JPS6114842B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a solid-liquid compression separation method after pressure crystallization of a mixture.

Since conventional fractional crystallization methods use temperature as a parameter, in order to solidify and separate a specific component from a raw material mixture containing two or more components, it must be cooled to a predetermined temperature or lower. However, with this method, it is extremely difficult to control the temperature in order to increase the amount of crystallization of a specific component and to obtain a rate of increase in crystals that contains as few impurities as possible. In particular, when the melting point is below 0°C, it is necessary to choose a means of cooling to below the melting point, and even though the cost is high, it may not be possible to expect a sufficient effect to compensate for the high cost. many. The crystal growth rate is generally extremely slow, and it is not uncommon for it to take 1 to 2 hours per raw material mixture.

For this reason, the present inventors have been studying a fractional crystallization method using pressure as a parameter for some time, and have established a crystallization method that applies high pressure to a raw material mixture to crystallize a specific component. This method has the advantage that the pressure in the system is always uniform and the rate of change can be freely adjusted, and a suitable increase in crystals can be obtained within a short time. When extracting the mother liquor from the produced solid-liquid coexistence material and performing solid-liquid separation, the compression separation method is preferred as a simple separation method. However, a solid-liquid coexistence state is not just a situation in which a solid phase is mixed, but also a situation in which a liquid phase is incorporated into a group of crystals of various sizes. As the liquid phase is squeezed out of the filter, the above-mentioned tendency becomes more pronounced. 1st, 2nd
The diagram explains the _{circumstances} during that time.
indicates large-grain crystals, S _B indicates small-grain crystals, and L indicates a liquid phase. Figure 1 shows the situation before the start of compression or after the compression has progressed slightly, and the distance between crystals S _A and S _B is maintained long enough to allow the liquid phase L to pass through. , this state is considered to be a state where the solid phase fraction is not high. On the other hand, FIG. 2 shows a situation where the compression has progressed to some extent, and the liquid phase L is being incorporated into the crystal group consisting of crystals S _A and S _B. In particular, the small grain size crystals S _B are located at the grain boundaries of the large grain size crystals S _A and play a role of filling these gaps, so that the liquid phase L
The extraction passage is in a blocked state, and even if more compression is applied, there will only be compression of the solid phase and liquid phase themselves, and it is extremely difficult to expect separation and extraction of the liquid phase. Therefore, there is a certain limit to the compression separation of solid and liquid, and this in itself is unavoidable, but if the entire inside of the pressure vessel is made as uniform as possible in the state shown in Figure 2, the solid-liquid separation effect can be improved. should be higher. However, in an actual pressure vessel, although the state shown in Figure 2 is obtained near the filter, the state shown in Figure 1 or similar to this is often obtained in the center of the vessel, and the overall solidity is There is a problem that the phase fraction is reduced. The reason for this is thought to be that the compression in the vicinity of the filter progresses first, and the front surface of the filter reaches the state shown in FIG. 2 first, closing the liquid phase discharge path.

