Air enthalpy difference refrigeration natural gas temperature real-time monitoring and early warning method and device

Abstract

The invention relates to the technical field of natural gas air cooling, in particular to an air enthalpy difference refrigeration natural gas temperature real-time monitoring and early warning method and device. The air enthalpy difference refrigeration natural gas temperature real-time monitoring and early warning method comprises the following steps that an outer clamping type thermometer is installed on a heat exchange tube bundle at the center position of each grid, and the natural gas temperature of an air cooler outlet header pipe is collected through a far-end controller; and according to the temperature difference value, early warning of local over-freezing blockage of the heat exchange tube bundle is achieved, and specific different air cooler anti-freezing measures are adopted, wherein the air cooler anti-freezing measures comprise an air cooler, an air blower, an outer clamping type thermometer and a far-end controller. By monitoring the real-time temperatures of different heat exchange tube bundle positions of the air cooler and comparing the real-time temperatures with the air-cooled natural gas temperature, the local over-freezing blockage risk of the heat exchange tube bundles of the air cooler can be warned, anti-freezing measures are guided to be taken in advance, stable control over the natural gas air-cooling refrigeration process is achieved, and the air-cooling refrigeration efficiency is improved. Technical guarantee is provided for air cooling refrigeration anti-freezing and anti-blocking and safe operation.

Description

Technical Field

[0001] The invention relates to the technical field of natural gas air cooling and temperature reduction, and is a method and device for real-time monitoring and early warning of natural gas temperature by air enthalpy difference refrigeration. Background Art

[0002] In the cold northern regions, air coolers are used to cool natural gas in winter. Natural gas has high pressure and low temperature, which easily generates natural gas hydrates and causes freezing and blockage, indirectly increasing the risk of freezing and cracking of the heat exchange tube bundle. Antifreeze of the heat exchange tube bundle of the air cooler is a difficult problem that needs to be solved in the natural gas air cooling refrigeration process, and it is also an important factor restricting the minimum temperature of air cooling.

[0003] When the air-cooling temperature is greater than or equal to the gas hydrate formation temperature, the temperature interlock control generally does not cause freezing of the heat exchange tube bundle. However, when the air cooler is used for natural gas refrigeration in cold northern regions, the air-cooling temperature is much lower than the natural gas hydrate formation temperature. After the natural gas enters the pipe box, it is dispersed into each heat exchange tube bundle, and after heat exchange and cooling with the air, it converges to the downstream. Although the air-cooling temperature can be monitored by installing a thermometer on the outlet pipe of the air cooler, the air cooler has many heat exchange tube bundles and is small in size (heat exchange tubes with a diameter of about φ18), so it is impossible to install an internal thermometer, and the natural gas temperature in different heat exchange tube bundles cannot be monitored.

[0004] During the operation of the air cooler, the main temperature monitored is the inlet and outlet main pipe temperature. The outlet temperature of the air cooler may be displayed as a normal value, but the actual air-cooling temperature of some heat exchange tube bundles is much lower than the actual outlet main pipe temperature, while the air-cooling temperature of another part of the heat exchange tube bundle is higher than the outlet main pipe temperature. This low temperature difference can easily lead to overcooling of the heat exchange tube bundle of the air cooler, forming natural gas hydrate freezing and blockage, which is not easy to detect. Therefore, it is necessary to develop a new method for real-time monitoring and early warning of natural gas temperature. Summary of the invention

[0005] The present invention provides a method and device for real-time monitoring and early warning of natural gas temperature in air enthalpy difference refrigeration, which overcomes the shortcomings of the above-mentioned prior art and can effectively solve the problems of low temperature monitoring and control accuracy of natural gas air cooling and the temperature difference generated by air cooling tube bundles at different positions that easily causes local over-freezing and blockage of heat exchange tube bundles.

