CN110229960B - Method for preparing magnesium-containing pellets from coarse iron-containing ore - Google Patents

Method for preparing magnesium-containing pellets from coarse iron-containing ore Download PDF

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CN110229960B
CN110229960B CN201910590146.9A CN201910590146A CN110229960B CN 110229960 B CN110229960 B CN 110229960B CN 201910590146 A CN201910590146 A CN 201910590146A CN 110229960 B CN110229960 B CN 110229960B
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pellets
drying
coarse
iron
roasting
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CN110229960A (en
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潘建
朱德庆
李启厚
郭正启
田宏宇
杨聪聪
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Beijing zhonghonglian Engineering Technology Co.,Ltd.
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Central South University
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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
    • C22B1/00—Preliminary treatment of ores or scrap
    • C22B1/14—Agglomerating; Briquetting; Binding; Granulating
    • C22B1/16—Sintering; Agglomerating
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
    • C22B1/00—Preliminary treatment of ores or scrap
    • C22B1/14—Agglomerating; Briquetting; Binding; Granulating
    • C22B1/24—Binding; Briquetting ; Granulating
    • C22B1/2406—Binding; Briquetting ; Granulating pelletizing
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
    • C22B1/00—Preliminary treatment of ores or scrap
    • C22B1/14—Agglomerating; Briquetting; Binding; Granulating
    • C22B1/24—Binding; Briquetting ; Granulating
    • C22B1/2413—Binding; Briquetting ; Granulating enduration of pellets
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
    • C22B1/00—Preliminary treatment of ores or scrap
    • C22B1/14—Agglomerating; Briquetting; Binding; Granulating
    • C22B1/24—Binding; Briquetting ; Granulating
    • C22B1/242—Binding; Briquetting ; Granulating with binders
    • C22B1/244—Binding; Briquetting ; Granulating with binders organic
    • C22B1/245—Binding; Briquetting ; Granulating with binders organic with carbonaceous material for the production of coked agglomerates
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P10/00—Technologies related to metal processing
    • Y02P10/20—Recycling

Abstract

The invention discloses a method for preparing magnesium-containing pellets from coarse iron-containing ore, which comprises the following steps: (1) crushing the coarse-grained iron-containing ore by using 1-N sections of double rollers or crushing the coarse-grained iron-containing ore by using 1-N sections of double rollers and then performing combined treatment by using a high-pressure roller mill to crush the coarse-grained iron-containing ore to meet the requirements of the granularity and the specific surface area of a pelletizing raw material so as to obtain fine-grained concentrate; (2) uniformly mixing fine-grained concentrate, bentonite, internally-matched carbon powder, light-burned magnesite and limestone for pelletizing to obtain green pellets with proper granularity and performance; (3) drying, preheating and roasting the green ball cloth on special drying, preheating and roasting equipment. The invention solves the problem of ore grinding process for preparing fine-grain refined powder required by pelletizing from coarse-grained iron-containing raw materials, and simultaneously realizes the aim of directly producing high-quality pellets from coarse-grained fine ores and difficult-to-calcine fine ores by the aid of alkalinity and MgO cooperation and internal carbon blending technology.

Description

Method for preparing magnesium-containing pellets from coarse iron-containing ore
Technical Field
The invention belongs to the technical field of metallurgical materials, and particularly relates to a method for preparing magnesium-containing pellets from coarse iron-containing ores.
Background
The pellet ore is used as a high-quality furnace charge for modern blast furnace ironmaking, and has the characteristics of uniform particle size, high cold strength, high iron grade and good reducibility, so that the proportion of the pellet ore used in the furnace charge is higher and higher. For the production of pellet ore, the characteristics of raw materials not only determine the processing and smelting performance of the pellet ore entering the furnace, but also determine the selection of the production system and the process of the pellet ore.
With the increase of the mining and selecting and purchasing costs of high-quality magnetite, modern steel enterprises need to innovate production application and process in order to control the cost and improve market competitiveness, iron-containing ores such as hematite, limonite or limonite, and the like meet the raw material component requirements of pellet production and are low in price, but the particle size is thick, and according to related production practices, acid oxidized pellets with good quality are successfully produced through a ball milling-grate-rotary kiln process (or a belt type roasting machine). However, compared with the conventional production process of fine-grained magnetite concentrate pellets, the addition of the wet ball milling process brings new problems, such as the wet ore milling process has the defects of long production flow (ball milling-grading-concentrating-settling-filtering), easy red running of a sedimentation tank to cause water pollution and over-grinding; the dry ball milling process needs dry raw materials and is easy to cause dust pollution. With the popularization of the blast furnace concentrate guideline, higher requirements are provided for comprehensive furnace charge alkalinity and metallurgical performance, and how to apply the low-price iron-containing minerals such as coarse-fraction hematite, limonite or limonite and the like to pellet production to prepare high-grade, high-strength and high-metallurgical-performance pellets is an important way for improving the market vitality and competitiveness of pellet production, even blast furnace smelting process.