That is, FIG. 3 is a cross-sectional view schematically showing a typical pressure vessel 1. The vessel 1 is composed of a cylinder body 2, a piston 3, and a bottom cover 4. The piston 3 slides inside the barrel 2, and the bottom cover 4 is fixed, but the bottom cover 4 may also be configured to be able to slide up and down. The container may be moved up and down to facilitate assembly and disassembly. In any case, there are wire meshes 5a, 5b, 5c inside the pressure vessel 1.
and a perforated plate 6a that supports these and allows the liquid phase to pass through.
Filters A, B, and C consisting of filters 6b and 6c are arranged. Further, a heat insulating layer made of heat insulating materials 7a, 7b, and 7c is formed on the back surface of the filters A, B, and C. In this way, the filtration surface is formed on the entire inner surface of the pressure vessel 1 in the figure, but some of these surfaces may be omitted, or all or part of the heat insulating layer on the back surface of each filter A, B, and C may be omitted. Furthermore, it is also possible to arrange a heat insulating material with a smooth inner surface exposed on the inner surface side or embedded in the container material in a part where the filter surface is omitted, and these changes can be implemented according to the present invention described later. It can also be applied in The raw material mixture is then pressurized by a pressurizer 8, and a check valve 9
The raw material enters the pressure vessel 1 through the raw material passage P provided with the following. As it is, or if necessary, the piston 3 is lowered to further increase the pressure in the container to solidify part or all of the specific component in the raw material mixture (the entire liquid phase or solid-liquid coexistence such as slurry). Next, while adjusting the pressure of the drain pressure regulating device 10 (in some cases, it may be a simple small-diameter nozzle), or by raising the piston 3, the inside of the container 1 is returned to atmospheric pressure or a pressure close to it, and the pressure is fixed. Melting part of the phase. As a result, the solid phase is self-cleaned and the solid-liquid coexistence material in the container 1 is squeezed out while the piston 3 is lowered, but this squeezing pressure is applied to the filters A and B at the tip of the piston 3 or in the vicinity. Naturally, it is transmitted to the solid-liquid coexisting material on the front surface of the filter (upper part), but also easily to the solid-liquid coexisting material on the front surface of the filters B (lower part) and C, which are far away from the piston 3. Therefore, the solid-liquid coexistence material in the state shown in FIG. 1 in this part is squeezed, and the liquid phase L passes through filters A, B, and C to mother liquor discharge channels Qa, Qb, and Qc. Released outside the system. On the other hand, squeezing pressure is also applied to the center part R of the container, and the solid-liquid coexistence material, which is also in the state shown in Fig. 1, releases its liquid phase and tries to become the state shown in Fig. 2, but filters A, B, and C have already been removed. Since the front surface has a structure that does not allow the liquid phase to pass through, squeezing in the central portion R becomes virtually impossible, resulting in the above-mentioned problem.

The present invention has been made in view of these circumstances, and it is an object of the present invention to provide a solid-liquid compression separation method that can perform uniform compression in a compression chamber and increase the solid phase fraction as a whole. The configuration of the present invention that achieves this object is that when performing the separation, the reduction rate of the space length between the top and bottom of the container due to the advancement of the piston is reduced to the center of the pressure container. The gist lies in increasing the solid phase fraction at the center of the pressure vessel by increasing the solid phase fraction at the center of the pressure vessel.

The configuration and effects of the present invention will be explained below based on drawings showing examples, but the following examples and their explanations are not intended to limit the present invention as well as the embodiments described in the claims. It is within the technical scope of the present invention to make changes in line with the spirit of the preceding and following. Furthermore, the figure numbers described in the claims are for the purpose of aiding understanding and should not be interpreted as limiting.

4 to 11 are schematic cross-sectional views showing typical examples of pressure vessels suitable for carrying out the present invention, and the small x mark on the inner wall of the vessel means a filter, and the formation position of this filter is also as follows: The invention is not limited as described above.

First, Fig. 4 shows a piston 3 with a tapered protrusion 3 formed in its center, and the length of the space formed between the tip of the piston and the bottom cover 4 is M at the center of the pressure vessel, and the length of the space formed between the piston 3 and the bottom cover 4 is M at the center of the pressure vessel. N near the inner surface of , and of course M<N
It is. Therefore, when the piston 3 descends by △L, the reduction rate of the space length available in the center of the pressure vessel is △
L/M, and the reduction rate of the space length in the cylinder body is ΔL/N, and the relationship between these is ΔL/M>ΔL/N. Under these conditions, when the piston 3 descends, the protrusion 3 first reaches the center of the pressure vessel, so the solid-liquid mixed state in the center as shown in FIG. 1 is quickly destroyed as the piston 3 descends. Ru. Therefore, the liquid phase squeezed out from the center is sequentially mixed with the liquid phase of the solid-liquid coexistence material around it, and is squeezed out together with the liquid phase to reach the front surface of the filter. On the other hand, piston 3 is also located in front of the filter.
The liquid phase is being pushed out toward the filter to form a crystalline state as shown in Figure 2, but the liquid phase moves extremely quickly from the center of the container as described above. Therefore, the liquid phase is allowed to pass through more and more in the state immediately before reaching the state shown in FIG. 2, and the solid phase fraction in the pressure vessel can be increased uniformly and on average. That is, in the present invention, a squeezing pressure distribution is generated that gradually decreases from the central part of the pressure vessel (more precisely, the part far away from the filter) toward the filter surface, so the mother liquor is forced to flow from the central part toward the filter surface. , the efficiency of discharging the mother liquor out of the container is extremely high.

