Fine grinding powder as well as preparation method, preparation system and application thereof

Abstract

The invention belongs to the technical field of steel smelting, and particularly relates to fine grinding powder as well as a preparation method, a preparation system and application thereof. The method comprises the following steps: mixing limonite and specularite according to a mass ratio of (6-8): 3, and then rolling under dynamic drying of a thermal medium to obtain the fine grinding powder, and the dynamic drying of the thermal medium comprises the step of blowing by adopting hot air at 450-550 DEG C. The fine grinding powder prepared through the method is excellent in performance, the fine grinding powder is used as a green pellet raw material for preparing pellets, the strength and heat burst resistance of the green pellets are improved, the influence of roasting of iron ore powder with high burning loss and high crystal water on the pellet structure is reduced, and bentonite does not need to be added in the preparation process; and the finished pellets are excellent in compression resistance.

Description

Technical Field

[0001] The present invention belongs to the technical field of steel smelting, and in particular relates to a finely ground powder and a preparation method, a preparation system and applications thereof. Background Art

[0002] The entire pellet roasting process—drying, preheating, roasting, soaking, and cooling—is completed on a single piece of equipment. This features high single-unit production capacity, simple process flow, compact layout, lightweight equipment, and low energy consumption due to the recycling of hot exhaust gases. Throughout the roasting process, the pellets remain in a static layer, eliminating the generation of powder due to changes in pellet strength or relative motion during heating. As a result, the belt roasting process has been widely developed.

[0003] However, most domestic pellet production lines use more than 90% magnetite plus a small amount of other iron-containing raw materials to produce pellets. A small number of them will also use a small proportion of hematite. There is basically no production of pellets using a large proportion of limonite as raw material. Limonite raw material cost is low, but the main problems of using limonite for pellet roasting production are as follows:

[0004] 1) Limonite has high porosity and strong water holding capacity, making it difficult to settle and filter during wet grinding;

[0005] 2) When the ratio of hematite to limonite is high, the thermal stability of the green pellets is poor, the bursting temperature is low, and the crack rate of the pellets is high;

[0006] 3) Limonite contains a large amount of crystal water, which consumes a lot of heat in the drying and preheating stages, and the roasting temperature is high, resulting in high energy consumption in the process;

[0007] 4) The finished pellets have poor consolidation, low compressive strength and high powder content. Summary of the Invention

[0008] In response to the above-mentioned problems existing in the prior art, the present invention provides a finely ground powder and a preparation method, a preparation system and an application thereof, which can obtain high specific surface area finely ground powder using limonite as raw material, and the finely ground powder is suitable for the preparation of pellets with excellent performance.

[0009] To achieve the above-mentioned purpose, the technical solution provided by the present invention is as follows:

[0010] In a first aspect, the present application provides a method for preparing fine ground powder by dynamic dry grinding, characterized in that it comprises: mixing limonite and specularite in a mass ratio of (6-8):3, and then roller grinding under dynamic drying with a hot medium to obtain the fine ground powder.

[0011] Optionally, the heat medium dynamic drying includes: using hot air at 450-550° C. for blowing.

[0012] Optionally, the dynamic drying time of the heat medium is 28s-3min.

[0013] Optionally, the roller milling pressure is 6.8-9.0 MPa, and the roller milling treatment time is 28 s-3 min.

[0014] Optionally, the mass ratio of limonite to specularite is 7:3.

[0015] Optionally, 5% to 30% of the limonite phase is converted into hematite during roller milling under dynamic drying with hot medium.

[0016] In the second aspect, the present application also provides a finely ground powder prepared according to the method of the first aspect, wherein the finely ground powder has a -200 mesh size of ≥80% and an average specific surface area of ​​≥3000 cm 2 / g.

[0017] In a third aspect, the present application further provides a system for preparing the finely ground powder according to the second aspect, comprising:

[0018] Material bin, which is equipped with a disc feeder;

[0019] The grinding wheel and the grinding roller of the grinding wheel cooperate to grind the material into powder by roller grinding. The disc feeder conveys the material to the space between the grinding wheel and the grinding roller through the metering belt conveyor. The grinding wheel is provided with an air nozzle ring, which is opposite to the gap between the grinding wheel and the grinding roller.