Disclosure of Invention
Aiming at the defects existing in the ball milling process of iron-containing ores such as hematite, limonite or hematite and limonite and the like in the prior art and the prepared pellets can not meet the requirements of furnace charge alkalinity and metallurgical performance, the invention aims to provide the method for preparing magnesium-containing pellets from coarse-grained iron-containing ores, which has the advantages of short flow, convenient operation and low cost.
The invention provides the following technical scheme: a method for preparing magnesium-containing pellets from coarse iron-containing ore comprises the following steps:
(1) crushing the coarse-grained iron-containing ore by using 1-N sections of double rollers (N is more than or equal to 1), or crushing the coarse-grained iron-containing ore by using 1-N sections of double rollers and performing combined treatment by using a high-pressure roller mill until the granularity and the specific surface area of the pelletizing raw materials meet the requirements, so as to obtain fine-grained concentrate;
(2) uniformly mixing the fine-grained concentrate obtained in the step (1), bentonite, internally-prepared carbon powder, light-burned magnesite and limestone for pelletizing to obtain green pellets with proper granularity and performance;
(3) and (3) drying, preheating and roasting the green ball cloth obtained in the step (2) on special drying, preheating and roasting equipment to obtain roasted balls, namely the magnesium-containing pellets.
Preferably, the coarse-grained iron-containing ore is one or more of hematite, hematite-limonite, limonite and laterite-nickel ore; the coarse iron-containing ore has a particle size of more than 3mm and accounts for more than 60 percent, the maximum particle size is less than 25mm, the water content is 6 to 10 percent, and the Mohs hardness is less than or equal to 7.
Preferably, in the step (1), the gap between the pair of rollers for crushing the pair of rollers is one or more of 10mm, 5mm, 3mm and 1 mm;
feeding granularity of the high-pressure roller mill<3mm, and adjusting the pressure intensity range between the rollers of the high-pressure roller mill to be 30N/mm according to the hardness of the material2～100N/mm2The high pressure roller mill can pass through once, and 20-50% of rim charge circulation can be adopted.
Preferably, in the step (1), the granularity of the fine-grained concentrate is 75-90% in the range of-0.074 mm, -40-65% in the range of-0.045 mm, and the specific surface area is more than 1500cm2·g-1The water content is less than 9.0 percent; the TFe content is 61.5% -70%, and SiO2The content is 1.0-5.5%.
Preferably, in the step (2), the ratio of each raw material to the fine particle concentrate is as follows: 0.5-1.0 percent of bentonite, 0.75-1.00 percent of internal carbon powder, 1.0-3.0 percent of light-burned magnesite and binary alkalinity (CaO/SiO)2) 0.3 to 1.0.
Preferably, in the step (2), the pelletizing time is 12-14 min, and the green pellet granularity is 10-16 mm; the falling strength of the obtained green pellets is more than 4 times/0.5 m, the compressive strength of the green pellets is more than 15N/green pellets, and the bursting temperature of the green pellets is more than 300 ℃.
Preferably, in the step (3), the special drying, preheating and roasting equipment is a grate-rotary kiln or a belt roasting machine.
Further, in the step (3), the thickness of the material layer in the grate-rotary kiln process is 150-250 mm, drying of the grate is divided into blast drying and air draft drying, the blast drying temperature is 240-280 ℃, the drying time is 2-4 min, and the wind speed is 0.8-1.2 m.s-1The temperature of air draft drying is 320-380 ℃, the drying time is 3-6 min, and the wind speed is 1.2-1.6 m.s-1Preheating temperature is 950-1000 ℃, preheating time is 8-10 min, and wind speed is 1.6-1.8 m.s-1The roasting temperature of the rotary kiln is 1220-1280 ℃, and the roasting time is 15-20 min.
Further, in the step (3), the thickness of the material layer in the belt type roasting machine process is 300-450 mm, wherein the thickness of the bedding material is 50mm, the drying of the belt type roasting machine is divided into blast drying and air draft drying, the blast drying temperature is 240-280 ℃, the drying time is 3-6 min, and the wind speed is 1.0-1.4 m.s-1The temperature of air draft drying is 250-380 ℃, the drying time is 3-6 min, and the wind speed is 1.2-1.6 m.s-1Preheating at 850-1050 deg.c for 5-10 min and at 1.6-1.8 m.s-1The roasting temperature is 1200-1280 ℃, the roasting time is 10-15 min, and the roasting wind speed is 1.6-2.4 m.s-1The soaking temperature is 950-1100 ℃, and the soaking time is 3-5 min.