Figure 5 is a reversal of the idea in Figure 4,
The tip of the piston 3 is configured with a flat surface,
At the top of the bottom cover 4, there is a projection 4' which is tapered in the same manner as described above.
, and the same effect as in the case of FIG. 4 can be obtained. In FIG. 6, the protrusions 3' and 4' are formed in a trapezoidal shape, but a combination of FIGS. 4 and 5 will yield even more advantageous results.

FIGS. 7-9 show these modified embodiments, which are better than those in FIGS. 4-6. That is, the feature of this example is that a tapered surface 11 is formed on the inner surface of the cylinder body 2, which expands in the direction in which the piston 3 enters. good. That is, in the examples shown in Figs. 3 to 6, since the piston 3 enters in contact with the inner wall surface of the cylinder body, the crystalline state shown in Fig. 2, which is formed sequentially as it enters, is as follows. This causes frictional resistance to the entry of the piston 3, and this frictional resistance increases proportionally as the compression progresses. Therefore, a large compression load is required, and even then, the compression speed gradually becomes slower. However, in the method using the apparatus shown in Figs. 7 to 9, the gap is gradually enlarged in the direction of piston movement where the amount of solid phase increases in absolute terms, so there is less friction as described above.
Therefore, the compression load may be small, and the compression speed can also be increased. Furthermore, the solid phase obtained by squeezing often takes the form of a hard cake inside the container, but in the case of the apparatus shown in Figs. However, with the device shown in Figs. 7 to 9, if the cake can be moved slightly downward after removing the bottom cover 4, the cake and the cylinder body can be easily removed. Since the contact area with the inner wall becomes zero or small, no excessive force is required after that, and the solid can be taken out with an extremely small force. Incidentally, the inclination angle of this tapered surface 11 is not particularly limited, but it is usually preferably selected from a range of 3 to 20 degrees. However, in the example shown in FIG. 7, a straight piston 3 similar to that shown in FIG. 5 is used, and a flat bottom cover 4 is used similarly to that shown in FIG. 4. Therefore, the space length between the piston tip and the bottom cover is all the same as far as the area where the piston is located, and the rate of reduction in space length as the piston moves forward is also limited to the same area. In other words, they are the same.
However, when looking at the pressure vessel as a whole, a constant space length is maintained between the side wall part with the tapered surface and the bottom cover regardless of the forward movement of the piston, and therefore the shortening rate is always zero. Since the shortening rate at is always a positive value and is larger than this, the requirements of the present invention are satisfied. FIG. 8 is an application of the concept of FIG. 4, and it goes without saying that the same effect can be obtained. Figure 9 shows tapered surface 1
1' is limited to the lower part of the cylinder body, and the upper part is a vertical surface, but this is not inconvenient since there is little frictional resistance at the initial stage of compression.

FIG. 10 shows another embodiment, in which a foreign object 12 is loosely supported by a spring 13 between the piston 3 and the bottom cover 4.
and 12' are present. And this foreign body 12,1
2' is arranged so as not to come into contact with the barrel 2, so that the length of the space between the top and bottom inside the pressure vessel is shortened only in the center of the pressure vessel. Therefore, regarding the reduction rate of the space length when the piston is lowered, the central portion becomes larger for the same reason as described in FIG. 4, and as a result, the same effect can be obtained.

