SU1031448A1 - Vacuum crystallizer - Google Patents

Abstract

VACUUM CRYSTALLIZER, including a housing, an evaporator, a central circulation pipe, a suspension circulation device located inside the pipe and equipped with a drive, a collector with nozzles located in the upper part of the case, an overflow device, a hydraulic solution, fittings for supplying the initial solution, , removal of slurry and secondary steam, characterized in that, with the aim of increasing productivity and improving quality. product, the device for circulation is made in the form of a piston having a bore and fitted with a disk valve mounted above it on its stem. .

Description

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The invention relates to chemical engineering, in particular to vacuum crystallizers used in the chemical industry for the crystallization of organic and inorganic substances from solutions.

A vacuum mold is known for producing a crystalline product a consisting of a casing (crystal grower), a pump for circulating the solution, circulation pipes, fittings for supplying the solution, evacuating the secondary steam and suspension 1.

 The disadvantage of this crystallizer is that in the process of circulating the suspension in a closed loop, the pump blades are crushed. In addition, the hot saturated solution, mixed with the suspension, quickly gets into the boiling zone, where it cools rapidly, which leads to the formation of a large number of crystallization centers, since the crystals in the solution do not have time to remove all supersaturation proportional to the temperature change.

The closest in technical essence to the present invention is a vacuum cooler of Swenson type DTB, consisting of a closed vessel, Yes, with an internal partition forming a settling chamber. At the center of the apparatus, a vertical, somewhat expanding circulation pipe extends upwards. A mixer with a lower or upper drive is installed in the center of the mold in the lower part of the circulation tube. It provides axial flow 2.

The Swenson vacuum crystallizer makes it possible to obtain a better product with a grain-size composition, however, such disadvantages as grinding the crystals by the blades of a circulation pump and the formation of crystallization centers in the boiling zone of the solution also take place in this vacuum crystallizer.

The purpose of the invention is to improve the performance of the mold due to the intensification of heat and mass transfer and improving the quality of the product.

This goal is achieved by the fact that in a vacuum crystallizer, including a housing, an evaporator, a central circulation pipe, a device for circulating a suspension, located inside the pipe and equipped with STS8 .2

water, a manifold with nozzles located in the upper part of the body, an overflow device, a hydraulic valve, fittings for supplying the initial solution, removing the suspension and secondary steam, the device for circulating is made in the form of a piston having a hole and fitted with a disk mounted above it on its stem flap.

In addition, the flow areas of the ends of the circulation pipe are 0.2-0.5 times its diameter.

Figure 1 shows a vacuum mold, a longitudinal section; figure 2 - the piston without flow holes; in fig. 3 - a piston provided with overflow openings and a movably mounted disc valve closing the overflow openings in the upward movement of the piston; in fig. - the same, when moving it down,

The vacuum crystallizer includes a housing 1, a circulation pipe 2 with a piston 3 to create a mixing of the suspension inside the crystallizer, an overflow device for maintaining a given solution level inside the crystallizer, a water seal 5, a drive 6, a pipeline 7 for taking the suspension from the lower part of the housing 1, a pipeline 8 for connecting the overflow device i with a water seal 5, a pipeline 9 for connecting the cavity of the vacuum crystallizer with the cavity of the overflow device, a fitting 10 for supplying the initial solution, a fitting 11 for Water vapor, fitting 12 for removal of the clarified mother liquor, fitting 13 for removing the suspension for processing, fitting N. - for supplying washing liquid.

Inside the housing 1, a collector 15 is provided with nozzles 16 for irrigating the walls of the housing with condensate and an annular conical shell 17 located concentrically to the conical part of the housing, while in the upper part it is connected to the housing 1, forming a settling chamber to drain the clarified mother liquor. The water seal 5 is provided with a fitting 18 for connection to the atmosphere. At the upper and lower ends of the circulation pipe 2, nozzles 19 to 20 are provided to create a rate of flow of solution from the circulation pipe. The fitting 21 is designed to connect the evaporator to a vacuum system.

To create a closed circuit Circulating the solution inside the crystallizer, the piston 3 (FIGS. 3 and 3) can be made with overflow holes 22 and a disk valve 23 mounted on the piston rod 3 of the closing opening 22 when the piston moves up (FIG. 3) and opens downflow holes when the piston 3 moves (FIG.) down.

The vacuum mold works as follows.

The hot saturated solution through the nozzle 10 is fed into the housing 1 before overflowing it through the overflow device, then the actuator 6 is turned on, which reciprocates the piston 3 placed inside the circulation pipe 2, while the evaporator is under vacuum. the piston 3, the solution that is in the housing makes B (a reciprocating motion or fig, 3 and k pulsing in one direction along a closed loop, slowly cooling to a predetermined temperature. In this case roiskhodit nucleation and growth of crystals. fishing in the entire volume of the mold.

After the solid phase appears in solution, the crystallizer is switched to continuous operation. For this purpose, the feed of the initial hot solution is included. At the same time, the overflow device i and the nozzle 12 are activated for removal of the clarified mother liquor,

During the operation of the crystallizer, the amount of supplied hot concentrated solution is equal to the sum of the withdrawn suspension and clarified mother liquor, which ensures a constant level of solution in the evaporator.

The operation of the crystallizer is accompanied by boiling of the solution in the evaporator and the growth of crystals due to the removal of supersaturation. At the same time, on the walls of the evaporator there are sprays of solution that contribute to the rapid incrustation of the walls of the evaporator. To prevent incrustation, the period-. The nozzles 1b are included, which splash condensate on the walls of the evaporator, flushing the incrustation,

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In the process of boiling the solution, secondary steam is formed, which through the nozzle 11 is removed for condensation, and after condensation as a liquid phase is supplied through the nozzle 4 and

5 collector 15 to nozzles 16 for irrigating the walls of the evaporator.

The proposed vacuum crystallizer design allows to obtain an I higher quality product due to the fact that it does not have mechanical grinding of the crystals and. the process of removing supersaturation itself is slow, resulting in

5, in general, the crossflow is reduced by crystals that are in solution with minimal formation of new crystallization centers.

 When working on solutions with low. visually, gyu can recommend the design of the piston shown in FIG. 2 / which creates a pulsating mixing of the solution in the entire volume of the mold by creating a reciprocating movement of the solution in the circulation pipe, which is ejected into the body of the mold through the upper and lower nozzles. In that case,; when the solution is viscous and has high inertia, to improve its mixing in the entire volume of the mold, a piston design with perforated 5 holes in the piston, as shown in FIGS. 3 and f, can be recommended, allowing one-way movement of the solution along a closed contour inside the crystallizer body .

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Claims (1)

VACUUM CRYSTALIZER, including a housing, an evaporator, a central circulation pipe, a suspension circulation device located inside the pipe and equipped with a drive, a manifold with nozzles located in the upper part of the housing, an overflow device, a hydraulic shutter ·, fittings for supplying the initial solution, drainage of the suspension and the secondary steam, characterized in that, in order to increase productivity and improve the quality of the product, the circulation device is made in the form of a piston having holes and equipped with a mounted above it on its stock by a disk shutter. · '·