Preferably, in the step (3), the preheated pellets with the strength of more than 500N/pellet are obtained through drying and preheating, moisture removal and primary consolidation, and the preheated pellets are further roasted to obtain the roasted pellets with the final strength of more than 2800N/pellet.
The invention adopts a multi-segment double-roll crushing process or a multi-segment double-roll crushing-high pressure roller mill combined treatment process, under the natural moisture (moisture content is 6-10%), coarse grain iron-containing ores with Mohs hardness not more than 7, such as hematite, limonite, laterite-nickel ore, and the like with lower price are subjected to raw material pretreatment, so that the finely ground iron ore powder meets the requirements of granulation on the granularity and the specific surface area of the raw materials, the obtained finely ground ore powder is subjected to alkalinity and MgO content adjustment by adding internal carbon, limestone, light-burned magnesite, and the like, and is dried, preheated and roasted on a grate-rotary kiln or a belt roasting machine after granulation and green ball production, and the magnesium-containing pellets with high strength, low reduction and pulverization expansion and low reduction are produced.
The process flow of the invention does not need to pre-dry the powder ore, the pellet raw material obtained after pretreatment does not need to be filtered, dehydrated or graded, the pellet raw material can be directly used for pelletizing, and the invention has the advantages of short flow, easy operation, no dust and water pollution, low cost, good quality of finished pellets and the like, can greatly expand the source of the pellet raw material and improve the metallurgical performance of the pellets.
The invention has the advantages and positive effects that:
(1) the method has the advantages of short process flow, no water pollution and no need of drying the raw materials.
(2) The invention can reduce the iron lattice constant of the hematite reduced into magnetite during the reduction process of the pellets by adding magnesium additive-light burned magnesite and magnesium-iron mutual solution formed by iron oxide, thereby solving the defects of high reduction expansion rate and reduction degradation of the roasted pellets taking iron-containing minerals as raw materials.
(3) According to the invention, by adding a proper amount of internal carbon powder, an internal heat source can be provided, the problem of high roasting temperature caused by adding a magnesium additive is solved, part of hematite can be reduced into magnetite in the preheating roasting process, the activity of secondary hematite crystals formed by reoxidation is higher than that of primary hematite, and Fe is facilitated2O3Recrystallization and consolidation are carried out, and the pellet strength is improved.
(4) The method for preparing magnesium-containing pellets solves the problem of ore grinding process for preparing fine-grain fine powder required by pelletizing from coarse-grained iron-containing raw materials, and simultaneously realizes the aim of directly producing high-quality pellets from coarse-grained fine ores and difficult-to-calcine fine ores by the aid of alkalinity and MgO cooperation and an internal carbon mixing technology.
Drawings
FIG. 1 is a process flow diagram of example 8 of the present invention.
Detailed Description
The technical solution of the present invention is explained in detail by the following embodiments and the accompanying drawings.
The following examples and comparative examples, unless otherwise stated, use coarse grained iron-containing ore from brazil and philippines, coarse grained iron-containing ore comprising hematite (40% -70%), limonite (10% -20%), laterite nickel ore (10% -20%), coarse grained iron-containing ore having a grain size of more than 3mm accounting for more than 60%, maximum grain size of less than 25mm, moisture content of 6-10%, mohs hardness of less than or equal to 7.
The following are some examples and comparative examples.
Comparative example 1
(1) Carrying out wet ball milling treatment on the coarse-grained hematite powder, wherein the ball filling rate of a ball mill is 30%, the filling rate of iron-containing minerals is 10%, the ore pulp concentration is 70%, the ore milling time is 15min, the discharging particle size of the ball mill is-200 meshes and is 62.1%, and the discharging particle size of the ball mill is-325 meshes and is 40.5%; classifying by a hydrocyclone, wherein the proportion of-200 meshes of the first-stage overflow product accounts for 91.1 percent, the proportion of-325 meshes accounts for 77.5 percent, the concentration of the second-stage overflow product is 22.3 percent, the concentration of the second-stage settled sand is 77.5 percent, settling and concentrating are carried out on the second-stage overflow ore, then the second-stage overflow ore is mixed with the second-stage settled sand for filtering and dewatering, the water content of the filtered ore is 9.0 percent, and the specific surface area is2·g-1The TFe content of the obtained iron ore concentrate is 65.3 percent, and the SiO content2The content is 2.1 percent;
(2) adding bentonite with the content of 1.0% for pelletizing, wherein the pelletizing time is 12min, the green pellet granularity is 10mm-16mm, the falling strength of the obtained green pellets is 5.2 times/0.5 m, the compression strength of the green pellets is 14.8N/green pellet, and the green pellet bursting temperature is 370 ℃;
(3) drying and preheating the raw ball cloth on a chain grate at the blast drying temperature of 260 ℃ for 3min and the wind speed of 1.2 m.s-1The temperature of air draft drying is 350 ℃, the drying time is 5min, and the wind speed is 1.6 m.s-1. Preheating temperature is 1000 ℃, preheating time is 10min, and wind speed is 1.6 m.s-1The compression strength of the pellets is more than 500N/pellet, the preheated pellets enter a rotary kiln for roasting, the roasting temperature is 1270 ℃, and the roasting time is 20 min.
