Gas measuring device and measuring method suitable for long-term monitoring in situ in the sea

Abstract

The application belongs to the technical field of marine in-situ monitoring, and relates to a gas measuring device and a measuring method suitable for marine in-situ long-term monitoring. The device comprises a gas-liquid separation module, a dehumidification module, a detection module and a calibration module arranged in a pressure-resistant cabin; two water inlets are oppositely arranged on the pressure-resistant cabin; the degassing pipe in the gas-liquid separation module is in communication with the two water inlets at two ends, a water pump is arranged at one end of the degassing pipe, and sample gas discharged from the degassing pipe enters the dehumidification module through a gas outlet; the dehumidification module comprises a Nafion pipe, a cold trap and a drying pipe connected in sequence, and the cold trap is attached with a refrigeration fin; the gas detector in the detection module is connected with the drying pipe through a sample gas pipe, a gas pump and a normally open electromagnetic valve are arranged on the sample gas pipe, and the gas detected by the gas detector returns to the degassing pipe through the Nafion pipe; the calibration module is connected to the sample gas pipe after the normally open electromagnetic valve. The application can accurately, stably and continuously monitor the concentration of specified types of gases in seawater, and can meet the demand of marine in-situ long-term monitoring.

Description

Technical Field

[0001] This invention belongs to the field of marine in-situ monitoring technology, specifically relating to a gas measurement device and method suitable for long-term in-situ marine monitoring. Background Technology

[0002] Dissolved gases in the ocean are important carriers of geochemical cycles. Long-term monitoring of the concentration of certain gases (such as carbon dioxide and methane) in seawater is of great scientific and environmental significance for understanding the operation of the Earth system, assessing ecological health, responding to climate change, and fisheries management. Therefore, accurate, stable, and continuous long-term in-situ underwater monitoring of the concentration of certain gases in seawater is very important and necessary.

[0003] Currently, most marine in-situ gas sensor products are imported. The structure of these sensors is as follows: Figure 1 As shown, it first separates seawater into gas and liquid phases through a permeation membrane, and then measures the concentration of a specified type of gas in the separated sample gas; however, this type of sensor has the following shortcomings:

[0004] 1) Gas-liquid separation using a permeable membrane on the end cap is simple in structure and small in size, but the gas-liquid separation efficiency of the permeable membrane is low, and the permeation efficiency decreases over time. Especially in areas with vigorous biological activity, such as nearshore areas, the lifespan of the permeable membrane is very short due to severe biological attachment, and it usually fails completely within three months.

[0005] 2) During long-term in-situ monitoring in the ocean, the aging of internal components of the sensor can lead to a decrease in measurement efficiency, attenuation of measurement signals, and drift in measurement results. The usual solution is to periodically retrieve, recalibrate, and redeploy the sensor, but this consumes a lot of time, manpower, and financial resources, resulting in high maintenance costs and data interruption during maintenance.

[0006] 3) During long-term in-situ monitoring at sea, the sensor is exposed to a high-humidity environment for extended periods. Water vapor enters the gas chamber through the permeation membrane and accumulates continuously, leading to a continuous increase in humidity within the chamber. Excessive humidity can easily damage internal components such as probes or cause inaccurate data, and it can also severely affect the lifespan of the sensor. The usual solution is to dry the separated sample gas before it enters the gas detector. However, the method of using desiccants extensively for dehumidification in shore-based or shipborne operations cannot be directly applied to underwater in-situ monitoring. Using large amounts of desiccants underwater to extend the maintenance-free time would result in an excessively large size and weight of the sensor, as well as an excessively long response time, making it difficult to reflect the true measurement results.

[0007] 4) Currently, when the sensor has problems during use, such as too high humidity, desiccant failure, data anomaly or interruption, etc., it needs to be returned to the factory for repair; even if there is no problem, it also needs to be returned to the factory for calibration regularly, which consumes a lot of financial and time costs, and is difficult to meet the demand of long-term monitoring in situ in the sea. SUMMARY

[0008] In view of the deficiencies in the related art, the present application provides a gas measuring device and a measuring method suitable for long-term monitoring in situ in the sea to solve the technical problems of the existing marine in-situ gas sensor mentioned in the background art.

[0009] The present application provides a gas measuring device suitable for long-term monitoring in situ in the sea, which is used for measuring the concentration of a specified type of gas in seawater; the gas measuring device comprises a measurement and control system, a pressure-resistant cabin, a gas-liquid separation module arranged in the pressure-resistant cabin, a dehumidification module, a detection module and a calibration module; wherein,

[0010] The pressure-resistant cabin is located underwater, and two water inlets are relatively arranged on the pressure-resistant cabin, and a filter screen is arranged at the water inlet;

[0011] The gas-liquid separation module comprises a degassing pipe and a water pump; the two ends of the degassing pipe in the length direction are connected with the two water inlets respectively, and the side wall of the degassing pipe is provided with a gas outlet and a gas return port; the water pump is arranged between one water inlet and the degassing pipe, and the water pump is controlled by the measurement and control system to rotate forward or reverse to make the seawater outside the pressure-resistant cabin flow through the degassing pipe; the inside of the degassing pipe is a hollow fiber bundle to deaerate the seawater flowing through the degassing pipe, and the sample gas discharged is introduced into the dehumidification module through the gas outlet;

