阅读说明：本技术 一种配加含氟磁铁精矿生产的石灰石型熔剂性球团矿及其制备方法 (Limestone type fluxed pellet produced by adding fluorine-containing magnetite concentrate and preparation method thereof ) 是由 付国伟 白晓光 候贵生 吕志义 张永 于 2021-08-18 设计创作，主要内容包括：本发明公开了一种配加含氟磁铁精矿生产的石灰石型熔剂性球团矿,其原料按照重量百分比包括：含氟磁铁精矿75％、无氟磁铁精矿25％,以及外配皂土1.5％～2.7％、外配石灰石2.6％～3.8％。还公开了一种适宜于链篦机-回转窑-环冷机工艺利用含氟磁铁精矿为主要铁料搭配石灰石制备熔剂性球团矿的方法。本发明制备的球团矿抗压强度、转鼓强度及冶金性能均可满足大型高炉冶炼需求同时确定了适宜于链篦机-回转窑-环冷机工艺使用含氟磁铁精矿为主要铁料搭配石灰石生产高质量熔剂性球团矿的干燥、预热、焙烧及冷却制度。(The invention discloses limestone type fluxed pellets produced by adding fluorine-containing magnetite concentrate, which comprises the following raw materials in percentage by weight: 75 percent of fluorine-containing magnetite concentrate, 25 percent of fluorine-free magnetite concentrate, 1.5 to 2.7 percent of external bentonite and 2.6 to 3.8 percent of external limestone. Also discloses a method for preparing the fluxed pellets by using the fluorine-containing magnetite concentrate as a main iron material and matching limestone in the process of a chain grate machine, a rotary kiln and a circular cooler. The compression strength, the drum strength and the metallurgical performance of the pellet ore prepared by the invention can meet the smelting requirement of a large-scale blast furnace, and simultaneously, a drying, preheating, roasting and cooling system suitable for producing high-quality fluxed pellet ore by using fluorine-containing magnetite concentrate as a main iron material and matching limestone in a grate-rotary kiln-circular cooler process is determined.)

1. A limestone type fluxed pellet produced by adding fluorine-containing magnetite concentrate is characterized in that: the raw materials comprise the following components in percentage by weight: 75 percent of fluorine-containing magnetite concentrate, 25 percent of fluorine-free magnetite concentrate, 1.5 to 2.7 percent of external bentonite and 2.6 to 3.8 percent of external limestone.

2. The limestone type fluxed pellets produced by blending fluorine-containing magnetite concentrate according to claim 1, characterized in that: the fluorine-containing magnetite concentrate comprises the following chemical components in percentage by weight: 65.5 to 66.5 percent of TFe, 28.5 to 29.5 percent of FeO and 0.60 to 0.80 percent of MgOCaO 1.70-2.40%, Al₂O₃≤0.20％，SiO₂0.80-1.70 percent of S, 0.65-1.05 percent of F, 0.25-0.35 percent of K₂O≤0.10％，Na₂O is less than or equal to 0.10 percent; and the concentrate with the granularity less than or equal to 0.074mm in the fluorine-containing magnetite concentrate accounts for at least 95 percent of the total weight of the first iron concentrate.

3. The limestone type fluxed pellets produced by blending fluorine-containing magnetite concentrate according to claim 1, characterized in that: the chemical components of the fluorine-free magnetite concentrate comprise, by weight, 64.0-66.50% of TFe, 27.0-29.0% of FeO, 0.50-0.70% of MgO, 0.60-0.75% of CaO, and Al₂O₃Less than or equal to 0.5 percent of SiO₂4.50 to 5.50 percent of S, 0.10 to 0.15 percent of S, less than or equal to 0.05 percent of F, K₂O≤0.08％，Na₂O is less than or equal to 0.08 percent; and the percentage of the concentrate with the granularity less than or equal to 0.074mm in the fluorine-free magnetite concentrate to the total weight of the fluorine-free magnetite concentrate is at least 80%.

4. The limestone type fluxed pellets produced by blending fluorine-containing magnetite concentrate according to claim 1, characterized in that: the chemical components of the bentonite comprise SiO according to weight percentage₂54.0 to 56.0 percent of the total weight of the alloy, and less than or equal to 14.0 percent of Ig; the limestone comprises 50.0-52.0% of CaO and SiO in percentage by weight₂2.0-4.0 percent of the total weight of the magnesium oxide, 1.0-3.0 percent of MgO and less than or equal to 42.0 percent of Ig.

