physicochemical reaction in conjunction with alkaline components during the two-stage ball milling process. One end is inserted into the interlayer structure of the inorganic matrix material, and the other end is cross-linked with the organic modifier, achieving joint targeted modification of the interlayer and surface. This forms a composite macromolecule of inorganic matrix material-structure modifier-organic modifier, thereby constructing inorganic-organic composite binder particles with micro-nano structures. At the same time, it strengthens the structural strength of the micro-nano structures, reduces the damage of the micro-nano structures, and improves the preparation stability and the preparation stability of the pellets.

[0048] Preferably, the alkaline component is at least one of alkali metal hydroxide, alkali metal carbonate, phosphate, and pyrophosphate; more preferably, it is at least one of sodium hydroxide, sodium carbonate, and sodium pyrophosphate.

[0049] In this invention, the weight ratio of inorganic matrix material, organic modifier, structure regulator and alkaline component is 70~80:10~20:3~4:3~5.

[0050] For example, as an optional option, the percentage content of inorganic matrix material in the raw materials can be 67~93 wt.%, more preferably 70~80 wt.%; the percentage content of organic modifier can be 4~23 wt.%, more preferably 10~20 wt.%; the percentage content of structure regulator can be 1~4 wt.%, more preferably 3~4 wt.%; and the balance is alkaline components.

[0051] In this invention, the weight ratio of raw materials to water is 1:1.2~1.7.

[0052] In the first stage of ball milling, the size of the ball milling media is 1.5 to 2.5 times that of the ball milling media in the second stage; the ball milling speed is 0.7 to 0.85 times that of the ball milling speed in the second stage.

[0053] The grinding media in the first stage of ball milling are steel balls or forged steel with a diameter of 18-22 mm and a content of ≥50% (more specifically, 55-65%). The ball milling speed is 76%-88% of the critical speed; the time is 5-30 min (more specifically, 10-30 min).

[0054] The grinding media for the second stage of ball milling are steel balls or forged steel with a milling media ratio of ≥50% (more specifically, 55-65%) of 8-12 mm. The rotational speed of the second stage of ball milling is 88%-95% of the critical speed, and the time is 20-50 min (more specifically, 35-45 min).

[0055] In this invention, the air temperature for spray drying is 200℃~300℃, the material temperature after drying is 40℃~80℃, the drying time is 5~40min, and the moisture content of the adhesive after drying is less than 5%.

[0056] The present invention also provides a micro / nano composite binder, which is prepared by the preparation method described in the present invention.

[0057] Preferably, it contains a large number of soluble inorganic-organic micro-nano composite particles, wherein the particle size distribution of the micro-nano composite binder after dispersion in the concentrate powder is D90≤500nm and D30≤100nm, and the specific surface area is ≥25 m². 2 / g.

[0058] The present invention also provides an application of the aforementioned micro-nano composite binder, wherein the binder is mixed evenly with concentrate powder and then used for the preparation of green pellets or green lumps;

[0059] The method of using the high-efficiency micro-nano composite binder in the preparation of pellets or lumps includes: mixing the binder with concentrate powder, and then subjecting it to high-pressure roller milling and strong mixing treatment for the preparation of green pellets or green lumps.

[0060] The present invention does not impose any special requirements on the addition and mixing method of the binder in the concentrate, and is applicable to all types of concentrates, using methods well known to those skilled in the art.

[0061] Preferably, the concentrate powder is iron concentrate powder.

[0062] Preferably, the amount of micro-nano composite binder added relative to the concentrate powder is 0.5% to 1.0%, and the residual amount in the finished pellet is 0.3% to 0.8%. Further, the amount of micro-nano composite binder added relative to the concentrate powder is 0.75% to 0.85%.

[0063] The present invention also provides a raw ball or raw lump as described in the application.

[0064] Iron concentrate with added high-efficiency micro-nano composite binder is pelletized and calcined to obtain green pellets and finished pellets, respectively. The present invention does not have special requirements for the preparation method of the pellets, and any method known to those skilled in the art can be used.

