JPH0438689B2 - - Google Patents

Description

[Detailed description of the invention] <Industrial application field> The present invention relates to a method for producing ammonium sulfate.

<Prior art> The conventional method for producing ammonium sulfate is to introduce ammonium sulfate solution (also called ammonium sulfate mother liquor) generated in the process of refining coke oven gas into an evaporator and evaporate it by suction from a vacuum generator to form a supersaturated solution. (46% or more), and is supplied in a downward swirling flow to the inverted truncated cone-shaped center of the crystallizer via a downcomer connected to the lower part of the evaporator, causing a reverse upward flow inside the crystallizer, and in this process, ammonium sulfate is promoting the growth of crystals and their grains, and causing the growing crystal grains to settle to the bottom of an inverted truncated cone;
The slurry was extracted outside the can, dehydrated, and the ammonium sulfate crystal grains were separated and recovered.

Ammonium sulfate produced in this way is usually applied as a simple fertilizer to rice, millet, etc.
It is sometimes spread mixed with potassium fertilizer, and in the latter case, it has traditionally been granulated by mixing and harmonizing under warm and humid conditions, but in recent years it has been made by simply mixing the crystal grains of the single fertilizer of each component. A bulk blending method is employed. This is because the mixing ratio of each component can be easily adjusted and the warm mixing and granulation steps can be omitted, which is advantageous in terms of cost.

The bulk blending method usually uses 1.7-3.3 (6-3.
Ammonium sulfate grains of size (10 mesh) are required.

On the other hand, in recent years, the application of fertilizers such as ammonium sulfate in agriculture has been
Manual methods are being replaced by mechanical methods of spraying using pneumatic mechanisms and spray nozzles.

The problem with this spraying method is that the crystal form of ammonium sulfate is a large prismatic orthorhombic crystal, which causes the inner walls of the pneumatic pipe, nozzle, etc. to wear quickly, and the corners of the crystals to chip and become small, resulting in dust generation. Nozzle clogging occurs frequently.

For this purpose, the crystallized ammonium sulfate is placed in a storage tank.
A method in which the particles are stirred in advance using an impeller, etc., and the particles collide with each other to wear away the corners of the hexagonal prism orthorhombic crystal, giving it a rounded appearance.

Also, as disclosed in JP-A No. 56-109816, ammonium sulfate mother liquor (concentration <42%) is mixed with nitric acid or ammonium nitrate from 1 to 10% in terms of ammonium nitrate, and sulfamic acid or ammonium sulfamate from 0.5 to 0.5 in terms of ammonium sulfamate. 5
There is a method in which spheroidization is attempted by adding % as a crystal modifier and stirring.

<Problems to be Solved by the Invention> In the above production method, the particle size distribution of the crystalline ammonium sulfate that settles and accumulates at the inverted truncated conical bottom of the crystal can is such that the lower the layer is, the larger the particles are, but the distribution is mixed with coarse and fine particles. becomes.

Therefore, in order to obtain ammonium sulfate crystal grains of a predetermined large size required for the bulk blending method etc. from ammonium sulfate extracted from the crystallizer and dehydrated, the yield was extremely low and productivity was poor.

Regarding the rounding of crystal grains during ammonium sulfate dispersion, the above-mentioned conventional agitation using an impeller can produce ammonium sulfate grains with rounded corners, but the yield decreases due to crushing, and the addition of a sizing process and this There are problems such as dust generation during the process.

In addition, the addition of a crystallizing agent to the ammonium sulfate mother liquor and stirring of the mixed liquid are expensive, and the manufacturing cost is high.
Although the height ratio is 1:1:1, it is difficult to make it completely spherical, and corners remain, and as mentioned above, during spraying, wear and dust of the pneumatic pipe, nozzle, etc., and nozzle clogging may occur. Although it has improved somewhat, it still occurs to a degree that it is a problem.

In addition, there is a large amount of coarse and fine grains mixed in, and the yield of large grains is low.

