JPH06191831A - Production of granular ammonium sulfate - Google Patents

Abstract

PURPOSE:To obtain large spherical crystal-shaped ammonium sulfate by adding guanidine sulfamate into an ammonium sulfate mother liquor made by absorbing ammonia in a coke oven gas into sulfuric acid. CONSTITUTION:In a process for producing the granular ammonium sulfate from the ammonium sulfate mother liquor by using a crystallizer, the granular ammonium sulfate is inexpensively produce by adding guanidine sulfamate into the ammonium sulfate mother liquor as a crystallization medium agent.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing granular ammonium sulphate from an ammonium sulphate mother liquor obtained by absorbing and recovering the ammonia content in coke oven gas with sulfuric acid.

[0002]

2. Description of the Related Art As a method for producing granular ammonium sulfate from a coke oven gas, generally, the ammonia content in the coke oven gas is absorbed and recovered as a ammonium sulphate mother liquor by a mother liquor containing free sulfuric acid in a saturator. It is carried out by a method in which the ammonium sulphate mother liquor is concentrated and the degree of supersaturation is increased by evaporating the water in the ammonium sulphate mother liquor, and the resulting crystalline ammonium sulphate is further grown and granulated.

The ammonium sulfate crystals produced in the above process are used for simple fertilization or bulk blending. Among them, those for bulk blending are optionally and rapidly in granular form with granular phosphorus and potassium components. Since it is used in the method of applying fertilizer by blending with, the large and round spherical crystal shape is required.

However, in the above-mentioned steps, the ammonium sulfate crystals produced by the ordinary method were not columnar or plate-like, and large and rounded crystalline ammonium sulfate could not be produced.

Therefore, as a countermeasure against this, in the step of producing granular ammonium sulfate from the ammonium sulphate mother liquor through a crystallization apparatus, crystallization is carried out by adding 1 to 10% of nitric acid or ammonium nitrate as a habit modifier to the ammonium sulphate mother liquor in terms of ammonium nitrate conversion value. (Japanese Patent Publication No. 60-38336), a method of adding 0.5 to 5% of sulfamic acid or ammonium sulfamate as a habit modifier to ammonium sulphate in terms of sulfamic acid and crystallizing (Japanese Patent Publication No. 60-38337), Alternatively, ammonium sulphate as a habit modifier is nitric acid or ammonium nitrate in an amount of 1 to 10% in terms of ammonium nitrate and sulfamic acid or ammonium sulfamate in a value of 0.1 in terms of sulfamic acid.
A method of adding 5 to 5% for crystallization (Japanese Patent Publication No. 60-3833).
8), less than 0.5% of sulfamic acid or ammonium sulfamate as a habit modifier in ammonium sulphate in terms of sulfamic acid equivalent, and hydrosulfite, oxalic acid, and / or chelating effect that exerts a habit effect by reducing action. By adding condensed phosphoric acid or a salt thereof exhibiting a habit modifier effect by crystallization (Japanese Patent Laid-Open No. 58-217428)
Etc. have been proposed.

[0006]

When sulfamic acid or ammonium sulfamate is added among the above-mentioned production methods, the addition amount is required to be as high as 2-3% in terms of sulfamic acid conversion. If the amount is small, the crystal shape of ammonium sulfate becomes columnar, on the other hand, if the addition amount is too large, problems such as the crystal becoming brittle occur, and when nitric acid or ammonium nitrate is added, the addition amount is the ammonium nitrate conversion value. There are problems that a high concentration of about 5% is required, that if the addition amount is too small, the effect is difficult to obtain, and conversely if the addition amount is too large, the hue of crystals deteriorates. In particular, the concentration of sulfamic acid in ammonium sulfate for fertilizer itself is regulated (0.01 [% / N-1%]), and sulfamic acid and sulfamine in the mother liquor that affect the concentration of sulfamic acid in ammonium sulfate are regulated. It is desirable that each concentration of ammonium acid is as low as possible.

When adding a plurality of different habit modifiers,
Problems such as an increase in habit modifier cost and complicated operation management occur.

