JP5778921B2 - Method for producing lime granular material - Google Patents

Description

The present invention is a lime granule obtained by granulating a high water content containing limestone powder generated in the limestone product manufacturing process (hereinafter referred to as “limestone washing and dewatering cake”) by adding a swellable clay with a vacuum granulator. The present invention relates to a method for manufacturing a body.
In more detail, this invention relates to the manufacturing method of the lime granular material which is excellent in high hardness and disintegration and can be used conveniently as a fertilizer.

  Limestone is used in various applications such as cement raw materials, iron-making auxiliary raw materials, crushed stones, papermaking, resins, rubber, paints, fertilizers, feeds, foods and the like. In the limestone product manufacturing process used in these applications, the crushed limestone surface is usually washed with water to remove the adhering fine powder. Or dehydrated by a combination of thickener and filter press. By this process, a large amount of limestone washed dehydrated cake, which is a highly water-containing cake containing limestone fine powder, is generated.

This limestone washed dehydrated cake contains 10 to 30% by mass of water despite the fact that most of its solid content is limestone powder, so there are significant restrictions on its use, and some of it has been discarded and is sufficient It was not used for.
In order to make effective use of this limestone washed dehydrated cake, several methods have been disclosed. For example, Patent Documents 1 and 2 disclose a method of mixing and granulating a byproduct of a lime baking furnace mainly composed of quicklime in a limestone washed dehydrated cake. Patent Document 3 discloses a method of granulating a limestone washed dehydrated cake alone or by adding a small amount of clay mineral using clay minerals contained in the limestone washed dehydrated cake.

Japanese Patent Laid-Open No. 53-137897 JP 2009-114029 A JP 2001-122683 A

However, the grains obtained by mixing limestone washed dehydrated cake and quicklime are very hard, so they do not disintegrate easily when contacted with water. Therefore, soil acidity correction, fertilizer use, snow melting agent use, etc. Not suitable for.
On the other hand, in the method described in Patent Document 3 in which clay mineral is added to a limestone washed dehydrated cake and granulated by extrusion molding, rolling granulation, or the like, there is a phenomenon that the hardness of the granulated product decreases due to a change with time after granulation. It was seen. And after hardness reached a stable state, it was difficult to obtain high hardness of 1.0 kgf or more.

  Therefore, as a result of intensive investigations to use the limestone washed dewatered cake as a granular fertilizer, the present inventors use a vacuum granulator as a granulator for the limestone washed dewatered cake. It was found that the air in the limestone washed dehydrated cake was removed and a dense granular material was obtained. However, in this method, dilatancy, that is, when force is applied and the particles are densely packed, the gaps between the particles are reduced and the strength is increased to become solid, but when the application of force is stopped, the gaps between the particles are expanded again to the original liquid state. The return phenomenon occurred. As a result of further investigations, it was found that the dilatancy phenomenon hardly occurs when the limestone washed dehydrated cake and the swellable clay are mixed in a predetermined blending amount and then granulated with a vacuum granulator. This invention completes the invention regarding the lime granular material which has high hardness based on these knowledge.

That is, in the present invention, after mixing the limestone washed dewatered cake and the swellable clay with 100 parts by mass (solid content) of the limestone washed dehydrated cake at a ratio of 1 to 5 parts by mass, vacuum granulation is performed. It is related with the manufacturing method of the lime granular material characterized by granulating with a machine and drying.
Moreover, this invention relates to the manufacturing method of the lime granular material which crushes further the lime granular material obtained by the said manufacturing method.
Furthermore, the present invention relates to a method for producing a lime granule, wherein the swellable clay is at least one selected from the group consisting of bennite, natural smectite, synthetic smectite, and swellable mica.

The lime granule according to the present invention is suitable for machine spraying because it has a high hardness. Especially when this is used as soil acidity correction or as a fertilizer, the swellable clay also acts as a disintegrating agent, so that water is applied after spraying. It is easy to disintegrate by contact with, that is, it has an advantage of exhibiting its effect at an early stage.

