Novel cryogenic low-temperature liquid turbo expander

Abstract

The utility model relates to the field of isentropic expansion of cryogenic low-temperature liquid, and discloses a novel cryogenic low-temperature liquid turbo expander which comprises a volute, an adjusting valve is arranged at an inlet of the volute, a nozzle is arranged at an inlet of an impeller, and the impeller is arranged at the outlet end of the nozzle. The permanent magnet high-speed generator assembly comprises a rotor assembly and a stator assembly, the rotor assembly comprises a rotating shaft, an impeller and the like, the impeller and the rotating shaft are coaxially and fixedly connected, and the two ends of a rotor suspend through magnetic bearings; cryogenic low-temperature liquid is subjected to isentropic expansion through rotation of the nozzle and the impeller, and the impeller drives the rotor assembly to rotate for power generation. The expansion machine has the advantages of wide application range, low cost, energy conservation, high efficiency and the like.

Description

Technical Field

[0001] This utility model relates to the field of cryogenic liquid energy recovery and utilization, and in particular to a novel cryogenic liquid turbine expander. Background Technology

[0002] Currently, due to safety concerns, most international air separation units utilize internal compression processes. This involves a process where high-pressure cryogenic liquid is throttled to low pressure, a process also present in cryogenic liquefaction and cryogenic liquid air separation units. Currently, cryogenic throttling valves are commonly used to simply and crudely throttle the cryogenic liquid to low pressure, resulting in significant energy loss. In the past decade or so, traditional cryogenic liquid expanders have been adopted for large and ultra-large internal compression air separation processes to achieve isentropic decompression expansion of the cryogenic liquid, avoiding this energy waste. However, these traditional cryogenic liquid expanders use lubricated bearings, requiring a large lubrication oil supply system, gear reducers, and conventional generators and couplings. This makes the unit extremely bulky, large, and complex, with numerous connections, resulting in extremely high costs. Consequently, many process units cannot use such units, leading to the waste of high-quality energy. For example, Chinese patent CN112145240A discloses a pipeline-type magnetic levitation turbine high-speed permanent magnet generator set, representing a certain exploration in this area.

[0003] However, none of the medium and small-sized internal compression air separation units, liquefaction units, and liquid air separation processes worldwide currently use liquid expanders for energy-saving isentropic expansion and depressurization processes. Instead, they all use inexpensive throttling valves for isenthalpic throttling and depressurization, resulting in energy loss. Moreover, this type of equipment accounts for about 2 / 3 of the total number of such units, which is a huge waste and a real pity. Utility Model Content

[0004] This invention addresses the shortcomings of existing technologies by providing a novel cryogenic liquid turbine expander.

[0005] A novel cryogenic liquid turbine expander includes a volute, an inlet valve for regulating and shutting off the volute, a nozzle downstream of the volute, and an impeller at the outlet of the nozzle. It also includes a generator assembly comprising a rotor assembly and a stator assembly. The rotor assembly includes a shaft, with magnetic bearings at both ends suspending the rotor. The impeller is coaxially and fixedly connected to the shaft. The cryogenic liquid undergoes isentropic expansion through the nozzle and impeller, and the impeller drives the rotor assembly to rotate and generate electricity.

[0006] Preferably, the nozzle is a fixed nozzle, and the system also includes a frequency converter connected to the generator assembly to control the impeller speed; it also includes a unit controller, which controls the current impeller speed through the frequency converter, and the speed adjustment amount and the frequency adjustment amount of the frequency converter are adjusted equally according to the change in flow rate measured in the process.

[0007] Preferably, the system also includes a cold box, a volute, a fixed nozzle, and an impeller, all housed within the cold box to isolate the deep low-temperature zone from the normal temperature zone.

[0008] Preferably, the device also includes a magnetic bearing controller. The magnetic bearings include a magnetic radial bearing I near the impeller end, a magnetic radial bearing II at the tail of the shaft, and a magnetic thrust bearing. The magnetic bearing controller controls the operation of the magnetic radial bearing I, the magnetic radial bearing II, and the magnetic thrust bearing.

[0009] Preferably, the assembly also includes a housing, with the impeller located outside the housing, the generator assembly and the magnetic bearing located inside the housing, and a seal provided at the end of the housing near the impeller.

[0010] Preferably, the unit controller is electrically connected to the magnetic bearing controller and the frequency converter.

[0011] Preferably, the regulating valve is a shut-off regulating valve.

