JP4786593B2 - VOC cooling recovery equipment - Google Patents

Description

  The present invention relates to a cooling and recovery device for liquefying and recovering this VOC gas when a volatile organic compound (VOC) is a gas.

VOC is an organic compound that is volatile and is gaseous in the atmosphere, and includes various substances such as toluene, xylene, ethyl acetate, and decane.
VOC gas containing gaseous VOC is discharged in various facilities such as paint-related facilities, adhesive drying facilities, printing-related facilities, chemical product manufacturing facilities, and industrial cleaning facilities. However, VOC is a cause of suspended particulate matter (SPM) and photochemical oxidant, and in recent years, its emission is required to be suppressed from the viewpoint of preventing air pollution.

Therefore, in order to recover the discharged VOC gas, a gas recovery device for cooling the VOC gas to condense and liquefy it is conventionally known (for example, see Patent Document 1 and Patent Document 2).
Hereinafter, based on FIG. 2, the structure of the gas collection | recovery apparatus as shown by patent document 1 and patent document 2 is demonstrated.
The gas recovery device 10 includes a cooling device 11 configured as an airtight container and a refrigerator 12. The gas to be collected flows through the flow pipe 13 and is introduced into the cooling device 11. Two coils of a first coil 14 and a second coil 15 are arranged in the cooling device 11.

The refrigerator 12 is provided with a compressor 16 and a condenser 18 in a refrigerant flow pipe 17 through which the refrigerant flows. In addition, an expander 19 is provided between the condenser 18 and the first coil 14, and the refrigerant flow pipe 17 extending from the condenser 18 branches off before the expander 19 and branches off. 21 is connected, and the branch pipe 21 is provided with an expander 20 and a second coil 15.
The branch pipe 21 on the downstream side of the second coil 15 is connected to the suction portion of the ejector 22, and the second coil 15 becomes negative pressure by the ejector 22, and becomes lower temperature than the first coil 14.

Japanese Utility Model Publication No. 6-29603 (FIG. 2 etc.) JP-A-7-260345 (FIG. 2 etc.)

  In the conventional gas recovery apparatus as described above, defrost (removal of frost) is not particularly disclosed. That is, when the gas is cooled and recovered, frost adheres to the cooling device as long as the gas contains moisture. If this frost is not removed, the cooling efficiency is extremely deteriorated, and therefore there is a problem that it is necessary to perform defrosting after operating for a predetermined time.

  Defrosting methods include heater defrosting and hot gas defrosting, but these methods are difficult to adopt because of the danger of explosion.

  Moreover, although the structure which introduces the air of about normal room temperature into a precooler and a main cooler for a defrost is also considered, when introducing the air for a defrost, since there is a possibility that VOC may also mix into the air after a defrost, The defrost air cannot be discharged as it is, and must be treated in some way.

  Accordingly, the present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a VOC cooling and recovery apparatus that can safely process air mixed with VOC by the defrost when performing defrost. It is to provide.

That is, the VOC cooling / recovering device according to the present invention is a VOC cooling / recovering device that liquefies and recovers VOC from VOC gas containing VOC as a gas, and is a high-temperature circuit that is cooled by the first refrigerant. And a low-temperature side circuit cooled by the second refrigerant are thermally connected via a cascade capacitor, and the evaporator of the high-temperature side circuit is disposed in the first sealed container. A precooler for precooling the VOC gas to be introduced, an evaporator for the low-temperature circuit in the second sealed container, and a main cooler for cooling the precooled VOC gas, A gas introduction pipe for introducing VOC gas into the cooler, a gas distribution pipe for introducing VOC gas preliminarily cooled and discharged in the precooler into the main cooler, and the main cooler. A gas discharge pipe for discharging the remaining gas from which the VOC has been recovered from the main cooler, an inlet valve for opening and closing the gas introduction pipe, an outlet valve for opening and closing the gas discharge pipe, the gas discharge pipe and the gas introduction pipe When the inlet valve and the outlet valve are closed, a connecting pipe that forms a closed pipe line together with a gas introduction pipe, a gas flow pipe, and a gas discharge pipe, and a blower disposed in the middle of the connecting pipe A drain port provided at a lower portion of the precooler and the main cooler, and a drain port connected to each drain port of the precooler and the main cooler for circulating the VOC liquefied in the precooler and the main cooler. It is characterized by comprising a recovery pipe and a recovery tank connected to the drain recovery pipe and storing the recovered VOC.
The effect | action by employ | adopting this structure is as follows.
That is, at the time of defrosting, the operation of the precooler and the main cooler is stopped, and then the inlet valve and the outlet valve are closed to form a closed pipe line with the gas introduction pipe, the gas flow pipe, the gas discharge pipe, and the connection pipe. The gas remaining in the passage is circulated by a blower. That is, it is not necessary to introduce any air for defrosting, and defrosting can be performed using VOC gas. After the defrosting is completed, the VOC mixed during the defrosting can be removed by operating the precooler and the main cooler.