5. The limestone type fluxed pellets produced by blending fluorine-containing magnetite concentrate according to claim 1, characterized in that: according to the weight percentage, the fluorine-containing magnetite concentrate is 75%, the fluorine-free magnetite concentrate is 25%, the external bentonite is 1.5%, and the external lime is 3.2%.

6. A method for preparing the fluxed pellets by using fluoride-containing magnetite concentrate as a main iron material and matching limestone in a grate-rotary kiln-circular cooler process is characterized by comprising the following steps:

pelletizing the mixture in a pelletizing disc of phi 6m to obtain green pellets; the pelletizing disc process control parameters are as follows: raw ball moisture is 8.0-8.5%, the inclination angle of the ball tray is 45-45.5%, the falling strength of the raw ball reaches more than 5 times/P, the raw ball granularity composition is controlled to be 8-16 mm by screening, the proportion reaches more than 95%, and the wet return rate is controlled within 20%;

uniformly spreading green balls on a chain grate machine through a green ball distributing device and a screening device, wherein the green ball thickness of the chain grate machine is 180-191 mm, and the machine speed of the chain grate machine is 1.80-1.90 m/min;

drying green balls through a grate blower drying section and an air draft drying section, wherein the conditions of the blower drying section are as follows: the temperature of an air box of the blast drying section is controlled to be 220-300 ℃, the pressure of the air box of the blast drying section is controlled to be 0.10-0.15 kpa, the temperature of a hood of the blast drying section is controlled to be 75-85 ℃, and the time is 3.16-3.33 min; the conditions of the air draft drying section are as follows: the temperature of a hood of the air draft drying section is controlled to be 560-570 ℃, the temperature of an air box of the air draft drying section is controlled to be 100-130 ℃, the pressure of the air box of the air draft drying section is controlled to be-0.90-1.10 kpa, and the time is 6.32-6.67 min;

preheating the dry balls through a first preheating section and a second preheating section of a chain grate, wherein the first preheating section is preheated under the conditions that: the temperature of the fume hood at the preheating section is controlled to be 800-820 ℃, the temperature of the air box at the preheating section is controlled to be 170-210 ℃, the pressure of the air box at the preheating section is controlled to be-0.90-1.10 kpa, and the time is 3.16-3.33 min; the temperature of the preheating second-stage smoke hood is controlled to be 945-960 ℃, the temperature of the preheating second-stage air box is controlled to be 460-510 ℃, the pressure of the preheating second-stage air box is controlled to be-0.80 kpa-1.00 kpa, and the time is 9.47 min-10.00 min; the quality control requirement of the preheating ball is as follows: the FeO content is less than 5.0 percent, the S content is less than 0.40 percent, and the compressive strength is more than or equal to 1000N/P;

roasting the preheating balls in a rotary kiln, wherein the roasting conditions of the rotary kiln are as follows: the speed of the rotary kiln is controlled to be 0.90 r/min-0.96 r/min, the temperature of a kiln tail cover is controlled to be 810-840 ℃, the temperature of a kiln head cover is controlled to be 1040-1120 ℃, the roasting time in the kiln is 35-40 min, and the coal feeding amount is 2.2 t/h-2.2 t/h; the quality control requirement of the roasted spheres is as follows: the FeO content is less than 3.0 percent, the S content is less than 0.20 percent, and the compressive strength is more than or equal to 2000N/P;

cooling and recrystallizing the baked balls through a circular cooler, wherein the process conditions of the circular cooler are as follows: the machine speed of the ring cooling machine is controlled to be 0.85 m/min-0.90 m/min, the temperature of secondary air is controlled to be 1050 ℃ to 1100 ℃, the temperature of secondary air is controlled to be-12 kpa-15 kpa, the temperature of ring cooling two-stage waste gas is controlled to be 950 ℃ to 1010 ℃, the temperature of ring cooling three-stage waste gas is controlled to be 450 ℃ to 550 ℃, and the cooling time is 40 min-45 min; and cooling the baked pellets to finally obtain the limestone type fluorine-containing fluxed pellets.

