JPH0236281B2 - TADANSHIKIJOHATSUSHOSEKISOCHI - Google Patents

Description

[Detailed description of the invention] Industrial application field Contact with gas other than solvent vapor (carrier gas),
It mainly relates to a crystallizer that produces solute crystals by evaporating a solvent on the surface of a solution.

Conventional technology Conventional technology involves supplying the solution into a flat can (circular or other shallow tank) and using an umbrella-shaped draft duct to draw in atmospheric air or natural ventilation to evaporate the solvent and precipitate the solute. The precipitated crystals are collected in a crystal slurry receiving tank with a scraper, and the slurry is taken out with a pump, etc., or the crystals are pushed out of the evaporating dish with a scraper and carried out with a belt conveyor to take out the precipitated crystals.

As an example, the literature (“Sodium Chloride The
Production and Properties of Salt and
Alberger-Gröner, as shown in "Brine", edited by D.W. Kaufmamn, 1971).

As shown in Fig. 6, this Alberger-Gräner has two shallow circular tanks with a diameter of 40 feet connected horizontally to serve as an evaporating dish 1. Saturated salt water is supplied to the evaporating dish 1, and solvent vapor is vaporized through a draft duct 11. and carrier gas are exhausted by natural ventilation. The precipitated salt crystals are collected by a crystal scraper 2 in a salt slurry receiving tank 12 provided in the center of the evaporating dish 1.

Problems to be Solved by the Invention Conventional surface evaporation crystallizers have an extremely large evaporation area per capacity, several tens of times larger than ordinary vacuum evaporators, etc., and in order to secure the necessary evaporation area, requires a device installation area equivalent to the evaporation area.

If the evaporation surface is multi-staged, the evaporation area can be freely increased without increasing the installation area of the device, but in conventional devices, it is difficult to take out the precipitated crystal slurry while keeping the liquid level in the evaporation dish constant. ,
Either a slurry receiving tank as shown in the salt slurry receiving tank 12 in Figure 6 is installed, or equipment is provided to push the precipitated crystals out of the evaporating dish with a scraper and carry them out with a belt conveyor.
It has the disadvantage that it is complicated and requires equipment such as a conveyor for crystal precipitation, and since an umbrella-shaped draft duct is provided to discharge the gas phase, the height per stage is high, so it is difficult to use conventional equipment. If they are stacked as they are in multiple stages, the height of the entire device becomes abnormally high, making it complicated, impractical for operation and maintenance, and lacking in high efficiency. Here, the gas phase refers to either a carrier gas or a solvent vapor, or a mixed gas of a carrier gas and a solvent vapor.

Means for Solving the Problems The present invention provides a method in which a plurality of flat-bottomed evaporation dishes are provided in multiple layers spaced apart from each other, a shaft is provided so as to pass through the evaporation dishes, and a circular sloped embankment is provided above each evaporation dish. ,
At least one of the notch ring and the valve plate is provided with a crystal scraper, and a ventilation device is provided to forcefully ventilate solvent vapor and/or gas other than solvent vapor (carrier gas). This is a multi-stage evaporation crystallizer.

This will be explained based on the drawings.

As shown in FIG. 1, a plurality of flat-bottomed evaporating dishes 1 are provided in a multi-layered manner, with a hollow shaft 6 and a shaft 10 passing through them, and a crystal scraper 2 is provided on each evaporating dish. is moved to move the precipitated crystals to the inclined embankment 3 on the outer periphery of the evaporating dish 1. The raw material solution is supplied from the hollow shaft 6 and onto each evaporating dish 1 via the branch pipe 15. A heating medium jacket 7 is provided on the lower surface of the evaporating dish 1, and a heating medium is circulated inside to heat the raw material solution on the evaporating dish 1. Then, the gas phase is introduced from the gas phase inlet section 8 by the blower 17, and the gas phase is discharged from the gas phase outlet section 16 through the spaces between the evaporation plates 1 and the apertures 9.

Each evaporating dish is provided with one of a circular slope bank 3 shown in FIG. 3, a cutout ring 4 shown in FIG. 4, and a valve plate 5 shown in FIG. 5. This is a mechanism that allows the precipitated crystals to be discharged to the outer periphery in the form of a slurry while retaining the solution on each evaporating dish. As shown in Fig. 3, the ring-shaped inclined embankment 3 has a plate inclined on the inside of the outer periphery of the circle, and at the same time holds the solution, the precipitated crystals are scraped up by the movement of the crystal scraper and turned into a slurry together with the solution. and is discharged to the outside of the sloping embankment.

As shown in FIG. 4, the notched ring 4 has a notched portion 13 in a thin plate ring, and by appropriately selecting the area of the notched portion 13, it is possible to hold the solution and remove it by the crystal scraper. The precipitated crystals can be discharged from the notch 13 to the outer periphery. This notched ring 4 is preferably connected to a crystal scraper and slides over the evaporating dish. Further, it is preferable that the notch portion 13 of the notch ring is provided at the front of the crystal scraper so that the scraped crystals can be easily discharged.

