Total organic carbon measurement device

Abstract

The present invention comprises: an oxidation unit (6) that has an inlet and an outlet and is configured to convert a carbon component in a sample injected through the inlet into carbon dioxide and cause the carbon dioxide to flow out from the outlet; a syringe pump (2) for injecting a sample into the oxidation unit through the inlet of the oxidation unit (6); a detection unit (10) that outputs a signal having an intensity corresponding to the amount of carbon dioxide that flowed out from the outlet of the oxidation unit (6); a control unit (12) configured to control the operation of the syringe pump (2); and a signal processing unit (14) configured to process the signal output from the detection unit (10). The signal processing unit (14) stores, as a reference waveform, the waveform of an output signal from the detection unit (10) for atmospheric air, the waveform being acquired by injecting a prescribed amount of atmospheric air into the oxidation unit (6) by using the syringe pump (2) in a state in which there is no leakage in a flow path from the oxidation unit (6) to the detection unit (10). The control unit (12) is configured such that when an inspection mode is selected, the prescribed amount of atmospheric air is injected into the oxidation unit (6) by using the syringe pump (2), and the waveform of the output signal from the detection unit (10) for the atmospheric air is acquired as a test waveform. The signal processing unit (14) is configured to determine whether a leak is present in the flow path from the oxidation unit (6) to the detection unit (10) by comparing the test waveform and the reference waveform.

Description

Total organic carbon measuring device

[0001] The present invention relates to a total organic carbon measuring device.

[0002] In a combustion-type total organic carbon measuring device, the carbon component in the sample is oxidized and decomposed into carbon dioxide in the oxidation section, and the generated carbon dioxide is sent to the detection section by a carrier gas. Based on the signal of the intensity corresponding to the carbon dioxide concentration output from the detection section, the amount of the carbon component contained in the sample is quantified (see Patent Document 1).

[0003] Patent No. 7343038

[0004] When there is looseness in the piping connection after replacing some parts of the total organic carbon measuring device or during overhaul, there is a high possibility that gas leakage will occur in the flow path that guides the sample gas containing carbon dioxide to the detection section, resulting in an inability to obtain accurate analysis results. Therefore, it is desirable to perform a leak inspection to confirm whether there is a leak in the flow path up to the detection section. In the leak inspection, it is common to block the outlet of the detection section and pressurize the flow path between the oxidation section and the detection section. By observing the rate of pressure drop in the pressurized flow path, it is possible to confirm whether there is a leak in the flow path up to the detection section. To perform the leak inspection, tools for blocking the flow path and a manometer for measuring the pressure in the flow path are required, and after the leak inspection is completed, an operation to return the flow path to its original configuration is required in order to implement a partial change in the flow path configuration. Therefore, it has been difficult to perform the leak inspection unless the person has certain techniques and knowledge about the TOC meter.

[0005] The present invention has been made in view of the above problems, and an object thereof is to provide a total organic carbon measuring device capable of easily performing a leak inspection.

[0006] The total organic carbon analyzer according to the present invention comprises: an oxidation unit having an inlet and an outlet, configured to convert carbon components in a sample injected from the inlet into carbon dioxide and discharge it from the outlet; a syringe pump for injecting a sample into the oxidation unit from the inlet; a detection unit that outputs a signal of intensity corresponding to the amount of carbon dioxide discharged from the outlet of the oxidation unit; a control unit configured to control the operation of the syringe pump; and a signal processing unit configured to process the signal output from the detection unit. The signal processing unit stores the waveform of the output signal from the detection unit for air, obtained by injecting a predetermined amount of air into the oxidation unit by the syringe pump while there is no leakage in the flow path from the oxidation unit to the detection unit, as a reference waveform. When an inspection mode is selected, the control unit is configured to inject the predetermined amount of air into the oxidation unit by the syringe pump and obtain the waveform of the output signal from the detection unit for air as a test waveform. The signal processing unit is configured to determine whether or not there is leakage in the flow path from the oxidation unit to the detection unit by comparing the obtained test waveform with the reference waveform.

[0007] According to the total organic carbon analyzer of the present invention, when an inspection mode is selected, a predetermined amount of air is injected into the oxidation section by a syringe pump, and the waveform of the output signal from the detection section for the air is acquired as a test waveform. By comparing the acquired test waveform with a pre-prepared reference waveform, it is automatically determined whether or not there is a leak in the flow path from the oxidation section to the detection section. Therefore, leak testing can be performed without changing the flow path configuration of the device or using a special gas for leak testing. This provides a total organic carbon analyzer that can easily perform leak testing.

