A magnesium-based composite binder, a preparation method thereof, and application in iron ore pelletizing

Abstract

The present invention discloses a magnesium-based composite binder, a preparation method thereof, and its application in iron ore pelletization, belonging to the technical field of pelletization production. The magnesium-based composite binder comprises, among other components, fine-grained magnesium-containing material powder, sodium carboxymethyl cellulose, and humic acid. The preparation method comprises uniformly mixing the fine-grained magnesium-containing material powder with the sodium carboxymethyl cellulose, humic acid, and water, followed by ultrasonic treatment to obtain a mixture. The mixture is then dried, crushed, and ground to obtain the magnesium-based composite binder. The binder is used in the production of iron ore concentrate pellets, ensuring that the finished pellets have a high iron grade while also achieving good metallurgical properties.

Description

Technical Field

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

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

[0003] In view of the technical problems of high binder usage and poor metallurgical properties of the finished balls in the production process of existing iron ore pellets, especially fluorine-containing iron ore pellets, the first object of the present invention is to provide a magnesium-based composite binder, which can replace conventional iron ore pellet binders, and is used to reduce the amount of binder used in the iron ore pellet production process to improve the iron grade of the iron ore pellets, and at the same time obtain iron ore pellets with better metallurgical properties.

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

[0005] The third object of the present invention is to provide an application of a magnesium-based composite binder in the preparation of iron ore pellets. When used in the iron ore pellet production process, the added amount is small, and the bonding effect is excellent. While being able to ensure a higher iron grade of the pellets, a finished pellet with good metallurgical properties can be obtained.

[0006] In order to achieve the above technical objectives, the present invention provides a magnesium-based composite binder, which is composed of the following components in mass percentage: 90-95% of fine-grained magnesium-containing material powder; 3-8% of sodium carboxymethyl cellulose; 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 is used as an inorganic component. On the one hand, it provides the required MgO and SiO2 components for the pellets, 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 carboxymethyl cellulose and humic acid on its surface, which can better play the bonding effect of the organic binder. Sodium carboxymethyl cellulose and humic acid, as organic binder components with low combustion residue, have strong hygroscopicity, high viscosity, good bonding performance and other advantages, which can ensure the green ball and dry ball strength of the pellets. At the same time, sodium carboxymethyl cellulose and humic acid are stably attached to the surface of the magnesium-containing material powder, which can rely on the bonding effect of the organic binder to strengthen the high dispersion of the magnesium-containing material powder in the pellets, which can better play the performance of the magnesium-containing material powder and improve the strength and metallurgical properties of the oxidized pellets.

[0008] The magnesium-based composite binder of the present invention contains magnesium material powder as the main component. If the content is too low, the MgO and SiO2 content of the binder will be reduced. If the proportion is too high, the bonding effect of the magnesium-based composite binder will be reduced. The appropriate amount of humic acid and sodium carboxymethyl cellulose can improve the complexation between polar groups in the organic binder and improve the bonding effect of the organic binder. If the proportion of humic acid and sodium carboxymethyl cellulose is too low, the stability of the magnesium-based composite binder will be deteriorated and the sintering strength of the pellets will be reduced. The proportion of sodium carboxymethyl cellulose and humic acid, two organic binders, needs to be coordinated and controlled to strengthen the synergistic effect of the two to ensure the excellent bonding performance of the magnesium-based composite binder.

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

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

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

[0012] The present invention also provides a method for preparing a magnesium-based composite binder, which comprises uniformly mixing fine-grained magnesium-containing material powder with sodium carboxymethyl cellulose, humic acid and water, and then performing ultrasonic treatment to obtain a mixed material, and then drying, crushing and grinding the mixed material to obtain the mixed material.

[0013] In the preparation process of the magnesium-based composite binder of the present invention, fine-grained magnesium-containing material powder is mixed with sodium carboxymethyl cellulose and humic acid by a wet method, which can improve the adsorption efficiency of sodium carboxymethyl cellulose and humic acid on the surface of the magnesium-containing material powder, especially under the action of ultrasound, which can improve the dispersion degree of the magnesium-containing material powder, and also can promote the uniform adsorption of the organic binder on the surface of the serpentine powder particles, thereby achieving a better modification effect.

[0014] As a preferred solution, the ultrasonic treatment conditions are: temperature of 60-90°C, ultrasonic frequency of 20-30KHz, and ultrasonic time of 15-40min. Mixing under ultrasonic assistance and appropriate temperature conditions is conducive to promoting uniform adsorption of the organic binder on the surface of serpentine powder particles, achieving better modification effects, and ensuring 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 performed to meet the particle size of -0.045 mm particle size with a mass percentage content of not less than 92%.