[0065] Beneficial effects

[0066] This invention, starting from component design, innovatively mixes raw materials containing inorganic matrix materials, organic modifiers, structure regulators, and alkaline components with water and then performs a two-stage mechanical treatment. Further, it combines this with the joint control of parameters such as components and component ratios. The semi-dry production method helps reduce subsequent drying costs. Simultaneously, the two-stage ball milling enhances the co-reaction effect of the binder. During the reaction, the interlayer spacing of the silicate structure in the inorganic matrix material is expanded by the structure regulator and alkaline components. The expanded interlayer spacing of the silicate structure makes it easier to combine with the organic modifier and structure regulator, allowing the organic modifier and structure regulator to insert into the silicate interlayer, while simultaneously enhancing the alkaline solubility of the organic modifier. Furthermore, the monomers are polymerized through ball milling, and the layered silicates are dispersed in the polymer matrix at the micro- and nano-scale. This allows for synergistic effects based on the combination of components and preparation methods, successfully constructing a micro- and nano-structured composite binder. This reduces the problem of particles sticking together and being difficult to disperse during drying and use. In addition, the two-stage ball milling ensures the reaction effect of the binder and the particle size of the monomer particles. The special component ratio and drying method can also prevent the agglomeration of micro- and nano-structures during production and use, enhance the dispersibility of the binder in the concentrate, and achieve excellent pellet performance with a low binder dosage. Attached Figure Description

[0067] Figure 1 The particle size distribution is shown in Example 1 for the micro / nano composite binder.

[0068] Figure 2 The image shows the microstructure of the micro / nano composite binder prepared in Example 1.

[0069] Figure 3 The phase structure of the micro / nano composite binders prepared in Examples 1 and 2 is shown. Detailed Implementation

[0070] The present invention will be further explained and described below.

[0071] In this invention, the structure regulator is synthesized by aqueous solution polymerization. It is obtained by free radical copolymerization of raw material a and raw material b under the action of an initiator. The steps are as follows: First, raw material a and raw material b are dissolved in aqueous solution by stirring. After adjusting the pH of the solution to 6, high-purity nitrogen gas is passed into the solution for 40 min. After heating the solution to 60°C, an initiator (azobisisobutyramidine hydrochloride, the amount of which is 0.12% of the total weight of the raw materials) is added. The reaction is continued to be stirred at this temperature for 1 h to obtain the structure regulator.

[0072] For example, in structure modifier A1, raw material a is of formula 1a ( Raw material b is carboxymethyl cellulose (molecular weight 240 Da), and the weight ratio of raw material a to raw material b is 1:0.5.

[0073] In structure modifier A2, raw material a is of formula 1a ( Raw material b is corn starch (molecular weight 274 Da), and the weight ratio of raw material a to raw material b is 1:0.67.

[0074] In structure modifier B, raw material a is of formula 2a ( ), raw material b is formula 2b ( The weight ratio of raw material a to raw material b is 1:0.7. The oligomer obtained by the above reaction is ( ).

[0075] Example 1

[0076] A micro / nano composite binder was prepared using calcium-based bentonite (from Liaoning, with 77% montmorillonite content, 274% water absorption, and 13.9 mL / g expansion capacity), weathered coal (from Xinjiang, with 72% alkali-soluble macromolecules and 16% alkali-insoluble macromolecules), a structure modifier (structure modifier A1), and NaOH in a weight ratio of 80:13:3:4. The mixture was then pre-milled in a first stage for 20 min (60% 20mm steel balls, 78% of the critical speed) followed by a second stage of deep ball milling for 45 min (65% 10mm steel balls, 90% of the critical speed). Finally, it was dried by spray drying for 30 min (air temperature 250℃, material temperature 73℃, moisture content 1.2%).

[0077] The micro / nano composite binder produced had an average particle size distribution of -38μm (100%), -500nm (91.2%), and -100nm (44.5%) across multiple batches; the specific surface area was 32.4 m². 2 / g, standard deviation 4.6 m 2 / g, coefficient of variation 0.067; average water absorption rate 465.4%, standard deviation 23.7%, coefficient of variation 0.051, product performance is stable.

