Process for preparing metallurgical pellet binder from bentonite with low montmorillonite content

Abstract

The invention discloses a process for preparing a metallurgical pellet binder from bentonite with low montmorillonite content, the process adopts a two-time wet modification process, after the first modification is subjected to basic conversion, calcium oxide and hydrolyzed polyacrylonitrile sodium salt are innovatively introduced during the second modification, and then the modified bentonite is subjected to secondary modification to prepare the metallurgical pellet binder. According to the present invention, the phase acting force between the organic material and the inorganic material is enhanced through the calcium ion bridging effect, the interlayer defect of the montmorillonite is filled, the bonding network is enhanced, the low-grade bentonite montmorillonite can be converted into the high-performance metallurgical pellet binder, the performance requirement of the metallurgical pellet binder can be met, and the efficient utilization of the low-value mineral product can be achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of metallurgical pellet binder preparation, and particularly relates to a process for preparing a metallurgical pellet binder by utilizing bentonite with low montmorillonite content through a two-step wet modification process. Background Art

[0002] Sodium bentonite is the industry's preferred choice due to its superior expansion and water absorption properties compared to calcium bentonite. The typical process involves modifying calcium bentonite by adding sodium carbonate to enhance its colloidal properties, significantly reducing the binder dosage and improving the iron grade of the pellets. Mainstream technology requires the bentonite to have a montmorillonite content of ≥65% to ensure that the expanded capacity and colloidal value after conversion meet national standards. This results in low-grade ore (montmorillonite content <50%) being discarded or downgraded due to substandard performance.

[0003] The core reason is that bentonite with low montmorillonite content (such as 47% montmorillonite from the original mine in Linli County, Hunan) has low interlayer charge density and weak cation exchange capacity. During conventional sodiumization, sodium carbonate is difficult to fully replace the interlayer calcium ions, and the modification efficiency is low. To improve performance, the industry has tried to add organic polymers (such as CMC, sodium polyacrylate), but low-grade bentonite has many impurities and a small specific surface area, making it difficult for organic matter to be effectively grafted. For example: the modification scheme of directly mixing 2% CMC in bentonite with montmorillonite content less than 47% is unevenly dispersed, resulting in a decrease in the strength of the binder ball.

[0004] Furthermore, the existing traditional wet process only performs a single sodiumization step, with an aging period of 4-10 days. Low-grade bentonite, due to impurities (quartz and feldspar) that hinder ion diffusion, still retains a large amount of untransformed calcium-based montmorillonite after sodiumization, resulting in poor performance. While attempts have been made to add sodium fluoride or light-burned magnesia (such as 0.5% light-burned magnesia to increase the decomposition temperature), these efforts have not addressed the core issue of low transformation efficiency in low-grade ore.

[0005] Therefore, there is an urgent need in the art for a process for preparing a binder with qualified performance using low-grade (montmorillonite <50%) bentonite. Summary of the Invention

[0006] In view of the deficiencies of the prior art, the technical solutions provided by the present invention are as follows:

[0007] S1: crushing the calcium-based bentonite wet ore into blocks, and then drying the crushed blocks of calcium-based bentonite wet ore to a moisture content of ≤10%;

[0008] S2: After the dried calcium bentonite wet ore is fully mixed with 2%-3% soda ash, it is put into the automatic spraying system for spraying at 25-35℃ with a water-soil ratio of 1:4, and then fully squeezed;

[0009] S3: Aging at 20-30°C for 7 days, then sun-drying or drying to a moisture content of ≤10% to obtain a primary modified mineral powder;

[0010] S4: After fully mixing the primary modified mineral powder with 0.4%-0.7% calcium oxide and 0.1%-0.3% hydrolyzed polyacrylonitrile sodium salt, put it into the automatic spraying system for spraying at 25-35℃ with a water-to-soil ratio of 1:4, and then fully squeeze it;

[0011] S5: Aging again for 7 days at 20-30°C and drying to a moisture content of ≤13% to obtain a finished adhesive;

[0012] S6: crush the finished adhesive, pack and seal it in bags.

[0013] Preferably, in step S1 and step S5 of the above preparation process, the drying method is natural sun drying or drying in a dryer, and the drying temperature of the dryer is 100-105°C.

[0014] Preferably, in step S2 and step S4 of the above preparation process, the extrusion method is wet extrusion, and the extrusion time is 40 minutes.

[0015] Preferably, in step S1 of the above preparation process, a rotary tiller is used to crush the calcium-based bentonite wet ore into blocks of about 15 cm.

[0016] Preferably, in step S6 of the above preparation process, the finished binder is crushed into 200 mesh.

[0017] The present invention uses the above-mentioned secondary modification preparation process, through a specific additive combination and process timing design, to use soda ash to achieve the conversion of calcium base to sodium base, and secondary introduction of CaO and high molecular polymer to synergistically enhance the effect. Among them, CaO improves structural stability, and hydrolyzes polyacrylonitrile sodium salt to fill the interlayer defects of montmorillonite and strengthen the bonding network.