And since the raw material utilized for this invention is a thing in a discard state, it has many advantages, such as being able to manufacture this invention lime granular material very cheaply. The lime granular material of the present invention can be effectively used as a fertilizer, as well as a snow melting agent.
As described above, the lime granular material of the present invention has great industrial significance from the viewpoint of environmental conservation as well as substantial value as a fertilizer.

Below, the manufacturing method of the lime granular material of this invention is demonstrated still in detail.
As described above, the limestone washing dehydrated cake according to the present invention is obtained by solid-liquid separation of the washing wastewater generated in the washing step of removing / separating fine powder adhering to the surface of the limestone in the limestone product production process with a filter press or the like. It is the dehydrated cake obtained. It is preferable that the moisture content of the limestone washing | cleaning dehydration cake utilized for this invention is 10-30 mass%. In the present invention, any water content within the above range can be used without any problem, but 15 to 25% by mass is particularly preferable.

  The swelling clay is a clay that absorbs water and swells upon contact with water, and any clay having such properties can be used without limitation. As a swellable clay recommended by the present inventors, at least one selected from the group consisting of bennite, natural smectite, synthetic smectite, and swellable mica can be cited as a good example.

  The mixing ratio of the limestone washed dewatered cake and the swellable clay is 1 to 5 parts by mass of the swellable clay with respect to 100 parts by mass (solid content) of the limestone washed dehydrated cake. If the mixing ratio of the swellable clay is less than 1 part by mass, it is not sufficient to prevent the dilatancy phenomenon. On the other hand, even if the mixing ratio exceeds 5 parts by mass, an effect commensurate with the amount added cannot be obtained, which is not economical.

The mixing of the limestone washing dewatered cake and the swellable clay may be performed by any method as long as the two are sufficiently mixed, but even if the vacuum granulator has a kneading function, before introduction into the vacuum granulator It is desirable to be mixed in
The vacuum granulator is an apparatus that can perform granulation under reduced pressure, and is not particularly limited as long as it is an apparatus that contributes to such raw material degassing. Examples of the vacuum granulator include a vacuum pressurizer, a vacuum kneader, a vacuum extruder, and the like. Any of these can be applied to the present invention, but a vacuum kneader or a vacuum extruder is particularly preferable from the viewpoint of production efficiency. . A vacuum kneader and a vacuum extruder are generally configured by a screw portion having a kneading function or an extrusion function, a vacuum chamber (decompression chamber) provided in a part thereof, and an extrusion port having a hole of an arbitrary hole diameter. Yes. The hole diameter of the extrusion port may be appropriately set from the granulation property and the required particle diameter, but is preferably about 0.5 to 8 mm when used for fertilizers and the like. The columnar material discharged from the extrusion port may be cut or pulverized for granulation, and a method of cutting with a cutter or the like provided at the outlet of the extrusion port is simple.
In addition, when the water content of the mixture of the limestone washed dewatered cake and the swellable clay is not suitable for granulation, the water content may be adjusted by adding water or a dry powder as necessary. . The dry powder is preferably one that does not generate gas by reacting with the components of the mixture among those generally used as fertilizer raw materials, such as lime, slaked lime, magnesium carbonate, magnesium hydroxide, potassium chloride, phosphoric acid. Potassium etc. can be mentioned. In addition, although the suitable moisture content of the said mixture changes with granulators, about 10-30 mass% is preferable in general, More preferably, it is 10-20 mass%.

  Next, regarding the drying of the obtained granular material, an apparatus is not particularly selected, but it is preferable to use a rolling hot air dryer from the viewpoint of prevention of adhesion between the granular materials and drying efficiency. The drying temperature is preferably 80 to 150 ° C.

  The lime granular material obtained by the above production method may be further crushed to reduce the particle size. A crusher can be suitably used for crushing, and examples thereof include a jaw crusher and a roll crusher. The crushing is desirably performed by a method that generates as little powder as possible.

The shape of the particles obtained by the production method of the present invention is not particularly limited, and various shapes and particle sizes can be adopted depending on the application. If a spherical shape is desired depending on the application, the columnar product after granulation may be sized with a sizing machine. When the lime granular material of the present invention is used as a fertilizer or the like, when it is necessary to select according to particle size, an appropriate particle size can be obtained by classification using a sieve or the like. As a standard of the particle size obtained by classification with a sieve, a particle size of 0.5 to 8 mm with a sieve opening is preferable, of which 1 to 4 mm is particularly preferable, and more preferably 1.5 to 3 mm.

