Iron ore powder briquetting composite binder and application thereof

Abstract

The invention discloses an iron ore powder briquetting composite binder and application thereof, and belongs to the technical field of binders for cold-bonded pellets. The composite adhesive comprises a modified water glass solution, an organic binder and a nucleating aid, and the modified water glass solution is obtained by modifying water glass with boric acid and / or formic acid. According to the invention, the composition of the adhesive is optimally designed, so that the adhesive can be effectively applied to cold-bonded pellets, especially sintered return mine-based cold-bonded pellets, not only is the resource utilization of sintered return mines realized, but also alkali metal ions in the water glass adhesive can be effectively prevented from entering the pellets, and the service life of the pellets is prolonged. And the wet strength and the dry strength of the pellets are remarkably improved, so that the pellets can meet the production requirements of a blast furnace.

Description

Technical Field

[0001] The invention belongs to the technical field of cold-consolidated pellet adhesives, and more specifically, relates to an iron ore powder briquetting composite adhesive and application thereof. Background Art

[0002] Sintered ore is one of the main raw materials for domestic blast furnace production, accounting for about 70% of the blast furnace charge. In the production process of sintered ore, sintered return ore with a particle size of less than 5 mm will be produced. These sintered return ores directly entering the blast furnace will block the gaps in the material column and hinder the flow of coal gas in the blast furnace to the top of the furnace. In order to avoid affecting the smooth operation of the blast furnace, the sintered return ore is generally returned to the sintering process for sintering, and about 30% of the return ore is recycled. This process flow not only reduces the output of sintered ore, but also increases the energy consumption of the sintering process. Therefore, in order to save energy and efficiently process sintered return ore, it is of great significance to apply it to cold consolidation pellet technology and prepare a new type of blast furnace charge-sintered return ore-based cold consolidation pellets.

[0003] Cold-consolidated pellets can significantly reduce energy consumption and pollution because their preparation process does not involve high-temperature treatment, providing a solution for the green and efficient treatment of sintered return ore. However, due to the low hydrophilicity and uneven particle size distribution of sintered return ore, it is difficult to form pure sintered return ore by adding water and directly pressing it into balls, and there is almost no strength. Therefore, by adding a certain amount of binder to the sintered return ore, the cold strength of the cold-consolidated pellets can be effectively improved.

[0004] At present, the binders used in pellet production can be divided into inorganic binders, organic binders and organic-inorganic composite binders. Inorganic binders are cheap and have high dry ball and high temperature mechanical strength. Commonly used inorganic binders include bentonite, silicates, cement, etc. Among them, water glass is widely used because it can significantly improve the dry ball compressive strength, but the Na contained in it + This will cause excessive alkali metals to enter the blast furnace, reducing the permeability of the blast furnace and corroding refractory materials.

[0005] After searching, a Chinese patent (CN 114717412A) discloses a binder for cold-pressed pellets, cold-consolidated pellets and a preparation method thereof, wherein the raw materials are alkaline or amphoteric oxides, such as ferrous oxide, ferroferric oxide, calcium oxide, magnesium oxide, and aluminum oxide, and a composite binder is used to prepare cold-consolidated pellets, but does not involve the recycling of iron-containing resources in sintered return ore.

[0006] A Chinese patent (CN102628099A) discloses a method for preparing cold-consolidated pellets of mineral powder using water glass as a binder. The mineral powder is modified with a strong base (NaOH) and water glass is added to prepare cold-consolidated pellets to improve their strength. However, the problem of alkali metal introduction has not been effectively solved.

[0007] A Chinese patent (CN101407860A) discloses a cold-pressed composite pellet binder, which has solid sodium silicate as the main component, with potassium aluminum sulfate and sodium fluorosilicate added. It is mainly used to meet the dry ball strength and keep the pellets from breaking at high temperatures. However, the basic raw materials are mainly manganese-containing powder and coal powder, and do not involve the recycling of iron-containing resources in sintered return ore. Summary of the invention

[0008] 1. Problem to be solved

[0009] The object of the present invention is to provide a composite binder for iron ore powder briquetting, so as to solve the problem that when water glass is used as a pellet binder in the prior art, excessive alkali metals easily enter the blast furnace, which reduces the air permeability of the blast furnace and corrodes the refractory materials.

[0010] The present invention also provides the use of the above-mentioned iron ore powder briquette composite binder in cold consolidation pellets, especially in sintered return ore-based cold consolidation pellets. The use of the above-mentioned composite binder can not only apply the sintered return ore to the cold consolidation pellets and effectively prevent excessive alkali metals from entering the blast furnace, but also effectively ensure the mechanical strength of the pellets to meet the use requirements of the blast furnace.