[0008] This is a schematic diagram showing one embodiment of a total organic carbon analyzer. This is a flowchart showing an example of the operation of the same embodiment in inspection mode.

[0009] Hereinafter, an embodiment of the total organic carbon measurement device according to the present invention will be described with reference to the drawings.

[0010] As shown in Figure 1, the total organic carbon measurement device 1 mainly comprises a syringe pump 2, a multi-port valve 4, an oxidation unit 6, a dehumidification unit 8, a detection unit 10, a control unit 12, and a signal processing unit 14.

[0011] Syringe pump 2 is used for drawing in and discharging fluid. A venting gas supply channel 28 is connected to the cylinder of syringe pump 2, allowing the sample to be aerated with venting gas within the cylinder of syringe pump 2.

[0012] The multi-port valve 4 is equipped with a common port located in the center and multiple selectable ports surrounding the common port. The multiple selectable ports of the multi-port valve 4 include a port to which a sample injection channel 24 for injecting a sample into the combustion tube 16 (combustion port), a port to which a channel leading to the sample tank is connected, a port to which a channel leading to a container for acid is connected, a port to which a channel leading to a container for cleaning solution is connected, and a port to which a channel leading to a drain is connected (atmospheric release port). The common port of the multi-port valve 4 is a pump port to which the suction and discharge ports of the syringe pump 2 are connected, and the destination of the suction and discharge ports of the syringe pump 2 can be switched depending on which selectable port the pump port is connected to for fluid communication. The injection of the sample into the combustion tube 2 is performed by connecting the syringe pump 2 to the sample tank, collecting the sample from the sample tank into the syringe pump 2, performing treatments such as adding acid or aeration to the sample as needed within the syringe pump 2, and then connecting the syringe pump 2 to the inlet 16a of the combustion tube 16, after which the sample is discharged from the syringe pump 2.

[0013] The oxidation section 4 comprises a combustion tube 16 and an electric furnace 18. The combustion tube 16 is made of, for example, quartz glass and has an oxidation catalyst placed inside. The combustion tube 16 is heated to a high temperature (for example, 680°C) by the electric furnace 18 and oxidizes and decomposes the carbon components in the sample injected into it through the inlet 16A, converting them into carbon dioxide. A carrier gas supply channel 20 is connected to the combustion tube 16. A flow rate control unit 22 is provided on the carrier gas supply channel 20.

[0014] The outlet 16b of the combustion tube 16 is connected to the dehumidifier 8 and the detection unit 10 by a sample gas flow path 26. The dehumidifier 8 is for removing moisture from the sample gas that flows out from the outlet 16b of the combustion tube 16. The detection unit 10 is for measuring the carbon dioxide concentration generated inside the combustion tube 16, and is, for example, an NDIR.

[0015] The control unit 12 controls the operation of the syringe pump 2, the multi-port valve 4, and the flow control unit 22. The control unit 12 can be implemented using an electronic circuit equipped with a CPU or the like.

[0016] The signal processing unit 14 reads the signal output from the detection unit 10 via the control unit 12 and performs processing such as the quantification of total organic carbon contained in the sample. The signal processing unit 14 can be implemented by a computer device equipped with a CPU, information storage memory, etc.

[0017] Furthermore, the signal processing unit 14 has a function to determine whether or not a leak is occurring between the combustion tube 16 and the detection unit 10. The determination of whether or not a leak is present is made by the user inputting an instruction to the signal processing unit 14 to select an inspection mode.

[0018] An example of operation during inspection mode will be explained using the flowchart in Figure 2 along with Figure 1. In this embodiment, leak detection is performed by determining whether the waveform of the signal from the detection unit 10 for a predetermined amount of air has changed from the waveform of the signal from the detection unit 10 for a predetermined amount of air acquired when no leak has occurred. The signal processing unit 14 stores in advance the waveform of the signal from the detection unit 10 for a predetermined amount of air when no leak has occurred as a reference waveform. The reference waveform can be acquired by injecting a predetermined amount of air into the combustion tube under the same conditions as the inspection mode described later, after it has been confirmed that no leak has occurred between the combustion tube 16 and the detection unit 10.

