CN116990376A

CN116990376A - Calibration system, calibration method and detection method of nitroxyl chloride detection instrument

Info

Publication number: CN116990376A
Application number: CN202310758265.7A
Authority: CN
Inventors: 周文鑫; 王海潮; 楼晟荣; 黄成�; 黄丹丹; 吴宇航; 黄聪艳
Original assignee: Shanghai Academy of Environmental Sciences
Current assignee: Shanghai Academy of Environmental Sciences
Priority date: 2023-06-26
Filing date: 2023-06-26
Publication date: 2023-11-03

Abstract

The embodiment of the disclosure provides a calibration system, a calibration method and a detection method of a nitroxyl chloride detection instrument, wherein the calibration system comprises a nitroxyl chloride generation subsystem, a reaction container and a heating channel and a non-heating channel, wherein the reaction container is used for receiving chlorine to be introduced, and the input end of the heating channel is communicated with the reaction container; the reaction output is passed through a non-heating channel and a heating channel when being alternatively conducted so as to output gas before pyrolysis and gas after pyrolysis at the occurrence source port; the detection subsystem comprises: the nitrogen dioxide measuring instrument is used for measuring and obtaining a first nitrogen dioxide concentration and a second nitrogen dioxide concentration based on gas before and after pyrolysis, so as to calculate a nitroxyl chloride concentration value; the nitroxyl chloride detection instrument is used for obtaining a first detection response signal and a second detection response signal based on gas measurement before and after pyrolysis to obtain a nitroxyl chloride concentration signal value of a nitroxyl chloride concentration value; the nitroxyl chloride detection instrument obtains calibration based on the mathematical relation between the calculated nitroxyl chloride concentration signal value and the corresponding nitroxyl chloride concentration value, and the nitroxyl chloride concentration value is directly obtained by using atmospheric detection.

Description

Calibration system, calibration method and detection method of nitroxyl chloride detection instrument

Technical Field

The disclosure relates to the technical field of environment-friendly detection, in particular to a calibration system, a calibration method and a detection method of a nitroxyl chloride detection instrument.

Background

Nitroxyl chloride is an important gaseous pollutant in the atmosphere, has important effects on atmospheric oxidability, degradation of primary pollutants and formation of secondary pollutants, and plays a non-negligible role in the global nitrogen and chlorine cycles. The study of the change of the concentration value of the nitroxyl chloride in the atmosphere plays a very important role in night atmospheric chemistry and daytime photochemistry.

The measurement of nitroxyl chloride is currently mainly measured by chemical ionization mass spectrometry (Chemical Ionization Mass Spectrometry, CIMS), which uses iodide (I-) as a reactive ion, and the nitroxyl chloride is combined with iodide to form [ I.ClNO ] ₂ ]-an ion cluster, the signal of which is measured using mass spectrometry. In order to obtain the accurate concentration of the nitroxyl chloride, a response relation between the detection response signal of the ion cluster and the concentration value of the nitroxyl chloride is required to be established, and a device and a method for stably generating the low-concentration nitroxyl chloride standard gas are required.

At present, few methods for generating the nitroxyl chloride standard gas are reported at home and abroad. The conventional method for preparing the nitroxyl chloride in the laboratory is to mix 30% fuming sulfuric acid with 91.6% nitric acid solution in a closed container at 0 ℃ to react to prepare the nitroxyl chloride gas. The method is inconvenient to operate and has high risk. The reaction equation is shown below:

HNO ₃ +ClSO ₃ H→ClNO ₂ +H ₂ SO _{4 。}

In the production of low-concentration nitroxyl chloride, NO has been studied and utilized ₂ With O ₃ Generating a certain amount of N ₂ O ₅ Then the mixture is reacted with wet NaCl to obtain ClNO ₂ . The reverse directionIt should be possible to do this at a low pressure of 5 kPa. The reaction equation is shown below:

N ₂ O ₅ (g, aq) +NaCl- (s, aq, i.e., solid, solution) →NO ₂ Cl(g)+NaNO ₃ -(s,aq) 。

