A binder for pellets and a method for using the same

Abstract

The object of the present invention is to provide a binder for pellets and its usage method in view of the problems existing in the prior art. A binder for pellets of the present invention is composed of the following raw materials in mass percentages: 30-45% of corn starch, 20-30% of bamboo fiber, 10-20% of sugar, and 20-40% of bentonite. The usage method of the binder for pellets of the present invention is that the mass percentage of iron ore concentrate to the binder is 99.2-98.0%: 0.8-2.0%. The raw materials of the binder for pellets of the present invention have a wide source and little influence on the grade of pellet ore.

Description

Technical Field

[0001] The present invention belongs to the technical field of iron and steel metallurgy, and particularly relates to a binder for pellets and a method for using the same. Background Art

[0002] In pellet production, almost all pelletizing processes require adding a certain amount of bentonite as a binder for pellets. Bentonite can improve the pelletizing performance of raw materials, increase the strength and bursting temperature of green pellets, and have a certain impact on the strength of pellet ore. However, the main component of bentonite is silicate, and when added to pellets, it will cause a large amount of impurities such as silicon and aluminum to remain in the pellet ore, reducing the grade of the pellet ore. Experiments have shown that for every one percentage point increase in the bentonite addition amount, the grade of the pellet ore with natural alkalinity decreases by about 1.2 percentage points. Since the addition of bentonite has a great impact on the grade of pellet ore, the concept of minimizing the addition amount of bentonite as much as possible when the green pellet indexes meet the production requirements has become a consensus in the industry.

[0003] In order to reduce the addition amount of bentonite in pellets, experts in sintering and pelletizing have also conducted a lot of research. For example, by increasing the fineness of iron ore concentrate or blending concentrates of different ore types, improving the pelletizing performance of pelletizing raw materials, thereby reducing the amount of bentonite used and increasing the grade of pellet ore; or by modifying ordinary bentonite or adding a certain amount of organic binder to form modified bentonite or composite bentonite, reducing the amount of residual impurities of bentonite in pellet ore and increasing the grade of pellet ore. Various methods for reducing the amount of bentonite in pellet ore have also been proposed in many literatures.

[0004] In addition to the literature, some patents also introduce methods for reducing the amount of bentonite used in pellet ore. For example, the patent with the application number CN202011404248.6 discloses a composite binder for improving the pelletizing performance of super iron concentrate powder and its usage method. The components are in mass percentages as follows: sodium-based bentonite 55% - 60%; coarse-grained pulverized coal 25% - 30%; superabsorbent resin 5% - 10%; sodium carboxymethyl cellulose 5% - 10%. This kind of composite binder can replace bentonite as the binder for pellet ore. For example, the patent with the application number CN202110590600.8 discloses a preparation method of an organic binder. The formula is: carbon black 15 - 16%; dolomite 27.5 - 28.5%; glycerol 0.5 - 1.5%; polyethylene 37 - 38%; polyether 1 - 2%; water 16 - 17%. When the dosage is 0.003 - 0.005wt% of iron concentrate, the green pellets and finished pellets obtained have good strength and quality. For example, the patent with the application number CN201010505877.8 discloses a metallurgical pellet composite binder, which mentions using caustic soda and superfine wheat flour to replace sodium carboxymethyl cellulose and configuring it into a composite binder. With a dosage of 0.5%, it can replace 0.8% - 1.2% of bentonite, achieving the purpose of reducing the amount of bentonite used. The components of the composite binders introduced in the above patents are different, and their performances have their own characteristics. However, the general characteristics are that the composition is relatively complex, and the prices of the binder raw materials are relatively high. Summary of the Invention

[0005] The purpose of the present invention is to provide a binder for pellets and its usage method in view of the problems existing in the prior art. The binder for pellets of the present invention has a wide range of raw material sources and little influence on the grade of pellet ore.

[0006] The purpose of the present invention is achieved through the following technical solutions:

[0007] A binder for pellets of the present invention is composed of the following raw materials in mass percentages: corn starch 30 - 45%, bamboo fiber 20 - 30%, sugar 10 - 20%, and bentonite 20 - 40%.

[0008] Further, the sugar is natural disaccharide or polysaccharide or a mixture of multiple disaccharides or a mixture of multiple polysaccharides.

