A colloidal pellet binder and its preparation and application

Abstract

The present invention relates to the field of iron and steel metallurgy, and specifically discloses a method for preparing a colloidal pellet binder and its application; after crushing raw materials containing humic acid substances and clay components to a certain particle size, alkaline substances and water are added according to a certain mass ratio, and mechanical activation treatment is performed at room temperature and pressure to obtain a colloidal pellet binder with uniform composition, stable viscosity, and good bonding performance, which can be stored in a liquid storage tank for a long time. The colloidal binder product prepared by the present invention has low usage, good bonding performance, is easy to disperse on the surface of iron concentrate, and can significantly improve the pelletizing performance of iron ore powder. Compared with bentonite, the colloidal binder of the present invention can increase the iron grade of pellets by more than 1%. Based on the current annual output of pellets in my country of 200 million tons, the promotion and application of the new binder can reduce CO2 emissions by about 3 million tons per year, which will play a certain role in promoting the realization of the "dual carbon" goals of steel.

Description

Technical Field

[0001] The invention belongs to the technical field of iron and steel metallurgy, and in particular relates to a pellet binder. Background Art

[0002] The steel industry is a pillar of national economic development, but it is also a major energy consumer and carbon emitter, making it a key sector for green and low-carbon development. The steel industry accounts for approximately 15% of China's carbon emissions, second only to the power industry. my country consumes over 1.2 billion tons of various iron-containing raw materials annually, 90% of which requires sintering and pelletizing before smelting. Pellets are recognized as high-quality ironmaking feed and the development direction of blast furnace ironmaking concentrate. Pellets have an iron grade approximately 7% higher than sintered ore, and pollutant emissions during pellet production are one-third of sintered ore. The pelletizing process consumes approximately 20 kgce / t less energy than sintering. Furthermore, due to their uniform particle size and excellent mechanical strength, pellets can significantly reduce coke consumption in blast furnace ironmaking. While pellets account for over 90% of blast furnace production in Europe and the United States, this figure is only 13% in my country. Increasing the proportion of pellets in blast furnace charge is a major development direction for ironmaking technology.

[0003] Binders are essential raw materials for pellet production. Based on their source, pellet binders can be divided into three categories: inorganic, organic, and composite. Bentonite is currently the most widely used inorganic binder both domestically and internationally. However, due to the poor quality of bentonite in my country, pellet production suffers from high mixing ratios (~2.0%, with some reaching 3.5%), residual aluminum and silicon, and reduced iron grade in the pellets, leading to high fuel consumption in blast furnace ironmaking. Organic binders are used in low dosages and produce minimal residuals during pellet production, but they are expensive and have poor thermal stability, making them rarely used in China. Inorganic-organic composite binders have become a focus of research and development in recent years, with the most typical example being the organic modification of bentonite. Organically modified bentonite significantly improves its bonding properties, allowing its addition level in pellets to be reduced from 3.5% to 1.0% to 1.5%. However, the price of modified bentonite increases significantly, and it does not fundamentally address the issue of bentonite lowering iron grade in pellets. Research has shown that adding 1.0% bentonite can reduce the iron content of pellets by 0.6%. For blast furnace ironmaking, a 1% increase in charge iron grade reduces the fuel ratio by 1.5%, increases output by 2.5%, and reduces the production cost per ton of hot metal by 15 to 20 yuan. my country's steel production is massive, and developing new, high-quality, and efficient binders with low residues to replace bentonite and improve the iron grade of pellets is crucial for promoting green development of the country's steel industry and achieving its "dual carbon" goals.

[0004] After years of research, the inventor's team developed a composite binder based on the organic polymer humic acid, using lignite as raw material and sodium alkali as an extractant. Its functional components are humic acid and fulvic acid. This binder exhibits advantages such as high viscosity, low residue, and low price, and has been successfully applied in direct reduction pellet production. However, its use in oxidation pellet production suffers from problems such as poor thermal stability and low strength, hindering its industrial application to date. Furthermore, achieving uniform dispersion of the binder in iron ore concentrate at low dosages presents another challenge in the application of this new binder in pellet production.

