System for a process for compressing

Abstract

The invention relates to a system (2) for a process for compressing a process fluid by means of a flow machine (1), comprising: a flow machine (1) for compressing a process fluid (3), wherein the flow machine (1) comprises a rotor (6); a bearing (4, 5) operated with a bearing oil (7) for bearing the rotor (6) of the flow machine (1); a first shaft seal (8) and a second shaft seal (12), wherein the first shaft seal (8) is supplied with a sealing oil (9); furthermore an expansion vessel (14) which is designed to provide the sealing oil (9), wherein the first shaft seal (8) is supplied with sealing oil (9) from the expansion vessel (14), wherein in the first shaft seal (8) a first mixed oil (11) is produced, wherein the first mixed oil (11) comprises sealing oil (9) and the process fluid (3), wherein the second shaft seal (12) is supplied with a second mixed oil (15), wherein the second mixed oil (15) is formed from the sealing oil (9) from the expansion vessel (14) and the first mixed oil (11).

Description

[0001] Description

[0002] System for a compaction process

[0003] The invention relates to a system for a process for compressing a process fluid with a turbo machine, comprising a turbo machine for compressing a process fluid, wherein the turbo machine comprises a rotor, a bearing operated with a bearing oil for supporting the rotor of the turbo machine, a first shaft seal and a second shaft seal, wherein the first shaft seal is supplied with a barrier oil, furthermore an expansion vessel which is designed to provide the barrier oil, wherein the first shaft seal is supplied with barrier oil from the expansion vessel, wherein a first mixed oil is produced in the first shaft seal, wherein the first mixed oil comprises barrier oil and the process fluid.

[0004] A turbo compressor, as an embodiment of a turbo machine, is used to compress a process fluid or a process gas in a manufacturing process. The turbo compressor has a rotor which is mounted on bearings outside a housing enclosing the rotor. Since there is relative movement between the rotor and the housing when the turbo compressor is in operation, a gap must be maintained at the point where the rotor shaft emerges from the inside of the housing to the outside. The gap must be bridged with a shaft seal in order to prevent any leakage of process gas from the inside of the turbo compressor to the outside, or at least to keep it acceptably small. If the process gas is flammable, toxic and / or environmentally hazardous, the demands on the shaft seal with regard to its sealing effect are high.

[0005] It is known to use oil-lubricated plain bearings, especially oil-lubricated tilting-pad plain bearings, for the bearings. The design of the plain bearings is tailored to the operating speed and the rotor dynamics, with the shaft seal and the bearing arranged directly adjacent to each other on the shaft.

[0006] In a cyclic process, such as a refrigeration cycle, in which a refrigerant is used as the process fluid, high demands are placed on the shaft seal. Leakage of the process gas from the turbo compressor must be kept to a minimum. If, for example, the shaft seal is designed as a liquid seal which is sealed with a barrier oil, the barrier oil must be selected to be chemically compatible with the refrigerant. Traditionally, the barrier oil is also used as the lubricating oil for the bearings, so the turbo compressor is supplied by a combined lubricating / barrier oil system, whereby the barrier oil must also be suitable for lubricating and cooling the bearings, which means that the barrier oil has to meet a wide range of requirements.For example, mineral oil may be unsuitable as a barrier oil for lubricating bearings and locking shaft seals because it may not be compatible with the refrigerant used in the refrigeration process. Special synthetic oils can provide a solution, but they are highly hygroscopic and therefore must not be exposed to the humidity of the outside atmosphere.

[0007] The object of the invention is to provide a system for a process for compressing a process fluid with a turbomachine, wherein the turbomachine is safely mounted with a low leakage of process fluid.

[0008] This object is achieved by the features of patent claims 1 to 10. Preferred embodiments are specified in the further patent claims.

[0009] The invention can be used for a gear compressor with four compression stages for a heat pump process.

