System for compression process

Abstract

System (2) comprises a fluid machine (1) for compressing a process fluid (3), the fluid machine (1) includes a rotor (6), bearings (4, 5) lubricated with lubricating oil (7) for supporting the rotor (6) of the fluid machine (1), a first shaft seal (8) and a second shaft seal (12), the first shaft seal (8) being supplied with sealing oil (9), an expansion vessel (14) for supplying the sealing oil (9), the first shaft seal (8) being supplied with sealing oil (9) from the expansion vessel (14), a first mixed oil (11) consisting of the sealing oil (9) and the process fluid (3) being generated within the first shaft seal (8), and the second shaft seal (12) being supplied with a second mixed oil (15), the second mixed oil (15) being formed from the sealing oil (9) from the expansion vessel (14) and the first mixed oil (11).

Description

Technical Field

[0001] The present invention relates to a system for a process of compressing a process fluid by a fluid machine. The system comprises a fluid machine with a rotor for compressing the process fluid, a bearing lubricated by lubricating oil for supporting the rotor of this fluid machine, first and second shaft seals, with seal oil supplied to the first shaft seal, and further comprises an expansion vessel configured to supply this seal oil. Seal oil is supplied from this expansion vessel to the first shaft seal, and a first mixed oil is generated within the first shaft seal, which first mixed oil contains seal oil and process fluid.

[0002] A turbo compressor as a form of fluid machine is used for compressing a process fluid or a process gas in an engineering process step. The turbo compressor has one rotor, and the rotor is supported by bearings provided outside a housing surrounding the rotor. Since relative movement occurs between the rotor and the housing during operation of the turbo compressor, a gap needs to be provided at the location where the rotor shaft exits from the inside of the housing to the outside. This gap is bridged by a shaft seal to prevent the process gas from leaking from inside the turbo compressor to the outside, or at least to suppress it to an acceptable level. When the process gas is flammable, toxic, or environmentally harmful, the requirements for the sealing performance of this shaft seal become higher.

[0003] As such bearings, it is known to use oil-lubricated sliding bearings, particularly tilting segment sliding bearings. The design of these sliding bearings is adapted to the operating rotational speed and the rotational dynamics of the rotor, and the shaft seal and the bearing are arranged adjacent to each other on the shaft.

[0004] In circulating processes such as cooling cycles that use a refrigerant as the process fluid, high precision is required for shaft seals. Leakage of process gas from the turbo compressor must be minimized. If this shaft seal is configured as a liquid seal, for example, sealed with a sealing oil, the sealing oil must be selected to be chemically compatible with the refrigerant. Traditionally, sealing oil has also been used as a lubricant for bearings, so turbo compressors are supplied with a lubricant / sealing oil composite system. In this case, the sealing oil must also be suitable for lubricating and cooling the bearings, and therefore this sealing oil must meet a variety of requirements. For example, mineral oil may not be compatible with the refrigerant used in the cooling process, making it unsuitable as a sealing oil for both lubricating bearings and sealing shaft seals. Special synthetic oils may be used as an improvement measure, but these have strong hygroscopic properties and should not be exposed to humidity in the outside air. [Overview of the project] [Problems that the invention aims to solve]

[0005] The object of the present invention is to provide a system for a process of compressing a process fluid using a fluid machine, wherein the fluid machine is reliably supported while minimizing leakage of the process fluid. [Means for solving the problem]

[0006] This problem is solved by the features described in claims 1 to 10. Preferred embodiments thereof are shown in the dependent claims.

[0007] The present invention is applicable to a geared compressor having four compression stages for a heat pump process.

[0008] The system of the present invention is characterized by a sealing concept that uses sealing oil as a separation medium.

[0009] A preferred embodiment of the turbo compressor according to the present invention, equipped with the bearing system according to the present invention, will be described below based on the attached schematic diagram. The following diagram is shown. [Brief explanation of the drawing]

[0010] [Figure 1] This is a schematic diagram of a shaft seal. [Figure 2] This is a schematic diagram of a part of the system according to the present invention. [Figure 3] This is a schematic diagram of a part of the system according to the present invention. [Figure 4] This is a schematic diagram of a part of the system according to the present invention. [Modes for carrying out the invention]

[0011] As is evident from these figures, the turbo compressor 1, as a form of fluid machinery, comprises system 2. This turbo compressor 1 can also be configured as a heat pump. This turbo compressor 1 is incorporated into a process that compresses a process fluid 3.