[0006] One of the technical solutions of the present invention is achieved through the following measures: a real-time monitoring and early warning method for natural gas temperature of air enthalpy difference refrigeration, which is carried out according to the following steps: the first step is to take the central axis of the blower blade of the natural gas air cooler as the origin, and divide the heat exchange tube bundle area above the blower blade of the natural gas air cooler into grids of the same size according to the monitoring accuracy requirements; the second step is to install an external clamp-on thermometer on the heat exchange tube bundle at the center position of each grid, and after the external clamp-on thermometer monitors the outer wall temperature of the heat exchange tube bundle, it is uploaded to the remote controller by the temperature sensor; the third step is to collect the natural gas temperature of the air cooler outlet main pipe through the remote controller; the fourth step is to compare the outer wall temperature measured by the external clamp-on thermometer at different heat exchange tube bundle positions with the natural gas temperature in the air cooler outlet main pipe collected by the remote controller, and realize the early warning of local over-freezing and blockage of the heat exchange tube bundle according to the temperature difference value; the fifth step is to take specific and different air cooler anti-freezing measures according to the early warning information.

[0007] The following is a further optimization and / or improvement of one of the above-mentioned technical solutions: In the fifth step above, the anti-freezing measures taken for the air cooler include: when the temperature difference between the outer wall temperature of the heat exchange tube bundle and the natural gas temperature in the air cooler outlet main pipe is not greater than -3°C, the heat exchange tube bundle of the air cooler is not locally frozen; when the temperature difference is greater than -3°C, the hot air circulation system of the blower is turned on or the shutter opening of the blower blades is adjusted to control the temperature difference between the natural gas hydrate formation temperature and the detection temperature to be greater than -3°C.

[0008] In the fifth step above, when the temperature difference is greater than -3°C, the injection amount of antifreeze such as methanol or ethylene glycol is increased before the natural gas enters the air cooler to control the temperature difference between the natural gas hydrate formation temperature and the detection temperature to be greater than -3°C.

[0009] The second technical solution of the present invention is achieved through the following measures: a device for implementing a real-time monitoring and early warning method for natural gas temperature by air enthalpy difference refrigeration, an air cooler, a blower, an external clamp-on thermometer, and a remote controller. A blower is arranged below the air cooler. The air cooler comprises an inlet pipe box, an outlet pipe box and a heat exchange tube bundle. An inlet pipe box is arranged at the inlet of the air cooler, and an outlet pipe box is arranged at the outlet of the air cooler. A plurality of heat exchange tube bundles are dispersedly connected between the inlet pipe box and the outlet pipe box. The heat exchange tube bundle area above the blower blade is divided into grids of the same size with the central axis of the blower blade as the origin. An external clamp-on thermometer is fixedly installed on the heat exchange tube bundle at the center position of each grid. A temperature sensor is arranged on the external clamp-on thermometer. The temperature sensor is electrically connected to the remote controller. The inlet of the inlet pipe box is fixedly connected to a natural gas intake main pipeline, and the outlet of the outlet pipe box is fixedly connected to a natural gas outlet main pipeline. The driving end of the blower is electrically connected to the remote controller.

[0010] The following is a further optimization and / or improvement of the second technical solution of the above invention: The inlet pipe box is provided with a plurality of pipe box inlets, the outlet pipe box is provided with a plurality of pipe box outlets, the pipe box inlets are fixedly connected to the natural gas inlet main pipeline with natural gas inlet branch pipelines, and the pipe box outlets are fixedly connected to the natural gas outlet main pipeline with natural gas outlet branch pipelines.

[0011] A natural gas inlet temperature monitor is provided on the natural gas inlet main pipeline, and a natural gas outlet temperature monitor is provided on the natural gas outlet main pipeline. Both the natural gas inlet temperature monitor and the natural gas outlet temperature monitor are electrically connected to the remote controller.

[0012] The outer wall of the above-mentioned external clamp-on thermometer is provided with a heat-insulating layer.

[0013] The above grid size is 1000mm×1000mm.

[0014] The present invention monitors the real-time temperature of different heat exchange tube bundle positions of the air cooler and compares it with the temperature of the natural gas after air cooling, so as to warn of the risk of local overfreezing and blockage of the heat exchange tube bundle of the air cooler, guide to take antifreeze measures in advance, realize stable control of the natural gas air-cooling refrigeration process, and provide technical guarantee for antifreeze and blockage and safe operation of air cooling. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Attached Figure 1 It is a schematic diagram of the top view structure of embodiment 4 of the present invention.

