Composite binder for metallized pellets of rotary hearth furnace

Abstract

The invention discloses a composite binder for metallized pellets of a rotary hearth furnace, which comprises the following components in percentage by mass: 15-40% of organic matter which is formed by compounding 10-30% of high-molecular polymer, 3-10% of starch and 2-8% of modified lignin; 20%-40% of bentonite which is a mixture of calcium bentonite and sodium bentonite in proportion; the slag blender is formed by compounding at least two of 10%-30% of sodium silicate, 5%-20% of sodium sulfate, 5%-15% of magnesium sulfate, 3%-10% of sodium hydroxide and 3%-10% of sodium bicarbonate; 0.5%-5% of a surfactant which is a mixture of at least two of 0.3%-3% of lignin sodium carbonate, 0.2%-2% of lignin calcium carbonate, 0.1%-1% of sodium humate, 0.1%-1% of tripolyphosphate and 0.1%-1% of sodium borate; the high molecular material, the bentonite and the slag blender are polymerized to form the high molecular material bentonite slag blender. The pressure of concentrated release of steam in the roasting process is reduced, the phenomena of burst and pulverization of pellets are reduced, the pelletizing rate and the yield of fine powder such as zinc are increased, and the production requirements of the metallurgical industry are met.

Description

Technical Field

[0001] This invention relates to the field of composite binder technology, and in particular to a composite binder for metallization pelletizing in rotary hearth furnaces. Background Technology

[0002] In the fields of environmental protection and metallurgical technology, the rotary hearth furnace pelletizing process is a mature and effective method for treating metallurgical dust and sludge. This process can centrally treat various solid wastes generated during metallurgical production, ultimately obtaining high-quality metallized pellets and achieving resource recycling. In the pelletizing process, the binder plays a crucial role; it is one of the key factors ensuring pellet quality and smooth production operation.

[0003] Currently, the pelletizing process largely utilizes bentonite binders commonly used in sintering production, along with various modified and compounded formulations. Bentonite is the most widely used and the technology is relatively mature. When the bentonite content reaches 5%, production remains stable, and all indicators meet basic production requirements. However, with the development of the metallurgical industry, the requirements for pellet quality and production efficiency are increasing, and the bentonite binders used in existing technologies are gradually revealing some shortcomings. In the low-temperature, humid stage of pellet production, pellets using bentonite as a binder have poor drop resistance. This means that during transportation and transfer, the pellets are easily damaged by impacts, affecting their integrity and subsequent production processes. Bentonite is a medium-temperature binder with a narrow dehydration temperature range. In the medium-temperature stage, the dehydration process of the pellets is concentrated, rapidly releasing a large amount of water vapor. This water vapor accumulates inside the pellets, generating high pressure, which can easily lead to pellet bursting and pulverization. This not only reduces the pelletizing rate but also increases the pulverization rate of the pellets, leading to increased material losses and production costs during the production process.

[0004] At the reduction temperature of a rotary hearth furnace, bentonite forms complex, low-melting-point mixtures with other substances. The presence of these mixtures hinders the removal of metal vapors such as zinc, limiting the recovery rate of zinc powder. This is a pressing problem for metallurgical production requiring efficient recovery of metals like zinc. Therefore, to address the problems of the existing technology, this invention provides a composite binder for rotary hearth furnace metallization pelletizing. Summary of the Invention

[0005] The purpose of this invention is to at least solve one of the technical problems existing in the prior art, and to provide a composite binder for rotary hearth furnace metallization pelletizing. This composite binder is polymerized from polymer materials, bentonite, and slag modifiers through a reasonable composition design. Its aim is to improve the mass transfer conditions inside the pellets, reduce the pressure of concentrated steam release during roasting, reduce pellet bursting and pulverization, thereby increasing the pelletizing rate and the yield of fine powders such as zinc, and meeting the growing production needs of the metallurgical industry.

