JPH0346426B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Technology] The present invention relates to well-shaped granular potassium sulfate and a method for producing the same. More specifically, the present invention involves adding a neutralizing agent such as calcium hydroxide to a predetermined amount of modified potassium sulfate containing unreacted sulfuric acid for wet neutralization,
The present invention relates to granular potassium sulfate obtained by drying and pulverizing the neutralized product and then wet granulating it, and a method for producing the same.

[Prior Art] Generally, granulation of fertilizers in recent years has been carried out for the purpose of improving fertilization workability and adapting to mechanical fertilization.
In particular, mechanical fertilization has recently become widespread, and there is a strong demand for spherical potassium sulfate with good fluidity. In addition, granulated simple fertilizers are used in bulk blend fertilizers, which have recently become popular. Currently, various types of fertilizers are granulated using methods suited to their physical properties and provided on the market. Granular products are also required for potassium sulfate as a raw material for potassium fertilizer. However, regarding the granulation of potassium sulfate, there are various manufacturing and quality problems as described below. for example,
In the wet refining method in which 5% by weight or more of water is mixed with the raw material potassium sulfate, it is difficult to efficiently obtain granular products with the desired particle size range because the potash sulfate has poor granulation properties. be. When granular potassium sulfate obtained by compression granulation of a potassium sulfate-water mixture using a roll press or the like is used as the raw material for the bulk blend fertilizer described above, granular sulfuric acid is produced during handling and transportation of the resulting bulk blend fertilizer. As a result of the pulverization of the potash portion, classification of the bulk blend fertilizer occurs, and segregation of fertilizing ingredients by particle size becomes a problem.

Incidentally, 6 to 12 mesh granular potassium sulfate is generally used as a raw material for compound fertilizers or bulk blend fertilizers. In such applications,
The granular potassium sulfate obtained by the above-mentioned compression granulation method has undergone a process of compression, crushing, and sieving, so its surface has many protrusions and its compression hardness is relatively high, but the surface to be crushed is worn out. Cheap. When handling and transporting the granulated product with flow, the fragile surfaces of the individual particles are pulverized. Potassium sulfate, which is compressed and granulated using a roll press using the conventional method, is used as a raw material for bulk blend fertilizer, but the pulverization rate of this product is approximately 10%, which is lower than the average pulverization rate of other granular fertilizers. This is significantly higher than 2-3%. Therefore, regarding granular potassium sulfate, there is a demand for a granulated product that is re-sieved before bulk blending and does not require re-sieving.

[Object of the Invention] As a result of various studies in order to obtain the above-mentioned desirable potassium sulfate, the present inventors added a predetermined amount of a neutralizing agent such as calcium hydroxide to modified potassium sulfate containing unreacted sulfuric acid and carried out a wet process. The present invention was completed based on the knowledge that the above-mentioned problems could be solved by neutralizing, drying and pulverizing the neutralized product, and then performing wet granulation.

As is clear from the above description, an object of the present invention is to provide a method for granulating potassium sulfate that has a significantly lower pulverization rate and has good fluidity, and to provide granular potassium sulfate obtained by the method. be.

[Configuration and Effects of the Invention] The present invention has the main configurations (1) and (2) and the embodiment configuration (3).

(1) Modified potassium sulfate containing unreacted sulfuric acid obtained by dry reaction of potassium chloride and sulfuric acid is mixed with calcium hydroxide, calcium oxide or calcium carbonate in an amount of 0.5 to 2 times the amount of unreacted sulfuric acid. A method for producing granular potassium sulfate, which comprises adding one or more selected neutralizing agents for wet neutralization, drying the neutralized product, pulverizing the dry product, and then performing wet granulation.

(2) Unreacted sulfuric acid obtained by dry reaction of potassium chloride and sulfuric acid is converted into modified potassium sulfate from 0.5 to 2 times equivalent amount of calcium hydroxide, calcium oxide or calcium carbonate to the unreacted sulfuric acid. Wet-neutralize by adding one or more selected neutralizing agents, dry the wet-neutralized product, and crush the dry product. A method for producing granular potassium sulfate, which comprises granulating a mixture of neutralized, dried and pulverized products in a ratio of 2:1 or more.

(3) The method according to item 1 or 2 above, wherein in the wet neutralization, the amount of water added is 2 to 20% by weight based on the modified potassium sulfate.

