Carbon dioxide 14 C Direct and rapid detection method and detection system

Abstract

The present invention relates to the field of power generation technology, and provides a method and a detection system for directly and rapidly detecting 14C of carbon dioxide, which can rapidly complete the measurement of the 14C activity of carbon dioxide, and at the same time can further improve the uniformity and accuracy of the direct and rapid detection of 14C of carbon dioxide. A method for directly and rapidly detecting 14C of carbon dioxide provided by the present invention comprises the following steps: a pressurization step of pressurizing gaseous carbon dioxide to be liquefied to obtain liquid carbon dioxide; a mixing step of mixing the liquid carbon dioxide with a cosolvent and a scintillator in a pressure vessel to obtain a mixed solution; and a detection step of placing the pressure vessel in a liquid scintillation counter for radioactive carbon activity detection.

Description

Technical Field

[0001] The present invention relates to the field of power generation technology, in particular to a method of 14 C Direct and rapid detection method and detection system. Background Art

[0002] At present, coal is still the main energy source in the power generation industry, and biomass-coal coupled power generation will develop rapidly. However, the accurate measurement of biomass blending ratio has always been a major problem in the field of co-combustion power generation.

[0003] Radiocarbon ( 14 C) Measurement is an effective technical means to determine the mixing ratio of biomass and coal for coupled power generation. Liquid scintillation counting test is the most commonly used 14 In the existing technology, it is usually necessary to convert the carbon dioxide to be tested in the flue gas into benzene before testing. 14 The detection of C is due to the fact that benzene is the liquid substance with the highest carbon enrichment. The accuracy of the liquid scintillation counting test is positively correlated with the carbon enrichment of the sample to be tested. However, converting the carbon dioxide to be tested into benzene requires a series of complex processes including high-temperature reduction, hydrolysis and catalytic polymerization. The preparation time of a single sample is long and the conversion rate is low.

[0004] In this regard, the inventor proposed in his prior application CN107942368A that CO 2 Pressurized liquefaction replaces the existing technology of CO 2 The conversion step into benzene can improve the conversion rate and shorten the detection time, thus improving the timeliness of biomass blending ratio determination. 14 In the mixed system for C activity detection, benzene is fully miscible with the scintillator, while liquid carbon dioxide and the scintillator cannot form a uniform mixed system, which affects the detection efficiency and accuracy. Summary of the invention

[0005] In view of the above problems, the present invention provides a carbon dioxide 14 C direct and rapid detection method and detection system, capable of quickly forming a mixed and uniform sample for scintillation counting test near the sampling point of carbon dioxide and completing 14 C activity detection, and then complete the determination of biomass blending ratio, improve carbon dioxide 14 C measurement detection efficiency and accuracy, and improve the timeliness of biomass blending ratio determination.

[0006] A first aspect of the present invention provides a carbon dioxide 14C direct and rapid detection method, comprising the following steps: a pressurization step, pressurizing and liquefying gaseous carbon dioxide to obtain liquid carbon dioxide; a mixing step, mixing the liquid carbon dioxide with a co-solvent and a scintillator in a pressure vessel to obtain a mixed solution; a detection step, placing the pressure vessel in a liquid scintillation counter to perform radioactive carbon activity detection.

[0007] According to the technical solution, first, carbon enrichment is completed by pressurizing carbon dioxide to a liquid state, which can greatly reduce the time required for the carbon enrichment process and complete the removal of carbon dioxide from flue gas within 1 to 3 hours. 14 C is measured and the biomass blending ratio is calculated. Compared with the original method of at least 24 hours of benzene sample preparation time, the timeliness is greatly improved.

[0008] Secondly, the accuracy of the liquid scintillation counting test is closely related to the carbon enrichment in the unit volume of the test sample. The higher the carbon enrichment in the unit volume of the test sample, the higher the accuracy of the test. By adding a cosolvent to the liquid carbon dioxide, the carbon enrichment in the unit volume of the liquid carbon dioxide in the obtained mixed system can reach 165-175 mg / mL, which can reduce the detection error, uncertainty and detection limit. Therefore, the carbon dioxide is processed into a liquid state for 14 C measurement enables the determination of biomass blending ratios with high accuracy.

[0009] Finally, by mixing liquid carbon dioxide with a solvent and a scintillator, the solvent can dissolve the scintillator, thereby solving the problem of poor miscibility between liquid carbon dioxide and the scintillator, achieving uniform mixing of liquid carbon dioxide and the scintillator, and ensuring the accuracy of radiocarbon detection.

[0010] As a preferred technical solution, the mixing step includes the following sub-steps: a first mixing step, mixing the co-solvent and the scintillator to obtain a premixed solution; a second mixing step, mixing the premixed solution with liquid carbon dioxide in a pressure container to obtain a mixed solution.

[0011] According to the technical solution, since the liquid carbon dioxide is built into a pressure vessel, and it is difficult to inject liquid into a pressure vessel under high pressure, the scintillator is first mixed with the cosolvent to obtain a premixed solution in which the scintillator and the cosolvent are mutually soluble, so that the premixed solution can be directly injected into the liquid carbon dioxide in the subsequent process without the need to inject the liquid multiple times; and since the scintillator can be dissolved in the cosolvent, the premixing can make the scintillator and the cosolvent fully soluble in each other, thereby increasing the uniformity of the obtained mixed solution, further increasing 14 The accuracy of the detection of C.

