JPH0684259B2 - Method for producing high-purity low-phosphorus quicklime - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention does not require visual selection at a mining site, a treatment system for each product and a water washing step, and is usually contained in slaked limestone. The present invention relates to a method for producing high-purity low-phosphorus quicklime in which the content of impurities such as alumina, silica, iron compounds (hereinafter referred to as alumina) and phosphorus is reduced.

[Conventional technology]

In a limestone mine that supplies limestone for cement raw materials and manufactures rough ore for lime products such as quick lime that requires high-purity limestone, usually two or more series of treatment systems are installed for each purpose.

In such a mine, generally, limestone blasted by blasting at the mining site is transported by a large dump truck or wheel loader to a vertical shaft leading to a crushing system installed at the bottom of the mining site, but high purity is required at this time. Since the rough stones to be processed and the rough stones for the cement factory are visually selected, separate processing systems and storage places were required.

In the treatment system for high-purity rough stones that have been visually selected, the rough stones are first crushed with a jaw crusher, etc., then sieved with a vibrating sieve, etc. This is secondly crushed with a corn crusher or an impact crusher, then washed with water, baked as a rough stone for producing quick lime in a quick lime firing kiln, and shipped for each purpose.

In particular, quicklime for iron and steel has its upper limit set by standards that dislike mixing alumina and phosphorus, and there is a great demand for high-purity, low-phosphorus quicklime with the upgrading of steel products.

However, the phosphorus content in quicklime is derived from the phosphorus content in the rough stone, and the phosphorus content in the rough stone also depends on the generation state thereof, so it was a difficult situation.

[Problems to be Solved by the Invention]

The present invention, in order to improve the purity of the minced limestone limestone, without providing a treatment system for each product consisting of visual observation and a water washing treatment step, etc., in the same dry treatment system as the raw material for cement production, alumina It is an object of the present invention to provide a method for producing high-purity quicklime having a low content of phosphorus and a reduced phosphorus content.

[Means for Solving the Problems]

The present inventors, as a result of research to achieve the above object,
Impurities such as phosphorus and alumina are widely distributed in the intrusive rock and its weathered matter, and phosphorus is also contained as impurities with alumina and the like in the crystalline limestone lumps. It was discovered that the content of alumina, etc. and phosphorus content differed depending on the particle size when crushed into the constituent crystal units and classified, and the method for producing high-purity low-phosphorus quick lime shown below was developed.

That is, the present invention, after crushing limestone mined in a mine to a particle size of several tens of mm that can be handled, heated at a temperature of 200 ° C. or higher at a heat amount of energy below the energy for decarboxylation reaction, and thermal shock The limestone particles that were given and crushed to crystal units were
Sieving with a sieve of ~ 0.15 mm, the particle size range such that the content of alumina and the like in the limestone particles and the phosphorus content are below a predetermined value is determined in advance based on actual survey data, and other than this particle size range. After removing particles, it is necessary to calcine at a temperature above decarbonation, and to crush mined limestone to a particle size of several tens of mm, and to obtain quicklime obtained by calcining at a temperature above decarbonation. After crushing in accordance with the above, sieving with a sieve of 5.0 to 0.15 mm, the particle size range such that the content of alumina and the like in the quicklime particles and the phosphorus content become a predetermined value or less based on actual survey data in advance. This is a method of removing particles out of this particle size range.

[Action]

Limestone usually contains intrusive rocks around the production site and its weathering as impurities.

Since the intrusive rock and its weathering material contain more alumina and phosphorus as compared with limestone, the removal of these can increase the purity of limestone and reduce the phosphorus content.

In the case of spheroidal limestone, although the reason is unknown, it is crushed to the crystal particles that make up the limestone mass and the alumina content and phosphorus content of each particle size are measured. It was found that the content of these was large in the grain portion. That is, if limestone is crushed into crystalline particles to remove coarse-grained portions and fine-grained portions, the purity of limestone can be increased and the phosphorus content can be reduced.