[0017] The present invention also provides an application of a magnesium-based composite binder for preparing iron ore pellets.

[0018] As a preferred solution, a magnesium-based composite binder is mixed with an iron ore concentrate raw material to form balls, and the obtained green balls are subjected to heat treatment to obtain finished balls.

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

[0020] As a more preferred solution, 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. Compared with the existing bentonite binder, the magnesium-based composite binder has the characteristics of less dosage and better bonding effect.

[0021] As a preferred solution, the particle size of the iron ore concentrate satisfies that the mass percentage 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 contact and bonding with magnesium-based composite binder.

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

[0023] Compared with the prior art, the technical solution of the present invention has the following beneficial effects: The magnesium-based composite binder of the present invention has the characteristics of high MgO and SiO2 contents, and is used in pellet production, with the characteristics of small addition amount, excellent bonding effect, etc., and can improve the iron grade of iron ore pellets, and obtain pellets with good metallurgical properties. For example, when the amount of the magnesium-based composite binder is 1.5% to 2.5%, the obtained green ball strength is not less than 5.4 times / 0.5m, the compressive strength of the roasted ball can reach more than 2500 N / piece, the reduction pulverization is not less than 98%, and the total iron grade TFe of the finished pellet can be increased by more than 1%.

[0024] The preparation method of the magnesium-based composite binder of the present invention is simple to operate, has a short process, has a wide source of raw materials, is low in cost, and meets the requirements of industrial production. DETAILED DESCRIPTION

[0025] The following examples are intended to illustrate the present invention rather than to limit the scope of protection of the claims of the present invention.

[0026] In the following examples and comparative examples: the magnesium-containing material used is at least one of serpentine powder, Pidgeon magnesium slag powder, and waste magnesia refractory brick powder.

[0027] In the following examples and comparative examples: the sodium carboxymethyl cellulose used was purchased from Shanghai MacLean Biochemical Technology Co., Ltd., CAS No.: 9004-32-4; ​​humic acid is a conventional commercial reagent.

[0028] In the following examples and comparative examples, 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%) are used as examples. The iron concentrate particle size used is -0.044 mm, the mass percentage of the particle size is 90%, and the specific surface area is 870 cm 2 / g. The preheating and roasting conditions of the pellets were fixed as follows: preheating temperature was 950°C, preheating time was 10 min, roasting temperature was 1250°C, and roasting time was 20 min.

[0029] Example 1 The magnesium-containing material (waste magnesia refractory bricks: MgO=61%, SiO2=30%) was crushed and finely ground to -0.074 mm, accounting for 90%. 95g was ground in a nano sand mill to -10μm, accounting for 93%. Then, it was mixed with 3g sodium carboxymethyl cellulose and 2g humic acid in 250mL water, and kept in an ultrasonic water bath at 80℃ for 15 min at an ultrasonic frequency of 29 KHz. After drying at 95℃, the magnesium-based binder was obtained by grinding.

[0030] When used, the magnesium-based binder is added to the fluorine-containing iron ore at a ratio of 1.0% of the dry basis weight of the fluorine-containing iron ore and mixed evenly, and then balled after pre-treatment with grinding. The drop strength of the obtained green ball is 6.4 times / 0.5m, the compressive strength of the roasted ball is 2528N / piece, the total iron grade TFe of the finished pellet is 64%, the reduction powder is 99%, and the reduction expansion index is 10%.

[0031] Example 2

[0032] The magnesium-containing material (serpentine: MgO=44%, SiO2=42%) was crushed and finely ground to -0.074 mm, accounting for 90%. 93g was taken and ground in a nano sand mill to -10μm, accounting for 90%. Then, it was mixed with 4g sodium carboxymethyl cellulose and 3g humic acid in 250 mL of water, and kept in an ultrasonic water bath at 80℃ for 30min at an ultrasonic frequency of 29 KHz. After drying at 95℃, the magnesium-based binder was obtained by grinding.

[0033] When used, the magnesium-based binder is added to the fluorine-containing iron ore at a ratio of 1.5% of the dry basis weight of the fluorine-containing iron ore and mixed evenly, and then balled after pre-treatment with grinding. The drop strength of the obtained green ball is 5.4 times / 0.5m, the compressive strength of the roasted ball is 2558 N / piece, the total iron grade TFe of the finished pellet is 64%, the reduction powder is 99%, and the reduction expansion index is 11%.