[0009] The usage method of the binder for pellets of the present invention is that the mass percentage of iron concentrate to the binder is 99.2 - 98.0%: 0.8 - 2.0%.

[0010] Further, the usage method of the above-mentioned binder for pellets includes the following steps:

[0011] Step 1: Pretreat the iron concentrate

[0012] Dry-grind the iron concentrate finely so that the specific surface area of the iron concentrate ≥ 1500 cm 2 / g, and -200 mesh ≥ 90%;

[0013] Step 2: Raw material batching

[0014] Take raw materials of iron concentrate, corn starch, bamboo fiber, sugar and bentonite according to the weight ratio. The mass percentage of iron concentrate to binder (composed of corn starch, bamboo fiber, sugar and bentonite) is 99.2 - 98.0%: 0.8 - 2.0%;

[0015] Step 3: Mixing and pelletizing

[0016] Fully mix the weighed iron concentrate, bamboo fiber, sugar and bentonite in Step 2 to obtain a premixed material; add corn starch to water at 70°C - 80°C and continuously stir until complete, then add the corn starch solution to the premixed material and mix well, and then pelletize to obtain green pellets;

[0017] Step 4: Drying and roasting

[0018] Dry the green pellets qualified in drop and compression strength. After drying the green pellets, preheat and roast them on a horizontal tube furnace. Under the conditions of a preheating temperature of 950°C - 980°C and a preheating time of 9 - 11 min, obtain preheated pellets; then obtain roasted pellets under the conditions of a roasting temperature of 1200°C - 1250°C and a roasting time of 9 - 11 min.

[0019] Further, for the above-mentioned method of using the binder for pellets, in Step 3, the addition amount of water is 7.5 - 8.5% of the total mass of the premixed material.

[0020] Further, for the above-mentioned method of using the binder for pellets, in Step 3, the green pellets qualified in drop and compression strength have the following strength parameters: drop strength ≥ 5.0 times / ball, compression strength ≥ 9.8 N / ball.

[0021] Further, for the above-mentioned method of using the binder for pellets, the compression strength of the preheated pellets ≥ 300 N / ball; the compression strength of the roasted pellets ≥ 2300 N / ball.

[0022] Compared with the prior art, the advantages of the present invention are:

[0023] 1. Most of the binder raw materials used in the present invention belong to natural organic substances, with wide sources, and can be burned during the roasting process of pellet ore, hardly affecting the grade of pellet ore.

[0024] 2. The proportion of the binder incorporated in the present invention is relatively small, only 0.8 - 2.0%.

[0025] 3. The green pellets of the binder of the present invention have high compressive strength. When the green pellets are dropped 5.0 - 5.5 times per pellet, the compressive strength of the green pellets is above 15.0 N per pellet.

[0026] 4. The dry pellets prepared with the binder of the present invention have high strength, and the dry pellet strength is all above 50 N per pellet, meeting the requirements of grate - kiln production. The corn starch, sugars, and bamboo fibers in the binder of the present invention effectively improve the drop strength and compressive strength of the pellets before entering the roasting stage under their combined action; using only one or two of corn starch, sugars, and bamboo fibers alone cannot achieve such an effect.

[0027] 5. The binder of the present invention has little influence on the grade of pellet ore. When the binder dosage is increased by one percentage point, the grade of pellet ore decreases by less than 0.5 percentage points. Detailed implementation manners

[0028] Example 1

[0029] In this example, the main chemical components of the treated raw materials are shown in Table 1.

[0030]

[0031] A method for using a binder for pellets includes the following steps:

[0032] Step 1: Pretreat the iron ore concentrate

[0033] Dry - grind the iron ore concentrate finely so that the specific surface area of the iron ore concentrate is 1564 cm 2 / g, and - 200 mesh accounts for 91%;

[0034] Step 2: Mixing ratio

[0035] Charge the iron ore concentrate from Step 1, corn starch, bamboo fiber, industrial corn syrup, and bentonite according to the dry - material weight ratio, where the iron ore concentrate is 98.0%. The remaining part is corn starch, industrial corn syrup, bamboo fiber, and bentonite. The composition of the binder is shown in Table 2, and the addition amount of the binder is 2.0%;

[0036] Table 2 Composition ratio of the binder

[0037] Name Content % Corn starch 32 Sugar content 18 Bamboo fiber 28 Bentonite 22 Total 100

[0038] Step 3: Mixing and pelletizing

[0039] Fully mix the weighed iron ore concentrate, bamboo fiber, sugar, and bentonite from Step 2. Add corn starch to water at 70 - 80 °C and continuously stir. The addition amount of water is 8% of the total weight of the iron ore concentrate, bamboo fiber, sugar, and bentonite until it is fully dissolved without precipitation. Add the corn starch solution to the iron ore concentrate and mix well again for pelletizing.