[0006] The present invention also provides a composite binder for rotary hearth furnace metallization pelletizing, comprising, by weight percentage: organic matter: 15%–40%, composed of 10%–30% polymer, 3%–10% starch, and 2%–8% modified lignin; bentonite: 20%–40%, a mixture of calcium-based bentonite and sodium-based bentonite in a specified proportion; and slag conditioner: 5%–50%, composed of 10%–30% sodium silicate, 5%–20% sodium sulfate, and 5%–15% magnesium sulfate. The active ingredient is composed of at least two of the following: sodium hydroxide (3%–10%), sodium bicarbonate (3%–10%), and sodium oxycarbonate (3%–10%). The surfactant is 0.5%–5%, a mixture of at least two of the following: sodium lignin carbonate (0.3%–3%), calcium lignin carbonate (0.2%–2%), sodium humate (0.1%–1%), tripolyphosphate (0.1%–1%), and sodium borate (0.1%–1%). The reinforcing agent is 0.5%–5%, consisting of SiO2 particles with a particle size of 5–20 μm or a SiO2 gel precursor containing sodium silicate.

[0007] According to the present invention, a composite binder for metallization pelletizing in a rotary hearth furnace is provided, wherein the polymer is at least one of polyvinyl alcohol, polyacrylamide, and carboxymethyl cellulose, and the modified lignin is sulfonated lignin or alkali-processed lignin.

[0008] According to the present invention, a composite binder for metallization pelletizing in a rotary hearth furnace is provided, wherein the mass ratio of sodium silicate to magnesium sulfate in the slag blending agent is 2:1-5:1; and the mass ratio of sodium lignin carbonate to sodium humate in the surfactant is 3:1-5:1.

[0009] According to the present invention, a composite binder for metallization pelletizing in a rotary hearth furnace has a particle size ≥80 mesh and a moisture content ≤14%; the bentonite has a montmorillonite content ≥85% and a cation exchange capacity ≥70mmol / 100g.

[0010] According to the present invention, a composite binder for rotary hearth furnace metallization pellets is prepared by a method comprising the following steps:

[0011] Step 1: Mix the polymer, starch, and modified lignin in a certain proportion to obtain an organic masterbatch;

[0012] Step 2: Mix bentonite and slag material modifier in a certain proportion to obtain inorganic masterbatch;

[0013] Step 3: Dissolve the surfactant and reinforcing agent in deionized water, wherein the solid-liquid ratio is 1:5 to 1:10, to obtain a modified solution;

[0014] Step 4: Mix the organic masterbatch, inorganic masterbatch and modification solution, stir at 50-80℃ for 30-60 minutes, dry and then pulverize to a particle size ≥80 mesh.

[0015] A pelletizing method according to the present invention includes the following processing steps:

[0016] Raw material pretreatment: Mix metallurgical dust and sludge with composite binder at a mass ratio of 96:4-98:2, and add water accounting for 8% to 12% of the total mass;

[0017] Pelletizing process: After mechanical mixing for 3-5 minutes, the mixture is rolled into pellets in a pelletizing pan, with a set rotation speed of 15-25 rpm and a set time of 10-15 minutes; pellets with a particle size of 8-16 mm are then sieved out.

[0018] Heat treatment: Hot air drying: Hold at 200±10℃ for 15~20 minutes;

[0019] Calcination and reduction: Calcination at 1250-1300℃ for 15-18 minutes, followed by carbonization and cooling to room temperature.

[0020] According to the present invention, a composite binder for metallization pellets in a rotary hearth furnace is provided, wherein the mechanical mixing is performed using a twin-shaft mixer at a speed of 30-50 rpm; and the calcination process is carried out by introducing a reducing gas with a CO content ≥20% at a flow rate of 0.5-1.5 m³ / h. 3 / h.

[0021] According to the present invention, a composite binder for metallization pellets in a rotary hearth furnace has a wet pellet compressive strength ≥8N and a dried pellet compressive strength ≥20N; the pellets do not crack when directly heated in a tube furnace at 1000℃, and the zinc removal rate is ≥85%.

