JPH0151471B2 - - Google Patents

Description

[Detailed Description of the Invention] (a) Purpose of the Invention [Field of Industrial Application] The present invention relates to a method for producing granular fertilizer, and in particular, it is a method for producing granular fertilizer, and in particular, it is a method for producing granular fertilizer using materials that are low in value due to water content, etc. The aim is to obtain granular fertilizer with excellent granulation efficiency.

[Conventional technology]

The productivity and energy consumption of granular fertilizers depend largely on granulation efficiency, and manufacturers have been making efforts to improve this for many years.

In the production process of granular fertilizers, the granulation method often adopted is rolling granulation, ie, mainly using a rotating drum, or using a rotating plate type, or a modification thereof. In these granulators,
A method of directly introducing powder raw materials and dispersing them and rolling granulation, or as a pre-process, a pug mill,
There is a method of installing a mixer such as an edge runner, preparing wet powder in advance, and then performing rolling granulation.

The powder raw material introduced into the granulator is joined by the added liquid to form loose aggregates. This is tightened as it rolls, the gaps between the particles are reduced, and liquid is present on the surface of the aggregate, and when this liquid comes into contact with the small pieces, they are swallowed together to form a larger aggregate. These aggregates grow as they roll and become almost spherical, becoming more compacted, and eventually the liquid is drawn into the granules from the surface by capillary force, forming stronger granules. This granule is dried and dehydrated in a dryer to make a complete granular fertilizer. Next, the fertilizer is sieved to obtain a granular fertilizer with a diameter of about 1 to 4 m/m in order to select the desired particle size. Oversized and undersized fertilizers are ground again and returned to the granulation process as fine powder.

The ratio of the product yield to the amount passed through the granulation process is called granulation efficiency, and the granulation efficiency in the production of granular fertilizer depends on the type of fertilizer being produced, for example, the total amount of nitrogen compounds, phosphoric acid compounds, and potassium compounds. ,
In terms of N, P ₂ O ₅ and K ₂ O, respectively, high chemical fertilizers containing more than 30 parts, low chemical fertilizers containing less than that, and organic chemical fertilizers containing bark powder and other organic matter, etc. Even in the same type of chemical fertilizer, the type of compound formed, for example, in the case of nitrogen compounds, it depends on whether urea or ammonium sulfate is used, or the ratio of the amounts of nitrogen compounds and phosphorus used simultaneously. It is difficult to make a general statement because it depends on the ratio of amounts of acid compounds, potash compounds, etc., but it varies over a wide range of 30 to 70%. Even if the ingredients of each fertilizer are the same,
The granulation efficiency is also influenced by the amount of sprayed liquid, its physical properties, the method of spraying, the presence or absence of a binder in the granulation device, its amount, its type, etc.

Water is often used as a spraying liquid.
When mixed in advance before granulation, the washing water used for washing the drying gas is often used.

Fresh water is sometimes used as the water to be sprayed directly to the granulator, taking into consideration the possibility of clogging of the spray port. Sulfuric acid or ammonia may also be added therein, and steam may also be sprayed.

On the other hand, ammonium sulfate is generated from some processes in chemical factories, such as ammonia synthesis process, its transportation equipment, neutralization and other reactions in various chemical reaction processes, metal refining process, drug manufacturing process, etc. There are water-based solutions such as ammonium hydrochloride, nitrates, and phosphates, and their use is expected from the perspective of resource conservation.

[Problem that the invention seeks to solve]

As a method for recovering the active ingredients of fertilizers generated at the above-mentioned chemical factories and other places, it is expected that they will be used as additives in the granulation process of granular liquid fertilizers. Although it depends on its concentration, it always lowers the granulation efficiency and is not economical. The extent of this decrease in granulation efficiency depends on the type and quantity of the high-grade chemical fertilizer, low-grade chemical fertilizer, or organic chemical fertilizer mentioned above, as well as the nitrogen compound, phosphoric acid compound, potassium compound, etc. It varies, but sometimes it can be reduced by half. Therefore, even if an attempt is made to recover these active ingredients, it may not be profitable in terms of energy loss.

