KR101848731B1 - Method of sorting high-grade limestone from low-grade limestone - Google Patents

Abstract

One embodiment of the present invention provides a method for sorting a high-quality limestone, comprising: a step (step 1) of heat treating a crushed low-quality limestone in an oxygen atmosphere; and a step (step 2) of sorting the heat-treated material by color.

Description

[0001] METHOD OF SORTING HIGH-GRADE LIMESTONE FROM LOW-GRADE LIMESTONE [0002]

The present invention relates to a method for selecting high-grade limestone from low-grade limestone, and more particularly to a method for sorting high-grade limestone comprising a step of color-sorting low-grade limestone after heat treatment.

Generally, the low-grade limestone produced in Korea contains not only limestone (CaCO ₃ ) but also dolomite (MgCO ₃ ), trace amount of silica (SiO ₂ ) and clay minerals, so that not only the purity of CaO is low but also the raw material It is difficult to apply it to high value-added industries such as steelmaking and fine chemical processing because basic characteristics are not good.

It has been reported that high-grade limestone is used not only as a limestone ores itself but also as a lime and a calcium compound. Among these various uses, limestone is widely used as cement and steel industry. In Korea, the steel cement industry accounts for most of limestone demand.

Since the amount of high-quality and coarse-color ore in the limestone that is present in Korea is limited, imports of high-grade raw materials and high-grade pulverized products with high added value are on the increase, and research on high quality of domestic limestone ores is needed.

As a related prior art, Korean Patent Registration No. 10-1161755 discloses "a method for improving the quality of low-grade limestone and its limestone ".

Korean Patent Registration No. 10-1161755

It is an object of the present invention to provide a high-quality limestone sorting method which is complicated in the process of selecting high-grade limestone from low-grade limestone and solves the problem of high processing cost .

This is to provide a method for easily obtaining high-quality limestone by selecting mineral limestone by color by heat treatment in an oxygen atmosphere using mineralogical characteristics of low-grade limestone dolomite.

In order to accomplish the above object, one aspect of the present invention is a method for manufacturing a low limestone comprising the steps of: (1) heat treating low grade limestone in an oxygen atmosphere; And sorting the heat-treated material by color (step 2).

In one embodiment, the low limestone of step 1 may be milled to a particle size of 3 mm or less.

In one embodiment, the low grade limestone of step 1 comprises calcite, dolomite, and the calcium oxide content is 40.8 wt% to 46.4 wt%.

In one embodiment, the low limestone of step 1 may further comprise iron oxide (Fe ₂ O ₃ ), iron sulfide (FeS), silica (SiO ₂ ), and alumina (Al ₂ O ₃ ).

In one embodiment, the heat treatment temperature in step 1 may be 400 ° C to 600 ° C.

In one embodiment, the heat treatment time in step 1 may be from 0.5 hours to 3 hours.

In one embodiment, the selection of the step 2 may measure the color of a part of the heat-treated material, and if the measured color area satisfies a predetermined color area, the measured material may be separated through the sorting means.

In one embodiment, the selection of the step 2 may be performed by separating the white, gray and brown colored substances from the heat-treated substances.

According to another aspect of the present invention, there is provided a method of manufacturing a low-grade limestone comprising the steps of: (1) heat treating low-grade limestone in an oxygen atmosphere; Crushing the heat-treated material to a predetermined particle size (step 1a); And a step (step 2) of sorting the crushed materials by color and grain size.

According to one aspect of the present invention, white minerals are selected after heat treatment of low-grade limestone, and limestone having a calcium oxide content of 53 wt% or more can be easily selected.

Further, the low-grade limestone can be easily separated and sorted after the heat treatment by crushing and selecting the low-grade limestone to a predetermined particle size.

It should be understood that the effects of the present invention are not limited to the above effects and include all effects that can be deduced from the detailed description of the present invention or the configuration of the invention described in the claims.

