Stirling low-temperature liquefaction system

Abstract

The utility model discloses a Stirling low-temperature liquefaction system which comprises a Stirling cryocooler unit, a liquid storage unit, a cooling water unit and a control unit. The Stirling cryocooler unit comprises a Stirling cryocooler and an internal combustion engine which are connected through a power transmission mechanism; the Stirling cryocooler comprises a condensation head used for liquefying gas, a cold end heat exchanger is arranged in the condensation head, and the cold end heat exchanger is a finned heat exchanger or a tubular heat exchanger. The cold end heat exchanger is directly connected with the liquid storage unit; a water cooler of the Stirling cryocooler is connected with an inlet and an outlet of the cooling water unit; the control unit is electrically connected with the internal combustion engine, the work transmission mechanism, the liquid storage unit and the cooling water unit. By means of the system, the liquefaction efficiency of the liquefaction system is improved, zero emission in the liquefaction process is achieved, meanwhile, the internal combustion engine drives the Stirling cryocooler to conduct gas liquefaction, the energy utilization efficiency is improved, and therefore the problem that a conventional liquefaction system depends on electric power is solved.

Description

Technical Field

[0001] The utility model relates to the technical field of gas liquefaction, in particular to a Stirling cryogenic liquefaction system. Background Art

[0002] Gas liquefaction refers to the process of converting a substance from gas to liquid. There are two ways to achieve gas liquefaction: one is to lower the temperature, and the other is to compress the volume. Gas cryogenic liquefaction is a technology that physically converts gas into liquid through compression and cooling. The volume of liquefied gas is greatly reduced, which is convenient for storage, transportation and utilization, but it also faces problems such as high energy consumption, high technical requirements and high equipment costs.

[0003] In the gas liquefaction production process, apart from fixed costs such as raw gas purchase, labor wages, and financial expenses, electricity costs account for the vast majority of the entire processing costs, and the electricity consumed by the refrigeration system during gas cooling and cooling accounts for the largest proportion of the total energy consumption in the gas liquefaction process. Therefore, improving the refrigeration efficiency and heat transfer efficiency of the refrigeration system and rationally and efficiently utilizing energy are important aspects of energy conservation and consumption reduction in the gas liquefaction system.

[0004] Chinese patent document with publication number CN108518919A discloses a cascade natural gas liquefaction system using a pulse tube Stirling refrigerator, and Chinese patent document with publication number CN108413705A discloses a cascade regenerative natural gas liquefaction system using a pulse tube Stirling refrigerator.

[0005] The liquefaction system using the pulse tube Stirling refrigerator has the advantages of reducing system power consumption and improving system efficiency, but there are problems such as too many devices and insufficient compactness of the structure. In addition, the current Stirling refrigerator generally uses electric energy to drive the motor, which greatly reduces the energy utilization efficiency. Utility Model Content

[0006] The utility model provides a Stirling cryogenic liquefaction system, which improves the liquefaction efficiency of the liquefaction system and drives a Stirling refrigerator to liquefy gas, thereby improving energy utilization efficiency and solving the problem of conventional liquefaction systems being dependent on electricity.

[0007] A Stirling cryogenic liquefaction system comprises a Stirling refrigerator unit, a liquid storage unit, a cooling water unit and a control unit;

[0008] The Stirling refrigerator unit comprises a Stirling refrigerator and an internal combustion engine connected by a work transfer mechanism; the Stirling refrigerator comprises a condensing head for liquefying gas, and a cold end heat exchanger is arranged in the condensing head; the cold end heat exchanger adopts a fin type heat exchanger or a tube type heat exchanger, and is vacuum sealed inside a vacuum cover;

[0009] The cold end heat exchanger is directly connected to the liquid storage unit; the water cooler of the Stirling refrigerator is connected to the inlet and outlet of the cooling water unit.

[0010] The control unit is electrically connected to the internal combustion engine, the power transmission mechanism, the liquid storage unit and the cooling water unit respectively.