[0020] Hot air furnace heating system, used to supply hot air to the nozzle ring on the mill;

[0021] The powder collector is connected to the mill through the powder selector and is used to collect the finely ground powder that meets the particle size requirements after roller grinding.

[0022] In a fourth aspect, the present application also provides a use of the finely ground powder described in the second aspect in pellet preparation.

[0023] Compared with the prior art, this application has at least the following beneficial effects:

[0024] The invention obtains fine ground powder by mixing limonite and specularite in a certain ratio and then roller-grinding the mixture under dynamic drying of a hot medium. The prepared fine ground powder has a large specific surface area, can obtain hydrophilic fine ground powder suitable for pelletizing, and improves the pelletizing performance of the raw materials.

[0025] The finely ground powder of the present invention is used as a raw material for preparing pellets, which improves the strength and thermal cracking resistance of the green balls, reduces the influence of roasting high-burning loss and high-crystallization water iron ore powder on the pellet structure, and does not require the addition of adhesives such as bentonite during the preparation process; the finished pellets have excellent compressive resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1Schematic diagram of the system for preparing finely ground powder in this application. DETAILED DESCRIPTION

[0027] The present invention is described in further detail below with reference to the accompanying drawings:

[0028] Unless otherwise specified, the experimental methods used in the embodiments of the present invention are conventional methods.

[0029] The reagents and materials used in this example can be purchased conventionally. The quantitative experiments involved in the examples were repeated at least three times, and the results were averaged.

[0030] Example 1

[0031] A finely ground powder, the preparation method of which is as follows:

[0032] Limonite and specularite were mixed in a mass ratio of 7:3 and then subjected to dynamic drying and roller grinding in a vertical roller mill using a hot medium to obtain fine ground powder; the fine ground powder had a particle size of 83% at -200 mesh and an average specific surface area of ​​3000 cm 2 / g;

[0033] Among them, the dynamic drying temperature of the heat medium is 500℃, the processing time is 40 s, the roller grinding pressure is 7.2MPa, and the roller grinding processing time is 28S. During the process, 5%-10% of the limonite phase can be converted into hematite.

[0034] The pellets are prepared using the finely ground powder as follows:

[0035] The finely ground powder is humidified to a moisture content of 8% by mass to obtain prefabricated iron ore powder;

[0036] A mixture, calculated by mass percentage, is prepared by mixing 22.2% prefabricated iron ore fines, 48.5% low-grade mixed ore, 18.2% magnetite, 7.1% sulfuric acid slag, and 4% highly dusted ash. The mixture is then pelletized and sieved to produce green balls. The green ball diameter is controlled to be 8-16 cm, and the balls fall between 5-8 times. The composition of the mixture is shown in Table 1. Other components are not listed, as they have little impact on pellet performance. In the following table, -200 indicates the percentage of material that falls through a 200-mesh sieve within a given component.

[0037] Table 1 Composition of components in the mixture

[0038] variety Moisture TFe FeO <![CDATA[SiO2]]> S P CaO Zn Cr <![CDATA[TiO2]]> -200 Low-grade mixed ore 11.3 60.80 7.50 5.15 0.340 0.090 0.40 0.030 0.020 0.740 65.0 sulfuric acid slag 17.0 61.00 4.42 6.32 1.000 0.040 1.90 0.090 0.003 0.056 80.0 magnetite 11.1 65.66 27.16 4.20 0.041 0.013 0.59 0.005 0.010 0.333 96.0 Blast furnace dust 0.0 50.00 3.77 5.50 0.335 0.065 6.86 0.021 0.003 0.177 60.0 Prefabricated iron ore powder 7.0 57.50 0.50 3.30 0.08 0.03 0.05 0.015 0.60 0.250 83.0

[0039] The green pellets are sequentially dried by forced air and exhausted air, preheated, calcined, soaked and cooled in two stages to obtain finished pellets. The obtained pellets have a compressive strength of 2400 N / P, RI of 81% and RDI of 1. +3.15 The temperature of each section is shown in Table 2.

