Anti-explosion low-temperature oil-free centrifugal compressor unit

Abstract

The utility model discloses an anti-explosion low-temperature oil-free centrifugal compressor unit which comprises a centrifugal compressor, a connecting pipe, a heat preservation loop and a heat insulation material. The centrifugal compressor comprises a motor, an impeller, a volute and a bearing; the motor adopts an explosion-proof design; the motor works at a low temperature and does not need to be cooled; a gas circuit is additionally arranged at the volute, and the gas circuit is communicated with the compressor shell to form a heat preservation loop; the bearing is divided into a gas bearing and a gas-magnetic hybrid bearing; the outer sides of the compressor shell, the volute, the connecting pipe and the gas circuit are all wrapped with heat insulation materials. The same impellers are adopted at the two ends of the first-stage compressor and the second-stage compressor, axial force does not need to be considered, and thrust plates do not need to be arranged; a heat insulation material is adopted, a heat preservation loop is arranged, and the compressor can operate within the inlet temperature range of-250 DEG C to-20 DEG C; by adopting the gas bearing for supporting, the friction loss is small, the efficiency is high, and the service life is long; pure oil-free operation is achieved, and the size and weight of the system are greatly reduced.

Description

Technical Field

[0001] The utility model relates to the technical field of centrifugal compressors used in the low-temperature field, and particularly designs an explosion-proof low-temperature oil-free centrifugal compressor unit. Background Art

[0002] Centrifugal compressors play a vital role in the field of gas liquefaction, such as hydrogen, natural gas, permeate gas, analytical gas, and regeneration gas. The gas liquefaction process usually involves cooling the gas to a very low temperature to convert it from a gaseous state to a liquid state. In the gas liquefaction process, centrifugal compressors provide the necessary pressure and energy for the refrigeration cycle by compressing the working gas to high pressure. The high-pressure gas releases heat during the expansion process, thereby achieving cooling. Centrifugal compressors have a high energy efficiency ratio and can provide a large flow rate and a high pressure, which helps to reduce energy consumption in the working gas liquefaction process, improve overall energy efficiency, and adapt to large-scale production needs.

[0003] Conventional compressors need to heat the gas to room temperature before compressing it. The compressed gas is de-oiled and filtered before being cooled and expanded. The system needs to be equipped with air temperature controllers, heat exchangers and other devices, which greatly increases the system cost and floor space. At the same time, the process of heating up and then cooling down causes a large energy loss.

[0004] At the same time, conventional compressors cannot operate at lower ambient temperatures due to the oil bearing support they use. When operating at room temperature, the compressor power consumption is high. Existing compressors are usually labyrinth compressors, where the impeller operates at low temperatures and the motor operates at room temperature. This is achieved through structures such as multiple labyrinth seals, gearboxes, and long shaft extensions. The device is complex and the compressor efficiency is very low. Since the compression work of a compressor is closely related to the inlet temperature of its working fluid, an effective way to reduce the power consumption of the compressor is to lower the inlet temperature of the compressor. When a centrifugal compressor operates in an extremely low temperature environment, the inlet temperature of the centrifugal compressor is extremely low, requiring the centrifugal compressor to reduce heat exchange with the outside world, and requiring the compressor motor to operate normally.

[0005] When the working gas is flammable and explosive, the reliability of the working equipment must be guaranteed during the gas liquefaction process, which puts higher requirements on the structural type and rotor support method of the compressor. Summary of the invention

[0006] In order to solve the above-mentioned technical problems, the utility model proposes an explosion-proof low-temperature oil-free centrifugal compressor unit. The centrifugal compressor can operate within the inlet temperature range of -250℃~20℃, adopts an explosion-proof motor design, and is equipped with a flameproof section or high-pressure gas protection inside the compressor, which greatly improves the safety of equipment use and meets the needs of industrial production use.

[0007] In order to achieve the above object, the utility model provides an explosion-proof low-temperature oil-free centrifugal compressor unit, comprising:

[0008] The centrifugal compressor includes a motor, an impeller, a volute, and a bearing;

[0009] The centrifugal compressor motor includes a motor stator, a rotor and an end cover. The motor housing is provided with an air inlet and an air outlet. A flameproof section is provided between the compressor impeller and the motor stator. The motor rotor is supported by a gas bearing or a gas-magnetic hybrid bearing. The end cover is connected to the housing by welding.