[0011] 2. Technical solution

[0012] In order to solve the above problems, the technical solution adopted by the present invention is as follows:

[0013] The first aspect of the present invention provides a composite binder for iron ore powder briquetting, wherein the composite binder comprises the following components in parts by weight:

[0014] 5-8 parts of modified water glass solution;

[0015] 0.3-0.7 parts of organic binder;

[0016] Nucleating agent 0.1-0.3 parts;

[0017] Wherein, the modified water glass solution is obtained by modifying water glass with boric acid and / or formic acid, and the nucleating agent is nano silicon dioxide and / or nano aluminum oxide.

[0018] Aiming at the problem that water glass is used as a binder for cold-consolidated pellets in the prior art, which easily leads to excessive alkali metal entering the blast furnace, the present invention, on the one hand, modifies the water glass, and on the other hand, compounding an organic binder and a nucleating agent with the water glass, thereby further reducing the amount of water glass added on the basis of effectively preventing the alkali metal in the water glass from entering the pellets, and ensuring the mechanical strength of the obtained pellets so that they can meet the requirements for blast furnace use.

[0019] Specifically, the modified water glass solution is obtained by modifying water glass with boric acid and / or formic acid, that is, boric acid and / or formic acid react with water glass to generate water-insoluble silicate glue and sodium salt. Since sodium ions can be dissolved in water, in the subsequent cold-pressed pelletizing process, the sodium ions are squeezed out together with the solvent, while the silicate glue is retained in the pellets due to its low fluidity, thereby effectively reducing the alkali metal content in the pellets; wherein the effect is best when a mixed acid of boric acid and formic acid is used for modification. However, the removal of alkali metals will lead to a loss of pellet strength to a certain extent. For this reason, the present invention further adds an organic binder and a nucleation aid to the adhesive, thereby effectively improving the wet ball strength and dry ball strength of the pellets, meeting the requirements of transportation and automated batching for pellet strength, and especially meeting the production requirements of blast furnaces. Among them, the particle size of the nucleation aid is extremely fine, and it can be used as a nucleation aid. The surface active hydroxyl groups (for example, when nano-silicon dioxide is used as a nucleation aid, after the silicon atom combines with the oxygen atom, the remaining valence bond is connected with the hydrogen atom to form the surface active hydroxyl groups) can form a large number of nucleation sites, promote the heterogeneous nucleation of water glass, and thus accelerate the formation of a three-dimensional network structure. More preferably, the particle size range of the nucleation aid is 50-200 nanometers.

[0020] As a further improvement of any technical solution of the first aspect of the present invention, the mass ratio of the boric acid and / or formic acid to the water glass is (1-3): (4-5), and anhydrous ethanol is used as a solvent when the water glass is modified. Sodium ions can be better dissolved in anhydrous ethanol, and silicic acid is insoluble in ethanol and has lower fluidity than ethanol, so it is more conducive to the subsequent removal of sodium ions from the pellets. By controlling the mass ratio of boric acid and / or formic acid to water glass, the degree of modification of the water glass can be controlled to increase the removal rate of sodium ions while minimizing the effect on the bonding of the water glass, that is, only part of the water glass reacts with the acid to generate silicic acid.

[0021] Furthermore, the modification process of water glass comprises: contacting / mixing water glass with boric acid and / or formic acid in anhydrous ethanol, and generating viscous silicate and sodium salt which are insoluble in ethanol after standing. + Dissolved in anhydrous ethanol;

[0022] And / or the mass percentage of the anhydrous ethanol to the total amount of boric acid and / or formic acid and water glass is 2-4%.

[0023] As a further improvement of any technical solution of the first aspect of the present invention, the modulus n of the water glass is 2.3 to 2.5.

[0024] The modulus n of water glass refers to the molecular ratio or molar ratio of silicon dioxide to alkali metal oxide. The bonding force of water glass increases first and then decreases with the increase of the modulus. If the modulus is too small, the bonding force of water glass is too small, and the strength improvement effect of cold-solidified pellets becomes low. However, when the modulus is too high, the solubility of water glass becomes poor, and it is difficult to disperse evenly in the solution. + The Na-containing particles are encapsulated, which is not conducive to the reaction and affects the removal of alkali metals. In addition, the curing speed is too fast, resulting in insufficient contact and reaction with the material particles, and the bonding force is reduced. 2 O·nSiO 2 The modulus n is optimized to ensure better bonding effect, which is beneficial to further improve the strength of the pellets; on the other hand, it can prevent the reaction between water glass and boric acid and / or formic acid from being hindered, thereby preventing the removal effect of alkali metal Na from being affected. That is, when the amount of adhesive used is the same, by optimizing Na 2 O·nSiO 2 The modulus can further ensure the structural strength of the pellets.