As the potassium sulfate used in the present invention, modified potassium sulfate obtained by dry reaction of potassium chloride and sulfuric acid is preferably used. However, potassium sulfate obtained by other manufacturing methods can of course also be used.

The powdery degree, ie, the particle size, of such raw material potassium sulfate is not limited. Any substance that can be sufficiently wet neutralized can be used in the present invention. That is, its form is, for example, 20 meshes (Italar,
(The same applies hereafter) A bath-like powder is desirable, and coarse particles such as a 5 mesh are not desirable. If coarse particles such as 5 mesh are used, wet neutralization will be incomplete and the effectiveness of the present invention will be reduced. That is,
There is a tendency for the granulation properties of the wet neutralized product to deteriorate, the yield of granular products to decrease, and the hardness (compression fracture pressure) of the obtained granular products to decrease.

As the neutralizing agent used in the present invention, a powdered calcium compound can be used. Specifically, one or more compounds selected from calcium compounds such as calcium hydroxide, calcium oxide, or calcium carbonate are preferably used.

The amount used is 0.5 to 2.0 times equivalent, preferably 0.8 to 1.5 times equivalent, relative to the unreacted sulfuric acid content in the modified potassium sulfate determined in advance. If the amount is less than 0.5 times equivalent, the acidity of the potassium sulfate after neutralization will be extremely high (PH is low), making it unsuitable as a fertilizer. If it exceeds 2 times equivalent, the fertilizing component (K ₂ O Although the concentration of (min) tends to decrease, the granulation property does not particularly improve, which is undesirable.

The amount of water used in wet neutralization of the method of the invention is not limited. It is sufficient that the neutralization progresses sufficiently. It is usually 2 to 20 percent by weight (wet product basis, same hereinafter), preferably 4 to 15 percent by weight, based on the modified potassium sulfate. If the amount is less than 2% by weight, neutralization will not proceed sufficiently and the effect of the present invention will be reduced. Moreover, if it exceeds 20% by weight, the energy required for drying increases, making it uneconomical.

The method of mixing the above modified potassium sulfate, neutralizing agent, and water is not limited. For example, three types of mixed raw materials are charged simultaneously or sequentially into an open or closed mixer and heated to 0 to 100°C, preferably 20 to 80°C.
Mix for minutes to 1 hour, preferably 5 minutes to 30 minutes. However, as long as the effects of the present invention are not impaired, it is also possible to advance neutralization by mixing only the modified potassium sulfate and the neutralizing agent in advance and supplying the mixture together with water to the wet granulator. . The water supply ratio can be within a range of 0.5 or less by weight to the neutralized potassium sulfate supplied to the wet type machine. By doing this, during the two drying steps in the entire process from raw materials to products,
The drying process for neutralized products can be partially omitted.

The above-mentioned mixer is not limited as long as it can mix materials such as powder in a short time, and for example, a tank-type blender with an agitator, a ribbon blender, etc. can be used.

Further, the above-mentioned wet granulation is usually carried out using a rolling granulator such as a dish-type granulator or a drum-type granulator, or an extruder, but is not limited thereto.
The amount of water supplied to the granulator is not limited as long as it is below the above upper limit (0.5).

However, as mentioned above, the amount of water used for wet neutralization is usually 2 to 20 weight percent, preferably 4 to 15 weight percent.

Further, the type of dryer and drying method used in the present invention are not limited, but it is desirable to select mild conditions in order to reduce powdering during drying of the wet granulated product. As long as the effects of the present invention are not impaired, the same dryer may be used for drying the wet neutralized product and the wet granulated product. Prior to this drying, the above-mentioned granulation conditions should be selected so that neutralization of the wet granulation product proceeds sufficiently. This is because, in the method of the present invention, the neutralization reaction does not necessarily proceed to the necessary and sufficient extent only by the initial wet neutralization of the modified potassium sulfate, and the wet-neutralized product is wet-processed through subsequent pulverization. This is because neutralization often does not proceed sufficiently until the grains are received.

The dried potassium sulfate is classified using a sieve machine and divided into oversize products, finished products, and undersize products.

Oversized products are pulverized and undersized products are recycled to the wet granulator without being pulverized or after being pulverized. When the same dryer is used for both dryer use steps, the wet neutralized and dried product is present in the undersized product mentioned above. The progress of neutralization of the oversized product is usually sufficient, and by pulverizing it and feeding it to the wet granulator, it is possible to replace the wet-neutralized dry product by pulverizing it and feeding it to the wet granulator. .