[0005] Chinese invention patent publication number CN 104164560 B discloses a sodium humate binder solution for iron ore pellets, its preparation method, and its application. The binder solute prepared by this method has a low viscosity of 100-150 g / L and lacks the characteristics of a colloidal solution. Chinese invention patent publication number CN 101693950 B discloses a complex-type organic binder for iron ore pellets and its use method. This method requires first fractional purification to obtain sodium humate and sodium fulvic acid, and then prepares the binder product. The resulting binder is a solid powder with poor dispersibility in actual production. Chinese invention patent publication number CN 111254278 B discloses an oxidized pellet binder made from low-rank coal, its preparation method, and its application. This method requires high-temperature processing (50°C to 100°C) and a long reaction time (1h to 5h) to prepare the binder. Summary of the Invention

[0006] The first object of the present invention is to provide a method for preparing a colloidal pellet binder, aiming to produce a new colloidal pellet binder with uniform composition, stable viscosity, good bonding performance, good dispersibility and good thermal stability.

[0007] The second object of the present invention is to provide a colloidal pellet binder obtained by the preparation method.

[0008] The third object of the present invention is to provide the use of the colloidal pellet binder prepared by the preparation method in pellet preparation.

[0009] A fourth object of the present invention is to provide pellets containing the colloidal pellet binder.

[0010] The existing binders used in the production of iron ore pellets are mainly solid binders; however, solid binders have shortcomings such as unsatisfactory dispersibility, high addition amount, and unsatisfactory compatibility with iron ore. In addition, there are a small number of newly prepared solution-based binders in the prior art. Such binders are non-stable systems with poor solution stability and unsatisfactory pelletizing stability. In order to solve the problems existing with existing binders, the present invention breaks through the existing ideas and attempts to propose a colloidal binder. However, as the research progresses, the inventors find that compared with solid binders, the colloidal type is not just a simple replacement of the material form, but also faces many unknown problems. For example, it is necessary to solve many technical problems such as system instability caused by the sedimentation of colloidal binders, unsatisfactory rheology, and obvious attenuation of bonding and roasting performance as the system becomes unstable (system sedimentation); in response to this technical problem, the present invention has conducted in-depth research and proposed the following solutions:

[0011] A method for preparing a colloidal pellet binder comprises mechanically activating raw materials containing humic acid substances and clay components with an alkaline substance in water to obtain the colloidal pellet binder;

[0012] The raw materials contain humic acid substances with a content of more than 30%, a total acid group content of 2.0 to 4.5 meq / g, and a clay content of 10 to 40%.

[0013] The amount of water added is 4 to 7 times the dry weight of the raw material, and the amount of alkaline substance added is 10% to 20% of the dry weight of the raw material;

[0014] The temperature of mechanical activation is 20℃~50℃.

[0015] The present invention has found that by mechanically activating raw materials containing humic acid substances and clay components and alkaline substances, and further controlling the humic acid substances, total acid group content, clay components, water, alkaline substance dosage and temperature during the mechanical activation stage, a colloidal binder with good rheological properties and good system stability can be produced. The colloidal binder can achieve better green ball performance and roasting performance at a lower dosage. The method of the present invention has a wide range of raw material sources, low price, simple preparation process, small dosage of the prepared binder product, good bonding performance, good raw material adaptability, low cost of use, and the iron grade of the pellets is not affected.

[0016] In the present invention, the joint control of the raw material components and mechanical activation parameters is the key to improving the rheological properties and ball-forming performance of the binder colloid solution.

[0017] In the present invention, the humic acid substances are humic acid and its salts;

[0018] Preferably, the clay is at least one of clay and colloidal mineral. The clay component contains elements such as silicon and aluminum. Preferably, the clay is at least one of kaolinite, illite, and montmorillonite.

[0019] In the present invention, the raw material can be a coal-based raw material containing the required humic acid and clay content, preferably at least one of peat, lignite, or weathered coal containing the required humic acid and clay content. Research has shown that using coal-based raw materials that meet the requirements for humic acid, total acid groups, and clay content as raw materials can further improve the synergy with mechanical activity, and further improve the system stability, adhesion, and pelletizing performance of the resulting colloidal binder.

[0020] Preferably, in the present invention, the raw material is lignite or peat, with a humic acid content greater than 40% and a total acid group content of 3.0-4.5 meq / g; more preferably, the humic acid content is 45%-75% and the total acid group content is 4-4.5 meq / g. The raw material is weathered coal, with a humic acid content greater than 30% and a total acid group content of 2.0-4.5 meq / g; preferably, the humic acid content is 35%-45% and the total acid group content is 2.5-3.5 meq / g.

[0021] In the present invention, the particle size of the raw material is controlled to be less than or equal to 0.5 mm.

[0022] In the present invention, the alkaline substance 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.

[0023] Preferably, the amount of alkaline substance added is 14% to 16% of the dry weight of the raw material.