[0025] As a further improvement of any technical solution of the first aspect of the present invention, the organic binder is preferably one or more of sodium carboxymethyl cellulose, starch, and organic resin adhesives, but other organic binders may also be used.

[0026] The second aspect of the present invention also provides an application of the composite adhesive as described in any technical solution of the first aspect in cold consolidation pellets.

[0027] Furthermore, the mineral raw material for cold-consolidated pellets includes sintered return ore. By optimizing the composition of the adhesive, it can be effectively used for cold-consolidated pellets based on sintered return ore, which not only realizes the resource utilization of sintered return ore, but also effectively prevents alkali metal ions in the water glass adhesive from entering the pellets, and significantly improves the wet strength and dry strength of the pellets, so that it can meet the production requirements of the blast furnace.

[0028] As a further improvement of any technical solution of the second aspect of the present invention, the added amount of the binder accounts for 5-9% of the mass percentage of the mineral raw material.

[0029] As a further improvement of any technical solution of the second aspect of the present invention, the sintered return ore is screened and graded according to the particle size: 0-1mm, 1mm-2mm, 2mm-3mm, 3mm-4mm, 4mm-5mm, and preferably, the mass proportion of particles in the above-mentioned particle size ranges is 38-53%, 16-20%, 12-16%, 9-14%, 8-13%, respectively; further preferably, the mass proportion of particles in the above-mentioned particle size ranges is 44-45%, 18-19%, 14-15%, 11-12%, 10-11%, respectively.

[0030] Through the optimized design of the above-mentioned particle grading, the distribution of sintered return ore particles presents a discontinuous characteristic, eliminating the gaps caused by the blocking and supporting effect of smaller particles, and minimizing the void ratio of aggregates. This graded mixture has both a certain amount of coarse aggregate and a sufficient amount of fine aggregate filling, with a high internal friction angle and cohesion, a small void ratio, a small surface area, and a more significant skeleton effect. Therefore, it can effectively save binders on the basis of meeting the requirements of blast furnace use.

[0031] As a further improvement of any technical solution of the second aspect of the present invention, the mineral raw material also includes magnetite concentrate. By using a combination of magnetite concentrate and sintered return ore as the skeleton of cold-solidified pellets, it is beneficial to further improve the strength of cold-solidified pellets, and it is also beneficial to further reduce the amount of binder used and save costs.

[0032] It is further preferred that magnetite concentrate replaces particles in the range of 0-1 mm in the sintered return ore, that is, the mass proportions of magnetite concentrate and sintered return ore (relative to the total amount of mineral raw materials) are 38-53% and 47-62%, respectively, which is conducive to further improving the strength of the cold-solidified pellets. In addition, it should be noted that a certain amount of magnetite concentrate powder can also be directly added, and the original particles in the range of 0-1 mm in the sintered return ore are retained.

[0033] As a further improvement of any technical solution of the second aspect of the present invention, the green ball compressive strength of the pellets is 20-60N / Pellet, the green ball drop strength is greater than 20 times / 0.5m, and the dry ball compressive strength is 2100-2700N / Pellet.

[0034] As a further improvement of any technical solution of the second aspect of the present invention, the method for preparing cold-consolidated pellets comprises: cold-pressing a pellet mixture containing mineral raw materials and a binder to obtain cold-consolidated pellets.

[0035] Furthermore, the method further comprises: drying the cold-consolidated pellets obtained by the cold-pressing process to obtain cold-consolidated pellet dry balls, preferably drying at 90-110° C. for 7-9 hours, wherein the ethanol solution that is not squeezed out further evaporates and leaves the pellets under high-temperature drying.

[0036] Furthermore, the cold pressing balling process is carried out by a powder tablet press, the molding pressure is 30-90MPa, and the pressing time is 30-45s; the molding pressure is further preferably 45-90MPa, further preferably 45-75MPa, and further preferably 60-75MPa. By strictly controlling the molding pressure, the Na dissolved in the solvent can be + The silicate is squeezed out with the solvent, while the gel-like substance, silicate, remains in the cold-solidified pellets because its fluidity is lower than that of ethanol, and makes the pellets stronger than Na + The removal rates are well coordinated.