1 and 2 are schematic views showing an example of a high-quality limestone sorting method according to an embodiment of the present invention.
3 is a photograph showing a crystal structure according to whiteness characteristics of limestone.
4 is a graph showing the results of X-ray diffraction analysis of high-quality and low-grade limestone.
5 is a graph showing the results of X-ray diffraction analysis according to the size of the crushed particles in Comparative Example 1 of the present invention.
6 is a graph showing the results of thermogravimetric analysis of magnesium carbonate, dolomite, calcite, low-grade and high-grade limestone.
7 is a graph showing changes in color after the step 1 of Examples 1 and 2 of the present invention.
FIG. 8 is a photograph showing the results of color selection performed by Embodiment 1 of the present invention. FIG.
FIG. 9 is a graph showing the results of X-ray diffraction analysis of a color-sorted material on which Example 1 of the present invention has been performed.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS The advantages and features of the present invention and the manner of achieving it will become apparent with reference to the embodiments described in detail below with reference to the accompanying drawings.

It should be understood, however, that the present invention is not limited to the disclosed embodiments, but may be embodied in many different forms and should not be construed as limited to the exemplary embodiments set forth herein. To fully inform the inventor of the category of invention. Further, the present invention is only defined by the scope of the claims.

Further, in the following description of the present invention, if it is determined that related arts or the like may obscure the gist of the present invention, detailed description thereof will be omitted.

According to an aspect of the present invention,

Heat treating the crushed low-grade limestone in an oxygen atmosphere (step 1) (S10); And

And a step (S20) of sorting the heat-treated substances by color (step 2).

Hereinafter, a high-grade limestone sorting method according to an embodiment of the present invention will be described for each step.

In the high-grade limestone selecting method according to an embodiment of the present invention, the step 1 (S10) heat-treats the crushed low-grade limestone in an oxygen atmosphere.

The low grade limestone of step 1 above may be crushed to a particle size of 3 mm or less and crushed to a particle size of 0.54 mm to 3 mm. By crushing the low limestone to a particle size of 3 mm or less, it is possible to improve the heat treatment efficiency in a specific condition at a subsequent stage, and then to perform color sorting more easily. If the particle size of the low limestone exceeds 3 mm, there is a fear that the yield is reduced in the subsequent step of color sorting and the economical efficiency is lowered. The crushing means of the low-grade limestone may be a jaw crusher, a hammer crusher, a roll crusher or the like, but is not limited thereto as long as it can crush the low-grade limestone to the above-mentioned particle size range.

The low-grade limestone of step 1 may include calcite, dolomite, and the dolomite may include pyrite or magnetite iron.

 The low-grade limestone may have a calcium oxide content of 40.8 wt% to 46.4 wt%.

The low-grade limestone of the step 1 may have the following composition.

40.8 wt.% To 46.4 wt.% Of calcium oxide (CaO);

From 7.5 wt% to 13.5 wt% of magnesium oxide (MgO);

0.2 wt% to 0.9 wt% of iron oxide (Fe ₂ O ₃ );

Silica (SiO ₂₎ 0.01 wt% to 0.3 wt%;

0.01 wt% to 0.2 wt% alumina (Al ₂ O ₃ );

Ignition loss 43.2 wt% to 48.2 wt%; And

Other impurities may be included. The other impurities may include potassium oxide (K ₂ O), sodium oxide (Na ₂ O), titanium oxide (TiO ₂ ), manganese oxide (MnO), phosphorus oxide (P ₂ O ₅ )

The step 1 may heat-treat the low-grade limestone which has been crushed to the above-mentioned range.

The heat treatment in step 1 may be performed in an oxygen atmosphere, and preferably in an atmospheric environment.

The heat treatment temperature in step 1 may be 400 ° C to 600 ° C, and preferably 550 ° C to 600 ° C. If the heat treatment temperature is less than 400 ° C, the color change of the treated product can not be clearly displayed and color sorting may not be effectively performed. If the heat treatment temperature is higher than 600 ° C, calcite starts to be decarbonated, There may be a problem in that the rate is decreased. This is because the high-grade limestone becomes lime in the above-mentioned temperature, which makes it difficult to sort.