[0022] Compared with existing technologies, the present invention provides a composite binder for rotary hearth furnace metallization pelletizing. This composite binder is polymerized from high-molecular materials, bentonite, and slag modifiers through a rational composition design. Its purpose is to improve the mass transfer conditions within the pellets, reduce the pressure of concentrated steam release during roasting, decrease pellet bursting and pulverization, thereby increasing the pelletizing rate and the yield of fine powders such as zinc, and meeting the growing production demands of the metallurgical industry. Attached Figure Description

[0023] The present invention will be further described below with reference to the accompanying drawings and embodiments;

[0024] Figure 1 This is a schematic diagram of the test results of a single ball falling from a 500mm diameter ball onto a 10mm diameter steel plate according to the present invention.

[0025] Figure 2 This is a graph showing the cooling and detection data of the material after being kept at 1250℃~1300℃ for 15 minutes and then discharged with embedded carbon.

[0026] Figure 3 This is a schematic diagram showing the mass percentage of the composite adhesive prepared according to Embodiment 1 of the present invention;

[0027] Figure 4 This is a schematic diagram showing the mass percentage of the composite adhesive prepared in Embodiment 2 of the present invention;

[0028] Figure 5 This is a schematic diagram showing the mass percentage of the composite adhesive prepared in Embodiment 3 of the present invention. Detailed Implementation

[0029] This section will describe in detail specific embodiments of the present invention. Preferred embodiments of the present invention are shown in the accompanying drawings. The purpose of the drawings is to supplement the textual description with graphics, so that people can intuitively and vividly understand each technical feature and overall technical solution of the present invention, but they should not be construed as limiting the scope of protection of the present invention.

[0030] Example 1

[0031] Reference Figure 1 , 2 3. An embodiment of the present invention provides a composite binder for metallization pelletizing in a rotary hearth furnace, comprising the following steps:

[0032] Preparation of the composite binder: Accurately weigh the following components by mass percentage: 15% polymer, 10% starch, and 5% modified lignin; 30% bentonite (including calcium-based bentonite); 20% sodium silicate and 10% magnesium sulfate as a slag modifier; 5% sodium lignin carbonate as a surfactant; and 5% SiO2-containing microparticles as a reinforcing agent. First, mix the polymer, starch, and modified lignin evenly to obtain a homogeneous organic mixture. Then, thoroughly mix the calcium-based bentonite with sodium silicate and magnesium sulfate to form a homogeneous slag mixture. Next, dissolve the sodium lignin carbonate and SiO2-containing microparticles separately in appropriate amounts of water to prepare solutions. Finally, stir the above organic mixture, slag mixture, and both solutions together for 30 minutes at a stirring speed of 200 r / min to ensure uniform dispersion of all components, thus obtaining the composite binder for rotary hearth furnace metallization pellets.

[0033] Pelletizing and processing: Metallurgical dust and sludge are selected as raw materials, and a prepared composite binder is added at 3% of the slag weight. First, the metallurgical dust and sludge and the dry powder of the composite binder are added to a high-speed mixer and mixed for 5 minutes at a mixing speed of 150 r / min. Then, pre-added water is added at a rate of 10% of the total mass of the raw materials, and mechanical mixing continues for 8 minutes. After uniform mixing, the mixture is fed into a pelletizing disc for pelletizing for 12 minutes at a disc speed of 20 r / min. After the water atomization is completed, the pellets are discharged 4 minutes later and screened to obtain pellets of 8-16 mm. The screened pellets are then sent to a hot air drying device and dried at 200℃ for 25 minutes. The dried pellets are then placed in a calcining furnace at 1280℃ and calcined for 16 minutes. After calcination, carbon is embedded and the pellets are discharged.