[0037] Furthermore, during the pressing process of the cold-consolidated pellets, a proper amount of pure water is added to the pellet mixture, and the total amount of water added accounts for 5% to 9% of the total mass of the mineral raw materials. Considering that the binder contains moisture, the amount of water added can be reduced appropriately.

[0038] Furthermore, after cold pressing, the cold-consolidated pellets are dried to obtain finished pellets, wherein the unextruded solution evaporates and leaves the pellets under high temperature drying. More preferably, the drying is carried out at 100-120°C for 6-10 hours.

[0039] 3. Beneficial effects

[0040] Compared with the existing sintering return ore utilization technology, the beneficial effects of the present invention are:

[0041] (1) The present invention provides a composite binder, which can effectively reduce the amount of water glass added and prevent the alkali metal ions in the water glass from entering the pellets through the modification of water glass on the one hand and the compounding of an organic binder and a nucleating agent on the other hand; at the same time, it can also effectively improve the quality of the pellets, increase the strength and burst temperature of the green pellets, and increase the compressive strength of the finished pellets to meet the production requirements of the blast furnace.

[0042] (2) The present invention uses boric acid and / or formic acid as a modifier to modify water glass, and uses anhydrous ethanol as a solvent, so that boric acid and / or formic acid react with water glass to generate silicic acid and sodium salt that are insoluble in water and ethanol, wherein sodium ions are dissolved in anhydrous ethanol. Since the fluidity of silicic acid is significantly lower than that of ethanol, it is convenient to squeeze out sodium ions along with ethanol in the subsequent pressing process to form pellets, while silicic acid is retained in the pellets, thereby achieving effective removal of sodium ions.

[0043] (3) The present invention optimizes the particle size distribution of the sintered return ore and adds magnetite concentrate to replace part of the sintered return ore as the cold-consolidated pellet skeleton, thereby reducing the porosity of the pellet aggregate, further enhancing the cold compressive strength of the pellet and reducing the amount of adhesive used. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 The morphology of dry balls of cold pressed pellets under different molding pressures. DETAILED DESCRIPTION

[0045] In order to further understand the content of the present invention, the present invention is now described in detail in conjunction with specific embodiments.

[0046] It should be noted that the specific composition of the sintered return ore and the magnetite concentrate powder is not limited in the present application. The composition of the sintered return ore preferably includes: wTFe: 55-60%, wFeO: 5-10%, wCaO: 8-12%; the composition of the magnetite concentrate powder preferably includes: wTFe: 65-70%, wFeO: 20-30%, wSiO 2 : 1-2%, and more preferably the particle size composition is: the mass of particles less than 200 mesh accounts for 25%-30%, the mass of particles from 200 mesh to 400 mesh accounts for 50%-70%, and the particle size of the remaining particles is greater than 400 mesh.

[0047] In addition, due to limited space, only some embodiments are listed below, but the protection scope of this application, especially the mass proportion of each component, the process parameter value, and the chemical composition of the sintered return ore and the magnetite concentrate, are not limited to the following specific embodiments, and each process parameter value can be any range value within the corresponding parameter value range in the technical solution, or any specific value. For example, the cold pressing pressure is 30-90MPa, and its value can be 30-45MPa, 40-60MPa, 65-80MPa, 70-90MPa, etc., or 30MPa, 45MPa, 60MPa, 70MPa, 90MPa, etc., or specific values.

[0048] Example 1

[0049] The present embodiment provides a cold-consolidated pellet based on sintered return ore, wherein the pellet raw materials include mineral raw materials and a composite adhesive, wherein: the mineral raw materials include sintered return ore, the composite adhesive includes a modified water glass solution, an organic binder and a nucleation aid, the modified water glass solution is obtained by modifying water glass with boric acid, and anhydrous ethanol is added as a solvent during the modification, and after the modification, colloidal silicic acid and sodium salt insoluble in water and ethanol are obtained, wherein the sodium ions are soluble in ethanol; the organic binder is sodium carboxymethyl cellulose, and the nucleation aid is nano-silica, and the particle size of which is 50-100 nanometers.

[0050] Specifically, the chemical composition of the sintered return ore in this embodiment is shown in Table 1 below, and the grading is screened and graded according to the grading scheme in Table 2 below; the addition amount of each component in the composite adhesive is calculated as a percentage of the mass of the mineral raw material, water glass Na 2 O·nSiO 2 It accounts for 4% (the modulus n is 2.5), boric acid accounts for 1%, organic binder accounts for 0.7%, nucleation aid accounts for 0.3%, and the added mass of anhydrous ethanol when modifying water glass accounts for 2% of the total mass of water glass and boric acid.