[0012] Preferably, the medium is a cryogenic liquid (liquid air, liquid nitrogen); the inlet pressure of the volute is 20 bar to 90 bar; the temperature is below -100 degrees Celsius; the outlet pressure after passing through the impeller is 5 bar to 10 bar; the flow rate is greater than or equal to 10000 Nm3 / h; and the power is greater than or equal to 10 kW.

[0013] Compared with existing technologies, this solution offers the following advantages: The high-efficiency hydraulic turbine impeller technology more closely approximates the isentropic decompression expansion process, resulting in significant energy savings. The adoption of active magnetic levitation bearings avoids traditional oil-lubricated sliding bearings and the large, complex auxiliary lubrication system, greatly reducing mechanical losses. Simultaneously, the unit configuration is significantly simpler than before, eliminating the numerous potential equipment failures caused by the complex configuration of previous units, thus greatly improving the stability and reliability of the unit. The use of high-frequency motors directly eliminates the need for reduction gearboxes, couplings, and other equipment, while also removing concerns about gearbox reduction ratio limitations, further broadening the application range of hydraulic turbines. This is of great significance for the miniaturization of hydraulic turbines. The adoption of variable frequency technology eliminates the need for fixed-frequency grid connection of the previous reducer. Furthermore, variable frequency regulation, i.e., variable speed regulation, achieves zero-angle adjustment of process fluid flow rate, directly converting previously adjustable nozzles into fixed nozzles. This not only does not affect the unit's performance but also avoids internal and external leakage losses from adjustable nozzles, improving unit performance. The unit's structure and configuration have been greatly simplified, resulting in smaller units that are safer, more reliable, and significantly reduced in cost. This makes it possible to achieve energy savings by using this unit in smaller air separation plants, and also greatly shortens the investment payback period. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the overall device design.

[0015] Figure 2 This is a schematic diagram of the impeller and fixed nozzle structure.

[0016] The technical names of the reference numerals in the figure are as follows: 1—volute, 2—regulating valve, 3—nozzle, 4—impeller, 5—generator assembly, 6—rotor assembly, 7—stator assembly, 8—shaft, 9—frequency converter, 10—flow measurement mechanism, 11—unit controller, 12—magnetic bearing controller, 13—magnetic radial bearing I, 14—magnetic radial bearing II, 15—magnetic thrust bearing, 16—casing, 17—seal. Detailed Implementation

[0017] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments.

[0018] Example 1

[0019] A novel cryogenic liquid turbine expander includes a volute 1, with a regulating valve 2 at the inlet and a nozzle 3 at the outlet, and an impeller 4 at the outlet end of the nozzle 3; it also includes a generator assembly 5, which includes a rotor assembly 6 and a stator assembly 7. The rotor assembly 6 includes a rotating shaft 8, which is suspended at both ends by magnetic bearings. The impeller 4 is coaxially and fixedly connected to the rotating shaft 8. The cryogenic liquid enters the impeller 4 after passing through the nozzle and rotates to perform isentropic expansion. The impeller 4 drives the rotor assembly 6 to rotate and generate electricity.

[0020] The overall concept of this scheme is that the cryogenic liquid passes through the inlet shut-off valve regulating valve 2, the unit volute and nozzle 3 for depressurization and expansion acceleration, and then enters the impeller 4 for further depressurization and isentropic expansion before leaving the unit. That is, the internal energy of the fluid is converted into mechanical energy, which at the same time drives the impeller 4 and the high-frequency generator rotor, cutting magnetic lines of force to generate high-frequency electricity. After being converted into the same frequency as the main grid by the frequency converter 9, it is connected to the main grid and output to the main grid. In other words, mechanical energy is converted into electrical energy.

[0021] In this design, nozzle 3 is a fixed nozzle, and the unit also includes a frequency converter 9, which is connected to the generator assembly 5 to control the speed of impeller 4; it also includes a unit controller 11, which controls the current speed of impeller 4 through the frequency converter 9. The fixed nozzle 3 greatly simplifies the unit structure, while maintaining the same adjustment characteristics as the adjustable nozzle 3. Furthermore, it eliminates the internal leakage of the adjustable nozzle gap and the external leakage loss of the adjustable mechanism, thereby improving the unit's performance. This is because the unit uses a frequency converter, and the speed of the adjustable impeller 4 can still achieve zero-angle flow regulation. The speed adjustment and the frequency adjustment of the frequency converter are adjusted equally according to the changes in flow measurement in the process.

