JPS6340720A - Granular potassium sulfate and its production - Google Patents

Abstract

PURPOSE:To produce a granular K2SO4 having an excellent granular shape, a high hardness and a low pulverizing rate, and suitable for mechanical fertilizing by crushing and wet-granulating a product which is produced by adding a specified amt. of a neutralizing agent to a denaturated K2SO4 contg. an unreacted sulfuric acid, compressing and molding the obtained mixture. CONSTITUTION:A molded product is produced by compressing and molding a mixture of a denaturated K2SO4 contg. an unreacted sulfuric acid obtained by allowing KCl and sulfuric acid to cause dry reaction and 0.5-2.0 times mol equiv. of one or more kind of neutralizing agent among Ca(OH)2, CaO, CaCO3, Mg(OH)2, MgO and MgCO3 based on the unreacted sulfuric acid. The granular K2SO4 is produced by crushing the molded product to powder and wet-granulating the obtained powder. In this way, the excellent shaped (spherical) granular product having a high hardness and a low pulverizing rate is obtained and the product has an excellent flowability on account of the above properties and suitable for the mechanical fertilizing. In addition the equipment for production can be made small is size because the amount of circulating powder to the amount of product is reduced owing to excellent granulating property of the powder and a higher yield of the product in the wet-granulating process.

Description

[Detailed description of the invention] [Field of technology] The present invention relates to granular potassium sulfate and a method for granulating the same.

More specifically, the present invention is made by adding a predetermined amount of a neutralizing agent such as calcium hydroxide to modified potassium sulfate containing unreacted sulfuric acid, compression molding the molded product, crushing the molded product, and then wet-granulating it. This article relates to granular potassium sulfate and its granulation method.

[Conventional technology]

Generally, granulation of fertilizers in recent years has been carried out for the purpose of improving the workability of fertilizer application4 and making it compatible with mechanical fertilizer application.

Particularly recently, mechanical fertilization has become widely accepted, and there is a strong demand for spherical potassium sulfate with good fluidity. In addition, granulated single fertilizers are now being used for bulk blend fertilizers, which have recently seen a significant decline. 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 oxide, there are various problems in production and quality ratio as described below. For example, in a wet granulation method in which 5 tonne % or more of water is mixed with the raw material potassium sulfate, the granulation properties of the potassium sulfate are poor, so granular products with a desired particle size range cannot be efficiently produced. It is difficult to obtain. When granular potassium sulfate obtained by compressing and granulating a potassium sulfate-water mixture using a roll press or the like is used as the raw material for the bulk blend fertilizer, the resulting bulk blend fertilizer is sealed during handling and transportation. As a result of the pulverization of the potassium sulfate portion, classification of the bulk blend fertilizer occurs, and segregation of fertilizing components 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, disintegration, and sieving, so its surface has many protrusions and its compression hardness is relatively high. The crushing surface is P! During handling and transportation of the granulated product, which is subject to wear and flow, pulverization of the fragile surfaces of the individual particles occurs. source of bulk blend fertilizer,
Potassium sulfate, which has been compressed and granulated using a roll press using the conventional method, is used as a raw material, but the pulverization rate of this material is
At about lθ%, the average powderization of other granular fertilizers is 2 to 3 of 2.
%. Therefore, granular potassium sulfate is recycled before bulk blending, and there is a demand for a granular product that does not require recycling.

[Purpose of the invention]

As a result of various studies in order to obtain the above-mentioned desirable potassium sulfate granules, the inventors of the Wood Inventors added a predetermined amount of a neutralizing agent such as calcium hydroxide to modified potassium sulfate containing unreacted sulfuric acid, and compression-molded the mixture. The present invention (second invention) was completed based on the knowledge that the above-mentioned problems could be solved by wet granulation after crushing the molded product. As is clear from the above description,
An object of the present invention is to provide a method for granulating potassium sulfate with extremely low powdering rate and good fluidity, and granular potassium sulfate granulated by the method.

[Structure and effects of the invention]

The present invention (second invention) has the following main star configurations (1) and (2) and embodiment configurations (3) to (6).

(1) [Modified potassium sulfate containing unreacted sulfuric acid obtained by dryly reacting potassium dioxide with sulfuric acid, calcium hydroxide and calcium oxide in an amount of 0.5 to 2 times equivalent to the unreacted sulfuric acid] , compression molding with the addition of one or more powdered neutralizing agents selected from calcium oligoacid, magnesium oxide, magnesium oxide, or magnesium carbonate, and wet granulation of the powder obtained by crushing the molded product. Granular potassium sulfate.