In addition, the formation of 2, 4-dichlorobenzene and nitroxyl chloride by the nitrochlorination reaction of 3-chloro-4-fluoronitrobenzene with chlorine in the presence of a catalyst and under heating has been studied. However, the preparation is complicated, and the raw material 3-chloro-4-fluoronitrobenzene is also prepared through multiple reactions, and the reaction equation is as follows:

C ₆ H ₃ ClFNO ₂ +Cl ₂ →NO ₂ Cl+C ₆ H ₃ Cl ₂ F 。

the steps of the methods for generating the standard gas are complicated, and the method is only suitable for laboratory conditions and has certain danger. In addition, the ambient atmosphere ClNO ₂ The concentration range is 0.01-2 ppbv, and the concentration of the generated standard gas cannot be accurately controlled by the methods, so that the method can be used for simple verification of measuring equipment, but is not suitable for accurate calibration of nitroxyl chloride measurement in the atmospheric environment.

Disclosure of Invention

In view of the above-mentioned drawbacks of the prior art, an object of the present disclosure is to provide a calibration system, a calibration method and a detection method of a nitroxyl chloride detection instrument, which solve the problems in the related art.

A first aspect of the present disclosure provides a calibration system for a nitroxyl chloride detection instrument, comprising: a nitroxyl chloride generation subsystem comprising: the reaction vessel is used for receiving the introduction of chlorine, and the input end of the reaction vessel is communicated with a heating channel and a non-heating channel of the reaction vessel; the output end of the heating channel or the non-heating channel is communicated with the generation source port, and the heating channel and the non-heating channel are alternatively conducted; wherein the reaction vessel is provided with a wet sodium chloride and sodium nitrite powder mixture for reaction with chlorine gas to form nitroxyl chloride; the output gas of the reaction vessel passes through the non-heating channel when being conducted so as to output the gas before pyrolysis at the generation source port, and the output gas of the reaction vessel passes through the heating channel when being conducted so as to output the gas after pyrolysis at the generation source port; the nitroxyl chloride is pyrolyzed in the heating channel to form nitrogen dioxide; a detection subsystem, comprising: the nitrogen dioxide measuring instrument is communicated with the generation source port through a pipeline and is used for obtaining a first nitrogen dioxide concentration based on the gas measurement before pyrolysis and a second nitrogen dioxide concentration based on the gas measurement after pyrolysis so as to obtain a nitroxyl chloride concentration value of the generated nitroxyl chloride according to the difference between the first nitrogen dioxide concentration and the second nitrogen dioxide concentration; the pipeline is communicated with the nitroxyl chloride detection instrument of the generation source port and is used for obtaining a first detection response signal based on the gas measurement before pyrolysis and obtaining a second detection response signal based on the gas measurement after pyrolysis so as to obtain a nitroxyl chloride concentration signal value corresponding to the nitroxyl chloride concentration value according to the difference between the first detection response signal and the second detection response signal; the relation between the nitroxyl chloride concentration signal value and the corresponding nitroxyl chloride concentration value is used for calibrating the nitroxyl chloride detection instrument.

In an embodiment of the first aspect, the calibration system comprises: a chlorine dilution subsystem comprising: the pipeline is communicated with a chlorine gas mass flow controller of a chlorine gas source and at least one nitrogen gas mass flow controller of a nitrogen gas source, the output ends of the chlorine gas mass flow controller and the at least one nitrogen gas mass flow controller are communicated to a chlorine gas port through a mixing space, and the chlorine gas port is communicated to the reaction container so as to output mixed gas obtained after the chlorine gas is diluted by nitrogen gas.

In an embodiment of the first aspect, the at least one nitrogen mass flow controller comprises: the first nitrogen mass flow controller is communicated with a nitrogen source and the mixing space through a pipeline and is used for controlling the flow of the first nitrogen which is preliminarily diluted with chlorine; the second nitrogen mass flow controller is communicated with a nitrogen source and the mixing space through a pipeline and is used for controlling the flow of second-path nitrogen for secondarily diluting the primarily diluted chlorine; the flow rate of the second path of nitrogen is higher than that of the first path of nitrogen.