[0078] The binder was used in the industrial production of magnetite pellets at a dosage of 0.8%. After thorough mixing, the pellets were formed by high-pressure roller milling in 12 minutes, resulting in green pellets with a particle size of 10-16 mm. Sampling of the pellets was conducted hourly for 24 hours. The average drop strength of the green pellets was 7.3 drops / (0.5 m), with a standard deviation of 2.0 drops / (0.5 m). The average compressive strength of the green pellets was 23.6 N / p, with a standard deviation of 3.4 N / p. The bursting temperature of the green pellets was 500℃. After preheating at 860℃ for 10 minutes and calcining at 1250℃ for 12 minutes, the average compressive strength of the preheated pellets was 472 N / p, with a standard deviation of 49 N / p, and the compressive strength of the calcined pellets was 2339 N / p, with a standard deviation of 253 N / p, both meeting the requirements for industrial pellet production.

[0079] Example 2

[0080] Using calcium-based bentonite, lignite (originating from Yunnan, with 56% alkali-soluble macromolecules and 28% alkali-insoluble macromolecules), structure modifier B, and sodium pyrophosphate-sodium hydroxide as raw materials in Example 1 with a weight ratio of 75:18:3:4, the mixture was mixed with 1.7 times its weight of water and pre-milled in the first stage for 30 minutes (60% of the balls were 20mm steel balls, and the rotation speed was 78% of the critical speed). Then, it was subjected to a second stage of deep ball milling for 45 minutes (65% of the balls were 10mm steel balls, and the rotation speed was 90% of the critical speed). Finally, it was dried by spray drying for 10 minutes (air temperature 220℃, material temperature 59℃, moisture content 1.4%) to prepare a micro-nano composite binder.

[0081] The micro / nano composite binder produced had an average particle size distribution of -38μm (100%), -500nm (92.0%), and -100nm (43.9%), with a specific surface area of ​​31.8 m². 2 / g, standard deviation 4.5 m 2 / g, coefficient of variation 0.065, average water absorption rate 434.8%, standard deviation 25.6%, coefficient of variation 0.054, product performance is stable.

[0082] The binder was used in the preparation of vanadium-titanium magnetite pellets at a dosage of 0.6%. After thorough mixing, the pellets were formed by high-pressure roller milling for 12 minutes, resulting in green pellets with a particle size of 10-16 mm. The green pellet drop strength was 7.3 drops / (0.5 m), with a standard deviation of 2.2 drops / (0.5 m), the green pellet compressive strength was 22.9 N / p, with a standard deviation of 3.1 N / p, and the green pellet bursting temperature was 550℃. After preheating at 880℃ for 16 minutes and calcining at 1250℃ for 14 minutes, the preheated pellets had a compressive strength of 463 N / p, with a standard deviation of 54 N / p, and the calcined pellets had a compressive strength of 2294 N / p, with a standard deviation of 282 N / p, both meeting the requirements for pellet production.

[0083] Example 3

[0084] Using iron tailings (originating from Jiangsu, with 28% kaolinite content, 174% water absorption, and 1.9 mL / g expansion capacity) in a weight ratio of 77:17:3:3, lignite from Example 2, structure modifier A2, and NaOH as raw materials, 1.2 times the amount of water was added to the raw materials and mixed. The mixture was then ball-milled for 10 minutes in the first stage (60% of the balls were 20 mm in diameter, and the rotation speed was 78% of the critical speed), followed by a second stage of deep ball milling for 40 minutes (65% of the balls were 10 mm in diameter, and the rotation speed was 90% of the critical speed). Finally, the mixture was dried by spray drying for 12 minutes (air temperature 290℃, material temperature 78℃, and moisture content 0.9%) to enhance the co-reaction and prepare a micro-nano composite binder.

[0085] The micro / nano composite binder produced had an average particle size distribution of -38μm (100%), -500nm (81.1%), and -100nm (33.9%), with a specific surface area of ​​26.2 m². 2 / g, standard deviation 2.6 m 2 / g, coefficient of variation 0.034.

