JPH0422852B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to a method for processing xenocrystalline limestone, and more particularly to a simple processing method for producing raw material for producing heavy calcium carbonate or crushed sand. [Prior Art] Limestone mines that supply limestone for cement raw materials and also produce heavy calcium carbonate and lime-related products usually have two or more lines of production equipment for different products depending on their use. In such limestone mines, generally, at the mining site,
The blasted limestone is transported by large dump truck or wheel loader to the shaft connected to the crushing system installed at the bottom of the mining site. At this time, the raw stone for lime products that requires particularly high purity is transported. and raw ore destined for cement factories are visually sorted and processed through separate processing systems.
In the processing system for high-purity products, this visually sorted raw stone is first crushed, then sieved with a vibrating sieve, and the screened material is used for products, and if necessary, it is further sorted by hand to be used for the next process. They are sent to a water washing process, crushed, washed with water, and sieved into particle sizes suitable for each purpose to produce products. Generally, the method for manufacturing crushed sand for building materials is to first crush the mined rough stone using a geo crusher, etc., then secondly crush it using a cone crusher, impact crusher, etc., then use trommel and vibration. It is sieved into predetermined sizes using sieves and shipped as crushed stone for civil engineering and concrete use. Furthermore, in order to produce crushed sand, which has been in increasing demand due to the depletion of river sand and the regulation of the use of sea sand as a countermeasure against salinity, it is necessary to use a rotary mill such as a rod mill or an impact mill such as a disk integrator (cage mill). After crushing crushed stone and classifying it to a predetermined particle size using a wet or dry classifier, the particle size is adjusted to have a predetermined particle size distribution depending on the purpose of use and then shipped. [Problems to be solved by the invention] In order to manufacture limestone products such as calcium carbonate that require high purity, conventionally, visual selection at the mining site, separate crushing equipment, storage space, washing equipment and Water treatment equipment is required, requiring a complex treatment system and a large treatment area. In particular, if you are trying to produce calcium carbonate by using the same processing system as limestone for other uses, such as cement production, you will need equipment to increase the purity of the limestone. Additional parallel installation is required. In this case, the crystalline limestone is unsuitable for manufacturing products other than calcium carbonate, so there is a problem in that the manufacturing cost increases. In addition, even large blocks of limestone with high purity contain impurities between the crystal particles, and the purity can only be obtained at around 98%, making it impossible to use it as a raw material for producing high-purity heavy calcium carbonate, which requires a purity of 99% or higher. There was a problem as mentioned above. The present invention provides a method for selecting a high-purity limestone raw material for calcium carbonate by treating the raw crystalline limestone in the same treatment system without using a separate treatment system or washing process. . In addition, to produce crushed sand, impact crushers such as rotary mills or cage mills are mainly used, but in both cases the crushing efficiency is poor due to the small size of the crushed particles, and the power consumption increases. Therefore, when performing wet classification, water treatment equipment such as filtration equipment and a waste soil treatment plant are required, while dry classification has the problem of dust generation due to fine particles. In addition, there are other problems such as the need for processing or special storage equipment for the recovered fine powder. In addition to this, there were other problems such as the generation of noise pollution due to noise caused by the crushing and impact sounds caused by the crusher, and the deterioration of the working environment for employees due to the noise and dust. [Means for solving the problem] As a result of various studies to solve the above problem,
We have developed a first method for producing high-purity heavy calcium carbonate using heat-denatured crystalline limestone as a raw material. (1) Limestone mined in a limestone mine is crushed into medium-sized chunks of several tens of millimeters or smaller. (2) The medium-sized limestone is heated to 700℃ or less at 200℃ using a heating device equipped with a rotary heating device and a moving device.
Heat above ℃. (3) The heated limestone is crushed into crystal units using crushing equipment that can apply thermal shock due to rapid cooling and dynamic shock due to falling. (4) Sieve the crushed limestone particles into coarse, medium, and fine particles using a vibrating sieve with openings, a rotary sieve, etc. to obtain medium particles with the highest limestone purity. In this case, the mesh size of the sieve is determined based on actual survey data of grades by purity so that the purity of medium particles is maximized depending on the particle size of the crystal particles constituting the limestone. It is also possible to use a gravity type or wind type classifier for the limestone particles, or to use a combination of these classifiers. Furthermore, as a second invention, a method for producing crushed sand from the above limestone was developed. (1) Limestone mined in a limestone mine is crushed into medium-sized chunks of several tens of millimeters or smaller. (2) The medium-sized limestone is heated to 700℃ or less at 200℃ using a heating device equipped with a rotary heating device and a moving device.
Heat above ℃. (3) Using crushing equipment that can rapidly cool heated limestone and apply thermal shock and dynamic shock due to falling, the limestone is crushed into crystal units and separated into particle sizes of 10 mm or more, 10 mm or less, 5 mm or more, and 5 mm or less. Then, take out items with a diameter of 5 mm or less as products. In addition, 10mm or less 5mm
In principle, particles of the above particle size are returned to the heating process and circulated, but if this product is manufactured in parallel with the manufacturing process of other products, such as the cement manufacturing process, the circulation process can be omitted and the cement manufacturing process It can also be used as a raw material. [Action] When heat-denatured crystalline limestone is heated,
The crystal grains that make up the limestone block take contradictory actions such as expansion and contraction in the direction of the crystal axes pointing in various directions, so the bonds between the crystal grains become loose and each crystal can be broken down by just a light impact. It becomes possible to crush each particle. On the other hand, hard impurities such as aplite and gangue, which are mined as impurities when mining limestone, do not have the effect of loosening the bonds between crystal particles even when heated within the heating temperature range of the present invention, and they do not cause any slight impact. Since it will not be crushed by simply applying it, it can not only be easily separated but also used as an impact material during crushing. In addition, impurities such as clay and topsoil are dried during heating and easily turned into fine powder during crushing, so they can be easily separated from limestone crystal particles by sieving, air classification, etc. Furthermore, during crushing, impurities sandwiched between crystal particles can be separated in the same way as clay and the like. Furthermore, since the amount of impurities contained in limestone crystal particles differs depending on the particle size, a particle size that satisfies a predetermined lime content may be selected. In other words, as particles with large particle sizes take in more impurities during crystal formation, lime purity (CaCO ₃ content) tends to increase as the particle size decreases, but Contains clay and impurities between crystal particles, so the lime content tends to decrease. Therefore, by selecting the particle size so that the lime purity becomes a predetermined purity, a highly pure raw material for heavy calcium carbonate can be produced. It is better to heat limestone at a higher temperature.
When heated above 750℃, limestone begins to dissociate,