[0011] Furthermore, the material of the fin-type heat exchanger is red copper, and the structure includes an outer shell and external heat exchange fins, external heat exchange channels and internal heat exchange fins arranged in the outer shell; the external heat exchange fins and internal heat exchange fins can be obtained by milling on the same material, or by welding multiple groups of fins; along the gas flow direction, the flow area of ​​the external heat exchange channel gradually decreases; a first air inlet pipe is provided at the upper part of the outer shell, and a first liquid outlet pipe connected to the liquid storage unit is provided at the lower part; the external heat exchange channel is connected to the first liquid outlet pipe through the first liquid collecting channel.

[0012] Furthermore, the tubular heat exchanger includes a base, a shell arranged on the base, a second air inlet pipe arranged on the upper part of the shell, and a second liquid outlet pipe arranged on the base, and the second liquid outlet pipe is connected to the liquid storage unit; a U-shaped heat exchange tube, supporting fins and heat exchange fins are arranged in the shell, and the supporting fins and heat exchange fins are inserted into the U-shaped heat exchange tube at a certain interval to form an upper heat exchange channel, an intermediate heat exchange channel, and a lower heat exchange channel, which are connected end to end in sequence, and the number of channels decreases step by step; the U-shaped heat exchange tube is welded on the base; the inlet of the upper heat exchange channel is connected to the second air inlet pipe, and the outlet of the lower heat exchange channel is connected to the second liquid outlet pipe through the second liquid collecting channel.

[0013] Furthermore, the support fins are made of stainless steel, the heat exchange fins are made of copper, the U-shaped heat exchange tube is a thin-walled round tube made of stainless steel, and the support fins and heat exchange fins are welded and fixed to the outer wall of the U-shaped heat exchange tube.

[0014] Furthermore, the liquid storage unit includes a low-temperature storage tank and a pressure sensor and a liquid level sensor arranged in the low-temperature storage tank; the low-temperature storage tank is provided with an air supply pipeline with an electromagnetic shut-off valve, and is connected to the cold end heat exchanger through the pipeline;

[0015] The control unit is electrically connected to the pressure sensor, the liquid level sensor and the electromagnetic stop valve in the liquid storage unit.

[0016] Furthermore, the pipeline adopts a single pipeline structure, and the outlet of the pipeline is placed in the upper gas phase space of the cryogenic storage tank;

[0017] Alternatively, the pipeline adopts a double pipeline structure, including an air outlet pipeline and a liquid inlet pipeline, the inlet of the air outlet pipeline is located in the upper gas phase space of the low-temperature storage tank, and the outlet of the liquid inlet pipeline is located in the lower liquid phase space of the low-temperature storage tank.

[0018] Further, the power transmission mechanism comprises a torque and speed sensor, a coupling, a clutch and a cross transmission shaft connected in sequence, the torque and speed sensor is connected in sequence with a high elastic coupling and a flywheel of a Stirling refrigerator, and the cross transmission shaft is connected with a crankshaft of an internal combustion engine;

[0019] The control unit is electrically connected to the torque speed sensor and the clutch in the power transmission mechanism.

[0020] A control method for a Stirling cryogenic liquefaction system, comprising:

[0021] The cryogenic tank is provided with an air supply pipeline with an electromagnetic stop valve for controlling the pressure of the cryogenic tank. When the pressure sensor provided on the cryogenic tank detects that the pressure of the cryogenic tank is lower than the set pressure, the control unit controls the electromagnetic stop valve to open for air supply; the temperature of the cold end heat exchanger of the Stirling refrigerator is adjusted by regulating the gas pressure of the cryogenic tank;

[0022] A liquid level sensor is provided on the cryogenic storage tank to monitor the liquid level of the cryogenic storage tank. When the liquid level of the cryogenic storage tank is detected to be higher than the set liquid level, the control unit controls the internal combustion engine to shut down, thereby stopping the Stirling refrigerator.

[0023] The torque speed sensor in the power transfer mechanism is used to monitor the speed and input power of the Stirling refrigerator. If the speed and input power are abnormal, the control unit controls to reduce or increase the fuel supply to the internal combustion engine;

[0024] The clutch in the power transmission mechanism is used to control the connection and disconnection of the Stirling refrigerator and the internal combustion engine, which is achieved by controlling the on and off of the clutch in the transmission mechanism by the control unit.

