JP2008173563A - Perforated-plate extraction column and its operation method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a perforated-plate extraction column which allows accurate, convenient and efficient monitor of the dispersed conditions of the liquid contents and thereby enables liquid-liquid extraction operation consistently under good conditions and a method of operating this column. <P>SOLUTION: The perforated-plate extraction column has a capillary type differential pressure meter measuring the differential pressure between the upper and lower stages containing one or more stages of dispersion plates. The differential pressure meter is operated by arranging pressure-receiving nozzles above and below a target portion consisting of one or more stages of dispersion plates, applying measurement pressures to the lower pressure-receiving diaphragm as the high-pressure side and to the upper pressure-receiving diaphragm as the low-pressure side and transmitting to a differential pressure transmitter through a capillary sealed with a silicone oil. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a perforated plate extraction tower and a method for operating the perforated plate extraction tower. More specifically, the present invention is capable of accurately, simply and efficiently monitoring the dispersion state of the liquid inside, and thus is excellent in that the liquid-liquid extraction operation can always be performed in a good state. The present invention relates to a perforated plate extraction tower having characteristics and a method of operating the perforated plate extraction tower.

  The extraction tower is a cylindrical vessel that supplies heavy liquid at the top of the tower, supplies light liquid to the bottom of the tower, the heavy liquid descends, and both liquids come into contact with each other while the light liquid rises. It is an apparatus in which mass transfer occurs in a part of the liquid component and the extraction operation is executed.

  Typical extraction towers include a powered rotary disk extraction tower and a non-powered perforated plate extraction tower. The rotating disk extraction tower has a plurality of sections divided by a rotating disk in the tower and a baffle that prevents back-mixing, and the shear stress of the rapidly rotating disk is used for phase dispersion, and mixing in the section is performed. While improving the extraction efficiency by reducing back-mixing between each section and adjusting the rotational speed of the disk, the mixing state can be flexibly adjusted, but the drive unit is installed in the equipment In addition, it has disadvantages that the internal structure is complicated, and that the backmixing inevitably increases at large tower diameters. On the other hand, the perforated plate extraction tower has a perforated plate fixed in the tower and has a simple structure, and there is no back-mixing of the continuous phase between the stages, and the extraction efficiency is relatively high. In addition, it has an advantage that it can be easily scaled up. On the other hand, liquid droplets are dispersed through the perforated plate, and dispersion and coalescence of the dispersed phase are repeated for each stage, but the operation flexibility is inferior.

  By the way, in the liquid-liquid extraction operation, it is necessary to sufficiently bring both liquids into contact. For that purpose, one liquid (dispersed phase) must be sufficiently dispersed in the other liquid (continuous phase). . The sufficiently contacted liquid needs to be separated into both phases before being taken out from the column. In other words, phase dispersion and separation are the points of operation of the extraction tower.

  However, in actual operation, the dispersed phase droplets may become too small, making it difficult to separate the two phases. This phenomenon is known as “separation failure” and is an important point that must be avoided when operating the extraction tower.

  In order to monitor the maintenance of dispersion and the occurrence of liquid separation failure, there is a method of providing a viewing window in the extraction tower and visually monitoring. However, this method has a problem in accuracy and efficiency of judgment. Further, Patent Document 1 discloses a method for measuring a differential pressure between a pressure and a reference head pressure at the bottom of the extraction tower using a differential pressure system for a rotary plate extraction tower. However, this method is intended for a rotary plate extraction tower, and there is a problem that it is necessary to keep the temperature of the liquid introduced into the reference liquid head pressure pipe from the viewpoint of specific gravity management.

JP 59-169506 A

  In such a situation, the problem to be solved by the present invention is that the dispersion state of the liquid inside can be accurately, simply and efficiently monitored, and therefore the liquid-liquid extraction operation can always be performed in a good state. The object of the present invention is to provide a perforated plate extraction tower having an excellent feature of being possible and a method of operating the perforated plate extraction tower.

That is, the first invention of the present invention relates to a perforated plate extraction tower having a capillary type differential pressure gauge for measuring a pressure difference between the upper and lower sides sandwiching one or more stages of dispersion plates. .
The second invention of the present invention is a method for operating a perforated plate extraction tower, in which a differential pressure in the upper and lower sides sandwiching one or more stages of dispersion plates is continuously measured using a capillary type differential pressure gauge. The present invention relates to a method for operating a perforated plate extraction tower that monitors the dispersion state of the liquid inside the extraction tower.