[0010] The impeller of the centrifugal compressor is fixed on the motor rotor of the centrifugal compressor and is located inside the volute. The two compressors use the same impeller at both ends. The rotor structure is symmetrically distributed, and there is no need to consider the axial force. The centrifugal compressor does not need to be equipped with a thrust plate. The thrust surface is the surface on the rotor main shaft that is perpendicular to the rotor.

[0011] The volute is divided into a primary volute and a secondary volute. The inlet of the primary volute is the air inlet of the primary compressor, and the outlet of the secondary volute is the exhaust port of the secondary compressor.

[0012] There is another gas path at the secondary volute, which is connected with the primary and secondary compressor casings to form a heat preservation circuit. A temperature sensor is provided on the heat preservation circuit to judge the motor temperature and control the gas path direction and gas volume through the opening regulating valve.

[0013] Gas bearings are divided into radial bearings and thrust bearings, and the bearing types are full dynamic pressure, dynamic and static pressure, or full static pressure;

[0014] The connecting pipe connects the exhaust port of the first-stage compressor and the air inlet of the second-stage compressor;

[0015] The compressor stator, end cover, volute, connecting pipe, and gas pipeline are all made of heat-insulating materials;

[0016] The compressor casing and the outside of the gas pipeline are wrapped with insulation materials. The compressor operates in the atmospheric environment or working environment. The compressor inlet temperature ranges from -250℃ to 20℃. There is no need to consider motor cooling when operating under low temperature conditions.

[0017] Furthermore, the low-temperature centrifugal compressor can operate at an inlet temperature of -250°C, the power consumption of the compressor is greatly reduced compared with normal temperature, and the working gas can be hydrogen, natural gas, permeate gas, analytical gas, regeneration gas or other gases.

[0018] Furthermore, since the compressor's variable compression work is proportional to the intake temperature, the expression is as follows:

[0019]

[0020] Wherein, W is the multi-table compression work, m is the multi-variable index, R is a constant, is the inlet temperature, and p2 / p1 is the compressor compression ratio. When the centrifugal compressor operates at an extremely low inlet temperature, part of the cooling capacity is required to maintain the low temperature environment. When the compression ratio remains unchanged, when the inlet temperature of the compressor is -200°C, the compression work of the compressor is about 25% of the inlet temperature of 20°C, which greatly reduces the power consumption of the compressor and saves system energy.

[0021] Furthermore, when the low-temperature centrifugal compressor is operating at low temperatures, there is no need to consider motor cooling. Through the insulation circuit, the higher temperature gas at the outlet of the secondary volute is used to heat the centrifugal compressor motor to ensure that the motor operating temperature is higher than the compressor inlet gas temperature.

[0022] Furthermore, the motor is a permanent magnet synchronous motor with a flameproof section or a permanent magnet synchronous motor without a flameproof section. When a permanent magnet synchronous motor without a flameproof section is used, an air inlet and an exhaust hole are required to be provided on the motor casing of the centrifugal compressor. A protective gas with a certain pressure is filled into the gap between the motor rotor and the stator through the air inlet to prevent the working gas from entering. The protective gas is nitrogen or an inert gas.

[0023] Furthermore, when a permanent magnet synchronous motor without an explosion-proof section is used, the introduced protective gas can keep the motor warm. At the same time, the motor temperature can be monitored by a temperature sensor installed on the insulation circuit. When the protective gas cannot fully achieve the insulation function, the opening regulating valve can be used to adjust the airflow size of the insulation circuit to assist in achieving the insulation work of the motor.

[0024] Furthermore, the centrifugal compressor unit may have 1 to 12 stages, and interstage cooling may be further arranged between the compressors of each stage. The centrifugal compressor unit may have 1 to 8 centrifugal compressors with the same structure on both sides connected in parallel.

[0025] Furthermore, a labyrinth seal is arranged on the inner side of the motor end cover, an interference fit or a transition fit is adopted between the impeller and the main shaft, and the impeller is a semi-open impeller or a closed impeller.

[0026] Furthermore, the centrifugal compressor is supported by gas bearings or gas-magnetic hybrid bearings, and the entire system operates purely oil-free, without the need for oil removal and oil return devices.

[0027] Furthermore, the connecting pipe is made of a stretchable heat-insulating material to avoid stress caused by thermal expansion and contraction.