As shown in FIG. 5, the valve plate 5 is a flat ring plate with holes 14. By selecting the area of the holes 14 appropriately, the valve plate 5 retains the solution and discharges the discharged crystals together with the solution in the form of a slurry downward. do.

This valve plate 5 is attached to the crystal scraper 2 and slides on the evaporating dish 1, and the hole 14 is attached to the crystal scraper 2.
It is preferable that the pores are opened and the scraped crystals are always discharged.

In this way, the crystal scraper and circular slope embankment,
In combination with either a notch ring or a valve plate, the precipitated crystals can be easily discharged, and the precipitated crystals can be easily taken out using an appropriate device, such as receiving the precipitated crystals in a tank provided at the bottom of the evaporating dish.

By combining the gas phase inlet section 8, the opening section 9, and the gas phase outlet section 16 attached to the side surface of each evaporation dish, and supplying and discharging the gas phase by a blower 17, the conventional device It is possible to flow the necessary gas phase through a narrow flow path without installing large umbrella-shaped draft ducts at each stage.

FIG. 2 shows another embodiment, in which a plurality of gas phase inlets 8 are provided, and a plurality of gas phase outlet portions 16 are provided on the opposite side.

As described above, it is now possible to continuously discharge precipitated crystals and supply and discharge the gas phase without increasing the height of each stage, making it possible to create a multi-stage evaporative crystallizer with an appropriate height. did.

[Example] Fig. 1 shows an example of a multi-stage evaporative crystallizer for common salt.

Evaporating dishes 1 with a diameter of 2 m are stacked in multiple stages at intervals of 20 cm, and the solution is poured from the hollow shaft 6 in the center into the inclined bank 3 shown in FIG. 3, the notched ring 4 shown in FIG. 4, and the notched ring 4 shown in FIG. The solution was supplied to an evaporation dish 1 equipped with a valve plate 5 as shown, the solvent was evaporated, and salt crystals were precipitated on the surface of the solution.

It is effective to attach a heating medium jacket 7 to the lower surface of the evaporating dish 1 to supply at least part of the heat required for the solvent, and also to allow part of the evaporation to take place in the liquid, which is different from only surface evaporation. You can also obtain habit crystals.

The precipitated salt crystals are attached to the hollow shaft 6,
The evaporating dish 1 is removed by the scraper 2 that moves according to the rotation of the hollow shaft.
It is pushed out toward the outer edge, slides up, for example, the slope bank 3, and falls in the form of a slurry through the openings 9 on the periphery of the evaporating dish into the slurry tank at the bottom, where it is accumulated.

Furthermore, pouring a portion of the solution onto the front edge of the crystal scraper is extremely effective for quickly draining the salt from the front of the crystal scraper and washing away adhering salt.

It is preferable that the crystal scraper has a conformal spiral shape to prevent the precipitated salt from remaining partially.

The gas phase passes through the hollow shaft from the top of the multi-stage evaporator, is evenly supplied to each evaporating dish, and flows out from the openings in the outer periphery of the evaporating dish.

Effects of the Invention According to the present invention, the evaporating dish can be multi-staged from several stages to several tens of stages with a height of 1 m to 5 m, and the evaporation area can be obtained several times to several tens of times with the installation area of a conventional device. As a result, the crystallization ability can be increased several times to several tens of times.

[Brief explanation of drawings]

1 and 2 are longitudinal cross-sectional views of a crystallizer showing an embodiment of the present invention, FIG. 3 is a perspective view showing a circular sloped embankment, and FIG. 4 is a thin plate ring with a notch. 5 is a perspective view showing a valve plate attached to a crystal scraper, and FIG. 6 is a longitudinal sectional view showing a conventional device. 1...Evaporating dish, 2...Scraper, 3...Slope embankment, 4
... Notch ring, 5 ... Valve plate, 6 ... Hollow shaft, 7 ... Heat medium jacket, 8 ... Gas phase inlet part, 9 ... Opening part, 1
0... Shaft, 11... Draft duct, 12... Salt slurry receiving tank, 13... Notch, 14... Hole, 15... Branch pipe, 16... Gas phase outlet, 17... Blower. 18...
Solution inlet.

Claims (1)

[Claims] 1. A plurality of flat-bottomed evaporation dishes are provided in a multi-layered manner spaced apart from each other, a shaft is provided so as to pass through them, and on top of each evaporation dish there is one of a circular slope bank, a notch ring, and a valve plate. A multi-stage evaporative crystallizer, which is equipped with a crystal scraper and a ventilation device for forcibly ventilating solvent vapor and/or a gas other than the solvent vapor (carrier gas).