The outlet valve may be provided with anti-freezing means.
According to this configuration, it is possible to prevent the outlet valve from freezing due to low-temperature exhaust from the exhaust outlet.

Further, the connection pipe is provided with a first connection pipe valve and a second connection pipe valve sandwiching the blower to open and close the connection pipe, and the first connection pipe valve and the second connection pipe are provided. The pipe valve may be provided with antifreezing means.
According to this configuration, when the VOC is recovered, the first connecting pipe and the second connecting pipe are closed to close the connecting pipe so that the VOC gas does not enter the blower of the connecting pipe, thereby preventing the blower from freezing. Can be planned.

  According to the VOC cooling and recovery apparatus according to the present invention, defrosting can be performed safely, and processing of air mixed with VOC during defrosting can be performed reliably.

DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described in detail with reference to the accompanying drawings.
FIG. 1 shows the overall configuration of this embodiment.
The VOC cooling / recovery device 30 of the present embodiment uses a binary refrigerator 32, and after the VOC gas is precooled by the high temperature side circuit 33 of the binary refrigerator 32, it is further cooled by the low temperature side circuit 34. The VOC can be efficiently liquefied.

First, the configuration of the binary refrigerator 32 will be described.
The binary refrigerator 32 is configured by thermally connecting a high temperature side circuit 33 and a low temperature side circuit 34 by a cascade capacitor 36.
The high temperature side circuit 33 includes a high temperature side compressor (compressor) 38, a high temperature side condenser 40, a high temperature side pressure reducing valve 43, and a first high temperature side evaporator 44 constituting a cascade condenser. These devices are connected in series by a refrigerant flow pipe 45 through which the high-temperature side refrigerant flows.

A refrigerant dryer 50 is provided on the downstream side of the high-temperature side condenser 40 in the high-temperature side circuit 33 to remove moisture in the refrigerant.
A control valve 37 for adjusting the flow rate of the refrigerant flowing through the refrigerant flow pipe 45 is provided between the high temperature side pressure reducing valve 43 and the first high temperature side evaporator 44.

Further, the high temperature side circuit 33 is provided with a second high temperature side evaporator 46 in parallel with the first high temperature side evaporator 44. The first high temperature side evaporator 44 and the second high temperature side evaporator 46 use the high temperature side compressor 38 and the high temperature side condenser 40 in common, and the second high temperature side evaporator 46 is a refrigerant. It is provided in the branch pipe 49 which branches between the site | part connected to the high temperature side compressor 38 of the flow pipe 45, and the site | part connected to the high temperature side condenser 40 of the refrigerant | coolant flow pipe 45.
The branch pipe 49 is provided with a second high temperature side pressure reducing valve 43. A control valve 39 for adjusting the flow rate of the refrigerant flowing through the branch pipe 49 is provided between the high temperature side pressure reducing valve 43 of the branch pipe 49 and the second high temperature side evaporator 46.

The high-temperature side condenser 40 in the present embodiment is provided with a fan 35 so that the refrigerant is cooled and condensed by the outside air introduced by the fan.
In the high temperature side circuit 33 having such a configuration, a refrigerant having excellent characteristics at high temperatures is used.

Next, the configuration of the low temperature side circuit 34 will be described.
The low temperature side circuit 34 includes a low temperature side compressor (compressor) 51, a low temperature side condenser 52 constituting a cascade condenser 36, a low temperature side pressure reducing valve 54, and a low temperature side evaporator 56. The devices are connected by a refrigerant flow pipe 55 through which the low-temperature side refrigerant flows. Further, a refrigerant dryer 57 is provided on the downstream side of the low-temperature side condenser 52 in the low-temperature side circuit 34 so as to remove moisture in the refrigerant.
An oil separator 59 is provided between the low temperature side compressor 51 and the low temperature side condenser 52. The oil separator 59 separates the oil and returns it to the low temperature side compressor 51 so that the oil generated from the low temperature side compressor 51 does not flow into other devices.

A temperature sensor 53 for detecting the temperature in the cascade capacitor 36 is provided in the cascade capacitor 36.
A controller 58 is connected to the temperature sensor 53. The control unit 58 is provided so as to be able to control the operations of the high temperature side compressor 38 and the low temperature side compressor 51 so that the detected temperature in the cascade capacitor 36 becomes a predetermined temperature set in advance. Control. Specifically, the temperature in the cascade capacitor 36 is controlled to be about −10 ° C.