[0028] Compared with the prior art, the utility model has the following advantages and technical effects:

[0029] When a permanent magnet synchronous motor with a flameproof section is used, the setting of the flameproof section inside the compressor housing greatly improves the safety of the equipment. When a permanent magnet synchronous motor without a flameproof section is used, the setting of the high-pressure protection gas path prevents the flammable and explosive working gas from entering the compressor motor, thereby improving the reliability of the equipment. By using the same specifications of the first-stage impeller or the second-stage impeller at both ends of the motor rotor, the rotor structure is symmetrical, eliminating the influence of the axial force on the operation of the equipment, and there is no need to set up a thrust plate. By setting the insulation circuit and the temperature sensor and the opening regulating valve on the circuit, the motor temperature can be monitored and the gas volume of the insulation circuit can be adjusted, so as to realize the insulation function of the motor running under low temperature conditions and ensure the normal operation of the motor. By setting the insulation material on the compressor housing and the outer side of the gas path, the heat leakage during the operation of the compressor is reduced and the energy efficiency of the system is improved. By using gas bearings or gas-magnetic hybrid bearing supports, the entire system can be operated purely without oil, reducing friction losses and increasing service life. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The drawings constituting a part of the present application are used to provide a further understanding of the present application. The illustrative embodiments and descriptions of the present application are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0031] Figure 1 It is a structural schematic diagram of an explosion-proof low-temperature oil-free centrifugal compressor unit using a permanent magnet synchronous motor with a flameproof section;

[0032] Figure 2 It is a structural schematic diagram of an explosion-proof low-temperature oil-free centrifugal compressor unit using a permanent magnet synchronous motor without an explosion-proof section;

[0033] Among them, 1-first-stage compressor, 111-first-stage compressor casing, 112-first-stage compressor rotor, 113-first-stage compressor end cover, 114-first-stage compressor flameproof section, 115-insulation circuit opening 1, 116-insulation circuit opening 2, 117-insulation circuit temperature sensor 1, 118-first-stage compressor safety gas path inlet, 119-first-stage compressor safety gas path outlet, 12-first-stage compressor impeller, 13-first-stage compressor volute, 141-first-stage compressor radial bearing, 142-first-stage compressor thrust bearing, 2-second-stage compressor, 211-second-stage compressor casing, 212- Secondary compressor rotor, 213-secondary compressor end cover, 214-secondary compressor explosion-proof section, 215-insulation circuit opening 3, 216-insulation circuit opening 4, 217-insulation circuit temperature sensor 2, 218-secondary compressor safety gas circuit inlet, 219-secondary compressor safety gas circuit outlet, 22-secondary compressor impeller, 23-secondary compressor volute, 231-secondary compressor volute opening 1, 232-secondary compressor volute opening 2, 241-secondary compressor radial bearing, 242-secondary compressor thrust bearing, 3-connecting pipe, 4-opening regulating valve, 5-thermal insulation material. DETAILED DESCRIPTION

[0034] The following will be combined with the drawings in the embodiments of the utility model to clearly and completely describe the technical solutions in the embodiments of the utility model. Obviously, the described embodiments are only part of the embodiments of the utility model, not all of the embodiments. Based on the embodiments in the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the utility model.

[0035] In order to make the above-mentioned purposes, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0036] Embodiment 1:

[0037] Attached Figure 1 This is a structural diagram of an explosion-proof low-temperature oil-free centrifugal compressor unit using a permanent magnet synchronous motor with an explosion-proof section. As shown in the figure, an explosion-proof low-temperature oil-free centrifugal compressor unit using a permanent magnet synchronous motor with an explosion-proof section includes a primary compressor 1, a secondary compressor 2, a connecting pipe 3, an opening regulating valve 4, and a heat insulation material 5. Figure 1The structural schematic diagram shown completes the assembly and welding of an explosion-proof low-temperature oil-free centrifugal compressor unit using a flameproof motor. When the centrifugal compressor is working, the working gas enters the flow channel of the primary compressor 1 from the inlet of the primary compressor volute 13, flows through the primary compressor impeller 12, and flows into the connecting pipe 3 from the outlet of the primary compressor volute 13. After that, the working gas enters the flow channel of the secondary compressor 2 from the inlet of the secondary compressor volute 23, flows through the secondary compressor impeller 22, and is discharged from the outlet of the secondary compressor volute 23, thereby completing the compression process of the working gas.

