A magnesium-based composite binder, its preparation method and application in iron ore pellets

Abstract

The present invention discloses a magnesium-based composite binder, a preparation method thereof and an application in iron ore pellets, belonging to the technical field of pellet production. The magnesium-based composite binder comprises components such as fine-grained magnesium-containing material powder, sodium carboxymethyl cellulose and humic acid. The preparation method is to uniformly mix the fine-grained magnesium-containing material powder with sodium carboxymethyl cellulose, humic acid and water, then perform ultrasonic treatment to obtain a mixed material, and the mixed material is dried, crushed and ground to obtain the magnesium-based composite binder. When it is used in the production of iron concentrate pellets, it can ensure that the finished pellet ore has a high iron grade while obtaining good metallurgical properties.

Description

Technical Field

[0001] The present invention relates to a binder, in particular to a magnesium-based composite binder, and also relates to a preparation method of the magnesium-based composite binder and its application in iron ore pellets, belonging to the technical field of pellet ore preparation. Background Art

[0002] At present, the domestic iron concentrate resources have poor endowments and low utilization rates. For example, fluorine-containing iron ore, as one of the iron ores with rich reserves in China, has the characteristics of high calcium, low silicon, and rich in impurity elements (fluorine, sulfur, potassium, and sodium). In the prior art, serpentine is usually added to fluorine-containing iron concentrate pellets to improve the strength of oxidized pellets and regulate metallurgical properties. However, when serpentine is selected as the magnesian flux, the pellets prepared from fluorine-containing iron concentrate have problems such as low strength of the finished pellets (lower than 2500 N) and high reduction swelling index (higher than 50%). In addition, a binder usually needs to be added during the production of fluorine-containing pellet ore to ensure the pellet quality. The existing binders used in the production of fluorine-containing pellet ore are mainly bentonite, and the addition amount is generally 2.0% - 3.0%, and even up to 4.0% in some cases. The addition of excessive bentonite not only increases the production cost, but also reduces the iron grade of the finished pellet ore, which is not conducive to blast furnace smelting. Therefore, developing a binder product to replace bentonite, reducing the pellet production cost, and improving the properties of fluorine-containing iron ore pellets are of great significance for expanding the utilization rate of iron ore resources. Summary of the Invention

[0003] Aiming at the technical problems existing in the production of existing iron ore pellets, especially fluorine-containing iron ore pellets, such as high binder consumption and poor metallurgical properties of the finished pellets, the first object of the present invention is to provide a magnesium-based composite binder, which can be used to replace the conventional iron ore pellet binder, reduce the binder consumption during the production of iron ore pellets to improve the iron grade of the iron ore pellets, and simultaneously obtain iron ore pellets with better metallurgical properties.

[0004] The second object of the present invention is to provide a preparation method of the magnesium-based composite binder, which has simple operation, short process, wide raw material sources, and low cost, and meets the requirements of industrial production.

[0005] The third object of the present invention is to provide an application of the magnesium-based composite binder in the preparation of iron ore pellets. When it is used in the production process of iron ore pellets, its addition amount is small, and the binding effect is excellent. While ensuring a relatively high iron grade of the pellet ore, finished pellet ore with good metallurgical properties can be obtained.

[0006] To achieve the above technical objectives, the present invention provides a magnesium-based composite binder, which is composed of the following components by mass percentage: 90-95% of fine-grained magnesium-containing material powder; 3-8% of sodium carboxymethylcellulose; 2-4% of humic acid; the mass content of MgO in the fine-grained magnesium-containing material powder is 40%-65%, and the mass content of SiO2 is 30%-60%; the particle size of the fine-grained magnesium-containing material powder satisfies that the mass proportion of the -10μm particle size is more than 90%.