As a result of many years of research and consideration into improving granulation efficiency and the use of active ingredients generated from chemical processes, the inventors have found that it is possible to significantly improve granulation efficiency and recover active ingredients at the same time. We developed a method and completed the present invention.

(B) Structure of the Invention [Means for Solving the Problems] The present invention provides a method in which a crystalline substance is present in a fertilizer containing at least one of nitrogen, phosphoric acid, and potassium as a main component. The solution or mud crystal liquid is in a state in which the above-mentioned crystalline substance is supersaturated in a solvent mainly composed of water, or in which microparticles are It is either in the existing state or in the state in which microcrystals are growing.

The above-mentioned crystalline substances are desirably those which themselves can be effectively used as fertilizer components, and the following compounds are preferably used.

Namely ammonium sulfate, ammonium hydrogen sulfate, ammonium magnesium sulfate, ammonium hydrochloride, ammonium nitrate, ammonium phosphate, diammonium hydrogen phosphate, ammonium dihydrogen phosphate, sodium ammonium hydrogen phosphate, potassium ammonium hydrogen phosphate, ammonium bicarbonate, potassium nitrate, Calcium nitrate, sodium nitrate, magnesium nitrate, urea, potassium phosphate, disodium hydrogen phosphate, potassium dihydrogen phosphate, sodium dihydrogen phosphate, calcium dihydrogen phosphate, potassium chloride, potassium sulfate,
Magnesium chloride, magnesium sulfate, etc., or a mixture of two or more thereof.

The above crystalline substances are made to exist in a solvent mainly composed of water, but solvents other than water include alcohols such as methanol, ethanol, and isopropanol, organic acids such as formic acid, acetic acid, and humic acid, sulfuric acid, and phosphoric acid. , inorganic acids such as hydrochloric acid and nitric acid, ketones such as acetone, methyl ethyl ketone, and acetaldehyde, aldehydes, and others.

Such a compound is added to a mixer before a granulator, a rolling granulator, or both in the granular fertilizer manufacturing process, but during granulation, if necessary, water is added to bind the mixture. As the agent, molasses, its alcoholic fermentation residue, lignin sulfite, etc. can be used.

As mentioned above, granulation efficiency depends on the type of high-grade chemical fertilizer, low-grade chemical fertilizer, organic chemical fertilizer, nitrogen compound, phosphoric acid compound, potassium compound, etc.
Not only does it vary depending on the ratio of these amounts, but the presence or absence of a binder also makes a large contribution.

If the method of the present invention is directly applied to a binder that uses alcoholic fermentation residue to obtain high granulation efficiency, excessive granulation will occur, resulting in a large number of large-diameter particles, and the granulation will be reduced. This may result in a decrease in grain efficiency. At this time, it is necessary to reconsider the amount of binder added.

The amount of the solution or mud crystal liquid containing the crystalline substance described above depends on the solubility of the crystalline substance, but the preferable upper limit is the amount of water added to the powdered raw material fertilizer, usually 3 to 10% (compounded). amount). A blended moisture content of 6 to 8% particle size seems to have good granulation efficiency and is economical, but this cannot be determined unconditionally due to the drying process capacity, fuel cost, etc. Therefore, the maximum amount of the solution or mud crystal liquid is determined in consideration of the moisture in the raw materials, the moisture added to the granulator, etc. The larger the amount added, the better the granulation will be, but the economical optimum amount differs depending on the individual granular fertilizer, so it is desirable to determine it on an individual basis after trial.

Thus, the method of the present invention can utilize crystalline substances that are by-products or discharged from processes such as chemical factories, metal refining, and drug manufacturing.

For example, dilute ammonium sulfate or ammonium hydrochloride produced in the oxime formation process of ketones and aldehydes, ammonium nitrate and phosphate obtained during metal refining and drug manufacturing, but many of these by-products have low concentrations, and the oxime Ammonium sulfate etc. emitted during the process accounts for 20-30%
If this concentration is directly introduced into the granulation process of the present invention, the granulation efficiency tends to be worse than when simply using water.