[0051] Table 1 Chemical composition of sintered ore (wt.%)

[0052]

[0053] Table 2 Grading scheme of sintered ore

[0054]

[0055] The method for preparing the cold-consolidated pellets of this embodiment comprises the following steps:

[0056] Step 1: Screen the sintered ore according to the particle size classification and prepare it according to the particle size grading.

[0057] Step 2: Pre-modify the water glass in the composite binder: 4 g of water glass and 1 g of boric acid were mixed and stirred, and 2% anhydrous ethanol (2% of the total mass of water glass and boric acid) was slowly added, stirred for 7 minutes and allowed to stand for 30 minutes to modify the water glass, producing a water-insoluble viscous substance of silicate and sodium salt, wherein Na + Dissolved in anhydrous ethanol.

[0058] Step 3: Mix the sintered ore, modified water glass solution, organic binder and nucleation aid in proportion to prepare a mixture, and add a proper amount of pure water to the mixture, the total amount of water added accounts for 7% of the total mass of the mineral raw materials.

[0059] Step 4: using a pellet press to prepare cold-consolidated pellets;

[0060] The cold-pressed pellets were prepared using a ZYP-20TS fully automatic powder tablet press with a molding pressure of 60 MPa, a mold diameter of 20 mm, and a pressing time of 40 s.

[0061] Step 4: Dry the cold-consolidated pellets at 100° C. for 8 hours to obtain cold-consolidated pellet dry balls.

[0062] Example 2

[0063] The present embodiment provides a cold-consolidated pellet based on sintered return ore, wherein the pellet raw materials include mineral raw materials and a composite adhesive. Compared with Embodiment 1, the present embodiment is mainly different in that magnetite concentrate is added to the mineral raw materials to replace the 0-1 mm sintered return ore to further improve the cold compressive strength of the pellets, that is, the mass of the magnetite concentrate and the sintered return ore in the present embodiment accounts for 44.72% and 55.28% of the total mineral raw materials, respectively.

[0064] Comparative Example 1

[0065] The mineral raw material composition of the cold-consolidated pellets in this comparative example is the same as that in Example 2, the main difference is that in this comparative example, 7% water is added to the mineral raw material during the cold-consolidated pellet molding, but no adhesive is added.

[0066] Comparative Example 2

[0067] The composition of the cold-consolidated pellets in this comparative example is basically the same as that in Example 2, except that this comparative example only uses water glass as a binder.

[0068] Comparative Example 3

[0069] The composition of the cold-consolidated pellets in this comparative example is basically the same as that in Example 2, except that this comparative example only uses boric acid-modified water glass as a binder.

[0070] Comparative Example 4

[0071] The composition of the cold-consolidated pellets in this comparative example is basically the same as that in Example 2, except that this comparative example uses a mixture of unmodified water glass, an organic binder and a nucleating aid as a binder.

[0072] Comparative Example 5

[0073] The cold-consolidated pellets of this comparative example have a composition substantially similar to that of Example 2, with the main difference being that this comparative example uses a mixture of a boric acid-modified water glass solution and a nucleation aid as a binder.

[0074] Comparative Example 6

[0075] The composition of the cold-consolidated pellets in this comparative example is basically the same as that in Example 2, except that this comparative example uses a mixture of a boric acid-modified water glass solution and an organic binder as a binder.

[0076] Performance test results:

[0077] The green ball compressive strength of the pellets prepared in Comparative Example 1 is 2-4N / Pellet, the green ball drop strength is 0-4 times / 0.5m, and the dry ball compressive strength is 1000-1500N / Pellet. The dry ball compressive strength of the pellets prepared in Comparative Example 2 is improved compared with that in Comparative Example 1, but all the Na + All of them enter the pellets without being removed; specifically, in Comparative Example 2, the green ball compressive strength of the pellets is 3-6N / Pellet, the green ball drop strength is 1-5 times / 0.5m, and the dry ball compressive strength is 1300-1800N / Pellet, which does not meet the blast furnace production requirements (2000N / Pellet). Comparative Example 3 By modifying the water glass, part of the Na-containing can be effectively removed during the pellet pressing process. + of water, which reduces the alkali metal content of the pellets, but the dry ball compressive strength of the pellets is slightly lower than that of the pellets in Comparative Example 2. The green ball compressive strength of the obtained pellets is 2-6N / Pellet, the green ball drop strength is 1-4 times / 0.5m, and the dry ball compressive strength is 1000-1600N / Pellet, which still does not meet the blast furnace production requirement (2000N / Pellet).