[0034] Performance Testing: The wet pellets underwent a compressive strength test, yielding a strength of 8.5 N. The dried pellets were subjected to a 500mm drop test on a 10mm steel plate; after 10 drop tests, no cracking or severe deformation occurred. The dried pellets were then placed at 1250-1300℃ for 15 minutes, discharged, and cooled with carbon embedded in the pellets. An anti-bursting performance test was conducted, showing no bursting and a pulverization rate of less than 5%. Simultaneously, the zinc removal rate of the pellets was tested, and chemical analysis revealed a removal rate of 88%.

[0035] Example 2

[0036] Reference Figure 1 , 2 4. An embodiment of the present invention provides a composite binder for metallization pelletizing in a rotary hearth furnace, comprising the following steps:

[0037] Preparation of the composite binder: The following organic materials were weighed by mass percentage: 20% high molecular weight polymer, 8% starch, 7% modified lignin; 35% sodium bentonite (including sodium bentonite); 15% sodium sulfate, 5% sodium hydroxide, and 10% sodium bicarbonate as a slag conditioner; 3% sodium humate and 2% tripolyphosphate as a surfactant; and 5% as a reinforcing agent capable of producing SiO2 gel. The preparation process was similar to that in Example 1: the organic materials and slag were mixed separately, then the surfactant and reinforcing agent were prepared into a solution, and finally, the mixture was stirred for 40 minutes at a stirring speed of 250 r / min to obtain the composite binder.

[0038] Pelletizing and processing: Metallurgical dust and sludge were selected, and a composite binder was added at 2.5% of the slag weight. The parameters for mixing, pelletizing, screening, drying, and calcination were slightly different from those in Example 1. The mixing time in the high-intensity mixer was 6 minutes at a speed of 180 r / min; the pre-added water accounted for 9% of the total mass of the raw materials; mechanical mixing lasted 9 minutes; pelletizing time was 13 minutes at a pelletizing disc speed of 22 r / min; pellets were discharged 4.5 minutes after the atomization of water ended; after screening, the pellets were dried at 200℃ for 22 minutes; and after calcination at 1270℃ for 15 minutes, they were carbonized and discharged.

[0039] Performance testing: Wet bulb compressive strength is 8.2N; in the 500mm drop test / 10mm steel plate drop test of dried pellets, no abnormalities were observed after 10 drops; after being held at 1250-1300℃ for 15 minutes and then cooled with carbon, the pellets showed good anti-bursting performance, with a pulverization rate of 4.5%. The zinc removal rate was 86%.

[0040] Example 3

[0041] Reference Figure 1 , 2 5. An embodiment of the present invention provides a composite binder for metallization pelletizing in a rotary hearth furnace, comprising the following steps:

[0042] Preparation of the composite binder: The following components were prepared: 25% organic polymer, 5% starch, and 10% modified lignin; 25% calcium-based bentonite and 15% sodium-based bentonite; 15% sodium silicate, 10% magnesium sulfate, and 5% sodium sulfate as a slag blending agent; 4% lignin-calcium carbonate and 1% sodium borate as a surfactant; and 5% SiO2 particles as a reinforcing agent. The mixing time was 35 minutes, and the mixing speed was 220 r / min.

[0043] Pelletizing and processing: Metallurgical dust and sludge are used, with a composite binder added at 3.5% of the slag weight. The mixture is stirred in a high-speed mixer for 7 minutes at 160 r / min; 11% of the total raw material mass is pre-added; mechanical mixing continues for 7 minutes; pelletizing takes 11 minutes at a pelletizing disc speed of 18 r / min; pellets are discharged 5 minutes after the atomization water is finished; the sieved pellets are dried at 200℃ for 28 minutes; and then calcined at 1290℃ for 17 minutes before being carbonized and discharged.

[0044] Performance testing: Wet bulb compressive strength reached 8.8N; dried pellets passed 10 drops (500mm drop / 10mm steel plate drop test) without damage; after carbon embedding and cooling at 1250-1300℃ for 15 minutes, the pellets did not crack, with a pulverization rate of 3.8%. Zinc removal rate reached 90%.

[0045] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention.