[0012] The dehumidification module comprises a Nafion tube, a cold trap and a drying tube connected in sequence; the Nafion tube comprises an inner tube and an outer tube which are sleeved with each other to form a sample gas passage in the inner tube and a purge passage between the inner tube and the outer tube; one end of the sample gas passage is connected with the gas outlet of the degassing pipe, and the other end is connected with the inlet of the cold trap; a refrigeration fin is attached to the outer wall of the cold trap, and the refrigeration fin is controlled by the measurement and control system to open or close the refrigeration function; the outlet of the cold trap is connected with the inlet of the drying tube;

[0013] The detection module comprises a sample gas tube and a gas detector, the two ends of the sample gas tube are connected with the outlet of the drying tube and the inlet of the gas detector respectively, a gas pump and a normally open electromagnetic valve are arranged on the sample gas tube in sequence, the gas pump is opened under the control of the measurement and control system, the normally open electromagnetic valve is closed under the control of the measurement and control system, the gas detector measures the concentration of a specified type of gas in the gas entering it and transmits the measurement result to the measurement and control system in real time; one end of the purge passage of the Nafion tube is connected with the outlet of the gas detector, and the other end is connected with the gas return port of the degassing pipe;

[0014] The calibration module comprises a first calibration gas tank and a second calibration gas tank, the first calibration gas tank stores a first calibration gas which is different from the specified kind of gas, and the second calibration gas tank stores a second calibration gas which is the specified kind of gas; the first calibration gas tank and the second calibration gas tank are connected to the sample gas pipe between the normally open electromagnetic valve and the gas detector through the first gas pipe and the second gas pipe respectively; the first gas pipe and the second gas pipe are respectively provided with a normally closed electromagnetic valve and a flow regulating valve, the normally closed electromagnetic valve is opened under the control of the measurement and control system, and the flow regulating valve adjusts the flow of the gas in the first gas pipe or the second gas pipe under the control of the measurement and control system.

[0015] In some embodiments, the gas-liquid separation module further comprises a flow meter arranged between the water pump and the degassing pipe; the flow meter monitors the flow of seawater flowing through the degassing pipe and transmits the monitoring result to the measurement and control system in real time.

[0016] In some embodiments, the detection module further comprises a temperature and humidity pressure sensor arranged on the sample gas pipe and close to the gas detector; the temperature and humidity pressure sensor monitors the temperature, humidity and pressure of the gas entering the gas detector and transmits the monitoring result to the measurement and control system in real time.

[0017] In some embodiments, a molecular sieve adsorption package is arranged below the cold trap, the bottom of the cold trap is connected to the molecular sieve adsorption package through a communication pipe, and a one-way valve is arranged on the communication pipe.

[0018] The measurement method of the gas measurement device for long-term monitoring of the ocean in situ as described above comprises a measurement step, and the measurement step comprises:

[0019] S1, start the water pump and the gas pump;

[0020] S2, the seawater outside the pressure-resistant cabin continuously flows through the degassing pipe under the driving of the water pump through the water inlet, and the degassing pipe performs degassing treatment on the flowing seawater;

[0021] S3, the sample gas discharged from the degassing pipe is subjected to dehumidification treatment by the dehumidification module under the driving of the gas pump;

[0022] S4, the sample gas after dehumidification enters the gas detector to measure the concentration of the specified kind of gas, and the detected gas returns to the degassing pipe through the sweeping path of the Nafion pipe.

[0023] In some embodiments, during the execution of the measurement step, when the flow meter detects that the flow of seawater flowing through the degassing pipe is lower than a preset flow threshold, the measurement and control system changes the rotation direction of the water pump.

[0024] In some embodiments, during the measurement process, when the temperature, humidity and pressure sensor detects that the humidity of the gas entering the gas detector is higher than the preset maximum humidity value, the control system activates the cooling function of the cooling chip; when the temperature, humidity and pressure sensor detects that the humidity of the gas entering the gas detector is lower than the preset minimum humidity value, the control system deactivates the cooling function of the cooling chip.

[0025] In some embodiments, during the measurement process, if the temperature, humidity and pressure sensor detects that the humidity of the gas entering the gas detector is increasing instead of decreasing after the cooling function of the cooling chip is turned on, the measurement and control system will issue an alarm to prompt manual intervention to retrieve, repair or replace the gas measuring device.

[0026] In some embodiments, a calibration step is also included, which is performed automatically according to a preset calibration cycle within the measurement and control system, and includes:

[0027] D1. Close the normally open solenoid valve on the air pump and sample gas tube;

[0028] D2. Open the normally closed solenoid valve on the first gas tube to allow the first standard gas from the first standard gas cylinder to enter the gas detector for concentration measurement of the specified gas type, and record the measured value as follows: Close the normally closed solenoid valve on the first gas tube, open the normally closed solenoid valve on the second gas tube, allowing the second standard gas from the second standard gas cylinder to enter the gas detector for concentration measurement of the specified gas type, and record the measured value as follows: The calibration coefficients are calculated according to equation (1). and ,in, The preset concentration of a specified type of gas in the first standard gas. The preset concentration of a specified type of gas in the second standard gas;

[0029] (1);

[0030] After the calibration steps are completed, close the normally closed solenoid valve on the second gas tube, open the normally open solenoid valves on the gas pump and sample gas tube, execute the measurement steps, and use the calibration coefficients calculated in the calibration steps. and According to equation (2), the concentration measurement value of the specified type of gas obtained in step S4 is... Correction is performed to obtain the corrected concentration values ​​of the specified gas in seawater. ;

[0031] (2).