(2) Modified potassium sulfate containing unreacted sulfuric acid obtained by dry reaction of potassium chloride and sulfuric acid, Calcilla hydroxide 11, calcium oxide, in an amount of 0.5 to 2 times equivalent to the unreacted sulfuric acid, Granular sulfuric acid, which is characterized by adding one or more powdered neutralizing agents selected from calcium carbonate, magnesium hydroxide, magnesium oxide, or magnesium carbonate, compression molding, pulverizing the molded product, and then performing wet granulation. Method of producing potash.

(3) Compression molding) The above-mentioned (compression molding)
The method described in section 2).

(4) The method according to item (2) above, wherein the wet granulation is performed using a dish-type granulator, a drum-type granulator, or an extruder.

(5) Add water, potassium sulfate aqueous solution, or potassium sulfate slurry so that the granulation moisture in the wet granulation (water in the undried wet granulator) is 2 to 20% by weight. The method described in section 2).

(6) After drying and classifying wet granulated products to obtain granular potassium sulfate, oversized products are pulverized, and undersized products are granulated without being pulverized or after being pulverized and circulated to the wet granulator. The method according to item (2) above.

As the powdered 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 degree of powderiness, that is, the particle size, of the raw material potassium sulfate is not limited, and it can be used in the present invention as long as it is of a level used as a raw material for pressure plates.

The neutralizing agent used in the present invention is capable of reacting with unreacted sulfuric acid in modified potassium sulfate at 0 to 200°C, and the product after the reaction (sulfuric acid 11 has a harmful effect on potassium sulfate as a fertilizing ingredient). It can be used as long as it does not add.Specifically, calcium hydroxide, calcium oxide, )RS calcium, magnesium hydroxide, magnesium oxide, magnesium carbonate, and other calcium or magnesium compounds can be used. Powdered compounds are preferably used.

Its use? is 0.5 to 2.0 times the unreacted sulfuric acid content in the modified potassium sulfate determined in advance, preferably 0.8
~1.5 times equivalent. If the amount is less than 0.5 times equivalent, the acidity of the potassium sulfate after neutralization will be extremely high (low pH), making it unsuitable for use as a bulk blend fertilizer, and if it exceeds 2 times the equivalent, the effectiveness of the fertilizer in the potassium sulfate after neutralization will be This is not desirable because the concentration of the component (K2O component) tends to decrease.

The method of mixing and neutralizing the neutralizing agent with the modified potassium sulfate is not limited, for example, while stirring the granular modified potassium sulfate in a known rotary or stirring mixer A fixed amount of the neutralizing agent powder is added all at once or gradually so that it is uniformly mixed within a short period of time (for example, within 30 minutes). In order to prevent the neutralizing agent from adhering to the wall of the mixer or to a part of the modified potassium sulfate, the entire amount of the neutralizing agent and the modified potassium sulfate are mixed in advance. A diluted neutralizing agent by mixing with a portion of sulfuric acid may be used in the above mixing.

In addition, the above-mentioned neutralization does not proceed simultaneously with the above-mentioned mixing because the water contained in the modified potassium sulfate and the neutralizing agent is usually extremely small (for example, 0.1% by weight). The subsequent steps of the process, such as compression molding and milling and wet granulation, proceed as the process progresses, in other words over time, and are substantially complete at the end of the granulation.

Compression molding is done using roll presses and priquette machines.

This is carried out using a compression molding machine such as an extruder or tablet machine. The conditions for compression molding are not limited, but are preferably selected to the extent that the material to be compressed can be sufficiently molded.

The shape of the compressed product thus produced (f') varies depending on the type of compression molding machine used, such as a plate-like shape, a crumb-like shape, a rod-like shape, or a tablet-like shape. crushed to. The type of pulverizer used and the pulverizing conditions are not limited as long as the particle size described below can be obtained. For example, a ball mill, a roll mill, etc. can be used. Grinding is carried out continuously at room temperature to 50° C. or in the case of a batch method, from 5 minutes to 5 hours, preferably from 10 minutes to 3 hours.

The degree of powderiness of the compression-molded product after pulverization, that is, the particle size, is not limited. Generally, as a raw material for wet granulation, it is desirable that the material be fine, for example, pulverized to about 100 mesh passes or less.

The powdery neutralized product thus obtained is wet-granulated using a granulator in the next step. This makes the granulation process more effective.

Wet granulation is usually carried out using a transfer granulator such as a dish-type granulator, a drum-type granulator, or an extruder, but is not limited thereto.