The compression strength of the finished pellets is 3020N/piece, the reduction expansion rate is 21.3%, and the low-temperature reduction pulverization is 4.0%.
Example 1
The method for preparing magnesium-containing pellets from coarse iron-containing ore comprises the following steps:
(1) crushing coarse-grained hematite powder in a natural water state (with water content of 8.5%) by two pairs of rollers until the grain size is-3 mm and accounts for 100%, wherein the gaps between the rollers for crushing the rollers are respectively 10mm and 3mm, then pretreating by adopting a high-pressure roller mill once, circulating without edge materials, and controlling the pressure between the rollers of the high-pressure roller mill to be 50N/mm2To obtain 72.44% powder ore with-0.074 mm35.19% of 0.045 mm), and 1310cm of specific surface area2·g-1The TFe content of the obtained fine iron ore concentrate is 65.3 percent, and the SiO content is2The content is 2.1 percent;
(2) adding 1.0% of bentonite for pelletizing, wherein the pelletizing time is 12min, the pellet granularity is 10-16 mm, the dropping strength of the obtained green pellets is 6.4 times/0.5 m, the compressive strength is 15.3N/pellet, and the bursting temperature is 410 ℃;
(3) drying and preheating the raw ball cloth on a chain grate at the blast drying temperature of 260 ℃ for 3min and the wind speed of 1.2 m.s-1The temperature of air draft drying is 350 ℃, the drying time is 5min, and the wind speed is 1.6 m.s-1. Preheating temperature is 1000 ℃, preheating time is 10min, and wind speed is 1.6 m.s-1And the compression strength of the pellets is more than 500N/pellet, the preheated pellets enter a rotary kiln for roasting at the roasting temperature of 1270 ℃ for 20min, and the magnesium-containing pellets are obtained.
The compression strength of finished pellets (magnesium-containing pellets) is 2550N/pellet, the reduction expansion rate is 19.6%, and the low-temperature reduction degradation rate is 4.5%.
Example 2
The method for preparing magnesium-containing pellets from coarse iron-containing ore comprises the following steps:
(1) crushing coarse-grained hematite powder in a natural water state (with water content of 8.5%) by two pairs of rollers until the grain size is-3 mm and accounts for 100%, wherein the gaps between the rollers for crushing the rollers are respectively 10mm and 3mm, and performing circulating pretreatment on the edge materials by a high-pressure roller mill once, wherein the pressure between the rollers of the high-pressure roller mill is 50N/mm2The ratio of rim charge circulation is 20%, the rim charge is treated to-0.074 mm 75.31% (-0.045mm 39.21%), the specific surface area is 1420cm2·g-1The TFe content of the obtained iron ore concentrate is 65.3 percent, and the SiO content2The content is 2.1 percent;
(2) adding 1.0% of bentonite for pelletizing, wherein the pelletizing time is 12min, the pellet granularity is 10-16 mm, the falling strength of the obtained green pellets is 7.0 times/0.5 m, the compressive strength is 16.1N/pellet, and the bursting temperature is 395 ℃;
(3) drying and preheating the raw ball cloth on a chain grate at the blast drying temperature of 260 ℃ for 3min and the wind speed of 1.2 m.s-1The temperature of air draft drying is 350 ℃, the drying time is 5min, and the wind speed is 1.6 m.s-1. Preparation ofThe heat temperature is 1000 ℃, the preheating time is 10min, and the wind speed is 1.6 m.s-1And the compression strength of the pellets is more than 500N/pellet, the preheated pellets enter a rotary kiln for roasting, the roasting temperature is 1250 ℃, and the roasting time is 20min, so that the magnesium-containing pellets are obtained.
The compression strength of finished pellets (magnesium-containing pellets) is 2640N/pellet, the reduction expansion rate is 18.3%, and the low-temperature reduction degradation rate is 3.7%.