[0012] As a preferred technical solution, in the first mixing step, the mixing ratio of the scintillator and the co-solvent is 12-15 mg / mL.

[0013] According to the technical solution, the inventors found that too much co-solvent may lead to a low content of scintillator in the mixed solution and a low degree of carbon enrichment; too little co-solvent cannot make the scintillator and liquid carbon dioxide mix evenly. When the mixing ratio of scintillator to co-solvent is within the range of 12-15 mg / mL, the scintillator and liquid carbon dioxide can be evenly mixed in the co-solvent, and at the same time, the content of scintillator in the mixed solution is moderate. 14 The detection result of C has better accuracy.

[0014] As a preferred technical solution, in the first mixing step, the scintillator is an organic solid scintillator, the cosolvent is an organic solvent, and the carbon element in the scintillator and the cosolvent is 14 The C activity is zero.

[0015] According to the technical solution, under high pressure, liquid carbon dioxide and organic solvents have good mutual solubility and can be naturally mixed and dissolved without stirring, heating, shaking or other mixing methods, and organic solid scintillators can also be dissolved in organic solvents, thus forming a uniform mixed system under high pressure conditions. 14 Scintillators and cosolvents with zero C activity can avoid the introduction of external C into the mixed system. 14 C pollution.

[0016] As a preferred technical solution, in the second mixing step, the volume ratio of the premixed solution to the liquid carbon dioxide is 1:5-1:6.

[0017] According to the technical solution, the ratio range of the premixed solution to the liquid carbon dioxide depends on two aspects. On the one hand, the ratio of the liquid carbon dioxide to the scintillator needs to be in a suitable range to ensure that the decay energy of the radioactive carbon in the liquid carbon dioxide can make the scintillator molecules emit fluorescence; on the other hand, the ratio of the liquid carbon dioxide to the cosolvent needs to be in a suitable range to ensure that the cosolvent can be evenly dissolved in the liquid carbon dioxide, evenly mixed with the scintillator also dissolved in the liquid carbon dioxide, and the carbon enrichment degree can be ensured as much as possible. The inventors have found that when the volume ratio of the premixed solution to the liquid carbon dioxide is in the range of 1:5-1:6, both factors can be taken into account at the same time to ensure that the scintillator and the liquid carbon dioxide are evenly mixed at a suitable ratio.

[0018] As a preferred technical solution, in the pressurization step, the pressurization rate of the gaseous carbon dioxide is controlled according to the temperature and pressure of the liquid carbon dioxide.

[0019] According to this technical solution, if the pressurization rate of carbon dioxide is too fast, a large amount of carbon dioxide will accumulate in the pressure vessel instantly, causing the carbon dioxide to liquefy rapidly, emitting a large amount of heat, and eventually causing the liquid carbon dioxide to become supercritical or causing its density to be greatly reduced compared to the liquid state, thereby reducing the accuracy of the test. By detecting the temperature in the pressure vessel during the pressurization process and then controlling the pressurization rate based on the temperature, the temperature in the pressure vessel can be prevented from being too high, making the process of pressurizing and liquefying carbon dioxide safer and more reliable.

[0020] The second aspect of the present invention also provides a carbon dioxide 14 C direct and rapid detection system, which includes: 14 C detection device, 14 The C detection device is a pressure vessel with a light-transmitting area, which is used to contain a mixed solution of liquid carbon dioxide and scintillator; a pressurizing system, and 14 C detection device is connected to the gaseous carbon dioxide to pressurize and liquefy it into liquid carbon dioxide, and then pass the liquid carbon dioxide into 14 C detection device; mixed solution addition system, and 14 C detection device is connected to pre-mix the scintillant and the co-solvent, and the pre-mixed solution of the scintillant and the co-solvent is passed into 14 C detection device; liquid scintillation counter, having a suitable 14 C detection device is placed in the sample slot and measurement cavity, and the liquid scintillation counter uses 14 The radioactive carbon activity is detected in the light-transmitting area of ​​the C detection device.

[0021] According to the technical solution, the carbon dioxide 14 The direct and rapid detection system can quickly form a mixed and uniform sample for scintillation counting test near the sampling point of carbon dioxide, improving the 14 The detection efficiency and accuracy of the measurement of C.

[0022] As a preferred technical solution, the carbon dioxide 14 C direct and rapid detection system also includes a pretreatment system, which is connected to the gas source of gaseous carbon dioxide and the pressurizing system, and the gaseous carbon dioxide sample collected from the gas source of gaseous carbon dioxide is purified and then passed into the pressurizing system.

[0023] According to the technical solution, the pretreatment system can remove impurities in gaseous carbon dioxide and prevent other impurities in the carbon dioxide from affecting the measurement results.

[0024] As a preferred technical solution, 14The C detection device includes: a pressure-bearing shell, which encloses a light-transmitting cylindrical cavity; a pressure-bearing plate, which is respectively arranged on the upper bottom surface and the lower bottom surface of the cylindrical cavity; fixed tie rods, and the two ends of multiple fixed tie rods are respectively fixed to the pressure-bearing plates on the upper bottom surface and the lower bottom surface of the cylindrical cavity; a cooling water channel, which is arranged inside at least one pressure plate.