  According to the present invention, the dispersion state of the liquid inside can be accurately, simply and efficiently monitored, and therefore, the liquid-liquid extraction operation can always be performed in a good state. A perforated plate extraction tower and a method for operating the perforated plate extraction tower can be provided.

  The perforated plate extraction tower of the present invention has a capillary-type differential pressure gauge that measures the pressure difference between the upper and lower sides with one or more dispersed plates interposed therebetween.

  Hereinafter, the present invention will be described in the case where the continuous phase is a light liquid and the dispersed phase is a heavy liquid, but the same applies to the case where the continuous phase is a heavy liquid and the dispersed phase is a light liquid.

  The extraction device for performing continuous extraction is a perforated plate extraction tower in which a dispersion plate having a large number of holes in a tower-like container is installed at an appropriate interval, and supplies heavy liquid from the top and light liquid from the bottom. Supply nozzles for extracting light liquid from the tower top and heavy liquid from the tower bottom.

  The inside of the perforated plate extraction tower consists of a dispersed plate with a large number of holes for dispersing the dispersed phase in the form of fine droplets, and a flow path (called an upcomer) for the continuous phase to rise. In general, a perforated plate called a sieve tray is used, but the structure of the dispersion plate is not limited to this.

  The actual number of installed dispersion plates is determined by the required number of theoretical plates and the efficiency of extraction, and can be determined by the practitioner of the present invention as necessary.

  A space between the dispersion plates is called an interstage, and this height is called a step interval. The step interval is generally designed so that the dispersed phase that has passed through the holes can be sufficiently dispersed, and the flow velocity flowing between the dispersion plates is slower than the flow velocity of the continuous phase that flows through the upcomer section. However, when installing a manhole or handhole for cleaning or maintenance of the dispersion plate, the step interval may be further increased. On the other hand, if the step spacing is too large, the height of the facility becomes excessively high, leading to an increase in cost, which is not preferable.

  In the differential pressure gauge used in the present invention, nozzles for pressure reception are installed above and below at least one stage of a dispersion plate, the lower side is a high pressure side pressure receiving diaphragm, and the upper side is a low pressure side pressure receiving diaphragm. Then, it is transmitted to the differential pressure transmitter with a capillary filled with silicon oil or the like.

  That is, the differential pressure gauge of the present invention has a function of detecting a change in apparent specific gravity of a mixed phase of a continuous phase and a dispersed phase existing between stages.

  In the present invention, the high-pressure side and the low-pressure side of the capillary differential pressure gauge may be installed with at least one or more stages of dispersion plates interposed therebetween. It is preferable to measure with two differential pressure gauges. Furthermore, it is preferable to measure as wide as possible within the allowable range of the length of the capillary because the dispersion and the liquid separation state of the entire tower can be grasped with one differential pressure gauge.

  In the present invention, a capillary method is used for the differential pressure measurement method. When the method using the reference head pressure pipe described in Patent Document 1 as described above or the method using the pressure guiding pipe is used, it is caused by the change in specific gravity due to the temperature change of the liquid introduced into the reference head pressure piping or the pressure guiding pipe. This is because a measurement error may occur, and in order to prevent this, heat insulation as described in Patent Document 1 or coating with a heat insulating material or the like is required.

  Therefore, the perforated plate extraction tower of the present invention, which has a capillary type differential pressure gauge for measuring the differential pressure between the upper and lower sides with one or more stages of dispersion plates interposed therebetween, does not have the conventional problems.

  The operation method of the present invention is an operation method of a perforated plate extraction tower, and by continuously measuring the upper and lower differential pressure across one or more stages of dispersion plates using a capillary type differential pressure gauge, This is an operation method of a perforated plate extraction tower for monitoring the dispersion state of the liquid.

  Specifically, the differential pressure is continuously measured and monitored since the mixed phase specific gravity of the continuous phase and the dispersed phase between the stages and the differential pressure are proportional.

  The change in the mixed phase specific gravity between the continuous phase and the dispersed phase represents a change in the ratio of the dispersed phase existing in the continuous phase. In other words, continuously measuring the differential pressure change is continuously monitoring the dispersed phase hold-up state in the continuous phase.

