JP3683054B2 - Water-based rectification equipment - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an aqueous rectification apparatus used for ammonia absorption refrigerators, alcohol rectification, and the like, and more specifically, a bottom surface portion that allows inflow of steam from below into a recirculating liquid that stays, and a recirculating liquid from above. An inflow part to be flowed and an outflow part to flow down the reflux liquid staying downward, and a stage part for generating steam having a higher low boiling point component concentration from the staying reflux liquid in a rectification column. The present invention relates to an aqueous rectification apparatus for rectifying a low boiling point component from a low boiling point component aqueous solution.
[0002]
[Prior art]
As a conventional ammonia absorption refrigeration cycle, the one shown in FIG. 1 is common. That is, the ammonia vapor evaporated in the evaporator 1 under the pressure Pe is absorbed by the aqueous ammonia solution so as to be maintained at the evaporation pressure Pe 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. 2 specifically shows the influence of the moisture concentration in the refrigerant on the cooling operation coefficient.
[0004]
[Problems to be solved by the invention]
In the above cycle, when evaporation occurs in the rectification tower, evaporation bubbles and vapor lumps are generated inside the liquid by heating, and vapor bubbles burst on the liquid surface and in the vicinity of the liquid surface. At that time, the generated droplets have a particle size distribution having peaks of a droplet having a small particle size (about 20 μm) and a droplet having a relatively large particle size (about 480 μm) as shown in FIG.
[0005]
If droplets (mist) containing impurities that have not evaporated yet are entrained in the vapor of high purity components, the purity of the liquid obtained by condensing the vapor will decrease, so the entrainment of this mist will occur on the top of the evaporation surface. It is necessary to keep the vapor velocity rising in the space (hereinafter referred to as “free board part”) below the final particle velocity (Vt: m / sec) obtained by the following equation.
Vt = (4 × g × Dp × (ρp−ρ) / (3 × ρ × C) ^0.5
Where Dp: particle diameter of mist (m), g: acceleration of gravity (m / sec ² ),
ρp: density of mist (kg / m ³ ), ρ: density of steam (kg / m ³ ),
C: resistance coefficient
In addition to entraining in the vapor of the particle mist, the mist may jump when the bubbles burst on the liquid surface, and the impurities may be transported to the upper stage. In order to prevent this, the caliber and height of the free board and the number of stages of the rectifying column are increased to cope with this problem. However, in order to reduce the size of the apparatus, a demister such as reverse separation or wire mesh is adopted. However, in such a demister, a large mist can be easily separated, but a fine mist has a small mass and a small inertial force. In addition, the height of the free board section and the number of stages of the rectifying tower must be increased to some extent, which prevents the downsizing of the apparatus, and must be a tall rectifying tower.
[0007]
On the other hand, ammonia is designated as a toxic and flammable gas by the High Pressure Gas Control Law, and for safety measures, to minimize the amount of refrigerant (ammonia) charged in the device, and to improve production quality control, It is necessary to stop the field work as much as possible and 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 transportation reasons.
[0008]
Further, as shown in FIG. 4, there are two types of trays (shelf steps) of the rectification tower: a perforated plate type and a bubble bell type. The former has a simple structure but a narrow safe operating range, and the latter has been used for many years because of its complicated structure and high cost but stable operation over a wide range. There are merits and demerits of various trays designed to compensate for these drawbacks.
The operation behavior of the rectification column is that if the feed rate and the reflux ratio are changed, the amount of liquid and vapor in the rectification column will also be changed. ) When the 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. 5 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.
In addition, the rectifying column tray can be used under a wide range of operating conditions by minimizing the bubble size of the bubbling to improve gas-liquid mixing to improve gas-liquid contact efficiency and minimize entrainment. In addition, a low cost is desired.
[0009]
In addition, the problem of the rectification efficiency fall by the mist droplet entrainment as mentioned above and the stable operation range is not limited to the rectification apparatus used for the ammonia absorption refrigerator, but various kinds used for alcohol distillation, ammonia distillation, etc. This is a problem widely related to the rectification apparatus.
[0010]
Therefore, the object of the present invention is to prevent entrainment of mist, increase the rectification efficiency and reduce the size, and further suppress the liquid leaking (weeping) phenomenon that occurs at low loads, enabling stable operation over a wide range. It is to provide an aqueous rectification apparatus.
[0011]
[Means for Solving the Problems]
In order to achieve this object, the characteristic configuration of the present invention includes a bottom surface portion that allows inflow of steam from below into the staying reflux liquid, an inflow section through which reflux liquid flows from above, and the reflux liquid staying down. The rectifying column is provided with a multi-stage shelf section for generating steam having a higher low-boiling component concentration from the reflux liquid that has flowed down, and the low-boiling component is purified from the low-boiling component aqueous solution. In the aqueous rectification device
A hydrophobic porous membrane is provided at a position where the space between the shelf steps provided in multiple stages is vertically divided, or a hydrophobic porous membrane is provided on the bottom surface of the shelf steps provided in multiple stages. It is in the point which is arranged.
In the case of the latter, it is more preferable than the effect mentioned later that the bottom face part of the said shelf step part is comprised with the hydrophobic porous membrane supported on the support body.