[0032] In some embodiments, during the execution of step D2, if and Differences between or and When the difference exceeds the preset tolerance, the monitoring and control system will issue an alarm, prompting manual intervention to retrieve, repair, or replace the gas measuring device.

[0033] Based on the above technical solutions, the gas measurement device and method for long-term in-situ monitoring of the ocean in this embodiment of the invention, through the integrated design and joint application of gas-liquid separation module, dehumidification module, detection module and calibration module, solves many shortcomings of existing in-situ gas sensors for the ocean. It can accurately, stably and continuously monitor the concentration of a specified type of gas in seawater for long-term in-situ underwater, significantly improving the accuracy and reliability of monitoring data during long-term in-situ monitoring of the ocean, and better meeting the needs of long-term in-situ monitoring of the ocean. Attached Figure Description

[0034] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this application, illustrate exemplary embodiments of the invention and, together with their description, serve to explain the invention and do not constitute an undue limitation thereof. In the drawings:

[0035] Figure 1 A schematic diagram of an existing in-situ marine gas sensor;

[0036] Figure 2 This is a schematic diagram of the gas measurement device for long-term in-situ monitoring of the ocean according to the present invention;

[0037] Figure 3 This is a schematic diagram of the Nafion tube in this invention. Detailed Implementation

[0038] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0039] In the description of this invention, it should be understood that the terms "center", "lateral", "longitudinal", "upper", "lower", "top", "bottom", "inner", "outer", "left", "right", "front", "rear", "vertical", "horizontal", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0040] The terms "first", "second", etc. are only used for descriptive purposes and should not be construed as indicating or implying relative importance or an indicated number of technical features. Thus, the features defined with "first", "second", etc. can explicitly or implicitly include one or more of the features.

[0041] In the description of the present application, it should be noted that unless specifically defined and limited, the terms "mounting", "connection", "connecting" should be understood broadly, for example, it can be fixed connection, or detachable connection, or integrally connected; it can be directly connected, or indirectly connected through an intermediate medium, or the internal communication of two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0042] Reference Figure 2 , Figure 3 As shown in FIGS. 1-2, the present application provides a gas measuring device suitable for long-term monitoring in situ in the ocean, which is used for measuring the concentration of a specified type of gas in seawater. The gas measuring device comprises a measurement and control system, a pressure-resistant cabin, a gas-liquid separation module arranged in the pressure-resistant cabin, a dehumidification module, a detection module and a calibration module.

[0043] The pressure-resistant cabin is located underwater, and two water inlets are relatively arranged on the pressure-resistant cabin. A filter screen is arranged at each water inlet.

[0044] The gas-liquid separation module comprises a degassing pipe and a water pump. The two ends of the degassing pipe in the length direction are connected with the two water inlets, respectively. An air outlet and a gas return port are arranged on the side wall of the degassing pipe. The water pump is arranged between one of the water inlets and the degassing pipe. The water pump is controlled by the measurement and control system to rotate forward or reverse, so as to pump the seawater outside the pressure-resistant cabin into the degassing pipe through one of the water inlets, and then return to the seawater outside the pressure-resistant cabin through the other water inlet, so that the seawater outside the pressure-resistant cabin flows through the degassing pipe. The filter screen at the water inlet filters the seawater entering the degassing pipe. The degassing pipe performs degassing treatment on the seawater flowing through the degassing pipe, and the sample gas discharged is introduced into the dehumidification module through the air outlet. It should be noted that the inside of the degassing pipe is a hollow fiber bundle, and the membrane area of the hollow fiber bundle is much larger than the permeation membrane on the end cap in the prior art. Therefore, the permeation efficiency of the degassing pipe with the hollow fiber bundle is higher, and a faster response speed can be obtained. Therefore, compared with the permeation membrane degassing in the prior art, the degassing pipe in the present embodiment has higher degassing efficiency.

[0045] Further, when the water pump rotates, the seawater outside the pressure-resistant cabin is pumped into the degassing pipe through one of the water inlets, and then returned to the seawater outside the pressure-resistant cabin through the other water inlet, as shown in FIG. 3. Figure 2The solid arrow shown in the gas-liquid separation module; after the water pump runs for a period of time, the impurities such as silt and plankton in seawater will gradually block the filter screen at the water inlet side of the water inlet, which will cause poor water inlet of the degassing pipe and decrease the gas-liquid separation efficiency. The control system can change the direction of the water pump to make the seawater outside the pressure cabin pumped into the degassing pipe through another water inlet, such as Figure 2 The dotted arrow shown in the gas-liquid separation module; since the degassing pipe has no direction restriction, water inlet from either side of the water inlet can achieve gas-liquid separation, so the forward and reverse rotation of the water pump can be switched. On the one hand, it ensures that seawater outside the pressure cabin continuously flows through the degassing pipe, and on the other hand, it can flush away the impurities blocked in the filter screen of the water inlet side before the water pump direction is changed, ensuring that the gas-liquid separation module has stable and efficient gas-liquid separation effect.

