JPH04250801A - Method and apparatus for distillation - Google Patents

Abstract

PURPOSE:To efficiently cool the condenser and to heat the reboiler by separating the feed steam into a gas and liquid, passing the separated liquid through the condenser under a reduced pressure state and passing the steam being at the lower place of the condensation part through the reboiler. CONSTITUTION:The liquid separated with a gas-liquid separator 12 is fed in the condenser cooling path 17 and is introduced into the condenser 20 under a reduced pressure state. Here the liquid evaporates by heat exchange with the distilled fraction. As the liquid evaporates and moves to the upper place of a recovering tower 28, the distilled fraction condenses. The remaining liquid in the bottom place of the recovery tower 28 moves to the reboiler 35 through a path 34 and the steam in the lower place of a condensation tower 16 enters the reboiler 35 through a reboiler heating path 38. By exchanging the heat of the steam with the prescribed liquid in the reboiler 35, the liquid evaporates and returns in the recovery tower 28 through the path 36. Simultaneously the steam is condensed with the reboiler 34 and it is introduced at the top part of the recovery tower 28 together with a condensation tower bottom liquid FWE. The steam FR at the top place of the recovery tower 28 is compressed with a heat pump 29 and is fed to the lower place of the condensation tower 18 together with the feed steam.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for carrying out distillative separation.

0002

2. Description of the Related Art Conventionally known distillation systems are equipped with a distillation column having a concentration section and a recovery section, and the vapor at the top of this distillation column is recondensed in a condenser, and the liquid at the bottom is sent to a reboiler. The introduced steam is distilled while being re-evaporated.

Furthermore, in recent years, in order to reduce the heat load on the condenser and reboiler, a distillation apparatus equipped with two concentrating columns, a concentrating column 90 and a recovery column 93, as shown in FIG. 5, has been proposed. There is.

In the figure, feed vapor is introduced into the lower part of a concentrating column 90, and while rising in the concentrating column 90, a part of it exchanges heat with a recovery column 93 and is cooled and liquefied, and the remainder is sent to a condenser at the top of the column. It is liquefied at 91. A part of it is taken out as a distillate, and the rest returns to the concentration column 90 as a reflux liquid. The bottom liquid of this concentration column 90 is depressurized and then transferred to a recovery column 93.
is supplied to the top of the While descending through the recovery tower 93, a portion of this liquid evaporates through heat exchange with the concentration tower 90, a portion of which evaporates in the reboiler 94 at the bottom of the tower, and the remainder is extracted as bottoms. Further, the vapor at the top of the column is compressed by a compressor 95 and then supplied to the lower part of the concentrating column 90 as a reflux liquid.

[0005]

In the apparatus shown in FIG. 5, the heat load on the condenser 91 and reboiler 94 is reduced by the internal heat exchange between the concentration column 90 and the recovery column 93; is still applied from outside the distillation system, so the heat load remains a non-negligible amount, and further reduction is an issue.

[0006]Furthermore, high-grade energy is also required when compressing the steam in the compressor 95, and if the amount of compressed steam can be reduced, the economical efficiency will be further improved.

In view of these circumstances, the present invention enables the heat load of the condenser and reboiler to be covered by the heat within the distillation system, and more preferably significantly reduces the compression load of the vapor sent from the recovery section to the concentration section. It is an object of the present invention to provide a distillation method and apparatus that can reduce the number of distillations.

[0008]

[Means for Solving the Problems] The present invention introduces feed steam into the lower part of the concentrating section, causes this steam to rise in the concentrating section, and condenses the steam at the upper part of the concentrating section in the concentrating section. At the same time, the liquid at the bottom of this concentration section is introduced under reduced pressure into the top of the recovery section and lowered in this recovery section, and the bottoms are extracted from the bottom of this recovery section. In a distillation method in which the liquid at the bottom is evaporated in a reboiler, and the vapor at the top of the recovery section is pressurized and introduced into the bottom of the concentration section, the feed vapor is separated into gas and liquid. Steam is introduced into the lower part of the concentrating section, and the separated liquid is introduced under reduced pressure into the condenser, where it is evaporated and then introduced into the upper part of the collecting section, while the vapor in the lower part of the concentrating section is introduced into the upper part of the collecting section. It is introduced into the reboiler, where it is liquefied, and then introduced into the upper part of the recovery section (Claim 1).
.

