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

Abstract

The invention belongs to the technical field of ocean in-situ monitoring, and relates to a gas measuring device and method suitable for ocean in-situ long-term monitoring. The device comprises a gas-liquid separation module, a dehumidification module, a detection module and a calibration module which are arranged in a pressure-resistant cabin, two water through holes are oppositely formed in the pressure-resistant cabin; two ends of a degassing pipe in the gas-liquid separation module are respectively communicated with the two water ports, one end of the degassing pipe is provided with a water pump, and sample gas separated by the degassing pipe enters the dehumidification module through a gas outlet; the dehumidification module comprises a Nafion tube, a cold trap and a drying tube which are connected in sequence, and a refrigeration sheet is attached to the cold trap; a gas detector in the detection module is connected with the drying pipe through a sample gas pipe, a gas pump and a normally open solenoid valve are arranged on the sample gas pipe, and gas detected by the gas detector returns to the degassing pipe through a Nafion pipe; and the calibration module is connected to the sample gas pipe behind the normally open solenoid valve. The device can accurately, stably and continuously monitor the concentration of a specified type of gas in seawater, and can meet the requirement of ocean in-situ long-term monitoring.

Description

Technical Field

[0001] The present invention belongs to the technical field of ocean in-situ monitoring, and in particular relates to a gas measuring device and a measuring method suitable for long-term in-situ monitoring of the ocean. Background Art

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

[0003] At present, most of the marine in-situ gas sensor products come from abroad. The structure of this type of sensor is as follows: Figure 1 As shown in the figure, it first separates the gas and liquid of seawater through a permeable membrane, and then measures the concentration of the specified gas type in the separated sample gas; however, this type of sensor has the following shortcomings: 1) The permeable membrane on the end cap is used for gas-liquid separation. Although it has a simple structure and a small size, the gas-liquid separation efficiency of the permeable membrane is low, and the permeation efficiency decreases with the passage of time. Especially in areas with strong biological activity such as offshore areas, due to severe biological attachment, the life of the permeable membrane is very short, usually completely failing within three months; 2) During long-term in-situ ocean monitoring, the aging of internal components of sensors can lead to decreased measurement efficiency, attenuation of measurement signals, and drift in measurement results. The usual solution is to regularly recover and recalibrate the sensors before redeploying them, but this consumes considerable time, manpower, and financial resources, resulting in high maintenance costs and data interruptions during maintenance. 3) During long-term in-situ marine monitoring, the sensor is exposed to high humidity for extended periods. Water vapor enters the gas chamber through the permeable membrane and accumulates continuously, causing the humidity in the chamber to increase continuously. Excessive humidity can easily damage internal probes and other components, or cause inaccurate data, seriously affecting the sensor's service life. The usual solution is to dry the separated sample gas before it enters the gas detector. However, the extensive use of desiccant for dehumidification during shore-based or shipborne operations cannot be directly applied to underwater in-situ monitoring. The extensive use of desiccant underwater to extend the maintenance-free period would make the entire sensor too large and heavy, and would also result in a prolonged sensor response time, making it difficult to reflect true measurement results. 4) Currently, when problems arise during the use of sensors, such as excessive humidity, desiccant failure, data anomalies or interruptions, etc., they need to be returned to the factory for repair; even if there are no problems, they need to be returned to the factory for calibration regularly, which will consume a lot of financial and time costs and cannot meet the needs of long-term in-situ ocean monitoring. Summary of the Invention

[0004] 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 of the ocean in situ, to solve the technical problems of the existing ocean in-situ gas sensor mentioned in the background art.

