JPH04326901A - Solvent recovery apparatus - Google Patents

Abstract

PURPOSE:To recover a solvent without using an adsorbing material based on a novel theory due to the condensation and freezing of the solvent and to also recover a solvent with a high b.p. in high recovery. CONSTITUTION:First and second coolers 2, 3 are parallelly arranged to the post stage of a first cooler 1 and, at first, solvent-containing gas is cooled by the first cooler 1 and a part thereof is liquefied to be collected in a separator 10. The residual solvent-containing gas is introduced into the second cooler 2 and the solvent in the gas is condensed along with moisture to be frozen. By this method, clean gas 5 is obtained. In the third cooler 3, the solvent and moisture frozen in the previous process are thawn to be collected in the separator 10 as a liquid. The solvent and moisture are separated by this separator 10. For example, a liquid cooling medium of -35 deg.C and a gaseous cooling medium of relatively high temp. (20 deg.C) are alternately passed through the coolers 2, 3 and the coolers 2, 3 repeat the condensation of the solvent-containing gas and the thawing of the frozen matter.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to a solvent recovery device for recovering solvents such as fluorocarbons from gases, and particularly to a solvent recovery device suitable for recovering high-boiling point solvents from gases containing such solvents. Regarding.

0002

[Prior Art] Air containing organic solvents such as fluorocarbons discharged from semiconductor manufacturing equipment, etc. is conventionally purified by separating and removing the contained solvent using a steam regeneration type solvent recovery device or a dry regeneration type recovery device. can do.

[0003] In these solvent recovery devices, a plurality of adsorption towers, for example, a pair, containing a solvent adsorbent such as activated carbon are provided, and air containing the solvent is introduced into one of the adsorption towers to transfer the contained solvent to the adsorption material. Remove by adsorption. Then, the refrigerant that has already been adsorbed in the previous adsorption step is desorbed from the other adsorption tower. That is, in the case of a steam regeneration type solvent recovery apparatus, steam is introduced into the other adsorption tower to heat the adsorbent and desorb the solvent. This regenerates the adsorbent. on the other hand,
In the case of a dry regeneration recovery device, a sheet heater is placed in contact with the adsorbent, and the sheet heater is energized to generate resistance heat to heat the adsorbent, thereby desorbing the solvent.

In either case, the solvent is continuously removed from the gas by selectively and alternately repeating the solvent adsorption process and the desorption (regeneration) process using multiple adsorption towers. and collect it.

[0005]

However, among the solvents used in semiconductor equipment and the like, there are solvents such as fluorocarbons (hereinafter abbreviated as FC) that have a low vapor pressure and a high boiling point. This FC has a boiling point of, for example, 215
℃ and is easily polymerized under the influence of heat.
When activated carbon is used as an adsorbent, there is a drawback that a polymerization reaction is likely to occur due to the energy during its regeneration. Furthermore, since FC has a high boiling point, it tends to wet utensils. For this reason, FC adheres to the inner walls of adsorption towers, piping, etc., and it becomes necessary to recover this adhered FC by means such as hot air or vacuum. In this case, even if this FC can be recovered, the concentration will be low and the recovery efficiency will be low.

[0006] The present invention was made in view of such problems, and does not require the use of adsorbents as in the past.
In other words, the solvent can be recovered based on a new principle of condensation or freezing of the solvent without the process of adsorption and regeneration using an adsorbent, and even solvents with high boiling points can be recovered at a high recovery rate. The purpose is to provide a collection device.

[0007]

[Means for Solving the Problems] A solvent recovery device according to the present invention includes a pre-condensing means for cooling a solvent-containing gas introduced from an external system to condense a part of the contained solvent and recovering it as a liquid, and a 0°C a second-stage condensing means equipped with a plurality of coolers that freeze or liquefy the contained solvent by cooling to the following temperature; and a thawing gas that thaws the gas discharged from the first-stage condensing means and the condensate in the cooler. gas introduction means that selectively and alternately introduces the gas into the cooler of the second-stage condensing means; and liquid separation means that separates the solvent and water from the liquid discharged from the first-stage and second-stage condensing means to recover the solvent. It is characterized by having the following.

[0008]

[Operation] When a solvent has a high boiling point, it tends to turn into a liquid or a condensate by cooling. Therefore, a solvent with a high boiling point can be easily recovered as a liquid. Therefore, in the present invention, first, the solvent-containing gas introduced from the outside system is cooled to, for example, 5° C. by the pre-condensing means. Then, part of the water and solvent in this solvent-containing gas is cooled and condensed, and is recovered as a liquid.

