Combustible gas compressor

Abstract

A combustible gas compressor includes a compressor housing (24a, 24b) having an impeller (30a, 30b) rotatably disposed inside thereof, a motor housing (12) having a motor (14) for driving the impeller (30a, 30b) inside thereof, and a bearing (18) rotatably supporting a rotating shaft (16a, 16b) for transmitting a rotational driving force of the motor (14) to the impeller (30a, 30b). The compressor housing (24a, 24b) can be integrally formed with the motor housing (12).

Description

[0001] This application is a divisional application of Chinese Patent Application No. 201980042916.4. The Chinese Patent Application is based on International Application PCT / KR2019 / 007588, filed on June 24, 2019, entitled "BOG COMPRESSOR FOR LNG FUELLED SHIP". TECHNICAL FIELD

[0002] The present application relates to a BOG compressor for an LNG fuelled ship using liquefied natural gas (LNG) as fuel for its propulsion engine, and more particularly, to a BOG compressor for an LNG fuelled ship in which a compressor housing is integrally formed with a motor housing. BACKGROUND

[0003] Generally, LNG carrier ships for transporting liquefied natural gas (LNG) have used LNG as fuel. However, in recent years, various LNG fuelled ships using LNG as the main fuel have been built in addition to LNG carrier ships, the LNG being cheaper than fuel oil and being advantageous in meeting regulations on exhaust gas in terms of preventing environmental pollution.

[0004] The amount of LNG used as fuel loaded in the LNG fuelled ship is about 1 / 50 to 1 / 10 of the amount of LNG loaded in the LNG carrier ship, and the LNG fuelled ship produces much less BOG in the LNG storage tank in proportion to the volume of the tank compared to the LNG carrier ship.

[0005] However, as with the LNG carrier ship, although a relatively small amount of BOG is produced, it is still necessary for the LNG fuelled ship to effectively treat the BOG to prevent risks due to an increase in the pressure of the storage tank. In addition, since the main purpose of the LNG fuelled ship is not to transport LNG, the crew of the LNG fuelled ship is not an expert in handling LNG, and thus it is necessary to simplify the systems and equipment related to LNG.

[0006] In a ship designed to use LNG as fuel for a main engine (e.g., a propulsion engine), the amount of BOG produced in the LNG storage tank is much smaller than the amount of BOG consumed by the main engine, and a fuel supply system including an LNG pump and an LNG vaporizer is generally used to reduce the power required for fuel compression. As a result, if the BOG is not removed from the LNG storage tank, the internal pressure of the tank continuously increases.

[0007] As a method of controlling the internal pressure of the storage tank, an LNG storage tank capable of withstanding high pressure is prepared to prevent the internal pressure of the storage tank from increasing above a predetermined level by supplying fuel to an auxiliary engine including a generator by means of the natural pressure of the storage tank. However, this method has a problem in that it is difficult to maintain the pressure in the LNG storage tank, and a problem in that there is an economic burden due to the preparation of an expensive and high-pressure-resistant LNG storage tank. SUMMARY

[0008] TECHNICAL PROBLEM

[0009] To solve these problems, a BOG compressor can also be provided on an LNG fuel-powered ship. Despite the small capacity, the BOG compressor still has various technical problems due to the extremely low temperature and low flow rate. Generally, a low flow rate compressor has difficulty in implementing a centrifugal compressor. This is because the centrifugal compressor needs to operate at a high speed due to the low flow rate and a small impeller size corresponding thereto. Therefore, a screw compressor or a reciprocating compressor is generally used as a BOG compressor of an LNG fuel-powered ship.

[0010] Due to the characteristic of using a large amount of lubricating oil, the screw compressor is provided with a complicated device for removing the lubricating oil at its outlet to secure the quality of LNG. In addition, since the screw compressor cannot directly handle BOG having a low temperature, a heater is provided at the inlet of the screw compressor to protect the compressor. In this way, in order to use the screw compressor, various devices are added thereto, thereby causing a decrease in system reliability, and the compressor operates at a relatively high temperature, thereby causing a decrease in efficiency of the compressor.