[0025] According to this technical solution, 14 The C detection device adopts an overall cylindrical design, with the side wall being a light-transmitting pressure-bearing shell, and the upper and lower bottom surfaces being pressure-bearing plates, which are fixed and sealed by fixed tie rods, so that high-pressure carbon dioxide can 14 C detection device exists safely and stably. In addition, liquid carbon dioxide 14 The fluorescence emitted by the scintillator molecules after the decay of C can be captured and recorded by the photomultiplier tube of the liquid scintillation counter through the pressure-bearing shell, so as to test the radiocarbon activity of the carbon dioxide sample.

[0026] In addition, a cooling water channel is provided in at least one pressure plate, and cooling media of different temperatures are introduced into the cooling water channel to achieve 14 The cooling of the liquid carbon dioxide in the C detection device absorbs a large amount of heat generated by the liquefaction of carbon dioxide, while promoting the conversion of gaseous carbon dioxide to liquid phase and increasing the density of liquid carbon dioxide.

[0027] As a preferred technical solution, 14 The C detection device also includes a temperature detector arranged in the cylindrical cavity; the pressurization system also includes a pressure detector and a pressure control device, and the pressure control device controls the pressurization rate of the pressurization system based on the detection results of the temperature detector and the pressure detector.

[0028] According to the technical solution, the temperature detector can be used to detect the temperature during the pressurization process. 14 C detects the temperature in the device, and the pressure detector can detect the pressure in the pressurized system. Based on the pressurization speed and 14 C. Temperature of the detection device. If the pressure increase speed in the pressurized system is fast and 14 C The temperature of the detection device is high, use the pressure control device to reduce the pressurization rate of the pressurization system; if the pressurization rate in the pressurization system is low and 14 The temperature of the C detection device is low, and the pressure control device is used to increase the pressurization rate of the pressurization system. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a method applicable to the first embodiment of the present invention. 14 Schematic diagram of the detection system of C;

[0030] Figure 2The carbon dioxide provided by the first embodiment of the present invention 14 C Flow chart of direct and rapid detection method;

[0031] Figure 3 A preferred carbon dioxide provided by the first embodiment of the present invention is 14 C direct and rapid detection method;

[0032] Figure 4 The carbon dioxide provided by the second embodiment of the present invention 14 C. Schematic diagram of the structure of the direct and rapid detection system;

[0033] Figure 5 The preferred embodiment of the second embodiment of the present invention is shown. 14 C. Schematic diagram of the structure of the detection device;

[0034] Figure 6 The preferred embodiment of the second embodiment of the present invention is shown. 14 C Schematic diagram of the bottom surface of the detection device.

[0035] Description of reference numerals:

[0036] 100-Carbon Enrichment Unit; 200-Detection Unit; 300-Liquid Scintillation Counter;

[0037] 1- 14 C detection device;

[0038] 11-cylindrical cavity; 111-upper bottom surface; 112-lower bottom surface; 12-pressure-bearing shell; 13-fixing nut; 14-high-pressure needle valve; 15-fixing tie rod; 16-pressure-bearing plate; 161-cooling water channel; 17-temperature detector;

[0039] 2- Pressurization system;

[0040] 21-boosting pump; 22-high pressure valve; 23-pressure pipeline; 24-pressure detector; 25-pressure control device;

[0041] 3-Mixed solution adding system;

[0042] 31-premixing chamber; 32-mixed solution adding valve; 33-vacuum valve; 34-vacuum pump;

[0043] 4- Pretreatment system;

[0044] 41- vacuum pump; 42- gaseous carbon dioxide source; 43- gas valve; 44- solid phase impurity removal system; 45- gas phase impurity removal system; 46- mass flow controller. DETAILED DESCRIPTION

[0045] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0046] First embodiment

[0047] Figure 1 This embodiment is applicable to a 14 Schematic diagram of the detection system of C. Figure 1 Taking the detection system in the example, the gaseous carbon dioxide enters the carbon enrichment unit 100 and is converted into liquid carbon dioxide with a higher carbon enrichment degree. The enriched liquid carbon dioxide then enters the detection unit 200. The scintillator absorbs the decay energy released by the radioactive carbon and emits fluorescence. The fluorescence is captured by the liquid scintillation counter 300 to measure the liquid carbon dioxide. 14 The carbon dioxide enrichment degree in the carbon enrichment unit 100 and the mixing uniformity of the liquid carbon dioxide and the scintillator determine 14 The accuracy of C detection; the carbon enrichment process of gaseous carbon dioxide will affect the overall device complexity of the detection system and the sample preparation and detection time.

[0048] In this embodiment, the carbon enrichment unit 100 is usually arranged near the sampling point. For example, the carbon dioxide in the flue gas collected near the sampling point is enriched and then sent to the laboratory for 14 C scintillation counting detection or local implementation at the sampling point 14 C Scintillation counting assay.

[0049] The first embodiment of the present invention provides a carbon dioxide 14 C direct and rapid detection method, Figure 2 The carbon dioxide provided by this embodiment 14 C Flowchart of the direct and rapid detection method.

[0050] like Figure 2 As shown, the carbon dioxide provided by this embodiment 14 C direct, rapid detection method includes the following steps:

[0051] Pressurizing step S1, pressurizing and liquefying gaseous carbon dioxide to obtain liquid carbon dioxide;

[0052] Mixing step S2, mixing liquid carbon dioxide with a co-solvent and a scintillator in a pressure vessel to obtain a mixed solution;

[0053] In the detection step S3, the pressure container is placed in a liquid scintillation counter 300 to detect the radioactive carbon activity.