Next, the distribution route of the VOC gas will be described.
First, the 1st high temperature side evaporator 46 of the high temperature side circuit 33 comprises the precooler 60 which is arrange | positioned in an airtight container and precools VOC gas. By pre-cooling the VOC gas, the moisture contained in the VOC gas can be attached as frost to remove the moisture.
The low temperature side evaporator 56 of the low temperature side circuit 34 is also arranged in the sealed container, and constitutes a main cooler 62 that liquefies VOC.

  The VOC to be recovered is provided so as to flow through the gas introduction pipe 64 connected to a VOC generation source (not shown) and be introduced into the VOC cooling and recovery apparatus 30. The gas introduction pipe 64 is provided with a blower and an inlet valve 68 (not shown) so that the VOC gas is fed into the gas introduction pipe 64 by the blower. The VOC gas sent into the gas introduction pipe 64 is introduced into the precooler 60 and precooled.

A gas circulation pipe 67 is disposed between the precooler 60 and the main cooler 62, and the VOC gas precooled by the precooler 60 is introduced into the main cooler 62 through the gas circulation pipe 67.
The main cooler 62 is provided with a gas discharge pipe 71 for discharging the remaining gas from which the VOC has been separated. In this way, the VOC gas passes through both the precooler 60 and the main cooler 62 and is cooled in two stages, after which the VOC is removed and exhausted from the gas exhaust pipe 71. An exhaust outlet 65 is provided at the end of the gas exhaust pipe 71.
Further, the gas exhaust pipe 71 is provided with an outlet valve 70 for closing the exhaust outlet 65.

A heat insulating member 91 is provided around the gas circulation pipe 67 so as to maintain a low temperature state of the VOC gas flowing while blocking the ambient temperature. For example, the heat insulating member 91 may be configured by winding a heat insulating material around the gas circulation pipe 67.
In the present embodiment, a heat insulating member 91 is also provided in a part of the gas introduction pipe 64 and a part of the gas discharge pipe 71 to further improve the cooling efficiency.

A connecting pipe that connects the gas introduction pipe 64 and the gas discharge pipe 71 between a part of the gas introduction pipe 64 downstream of the inlet valve 68 and a part of the gas discharge pipe 71 upstream of the outlet valve 70. 82 is connected.
The connecting pipe 82 includes a gas introduction pipe 64, a gas circulation pipe 67, and a gas discharge pipe so that the VOC gas is circulated between the gas introduction pipe 64, the gas circulation pipe 67, and the gas discharge pipe 71 during defrosting. 71 and the connecting pipe 82 constitute a closed pipe path.

A blower 86 is provided in the middle of the connecting pipe 82. When the blower 86 is driven, air in each pipe is circulated during defrosting.
On both sides of the blower 86, a first connection pipe valve 84 and a second connection pipe valve 87 for opening and closing the connection pipe 82 are provided. The first connecting pipe valve 84 and the second connecting pipe valve 87 are controlled so that both are closed when the VOC is recovered and both are opened when defrosting.

Drain ports 72 and 74 are provided at the lower portions of the precooler 60 and the main cooler 62, respectively. The drain ports 72 and 74 are connected to a recovery tank 78 via drain recovery pipes 76 and 77.
When the VOC is condensed and liquefied by the precooler 60 and the main cooler 62, the liquefied VOC is stored in the recovery tank 78 via the drain recovery pipe 76 and the drain recovery pipe 77. The recovery tank 78 is provided with an exhaust pipe 79 that exhausts the air in the recovery tank 78, and an exhaust filter 80 is attached to the exhaust pipe 79. The exhaust filter 80 uses a catalyst or the like that decomposes VOC.

The outlet valve 70, the first connecting pipe valve 84, and the second connecting pipe valve 87 described above may be provided with anti-freezing means.
As the freeze prevention means, for example, a heater using a heating wire is preferably wound around the bulb.

Hereinafter, the operation of the VOC cooling recovery apparatus 30 in the present embodiment will be described.
First, before the operation of the VOC cooling and recovery apparatus 30, the inlet valve 68 of the gas introduction pipe 64 and the first and second connection pipe valves 84 and 87 of the connection pipe 82 are closed. In addition, the control valve 37 of the high temperature side circuit 33 is also closed so that the precooler 60 is not initially operated.