Next, the gas discharged from the pre-condensing means is selectively introduced into the plurality of coolers of the post-condensing means by the gas introducing means. This cooler cools the solvent in the gas to a temperature below the solidification temperature of the solvent, such as -30°C. As a result, the solvent in the gas is frozen together with the moisture and recovered.

[0010] On the other hand, thawing gas at a temperature capable of thawing the frozen material is introduced by the gas introducing means into the cooler in which the solvent and water have already been frozen in the previous process. As a result, the frozen material in this cooler is thawed and the solvent and water are recovered as liquid. Furthermore, since the frozen matter is removed from this cooler, its cooling capacity is restored and the cooler can be used for the next cooling and freezing process.

In the latter stage condensing means, the cooling/freezing process and the thawing process are alternately repeated. Furthermore, when a part of the plurality of coolers is performing the cooling/freezing process, another cooler is performing the thawing process. In this way, the gas discharged from the first stage condensing means is continuously recovered as a liquid by the second stage cooling means. This liquid is separated into a solvent and water by a liquid separation means.

The cooler of the latter stage condensing means may cool the gas at a temperature higher than the solidification temperature of the solvent. In this case, the solvent is recovered as a liquid without freezing. However, since the moisture in the gas freezes and reduces the cooling ability of the cooler, this condensate is removed through a thawing process.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Examples of the present invention will now be described in detail with reference to the accompanying drawings.

FIG. 1 is a block diagram showing a solvent recovery apparatus according to an embodiment in which the present invention is applied to the recovery of fluorocarbon, and FIG. 2 is a block diagram showing the refrigerant piping.

A processing gas 4 containing a solvent is supplied to the first cooler 1 from an external system via a pipe 6 . This gas outlet is connected to the second and third coolers 2 via branch piping 7.
, 3 are connected to the gas inlets. Further, a confluence pipe 8 is connected to the gas discharge ports of the second and third coolers 2 and 3, and the gas 5 purified by the condensers 2 and 3 enters the atmosphere through this confluence pipe 8. is discharged. In the coolers 1 to 3, a solvent-containing gas and a refrigerant are supplied,
The solvent-containing gas is cooled by this refrigerant.

A blower 14 is installed in the pipe 6 , and the processing gas 4 is fed to the first cooler 1 by the blower 14 . Further, the pipe 6 is also provided with an atmosphere release valve 15 . Further, the branch pipe 7 is provided with on-off valves 16 and 17 for switching the flow path of the flowing gas, and by opening and closing the on-off valves 16 and 17, the second and third coolers 2 and 3 are connected. The gas is selectively passed through.

The liquid condensed in the first cooler 1 is transferred to the pipe 1
1 to the separator 10. In addition, the liquid condensed in the second and third coolers 2 and 3 and the liquid that was thawed after being frozen in the second and third coolers 2 and 3 are
They are similarly collected in the separator 10 via pipes 12 and 13, respectively. In this separator 10, water and solvent are separated by gravity, the water is discharged through a drain, and the solvent is collected in a solvent storage tank 18. The solvent liquid in the tank 18 is transferred to an appropriate recovery tank (
(not shown).

Antifreeze is circulated and supplied to the first cooler 1 from an antifreeze tank 20 via a pipe 22 . This piping 22
A pump 24 for feeding antifreeze liquid is interposed therein. In addition, the chiller water is supplied from the chiller unit 21 to a pipe 23 and a pump 25 for feeding the chiller water installed in the pipe 23.
The antifreeze solution is circulated and supplied to the antifreeze tank 20.

FIG. 2 is a diagram showing the flow of refrigerant piping to the second and third coolers 2 and 3. This figure 2 shows that the second cooler 2 carries out the cooling cycle and the third cooler 3
is running a defrost cycle.

Pipes 31a and 31 are connected between one end of the refrigerant flow pipes disposed in the coolers 2 and 3 and the refrigerator 30.
b and a confluence pipe 31. Piping 31a
, 31b are provided with evaporative gas electromagnetic on-off valves 32a, 32b. In addition, an evaporation pressure regulating valve 33 is provided in the pipe 31.
is interposed. The refrigerator 30 compresses the introduced gas into high-temperature gas. A gas outlet of this refrigerator 30,
The one ends of the coolers 2 and 3 are connected to each other by a pipe 34 and branch pipes 34a and 34b. In addition, a hot gas switching electromagnetic on-off valve 3 is provided in the piping 34a, 34b.
5a and 35b are interposed.