[0011] The reciprocating compressor also requires a separate lubricant system. In addition, the reciprocating compressor operates at a low RPM, and thus is much larger and heavier than the centrifugal compressor.

[0012] For such reasons, although the centrifugal compressor is superior in volume or reliability compared to the screw compressor or the reciprocating compressor, it is difficult to implement the application of the centrifugal compressor to an LNG fuel-powered ship due to the problem of a low flow rate. In a typical LNG carrier configured to handle a large amount of BOG, a high flow rate centrifugal BOG compressor is used. In this case, since the compressor impeller needs to operate at a rotational speed of 20,000 RPM (revolutions per minute) or more to obtain a certain compression ratio, and an electric motor has a characteristic of having a maximum rotational speed of about 3600 RPM, it is necessary to employ a speed-adjusting gear box.

[0013] In a BOG compressor for an LNG fuel-powered ship, which has a relatively small capacity, a speed-adjusting gear box and a lubricant system have a significant disadvantage in terms of cost and simplification of the overall equipment. Since a low-flow centrifugal compressor is required to be operated at a high RPM, it is technically more difficult to implement a low-flow centrifugal compressor compared to a large-capacity centrifugal compressor.

[0014] Furthermore, in all typical centrifugal, screw, and reciprocating compressors, a motor, a compressor impeller, a screw, and a cylinder are provided as separate components, and leakage of combustible gas inevitably occurs at connection parts between these components. To solve this problem, a gas seal device is used in multiple stages. The gas seal device is very expensive and requires continuous injection of inert gas such as nitrogen or the like, and a separate system for discharging a trace amount of gas leaked from the seal device. However, there is a safety problem in that the seal device cannot fundamentally prevent the leakage of combustible gas. Since the motor is also disposed in an area in which gas leakage can occur, the compressor requires an explosion-proof motor, resulting in a significant increase in cost.

[0015] Due to these technical and cost problems, the BOG compressor used in an LNG fuel-powered ship still has many problems as described above.

[0016] The present application was conceived to solve such problems in the related art, and an embodiment of the present application provides a boil-off gas compressor for an LNG fuel-powered ship using liquefied natural gas (LNG) as fuel for its propulsion engine, in which a compressor housing is integrally formed with a motor housing, fundamentally preventing leakage of combustible gas (i.e., boil-off gas) and inflow of external air.

[0017] An embodiment of the present application provides a boil-off gas compressor for an LNG fuel-powered ship, which adopts a centrifugal compressor capable of compressing boil-off gas in a low-temperature state without heating the boil-off gas using an inlet heater, thereby improving compression efficiency.

[0018] An embodiment of the present application provides a boil-off gas compressor for an LNG fuel-powered ship, which uses a self-lubricating bearing to prevent leakage of lubricating oil from affecting the quality of compressed boil-off gas, and is capable of increasing the rotational speed of a motor to obtain a target rotational speed of an impeller without using a speed-adjusting gear by a high-frequency inverter.

[0019] Technical Solution

[0020] According to an aspect of the present application, a boil-off gas compressor for an LNG-fueled power ship using liquefied natural gas (LNG) as fuel for a propulsion engine thereof includes a compressor housing having an impeller rotatably disposed inside thereof, a motor housing having a motor for driving the impeller inside thereof, and a bearing rotatably supporting a rotating shaft for transmitting a rotational driving force of the motor to the impeller, wherein the compressor housing is integrally formed with the motor housing.

[0021] The motor can be driven by a high-speed frequency converter, and the impeller is directly connected to the motor without passing through an additional speed regulation gear.

[0022] The bearing can be a self-lubricating type bearing that does not use lubricating oil.

[0023] A set of the impellers and the compressor housing can be respectively disposed on both sides of the motor housing.

[0024] The impellers can include a first impeller disposed on one side of the motor housing and a second impeller disposed on the other side of the motor housing, and boil-off gas compressed by the first impeller can be cooled by an intercooler and then supplied to the second impeller to be further compressed.