[0016] The codes in the attached drawings are: 1 is the natural gas inlet main pipeline, 2 is the natural gas inlet temperature monitor, 3 is the natural gas inlet branch pipeline, 4 is the inlet pipe box, 5 is the heat exchange tube bundle, 6 is the external clamp-on thermometer, 7 is the grid, 8 is the blower blade, 9 is the outlet pipe box, 10 is the natural gas outlet main pipeline, 11 is the natural gas outlet temperature monitor, and 12 is the natural gas outlet branch pipeline. DETAILED DESCRIPTION

[0017] The present invention is not limited by the following embodiments, and specific implementation methods can be determined based on the technical solution of the present invention and actual conditions.

[0018] The present invention will be further described below in conjunction with embodiments: Embodiment 1: As attached Figure 1As shown, the real-time monitoring and early warning method for natural gas temperature by air enthalpy difference refrigeration is performed according to the following steps: the first step is to take the central axis of the blower blade 8 of the natural gas air cooler as the origin, and divide the heat exchange tube bundle 5 area above the blower blade 8 of the natural gas air cooler into grids 7 of the same size according to the monitoring accuracy requirement; the second step is to install an external clamp-on thermometer 6 on the heat exchange tube bundle 5 at the center position of each grid 7, and after the external clamp-on thermometer 6 monitors the outer wall temperature of the heat exchange tube bundle 5, the temperature sensor is uploaded to the remote controller; the third step is to collect the natural gas temperature of the air cooler outlet main pipe through the remote controller; the fourth step is to compare the outer wall temperature measured by the external clamp-on thermometer 6 at different positions of the heat exchange tube bundle 5 with the natural gas temperature in the air cooler outlet main pipe collected by the remote controller, and realize the early warning of local over-freezing and blockage of the heat exchange tube bundle 5 according to the temperature difference value; the fifth step is to take specific and different anti-freezing measures for the air cooler according to the early warning information.

[0019] The purpose of the present invention is to solve the problem that the temperature monitoring and control accuracy of the existing air cooler in the process of refrigerating natural gas is not high, and the temperature difference of the air cooling tube bundles at different positions caused by the inhomogeneous convection of air in extremely cold climates easily causes local super-freezing and blocking of the heat exchange tube bundle 5. By developing the external temperature monitoring technology of the heat exchange tube bundle 5 of the air cooler and the real-time monitoring technology of the natural gas temperature at the outlet of the air cooler, as well as monitoring the real-time temperature of different positions of the heat exchange tube bundle 5 of the air cooler and comparing it with the natural gas temperature after air cooling, the risk of local super-freezing and blocking of the heat exchange tube bundle 5 of the air cooler can be warned, and anti-freezing measures can be taken in advance.

[0020] Embodiment 2: As attached Figure 1 As shown, as an optimization of the above embodiment, in the fifth step, the anti-freezing measures for the air cooler include: when the temperature difference between the outer wall temperature of the heat exchange tube bundle and the natural gas temperature in the air cooler outlet main pipe is not greater than -3°C, the heat exchange tube bundle 5 of the air cooler is not locally frozen; when the temperature difference is greater than -3°C, the hot air circulation system of the blower is turned on or the shutter opening of the blower blade 8 is adjusted to control the temperature difference between the natural gas hydrate formation temperature and the detection temperature to be greater than -3°C.

[0021] Embodiment 3: As attached Figure 1 As shown, as an optimization of the above embodiment, in the fifth step, when the temperature difference is greater than -3°C, the injection amount of antifreeze such as methanol or ethylene glycol is increased before the natural gas enters the air cooler to control the temperature difference between the natural gas hydrate formation temperature and the detection temperature to be greater than -3°C.

[0022] Embodiment 4: As attached Figure 1As shown, the device for implementing the real-time monitoring and early warning method of natural gas temperature by air enthalpy difference refrigeration includes an air cooler, a blower, an external clamp-on thermometer 6, and a remote controller. The blower is arranged below the air cooler. The air cooler includes an inlet pipe box 4, an outlet pipe box 9 and a heat exchange tube bundle 5. The inlet pipe box 4 is arranged at the inlet of the air cooler, and the outlet pipe box 9 is arranged at the outlet of the air cooler. A plurality of heat exchange tube bundles 5 are dispersedly connected between the inlet pipe box 4 and the outlet pipe box 9. The central axis of the blower blade 8 is taken as the origin, and the area of ​​the heat exchange tube bundle 5 above the blower blade 8 is divided into grids 7 of the same size. The heat exchange tube bundle 5 at the center position of each grid 7 is fixedly installed with an external clamp-on thermometer 6, and a temperature sensor is arranged on the external clamp-on thermometer 6. The temperature sensor is electrically connected to the remote controller. The inlet of the inlet pipe box 4 is fixedly connected with a natural gas inlet main pipeline 1, and the outlet of the outlet pipe box 9 is fixedly connected with a natural gas outlet main pipeline 10. The driving end of the blower is electrically connected to the remote controller.