A pipe 34 connected to the high temperature gas outlet of the refrigerator 30 is connected to a pipe 36 connected to the condenser 31, so that a part of the gas discharged from the refrigerator 30 is transferred to the condenser. 31. Condenser 3
Cooling water is supplied and flows inside the condenser 1, and the high-temperature gas supplied to the condenser 31 is condensed into a high-temperature liquid. The refrigerant liquefied in the condenser 31 is transferred to the pipe 3
7 and branch piping 37a, 37b, respectively, to the cooler 2.
, 3 is supplied to the other end of the refrigerant flow pipe. A discharge gas bypass electromagnetic on-off valve 38 is interposed in the pipe 36 . Further, a flow rate regulating valve 39 and a refrigerant dryer 40 are interposed in the pipe 37, and the pipes 37a, 37
Cooling circuit switching electromagnetic on-off valves 41a, 41b and temperature-type automatic expansion valves 42a, 42b are interposed in b, respectively. These expansion valves 42a and 42b transfer the liquid refrigerant to the coolers 2 and 3.
The heat of evaporation is used to cool the coolers 2 and 3.
It is designed to cool the solvent-containing gas inside.

Furthermore, the other end of the coolers 2 and 3 is
Piping 36 via piping 43a, 43b and confluence piping 43
The gas after thawing the condensate in the coolers 2 and 3 is supplied to the condenser 31 via pipes 43a, 43b, pipe 43, and pipe 36. Check valves 44a and 44b are installed in the pipes 43a and 43b, respectively, and a condensation pressure regulating valve 45 is installed in the pipe 43.

A differential pressure regulating valve 46 is disposed between the pipe 34 and the pipe 43, and a pressure type water control valve 47 is interposed in the cooling water drain pipe of the condenser 31. The opening degree of this pressure-type water control valve 47 is adjusted by the pressure inside the pipe 34.

Next, the operation of the high boiling point solvent recovery apparatus constructed as described above will be explained. The first stage cooling means
The antifreeze liquid in the antifreeze tank 20 is circulated and supplied to the cooler 1 by a pump 24, so that the solvent-containing gas flowing through the pre-cooler 1 is cooled by the antifreeze liquid. This antifreeze has excellent temperature stability as a refrigerant. The temperature of the antifreeze is detected by a temperature detector (not shown) installed in the antifreeze tank 20, and the chiller unit 21 cools the antifreeze to a constant temperature based on the detected temperature. It looks like this.

On the other hand, the second and third coolers 2 and 3 of the downstream cooling means are cooled as shown in FIG.

First, when the coolers 2 and 3 are performing a cooling cycle and a defrosting (thawing) cycle, respectively, the electromagnetic on-off valves 41a, 32a, 35b, and 44b are opened; , 44a are closed. The relatively high temperature liquid refrigerant supplied from the condenser 31 is dried by the dryer 40 and then injected into the cooling pipe in the cooler 2 from the automatic expansion valve 42a. This refrigerant expands within the cooler 2 and evaporates to cool the solvent-containing gas within the cooler 2. After this refrigerant is discharged from the cooler 2, it is returned to the refrigerator 30 via the evaporation pressure regulating valve 33. This evaporation pressure adjustment valve 33 adjusts the pressure of the refrigerant in the coolers 2 and 3 to set its evaporation temperature (for example, -45°C), thereby keeping the load on the coolers 2 and 3 constant. Hold. In the refrigerator 30, a gaseous refrigerant is compressed, and this refrigerant is converted into a relatively high temperature gas and sent to a condenser 31.
Return to

On the other hand, relatively high temperature refrigerant gas discharged from the refrigerator 30 is also supplied into the cooler 3. and,
After thawing the condensate in the cooler 3, this refrigerant gas is returned to the condenser 31 via the condensation pressure regulating valve 45. This condensing pressure regulating valve 45 regulates the pressure inside the cooler 3 so that the condensing temperature of the refrigerant becomes 20°C.

[0028] In this way, the liquid refrigerant condensed in the condenser 31 is supplied to the cooler 2 carrying out the cooling cycle, and the liquid refrigerant is always evaporated at a constant temperature (-45°C). The solvent-containing gas in the cooler 2 is cooled. On the other hand, in the cooler 3 that is performing a thawing cycle, a relatively high temperature (20° C.) gaseous refrigerant is supplied from the refrigerator 30 to thaw the condensate in the cooler 3. and,
The cooling cycle and the thawing cycle are switched at a predetermined period by switching the electromagnetic on-off valve, and the cooling cycle and the thawing cycle are repeated.

A solvent-containing gas (processing gas 4) discharged from a factory or the like is sent into the cooler 1 by a blower 14. The solvent-containing gas is cooled in the cooler 1 by an antifreeze refrigerant. This causes some of the solvent contained to liquefy,
This liquid solvent is collected in separator 10.