[0005] The present application provides a gas measuring device suitable for long-term monitoring of the ocean in situ, 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, The pressure-resistant cabin is located underwater, and two water inlets are oppositely arranged on the pressure-resistant cabin, and a filter screen is arranged at the water inlet; 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 respectively connected with the two water inlets, 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 enters the dehumidification module through the gas outlet; 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 arranged in 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; The detection module comprises a sample gas tube and a gas detector, the two ends of the sample gas tube are respectively connected with the outlet of the drying tube and 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, the normally open electromagnetic valve is closed under the control of the measurement and control system, the gas detector measures the concentration of the specified type of 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; 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 different from the specified type of gas, and the second calibration gas tank stores a second calibration gas of the specified type of gas; the first calibration gas tank and the second calibration gas tank are connected to the sample gas tube between the normally open electromagnetic valve and the gas detector through a first gas tube and a second gas tube; a normally closed electromagnetic valve and a flow regulating valve are arranged on the first gas tube and the second gas tube, the normally closed electromagnetic valve is opened under the control of the measurement and control system, and the flow regulating valve adjusts the gas flow in the first gas tube or the second gas tube under the control of the measurement and control system.

[0006] 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 rate of seawater flowing through the degassing pipe and transmits the monitoring result to the monitoring and control system in real time.

[0007] 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 monitoring and control system in real time.

[0008] In some embodiments, a molecular sieve adsorption package is arranged below the cold trap, and 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.

[0009] The measurement method of the gas measurement device for long-term monitoring of the sea in situ as described above comprises a measurement step, which comprises: S1, start the water pump and the air pump; S2, the seawater outside the pressure-resistant cabin flows through the degassing pipe under the driving of the water pump, and the degassing pipe performs degassing treatment on the seawater flowing therethrough; S3, the sample gas discharged from the degassing pipe is subjected to dehumidification treatment by the dehumidification module under the driving of the air pump; S4, the sample gas dehumidified by the dehumidification module enters the gas detector to measure the concentration of a specified type of gas, and the detected gas returns to the degassing pipe through the sweeping path of the Nafion pipe.

[0010] In some embodiments, during the execution of the measurement step, when the flow meter detects that the flow rate of seawater flowing through the degassing pipe is lower than a preset flow rate threshold, the monitoring and control system changes the rotation direction of the water pump.

[0011] In some embodiments, during the execution of 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 monitoring and 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 monitoring and control system stops the refrigeration function of the refrigeration piece.

[0012] In some embodiments, during the execution of 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 monitoring and control system issues an alarm to prompt manual intervention, and the gas measurement device is recovered and repaired or replaced.

[0013] In some embodiments, the method further comprises a calibration step, which is automatically performed according to a preset calibration period in the monitoring and control system, and comprises: D1, close the air pump and the normally open electromagnetic valve on the sample gas pipe; D2, open the normally closed electromagnetic valve on the first gas pipe, so that the first standard gas in the first standard gas tank enters the gas detector to measure the concentration of the specified gas and record the measured value as ; close the normally closed electromagnetic valve on the first gas pipe and open 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 ; according to formula (1), the calibration coefficient and are calculated, wherein, is the preset concentration of the specified gas in the first standard gas, 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 air pump and the sample gas pipe is opened, and the measurement step is performed. The calibration coefficients and calculated in the calibration step are used to correct the concentration measurement value of the specified gas obtained in step S4 according to formula (2) to obtain the corrected concentration value of the specified gas in seawater. (2).

[0014] In some embodiments, during the execution of step D2, if the difference between and or the difference between and exceeds the preset tolerance, the measurement and control system issues an alarm to prompt manual intervention to recover and repair or replace the gas measurement device.

[0015] Based on the above technical solutions, the gas measurement device and measurement method suitable for long-term in-situ monitoring of the sea in the embodiments of the present application solve the various shortcomings of existing in-situ marine gas sensors through the integrated design and joint application of the gas-liquid separation module, the dehumidification module, the detection module and the calibration module. The device can accurately, stably and continuously monitor the concentration of the specified gas in seawater underwater and in-situ for a long time, significantly improves the accuracy and reliability of the monitoring data during long-term in-situ monitoring of the sea, and better meets the demand for long-term in-situ monitoring of the sea. BRIEF DESCRIPTION OF DRAWINGS