[0024] In the present invention, the raw materials and alkaline substances are mechanically activated in water.

[0025] In the present invention, the mechanical activation is ball milling activation;

[0026] Preferably, in the present invention, the raw material is lignite or peat, and the amount of water added is 5 to 7 times the dry mass of the raw material; the raw material is weathered coal, and the amount of water added is 5 to 6 times the dry mass of the raw material.

[0027] Preferably, the rotation speed of the ball milling activation is 75% to 90% of the critical rotation speed, preferably 76% to 88%.

[0028] In the present invention, there is no particular requirement for the shape and material of the ball milling medium for ball milling activation. For example, it can be a ball, a rod, a forging, etc. The material of the ball milling medium can be steel, ceramics, etc.

[0029] Preferably, the temperature during the mechanical activation stage is 20°C to 40°C, more preferably room temperature, for example 20°C to 30°C.

[0030] Preferably, the mechanical activation treatment time is 10 min to 100 min, preferably 30 min to 60 min.

[0031] In the present invention, after the mechanical activation treatment, the sieving treatment is carried out, and the sieve mesh is 100 to 300 meshes.

[0032] The invention also provides a colloidal pellet binder prepared by the preparation method.

[0033] In the present invention, by controlling the composition of the raw materials and combining the chemical and physical activation treatments, a novel colloidal binder system can be obtained. The colloidal binder exhibits excellent storage stability and rheological properties. Furthermore, it exhibits excellent pelletizing and calcining properties, while also maintaining excellent performance stability.

[0034] The colloidal pellet binder is a pseudoplastic fluid, which has a viscosity of 1s at 25°C. -1 The apparent viscosity is greater than 2000 mPa·s, the pH value is 11-13, and the zeta potential is -40 mV to -50 mV. The colloidal adhesive of the present invention preferably has a solid content of 10% to 20% after drying. In addition, the ash content of the colloidal adhesive product after high-temperature combustion is preferably less than 4%.

[0035] Preferably, the adhesive product is a colloidal solution with uniform composition and stable viscosity, and can be stored in a liquid storage tank for a long time.

[0036] The present invention also provides an application of the colloidal pellet binder prepared by the preparation method, which is used as a binder for pelletizing iron ore powder to produce green pellets.

[0037] Preferably, the iron ore powder is iron concentrate. The iron ore powder can be an iron-containing mineral with smelting metallurgical value well-known in the industry.

[0038] Preferably, the colloid adhesive is used at 25°C for 1s. -1 The apparent viscosity is less than 30000mPa·s.

[0039] Preferably, the colloidal adhesive 1s -1 When the apparent viscosity is greater than 30,000 mPa·s, the apparent viscosity can be reduced by heating, stirring, etc.

[0040] Further preferably, the colloidal pellet binder is evenly mixed with the iron ore powder by atomizing and spraying, and the mixture is subjected to high-pressure roller grinding to form qualified green pellets; and further subjected to oxidative roasting or reduction roasting to produce oxidized pellets or reduced pellets;

[0041] Preferably, the addition amount of the colloidal pellet binder is 0.5% to 3.0% of the mass of the iron ore powder, and the dry basis mass of the binder is 0.1% to 0.6% of the mass of the iron ore powder.

[0042] Furthermore, in producing oxidized pellets, the amount of the colloidal binder added is 0.5% to 2.0% of the mass of the iron ore powder, and the dry mass of the binder is 0.1% to 0.4% of the mass of the iron ore powder.

[0043] The present invention also provides an iron ore green pellet, comprising iron ore powder and a colloidal pellet binder prepared by the preparation method; preferably, the iron ore green pellet is a green pellet prepared by the colloidal binder.

[0044] The present invention also provides an iron ore pellet, which is an oxidized pellet obtained by oxidative roasting of the green pellet, and / or a reduced pellet obtained by reduction roasting.

[0045] In the present invention, the iron grade of the iron ore pellets is increased by more than 1% compared with bentonite.

[0046] In the present invention, the colloidal pellet binder can be used to make iron ore powder into pellets of qualified quality based on existing methods, and the pellets can be smelted based on existing means and equipment.

[0047] In the present invention, raw materials containing humic acid and clay components are used. By regulating the raw material components and the reaction processes and action behaviors of organic / inorganic components such as dissolution, ion / ligand exchange, adsorption, and hydrogen bonding under the action of alkaline substances, a colloidal binder with uniform composition, stable viscosity, good adhesion and dispersibility is prepared.