[0007] The fine-grained magnesium-containing material powder in the magnesium-based composite binder of the present invention serves as an inorganic component. On the one hand, it provides the required MgO and SiO2 components for the pellet, which can improve the pellet strength and metallurgical properties. On the other hand, as a micro-nano-level carrier material, it can adsorb organic components such as sodium carboxymethylcellulose and humic acid on its surface, enabling the better exertion of the binding effect of the organic binder. Sodium carboxymethylcellulose and humic acid, as organic binder components with low combustion residues, have strong hygroscopicity and advantages such as high viscosity and good binding performance, which can ensure the green pellet and dry pellet strength of the pellet. At the same time, by stably attaching sodium carboxymethylcellulose and humic acid to the surface of the magnesium-containing material powder, the highly dispersed state of the magnesium-containing material powder in the pellet can be strengthened by the binding effect of the organic binder, enabling the better exertion of the performance of the magnesium-containing material powder and improving the oxidation pellet strength and metallurgical properties.

[0008] In the magnesium-based composite binder of the present invention, the magnesium-containing material powder is the main component. If its content is too low, the MgO and SiO2 contents of the binder will be reduced. If its proportion is too high, the binding effect of the magnesium-based composite binder will be reduced. Appropriate amounts of humic acid and sodium carboxymethylcellulose can improve the complexation between polar groups in the organic binder and improve the binding effect of the organic binder. If the proportion of humic acid and sodium carboxymethylcellulose is too low, the stability of the magnesium-based composite binder will become poor and the sintering strength of the pellet will be reduced. The proportions of these two organic binders, sodium carboxymethylcellulose and humic acid, need to be coordinated and controlled to strengthen the synergistic effect between them and ensure the excellent binding performance of the magnesium-based composite binder.

[0009] The MgO and SiO2 contents of the magnesium-containing material powder of the present invention are relatively high, which can improve the oxidation strength and reduction swelling performance of iron ore pellets.

[0010] The magnesium-containing material powder with a micro-nano level in the present invention can greatly increase its specific surface area to provide more attachment surfaces, which is also more conducive to its uniform dispersion in the pellet and has high reaction activity.

[0011] As a preferred solution, the magnesium-containing material powder is at least one of serpentine powder, Pidgeon process magnesium smelting slag powder, and waste magnesium refractory brick powder. The present invention selects natural magnesium-containing minerals or solid wastes as the main components of the magnesium-based composite binder. While achieving the goal of resource utilization of magnesium-containing solid wastes, it replaces the use of binders in iron ore pellet production to reduce the amount of binder used, increase the iron grade of iron ore pellets, and improve the metallurgical properties of iron ore pellets.

[0012] The present invention also provides a preparation method of a magnesium-based composite binder. In this method, fine-grained magnesium-containing material powder is mixed evenly with sodium carboxymethylcellulose, humic acid, and water, and then ultrasonic treatment is carried out to obtain a mixed material. The mixed material is dried, crushed, and ground to obtain the product.

[0013] In the preparation process of the magnesium-based composite binder of the present invention, by wet-mixing the fine-grained magnesium-containing material powder with sodium carboxymethylcellulose and humic acid, the adsorption efficiency of sodium carboxymethylcellulose and humic acid on the surface of the magnesium-containing material powder can be improved. Especially under the action of ultrasonic waves, the dispersion degree of the magnesium-containing material powder can be increased, and at the same time, the uniform adsorption of the organic binder on the surface of the serpentine powder particles can also be promoted, achieving a better modification effect.

[0014] As a preferred solution, the conditions for ultrasonic treatment are: the temperature is 60 - 90 °C, the ultrasonic frequency is 20 - 30 KHz, and the ultrasonic time is 15 - 40 min. By mixing under ultrasonic assistance and appropriate temperature conditions, it is beneficial to promote the uniform adsorption of the organic binder on the surface of the serpentine powder particles, achieving a better modification effect and ensuring the stable performance of the magnesium-based composite binder.

[0015] As a preferred solution, the drying temperature is 80 - 90 °C.

[0016] As a preferred solution, the grinding is carried out to ensure that the mass percentage content of the particle size -0.045 mm particle size grade is not less than 92%.

