KR101052513B1 - Cooling cycle system for multistage compressor - Google Patents

Abstract

The present invention relates to a cooling cycle apparatus for a multi-stage compressor, and is provided on a gas supply line through which cryogenic gas is introduced and discharged, and a heating unit for heating the cryogenic gas to room temperature, and a gas installed at the rear end of the heating unit and heated to room temperature. A first compressor for compressing the gas at a high temperature and high pressure, a first intermediate cooler provided to lower the temperature of the compressed gas compressed by the first compressor, and a compressed gas whose temperature is lowered from the first intermediate cooler at high temperature and high pressure And a second intermediate cooler installed at a rear end of the second compressor and cooling and discharging the compressed gas, which has become a high temperature in the compression process, and installed to circulate the heating unit and the first and second intermediate coolers. And a refrigerant circulation line through which heat exchange is performed, and a refrigerant supply control unit installed on the refrigerant circulation line. Therefore, according to the present invention, there is provided a cooling system in which the cryogenic gas is heated to room temperature gas at the front of the compressor, and the refrigerant is circulated so as to cool the rear end of each compressor. Therefore, there is no need for a separate cooling system for recooling the refrigerant through a simple circulation structure, thereby simplifying the installation, reducing installation and operating costs, and providing efficient thermal management.

Compressor, Cooling Cycle, Multistage, Gas, Circulation, Refrigerant, Cooler

Description

Cooling cycle unit for multi-stage compressor {APPARATUS FOR COOLING CYCLE FOR MULTI-STAGE COMPRESSOR}

The present invention relates to a refrigeration cycle device for a multistage compressor, and more particularly, to perform a heat exchange at a rear end of each compressor of a multistage in compressing an ultra low temperature gas, such as liquefied natural gas (LNG), on demand. A multistage refrigeration cycle apparatus.

Generally, liquefied natural gas (LNG) is a natural gas (NG; natural gas) containing methane as its main component, cooled to an ultra low temperature of -163 ° C to reduce its volume to about 1/600.

In order to use such liquefied natural gas as an energy source, it is necessary to transfer a large amount of LNG from the production base of the liquefied natural gas (LNG) to the demand site, and thus, a liquefied natural gas carrier is required.

That is, liquefied natural gas in a gaseous state at the loading port, the place of production of natural gas, is stored in a storage tank of a liquefied natural gas carrier and, after arriving at an unloading port, liquefied natural gas at low temperature. After converting the gas into natural gas, it is supplied to the consumer through piping and the like.

In the storage tank of the liquefied natural gas carrier, liquefied natural gas is continuously vaporized to generate a natural boil off gas (BOG). On the other hand, when the pressure of the storage tank exceeds the set safety pressure due to the generation of the BOG, the BOG is discharged to the outside of the storage tank through the safety valve, the discharged BOG is used as the fuel of the vessel or re-liquefied and stored again Should be returned to the tank.

Usually, the reliquefaction apparatus of BOG has a refrigeration cycle, and it reliquefies by cooling BOG by this refrigeration cycle.

In the reliquefaction cycle shown in FIG. 1 according to the related art, the circulation line 12 connected from the storage tank 10 and the circulation line 12 are installed on the circulation line 12 to pressurize and cool the boil-off gas in a plurality of compressors. It consists of a multi-stage compressor (14) in which the process is repeated, a liquefier (16) for cooling and condensing the evaporated gas compressed in the multi-stage compressor (14) and a separator (18) for re-separating the liquefied gas and liquid do.

However, a compressor that compresses cryogenic gas at -100 ° C, such as evaporative gas, requires special materials and designs as it is designed for ultra low temperatures. Moreover, when compressing cryogenic gases to room temperature, the gas is increased due to the increase in gas temperature due to the heat of compression. The cooling system must be provided together, and in general, such a gas cooling system requires a separate second cooling system for re-cooling the heat transfer medium, resulting in complicated apparatus and heat loss.

Therefore, in the present invention, by cooling the cryogenic gas to the normal temperature gas in front of the compressor, and by configuring a cooling system in which the refrigerant is circulated to cool the rear end of each compressor, a separate cooling system for cooling the refrigerant again through a simple circulation structure It is an object of the present invention to provide a refrigeration cycle device for a multi-stage compressor, which is not required, and in which efficient thermal management can be achieved.

In order to achieve the above object, an embodiment of the present invention is a multi-stage compressor cooling cycle apparatus, which is installed on a gas supply line through which cryogenic gas is introduced and discharged, and a heating unit for heating the cryogenic gas to room temperature, and a heating unit. A first compressor installed at the rear stage and compressing the gas heated to room temperature to be a gas of high temperature and high pressure, a first intermediate cooler provided to lower the temperature of the compressed gas compressed in the first compressor, and a first intermediate cooler A second compressor for compressing the compressed gas at a high temperature and high pressure, and a second intermediate cooler installed at a rear end of the second compressor and cooling and discharging the compressed gas which has become a high temperature in the compression process. Refrigerant circulation line is installed to circulate 1, 2 intermediate cooler to perform heat exchange, and refrigerant supply control unit installed on the refrigerant circulation line Provides a multi-stage for a compressor cooling cycle apparatus comprising.