7. The method of claim 6, wherein: the mineral content control requirements of the molten pellets are as follows: TFe is more than or equal to 62.0 percent, FeO content is less than 0.5 percent, S content is less than 0.15 percent, MgO content is more than or equal to 1.0 percent, and SiO₂The content is less than or equal to 3.5 percent, the content of F is less than or equal to 0.30 percent, and R_OMore than or equal to 1.0, the compressive strength more than or equal to 2200N/P, the drum strength more than or equal to 96 percent and the abrasion resistance index less than or equal to 3.5 percent.

Technical Field

The invention relates to the field of agglomeration of ironmaking raw material pellets, in particular to limestone type fluxed pellets produced by adding fluorine-containing magnetite concentrate and a preparation method thereof.

Background

770 million tons of Bayan Obo iron ore concentrates produced annually belong to ultrafine-granularity magnet ore concentrates, the proportion of 200 meshes is more than 90 percent, and the proportion of 325 meshes is more than 75 percent, so the method is more suitable for pellet production compared with the method for sintering raw materials. But because harmful elements such as potassium, sodium, fluorine and the like are contained at the same time, the reduction expansion rate of the pellet ore is high, the proportion of the special bayan obo concentrate ore cannot exceed 35 percent when the acid pellet ore is produced, and the problem that how to improve the large-proportion application of the bayan obo iron concentrate ore in the pellet production becomes a great need for steel cladding. Previous studies have shown that: the reduction expansion rate of the pellets prepared by using a large proportion of baiyuneboite concentrate can be inhibited by carrying out the production of the fluxed pellets.

In order to realize the high-proportion and high-quality application of the baiyuneboite concentrate in the production of the steel-coated pellets, basic theory, laboratory tests and industrial application research are systematically developed according to the particularity of the baiyuneboite concentrate, and the alkaline pellets with low reduction expansion rate added with the high-proportion baiyuneboite concentrate are researched and developed, so that technical support is provided for reducing the molten iron cost for steel coating, and meanwhile, a demonstration and leading effect is achieved for producing the pellets by utilizing the ultrafine-grained magnetite concentrate and the complex paragenic ore containing alkali metal for metallurgical enterprises in China.

The main contradiction faced by the steel industry in China in the new era is also converted into the contradiction that the industrial structure is not suitable for the competitive demand of the market and the green development level is not suitable for the demand of the ecological environment. Compared with the sintering process, the energy consumption of the oxidized pellet process is only half of that of the sintering process; the pellet ore has high iron-containing grade, so that the yield of the blast furnace is improved and the fuel ratio is reduced; the emission of pollutants such as NOx, dioxin and the like is reduced, so that the proportion of the pellets in the raw materials of the blast furnace is improved, the active improvement of the quality of the pellets is an important direction for realizing iron-making concentrate, energy conservation and emission reduction, and the requirements of environment-friendly and efficient upgrading of iron-making are met.

In 6-month middle-late 2020, companies respond to government regional emission reduction requirements, stop the production of a No. 2 machine for sintering, and generate a gap of nearly 6000t every day for the whole company sintered ore, so that in order to ensure the structural balance of the raw materials charged into a blast furnace, an iron-making plant gradually improves the proportion of the acid pellets to replace the shortage sintered ore. The industrial test is mainly carried out in a large-scale blast furnace (No. 5), and the proportion of the pellets fed into the furnace is gradually increased from 23 percent to 50 percent. From the overall test results, the yield is basically stabilized above 3850t/d, but due to the influence of factors such as the improvement of the pellet proportion, the adjustment of the distribution system, the adjustment of the slag alkalinity, and the like (the current limestone proportion is 1.5 t/batch, and the coke ratio is increased by about 16kg according to theoretical calculation), the fuel ratio is high, and the yield is also slightly reduced. The method shows that the blast furnace smelting is not favorable by completely using the acid pellet ore under the smelting condition of high pellet ratio. In order to improve the comprehensive feeding grade and technical and economic indexes of a large-scale blast furnace under the condition of high-ball ratio smelting and reduce the adding amount of limestone, the limestone type fluorine-containing fluxed pellet produced by a grate-rotary kiln-circular cooler is developed.