[0040] Step 4: Drying and roasting

[0041] The green pellets that pass the drop and compressive strength tests are dried. After drying, the green pellets are preheated and roasted in a horizontal tube furnace. Preheated pellets are obtained under the conditions of a preheating temperature of 950°C and a preheating time of 10 minutes. Then, roasted pellets are obtained under the conditions of a roasting temperature of 1250°C and a roasting time of 10 minutes.

[0042] In Step 3, the green pellets have the following strength parameters: drop strength of 8.1 times per pellet and compressive strength of 15.4 N per pellet.

[0043] In Step 4, the preheated pellets have a compressive strength of 350 N per pellet, and the roasted pellets have a compressive strength of 2660 N per pellet, with a TFe content of 65.02%.

[0044] Example 2

[0045] In this example, the main chemical components of the treated raw materials are shown in Table 3.

[0046] Table 3. Main chemical components of the raw materials used in Example 2

[0047]

[0048] A method for using a binder for pellets includes the following steps:

[0049] Step 1: Pretreatment of iron concentrate

[0050] The iron concentrate is finely ground dry, so that the specific surface area of the iron concentrate is 1589 cm 2 / g, and the -200 mesh fraction is 89%;

[0051] Step 2: Batching

[0052] The iron concentrate, corn starch, bamboo fiber, industrial polyfructose, and bentonite from Step 1 are batched according to the dry material weight ratio, where the iron concentrate is 98.5%. The remaining part is corn starch, industrial polyfructose, bamboo fiber, and bentonite. The binder composition is shown in Table 4, and the binder dosage is 1.5%;

[0053] Table 4. Binder composition ratio

[0054] Name Content % Corn starch 40 Sugar content 10 Bamboo fiber 30 Bentonite 20 Total 100

[0055] Step 3: Mixing and pelletizing

[0056] Mix the iron ore concentrate, bamboo fiber, sugar, and bentonite weighed in Step 2 thoroughly. Add corn starch to water at 70 - 80°C and stir continuously. The amount of water added is 8.5% of the total weight of the iron ore concentrate, bamboo fiber, sugar, and bentonite until it is fully dissolved without precipitation. Add the corn starch solution to the iron ore concentrate and mix thoroughly again to form pellets.

[0057] Step 4. Drying and roasting

[0058] Dry the green pellets that pass the drop and compression tests. After drying the green pellets, preheat and roast them on a horizontal tube furnace. Obtain preheated pellets under the conditions of a preheating temperature of 900°C and a preheating time of 10 min; then obtain roasted pellets under the conditions of a roasting temperature of 1220°C and a roasting time of 10 min.

[0059] In Step 3, the green pellets have the following strength parameters: drop strength of 5.3 times per pellet and compression strength of 9.9 N per pellet.

[0060] In Step 4, the preheated pellets have a compression strength of 420 N per pellet, the roasted pellets have a compression strength of 2730 N per pellet, and the TFe is 67.71%.

[0061] Example 3

[0062] In this example, the main chemical components of the treated raw materials are shown in Table 5.

[0063] Table 5. Main chemical components of the raw materials in Example 3

[0064]

[0065]

[0066] A method for using a binder for pellets, comprising the following steps:

[0067] Step 1. Pretreat the iron ore concentrate

[0068] Dry-grind the iron ore concentrate so that the specific surface area of the iron ore concentrate is 1572 cm 2 / g and -200 mesh is 86%;

[0069] Step 2. Batching

[0070] Batch the iron ore concentrate, corn starch, bamboo fiber, industrial white sugar, and bentonite from Step 1 according to the dry material weight ratio, where the iron ore concentrate is 98.4%. The remaining part is corn starch, sugar, bamboo fiber, and bentonite. The binder composition is shown in Table 6, and the binder dosage is 1.6%;

[0071] Table 6. Binder composition ratio

[0072] Name Content % Corn starch 32 Sugar content 15 Bamboo fiber 25 Bentonite 28 Total 100

[0073] Step 3: Mixed pelletizing

[0074] Mix the iron ore concentrate, bamboo fiber, sugar and bentonite weighed in Step 2 thoroughly. Add corn starch to water at 70 - 80°C and stir continuously. The amount of water added is 7.5% of the total weight of the iron ore concentrate, bamboo fiber, sugar and bentonite until it is fully dissolved without precipitation. Add the corn starch solution to the iron ore concentrate and mix thoroughly again for pelletizing.