When sillitec limestone is heated, the crystal grains that make up the limestone lumps take the opposite actions of expansion and contraction in each crystal axis direction, so it is possible to easily disintegrate into crystal units only by giving a light impact. You can This effect can be obtained by heating to 200 ° C. or higher, and is carried out with an amount of heat equal to or lower than the energy for causing the decarboxylation reaction so that the limestone particles do not change into quicklime.

On the other hand, the intrusive rock does not have a crushing action due to such heating, so the limestone particles crushed by the above method are classified into coarse particles, medium particles and fine particles, which are determined based on the data obtained in advance, By collecting medium particles from it, it is possible to obtain a raw material for quick lime with a low content of alumina and phosphorus, and if this is calcined at a temperature of decarbonation temperature or higher, for example 800 ° C or higher and 1800 ° C or lower. High-purity low-phosphorus quicklime can be produced.

Further, by crushing the mined limestone to a particle size that can be calcined, and calcining at a temperature of decarbonation temperature or higher, for example, a temperature of 80 ° C. or higher and 1800 ° C. or lower, quick lime that has been crushed to crystal units can be obtained for the above reason. Similarly to the above, high-purity low-phosphorus quick lime can be produced by classifying into coarse particles, medium particles, and fine particles determined based on previously measured data, and collecting the medium particles from them.

The present invention can be implemented by the following procedures.

The crushed crystalline limestone is medium crushed, heated, crushed and classified, and then the medium particles are burned: 1) The limestone mined at the limestone mine is tens of millimeters using a jaw crusher and an impact crusher. Crush into medium chunks.

The particle size of crushed limestone is determined by an actual survey so that the efficiency of the following steps will be the best.

2) In order to prevent limestone from breaking into limestone in a crystal grain unit and thermally decomposing into quick lime with a heating device or the like having a rotary heating device or a moving device installed therein, 200
The heating is performed at a temperature of ℃ or more and with an amount of heat equal to or less than the energy that causes the decarboxylation reaction.

3) The heated limestone is crushed to crystal units of limestone by a crushing facility that gives a thermal shock by quenching and a dynamic shock by dropping, such as a ball mill.

4) Use crushed limestone particles to obtain coarse particles, medium particles, fine particles by using a vibrating sieve having a mesh to obtain alumina particles and other medium particles in the limestone particles and a medium particle size that reduces the phosphorus content. Classify into grains.

In this case, the size of the mesh of the sieve should be based on the actual survey data of the content by particle size so that the content of alumina, etc. in the medium particles and phosphorus content will be below the specified value depending on the particle size of the crystal particles that make up limestone. Make a decision based on

For classifying the limestone particles, it is possible to use a wind classifier, a gravity classifier, or the like, or to use these classifiers and a sieve in combination.

5) The medium particles obtained above are heated to a temperature not lower than the decarbonation temperature, for example, 80
High-purity low-phosphorus quicklime is produced by firing at a temperature of 0 ° C to 1800 ° C.

The method to crush, crystallize, and classify the crystallized limestone that has been mined is as follows: 1) Crush the limestone mined at the limestone mine into a lump of dozens of mm that can be calcined using a jaw crusher, impact crusher, etc. .

In addition, when crushing the mined limestone to a particle size that can be handled, it is suitable for the next step to remove the fine powder such as weathering of the intrusive rock by appropriately drying and sieving.

2) Remove the medium mass obtained above from the decarboxylation temperature, for example 80
Quick lime is produced by firing at a temperature of 0 ° C or higher and 1800 ° C or lower.

3) Coarse and medium-sized particles of quicklime particles that have been crushed during firing are obtained by using a vibrating sieve and a rotary sieve that have a mesh to obtain medium particles that reduce the alumina content and the phosphorus content in the quicklime. , Classify into fine granules. In this case, the size of the mesh of the sieve is based on the actual survey data of the content by particle size so that the content of alumina, etc. in the medium particles and the phosphorus content will be below the specified value depending on the particle size of the crystal particles that compose quicklime. To decide.