[0048] Beneficial effects

[0049] (1) The present invention physically and chemically activates raw materials containing humic acid substances and clay components and alkaline substances under mechanical action. By regulating the raw material components and activation process parameters, a colloidal binder with good bonding properties and good system stability can be produced. The colloidal binder can also achieve better green ball performance and roasting performance at a lower dosage. The preparation process of the present invention is simple and the process is short. The preparation can be completed at room temperature and pressure, eliminating the steps of drying and fine grinding the raw coal and solid binder. The process is short, energy consumption is low, and process efficiency is high.

[0050] (2) The present invention provides a colloidal binder with excellent bonding properties and extremely low residue in pellets. Compared with bentonite, the colloidal binder can increase the iron grade of pellets by more than 1%. Based on my country's current pellet production of 200 million tons / year, the promotion and application of the new binder can reduce CO2 emissions by approximately 3 million tons per year, which will play a certain role in promoting the realization of the "dual carbon" goals of steel.

[0051] (3) The colloidal adhesive product described in the present invention is a colloidal solution with uniform composition, stable viscosity and good bonding performance. It can be stored in a liquid storage tank for a long time and mixed with iron ore concentrate by atomization spraying, and is easy to disperse on the surface of the iron ore concentrate.

[0052] (4) The colloidal binder of the present invention has a low addition amount and low cost. When bentonite is used as a binder, the addition amount is only 2% or less, and the cost per ton of pellets is 10 to 12 yuan. However, when the colloidal binder prepared by the present invention is added to the oxidized pellets, only 0.5% to 2.0% is required, with a binder dry basis content of 0.1% to 0.4%, to achieve the same effect as bentonite pellets, and the binder cost per ton of pellets is only 5 to 6 yuan. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] Figure 1 The static stability diagram of the colloidal adhesive prepared in Example 1, wherein the left side is the newly prepared sample and the middle is the storage stability diagram at different times; (test temperature 25 ° C, shear rate 1s -1 )

[0054] Figure 2 This is a graph showing the change in apparent viscosity of the colloid adhesive prepared in Example 1 at different storage times; (after standing for 338 hours, the adhesive still maintains pseudoplastic fluid properties)

[0055] Figure 3 This is a picture of the product obtained in Comparative Example 4; DETAILED DESCRIPTION

[0056] The present invention is further explained and illustrated below. In the examples of the present invention, lignite or weathered coal is selected as a raw material, sodium hydroxide is added at 10% to 18% of the raw material's dry weight, and water is added at 4 to 7 times the raw material's dry weight. After mixing, the mixture is mechanically activated for 10 to 100 minutes to obtain a colloidal adhesive product having a particle size of 100% less than 200 mesh.

[0057] In the following cases, unless otherwise stated, the particle size of the raw materials is less than or equal to 0.5 mm;

[0058] The mechanical activation is ball milling activation, the medium is steel balls, the steel ball filling rate is 30% to 40%, and the material filling rate is 20% to 40%; the speed of the mechanical activation stage is 76% to 88% of the critical speed;

[0059] In the following cases, the mechanical activation stage is carried out at room temperature, and the room temperature is, for example, 25° C. to 30° C. The temperature of the mechanical activation stage refers to the temperature of the system at the initial stage of the treatment.

[0060] After mechanical activation and standing, the product was screened through a 200-mesh sieve.

[0061] The colloidal binder is added by spraying.

[0062] The addition amount of the colloidal binder is based on the mineral content.

[0063] In the present invention, conventional methods can be used to prepare oxidized and reduced pellets using the colloidal binder described herein. For example, the colloidal binder described herein can be sprayed onto iron ore concentrate, followed by conventional pelletizing to produce green pellets. The green pellets can then be preheated and calcined in an oxidizing atmosphere using conventional methods to produce oxidized pellets. Alternatively, reduced pellets can be produced by preheating in an oxidizing atmosphere and then calcining in a reducing atmosphere.

[0064] The oxidizing atmosphere can be pure oxygen, air, or a mixture of oxygen and an inert gas. For cost reasons, the oxygen-containing atmosphere in the following examples is air. The reducing atmosphere can be, for example, a reducing atmosphere such as hydrogen, CO, or the like. There are no specific requirements for the reducing gas content in the reducing atmosphere; for example, in the following examples, the reducing atmosphere is 100% CO. Furthermore, the temperatures in the roasting stage can be any temperature known in the industry.