[0009] Here, it is more preferable that the concentration section and the recovery section exchange heat with each other (Claim 2). Further, by extracting the liquid from the concentration section and introducing it into the top of the recovery section, and discharging steam from the top of the recovery section, better effects as described below can be obtained (claims 3).

[0010] Furthermore, the apparatus for realizing the above method includes a concentration section and a recovery section (preferably those that exchange heat with each other), and an introduction section for introducing feed steam into the lower part of the concentration section. a condenser for condensing vapor in the upper part of the concentrating part; a first reflux passage for introducing the liquid at the bottom of the concentrating part into the upper part of the collecting part under reduced pressure; a recovery section for recovering the bottom liquid from the bottom; a reboiler for evaporating the liquid at the bottom of the recovery section; and a reboiler for introducing the steam at the top of the recovery section into the bottom of the concentration section under pressure. a second reflux passage; a separation means for separating the feed vapor into gas and liquid; an introduction passage for introducing the separated vapor into the lower part of the concentration section; A condenser cooling passage for introducing steam into the condenser under reduced pressure, evaporating it here, and introducing it into the upper part of the recovery section; and introducing steam at the lower part of the concentrating section to the reboiler, where it is liquefied and then introduced into the upper part of the recovery section. A reboiler heating passage for introducing into the upper part of the recovery part (claim 4), and further,
Preferably, the device includes a liquid transfer passage for extracting the liquid in the concentration section and introducing it into the top of the recovery section, and a discharge passage for discharging steam from the top of the recovery section (Claim 6). It is.

[0011]

According to the above structure, the liquid separated from the feed vapor is introduced into the condenser and evaporated there, thereby cooling the condenser with its latent heat of vaporization. On the other hand, the steam in the lower part of the concentration section is introduced into the reboiler, where it is liquefied, thereby heating the reboiler with its latent heat of condensation. In other words, the heat sources for the condenser and reboiler are supplied with heat within the device.

Furthermore, by performing heat exchange between the concentration section and the recovery section, the heat load is further reduced by the amount of heat exchange.

[0013] Furthermore, if the liquid is extracted from the concentration section and introduced into the top of the recovery section, and the steam is discharged from the top of the recovery section, when the steam is discharged from the downstream side of the condenser, In comparison, the amount of steam to be pumped from the top of the recovery section to the bottom of the concentration section is reduced.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an example of an apparatus for carrying out the method of the present invention.

This apparatus is equipped with a bottoms evaporator 10, a gas-liquid separator (separation means) 12, a concentration column 16, and a recovery column 28, and a condenser 20 is provided above the concentration column 16. , a reboiler 35 is installed at the bottom of the recovery tower 28.
The towers 16 and 28 are configured to exchange heat with each other (internal heat exchange) via a heat exchange section 30.

In this apparatus, the feed vapor is sent to the bottoms liquid evaporator 10, and a part of it is liquefied as the bottoms evaporates as described below. The remainder is separated into gas and liquid by the gas-liquid separator 12, and the vapor is supplied to the bottom of the concentrating column 16 through the introduction passage 14. This vapor rises within the concentration column 16 while exchanging heat with the recovery column 28, and is sent to the condenser 20 as a distillate fraction.

On the other hand, the liquid separated by the gas-liquid separator 12 enters the condenser cooling passage 17 and is introduced into the condenser 20 under reduced pressure, where it exchanges heat with the distillate fraction to cool the liquid. It is evaporated and introduced into the upper part of the recovery tower 28, and the distilled fraction is condensed. This condensed fraction is returned to the top of the concentration column 16 as a reflux liquid, and the remaining vapor is taken out of the apparatus as a distillate via the discharge passage 24.

The liquid FWE at the bottom of the concentration column 16 is
The vapor that has evaporated through the first reflux passage 27 and the liquid that has passed through the bypass passage 26 that bypasses the condenser 20 is also introduced into the upper part of the recovery column 28. be done.

The steam introduced into the upper part of the recovery column 28 exchanges heat with the concentration column 16 as it descends inside the column, a part of the liquid evaporates, and the bottoms Fw flows from the bottom of the column into the recovery passage. 32 into the bottoms evaporator 10, where it is evaporated and recovered as a bottoms fraction.

The remaining liquid at the bottom of the recovery column 28 is transferred to the passage 34.
It is introduced into the reboiler 35 through. On the other hand, the steam from the lower part of the concentration column 16 is introduced into the reboiler 35 through the reboiler heating passage 38, and as this steam and the liquid exchange heat in the reboiler 35, the liquid The vapor is evaporated and returned to the recovery tower 28 through the passage 36, and the vapor is condensed in the reboiler 34.
The concentrated column bottom liquid FWE is introduced into the top of the recovery column 28.