[0023] Embodiment 5: As attached Figure 1 As shown, as an optimization of the above embodiment, a plurality of pipe box inlets are provided on the inlet pipe box 4, a plurality of pipe box outlets are provided on the outlet pipe box 9, a natural gas inlet branch pipeline 3 is fixedly connected between the pipe box inlet and the natural gas inlet main pipeline 1, and a natural gas outlet branch pipeline 12 is fixedly connected between the pipe box outlet and the natural gas outlet main pipeline 10.

[0024] Embodiment 6: As attached Figure 1 As shown, as an optimization of the above embodiment, a natural gas inlet temperature monitor 2 is provided on the natural gas inlet main pipeline 1, and a natural gas outlet temperature monitor 11 is provided on the natural gas outlet main pipeline 10, and the natural gas inlet temperature monitor 2 and the natural gas outlet temperature monitor 11 are both electrically connected to the remote controller.

[0025] Embodiment 7: As attached Figure 1 As shown, as an optimization of the above embodiment, the outer wall of the external clamp-on thermometer 6 is provided with a heat-insulating layer.

[0026] Embodiment 8: As attached Figure 1 As shown, as an optimization of the above embodiment, the size of the grid 7 is 1000 mm×1000 mm.

[0027] During the operation of the air cooler, the main temperatures monitored are the inlet and outlet main pipes. The outlet temperature of the air cooler may be displayed as a normal value, but the actual air-cooling temperature of part of the heat exchange tube bundle 5 is much lower than the actual outlet main pipe temperature, while the air-cooling temperature of another part of the heat exchange tube bundle 5 is higher than the outlet main pipe temperature. This low temperature difference can easily lead to overcooling of the heat exchange tube bundle 5 of the air cooler, forming natural gas hydrate freezing and blockage, which is not easy to detect.

[0028] In the present invention, the basic process of natural gas air cooling is as follows: natural gas enters the pipe box inlet of the air cooler through the natural gas inlet main pipeline 1, and is dispersed into each heat exchange tube bundle 5 (heat exchange tube with a diameter of about φ18) in the pipe box. The blower blows air (low-temperature air) upward to exchange heat with the heat exchange tube bundle 5. The cooled natural gas is collected at the pipe box outlet at the other end of the heat exchange tube bundle 5, and is discharged to the downstream system through the natural gas outlet main pipeline 10. The natural gas inlet main pipeline 1 and the natural gas outlet main pipeline 10 are designed with a natural gas inlet temperature monitor and a natural gas outlet temperature monitor 11 to monitor the inlet and outlet temperatures of the air cooler, and then an external clamp-on thermometer 6 is installed on the heat exchange tube bundle 5 at different positions above the blower blade 8. By monitoring the outer wall temperature of the heat exchange tube bundle 5, the temperature of the natural gas medium flowing in the heat exchange tube bundle 5 is indirectly grasped. By comparing the outer wall temperature of the heat exchange tube bundle 5 at different positions above the blower blade 8 and the air cooler outlet main pipe temperature, it is possible to determine whether there is partial overcooling of the heat exchange tube bundle 5 of the air cooler.