First, the high temperature side compressor 38 is turned on.
When the high temperature side compressor 38 is operated, the refrigerant in the high temperature side circuit 33 is compressed and sent to the high temperature side condenser 40, and the high temperature side condenser 40 cools and liquefies the refrigerant at a constant pressure. The liquefied refrigerant is expanded by the high temperature side pressure reducing valve 43 to lower the boiling point, and the first high temperature side evaporator 44 in the cascade condenser 36 takes the heat of the low temperature side condenser 52 of the low temperature side circuit 34. Evaporate.

Next, after a predetermined time has elapsed since the high temperature side compressor 38 was turned on, the low temperature side compressor 51 is turned on in the low temperature side circuit 34.
Then, the refrigerant in the low-temperature side circuit 34 is compressed and sent to the low-temperature side condenser 52, and heat is exchanged with the high-temperature side evaporator 44 so that the refrigerant is cooled and liquefied at a constant pressure.
The liquefied refrigerant is expanded by the low temperature side pressure reducing valve 54 to lower the boiling point. In the low temperature side evaporator 56, the refrigerant takes the heat in the main cooler 62 and evaporates. Then, the evaporated and vaporized refrigerant flows into the low temperature side compressor 51.

  When the control unit 58 detects that the temperature in the cascade capacitor 36 has reached −10 ° C., the control unit 58 opens the control valve 37 and causes the refrigerant to flow through the branch pipe 49 on the precooler 60 side. The liquefied refrigerant is expanded by the high temperature side pressure reducing valve 43 of the branch pipe 49 to lower the boiling point, and in the second high temperature side evaporator 46, the heat in the precooler 60 is taken away and evaporated.

  At the same time, the controller 58 adjusts the opening degree of the control valve 39 so that the amount of refrigerant flowing to the precooler 60 side and the amount of refrigerant flowing to the cascade capacitor 36 are adjusted so that the temperature in the cascade capacitor 36 becomes constant. To distribute.

Next, by opening the inlet valve 68 and starting the operation of a blower (not shown), the VOC gas flows into the precooler 60 through the gas introduction pipe 64.
When the VOC gas flows into the precooler 60, in the second high temperature side evaporator 46 in the precooler 60, the refrigerant that has been expanded by the high temperature side pressure reducing valve 43 to lower the boiling point is introduced from the gas introduction pipe 64. VOC gas takes heat and evaporates. At this time, moisture contained in the VOC gas becomes frost and adheres to the precooler 60. For this reason, the VOC gas that has been preliminarily cooled after the removal of moisture is introduced into the next main cooler 62.
At this time, the temperature in the precooler 60 is about −10 ° C.

The VOC gas precooled by the precooler 60 is introduced into the main cooler 62 through the gas distribution pipe 67.
When the VOC gas flows into the main cooler 62, in the low temperature side evaporator 56 in the main cooler 62, the refrigerant that has been expanded by the low temperature side pressure reducing valve 54 to lower its boiling point is introduced from the gas circulation pipe 67. Takes away the heat and evaporates.
At this time, the temperature in the main cooler 62 is about −55 to −65 ° C.

  In this way, the VOC gas is cooled in the precooler 60 and the main cooler 62, and condensed and liquefied. The liquefied VOC accumulates in the lower part inside the precooler 60 and the main cooler 62. Since drain ports 72 and 74 are provided below the precooler 60 and the main cooler 62, the liquefied VOC flows out from the drain ports 72 and 74 through the drain recovery pipes 76 and 77 into the recovery tank 78, Collected.

In addition, when the VOC cooling and recovery operation is continuously performed, it is necessary to perform defrosting for removing frost attached to the precooler 60 in particular. In order to increase the cooling efficiency, it is necessary to defrost about every 8 hours.
At the time of defrosting, the high temperature side compressor 38 and the low temperature side compressor 51 are turned off to stop the refrigeration cycle. Then, the inlet valve 68 is closed to prevent the VOC gas from flowing into the VOC gas introduction pipe 64, and the outlet valve 70 is closed to prevent the VOC gas from being exhausted from the exhaust outlet 65. Further, the first connecting pipe valve 84 and the second connecting pipe valve 87 are opened. Thereby, the gas introduction pipe 64, the gas distribution pipe 67, the gas discharge pipe 71, and the connection pipe 82 constitute a closed pipe line that is closed without an inlet and an outlet.

After the closed line is constructed, the blower 86 starts to operate. Then, the VOC gas remaining in each pipe starts to circulate in the closed pipe line.
In this way, when defrosting is performed by configuring the closed pipe line and circulating the VOC gas, the frost in the precooler 60 and the frost in the main cooler 62 are melted and the water is liquefied. The liquefied water is recovered in the recovery tank 78 through the drain recovery pipes 76 and 77.