[0086] The prepared binder was used in the preparation of magnetochre mixed iron ore pellets at a dosage of 1.0%. After thorough mixing, the pellets were formed by high-pressure roller milling for 12 minutes, resulting in green pellets with a particle size of 10-16 mm. The green pellet drop strength was 7.4 drops / (0.5 m), with a standard deviation of 2.5 drops / (0.5 m), a compressive strength of 28.0 N / p, with a standard deviation of 3.7 N / p, and a bursting temperature of 500℃. After preheating at 1050℃ for 16 minutes and calcining at 1220℃ for 12 minutes, the preheated pellet strength was 546 N / p, with a standard deviation of 73 N / p, and the calcined pellet strength was 2909 N / p, with a standard deviation of 336 N / p, both meeting the requirements for pellet production.

[0087] Example 4

[0088] Using boron mud (originating from Liaoning, with 73% magnesium olivine and serpentine content) in a weight ratio of 71:20:4:5, weathered coal from Example 1, structure modifier A1, and sodium carbonate as raw materials, 1.5 times the amount of water was added to the raw materials and mixed. The mixture was then ball-milled for 20 minutes in the first stage (55% of 20mm steel forging, speed at 80% of the critical speed), followed by a second stage of deep ball milling for 40 minutes (60% of 10mm steel forging, speed at 90% of the critical speed). Finally, it was spray-dried for 14 minutes (air temperature 270℃, material temperature 73℃, moisture content 1.1%) to prepare a micro-nano composite binder.

[0089] The micro / nano composite binder produced had an average particle size distribution of -38μm (100%), -500nm (91.6%), and -100nm (65.5%), with a specific surface area of ​​29.1 m². 2 / g, standard deviation 3.3 m 2 / g, coefficient of variation 0.041. The prepared binder was used for the preparation of magnetite pellets. The binder addition amount was 1.0%. After thorough mixing, the pellets were formed by high-pressure roller milling for 12 min, and the green pellet size was 10~16 mm. The green pellet drop strength was 6.8 times / (0.5m), standard deviation 2.3 times / (0.5m), compressive strength 21.5 N / p, standard deviation 3.5 N / p, and bursting temperature 530℃. After preheating at 970℃ for 14 min and calcining at 1250℃ for 14 min, the preheated pellet strength was 497 N / p, standard deviation 75 N / p, and the calcined pellet strength was 2529 N / p, standard deviation 380 N / p, both of which met the requirements for pellet production.

[0090] Example 5

[0091] Compared with Example 1, the only difference is that the structure modifiers are structure modifier A1 and structure modifier B in a weight ratio of 1:1, and the total amount of structure modifiers and other operations and parameters are the same as in Example 1.

[0092] The micro / nano composite binder produced had an average particle size distribution of -38μm (100%), -500nm (94.5%), and -100nm (49.7%) across multiple batches; the specific surface area was 35.2 m². 2 / g, standard deviation 3.6 m 2 / g, coefficient of variation 0.053; average water absorption rate 506.0%, standard deviation 20.7%, coefficient of variation 0.042, product performance is further improved compared with Example 1.

[0093] The binder was used in the industrial production of magnetite pellets at a dosage of 0.8%. After thorough mixing, the pellets were formed by high-pressure roller milling for 12 minutes, resulting in green pellets with a particle size of 10-16 mm. Sampling of the pellets was conducted hourly for 24 hours. The average drop strength of the green pellets was 7.8 drops / (0.5 m), with a standard deviation of 2.2 drops / (0.5 m). The average compressive strength of the green pellets was 25.2 N / p, with a standard deviation of 3.2 N / p. The bursting temperature of the green pellets was 500℃. After preheating at 860℃ for 10 minutes and calcining at 1250℃ for 12 minutes, the average compressive strength of the preheated pellets was 498 N / p, with a standard deviation of 45 N / p. The compressive strength of the calcined pellets was 2452 N / p, with a standard deviation of 230 N / p. The pellet performance was further improved compared to Example 1.

[0094] Example 6

[0095] Compared with Example 1, the only difference is that the structure modifier is structure modifier B, and all other operations and parameters are the same as in Example 1.