[0038] In the attached Figure 1 During operation of the centrifugal compressor shown, the first-stage compressor rotor 112 is supported by the first-stage compressor radial bearing 141 and the first-stage compressor thrust bearing 142, driving the first-stage compressor impeller 12 to rotate. During operation, since the first-stage compressor impeller 12 of the same structure is used on both sides of the first-stage compressor 1, there is basically no need to consider the impact of axial force on the operation of the compressor, and there is no need to set up a thrust plate. A labyrinth sealing structure is provided inside the first-stage compressor end cover 113 to prevent gas leakage. The first-stage compressor end cover 113 is welded to the first-stage compressor casing 111 to prevent heat leakage. The working process of the second-stage compressor 2 is similar to that of the first-stage compressor 1, so it will not be described in detail.

[0039] The stator, end cover, volute, connecting pipe and gas pipeline of the low-temperature oil-free air-floating centrifugal compressor are all made of heat-insulating materials. The compressor end cover and the outer shell, the compressor shell and the outer side of the gas pipeline are wrapped with heat-insulating materials 5, which can reduce heat leakage during operation. Due to heat transfer inside the compressor during operation, the lower temperature at the impeller will be transferred to the inside of the motor. Therefore, the utility model is provided with a heat preservation circuit, and the heat preservation circuit is provided with a temperature sensor 117 and a temperature sensor 217, which can monitor the motor temperature. Since the pressure and temperature of the compressor are both rising during the compression process, the outlet temperature of the secondary compressor volute 23 is relatively high, and the working gas with a higher temperature can be introduced into the heat preservation circuit opening 115 and the heat preservation circuit opening 215 through the secondary compressor volute opening 231, and the motor is heated by the heat preservation circuit set inside the motor shell, and then the airflow returns to the secondary compressor volute opening 232 through the heat preservation circuit opening 116 and the heat preservation circuit opening 216. According to the feedback of the temperature sensor, the opening regulating valve 4 set in the heat preservation circuit can be used to adjust the size of the loop airflow to achieve precise temperature control. Through the above measures, the heat leakage during the operation of the compressor is reduced and the normal operation of the compressor motor is guaranteed, so that the compressor can operate normally under the condition of an inlet temperature of -250°C.

[0040] When the working gas of the low-temperature oil-free centrifugal compressor is inflammable and explosive gas such as hydrogen, natural gas, permeate gas, analytical gas, regeneration gas, etc., if the inflammable and explosive working gas enters the motor and comes into contact with the sparks or arcs generated inside the motor, it is easy to cause an explosion, endangering the safety of personnel and equipment. Therefore, the reliability of the working equipment must be guaranteed. Taking the first-stage compressor 1 as an example, a first-stage compressor explosion-proof section 114 is provided inside the compressor. If an explosion occurs, the harm caused by the explosion is greatly reduced due to the existence of the explosion-proof section, thereby improving the safety of the working equipment.

[0041] Embodiment 2:

[0042] Attached Figure 2 This is a structural diagram of an explosion-proof low-temperature oil-free centrifugal compressor unit using a permanent magnet synchronous motor without an explosion-proof section. The working process of the low-temperature centrifugal compressor is similar to that of the attached Figure 1 The working process of the centrifugal compressor with flameproof permanent magnet synchronous motor is similar, so it will not be described in detail here. Figure 1 The difference between the centrifugal compressors shown is that the centrifugal compressor 1 and the centrifugal compressor 2 are not provided with the first compressor flameproof section 114 and the second compressor flameproof section 214, and the centrifugal compressors 1 and 2 are additionally provided with a safety gas path.

[0043] Attached Figure 2 The centrifugal compressor 1 and the centrifugal compressor 2 shown are filled with high-pressure protective gas into the gap between the motor rotor and the stator through the first-stage compressor safety gas path inlet 118 and the second-stage compressor safety gas path inlet 218, and then the high-pressure protective gas is discharged from the compressor through the first-stage compressor safety gas path outlet 119 and the second-stage compressor safety gas path outlet 219. The high-pressure protective gas prevents the inflammable and explosive working gas from entering the motor, thereby avoiding the explosion of the equipment. The protective gas can be high-pressure air, inert gas or other gas. The protective gas not only plays a protective role, but also plays a role in heat preservation of the motor. When the safety gas path is working, the valve 4 of the heat preservation circuit can be closed first, and the temperature of the motor can be monitored by the established temperature sensors 117 and 217. If the gas in the safety gas path can complete the heat preservation function of the motor, there is no need to use the heat preservation circuit. If the gas in the safety gas path cannot fully realize the heat preservation function, it is necessary to assist the heat preservation work of the motor by adjusting the opening of the opening regulating valve 4, so as to ensure the normal operation of the motor.