[0046] The dehumidification module includes a Nafion tube, a cold trap and a drying tube connected in sequence. The Nafion tube has a double-layer nested structure, which includes an inner tube and an outer tube nested with each other to form a sample gas passage in the inner tube and a purge passage between the inner tube and the outer tube. One end of the sample gas passage is a sample gas inlet connected with the gas outlet of the degassing pipe, and the other end of the sample gas passage is a sample gas outlet connected with the inlet of the cold trap. One end of the purge passage is a purge gas inlet, and the other end is a purge gas outlet. The sample gas inlet and the purge gas inlet are away from each other, so the gas flow directions in the sample gas passage and the purge passage are opposite. The outer wall of the cold trap is attached with a refrigeration fin, which is controlled by the control system to open or close the refrigeration function. The outlet of the cold trap is connected with the inlet of the drying tube. The drying tube stores a desiccant.

[0047] Further, the high-humidity sample gas discharged from the gas-liquid separation module enters the sample gas passage through the sample gas inlet of the Nafion tube, while dry gas is introduced into the purge passage of the Nafion tube in the reverse direction. Because the material of the inner tube of the Nafion tube has good selectivity and permeability to water vapor, the water vapor in the sample gas will be transferred to the gas flow in the purge passage through the inner tube, thereby reducing the humidity of the sample gas and achieving the first dehumidification of the sample gas. Since the humidity of the sample gas and the dry gas is relatively large at this time, the dehumidification effect of the Nafion tube on the sample gas is better. The sample gas dehumidified by the Nafion tube enters the cold trap, and the refrigeration function of the refrigeration sheet is turned on to maintain a low-temperature environment in the cold trap. The water vapor in the sample gas condenses into water droplets in the cold trap and is adsorbed and collected, achieving the second dehumidification of the sample gas. Since the sample gas has been dehumidified once in the Nafion tube, the humidity of the sample gas entering the cold trap has been greatly reduced. Therefore, the dehumidification of the Nafion tube before the cold trap can save the working energy consumption of the refrigeration sheet. The sample gas flowing out of the cold trap enters the drying tube, and the drying tube dehumidifies the sample gas for the third time. Thus, through the combined use of the Nafion tube, the cold trap, and the drying tube, three-stage dehumidification of the sample gas can be achieved, which can significantly reduce the humidity of the sample gas to be measured, and is beneficial to prolong the maintenance period and service life of the gas measurement device. Compared with the dehumidification method using a large amount of desiccant, the dehumidification module of the present embodiment is more compact, lighter in weight, and faster in response speed, and can achieve the technical effect of stable dehumidification for a long time.

[0048] The detection module includes a sample gas tube and a gas detector. One end of the sample gas tube is connected to the outlet of the drying tube, and the other end is connected to the inlet of the gas detector. A gas pump and a normally open electromagnetic valve are arranged in sequence on the sample gas tube. The gas pump is opened under the control of the measurement and control system, and the normally open electromagnetic valve is closed under the control of the measurement and control system, i.e., the gas pump is in a default closed state and is turned on with power and turned off without power, and the normally open electromagnetic valve is in a default open state and is turned off with power and turned on without power. The low-humidity sample gas dehumidified by the three-stage dehumidification module enters the gas detector through the sample gas tube under the action of the gas pump. The gas detector measures the concentration of a specified type of gas entering it and transmits the measurement results to the measurement and control system in real time.

[0049] Further, one end of the purging passage of the Nafion tube, i.e. the purging gas inlet, is connected with the outlet of the gas detector, and the other end, i.e. the purging gas outlet, is connected with the back gas inlet of the degassing tube; thus, the gas after detection by the gas detector can enter the purging passage of the Nafion tube as dry gas to participate in the dehumidification of the sample gas by the Nafion tube, so that no dry gas is needed to be prepared for the purging passage of the Nafion tube, the equipment is reduced, the response time is reduced, and the use of the drying agent is reduced; then, the part of the gas enters the degassing tube through the back gas inlet of the degassing tube, and the seawater after degassing in the degassing tube is discharged to the outside of the pressure cabin, so that on the one hand, the pressure balance in the whole gas path can be maintained, and the measurement result is not affected by the air pressure, and on the other hand, the problem of discharge of the detected gas is solved.

