JP3761320B2 - Water-based rectification equipment - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an aqueous rectification apparatus used for an ammonia absorption refrigeration machine, alcohol rectification, and the like, and more specifically, an inflow part for introducing a reflux liquid from above and an outflow part for flowing down the reflux liquid staying downward. Provided with a plurality of shelf steps for guiding and flowing the reflux liquid downward from above, and arranged in multiple upper and lower stages, and a hole for allowing the inflow of steam from below into the reflux liquid retained in the shelf steps. The present invention relates to a water-based rectification apparatus that generates a large number of vapors having a low low-boiling component concentration from the recirculated liquid that is provided and stays to rectify low-boiling components from a low-boiling component aqueous solution.
[0002]
[Prior art]
As a conventional ammonia absorption refrigerating cycle, the one shown in FIG. 4 is common. That is, the ammonia vapor evaporated in the evaporator 1 under the predetermined pressure Pa is absorbed by the aqueous ammonia solution so as to be maintained at the evaporation pressure Pb by the absorber 2. The absorbed heat generated at that time is released to the outside by cooling water or the like. The solution that has become a strong solution (a solution in which ammonia concentration is increased by absorbing ammonia) by absorbing ammonia vapor is sent to the generator 3 by the pump P. Here, it is heated by an external heat source under pressure Pc, and since the boiling point difference between the refrigerant ammonia and the water of the absorbent is not so large, ammonia vapor containing moisture is generated. This steam enters the rectifying column 4 and the partial condenser 5 and is refined to an ammonia concentration of about 99.8% or more to increase the concentration. Then, the vapor enters the condenser 6 and is cooled and liquefied with cooling water or the like to produce high purity ammonia. Use liquid (refrigerant liquid). This refrigerant liquid enters the evaporator 1 via the expansion valve 7 and evaporates to cool the external heat load.
[0003]
The necessity of setting the ammonia concentration of the refrigerant liquid to about 99.8% or more is because this greatly affects the efficiency of the refrigerator. For example, in the case of 100% concentration of ammonia, the refrigerant evaporates at isothermal and isobaric pressure in the evaporator and completely evaporates. However, when water is mixed, isobaric evaporation continues, but water-containing ammonia raises the boiling point. The temperature difference of heat transfer becomes smaller and the heat exchange amount of the evaporator is reduced. In addition, ammonia and water are completely dissolved and do not effectively use the latent heat of vaporization of the refrigerant. Some of the ammonia and water leave the evaporator without being evaporated, impairing the refrigeration effect on the refrigeration cycle. A stay is essential. FIG. 5 specifically shows the influence of the moisture concentration in the refrigerant on the cooling operation coefficient.
[0004]
[Problems to be solved by the invention]
That is, it can be said that limiting the water concentration in the refrigerant as much as possible is the ultimate problem, and adopting various rectification towers to improve the rectification accuracy has been studied.
On the other hand, the above-mentioned ammonia is designated as a toxic and flammable gas by the High Pressure Gas Safety Law. For safety measures, to minimize the refrigerant (ammonia) filling amount in the equipment and to improve the quality control in production. Therefore, it is necessary to stop the field work as much as possible and to make a package product at the factory. However, as described above, the height of the product is limited only by the rectifier, and complete packaging is difficult for reasons of transportation. Therefore, even if the precision of rectification is increased, a means that does not cause an increase in the size of the apparatus is required.
Also, the tray (shelf) of the rectification column theoretically reduces the bubble size of the bubbling as much as possible so that gas-liquid mixing is well mixed, and increases the amount of the reflux liquid retained on the tray. Thus, it is considered that by increasing the gas-liquid contact efficiency, it is possible to provide a low-cost one that can be handled under a wide range of operating conditions. There are two types of trays in the rectification column: perforated plate type and bubble bell type. The former has the advantage that the safe operation range is narrow but the structure is simple. It has been used for many years in order to obtain high but stable operation over a wide range. In the present invention, in order to reduce the size of the apparatus, the perforated plate mold is focused on and the rectification accuracy is improved.
The operation behavior of the perforated plate type rectification column is that when the feed rate and the reflux ratio are changed, the amount of liquid and the amount of steam in the rectification column are also changed. When the ping) phenomenon occurs and the amount of steam increases extremely, a flooding phenomenon is observed in which the liquid on the shelf is pushed up to the top (freeboard) part. FIG. 6 shows this relationship. Weeping (channeling) indicates the lower limit of steam volume (point A), and flooding indicates the upper limit (point B). The range between these ranges allows the rectification column to operate stably (stable operating range). Is shown. However, in order to set a large amount of the reflux liquid held on the tray, the holes must be set small, and the pressure loss when passing the steam to be refluxed through the tray becomes large, making it difficult to operate the rectification column. Therefore, there is a drawback that the rectification accuracy is lowered, and if the hole is set to be large so as to reduce the pressure loss, the weeping is likely to occur, and this also causes a decrease in the rectification accuracy.