[0078] According to the above comparative experiments, the alkali metal content in the cold-consolidated pellets can be effectively reduced by modifying the water glass, but it will also reduce the dry ball compressive strength of the cold-consolidated pellets. On this basis, the present invention can effectively improve the wet ball strength and dry ball strength of the pellets by adding organic binders and nucleating aids to the binder, meet the requirements of transportation and automated batching for pellet strength, and maintain the pellets without breaking at high temperatures; and when the modified water glass is used in combination with the organic binder and the nucleating aid, through the mutual promotion of the three, compared with the composite use of unmodified water glass with the organic binder and the nucleating aid, it can not only effectively improve the de-sodium effect of the pellets, but also further improve the solidification effect of the pellets and improve the structural strength of the pellets. The dry ball compressive strength of the pellets prepared by the present invention can exceed 2000N / Pellet, which can meet the production requirements of the blast furnace, and at the same time reduce the Na in the cold-consolidated pellets. + concentration, thus reducing the amount of alkali metals entering the furnace and the damage to the blast furnace as a whole.

[0079] The specific principle of the present invention is as follows: water glass reacts with acid: Na 2 O·nSiO 2 +H+ →H 2 SiO 3 +Na + +H 2 O, producing water-insoluble silica, which can not only improve the raw ball compression and drop strength of cold-consolidated pellets. At the same time, under the molding pressure of 30-90Mpa, Na + It is squeezed out with water and ethanol, of which more than 40% of Na ions are discharged with water and ethanol. However, the fluidity of silica gel during pellet pressing is lower than that of water and ethanol, and it is not easy to be squeezed out. If the molding pressure is too high, colloidal silica will be squeezed out of the pellet. If the molding pressure is too low, the Na + Most of the solution will remain in the pellets. Since the surface of the sintered ore is not smooth and has many gaps, the organic binder penetrates into the gaps or bumps of the sintered ore. After solidification, it generates a meshing force in the interface area, which adheres the sintered ore of different particle sizes together, which is conducive to further improving the bonding force of the cold-consolidated pellets and reducing the porosity of the finished balls. It also binds the hydroxyl or carboxyl functional groups to the H in the silicate colloid. + react to replace H + Play Na + Consolidation effect on cold consolidated pellets.

[0080] Specifically, the green ball compressive strength of the pellets in Example 1 is 25-35 N / Pellet, the green ball drop strength is 15-20 times / 0.5 m, and the dry ball compressive strength is 2217.43 N / Pellet. The green ball compressive strength of the pellets in Example 2 is 35-45 N / Pellet, the green ball drop strength is >20 times / 0.5 m, and the dry ball compressive strength is 2100-2700 N / Pellet. The dry ball compressive strength data of the pellets in Examples 1, 2 and Comparative Examples 1-4 are specifically shown in Table 3 below.

[0081] Table 3 Comparison of dry ball strength of cold-consolidated pellets in Examples 1, 2 and Comparative Examples 1-6

[0082]

[0083] In addition, taking Example 2 as an example, the effects of different pressing pressures on the dry ball strength and Na + The removal rate is affected by the following table 4 and Figure 1 As shown in Table 4 and Figure 1 It can be seen that when the ball-forming pressure is changed, the sodium ion removal rate increases with the increase of the ball-forming pressure. When the ball-forming pressure exceeds 60MPa, the silica-like composite binder is squeezed out of the cold-consolidated pellets, resulting in a decrease in the compressive strength of the cold-consolidated pellets. Therefore, the optimal ball-forming pressure is 60MPa, at which the sodium ion removal rate is 43.27%.

[0084] Table 4 Effect of pelletizing pressure on dry ball strength and Na + Effect of removal rate

[0085]

[0086] Example 3

[0087] The cold-consolidated pellets of this embodiment have the same components as those of embodiment 2, except that: 2 O·nSiO 2 The modulus n is 2.3.

[0088] Example 4

[0089] The cold-consolidated pellets of this embodiment have the same components as those of embodiment 2, except that: 2 O·nSiO 2 The modulus n is 2.4.

[0090] Comparative Example 7

[0091] The cold-consolidated pellets in this comparative example have the same components as those in Example 2, except that: 2 O·nSiO 2 The modulus n is 2.

[0092] Comparative Example 8

[0093] The cold-consolidated pellets in this comparative example have the same components as those in Example 2, except that: 2 O·nSiO 2 The modulus n is 3.

[0094] Example 5

[0095] The cold-consolidated pellets of this embodiment have basically the same components as those of Embodiment 2, with the main difference being that the grading index m of the sintered return ore in this embodiment is 0.4, and magnetite concentrate is used instead of the 0-1 mm sintered return ore, that is, the mass proportion of magnetite concentrate in the mineral raw material is 52.53%.