[0054] Among them, "cosolvent" refers to a reagent that can promote the mutual solubility of liquid carbon dioxide and scintillator. The specific type of "cosolvent" is not limited. It can be a solvent that can dissolve liquid carbon dioxide and scintillator at the same time, or it can be a reagent that can change the solubility of scintillator in liquid carbon dioxide. The use of cosolvent can improve the mutual solubility and mixing uniformity of liquid carbon dioxide and scintillator, thereby ensuring the smooth progress of liquid carbon dioxide liquid scintillation counting test. Preferably, the scintillator is an organic solid scintillator, and the cosolvent is an organic solvent. Under high pressure, liquid carbon dioxide and organic solvents have good mutual solubility, and can be naturally mixed and dissolved without stirring, heating, shaking and other mixing methods, and organic solid scintillator can also be dissolved in organic solvents, so that a uniform mixed system under high pressure conditions can be formed.

[0055] Further preferably, the organic solid scintillator is 2-(4'-tert-butylphenyl)-5-(4"-biphenyl)-1,3,4-oxadiazole, or 2,5-diphenyloxazole, and the cosolvent is toluene. Toluene, as a common organic solvent, is easily available and has good solubility with the scintillator (2-(4'-tert-butylphenyl)-5-(4"-biphenyl)-1,3,4-oxadiazole, or 2,5-diphenyloxazole) and liquid carbon dioxide.

[0056] "Pressure vessel" refers to a closed container in the detection unit 200 that can withstand the pressure required to liquefy carbon dioxide. Its shape and size are not limited and can be applicable to an existing liquid scintillation counter or a new liquid scintillation counter that has been designed and modified. The carbon enrichment method adopted in this embodiment is to pressurize and liquefy gaseous carbon dioxide. The carbon-enriched material injected into the detection unit 200 by the carbon enrichment unit 100 is high-pressure liquid carbon dioxide. The detection unit 200 in this embodiment includes a closed container that can withstand pressure, which is used to contain and mix high-pressure liquid carbon dioxide and scintillator.

[0057] Specifically, combined Figure 1 and Figure 2 From the perspective of the carbon enrichment unit 100, the pressurization step S1 is performed, and the gaseous carbon dioxide is pressurized and liquefied to form liquid carbon dioxide, thereby completing the carbon enrichment, greatly reducing the time required for the carbon enrichment process and the complexity of the device, and the flue gas carbon dioxide can be completed within 1 to 3 hours. 14C measurement can quickly complete the determination of biomass blending ratio, which greatly improves the timeliness compared to the existing method of at least 24 hours of benzene sample preparation time. In addition, the carbon enrichment per unit volume of liquid carbon dioxide can reach 165-175 mg / mL, which can reduce detection errors, uncertainties and detection limits. Therefore, carbon dioxide is processed into liquid for 14 C measurement also enables the determination of biomass blending ratios with high accuracy.

[0058] Next, a mixing step S2 is performed in the detection unit 200, where the enriched liquid carbon dioxide is mixed with the cosolvent and the scintillator in the detection unit 200. Under the action of the cosolvent, the scintillator and the liquid carbon dioxide can form a uniform mixed system. 14 C activity is zero, for example, scintillators and cosolvents produced from fossil carbon sources can be used to avoid introducing 14 C pollution.

[0059] Finally, the detection step S3 is performed, and the liquid carbon dioxide 14 After C decays, its decay energy is absorbed by the scintillator molecules. After absorbing the decay energy, the scintillator molecules transition from the ground state to the excited state. When the molecules are de-excited, their energy is released in the form of fluorescence. The fluorescence is captured and recorded by the photomultiplier tube of the liquid scintillation counter 300, so as to measure the radioactive carbon activity of the carbon dioxide sample. The uniform mixing system can effectively ensure 14 The correlation between the decay of C and the fluorescence emission improves 14 C detection accuracy.

[0060] Among them, during the pressurization process of the pressurization step S1, if the pressurization rate of carbon dioxide is too fast, a large amount of carbon dioxide will be instantly accumulated in the pressure vessel, causing the carbon dioxide to liquefy rapidly, releasing a large amount of heat, and eventually causing the liquid carbon dioxide to become a supercritical state or causing its density to be greatly reduced compared to the liquid state, thereby reducing the test accuracy. Therefore, in a preferred embodiment of the present invention, in the pressurization step S1, the pressurization rate of gaseous carbon dioxide can be controlled according to the temperature and pressure of the liquid carbon dioxide, so as to avoid the temperature in the pressure vessel from being too high, making the process of pressurizing liquefied carbon dioxide safer and more reliable, and obtaining liquid carbon dioxide with a greater carbon enrichment degree.

[0061] Figure 3 A preferred carbon dioxide provided by the first embodiment of the present invention is 14 C direct and rapid detection method. Figure 3As shown, the mixing step S2 includes the following sub-steps: a first mixing step S21, mixing the co-solvent and the scintillator to obtain a premixed solution; a second mixing step S22, mixing the premixed solution with liquid carbon dioxide in a pressure container to obtain a mixed solution.

[0062] Specifically, combined Figure 1 and Figure 3 From the above, in the mixing step S2, since the liquid carbon dioxide is built into the pressure vessel, and it is difficult to inject liquid into the pressure vessel under high pressure, the first mixing step S21 is first performed to mix the scintillator and the co-solvent outside the detection unit 200 to obtain a premixed solution in which the scintillator and the co-solvent are mutually soluble; then the second mixing step S2 is performed to directly inject the premixed solution into the liquid carbon dioxide to obtain a mixed solution of the scintillator, the mutual solvent and the liquid carbon dioxide. There is no need to inject the liquid multiple times, and since the scintillator can be dissolved in the co-solvent, the premixing can make the scintillator and the co-solvent fully soluble in each other, thereby increasing the uniformity of the obtained mixed solution, further increasing 14 The accuracy of the detection of C.