[0016] The accompanying drawings, which are included to provide a further understanding of the application and are incorporated in and constitute a part of this application, illustrate embodiments of the application and together with the description serve to explain the application. In the drawings: Figure 1 A schematic diagram of an existing marine in-situ gas sensor; Figure 2 A schematic diagram of a gas measurement device of the application suitable for marine in-situ long-term monitoring; Figure 3 A schematic diagram of a Nafion tube of the application. DETAILED DESCRIPTION

[0017] The technical solutions in the embodiments will be clearly and completely described below with reference to the drawings in the embodiments of the application. Obviously, the described embodiments are only part of the embodiments of the application, rather than all the embodiments of the application. Based on the embodiments of the application, all other embodiments obtained by a person of ordinary skill in the art without creative work fall within the protection scope of the application.

[0018] In the description of the application, it should be understood that the terms "center", "transverse", "longitudinal", "upper", "lower", "top", "bottom", "inner", "outer", "left", "right", "front", "back", "vertical", "horizontal" and the like indicate the orientation or positional relationship shown in the drawings based on the orientation or positional relationship shown in the drawings, and are only for the purpose of facilitating the description of the application and simplifying the description, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation of the application.

[0019] The terms "first", "second", and the like are only for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the technical features indicated. Therefore, the features defined with "first", "second", and the like can explicitly or implicitly include one or more of the features.

[0020] In the description of the application, it should be noted that unless otherwise explicitly specified and limited, the terms "mounting", "connecting", "connection" should be understood broadly, for example, it can be fixed connection, or detachable connection, or integral connection; it can be directly connected, or indirectly connected through an intermediate medium, or the communication between the two elements inside. For a person of ordinary skill in the art, the specific meaning of the above terms in the application can be understood according to the specific circumstances.

[0021] Reference Figure 2 , Figure 3As shown, the present application provides a gas measuring device suitable for long-term monitoring in situ in the sea, for measuring the concentration of a specified kind 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.

[0022] The pressure-resistant cabin is located underwater, and two water inlets are oppositely arranged on the pressure-resistant cabin, and a filter screen is arranged at each water inlet.

[0023] 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 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 that the seawater outside the pressure-resistant cabin is pumped into the degassing pipe through one water inlet, and then returned 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 gas 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, so that the permeation efficiency of the degassing pipe with the hollow fiber bundle is higher, and a faster response speed can be obtained; thus, compared with the permeation membrane degassing in the prior art, the degassing pipe in the present embodiment has higher degassing efficiency.

[0024] Further, when the water pump rotates, the seawater outside the pressure-resistant cabin is pumped into the degassing pipe through one water inlet, and then returned to the seawater outside the pressure-resistant cabin through the other water inlet, as shown by the solid arrows at the gas-liquid separation module; after the water pump runs for a period of time, the impurities such as silt and plankton in the seawater will gradually block the filter screen at the water inlet of the water inlet side, which will cause poor water inlet of the degassing pipe and decrease the gas-liquid separation efficiency, and the measurement and control system can change the rotation direction of the water pump, so that the seawater outside the pressure-resistant cabin is pumped into the degassing pipe through the other water inlet, as shown by the dashed arrows at the gas-liquid separation module; since the degassing pipe has no direction restriction, water inlet from either side of the water inlet can realize gas-liquid separation, so that the forward and reverse rotation of the water pump can be switched, on the one hand, to ensure that the seawater outside the pressure-resistant cabin continuously flows through the degassing pipe, and on the other hand, to flush away the impurities blocked on the filter screen of the water inlet side before the rotation direction of the water pump is changed, so as to ensure that the gas-liquid separation module has stable and efficient gas-liquid separation effect. Figure 2 Figure 2

[0025] ​​The dehumidification module comprises a Nafion tube, a cold trap and a drying tube connected in sequence. The Nafion tube is a double-layer nested structure comprising 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 tube, 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 of the purge passage is a purge gas outlet. The sample gas inlet and the purge gas inlet are away from each other, so that the gas flow directions in the sample gas passage and the purge passage are opposite. 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. The drying tube stores a drying agent.