[0012] This turbo compressor 1 has a first stage 1a, a second stage 1b, a third stage 1c, and a fourth stage 1d. A first bearing 4 is positioned between the first stage 1a and the second stage 1b, and a second bearing 5 is positioned between the third stage 1c and the fourth stage 1d.

[0013] The hydrodynamically functional part of this turbo compressor 1 is the process side, which is isolated from the atmosphere. The rotor 6 of the turbo compressor 1 is supported by bearings 4 and 5 located outside the process side. Bearings 4 and 5 are isolated from the atmosphere by atmospheric-side shaft seals and from the process side by process-side shaft seals. Thus, these shaft seals hermetically seal bearings 4 and 5 from the atmosphere and the process. Bearings 4 and 5 and their shaft seals are incorporated into a bearing seal housing, which is sealed except for the inlet and outlet.

[0014] System 2 is configured for a process in which a process fluid 3 is compressed by a fluid machine 1.

[0015] The bearings 4 and 5 are lubricated by lubricating oil 7. Furthermore, system 2 includes a first shaft seal 8, which can be configured as a double mechanical seal.

[0016] A sealing oil 9 is supplied to the first shaft seal 8. The sealing oil 9 acts, on the one hand, as a cooling medium for the first shaft seal 8, and on the other hand, as a sealing fluid for the first leak flow 10 from the turbo compressor 1. The first leak flow 10 mixes with the sealing oil 9 to form a first mixed oil 11, which contains a process fluid 3.

[0017] System 2 further includes a second shaft seal 12, which can be configured as a single mechanical seal.

[0018] The sealing oil 9 is supplied from an expansion container 14 configured to supply the sealing oil 9.

[0019] The second shaft seal 12 is supplied with a second mixed oil 15, which is formed from the seal oil 13 from the expansion container 14 and the first mixed oil 11.

[0020] The bearing housing 16 separates the bearings 4 and 5 from the shaft seals 8 and 12. Nitrogen is used as the separation gas 17, which prevents the lubricating oil 7 from diffusing into the shaft seals 8 and 12. For this purpose, a third mixed flow 18 is supplied, which contains the separation gas 17 and a second mixed oil 15 from system 2.

[0021] Figure 2 is a schematic diagram of the supply of seal oil 9. First, the seal oil 9 is prepared in the expansion vessel 14. The seal oil 9 flows into the heat exchanger 20 through the first pipe 19, where the seal oil 9 is heated. After that, the heated seal oil 9 passes through the first filter 21. From there, the seal oil 9 is supplied to each of the first shaft seals 8 through four pipes respectively. In the embodiment shown in Figure 2, four first shaft seals 8 are shown.

[0022] The seal oil 9 for the second mechanical seal 12 is also supplied from the expansion vessel 14 in the same manner. However, in this case, the seal oil 9 branches at the branch point 22 upstream of the heat exchanger 20 and passes through the filter 24 via the pipe 23. This seal oil 13 is supplied to the second shaft seal 12 after passing through the filter 24, but is mixed with the leakage flow before that. This leakage flow is the process fluid.

[0023] Its pressure is adjusted by a plurality of throttle valves 25. The mixed oil from the first shaft seal 8 and the second shaft seal 12 is returned to the expansion vessel 14 via the return pipe 26a. However, reprocessing is performed before that.

[0024] Since there are four compression stages 1a, 1b, 1c, and 1d, four shaft seals 8, 12 are required to separate the bearings from the process gas. When the fluid machine 1 is configured as a heat pump, the process gas is a refrigerant gas. These shaft seals are configured as a combination of a single mechanical seal 8 and a double mechanical seal 12, thereby minimizing the amount of seal oil passing through the seal as much as possible. The double mechanical seal 12 receives a load on the pressurized side and operates at different pressure levels.