[0096] Table 5 Grading scheme of sintered ore

[0097]

[0098] Example 6

[0099] The cold-consolidated pellets of this embodiment have basically the same components as those of Embodiment 1, with the main difference being that the grading index m of the sintered return ore in this embodiment is 0.6, and magnetite concentrate is used instead of the 0-1 mm sintered return ore, that is, the mass proportion of magnetite concentrate in the mineral raw material is 38.07%.

[0100] Table 6 Grading scheme of sintered ore

[0101]

[0102] Comparative Example 9

[0103] The cold-consolidated pellets in this comparative example have the same components as those in Example 1, with the main difference being that the gradation index m of the sintered return ore in this comparative example is 0.3.

[0104] Comparative Example 10

[0105] The cold-consolidated pellets of this comparative example have the same components as those of Example 1, with the main difference being that the gradation index m of the sintered return ore in this comparative example is 0.7.

[0106] Combining Example 2, Example 5, Example 6, and Comparative Example 9 and Comparative Example 10, it can be seen that when the amount of adhesive used is the same, when the gradation index m is 0.4-0.6, the porosity of the aggregate can be effectively reduced, which is beneficial to improving the strength of the pellet and reducing the amount of adhesive used. It is further preferred that m=0.5, and magnetite concentrate is used to replace the 0-1mm particles in the graded sintered return ore, and the strength of the resulting cold-consolidated pellet is optimal. When the gradation index m is too low, due to the excessive proportion of fine particles in the pellet raw material, the specific surface area of ​​the particles inside the pellet is large, and the average distribution of the binder on the particle surface is reduced, resulting in a decrease in the compressive strength of the pellet; when the gradation index m is too high, the proportion of coarse particles in the pellet is large, there are many internal voids, and the fine iron concentrate cannot effectively fill the voids, resulting in a loose pellet structure and a decrease in overall compressive strength. At the same time, the cold-solidified pellets formed by the composite of sintered return ore and magnetite concentrate under the grading index m of the present invention have significantly lower porosity and significantly improved density than the pellets made of ungraded sintered return ore and the pellets prepared entirely from graded sintered return ore (without adding magnetite concentrate).

[0107] Example 7

[0108] The cold-consolidated pellets of this embodiment have the same components as those of embodiment 2, except that: in the composite adhesive of this embodiment, starch is used as the organic binder, and nano-alumina is used as the nucleating aid, and the particle size is 100-200 nanometers; the addition amount of each component in the adhesive is calculated as the mass percentage of the mineral raw materials (sintering return ore + magnetite concentrate), and water glass Na 2 O·nSiO 2(n is 2.5) accounts for 5%, boric acid accounts for 2%, organic binder accounts for 0.3%, nucleation aid accounts for 0.1%, and the amount of anhydrous ethanol added when modifying the water glass accounts for 4% of the total amount of water glass and boric acid.

[0109] The method for preparing the cold-consolidated pellets of this embodiment comprises the following steps:

[0110] Step 1: Screen the sintered ore according to the particle size classification and prepare it according to the particle size distribution;

[0111] Step 2, pre-modifying the water glass in the composite binder;

[0112] Step 3: Mix the sintered return ore, magnetite concentrate A, modified water glass solution, organic binder and nucleation aid in proportion to prepare a mixture, and add an appropriate amount of pure water to the mixture, the total amount of water added accounts for 9% of the total mass of the mineral raw materials;

[0113] Step 4: using a pellet press to prepare cold-consolidated pellets;

[0114] The cold-pressed pellets were prepared using a ZYP-20TS fully automatic powder tablet press, with the molding pressure set to 90 MPa, the die diameter to 20 mm, and the pressing time to 30 s;

[0115] Step 4: Dry the cold-consolidated pellets at 110° C. for 7 hours to obtain dry balls of the cold-consolidated pellets. The dry ball compressive strength of the cold-consolidated pellets prepared in this example is shown in Table 7.

[0116] Example 8

[0117] The cold-consolidated pellets of this embodiment have the same components as those of embodiment 2, except that: in the composite adhesive of this embodiment, the modified water glass solution is obtained by modifying water glass with formic acid, the organic binder is sodium carboxymethyl cellulose and an organic resin adhesive (mixed in a mass ratio of 1:1), the nucleating aid is nano-silicon dioxide and nano-alumina (mixed in a mass ratio of 2:1), and the addition amount of each component in the adhesive is calculated as a mass percentage of the mineral raw materials (sintered return ore + magnetite concentrate), and the water glass Na is 0.0447 W / m2 / g / cm2. 2 O·nSiO 2 The amount of anhydrous ethanol added during the modification of water glass accounts for 3% of the total amount of water glass and formic acid, while the amount of formic acid added accounts for 3%.