[0050] The calibration module comprises a first calibration gas tank and a second calibration gas tank, the first calibration gas tank stores a first calibration gas which is different from the specified kind of gas, and the second calibration gas tank stores a second calibration gas which is the specified kind of gas; for example, if the gas measuring device is used for measuring the concentration of CO2 in seawater, the first calibration gas can be N2, and the second calibration gas can be CO2 with a preset concentration. The first calibration gas tank and the second calibration gas tank are respectively connected to the sample gas pipe between the normally open electromagnetic valve and the gas detector through the first gas pipe and the second gas pipe; further, a four-way joint can be arranged on the sample gas pipe, two interfaces of the four-way joint are respectively connected to the sample gas pipes before and after the four-way joint, and the other two interfaces are respectively connected to the first gas pipe and the second gas pipe. The first gas pipe and the second gas pipe are respectively provided with a normally closed electromagnetic valve and a flow regulating valve; the normally closed electromagnetic valve is opened under the control of the measurement and control system, i.e. the normally closed electromagnetic valve is in a closed state by default, and is opened by power-on and closed by power-off; the flow regulating valve adjusts the flow of the gas in the first gas pipe or the second gas pipe under the control of the measurement and control system.

[0051] Further, when the gas measuring device needs to be calibrated, the gas pump and the normally open electromagnetic valve on the sample gas pipe are closed, and the normally closed electromagnetic valves on the first gas pipe and the second gas pipe are opened in sequence, i.e. the sample gas passage of the gas measuring device is disconnected and the two calibration gas passages are opened in sequence, the concentration of the two different calibration gases is measured by the gas detector, the measured value is linearly fitted with the preset concentration value of the calibration gas, and the calibration coefficient is obtained; after the calibration is completed, the normally closed electromagnetic valves on the first gas pipe and the second gas pipe are closed, and the gas pump and the normally open electromagnetic valve on the sample gas pipe are opened, i.e. the two calibration gas passages of the gas measuring device are disconnected and the sample gas passage is switched back, the concentration of the sample gas is measured by the gas detector, and the measured value is corrected by using the calibration coefficient, so that the concentration value of the specified kind of gas in the seawater after correction is obtained.

[0052] In addition, it should be noted that the measurement and control system can be located underwater or above water, and the specific determination is made according to the platform on which the measurement and control system is carried, the connection of the communication cable between the measurement and control system and the pressure cabin, etc.

[0053] The above-mentioned schematic embodiment can ingeniously solve the problem of the decline of gas-liquid separation efficiency caused by the easy blockage of the water inlet during the measurement process by the arrangement of the degassing pipe and the forward-reverse water pump, and ensure that the gas-liquid separation module always has stable and efficient gas-liquid separation effect; the arrangement of the Nafion pipe, the cold trap and the drying pipe can realize three-stage dehumidification of the sample gas, significantly reduce the humidity of the sample gas, and improve the accuracy of the measurement result; by introducing the detected gas into the purge channel of the Nafion pipe as dry gas to participate in the dehumidification of the sample gas, there is no need to additionally prepare dry gas for the Nafion pipe, which reduces the equipment and response time of the device; the arrangement of the calibration module can realize in-situ self-calibration of the gas measurement device under water, avoid problems such as inaccurate monitoring data caused by measurement signal attenuation, drift and other reasons during long-term measurement under water, and also avoid problems such as high maintenance cost and data interruption caused by the need to regularly recover and recalibrate the sensor and then place it under water in the prior art; thus, the embodiment can prolong the maintenance-free period and service life of the device, improve the accuracy and reliability of the monitoring data, and better meet the needs of long-term in-situ monitoring of the ocean.

[0054] Reference Figure 2 As shown in some embodiments, the gas-liquid separation module further comprises a flow meter arranged between the water pump and the degassing pipe; the flow meter monitors the flow of seawater flowing through the degassing pipe and transmits the monitoring result to the measurement and control system in real time. Further, when the flow meter detects that the flow of seawater flowing through the degassing pipe decreases beyond the limit, it indicates that the filter screen at the water inlet side of the water inlet is seriously blocked by impurities such as silt and plankton in seawater, at which time the measurement and control system changes the direction of the water pump so that the seawater outside the pressure-resistant cabin enters the degassing pipe through another water inlet, that is, the timing of changing the rotation direction of the water pump is determined by the arrangement of the flow meter and the flow monitoring result.

[0055] Reference Figure 2 As shown in some embodiments, the detection module further comprises a temperature and humidity pressure sensor arranged on the sample gas pipe close to the gas detector, specifically, the temperature and humidity pressure sensor is arranged on the sample gas pipe between the four-way joint and the gas detector. The temperature and humidity pressure sensor monitors the temperature, humidity and pressure of the gas entering the gas detector and transmits the monitoring result to the measurement and control system in real time; thereby, the temperature, humidity and pressure of the gas entering the gas detector can be monitored in real time.

[0056] Reference Figure 2As shown, in some embodiments, a molecular sieve adsorption package is arranged below the cold trap, the bottom of the cold trap is connected with the molecular sieve adsorption package through a communication pipe, and the molecular sieve adsorption package is filled with molecular sieves capable of adsorbing water molecules; thus, the water condensed from the water vapor in the sample gas flowing through the cold trap can be adsorbed into the molecular sieve adsorption package through the communication pipe, ensuring the dehumidification effect of the cold trap on the sample gas; further, a one-way valve is arranged on the communication pipe to prevent the water in the molecular sieve adsorption package from flowing back into the cold trap.