[0010] The system according to the invention is characterized by a sealing concept with barrier oil as the separating medium. In the following, a preferred embodiment of the turbocompressor according to the invention with the bearing system according to the invention is explained with reference to the attached schematic drawing. They show

[0011] Figure 1 is a schematic representation of the shaft seals

[0012] Figure 2 is a schematic representation of part of the system according to the invention

[0013] Figure 3 is a schematic representation of part of the system according to the invention

[0014] Figure 4 is a schematic representation of part of the system according to the invention.

[0015] As can be seen from the figures, a turbocompressor 1 as an embodiment of a turbomachine has a system 2. The turbocompressor 1 could also be designed as a heat pump. The turbocompressor 1 is integrated into a process for compressing process fluid 3.

[0016] The turbocompressor 1 has a first stage 1a, a second stage 1b, a third stage 1c, and a fourth stage 1d. A first bearing 4 is arranged between the first stage 1a and the second stage 1b. A second bearing 5 is arranged between the third stage 1c and the fourth stage 1d.

[0017] The fluidically effective area of ​​the turbocompressor 1 is the process side, which is separated from the atmosphere. A rotor 6 of the turbocompressor 1 is supported by the bearing 4, 5, which is arranged outside the process side. The bearing 4, 5 is insulated from the atmosphere by an atmosphere-side shaft seal and from the process side by a process-side shaft seal. As a result, the shaft seals hermetically seal the bearing 4, 5 from the atmosphere and the process. The bearing 4, 5 and the shaft seals are integrated in a bearing seal housing, which is closed except for the inlets and outlets.

[0018] The system 2 is designed for a process for compressing a process fluid 3 with the turbo machine 1.

[0019] The bearing 4, 5 is operated with a bearing oil 7. The system 2 further comprises a first shaft seal 8, which can be designed as a double-acting mechanical seal.

[0020] The first shaft seal 8 is supplied with barrier oil 9. The barrier oil 9 acts, on the one hand, as a coolant for the first shaft seal 8 and, on the other hand, as a barrier fluid for a first leakage flow 10 from the turbocompressor 1. The first leakage flow 10 mixes with the barrier oil 9 to form a first mixed oil 11, wherein the leakage flow 10 contains the process fluid 3.

[0021] The system 2 further comprises a second shaft seal 12, which can be designed as a single-acting mechanical seal 12.

[0022] The barrier oil 9 comes from an expansion tank 14 which is designed to provide the barrier oil 9.

[0023] The second shaft seal 12 is supplied with a second mixed oil 15 , wherein the second mixed oil 15 is formed from the barrier oil 13 from the expansion tank 14 and the first mixed oil 11 .

[0024] A bearing housing 16 separates the bearing 4 , 5 from the shaft seal 8 , 12 .

[0025] Nitrogen is used as the separating gas 17 to prevent bearing oil 7 from spreading into the shaft seal 8, 12. For this purpose, a third mixed stream 18, comprising the separating gas 17 and the second mixed oil 15 is led from the system 2. Figure 2 shows a schematic overview of the supply of barrier oil 9. First, the barrier oil 9 is provided in an expansion vessel 14. Via a first line 19, the barrier oil 9 flows to a heat exchanger 20, where the barrier oil 9 is heated. The heated barrier oil 9 then passes through a first filter 21. From there, the barrier oil 9 passes via four lines to the respective first shaft seal 8. In the embodiment according to Figure 2, four first shaft seals 8 can be seen.

[0026] The sealing oil 9 for the second mechanical seal 12 also originates from the expansion tank 14. However, here the sealing oil 9 is branched off at a branch 22 upstream of the heat exchanger 20 and from there passes through a filter 24 via a line 23. From the filter 24, the sealing oil 13 reaches the second shaft seal 12, but is first mixed with the leakage flow, which is the process fluid.

[0027] The pressure is adjusted via restriction orifices 25. The mixed oil from the first shaft seal 8 and the second shaft seal 12 returns to the expansion tank 14 via a return line 26a. However, it is first treated.