The heat treatment time in step 1 is preferably 0.5 to 3 hours in terms of the particle size. If the heat treatment time is less than 0.5 hour, the color change of the heat treatment product may not be clearly displayed, so color selection may not be effectively performed. If the heat treatment time is more than 3 hours, excessive energy waste May occur.

The above-mentioned heat treatment condition is a condition inducing discoloration through oxidation reaction of dolomite or magnetite in dolomite crystals, and there is a fear that whiteness of high-grade limestone may be lowered due to phase change of limestone or clay minerals have.

Through the heat treatment in step 1, the dolomite contained in the low-grade limestone can be decarbonated, and phase changes of other minerals and the like can occur. Accordingly, the heat-treated products can exhibit different colors, and can exhibit white, brown, and gray. At this time, white of the heat treatment product may be mainly containing calcite, brown mainly contains dolomite and may contain a small amount of calcite and periclase, gray includes mainly dolomite and small amount of calcite Muscovite. ≪ RTI ID = 0.0 >

In the high-grade limestone sorting method according to an embodiment of the present invention, the step 2 (S20) selects the heat-treated material by color.

The color separation in the step 2 may measure the color of a part of the heat-treated material, and if the measured color area satisfies a predetermined color area, the measured material may be separated through the sorting means.

Specifically, the conveying means conveys the heat-treated material so as to be a continuous flow; Measurement means for measuring the color of the substance transferred by the transfer means; Discriminating means for discriminating whether or not to sort on the basis of color information of each of the heat-treated substances measured by said measuring means; And sorting means for sorting the sorting object discriminated by the discriminating means from a continuous flow.

The measuring unit may include an irradiating unit for irradiating the heat-treated material with light, and a sensing unit for sensing the light transmitted through the heat-treated material or the reflected light. The irradiating unit may be a lighting device, the sensing unit may be a CCD or a CMOS camera, and a sensor capable of sensing light in a visible light region may be used. Dimensional color space data by plotting RGB wavelength components of the optical data sensed by the sensing unit in a three-dimensional color space, comparing the wavelength components with preset color distribution data, and if the measured data is within a predetermined distribution data area, The substance heat-treated by the discriminating means can be regarded as a sorting object, and can be selected by the sorting means.

The selection of the step 2 can be performed by separating the white, gray and brown colored substances from the heat-treated substances and separating them using the conveying means, measuring means, discriminating means and sorting means.

As described above, the white color material may be mainly composed of calcite, and the calcium oxide content is 53 wt% or more. Therefore, high quality limestone of white color can be selected through the above method.

According to another aspect of the present invention,

Heat treating the low-grade limestone in an oxygen atmosphere (step 1) (S10);

Crushing the heat-treated material to a predetermined particle size (step 1a) (S11); And

And sorting the selected materials by color and grain size (step 2) (S20).

In the high-grade limestone sorting method according to an embodiment of the present invention, the concrete structure, effect, and the like of the step 1 may be as described above.

In the high-grade limestone sorting method according to an embodiment of the present invention, the step 1a shreds the heat-treated material.

In the crushing of the step 1a, the target particle size of the object may be made to be 3 mm or less, and may be performed to be 0.074 mm to 3 mm.

In the crushing of the step 1a, dolomite can be easily crushed compared to calcite. This is due to the difference in hardness (hardness) according to the difference in thermal characteristics between calcite and dolomite according to the heat treatment in step 1, thereby increasing the screening efficiency of the subsequent step.

In the high-grade limestone sorting method according to an embodiment of the present invention, the step 2 (S20) selects the crushed material by color separation in the case of minerals having a particle size of several millimeters, and selects it by particle size of 1 mm or less.

When the crushed material is selected for each color by the heat treatment in the step 2, its specific structure, effects and the like may be as described above.

In the step 2, when the crushed material is selected by particle size after the heat treatment, it is preferable to select 200 mesh to 325 mesh in order to select high-grade limestone.

Hereinafter, the present invention will be described in more detail with reference to Examples and Experimental Examples. However, the following examples and experimental examples are for illustrative purposes only and are not intended to limit the scope of the present invention.