[0057] Reference Figure 2 , Figure 3 As shown, the present application also provides a measuring method of the gas measuring device suitable for long-term monitoring of the sea in situ, which comprises a measuring step, and the measuring step comprises:

[0058] S1, the measuring and control system starts the water pump and the gas pump; it can be understood that at this time, the normally open electromagnetic valve on the sample gas pipe is in the default open state, and the normally closed electromagnetic valves on the first gas pipe and the second gas pipe are in the default closed state, that is, the sample gas passage of the gas measuring device is opened and the two calibration gas passages are disconnected.

[0059] S2, the seawater outside the pressure cabin is pumped into the degassing pipe through one side water inlet under the drive of the water pump, and then returned to the seawater outside the pressure cabin through the other side water inlet, so that the seawater continuously flows through the degassing pipe; the degassing pipe performs degassing treatment on the seawater flowing through the degassing pipe.

[0060] S3, the sample gas discharged through the degassing pipe flows to the dehumidification module through the gas outlet of the degassing pipe under the drive of the gas pump, and sequentially flows through the Nafion pipe, the cold trap and the drying pipe for dehumidification treatment; it is further explained that at the beginning of measurement, the humidity of the sample gas discharged through the degassing pipe and entering the dehumidification module is not high, so the refrigeration function of the refrigeration fin on the cold trap can be not started; after the humidity of the sample gas increases, the refrigeration function of the refrigeration fin is started.

[0061] S4, the sample gas dehumidified by the dehumidification module enters the gas detector through the sample gas pipe, and the gas detector measures the concentration of the specified type of gas; the detected gas flows out of the gas detector, enters the purge passage of the Nafion pipe through the purge gas inlet of the Nafion pipe, then flows out of the Nafion pipe through the purge gas outlet of the Nafion pipe, and then returns to the degassing pipe through the gas return port of the degassing pipe, and then is discharged to the outside of the pressure cabin with the degassed seawater in the degassing pipe.

[0062] The above schematic embodiments realize the functions of seawater degassing, sample gas dehumidification and sample gas concentration measurement through the joint application of the gas-liquid separation module, the dehumidification module and the detection module, and further realize the concentration monitoring of the specified type of gas in seawater.

[0063] In some embodiments, during the measurement step, when the flow meter detects that the flow of seawater flowing through the degassing pipe is lower than a preset flow threshold, the control system changes the rotation direction of the water pump; thus, the rotation direction of the water pump is automatically controlled, the problem of poor water inflow due to the blockage of the water inlet of the pressure hull by impurities in the seawater is avoided, and the gas-liquid separation efficiency of the gas-liquid separation module is ensured to be long-term, stable, and efficient.

[0064] In some embodiments, during the measurement step, when the temperature and humidity pressure sensor detects that the humidity of the gas entering the gas detector is higher than the preset maximum humidity value, the control system starts the refrigeration function of the refrigeration piece, i.e., starts the desiccation work of the cold trap on the sample gas, to ensure the desiccation effect of the sample gas; when the temperature and humidity pressure sensor detects that the humidity of the gas entering the gas detector is lower than the preset minimum humidity value, the control system stops the refrigeration function of the refrigeration piece, i.e., suspends the desiccation work of the cold trap on the sample gas, to reduce the energy consumption of the refrigeration piece. This illustrative embodiment can ensure the desiccation effect of the sample gas while reducing the power consumption of the device, which is conducive to prolonging the maintenance period of the device.

[0065] In some embodiments, during the measurement step, after starting the refrigeration function of the refrigeration piece, if the temperature and humidity pressure sensor detects that the humidity of the gas entering the gas detector does not decrease but increases, it indicates that the molecular sieve in the molecular sieve adsorption package for collecting condensed water in the cold trap has failed, and the desiccant in the drying pipe has also failed. At this time, the control system issues an alarm to prompt manual intervention, and the gas measurement device is recovered and repaired or replaced in time, to avoid obtaining incorrect long-term monitoring data of the ocean in situ and to avoid serious damage or even scrapping of the key component, the gas detector.

[0066] In some embodiments, the calibration step is automatically performed according to a preset calibration period in the control system; usually, the calibration step is performed once when the gas measurement device is initially put into water, and then the calibration step is automatically performed once every preset time interval. Further, if the temperature, humidity, or pressure of the sample gas in the sample gas pipe exceeds the theoretical limit value during the preset time interval between the two calibration steps, the calibration step is immediately started, and the next calibration is calculated from the current calibration and performed again after a preset time interval.

[0067] Further, the calibration step includes:

[0068] D1, close the gas pump and the normally open electromagnetic valve on the sample gas pipe, i.e., disconnect the sample gas passage of the gas measurement device.

[0069] D2, open the normally closed electromagnetic valve on the first gas pipe, so that the first calibration gas in the first calibration gas tank enters the gas detector for concentration measurement of the specified type of gas and the measurement value is recorded as ; closing the normally closed electromagnetic valve on the first gas pipe and opening the normally closed electromagnetic valve on the second gas pipe, so that the second standard gas in the second standard gas tank enters the gas detector to measure the concentration of the specified gas and record the measured value as ; that is, opening the two standard gas passages in sequence, and using the gas detector to measure the concentration of the specified gas in the two different standard gases in sequence. Then, the calibration coefficient is calculated according to formula (1) and , wherein, is the preset concentration of the specified gas in the first standard gas, and since the first standard gas is different from the specified gas, is substantially 0, that is, the first standard gas is used for zero-point calibration; is the preset concentration of the specified gas in the second standard gas, that is, the second standard gas is used for range calibration; thus, the in-situ self-calibration of the gas measuring device under water is realized, and a new calibration coefficient is obtained;

[0070] (1).