The upper limit is set at 700℃ because there is a possibility that it will turn into powder during crushing and be disposed of along with foreign substances. On the other hand, if the lower limit temperature is less than 200°C, the crushability will deteriorate and it is inappropriate. Therefore, in consideration of economic efficiency, it is preferable that the upper limit of the heating temperature for limestone is 700°C and the lower limit is 300°C or higher. The heating method may be any device that can heat to the above temperature and does not introduce harmful substances into the product, and the heating source may be a dedicated heating furnace or an exhaust source such as a steel, cement, or boiler. Heat is available. Methods for crushing heated limestone include quenching it with water in a heated state, or applying a light impact using a trommel, rotary hollow cylinder, etc. This method is particularly useful for producing special aggregates such as kansui stone. In this case, a water cooling method is effective, but a dry method can also be used if the fine powder is completely removed using hot or cold air. Furthermore, specific embodiments of the present invention are as follows:
The following is a description of the embodiment shown in FIGS. 3 to 12. FIG. 3 is a schematic vertical cross-sectional view of a chain conveyor installed in a cement clinker cooling device as a limestone heating device. Figure 3 shows a case where the exhaust heat of the cement clinker cooling system is used. Install. This device includes a limestone heating pipe 1 and a limestone supply port 5 installed on the grate plate of a cement cooler passing through both side walls of the cooler, a chain conveyor 6 for transporting the supplied limestone, and a limestone discharge port 7. The heating tube 1 is divided into two stages, upper and lower, and has a structure in which preheating is performed on the upper stage and heating is performed on the lower stage. The limestone heating pipe 1 installed on the grate plate 3 of the clinker cooler is heated by a heating device using limestone separated from a limestone system for cement production crushed into pieces of several tens of millimeters or less via a supply device (not shown) as a raw material. While being transported by a chain conveyor 6 in the direction of the arrow in the figure, it is heated to a predetermined temperature and is discharged from the limestone discharge port 7 to the outside of the apparatus. Note that the shape, material, and mounting position of the limestone heating tube 1 are appropriately selected depending on the size of crushed limestone, heating temperature, etc. Various crushing devices can be used to crush the heated limestone, and for example, the crushing device shown in FIG. FIG. 5 is an end view taken along the line A--A in FIG. 4, in which the arrow indicates the rotation direction of the crusher, and FIG. 6 is an enlarged view of section A in FIG. The heated limestone is supplied from the limestone supply chute 21 to the crusher 22, and is repeatedly lifted and discharged by the convex portion 23 provided on the inner surface by the rotation of the crusher 22, and then crushed.
The limestone falls further and is discharged from the limestone discharge port 25. Air at high temperature, low temperature, or room temperature may be blown through the gas inlet 26. 27 is a discharge port for the supplied gas;
8 is a bearing section. When producing special crushed sand such as kansui stone, it is effective to cool heated limestone with water. Heating and crushing can be performed in the same device; for example, a heating/crushing device whose vertical cross-sectional schematic diagram is shown in FIG. 7 is used, and FIG. It is a diagram. The crushed limestone is sent to the limestone supply chute 41
The heated air is supplied to the heating/crushing machine 42 and the hot air is sent through the hot air insertion port 43. The heating/crushing machine 42 rotates in the direction of the arrow in FIG.
Since a scraping plate 44 is arranged on the inner surface of the
While moving within the crusher 42, the limestone is heated and crushed by hot air, and the crushed limestone is discharged from the limestone discharge port 45. The hot air heats the limestone and is then discharged from the exhaust port 46. Various classification apparatuses can be used to classify the crushed limestone, and for example, the classification apparatus shown in FIG. FIG. 10 is a schematic view taken along the line A--A in FIG. 9. The crushed limestone is supplied to a classifier 62 by a limestone supply chute 61. Inside the classifier 62, a cylindrical sieve screen with a predetermined separation particle size is installed. The figure shows the case where two sieve screens are stretched.
A sieve screen 63 with a large opening is placed on the inside, and a sieve screen 64 with a small opening is placed on the outside. The coarse limestone remaining on the sieve screen 63 is sent to the hopper 65, passes through the sieve screen 63, and is transferred to the sieve screen 63.
The medium-grained limestone remaining on the sieve screen 64 is classified and stored in a hopper 66, and the fine-grained limestone that has passed through the sieve screen 64 is classified and stored in a hopper 67. When producing raw materials for heavy calcium carbonate, the opening of the sieve screen to be used is determined by the relationship between the separation particle size and limestone purity determined by a sieving test conducted on crushed limestone. , the purity of the classified limestone is determined to be 99% or more, and the number of sieve screens is determined so that if only limestone larger or smaller than the opening of a certain sieve screen can be used as the raw material, one If a sieve screen is used and the top or bottom of the screen is the raw material, and only the limestone between the opening of one sieve screen and the opening of another sieve screen can be used as the raw material, then 2. Two sieve screens are used, and the limestone between the openings of each sieve screen becomes the raw material. When producing crushed sand, the opening of the sieve screen should be 5 mm.
Crushed sand can be produced by using one sieve screen as the bottom of the screen, but a sieve screen with apertures larger than 5 mm may be added for reprocessing on the screen. The number of hoppers is determined according to the number of sieves used. When gas is introduced through the gas inlet 68, the fine powder is discharged together with the gas through the gas outlet 69, and the fine powder in the fine limestone stored in the hopper 67 can be removed. Crushing and classification can be performed in one device,
For example, a crushing/classifying device whose vertical cross-sectional schematic diagram is shown in Fig. 11 is used, and Fig. 12 shows A-A in Fig. 11.
FIG. This crushing/classifying device is a combination of the devices shown in Figures 7 and 9.
Each of the effects of the apparatus shown in the figure can be obtained. The heated limestone is transferred to the limestone supply chute 8.
1 to the crushing/classifying machine 82, which rotates in the direction shown by the arrow in FIG.
Since it has a scraping board 85 disposed inward of 3,
Limestone is classified into coarse, medium, and fine particles, and is stored in hoppers 86, 87, and 88, respectively. The opening of the sieve screen, the number of sieve screens and hoppers are determined in the same manner as in the classification apparatus shown in FIG. When gas is introduced from the gas inlet 89, the fine powder is discharged together with the gas from the gas outlet 90. When unheated limestone is supplied from the limestone supply chute 81 and high-temperature gas is introduced from the gas inlet, the limestone is heated and decomposed. Crushing and classification can be performed with one device. [Examples] The present invention is not limited to the following examples, but any method and apparatus that can perform heating and crushing are included within the technical scope of the present invention. Example 1 A large lump collected from a limestone storage site was crushed into 50-40 mm pieces and collected as a sample. Next, the collected sample is heated to a predetermined temperature in an electric furnace for a predetermined time, and then taken out from the electric furnace and cooled in air to room temperature. Afterwards, cut the limestone into 20 pieces vertically.
Table 1 shows the results of cutting the pieces into pieces of 20 mm wide and 20 mm high and measuring the burst pressure using an Amsler pressure tester. The results of this test revealed that heating limestone to a temperature of 200°C or higher reduces the strength of the limestone, and that heating it to a temperature of 300°C or higher is particularly effective.