Therefore, although ammonium sulfate is useful as a fertilizer, it is economically worthless.
It can become a negative additive.

Fortunately, a large amount of waste gas is generated during the drying and cooling steps during the manufacturing process of granular fertilizer, and a process is often included to wash away fertilizer components and other fine particles floating in this waste gas.

When ammonium sulfate generated in the chemical factory mentioned above is used as a washing liquid in such a process, a portion of the volatile matter is evaporated and concentrated, resulting in a nearly saturated solution. Even if it is blended, it will not lead to a significant improvement in granulation efficiency.

The present invention actively supersaturates the crystalline substance in the liquid after washing and removing the fine powder in the waste gas to generate crystals of the active ingredient to form a slurry crystal liquid, which is blended and added to the granulation process. By doing so, it is possible to economically recover fertilizer active ingredients and obtain granular fertilizer with a high blending amount and excellent granulation efficiency that overwhelmingly exceeds conventional granulation efficiency.

[Effect]

In the present invention, the granulation efficiency can be dramatically improved by blending the fertilizer with a solution or mud crystal liquid in a supersaturated state of crystalline substances, in the presence of microparticles, or in a state in which microcrystals are growing. Although it will be improved,
The reason is not clear.

As expected, the raw fertilizer has particles with a significantly larger diameter than the crystalline substances, and the crystalline substances enter between the grains of the fertilizer powder as a supersaturated solution or as small crystals on the micron order, causing surface activity on the powder wall surface. This seems to be because the rich small crystals adhere and contribute to the bonding of both powders.

〔Example〕

As mentioned above, one of the advantages of the present invention is that it is possible to effectively utilize crystalline substances produced as by-products in other factories. The embodiment will be described below with reference to the drawings.

That is, FIG. 1 is a process diagram showing an example of the method of the present invention, and 1 is a mixing tank. In this mixing tank, a fresh liquid of a crystalline substance is passed through a tube 3 and crystallized by a crystal separator 12 to be described later. A part of the solution from which most of the liquid has been separated is used as a circulating liquid, and is fed through tube 2 and mixed. This circulating fluid is usually several to several ten times the amount of fresh fluid. Although it is expected that the supersaturation of the circulating fluid will be reduced in the mixing tank, during operation, this may not necessarily be necessary. If necessary, acid or alkali is introduced through pipe 4 to adjust the pH of the tank liquid, and water is also introduced as necessary.

The liquid leaving the mixing tank 1 is sprayed into a washer 6 through a pipe 5. The waste gas generated in the granulation process of the present invention or the drying or cooling process (not shown) of the granulation process in other granular fertilizer production is fed into the washer 6 through a pipe 7 to remove the waste gas contained. A portion of the dust that has been stored is transferred to the liquid side, and a portion of the volatile matter is transferred to the gas side and concentrated to form a supersaturated liquid.

The dust-free waste gas leaves from the pipe 8, and if necessary, is further removed by a cottle or the like. The supersaturated solution containing dust is sent through a tube 9 to a crystal growth tank 10 to grow crystals. There is usually no need to add seeds to maximize the number of crystals. The generation of crystals occurs smoothly, probably because the captured dust becomes seeds. Most of the mud crystals and a part of the solution, which have been fed from the crystal growth tank 10 to the crystal separator 12, are fed to the granulator 15 and mixed with powder fertilizer fed from the input port 16. The solution that has lost most of its crystals is returned to the mixing tank 1 again. In addition, crystal separator 1
2 is provided with a water injection pipe 13, etc. in case the operation is stopped.

The thus granulated fertilizer is taken out as a product through the outlet 17.

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

Example 1 For the production of granular fertilizer (N-P-K) 11-8-10, per 1T, ammonium sulfate 420Kg, 18-46 ammonium phosphate 87Kg, 17% superphosphate lime 254Kg,
173Kg of potassium chloride was pulverized and 13T/hour was supplied to the pug mill, which is a pre-granulation process. Pug mill separately oversized and undersized granular fertilizer, crushed powder
8T/H is circulating.