< Low-grade  And high-quality limestone>

The contents of oxides of the low-grade limestone and the high-grade limestone treated in the following examples and comparative examples were measured by X-ray fluorescence analysis, and the results are shown in Tables 1 and 2, respectively.

ingredient content SiO ₂ 0.11 Al ₂ O ₃ 0.05 Fe ₂ O ₃ 0.59 CaO 43.39 MgO 10.55 K ₂ O 0.03 Na ₂ O 0.03 TiO ₂ 0.01 MnO 0.11 P ₂ O ₅ 0.02 Ig. loss * 45.26

(Ig loss: loss on ignition by decarbonation, unit: wt%)

ingredient content SiO ₂ 0.54 Al ₂ O ₃ 0.28 Fe ₂ O ₃ 0.24 CaO 53.74 MgO 1.31 K ₂ O 0.11 Na ₂ O 0.02 TiO ₂ 0.01 MnO 0.03 P ₂ O ₅ 0.02 Ig. loss * 43.51

(Ig loss: loss on ignition by decarbonation, unit: wt%)

In case of high-grade limestone, as shown in Table 2, the reference grade of CaO was 53.7%, and in case of low-grade limestone, the grade was 43.4% as shown in Table 1. In the case of low-grade limestone, ignition loss by decarbonation was 45.3% and MgO content was 10.6%. These results suggest that low - grade limestone contains large amount of dolomite in addition to calcite. Furthermore, the whiteness of the low-grade limestone was 74 to 76, and the high-grade limestone was 85.

<Analysis of crystal structure according to whiteness characteristics of limestone>

The crystal structure and constituent minerals of limestone showing different whiteness were analyzed and the results are shown in FIG.

Referring to FIG. 3, white A is mostly composed of calcite, and light gray B and C limestone partially contains quartz. On the other hand, as gray to deep as D to F, a large amount of dolomite appeared. Particularly, pyrite with grain size of 90 ㎛ to 110 ㎛ was observed along with dolomite in F limestone showing the darkest gray. In other words, the decrease of whiteness of limestone is believed to be caused by the increase of the content of quartz, which is an impurity, and dolomite, which is an accompanying mineral, and pyrite is contained in dolomite. In this connection, it can be seen that a large amount of MgO and Fe2O3 was confirmed in the low-grade limestone compared to the high-grade limestone.

<High quality and Low-grade  X-ray diffraction analysis of limestone>

X-ray diffraction analysis of high-quality and low-grade limestone was carried out, and the results are shown in FIG.

Referring to FIG. 4, the major minerals of high-grade limestone are calcite, while the major minerals of low-grade limestone contain large amounts of dolomite in addition to calcite.

<Magnesium carbonate, dolomite , Calcite, Low-grade  And high-grade limestone Thermogravimetry >

The thermogravimetric analysis of magnesium carbonate, dolomite, calcite, low-grade and high-grade limestone was carried out, and the results are shown in FIG.

Referring to FIG. 6, a mass reduction was observed at 700 ° C or higher for calcite, and a secondary mass decrease was observed at 700 ° C after the primary mass decrease at 550 ° C to 600 ° C for dolomite. The first mass reduction of dolomite is attributed to the decarboxylation of magnesium carbonate of dolomite (CaMg (CO ₃ ) ₂ ↔ CaCO ₃ + MgO + CO ₂ ) as seen from pyrolysis curve of magnesium carbonate. The secondary mass reduction is also attributed to the de-carbonation of calcium carbonate (CaCO ₃ → CaO + CO ₂ ). Mass changes of low-grade limestone include decarboxylation of dolomite.

In the following, experiments were conducted to select calcite and accompanying dolomite for low-grade limestone.

< Comparative Example  1> Low-grade  Screening by crushing limestone

The low-grade limestone was crushed to 3 mm or less by using a jaw crusher.

< Example  1> 600 ℃  Heat treatment / color selection

Step 1: The low-grade limestone was crushed to a depth of about 3 mm, and then heat-treated at a temperature of 600 ° C for 1 hour in an air atmosphere.