[0063] Among them, preferably, in the first mixing step S21, the mixing ratio of the scintillator and the co-solvent is 12-15 mg / mL. The inventors have found that too much co-solvent may result in a lower content of scintillator in the mixed solution and a lower degree of carbon enrichment; too little co-solvent cannot make the scintillator and liquid carbon dioxide mix evenly. When the mixing ratio of the scintillator and the co-solvent is within the range of 12-15 mg / mL, the scintillator and the liquid carbon dioxide can be evenly mixed in the co-solvent, and at the same time, the content of the scintillator in the mixed solution is moderate. 14 The detection result of C has better accuracy.

[0064] Further preferably, in the second mixing step S22, the volume ratio of the premixed solution to the liquid carbon dioxide is 1:5-1:6. The ratio range of the premixed solution to the liquid carbon dioxide depends on two aspects. On the one hand, the ratio of the liquid carbon dioxide to the scintillator needs to be in a suitable range to ensure that the decay energy released by the radioactive carbon in the liquid carbon dioxide can make the scintillator emit fluorescence; on the other hand, the ratio of the liquid carbon dioxide to the co-solvent needs to be in a suitable range to ensure that the liquid carbon dioxide can be uniformly dissolved in the co-solvent and uniformly mixed with the scintillator that is also soluble in the co-solvent. The inventors have found that when the volume ratio of the premixed solution to the liquid carbon dioxide is in the range of 1:5-1:6, both factors can be taken into account at the same time to ensure that the scintillator and the liquid carbon dioxide are uniformly mixed at a suitable ratio.

[0065] In this embodiment, first, carbon enrichment is completed by pressurizing carbon dioxide to a liquid state, which can greatly reduce the time required for the carbon enrichment process and complete the carbon dioxide enrichment of flue gas within 1 to 3 hours. 14 C measurement, and then quickly complete the determination of the biomass blending ratio.

[0066] Secondly, the accuracy of the liquid scintillation counting test is closely related to the carbon enrichment in the unit volume of the test sample. The higher the carbon enrichment in the unit volume of the test sample, the higher the accuracy of the test. By adding a cosolvent to the liquid carbon dioxide, the carbon enrichment in the unit volume of the liquid carbon dioxide in the obtained mixed system can reach 165-175 mg / mL, which can reduce the detection error, uncertainty and detection limit. Therefore, the carbon dioxide is processed into a liquid state for 14 C measurement enables the determination of biomass blending ratios with high accuracy.

[0067] Finally, by mixing liquid carbon dioxide with a solvent and a scintillator, the solvent can dissolve the scintillator, thereby solving the problem of poor miscibility between liquid carbon dioxide and the scintillator, and further providing the types and proportions of the scintillator and the solvent, achieving uniform mixing of liquid carbon dioxide and the scintillator, and improving the uniformity and accuracy of radiocarbon detection.

[0068] Test Case

[0069] In the test example, the organic solid scintillator is 2-(4'-tert-butylphenyl)-5-(4"-biphenyl)-1,3,4-oxadiazole (Bulty-PBD), and the cosolvent is toluene. The mixing ratio of the scintillator and the cosolvent toluene is 15 mg / mL, and the volume ratio of the premixed solution to liquid carbon dioxide is 1:5.

[0070] Test process: After a pressure vessel with a visual window is connected to a detachable sampling container, a certain volume (1 / 6 of the total volume of the container) of a premixed solution of toluene and scintillator is first placed in the pressure vessel (the mixing ratio of scintillator to toluene is 15 mg / mL), and a certain amount of carbon dioxide is pressurized to a predetermined pressure, and the theoretical mass mixing ratio of carbon dioxide and the premixed solution is calculated according to the temperature, pressure and volume of the pressure vessel; after the mixture is uniformly mixed, the sampler is removed, and the total mass of the sample taken out is calculated according to the mass difference before and after the sampler is sampled, and then the liquid carbon dioxide in the sampling cavity is released into a measuring cavity with a known volume, measurable temperature and pressure, and the mass of carbon dioxide in the sample is calculated according to the temperature, pressure and volume of the cavity, and then the mass of the premixed solution in the sample is calculated. By comparing the mixing ratio of liquid carbon dioxide and premixed solution in the sample with the theoretical value of the ratio of the two in the container, the mixing uniformity of liquid carbon dioxide and scintillator can be verified.

[0071] The test results are shown in Table 1 for three sets of mixing experimental data. The results show that under the condition of a mixing system pressure of 7.5-8.5 MPa, liquid carbon dioxide and the premixed solution can be uniformly mixed, and the actual mass ratio of the sampled liquid carbon dioxide to the premixed solution is in good agreement with the theoretical mass ratio.

[0072] In addition, during the experiment, through intuitive observation through the visual window, it can be seen that the liquid carbon dioxide and the premixed solution can be evenly mixed into one, and the solution is clear and transparent, which intuitively illustrates that the detection method proposed in this embodiment can achieve the uniformity and stability of the liquid carbon dioxide and scintillator mixed system. In addition, during the carbon dioxide pressurization process, the amount of liquid carbon dioxide gradually increases, and carbon dioxide can be directly and evenly miscible with the premixed solution of toluene and scintillator during the liquefaction process, without taking measures such as stirring and heating to promote miscibility.

