JPS61286216A - Production of granular ammonium sulfate - Google Patents

Abstract

PURPOSE:To freely control the form of a crystal grain of ammonium sulfate produced without the change of the operation conditions and the addition of a crystallizing agent by adding the finely-ground ammonium sulfate having the aimed form or the fine crystal thereof to an ammonium sulfate mother liquor as a crystal nucleus and performing the crystallization. CONSTITUTION:A heated and saturated ammonium sulfate mother liquor 2 is introduced into a feed vessel 1 and while stirring 3 lightly it, a supernatant mother liquor 4 free from ammonium sulfate crystal is fed to a crystallization vessel 5 proprotionate to a granulation device. In the crystallization vessel 5, 1-20% seed ammonium sulfate obtained by finely-grinding rice-shaped ammonium sulfate is added for the mother liquor 2 and it is kept at the prescribed temp. while stirring 3 it and the degree of supersaturation of ammonium sulfate is increased and the crystallization is performed. The deposited crystal 7 is drawn out through a crystal drawing-out pipe 8. On the other hand, the mother liquor free from ammonium sulfate crystal incorporated in the crystallization vessel 5 is circulated to the inside of the feed vessel 1. In this inven tion, the form of crystal granule of ammonium sulfate can be freely controlled and it is especially made to a granule having the rounding and the grain size can be made large.

Description

[Detailed description of the invention] Industrial applications The present invention relates to a method for producing granular ammonium sulfate.

Prior Art Ammonium sulfate is hygroscopic and will solidify if stored for a long period of time, requiring pulverization. In addition, in recent years, methods have been taken to reduce costs by mixing several types of granular raw materials, transporting them in bulk, and fertilizing them in order to quickly and arbitrarily produce and mix nitrogen, phosphorus, and potassium components. ing.

Under these circumstances, ammonium sulfate is also required to be in the form of granules, and its crystal grains are required to be large and rounded, for example, in the form of rice.

Conventional production of granular ammonium sulfate involves producing ammonium sulfate from a mother liquor containing free sulfuric acid and ammonia in a saturator, then supplying the mother liquor with a constant degree of saturation, free soap concentration, and temperature to a granulation machine, where water is removed. By evaporating the mother liquor, the degree of supersaturation is increased and ammonium sulfate crystals are generated. At the same time, the crystals are grown and classified, and the granular ammonium sulfate is taken out from the bottom of the granulator. After removing the liquid,
It circulates to the saturator.

Problems to be Solved by the Invention However, the ammonium sulfate crystals produced from coke oven gas in this way are all hexagonal prism-like, square prism-like, or plate-like, and have a large diameter and a rounded shape. It has been difficult to produce granular ammonium sulfate in the shape. However, the present applicant
As disclosed in 9 [115 and JP-A-56-109818, ammonium nitrate,
It is known that crystals grow into spherical shapes by adding sulfamic acid or the like.

However, although this method has the effect of making the crystal shape spherical, it has a first-order problem.

■Since a crystal modifier is added directly to the ammonium sulfate mother liquor, impurities (sulfamic acid, nitrate nitrogen, etc.) are included in the ammonium sulfate crystal.

■Since a large amount of crystal modifier is added to the mother liquor and circulated through the granulation process, it is affected by alteration and decomposition during the process.

In other words, in the conventional ammonium sulfate crystal granulation method, everything from the generation to growth of crystal nuclei is affected by the properties of the mother liquor (types of impurities, concentration, etc.), so the granulation conditions must be changed widely to change the crystal shape. It is necessary to change the crystallization agent or add a large amount of crystallizing agent to the mother liquor, which is difficult to implement due to quality or economic issues.

Means for Solving the Problems The present invention has been made in view of the above circumstances.
In the process of producing granular ammonium sulfate from an ammonium sulfate mother liquor through a crystallizer, it is characterized by adding finely pulverized ammonium sulfate in the desired crystal shape or its fine crystals to the ammonium sulfate mother liquor, and crystallizing it. This is a method for producing granular ammonium sulfate.

That is, the present invention focuses on the properties of the mother liquor (types of impurities, concentration, etc.),
This method provides a means to freely change the crystal shape of ammonium sulfate to a desired shape without changing operating conditions or adding a crystal modifier.