Disclosure of Invention

The invention aims to provide limestone type fluxed pellets produced by adding fluorine-containing magnetite concentrate and a preparation method thereof, wherein the compression strength, the drum strength and the metallurgical performance of the prepared pellets can meet the smelting requirement of a large-scale blast furnace, and simultaneously, a drying, preheating, roasting and cooling system suitable for producing high-quality fluxed pellets by using the fluorine-containing magnetite concentrate as a main iron material and matching limestone in a grate-rotary kiln-circular cooler process is determined.

In order to solve the technical problems, the invention adopts the following technical scheme:

a limestone type fluxed pellet produced by adding fluorine-containing magnetite concentrate comprises the following raw materials in percentage by weight: 75 percent of fluorine-containing magnetite concentrate, 25 percent of fluorine-free magnetite concentrate, 1.5 to 2.7 percent of external bentonite and 2.6 to 3.8 percent of external limestone.

Further, the fluorine-containing magnetite concentrate comprises the following chemical components in percentage by weight: 65.5 to 66.5 percent of TFe, 28.5 to 29.5 percent of FeO, 0.60 to 0.80 percent of MgO, 1.70 to 2.40 percent of CaO, and Al₂O₃≤0.20％，SiO₂0.80 to 1.70 percent0.65-1.05% of S, 0.25-0.35% of F, and K₂O≤0.10％，Na₂O is less than or equal to 0.10 percent; and the concentrate with the granularity less than or equal to 0.074mm in the fluorine-containing magnetite concentrate accounts for at least 95 percent of the total weight of the first iron concentrate.

Further, the chemical components of the fluorine-free magnetite concentrate comprise, by weight, 64.0-66.50% of TFe, 27.0-29.0% of FeO, 0.50-0.70% of MgO, 0.60-0.75% of CaO, and Al₂O₃Less than or equal to 0.5 percent of SiO₂4.50 to 5.50 percent of S, 0.10 to 0.15 percent of S, less than or equal to 0.05 percent of F, K₂O≤0.08％，Na₂O is less than or equal to 0.08 percent; and the percentage of the concentrate with the granularity less than or equal to 0.074mm in the fluorine-free magnetite concentrate to the total weight of the fluorine-free magnetite concentrate is at least 80%.

Further, the chemical components of the bentonite comprise SiO in percentage by weight₂54.0 to 56.0 percent of the total weight of the alloy, and less than or equal to 14.0 percent of Ig; the limestone comprises 50.0-52.0% of CaO and SiO in percentage by weight₂2.0-4.0 percent of the total weight of the magnesium oxide, 1.0-3.0 percent of MgO and less than or equal to 42.0 percent of Ig.

Further, according to the weight percentage, the fluorine-containing magnetite concentrate is 75%, the fluorine-free magnetite concentrate is 25%, the external bentonite is 1.5%, and the external lime is 3.2%.

A method for preparing the fluxed pellets by using the fluorine-containing magnetite concentrate as the main iron material and matching limestone in the process of a chain grate machine, a rotary kiln and a circular cooler comprises the following steps:

pelletizing the mixture in a pelletizing disc of phi 6m to obtain green pellets; the pelletizing disc process control parameters are as follows: raw ball moisture is 8.0-8.5%, the inclination angle of the ball tray is 45-45.5%, the falling strength of the raw ball reaches more than 5 times/P, the raw ball granularity composition is controlled to be 8-16 mm by screening, the proportion reaches more than 95%, and the wet return rate is controlled within 20%;

uniformly spreading green balls on a chain grate machine through a green ball distributing device and a screening device, wherein the green ball thickness of the chain grate machine is 180-191 mm, and the machine speed of the chain grate machine is 1.80-1.90 m/min;

drying green balls through a grate blower drying section and an air draft drying section, wherein the conditions of the blower drying section are as follows: the temperature of the air box of the blast drying section is controlled to be 220-300 ℃, the pressure of the air box of the blast drying section is controlled to be 0.10-0.15 kpa, the temperature of the hood of the blast drying section is controlled to be 75-85 ℃, and the time is 3.16-3.33 min. The conditions of the air draft drying section are as follows: the temperature of a hood of the air draft drying section is controlled to be 560-570 ℃, the temperature of an air box of the air draft drying section is controlled to be 100-130 ℃, the pressure of the air box of the air draft drying section is controlled to be-0.90-1.10 kpa, and the time is 6.32-6.67 min;