[0073] Table 1

[0074]

[0075] Second embodiment

[0076] A second embodiment of the present invention provides a carbon dioxide 14 C direct and rapid detection system, the carbon dioxide provided by this embodiment 14 C direct, rapid detection system can perform the carbon dioxide in the first embodiment 14 C direct and rapid detection method.

[0077] Figure 4 is a schematic diagram of the structure of the detection system provided in this embodiment, such as Figure 4 As shown, the detection system provided in this embodiment includes 14 C detection device 1, pressurizing system 2, mixed solution adding system 3, pretreatment system 4 and liquid scintillation counter ( Figure 4 not shown).

[0078] in, 14 C detection device 1 is a pressure vessel with a light-transmitting area, used to contain the collected liquid carbon dioxide and to mix various liquids therein. 14 The specific structure of the C detection device 1 is not limited. Figure 5 The preferred embodiment provided by this embodiment is shown as follows 14 C structural diagram of the detection device 1, as shown in Figure 5 As shown, 14The C detection device 1 includes a pressure-bearing shell 12, a pressure-bearing plate 16, fixed tie rods 15 and a cooling water channel 161, wherein the pressure-bearing shell 12 encloses a light-transmitting cylindrical cavity 11, the pressure plates 16 are respectively arranged on the upper bottom surface 111 and the lower bottom surface 112 of the cylindrical cavity 11, the two ends of a plurality of fixed tie rods 15 are respectively fixed to the pressure plates 16 on the upper bottom surface 111 and the lower bottom surface 112 of the cylindrical cavity 11, and the cooling water channel 161 is arranged inside at least one pressure plate 16.

[0079] Specifically, the light-transmissive pressure-bearing shell 12 is used to contain high-pressure liquid carbon dioxide and provide a path for the emission of fluorescence. The two ends of the fixed tie rod 15 are fixed to the pressure plate 16 by fixing nuts 13, so that the pressure plate 16 and the pressure-bearing shell 12 form a closed cylindrical cavity 11, and the cylindrical cavity 11 is used to contain high-pressure liquid carbon dioxide or a mixed solution.

[0080] Preferably, a perfluoro gasket is used to seal between the pressure shell 12 and the pressure plate 16. Compared with other gaskets, the perfluoro gasket has excellent resistance to the swelling effect of liquid carbon dioxide.

[0081] Among them, preferably, 14 The C detection device 1 further comprises a high-pressure needle valve 14, which can be used to charge and discharge carbon dioxide and add a premixed solution in a high-pressure environment.

[0082] In this embodiment, the pressure vessel can be formed as a partially or fully light-transmissive container. For example, in some embodiments, the pressure shell 12 can be an opaque shell made of a pressure-resistant metal material, and an optical fiber channel is inserted into the interior of the pressure vessel through the metal shell and connected to the solution to be tested. The other end of the optical fiber channel is connected to the photomultiplier tube of the liquid scintillation counter. The number of optical fiber channels is determined according to the number of photomultiplier tubes of the liquid scintillation counter, which is two or three. The end of the optical fiber channel adopts a convex lens design, which has a focusing effect. The inner surface of the pressure vessel adopts a high-pressure mirror design to enhance the reflection and propagation of fluorescence. The fluorescence generated by the scintillator is reflected by the mirror on the inner surface of the container and propagates to the end of the optical fiber channel. After being aggregated by the convex lens, it is transmitted to the photomultiplier tube for measurement through the optical fiber channel. Alternatively, in other embodiments, the pressure shell 12 is made of a transparent material as a whole, and the opaque fixed tie rods 15 are distributed on the pressure shell 12, so that the pressure shell 12 between the fixed tie rods 15 can provide an emission path for the fluorescence. Further preferably, see Figure 6 As shown, the present embodiment 14In the C detection device 1, three fixing nuts 13 and three fixing ties 15 are used, which are evenly distributed on the pressure plate 16 along the circumferential direction, so that the fluorescence can be emitted from between the three fixing ties 15, and the part of the pressure-bearing shell 12 between each fixing ties 15 can just be aligned with the three photomultiplier tubes of the liquid scintillation counter, so that the photomultiplier tubes are more conducive to capturing the fluorescence scintillation data.

[0083] As a preferred example, 14 The overall design size of the C detection device 1 can be 48mm in diameter and 105mm in height, which is the size of the sample slot and measurement cavity of the currently common liquid scintillation counter. Under this design size, the 14 The C detection device 1 can be directly applied to a liquid scintillation counter without major modifications to the instrument. More specifically, in the radial direction, in order to ensure a maximum safety pressure of 10mPa in the device, the annular thickness of the pressure shell 12 can be set to 8mm, the material can be sapphire, and the diameter of the cylindrical cavity 11 is set to 20mm; in the axial direction, the total height of the device is 105mm, of which the design height of the cylindrical cavity 11 and the pressure shell 12 is 65mm, the height of the upper and lower pressure plates 16 is 5mm, and the height of the high-pressure needle valve 14 is 30mm. Under this size design, the volume of the cylindrical cavity 11 is 20.41mL, and the carbon enrichment level of liquid carbon dioxide reaches 165-175mg / mL, which is sufficient to meet the liquid scintillation counting measurement with high precision. Under this size design, it can meet the needs of using existing liquid scintillation counters to complete carbon dioxide 14 The direct and rapid test of C activity eliminates the traditional complex process of converting carbon into benzene, while achieving extremely high carbon enrichment levels, ensuring test accuracy and saving time and economic costs.