The refrigerant supply control unit is controlled by the amount of refrigerant supplied through a control unit installed on the gas supply line.

In addition, the refrigerant supply control unit includes a refrigerant line branched from the refrigerant circulation line, an expansion valve installed on the refrigerant line, a pump provided at the rear end of the expansion valve to assist the circulation of the refrigerant, and a refrigerant line. And a refrigerant amount control valve for adjusting the supply amount of the refrigerant.

In addition, glycol may be used as the refrigerant supplied from the refrigerant supply control unit.

As described above, according to the cooling cycle apparatus for a multi-stage compressor according to an embodiment of the present invention, a cooling system is provided in which a cryogenic gas is heated to room temperature gas at the front of the compressor, and a refrigerant is circulated to cool the rear end of each compressor. do. Therefore, there is no need for a separate cooling system for recooling the refrigerant through a simple circulation structure, thereby simplifying the installation, reducing installation and operating costs, and providing efficient thermal management.

Hereinafter, with reference to the accompanying drawings will be described in detail the operating principle of an embodiment according to the present invention. In the following description of the present invention, if it is determined that a detailed description of a known function or configuration may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted. The terms to be described below are terms defined in consideration of functions of an embodiment according to the present invention, which may vary according to intention or custom of a user or an operator. Therefore, the definition should be based on the contents throughout this specification.

2 is a block diagram of a cooling cycle apparatus for a multi-stage compressor according to an embodiment of the present invention.

As shown in FIG. 2, the heating unit 110, the first compressor 120, the first intermediate cooler 140, and the second compressor 130 are sequentially on the gas supply line 100 through which the cryogenic gas is introduced and discharged. ) And a second intermediate cooler 150, installed to circulate the heating unit 110, the first and second intermediate coolers 140 and 150, and a refrigerant circulation line 160 for performing heat exchange, and a refrigerant circulation. Refrigerant supply control unit 170 is installed on the line 160.

The first compressor 120 and the second compressor 130 installed on the gas supply line 100 are composed of a plurality of compressors such that the pressurizing and cooling processes are repeated to pressurize and supply the cryogenic gas at about -100 ° C. In some cases, it may be composed of three stages, in which case more intermediate coolers may be required.

In the first compressor 120, the gas is compressed to high pressure and high temperature, and in the second compressor 130, the gas is compressed to high temperature and high pressure.

In addition, the heating unit 110 installed at the front end of the first compressor 120 heats the gas flowing into the cryogenic temperature to be close to room temperature, that is, 0 ° C.

In addition, the first and second intermediate coolers 140 and 150 provided at the rear ends of the first and second compressors 120 and 130, respectively, are generated by the first and second compressors 120 and 130. It is installed in order to cool the heat and lower the temperature of the compressed compressed gas.

Meanwhile, the refrigerant circulation line 160 is installed to circulate the heating unit 110 and the first and second intermediate coolers 140 and 150 continuously so that heat exchange is performed, and the refrigerant supply control on the refrigerant circulation line 160 is performed. The unit 170 is installed.

Refrigerant supply control unit 170, the expansion valve 172 for cooling the refrigerant on the refrigerant circulation line 160 and the pump 174 to assist the circulation of the refrigerant to the rear end of the expansion valve 172 is installed. A refrigerant line 171 branched from the refrigerant circulation line 160 and having a circulation structure is installed, and a refrigerant amount control valve 176 is provided on the refrigerant line 171 to adjust the supply amount of the refrigerant.

Here, glycol may be used as the refrigerant circulating in the refrigerant circulation line 160, and the refrigerant amount control valve 176 may be disposed between the heating unit 110 and the first compressor 120 in the gas supply line 100. The supply amount may be controlled through the control unit 180 installed in the control unit 180.

The controller 180 determines whether the temperature of the gas should be further lowered or higher by measuring the temperature of the gas passing through the heating unit 110, thereby controlling the supply amount of the refrigerant.

Referring to the cooling cycle device for a multi-stage compressor having such a structure is made as follows.

Referring back to FIG. 2, first, when the cryogenic gas is introduced through the gas supply line 100, the cryogenic gas is heated to be close to a temperature of about 0 ° C. through the heating unit 110.

At this time, the refrigerant of the glycol supplied from the refrigerant supply control unit 170 passes through the heating unit 110 along the refrigerant circulation line 160 and exchanges the cryogenic gas at a temperature of 0 ° C. through heat exchange with the cryogenic gas. Heating to close.

The reason why the temperature is increased before the cryogenic gas is compressed in the first compressor 120 is that when the low temperature gas flows into the first compressor 120 without being heated (preheated), the first compressor 120 receives thermal stress. Mechanical damage is likely to occur at 120, particularly since the greatest thermal stress can be applied to the first first compressor 120 where the low temperature gas is first contacted.