[0028] Due to the four compressor stages 1a, 1b, 1c, and 1d, four shaft seals 8, 12 must separate the bearings 4, 5 from the process gas, which in the case of a heat pump is the turbomachine 1. The shaft seals are designed as a combined single mechanical seal 8 and double mechanical seals 12, thus achieving the lowest possible barrier oil quantity via the seal. The double mechanical seals 12 are loaded on the pressure side and operate at different pressure levels.

[0029] Additionally, a seal must also be provided to the gearbox, as the bearing oil 7 must not mix with the barrier oil mixture, which includes barrier oil 9 and the process fluid 3. The separation from the bearing oil 7, which can also be referred to as gear oil, is achieved via the individual seal 12 with nitrogen 17 as the separation medium. This means that a mixture of barrier oil 9, process fluid leakage 9, and nitrogen 17 is created in the mixing chamber.

[0030] An oil tank open to the atmosphere was omitted because the oil should not come into contact with the outside atmosphere and coolant dissolved in the oil can also outgas.

[0031] For volume compensation, a manifold completely filled with oil with the expansion tank 14 is provided in the sealing oil circuit. To reduce the number of control valves for cooling oil 9, two compressor stages have been combined. The process-side leaks from oil and refrigerant are separated by means of oil separators and a degassing system and returned to the respective circuits. The leaks on the bearing and gear side are also collected in a container and returned to the oil circuit.

[0032] The double-acting mechanical seal 8 consists of two mechanical seals, one sealing on the process side and one on the bearing side. Cooling oil 9 flows through the seal housing, thereby cooling the seal rings. At the same time, the pressure in the cooling oil 9 must also be higher than the pressure on the process side. The barrier oil system must therefore have sufficient cooling oil 9 for cooling and a correspondingly positive delta p on the process side. It is also desirable that no gas pockets can form inside the housing of the double-acting mechanical seal 8. If necessary, the return line should be arranged at the highest point for this purpose.

[0033] The single-acting mechanical seal 12 is arranged next to the double-acting mechanical seal 8 toward the bearing and gearbox side. It serves as an additional seal and, due to the lower delta p, minimizes leaks toward the bearing and gearbox sides. Figure 2 shows the concept for the barrier oil supply to the double-acting mechanical seals 8. The oil system should only provide the required barrier oil 13. The lubricating oil system is separate.

[0034] In order to maintain the oil pressure in accordance with the requirements of the double mechanical seals 8 during operation and at standstill, differential pressure control valves 26 are installed in the cooling oil return of the double mechanical seals 8. These differential pressure control valves 26 throttle the cooling oil return and thereby maintain the oil pressure above the sealing pressure of the process medium.

[0035] At the same time, the required cooling oil quantity must be ensured during operation. To achieve this, the required cooling oil quantities must be ensured in the supply line by appropriate measures. This is achieved here by orifices.

[0036] The sealing oil system is operated with refrigeration oil. To prevent contact of the refrigeration oil with the atmosphere, the conventional oil reservoir is omitted. As shown in Figure 2, the oil reservoir is replaced by a manifold with an expansion tank 14. The manifold with expansion tank 14 contains only oil. A vent is opened when the system is filled with oil. It is closed during operation.

[0037] The expansion tank 14 compensates for volume changes in the sealing oil circuit without major pressure changes. These volume changes arise primarily from thermal expansion of the sealing oil, e.g., due to maintenance, changing the filter elements, or leaks in the mechanical seals 8, 12. These leaks are collected and separated from dissolved refrigerant in a degassing unit, and then returned to the sealing oil circuit at intervals.

[0038] The pressure in the manifold with expansion tank 14 is slightly above atmospheric pressure. If required, an electric heater can be installed in the manifold to heat the oil before startup. The sealing oil is extracted from the manifold with expansion tank 14 by pumps 27. The main and auxiliary oil pumps are used as pumps 27. Figure 2 shows only one pump 27 as an example.