  Further, since the blower 86 only circulates the VOC gas remaining in each pipe, a small-capacity blower can be used as compared with a case where air for defrost is separately fed. Therefore, the running cost for driving the blower 86 can be reduced, and it contributes to downsizing of the entire apparatus.

  When the defrosting is completed, it seems that the VOC concentration in the circulated VOC gas is slightly increased. Therefore, the inlet valve 68 and the outlet valve 70 are briefly opened after the operation of the precooler 60 and the main cooler 62 is started. Is closed and the VOC is cooled and recovered. Thereafter, the outlet valve 70 is opened to discharge the gas after the VOC recovery. Also. The outlet valve 70 is opened, the first connecting pipe valve 84 and the second connecting pipe valve 87 are closed to prevent the VOC gas from flowing in the connecting pipe 82, and the inlet valve 68 is opened to obtain a new VOC gas. Is introduced into the gas introduction pipe 64, and the cooling and recovery operation of the VOC is resumed.

  The switching operation of each control valve as described above may be performed manually, or the control unit 58 may automatically control the control valve by outputting a control signal to each control valve.

  While the present invention has been described above with reference to a preferred embodiment, the present invention is not limited to this embodiment, and it goes without saying that many modifications can be made without departing from the spirit of the invention. .

It is explanatory drawing which shows the whole structure of the VOC cooling recovery apparatus of this invention. It is explanatory drawing which shows the conventional gas collection | recovery apparatus.

Explanation of symbols

Reference Signs List 30 Cooling recovery device 32 Dual refrigerator 33 High temperature side circuit 34 Low temperature side circuit 35 Fan 36 Cascade capacitor 37 Control valve 38 High temperature side compressor 39 Control valve 40 High temperature side condenser 43 High temperature side pressure reducing valve 44 First high temperature side evaporation 45 Refrigerant flow pipe 46 Second high temperature side evaporator 49 Branch pipe 50 Refrigerant dryer 51 Low temperature side compressor 52 Low temperature side condenser 53 Temperature sensor 54 Low temperature side pressure reducing valve 55 Refrigerant flow pipe 56 Low temperature side evaporator 57 Refrigerant dryer 58 Control unit 59 Oil separator 60 Precooler 62 Main cooler 64 Gas inlet pipe 65 Exhaust outlet 67 Gas distribution pipe 68 Inlet valve 70 Outlet valve 71 Gas exhaust pipe 72 Drain port 72, 74 Drain port 76, 77 Drain recovery pipe 78 Recovery tank 79 Exhaust pipe 80 Exhaust filter 82 Connecting pipe 84 First connection pipe valve 86 Blower 87 Second connection pipe valve 91 Heat insulation member

Claims (3)

A VOC cooling and recovery device that liquefies and recovers VOC from VOC gas containing VOC that is in the form of gas,
A binary refrigerator in which a high temperature side circuit cooled by a first refrigerant and a low temperature side circuit cooled by a second refrigerant are thermally connected via a cascade capacitor;
A precooler that preliminarily cools the VOC gas to be introduced, wherein the evaporator of the high-temperature circuit is disposed in the first sealed container;
A main cooler for cooling the pre-cooled VOC gas, wherein the evaporator of the low-temperature circuit is disposed in a second sealed container;
A gas introduction pipe for introducing VOC gas into the precooler;
A gas distribution pipe for introducing the VOC gas preliminarily cooled and discharged in the precooler into the main cooler;
A gas discharge pipe for discharging the remaining gas from which the VOC has been recovered by the main cooler from the main cooler;
An inlet valve for opening and closing the gas introduction pipe;
An outlet valve for opening and closing the gas discharge pipe;
When the gas discharge pipe and the gas introduction pipe are connected, and the inlet valve and the outlet valve are closed, a connection pipe constituting a closed pipe line together with the gas introduction pipe, the gas flow pipe, and the gas discharge pipe;
A blower disposed in the middle of the connecting pipe;
A drain port provided at a lower portion of the pre-cooler and the main cooler;
A drain recovery pipe connected to each drain port of the precooler and the main cooler, and for circulating VOCs liquefied in the precooler and the main cooler;
A VOC cooling and recovery apparatus, comprising: a recovery tank connected to the drain recovery pipe and storing the recovered VOC.   2. The VOC cooling and recovery apparatus according to claim 1, wherein the outlet valve is provided with anti-freezing means. The connection pipe is provided with a first connection pipe valve and a second connection pipe valve with the blower interposed therebetween to open and close the connection pipe.
3. The VOC cooling and recovery apparatus according to claim 1, wherein the first connecting pipe valve and the second connecting pipe valve are provided with anti-freezing means.

Images