Next, the ultra-low temperature gas heated to room temperature is compressed to high temperature and high pressure in the first compressor 120, and the refrigerant deprived of heat by heat exchange in the heating unit 110 is cooled down to about -50 ° C so that the cooling circulation line 160 The heat exchange is performed while moving along the first intermediate cooler 140 or the second intermediate cooler 150.

Therefore, since the gas compressed at high temperature and high pressure while passing through the first compressor 120 is in a high temperature state of about 110 ° C., the first intermediate cooler 140 is cooled again before the second compressor 130. The coolant is cooled to about -50 ° C as described above to cool the hot gas by heat exchange with the hot gas of about 110 ° C while the refrigerant moving along the cooling circulation line 160 passes through the first intermediate cooler 140. do.

On the other hand, while passing through the first intermediate cooler 140, the temperature is down to about 50 ℃ to about 50 ℃ is compressed to high temperature and high pressure through the second compressor 130, before being discharged to the gas supply line 100 In the second compressor 130 is compressed to a high temperature gas is cooled again to the low temperature in the second intermediate cooler 150 is discharged.

In the second intermediate cooler 150, the refrigerant at a temperature of about −50 ° C. and the high temperature gas exchanged by the heating unit 110 are exchanged.

As such, the refrigerant heat-exchanged while passing through the first and second intermediate coolers 140 and 150 is heated to about 30 ° C. to 50 ° C., and then flows into the refrigerant supply control unit 170 along the cooling circulation line 160 to be cooled. do.

In the refrigerant supply controller 170, the refrigerant is cooled while passing through the expansion valve 172, recycled through the pump 174, and the temperature of the heat exchanged gas while passing through the heater 110 is measured by the controller 180. In this case, when the measured temperature is lower than the predetermined temperature, the amount of refrigerant is increased by the controller 180 so that the amount of refrigerant is greater than the amount passing through the expansion valve 172 to increase the temperature of the refrigerant circulated. By increasing the opening degree, the overall temperature of the refrigerant is increased to be supplied. On the contrary, if the measured temperature is measured to be higher than a predetermined temperature, the opening degree of the refrigerant amount control valve 176 is controlled by the controller 180 such that the amount of refrigerant becomes smaller than the amount passing through the expansion valve 172 to lower the temperature of the supplied refrigerant. By lowering the temperature, the overall temperature of the refrigerant is lowered and supplied.

Therefore, a separate cooling system for cooling the refrigerant again through a simple circulation structure by configuring a cooling system in which the cryogenic gas is heated to room temperature gas at the front of the first compressor 120 and the refrigerant is circulated so as to cool the rear end. This eliminates the need for efficient thermal management.

What has been described above is just one embodiment of the cooling cycle apparatus for a multi-stage compressor according to the present invention, the present invention is not limited to the above embodiment, as claimed in the following claims of the present invention Without departing from the gist of the present invention, one of ordinary skill in the art will have the technical spirit of the present invention to the extent that various modifications can be made.

1 is a block diagram of a re-liquefaction cycle of cryogenic gas according to the prior art,

2 is a block diagram of a cooling cycle apparatus for a multistage compressor according to an embodiment of the present invention.

<Description of the symbols for the main parts of the drawings>

100: gas supply line 110: heating unit

120, 130: first and second compressors 140, 150: first and second intermediate coolers

160: refrigerant circulation line 170: refrigerant supply control unit

171: refrigerant line 172: expansion valve

174: pump 176: refrigerant amount control valve

180: control unit

Claims (4)

A heating unit installed on a gas supply line through which cryogenic gas is introduced and discharged, and heating the cryogenic gas to room temperature; A first compressor installed at a rear end of the heating unit and compressing the gas heated to room temperature to be a gas of high temperature and high pressure; A first intermediate cooler installed to lower the temperature of the compressed gas compressed by the first compressor; A second compressor for compressing the compressed gas lowered in temperature from the first intermediate cooler at high temperature and high pressure; A second intermediate cooler installed at a rear end of the second compressor and cooling and discharging the compressed gas that has become hot in the compression process again; A refrigerant circulation line installed to circulate the heating unit and the first and second intermediate coolers to perform heat exchange; A refrigerant supply control unit installed on the refrigerant circulation line to control the amount of refrigerant Cooling cycle device for a multi-stage compressor comprising a. The method of claim 1, Cooling cycle device for a multi-stage compressor in which the refrigerant supply control unit is controlled to supply the refrigerant through a control unit installed on the gas supply line. The method of claim 1, The refrigerant supply control unit, A refrigerant line branched from the refrigerant circulation line; An expansion valve installed in the refrigerant line to cool the refrigerant; A pump installed at a rear end of the expansion valve to help circulation of the refrigerant; Refrigerant amount control valve installed in the refrigerant line to control the supply amount of the refrigerant Cooling cycle device for a multi-stage compressor comprising a. 4. The method according to any one of claims 1 to 3, Cooling cycle device for a multi-stage compressor is a refrigerant supplied from the refrigerant supply control unit (glycol).

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