In an embodiment of the first aspect, the calibration system comprises: a chlorine humidity control subsystem comprising: the third nitrogen mass flow controller is communicated with a nitrogen source through a pipeline and used for controlling the flow of the output third nitrogen; the pipeline is communicated between the third nitrogen mass flow controller and the humidifying port so as to respectively humidify and non-humidify the third nitrogen and then output the third nitrogen at the humidifying port; wherein, a first humidifying valve and a humidifying device are arranged in the humidifying channel; a second humidifying valve is arranged in the non-humidifying channel; the opening and closing degree of the first humidifying valve and the second humidifying valve is used for adjusting the humidity of third nitrogen in the humidifying port; the humidifying port is communicated with the generating source port so as to output the third nitrogen to be mixed with the pre-pyrolysis gas to form a first standard gas and the post-pyrolysis gas to form a second standard gas, and the second standard gas is output to the detection subsystem.

In an embodiment of the first aspect, the detection subsystem further comprises: and the pipeline is communicated with the hygrothermograph of the generating source port.

In an embodiment of the first aspect, the mixing space comprises: the first mixing chamber is provided with a pressure gauge and is used for introducing chlorine and nitrogen to generate mixed gas; the second mixing chamber is communicated between the first mixing chamber and the chlorine port; the second mixing chamber is also communicated with an air extracting pump through an air extracting mass flow controller pipeline, and the air extracting pump is used for extracting air based on the air extracting flow set by the air extracting mass flow controller so as to enable the mixed gas conveyed by the chlorine port to be at a preset flow; and/or a first switch valve and a heating device which are communicated through pipelines are arranged in the heating channel; and a second switch valve is arranged in the non-heating channel.

In an embodiment of the first aspect, the calibration system comprises at least one of: 1) The mixing space of the chlorine and the nitrogen comprises at least one mixing chamber, and each mixing chamber is formed by a Teflon pipeline with a preset diameter length so as to uniformly mix the mixed gases; 2) A tail gas pipeline communicated with the generation source port; 3) The heating temperature of the heating device in the heating channel is 350 ℃; and/or the heating device comprises a quartz tube wrapped by heat preservation cotton and comprises a heating source with the upper heating limit of 400 ℃; 4) Ball valves for controlling on/off are respectively arranged in the heating channel and the non-heating channel; 5) The secondary chlorine humidity control subsystem comprises a third nitrogen mass flow controller, a humidifying channel and a non-humidifying channel; needle valves are respectively arranged in the humidifying channel and the non-humidifying channel, and/or the flow range of nitrogen conveyed under the control of the third nitrogen mass flow controller is 4 l/min-5 l/min, and/or the humidity of nitrogen output by a humidifying port of the secondary chlorine humidity control subsystem is 20% -40% or 40% -60%; 6) The flow rate of the chlorine gas conveyed under the control of the chlorine gas mass flow controller is 10ml/min, the flow rate of the first path of nitrogen gas which is primarily diluted with the chlorine gas is controlled to be 200ml/min by the first nitrogen gas mass flow controller, and the flow rate of the second path of nitrogen gas which secondarily dilutes the primarily diluted gas is controlled to be 4l/min to 5l/min by the second nitrogen gas mass flow controller; and/or the flow control range of the first nitrogen mass flow controller is 0-500 ml/min and/or the flow control range of the second nitrogen mass flow controller is 0-10 l/min; and/or the chlorine concentration provided by the chlorine source is 9.98ppm, and the flow control range of the chlorine mass flow controller is 0-500 ml/min; 7) The flow of the gas output by the generation source port to the detection subsystem is 4l/min, wherein the sampling flow distributed to the nitrogen dioxide measuring instrument is 1.5l/min, and the sampling flow distributed to the nitroxyl chloride detecting instrument is 2l/min; 8) The mixing space includes: the first mixing chamber is provided with a pressure gauge and is used for introducing chlorine and nitrogen to generate mixed gas; the second mixing chamber is communicated between the first mixing chamber and the chlorine port; the second mixing chamber is also communicated with an air extracting pump through an air extracting mass flow controller pipeline, and the air extracting pump is used for extracting air based on the air extracting flow set by the air extracting mass flow controller so as to enable the chlorine conveyed by the chlorine port to be at a preset flow; the range of the preset flow is 100 ml/min-200 ml/min; and/or the suction flow rate of the suction pump is 5l/min-20 l/min; 9) The reaction vessel is made of polytetrafluoroethylene.