[0019] When the inspection mode is selected, the control unit 12 instructs the flow rate control unit 22 to control the carrier gas flow rate to a predetermined flow rate (step 101), and connects the syringe pump 2 to the drain via the multiport valve 4 (step 102). The carrier gas flow rate used in this example is the same as the carrier gas flow rate when the reference waveform was acquired. Since the end of the flow path leading to the drain is open to the atmosphere, if the syringe pump 2 is made to perform a suction operation in this state, air can be drawn into the syringe pump 2. After the syringe pump 2 has drawn in a predetermined amount of air (step 103), the control unit 12 connects the syringe pump 2 to the combustion tube 16 via the multiport valve 4 (step 104), and injects a predetermined amount of air into the combustion tube 16 via the syringe pump 2 (step 105). The amount of air injected into the combustion tube 16 here is the same as the amount of air injected into the combustion tube 16 when the reference waveform was acquired.

[0020] The signal processing unit 14 reads the signal from the detection unit 10 through the control unit 12, draws a waveform of the time change in signal intensity, and records it as a test waveform (step 106). The signal processing unit 14 compares the recorded test waveform with a reference waveform (step 107), and determines whether or not there is leakage based on whether or not the test waveform is different from the reference waveform (step 108).

[0021] Since there is approximately 400 ppm of carbon dioxide in the atmosphere, when air is injected into the combustion tube 16, the carbon dioxide in the atmosphere appears as a peak in the signal of the detection unit 10. If the carrier gas flow rate is the same as when the reference waveform was acquired, the shape of the peak will be almost the same if there is no leak between the combustion tube 16 and the detection unit 10. However, if there is a leak, phenomena such as a lower peak height, tailing of the peak end, and a smaller peak area will occur. Thus, the leak test performed in inspection mode checks whether there is a leak between the combustion tube 16 and the detection unit 16 by determining whether the peak appearing in the detector signal acquired when a predetermined amount of air is injected into the combustion tube 16 is different from the peak appearing in the detector signal acquired under normal conditions (when no leak occurs). Since this leak test involves injecting air into the combustion tube 16, there is no need to change the flow path configuration of the device, and there is no need to prepare a special gas for the leak test. The presence or absence of a leak may be determined using all of the parameters such as peak height, peak end, and peak area, or it may be determined using only some of these parameters. When using all parameters, a leak can be determined to exist if even one of the following phenomena is observed: for example, a decrease in peak height, tailing of the peak end, or a decrease in peak area.

[0022] Whether or not each parameter differs between the test waveform and the reference waveform can be determined by whether or not the difference between each parameter of the test waveform and the reference waveform exceeds a predetermined threshold.

[0023] After making the determination as described above, the determination result is displayed on a screen or the like (109).

[0024] In the above operation, the same carrier gas flow rate as when the reference waveform was acquired is used, but a different carrier gas flow rate may be used. In that case, even if there is no leak, the peak height and peak end of the acquired test waveform will differ from the reference waveform, but since the total amount of carbon dioxide contained in the injected air is the same, the peak area will be close to that of the reference waveform. If there is a leak, the peak area will be smaller, so even if a different carrier gas flow rate than when the reference waveform was acquired is used, the presence or absence of a gas leak can be determined using the peak area.

[0025] The embodiments described above are merely examples of embodiments of the total organic carbon measurement device according to the present invention. Embodiments of the total organic carbon measurement device according to the present invention are as follows.

[0026] In one embodiment of the total organic carbon analyzer according to the present invention, the apparatus comprises: an oxidation unit having an inlet and an outlet, configured to convert carbon components in a sample injected from the inlet into carbon dioxide and discharge it from the outlet; a syringe pump for injecting a sample into the oxidation unit from the inlet; a detection unit that outputs a signal of intensity corresponding to the amount of carbon dioxide discharged from the outlet of the oxidation unit; a control unit configured to control the operation of the syringe pump; and a signal processing unit configured to process the signal output from the detection unit. The signal processing unit stores the waveform of the output signal from the detection unit for air, obtained by injecting a predetermined amount of air into the oxidation unit by the syringe pump while there is no leakage in the flow path from the oxidation unit to the detection unit, as a reference waveform. When an inspection mode is selected, the control unit is configured to inject the predetermined amount of air into the oxidation unit by the syringe pump and obtain the waveform of the output signal from the detection unit for air as a test waveform. The signal processing unit is configured to determine whether or not there is leakage in the flow path from the oxidation unit to the detection unit by comparing the test waveform and the reference waveform.

[0027] In the first embodiment of the above-described model, the signal processing unit is configured to determine whether or not there is leakage in the flow path from the oxidation unit to the detection unit based on whether or not the difference in the peak areas of the test waveform and the reference waveform exceeds a preset threshold.