[0025] The cooling water unit must be turned on before the Stirling refrigerator. When the cooling water temperature is lower than the set temperature, the control unit can control the clutch to cut off power and close to start the Stirling refrigerator. When the temperature and pressure of the cooling water in the cooling water unit deviate from the set target value, the control unit controls the shutdown of the internal combustion engine.

[0026] The utility model uses an internal combustion engine to drive a Stirling refrigerator, and the internal combustion engine can use coalbed methane, shale gas, biogas, diesel, gasoline, etc. as fuel. More preferably, the internal combustion engine can directly use natural gas as fuel, using local materials. Part of the natural gas is used for combustion to drive the engine to work, and part can enter the cold end heat exchanger of the Stirling refrigerator for liquefaction and recovery as product output. In addition, it is also very friendly to the field of gas liquefaction such as hydrogen and oxygen, and has broad application prospects.

[0027] Compared with the prior art, the utility model has the following beneficial effects:

[0028] 1. The liquid storage system of the utility model is directly connected to the condensing head of the Stirling refrigerator through a pipeline. Under the low temperature negative pressure of the condensing head, the gas enters the cold end heat exchanger along the pipeline to be cooled and liquefied, and flows back to the low temperature storage tank under the action of gravity. In particular, in the case of a double-pipeline structure, the gas enters the cold end heat exchanger from the top of the condensing head along the gas outlet pipeline, and continues to cool down along the direction of gas flow and gravity until it is liquefied, and flows back to the low temperature storage tank along the liquid inlet pipeline. The flow resistance is small and the flow rate is high during the gas liquefaction process, which greatly improves the liquefaction efficiency and realizes the non-powered circulation liquefaction of the gas. The gas liquefaction process is closed, without any gas emissions, no cold energy waste or environmental pollution, and the system cost is low and the structure is simple.

[0029] 2. The Stirling cryogenic liquefaction system of the utility model uses an internal combustion engine as a power source, directly drives the piston of the Stirling refrigerator to push the working gas to do work, and generates thermal potential energy, that is, temperature difference, without relying on motor drive. It not only solves the problem of power shortage, but also has outstanding advantages in the liquefaction and recovery of unconventional natural gas such as coalbed methane and rock formation methane.

[0030] 3. The finned heat exchanger is processed with the same material and has good heat transfer performance. Along the gas flow direction, the flow area of ​​the external heat exchange channel of the finned heat exchanger gradually decreases. The gas flows in the heat exchange channel to absorb heat, the volume gradually decreases, and the flow rate slows down. Reducing the flow area can ensure that the gas maintains a high flow rate during the liquefaction process and improve the heat transfer efficiency. The tubular heat exchanger has the advantage of a large heat exchange area, which is more conducive to pre-cooling the gas in the shell and forming a large negative pressure, and the gas flow resistance is small. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is a schematic diagram of the structure of a Stirling cryogenic liquefaction system of the utility model;

[0032] Figure 2 This is a structural diagram of a fin-type cold-end heat exchanger used in the utility model;

[0033] Figure 3 This is a structural diagram of a tubular cold end heat exchanger used in the utility model;

[0034] Figure 4 This is a single-pipeline liquefaction process of a Stirling cryogenic liquefaction system of the utility model;

[0035] Figure 5 The utility model discloses a double-pipeline liquefaction process of a Stirling cryogenic liquefaction system.