[0118] The method for preparing the cold-consolidated pellets of this embodiment comprises the following steps:

[0119] Step 1: Screen the sintered ore according to the particle size classification and prepare it according to the particle size distribution;

[0120] Step 2, pre-modifying the water glass in the composite binder;

[0121] Step 3: Mix the sintered return ore, magnetite concentrate A, modified water glass solution, organic binder and nucleation aid in proportion to prepare a mixture, and add an appropriate amount of pure water to the mixture, the total amount of water added accounts for 5% of the total mass of the mineral raw materials;

[0122] Step 4: using a pellet press to prepare cold-consolidated pellets;

[0123] The cold-pressed pellets were prepared using a ZYP-20TS fully automatic powder tablet press with a molding pressure of 30 MPa, a mold diameter of 20 mm, and a pressing time of 45 s.

[0124] Step 4: Dry the cold-consolidated pellets at 95° C. for 9 hours to obtain dry balls of cold-consolidated pellets. The dry ball compressive strength of the cold-consolidated pellets prepared in this example is shown in Table 7.

[0125] Example 9

[0126] The cold-consolidated pellets of this embodiment have basically the same components as those of Embodiment 2, with the main difference being that in the composite adhesive of this embodiment, the modified water glass solution is obtained by modifying water glass with a mixed acid of formic acid and boric acid (mass ratio 1:1). When water glass is modified with a mixed acid of formic acid and boric acid, the dry ball strength of the obtained pellets can be further improved.

[0127] Table 7 Comparison of dry ball strength of cold consolidated pellets in Examples 3-9 and Comparative Examples 7-10

[0128]

Claims

1. Iron ore powder briquetting composite binder, characterized in that: The composite binder comprises the following components in parts by weight: 5-8 parts of modified water glass solution; 0.3-0.7 parts of organic binder; Nucleating agent 0.1-0.3 parts; Wherein, the modified water glass solution is obtained by modifying water glass with boric acid and / or formic acid, and the nucleating agent is nano silicon dioxide and / or nano aluminum oxide.

2. The composite adhesive according to claim 1, characterized in that: The mass ratio of the boric acid and / or formic acid to the water glass is (1-3):(4-5), and anhydrous ethanol is used as a solvent when modifying the water glass.

3. The composite adhesive according to claim 2, characterized in that: The modification process of water glass comprises: contacting / mixing water glass with boric acid and / or formic acid in anhydrous ethanol, and generating silicic acid and sodium salt, which are viscous substances insoluble in ethanol, after standing. + Dissolved in anhydrous ethanol; And / or the mass percentage of the anhydrous ethanol to the total amount of boric acid and / or formic acid and water glass is 2-4%.

4. The composite adhesive according to any one of claims 1 to 3, characterized in that: The modulus n of the water glass is 2.3-2.5; and / or the organic binder is one or more of sodium carboxymethyl cellulose, starch, and organic resin adhesives.

5. Use of the composite binder according to any one of claims 1 to 4 in cold consolidation pellets.

6. The use according to claim 5, characterized in that: The mineral raw material for cold-consolidated pellets comprises sintered return ore.

7. The use according to claim 6, characterized in that: The added amount of the composite binder accounts for 5-9% of the mass percentage of the mineral raw material; and / or The sintered return ore is screened and graded according to the particle size: 0-1mm, 1mm-2mm, 2mm-3mm, 3mm-4mm, and 4mm-5mm, and the mass proportion of particles in the above particle size ranges is 38-53%, 16-20%, 12-16%, 9-14%, and 8-13%, respectively.

8. The cold-consolidated pellets based on sintered return ore according to claim 7, characterized in that: The mineral raw material also contains magnetite concentrate, and the magnetite concentrate is used to replace the sintered return ore within the range of 0-1 mm.

9. The use according to any one of claims 5 to 8, characterized in that: The green ball compressive strength of the cold-consolidated pellets is 20-60 N / Pellet, the green ball drop strength is greater than 20 times / 0.5 m, and the dry ball compressive strength is 2100-2700 N / Pellet.

10. The use according to any one of claims 5 to 8, characterized in that: The cold-consolidated pellets are pelletized by a powder tablet press, with a molding pressure of 30 to 90 MPa and a pressing time of 30 to 45 seconds.

Images