[0071] After the calibration step is completed, the normally closed electromagnetic valve on the second gas pipe is closed, the normally open electromagnetic valves on the gas pump and the sample gas pipe are opened, that is, the two standard gas passages of the gas measuring device are disconnected and switched back to the sample gas passage, and the measurement step is performed, using the newly calculated calibration coefficient and in the calibration step, the measured value of the concentration of the specified gas obtained in step S4 is corrected according to formula (2) to obtain the corrected concentration value of the specified gas in seawater ;

[0072] (2).

[0073] The above exemplary embodiment realizes the in-situ self-calibration of the gas measuring device under water, and corrects the measured value of the specified gas in seawater according to the calibration coefficient, avoiding the situation that the monitoring data is inaccurate due to the attenuation and drift of the measurement signal during long-term measurement under water, and also avoiding the situation that the error of the concentration inversion result becomes larger and larger when using the laboratory calibration coefficient to correct the measured value of the concentration, significantly improving the accuracy of the monitoring data during the long-term monitoring of the ocean in-situ.

[0074] In some embodiments, during the execution of step D2, if the difference between and or the difference between and ​When the difference between the two is greater than the preset tolerance, it indicates that the first or second standard gas has been used up, at which time the measurement and control system issues an alarm to prompt manual intervention, and timely recovers and repairs or replaces the gas measurement device to avoid obtaining an incorrect calibration coefficient and further affecting the correction of the concentration measurement value.

[0075] In summary, the gas measurement device and measurement method suitable for long-term in-situ monitoring of the sea of the application, through the setting of the degassing pipe and the forward and reverse water pump, the operation of switching the water pump direction according to the flow condition, ingeniously solves the problem of the decline of the gas-liquid separation efficiency caused by the easy blockage of the water inlet during the measurement process, ensures that the gas-liquid separation module always has stable and efficient gas-liquid separation effect; through the setting of the Nafion tube, the cold trap and the drying tube, three-stage dehumidification of the sample gas can be realized, the humidity of the sample gas is significantly reduced, the service life of the device is prolonged, and the switch state of the cold plate refrigeration function is adjusted according to the humidity of the sample gas, to ensure the energy saving and consumption reduction under the premise of ensuring the dehumidification effect of the sample gas; by introducing the detected gas into the purge channel of the Nafion tube as dry gas to participate in the dehumidification of the sample gas, there is no need to prepare dry gas for the Nafion tube, which reduces the equipment and response time of the device; through the setting of the calibration module, the in-situ self-calibration of the gas measurement device under water is realized, avoiding the problems of inaccurate monitoring data caused by signal attenuation, drift and other reasons during long-term measurement under water, and also avoiding the problems of high maintenance cost and data interruption caused by the need for regular recovery, calibration and re-deployment of sensors under the prior art; thus, through the integrated design and joint application of the gas-liquid separation module, the dehumidification module, the detection module and the calibration module, the application can accurately, stably and continuously monitor the concentration of a specified type of gas in seawater under water in-situ for a long time, and can achieve the effect of continuous use in seawater for at least half a year without maintenance.

[0076] Finally, it should be noted that: the embodiments in the specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts of each embodiment can be referred to.

[0077] The above embodiments are only used to illustrate the technical solutions of the application but not to limit it; although the application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the specific embodiments of the application can be modified or some technical features can be replaced by equivalents without departing from the spirit of the technical solutions of the application, which should be covered in the technical solution range of the application claimed.