[0025] The rotating shaft can extend into the compressor housing through a partition wall between the motor housing and the compressor housing, and the compressor housing can be communicated with the motor housing through a gap between the rotating shaft and the partition wall to allow boil-off gas to flow from the compressor housing to the motor housing.

[0026] The partition wall between the motor housing and the compressor housing is provided with a heat insulating member. In addition, a portion of each of the partition wall and the heat insulating member through which the rotating shaft passes can be provided with an air-tight / heating member having both an air-tight function and a heating function, and a temperature decrease of the motor is alleviated by the heat insulating member and the air-tight / heating member.

[0027] The boil-off gas compressor can further include a pressure sensor for detecting an internal pressure of the motor housing.

[0028] The motor housing can be formed with a supply hole for supplying gas from the outside to the motor housing and an exhaust hole for exhausting internal gas.

[0029] Advantageous effects

[0030] Embodiments of the present application provide a boil-off gas compressor for an LNG fuel-powered ship using liquefied natural gas (LNG) as fuel for its propulsion engine, in which a compressor housing is integrally formed with a motor housing, fundamentally preventing leakage of flammable gas (i.e., boil-off gas) and inflow of outside air.

[0031] Embodiments of the present application provide a boil-off gas compressor for an LNG fuel-powered ship, which can effectively compress boil-off gas generated in an LNG storage tank of an LNG fuel-powered ship or an LNG carrier by centrifugal compression before supplying the compressed boil-off gas to an engine, thereby preventing loss of boil-off gas while maintaining the internal pressure of a liquefied natural gas storage tank within a safe range.

[0032] Embodiments of the present application provide a boil-off gas compressor for an LNG fuel-powered ship, which has a small volume, is inexpensive, is capable of directly compressing boil-off gas at a low temperature without using a separate heater, and eliminates a speed-adjusting gear box, a lubrication device, a gas sealing device, and an explosion-proof motor structure. In addition, the compressor housing is integrally formed with the motor housing, thereby fundamentally solving the problem of leakage of lubricating oil or gas by using a simple structure, and thus having advantages in safety and maintainability.

[0033] Embodiments of the present application provide a boil-off gas compressor for an LNG fuel-powered ship, which uses a self-lubricating bearing to prevent leakage of lubricating oil from affecting the quality of compressed boil-off gas, and is capable of increasing the rotational speed of a motor to obtain a target rotational speed of an impeller by using a high-frequency inverter without using a speed-adjusting gear. BRIEF DESCRIPTION OF DRAWINGS

[0034] Figure 1 is a conceptual view of a fuel supply system of an LNG fuel-powered ship provided with a boil-off gas compressor according to the present application.

[0035] Figure 2 is a schematic side view of a boil-off gas compressor for an LNG fuel-powered ship according to an embodiment of the present application.

[0036] Figure 3 is a schematic side view of a modified version of a boil-off gas compressor for an LNG fuel-powered ship according to an embodiment of the present application. DETAILED DESCRIPTION

[0037] Hereinafter, embodiments of the present application will be described in detail with reference to the accompanying drawings.

[0038] For an LNG fuel-powered ship, efficient use of boil-off gas is a very important issue, not only in terms of economic feasibility but also in terms of the environment. If boil-off gas (BOG) generated in an LNG fuel-powered ship is not properly treated, the boil-off gas must be discharged to the atmosphere to protect the storage tank. BOG is mainly composed of methane gas, which has a global warming index about 23 times higher than that of carbon dioxide, and thus must be strictly limited from being discharged from an LNG fuel-powered ship.

[0039] Although a screw compressor or a reciprocating compressor can be used to treat boil-off gas of an LNG fuel-powered ship, these compressors cannot directly treat boil-off gas at a low temperature, or can contaminate LNG products due to lubricating oil. When the capacity of a centrifugal compressor is small, it is difficult to implement a compression system, and there are problems related to a speed regulation gear, a gas seal device, and an increase in cost.

[0040] According to the present application, there is provided a centrifugal compression boil-off gas compressor for an LNG fuel-powered ship using liquefied natural gas (LNG) as fuel for a propulsion engine, in which a compressor housing is integrally formed with a motor housing, thereby fundamentally preventing leakage of flammable gas (i.e., boil-off gas) and inflow of outside air.