[0026] 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, and dry gas is introduced into the purge passage of the Nafion tube in the opposite 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. At this time, the humidity of the sample gas and the dry gas is quite different, and 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 fin 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 absorbed and collected, achieving the second dehumidification of the sample gas. Because 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, so the dehumidification of the Nafion tube first and the cold trap later can save the working energy consumption of the refrigeration fin. 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 arrangement 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 mode using a large amount of drying agent, the dehumidification module of the 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.

[0027] The detection module comprises a sample gas pipe and a gas detector. One end of the sample gas pipe is connected to the outlet of the drying pipe, and the other end is connected to the inlet of the gas detector. A gas pump and a normally open electromagnetic valve are arranged on the sample gas pipe in sequence. 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. That is, the gas pump is in a default closed state, and is opened when powered on and closed when powered off. The normally open electromagnetic valve is in a default open state, and is closed when powered on and opened when powered off. The low-humidity sample gas after three-stage dehumidification by the dehumidification module enters the gas detector under the action of the gas pump. The gas detector measures the concentration of the specified type of gas entering the gas detector and transmits the measurement results to the measurement and control system in real time.

[0028] Further, one end of the purge passage of the Nafion pipe, i.e., the purge gas inlet, is connected to the outlet of the gas detector, and the other end, i.e., the purge gas outlet, is connected to the gas return port of the degassing pipe. Therefore, the gas after detection by the gas detector can enter the purge passage of the Nafion pipe as dry gas and participate in the dehumidification of the sample gas by the Nafion pipe. Thus, there is no need to prepare dry gas for the purge passage of the Nafion pipe, which reduces the equipment and response time of the device and reduces the use of drying agent. Then, this part of the gas enters the degassing pipe through the gas return port of the degassing pipe, and the degassed seawater in the degassing pipe is discharged to the pressure-resistant cabin. In this way, on the one hand, the pressure balance in the entire gas circuit can be maintained to ensure that the measurement results are not affected by the gas pressure. On the other hand, the problem of discharging the detected gas is also solved.

[0029] 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 different from the specified type of gas, and the second calibration gas tank stores a second calibration gas of the specified type of gas. For example, if the gas measurement device is used for CO2 concentration measurement 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 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. Further, a four-way joint can be arranged on the sample gas pipe. Two interfaces of the four-way joint are connected to the sample gas pipes before and after the four-way joint, respectively, and the other two interfaces are connected to the first gas pipe and the second gas pipe, respectively. A normally closed electromagnetic valve and a flow regulating valve are arranged on the first gas pipe and the second gas pipe. 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 default closed state and is opened when powered on and closed when powered 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.

[0030] Further, when the gas measuring device is to be calibrated, the normally open electromagnetic valves on the gas pump and 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 gas detector is used to measure the concentrations of the two different calibration gases respectively, the measured values are linearly fitted with the preset concentration values of the calibration gases to obtain the calibration coefficient; after the calibration is completed, the normally closed electromagnetic valves on the first gas pipe and the second gas pipe are closed, and the normally open electromagnetic valves on the gas pump and 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 gas detector is used to measure the concentration of the sample gas, and the measured value is corrected by using the calibration coefficient, so that the concentration value of the specified type of gas in the seawater after correction is obtained.

[0031] In addition, it should be noted that the measurement and control system can be located underwater or above water, and the specific determination is based on 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.

[0032] The above-mentioned schematic embodiments can ingeniously solve the problem of reduced gas-liquid separation efficiency caused by the easy blockage of the water inlet during the measurement process, ensure 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, and the accuracy of the measurement result is improved; 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 additionally prepare dry gas for the Nafion tube, the equipment and response time of the device are reduced; through the setting of the calibration module, in-situ self-calibration of the gas measuring device under water can be realized, problems such as inaccurate monitoring data caused by signal attenuation and drift during long-term measurement under water are avoided, and problems such as high maintenance cost and data interruption caused by the need to regularly recover and recalibrate the sensor under the prior art are also avoided; thus, the maintenance-free period and service life of the device can be prolonged, the precision and reliability of the monitoring data are improved, and the demand for long-term in-situ monitoring of the ocean is better met.