[0034] Example 3

[0035] The magnesium-containing material (slurry magnesium slag powder: MgO=45%, SiO2=41%) was crushed and finely ground to -0.074 mm, accounting for 90%. 93g was ground in a nano sand mill to -10μm, accounting for 90%, and then mixed with 4g sodium carboxymethyl cellulose and 3g humic acid in 250mL water, and kept in an ultrasonic water bath at 80℃ for 30 min at an ultrasonic frequency of 29 KHz. After drying at 95℃, the magnesium-based binder was obtained by grinding.

[0036] When used, the magnesium-based binder is added to the fluorine-containing iron ore at a ratio of 1.5% of the dry basis weight of the fluorine-containing iron ore and mixed evenly, and then pre-treated by grinding to form balls. The drop strength of the obtained green ball is 5.6 times / 0.5m, the compressive strength of the roasted ball is 2514 N / piece, the total iron grade TFe of the finished pellet is 63%, the reduction powder is 99%, and the reduction expansion index is 12%.

[0037] Example 4 The magnesium-containing material (serpentine: MgO=44%, SiO2=42%) was crushed and finely ground to -0.074mm accounting for 90%, and 91g was taken and ground in a nano sand mill to -10μm accounting for 92%, and then mixed with 5g sodium carboxymethyl cellulose and 4g humic acid in 250mL water, and kept in an ultrasonic water bath pot at an ultrasonic frequency of 29KHz and kept at 80℃ for 15 minutes. After drying at 95℃, the magnesium-based composite binder was obtained by grinding.

[0038] When used, the magnesium-based composite binder is added to the fluorine-containing iron ore at a ratio of 1.0% of the dry basis weight of the fluorine-containing iron ore and mixed, and then balled after pretreatment with grinding. The drop strength of the obtained green ball is 5.9 times / 0.5m, the compressive strength of the roasted ball is 2617 N / piece, the total iron grade TFe of the finished pellet is 64%, the reduction powder is 98%, and the reduction expansion index is 13%.

[0039] Example 5 The magnesium-containing material (serpentine: MgO=44%, SiO2=42%) was crushed and finely ground to -0.074mm accounting for 90%, and 90 g was ground in a nano sand mill to -10 μm accounting for more than 70%, and then mixed with 6g sodium carboxymethyl cellulose and 4g humic acid in 250 mL of water, and kept in an ultrasonic water bath at 80°C for 15 minutes at an ultrasonic frequency of 29 KHz. After drying at 95°C, the magnesium-based composite binder was obtained by grinding.

[0040] When used, the magnesium-based composite binder is added to the ordinary magnetite at a ratio of 1.0% of the dry mass of the ordinary magnetite and mixed, and the pellets are directly made without treatment. The drop strength of the obtained green ball is 6.2 times / 0.5m, the compressive strength of the roasted ball is 2996N / piece, the total iron grade TFe of the finished pellet is 64%, the reduction powder is 99%, and the reduction expansion index is 11%.

[0041] Comparative Example 1 Compared with Example 1, the only difference is that the waste magnesia refractory bricks are ground to -10 μm in the nano sand mill, accounting for 70%. Other operations and conditions are the same as those in Example 1.

[0042] When applied, the magnesium-based composite binder is added to the fluorine-containing iron ore in a ratio of 1.0% of the dry basis mass of the fluorine-containing iron ore and mixed, and the ball is formed after pretreatment by grinding. The resulting green ball has a drop strength of 3.5 times / 0.5m, a calcined ball compressive strength of 2223 N / piece, a finished pellet ore full iron grade TFe of 64%, a reduction pulverization of 98%, and a reduction expansion index of 13%. Compared with Example 1, the pellet strength is reduced by 305 N, the reduction pulverization is reduced by 1%, and the reduction expansion is increased by 3%. Under the condition that other process conditions remain unchanged, due to the short nano-sand grinding time of the discarded magnesia refractory brick, the powder particle size is too coarse, resulting in the subsequent ultrasonic treatment. The humic acid is not uniformly adsorbed on the particle surface. In addition, the coarser particle size also leads to a decrease in the strength of the green ball, weakening the crystallization effect of hematite during the roasting process. Therefore, the performance of the finished pellet is significantly reduced.