[0028] In the second embodiment of the above-described embodiment, the control unit uses the same carrier gas flow rate as when the reference waveform was acquired in the inspection mode, and the signal processing unit is configured to determine whether or not there is leakage in the flow path from the oxidation unit to the detection unit based on whether or not the difference between the peak heights and / or peak ends of the test waveform and the reference waveform exceeds a preset threshold. This second embodiment can be combined with the first embodiment.

[0029] In a third aspect of the above embodiment, the device further comprises a multiport valve having a pump port leading to the suction and discharge ports of the syringe pump, and a plurality of selectable ports selectively fluid-connected to the pump port, wherein the plurality of selectable ports of the multiport valve include a combustion port leading to the oxidation section and an atmospheric outlet port that is open to the atmosphere, and the control unit is configured to, when injecting a predetermined amount of air into the oxidation section by the syringe pump, to cause the syringe pump to draw in the predetermined amount of air by fluid-connecting the pump port and the atmospheric outlet port of the multiport valve, and then to cause the syringe pump to inject the predetermined amount of air into the oxidation section by fluid-connecting the pump port and the combustion port of the multiport valve. This third aspect can be combined with the first aspect and / or the second aspect.

[0030] In the third embodiment described above, the atmospheric vent port of the multi-port valve may be a port to which a flow path leading to a drain is connected. Since a drain is conventionally provided for connecting a syringe pump when disposing of cleaning fluid or when performing aeration treatment, by using a port to which a flow path leading to a drain is connected as an atmospheric vent port, air can be drawn in without changing the existing configuration.

[0031] 1 Total organic carbon analyzer 2 Syringe pump 4 Multi-port valve 6 Oxidation unit 8 Dehumidification unit 10 Detection unit 12 Control unit 14 Signal processing unit 16 Combustion tube 16a Combustion tube inlet 16b Combustion tube outlet 18 Electric furnace 20 Carrier gas supply channel 22 Flow rate control unit 24 Sample injection channel 26 Sample gas channel 28 Aeration gas supply channel

Claims

1. A total organic carbon analyzer comprising: an oxidation unit having an inlet and an outlet, configured to convert carbon components in a sample injected from the inlet into carbon dioxide and discharge it from the outlet; a syringe pump for injecting a sample into the oxidation unit from the inlet; a detection unit that outputs a signal of intensity corresponding to the amount of carbon dioxide discharged from the outlet of the oxidation unit; a control unit configured to control the operation of the syringe pump; and a signal processing unit configured to process the signal output from the detection unit, wherein the signal processing unit stores the waveform of the output signal from the detection unit for air, obtained by injecting a predetermined amount of air into the oxidation unit by the syringe pump while there is no leakage in the flow path from the oxidation unit to the detection unit, as a reference waveform; the control unit is configured to inject the predetermined amount of air into the oxidation unit by the syringe pump and obtain the waveform of the output signal from the detection unit for air as a test waveform when an inspection mode is selected; and the signal processing unit is configured to determine whether or not there is leakage in the flow path from the oxidation unit to the detection unit by comparing the test waveform and the reference waveform.

2. The total organic carbon measuring device according to claim 1, wherein the signal processing unit is configured to determine whether or not there is leakage in the flow path from the oxidation unit to the detection unit based on whether or not the difference in the peak areas of the test waveform and the reference waveform exceeds a preset threshold.

3. The total organic carbon measuring device according to claim 1, wherein the control unit uses the same carrier gas flow rate as when the reference waveform was acquired in the inspection mode, and the signal processing unit is configured to determine whether or not there is leakage in the flow path from the oxidation unit to the detection unit based on whether or not the difference in peak height and / or peak end between the test waveform and the reference waveform exceeds a preset threshold.

4. The total organic carbon measuring device according to claim 1, further comprising a multiport valve having a pump port leading to the suction and discharge ports of the syringe pump, and a plurality of select ports selectively fluid-connected to the pump port, wherein the plurality of select ports of the multiport valve include a combustion port leading to the oxidation section and an atmospheric outlet port that is open to the atmosphere, and the control unit is configured to, when injecting a predetermined amount of air into the oxidation section by the syringe pump, to cause the syringe pump to draw in the predetermined amount of air by fluid-connecting the pump port and the atmospheric outlet port of the multiport valve, and then to cause the syringe pump to inject the predetermined amount of air into the oxidation section by fluid-connecting the pump port and the combustion port of the multiport valve.

5. The total organic carbon measuring device according to claim 4, wherein the atmospheric vent port of the multi-port valve is a port to which a flow path leading to a drain is connected.

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