[0041] Figure 1 is a conceptual view of a fuel supply system of an LNG fuel-powered ship provided with a boil-off gas compressor according to the present application. Referring to Figure 1 , the fuel supply system of the LNG fuel-powered ship includes a storage tank 2 adapted to store LNG and boil-off gas (i.e., natural gas generated by vaporization of LNG) used as fuel, and a main engine 8 and an auxiliary engine 9 use the LNG and the boil-off gas supplied from the storage tank 2 as fuel.

[0042] The main engine 8 can be a propulsion engine for providing a propulsion force required for a ship to sail, and the auxiliary engine 9 can be a power generation engine for providing power to be consumed in the ship.

[0043] The LNG stored in the storage tank 2 can be compressed by an LNG pump 4, and can be supplied as fuel to at least one of the main engine 8 and the auxiliary engine 9 through an LNG vaporizer 5 in which the LNG is heated. The boil-off gas generated from the LNG within the storage tank 2 can be compressed by the boil-off gas compressor 10 according to the present application, and then supplied as fuel to at least one of the main engine 8 and the auxiliary engine 9.

[0044] The LNG compressed by the LNG pump 4 and heated by the LNG vaporizer 5 can be mainly supplied as fuel to the main engine 8, and the boil-off gas compressed by the boil-off gas compressor 10 can be mainly supplied as fuel to the auxiliary engine 9.

[0045] If the amount of boil-off gas generated in the storage tank is less than the amount of fuel required by the auxiliary engine 9, some of the fuel gas supplied to the main engine 8 (i.e., compressed and heated LNG) may be supplied as fuel to the auxiliary engine 9. Here, if the pressure of the fuel gas required by the auxiliary engine 9 is lower than the pressure of the fuel gas required by the main engine 8, the fuel gas may be decompressed by a pressure reducer (not shown) such as a JT valve (Joule-Thomson throttling expansion valve) before entering the auxiliary engine 9.

[0046] On the other hand, if the pressure of the evaporated gas compressed by the evaporated gas compressor 10 cannot meet the pressure of the fuel gas required by the main engine 8, and the amount of evaporated gas generated in the storage tank is greater than the amount of fuel gas required by the auxiliary engine 9, some of the fuel gas provided to the auxiliary engine 9 (i.e., the compressed and heated evaporated gas) can be provided to the main engine 8.

[0047] It should be noted that Figure 1 Only one example of a fuel supply system of an LNG fuel-powered ship provided with the boil-off gas compressor 10 according to the present invention is shown, and the boil-off gas compressor 10 according to the present invention is provided to Figure 1 In addition to the fuel supply system shown in FIG, the boil-off gas compressor 10 can also be provided to other types of fuel supply systems. Furthermore, the boil-off gas compressor 10 according to the present invention can be applied not only to fuel supply systems that supply boil-off gas as fuel to engines, but also to any system that requires compressing boil-off gas. Furthermore, the material compressed by the boil-off gas compressor 10 according to the present invention is not limited to boil-off gas, i.e., natural gas, but may also include gas evaporated from liquefied petroleum gas or petroleum, as well as any potentially explosive combustible gas.

[0048] Figure 2 is a schematic side view of a boil-off gas compressor for an LNG fuel-powered ship according to one embodiment of the present invention.

[0049] Reference Figure 2 The boil-off gas compressor 10 according to this embodiment includes compressor housings 24a, 24b, each of which has an impeller 30a or 30b rotatably arranged therein, and a motor housing 12, inside which a motor 14, such as an electric motor, is provided. The motor 14 is used to drive the impellers 30a, 30b. A set of impellers 30a or 30b and the compressor housing 24a or 24b may be provided on each of the two sides of the motor housing 12. Figure 2In this embodiment, the impeller and compressor casing arranged on the left side of the motor casing 12 are referred to as a first impeller 30a and a first compressor casing 24a, and the impeller and compressor casing arranged on the right side of the motor casing 12 are referred to as a second impeller 30b and a second compressor casing 24b.