[0022] The specific application methods of frequency converter regulation are as follows:

[0023] Zero-angle adjustment can be achieved by adjusting the frequency and speed by equal amounts based on the measured flow rate changes. See details. Figure 2 .

[0024] When the flow rate m of the unit changes, since the nozzle 3 is fixed, the change is also the change in the absolute velocity C in the nozzle 3, that is, from the original flow velocity C1 to the current flow velocity C1': the ratio is C1' / C1. According to the velocity triangle, we only need to adjust the rotational speed of the impeller 4 to the same ratio: n' / n=U1' / U1, where U1 is the component of velocity C in the tangential direction of the velocity triangle, where the tangential direction is the direction of the tangent line of the impeller 4 through the circumference, which is the velocity direction of the impeller 4 at the current position. The velocity component in the other direction is w1, where n' is the desired velocity of the impeller 4 and n is the current velocity of the impeller 4. This adjustment can ensure that the relative velocity changes from w1 to w1', which is zero angle of attack.

[0025] Where the change in flow velocity equals the change in flow rate, and the flow rate is represented by m, that is:

[0026] m / m=C1' / C1=n' / n=U1' / U1.

[0027] In actual operation, the unit adjustment can be calculated based on the ratio between the actual flow rate display value M' in the process flow and the design flow rate value m1 of the device: m' / m1. The design speed n1 of the unit is then adjusted to the frequency corresponding to the same speed value m' / m1 = n' / n1 through the frequency converter 9, thereby achieving zero-angle adjustment.

[0028] The isentropic expansion process of the unit replaces the isenthalpic process of the throttling valve. The isentropic cooling capacity of the unit is the isentropic enthalpy difference between the inlet and outlet (ΔHs), and the actual cooling capacity is the actual enthalpy difference between the inlet and outlet of the unit (ΔHr). The ratio of these two enthalpy differences is the unit efficiency (η): η = ΔHr / ΔHs

[0029] The relationship between the actual cooling capacity of the unit and the energy savings of the entire plant: The cooling capacity (CP) of the unit will bring several times the energy savings (WP) to the entire process plant.

[0030] WP = K * CP

[0031] In the above formula, K is called the amplification factor. It is generally related to the process fluid medium M and the temperature T. Lighter process fluid media have a larger K value, while heavier process fluid media have a smaller K value. The lower the temperature of the process, the larger the K value. Their relationship is: K∝(M,T). Generally, the K value of deep cryogenic liquids such as liquid air and liquid nitrogen is in the range of 5 to 7.

[0032] The scheme also includes a magnetic bearing controller 12. The magnetic bearings include a magnetic radial bearing 13 near the impeller 4, a magnetic radial bearing 14 at the tail of the shaft 8, and a magnetic thrust bearing 15. The magnetic bearing controller 12 controls the operation of the magnetic radial bearing 13, the magnetic radial bearing 14, and the magnetic thrust bearing 15.

[0033] The system also includes a housing 16, with the impeller 4 located outside the housing 16, and the generator assembly 5 and magnetic bearing located inside the housing 16. A seal 17 is provided at one end of the housing 16 near the impeller 4. The seal 17 isolates the cold chamber and the hot chamber, thereby reducing the loss of liquid cooling and improving efficiency. The unit controller 11 is electrically connected to the magnetic bearing controller 12 and the frequency converter 9. In this design, the regulating valve 2 is a shut-off regulating valve, which mainly functions to regulate and shut off the flow.

[0034] In this design, the medium is a cryogenic liquid (liquid air, liquid nitrogen); the inlet pressure range of the volute 1 is 20 bar to 90 bar; the temperature range is below -100 degrees Celsius; the outlet pressure range after passing through the impeller 4 is 5 bar to 10 bar; the flow rate is greater than or equal to 10000 Nm3 / h; and the power is greater than or equal to 10 kW.

[0035] There is an amplification factor K between the actual energy saving value of the unit and the electrical energy generated by the unit. This factor is inversely proportional to the liquid temperature. Only cryogenic liquids with low temperatures can achieve significant energy-saving effects, which is the area this paper focuses on. This differs from conventional refrigeration industries, such as refrigerant expanders in air conditioning and cold storage, and ORC circulating liquid expanders in waste heat recovery processes. Their temperatures are conventional refrigeration temperatures, many times higher than those in cryogenic air separation processes, resulting in significantly inferior energy-saving effects. Therefore, the cryogenic liquid expander discussed here is fundamentally different from liquid expanders used in other industries. It differs in structure, materials, power, speed, pressure, temperature, and medium. To date, such units have not been used in the air separation industry.