[0065] Example 1

[0066] The colloidal binder was prepared using Yunnan lignite with a humic acid content of 54%, a total acid content of 4.364 meq / g, and an inorganic clay mineral content of 13%. Sodium hydroxide (14% of the dry weight of the raw material) and water (6 times the dry weight of the raw material) were added and mixed. The mixture was mechanically activated at room temperature for 40 minutes. The prepared colloidal binder was allowed to stand for 30 minutes and then heated at 25°C for 1 second. -1 The apparent viscosity, pH value and zeta potential of the prepared product were 3815.0 mPa·s, 11.64 and -47.0 mV, respectively, at a shear rate of 1.5 %.

[0067] The prepared colloidal binder was used to prepare oxidized pellets from a vanadium-titanium magnetite concentrate from a Sichuan province. The colloidal binder was added at a 1% dosage. After thorough mixing, the pellets were passed through a high-pressure roller mill and pelletized for 12 minutes, resulting in a green pellet size of 14-16 mm. The green pellets achieved a drop strength of 15.2 times / (0.5 m), a compressive strength of 31.6 N / p, and a burst temperature of 570°C. Under the conditions of preheating at 880°C for 16 minutes and roasting at 1280°C for 16 minutes, the preheated pellets had a strength of 572 N / p, while the roasted pellets had a strength of 3352 N / p. The finished ductile iron had a grade of 54.5%, a reduction degree of 65.6%, and a reduction expansion index of 8.6%, all meeting pellet production requirements.

[0068] The obtained colloidal adhesive was stored and tested for stability. The results were Figure 1 ; Apparent viscosity changes see Figure 2 It can be seen that the colloidal adhesive prepared by the present invention has excellent storage stability.

[0069] Example 2

[0070] The colloidal binder prepared in Example 1 was used to prepare oxidized pellets from a magnetite concentrate in Anhui Province. The colloidal binder was added at a 1% dosage. After thorough mixing, the pellets were passed through a high-pressure roller mill and pelletized for 12 minutes. The green pellets had a drop strength of 8.6 times / (0.5 m), a compressive strength of 34.3 N / p, and a burst temperature of 480°C. Under the conditions of preheating at 900°C for 12 minutes and calcining at 1240°C for 10 minutes, the preheated pellets had a strength of 479 N / p, and the calcined pellets had a strength of 3398 N / p. The finished pellets had a reduction degree of 66.8% and a reduction expansion index of 11.4%, both meeting pellet production requirements.

[0071] Example 3

[0072] The colloidal binder prepared in Example 1 was used to prepare oxidized pellets from hematite concentrate from Yunnan. The colloidal binder was added at a 1% concentration. After thorough mixing, the pellets were passed through a high-pressure roller mill and pelletized for a controlled 12-minute pelletizing time. The green pellets had a drop strength of 13.5 times / (0.5 m), a compressive strength of 30.8 N / p, and a burst temperature of 470°C. Under the conditions of preheating at 1050°C for 15 minutes and calcining at 1300°C for 15 minutes, the preheated pellets had a strength of 516 N / p, and the calcined pellets had a strength of 3064 N / p. The finished pellets had a reduction degree of 60.6% and a reduction expansion index of 13.6%, both meeting pellet production requirements.

[0073] Comparative Example 1

[0074] A sodium bentonite was used to prepare oxidized pellets from a Sichuan vanadium-titanium magnetite concentrate (same as in Example 1). The binder was added at a 1.5% level. After high-pressure roller milling, the pellets were thoroughly mixed and pelletized for 12 minutes. The green pellets had a drop strength of 9.7 times / (0.5 m), a compressive strength of 26.1 N / p, and a burst temperature of 450°C. After preheating at 880°C for 16 minutes and calcining at 1280°C for 16 minutes, the calcined pellets had a strength of 3326 N / p. The finished ductile iron had a grade of 53.4%, a degree of reduction of 62.8%, and a reduction expansion index of 6.4%, essentially meeting the requirements for pellet production.

[0075] Comparative Example 2

[0076] A calcium-based bentonite was used to prepare oxidized pellets from a Sichuan vanadium-titanium magnetite concentrate (same as in Example 1). The binder was added at a 2.5% level, and the pellets were thoroughly mixed and pelletized after high-pressure roller milling for 12 minutes. The pelletizing time was 12 minutes, and the green pellet size was 14-16 mm. The green pellets had a drop strength of 7.6 times / (0.5 m), a compressive strength of 25.4 N / p, and a burst temperature of 430°C. Under the conditions of preheating at 880°C for 16 minutes and calcining at 1280°C for 16 minutes, the preheated pellets had a strength of 629 N / p, and the calcined pellets had a strength of 3180 N / p. The finished ductile iron had a grade of 52.6%, a reduction degree of 61.2%, and a reduction expansion index of 5.6%, essentially meeting the requirements for pellet production.