[0017] The present invention also provides an application of the magnesium-based composite binder, which is used for preparing iron ore pellets.

[0018] As a preferred solution, the magnesium-based composite binder is mixed with iron ore concentrate raw materials to make pellets, and the obtained green pellets are heat-treated to obtain finished pellets.

[0019] As a more preferred solution, the heat treatment includes preheating and roasting; the conditions for preheating are: the temperature is 920 - 950 °C, and the time is 10 - 15 min; the conditions for roasting are: the temperature is 1230 - 1250 °C, and the time is 15 - 20 min.

[0020] As a more preferred embodiment, the dry basis mass of the magnesium-based composite binder accounts for 1.5-2.5% of the dry basis mass of the iron concentrate. Compared with the existing bentonite binder, the magnesium-based composite binder has the characteristics of less dosage and good bonding effect.

[0021] As a preferred embodiment, the particle size of the iron concentrate satisfies that the mass percentage content of the particle size of -0.074 mm is not less than 80%, and the specific surface area is not less than 800 cm 2 / g. Iron concentrate with fine particle size and high specific surface area is more conducive to contacting and combining with the magnesium-based composite binder.

[0022] The iron concentrate of the present invention includes ordinary iron concentrates, such as magnetite, etc., and can also be fluorine-containing iron ore.

[0023] Compared with the prior art, the beneficial effects brought by the technical solution of the present invention are as follows:

[0024] The magnesium-based composite binder of the present invention has the characteristics of high contents of MgO and SiO2. When it is used in the production of pellet ore, it has the characteristics of less addition amount and excellent bonding effect. While being able to improve the iron grade of iron ore pellet ore, pellet ore with good metallurgical properties can be obtained. For example, when the dosage of the magnesium-based composite binder is 1.5% - 2.5%, the green pellet strength is not less than 5.4 times / 0.5m, the compressive strength of roasted pellets can reach more than 2500 N / piece, the reduction degradation is not less than 98%, and the total iron grade TFe of the finished pellet ore can be increased by more than 1%.

[0025] The preparation method of the magnesium-based composite binder of the present invention is simple in operation, short in process, wide in raw material source, low in cost, and meets industrial production. Specific Embodiments

[0026] The following examples are intended to illustrate the content of the present invention, rather than limiting the protection scope of the claims of the present invention.

[0027] In the following examples and comparative examples: the magnesium-containing materials used are at least one of serpentine powder, powder of magnesium produced by Pidgeon process slag, and waste magnesia refractory brick powder.

[0028] In the following examples and comparative examples: the sodium carboxymethyl cellulose used is purchased from Shanghai Macklin Biochemical Co., Ltd., CAS No.: 9004-32-4; the humic acid is a conventional commercial reagent.

[0029] In the following examples and comparative examples: Taking fluorine-containing iron concentrate (TFe is 64%, SiO2 is 2%, CaO is 2%, MgO is 1%, Al2O3 is 1%, F is 0.4%, Na2O is 0.12, K2O is 0.11%) and ordinary magnetite (TFe is 65%, SiO2 is 4%, CaO is 2%, MgO is 1%, Al2O3 is 1%) as examples. The particle size of the iron concentrate used is such that the mass percentage of the -0.044 mm particle size fraction is 90%, and the specific surface area is 870 cm 2 / g. The preheating and roasting conditions of the pellets are fixed as follows: the preheating temperature is 950 °C, the preheating time is 10 min, the roasting temperature is 1250 °C, and the roasting time is 20 min.

[0030] Example 1

[0031] Crush the magnesium-containing material (waste magnesia refractory brick: MgO = 61%, SiO2 = 30%), finely grind it to 90% passing -0.074 mm, take 95 g and grind it in a nano sand mill to 93% passing -10 μm, then mix it with 3 g of sodium carboxymethylcellulose and 2 g of humic acid in 250 mL of water, and in an ultrasonic water bath, the ultrasonic frequency is 29 KHz, and keep the water bath at 80 °C for 15 min. After drying at 95 °C and then grinding, a magnesium-based binder is obtained.