  When the droplet diameter of the dispersed phase is reduced, the holdup is increased, the liquid-liquid extraction interface is increased, and mass transfer between the two phases is likely to occur, thereby increasing the extraction efficiency.

  On the other hand, the excessively finely dispersed phase causes emulsification, and the heavy liquid is mixed into the light liquid clarified liquid extracted from the tower top, and the light liquid is mixed into the heavy liquid clarified liquid extracted from the tower bottom. In order to cause such a poor liquid separation state, it is important for stable operation to maintain an appropriate dispersion state between stages and a liquid separation state of the extracted liquid.

  Therefore, a method of visually checking by installing a viewing window or a glass gauge at a necessary part of the extraction tower, or collecting a liquid actually extracted from the top or bottom of the tower and checking a separation state is performed. .

  However, these methods have problems in the accuracy and efficiency of judgment, and cannot be said to be methods that can detect an abnormal state continuously and accurately.

  The operation method of this invention grasps | ascertains the extraction state in a tower by monitoring an operation state continuously from the change of the instruction | indication value of the differential pressure gauge which can be always measured.

  That is, if the differential pressure suddenly increases, it means that the dispersed phase holdup of the heavy liquid between the stages has increased, and there is a concern about separation failure, so action can be taken to improve separation. . Specifically, in order to improve the separation of the two liquids, it is possible to change the liquid composition by changing the supply ratio of heavy liquid and light liquid, or to change the extraction temperature. The practitioner only needs to implement the change factors allowed in the process within an appropriate range. On the other hand, when the differential pressure rapidly decreases, it means a state in which the hold-up of the dispersed phase is decreased, and there is a concern about a decrease in extraction efficiency. Therefore, the practitioner can similarly take necessary actions.

  In this way, the dispersion state of the liquid inside can be accurately, simply and efficiently monitored, and thus the liquid-liquid extraction operation can always be performed in a good state. It was possible to provide a perforated plate extraction tower and a method for operating the perforated plate extraction tower.

Next, the present invention will be described with reference to examples.
Example 1
Figure 1 shows an outline of a perforated plate extraction tower that has a function of continuously measuring the differential pressure by installing a pressure-receiving diaphragm by installing nozzles at the 25th stage and the top of the 100-stage sieve tray. Show. Using this perforated plate extraction tower, in a full liquid state under pressure, an extraction operation was performed between a light liquid mainly composed of ketones and a heavy liquid mainly composed of an alkaline aqueous solution as a dispersed phase. .
When differential pressure information during normal extraction operation is plotted in the plot described as normal in FIG. 2, the hold-up of heavy liquid as a dispersed phase rises, and the occurrence of separation failure is detected The differential pressure information was shown in the plot described as poor liquid separation. The horizontal axis in FIG. 2 is the elapsed time from the starting point of measurement. In the operation example with poor liquid separation, a rapid increase in the differential pressure was observed 12 hours after the starting point, and thus the supply amount of the heavy liquid as the dispersed phase was immediately adjusted. As a result, the pressure difference returned to normal after 24 hours from the starting point, and the operation of the extraction tower could be continued.

Comparative Example 1
A perforated plate extraction tower conventionally used is shown in FIG. The observation windows are installed at five locations on the tower bottom, 25th, 50th, 75th, and 100th, respectively. It is inferior in efficiency.

1 is a diagram illustrating an outline of a system according to a first embodiment. It is a figure which shows the example of the result of the differential pressure | voltage measurement in Example 1. FIG. 1 is a diagram showing an outline of a system of Comparative Example 1. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Heavy liquid supply line 2 Light liquid supply line 3 Light liquid extraction line 4 Heavy liquid extraction line 5 Extraction tower main body 6 Even number tray (all stages are not indicated)
7 Odd trays (all levels not shown)
8 1st tray 9 9 25th tray
10 50th tray
11 75th tray
12 100th tray
13 Pressure sensing diaphragm
14 Silicon-filled capillary
15 Differential pressure gauge
16 Viewing window

Claims (2)

A perforated plate extraction tower comprising a capillary type differential pressure gauge for measuring a differential pressure between the upper and lower sides sandwiching one or more stages of dispersion plates. This is a method for operating a perforated plate extraction tower, which monitors the dispersion state of the liquid inside the extraction tower by continuously measuring the upper and lower differential pressure across one or more stages of dispersion plates using a capillary differential pressure gauge. Operation method of perforated plate extraction tower.

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