The above steps will be explained with reference to the attached drawings.

In the figure, the modified potassium sulfate and neutralizing agent supplied from pipes 1 and 2 pass through pipe 3 to mixer A.
supplied to Inside the mixer, water is sprayed from pipe 4, the three raw materials are mixed, and a neutralization reaction proceeds. The neutralized mixture is sent via piping 5 to dryer B together with the wet granulated product sent via piping 15 (also serves as a dryer).
Potassium sulfate dried in step B is sent to sieve machine C via a bucket elevator 6, and is sieved in order of particle size into oversize products, products, and undersize products.

Oversized products are sent to crusher D via piping 7.
sent to be crushed.

The product is taken out of the system through piping 9.

The undersized product is sent to the crusher E via the pipe 11 and crushed, or is sent as is (without being crushed) through the pipe 10.

Potassium sulfate other than these products (note: over- or under-sized products after pulverization, under-sized products that have not been pulverized) are transported to the flow conveyor 13 and piping 1.
3' to the wet granulator F.

In F, water of about 50% by weight or less is sprayed onto the potassium sulfate from the pipe 14 to perform granulation.

The undried physical potassium sulfate that has been wet-granulated as described above is sent to the dryer B through the piping 15 as described above, and the neutralized potassium sulfate (note: wet neutralized product) is sent from the mixer A. dried at the same time.

The first effect of the present invention is that the obtained granular product has a good shape (spherical shape) and good fluidity. The granular products obtained according to the invention are therefore well suited for mechanical fertilization.

The second advantage of the present invention is that the pulverization rate of the resulting granular product is relatively low. The pulverization rate of the granular product obtained by the present invention will be described later (note: Example description).
It is less than 10% by weight according to the measurement method, and the powdering rate is lower than that of conventional compression granulated products (about 10% powdering rate).

Incidentally, the dry, neutralized product that has only been neutralized and dried but not crushed (Note: Sample A in Example-1 described later) was used in twice the amount of the dried, neutralized and ground product (Note: Sample B in Example-1 described later). However, if magnesium hydroxide is used in place of the calcium compound according to the present invention as a neutralizing agent, it is difficult to use a dry neutralized product. Even if the amount ratio exceeds twice the amount (weight ratio) of the dry, neutralized and pulverized product, the pulverization rate of the product (granular product) will not increase significantly (Note.
(See Comparative Example-3).

On the other hand, when magnesium hydroxide is used as a neutralizing agent, even if the amount of the dry neutralized product used is less than twice that of the dry neutralized pulverized product, the pulverization rate of the product will not be sufficient. No decrease (Note: See Comparative Example-4).

Therefore, magnesium hydroxide is not suitable as a neutralizing agent according to the present invention.

The present invention will be explained below with reference to Examples and Comparative Examples.

Example 1 Modified potassium sulfate containing 2.8% by weight of unreacted sulfuric acid was ground in a mortar to produce 10 mesh pieces (Tyler).
After passing, 500 g of the lime was placed in a mortar with a diameter of 20 cm, and ground for 30 minutes. Added an equivalent amount of slaked lime (calcium hydroxide purity of 95% by weight) powder and thoroughly crushed in a bag. A sample was prepared by shaking (referred to as sample A).

The sample was placed in a 2-liter kneader, water was sprayed with a sprayer while stirring, the mixture was stirred for a total of 10 minutes, and then dried for 4 hours in an electric dryer set at 110°C to obtain a neutralized product.

However, the amount of water added by the spraying was 7% by weight based on the sample.

The neutralized product obtained above was pulverized for 15 minutes using a disintegrator to form a powder (referred to as sample B).

Next, the diameter of the dish is 45 cm, the number of rotations
Using a dish-type granulator with a speed of 25 rpm and an angle of 45 degrees, sample B was introduced and water was sprayed with a sprayer, followed by drying in an electric dryer set at 110° C. for 4 hours. The physical properties of the obtained granular product were as follows.

Granular product hardness: 2.5Kg Granular product pulverization rate: 8.3% by weight (Reference) Granulation moisture: 10.3% by weight [Measurement method] Hardness Measurement of 20 grains of 6 to 7 mesh (Tyler) size by Kiya method hardness. Average value Pulverization rate Measured on grains with a particle size of 6 to 9 mesh according to the method of the Combination Granular Compound Fertilizer Study Group Comparative Example 1 A granular product was obtained in the same manner as in Example 1 except that neutralization was not performed. The physical properties of the granular product were as follows.