[0039] Due to the required pressures, the pumps 27 are designed as positive displacement pumps. Each pump is fitted with a safety valve 28. The main and auxiliary oil pumps are interlocked. Only one pump can be in operation at a time. On the pressure side downstream of the pumps, excess sealing oil is directed back to the collecting pipe with expansion tank 14 via a discharge regulator 29. The discharge regulator 29 regulates the oil pressure downstream of the filter 21 so that, depending on the operating point, the oil pressure is always a constant value higher than the maximum gas-side sealing pressure.

[0040] The maximum sealing pressure here is at the fourth stage Id. Behind the branch to the discharge regulator 29, the sealing oil enters the cooler or heat exchanger 20. The cooler can be designed as a single or double cooler with a temperature bypass.

[0041] The barrier oil then flows through the filter 21 to supply the double mechanical seals 8. The filter 21 is designed as a double filter with a changeover valve.

[0042] The single mechanical seals 12 are supplied with uncooled oil through a branch 22 upstream of the cooler 20. Due to the low delta p at the single mechanical seals 12, lower oil viscosities are required. The oil for the single mechanical seals 12 is also passed through a filter 24 after the branch 22 upstream of the cooler.

[0043] The expansion tank 14 is located on the suction side of the main and auxiliary oil pumps. It comprises a piston accumulator that is supplied with oil from the barrier oil system on one side and a reference oil on the other. The reference oil connection on the accumulator is connected via a pipe to a collecting tank with atmospheric venting. The collecting tank is positioned so that it is above the piston accumulator. This creates a slight overpressure on the suction side of the pumps.

[0044] The level of the piston in the piston accumulator is monitored. Monitoring can be done via a level sensor in the collecting container or directly on the piston accumulator.

[0045] The oil pressure in the flow direction downstream of the oil filter 21 is regulated via a predetermined differential pressure above the process-side pressure of the stage with the highest pressure level, which in this case is the fourth stage Id. If the process-side pressure changes, the oil pressure also changes in accordance with the predetermined differential pressure.

[0046] The four barrier oil inlets branch off from line 30 at this pressure level and lead, via a restriction orifice 25, to the four double-acting mechanical seals 8. Barrier oil 9 flows through the double-acting mechanical seals 8 and cools them. The first 1a and second 1b, as well as the third 1c and fourth stage 1d, are combined in the return line 26a of the double-acting mechanical seals 12.

[0047] Differential pressure controlled control valves 26 are arranged in these combined return lines and build up the oil pressure to the required delta p on the process side. The pulse pressure for the control valves 26 is always the higher of the two stages 1a, 1b and 1c, 1d on the process side. The restriction orifices 25 therefore have the task of providing the required amount of barrier oil for cooling and the differential pressure controlled control valves 26 have the task of maintaining the required barrier oil pressure. The restriction orifices 25 are to be designed individually for these conditions. If the process-side pressures change due to process requirements, the barrier oil pressures and also the delta p at the restriction orifices 25 also change.Even if the turbomachine 1, designed as a compressor, is shut down and a standstill pressure is reached, the barrier oil pressure must be regulated accordingly, and cooling oil 9 must be available at the appropriate pressure. During standstill, the cooling oil quantity may be lower, since there is no heat to dissipate.

[0048] For all possible operating points and possible standstill pressures, it must be ensured that sufficient cooling oil 9 flows through the restriction orifices 25 and that the differential pressure-controlled control valves in the return line 26a can build up the barrier oil to the required pressure. This is only possible if the operating points are not too far apart.

[0049] In order to maintain the sealing oil supply even during transient processes, such as pump switching, a bladder accumulator 32 is installed in the supply line 30.

[0050] The design of the cooling oil supply of the simple mechanical seal 12 is described below.

[0051] The single mechanical seals 12 also require cooling oil 9 and a defined pre-pressure in order to achieve the required delta p to the bearing or gear side. The cooling oil is regulated to the required pre-pressure via line 33 by a pressure reducing valve 34. The cooling oil quantity is dimensioned by orifices 35 in the return line. However, care must be taken to ensure that the minimum possible oil pressure that can prevail due to the pressure regulation of the double mechanical seals 8 is sufficiently high to then still ensure an adequate supply of barrier oil to the single mechanical seals 12. The discharge of the process-side oil leaks from the double mechanical seals 8 and the refrigerant is described below with reference to Figure 3.