[0096] The micro / nano composite binder produced had an average particle size distribution of -38μm (100%), -500nm (91.5%), and -100nm (45.1%) across multiple batches; the specific surface area was 32.6 m². 2 / g, standard deviation 4.4 m 2 / g, coefficient of variation 0.064; average water absorption rate 469.1%, standard deviation 24.2%, coefficient of variation 0.053, product performance is stable.

[0097] The binder was used in the industrial production of magnetite pellets at a dosage of 0.8%. After thorough mixing, the pellets were formed by high-pressure roller milling for 12 minutes, resulting in green pellets with a particle size of 10-16 mm. Sampling of the pellets was conducted hourly for 24 hours. The average drop strength of the green pellets was 7.5 drops / (0.5 m), with a standard deviation of 2.1 drops / (0.5 m). The average compressive strength of the green pellets was 24.3 N / p, with a standard deviation of 3.5 N / p. The bursting temperature of the green pellets was 500℃. After preheating at 860℃ for 10 minutes and calcining at 1250℃ for 12 minutes, the average compressive strength of the preheated pellets was 463 N / p, with a standard deviation of 52 N / p, and the compressive strength of the calcined pellets was 2351 N / p, with a standard deviation of 245 N / p.

[0098] Comparative Example 1

[0099] Compared with Example 1, the only difference is that no structure modifier A1 is added; all other operations and parameters are the same as in Example 1.

[0100] The micro / nano composite binder produced had an average particle size distribution of -38μm (95.1%), -500nm (74.4%), and -100nm (7.3%) across multiple batches; the specific surface area was 13.6 m². 2 / g, standard deviation 5.2 m 2 / g, coefficient of variation 0.078; average water absorption rate 342.3%, standard deviation 25.6%, coefficient of variation 0.058, product performance significantly decreased compared to Example 1.

[0101] The binder was used in the industrial production of magnetite pellets at a dosage of 0.8%. After thorough mixing, the pellets were formed by high-pressure roller milling for 12 minutes, resulting in green pellets with a particle size of 10-16 mm. Sampling of the pellets was conducted hourly for 24 hours. The average drop strength of the green pellets was 3.8 drops / (0.5 m), with a standard deviation of 3.5 drops / (0.5 m). The average compressive strength of the green pellets was 18.7 N / p, with a standard deviation of 4.5 N / p. The bursting temperature of the green pellets was 500℃. After preheating at 860℃ for 10 minutes and calcining at 1250℃ for 12 minutes, the average compressive strength of the preheated pellets was 388 N / p, with a standard deviation of 65 N / p. The compressive strength of the calcined pellets was 1973 N / p, with a standard deviation of 279 N / p. The pellet performance was significantly lower than that of Example 1.

[0102] Comparative Example 2

[0103] Compared with Example 1, the only difference is that carboxymethyl cellulose is used to replace the structure modifier A1 by weight; all other operations and parameters are the same as in Example 1.

[0104] The micro / nano composite binder produced had an average particle size distribution of -38μm (73.9%), -500nm (30.6%), and -100nm (1.2%) across multiple batches; the specific surface area was 7.5 m². 2 / g, standard deviation 4.7 m 2 / g, coefficient of variation 0.070; average water absorption rate 375.5%, standard deviation 23.9%, coefficient of variation 0.046, product performance significantly decreased compared to Example 1.

[0105] The binder was used in the industrial production of magnetite pellets at a dosage of 0.8%. After thorough mixing, the pellets were formed by high-pressure roller milling for 12 minutes, resulting in green pellets with a particle size of 10-16 mm. Sampling of the pellets was conducted hourly for 24 hours. The average drop strength of the green pellets was 5.6 drops / (0.5 m), with a standard deviation of 3.4 drops / (0.5 m). The average compressive strength of the green pellets was 19.7 N / p, with a standard deviation of 5.9 N / p. The bursting temperature of the green pellets was 500℃. After preheating at 860℃ for 10 minutes and calcining at 1250℃ for 12 minutes, the average compressive strength of the preheated pellets was 425 N / p, with a standard deviation of 58 N / p. The compressive strength of the calcined pellets was 2004 N / p, with a standard deviation of 288 N / p. The pellet performance was significantly lower than that of Example 1.