FIG. 11 shows a further modified example, in which the piston is composed of a large-diameter piston 3a and a small-diameter piston 3b inserted into it, and when the liquid phase fraction is high and the filtration resistance is low, the pistons 3a and 3b are At the same time, as shown in FIG. 11, from the point when the filtration resistance of the mother liquor becomes large, only the small-diameter piston 3b enters and squeezes the central part, and then, as shown in FIG. 11-2, the large-diameter piston 3a enters. Completing the compression. Therefore, in the state shown in FIG. 11, the space length reduction rate at the center of the container is clearly large, and the present invention also includes a container that satisfies the above conditions with such a time difference. In addition, in such a structure, when the compressed solid forms a cake, for example, if the small-diameter piston is temporarily retracted to further compress the solid, the cake deforms and breaks, making it easier for the liquid inside the cake to flow out. obtain. At this time as well, it is natural to squeeze the central part more. This method does not require a simple relationship between a sheath and a core, but may involve a plurality of cores arranged concentrically, and the same applies even if one of the cores is inserted from the bottom cover. And the 10th, 1st
1, the inner surface of the cylinder body 2 can be formed into a tapered shape as shown in FIGS. 7 to 9.

The present invention is carried out as described above, and its effects are summarized as follows.

(1) Since the pressure in the center of the pressure vessel is high, the liquid phase in the center can be sufficiently squeezed out, resulting in a high solid phase ratio, which ultimately makes it possible to purify to a high degree of purity.

(2) Since the pressure applied to the inner cake is not uniform, shear stress is generated within the cake, causing cracks in grain boundaries and their movement, which become passages for liquid and increase the above effects as a result.

(3) Excessive pushing force is not required when the piston enters, making it economical.

(4) Productivity was improved by increasing the pressing speed.

[Brief explanation of the drawing]

Figures 1 and 2 are explanatory diagrams showing the solid-liquid coexistence state, Figure 3
The figure is a cross-sectional view showing the concept of a pressure crystallizer, Nos. 4 to 1.
FIG. 1 is a schematic cross-sectional view of the apparatus used to carry out the invention. 1... Pressure vessel, 2... Cylinder body, 3... Piston, 4... Bottom cover, A, B, C... Filter, 11
...Tapered surface.

Claims (1)

[Scope of Claims] 1. A cylinder body 2, a bottom cover 4 that is in close contact with the cylinder body, and a piston 3 that advances and retreats within the cylinder body towards the bottom cover.
and filters A, B,
A raw material mixture is stored in a pressure vessel 1 in which C is arranged, high pressure is applied to the raw material mixture to promote crystallization of a specific component in the raw material mixture, and the piston is advanced toward the bottom cover to release the raw material mixture into the pressure vessel. A method for separating solid and liquid by applying squeezing force to the solid-liquid coexistence material and extracting the liquid phase from a filter, the reduction rate of the space length between the top and bottom of the container as the piston 3 moves forward By increasing the size in the center of the pressure vessel,
A solid-liquid compression separation method characterized by increasing the solid phase fraction in the center of a pressure vessel. 2. The separation method according to claim 1, wherein the center portion of the tip of the piston is formed to protrude 3'. 3. The separation method according to claim 1 or 2, which is carried out by forming a protrusion 4' at the center of the tip of the bottom cover. 4 In claim 1, 2 or 3,
A separation method in which foreign objects 12, 12' are suspended between the piston and the bottom cover. 5. A separation method according to any one of claims 1 to 4, which is carried out by forming a gap cross-sectional area that gradually increases in the direction of compression of the piston between the inner wall surface of the pressure vessel and the outer peripheral surface of the piston. . 6. In any one of claims 1 to 5, the piston includes a large-diameter piston 3a and a small-diameter piston 3b that moves forward and backward into the large-diameter piston, and the small-diameter piston 3b and the large-diameter piston 3a are out of synchronization. Separation method to be used. 7. The separation method according to any one of claims 1 to 6, in which the bottom cover is also moved forward in the direction of the piston. 8. A separation method according to any one of claims 1 to 7, which is carried out by arranging a filter at the tip of the piston. 9. The separation method according to any one of claims 1 to 8, which is carried out by arranging a filter at the tip of the bottom lid. 10. A separation method according to any one of claims 1 to 9, which is carried out by arranging a filter on the inner surface of the cylinder body.