[0036] In the figure: 1-Stirling refrigerator unit; 101-Stirling refrigerator; 102-condensing head; 103-cold end heat exchanger; 104-vacuum cover; 105-internal combustion engine; 106-finned heat exchanger; 107-tube heat exchanger; 108-housing; 109-external heat exchange fin; 110-external heat exchange flow channel; 111-internal heat exchange fin; 112-first air inlet pipe; 113-first liquid collecting flow channel; 114-first liquid outlet pipe; 115-housing; 116-base; 117-U-type heat exchange tube; 118-support fin; 119-heat exchange fin; 120-upper heat exchange flow channel; 121- Intermediate heat exchange channel; 122-lower heat exchange channel; 123-second air inlet pipe; 124-second liquid collecting channel; 125-second liquid outlet pipe; 126-high elastic coupling; 127-flywheel; 128-crankshaft; 129-water cooler; 2-liquid storage unit; 201-low temperature storage tank; 202-pressure sensor; 203-liquid level sensor; 204-pipeline; 205-air outlet pipeline; 206-liquid inlet pipeline; 207-air supply pipeline; 208-electromagnetic stop valve; 3-cooling water unit; 4-control unit; 5-torque speed sensor; 6-coupling; 7-clutch; 8-cross drive shaft. DETAILED DESCRIPTION

[0037] The present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be pointed out that the embodiments described below are intended to facilitate the understanding of the present invention and do not have any limiting effect on the present invention.

[0038] like Figure 1 As shown, a Stirling cryogenic liquefaction system mainly includes a Stirling refrigerator unit 1, a liquid storage unit 2, a cooling water unit 3 and a control unit 4.

[0039] The Stirling refrigerator unit 1 includes a Stirling refrigerator 101 and an internal combustion engine 105; the Stirling refrigerator 101 and the internal combustion engine 105 are connected through a work transmission mechanism. The work transmission mechanism includes a torque speed sensor 5, a coupling 6, a clutch 7 and a cross transmission shaft 8 connected in sequence, the torque speed sensor 5 is connected in sequence with a high elastic coupling 127 and a flywheel 126 of the Stirling refrigerator 101, and the cross transmission shaft 8 is connected with a crankshaft 128 of the internal combustion engine 105. In the utility model, the internal combustion engine 105 can use natural gas, diesel, gasoline, etc. as fuel.

[0040] The Stirling refrigerator 101 includes a condensing head 102 for liquefying gas; a cold end heat exchanger 103 is provided in the condensing head 102, and the cold end heat exchanger 103 is vacuum sealed inside a vacuum cover 104. The water cooler 129 of the Stirling refrigerator 1 is connected to the inlet and outlet of the cooling water unit 3 respectively.

[0041] The liquid storage unit 2 is directly connected to the condensing head 102 of the Stirling refrigerator 101 through the pipeline 204. The gas enters the cold end heat exchanger 103 along the pipeline 204 under the low temperature negative pressure of the condensing head 102 to be cooled and liquefied, and flows back to the low temperature storage tank 201 under the action of gravity. In the present utility model, the cold end heat exchanger 103 can adopt two structures: a finned heat exchanger 106 or a tubular heat exchanger 107.

[0042] like Figure 2 As shown, the finned heat exchanger 106 includes a shell 108, an outer heat exchange fin 109, an outer heat exchange channel 110, an inner heat exchange fin 111, a first air inlet pipe 112, a first liquid collecting channel 113 and a first liquid outlet pipe 114. The finned heat exchanger 106 is made of copper, and the flow area of ​​the outer heat exchange channel 110 gradually decreases along the gas flow direction.

[0043] like Figure 3 As shown, the tubular heat exchanger 107 includes a shell 115, a base 116, a U-shaped heat exchange tube 117, a support fin 118, a heat exchange fin 119, a second air inlet pipe 123, a second liquid collecting channel 124 and a second liquid outlet pipe 125. The support fins 118 and the heat exchange fins 119 are inserted into the U-shaped heat exchange tube 117 at a certain interval, and form an upper heat exchange channel 120, an intermediate heat exchange channel 121 and a lower heat exchange channel 122, and are connected end to end in sequence, and the number of channels decreases step by step. The support fins 118 are made of stainless steel; the heat exchange fins 119 are made of copper; the U-shaped heat exchange tube 117 is a thin-walled round tube made of stainless steel; the support fins 118 and the heat exchange fins 119 are welded to the outer wall of the U-shaped heat exchange tube 117 by vacuum brazing.

[0044] like Figure 4 As shown, the liquid storage unit 2 includes a cryogenic storage tank 201, a pressure sensor 202, a liquid level sensor 203, a pipeline 204, a gas supply pipeline 207 and an electromagnetic stop valve 208. The pipeline 204 can be a single pipeline structure, and the gas and liquid flow in the same pipeline. In the case of a single pipeline structure, the outlet of the pipeline 204 must be placed in the upper gas phase space of the cryogenic storage tank 201.