[0033] 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 of the water inlet side is seriously blocked by impurities such as silt and plankton in the seawater, at this time, the measurement and control system changes the direction of the water pump, so that the seawater outside the pressure cabin enters the degassing pipe through another water inlet, i.e. the timing of changing the rotation direction of the water pump is determined by the setting of the flow meter and the flow monitoring result.

[0034] refer to Figure 2 As shown, in some embodiments, the detection module further includes a temperature, humidity, and pressure sensor, which is disposed on the gas sample pipe and near the gas detector. Specifically, the temperature, humidity, and pressure sensor is disposed on the gas sample pipe between the cross-connector and the gas detector. The temperature, humidity, and pressure sensor monitors the temperature, humidity, and pressure of the gas entering the gas detector and transmits the monitoring results in real time to the measurement and control system; thus, the temperature, humidity, and pressure of the gas entering the gas detector can be monitored in real time.

[0035] refer to Figure 2 As shown, in some embodiments, a molecular sieve adsorption bag is provided below the cold trap, and the bottom of the cold trap is connected to the molecular sieve adsorption bag via a connecting tube. The molecular sieve adsorption bag contains molecular sieves that can adsorb water molecules; therefore, the water condensed when the water vapor in the sample gas flows through the cold trap can be adsorbed into the molecular sieve adsorption bag through the connecting tube, thereby ensuring the dehumidification effect of the cold trap on the sample gas; further, a one-way valve is provided on the connecting tube to prevent the water in the molecular sieve adsorption bag from flowing back into the cold trap.

[0036] refer to Figure 2 、 Figure 3 As shown, the present invention also provides a measurement method for a gas measurement device suitable for long-term in-situ monitoring of the ocean, comprising the following measurement steps: S1. The measurement and control system turns on the water pump and the air pump. It can be understood that at this time, the normally open solenoid valve on the sample gas pipe is in the default open state, and the normally closed solenoid valves on the first gas pipe and the second gas pipe are in the default closed state, that is, the sample gas path of the gas measuring device is open and the two standard gas paths are disconnected.

[0037] S2. Driven by a water pump, the seawater outside the pressure chamber is pumped into the degassing pipe through the water inlet on one side and then returns to the seawater outside the pressure chamber through the water inlet on the other side, thereby allowing the seawater to continuously flow through the degassing pipe; the degassing pipe degases the seawater flowing through the degassing pipe.

[0038] S3. Driven by the air pump, the sample gas discharged through the degassing tube flows to the dehumidification module through the outlet of the degassing tube, and flows through the Nafion tube, cold trap and drying tube in sequence for dehumidification treatment. It can be further explained that at the beginning of the measurement, the humidity of the sample gas discharged through the degassing tube and entering the dehumidification module is not high, so the cooling function of the cooling plate on the cold trap can be turned on first; after the humidity of the sample gas increases, the cooling function of the cooling plate can be turned on.

[0039] S4, the sample gas after dehumidification by the dehumidification module enters the gas detector through the sample gas pipe, the gas detector measures the concentration of the specified type of gas, the detected gas flows out of the gas detector, enters the sweeping path of the Nafion pipe through the sweeping gas inlet of the Nafion pipe, then flows out of the Nafion pipe through the sweeping gas outlet of the Nafion pipe, and then returns to the degassing pipe through the degassing pipe gas return port, and then is discharged to the outside of the pressure cabin with the degassed seawater in the degassing pipe.

[0040] The above schematic embodiment realizes 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 realizes the concentration monitoring of the specified type of gas in seawater.

[0041] 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 the preset flow threshold, the measurement and control system changes the rotation direction of the water pump; thereby realizing the automatic control of the rotation direction of the water pump, avoiding the problem that the water inlet of the pressure cabin is blocked by impurities in the seawater, affecting the gas-liquid separation efficiency, and ensuring that the gas-liquid separation module has long-term, stable and efficient gas-liquid separation effect.