[0005]
The problem of the stable operation range as described above is not limited to the rectification apparatus used for the ammonia absorption refrigerator, but is widely related to various rectification apparatuses used for alcohol distillation, ammonia distillation, and the like. is there.
[0006]
Accordingly, an object of the present invention is to improve the rectification efficiency and reduce the size, and further suppress the liquid leakage (weeping) phenomenon that occurs at a low load and enable a stable operation over a wide range. Is to provide.
[0007]
[Means for Solving the Problems]
In order to achieve this object, the characteristic configuration of the aqueous rectification apparatus according to the present invention has an inflow part for allowing the reflux liquid to flow in from above and an outflow part for causing the staying reflux liquid to flow downward. A plurality of shelf steps that guide and flow downward from above are arranged in multiple upper and lower stages, and a number of holes that allow the inflow of steam from below are provided in the reflux liquid that stays in the shelf steps, and the reflux liquid that remains In a water-based rectification device that generates higher-boiling-point steam from a low-boiling component aqueous solution and rectifies the low-boiling component from
At least the hole inner wall surface of the shelf step portion, preferably the hole inner wall surface and the upper / bottom surface of the shelf step portion are formed to be water repellent,
It is desirable that the shelf step portion is formed from a plate-like body processed by fluororesin coating.
[0008]
Further, the fluororesin is made of at least one selected from the group consisting of poly (tetrafluoroethylene), poly (trifluoroethylene), poly (chlorotrifluoroethylene), polyethylene, and polypropylene, It is more preferable than the following effects.
[0009]
Furthermore, in the aqueous rectification apparatus of the present invention, the low boiling point component is ammonia, and it is preferable to be used as an ammonia rectification apparatus of an ammonia absorption refrigerating machine from the following effects.
[0010]
[Function and effect]
In other words, the circulating liquid that uses the hole as a flow-down swells downward while contacting the inner wall of the hole and grows into a spherical droplet. This droplet grows greatly, and weaving occurs when the action of its own weight wins in the relationship between the surface tension that tries to stop on the reflux liquid side and its own weight that tries to drop downward. At this time, in the conventional normal configuration, the droplet to be grown propagates to the inner wall surface of the hole and starts to grow in a spherical shape from the bottom side edge of the shelf step portion. Therefore, this droplet can grow up to a diameter larger than the diameter of the hole, and can easily be bent to gravity corresponding to the thickness of the reflux liquid and easily fall down ( (See FIG. 3). On the other hand, if the surface of the shelf step portion is formed to be water repellent, the droplets that swell downward are repelled when trying to contact the inner wall of the hole, In order to suppress the growth to swell and to grow to the extent that it falls by its own weight, a greater force is required than in the conventional normal configuration. Therefore, compared with the conventional one, even if a large amount of gravity is applied from the reflux liquid existing above the droplet, the droplet is less likely to fall downward, and in short, the reflux liquid can be held deeply (see FIG. 2). (That is, it can be said that the transition from the state of FIG. 2b to the state of FIG. 2c is difficult.) Therefore, even if the amount of steam that the steam tries to pass from the lower side to the upper side decreases, Weeping is less likely to occur, so that gas-liquid contact is reliably performed and rectification accuracy can be improved.
[0011]
In addition, the water-repellent shelf portion only needs to have at least the inner wall surface of the hole formed to be water-repellent, but it is more preferable that the whole is formed to be water-repellent. This is because, assuming that the grown droplets are continuously dropped, the mist adhering to the bottom side is integrated with the droplets when the bottom of the shelf is water-repellent. This is because the situation in which the liquid drops easily can be prevented, and when the upper surface is water-repellent, the action of pushing the droplets upward can be made higher.
[0012]
In order to form the shelf step portion with water repellency, means such as forming the shelf step portion from a material having excellent water repellency such as fluororesin or water repellency processing of the shelf step portion can be adopted. Employing the water repellent processing method is effective because various general-purpose materials can be formed with water repellency and the shelf can be configured easily and inexpensively. Among these, when it is composed of one or more selected from the group consisting of poly (tetrafluoroethylene), poly (trifluoroethylene), poly (chlorotrifluoroethylene), polyethylene, and polypropylene, these are water at room temperature. The contact angle is as large as 90 ° or more, and the ability to suppress the droplet from trying to pass through the hole is particularly high. Therefore, the above-described effects of the present invention can be obtained more remarkably.
[0013]
In addition, when using the aqueous | water-based rectification apparatus of this invention for an ammonia absorption refrigerator, it can respond to the request | requirement of high purity as mentioned above, and the request | requirement of size reduction, and becomes an especially preferable embodiment.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
The water-based rectification apparatus of the present invention is provided with a large number of holes 12 that allow the inflow of steam from below into the recirculating liquid that remains, and the inflow part 13 through which the recirculating liquid flows from above, and the recirculating liquid that remains below flows down. The rectifying column 4 is provided with a shelf 11 for generating steam having a higher concentration of low-boiling components from the recirculating liquid that is retained, and is provided in multiple stages in the rectifying column 4 to lower the low-boiling components from the low-boiling component aqueous solution. Rectified.