[0029] Embodiment 9: As attached Figure 1 As shown, natural gas is cooled by air cooler. The natural gas temperature after air cooling is designed to be less than or equal to the ambient temperature plus 5°C, and the lowest is not less than -15°C. Before the natural gas enters the air cooler, ethylene glycol or methanol, a natural gas hydrate inhibitor, is injected to control the natural gas hydrate formation temperature to be less than or equal to -18°C. The air cooler is selected with a size of 6m long × 6m wide and a single fan structure. The following steps are followed to monitor and warn the temperature of natural gas for air enthalpy difference refrigeration in real time: the first step is to take the central axis of the blower blade 8 of the natural gas air cooler as the origin, and divide the heat exchange tube bundle 5 area above the blower blade 8 of the natural gas air cooler into a grid 7 of 1000mm×1000mm according to the monitoring accuracy requirements; the second step is to install an external clamp-on thermometer 6 on the heat exchange tube bundle 5 at the center of each grid 7, and the outer wall of the thermometer is insulated by wrapping insulation cotton. After the external clamp-on thermometer 6 monitors the outer wall temperature of the heat exchange tube bundle 5, it is uploaded to the remote controller by the temperature sensor, wherein the monitored temperature values ​​of all heat exchange tube bundles 5 are between -10.3℃ and -9.5℃; the third step is to collect the natural gas temperature of the air cooler outlet main pipe through the remote controller, which is -9.7℃; the fourth step is to compare the temperature monitoring values ​​at different positions of the heat exchange tube bundle 5 with the natural gas temperature difference of the air cooler outlet main pipe, and the temperature difference is 0.2℃ to 0.6℃, so it is judged that there is no risk of local freezing of the heat exchange tube bundle 5.

[0030] Embodiment 10: As attached Figure 1As shown, natural gas is cooled by air cooler. The natural gas temperature after air cooling is designed to be less than or equal to the ambient temperature plus 5°C, and the lowest is not less than -15°C. Before the natural gas enters the air cooler, ethylene glycol or methanol, a natural gas hydrate inhibitor, is injected to control the natural gas hydrate formation temperature to be less than or equal to -18°C. The air cooler is selected with a size of 6m long × 6m wide and a single fan structure. The following steps are followed to monitor and warn the temperature of natural gas for air enthalpy difference refrigeration in real time: the first step is to take the central axis of the blower blade 8 of the natural gas air cooler as the origin, and divide the heat exchange tube bundle 5 area above the blower blade 8 of the natural gas air cooler into a grid 7 of 1000mm×1000mm according to the monitoring accuracy requirements; the second step is to install an external clamp-on thermometer 6 on the heat exchange tube bundle 5 at the center of each grid 7, and the outer wall of the thermometer is insulated by wrapping insulation cotton. After the external clamp-on thermometer 6 monitors the outer wall temperature of the heat exchange tube bundle 5, the temperature sensor is uploaded to the remote controller, where a certain monitored temperature value is between -13.3 and -12.5°C; the third step is to collect the natural gas temperature of the air cooler outlet main pipe through the remote controller, which is -9°C; the fourth step is to compare the temperature monitoring values ​​at different positions of the heat exchange tube bundle 5 with the natural gas temperature difference of the air cooler outlet main pipe, and the temperature difference is 3.5 to 4.3°C, so it is judged that the heat exchange tube bundle 5 has a risk of local freezing. The fifth step is to reduce the speed of the blower and adjust the shutter opening to allow most of the hot air to return downward and mix with the surrounding air at the bottom of the air cooler, and then be sucked in by the upward blower, so as to achieve the purpose of forming a hot air circulation inside the air cooler bellows. Adjust in time according to the information of the remote controller to control the temperature difference between the heat exchange tube bundle 5 and the air cooler outlet main pipe within 3°C to prevent the air-cooled natural gas temperature from being too low and causing partial freezing of the heat exchange tube bundle 5.

[0031] In summary, the present invention monitors the real-time temperature of different heat exchange tube bundle positions of the air cooler and compares it with the temperature of the natural gas after air cooling, so as to warn of the risk of local over-freezing and blockage of the heat exchange tube bundle of the air cooler, guide the adoption of anti-freezing measures in advance, realize the stable control of the natural gas air-cooling refrigeration process, and provide technical guarantee for the anti-freezing and safe operation of air-cooling refrigeration.

[0032] The above technical features constitute the embodiments of the present invention, which have strong adaptability and implementation effect. Non-essential technical features can be added or reduced according to actual needs to meet the requirements of different situations.