[0008]

Means for Solving the Problems As a result of intensive studies on the habit modifier mechanism in order to solve the above problems, the present inventors have found that the concentration of guanidine sulfamate as a crystallization agent in the ammonium sulphate mother liquor Sulfamic acid equivalent concentration) of 0.
An inventor has invented a method for producing granular ammonium sulfate which is crystallized by adding 3 to 3.0% by weight.

That is, the present invention is characterized in that, in the step of producing granular ammonium sulfate from an ammonium sulfate mother liquor using a crystallizer, guanidine sulfamate as a habit modifier is added to the ammonium sulphate mother liquor for crystallization. A method for producing ammonium sulfate is provided.

The amount of guanidine sulfamate added is preferably 0.3 to 3.0% by weight in terms of sulfamic acid equivalent concentration in the ammonium sulfate mother liquor after the addition.

The ammonium sulfate mother liquor used in the present invention is an aqueous solution containing at least sulfuric acid and ammonia, and can be obtained by absorbing ammonia gas in an aqueous solution of sulfuric acid. In particular, it is obtained by absorbing ammonia in coke oven gas into an aqueous solution containing sulfuric acid.

To the obtained ammonium sulfate mother liquor, guanidine sulfamate as a habit modifier is added in an amount of 0.3 to 3.0% by weight, particularly 0.5 to 1.0% by weight, in terms of sulfamic acid equivalent concentration in the ammonium sulfate mother liquor. Is preferred.

When added in the range of about 0.3 to 3.0% by weight in terms of sulfamic acid, a crystal having a large and rounded shape can be obtained. Further, the change in the crystal shape with respect to the added amount is continuously observed as a change in the ratio of the crystal vertical axis and the horizontal axis, and the added amount can be arbitrarily determined according to the required shape depending on the application of ammonium sulfate. However, in the current industrial implementation, the effect on the shape,
Even considering various aspects such as economy and quality as a fertilizer, a sufficient effect can be obtained at a low concentration of about 0.5 to 1.0% by weight. In addition, addition in the range of more than 3.0% by weight causes less change in crystal shape as compared with addition of about 3.0% by weight, and inclusion of a habit modifier into the crystal increases. It is not desirable for some reasons.

Although the toxicity of guanidine sulfamate applied to the present invention to animals and plants is said to be extremely small by itself, the incorporation of guanidine sulfamate into ammonium sulfate crystals according to the present invention results in a sulfamic acid conversion concentration of 3
Crystallization with a mother liquor of 10% by weight was 0.1% by weight or less,
It is well below the numerical value of 5.0% by weight or less of the total nitrogen amount specified as the standard for guanylurea compound fertilizer.

The method for adding guanidine sulfamate may be such that it is supplied via a pipe branched from a supply pipe on the upstream side of the mother liquor tank or directly added to the mother liquor tank.

The addition form of guanidine sulfamate may be solid or in an aqueous solution.

Further, after stirring the ammonium sulphate mother liquor to which an appropriate amount of guanidine sulfamate was added, the mother liquor supernatant containing no ammonium sulphate crystals was transferred to a crystallization tank. The mother liquor supernatant transferred to the crystallization tank is cooled with stirring to crystallize ammonium sulfate crystals.

The present invention will be described conceptually in detail below with reference to the drawings, but the present invention is not limited thereto.

As shown in FIG. 1, the crystallization apparatus 1 used in the method for producing granular ammonium sulfate of the present invention comprises a mother liquor tank 3 and a crystallization tank 4.
Includes.

In the mother liquor tank 3, the ammonium sulphate mother liquor is stirred at a constant temperature, and the added guanidine sulfamate is made to have a uniform concentration in the tank, and the ammonium sulphate in the ammonium sulphate mother liquor is saturated.
Although not shown, the mother liquor tank 3 is provided with a thermostatic device for keeping the ammonium sulphate mother liquor in the tank at a constant temperature and a stirrer 5 for stirring the ammonium sulphate mother liquor.