Example 3
The method for preparing magnesium-containing pellets from coarse iron-containing ore comprises the following steps:
(1) crushing coarse-grained hematite powder in a natural water state (with water content of 8.5%) by two pairs of rollers until the grain size is-3 mm and accounts for 100%, wherein the gaps between the rollers for crushing the rollers are respectively 10mm and 3mm, and performing circulating pretreatment on the edge materials by a high-pressure roller mill once, wherein the pressure between the rollers of the high-pressure roller mill is 50N/mm2The edge material is circulated 50% and treated to-0.074 mm 80.42% (-0.045mm 45.99%) and the specific surface area is 1570cm2·g-1The TFe content of the obtained iron ore concentrate is 65.3 percent, and the SiO content2The content is 2.1 percent;
(2) adding 1.0% of bentonite for pelletizing, wherein the pelletizing time is 12min, the pellet granularity is 10-16 mm, the falling strength of the obtained green pellets is 7.0 times/0.5 m, the compressive strength is 16.1N/pellet, and the bursting temperature is 395 ℃;
(3) drying and preheating the raw ball cloth on a chain grate at the blast drying temperature of 260 ℃ for 3min and the wind speed of 1.2 m.s-1The temperature of air draft drying is 350 ℃, the drying time is 5min, and the wind speed is 1.6 m.s-1. Preheating temperature is 1000 ℃, preheating time is 10min, and wind speed is 1.6 m.s-1And the compression strength of the pellets is more than 500N/pellet, the preheated pellets enter a rotary kiln for roasting, the roasting temperature is 1250 ℃, and the roasting time is 20min, so that the magnesium-containing pellets are obtained.
The compression strength of finished pellets (magnesium-containing pellets) is 2690N/pellet, the reduction expansion rate is 17.5%, and the low-temperature reduction degradation rate is 3.4%.
Example 4
The method for preparing magnesium-containing pellets from coarse iron-containing ore comprises the following steps:
(1) mixing coarse-fraction hematite powderCrushing the mixture by two pairs of rollers in a natural water state (the water content is 8.5%) until the particle size of-3 mm accounts for 100%, wherein the gap between the crushed rollers is 10mm and 3mm, performing circular pretreatment on the edge material of the high-pressure roller mill once, and the pressure between the grinding rollers of the high-pressure roller mill is 50N/mm2The edge material is circulated 50% and treated to-0.074 mm 80.42% (-0.045mm 45.99%) and the specific surface area is 1570cm2·g-1The TFe content of the obtained iron ore concentrate is 65.3 percent, and the SiO content2The content is 2.1 percent;
(2) the bentonite content is 1.0%, and the binary alkalinity (CaO/SiO)2) Adjusting the pellet size to 0.3 for pelletizing, wherein the pelletizing time is 12min, the pellet size is 10-16 mm, the dropping strength of the obtained green pellets is 6.8 times/0.5 m, the compressive strength is 16.8N/pellet, and the bursting temperature is 390 ℃;
(3) drying and preheating the raw ball cloth on a chain grate at the blast drying temperature of 260 ℃ for 3min and the wind speed of 1.2 m.s-1The temperature of air draft drying is 350 ℃, the drying time is 5min, and the wind speed is 1.6 m.s-1. Preheating temperature is 1000 ℃, preheating time is 10min, and wind speed is 1.6 m.s-1And the compression strength of the pellets is more than 500N/pellet, the preheated pellets enter a rotary kiln for roasting, the roasting temperature is 1250 ℃, and the roasting time is 20min, so that the magnesium-containing pellets are obtained.
The compression strength of finished pellets (magnesium-containing pellets) is 3070N/pellet, the reduction expansion rate is 19.6%, and the low-temperature reduction degradation rate is 3.0%.
Example 5
The method for preparing magnesium-containing pellets from coarse iron-containing ore comprises the following steps:
(1) crushing coarse-grained hematite powder in a natural water state (with water content of 8.5%) by two pairs of rollers until the grain size is-3 mm and accounts for 100%, wherein the gaps between the rollers for crushing the rollers are respectively 10mm and 3mm, and performing circulating pretreatment on the edge materials by a high-pressure roller mill once, wherein the pressure between the rollers of the high-pressure roller mill is 50N/mm2The edge material is circulated 50% and treated to-0.074 mm 80.42% (-0.045mm 45.99%) and the specific surface area is 1570cm2·g-1The TFe content of the obtained iron ore concentrate is 65.3 percent, and the SiO content2The content is 2.1 percent;
(2) the bentonite content is 1.0%, the light-burned magnesite proportion is 1.0%, and the binary alkalinity (CaO/SiO)2) Adjusting the pellet size to 0.3 for pelletizing, wherein the pelletizing time is 12min, the pellet size is 10-16 mm, the dropping strength of the obtained green pellets is 6.5 times/0.5 m, the compressive strength is 15.5N/pellet, and the bursting temperature is 390 ℃;
(3) drying and preheating the raw ball cloth on a chain grate at the blast drying temperature of 260 ℃ for 3min and the wind speed of 1.2 m.s-1The temperature of air draft drying is 350 ℃, the drying time is 5min, and the wind speed is 1.6 m.s-1. Preheating temperature is 1000 ℃, preheating time is 10min, and wind speed is 1.6 m.s-1And the compression strength of the pellets is more than 500N/pellet, the preheated pellets enter a rotary kiln for roasting, the roasting temperature is 1250 ℃, and the roasting time is 20min, so that the magnesium-containing pellets are obtained.