The amount of water added to the potassium sulfate supplied in wet granulation is not limited. The moisture in the granulated product immediately after granulation (granulation moisture, the same hereinafter) varies depending on the model of the granulator and the particle size of the potassium sulfate supplied, but is usually 2 to 20%. (based on percent weight on weight, the same applies hereinafter), preferably 4 to 15
i amount percent.

As the granulation water, wood, a potassium sulfate aqueous solution, or a potassium sulfate slurry can be used. The granulation water rlT may contain other compounds as long as they do not interfere with the granulation of the sulfuric acid paste.

Potassium sulfate granulated using a wet granulator is dried using a dryer. Although the type of dryer and drying method are not limited, it is desirable to select mild conditions in order to reduce powdering during drying.

The granular products obtained as described above are processed by a sieve machine and are sieved into oversized products, products, and undersized products in the order of particle size.

Oversized products are pulverized by a pulverizer and circulated to a wet granulator, and undersized products are not pulverized or are pulverized by a pulverizer and then circulated to a wet granulator. Whether or not to pulverize undersized products is determined by the particle size balance of the entire potassium sulfate supplied to the wet granulator.

The above steps will be explained using figures.

In the figure, the variable I & supplied from piping 1 and piping 2
Potassium sulfate and neutralizing agent are mixed (mixer not shown), stored in hopper A via piping 3, and supplied to pressurized granulator B. The compressed 1'U compressed in B is sent to the crusher C via piping 4, and after being crushed, is supplied to the wet granulator along with circulating products (described later) via the packet elevator-5. be done.

At D, granulated water is sprayed from the pipe 6, and the powdered and finely granular potassium sulfate becomes wet granules, which are sent to the dryer E via the pipe 7. The granular product dried in E is sent to sieve F via packet elevator-8. This sieve machine sieves the granular products into oversize products, finished products, and undersize products in order of particle size.

The oversized product is then sent to the crusher G via piping 9 and crushed.

The product is taken out of the system through piping 11. Oversized and undersized products are taken out from pipes 10 and 12, respectively, and circulated to D via flow conveyor 13.

The first effect of the present invention is that the hardness of the obtained granular product is high;
The powdering rate is low. That is, Examples 1 and 2 described below
As is clear from Comparative Examples 1 to 1, the hardness (compression rupture pressure) of the granular products obtained by the present invention reaches 4 to 6 kg with a particle size of 6 to 7 meshes (Tyler), and the pulverization rate is 3 to 5% by weight, and it is clear that there is a significant difference in hardness and powdering rate compared to conventional products.

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

The third effect of the present invention is that the granulation property of the granular product is extremely good in wet granulation, and the yield of the product is high. That is, since the product yield is high, the amount of gI circulating to the product is small, and the equipment can be downsized.

Incidentally, as is clear from Examples 1 to 3 and Comparative Examples 1 to 3,
Compression molding tends to reduce the amount of granulation water used in wet granulation.

Although the reason is not clear, it is presumed that compression increases the density of the particles and decreases the particle surface area per unit weight (specific surface area).

The reduction in granulation moisture, together with the aforementioned downsizing of equipment, provides an energy saving effect.

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

Example 1 Pressure molded products made by adding slaked lime (calcium hydroxide purity 95 tons) as a neutralizing agent to modified potassium sulfate containing 2.8% unreacted sulfuric acid were dissolved in a mortar. It was crushed into 10 mesh passes. Next, put 500 g of the crushed product into a mortar with a diameter of 20 cm, and
It was ground for 0 minutes and used as a sample.

Using a dish-shaped granulator with a diameter of 45 cm, a rotation speed of 25 RP, and an angle of 45 degrees, the wood was granulated while being sprayed with a sprayer, and then granulated in an electric dryer set at a temperature of 110°C for 4 hours. After drying, granules were obtained.

The granulation water content and physical properties of the granular product were as follows.

Granulation moisture: 9.0% weight Granular product hardness: 4.3kg 1/Powdering rate: 4.1% weight Measuring method Hardness: Based on Mizuya hardness tester.

Average value of measurements for 20 grains of 6-7 mesh size.

Powdering-+i: According to the method of the Kumiai Granular Compounded Fertilizer Study Group.

Measured on grains with a grain size of 6 to 9 mesh.

Comparative Example-1 Modified potassium sulfate containing 2.8% by weight of unreacted sulfuric acid was ground in a mortar to make 10 mesh passes, and then ground in the same manner as in Example 1, and slaked lime powder was applied to this. was added, shaken well in a bag, and used as a sample.