Granular product hardness: 0.8 Kg Granular product pulverization rate: 65.8 weight percent (Reference) Granulation component: 13.6 weight percent Example 2 Same as Example-1 except that a mixed sample of 150 g of sample A and 350 g of sample B from Example-1 was used. Granular products were obtained in the same manner.

The physical properties of the granular product were as follows.

Granular product hardness: 2.1Kg Granular product pulverization rate: 9.8% by weight (Reference) Granulation moisture: 11.1% by weight Sample A (note, non-pulverized product) was transferred to Sample B as described above.
(Note: Even if it is mixed into a pulverized product), if the amount used is less than 1/2 (weight ratio) of sample B, the pulverization rate of the product will not increase significantly.

Comparative Example 2 A granular product was obtained in the same manner as in Example-2, except that a mixed sample of 350 g of Sample A and 150 g of Sample B of Example-1 was used.

The physical properties of the granular product were as follows.

Granular product hardness: 1.2Kg Granular product pulverization rate: 49.3% by weight (Reference) Granulation moisture: 11.2% by weight As shown above, when mixing sample A with sample B, the amount of the former used is twice that of the latter (weight ratio ), the pulverization rate of the product increased significantly, showing a contrasting result compared to the case of Example 2.

Comparative Example 3 A granulated product was obtained in the same manner as in Example 2, except that magnesium hydroxide (MgO 67% by weight) was used as a neutralizing agent.

The physical properties of the granular product were as follows.

Granular product hardness: 1.0Kg Granular product pulverization rate: 13.8% by weight (Reference) Granulation moisture: 12.3% by weight As shown above, the mixing ratio of Sample A and Sample B is the same as Comparative Example 2, and the amount of the former used is the latter. Even if the amount exceeds twice that of slaked lime, if magnesium hydroxide is used as a neutralizing agent instead of slaked lime, the pulverization rate of the product will not increase significantly. However, the powdering rate is
If it exceeds 10% by weight, the purpose of the present invention cannot be achieved.

Comparative Example 4 A granulated product was obtained in the same manner as in Example-1 except that magnesium hydroxide was used as a neutralizing agent.

The physical properties of the granular product were as follows.

Granular product hardness: 2.0Kg Granular product pulverization rate: 13.0% by weight (Reference) Granulation moisture: 10.4% by weight As described above, even if Sample B is used in the same manner as Example 1, neutralization When magnesium hydroxide is used as an agent instead of slaked lime,
Unable to obtain a good (note, less than 10 weight percent) product powdering rate. Therefore, it was confirmed that magnesium hydroxide is not suitable as a neutralizing agent for use in the present invention.

[Brief explanation of drawings]

The figure is a flow sheet of the apparatus used in the method of the invention.

Claims (1)

[Claims] 1. Modified potassium sulfate containing unreacted sulfuric acid obtained by dry reaction of potassium chloride and sulfuric acid, calcium hydroxide in an amount of 0.5 to 2 times the amount of unreacted sulfuric acid,
Granular potassium sulfate, which is characterized by wet neutralization by adding one or more neutralizing agents selected from calcium oxide or calcium carbonate, drying the neutralized product, pulverizing the dry product, and then performing wet granulation. manufacturing method. 2. The method according to claim 1, wherein in the wet neutralization, the amount of water added is 2 to 20 percent by weight based on the modified potassium sulfate. 3. Unreacted sulfuric acid obtained by dry reaction of potassium chloride and sulfuric acid is converted into modified potassium sulfate, and calcium hydroxide is added in an amount of 0.5 to 2 times equivalent to the unreacted sulfuric acid.
A neutralized dry pulverized product obtained by adding one or more neutralizing agents selected from calcium oxide or calcium carbonate to perform wet neutralization, drying the wet neutralized product, and pulverizing the dry product; A method for producing granular potassium sulfate, which comprises granulating a mixture of a neutralized product and a neutralized dry pulverized product in a weight ratio of 2:1 or more. 4. The method according to claim 3, wherein in the wet neutralization, the amount of water added is 2 to 20 percent by weight based on the modified potassium sulfate.