[0032] During application, add the magnesium-based binder to the fluorine-containing iron ore at a ratio of 1.0% of the dry basis mass of the fluorine-containing iron ore and mix well, and then pelletize after wet grinding pretreatment. The drop strength of the green pellets is 6.4 times / 0.5 m, the compressive strength of the roasted pellets is 2528 N / piece, the total iron grade TFe of the finished pellet ore is 64%, the reduction degradation is 99%, and the reduction expansion index is 10%.

[0033] Example 2

[0034] Crush the magnesium-containing material (serpentine: MgO = 44%, SiO2 = 42%), finely grind it to 90% passing -0.074 mm, take 93 g and grind it in a nano sand mill to 90% passing -10 μm, then mix it with 4 g of sodium carboxymethylcellulose and 3 g of humic acid in 250 mL of water, and in an ultrasonic water bath, the ultrasonic frequency is 29 KHz, and keep the water bath at 80 °C for 30 min. After drying at 95 °C and then grinding, a magnesium-based binder is obtained.

[0035] During application, add the magnesium-based binder to the fluorine-containing iron ore at a ratio of 1.5% of the dry basis mass of the fluorine-containing iron ore and mix well, and then pelletize after wet grinding pretreatment. The drop strength of the green pellets is 5.4 times / 0.5 m, the compressive strength of the roasted pellets is 2558 N / piece, the total iron grade TFe of the finished pellet ore is 64%, the reduction degradation is 99%, and the reduction expansion index is 11%.

[0036] Example 3

[0037] Crush the magnesium-containing material (powder of magnesium smelting slag by skin pulp method: MgO = 45%, SiO2 = 41%), finely grind it until 90% is -0.074 mm, take 93 g and grind it in a nano sand mill until 90% is -10 μm, then mix it with 4 g of sodium carboxymethylcellulose and 3 g of humic acid in 250 mL of water. In an ultrasonic water bath, the ultrasonic frequency is 29 KHz, and keep the water bath at 80 °C for 30 min. After drying at 95 °C, grind it to obtain a magnesium-based binder.

[0038] During application, add the magnesium-based binder to the fluorine-containing iron ore according to the proportion of 1.5% of the dry basis mass of the fluorine-containing iron ore and mix well. After pre-treatment by wet grinding, make pellets. The drop strength of the green pellets is 5.6 times / 0.5 m, the compressive strength of the roasted pellets is 2514 N / piece, the total iron grade TFe of the finished pellet ore is 63%, the reduction powdering is 99%, and the reduction expansion index is 12%.

[0039] Example 4

[0040] Crush the magnesium-containing material (serpentine: MgO = 44%, SiO2 = 42%), finely grind it until 90% is -0.074 mm, take 91 g and grind it in a nano sand mill until 92% is -10 μm, then mix it with 5 g of sodium carboxymethylcellulose and 4 g of humic acid in 250 mL of water. In an ultrasonic water bath, the ultrasonic frequency is 29 KHz, and keep the water bath at 80 °C for 15 min. After drying at 95 °C, grind it to obtain a magnesium-based composite binder.

[0041] During application, add the magnesium-based composite binder to the fluorine-containing iron ore according to the proportion of 1.0% of the dry basis mass of the fluorine-containing iron ore and mix well. After pre-treatment by wet grinding, make pellets. The drop strength of the green pellets is 5.9 times / 0.5 m, the compressive strength of the roasted pellets is 2617 N / piece, the total iron grade TFe of the finished pellet ore is 64%, the reduction powdering is 98%, and the reduction expansion index is 13%.