[0018] The carboxyl (—COO-) and nitrile (—CN) groups on the molecular chain of hydrolyzed sodium polyacrylonitrile (Na-HPAN) have strong polarity and can be inserted into the interlayer domain of bentonite, forming hydrogen bonds or electrostatic adsorption with the hydroxyl groups on the surface of montmorillonite sheets to strengthen the interlayer bonding force. Its molecular chain can form a cross-linked network at high temperature, and together with the bentonite sheets, it constructs a "skeleton-filling" structure to inhibit cracking during the pellet roasting process.

[0019] Based on the above-mentioned secondary modification process and the addition of hydrolyzed sodium polyacrylonitrile (Na-HPAN), low-grade bentonite (montmorillonite 47%) is converted into a high-performance metallurgical pellet binder.

[0020] The present invention has the following beneficial effects:

[0021] 1. The present invention adopts the above-mentioned technical scheme, firstly adopts the sodiumization by wet extrusion of soda ash for primary modification, performs basic transformation, and then innovatively introduces calcium oxide and hydrolyzed polyacrylonitrile sodium salt, enhances the organic-inorganic phase interaction force through the calcium ion bridging effect, and performs secondary modification, thereby converting low-grade bentonite (montmorillonite 47%) into a high-performance metallurgical pellet binder, and making it meet the performance requirements of metallurgical pellet binders, thereby realizing the efficient utilization of low-value minerals.

[0022] 2. The present invention introduces hydrolyzed polyacrylonitrile sodium salt in the secondary modification, and CaO and the high molecular polymer synergize to fill the interlayer defects of montmorillonite and enhance the bonding network, strengthen the interlayer bonding force, inhibit cracking during the pellet roasting process, and significantly improve the compressive strength. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 Create a process flow chart for the present invention; DETAILED DESCRIPTION

[0024] In order to better understand the present invention, the content of the present invention is further clearly set forth below in conjunction with the examples, but the protection content of the present invention is not limited to the following examples. In the following description, a large number of specific details are provided in order to provide a more thorough understanding of the present invention. However, it is obvious to those skilled in the art that the present invention can be implemented without one or more of these details.

[0025] In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not limiting. Therefore, other examples of the exemplary embodiments may have different values.

[0026] Various raw materials are used in the following examples. Unless otherwise specified, the bentonite used in the following examples is Hunan Linli calcium-based bentonite wet ore, which has a montmorillonite content of 47%, lower than 50%, and is a low-grade ore.

[0027] Example 1

[0028] A process for preparing a metallurgical pellet binder from bentonite with low montmorillonite content comprises the following steps:

[0029] S1: 1 ton of calcium bentonite wet ore is crushed into blocks using a rotary tiller, and then the crushed blocks of calcium bentonite wet ore are naturally dried to a moisture content of ≤10%;

[0030] S2: After the dried calcium bentonite wet ore is fully mixed with 25kg of soda ash, it is put into the automatic spraying system for spraying at 25℃ with a water-soil ratio of 1:4, and then wet-extruded for 40 minutes;

[0031] S3: Aging at 25°C for 7 days, then naturally drying in the sun until the moisture content is ≤10%, to obtain a primary modified mineral powder;

[0032] S4: After fully mixing the primary modified mineral powder with 5kg of calcium oxide and 2kg of hydrolyzed polyacrylonitrile sodium salt, the molecular weight of which is 10 million, the mixture is put into an automatic spraying system for spraying at 25°C with a water-to-soil ratio of 1:4, and then wet-extruded for 40 minutes;

[0033] S5: Aging again at 25°C for 7 days and naturally drying to a moisture content of ≤13% to obtain a finished adhesive;

[0034] S6: The finished adhesive is crushed into 200 meshes, and then packaged and sealed.

[0035] Example 2

[0036] A process for preparing a metallurgical pellet binder from bentonite with low montmorillonite content comprises the following steps:

[0037] S1: 1 ton of calcium bentonite wet ore is crushed into blocks using a rotary tiller, and then the crushed blocks of calcium bentonite wet ore are naturally dried to a moisture content of ≤10%;

[0038] S2: After the dried calcium bentonite wet ore is fully mixed with 20kg of soda ash, it is put into the automatic spraying system for spraying at 20℃ with a water-soil ratio of 1:4, and then wet-extruded for 40 minutes;

[0039] S3: Aging at 25°C for 7 days, then naturally drying in the sun until the moisture content is ≤10%, to obtain a primary modified mineral powder;

[0040] S4: After fully mixing the primary modified mineral powder with 4kg of calcium oxide and 1kg of hydrolyzed polyacrylonitrile sodium salt, the molecular weight of which is 8 million, the mixture is put into an automatic spraying system for spraying at 20°C with a water-to-soil ratio of 1:4, and then wet-extruded for 40 minutes;

[0041] S5: Aging again at 25°C for 7 days and naturally drying to a moisture content of ≤13% to obtain a finished adhesive;

[0042] S6: The finished adhesive is crushed into 200 meshes, and then packaged and sealed.