The compression strength of finished pellets (magnesium-containing pellets) is 2870N/pellet, the reduction expansion rate is 16.1 percent, and the low-temperature reduction degradation rate is 2.5 percent.
Example 6
The method for preparing magnesium-containing pellets from coarse iron-containing ore comprises the following steps:
(1) crushing coarse-grained hematite powder in a natural water state (with water content of 8.5%) by two pairs of rollers until the grain size is-3 mm and accounts for 100%, wherein the gaps between the rollers for crushing the rollers are respectively 10mm and 3mm, and performing circulating pretreatment on the edge materials by a high-pressure roller mill once, wherein the pressure between the rollers of the high-pressure roller mill is 50N/mm2The edge material is circulated 50% and treated to-0.074 mm 80.42% (-0.045mm 45.99%) and the specific surface area is 1570cm2·g-1The TFe content of the obtained iron ore concentrate is 65.3 percent, and the SiO content2The content is 2.1 percent;
(2) the bentonite content is 1.0%, the light-burned magnesite proportion is 1.5%, and the binary alkalinity (CaO/SiO)2) Adjusting the pellet size to 0.3 for pelletizing, wherein the pelletizing time is 12min, the pellet size is 10-16 mm, the dropping strength of the obtained green pellets is 6.3 times/0.5 m, the compressive strength is 15.1N/pellet, and the bursting temperature is 390 ℃;
(3) drying and preheating the raw ball cloth on a chain grate at the blast drying temperature of 260 ℃ for 3min and the wind speed of 1.2 m.s-1The temperature of air draft drying is 350 ℃, the drying time is 5min, and the wind speed is 1.6 m.s-1. Preheating temperature is 1000 ℃, preheating time is 10min, and wind speed is 1.6 m.s-1The compression strength of the pellets is more than 500N/pellet, preheatingAnd (3) roasting the pellets in a rotary kiln at the roasting temperature of 1250 ℃ for 20min to obtain magnesium-containing pellets.
The compression strength of finished pellets (magnesium-containing pellets) is 2710N/pellet, the reduction expansion rate is 13.0 percent, and the low-temperature reduction degradation rate is 2.1 percent.
Example 7
The method for preparing magnesium-containing pellets from coarse iron-containing ore comprises the following steps:
(1) crushing coarse-grained hematite powder in a natural water state (with water content of 8.5%) by two pairs of rollers until the grain size is-3 mm and accounts for 100%, wherein the gaps between the rollers for crushing the rollers are respectively 10mm and 3mm, and performing circulating pretreatment on the edge materials by a high-pressure roller mill once, wherein the pressure between the rollers of the high-pressure roller mill is 50N/mm2The edge material is circulated 50% and treated to-0.074 mm 80.42% (-0.045mm 45.99%) and the specific surface area is 1570cm2·g-1The TFe content of the obtained iron ore concentrate is 65.3 percent, and the SiO content2The content is 2.1 percent;
(2) the bentonite content is 1.0%, the light-burned magnesite proportion is 2.0%, and the binary alkalinity (CaO/SiO)2) Adjusting the pellet size to 0.3 for pelletizing, wherein the pelletizing time is 12min, the pellet size is 10-16 mm, the dropping strength of the obtained green pellets is 6.3 times/0.5 m, the compressive strength is 15.1N/pellet, and the bursting temperature is 390 ℃;
(3) drying and preheating the raw ball cloth on a chain grate at the blast drying temperature of 260 ℃ for 3min and the wind speed of 1.2 m.s-1The temperature of air draft drying is 350 ℃, the drying time is 5min, and the wind speed is 1.6 m.s-1. Preheating temperature is 1000 ℃, preheating time is 10min, and wind speed is 1.6 m.s-1And the compression strength of the pellets is more than 500N/pellet, the preheated pellets enter a rotary kiln for roasting, the roasting temperature is 1250 ℃, and the roasting time is 20min, so that the magnesium-containing pellets are obtained.
