JPH034487B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a method for dry-selecting high-purity limestone for heavy calcium carbonate from limestone mined in a limestone mine without going through a water washing process. [Prior Art] Limestone mines that supply limestone for cement raw materials and also manufacture lime products such as heavy calcium carbonate and limestone usually have two or more lines of product manufacturing equipment for each purpose. In such limestone mines, generally, at the mining site,
Limestone blasted by blasting is transported by large dump truck or wheel loader to a shaft leading to a crushing system installed at the bottom of the mining site. At this time, raw stone for limestone products that require 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 rough stone is first crushed, then sieved with a vibrating sieve, and the upper part of the sieve is used for products, and if necessary, it is further sorted by hand to be used for the next process. The product is sent to a water washing process, further crushed, washed with water, and sieved into particle sizes suitable for each purpose. [Problems to be solved by the invention] In order to manufacture limestone products such as calcium carbonate that require high purity, conventional methods require visual sorting at the mining site, separate crushing equipment and storage areas,
It requires washing equipment and water treatment equipment, and requires a complicated treatment system and a large treatment area.
In particular, sludge from water treatment processes is difficult to handle because it contains fine clay particles. If you try to produce calcium carbonate by using crystalline limestone and treating it with the same treatment system as limestone for other uses, such as cement production,
It will be necessary to install additional equipment to increase the purity of limestone. In this case, crystalline limestone is
Since it is unsuitable for manufacturing products other than calcium carbonate, there is a problem of high manufacturing costs. Another problem is that there are impurities between the limestone crystal particles, and even large lumps can only achieve a purity of about 98%. The present invention provides a method for selecting high-purity limestone for use in calcium carbonate by treating raw stone containing crystalline limestone in the same treatment system without using a separate treatment system or washing process. [Means for solving the problem] (1) After drying the limestone that has been crushed into pieces of several tens of millimeters, it is further crushed into medium particles of several millimeters using a crusher. (2) This medium-crushed limestone is sieved into coarse, medium, and fine particles using a vibrating sieve with openings to obtain medium particles with the highest limestone purity. In this case, the size of the mesh of the sieve is determined based on actual survey data of quality by particle size so that the purity of medium particles is maximized depending on the hardness of impurities and the particle size to be crushed. (3) After crushing the medium grains of the sieved limestone using a crusher such as a tube mill or a vertical mill,
This is classified into coarse powder and fine powder using an air classifier, and the coarse powder is recovered as a product. This classification point is also determined based on actual survey data. [Function] (a) Raw limestone usually contains impurities such as rocks around the place where it is produced and clays that have been weathered by these rocks. In particular, if these include aplite, dyke, etc., which are harder rocks than raw limestone, the crushability of these rocks is markedly different from that of limestone, so the mixture should be crushed by at least 10 mm.
If crushed below a certain level, the coarse grained portion will contain hard rock, the intermediate grained portion will contain lime, and the fine grained portion will contain a large amount of clay. Therefore, this can be sieved by determining the sieving particle size so that the purity of the intermediate particle size is maximized. The size of the fine grains (cut size) is desirably about 0.15 mm or less, but it may be the smallest mesh size that can be used industrially. (b) By further crushing the sieved intermediate particle size portion, the clay content and impurities distributed in the limestone crystal particles are removed by the difference in crushability with lime and the difference in the size of the original particles. Since there is a difference in specific gravity, this can be selected. That is, when the medium grain portion is crushed using a crusher such as a tube mill or a vertical mill, and then classified into coarse powder and fine powder using an air classifier, lime content is contained in the coarse powder, and fine powder is generated. It contains clay and impurities between crystal particles,
By separating the coarse powder, high-purity heavy limestone for calcium carbonate can be selected. [Example] Raw stone mined in a limestone mine is indiscriminately collected.
Raw stone roughly crushed to 25 mm or less was used, dried, and then medium crushed to 5 mm or less. Table 1 shows the particle size distribution and the CaCO ₃ analysis value for each particle size. Next, the above-mentioned medium crushed limestone is classified into mesh grain size of 2.5 mm or more, intermediate grain size, less than 2.5 mm, 0.15 mm or more, under mesh grain size, less than 0.15 mm, and those with a specific surface area of 1000
Finely pulverize to ¹ g/cm2, classify this into coarse powder and fine powder using a high efficiency air separator, remove 6% by weight of the fine powder, and convert the coarse powder into limestone for calcium carbonate containing 99% by weight or more of _CaCO3 . It was made into a product. Table 2 shows the relationship between the pulverization time, the yields of coarse and fine powders, and the CaCO ₃ analysis values. Next, for comparison, raw stone roughly crushed into pieces of 25 mm or less was washed with water and dried, and the same operations as described above were carried out, and the results are shown in Tables 3 and 4. Comparison of Tables 2 and 4 shows that the method of the present invention makes it possible to obtain products of the same quality as when washing with water. Furthermore, from Table 2, it is clear that 4% by weight or more of the fine powder can be removed with a grinding time of 5 minutes or more.

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〔Effect of the invention〕

The present invention has the following excellent effects. (1) There is no need to visually discriminate at limestone mining sites, making it easier to plan mining. (2) Equipment costs are low because there is no need to install a special dedicated crushing line. (3) Since there is no need for a water washing process, there is no need to pay for the treatment of residue. (4) The residue of limestone used for calcium carbonate can also be used as a raw material for cement without the need for special treatment. (5) It has become possible to manufacture limestone for heavy calcium carbonate at a cement factory using waste heat from clinker calcination and idle equipment. (6) Labor can be saved because there is no need for a manual selection process in the middle of the process.

[Brief explanation of drawings]

FIG. 1 is a flow sheet of an embodiment of the method of the present invention.

Claims (1)

[Claims] 1 Heavy lime with high purity, which is characterized by medium crushing of mined ore, finely pulverizing ore of intermediate particle size, classifying it into coarse powder and fine powder, and sorting the coarse powder as a product. Method for selecting lime raw materials for calcium carbonate.