[0042] Example 5

[0043] Crush the magnesium-containing material (serpentine: MgO = 44%, SiO2 = 42%), finely grind it until 90% is -0.074 mm, take 90 g and grind it in a nano sand mill until the proportion of -10 μm is more than 70%, then mix it with 6 g of sodium carboxymethylcellulose and 4 g of humic acid in 250 mL of water. In an ultrasonic water bath, the ultrasonic frequency is 29 KHz, and keep the water bath at 80 °C for 15 min. After drying at 95 °C, grind it to obtain a magnesium-based composite binder.

[0044] During application, the magnesium-based composite binder is added to ordinary magnetite according to the proportion of 1.0% of the dry basis mass of ordinary magnetite and mixed evenly, and then pelletized directly without treatment. The obtained green pellets have a drop strength of 6.2 times / 0.5 m, the roasted pellets have a compressive strength of 2996 N / piece, the total iron grade TFe of the finished pellet ore is 64%, the reduction powdering is 99%, and the reduction expansion index is 11%.

[0045] Comparative Example 1

[0046] Compared with Example 1, the only difference is that the waste magnesia refractory bricks are ground in a nano sand mill until the proportion of -10 μm accounts for 70%. Other operations and conditions refer to Example 1.

[0047] During application, the magnesium-based composite binder is added to fluorine-containing iron ore according to the proportion of 1.0% of the dry basis mass of fluorine-containing iron ore and mixed evenly, and then pelletized after wet grinding pretreatment. The obtained green pellets have a drop strength of 3.5 times / 0.5 m, the roasted pellets have a compressive strength of 2223 N / piece, the total iron grade TFe of the finished pellet ore is 64%, the reduction powdering is 98%, and the reduction expansion index is 13%. Compared with Example 1, the strength of the pellet ore decreases by 305 N, the reduction powdering decreases by 1%, and the reduction expansion increases by 3%. Under the condition that other process conditions remain unchanged, due to the short nano-grinding time of the waste magnesia refractory bricks and the too coarse powder particle size, the humic acid is not evenly adsorbed on the particle surface during the subsequent ultrasonic treatment. In addition, the coarser particle size also leads to a decrease in the strength of the green pellets and weakens the crystal connection effect of hematite during the roasting process. Therefore, the performance of the finished pellet ore decreases significantly.

[0048] Comparative Example 2

[0049] Compared with Example 2, the only difference is that the magnesium-based composite binder is added to fluorine-containing iron ore according to the proportion of 0.5% of the dry basis mass of fluorine-containing iron ore and mixed evenly, and then pelletized after wet grinding pretreatment. Other operations and conditions refer to Example 2.

[0050] The obtained green pellets have a drop strength of 4.4 times / 0.5 m, the roasted pellets have a compressive strength of 2456 N / piece, the total iron grade TFe of the finished pellet ore is 64%, the reduction powdering is 98%, and the reduction expansion index is 13%. Compared with Example 2, the strength of the pellet ore decreases by 102 N, the reduction powdering decreases by 1%, and the reduction expansion increases by 2%. Under the same process conditions, due to the lower addition amount of the magnesium-based composite binder, the lower SiO2 content in the pellets leads to a decrease in the pellet strength and an increase in the reduction expansion.

[0051] Comparative Example 3

[0052] Compared with Example 3, the only difference is that the ultrasonic frequency of 29 KHz and maintaining a water bath at 80 °C for 30 min are replaced with: stirring at 150 rpm and maintaining a water bath at 80 °C for 30 min. Other operations and conditions refer to Example 1.

[0053] The obtained green pellets have a drop strength of 4.1 times / 0.5 m, the roasted pellets have a compressive strength of 2316 N / piece, the total iron grade TFe of the finished pellet ore is 63%, the reduction degradation is 97%, and the reduction swelling index is 15%. Compared with Example 3, the pellet strength is reduced by 198 N, the reduction degradation is reduced by 2%, and the reduction swelling is increased by 3%. Under the condition that other process conditions remain unchanged, since it is difficult to uniformly adsorb the organic components in the humic acid on the surface of the magnesium smelting slag powder by the pulp method without ultrasonic treatment, cluster formation is caused. Therefore, the mineralization process of the pellets is affected, and the pellet properties are reduced.