[0077] Example 4

[0078] The colloidal binder prepared in Example 1 was used to pelletize reduced pellets from a magnetite concentrate in Anhui Province. The colloidal binder was added at a 2.5% concentration. After thorough mixing, the pellets were passed through a high-pressure roller mill and pelletized for 12 minutes. The green pellets had a drop strength of 9.8 times / (0.5 m), a compressive strength of 36.0 N, and a burst temperature of 450°C. After preheating at 940°C for 14 minutes, the preheated pellets had a strength of 607 N. After reduction at 1050°C for 80 minutes, the reduced powdering rate was 2.8%, the reduced expansion index was 8.5%, the reduced degree was 66.5%, and the metallization rate was 94.2%, all meeting the requirements for pellet production.

[0079] Example 5

[0080] The colloidal binder was prepared using Guizhou weathered coal with a humus content of 39%, a total acid content of 3.203 meq / g, and an inorganic clay mineral content of 28%. Sodium hydroxide (16% of the dry weight of the raw material) and water (5 times the dry weight of the raw material) were added and mixed. The mixture was mechanically activated at room temperature for 40 minutes. The prepared colloidal binder was allowed to stand for 30 minutes and then heated at 25°C for 1 second. -1The apparent viscosity measured at a shear rate of 2202.5 mPa·s, the pH was 11.86, and the zeta potential was -46.2 mV. The binder was used to prepare oxidized pellets from a vanadium-titanium magnetite concentrate in Sichuan (same as in Example 1). The colloidal binder was added in an amount of 1%. After thorough mixing, the pellets were passed through a high-pressure roller mill and pelletized for 12 minutes. The green pellet size was 14-16 mm. The green pellet drop strength was 31.7 times / (0.5 m), the compressive strength was 35.9 N / p, and the burst temperature was 570°C. Under the conditions of preheating at 880°C for 16 minutes and roasting at 1280°C for 16 minutes, the preheated pellet strength was 613 N / p, and the roasted pellet strength was 3545 N / p. The finished pellet reduction degree was 65.6%, and the reduction expansion index was 8.8%, both meeting the pellet production requirements.

[0081] Comparative Example 3

[0082] The colloidal binder was prepared by using Xinjiang lignite with a humus content of 72%, a total acid content of 5.726 meq / g, and an inorganic clay mineral content of 7%. Sodium hydroxide (15% of the dry weight of the raw materials) and water (4 times the dry weight of the raw materials) were added and mixed. The mixture was mechanically activated at room temperature for 40 minutes. The prepared colloidal binder was allowed to stand for 30 minutes and then heated at 25°C for 1 second. -1 The apparent viscosity measured at a shear rate of 1633.0 mPa·s, the pH was 11.70, and the zeta potential was -52.3 mV. The binder was used to prepare oxidized pellets from a vanadium-titanium magnetite concentrate from Sichuan (same as in Example 1). The colloidal binder was added at a rate of 1%. After thorough mixing, the pellets were passed through a high-pressure roller mill and pelletized for 12 minutes. The green pellet size was 14-16 mm. The green pellet drop strength was 3.3 times / (0.5 m), the compressive strength was 25.7 N / p, and the burst temperature was 600°C. Under the conditions of preheating at 880°C for 16 minutes and roasting at 1280°C for 16 minutes, the preheated pellet strength was 325 N / p and the roasted pellet strength was 1845 N / p, which could not meet the pellet production requirements.

[0083] Comparative Example 4

[0084] Compared with Example 1, the main difference is that the raw materials do not meet the requirements, specifically:

[0085] The colloidal binder was prepared using Yunnan lignite with a humus content of 18%, a total acid content of 1.128 meq / g, and an inorganic clay mineral content of 42%. Sodium hydroxide (18% of the dry weight of the raw material) and water (6 times the dry weight of the raw material) were added and mixed. The mixture was mechanically activated at room temperature for 40 minutes. The prepared colloidal binder was allowed to stand for 30 minutes and then heated at 25°C for 1 second. -1The apparent viscosity measured at a shear rate of 1.5 was 616.7 mPa·s, the pH was 11.61, and the zeta potential was -37.1 mV. The prepared binder was a suspension, which showed stratification after standing. The binder was used to prepare oxidized pellets from a vanadium-titanium magnetite concentrate in Sichuan (same as in Example 1). The binder was added in an amount of 1%, and the pellets were made after high-pressure roller grinding. The pelletizing time was 12 min, and the green pellet size was 14 to 16 mm. The green ball drop strength was 1.3 times / (0.5 m), the compressive strength was 12.8 N, and the burst temperature was 500 ° C. After preheating at 880 ° C for 16 min, the preheated pellet strength was 275 N, and after calcining at 1280 ° C for 16 min, the calcined pellet strength was 1363 N, which could not meet the pellet production requirements.

[0086] Comparative Example 5

[0087] Compared with Example 1, the main difference is that the amount of alkali does not meet the requirements, specifically:

[0088] The colloidal binder was prepared by using the Yunnan lignite of Example 1 as a raw material, adding 8% of the raw material dry weight of sodium hydroxide and 6 times of the raw material dry weight of water, mixing, and mechanically activating at room temperature for 40 minutes. The prepared colloidal binder was allowed to stand for 30 minutes and then heated at 25°C for 1 second. -1 The apparent viscosity measured at a shear rate of 7.0 mPa·s, the pH value was 8.57, and the zeta potential was -39.2 mV. The prepared binder was a suspension after standing for 8 hours, and the composition was not uniform. The binder was used to prepare oxidized pellets from a vanadium-titanium magnetite concentrate in Sichuan (same as in Example 1). The binder was added in an amount of 1%. After sufficient mixing, the pellets were passed through a high-pressure roller mill. The pelletizing time was 12 minutes, and the green pellet size was 14 to 16 mm. The green ball drop strength was 2.3 times / (0.5 m), the compressive strength was 14.4 N / p, and the burst temperature was 500°C. Under the conditions of preheating at 880°C for 16 minutes and roasting at 1280°C for 16 minutes, the preheated pellet strength was 331 N / p, and the roasted pellet strength was 1670 N / p, which could not meet the pellet production requirements.

[0089] Comparative Example 6

[0090] Compared with Example 1, the main difference is that the water content is not controlled within the required range, specifically:

[0091] The colloidal binder was prepared by using the Yunnan lignite of Example 1 as a raw material, adding 14% of the raw material dry weight of sodium hydroxide and 8 times of the raw material dry weight of water, mixing, and mechanically activating at room temperature for 40 minutes. The prepared colloidal binder was allowed to stand for 30 minutes and then heated at 25°C for 1 second. -1The apparent viscosity measured at a shear rate of 116.7 mPa·s, the pH value was 11.51, and the zeta potential was -54.6 mV. The prepared binder was a suspension after standing for 24 hours, and the composition was not uniform. The binder was used to prepare oxidized pellets from a vanadium-titanium magnetite concentrate in Sichuan (same as in Example 1). The binder was added in an amount of 1%. After sufficient mixing, the pellets were passed through a high-pressure roller mill. The pelletizing time was 12 minutes, and the green pellet size was 14 to 16 mm. The green ball drop strength was 2.1 times / (0.5 m), the compressive strength was 11.6 N / p, and the burst temperature was 500°C. Under the conditions of preheating at 880°C for 16 minutes and roasting at 1280°C for 16 minutes, the preheated pellet strength was 289 N / p, and the roasted pellet strength was 1536 N / p, which could not meet the pellet production requirements.

[0092] Comparative Example 7

[0093] Compared with Example 1, the only difference is that the temperature of mechanical activation is not controlled within the required range, specifically:

[0094] The colloidal binder was prepared by using the Yunnan lignite of Example 1 as a raw material, adding 14% of the raw material dry weight of sodium hydroxide and 6 times the raw material dry weight of water, mixing, and mechanically activating at 60°C for 40 minutes. The prepared colloidal binder was allowed to stand for 30 minutes and then heated at 25°C for 1 second. -1 The apparent viscosity measured at a shear rate of 1.5 wt % was 1124.6 mPa·s, the pH was 11.68, and the zeta potential was -47.3 V. The prepared binder was a gel-like solid after standing for 24 hours and could not be well dispersed.