Granulation and drying were performed in the same manner as in Example 1 to obtain granular products.

The measured values were as follows.

Granulation moisture + 13.6 % hardness Granular product hardness + 0.8 kg // Powdering rate: 65.8% heavy equipment Example-2 Other than using a sample obtained by pulverizing the granular product obtained in Example-1. The sample was granulated and dried in exactly the same manner as in Example-1.

The ΔIII constant values were as follows.

Granulation moisture content: 8.2% hair content Granular product hardness: 5.4 kg/I Powdering rate = 3.3% by weight Comparative Example-2 All samples were used except that a sample obtained by pulverizing the granular product obtained in Comparative Example-1 was used. <The sample was granulated and dried in the same manner as in Example-1.

The Δ11 constant values were as follows.

Granulation moisture: 10.6% by weight Granular product hardness: 2.8 kg/l Powdering rate = 8.1% by weight Example-3 Neutralized to modified potassium sulfate containing 2.7% by weight of unreacted sulfuric acid Slaked lime was added as an agent, and the pressurized product was granulated using an impact crusher and used as a raw material.

Dish diameter 3.9 meters, rotation speed 10 rpm, angle 50
Granulation was carried out continuously using a dish-type granulator equipped with a dryer and a sieve, and granules of between 5 and 9 meshes were made into a product.

The breakdown of the supply fee to the granulator is as follows: Raw material: 3.0 tons/hourly product 6. Ott Also, the breakdown of the deposits in the sieve machine was as follows.

O/He size: 0.6 tons/hour (pulverized and circulated) Product: 3.0 tons Undersize at 77 hours: 5.4 tons/hour (circulated directly) The measured values of granulation moisture and physical properties of the product are as follows. Granulation moisture: 5.4% by weight Product hardness (6-7Me): 5.9kg1/ Powdering rate: 4.7% by weight Comparative example-3 Unreacted sulfuric acid content 2.7% by weight #ig modified potassium sulfate containing
Particles were continuously granulated in the same manner as in Example 2, except that the raw material was crushed using a pulverizer and an equivalent amount of slaked lime was added as a neutralizing agent.

The breakdown of the amount supplied to the granulator is 2.5 tons of raw material/hourly circulation.
8.5 〃 The breakdown of the quantity on Aircraft Q was as follows.

Oversize 0.6 tons/hour (pulverized and circulated) Product 2.5 tons Undersize 7.9 tons/hour (circulated as it is) The measured values of granulation moisture and physical properties of the product are as follows. Granulation moisture: 5.8% by weight Product hardness: 2.3kg // Powdering rate: 9.2% by weight

[Brief explanation of drawings]

The figure is a flow sheet of the apparatus used in the method of the invention. that's all

Claims (6)

[Claims] (1) Modified potassium sulfate containing unreacted sulfuric acid obtained by dryly reacting potassium chloride and sulfuric acid is added with calcium hydroxide, calcium oxide, and carbonate in an amount of 0.5 to 2 times equivalent to the unreacted sulfuric acid. Granular sulfuric acid obtained by adding one or more powdered neutralizing agents selected from calcium, magnesium hydroxide, magnesium oxide, or magnesium carbonate, compression molding, pulverizing the molded product, and wet-granulating the resulting powder. Cali. (2) Modified potassium sulfate containing unreacted sulfuric acid obtained by dry reaction of potassium chloride and sulfuric acid is added with calcium hydroxide, calcium oxide, and carbonate in an amount of 0.5 to 2 times equivalent to the unreacted sulfuric acid. Granular potassium sulfate, which is characterized by adding one or more powdered neutralizing agents selected from calcium, magnesium hydroxide, magnesium oxide, or magnesium carbonate, compression molding, crushing the molded product, and then subjecting it to wet granulation. manufacturing method. (3) The method according to claim (2), in which compression molding is performed using a roll press, a ricket machine, an extruder, or a tablet machine. (4) The method according to claim (2), in which wet granulation is performed using a dish-type granulator, a drum-type granulator, or an extruder. (5) A patent claim in which water, a potassium sulfate aqueous solution, or a potassium sulfate slurry is added so that the granulation moisture in wet granulation (moisture in the undried wet granulation product) is 2 to 20% by weight. The method described in scope item (2). (6) After drying, wet granulation products are classified to obtain granular potassium sulfate, oversized products are crushed, and undersized products are granulated without being crushed or crushed and circulated to a wet granulator. The method according to claim (2).