[0050] According to this embodiment, the motor casing 12 is integrally formed with the first and second compressor casings 24a, 24b. Here, the "motor casing is integrally formed with (or integrally formed with) the compressor casing" means that the motor casing 12 is connected to the compressor casings 24a, 24b as one body, and the motor casing 12 is positioned adjacent to the compressor casings 24a, 24b so that the boil-off gas leaked from the compressor casings 24a, 24b can flow into the motor casing 12.

[0051] Although Figure 2 The impellers 30a, 30b and the compressor casings 24a, 24b are arranged on both sides of the motor casing 12 in the illustrated boil-off gas compressor 10, the impellers and the compressor casings can be arranged on only one side of the motor casing.

[0052] As Figure 2 In the structure in which the impellers 30a, 30b and the compressor casings 24a, 24b are arranged on both sides of the motor casing 12, as shown, the rotational driving force of the motor 14 is transmitted to the first impeller 30a through the first rotary shaft 16a and to the second impeller 30b through the second rotary shaft 16b. Here, the first rotary shaft 16a and the second rotary shaft 16b can be coaxially arranged shafts.

[0053] The first rotary shaft 16a and the second rotary shaft 16b can each be rotatably supported by a bearing 18. In this embodiment, the bearing 18 is a self-lubricating type bearing that does not use lubricating oil. The use of a self-lubricating type bearing can solve the problem of contamination caused by boil-off gas and can eliminate a lubricant supply system, thereby simplifying the overall structure of the compressor. For example, the self-lubricating type bearing can be a bearing configured to lift a rotary shaft using gas or electromagnetic force.

[0054] The first rotary shaft 16a extends into the first compressor casing 24a through a partition wall between the motor casing 12 and the first compressor casing 24a and is coupled to the first impeller 30a to rotate the first impeller 30a when the motor 14 is operated. Likewise, the second rotary shaft 16b extends into the second compressor casing 24b through a partition wall between the motor casing 12 and the second compressor casing 24b and is coupled to the second impeller 30b to rotate the second impeller 30b when the motor 14 is rotated.

[0055] Each of the partition walls between the motor housing 12 and the first and second compressor housings 24a, 24b is provided with a heat insulating member 20, which can prevent the cold of the evaporation gas having a very low temperature from being transferred into the motor housing 12. A portion of each of the partition walls and the heat insulating member 20 through which the first and second rotary shafts 16a, 16b pass is provided with an airtight / heating member 22. The heat insulating member 20 and the airtight / heating member 22 can prevent the temperature of the motor 14 from excessively decreasing, thereby preventing adverse effects on the device such as the motor 14.

[0056] In order to prevent the evaporation gas flowing in the first and second compressor housings 24a, 24b from being heated by the airtight / heating member 22, the heat insulating member 20 is advantageously provided between each airtight / heating member 22 and each of the first and second compressor housings 24a, 24b.

[0057] Referring to Figure 2 The first compressor housing 24a is formed with a first inlet 26a extending in an axial direction to allow the evaporation gas to be supplied therethrough to the first impeller 30a, and is further formed with a first outlet 28a extending in a direction perpendicular to the axial direction to allow the evaporation gas heated by the first impeller 30a to be discharged therefrom. The second compressor housing 24b is further formed with a second inlet 26b extending in the axial direction to allow the evaporation gas to be supplied therethrough to the second impeller 30b, and is further formed with a second outlet 28b extending in a direction perpendicular to the axial direction to allow the evaporation gas heated by the second impeller 30b to be discharged therefrom.

[0058] The motor housing 12 can be provided with a pressure sensor 32 to detect the internal pressure of the motor housing 12. In addition, the motor housing 12 can be provided with at least one temperature sensor (not shown). The temperature sensor can be provided not only on the motor housing but also at other places where temperature detection is required, for example, the compressor housing, etc.

[0059] The motor housing 12 can be formed with a supply hole 34 through which a gas is supplied from the outside to the motor housing 12, and a discharge hole 36 through which a gas is discharged from the motor housing 12. For example, the supply hole 34 can be used to supply an inert gas such as nitrogen into the motor housing 12 when the evaporation gas compressor is maintained, assembled, and disassembled.