The compression strength of finished pellets (magnesium-containing pellets) is 2580N/pellet, the reduction expansion rate is 11.2%, and the low-temperature reduction degradation rate is 2.0%.
Example 8
The method for preparing magnesium-containing pellets from coarse iron-containing ore, as shown in fig. 1, includes the following steps:
(1) the coarse-grained hematite powder is put in a natural water stateCrushing the mixture by two pairs of rollers until the particle diameter of-3 mm accounts for 100% in a state (the water content is 8.5%), wherein the gap between the pair of rollers for crushing the pair of rollers is 10mm and 3mm respectively, performing circular pretreatment on the edge materials of the high-pressure roller mill once, and controlling the pressure between the grinding rollers of the high-pressure roller mill to be 50N/mm2The edge material is circulated 50% and treated to-0.074 mm 80.42% (-0.045mm 45.99%) and the specific surface area is 1570cm2·g-1The TFe content of the obtained iron ore concentrate is 65.3 percent, and the SiO content2The content is 2.1 percent;
(2) the bentonite content is 1.0%, the light-burned magnesite proportion is 1.0%, and the binary alkalinity (CaO/SiO)2) Adjusting to 0.3, pelletizing with 0.6% of internal carbon, wherein the pelletizing time is 12min, the green pellet granularity is 10-16 mm, the falling strength of the obtained green pellets is 6.7 times/0.5 m, the compressive strength is 16.8N/green pellets, and the bursting temperature is 395 ℃;
(3) drying and preheating the raw ball cloth on a chain grate at the blast drying temperature of 260 ℃ for 3min and the wind speed of 1.2 m.s-1The temperature of air draft drying is 350 ℃, the drying time is 5min, and the wind speed is 1.6 m.s-1. Preheating temperature is 1000 ℃, preheating time is 10min, and wind speed is 1.6 m.s-1And the compression strength of the pellets is more than 500N/pellet, the preheated pellets enter a rotary kiln for roasting, the roasting temperature is 1250 ℃, and the roasting time is 20min, so that the magnesium-containing pellets are obtained.
The compression strength of finished pellets (magnesium-containing pellets) is 3190N/pellet, the reduction expansion rate is 11.4%, and the low-temperature reduction degradation rate is 1.5%.
It can be seen from the above examples that comparative example 1 has a longer flow than pellets prepared in examples 1 to 8, is likely to cause water pollution, and has poor metallurgical properties although pellet strength meeting the production requirements of blast furnaces can be obtained.
Example 1 pellets similar to those of comparative example 1 were produced without drying the raw material and without the need for filtration dewatering and classification of the fine concentrate.
In the embodiments 2 and 3, the edge material circulating load in the pretreatment of multi-section double-roller crushing combined with high-pressure roller grinding and rolling is respectively increased, the granularity of the fine ore is optimized, the specific surface area is increased, and the green ball performance is further improved. Example 1 by adjusting the alkalinity, the strength of the finished pellets is further increased, but the metallurgical properties are poorer.
In the embodiments 5 to 7, the content of magnesium is adjusted by the magnesium additive, and the metallurgical performance of the finished pellets is obviously improved along with the moderate increase of the addition amount, but the strength of the finished pellets is reduced.
In the embodiment 8, a small amount of internal carbon is added, so that the strength of the finished pellets is obviously improved on the premise of not influencing the green pellet performance and the metallurgical performance of the finished pellets. Therefore, the pellets with better green pellet performance, finished pellet strength and metallurgical performance are obtained under the comprehensive regulation and control of a plurality of measures such as raw material pretreatment, alkalinity, magnesium additives, internal carbon distribution and the like, and guarantee is provided for meeting the fine material policy of subsequent blast furnace production.
In conclusion, compared with the traditional pellet preparation process, the method for preparing the pellets by the coarse fraction iron-containing ore powder has the advantages that the process flow is obviously shortened, the water pollution is avoided, the production and operation cost is reduced, the defect that the metallurgical property of pellet products prepared by ball milling the coarse fraction ore powder is poor is overcome through the optimization of the additive, and the high-quality finished pellets are prepared at low cost.
The above description is only a preferred embodiment of the present invention, and the protection scope of the present invention is not limited to the above-described embodiments. Modifications and variations that may occur to those skilled in the art without departing from the spirit and scope of the invention are to be considered as within the scope of the invention.