[0106] Comparative Example 3

[0107] Compared with Example 1, the only difference is that polyacrylamide is used to replace the structure modifier A1 by weight; all other operations and parameters are the same as in Example 1.

[0108] The micro / nano composite binder produced had an average particle size distribution of -38μm (87.4%), -500nm (45.2%), and -100nm (18.5%) across multiple batches; the specific surface area was 11.4 m². 2 / g, standard deviation 4.2 m 2 / g, coefficient of variation 0.064; average water absorption rate 389.1%, standard deviation 30.2%, coefficient of variation 0.073, product performance significantly decreased compared to Example 1.

[0109] The binder was used in the industrial production of magnetite pellets at a dosage of 0.8%. After thorough mixing, the pellets were formed by high-pressure roller milling for 12 minutes, resulting in green pellets with a particle size of 10-16 mm. Sampling of the pellets was conducted hourly for 24 hours. The average drop strength of the green pellets was 5.2 drops / (0.5 m), with a standard deviation of 3.3 drops / (0.5 m). The average compressive strength of the green pellets was 16.5 N / p, with a standard deviation of 4.7 N / p. The bursting temperature of the green pellets was 500℃. After preheating at 860℃ for 10 minutes and calcining at 1250℃ for 12 minutes, the average compressive strength of the preheated pellets was 417 N / p, with a standard deviation of 59 N / p. The compressive strength of the calcined pellets was 2045 N / p, with a standard deviation of 274 N / p. The pellet performance was significantly lower than that of Example 1.

[0110] Comparative Example 4

[0111] Compared with Example 1, the only difference is that the first stage of ball milling is omitted, and the processing time of the second stage of ball milling is extended to 65 minutes. All other operations and parameters are the same as in Example 1.

[0112] The micro / nano composite binder produced had an average particle size distribution of -38μm (95.7%), -500nm (74.8%), and -100nm (53.2%) across multiple batches; the specific surface area was 34.6 m². 2 / g, standard deviation 10.5 m 2 / g, coefficient of variation 0.233; average water absorption rate 415.5%, standard deviation 30.6%, coefficient of variation 0.073, the binder part was not finely ground, and the product performance fluctuated more than that of Example 1.

[0113] The binder was used in the industrial production of magnetite pellets at a dosage of 0.8%. After thorough mixing, the pellets were formed by high-pressure roller milling in 12 minutes, resulting in green pellets with a particle size of 10-16 mm. Sampling of the pellets was conducted hourly for 24 hours. The average drop strength of the green pellets was 6.2 drops / (0.5 m), with a standard deviation of 3.5 drops / (0.5 m). The average compressive strength of the green pellets was 21.7 N / p, with a standard deviation of 6.8 N / p. The bursting temperature of the green pellets was 460℃. After preheating at 860℃ for 10 minutes and calcining at 1250℃ for 12 minutes, the average compressive strength of the preheated pellets was 445 N / p, with a standard deviation of 57 N / p, and the compressive strength of the calcined pellets was 2215 N / p, with a standard deviation of 298 N / p, both meeting the requirements for industrial pellet production.

[0114] Comparative Example 5

[0115] Compared with Example 1, the only difference is that the ball milling process is first performed according to the conditions of the second stage ball milling, and then the ball milling process is performed according to the conditions of the first stage ball milling. All other operations and parameters are the same as in Example 1.

[0116] The micro / nano composite binder produced had an average particle size distribution of -38μm (93.3%), -500nm (68.5%), and -100nm (37.2%) across multiple batches; the specific surface area was 24.9 m². 2 / g, standard deviation 7.5 m 2 / g, coefficient of variation 0.163; the average water absorption rate of the binder was 267.4%, standard deviation 35.3%, coefficient of variation 0.079, the binder was not finely ground, and the product performance was significantly lower than that of Example 1.

[0117] The binder was used in the preparation of magnetite pellets at a dosage of 0.8%. After thorough mixing, the pellets were formed by high-pressure roller milling for 12 minutes, resulting in green pellets with a particle size of 10-16 mm. The green pellet drop strength was 3.3 times / (0.5 m), the green pellet compressive strength was 14.5 N / p, and the green pellet bursting temperature was 500℃. The green pellets were of substandard quality.