[0060] Each of the first and second inlets 26a, 26b and the first and second outlets 28a, 28b can be provided with a flange (not shown) to facilitate the connection of a pipe thereto.

[0061] Next, the operation and effects of the boil-off gas compressor according to this embodiment will be described.

[0062] In the boil-off gas compressor 10 according to this embodiment, even if the boil-off gas having a very low temperature is directly introduced into the first and second compressor housings 24a, 24b, the thermal insulation member 20 prevents heat transfer to the boil-off gas having a very low temperature, thereby preventing the operation of the motor 14 operating at a high RPM from being affected by the heat transfer. In addition, the connecting portions between each of the first and second compressor housings 24a, 24b and the motor housing 12 can be provided with a separate heater having an air-tight function, i.e., an air-tight / heating member 22, to protect the motor. Furthermore, the heat generated due to the operation of the motor 14 can be discharged through a jacket cooling system (not shown) provided on the motor housing 12.

[0063] The first and second impellers 30a, 30b requiring a high RPM are directly connected to the motor 14 without the need for a speed reduction gear. The motor 14, i.e., a high-speed motor, can be driven by a high-speed frequency converter (not shown) disposed outside the motor housing 12.

[0064] In a typical compressor using a flammable gas such as boil-off gas, since the motor and the compressor are separate, a gas seal device must be provided in multiple stages on the rotating shaft. The typical compressor requires a continuous supply of inert gas to the gas seal device and additionally installs a discharge device to discharge the gas that has leaked from the gas seal device. However, since it is difficult to completely prevent gas leakage, the typical compressor has a safety problem.

[0065] However, in this embodiment, some components of the compressor and components of the motor, i.e., the first and second compressor housings 24a, 24b and the motor housing 12, are integrally formed with each other, and the inside of each of the first and second compressor housings 24a, 24b and the motor housing 12 is completely isolated from the outside, thereby fundamentally preventing the leakage of flammable gas.

[0066] According to the present embodiment, the motor housing 12 is provided with the first and second bearings 18, which adopt a self-lubricating type bearing system, thereby eliminating the need for a separate lubricant supply device, while fundamentally preventing the contamination of the boil-off gas with lubricating oil. The contamination of the boil-off gas with lubricating oil can cause many problems due to the condensation of the lubricating oil in liquefied natural gas carrier ships exposed to low temperature conditions or various equipment or storage tanks provided in liquefied natural gas fuel-powered ships.

[0067] In typical combustible gas compressors, the impeller section is separated from the motor section, and a special explosion-proof motor is used. However, according to this embodiment, despite the presence of the airtight / heating member 22, the compressor does not completely block gases such as BOG. ​​Instead, the compressor is configured to allow boil-off gas to flow between the first and second compressor housings 24a, 24b and the motor housing 12. In this compressor structure, the electrical equipment including the motor 14 operates while the housings are filled with combustible gas.

[0068] Preventing explosions caused by flammable gases is crucial in locations where they are used. To this end, specialized explosion-proof electrical equipment is typically used. However, according to this embodiment, the interior of motor housing 12, where motor 14 is located, is filled with flammable gas but oxygen is prevented from entering it, thereby fundamentally preventing the risk of explosion. Combustion or explosion requires three elements: combustible material, oxygen, and an ignition source. However, according to this embodiment, the possibility of oxygen entering the interior of motor housing 12 is eliminated, maintaining a safer state than typical explosion-proof devices.

[0069] The interior of the motor housing 12 is always maintained at a pressure higher than atmospheric pressure, thereby preventing external air, including oxygen, from entering the motor housing 12 under all circumstances. As described above, boil-off gas can flow from the interior of each of the first and second compressor housings 24a, 24b into the motor housing 12. Since the boil-off gas is compressed by the first and second impellers 30a, 30b within the first and second compressor housings 24a, 24b, the boil-off gas flowing into the motor housing 12 can be compressed to a pressure higher than atmospheric pressure. As a result, the internal pressure of the motor housing 12, in which the electric motor 14 is located, can be maintained at a pressure higher than atmospheric pressure.