This method was completed after confirming through various experiments and studies that the shape of crystalline ammonium sulfate is not affected by the properties of the mother liquor during crystal growth, but rather by the shape of the fine crystal nuclei. By pulverizing ammonium sulfate in the desired shape and supplying it as crystal nuclei to ammonium sulfate granulation equipment, it is possible to stably produce ammonium sulfate crystals in the desired shape, regardless of the properties of the ammonium sulfate mother liquor↑ be.

Example The present invention will be described in detail below based on the drawings.

FIG. 1 shows an embodiment. A saturated mother liquor 2 of ammonium sulfate heated to 50"C was put into a supply tank 1 with an internal volume of 1 m", which corresponds to a saturator, and while stirring lightly with a stirrer 3, a supernatant mother liquor 4 containing no ammonium sulfate crystals was produced. It was supplied to a crystallization tank 5 with an internal volume of 0.3rn'', which corresponds to a granulation device. In the crystallization tank 5, seed ammonium sulfate 6, which was made by finely pulverizing rice-like ammonium sulfate to a mesh size of 3° or less, was added to the saturated mother liquor 2. The ammonium sulfate supersaturation degree was increased by adding 1 to 10% and maintaining the temperature at 45° C. while stirring with a stirrer 3 to perform crystallization.

As a result, ammonium sulfate crystals 7 were precipitated and the crystal concentration increased, so the crystals 7 were successively extracted at a crystal sampling line indicated by 8 so that the crystal concentration was 25%. The mother liquor 9 that does not contain ammonium sulfate crystals in the crystallization tank 5 is
-100 sentences/l1nte were circulated into the supply tank l. Note that stirring the inside of the crystallization tank 5 has the effect that the ammonium sulfate crystal has a more rounded shape.

The properties of the ammonium sulfate obtained at this time are shown in Table 1 in comparison with those obtained by the conventional method without adding seed ammonium sulfate.

As shown in Table 1, the granulated ammonium sulfate produced by the method of the present invention in which 1% and 10% of seed ammonium sulfate, which is obtained by finely pulverizing rice-like ammonium sulfate, is added, has a lower value compared to ammonium sulfate produced by the conventional method without adding seed ammonium sulfate. The shape of the crystals becomes rounded and rice-like, and by setting the seed ammonium sulfate addition rate to 10%, the particle size of ammonium sulfate also increases. That is, by adding seed ammonium sulfate, it is possible to grow a crystal similar to the seed ammonium sulfate crystal.

The amount of seed ammonium sulfate added according to the present invention is 1% or more to achieve the desired ammonium sulfate crystal shape, and if it exceeds 20%, the shape of the crystal grains is good, but the grain size becomes small, so the seed The amount of ammonium sulfate added is in the range of 1 to 20%.

If the particle size of the seed ammonium sulfate exceeds 20 mesh, the shape of the crystal grains will be good, but the particle size will become too large, so it is preferable that the seed ammonium sulfate particle size is 20 mesh or less.

Effects of the Invention As described above, according to the present invention, the shape of crystal grains of ammonium sulfate can be freely controlled, and in particular, it is possible to obtain a rounded grain shape and a large grain size. Therefore, it is possible to prevent ammonium sulfate from caking, and it becomes easy to meet the market need for using a mixture of several types of granular fertilizers. Furthermore, since it is possible to grow crystals similar to the seed ammonium sulfate crystal, by changing the crystal shape of the seed ammonium sulfate, it is possible to produce ammonium sulfate with a wide variety of crystal shapes.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing one example of implementation of the present invention. 1... Supply tank, 2. Fist/saturated mother liquor, 3... Stirrer,
4...Supernatant mother liquor, 5...Crystallization tank, 6.φ type ammonium sulfate,
7...Crystal, 8...Crystal extraction line, 9.
Mother liquor containing no ammonium sulfate crystals, 10... pump.

Claims (1)

[Claims] In the process of producing ammonium sulfate from ammonium sulfate mother liquor through a crystallizer, 1 to 20% of finely ground ammonium sulfate of a target shape or fine crystals thereof is added to the ammonium sulfate mother liquor and crystallized. A method for producing granular ammonium sulfate.