[0043] Comparative Example 2 Compared with Example 2, the only difference is that the magnesium-based composite binder is added to the fluorine-containing iron ore at a ratio of 0.5% of the dry basis weight of the fluorine-containing iron ore and mixed evenly, and the pellets are formed after pre-treatment by grinding. Other operations and conditions refer to Example 2.

[0044] The drop strength of the obtained green ball is 4.4 times / 0.5m, the compressive strength of the roasted ball is 2456 N / piece, the total iron grade TFe of the finished pellet is 64%, the reduction pulverization is 98%, and the reduction expansion index is 13%. Compared with Example 2, the strength of the pellet is reduced by 102N, the reduction pulverization is reduced by 1%, and the reduction expansion is increased by 2%. Under the same process conditions, due to the low addition amount of magnesium-based composite binder, the lower SiO2 content in the pellet leads to a decrease in pellet strength and an increase in reduction expansion.

[0045] Comparative Example 3

[0046] Compared with Example 3, the only difference is that the ultrasonic frequency is 29 KHz and the temperature is kept at 80°C for 30 min, which is replaced by the temperature is kept at 80°C for 30 min at a stirring speed of 150 rpm. Other operations and conditions refer to Example 1.

[0047] The obtained green ball drop strength is 4.1 times / 0.5m, the roasted ball compressive strength is 2316 N / piece, the finished pellet ore has a total iron grade TFe of 63%, a reduction pulverization of 97%, and a reduction expansion index of 15%. Compared with Example 3, the pellet strength is reduced by 198N, the reduction pulverization is reduced by 2%, and the reduction expansion is increased by 3%. Under the condition that other process conditions remain unchanged, it is difficult to uniformly adsorb the organic components in the humic acid on the surface of the skin pulp magnesium slag powder due to the lack of ultrasonic treatment, resulting in cluster formation. Therefore, the mineralization process of the pellet is affected, reducing the performance of the pellet.

[0048] Comparative Example 4 Compared with Example 4, the only difference is that the magnesium-containing material (serpentine: MgO=44%, SiO2=42%) is crushed and finely ground to -0.074mm accounting for 90%, 94g is taken and ground in a nano sand mill to -10μm accounting for more than 70%, and then mixed with 5g sodium carboxymethyl cellulose and 1g humic acid in 250mL water, and in an ultrasonic water bath pot, the ultrasonic frequency is 29KHz, and the water bath is maintained at 80℃ for 15min. After drying at 95℃, the magnesium-based composite binder is obtained by grinding.

[0049] The drop strength of the obtained green ball is 3.8 times / 0.5m, the compressive strength of the roasted ball is 2461N / piece, the total iron grade TFe of the finished pellet is 64%, the reduction powder is 98%, and the reduction expansion index is 13%. Compared with Example 4, the green ball strength is reduced by 2.1 times / 0.5m, and the pellet strength is reduced by 156 N. Under the condition that other process conditions remain unchanged, due to the low amount of humic acid added in the magnesium-based composite binder, the bonding property is reduced, and the matching between the iron ore particles is weakened. Therefore, the performance of the green ball and the finished ball is reduced.

Claims

1. A magnesium-based composite binder, characterized in that: It is composed of the following components in percentage by weight: Fine-grained magnesium-containing material powder 90~95%; Sodium carboxymethyl cellulose 3~8%; Humic acid 2~4%; The mass content of MgO in the fine-grained magnesium-containing material powder is 40% to 65%, and the mass content of SiO2 is 30% to 60%; The mass proportion of the fine-grained magnesium-containing material powder having a particle size of -10 μm 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, Pidgeon magnesium slag powder, and waste magnesia refractory brick powder.

3. The method for preparing a magnesium-based composite binder according to claim 1 or 2, characterized in that: The fine-grained magnesium-containing material powder is uniformly mixed with sodium carboxymethyl cellulose, humic acid and water, and then subjected to ultrasonic treatment to obtain a mixed material. The mixed material is dried, crushed and ground to obtain the mixed material.

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

5. The use of a magnesium-based composite binder according to claim 1 or 2, characterized in that: Used to prepare iron ore pellets.

6. The use of a magnesium-based composite adhesive according to claim 5, characterized in that: The magnesium-based composite binder is mixed with the iron ore concentrate to form balls, and the obtained green balls are subjected to heat treatment to obtain finished balls.

7. The use of a magnesium-based composite adhesive according to claim 6, characterized in that: The heat treatment includes preheating and calcining; The preheating conditions are: temperature of 920-950°C and time of 10-15 minutes; The calcination conditions are as follows: temperature of 1230-1250° C. and time of 15-20 min.

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