A first aspect of the present disclosure provides a calibration method of a nitroxyl chloride detection instrument, applied to the system of any one of the first aspects, comprising: providing a wet sodium chloride and sodium nitrite powder mixture in a reaction vessel; introducing chlorine into a reaction vessel to produce nitroxyl chloride; respectively passing the output gas of the reaction container through a non-heating channel and a heating channel to obtain pre-pyrolysis gas and post-pyrolysis gas respectively; obtaining a first nitrogen dioxide concentration based on the pre-pyrolysis gas measurement and a second nitrogen dioxide concentration based on the post-pyrolysis gas measurement by a nitrogen dioxide measuring instrument, so as to obtain a nitroxyl chloride concentration value of the generated nitroxyl chloride according to the difference between the first nitrogen dioxide concentration and the second nitrogen dioxide concentration; obtaining a first detection response signal based on the pre-pyrolysis gas measurement and a second detection response signal based on the post-pyrolysis gas measurement by a nitroxyl chloride detection instrument, so as to obtain a nitroxyl chloride concentration signal value corresponding to the nitroxyl chloride concentration value according to the difference between the first detection response signal and the second detection response signal; calibrating the nitroxyl radical detection instrument based on the nitroxyl radical concentration signal value and the concentration relation.

In an embodiment of the second aspect, the calibrating the nitroxyl radical detection instrument based on the nitroxyl radical concentration signal value and the concentration relation comprises: and (3) by changing the flow of the chlorine gas to generate different low-concentration nitroxyl chlorides, obtaining a plurality of groups of nitroxyl chloride concentration signal values and corresponding nitroxyl chloride concentration values, and calibrating the relation between the nitroxyl chloride concentration signal values and the nitroxyl chloride concentration values of the nitroxyl chloride detection instrument.

In an embodiment of the second aspect, the method comprises at least one of: 1) Placing a mixture of Na nitrogen dioxide and NaCl into a reaction vessel and adding pure water for dissolution to prepare a wet sodium chloride and sodium nitrite powder mixture; 2) The first nitrogen source is controlled by a first nitrogen mass flow controller to output a first path of nitrogen and chlorine with corresponding flow for preliminary dilution; controlling a nitrogen source to output a second path of nitrogen with corresponding flow through a second nitrogen mass flow controller so as to output the primarily diluted chlorine after secondary dilution; pumping based on pumping flow set by a pumping mass flow controller so as to output the secondarily diluted chlorine to a reaction container at a preset flow; 3) Before preliminary dilution is carried out, 5-10 sccm of chlorine is continuously introduced into the nitroxyl chloride generation subsystem and maintained for a preset period of time, so that the stability of the chlorine in the pipeline is maintained.

A third aspect of the present disclosure provides a method for detecting nitroxyl chloride, comprising: detecting the nitroxyl chloride of the gas to be detected by the nitroxyl chloride detection instrument calibrated by the calibration method of the nitroxyl chloride detection instrument according to any one of the first aspects, and converting the detected nitroxyl chloride concentration signal value to obtain a corresponding nitroxyl chloride concentration value.

As described above, the embodiment of the disclosure provides a calibration system, a calibration method and a detection method of a nitroxyl chloride detection instrument, where the calibration system includes a nitroxyl chloride generation subsystem, and the calibration system includes a reaction vessel for receiving chlorine gas, and a heating channel and a non-heating channel, the input ends of which are communicated with the reaction vessel; the output gas of the reaction container passes through the non-heating channel when being conducted so as to output the gas before pyrolysis at the occurrence source port, and passes through the heating channel so as to output the gas after pyrolysis at the occurrence source port; the detection subsystem comprises: the nitrogen dioxide measuring instrument is used for measuring and obtaining a first nitrogen dioxide concentration and a second nitrogen dioxide concentration based on gas before and after pyrolysis, so as to calculate a nitroxyl chloride concentration value; the nitroxyl chloride detection instrument is used for obtaining a first detection response signal and a second detection response signal based on gas measurement before and after pyrolysis to obtain a nitroxyl chloride concentration signal value of a nitroxyl chloride concentration value; the nitroxyl chloride detection instrument obtains calibration based on mathematical relation between calculated nitroxyl chloride concentration signal values and corresponding nitroxyl chloride concentration values, and the nitroxyl chloride concentration values are directly obtained by using atmospheric detection, so that the problems of the related technologies are solved.