[0040] Table 2 Temperature of each section

[0041] project Blast drying section Exhaust drying section Preheating section Roasting section Soaking section A cold period Second cooling section Temperature index / ℃ 280 360 1170 1260 1060 900 300

[0042] Example 2

[0043] This embodiment provides a system for preparing finely ground powder, such as Figure 1 As shown, including:

[0044] Material bin, which is equipped with a disc feeder;

[0045] The grinding wheel and roller of the grinding wheel cooperate to grind the material into powder. The disc feeder conveys the material to the space between the grinding wheel and the roller through the metering belt conveyor. The grinding wheel is equipped with an air nozzle ring, which is opposite to the gap between the grinding wheel and the roller.

[0046] Hot air furnace heating system, used to supply hot air to the nozzle ring on the mill;

[0047] The powder collector is connected to the mill through the powder selector and is used to collect the finely ground powder that meets the particle size requirements after roller grinding.

[0048] After limonite and specularite are discharged from the disc feeder of the material bin, they are measured by a metering belt conveyor and transported to the grinding mill in proportion. Then, the pressure of the grinding roller is set, and the temperature of the hot air at the outlet of the hot air furnace heating system is set, and then roller grinding is carried out under dynamic drying of the heat medium. The fine powder obtained by roller grinding is selected by the powder classifier and the fine ground powder that meets the particle size requirements is collected in the powder collector to obtain fine ground powder.

[0049] Comparative Example 1

[0050] The difference between this comparative example and the embodiment is that no dynamic drying of the heat medium is performed during the roller milling process.

[0051] The finely ground powder obtained in this comparative example has a moisture content of 10.0% and an average specific surface area of ​​2000 cm 2 / g. Because dynamic drying of the heat medium is not carried out during the roller milling process, the moisture content of the ground powder increases and the specific surface area decreases, which is not conducive to the control of the subsequent ball making and roasting steps.

[0052] The compressive strength of the pellets obtained in this comparative example is 1800 N / P, RI 76%, RDI +3.15 92.5%, RSI 19%.

[0053] Comparative Example 2

[0054] The difference between this comparative example and the embodiment is that the mixture is mixed at a mass ratio of 5:5.

[0055] The proportion of limonite used in grinding is reduced, while the proportion of specularite is increased, and the average specific surface area of ​​the finely ground powder obtained is 1800 cm 2 / g, the ball index decreased. The compressive strength of the pellets obtained in this comparative example is 2100N / P, RI 70%, RDI +3.15 94.5%, RSI 18%.

Claims

1. A method for preparing fine ground powder by dynamic dry grinding, characterized in that: include: The limonite and specularite are mixed in a mass ratio of (6-8):3, and then roller-milled under dynamic drying with a hot medium to obtain the fine ground powder.

2. The method for preparing fine powder by dynamic dry grinding according to claim 1, characterized in that: The thermal medium dynamic drying includes: using hot air at 450-550° C. for blowing.

3. The method for preparing fine powder by dynamic dry grinding according to claim 1, characterized in that: The dynamic drying time of the heat medium is 28s-3min.

4. The method for preparing fine powder by dynamic dry grinding according to claim 1, characterized in that: The roller milling pressure is 6.8-9.0 MPa, and the roller milling processing time is 28 seconds to 3 minutes.

5. The method for preparing fine ground powder by dynamic dry grinding according to claim 1, characterized in that: The mass ratio of the limonite to the specularite is 7:

3.

6. The method for preparing fine ground powder by dynamic dry grinding according to claim 1, characterized in that: During the roller milling process under dynamic drying of hot medium, 5% to 30% of the limonite phase is converted into hematite.

7. A finely ground powder, characterized in that: The finely ground powder prepared by the method according to any one of claims 1 to 6, wherein the finely ground powder has a -200 mesh size of ≥80% and an average specific surface area of ​​≥3000 cm 2 / g.

8. A system for preparing the finely ground powder according to claim 7, characterized in that: include: Material bin, which is equipped with a disc feeder; The grinding wheel and the grinding roller of the grinding wheel cooperate to grind the material into powder by roller grinding. The disc feeder conveys the material to the space between the grinding wheel and the grinding roller through the metering belt conveyor. The grinding wheel is provided with an air nozzle ring, which is opposite to the gap between the grinding wheel and the grinding roller. Hot air furnace heating system, used to supply hot air to the nozzle ring on the mill; The powder collector is connected to the mill through the powder selector and is used to collect the finely ground powder that meets the particle size requirements after roller grinding.

9. Use of the finely ground powder according to claim 7 in pellet preparation.

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