On the other hand, 2800 kg/25% ammonium sulfate aqueous solution
Supply H to the mixing tank and mix it with circulating fluid 50T/H.
It was sprayed onto the washer and brought into contact with the waste gas. The spray liquid with some dust trapped enters a 10 m ³ crystal growth tank, and is then pumped up from the bottom of the tank and sent to a crystal separator at a speed of 9 T/H. 1080 kg of ammonium sulfate saturated liquid containing crystals is supplied to a pug mill and powdered. Added to fertilizer. In addition, 70% sulfuric acid is added to the bag mill from a separate outlet.
600Kg/H was added and blended. The blended mixture is
It is fed into a drum type granulator and sprayed with water.
After being granulated, the product was made into a product through a drying process, cooling process, and granulation process. The yield was 14T/H.

Comparative Example 1 In the production of the same granular fertilizer as in Example 1, 25%
ammonium sulfate 1400Kg/H in circulating fluid 50T/H
mixed with. Approximately 1500 kg/H of water was added to the circulating fluid to adjust the concentration (approximately 35%). An excess of 1 T/hour of the circulating fluid was sent directly from the mixing tank to the pug mill and mixed into powder fertilizer.

The fertilizers mixed at Pugmill are both old and new.
The yield of granular fertilizer was 22T/H, and the yield of granular fertilizer that could be obtained as a product was 7T/H. The granulation efficiency was 32%.
In this case, attempts were often made to increase yields;
When the temperature was raised to ~9T/H, the granular fertilizer lost its shape within a few hours, and the supply of new raw materials had to be stopped and circulation operation was performed.

Example 2 Granular fertilizer (N-P-K) 11-8-10 as in Example
Ammonium sulfate 440 per ton in the production of
Kg, 17% lime superphosphate 255Kg potassium chloride 173Kg and 18−
46 ammonium phosphate 81Kg as powder raw material
It was fed to the pug mill at 13T/H. The amount of circulating powder was 8T/H as in the previous example.

On the other hand, 2450Kg/25% ammonium sulfate aqueous solution
25% aqueous solution of H and ammonium phosphate 350Kg/H
was sent to the mixing tank as in the previous example. Other conditions are
Same as Example 1, and the amount of product obtained was also
It was 14T/H.

(C) Effects of the Invention According to the present invention described above, by blending and granulating a crystalline substance into fertilizer as a solution or mud crystal liquid in the above-mentioned state, granules can be formed with extremely high granulation efficiency. Fertilizers can be manufactured that have a lower content of phosphoric acid compounds, which are considered to have lower granulation efficiency even in the fertilizer industry, or that contain higher amounts of nitrogen, phosphoric acid, and potassium compounds. When applied to products, the granulation efficiency of conventional products, which was in the 30% range, can reach up to 60%.

In addition, by using fertilizer active ingredients produced by-products from other factories as crystalline substances, it is possible to effectively utilize the by-products and to obtain granular fertilizers economically and inexpensively. This is a highly valuable invention.

[Brief explanation of drawings]

FIG. 1 is a process diagram showing an example of the method of the present invention. 1... Mixing tank, 6... Washer, 10... Crystal growth tank, 12... Crystal separator, 15... Granulation device.

Claims (1)

[Claims] 1. At least one of nitrogen, phosphoric acid, and potassium fertilizer elements
For fertilizers mainly composed of seeds, 1% of crystalline substances
A solution or mud crystal in which a species or two or more species exist in a water-based solvent in a supersaturated state, in the presence of microparticles, or in a state in which microcrystals are growing. A method for producing granular fertilizer characterized by blending a liquid and granulating it. 2. The scope of the claims, wherein the mud crystal liquid in which the microcrystals are growing is a mud crystal liquid containing ammonium sulfate that was used for washing dust in the gas used in the drying or cooling process in the production of granular fertilizer. The method for producing granular fertilizer according to item 1.