Step 2: The heat-treated material was color-coded by white, gray and brown.

< Example  2> 600 ℃  Heat treatment / crushing screening

Step 1: Low-grade limestone was heat-treated at 600 ° C for 1 hour in an atmospheric environment.

Step 1a: The heat-treated material was fractured to 3 mm or less.

Step 2: Color separation was performed on the crushed materials, and screening was performed based on the mesh size when the crushed material was 1 mm or less.

< Experimental Example  1> Low-grade  Analysis of selection results according to crushing of limestone

The low-grade limestone was crushed to a size of 3 mm or less, and then the mineral structure analysis and the component analysis were performed according to the crushed particle size. The results are shown in FIG. 5 and Table 3.

5 and Table 3, the selection according to the particle size according to the simple crushing showed no selectivity effect between calcite and dolomite. In the component analysis, some changes in the CaO and MgO contents were observed according to the crushed particle size However, it was found that the quality standards of low - grade limestone were not exceeded.

ingredient SiO ₂ Al ₂ O ₃ Fe ₂ O ₃ CaO MgO Whiteness Raw sample 0.09 0.04 0.53 43.80 9.64 76.1 Greater than 3 mm 0.10 0.05 0.53 43.03 10.29 73.6 1.52-3 mm 0.10 0.05 0.57 41.87 11.31 72.6 1.13-1.52 mm 0.09 0.05 0.58 41.55 11.50 73.2 0.86-1.13 mm 0.40 0.05 0.61 41.53 11.60 74.0 0.54-0.86 mm 0.11 0.05 0.58 420.4 11.06 74.6 Less than 0.54 mm 0.15 0.07 0.47 45.57 8.23 78.3

(Unit: wt%)

This means that it is difficult to selectively crush calcite and dolomite by simply crushing low-grade limestone.

< Experimental Example  2> Low-grade  Analysis of heat treatment and color selection results of limestone

FIG. 7 shows the color of the low-grade limestone in which Step 1 of Example 1 was carried out. As a result, it was confirmed that the mineral color difference occurred due to the color change of the specific constituent mineral particles of the low limestone after the heat treatment.

In addition, FIG. 8 shows the result of performing the above-described Example 1, and FIGS. 9, 4 and 5 show X-ray diffraction analysis, quantitative analysis and X-ray fluorescence analysis results.

9 and Table 4, the white mineral is represented by calcite (A), the brown mineral is represented by periclase (MgO (+)), which is a major mineral such as dolomite, a small amount of calcite and a trace amount of magnesium mineral. FeO)) (B). Furthermore, the gray mineral is also dolomite. It is found that a small amount of calcite and a small amount of clay minerals of muscovite, KAl ₂ (AlSi ₃ ) O ₁₀ (F, OH) ₂ are contained (C).

White Brown grey calcite 100 15 7.6 dolomite - 83.1 89.4 Pericles - 1.9 - muscovite - - 3 Whiteness 85.7 63.4 - Weight ratio 54.5 40.6 4.9

(Unit: wt%)

As shown in Table 4, the whiteness of white minerals was 85.7, which was similar to that of high purity limestone (85), while that of brown minerals and gray minerals was as low as 63. In addition, it was confirmed that the ratio of total low - grade limestone to white mineral was 54.5 wt%.

division White Brown grey SiO ₂ 0.10 0.02 1.60 Al ₂ O ₃ 0.05 0.03 1.08 Fe ₂ O ₃ 0.04 1.09 1.10 CaO 56.23 32.68 31.17 MgO 0.22 21.20 19.83 K ₂ O 0.03 0.03 0.39 Na ₂ O 0.02 0.12 0.11 TiO ₂ 0.01 0.01 0.07 MnO 0.01 0.25 0.16 P ₂ O ₅ 0.01 0.02 0.02 Ig. loss * 42.92 44.09 43.46

(Ig loss: loss on ignition by decarbonation, unit: wt%)

As shown in Table 5, in the case of white minerals, CaO content is 56.00 wt%, which is close to the theoretical value (56 wt%) of CaO content of calcite.