[0025] Furthermore, a seal is also required for the gear housing. This is because the lubricating oil 7 must not be mixed with a seal oil mixture (including the seal oil 9 and the process fluid 3). The separation from the lubricating oil 7 (also called gear oil) is performed by a single seal 12 using nitrogen 17 as a separation medium. That is, in the mixing chamber, a mixture consisting of the seal oil 9, the process fluid leakage component 9, and nitrogen 17 is generated.

[0026] In order to prevent the oil from coming into contact with the outside air and also because the refrigerant dissolved in the oil may be released as a gas, an atmospheric open type oil tank is not used.

[0027] In order to compensate for volume changes, a header pipe completely filled with oil in the seal oil circuit is attached to the expansion vessel 14. In order to reduce the number of regulating valves for the cooling oil 9, two compression stages are grouped together. The leakage of oil and refrigerant occurring on the process side is separated by an oil separator and a degassing device and returned to their respective circuits. The leakage on the bearing and gear sides is similarly collected in one tank and returned to the oil circuit.

[0028] The double mechanical seal 8 is composed of two mechanical seals, one sealing against the process side and the other against the bearing side. The cooling oil 9 flows through the seal housing, thereby cooling the sliding ring. At the same time, the pressure of the cooling oil 9 must be higher than the pressure on the process side. Therefore, this seal oil system needs to supply sufficient cooling oil 9 for cooling and maintain a positive pressure difference (Δp) against the process side. Furthermore, it is desirable that no bubbles occur in the housing of the double mechanical seal 8. For this purpose, the return pipe is arranged at the highest position as necessary.

[0029] The single mechanical seal 12 is arranged adjacent to the bearing / gear side of the double mechanical seal 8. This functions as an auxiliary seal and, since the pressure difference (Δp) is smaller, minimizes leakage to the bearing and gear sides.

[0030] Figure 2 shows a schematic diagram of the supply of sealing oil to the double mechanical seal 8. This oil system supplies only the necessary sealing oil 13, and the lubrication oil system is a separate system.

[0031] Multiple differential pressure regulating valves 26 are provided in the coolant return system of the double mechanical seals 8 to maintain the necessary hydraulic pressure for the double mechanical seals 8, whether in operation or stopped. These differential pressure regulating valves 26 restrict the return flow of the coolant, thereby maintaining a hydraulic pressure higher than the sealing pressure of the pressurized process medium.

[0032] At the same time, it is necessary to ensure the required amount of coolant during operation. For this purpose, it is necessary to achieve a predetermined amount of coolant in advance by appropriate means. Here, this is achieved by multiple throttle valves.

[0033] This sealing oil system operates using refrigerant oil. To prevent the refrigerant oil from coming into contact with the atmosphere, a conventional oil tank is not used. As shown in Figure 2, the oil tank has been replaced with an oil collection pipe equipped with an expansion container 14. Only oil is present in this oil collection pipe with the expansion container 14. The exhaust port is opened when filling the system with oil, but remains closed during operation.

[0034] The expansion container 14 compensates for volume changes in the seal oil circuit without large pressure fluctuations. These volume changes are mainly caused by thermal expansion of the seal oil, such as maintenance work, replacement of filter elements, or leakage from mechanical seals 8 and 12. These leaks are collected, separated from the dissolved refrigerant in the degassing unit, and then returned to the seal oil circuit at regular intervals.

[0035] The pressure inside the oil collection pipe equipped with the expansion container 14 is slightly higher than atmospheric pressure. If necessary, an electric heater can be installed in this oil collection pipe to preheat the oil before operation begins. Seal oil is drawn from the oil collection pipe equipped with the expansion container 14 by a pump 27. Here, a main oil pump and an auxiliary oil pump are used as the pump 27. Figure 2 shows only one pump 27 as an example.

[0036] To obtain the required pressure, these pumps 27 are configured as positive displacement pumps. Each pump is equipped with one safety valve 28. The main oil pump and the auxiliary oil pump are interlocked with each other, so that only one of them can be operated at a time. On the pressure side downstream of the pump, excess sealing oil is returned to the oil collection pipe with expansion container 14 via the discharge flow regulator 29. This discharge flow regulator 29 adjusts the hydraulic pressure downstream of the filter 21 so that it is always a constant value higher than the maximum sealing pressure on the gas side, depending on the operating point.