The steam FR at the top of the recovery tower 28 is compressed by the heat pump 29 and then passed through the second reflux passage 3.
1 and is supplied to the lower part of the concentrating column 18 together with the feed vapor.

As described above, in this method and apparatus, the liquid separated by the gas-liquid separator 12 is sent to the condenser 20, and the condenser 20 is cooled by the latent heat of vaporization.
The steam from the lower part of the concentrating column 16 is sent to the reboiler 35, and the reboiler 35 is heated by the latent heat of condensation, so the condenser 20 and the reboiler 35 are heated by the heat within the system without requiring a special heat source outside the system. can cover the heat load of Further, the temperature of the condenser 20 can be easily adjusted by adjusting the flow rate of the liquid that bypasses the condenser 20, that is, the flow rate of the bypass passage 26.

Next, a second embodiment will be explained based on FIG. 2.

In the first embodiment, vapor is discharged as a distillate from the outlet of the condenser 20, but in this embodiment, the portion above the vapor extraction position in the upper part of the recovery tower 28 is An evaporation section 42 is provided in the evaporation section 42, and the liquid at the upper part of the concentration column 16 is introduced into the top of the evaporation section 42 through the liquid transfer passage 44, and the remaining vapor FD is discharged from the top of the evaporation section 42 through the discharge passage 24. That's what I do. Further, a heat pump 29 and an aftercooler 46 are arranged in series in the second reflux passage 31, and the upstream passage and the downstream passage are configured to mutually exchange heat through a heat exchanger 48.

According to such a method and apparatus, compared to the case where steam is discharged from the outlet of the condenser 20 as shown in FIG. The amount of steam required to be compressed is reduced, thereby reducing the compression energy requirements of the entire system.

FIG. 3 is a graph showing the relationship between the light fraction concentration of the feed and the heat pump flow rate in the apparatus shown in FIGS. 1 and 2 for a two-component system of nitrogen and oxygen. In the figure, a broken line 60 indicates a relationship determined by a theoretical formula for the device shown in FIG. 1, a solid line 62 indicates a relationship determined by a theoretical formula for the device shown in FIG. , shows the relationship determined by computer simulation for the device shown in FIG. As can be seen from this figure, in both devices, the heat pump flow rate decreases as the light distillate concentration increases, but the decrease in the heat pump flow rate in the device in Figure 2 is more pronounced than in the device in Figure 1. This suggests that distillation can be performed with less energy.

FIG. 4 also shows the ratio E2/E1 of the energy consumption E2 in the device of FIG. 2 to the energy consumption E1 of the device of FIG. 1 when the device of FIG. 1 and the device of FIG. 2 are operated under equal pressure. , and the ratio L2/L1 of the required compression energy L2 in the device of FIG. 2 to the required compression energy L1 in the device of FIG. 1 are shown by a broken line 66 and a solid line 68, respectively. As is clear from this figure, when the light fraction concentration is in the range of 20% to 80%, the energy consumption ratio E2/E1 of both devices is almost 1, that is, the required energies E2 and E1 are almost equal, whereas the compression The required energy ratio L2/L1 decreases significantly with increasing light fraction concentration. This shows that the higher the light fraction concentration, the smaller the proportion of energy that the apparatus of FIG. 2 spends on vapor compression, and the more efficiently the energy is used for separation.

The fact that such a result is obtained can also be predicted by comparing the energy of the steam FD discharged in both devices. That is, in the device shown in FIG. 1, relatively high pressure steam coming out of the condenser 20 is discharged, whereas in the device shown in FIG. 2, low pressure steam from the top of the recovery tower 28 is discharged. It can be seen that the pressure difference between the two vapors, that is, the energy difference, is effectively consumed as is as energy for distillation in the apparatus shown in FIG.

In each of the above embodiments, heat exchange is performed between the concentration column 16 and the recovery column 28, but
In the method and apparatus of the present invention, it is possible to significantly reduce the heat load compared to conventional methods and apparatuses even without such heat exchange. However, it goes without saying that if the heat exchange described above is performed, the heat load will be further reduced.

The substance to be distilled in the present invention is not particularly limited in type, and the present invention can be applied to various substances that are distilled in conventional distillation apparatuses.