[0042] In some embodiments, during the execution of 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 measurement and control system starts the refrigeration function of the refrigeration piece, i.e. starts the dehumidification work of the cold trap on the sample gas, to ensure the dehumidification 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 measurement and control system stops the refrigeration function of the refrigeration piece, i.e. suspends the dehumidification work of the cold trap on the sample gas, to reduce the energy consumption of the refrigeration piece. The above schematic embodiment can ensure the dehumidification effect of the sample gas while reducing the power consumption of the device, which is conducive to prolonging the maintenance period of the device.

[0043] In some embodiments, during the execution of the measurement step, if the temperature and humidity pressure sensor detects that the humidity of the gas entering the gas detector does not decrease but increases after starting the refrigeration function of the refrigeration piece, it indicates that the molecular sieve in the molecular sieve adsorption package for collecting the condensed water in the cold trap has failed, and the desiccant in the desiccant pipe has also failed. At this time, the measurement and control system issues an alarm to prompt manual intervention, so as to timely recover and repair or replace the gas measurement device, avoid obtaining incorrect marine in-situ long-term monitoring data, and avoid serious damage or even scrap of the key component of the gas detector.

[0044] In some embodiments, a calibration step is further included, which is automatically performed according to a preset calibration period in the measurement and control system; generally, the calibration step is performed once when the gas measurement device is initially put into water, and then performed again automatically after a preset time interval. Further, if the temperature, humidity or pressure of the sample gas in the sample gas pipe detected by the temperature, humidity and pressure sensor exceeds the theoretical limit, the calibration step is immediately started, and the next calibration is calculated from the current calibration and performed again after a preset time interval.

[0045] Further, the calibration step includes: D1, closing the normally open electromagnetic valve on the gas pump and the sample gas pipe, i.e. disconnecting the sample gas passage of the gas measurement device.

[0046] D2, opening 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 to measure the concentration of the specified gas and record the measurement value 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 calibration gas in the second calibration gas tank enters the gas detector to measure the concentration of the specified gas and record the measurement value as ; i.e. opening the two calibration gas passages in turn, and using the gas detector to measure the concentration of the specified gas in the two different calibration gases in turn. Then, the calibration coefficients and are calculated according to formula (1), wherein is the preset concentration of the specified gas in the first calibration gas, and since the first calibration gas is different from the specified gas, the value of is essentially 0, i.e. the first calibration gas is used for zero point calibration; is the preset concentration of the specified gas in the second calibration gas, i.e. the second calibration gas is used for range calibration; thus, the in-situ self-calibration of the gas measurement device under water is realized, and new calibration coefficients are obtained; (1).

[0047] After the calibration step is completed, the normally closed electromagnetic valve on the second gas pipe is closed, and the normally open electromagnetic valve on the gas pump and the sample gas pipe is opened, i.e. the two calibration gas passages of the gas measurement device are disconnected and switched back to the sample gas passage, and the measurement step is performed, using the new calibration coefficients and calculated in the calibration step to correct the concentration measurement value of the specified gas obtained in step S4 according to formula (2), to obtain the corrected concentration value of the specified gas in seawater . (2).

[0048] The above-mentioned illustrative embodiment realizes the in-situ self-calibration of the gas measuring device underwater, and corrects the measured values ​​of the specified type of gas in seawater according to the calibration coefficient, thereby avoiding inaccurate monitoring data due to measurement signal attenuation, drift, etc. during long-term underwater measurement, and also avoids the use of laboratory calibration coefficients to correct concentration measurement values, which leads to increasing errors in concentration inversion results, significantly improving the accuracy of monitoring data during long-term in-situ monitoring of the ocean.

[0049] In some embodiments, during the execution of step D2, if and The difference between and When the difference between the two exceeds the preset tolerance, it means that the first or second standard gas has been used up. At this time, the measurement and control system will issue an alarm, prompting manual intervention to promptly recover, repair or replace the gas measuring device to avoid obtaining the wrong calibration coefficient, which will affect the correction of the concentration measurement value.