At this time, further crushing may be performed if necessary.

[Example 1] A lumpy limestone having a particle size of less than 50 mm and 25 mm or more was randomly collected during the production process of a limestone mine, and the limestone was heated in an electric furnace at 600 ° C for 2 hours, and then the diameter was 450 mm and the length was 45
A 0 mm cylindrical crusher was used for crushing using alumina balls having a diameter of 30 mm as a crushing medium. The crushed product was sieved with a sieve of 5.0 to 0.15 mm as shown in Table 1, the yield and P ₂ O ₅ content of each particle size category were measured, and the measurement results are shown in Table 1. .

According to the measurement results, it was found that the P ₂ O ₅ content of each particle size of less than 5.0 mm and 0.15 mm or more is smaller than that of coarse particles of 5.0 mm or more and fine particles of less than 0.15 mm. Therefore particle size 5.0m
Sift as m or more as coarse particles and 0.15 mm or less as fine particles, and use intermediate particles of less than 5.0 mm and 0.15 mm or more as raw material, and use the furnace temperature in an electric furnace.
High-purity low-phosphorus quicklime could be obtained by firing at 1100 ° C for about 120 minutes.

[Example 2] Bulk limestone having a particle size of less than 50 mm and 25 mm or more was randomly picked from the middle of the production process of a limestone mine, and this limestone was calcined in an electric furnace at 1100 ° C for 2 hours to obtain quick lime. The quicklime thus obtained was sieved with a sieve of 5.0 to 0.15 mm as shown in Table 1, the yield and P ₂ O ₂ content of each particle size category were measured, and the measurement results are shown in Table 1. It was

According to the measurement results, it was found that the P ₂ O ₅ content of each particle size of less than 5.0 mm and 0.15 mm or more is smaller than that of coarse particles of 5.0 mm or more and fine particles of less than 0.15 mm. Therefore, high-purity low-phosphorus quick lime can be manufactured by collecting medium-sized particles having a particle size range of less than 5.0 mm and 0.15 mm or more.

[Effects of the Invention] By carrying out the present invention, it is possible not only to produce high-purity low-phosphorus quicklime with a reduced content of alumina, silica, iron compounds and phosphorus from limestone mined in a mine. Instead, it is possible to adjust the content of phosphorus in the product by adjusting the particle size of limestone for quicklime raw material.

In addition, since it is not necessary to perform visual selection at the limestone mining site, it is easy to make a mining plan, and it is not necessary to set up a crushing series for each product, and equipment installation costs, operating costs and maintenance inspection costs are low. is there.

Further, waste heat for cement burning, iron making, quick lime burning, etc. can be used, and washing with water and manual selection steps can be omitted in the process, so that it can be omitted.

Claims (2)

[Claims] 1. A crystal unit formed after crushing mined crystallized limestone to a particle size of several tens mm and heating the crushed material at a temperature of 200 ° C. or higher at a heat amount lower than the energy for decarboxylation reaction. Crushed, the crushed product is sieved with a sieve of 5.0 to 0.15 mm, the crushed product of the sieving is classified into coarse particles, medium particles and fine particles according to a predetermined particle size, and the medium particles are A method for producing high-purity low-phosphorus quicklime, which is calcined as a raw material at a decarbonation temperature or higher. 2. Crushed mined crystallized limestone to a particle size of several tens of mm, and then calcined at a temperature not lower than the decarbonation temperature to produce quick lime, and the quick lime is sieved with a sieve of 5.0 to 0.15 mm, A method for producing high-purity low-phosphorus quicklime, in which the sieved quicklime is classified into coarse particles, medium particles and fine particles according to a predetermined particle size, and the medium particles are collected as a product.