[0075] Step 4: Drying and roasting

[0076] Dry the green pellets that pass the drop and compressive strength tests. After drying, preheat and roast the green pellets on a horizontal tube furnace. Obtain preheated pellets under the conditions of a preheating temperature of 950°C and a preheating time of 10 min; then obtain roasted pellets under the conditions of a roasting temperature of 1280°C and a roasting time of 10 min.

[0077] In Step 3, the green pellets have the following strength parameters: drop strength of 5.5 times per pellet and compressive strength of 12.1 N per pellet.

[0078] In Step 4, the preheated pellets have a compressive strength of 450 N per pellet, and the roasted pellets have a compressive strength of 2480 N per pellet, with TFe of 61.34%.

[0079] Example 4

[0080] In this example, the main chemical components of the treated raw materials are shown in Table 7.

[0081] Table 7. Main chemical components of the raw materials in Example 4

[0082]

[0083] A method for using a binder for pellets, comprising the following steps:

[0084] Step 1: Pretreatment of iron ore concentrate

[0085] Fine grind the iron ore concentrate to make the specific surface area of the iron ore concentrate 1604 cm 2 / g, and -200 mesh is 88%;

[0086] Step 2: Batching

[0087] Batch the iron ore concentrate, corn starch, bamboo fiber, corn syrup and bentonite from Step 1 according to the dry material weight ratio, where the iron ore concentrate is 99.2%. The remaining part is corn starch, corn syrup, bamboo fiber and bentonite.

[0088] The binder composition is shown in Table 8, and the amount of the binder incorporated is 0.8%.

[0089] Table 8. Composition ratio of the binder

[0090] Name Content % Corn starch 40 Sugar content 15 Bamboo fiber 20 Bentonite 25 Total 100

[0091] Step 3. Mixing and pelletizing

[0092] Fully mix the iron concentrate, bamboo fiber, sugar and bentonite weighed in Step 2. Add corn starch to water at 70 - 80 °C and continuously stir. The amount of water added is 8% of the total weight of the iron concentrate, bamboo fiber, sugar and bentonite until it is fully dissolved without precipitation. Add the corn starch solution to the iron concentrate and mix well again to pelletize.

[0093] Step 4. Drying and roasting

[0094] Dry the green pellets with qualified drop and compressive strengths. After drying the green pellets, preheat and roast them on a horizontal tube furnace. Obtain preheated pellets under the conditions of a preheating temperature of 950 °C and a preheating time of 10 min; then obtain roasted pellets under the conditions of a roasting temperature of 1200 °C and a roasting time of 10 min.

[0095] In Step 3, the green pellets have the following strength parameters: drop strength of 5.2 times per pellet and compressive strength of 12.5 N per pellet.

[0096] In Step 4, the preheated pellets have a compressive strength of 356 N per pellet, the roasted pellets have a compressive strength of 2360 N per pellet, and TFe is 66.11%.

[0097] Comparative Example 1

[0098] A method for using a binder for pellets, Steps 1 - 3 are the same as in Example 4;

[0099] The difference lies in:

[0100] Step 4. Drying and roasting

[0101] Dry the green pellets with qualified drop and compressive strengths. After drying the green pellets, preheat and roast them on a horizontal tube furnace. Obtain preheated pellets under the conditions of a preheating temperature of 950 °C and a preheating time of 15 min; then obtain roasted pellets under the conditions of a roasting temperature of 1280 °C and a roasting time of 12 min.

[0102] In Step 4, the preheated pellets have a compressive strength of 350 N per pellet, the roasted pellets have a compressive strength of 2350 N per pellet, and TFe is 66.33%.