[0050] In summary, the gas measuring device and measuring method suitable for long-term in-situ monitoring of the ocean of the present invention, by setting a degassing tube and a forward and reverse water pump, and switching the direction of the water pump according to the flow conditions, cleverly solves the problem of reduced gas-liquid separation efficiency due to easy clogging of the water inlet during the measurement process, ensuring that the gas-liquid separation module always has a stable and efficient gas-liquid separation effect; by setting a Nafion tube, a cold trap and a drying tube, three-stage dehumidification of the sample gas can be achieved, which significantly reduces the humidity of the sample gas and prolongs the service life of the device, and regulates the on-off state of the refrigeration function of the refrigeration plate according to the humidity of the sample gas, thereby ensuring energy saving and consumption reduction under the premise of the dehumidification effect of the sample gas; by introducing the detected gas as dry gas into the blowing chamber of the Nafion tube The scanning channel is used to participate in the dehumidification of the sample gas, and there is no need to prepare dry gas for the Nafion tube additionally, which reduces the equipment and response time of the device; through the setting of the calibration module, the gas measuring device can be self-calibrated in situ underwater, avoiding problems such as inaccurate monitoring data due to measurement signal attenuation and drift in long-term underwater measurement, and also avoiding the problems of high maintenance costs and data interruption caused by the need to regularly recover and calibrate the sensor and then deploy it underwater under the existing technology; therefore, the present invention can accurately, stably and continuously perform long-term underwater in-situ monitoring of the concentration of specified types of gases in seawater through the integrated design and joint application of the gas-liquid separation module, the dehumidification module, the detection module and the calibration module, and can achieve the effect of maintenance-free continuous use in seawater for at least half a year.

[0051] Finally, it should be noted that the various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0052] The above examples are only used to illustrate the technical solutions of the present application but not to limit the present application; although the present application has been described in detail with reference to the preferred embodiments, it is understood by the person of ordinary skill in the art that the specific embodiments of the present application can be modified or some technical features can be replaced by equivalent ones without departing from the spirit of the technical solutions of the present application, and all of them should be covered in the technical solution range of the present application claimed.

Claims

1. A gas measurement device suitable for long-term in-situ monitoring of the ocean, characterized in that: It includes a measurement and control system, a pressure cabin, a gas-liquid separation module, a dehumidification module, a detection module and a calibration module located in the pressure cabin; wherein, The pressure cabin is provided with two water inlets opposite to each other, and a filter screen is provided at the water inlets; The gas-liquid separation module includes a degassing pipe and a water pump; the two ends of the degassing pipe in the longitudinal direction are respectively connected to two water ports, and the side wall of the degassing pipe is provided with an air outlet and an air return port; the water pump is arranged between one of the water ports and the degassing pipe, and the water pump rotates forward or reverse under the control of the measurement and control system; The dehumidification module includes a Nafion tube, a cold trap, and a drying tube connected in sequence; the Nafion tube has a sample gas passage and a purge passage; one end of the sample gas passage is connected to the gas outlet of the degassing tube, and the other end is connected to the cold trap; a cooling sheet is attached to the outer wall of the cold trap; The detection module includes a gas detector, the inlet of which is connected to a drying tube via a gas sample pipe, and an air pump and a normally open solenoid valve are sequentially provided on the gas sample pipe; one end of the purge passage of the Nafion tube is connected to the outlet of the gas detector, and the other end is connected to the return port of the degassing tube; The calibration module includes a first calibration gas tank and a second calibration gas tank, which are respectively connected to the sample gas pipe between the normally open solenoid valve and the gas detector through a first gas pipe and a second gas pipe; the first gas pipe and the second gas pipe are both provided with a normally closed solenoid valve.

2. The gas measurement device suitable for long-term in-situ monitoring of the ocean according to claim 1, characterized in that: The gas-liquid separation module further includes a flow meter, which 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.