Claims

1. An explosion-proof low-temperature oil-free centrifugal compressor unit, comprising a centrifugal compressor, a connecting pipe, a heat preservation circuit and a heat insulation material, characterized in that: The centrifugal compressor includes a motor, an impeller, a volute, and a bearing; The centrifugal compressor motor includes a motor stator, a rotor and an end cover. The motor housing is provided with an air inlet and an air outlet. A flameproof section is provided between the compressor impeller and the motor stator. The motor rotor is supported by a gas bearing or a gas-magnetic hybrid bearing. The end cover is connected to the housing by welding. The impeller of the centrifugal compressor is fixed on the motor rotor of the centrifugal compressor and is located inside the volute. The two compressors use the same impeller at both ends. The rotor structure is symmetrically distributed, and there is no need to consider the axial force. The centrifugal compressor does not need to be equipped with a thrust plate. The thrust surface is the surface on the rotor main shaft that is perpendicular to the rotor. There is another gas path at the secondary volute, which is connected to the centrifugal compressor casing to form a heat preservation circuit. A temperature sensor is provided on the heat preservation circuit to judge the motor temperature and control the direction of the gas path and the amount of gas through the opening regulating valve. Gas bearings are divided into radial bearings and thrust bearings, and the bearing types are full dynamic pressure, dynamic and static pressure, or full static pressure; The connecting pipe connects the exhaust port of the first-stage compressor and the air inlet of the second-stage compressor; The compressor stator, end cover, volute, connecting pipe, and gas pipeline are all made of heat-insulating materials; The compressor casing and the outside of the gas pipeline are wrapped with insulation materials. The compressor operates in the atmospheric environment or working environment. The compressor inlet temperature ranges from -250℃ to 20℃. There is no need to consider motor cooling when operating under low temperature conditions.

2. The explosion-proof low-temperature oil-free centrifugal compressor unit according to claim 1, characterized in that: The compressor can operate at an inlet temperature of -250°C, the power consumption of the compressor is greatly reduced compared with that at normal temperature, and the working gas can be hydrogen, natural gas, permeate gas, analytical gas and regeneration gas.

3. The explosion-proof low-temperature oil-free centrifugal compressor unit according to claim 1, characterized in that: When the compressor is running at low temperature, there is no need to consider motor cooling. Through the insulation circuit, the higher temperature gas at the outlet of the secondary volute is used to heat the centrifugal compressor motor to ensure that the motor operating temperature is higher than the compressor inlet gas temperature.

4. The explosion-proof low-temperature oil-free centrifugal compressor unit according to claim 1, characterized in that: The motor is a permanent magnet synchronous motor with a flameproof section or a permanent magnet synchronous motor without a flameproof section. When a permanent magnet synchronous motor without a flameproof section is used, an air inlet and an exhaust hole are required to be provided on the motor casing of the centrifugal compressor. A protective gas with a certain pressure is filled into the gap between the motor rotor and the stator through the air inlet to prevent the working gas from entering. The protective gas is nitrogen or an inert gas.

5. The explosion-proof low-temperature oil-free centrifugal compressor unit according to claim 4, characterized in that: When a permanent magnet synchronous motor without explosion-proof section is used, the introduced protective gas can keep the motor warm. At the same time, the motor temperature can be monitored by the temperature sensor installed on the insulation circuit. When the protective gas cannot fully achieve the insulation function, the opening regulating valve can be set to adjust the airflow size of the insulation circuit to assist in achieving the insulation work of the motor.

6. The explosion-proof low-temperature oil-free centrifugal compressor unit according to claim 1, characterized in that: The centrifugal compressor unit may have 1 to 12 stages, and interstage cooling may be further arranged between the compressors of each stage. The centrifugal compressor unit may have 1 to 8 centrifugal compressors with the same structure on both sides connected in parallel.

7. The explosion-proof low-temperature oil-free centrifugal compressor unit according to claim 1, characterized in that: A labyrinth seal is arranged on the inner side of the motor end cover, and an interference fit or a transition fit is adopted between the impeller and the main shaft. The impeller is a semi-open impeller or a closed impeller.

8. The explosion-proof low-temperature oil-free centrifugal compressor unit according to claim 1, characterized in that: The centrifugal compressor is supported by gas bearings or gas-magnetic hybrid bearings. The entire system operates purely oil-free and does not require oil removal and oil return devices.

9. The explosion-proof low-temperature oil-free centrifugal compressor unit according to claim 1, characterized in that: The connecting pipe is made of a stretchable heat-insulating material to avoid stress caused by thermal expansion and contraction.

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