[0054] Comparative Example 4

[0055] Compared with Example 4, the only difference is that the magnesium-containing material (serpentine: MgO = 44%, SiO2 = 42%) is crushed and finely ground to 90% passing -0.074 mm, 94 g is taken and ground in a nano sand mill to a proportion of more than 70% passing -10 μm, and then mixed with 5 g of sodium carboxymethyl cellulose and 1 g of humic acid in 250 mL of water, and in an ultrasonic water bath, the ultrasonic frequency is 29 KHz, and a water bath at 80 °C is maintained for 15 min. After drying at 95 °C and grinding, a magnesium-based composite binder is obtained.

[0056] The obtained green pellets have a drop strength of 3.8 times / 0.5 m, the roasted pellets have a compressive strength of 2461 N / piece, the total iron grade TFe of the finished pellet ore is 64%, the reduction degradation is 98%, and the reduction swelling index is 13%. Compared with Example 4, the green pellet strength is reduced by 2.1 times / 0.5 m, and the pellet strength is reduced by 156 N. Under the condition that other process conditions remain unchanged, due to the low addition amount of humic acid in the magnesium-based composite binder, the adhesiveness is reduced, and the matching between iron ore particles is weakened. Therefore, the properties of the green pellets and the finished pellets are reduced.

Claims

1. A magnesium-based composite binder, characterized in that: It is composed of sodium carboxymethylcellulose and humic acid stably attached to the surface of magnesium-containing material powder, and its mass percentage composition is as follows: Fine-grained magnesium-containing material powder: 90 - 95%; Sodium carboxymethylcellulose: 3 - 8%; Humic acid: 2 - 4%; In the fine-grained magnesium-containing material powder, the mass content of MgO is 40% - 65%, and the mass content of SiO2 is 30% - 60%; The particle size of the fine-grained magnesium-containing material powder satisfies that the mass proportion of the -10 μm particle size is more than 90%.

2. A magnesium-based composite binder according to claim 1, characterized in that: The fine-grained magnesium-containing material powder is at least one of serpentine powder, magnesium-smelting slag powder by Pidgeon process, and waste magnesium refractory brick powder.

3. The preparation method of a magnesium-based composite binder according to claim 1 or 2, characterized in that: The fine-grained magnesium-containing material powder is mixed evenly with sodium carboxymethylcellulose, humic acid and water, and then ultrasonic treatment is carried out to obtain a mixed material. The mixed material is dried, crushed and ground to obtain the product.

4. The preparation method of a magnesium-based composite binder according to claim 3, characterized in that: The conditions of the ultrasonic treatment are: temperature is 60 - 90 °C, ultrasonic frequency is 20 - 30 KHz, and ultrasonic time is 15 - 40 min.

5. Use of a magnesium-based composite binder according to claim 1 or 2, characterized in that: It is used for preparing iron ore pellets.

6. The application of a magnesium-based composite binder according to claim 5, wherein: The magnesium-based composite binder is mixed and pelletized with iron ore concentrate raw materials, and the obtained green pellets are heat-treated to obtain finished pellets.

7. An application of a magnesium-based composite binder according to claim 6, characterized in that: The heat treatment includes preheating and roasting; The conditions of the preheating are: temperature is 920 - 950 °C, and time is 10 - 15 min; The conditions of the roasting are: temperature is 1230 - 1250 °C, and time is 15 - 20 min.

8. An application of a magnesium-based composite binder according to claim 6, characterized in that: The dry basis mass of the magnesium-based composite binder accounts for 1.5 - 2.5% of the dry basis mass of the iron ore concentrate; The particle size of the iron concentrate meets the requirements that the mass percentage content of the -0.074 mm particle size fraction is not less than 80%, and the specific surface area is not less than 800 cm 2 / g.