Drawings

FIG. 1 shows a schematic structural diagram of a calibration system of a nitroxyl radical detection instrument in an embodiment of the disclosure.

Fig. 2 shows a schematic structural diagram of a calibration system of a nitroxyl chloride detection instrument in accordance with yet another embodiment of the disclosure.

Fig. 3 shows a schematic structural diagram of a calibration system of a nitroxyl chloride detection instrument according to yet another embodiment of the disclosure.

Fig. 4 shows a schematic structural diagram of a calibration method of a nitroxyl chloride detection instrument in an embodiment of the disclosure.

Fig. 5 shows a schematic graph of the signal response of the CIMS instrument to nitroxyl gas concentration in an experimental example of the present disclosure.

Fig. 6 shows a graphical representation of the concentration of nitroxyl chloride in the atmosphere as detected by the CIMS instrument in an experimental example of the present disclosure.

Description of the embodiments

Other advantages and effects of the present disclosure will be readily apparent to those skilled in the art from the following detailed description of the embodiments of the disclosure given by way of specific examples. The disclosure may be embodied or applied in other specific forms and details, and various modifications and alterations may be made to the details of the disclosure in various respects, all without departing from the spirit of the disclosure. It should be noted that, without conflict, the embodiments of the present disclosure and features of the embodiments may be combined with each other.

The embodiments of the present disclosure will be described in detail below with reference to the attached drawings so that those skilled in the art to which the present disclosure pertains can easily implement the same. The present disclosure may be embodied in many different forms and is not limited to the embodiments described herein.

In the description of the present disclosure, references to the terms "one embodiment," "some embodiments," "examples," "particular examples," or "some examples," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present disclosure. Furthermore, the particular features, structures, materials, or characteristics may be combined in any suitable manner in any one or a group of embodiments or examples. Furthermore, various embodiments or examples, as well as features of various embodiments or examples, presented in this disclosure may be combined and combined by those skilled in the art without contradiction.

Furthermore, the terms "first," "second," and the like, are used for descriptive purposes only and are not to be construed as indicating or implying a relative importance or the number of technical features indicated. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include at least one such feature. In the representations of the present disclosure, "a set" means two or more, unless specifically defined otherwise.

For the purpose of clarity of the present disclosure, components that are not related to the description are omitted, and the same or similar components are given the same reference numerals throughout the specification.

Throughout the specification, when a device is said to be "connected" to another device, this includes not only the case of "direct connection" but also the case of "indirect connection" with other elements interposed therebetween. In addition, when a certain component is said to be "included" in a certain device, unless otherwise stated, other components are not excluded, but it means that other components may be included.

Although the terms first, second, etc. may be used herein to connote various elements in some examples, the elements should not be limited by the terms. These terms are only used to distinguish one element from another element. For example, a first interface, a second interface, etc. Furthermore, as used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context indicates otherwise. It will be further understood that the terms "comprises," "comprising," "includes," and/or "including" specify the presence of stated features, steps, operations, elements, modules, items, categories, and/or groups, but do not preclude the presence, presence or addition of one or more other features, steps, operations, elements, modules, items, categories, and/or groups. The terms "or" and/or "as used herein are to be construed as inclusive, or meaning any one or any combination. Thus, "A, B or C" or "A, B and/or C" means "any of the following: a, A is as follows; b, a step of preparing a composite material; c, performing operation; a and B; a and C; b and C; A. b and C). An exception to this definition will occur only when a combination of elements, functions, steps or operations are in some way inherently mutually exclusive.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the language clearly indicates the contrary. The meaning of "comprising" in the specification is to specify the presence of stated features, regions, integers, steps, operations, elements, and/or components, but does not preclude the presence or addition of other features, regions, integers, steps, operations, elements, and/or components.