Claims

1. A gas measuring device suitable for long-term monitoring in situ in the sea, characterised in that The device comprises a measurement and control system, a pressure-resistant cabin, a gas-liquid separation module, a dehumidification module, a detection module and a calibration module. Two water inlets are oppositely arranged on the pressure-resistant cabin, and a filter screen is arranged at the water inlets. The gas-liquid separation module comprises a degassing pipe, a water pump and a flow meter. Two ends of the degassing pipe are connected with the two water inlets respectively. An air outlet and a gas return port are arranged on the side wall of the degassing pipe. The water pump is arranged between the water inlet and the degassing pipe. The water pump is driven to rotate in a forward direction or a reverse direction under the control of the measurement and control system, so that seawater outside the pressure-resistant cabin flows through the degassing pipe. The flow meter is arranged between the water pump and the degassing pipe. The flow meter monitors the flow of seawater flowing through the degassing pipe and transmits the monitoring result to the measurement and control system in real time. When the flow meter monitors that the flow of seawater flowing through the degassing pipe is lower than a preset flow threshold, the measurement and control system changes the rotating direction of the water pump. The dehumidification module comprises a Nafion pipe, a cold trap and a drying pipe which are connected in sequence. The Nafion pipe has a sample gas passage and a purge passage. One end of the sample gas passage is connected with the air outlet of the degassing pipe, and the other end is connected with the cold trap. A refrigeration fin is attached to the outer wall of the cold trap. A molecular sieve adsorption bag is arranged below the cold trap. The bottom of the cold trap is connected with the molecular sieve adsorption bag through a communication pipe. A one-way valve is arranged on the communication pipe. The detection module comprises a gas detector and a temperature and humidity pressure sensor. The inlet of the gas detector is connected with the drying pipe through a sample gas pipe. A gas pump and a normally open electromagnetic valve are arranged on the sample gas pipe in sequence. One end of the purge passage of the Nafion pipe is connected with the outlet of the gas detector, and the other end is connected with the gas return port of the degassing pipe. The temperature and humidity pressure sensor is arranged on the sample gas pipe and close to the gas detector. The temperature and humidity pressure sensor monitors the temperature, humidity and pressure of the gas entering the gas detector and transmits the monitoring result to the measurement and control system in real time. When the temperature and humidity pressure sensor monitors that the humidity of the gas entering the gas detector is higher than a preset maximum humidity value, the measurement and control system starts the refrigeration function of the refrigeration fin. When the temperature and humidity pressure sensor monitors that the humidity of the gas entering the gas detector is lower than a preset minimum humidity value, the measurement and control system stops the refrigeration function of the refrigeration fin. The calibration module comprises a first calibration gas tank and a second calibration gas tank. The first calibration gas tank stores a first calibration gas which is different from a specified kind of gas. The second calibration gas tank stores a second calibration gas which is the specified kind of gas. The first calibration gas tank and the second calibration gas tank are connected to the sample gas pipe between the normally open electromagnetic valve and the gas detector through a first gas pipe and a second gas pipe respectively. The first gas pipe and the second gas pipe are provided with normally closed electromagnetic valves.

2. The measurement method of the gas measuring apparatus suitable for long-term monitoring in situ in the sea according to claim 1, characterized by, The measurement step comprises: S1, starting the water pump and the gas pump; S2, seawater outside the pressure-resistant cabin flows through the degassing pipe under the drive of the water pump. The degassing pipe performs degassing treatment on the seawater flowing through the degassing pipe; S3, sample gas discharged from the degassing pipe is driven by the gas pump to pass through the dehumidification module for dehumidification treatment. S4, the sample gas after dehumidification by the dehumidification module enters the gas detector for concentration measurement of specified gas, and the detected gas returns to the degassing pipe through the purging passage of the Nafion pipe.

3. The method of measurement of a gas measuring device suitable for long-term monitoring in situ in the sea according to claim 2, characterized in that, During the measurement step, when the flow meter detects that the flow of seawater flowing through the degassing pipe is lower than a preset flow threshold, the control system changes the rotation direction of the water pump.

4. The measurement method of a gas measuring apparatus suitable for long-term monitoring in situ in the sea according to claim 2, characterized in that, During the measurement step, when the temperature and humidity pressure sensor detects that the humidity of the gas entering the gas detector is higher than a preset maximum humidity value, the control system starts the refrigeration function of the refrigeration piece; when the temperature and humidity pressure sensor detects that the humidity of the gas entering the gas detector is lower than a preset minimum humidity value, the control system stops the refrigeration function of the refrigeration piece.

5. The method of measurement of a gas measuring device suitable for long-term monitoring in situ in the sea according to claim 4, characterized in that, During the measurement step, when the refrigeration function of the refrigeration piece is started, if the temperature and humidity pressure sensor detects that the humidity of the gas entering the gas detector does not decrease but increases, the control system issues an alarm to prompt manual intervention, and the gas measurement device is recovered, repaired or replaced.

6. The measurement method of a gas measuring apparatus suitable for long-term monitoring in situ in the sea according to claim 2, characterized by, The calibration step is automatically performed according to a preset calibration period in the control system, which includes: D1, closing the normally open electromagnetic valve on the gas pump and the sample gas pipe; D2, opening the normally closed electromagnetic valve on the first gas pipe, making the first standard gas in the first standard gas tank enter the gas detector to measure the concentration of the specified gas and record the measured value as D3, closing the normally closed electromagnetic valve on the first gas pipe and opening the normally closed electromagnetic valve on the second gas pipe, making the second standard gas in the second standard gas tank enter the gas detector to measure the concentration of the specified gas and record the measured value as D4, calculating the calibration coefficient according to formula (1) and wherein, D1 is the preset concentration of the specified gas in the first standard gas, D2 is the preset concentration of the specified gas in the second standard gas. （1）； After the calibration step is completed, the normally closed electromagnetic valve on the second gas pipe is closed, the normally open electromagnetic valve on the gas pump and the sample gas pipe is opened, and the measurement step is performed using the calibration coefficient calculated in the calibration step and The concentration measurement value of the specified gas obtained in step S4 is corrected according to equation (2) to obtain a corrected concentration value of the specified gas in seawater ; and ; and （2）。 7. The method of measurement of a gas measuring device suitable for long-term monitoring in situ in the sea according to claim 6, characterized in that, During the execution of step D2, if and Differences between or and When the difference exceeds the preset tolerance, the measurement and control system issues an alarm, prompting manual intervention to retrieve, repair, or replace the gas measuring device.

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