Claims (8)

1. The method for preparing magnesium-containing pellets from coarse iron-containing ore is characterized by comprising the following steps:
(1) crushing the coarse-grained iron-containing ore by using 1-N sections of double rollers, wherein N is more than or equal to 1, or crushing the coarse-grained iron-containing ore by using 1-N sections of double rollers and performing combined treatment by using a high-pressure roller mill until the coarse-grained iron-containing ore meets the requirements of the granularity and the specific surface area of a pelletizing raw material to obtain fine-grained concentrate;
(2) uniformly mixing the fine-grained concentrate obtained in the step (1), bentonite, internally-prepared carbon powder, light-burned magnesite and limestone for pelletizing to obtain green pellets with proper granularity and performance;
(3) drying, preheating and roasting the green ball cloth obtained in the step (2) on special drying, preheating and roasting equipment to obtain roasted balls, namely the magnesium-containing pellets;
in the step (2), the ratio of the internally-mixed carbon powder is 0.75-1.00%;
the coarse-grained iron-containing ore is one or more of hematite, hematite-limonite, limonite and laterite-nickel ore; the coarse iron-containing ore has the granularity of more than 3mm and accounts for more than 60 percent, the maximum granularity is less than 25mm, the moisture content is 6-10 percent, and the Mohs hardness is less than or equal to 7;
in the step (2), the ratio of each raw material to the fine particle concentrate is as follows: 0.5-1.0 percent of bentonite, 1.0-3.0 percent of light-burned magnesite and binary alkalinity (CaO/SiO)2) 0.3 to 1.0.
2. The method for preparing magnesium-containing pellets from the coarse iron-containing ore according to claim 1, wherein in the step (1), the gap between the roller pair for crushing the roller pair is one or more of 10mm, 5mm, 3mm and 1 mm; the feed particle size of the high-pressure roller mill is<3mm, and adjusting the pressure intensity range between the rollers of the high-pressure roller mill to be 30N/mm according to the hardness of the material2~100N/mm2The high-pressure roller mill can pass through once, and 20% -50% of rim charge circulation can be adopted.
3. The method for preparing magnesium-containing pellets by using the coarse iron-containing ore according to claim 1, wherein in the step (1), the fine concentrate particle size of-0.074 mm is 75% -90%, the 0.045mm is 40% -65%, and the specific surface area is more than 1500cm2·g-1The water content is less than 9.0 percent; the TFe content is 61.5-70%, and SiO2The content is 1.0% -5.5%.
4. The method for preparing magnesium-containing pellets by using the coarse iron-containing ore according to claim 1, wherein in the step (2), the pelletizing time is 12-14 min, and the green pellet size is 10-16 mm; the falling strength of the obtained green ball is more than 4 times/0.5 m, the compressive strength of the green ball is more than 15N/green ball, and the bursting temperature of the green ball is more than 300 ℃.
5. The method for preparing magnesium-containing pellets from the coarse iron-containing ore according to claim 1, wherein in the step (3), the special drying, preheating and roasting equipment is a grate-rotary kiln or a belt roasting machine.
6. The method for preparing magnesium-containing pellets by using the coarse iron-containing ore as claimed in claim 5, wherein in the step (3), the thickness of the material layer in the grate-rotary kiln process is 150-250 mm, the drying of the grate is divided into blast drying and air draft drying, the blast drying temperature is 240-280 ℃, the drying time is 2-4 min, and the wind speed is 0.8-1.2 m-s-1The temperature of air draft drying is 320-380 ℃, the drying time is 3-6 min, and the air speed is 1.2-1.6 m.s-1Preheating temperature is 950-1000 ℃, preheating time is 8-10 min, and wind speed is 1.6-1.8 m.s-1The roasting temperature of the rotary kiln is 1220-1280 ℃, and the roasting time is 15-20 min.
7. The method for preparing magnesium-containing pellets by using the coarse iron-containing ore according to claim 5, wherein in the step (3), the thickness of the material layer in the belt type roasting machine process is 300-450 mm, wherein the thickness of the bedding material is 50mm, the drying of the belt type roasting machine is divided into air blast drying and air draft drying, the air blast drying temperature is 240-280 ℃, the drying time is 3-6 min, and the air speed is 1.0-1.4 m-s-1The temperature of air draft drying is 250-380 ℃, the drying time is 3-6 min, and the air speed is 1.2-1.6 m.s-1Preheating temperature is 850-1050 ℃, preheating time is 5-10 min, and wind speed is 1.6-1.8 m.s-1The roasting temperature is 1200-1280 ℃, the roasting time is 10-15 min, and the roasting wind speed is 1.6-2.4 m.s-1The soaking temperature is 950-1100 ℃, and the soaking time is 3-5 min.
8. The method for preparing magnesium-containing pellets by using the coarse iron-containing ore according to claim 1, wherein in the step (3), the preheated pellets with the strength of more than 500N/pellet are obtained by drying and preheating, removing water and performing primary consolidation, and the preheated pellets are further roasted to obtain the roasted pellets with the final strength of more than 2800N/pellet.
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