[0012]
The hydrophobic porous membrane is made of at least one selected from the group consisting of poly (tetrafluoroethylene), poly (trifluoroethylene), poly (chlorotrifluoroethylene), polyethylene, and polypropylene. Is more preferable than the following effects.
[0013]
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.
[0014]
[Function and effect]
That is, the hydrophobic porous membrane is disposed at a position that vertically partitions the space between the shelf steps provided in multiple stages, or on the bottom surface of the shelf steps provided in multiple stages. While the hydrophobic porous membrane prevents the transmission of low-purity mists (droplets) while allowing only high-purity vapor components to pass through, the purity of the liquid obtained by condensing the vapor is also low. Since it becomes high, the rectification efficiency of the whole rectification apparatus can be improved. In addition, the hydrophobic porous membrane itself does not take up installation space due to its small thickness, can prevent the drop in purity due to splashing of the droplets, which has been a problem in the past, and can increase the capacity by increasing the vapor velocity. Therefore, it is not necessary to increase the height and the number of stages of the free board section, and the rectification tower can be reduced in height by reducing the height. Further, with respect to flooding, the hydrophobic porous membrane can prevent flooding from being pushed up to the upper shelf, thereby preventing flooding.
[0015]
In the case where the bottom portion of the shelf step is formed of a hydrophobic porous membrane supported on a support, since the hydrophobic porous membrane does not allow permeation of the reflux liquid, the reflux liquid staying on the shelf step is hydrophobic. The liquid does not fall through the porous porous membrane, and even if the amount of vapor is extremely reduced, no liquid leakage (weeping) phenomenon occurs. In addition, vapor permeates through the hydrophobic porous membrane to disperse relatively uniformly and generate very small bubbles, resulting in high gas-liquid contact efficiency and purity due to passage of undissolved vapor into the staying liquid. A decrease can be prevented.
[0016]
When the hydrophobic porous membrane is composed of one or more selected from the group consisting of poly (tetrafluoroethylene), poly (trifluoroethylene), poly (chlorotrifluoroethylene), polyethylene, and polypropylene, Since the contact angle with water at room temperature is as large as 90 ° or more, and the ability to transmit only the vapor component while preventing the transmission of mist (droplets) is particularly high, the above-described effects of the present invention can be obtained more remarkably. It is done.
[0017]
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.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
The water-based rectification apparatus of the present invention includes a bottom surface portion that allows inflow of steam from below into a staying reflux solution, an inflow portion that allows reflux solution to flow from above, and an outflow portion that causes the reflux solution staying downward to flow down. The shelf part for generating higher vapor having a low boiling point component concentration from the refluxing liquid that is retained is provided in multiple stages in the rectification column to rectify the low boiling point component from the low boiling point component aqueous solution. .
Such a rectifying device generates a low-boiling component concentration vapor higher than the reflux liquid composition from the reflux liquid retained in the shelf, and dissolves the reflux liquid retained in the upper shelf through the bottom surface. (Absorption) is used to make a low-boiling component concentration higher in the reflux liquid composition in the upper stage, and to distill high-purity low-boiling-component vapor from the top of the column. It has a function of rectifying a low boiling point component from a low boiling point component aqueous solution while repeating mass transfer and heat transfer. Therefore, the present invention can be applied to any structure as long as it has a multi-stage rectification tower having such a function, and the number of stages and the shape of the tower are not particularly limited.
[0019]
Examples of the shelf step include a perforated plate type and a bubble bell type, but in consideration of cost, a perforated plate type is preferable, and a hydrophobic portion in which the bottom portion of the shelf step portion is supported on a support as described above is particularly preferable. It is comprised with a porous film.
[0020]
A part of the low boiling point component condensed by the partial condenser is refluxed at the top of the rectifying column. By adjusting the amount of liquid (reflux ratio), the purity of the low boiling point component, the separation efficiency, etc. can be improved. Can be adjusted.
[0021]
Evaporation means is provided at the bottom of the rectification column. Usually, a reboiler is provided outside, and the evaporated vapor is supplied into the rectification column and unvaporized components are discharged as bottoms. It has become. When used in an ammonia absorption refrigerator, an evaporator is provided at the bottom of the rectifying tower, and the vapor rises into the rectifying tower and supplies the unevaporated components to the absorber. (See FIG. 1). At this time, a heat exchanger for preheating the stock solution with the bottoms may be provided.
[0022]
In the water-based rectification apparatus of the present invention, in the above, a hydrophobic porous membrane is disposed at a position where the space between the shelf steps provided in multiple stages is vertically divided, or the multiple stages are provided. A hydrophobic porous film is disposed on the bottom surface of the shelf step.
[0023]
As described above, the hydrophobic porous membrane used is composed of one or more selected from the group consisting of poly (tetrafluoroethylene), poly (trifluoroethylene), poly (chlorotrifluoroethylene), polyethylene, and polypropylene. Those having a contact angle with water at room temperature of 60 ° or more can be used as long as they are water repellent.