<Means for solving the problems> The present invention provides an excellent method for producing ammonium sulfate that solves the above problems all at once. In a method for producing ammonium sulfate, the ammonium sulfate is supplied downward into the center of an inverted truncated conical bottom of a crystal can, is crystallized in the crystal can, and the grown crystal grains are allowed to settle in the truncated conical bottom for extraction. A nozzle is provided on the inner wall of the truncated cone-shaped bottom, and a saturated ammonium sulfate solution or a supersaturated solution is spouted from the nozzle in the circumferential direction of the inner wall or diagonally downward from the circumferential direction, so that the crystal grains that have settled in the truncated conical bottom are removed along the inner wall. It is constructed by making it flow.

In the present invention, a single nozzle or a plurality of nozzles are disposed at equal intervals in the circumferential direction of the inner wall of the inverted truncated conical bottom in a single stage or in multiple stages.

The injection direction of the nozzle is fixed or adjustable within a range of about 75° in the circumferential direction of the inner wall or diagonally downward therefrom.

Ammonium sulfate saturated solution (≧42
%) or supersaturated solution (≧46%) can be used by suctioning and extracting the surface liquid inside the crystallizer with a pump, or by extracting and dehydrating the separated saturated solution from the crystallizer, or using an evaporator. It may be procured by any other appropriate method, such as separately taking out and using a supersaturated solution from. In short, the ammonium sulfate solution used is a so-called saturated solution or supersaturated solution with a concentration of 42% or more.

<Function> The ammonium sulfate crystal grains that settle and accumulate on the inverted truncated conical bottom of the crystallizer are normally deposited in the downcomer pipe 3 as shown in Figure 1a and b.
The ammonium sulfate supersaturated solution is deposited in a concave shape along the entire circumferential wall of the inverted truncated conical bottom E by the swirling downward flow D and reverse upward flow K of the ammonium sulfate supersaturated solution from the lower end opening.

The distribution of the accumulated ammonium sulfate crystal grains changes from approximately small grains to large grains, although there are some mixed grains from the upper layer to the lower layer.

In the present invention, a saturated solution or supersaturated solution X of ammonium sulfate that does not decompose the crystal grains of the concave deposited layer Y is injected from nozzles 10a and 10b, and the injection directions A and B are directed along the peripheral wall in the circumferential direction or diagonally downward. By setting the vertical direction, the concave deposited layer Y
The crystal grains of ammonium sulfate in the layer collide with each other during this flow process, and then collide with the peripheral wall of the bottom of the inverted truncated cone, forming a hexagonal prism. The corners of the crystal grains (Figure 2 a) are worn away to form rounded grains (Figure 2 b), and the chipped corners and fine crystals mixed in the layer are removed into an inverted truncated cone shape. The supersaturated solution is separated and moved to the center of the bottom, carried by the upward reverse flow of the supersaturated solution from the downcomer pipe, and carried to the upper part of the can to form crystal nuclei and promote their growth. It activates the metabolism of the solution or supersaturated solution and forcibly promotes growth in areas other than the corners.

<Example> An example of the present invention will be described below with reference to FIGS. 3 and 4.

FIG. 3 is an example of an apparatus for carrying out the method of the present invention.

In Figure 3, ammonium sulfate crystallizer 1 is placed in evaporator 2.
A saturated solution of 3500Nm ² /hr is received and stored in the center of the inverted truncated conical bottom E through the downcomer pipe 3 from its lower end opening, and the process of the saturated solution rising inside the can promotes crystals and their growth. At the same time, the grown grains are classified and settled and deposited in a concave shape on the peripheral wall W of the inverted truncated conical bottom E,
Large particle size ammonium sulfate is continuously extracted from an extraction pipe 16 on the peripheral wall by a pump 17 and is sent to a dehydrator (not shown).

The saturated solution (170 m ³ ) in the crystallization can 1 is passed through an upward opening 7 along the outer periphery of the downcomer pipe 3 in the center of the upper part of the can.
It is circulated and supplied to the evaporator 2 by a pump 8 via a piping 12 from an overflow type extraction pipe 7 with an open port a.

The evaporator 2 communicates with the vacuum generator 9 and vacuum evaporates the circulating fluid introduced as described above to reduce the concentration to 46%.
The solution is raised to a supersaturated solution, which is again turned to the right in a downward flow 18 in the downcomer pipe 3 and supplied to the inner bottom E of the crystal vessel 1.