[Table] Shows something.
Example 2 The results of implementing the present invention using the apparatus shown in FIGS. 1 and 2 are as follows. FIG. 1 is a schematic vertical cross-sectional view of a case where a heating tube is installed in a cement clinker cooling device, and FIG. 2 is a view taken along the line A--A in FIG. 1. A SUS pipe with a diameter of 150 mm was installed as a limestone heating pipe 1 at an angle of 60 degrees above the third air chamber in the cement clinker cooling device 2, and the mined limestone was crushed into pieces of 20 mm or less without being sorted. The limestone was supplied to heating tube 1 and heated until the limestone temperature inside the tube reached 600°C. Thereafter, the limestone was taken out from the heating tube, cooled naturally, and crushed in a disc mill with a diameter of 300 mm and a length of 600 mm. In addition, the limestone immediately after being discharged from the heating device was rapidly cooled with cold water and crushed. After sieving these crushed limestones according to particle size, the results of analysis according to each particle size are shown in Table 2. From the above results, it has been found that if particles with a particle size of 5 mm or less and 0.15 mm or more are selected, high-purity limestone for producing heavy calcium carbonate with a limestone purity of 99% or more can be obtained. Furthermore, from the above sieving results, it was found that crushed sand could be produced by removing particles with a particle size of 5 mm or more.