Although not differently defined, including technical and scientific terms used herein, all terms have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. The term append defined in commonly used dictionaries is interpreted as having a meaning that is consistent with the meaning of the relevant technical literature and the currently prompted message, and is not excessively interpreted as an ideal or very formulaic meaning, so long as no definition is made.

The measurement of nitroxyl chloride is currently mainly measured by chemical ionization mass spectrometry (i.e. CIMS measurement instrument). However, the CIMS measuring apparatus needs to establish a response relationship between the detection response signal of the ion cluster and the concentration value of the nitroxyl chloride, and a device and a method thereof capable of stably generating the low-concentration nitroxyl chloride standard gas are needed.

The current standard gas generation method of nitroxyl chloride is less. For example, 30 percent fuming sulfuric acid and 91.6 percent nitric acid solution are mixed in a closed container at the temperature of 0 ℃ to react to prepare the nitroxyl chloride gas. The method is inconvenient to operate and has high risk. In addition, in the production of low-concentration nitroxyl chloride, nitrogen dioxide and O3 are used to produce a certain amount of N2O5, which is then reacted with wet NaCl to obtain ClNO2. However, the reaction has a pressure requirement that it be completed at a low pressure of 5 kPa. In addition, the formation of 2, 4-dichlorobenzene and nitroxyl chloride by the nitrochlorination reaction of 3-chloro-4-fluoronitrobenzene with chlorine in the presence of a catalyst and under heating has been studied. However, the preparation is complicated, and the raw material 3-chloro-4-fluoronitrobenzene also needs to be prepared through multiple reactions.

The steps of the methods for generating the standard gas are complicated, and the method is only suitable for laboratory conditions and has certain danger. In addition, the concentration of ClNO2 in the environment atmosphere ranges from 0.01 ppbv to 2ppbv, and the concentration of the generated standard gas cannot be accurately controlled by the methods, so that the method can be used for simple verification of measuring equipment, but is not suitable for accurate calibration of nitroxyl chloride measurement in the atmosphere environment.

In view of this, in some embodiments of the present disclosure, calibration systems, calibration methods, and detection methods of a nitroxyl chloride detection instrument may be provided that produce nitroxyl chloride gas (ClNO) by a safe and controllable production method ₂ ) The working principle is that Cl is utilized ₂ (chlorine) and NaNO ₂ (sodium nitrite) solution to produce a certain amount of ClNO ₂ . The chemical reaction formula is as follows: cl ₂ +NaNO ₂ →ClNO ₂ +NaCl 。

Further, clNO is utilized ₂ Pyrolysis by heating can be converted into nitrogen dioxide (NO) ₂ ) The principle of (2) is that ClNO can be determined by measuring the difference between nitrogen dioxide generated before and after pyrolysis as shown in the following chemical formula ₂ Is a concentration of (3).

And, through CIMS detecting instrument measuring the detection response signals before and after pyrolysis, calculate the response signal difference, can confirm corresponding ClNO ₂ ClNO2 concentration signal value of concentration value. From multiple sets of ClNOs ₂ concentration-ClNO ₂ Concentration signal value data, namely ClNO can be obtained by analysis ₂ Mathematical relationship (such as fitted relationship curve, relationship formula, relationship table, etc.) of concentration-nitroxyl chloride concentration signal value to complete calibration of the nitroxyl chloride detection instrument. After the calibrated CIMS detection instrument is used for detecting and obtaining the nitroxyl chloride concentration signal value of the ClNO2 concentration, the mathematical relationship can be used for directly obtaining the ClNO ₂ Concentration.

In particular, in the disclosure, the "nitroxyl chloride detection instrument" may be, but is not limited to, a CIMS detection instrument; "Nitrogen dioxide detection instrument" may refer to, but is not limited to, an absorption spectroscopy (CEAS) detection instrument.

As shown in fig. 1, a schematic structural diagram of a calibration system of a nitroxyl chloride detection instrument according to an embodiment of the disclosure is shown.

In fig. 1, the calibration system comprises: a nitroxyl chloride generation subsystem, and a detection subsystem.

The nitroxyl chloride generation subsystem comprises: a reaction vessel 101, a heating channel 102, and a non-heating channel 103.