[0045] like Figure 5 As shown, the pipeline can also be a double pipeline structure, including an air outlet pipeline 205 and a liquid inlet pipeline 206. In the double pipeline structure, the inlet of the air outlet pipeline 205 is located in the upper gas phase space of the low temperature storage tank 201, and the outlet of the liquid inlet pipeline 206 is located in the lower liquid phase space of the low temperature storage tank 201.

[0046] In particular, in the case of a dual-pipeline structure, the gas enters the cold-end heat exchanger 103 from the top of the condensing head 102 along the gas outlet pipeline 205, and continues to cool down along the gas flow and gravity direction until it is liquefied, and flows back to the cryogenic storage tank 201 along the liquid inlet pipeline 206. The gas liquefaction process has low flow resistance and high flow rate, which greatly improves the liquefaction efficiency and realizes the gas unpowered circulation liquefaction. The gas liquefaction process is closed, without any gas emission, no cold energy waste or environmental pollution, and the system cost is low and the structure is simple.

[0047] In the utility model, the control unit 4 is electrically connected to the torque speed sensor 5, the clutch 7 and the internal combustion engine 105 in the Stirling refrigerator unit 1, is electrically connected to the pressure sensor 202, the liquid level sensor 203 and the electromagnetic stop valve 208 in the liquid storage unit 2, and is electrically connected to the cooling water unit 3.

[0048] The control process of the control unit 4 specifically includes:

[0049] The electromagnetic stop valve 208 is used to control the pressure of the cryogenic storage tank 201. When the pressure sensor 202 detects that the pressure of the cryogenic storage tank 201 is lower than the set pressure, the control unit 4 controls the electromagnetic stop valve 208 to open for gas replenishment, and adjusts the temperature of the cold end heat exchanger 103 of the Stirling refrigerator by adjusting the gas pressure of the cryogenic storage tank 201.

[0050] The liquid level sensor 203 is used to monitor the liquid level of the cryogenic storage tank 201. When it is detected that the liquid level of the cryogenic storage tank 201 is higher than the set liquid level, the control unit 4 controls the internal combustion engine 6 to shut down, thereby stopping the Stirling refrigerator 101.

[0051] The torque speed sensor 5 is used to monitor the speed and input power of the Stirling refrigerator. If the speed and input power are abnormal, the control unit controls to reduce or increase the fuel supply to the internal combustion engine;

[0052] The clutch 7 is used to control the connection and disconnection between the Stirling refrigerator 101 and the internal combustion engine 105 , which is achieved by the control unit 4 controlling the on and off of the clutch 7 in the transmission mechanism.

[0053] The cooling water unit 3 must be turned on before the Stirling refrigerator 101. When the cooling water temperature is lower than the set temperature, the control unit 4 can control the clutch 7 to cut off the power and close to start the Stirling refrigerator 101; when the temperature and pressure of the cooling water in the cooling water unit 3 deviate from the set target value, the control unit 4 controls the shutdown of the internal combustion engine 105.

[0054] The embodiments described above provide a detailed description of the technical solutions and beneficial effects of the present invention. It should be understood that the above are only specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, supplements and equivalent substitutions made within the scope of the principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A Stirling cryogenic liquefaction system, characterized in that: It comprises a Stirling refrigerator unit (1), a liquid storage unit (2), a cooling water unit (3) and a control unit (4); The Stirling refrigerator unit (1) comprises a Stirling refrigerator (101) and an internal combustion engine (105) connected via a work transfer mechanism; the Stirling refrigerator (101) comprises a condensing head (102) for liquefying gas, and a cold end heat exchanger (103) is provided in the condensing head (102); the cold end heat exchanger (103) is a finned heat exchanger (106) or a tubular heat exchanger (107), and is vacuum-sealed inside a vacuum cover (104); The cold end heat exchanger (103) is directly connected to the liquid storage unit (2); the water cooler (129) of the Stirling refrigerator is connected to the inlet and outlet of the cooling water unit (3); The control unit (4) is electrically connected to the internal combustion engine (105), the work transfer mechanism, the liquid storage unit (2) and the cooling water unit (3) respectively.