[0037] The maximum sealing pressure occurs at the fourth stage 1d. Downstream of the branch to the discharge flow regulator 29, the sealing oil is sent to a cooler or heat exchanger 20. This cooler can be configured as a single or double cooler with a temperature bypass mechanism.

[0038] Subsequently, the sealing oil passes through filter 21 to be supplied to the double mechanical seal 8. Filter 21 is configured as a double filter with a switching valve. Supply to the single mechanical seal 12 is from branch 22 upstream of the cooler 20, and uncooled oil is used. Since the pressure difference Δp is small in the single mechanical seal 12, low viscosity oil is required. The oil for the single mechanical seal 12 is also led to filter 24 downstream of branch 22 and upstream of the cooler.

[0039] The expansion container 14 is located on the suction side of the main oil pump and the auxiliary oil pump. This expansion container is equipped with a piston-type accumulator, with oil from the sealing oil system acting on one side and reference oil acting on the other side. The reference oil connection port of this accumulator is connected by piping to a recovery tank equipped with an exhaust port to the atmosphere, and this recovery tank is located above the piston-type accumulator. This creates a slight overpressure on the suction side of the pump.

[0040] The piston position in the piston-type accumulator is monitored. This monitoring can be performed by measuring the level in the recovery tank or directly on the accumulator itself.

[0041] The hydraulic pressure downstream of filter 21 is controlled as a value obtained by adding a predetermined differential pressure to the process-side pressure of the highest pressure stage (in this case, the fourth stage 1d). When the process-side pressure changes, this hydraulic pressure also changes in accordance with this predetermined differential pressure.

[0042] Four seal oil supply lines branch off from this pressure-level piping 30 and lead to four double mechanical seals 8 via throttle valves 25. Seal oil 9 flows through these double mechanical seals 8, thereby cooling them. In the return piping 26a of the double mechanical seals 12, the first stage 1a and the second stage 1b, as well as the third stage 1c and the fourth stage 1d, are grouped together.

[0043] Multiple differential pressure regulating valves 26 are provided in these combined return pipes, and these differential pressure regulating valves maintain the hydraulic pressure up to the required pressure difference Δp on the process side. The instantaneous pressure for these regulating valves 26 is always the process-side pressure, whichever is higher of the two stages (1a and 1b, and 1c and 1d). That is, the throttle valves 25 are responsible for supplying the amount of sealing oil necessary for cooling, and the differential pressure regulating valves 26 are responsible for maintaining the required sealing hydraulic pressure. The throttle valves 25 are individually designed to meet these conditions.

[0044] When the process-side pressure changes due to process requirements, the seal hydraulic pressure and the pressure difference Δp in the throttle valve 25 also change. Even when the fluid machine 1, configured as a compressor, stops and static pressure is generated, this seal hydraulic pressure must be properly adjusted, and a cooling oil 9 at a predetermined pressure must be present. When stopped, there is no need for heat dissipation, so the amount of cooling oil may be less.

[0045] It must be ensured that a sufficient amount of cooling oil 9 flows through the throttle valve 25 for all operating points and static pressures, and that the differential pressure regulating valve in the return pipe 26a can maintain the sealing oil at a predetermined pressure. This is only possible if the operating points are not too far apart from each other.

[0046] To maintain the supply of sealing oil even during non-steady processes such as pump switching, a bladder-type accumulator 32 is provided in the supply line 30.

[0047] The following describes the configuration for supplying coolant to the single mechanical seal 12.

[0048] The single mechanical seal 12 also requires pre-filling with coolant 9 and a specified pressure to establish a predetermined pressure difference Δp with respect to the bearing or gear side. The coolant is regulated to a predetermined pressure by a pressure reducing valve 34 via piping 33. The amount of coolant is set by a throttle valve 35 in the return circuit. However, care must be taken to ensure that the minimum hydraulic pressure controllable by the pressure adjustment of the double mechanical seal 8 is sufficiently high to guarantee a sufficient supply of sealing oil to the single mechanical seal 12.