[0036] In summary, this paper combines traditional cryogenic liquid turbine expanders with other technologies, simplifying the internal structure of the old liquid turbine expander: complex adjustable nozzles are replaced with simple fixed nozzles, and performance is improved. At the same time, the unit is simplified: the expensive reduction gearbox and the large and complex lubrication system are eliminated, which greatly reduces the original mechanical losses, avoids too many auxiliary equipment, and eliminates the overall failure rate caused by the failure of auxiliary equipment during operation. This greatly improves the safety and stability of the overall unit, significantly reduces the cost of the unit, and reduces the footprint.

[0037] Example 2

[0038] The difference between this embodiment and Embodiment 1 is that the sealer is a labyrinth sealer.

[0039] Example 3

[0040] The difference between this embodiment and Embodiment 1 is that the temperature range is -190 degrees Celsius.

[0041] Example 4

[0042] The difference between this embodiment and Embodiment 1 is that the temperature range is below -150 degrees Celsius.

[0043] Example 5

[0044] The difference between this embodiment and Embodiment 1 is that it also includes a cold box 20. The volute 1, nozzle 3, and impeller 4 are all housed within this cold box 20 to isolate the deep cryogenic zone and the ambient temperature zone. The ambient temperature zone is the space where the generator set 5 is located, and the cryogenic zone is the area where the nozzle 3 and impeller 4 are located. Because of the introduction of the cryogenic liquid, there is a significant temperature difference between the two. The cold box 20 can prevent losses caused by heat exchange between the cryogenic and ambient temperatures. The cryogenic temperature range is below -100 degrees Celsius, and the ambient temperature range is from -30 degrees Celsius to 60 degrees Celsius.

Claims

1. A novel cryogenic liquid turbine expander, characterized in that: The system includes a volute (1), with a regulating valve (2) at the inlet and a nozzle (3) at the outlet, and an impeller (4) at the outlet end of the nozzle (3); it also includes a generator assembly (5), which includes a rotor assembly (6) and a stator assembly (7). The rotor assembly (6) includes a shaft (8), which is suspended at both ends by magnetic bearings. The impeller (4) is coaxially and fixedly connected to the shaft (8). The cryogenic liquid enters the impeller (4) after passing through the nozzle and rotates to undergo isentropic expansion. The impeller (4) drives the rotor assembly (6) to rotate and generate electricity.

2. The novel cryogenic liquid turbine expander according to claim 1, characterized in that: The nozzle (3) is a fixed nozzle (3), and also includes a frequency converter (9), which controls the speed of the impeller (4) through the generator assembly (5); it also includes a unit controller (11), which controls the operation of the frequency converter (9).

3. A novel cryogenic liquid turbine expander according to claim 2, characterized in that: It also includes a magnetic bearing controller (12), the magnetic bearings include a magnetic radial bearing one (13) near the end of the impeller (4), a magnetic radial bearing two (14) at the tail of the shaft (8) and a magnetic thrust bearing (15); the magnetic bearing controller (12) controls the operation of the magnetic radial bearing one (13), the magnetic radial bearing two (14) and the magnetic thrust bearing (15).

4. The novel cryogenic liquid turbine expander according to claim 1, characterized in that: It also includes a housing (16), an impeller (4) located outside the housing (16), a generator assembly (5) and a magnetic bearing located inside the housing (16), and a seal (17) provided at one end of the housing (16) near the impeller (4).

5. A novel cryogenic liquid turbine expander according to claim 3, characterized in that: The unit controller (11) is electrically connected to the magnetic bearing controller (12) and the frequency converter (9).

6. A novel cryogenic liquid turbine expander according to claim 1, characterized in that: The regulating valve (2) is a shut-off regulating valve (2).

7. A novel cryogenic liquid turbine expander according to claim 1, characterized in that: The inlet pressure range of the volute (1) is 20 bar to 90 bar; the outlet pressure range after passing through the impeller (4) is 5 bar to 10 bar; the flow rate is greater than or equal to 10000 Nm³. 3 / h; power greater than or equal to 10kw.

8. A novel cryogenic liquid turbine expander according to claim 1, characterized in that: The cryogenic liquid is liquid air or liquid nitrogen, with a temperature range below -100 degrees Celsius.

9. A novel cryogenic liquid turbine expander according to claim 1, characterized in that: It also includes a cold box (20), and the volute (1), nozzle (3) and impeller (4) are all located inside the cold box (20) to isolate the deep low temperature zone and the normal temperature zone.

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