Claims

1. A composite binder for metallization pelletizing in a rotary hearth furnace, characterized in that, Included by weight percentage: Organic matter: 15%–40%, composed of 10%–30% high molecular polymer, 3%–10% starch and 2%–8% modified lignin; Bentonite: 20%–40%, a mixture of calcium-based bentonite and sodium-based bentonite in a certain proportion; Slag blending agent: 5%–50%, composed of at least two of the following: sodium silicate 10%–30%, sodium sulfate 5%–20%, magnesium sulfate 5%–15%, sodium hydroxide 3%–10%, and sodium bicarbonate 3%–10%; Surfactant: 0.5%–5%, a mixture of at least two of the following: sodium lignin carbonate 0.3%–3%, calcium lignin carbonate 0.2%–2%, sodium humate 0.1%–1%, tripolyphosphate 0.1%–1%, and sodium borate 0.1%–1%; Reinforcing agent: 0.5% to 5%, consisting of SiO2 microparticles with a particle size of 5-20 μm and SiO2 gel precursor containing sodium silicate.

2. The composite binder for metallization pelletizing in a rotary hearth furnace according to claim 1, characterized in that, The polymer is at least one of polyvinyl alcohol, polyacrylamide, and carboxymethyl cellulose, and the modified lignin is sulfonated lignin or alkali-processed lignin.

3. The composite binder for rotary hearth furnace metallization pellets according to claim 1, characterized in that, The mass ratio of sodium silicate to magnesium sulfate in the slag blending agent is 2:1-5:1; the mass ratio of sodium lignin carbonate to sodium humate in the surfactant is 3:1-5:

1.

4. The composite binder for metallization pelletizing in a rotary hearth furnace according to claim 1, characterized in that, The composite binder has a particle size ≥80 mesh and a moisture content ≤14%; the bentonite has a montmorillonite content ≥85% and a cation exchange capacity ≥70 mmol / 100g.

5. The composite binder for metallization pelletizing in a rotary hearth furnace according to claim 1, characterized in that, The preparation method includes the following steps: Step 1: Mix the polymer, starch, and modified lignin in a certain proportion to obtain an organic masterbatch; Step 2: Mix bentonite and slag material modifier in a certain proportion to obtain inorganic masterbatch; Step 3: Dissolve the surfactant and reinforcing agent in deionized water, wherein the solid-liquid ratio is 1:5 to 1:10, to obtain a modified solution; Step 4: Mix the organic masterbatch, inorganic masterbatch and modification solution, stir at 50-80℃ for 30-60 minutes, dry and then pulverize to a particle size ≥80 mesh.

6. A pelletizing method for a composite binder for rotary hearth furnace metallization pellets according to any one of claims 1-4, characterized in that, The following processing steps are included: Raw material pretreatment: Mix metallurgical dust and sludge with composite binder at a mass ratio of 96:4-98:2, and add water accounting for 8% to 12% of the total mass; Pelletizing process: After mechanical mixing for 3-5 minutes, the mixture is rolled into pellets in a pelletizing pan, with a set rotation speed of 15-25 rpm and a set time of 10-15 minutes; pellets with a particle size of 8-16 mm are then sieved out. Heat treatment: Hot air drying: Hold at 200±10℃ for 15~20 minutes; Calcination and reduction: Calcination at 1250-1300℃ for 15-18 minutes, followed by carbonization and cooling to room temperature.

7. A pelletizing method according to claim 6, characterized in that, The mechanical mixing is performed using a twin-shaft mixer at a speed of 30-50 rpm; the calcination process introduces a reducing gas with a CO content ≥20% at a flow rate of 0.5-1.5 m³ / h. 3 / h.

8. A pelletizing method according to claim 6, characterized in that, The wet pellets have a compressive strength ≥8N, and the dried pellets have a compressive strength ≥20N; the pellets do not burst when directly heated in a tube furnace at 1000℃, and the zinc removal rate is ≥85%.

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