〔Effect of the invention〕

By implementing the method of the present invention to produce heavy calcium carbonate or crushed sand from crystalline limestone, there is no need to perform visual selection at the limestone mining site, making it easier to plan the mining and improve the quality of the product. Equipment costs are low because there is no need to install a separate dedicated crushing line. Furthermore, waste heat from cement firing, iron manufacturing, etc. can be used, and water washing and manual sorting steps can be omitted, so there is no need for residue processing costs, and labor can be saved. In addition, the residue of limestone and crushed sand used for calcium carbonate is also used for cement.
It can be used without any special processing. In addition, when producing crushed sand, the final crushing or crushing step can be omitted, so it is possible to produce aggregate with good stability without microcracks in the aggregate. Furthermore, since the generation of noise is reduced, it has been confirmed that there are excellent effects such as preventing pollution and improving the working environment.

[Brief explanation of drawings]

Fig. 1 is a vertical cross-sectional schematic diagram of a cement clinker cooling device equipped with limestone heating pipes used in the present invention, Fig. 2 is a view taken along the line A-A in Fig. 1, and Fig. 3 is a schematic diagram of a cement clinker cooling device used in the present invention. FIG. 4 is a schematic vertical cross-sectional view of a crushing device used in the present invention, FIG. 5 is an end view taken along the line A-A in FIG. 4, and FIG. An enlarged view of part A in the figure, FIG. 7 is a schematic vertical cross-sectional view of the heating/crushing device used in the present invention, FIG. 8 is an end view taken along the line A-A in FIG. 7, and FIG. A vertical cross-sectional schematic diagram of the classification device used, Figure 10 is
11 is a schematic vertical cross-sectional view of the crushing/classifying device used in the present invention, and FIG. 12 is a schematic view taken along the line A-A in FIG. 11. 1... Limestone heating tube, 1a... Damper, 2...
Cement clinker cooling device, 3... Cooler grate, 4... Side wall, 5... Limestone supply port, 6... Chain conveyor, 7... Limestone discharge port, 20... Crushing device, 21... Limestone supply chute, 22...
Crushing machine, 23...Convex portion, 24...Open hole, 25...
Limestone outlet, 26... Gas inlet, 27... Gas outlet, 28... Bearing section, 40... Heating/crushing device, 41... Limestone supply chute, 42... Heating/crushing machine, 43... ... Hot air inlet, 44 ... Scraping plate, 45 ... Limestone discharge port, 46 ... Exhaust port, 6
0... Classifying device, 61... Limestone supply chute,
62...Classifier, 63,64...Sieve screen, 65,6
6, 67...Hopper, 68...Gas inlet, 69
...Gas outlet, 80...Crushing/classifying device, 81
... Limestone supply chute, 82 ... Crushing/classifying machine, 83, 84 ... Sieve screen, 85 ... Scraping plate, 8
6, 87, 88...hopper, 89...gas inlet, 90...gas outlet.

Claims (1)

[Scope of Claims] 1. The mined subcrystalline limestone is medium crushed, the medium crushed limestone is heated to 200°C or more and 700°C or less, then crushed, and this is divided into coarse particles, medium particles, and fine particles. A method for processing limestone, which is characterized in that a limestone raw material for heavy calcium carbonate with high lime purity is obtained by classifying the inner and medium particles into products. 2 The mined subcrystalline limestone is medium crushed, the medium crushed limestone is heated to 200°C or more and 700°C or less, then crushed, and particles of 5 mm or less are sorted as crushed sand from the crushed material. How to treat limestone.