[0049] Next, with reference to Figure 3, the discharge of leaked oil and refrigerant from the process side of the double mechanical seal 8 will be described.

[0050] Leakage from the process side of the double mechanical seal 8 is led to the oil separator 37 along with the refrigerant leaking through the labyrinth into the reference gas chamber. Here the oil and refrigerant are separated. The separated refrigerant is returned to the suction side of the compressor 38 via the throttle valve 39. The separated oil is sent to the oil collection tank 14, which is under the suction pressure of the compressor 1, via a level-controlled discharge valve. This oil is sent from the oil collection tank 14 to the degassing device 40 at regular intervals.

[0051] The oil separator 37 is configured to be completely shut off, so that in the event of a failure, the oil separator 37 can be shut off, and the process-side leakage from the shut-off oil separator 37 can be directed to an adjacent separator via a connectable pipe 41. The discharge valve of the oil separator 37 is controlled by level measurement in the separator container. This allows the amount of process-side oil leakage to be determined from the time interval of operation of the discharge valve.

[0052] The discharge of leakage from a single mechanical seal is described below, with reference to Figure 4.

[0053] Leakage from the single mechanical seal 12, and the separation seal gas (N2) to the bearing and gear side, are both led to an oil collection tank 42 having an open-atmosphere vent 43. Through this open-atmosphere vent 43, the separation seal gas is released to the outside through an exhaust filter. Under level control, the oil in the oil collection tank 42 is discharged and returned to the seal oil circuit via a small pump 44.

[0054] Although the present invention has been illustrated and described in detail by preferred embodiments, the present invention is not limited to these disclosures. Those skilled in the art can derive other modifications without departing from the scope of protection of the present invention.

Claims

1. A system (2) for a process that compresses a process fluid using a fluid machine (1), The system comprises a fluid machine (1) for compressing a process fluid (3), the fluid machine (1) including a rotor (6), The fluid machine (1) is equipped with bearings (4, 5) that are lubricated with lubricating oil (7) to support the rotor (6), It comprises a first shaft seal (8) and a second shaft seal (12), and the first shaft seal (8) is supplied with sealing oil (9). The first shaft seal (8) is provided with an expansion container (14) configured to supply sealing oil (9), and the sealing oil (9) from the expansion container (14) is supplied to the first shaft seal (8). The first shaft seal (8) is configured to generate a first mixed oil (11) containing a sealing oil (9) and a process fluid (3), In the system, A second mixed oil (15) is supplied to the second shaft seal (12), and the second mixed oil (15) consists of the seal oil (9) from the expansion container (14) and the first mixed oil (11). System (2).

2. The system (2) according to claim 1, A system in which the fluid machine (1) is configured as a turbo compressor or a heat pump.

3. The system (2) according to claim 1 or 2, A system in which the first shaft seal (8) is configured as a double mechanical seal.

4. The system (2) according to claim 1, 2, or 3, A system in which the second shaft seal (12) is configured as a single mechanical seal.

5. A system (2) according to any one of claims 1 to 4, A system in which the first shaft seal (8) and the second shaft seal (12) are configured to isolate the bearings (4, 5) from the atmosphere.

6. A system (2) according to any one of claims 1 to 5, A system comprising a cooling device (20) wherein the sealing oil (9) flowing into the first shaft seal (8) can be cooled by the cooling device (20).

7. A system (2) according to any one of claims 1 to 6, A system in which the pressure of the sealing oil (9) flowing into the first shaft seal (8) and the second shaft seal (12) can be adjusted by a plurality of throttle valves (35).

8. A system (2) according to any one of claims 1 to 7, The fluid machine (1) is a system comprising four compression stages (1a, 1b, 1c, 1d).

9. A system (2) according to any one of claims 1 to 8, A system in which two compression stages (1a, 1b, or 1c, 1d) share a common bearing (4, 5).

10. A turbo compressor or heat pump comprising the system (2) according to any one of claims 1 to 9.

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