[0095] Comparative Example 8

[0096] Compared with Example 1, the only difference is that the content of alkali is not controlled within the required range, specifically:

[0097] The colloidal binder was prepared by using the Yunnan lignite of Example 1 as a raw material, adding 22% of the raw material dry weight of sodium hydroxide and 6 times the raw material dry weight of water, mixing, and mechanically activating at room temperature for 40 minutes. The prepared colloidal binder was allowed to stand for 30 minutes and then heated at 25°C for 1 second. -1 The apparent viscosity measured at a shear rate of 1.5 wt % was 8025.8 mPa·s, the pH was 12.86, and the zeta potential was -52.5 mV. The prepared adhesive was a gel-like solid after standing for 48 hours and could not be well dispersed.

Claims

1. A method for preparing a colloidal pellet binder, characterized in that: Mechanically activating raw materials containing humic acid substances and clay components with alkaline substances in water to prepare the colloidal pellet binder; The raw materials contain humic acid substances greater than 30%, a total acid group content of 2.0 to 4.5 meq / g, and a clay content of 10 to 40%. The raw materials are coal-based raw materials containing the required content of humic acid substances and clay components; The amount of water added is 4 to 7 times the dry weight of the raw materials, and the amount of alkaline substance added is 10% to 20% of the dry weight of the raw materials; The temperature for mechanical activation is 20℃~50℃.

2. The method for preparing the colloidal pellet binder according to claim 1, wherein: The humic acid substances are humic acid and its salts.

3. The method for preparing the colloidal pellet binder according to claim 1, wherein: The clay is at least one of clay and colloidal mineral.

4. The method for preparing the colloidal pellet binder according to claim 3, wherein: The clay is at least one of kaolinite, illite and montmorillonite.

5. The method for preparing the colloidal pellet binder according to claim 1, wherein: The raw material is at least one of peat, lignite or weathered coal containing the humic acid substance and clay content required.

6. The method for preparing the colloidal pellet binder according to claim 1, wherein: The particle size of the raw material is controlled to be less than or equal to 0.5 mm.

7. The method for preparing the colloidal pellet binder according to claim 1, wherein: The alkaline substance is at least one of alkali metal hydroxide, alkali metal carbonate, phosphate and pyrophosphate.

8. The method for preparing the colloidal pellet binder according to claim 7, wherein: The alkaline substance is at least one of sodium hydroxide, sodium carbonate and sodium pyrophosphate.

9. The method for preparing the colloidal pellet binder according to claim 1, wherein: The mechanical activation is ball milling activation.

10. The method for preparing the colloidal pellet binder according to claim 9, wherein: The rotation speed of the ball milling activation is 75% to 90% of the critical rotation speed.

11. The method for preparing a colloidal pellet binder according to claim 10, wherein: The rotation speed of the ball milling activation is 76% to 88% of the critical rotation speed.

12. The method for preparing a colloidal pellet binder according to claim 1, wherein: The temperature during the mechanical activation stage is 20°C~40°C.

13. The method for preparing a colloidal pellet binder according to claim 1, wherein: The time of mechanical activation treatment is 10min~100min.

14. A colloidal pellet binder prepared by the preparation method according to any one of claims 1 to 13.

15. The colloidal pellet binder according to claim 14, wherein The colloidal pellet binder is a pseudoplastic fluid, and the apparent viscosity of the binder colloid at room temperature is 2000-30000 mPa·s, the pH value is 11-13, and the zeta potential is -40mV--50mV.

16. Use of a colloidal pellet binder obtained by the preparation method according to any one of claims 1 to 13, characterized in that: It is used as a binder to make iron ore powder into balls to produce green balls.

17. The use according to claim 16, characterized in that The iron ore powder is iron concentrate.

18. The use according to claim 16, wherein: The colloidal pellet binder is evenly mixed with iron ore powder by atomizing and spraying, and the mixture is pelletized by high-pressure roller grinding to obtain green pellets; and further subjected to oxidative roasting or reduction roasting to produce oxidized pellets or reduced pellets.

19. The use according to any one of claims 16 to 18, wherein: The addition amount of the colloidal pellet binder is 0.5% to 3.0% of the mass of the iron ore powder, and the dry basis mass of the binder is 0.1% to 0.6% of the mass of the iron ore powder.

20. An iron ore green pellet, characterized in that: The invention comprises iron ore powder and a colloidal pellet binder prepared by the preparation method according to any one of claims 1 to 13.

21. The iron ore green pellets according to claim 20, wherein: The green pellets obtained by the application as claimed in claim 16.

22. An iron ore pellet, characterized in that: The oxidized pellets obtained by oxidative roasting and / or the reduced pellets obtained by reduction roasting as claimed in claim 18.

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