Next, the remaining solvent-containing gas is supplied to the cooler 2 and cooled to, for example, -45°C. As a result, the solvent in the gas condenses together with the moisture and freezes within the cooler 2. In this way, a clean gas 5 from which the solvent has been frozen is obtained. On the other hand, in the cooler 3 where the solvent and moisture have condensed in the previous process, the temperature is relatively high (2
A gaseous refrigerant at a temperature of 0° C.) is passed through, whereby the condensate is thawed and collected as a liquid in the separator 10. The liquid refrigerant collected in the separator 10 from the cooler 1 and the cooler 3 is separated by specific gravity in the separator 10, and the water is discharged as drain water, and the refrigerant is collected in the tank 18 and then recycled. put to use.

Thereafter, after a predetermined period of time has elapsed, the cooler 2 shifts to the thawing cycle, the cooler 3 shifts to the cooling cycle, and the cooler 2
The condensate within is thawed and the solvent and water are collected as liquid in separator 10. On the other hand, the solvent and moisture in the solvent-containing gas are frozen in the cooler 3, and a clean gas 5 from which the solvent has been removed is obtained. In this way, cooler 2
, 3, by alternately performing a cooling cycle and a thawing cycle, the solvent contained in the solvent-containing gas is continuously recovered. Note that the method of this example is used when the boiling point is 21
When applied to the recovery of fluorocarbon solvent at 5°C, the solvent concentration in exhaust air could be reduced to 1 ppm or less.

By freezing the solvent in this way, the gas containing the high boiling point solvent can be recovered without using an adsorbent. Therefore, various drawbacks when recovering high boiling point solvents using conventional adsorbents can be overcome.

[0033] Immediately before transitioning from the thawing cycle to the cooling cycle, the refrigerant from the condenser 31 is supplied to the cooler 2 or 3 that had been performing the thawing cycle. may be cooled. That is,
Just before switching to this cooling cycle, the on-off valves 41a and 41b are simultaneously opened. Thereby, the temperature inside the coolers 2 and 3 that are about to switch to the cooling cycle can be lowered, and the cooling cycle can be performed with high efficiency.

Furthermore, in the present invention, the solvent does not necessarily need to be frozen in the post-cooling means. In the case of a solvent with a higher boiling point than water, the water freezes first upon cooling. However, the solvent can be recovered with sufficiently high efficiency even without freezing.

Furthermore, the condensed material may be thawed by heating with a heater instead of using refrigerant gas.

[0036]

Effects of the Invention According to the present invention, by alternately repeating the cooling and thawing process, a gas containing a solvent with a high boiling point and easily wetted by an adsorbent can be continuously heated to a high temperature without using an adsorbent. It can be collected efficiently. Therefore, the present invention is extremely useful for recovering high-boiling solvent-containing gases.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a solvent recovery device according to an embodiment of the present invention.

FIG. 2 is a schematic diagram showing the cooling piping.

[Explanation of symbols]

1, 2, 3; Cooler, 10; Separator, 20; Antifreeze tank,
30; Freezer, 31; Condenser

Claims (3)

[Claims] Claim 1: A pre-condensing means for cooling a solvent-containing gas introduced from an external system to condense a part of the contained solvent and recovering it as a liquid; a post-condensing means comprising a plurality of coolers;
gas introduction means for selectively and alternately introducing the gas discharged from the first stage condensing means and the thawing gas for defrosting the condensate in the cooler into the cooler of the second stage condensing means; and the first and second stage condensing means. 1. A solvent recovery device comprising: liquid separation means for separating a solvent and water from a liquid discharged from the liquid and recovering the solvent. 2. An automatic expansion valve provided at a refrigerant inlet of a cooler of the second-stage cooling means, the automatic expansion valve injecting liquid refrigerant into the cooler to evaporate it and cooling the inside of the cooler with the heat of evaporation; a refrigerator whose hot gas outlet is connected to a refrigerant outlet side of a cooler of cooling means; an evaporation pressure regulating valve provided between a refrigerant outlet of the cooler and the refrigerator; and a refrigerant of the cooler. It is characterized by having a condensing pressure regulating valve provided between the inlet side and the condenser, and a valve means for alternately switching between the flow of the refrigerant and the flow of the hot gas to the cooler. The solvent recovery device according to claim 1. 3. A bypass valve used during steady cooling operation is provided between the outlet of the refrigerator and the outlet of the condenser;
3. The solvent recovery device according to claim 2, further comprising a differential pressure regulating valve used during parallel operation of the cooling step and the thawing step.