preheating the dry balls through a first preheating section and a second preheating section of a chain grate, wherein the first preheating section is preheated under the conditions that: the temperature of the fume hood at the preheating section is controlled to be 800-820 ℃, the temperature of the air box at the preheating section is controlled to be 170-210 ℃, the pressure of the air box at the preheating section is controlled to be-0.90-1.10 kpa, and the time is 3.16-3.33 min. The temperature of the preheating second-stage smoke hood is controlled to be 945-960 ℃, the temperature of the preheating second-stage air box is controlled to be 460-510 ℃, the pressure of the preheating second-stage air box is controlled to be-0.80 kpa-1.00 kpa, and the time is 9.47 min-10.00 min; the quality control requirement of the preheating ball is as follows: the FeO content is less than 5.0 percent, the S content is less than 0.40 percent, and the compressive strength is more than or equal to 1000N/P;

roasting the preheating balls in a rotary kiln, wherein the roasting conditions of the rotary kiln are as follows: the speed of the rotary kiln is controlled to be 0.90 r/min-0.96 r/min, the temperature of a kiln tail cover is controlled to be 810-840 ℃, the temperature of a kiln head cover is controlled to be 1040-1120 ℃, the roasting time in the kiln is 35-40 min, and the coal feeding amount is 2.2 t/h-2.2 t/h; the quality control requirement of the roasted spheres is as follows: the FeO content is less than 3.0 percent, the S content is less than 0.20 percent, and the compressive strength is more than or equal to 2000N/P;

cooling and recrystallizing the baked balls through a circular cooler, wherein the process conditions of the circular cooler are as follows: the machine speed of the ring cooling machine is controlled to be 0.85 m/min-0.90 m/min, the temperature of secondary air is controlled to be 1050 ℃ to 1100 ℃, the temperature of secondary air is controlled to be-12 kpa-15 kpa, the temperature of ring cooling two-stage waste gas is controlled to be 950 ℃ to 1010 ℃, the temperature of ring cooling three-stage waste gas is controlled to be 450 ℃ to 550 ℃, and the cooling time is 40 min-45 min; and cooling the baked pellets to finally obtain the limestone type fluorine-containing fluxed pellets.

Further, the fluxed pellet mineral quality controlThe method comprises the following steps: TFe is more than or equal to 62.0 percent, FeO content is less than 0.5 percent, S content is less than 0.15 percent, MgO content is more than or equal to 1.0 percent, and SiO₂The content is less than or equal to 3.5 percent, the content of F is less than or equal to 0.30 percent, and R_OMore than or equal to 1.0, the compressive strength more than or equal to 2200N/P, the drum strength more than or equal to 96 percent and the abrasion resistance index less than or equal to 3.5 percent.

Compared with the prior art, the invention has the beneficial technical effects that:

the invention realizes that on the premise of ensuring the normal operation of a flue gas purification system of a grate-rotary kiln-circular cooler process and controlling the reduction expansion rate of pellets within 20 percent, 75 percent of Bayan Obo iron ore concentrate is added to produce fluxed pellets with excellent quality, and the compression strength, the drum strength and the metallurgical performance of the pellets produced by the process can meet the smelting requirements of large-scale blast furnaces.

Drawings

The invention is further illustrated in the following description with reference to the drawings.

FIG. 1 is a flow chart of the preparation process of the present invention.

Detailed Description

The following examples further illustrate embodiments of the present invention, but the embodiments of the present invention are not limited to the following examples.

In each example, the raw material configuration, process parameters, pellet components and related properties used for producing limestone type fluorine-containing fluxed agent pellets by using the grate-rotary kiln-circular cooler process are shown in tables 1 to 7 respectively.

TABLE 1 raw material proportioning of each example

TABLE 2 raw ball quality data statistics for the examples

As can be seen from tables 1 and 2:

(1) during the project implementation period, the green ball moisture control is stable, the green ball performance is good, and the pellet granularity composition is good.

(2) During the implementation of the project, the moisture of the green pellets is not obviously changed after the limestone is added into the pelletizing mixture, the fluctuation range of the bentonite proportion is 1.5-2.7 percent due to the fluctuation of the particle size composition of the fluoride-free magnetite concentrate, and the limestone proportion control range is 2.6-3.8 percent for stabilizing the alkalinity of the pellet ore.

