JPH0152041B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a tank-type crystal production apparatus by cooling a solution. More specifically, there are 10 stirring blades in the center.
and has a supply port 11 for raw materials and circulating mother liquor above.
12 and a solution crystallization tank 1 equipped with a discharge port 13 for crystals and mother liquor below, a vibrating stand 6 that applies fine vertical vibrations to the cooling parts 2 and 3 inside the crystallization tank 1 or to them and the crystallization tank 1. .

(b) Prior Art In a solution whose solubility increases as the temperature rises, crystal precipitation and separation are generally performed by cooling. At this time, if the crystal grain size is irregular or the crystal is irregularly shaped, the purity of the crystal will decrease due to the mother liquor remaining when the crystals and the mother liquor are separated or the contamination of impurities in the crystal. Generation of perfect crystals is required.

To produce crystals by cooling in a tank, it is generally widely adopted to place a cooling part in the tank and perform stirring cooling, as the equipment structure is relatively simple, the equipment cost is low, and it is easy to operate. ing. However, the agitation of the solution on the surface of the cooling part is not necessarily uniform, creating a blind spot in the flow of the liquid, which causes the formation and adhesion of crystals in that part, which grows and develops, resulting in the generation of irregularly shaped crystals. make it easier For this reason, it has become an important problem to equalize the concentration of the solution in the tank by uniformly stirring the solution in the tank.

(c) Problems to be Solved by the Invention When a solution cools and reaches a supersaturated region, the solution grows using crystal particles in the liquid or other surrounding solids as nuclei. On a cooling surface that is supercooled relative to the solution, the solution is always brought to a supersaturated state, so when the solution in contact with the cooling surface becomes supersaturated, crystal particles are generated on that surface and grow in all directions. However, since the cooling surface becomes an obstacle in the direction of crystal growth, it becomes a cause of irregularly shaped crystals.

Therefore, in order to obtain a perfect crystal, the cooling surface must be constantly and uniformly agitated to maintain a uniform concentration around each particle and to allow the particles to grow freely in each direction. In other words, it is necessary that the crystal particles remain suspended in the solution at all times.

Particularly in supercooled areas such as the cooling surface, the viscosity of the liquid increases, which requires more special stirring than the flow of the liquid in the tank.

(d) Means for solving the problem From this point of view, in the crystallization tank 1 which has the raw material solution supply pipe 11 and the circulating mother liquor supply pipe 12 at the top and the crystal and mother liquor outlet 13 at the bottom, the crystallization tank 1 A rotating blade 10 for stirring the solution is provided in the center of the crystallization tank 1, and the cooling parts 2 and 3 inside the crystallization tank 1, or this and the crystallization tank 1, are respectively placed on micro-vibration stands 6 and 7 that apply micro-vibration with an amplitude of several mm. Further, the crystals and mother liquor are discharged from the discharge port 13 at the bottom of the crystallization tank, and the coarse crystals are separated from the crystal fine particles and the mother liquor by a sieving device 14 installed outside. 1 was repeatedly supplied to grow the particles into perfectly-faced coarse crystals.

(e) Effect The above technical means works as follows.

The raw material solution and mother liquor supplied into the crystallization tank 1 from the raw material solution supply pipe 11 and the circulation mother liquor supply pipe 12 are agitated and flowed into the crystallization tank 1 by the rotating stirring blades 10, and then cooled by cooling sections 2 and 3 in the crystallization tank 1. The mixture is cooled in a vacuum chamber to precipitate crystal particles, or flows while growing crystal particles, gradually developing into coarse crystals. The coarse crystals gradually settle against the flow of the solution due to the difference in specific gravity with the mother liquor and accumulate at the bottom of the tank, and are discharged from the crystal tank 1 together with the mother liquor through the discharge port 13 and are sieved by a sieving device 14. The crude crystals are recycled as products, and the crystal particles are circulated together with the mother liquor into the crystallization tank 1, where they become crystal nuclei in the solution.

Here, the solution is cooled and brought to a supersaturated state, and the crystal grains or other solid particles flowing in the solution grow and become coarse grains, using the surfaces of the crystal particles or other solid matter as nuclei. Since the solution is supercooled, its viscosity increases, and its flow becomes sluggish, making it easy for crystal nuclei to occur and grow on the cooling sections 2 and 3.

However, if the cooling parts 2, 3 or other solid parts are subjected to vertical vibrations, the solution will not remain stationary due to the flow and vibrations on those surfaces, so the crystals on those surfaces will Generation of particles or growth of crystals is prevented. That is, since crystal grains are generated and can grow freely in each direction in the solution at any time, it is easy to generate perfect crystals.

The crude crystals obtained in the present invention gradually settle to the bottom of the tank against the flow of the solution in the tank due to the difference in specific gravity with the mother liquor. The crystal grains are separated by a separation device 14, and the crystal grains are repeatedly fed together with the mother liquor into the crystallization tank 1, where they are used as nuclei for crystal formation. In this way, coarse-grained, perfect crystals can be produced.

(F) Effects of the Invention As detailed above, the present invention, in addition to stirring the inside of the crystallization tank 1, cools the cooling parts 2 and 3 or the crystallization tank 1 by applying vertical vibrations to the crystallization tank 1. This is a continuous manufacturing device for perfect coarse crystals that leads the crystals out of the crystallization tank 1 and sieves them to separate the coarse crystals, and also supplies the crystal particles together with the mother liquor to the crystallization tank 1 as a circulating mother liquor for growth and development. The economic effects that it contributes to the above can be said to be truly great.

(g) Examples An example of implementing the invention is shown below.

The composition of the solution was 18% FeSO ₄ by weight;
Steel pickling waste liquid showing H ₂ SO ₄ 20%, H ₂ O 62%
137Kg/h as shown, diameter 350mm, height 710mm
The crystallization tank 1 is charged with water, stirred by rotating the stirring blade 10 in the center of the tank, and the cooling part is heated while slightly vibrating the cooling parts 2, 3 and the crystallization tank 1 at an amplitude of 2 mm and a frequency of 650 times/min. -11℃ brine is introduced into the tube to cool it.

The mother liquor containing crystals was discharged from the outlet 13 at the bottom of the tank, coarse crystals were sieved by a sieving device 14, and the mother liquor containing crystal grains was sent to the crystallization tank 1 as a circulating mother liquor.

Through the above treatment, 32.6 kg/h of FeSO ₄ .7H ₂ O crystals with uniform grains were obtained.

[Brief explanation of drawings]

The drawing shows an outline of one example of the apparatus according to the present invention by means of a longitudinal cross-sectional view thereof, in which 1 is a crystallization tank, 2 and 3 are cooling sections, 4 and 5 are brine pipes for cooling, and 6 7 is the crystallization tank vibration stand, 7 is the cooling unit vibration stand,
8 is a micro-vibration support for the cooling part, 9 is a rotating shaft, 10 is a stirring blade, 11 is a raw material feed pipe, 12 is a circulation mother liquor pipe,
13 is a discharge port, 14 is a sieving device, 15 is a crystallization outlet, and 16 is a mother liquor discharge pipe.

Claims (1)

[Claims] 1 A solution crystallization tank 1 having a stirring blade 10 in the center, supply ports 11 and 12 for raw materials and circulating mother liquor in the upper part, and a discharge port 13 for crystals and mother liquor in the lower part.
, a continuous crystal production apparatus by cooling characterized in that the solution is stirred and cooled by being equipped with vibration stands 6 and 7 that give vertical vibrations to the cooling parts 2 and 3 inside the crystallization tank 1 or to them and the crystallization tank 1. .