3. The gas measurement device suitable for long-term in-situ monitoring of the ocean according to claim 2, characterized in that: The detection module also includes a temperature, humidity and pressure sensor, which is arranged on the sample gas pipe and close to the gas detector; the temperature, humidity and pressure sensor monitors the temperature, humidity and pressure of the gas entering the gas detector, and transmits the monitoring results to the measurement and control system in real time.

4. The gas measurement device suitable for long-term in-situ monitoring of the ocean according to claim 3, characterized in that: A molecular sieve adsorption bag is provided below the cold trap, and the bottom of the cold trap is connected to the molecular sieve adsorption bag via a connecting pipe, and a one-way valve is provided on the connecting pipe.

5. The measurement method of the gas measurement device suitable for long-term in-situ monitoring of the ocean according to claim 3 or 4, characterized in that: The method comprises a measuring step, wherein the measuring step comprises: S1, turning on the water pump and the air pump; S2. The seawater outside the pressure cabin continuously flows through the degassing pipe through the water inlet driven by a water pump, and the degassing pipe degases the seawater flowing through it; S3, the sample gas removed from the degassing pipe is driven by the air pump and dehumidified by the dehumidification module; S4. The sample gas dehumidified by the dehumidification module enters the gas detector to measure the concentration of the specified type of gas, and the detected gas returns to the degassing tube through the purge path of the Nafion tube.

6. The measurement method of the gas measurement device suitable for long-term in-situ monitoring of the ocean according to claim 5, characterized in that: During the measurement step, when the flow meter detects that the seawater flow rate flowing through the degassing pipe is lower than a preset flow rate threshold, the measurement and control system changes the rotation direction of the water pump.

7. The measurement method of the gas measurement device suitable for long-term in-situ monitoring of the ocean according to claim 5, characterized in that: During the measurement step, 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 measurement and control system turns on the cooling function of the cooling plate; 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 measurement and control system turns off the cooling function of the cooling plate.

8. The measurement method of the gas measurement device suitable for long-term in-situ monitoring of the ocean according to claim 7, characterized in that: During the measurement step, when the cooling function of the refrigeration plate is turned on, if the temperature, humidity and pressure sensor detects that the humidity of the gas entering the gas detector increases instead of decreases, the measurement and control system will issue an alarm, prompting manual intervention to recover, repair or replace the gas measuring device.

9. The measurement method of the gas measurement device suitable for long-term in-situ monitoring of the ocean according to claim 5, characterized in that: The system also includes a calibration step, which is automatically performed according to a calibration cycle preset in the measurement and control system, and includes: D1. Close the normally open solenoid valve on the air pump and the sample gas pipe; D2. Open the normally closed solenoid valve on the first gas pipe to allow the first standard gas in the first standard gas tank to enter the gas detector to measure the concentration of the specified type of gas and record the measured value as Close the normally closed solenoid valve on the first gas pipe, open the normally closed solenoid valve on the second gas pipe, and allow the second standard gas in the second standard gas tank to enter the gas detector to measure the concentration of the specified type of gas and record its measured value as ; Calculate the calibration coefficient according to formula (1) and ,in, is the preset concentration of the specified type of gas in the first standard gas, The preset concentration of the specified type of gas in the second standard gas; （1）； After the calibration step is completed, close the normally closed solenoid valve on the second air pipe, open the normally open solenoid valve on the air pump and the sample air pipe, perform the measurement step, and use the calibration coefficient calculated in the calibration step. and , according to formula (2), the concentration measurement value of the specified type of gas obtained in step S4 is Perform calibration to obtain the concentration value of the specified gas in the seawater after calibration ; （2）。 10. The measurement method of the gas measurement device suitable for long-term in-situ monitoring of the ocean according to claim 9, characterized in that: During the execution of step D2, if and The difference between and When the difference between the two exceeds the preset tolerance, the measurement and control system will issue an alarm, prompting manual intervention to recycle, repair or replace the gas measuring device.

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