[0084] Pressurization system 2 and 14 C detection device 1 is connected, preferably, the pressurization system 2 is connected to 14 The high-pressure needle valve 14 of the C detection device 1 is used to pressurize the gaseous carbon dioxide to liquefy it into liquid carbon dioxide, and pass the liquid carbon dioxide into the 14 C detection device 1.

[0085] like Figure 4 As shown, the pressurizing system 2 may include a pressurizing pump 21 , a high-pressure valve 22 , a pressure-bearing pipeline 23 , a pressure detector 24 , and a pressure control device 25 .

[0086] The booster pump 21 and the high pressure valve 22 are connected to the 14 The high pressure needle valve 14 of the C detection device 1 is connected to pressurize the gaseous carbon dioxide and inject it into the 14C detection device 1. The pressure detector 24 is arranged in the pressure-bearing pipeline 23 to measure the real-time pressure of the pressurizing system 2, and then obtain the pressurization rate of the pressurizing system 2; the pressure control device 25 is connected to the pressurizing pump 21 to control the pressurization rate of the pressurizing pump 21.

[0087] In the pressurizing system 2, if the pressurizing rate of carbon dioxide is too fast, 14 A large amount of carbon dioxide will be instantly accumulated in the C detection device 1, causing the carbon dioxide to liquefy rapidly, emitting a large amount of heat and causing the temperature to rise, eventually causing the liquid carbon dioxide to become supercritical or causing its density to be greatly reduced compared to the liquid state, thereby reducing the test accuracy.

[0088] Therefore, preferably, 14 C The temperature detector 17 is provided in the detection device 1 to detect the temperature during the pressurization process. 14 The temperature inside the C detection device 1, the pressure control device 25 can receive the detection results of the temperature detector 17 and the pressure detector 24, adjust the switch and speed of the pressurization, ensure the safety and stability of the carbon dioxide pressurized liquefaction process, and obtain liquid carbon dioxide with the highest possible carbon enrichment.

[0089] Further preferably, at least one pressure plate 16 is provided with a cooling water channel 161, and cooling water of different temperatures can be introduced into the cooling water channel 161 to achieve 14 The cooling of the liquid carbon dioxide in the C detection device 1 absorbs a large amount of heat generated by the liquefaction of carbon dioxide, and at the same time promotes the conversion of gas phase carbon dioxide to liquid phase, thereby increasing the density of liquid carbon dioxide. In addition to cooling water, the cooling medium introduced can also be cold alcohol or the like.

[0090] Mixed solution addition system 3 and 14 C detection device 1 is connected, preferably, with 14 The high-pressure needle valve 14 of the C detection device 1 is connected to pre-mix the scintillator and the co-solvent, and the pre-mixed solution of the scintillator and the co-solvent is introduced into the 14 C detection device 1.

[0091] like Figure 4 As shown, the mixed solution adding system 3 may include: a premixing chamber 31, a mixed solution adding valve 32, a vacuum valve 33, and a vacuum pump 34. The premixing chamber 31 is used to contain the cosolvent and the scintillator (premixed solution) mixed in proportion, and the mixed solution adding valve 32 can control the premixing chamber 31 and the scintillator. 14 C detection device 1 is connected and disconnected, and the vacuum valve 33 and the vacuum pump 34 are used to 14The C detection system is evacuated to a vacuum state to prevent impurities such as carbon dioxide in the air from contaminating the radiocarbon activity detection. After evacuation, the premixed solution is pressed into the premixing chamber 31 through the mixed solution adding valve 32 under pressure. 14 In the C detection device 1, a uniform and stable mixed system is formed with the liquid carbon dioxide.

[0092] The liquid scintillation counter can be an existing liquid scintillation counter or a new liquid scintillation counter that has been designed and modified. 14 The sample tank and the measuring cavity are placed in the C detection device 1, and the liquid scintillation counter includes two or more photomultiplier tubes, and the photomultiplier tubes and the measuring cavity are 14 The light-transmitting area of ​​the C detection device 1 is configured accordingly, and can capture the scintillation fluorescence emitted by the light-transmitting area to achieve radioactive carbon activity detection.

[0093] Among them, preferably, the carbon dioxide provided in this embodiment 14 C direct and rapid detection system also includes a pretreatment system 4, which is connected to the gas source of gaseous carbon dioxide and the pressurizing system 2, and the gaseous carbon dioxide sample collected from the gas source of gaseous carbon dioxide is removed from the gas source and purified before being passed into the pressurizing system 2.