At the inverted truncated conical bottom E, the upper layer liquid which has been stored in the crystallizer 1 and crystallized and whose concentration has decreased to a saturated state is extracted from the extraction pipe 4 by the pump 5, and is then removed from the pipe 14.
The water is ejected from two upper and lower nozzles 10a and 10b, one for the upper layer and one for the lower layer, which are installed protrudingly on the inner wall W of the bottom E through the nozzles 10a and 10b.

These nozzles 10a, 10b are arranged in the same direction as the reversed upward swirling flow of the supersaturated solution discharged from the downcomer pipe 3 in the circumferential direction of the inner wall W, and in a direction downward at a predetermined angle from the horizontal angle, so that the saturated solution is directed along the inner wall surface. The concave deposited layer Y of ammonium sulfate crystal grains, which has been deposited along the inner wall W of the bottom E, is rotated and rotated in the circumferential direction.

The arrangement of the nozzles 10a, 10b is shown in FIG.

In FIG. 4, the upper nozzles 10a are arranged facing each other on the same diameter line, and the upper nozzles 10a
It rotates and flows Yu, and has a structure in which the angle of the injection direction of the saturated solution can be adjusted.

The lower nozzle 10b is similar to the nozzle 10a and 1
They are disposed opposite each other on the same diameter line at the middle position of the nozzle 10b, and the upper layer Yl of the concave deposited layer Y is rotated and flowed, so that the spray angle can be adjusted like the nozzle 10a.

The rotational flow of the upper and lower layers caused by the saturated solution jetted from the same nozzle causes the bottom layer Yb to rotate as well.

Table 1 shows Examples (Nos. 1 to 28) using the device of this example together with Comparative Examples (Nos. 29 to 31).

As is clear from the table, the present invention Nos. 1 to 28 promote grain growth without attaching crystal grains to the peripheral wall surface of the inverted truncated conical bottom, and the continuous extraction amount is 5.1 ton/hr to 6.1 ton/hr. was gotten. This is Comparative Example No. 29-31.
This was a significant increase in production compared to 4.4ton/hr to 4.6ton/hr. Furthermore, for large crystal grains exceeding 1.4 mm, the present invention example
It showed an extremely high grain growth effect of 50-81% compared to 36-38% of the comparative example. In addition, the proportion of cornerless crystal grains in the total extraction amount is 65 to 93%, which is 0 to 45% in the comparative example.
A markedly more rounded granulation effect was obtained compared to the previous method.

<Effects of the Invention> As is clear from the above explanation, the present invention is capable of producing ammonium sulfate with large crystal grains in a crystal can with a good yield and high productivity with a simple configuration, and It is possible to efficiently reduce the angle of

Therefore, when applying fertilizer by the mechanical spreading method described above, it is possible to suppress wear on the inner walls of the ammonium sulfate air pipe, nozzle, etc., and to reliably prevent dust generation and nozzle clogging.

Furthermore, the bulk blending method described above requires
Ammonium sulfate with a particle size of 1.7 to 3.3 mm can also be extracted and supplied in large quantities with stability and good yield, which simplifies the classification process after extraction and greatly reduces manufacturing costs.

[Brief explanation of drawings]

Figures 1a and b are side sectional views and plan sectional views schematically showing the action of the present invention, Figures 2a and b are perspective views showing the shape of ammonium sulfate crystal grains, and Figure 3 is a diagram showing the method of the present invention. FIG. 4 is a side sectional view showing an example of a device for carrying out the method, and FIG. 4 is a plan view showing the nozzle arrangement on the inverted truncated conical bottom in FIG. 3.

Claims (1)

[Claims] 1. A supersaturated solution of ammonium sulfate from the evaporator is fed downward through a downcomer to the center of the inverted truncated conical bottom of the crystallizer to crystallize it in the crystallizer, and the growing crystal grains are allowed to settle on the truncated conical bottom. In the method for producing ammonium sulfate to be extracted, a nozzle is provided on the inner wall of the truncated conical bottom, and a saturated or supersaturated solution of ammonium sulfate is spouted from the nozzle in the circumferential direction of the inner wall or diagonally downward from the inner wall to form the conical bottom. A method for producing ammonium sulfate, which comprises causing crystal grains settled on the platform bottom to flow along the inner wall.