[0031]

[Effects of the Invention] As described above, the present invention has a condensing section and a recovery section, and a condenser and a reboiler are disposed above the concentrating section and below the recovery section, respectively, in which the feed vapor is separated into gas and liquid. , introducing the separated vapor into the lower part of the concentration section, and introducing the separated liquid into the upper part of the recovery section after passing it through the condenser under reduced pressure,
In addition, since the steam in the lower part of the concentrating section is passed through the reboiler and then introduced into the upper part of the recovery section, the heat within the system is used to reduce the This has the effect of extremely efficiently cooling the condenser and heating the reboiler.

Furthermore, by extracting the liquid from the concentration section and introducing it into the top of the recovery section, and discharging the steam from the top of the recovery section, the steam can be discharged in a lower energy state. This has the effect of allowing efficient distillation to proceed with less energy.

[Brief explanation of the drawing]

FIG. 1 is an overall configuration diagram of a distillation apparatus in a first embodiment of the present invention.

FIG. 2 is an overall configuration diagram of a distillation apparatus in a second embodiment of the present invention.

FIG. 3 is a graph showing the relationship between the light distillate concentration of the feed and the heat pump flow rate in each of the above devices.

FIG. 4 is a graph showing the relationship between the light distillate concentration of the feed in each of the devices and the required energy ratio and consumed energy ratio of both devices.

FIG. 5 is an overall configuration diagram showing an example of a conventional distillation apparatus.

[Explanation of symbols]

12 Gas-liquid separator (separation means) 14 Introduction passage 16 Concentration column 17 Condenser cooling passage 20 Capacitor 24 Discharge passage 27 First reflux passage 28 Collection tower 31 Second reflux passage 32 Collection passage 35 Reboiler 38 Reboiler heating passage 42 Evaporation section 44 Liquid transfer passage

Claims (6)

[Claims] Claim 1: Feed vapor is introduced into the lower part of the concentrating section, the vapor is raised in the concentrating section, and the vapor at the upper part of the concentrating section is condensed in a condenser and lowered in the concentrating section, and the vapor is raised in the concentrating section. The liquid at the bottom of the recovery section is introduced under reduced pressure into the top of the recovery section and lowered in this recovery section, the bottom liquid is extracted from the bottom of this recovery section, and the liquid at the bottom of this recovery section is evaporated in a reboiler. In addition, in a distillation method in which the vapor in the upper part of the recovery part is pressurized and introduced into the lower part of the concentrating part, the feed vapor is separated into gas and liquid, and the separated vapor is introduced into the lower part of the concentrating part. At the same time, the separated liquid is introduced under reduced pressure into the condenser, where it is evaporated and then introduced into the upper part of the recovery section, while the vapor in the lower part of the concentration section is introduced into the reboiler, where it is evaporated. A distillation method characterized in that the liquefaction is introduced into the upper part of the recovery section. 2. The distillation method according to claim 1, wherein heat exchange is performed between the concentration section and the recovery section. 3. The distillation method according to claim 1 or 2, wherein the liquid is extracted from the concentration section and introduced into the top of the recovery section, and vapor is discharged from the top of the recovery section. Distillation method. 4. A concentrating section and a recovery section, an introduction section for introducing feed steam into the lower part of the concentrating section, a condenser for condensing the vapor at the upper part of the concentrating section, and a condenser at the bottom of the concentrating section. a first reflux passage for introducing the liquid into the upper part of the recovery section under reduced pressure, a recovery section for recovering the bottom liquid from the bottom of the recovery section, and evaporating the liquid at the bottom of the recovery section. and a second reflux passage for introducing the vapor in the upper part of the recovery part into the lower part of the concentrating part in a pressurized state, the separation means for separating the feed vapor into gas and liquid. an introduction passage for introducing the separated vapor into the lower part of the concentration section; and an introduction passage for introducing the separated liquid under reduced pressure into the condenser, where it is evaporated and introduced into the upper part of the recovery section. A distillation apparatus comprising: a condenser cooling passage; and a reboiler heating passage for introducing the vapor in the lower part of the concentration section into the reboiler, where it is liquefied and introduced into the upper part of the recovery section. 5. The distillation apparatus according to claim 4, wherein the concentration section and the recovery section are configured to exchange heat with each other. 6. The distillation apparatus according to claim 4 or 5, comprising: a liquid transfer passage for extracting the liquid in the concentrating section and introducing the extracted liquid into the top of the recovery section; and discharging steam from the top of the recovery section. A distillation apparatus characterized by comprising a discharge passage for.