< Experimental Example  3> Low-grade  Statistical analysis of grain size after heat treatment and crushing of limestone

The properties of the limestone granules treated in Example 2 were measured by X-ray fluorescence analysis, and the results are shown in Table 6.

Referring to Table 6, it can be seen that the CaO quality was improved to 51.5 wt% and 52.3 wt% based on 200 mesh after crushing. In other words, it is considered that the crushing characteristics were changed due to the difference in the thermal decomposition characteristics between calcite and dolomite after heat treatment.

ingredient 400 ℃ heat treatment 600 ℃ heat treatment Less than 8 mesh 8-200 mesh More than 200 mesh Less than 8 mesh 8-200 mesh More than 200 mesh SiO ₂ 0.05 0.06 0.15 0.05 0.03 0.13 Al ₂ O ₃ 0.04 0.05 0.07 0.04 0.03 0.06 Fe ₂ O ₃ 0.46 0.42 0.26 0.36 0.51 0.24 CaO 43.38 44.51 51.46 47.28 43.6 52.32 MgO 10.84 9.79 3.63 8.14 11.6 3.2 K ₂ O 0.03 0.04 0.04 0.03 0.03 0.04 Na ₂ O 0.04 0.04 0.02 0.02 0.04 0.02 P ₂ O ₅ 0.02 0.02 0.02 0.01 0.01 0.02 Ig. loss * 45.37 45.18 43.92 43.72 43.9 43.54

(Ig loss: loss on ignition by decarbonation, unit: wt%)

Although a specific embodiment of the method of selecting a high-grade limestone from low-grade limestone according to an aspect of the present invention has been described above, it is apparent that various modifications can be made without departing from the scope of the present invention.

Therefore, the scope of the present invention should not be construed as being limited to the embodiments described, but should be determined by equivalents to the appended claims, as well as the following claims.

It is to be understood that the foregoing embodiments are illustrative and not restrictive in all respects and that the scope of the present invention is indicated by the appended claims rather than the foregoing description, It is intended that all changes and modifications derived from the equivalent concept be included within the scope of the present invention.

Claims (10)

Calcined and low-grade limestone containing calcite and dolomite in an oxygen atmosphere at a temperature of 550 to 600 ° C for 0.5 to 3 hours to induce discoloration of iron sulfide or magnetite contained in the limestone containing dolomite in the limestone ); And
(Step 2) of selecting substances of white, gray and brown color among the heat-treated substances,
The low grade limestone of step 1 is 40.8-46.4 wt% of calcium oxide (CaO); 7.5-13.5 wt% magnesium oxide (MgO); 0.0 &gt; 0-0. &Lt; / RTI &gt; 9 wt.% Iron oxide (Fe2O3)
Wherein the low-grade limestone of step 1 is crushed to a particle size of 0.54 mm to 3 mm.
delete delete delete delete delete The method according to claim 1,
In the selection of step 2,
And measuring the color of a part of the heat-treated material, and separating the measured material through a sorting unit when the measured color area satisfies a predetermined color area.
delete (Step 1) inducing discoloration of iron sulfide or magnetite contained in dolomite-containing limestone in the limestone by heat-treating the low-grade limestone including calcite and dolomite in an oxygen atmosphere at a temperature of 550-600 ° C for 0.5-3 hours;
Crushing the heat-treated material to a predetermined particle size (step 1a); And
Selecting a material of white, gray and brown color among the crushed materials, and sorting the crushed material by particle size (step 2) if the crushed material is 1 mm or less,
The low grade limestone of step 1 is 40.8-46.4 wt% of calcium oxide (CaO); 7.5-13.5 wt% magnesium oxide (MgO); 0.0 &gt; 0-0. &Lt; / RTI &gt; 9 wt.% Iron oxide (Fe2O3)
Wherein the crushing of step 1a is performed such that the heat treated material has a particle size of 0.74 mm to 3 mm.
10. The method of claim 9,
In the step 2,
Characterized in that a material having a particle size of 200 mesh to 325 mesh is selected.

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