EXAMPLES Hereinafter, although an Example is given and the detail of this invention is demonstrated, this invention is not limited by those Examples. In addition, unless otherwise indicated, all% shows the mass%.
[Limestone washed dehydrated cake]
Limestone washed dehydrated cake with 17.5% moisture generated at the limestone mining site and 54% CaO in the solid content was used. In the following description, the mass of the dehydrated limestone cake is expressed in terms of solid content.
[Vacuum granulator]
A vacuum kneader (model MPM120N-FS) manufactured by Takahama Kogyo Co., Ltd. was used. The pressure in the vacuum chamber was set in the range of -100 kPa to -90 kPa with the atmospheric pressure (about 100 kPa) as a reference (zero). The extrusion port had a configuration in which 90 holes with a hole diameter of 5 mm were arranged. The columnar material discharged from the extrusion port was cut into a length of about 5 to 10 mm with a cutter to obtain a granular material.
[Crusher and crushed product]
A roll crusher (model SH-10) manufactured by Takahama Kogyo Co., Ltd. was used. A sieved product having a particle size of 1.5 to 3.0 mm was used as a crushed product.

[Example 1]
After adding 0.03 kg of bentonite to 2 kg of the limestone washed dehydrated cake, the mixture was mixed with a mixer (manufactured by Shinto Kogyo Co., Ltd., Mix Maller MSG-05) and granulated with a vacuum granulator. Next, the obtained granular material was dried at 85 ° C. for 30 minutes in a rolling hot air dryer (hereinafter referred to as a granulated product).
The obtained granulated product was further crushed with a roll crusher, and then sieved to obtain a crushed product having a size of 1.5 to 3.0 mm.
[Examples 2 to 4]
The raw material composition shown in Table 1 was produced in the same manner as in Example 1.

[Comparative Example 1]
It was produced in the same manner as in Example 1 except that no swellable clay was added. However, due to the dilatancy phenomenon that occurred after exiting the extrusion port of the vacuum granulator, no granular material worthy of evaluation was obtained.
[Comparative Example 2]
Example 1 except that the granulator was a pellet molding machine (Fuji Paudal Co., Ltd., fine disk pelleter PV-5 type. A screen with a hole diameter of 3 mm and a thickness of 10 mm was used, and the roller rotation speed was 37 rpm). To produce a granulated product. Note that crushing was not performed.

[Measurement method of average grain hardness]
A Kiyama hardness tester was used. For the granulated product by the vacuum granulator and the granulated product by the pellet molding machine, the horizontal hardness of the cylinder was measured. In addition, the crushed product was measured by setting the surface where the cross-sectional area was determined to be maximum at the bottom. The measurement was performed on 20 grains each, and the average value was defined as the average grain hardness.

[Disintegration test]
A granulated product (length: about 5-10mm) by a vacuum granulator or a granulated product (length: about 15-20mm) by a pellet molding machine (both dry products) are arranged on a sieve with a mesh of 1.7mm. In a suitably sized container and gently pour water until the product is fully immersed in water. The disintegration date was defined as the number of days until the day when the ratio of the disintegrated particles calculated from the number of undisintegrated particles remaining on the sieve was 80% or more after gently removing the sieve.

The results are shown in Table 1.

Claims (3)

A screw part having a kneading function or an extruding function after mixing the swellable clay at a ratio of 1 to 5 parts by mass with 100 parts by mass (solid content) of the limestone washed dewatered cake and the swellable clay. Granulating with a vacuum granulator equipped with an extrusion port having holes, a cutter provided in the extrusion port in order from the raw material supply side, and a vacuum chamber (decompression chamber) provided in a part of the screw part Then, the method for producing lime granular material, which is dried.   The manufacturing method of the lime granular material which crushes further the lime granular material obtained by the manufacturing method of Claim 1.   The method for producing a lime granule according to claim 1 or 2, wherein the swellable clay is at least one selected from the group consisting of bentonite, natural smectite, synthetic smectite, and swellable mica.