[0024]
Further, the pore diameter of the hydrophobic porous membrane is not limited so long as it allows vapor to pass through to some extent and does not allow mist components to permeate. Specifically, although it depends on the hydrophobicity, it is about 0.001 to several hundred μm. .
As described above, various types of hydrophobic porous membranes having high water repellency and gas permeability are commercially available, but after pressing the polytetrafluoroethylene powder, it is rapidly A hydrophobic porous membrane (trade name Goretec), which is stretched and has a pore diameter of 0.02 to 15 μm and a porosity of 25 to 95%, has particularly high water repellency and gas permeability. Preferably used.
[0025]
FIG. 6 and FIG. 7 specifically show how the hydrophobic porous membrane is arranged. Hereinafter, each embodiment will be described with reference to the drawings.
[0026]
The rectifying column shown in FIG. 6 has a hydrophobic porous membrane 12 arranged at a position where the space between the shelf steps 11 provided in multiple stages is vertically divided. The shelf portion 11 includes a bottom surface portion 11a that allows inflow of steam from below into the recirculating liquid that stays, an inflow portion 11b that allows the recirculating liquid to flow in from above, and an outflow portion 11c that causes the recirculating liquid that stays down to flow down. And a higher vapor having a low boiling point component concentration is generated from the staying reflux liquid. In the present embodiment, the hydrophobic porous membrane 12 is disposed so as to be inclined, but this is for the purpose of efficiently flowing the attached droplets to one side. Moreover, what is necessary is just to support the hydrophobic porous membrane 12 with a support body as needed.
In this way, by disposing the fluid in the free board section above the evaporation liquid surface of the rectification tower, the fluid is allowed to pass through this membrane, so that mist contained in the fluid and droplets caused by splashing are prevented, and only the vapor is in the upper stage. High rectification efficiency is obtained with a short freeboard.
[0027]
The rectifying column shown in FIG. 7 has a hydrophobic porous membrane 12 arranged on the bottom surface of a multi-stage shelf 11, and the bottom 11 a is on a support (for example, a wire mesh or the like). ) Is supported by the hydrophobic porous membrane 12. In the same manner as described above, the shelf portion 11 causes the bottom surface portion 11a that allows the inflow of steam from below to the staying reflux liquid, the inflow portion 11b that allows the reflux liquid to flow from above, and the reflux liquid that stays downward. An outflow part 11c is generated and steam having a higher low boiling point component concentration is generated from the staying reflux liquid.
By arranging the hydrophobic porous membrane in this way, it is possible to prevent mist containing impurities and droplets from entering from the lower stage, and vapor penetrates the membrane relatively uniformly and generates very small bubbles. Thus, high gas-liquid contact efficiency can be obtained. In addition, when the flow rate of the steam is extremely reduced, the conventional perforated plate causes the liquid to flow down from the hole (weeping). This membrane has an inherent water-repellent function. Without occurring, stable operation over a wide range is possible.
[0028]
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.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram showing an ammonia absorption refrigeration cycle. FIG. 2 is a graph showing the effect of the moisture concentration in the refrigerant on the cooling performance coefficient. FIG. 3 is a droplet generated when evaporation occurs in the rectification column. FIG. 4 is a schematic view showing a typical shelf portion of the rectification column. FIG. 5 is an explanatory view showing the operation behavior of the rectification column. FIG. 6 is an embodiment of the present invention. FIG. 7 is a longitudinal sectional view of a rectifying column showing an embodiment of the present invention.
11 shelf step part 11a bottom part 12 hydrophobic porous membrane

Claims (5)

The bottom of the recirculating liquid that allows the inflow of steam from below, the inflow part that allows the recirculating liquid to flow from above, and the outflow part that causes the recirculating liquid that stays downward to flow down. A shelf that generates higher steam with a low boiling point component concentration from
A water-based rectification apparatus for rectifying low-boiling components from a low-boiling component aqueous solution in multiple stages in a rectification tower,
An aqueous rectification apparatus in which a hydrophobic porous membrane is disposed at a position where a space between the shelf steps provided in multiple stages is vertically divided. The bottom of the recirculating liquid that allows the inflow of steam from below, the inflow part that allows the recirculating liquid to flow from above, and the outflow part that causes the recirculating liquid that stays downward to flow down. A shelf that generates higher steam with a low boiling point component concentration from
A water-based rectification apparatus for rectifying low-boiling components from a low-boiling component aqueous solution in multiple stages in a rectification tower,
An aqueous rectification apparatus in which a hydrophobic porous membrane is disposed on the bottom surface of the shelf step provided in multiple stages. The water-based rectification apparatus according to claim 2, wherein a bottom surface portion of the shelf step portion is composed of a hydrophobic porous membrane supported on a support. 2. The hydrophobic porous membrane is made of one or more selected from the group consisting of poly (tetrafluoroethylene), poly (trifluoroethylene), poly (chlorotrifluoroethylene), polyethylene, and polypropylene. The aqueous rectification apparatus according to any one of -3. The aqueous rectification apparatus according to any one of claims 1 to 4, wherein the low-boiling component is ammonia, and is used as an ammonia rectification apparatus for an ammonia absorption refrigerator.

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