(3) During the implementation of the project, the stability of the pelletizing process is obviously improved, the wet return rate is obviously reduced, the wet return rate can be stably maintained at a level of 20 percent, and the pellet production requirements of a chain grate machine, a rotary kiln and a circular cooler can be met. This also demonstrates that the use of bayan obo fluorine-containing magnetite concentrate for pellet production improves the pelletizing process and green pellet quality.

TABLE 3 main technological parameters of grate-rotary kiln-circular cooler in each example

As can be seen from Table 3:

(1) during the project implementation, a basic process regime for stable high quality production of fluxed pellets using high sulfur self-produced concentrates for a large proportion (75%) is formed: the temperature of the second preheating stage smoke hood is controlled at 950 ℃, the temperature control range of the secondary air is 1050 +/-10 ℃, the thickness of the material layer of the chain grate is 180-190 mm, and the material layer is circularly cooled and paved. The third, fourth and fifth stages execute the process system to produce.

(2) During the project implementation period, no serious ring formation phenomenon of the rotary kiln occurs, which shows that the ring formation period of the rotary kiln cannot be greatly shortened when the limestone type fluxed pellets are produced.

(3) During the project implementation, the coal injection amount in the kiln is increased by about 16.7% compared with that of pellet ore which is 1-2 kg/t higher than that of the produced acid pellets, which indicates that the heat demand for producing the high-quality melt pellets is increased, mainly because the limestone is added, a large amount of heat is absorbed by decomposition in a preheating section, and simultaneously, the calcium ferrite and magnesium ferrite minerals formed in a roasting section also absorb a large amount of heat.

(4) During the project implementation period, the air quantity and the pressure of each circular cooling machine are stable, no hardening phenomenon occurs in the circular cooling machine, and no phenomenon that finished pellets are cooled and cannot fully discharge red materials is found, which shows that the production of the fluxed pellets has little influence on the circular cooling process.

Table 4 pellet chemical composition of each example

TABLE 5 Cold Strength and reduction Properties of the finished balls of the examples

From the analysis in table 5 it can be seen that:

(1) during the implementation period of the project, the chemical components of the finished product ball are stable, the TFe mean value of the pellet ore is about 62.61 percent, the CaO content mean value is 3.39 percent, and SiO is₂The average content was 3.18%, the F content was 0.21%, and the average alkalinity was 1.08.

(2) The TFe of limestone type fluxed pellets is improved by 0.16 percent compared with acid pellets; the average value of the FeO content is reduced by 1.29 percent compared with that of the acid pellets; the average CaO content is improved by 1.88 percent compared with the acid pellets; SiO 2₂The content average value is reduced by 1.88 percent compared with the acid pellets; the alkalinity is improved by 0.78 compared with the acidity pellet.

(3) Due to the fluorine-philic and sulfur-fixing characteristics of the fluxed pellets, the average value of S content residue is 0.09%, and the average value is improved by 0.086% compared with that of the acid pellets; the average value of the F content residual quantity is 0.20 percent, which is improved by 0.14 percent compared with the acid pellet.

TABLE 6 statistics of main indexes of flue gas purification in each example

As can be seen from Table 6:

(1) compressive strength: the average compressive strength of the pellets reaches 2229N/P during the implementation period, and the smelting requirement of a large-scale blast furnace can be met. (2) Drum strength. The mean value of the drum strength of the finished ball reaches 96.44 percent during the implementation period, and the smelting requirement of a large-scale blast furnace can be met.

(3) Reduction expansion rate: during the implementation period, the reduction expansion rate of the pellets meets the production requirement.

(5) From the yield, the average yield is stable during the implementation period, which shows that the raw material ratio is favorable for stable production during the implementation period.

(6) During the implementation, the smoke emission exceeding the standard does not occur.

The above-described embodiments are merely illustrative of the preferred embodiments of the present invention, and do not limit the scope of the present invention, and various modifications and improvements of the technical solutions of the present invention can be made by those skilled in the art without departing from the spirit of the present invention, and the technical solutions of the present invention are within the scope of the present invention defined by the claims.