[0118] Comparative Example 6

[0119] Compared to Example 1, the only difference was the addition of three times the amount of water as raw material and an extended spray drying time of 60 minutes (air temperature 250℃, material temperature 72℃, moisture content 3.8%). All other operations and parameters remained the same as in Example 1. Due to the excessive water addition, binder crystallization was more pronounced. The resulting binder had a particle size distribution of -74μm (90.6%), -38μm (58.4%), and -500nm (16.3%), indicating poor micro / nanoization.

[0120] Comparative Example 7

[0121] Compared to Example 1, the only difference was that a conventional rotary kiln was used for drying for 30 minutes (air temperature 250℃, material temperature 70℃, moisture content 13.9%), while all other operations and parameters remained the same as in Example 1. Because conventional drying could not completely dry the internal moisture of the binder, the binder agglomerated and stuck together significantly. The resulting binder had a particle size distribution of -74μm (95.2%), -38μm (45.4%), and -500nm (3.6%), failing to achieve micro-nano particle size levels.

[0122] Comparative Example 8

[0123] Compared with Example 3, the only difference is that the weight ratio of iron tailings (originating from Jiangsu, with 28% kaolinite content, 174% water absorption rate, and 1.9 mL / g expansion capacity), lignite from Example 2, structure modifier A2, and NaOH is 63:27:8:2, and the raw material compatibility is not within the required range. All other operations and parameters are the same as in Example 3.

[0124] The binder particle size distribution was -38μm (100%), -500nm (82.6%), and -100nm (39.7%). The prepared binder was used to prepare magnetochre mixed iron ore pellets at a dosage of 1.0%. After thorough mixing, the pellets were formed by high-pressure roller milling for 12 minutes, resulting in green pellets with a particle size of 14-16 mm. The green pellet drop strength was 4.5 drops / (0.5m), the compressive strength was 13.2 N / p, and the bursting temperature was 350℃, showing a significant decrease in green pellet indicators. After preheating at 970℃ for 14 minutes and calcining at 1250℃ for 14 minutes, the preheated pellet strength was 352 N / p, and the calcined pellet strength was 1892 N / p, indicating that the pellet quality was unqualified.

[0125] Comparative Example 9

[0126] Compared with Example 4, the only difference is that the weight ratio of the four raw materials, namely boron mud (originating from Liaoning, with a content of 73% magnesium olivine and serpentine), weathered coal in Example 1, structure modifier A1, and sodium carbonate, is 50:40:5:5. The raw material compatibility is not within the required range. All other operations and parameters are the same as in Example 4.

[0127] The obtained micro-nano composite binder had a particle size distribution of -38μm (100%), -500nm (87.7%), and -100nm (54.2%). The binder was used in the preparation of magnetite pellets at a dosage of 1.0%. After thorough mixing, the pellets were formed by high-pressure roller milling for 12 minutes, resulting in green pellets with a particle size of 14-16 mm. The green pellets exhibited a drop strength of 3.5 times / (0.5m), a compressive strength of 15.6 N / p, and a bursting temperature of 300℃, showing a significant decrease in green pellet performance. After preheating at 970℃ for 14 minutes and calcining at 1250℃ for 14 minutes, the preheated pellets had a strength of 309 N / p, and the calcined pellets had a strength of 1512 N / p, indicating that the pellet quality was unqualified.

Claims

1. A method for preparing a micro / nano composite binder, characterized in that: Raw materials containing inorganic matrix materials, organic modifiers, structure regulators and alkaline components are mixed with water and pre-processed through a first-stage ball milling process, followed by a second-stage ball milling process, and then spray-dried to obtain a micro-nano composite binder. The inorganic matrix material contains clay. The organic modifier is a component containing mineral-derived humic acid; The structure modifier is a polysaccharide or acrylamide oligomer chemically modified with a structural fragment of Formula 1; Formula 1; In Formula 1, R1 to R3 are individually C1 to C4 alkyl or allyl groups; The weight ratio of inorganic matrix material, organic modifier, structure regulator, and alkaline component is 67~93:4~23:1~4:2~6; The weight ratio of raw materials to water is 1:1.2~2; In the first stage of ball milling, the size of the ball milling media is 1.5 to 5 times that of the ball milling media in the second stage; the ball milling speed is 0.1 to 0.9 times that of the ball milling speed in the second stage.