[0052] The process-side leaks from the double mechanical seals 8 are fed into the oil separator 37 together with the refrigerant, which flows through the labyrinths into the reference gas chamber. This is where the oil and refrigerant are separated. After being separated from the oil, the refrigerant is fed back to the suction side of the compressor 38 via orifices 39. The separated oil is fed via level-controlled drain valves into the collection tank 14, which is under the suction pressure of the compressor 1. From this collection tank 14, the oil is then fed at intervals to a degassing system 40.

[0053] The oil separators 37 can be completely blocked off. In the event of a fault, one oil separator 37 can be blocked off and the process-side leaks from the blocked-off oil separator 37 can be directed to the adjacent separator via an openable connecting line 41. The drain valves on the oil separators 37 should be controlled by level measurement in the separator tanks. This allows a statement to be made about the extent of the process-side oil leaks based on the interval times for controlling the drain valves.

[0054] The drainage of leaks from single mechanical seals is described below using Figure 4.

[0055] The leaks from the single mechanical seals 12 and the separating barrier gas (N2) to the bearing and gear side are fed together into a collecting tank 42 with atmospheric vent 43. The separating barrier gas can escape through the atmospheric vent 43 via a vent filter. The oil contained in the collecting tank 42 is drained via a level control and fed to the barrier oil circuit via small pumps 44. Although the invention has been illustrated and described in detail using the preferred embodiment, the invention is not limited by the disclosed examples and other variants can be derived by those skilled in the art without departing from the scope of the invention.

Claims

Patent claims 1. System (2) for a process for compressing a process fluid with a turbomachine (1), comprising a turbomachine (1) for compressing a process fluid (3), wherein the turbomachine (1) comprises a rotor (6), a bearing (4, 5) operated with a bearing oil (7) for supporting the rotor (6) of the turbomachine (1), a first shaft seal (8) and a second shaft seal (12), wherein the first shaft seal (8) is supplied with a barrier oil (9), furthermore an expansion vessel (14) which is designed to provide the barrier oil (9), wherein the first shaft seal (8) is supplied with barrier oil (9) from the expansion vessel (14), wherein in the first shaft seal (8) a first mixed oil (11), wherein the first mixed oil (11) comprises barrier oil (9) and the process fluid (3), characterized in that the second shaft seal (12) is supplied with a second mixed oil (15), wherein the second mixed oil (15) is formed from the barrier oil (9) from the expansion vessel (14) and the first mixed oil (11).

2. System (2) according to claim 1, wherein the turbomachine (1) is designed as a turbocompressor or as a heat pump.

3. System (2) according to claim 1 or 2, wherein the first shaft seal (8) is designed as a double mechanical seal.

4. System (2) according to claim 1, 2 or 3, wherein the second shaft seal (12) is designed as a single mechanical seal.

5. System (2) according to one of claims 1 to 4, wherein the first shaft seal (8) and the second shaft seal (12) are designed such that the bearing (4, 5) is insulated from the atmosphere.

6. System (2) according to one of claims 1 to 5, with a cooling device (20), wherein the barrier oil (9) flowing into the first shaft seal (8) can be cooled in the cooling device (20).

7. System (2) according to one of claims 1 to 6, wherein the pressure of the barrier oil (9) flowing into the first shaft seal (8) and into the second shaft seal (12) can be regulated by restriction orifices (35).

8. System (2) according to one of claims 1 to 7, wherein the turbomachine (1) comprises four compressor stages (1a, 1b, 1c, 1d).

9. System (2) according to one of claims 1 to 8, wherein two compressor stages (1a, 1b or 1c, 1d) have a common bearing (4,5).

10. Turbo compressor or heat pump with a system (2) according to one of claims 1 to 9.

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