2. The Stirling cryogenic liquefaction system according to claim 1, characterized in that: The finned heat exchanger (106) is made of red copper and comprises a shell (108) and external heat exchange fins (109), external heat exchange channels (110) and internal heat exchange fins (111) arranged in the shell (108); along the gas flow direction, the flow area of ​​the external heat exchange channel (110) gradually decreases; the upper part of the shell (108) is provided with a first air inlet pipe (112), and the lower part is provided with a first liquid outlet pipe (114) connected to the liquid storage unit (2); the external heat exchange channel (110) is connected to the first liquid outlet pipe (114) through the first liquid collecting channel (113).

3. The Stirling cryogenic liquefaction system according to claim 1, characterized in that: The tubular heat exchanger (107) comprises a base (116), a shell (115) arranged on the base (116), a second air inlet pipe (123) arranged on the upper part of the shell (115), and a second liquid outlet pipe (125) arranged on the base (116), wherein the second liquid outlet pipe (125) is connected to the liquid storage unit (2); the shell (115) is provided with a U-shaped heat exchange tube (117), a supporting fin (118) and a heat exchange fin (119), wherein the supporting fin (118) and the heat exchange fin (119) are provided in the shell (115); 119) are inserted on the U-shaped heat exchange tube (117) at a certain interval to form an upper heat exchange channel (120), an intermediate heat exchange channel (121), and a lower heat exchange channel (122), which are connected end to end in sequence, and the number of channels decreases step by step; the U-shaped heat exchange tube (117) is welded on the base (116); the inlet of the upper heat exchange channel (120) is connected to the second air inlet pipe (123), and the outlet of the lower heat exchange channel (122) is connected to the second liquid outlet pipe (125) through the second liquid collecting channel (124).

4. The Stirling cryogenic liquefaction system according to claim 3, characterized in that: The support fin (118) is made of stainless steel; the heat exchange fin (119) is made of copper; the U-shaped heat exchange tube (117) is a thin-walled round tube made of stainless steel; the support fin (118) and the heat exchange fin (119) are welded and fixed to the outer wall of the U-shaped heat exchange tube (117).

5. The Stirling cryogenic liquefaction system according to claim 1, characterized in that: The liquid storage unit (2) comprises a low-temperature storage tank (201) and a pressure sensor (202) and a liquid level sensor (203) arranged on the low-temperature storage tank (201); the low-temperature storage tank (201) is provided with an air supply pipeline (207) with an electromagnetic stop valve (208), and is connected to the cold end heat exchanger (103) via a pipeline (204); The control unit (4) is electrically connected to the pressure sensor (202), the liquid level sensor (203) and the electromagnetic stop valve (208) in the liquid storage unit (2).

6. The Stirling cryogenic liquefaction system according to claim 5, characterized in that: The pipeline (204) adopts a single pipeline structure, and the outlet of the pipeline (204) is placed in the upper gas phase space of the low-temperature storage tank (201); Alternatively, the pipeline (204) adopts a double pipeline structure, including an air outlet pipeline (205) and a liquid inlet pipeline (206), wherein the inlet of the air outlet pipeline (205) is located in the upper gas phase space of the low-temperature storage tank (201), and the outlet of the liquid inlet pipeline (206) is located in the lower liquid phase space of the low-temperature storage tank (201).

7. The Stirling cryogenic liquefaction system according to claim 1, characterized in that: The power transmission mechanism comprises a torque speed sensor (5), a coupling (6), a clutch (7) and a cross transmission shaft (8) which are connected in sequence, wherein the torque speed sensor (5) is connected in sequence to a high elastic coupling (127) and a flywheel (126) of a Stirling refrigerator (101), and the cross transmission shaft (8) is connected to a crankshaft (128) of an internal combustion engine (105); The control unit (4) is electrically connected to a torque speed sensor and a clutch in the power transmission mechanism.

Images