[0043] Example 3

[0044] A process for preparing a metallurgical pellet binder from bentonite with low montmorillonite content comprises the following steps:

[0045] S1: 1 ton of calcium bentonite wet ore is crushed into blocks using a rotary tiller, and then the crushed blocks of calcium bentonite wet ore are passed through a dryer until the moisture content is ≤10%;

[0046] S2: After the dried calcium bentonite wet ore is fully mixed with 30kg of soda ash, it is put into the automatic spraying system for spraying at 30℃ with a water-soil ratio of 1:4, and then wet-extruded for 40 minutes;

[0047] S3: Aging at 25°C for 7 days, then drying in a dryer to a moisture content of ≤10% at a drying temperature of 105°C to obtain a primary modified mineral powder;

[0048] S4: After fully mixing the primary modified mineral powder with 7kg of calcium oxide and 3kg of hydrolyzed polyacrylonitrile sodium salt, the molecular weight of which is 12 million, the mixture is put into an automatic spraying system for spraying at 25°C with a water-to-soil ratio of 1:4, and then wet-extruded for 40 minutes;

[0049] S5: Aging again at 25°C for 7 days and naturally drying to a moisture content of ≤13% to obtain a finished adhesive;

[0050] S6: The finished adhesive is crushed into 200 meshes, and then packaged and sealed.

[0051] Comparative Example 1

[0052] S1: 1 ton of calcium bentonite wet ore is crushed into blocks using a rotary tiller, and then the crushed blocks of calcium bentonite wet ore are naturally dried to a moisture content of ≤10%;

[0053] S2: After the dried calcium bentonite wet ore is fully mixed with 30kg of soda ash, it is put into the automatic spraying system for spraying at 20℃ with a water-soil ratio of 1:4, and then wet-extruded for 40 minutes;

[0054] S3: Aging at 25°C for 7 days, then drying in a dryer to a moisture content of ≤13% at a drying temperature of 105°C to obtain a primary modified mineral powder;

[0055] S4: After fully mixing the primary modified ore powder with 5kg of light-burned magnesia and 2kg of CMC, directly crush it into 200 meshes, and then pack and seal it in bags.

[0056] Compared with Comparative Example 1, when low-grade bentonite is used for preparation, the water absorption rate, expansion capacity and colloid value of the low-grade bentonite are significantly improved without significantly increasing the blue absorption amount, so that it meets the performance requirements of the metallurgical pellet binder, the water absorption rate is increased to 450%, the colloid value is increased to 500ml / 15g, and the expansion capacity is increased by 50ml / g.

[0057] Among them, the water absorption rate is ≥400%, the expansion capacity is ≥45ml / g, and the gel value is ≥480ml / 15g, far exceeding the national standard (GB / T20973-2020).

[0058] Finally, it should be noted that the above embodiments do not limit the present invention in any form. Those skilled in the art will appreciate that modifications and improvements can be made based on the present invention. Therefore, any modifications or improvements made without departing from the spirit of the present invention are intended to fall within the scope of protection claimed in the present invention.

Claims

1. A process for preparing a metallurgical pellet binder from bentonite with low montmorillonite content, characterized in that: The preparation process includes the following steps: S1: crushing the calcium-based bentonite wet ore into blocks, and then drying the crushed blocks of calcium-based bentonite wet ore to a moisture content of ≤10%; S2: After the dried blocky calcium bentonite wet ore is fully mixed with 2%-3% soda ash, it is put into the automatic spraying system for spraying at 25-35℃ with a water-soil ratio of 1:4, and then fully squeezed; S3: Aging at 20-30°C for 7 days, then sun-drying or drying to a moisture content of ≤10% to obtain a primary modified mineral powder; S4: After fully mixing the primary modified mineral powder with 0.4%-0.7% calcium oxide and 0.1%-0.3% hydrolyzed polyacrylonitrile sodium salt, put it into the automatic spraying system for spraying at 25-35℃ with a water-to-soil ratio of 1:4, and then fully squeeze it; S5: Aging again for 7 days at 20-30°C and drying to a moisture content of ≤13% to obtain a finished adhesive; S6: crush the finished adhesive, pack and seal it in bags.

2. The process for preparing a metallurgical pellet binder from bentonite with low montmorillonite content according to claim 1, characterized in that: In step S1 and step S5, the drying method is natural sun drying or drying in a drying machine, wherein the drying temperature is 100-105°C.

3. The process for preparing a metallurgical pellet binder from bentonite with low montmorillonite content according to claim 1, characterized in that: In the step S2 and the step S4, the extrusion method is wet extrusion, and the extrusion time is 40 minutes.

4. The process for preparing a metallurgical pellet binder from bentonite with low montmorillonite content according to claim 1, characterized in that: In step S1, a rotary tiller is used to crush the calcium-based bentonite wet ore into blocks of about 15 cm.

5. The process for preparing a metallurgical pellet binder from bentonite with low montmorillonite content according to claim 1, characterized in that: In step S6, the finished adhesive is crushed into 200 meshes.

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