[0070] To measure the internal pressure of the motor case 12 , the motor case 12 or another portion having the same pressure as the motor case 12 is provided with a pressure sensor 32 to allow the operation of the motor 14 to be automatically stopped when the internal pressure of the motor case 12 drops below atmospheric pressure.

[0071] Figure 3 is a schematic side view of a modified version of a boil-off gas compressor for an LNG fuel-powered ship according to an embodiment of the present invention.

[0072] Reference Figure 3 According to this modified boil-off gas compressor 10, the boil-off gas compressor 10 is similar to Figure 2The evaporation gas compressor 10 shown differs in that, according to this modified variant, a duct is configured to allow the evaporation gas compressed by the first impeller 30a to be further additionally compressed by the second impeller 30b. Identical or similar components will be denoted by identical reference numerals and a detailed description thereof will be omitted.

[0073] With reference to Figure 3 , the evaporation gas compressor 10 can be a two-stage compressor. In the evaporation gas compressor, the evaporation gas that has been compressed by the first impeller 30a, from the output unit of the first stage, i.e. from the first outlet 28a, is subjected to heat exchange in the intercooler 40 to reduce the temperature of the evaporation gas, and then enters through the input unit of the second stage of the compressor, i.e. through the second inlet 26b, to be further additionally compressed by the second impeller. Furthermore, when the temperature of the evaporation gas that exits through the output unit of the first stage is low, the evaporation gas can be directly supplied to the input unit of the second stage without passing through the intercooler. To this end, the evaporation gas compressor 10 can be provided with a bypass line 42 along which the evaporation gas can bypass the intercooler 40.

[0074] Although some embodiments have been described herein, it should be understood that these embodiments are given by way of example only and are not to be construed in any way to limit the present application, as various modifications, changes, and equivalents will become apparent to those skilled in the art after reading the foregoing description. The scope of the present application should be limited only by the appended claims and equivalents thereof.

Claims

1. A combustible gas compressor comprising: a compressor housing having an impeller rotatably disposed therein; a motor housing having a motor therein for driving the impeller; and a bearing rotatably supporting a rotating shaft for transmitting the rotational driving force of the motor to the impeller, Wherein, the compressor housing and the motor housing are formed integrally, wherein, when the impeller is driven, the combustible gas leaking from the compressor housing may flow into the motor housing, and the internal pressure of the motor housing becomes higher than atmospheric pressure, The bearing is a self-lubricating bearing that does not use lubricating oil, and the self-lubricating bearing is configured to use gas to lift the rotating shaft.

2. The combustible gas compressor according to claim 1, characterized in that: The motor is driven by a high-speed frequency converter, and the impeller is directly connected to the motor without passing through an additional speed regulating gear.

3. The combustible gas compressor according to claim 1, characterized in that: A group of the impeller and the compressor housing are respectively arranged on both sides of the motor housing.

4. The combustible gas compressor according to claim 3, characterized in that: The impeller includes a first impeller provided at one side of the motor housing and a second impeller provided at the other side of the motor housing, and the combustible gas compressed while passing through the first impeller is cooled by an intercooler and then supplied to the second impeller to be further compressed.

5. The combustible gas compressor according to claim 1, characterized in that: The rotating shaft extends into the compressor housing through a partition wall between the motor housing and the compressor housing; and The compressor housing communicates with the motor housing through a gap between the rotating shaft and the partition wall to allow the combustible gas to flow from the compressor housing to the motor housing.

6. The combustible gas compressor according to claim 5, characterized in that: The partition wall between the motor housing and the compressor housing is provided with a heat insulating member.

7. The combustible gas compressor according to claim 1, further comprising: A pressure sensor is used to detect the internal pressure of the motor housing.

8. The combustible gas compressor according to claim 1, characterized in that: The motor housing is formed with a supply hole for supplying gas from the outside to the motor housing and an exhaust hole for exhausting internal gas.

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