Claims

1. A real-time monitoring and early warning method for natural gas temperature in air enthalpy difference refrigeration, characterized in that Proceed in the following steps: Step 1. Taking the central axis of the blower blade of the natural gas air cooler as the origin, divide the heat exchange tube bundle area above the blower blade of the natural gas air cooler into grids of the same size according to the monitoring accuracy requirements; Step 2. Install an external clamp-on thermometer on the heat exchange tube bundle at the center of each grid. After the external clamp-on thermometer monitors the outer wall temperature of the heat exchange tube bundle, the temperature sensor uploads it to the remote controller; Step 3. Collect the natural gas temperature of the air cooler outlet main pipe through the remote controller; Step 4. Compare the outer wall temperature measured by the external clamp-on thermometer at different heat exchange tube bundle positions with the natural gas temperature in the air cooler outlet main pipe collected by the remote controller, and realize the early warning of local over-freezing and blockage of the heat exchange tube bundle according to the temperature difference; Step 5. Take specific and different anti-freezing measures for the air cooler according to the early warning information.

2. The method for real-time monitoring and early warning of natural gas temperature by air enthalpy difference refrigeration according to claim 1 is characterized in that In the fifth step, the anti-freezing measures taken for the air cooler include: when the temperature difference between the outer wall temperature of the heat exchange tube bundle and the natural gas temperature in the air cooler outlet main pipe is not greater than -3°C, the heat exchange tube bundle of the air cooler is not locally frozen; when the temperature difference is greater than -3°C, the hot air circulation system of the blower is turned on or the shutter opening of the blower blades is adjusted to control the temperature difference between the natural gas hydrate formation temperature and the detection temperature to be greater than -3°C.

3. The method for real-time monitoring and early warning of natural gas temperature by air enthalpy difference refrigeration according to claim 2 is characterized in that In the fifth step, when the temperature difference is greater than -3°C, the injection amount of antifreeze such as methanol or ethylene glycol is increased before the natural gas enters the air cooler to control the temperature difference between the natural gas hydrate formation temperature and the detection temperature to be greater than -3°C.

4. A device for implementing the method for real-time monitoring and early warning of natural gas temperature by air enthalpy difference refrigeration according to claim 1, 2 or 3, characterized in that It includes an air cooler, a blower, an external clamp-on thermometer, and a remote controller. The blower is arranged under the air cooler. The air cooler includes an inlet pipe box, an outlet pipe box and a heat exchange tube bundle. An inlet pipe box is arranged at the inlet of the air cooler, and an outlet pipe box is arranged at the outlet of the air cooler. A plurality of heat exchange tube bundles are dispersedly connected between the inlet pipe box and the outlet pipe box. The central axis of the blower blade is taken as the origin, and the heat exchange tube bundle area above the blower blade is divided into grids of the same size. An external clamp-on thermometer is fixedly installed on the heat exchange tube bundle at the center of each grid. A temperature sensor is arranged on the external clamp-on thermometer, and the temperature sensor is electrically connected to the remote controller. The inlet of the inlet pipe box is fixedly connected to the natural gas intake main pipeline, and the outlet of the outlet pipe box is fixedly connected to the natural gas outlet main pipeline. The driving end of the blower is electrically connected to the remote controller.

5. The device according to claim 4, characterized in that The inlet pipe box is provided with multiple pipe box inlets, the outlet pipe box is provided with multiple pipe box outlets, the pipe box inlets are fixedly connected to the natural gas inlet main pipeline with natural gas inlet branch pipelines, and the pipe box outlets are fixedly connected to the natural gas outlet main pipeline with natural gas outlet branch pipelines.

6. The device according to claim 4 or 5, characterized in that A natural gas inlet temperature monitor is provided on the natural gas inlet main pipeline, and a natural gas outlet temperature monitor is provided on the natural gas outlet main pipeline. Both the natural gas inlet temperature monitor and the natural gas outlet temperature monitor are electrically connected to the remote controller.

7. The device according to claim 4 or 5, characterized in that The outer wall of the external clamp-on thermometer is provided with an insulation layer.

8. The device according to claim 6, characterized in that The outer wall of the external clamp-on thermometer is provided with an insulation layer.

9. The device according to claim 4, 5 or 8, characterized in that The grid size is 1000mm×1000mm.

10. The device according to claim 7, characterized in that The grid size is 1000mm×1000mm.

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