[0103] By comparing this comparative example with Example 4, it can be seen that extending the preheating time of the green balls from 10 min to 15 min in the preheating section and the roasting time from 10 min to 12 min in the roasting section does not improve the properties of the pellet ore. Therefore, the preheating and roasting processes of the present invention are reasonable and reduce the production cost.

[0104] Example 5

[0105] A method for using a binder for pellets, comprising the following steps:

[0106] Step 1: Pretreat the iron concentrate

[0107] In Example 5, the main chemical components of the raw materials are the same as those in Example 1.

[0108] Step 2: Weigh the iron concentrate, corn starch, bamboo fiber, industrial white sugar and bentonite obtained in Step 1 according to the dry material weight ratio, wherein the iron concentrate is 99.0%. The remaining part is corn starch, industrial white sugar, bamboo fiber and bentonite, and the components of the binder are also the same as those in Example 1. As shown in Table 2, the addition amount of the binder is 1.0%;

[0109] Step 3: Mix and pelletize

[0110] Fully mix the iron concentrate, bamboo fiber, sugar and bentonite weighed in Step 2. Add corn starch to water at 70 - 80 °C and continuously stir. The addition amount of water is 8% of the total weight of the iron concentrate, bamboo fiber, sugar and bentonite until it is fully dissolved without precipitation. Add the corn starch solution to the iron concentrate and mix well again to pelletize.

[0111] Step 4: Dry and roast

[0112] Dry the green balls that pass the drop and compressive strength tests. After drying the green balls, preheat and roast them on a horizontal tube furnace. Obtain preheated balls under the conditions of a preheating temperature of 950 °C and a preheating time of 10 min; then obtain roasted balls under the conditions of a roasting temperature of 1250 °C and a roasting time of 10 min.

[0113] In Step 3, the green balls have the following strength parameters: drop strength 5.0 times / ball, compressive strength 10.4 N / ball.

[0114] In Step 4, the preheated balls have a compressive strength of 350 N / ball, and the roasted balls have a compressive strength of 2710 N / ball, TFe 65.44%.

Claims

1. A method for using a binder for pellets, characterized in that, It includes the following steps: Step 1: Pretreat the iron concentrate Dry-grind the iron concentrate finely so that the specific surface area of the iron concentrate ≥ 1500 cm 2 / g, and the proportion of particles passing through 200 mesh ≥ 90%; Step 2: Prepare the raw material proportion Take raw materials of iron concentrate, corn starch, bamboo fiber, sugar and bentonite according to the weight ratio. The mass percentage of iron concentrate to binder is 99.2 - 98.0%: 0.8 - 2.0%; The binder for the pellets consists of the following raw materials in mass percentage: 30 - 45% of corn starch, 20 - 30% of bamboo fiber, 10 - 20% of sugar and 20 - 40% of bentonite; Step 3: Mix and pelletize Fully mix the iron concentrate, bamboo fiber, sugar and bentonite weighed in Step 2 to obtain a premixed material; add corn starch to water at 70°C - 80°C and continuously stir until it is fully dissolved without precipitation, then add the corn starch solution to the premixed material and mix well, and then pelletize to obtain green pellets; Step 4: Dry and roast Dry the green pellets qualified in drop and compression strength. After drying the green pellets, preheat and roast them on a horizontal tube furnace. Obtain preheated pellets under the conditions of a preheating temperature of 950°C - 980°C and a preheating time of 9 - 11 min; then obtain roasted pellets under the conditions of a roasting temperature of 1200°C - 1250°C and a roasting time of 9 - 11 min.

2. The method for using the binder for pellet according to claim 1, wherein The sugar is natural disaccharide or polysaccharide or a mixture of multiple disaccharides or a mixture of multiple polysaccharides.

3. The method for using the binder for pellet as claimed in claim 1, wherein In Step 3, the addition amount of water is 7.5 - 8.5% of the total mass of the premixed material.

4. The method for using the binder for pellets according to claim 1, characterized in that, In Step 3, the green pellets qualified in drop and compression strength have the following strength parameters: drop strength ≥ 5.0 times / ball, compression strength ≥ 9.8 N / ball.

5. The method for using the binder for pellet according to claim 1, wherein The compression strength of the preheated pellets ≥ 300 N / ball; the compression strength of the roasted pellets ≥ 2300 N / ball.

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