Such a rectification apparatus generates steam having a lower boiling point component concentration higher than the reflux liquid composition from the reflux liquid retained in the shelf section 11, and moves upward from the bottom surface 11 a to the reflux liquid retained in the upper shelf section 11. By making gas-liquid contact and dissolving (absorbing) while passing through, the reflux liquid composition having a higher low-boiling component concentration as the upper stage is formed, and high-purity low-boiling-component vapor is distilled from the top of the tower. It has the function of rectifying the low boiling point component from the low boiling point component aqueous solution while repeating such mass transfer and heat transfer between the reflux liquid and the rising vapor. Therefore, the present invention can be applied to any structure as long as the multi-stage rectification column 4 having such a function is provided, and the number of stages and the shape of the tower are not particularly limited.
[0015]
A part of the low boiling point component condensed in the fractionator 5 is refluxed at the top of the rectifying column 4. By adjusting the amount of the liquid (reflux ratio), the purity and separation efficiency of the low boiling point component are adjusted. Etc. can be adjusted.
[0016]
An evaporation means is provided at the bottom of the rectifying column 4, but usually a reboiler is provided outside to supply the evaporated vapor into the rectifying column 4 and discharge the unevaporated components as bottoms. It has a structure. When used in an ammonia absorption refrigerator, an evaporating can is provided at the bottom of the rectifying tower so that the vapor rises into the rectifying tower and supplies unevaporated components to the absorber 2. (See FIG. 4). At this time, you may provide the heat exchanger 8 which preheats undiluted | stock solution with a bottoms.
[0017]
The water-based rectification apparatus of the present invention is such that the shelf step portion 11 provided in multiple stages is subjected to water repellent finishing on the entire surface. That is, the bottom surface 11a, the top surface 11c of the shelf step portion 11 and the inner wall surface 11b of the hole portion 12 are all water-repellent.
[0018]
In consideration of water repellency, the water repellent finish is made of at least one selected from the group consisting of poly (tetrafluoroethylene), poly (trifluoroethylene), poly (chlorotrifluoroethylene), polyethylene, and polypropylene. It is preferable to use In particular, it is preferable to use a material (resin or the like) having a contact angle with water at room temperature of 60 ° or more for such a water repellent process.
[0019]
Moreover, the hole diameter of the hole 12 provided in the shelf step part 11 should just be a grade which does not permeate | transmit a vapor | steam more than a certain amount and does not produce a weeping. Degree. Moreover, it is preferable that the pitch of the individual hole portions 12 is about 15 mm and the aperture ratio is adjusted to about 7 to 10%.
This water-repellent finish can hold up to about 2 mm of the reflux liquid that was hardly held in the rectifying column in the past, achieving extremely high gas-liquid contact efficiency even at low loads. I understood that I could do it.
The aqueous rectification apparatus of the present invention is not a problem limited to the rectification apparatus used in the ammonia absorption refrigerator, but widely used in various rectification apparatuses used for distillation of low-boiling components such as alcohol or ammonia distillation. Can do.
[Another embodiment]
In the previous embodiment, the shelf step was water-repellent and the inner wall surface of the hole was formed to be water-repellent. However, the material constituting the shelf step itself may be water-repellent, The shelf step portion may be formed by molding a water-repellent fiber material or the like.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view of a rectifying column showing an embodiment of the present invention. FIG. 2 is an explanatory view showing the state of occurrence of weeping in the present invention. FIG. 3 is an explanatory view showing the state of occurrence of conventional weeping. Fig. 4 is an explanatory diagram showing the ammonia absorption refrigeration cycle. Fig. 5 is a graph showing the effect of the moisture concentration in the refrigerant on the cooling performance coefficient. Fig. 6 is an explanatory diagram showing the operation behavior of the rectification column. Explanation】
11 Shelf Step 11a Bottom 12 Hole

Claims (4)

It has an inflow part that allows the reflux liquid to flow in from above, and an outflow part that causes the staying reflux liquid to flow down, and is provided in multiple upper and lower stages by providing a plurality of shelf steps that guide and flow the reflux liquid downward. In addition, a large number of holes that allow the inflow of steam from below to the reflux liquid staying on the shelf portion are provided, and steam having a higher low boiling point component concentration is generated from the staying reflux liquid to reduce the low boiling point aqueous solution. An aqueous rectification device for rectifying boiling components,
An aqueous rectification apparatus in which at least the inner wall surface of the hole of the shelf step portion is water-repellent. An aqueous rectification apparatus in which the inner wall surface and the upper / bottom surface of the hole of the shelf step portion are formed to be water repellent. The water-based rectification apparatus according to claim 1, wherein the shelf step portion is formed from a plate-like body that is coated with a fluororesin. The water-based rectification apparatus according to any one of claims 1 to 3, wherein the low-boiling component is ammonia and is used as an ammonia rectification apparatus for an ammonia absorption refrigerator.

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