2. The method for preparing the micro / nano composite binder as described in claim 1, characterized in that: The inorganic matrix material includes natural clay minerals with layered or chain-like silicate structures and / or industrial solid waste rich in amorphous silica-alumina phases. The natural clay mineral is selected from at least one of bentonite, montmorillonite, kaolinite, illite, and chlorite, and is more preferably bentonite; The industrial solid waste includes at least one of iron ore tailings, titanium ore tailings, red mud, and boron mud; Preferably, the content of SiO2+Al2O3 in the inorganic matrix material is not less than 50%.

3. The method for preparing the micro / nano composite binder as described in claim 1, characterized in that: The organic modifier is a fossil-derived organic matter with thermal cross-linking properties, selected from at least one of lignite, weathered coal, asphalt, sulfonated asphalt, and fuel oil, and more preferably at least one of lignite and weathered coal containing mineral humic acid, comprising 35-75% alkali-soluble macromolecules and 25-65% alkali-insoluble macromolecules. Preferably, the number average molecular weight of the alkali-soluble macromolecule is 500-4000 Da, and the polar functional group content is 1.5-5 mmol / g; the number average molecular weight of the alkali-insoluble macromolecule is 4000-20000 Da, and the polar functional group content is less than 1.5 mmol / g.

4. The method for preparing the micro / nano composite adhesive as described in claim 1, characterized in that: The structure modifier is at least one of structure modifier A and structure modifier B; The structure modifier A is an oligomer of formula 1a chemically grafted with a polysaccharide; Equation 1a; In Formula 1a, R1 to R3 are individually C1 to C4 alkyl groups; The polysaccharide is at least one of cellulose components and starch components; The weight ratio of Formula 1a to the polysaccharide is 1:0.3~0.7; The structure modifier B is an oligomer of formula 2; Formula 2; Where x is 1~10; y is 1~8; R4~R5 are C1~C4 alkyl groups; and A is a halide anion.

5. The method for preparing the micro / nano composite adhesive as described in claim 4, characterized in that: The structure modifier B is obtained by copolymerization of raw materials of formula 2a and formula 2b: Equation 2a Equation 2b The molar ratio of the raw material of formula 2a to the raw material of formula 2b is 1:0.3~0.8; The number-average molecular weight of the oligomers of structure modifier B is 230~2200 Da.

6. The method for preparing the micro / nano composite adhesive as described in claim 1, characterized in that: The alkaline component is at least one of alkali metal hydroxide, alkali metal carbonate, and pyrophosphate; preferably at least one of sodium hydroxide, sodium carbonate, and sodium pyrophosphate.

7. The method for preparing the micro / nano composite adhesive as described in claim 1, characterized in that: The grinding media for the first stage of ball milling are steel balls or forged steel with a diameter of 18-22 mm and a proportion of ≥50%; the ball milling speed is 76%-88% of the critical speed; and the time is 5-30 minutes. The grinding media for the second stage of ball milling are steel balls or forged steel with a ratio of ≥50% and a diameter of 8~12mm; the rotational speed of the second stage of ball milling is 88%~95% of the critical speed, and the time is 20~50min.

8. A micro / nano composite binder prepared by any one of claims 1 to 7, characterized in that, The particle size distribution of the micro / nano composite binder dispersed in the concentrate powder is as follows: D90≤500nm, D30≤100nm, and specific surface area≥25 m². 2 / g.

9. An application of the micro / nano composite adhesive according to claim 8, characterized in that, The micro-nano composite binder is mixed evenly with concentrate powder and then used for the preparation of green pellets or green lumps; Preferably, the concentrate powder is iron concentrate powder; Preferably, the amount of micro-nano composite binder added relative to the concentrate powder is 0.5% to 1.0%.

10. A raw ball or raw lump as described in claim 9.

Images