The crystal tank 4 brings the ammonium sulfate-saturated mother sulphate mother liquor supernatant obtained in the mother liquor tank 3 into a supersaturated state by lowering the temperature and deposits ammonium sulphate crystals. Although not shown, the crystallization tank 4 is provided with a thermostatic device for keeping the ammonium sulfate mother liquor in the tank at a constant temperature and a stirrer 6 for stirring the ammonium sulfate mother liquor. Further, the crystallization tank 4 communicates with the mother liquor tank 3 via the transportation pipe 8, and the ammonium sulfate crystals obtained in the crystallization tank 4 are taken out from the extraction pipe 10.
It is taken out of the system via. The unreacted sulfuric acid can be returned to the mother liquor tank 3 via the transport pipe 9 and used again for absorbing ammonia.

According to the method of the present invention, ammonium sulfate mother liquor 2, which is an aqueous sulfuric acid solution in which ammonia is absorbed, is supplied to mother liquor tank 3 through supply pipe 7, and guanidine sulfamate is added to ammonium sulphate mother liquor 2 in an amount of 0.3. Add to a concentration of ˜3.0 wt%.

In the mother liquor tank 3, the sulfuric acid and the ammonia are sufficiently stirred to stir the ammonium sulfate so that the ammonium sulfate is sufficiently saturated.

The obtained saturated ammonium sulfate solution is transferred to the crystallization tank 4 through the transport pipe 8 and the temperature is adjusted to 45 ° C., for example.
To precipitate crystals of ammonium sulfate, the diameter of the crystals is 3 ~
After growing to 4 mm, the ammonium sulfate crystal 1 is passed through the take-out pipe 10.
Get one. The obtained ammonium sulfate crystals 11 are evaporated into water by an ordinary drying method to be the target granular ammonium sulfate.

[0025]

The present invention will be described in detail below with reference to examples.

Example 1 As Example 1, crystals were precipitated in a mother liquor containing 0.3% by weight of guanidine sulfamate (sulfamic acid conversion value). Adjust the guanidine sulfamate concentration in the mother liquor to 0.3 wt% (sulfamic acid equivalent value) in a mother liquor tank with an internal volume of about 100 L equivalent to a saturator and having a stirring and constant temperature effect, and
The saturated ammonium sulfate mother liquor heated to 0 ° C was added, and the mother liquor temperature was maintained at 50 ° C while stirring.

Next, the supernatant mother liquor containing no ammonium sulfate crystals in the upper layer of the mother liquor tank was supplied to a crystal tank having an internal volume of about 20 L corresponding to a granulating apparatus. The crystallization tank has the same stirring and isothermal effect as the mother liquor tank.
Crystallization was carried out by keeping the ammonium sulphate mother liquor supersaturation at 5 ° C. As a result, although crystals were precipitated in the mother liquor tank, the precipitated crystals were grown to a particle size of 3 to 4 mm at maximum, and then extracted with the accompanying mother liquor from the lower part of the crystal tank and dried to evaluate the crystal shape.

The crystal shape is shown in Table 1. The shape factor (a / b) in Table 1 is obtained by measuring randomly extracted ammonium sulfate crystals with a scale loupe and displaying the crystal growth axis as a and the axis orthogonal to a as b. In the case of 1, a /
Rounded crystals formed at b = 1.4.

(Comparative Example 1) As a comparative example of Example 1, precipitation of crystals in the mother liquor in which ammonium sulfamate was reduced by 0.3% by weight (sulfamic acid conversion value) was conducted.
The same procedure was performed using the experimental apparatus shown in Example 1. Table 1 shows the crystal shape. A columnar crystal with a / b = 2.2 was generated.

Example 2 As Example 2, precipitation of crystals in the mother liquor to which 0.75% by weight of guanidine sulfamate (sulfamic acid conversion value) was added was carried out.
The same procedure was performed using the experimental apparatus shown in. Table 1 shows the crystal shape. Rounded crystals were formed at a / b = 1.0.