[0094] Specifically, if Figure 4 As shown, the pretreatment system 4 may include a vacuum pump 41, a gaseous carbon dioxide source 42, a gas valve 43, a solid phase impurity removal system 44, a gas phase impurity removal system 45, and a mass flow controller 46. The vacuum pump 41 is used to evacuate the impurity gas in the pretreatment system 4 to prevent the impurity gas such as carbon dioxide in the air from contaminating the radiocarbon activity detection. Under the action of the pressurizing pump 21 of the pressurizing system 2, the gaseous carbon dioxide is extracted from the gaseous carbon dioxide source 42, such as the flue gas pipeline, and is successively passed through the gas valve 43, the solid phase impurity removal system 44, and the gas phase impurity removal system 45 to remove particulate matter and gas phase impurities, and then injected through the high-pressure needle valve 14 under the flow control of the mass flow controller 46. 14 C detection device 1. The mass flow controller 46 can be linked with the pressure control device 25 in the pressurization system 2 to control the pressurization rate to prevent 14 C detects overtemperature or overpressure in the device 1. In this embodiment, the pressurizing system 2 can perform a pressurizing step S1, where gaseous carbon dioxide enters the carbon dioxide from the pressurizing system 2. 14 In the C direct and rapid detection system, liquid carbon dioxide is obtained by pressurizing and liquefying through the pressurizing system 2; on the other hand, the mixed solution adding system 3 can perform the first mixing step S21, and the scintillation liquid and the co-solvent are mixed in the mixed solution adding system 3 to form a premixed solution.

[0095] Then, the second mixing step S22 is performed, the pressurizing system 2 and the mixed solution adding system 3 inject the liquid carbon dioxide and the premixed solution into the 14 In the C detection device 1, the premixed solution and liquid carbon dioxide are 14 The mixed solution can be obtained by mixing in the C detection device 1 without the need for mixing steps such as stirring and heating.

[0096] Finally, the detection step S3 is performed, 14 The C detection device 1 is placed in the sample slot and measurement cavity of the liquid scintillation counter. After the liquid carbon dioxide in the mixed solution undergoes radioactive decay, the decay energy is absorbed by the scintillator and emits fluorescence. 14 The transparent area of ​​C detection device 1 is captured by the photomultiplier tube of the liquid scintillation counter to perform radiocarbon testing.

[0097] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A carbon dioxide 14 C direct and rapid detection method, It is characterized in that The steps include: A pressurization step, pressurizing and liquefying the gaseous carbon dioxide to obtain liquid carbon dioxide; A mixing step, mixing the liquid carbon dioxide with a co-solvent and a scintillator in a pressure vessel to obtain a mixed solution; The detection step is to place the pressure container in a liquid scintillation counter to detect the radioactive carbon activity.

2. The carbon dioxide according to claim 1 14 C direct and rapid detection method, It is characterized in that The mixing step comprises the following sub-steps: A first mixing step, mixing the co-solvent and the scintillator to obtain a premixed solution; The second mixing step is to mix the premixed solution with the liquid carbon dioxide in a pressure container to obtain a mixed solution.

3. The carbon dioxide according to claim 2 14 C direct and rapid detection method, It is characterized in that In the first mixing step, the mixing ratio of the scintillator and the co-solvent is 12-15 mg / mL.

4. The carbon dioxide according to claim 2 14 C direct and rapid detection method, It is characterized in that In the first mixing step, the scintillator is an organic solid scintillator, the cosolvent is an organic solvent, and the carbon element in the scintillator and the cosolvent is 14 The C activity is zero.

5. The carbon dioxide according to claim 2 14 C direct and rapid detection method, It is characterized in that In the second mixing step, the volume ratio of the premixed solution to the liquid carbon dioxide is 1:5-1:

6.

6. The carbon dioxide according to claim 1 14 C direct and rapid detection method, It is characterized in that In the pressurizing step, a pressurizing rate of the gaseous carbon dioxide is controlled according to the temperature and pressure of the liquid carbon dioxide.

7. A carbon dioxide 14 C direct and rapid detection system, It is characterized in that include: 14 C detection device, 14 C detection device is a pressure vessel with a light-transmitting area, used to contain liquid carbon dioxide and a mixed solution; Pressurized system, with the 14 C detection device is connected to pressurize the gaseous carbon dioxide to liquefy it into liquid carbon dioxide, and pass the liquid carbon dioxide into the 14 C detection device; Mixing solution adding system, with the 14 C detection device is connected, and is used for premixing the scintillator and the cosolvent, and passing the premixed solution of the scintillator and the cosolvent into the 14 C detection device; Liquid scintillation counter, having a 14 The sample slot and measuring cavity into which the C detection device is placed, the liquid scintillation counter utilizes the 14 The light-transmitting area of ​​the C detection device is used to detect radioactive carbon activity.

8. The carbon dioxide according to claim 7 14 C direct and rapid detection system, It is characterized in that The pretreatment system is connected to the gas source of the gaseous carbon dioxide and the pressurizing system, and the gaseous carbon dioxide sample collected from the gas source of the gaseous carbon dioxide is removed from impurities and purified before being introduced into the pressurizing system.

9. The carbon dioxide according to claim 7 14 C direct and rapid detection system, It is characterized in that Said 14 C detection device includes: A pressure-bearing shell, wherein the pressure-bearing shell encloses a light-transmitting cylindrical cavity; A pressure-bearing plate, wherein the pressure-bearing plates are respectively arranged on the upper bottom surface and the lower bottom surface of the cylindrical cavity; Fixed tie bars, the two ends of which are respectively fixed to the pressure-bearing plates on the upper bottom surface and the lower bottom surface of the cylindrical cavity; A cooling water channel is arranged inside at least one of the pressure plates.

10. The carbon dioxide according to claim 9 14 C direct and rapid detection system, It is characterized in that Said 14 The C detection device also includes a temperature detector arranged in the cylindrical cavity; the pressurization system also includes a pressure detector and a pressure control device, The pressure control device controls a pressurization rate of the pressurization system based on detection results of the temperature detector and the pressure detector.

Images