Comparative Example 2 As a comparative example of Example 2, 0.75% by weight of ammonium sulfamate was added to the mother liquor.
(Sulfamic acid conversion value) Crystal precipitation in the added mother liquor was performed by the same method using the experimental apparatus shown in Example 1. Table 1 shows the crystal shape. A slightly rounded crystal with a / b = 1.7 was produced.

(Example 3) As Example 3, the experimental apparatus shown in Example 1 was used for the precipitation of crystals in the mother liquor to which guanidine sulfamate was added in an amount of 2.0% by weight (sulfamic acid conversion value). Used in a similar manner. Table 1 shows the crystal shape. Round crystals were formed at a / b = 0.5.

Comparative Example 3 As a comparative example of Example 3, precipitation of crystals in the mother liquor to which ammonium sulfamate was added in an amount of 2.0% by weight (sulfamic acid conversion value) was carried out.
The same procedure was performed using the experimental apparatus shown in Example 1. Table 1 shows the crystal shape. Rounded crystals with a / b = 0.9 were produced.

(Example 4) As Example 4, the experimental apparatus shown in Example 1 was used for the precipitation of crystals in the mother liquor to which guanidine sulfamate was added in an amount of 3.0% by weight (sulfamic acid conversion value). Used in a similar manner. Table 1 shows the crystal shape. Rounded crystals were formed at a / b = 0.4.

(Comparative Example 4) As a comparative example of Example 3, precipitation of crystals in a mother liquor to which 3.0% by weight of ammonium sulfamate (sulfamic acid conversion value) was added was carried out.
The same procedure was performed using the experimental apparatus shown in Example 1. Table 1 shows the crystal shape. Rounded crystals with a / b = 0.8 were produced.

(Comparative Example 5) As Comparative Example 5, precipitation of crystals in the mother liquor containing no habit modifier was carried out by the same method using the experimental apparatus shown in Example 1. Table 1 shows the crystal shape. Crystals having a columnar shape were generated at a / b = 2.4.

[0037]

[Table 1]

[0038]

EFFECT OF THE INVENTION According to the present invention, the ammonium sulphate mother liquor obtained by absorbing and recovering the ammonia content in the coke oven gas with sulfuric acid is guanidine sulfamate in a concentration of 0.3 to 3 in the ammonium sulphate mother liquor (sulfamic acid conversion concentration). Addition of about 0.0% by weight makes it possible to produce ammonium sulfate having a large and rounded crystal shape. Further, the ammonium sulfate crystals produced by the present invention satisfy the fertilizer standard sufficiently with the ammoniacal nitrogen content ≧ 21.1% by weight and the sulfamic acid content ≦ 0.15% by weight. It can fully support the market for fertilizers or bulk blends.

[Brief description of drawings]

FIG. 1 is a diagram conceptually showing an example of a crystallizer for producing granular ammonium sulfate of the present invention.

[Explanation of symbols]

 1 Crystallizer 2 Ammonium sulfate mother liquor 3 Mother liquor tank 4 Crystal tank 5,6 Stirrer 7 Supply pipe 8,9 Transport pipe 10 Extraction pipe 11 Ammonium sulphate crystal

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masao Tsuzaki Masao Tsushima, Kurashiki City, Okayama Prefecture 1-chome, Kawasaki-dori, Mizushima Works (72) Inventor Yasushi Yamamoto Kurashiki City, Okayama Prefecture Mizushima Kawasaki Dori 1-chome (no street number) Kawasaki Steel Works Mizushima Steel Works (72) Inventor Kazuo Ura 2-3-2 Uchisaiwaicho, Chiyoda-ku, Tokyo Kawasaki Steel Co., Ltd.

Claims (2)

[Claims] 1. A method for producing granular ammonium sulfate, characterized in that, in the step of producing granular ammonium sulfate from an ammonium sulfate mother liquor using a crystallizer, guanidine sulfamate as a habit modifier is added to the ammonium sulphate mother liquor for crystallization. . 2. The method for producing granular ammonium sulfate according to claim 1, wherein the added amount of guanidine sulfamate is 0.3 to 3.0% by weight in terms of sulfamic acid equivalent concentration in the ammonium sulfate mother liquor after the addition. .