The reaction vessel 101 may be provided with a wet sodium chloride and sodium nitrite powder mixture. The reaction vessel 101 is adapted to receive a chlorine gas feed such that the chlorine gas reacts with sodium nitrite to form a nitroxyl chloride gas. The output end pipeline of the reaction vessel 101 is communicated with the input ends of the heating channel 102 and the non-heating channel 103, and the output ends of the heating channel 102 and the non-heating channel 103 are communicated to the generation source port. The heating channel 102 and the non-heating channel 103 may alternatively be turned on. When the heating channel 102 is turned on, the output gas of the reaction vessel 101 is heated in the heating channel 102, and the gas after pyrolysis is output to the generation source port, wherein the nitroxyl gas is pyrolyzed and converted into nitrogen dioxide. When the non-heating channel 103 is turned on, the nitroxyl gas is not pyrolyzed, but contained in the pre-pyrolysis gas is output to the generation source port.

In some embodiments, a first on-off valve 121 and a heating device 122 are disposed in the heating channel 102 and are in pipeline communication; the non-heating channel 103 is provided with a second switch valve 131, and the on/off combination of the first switch valve 121 and the second switch valve 131 realizes alternative conduction of the heating channel 102 and the non-heating channel 103. Illustratively, the first and second switching valves 121 and 131 may be ball valves. For example, the heating temperature of the heating device 122 in the heating channel 102 may be 350 ℃, so that the nitroxyl gas is completely decomposed. Illustratively, the heating device 122 comprises a quartz tube wrapped with insulating cotton, for example, 30cm in length and 1cm in inside diameter, and containing a heating source with an upper heating limit of 400 ℃.

In some embodiments, the wet sodium chloride and sodium nitrite powder mixture may be formulated by dissolving a mixture of Na nitrogen dioxide and NaCl to the reaction vessel 101 and adding pure water. Illustratively, a mixture of 0.9g Na nitrogen dioxide and 9.1g NaCl may be added to the reaction vessel 101, and 5ml ultra-pure water may be added for dissolution. Illustratively, the material of the reaction vessel 101 may be Polytetrafluoroethylene (PTEE).

The detection subsystem includes: a nitrogen dioxide measuring instrument 201 and a nitroxyl chloride detecting instrument 202. In some embodiments, the detection subsystem further comprises: an exhaust line 203 communicating with the source port. The exhaust pipeline 203 can be connected with an exhaust pipe to ensure that the exhaust is safely exhausted. To determine if the pyrolysis temperature reaches 350 ℃, the detection subsystem may further include a thermometer 204.

The nitrogen dioxide measuring instrument 201 is connected to the generating source port through a pipeline, and is used for obtaining a first nitrogen dioxide concentration based on the gas measurement before pyrolysis and obtaining a second nitrogen dioxide concentration based on the gas measurement after pyrolysis. That is, the output gas after the reaction in the reaction vessel 101 maintains a stable concentration of nitroxyl chloride, which is retained therein as a non-pyrolysis gas through the non-heating channel 103, while the nitroxyl chloride in the pyrolysis gas through the heating channel 102 is decomposed. Thus, the nitroxyl chloride concentration value of the generated nitroxyl chloride is derived from the difference between the first and second nitrogen dioxide concentrations. The difference value of the nitrogen dioxide concentration is the corresponding increased partial nitrogen dioxide concentration of the decomposed nitroxyl chloride after pyrolysis, namely the concentration value of the generated nitroxyl chloride.

The nitroxyl chloride detection instrument 202 is in pipeline communication with the generation source port, and is configured to obtain a first detection response signal based on the pre-pyrolysis gas measurement and obtain a second detection response signal based on the post-pyrolysis gas measurement, so as to obtain a nitroxyl chloride concentration signal value corresponding to the nitroxyl chloride concentration value according to a difference between the first detection response signal and the second detection response signal. It will also be appreciated that the second detection response signal differs from the first detection response signal in terms of the nitroxyl chloride concentration signal value, and that the nitroxyl chloride concentration signal value thus corresponds to the concentration of nitroxyl chloride. Illustratively, the nitroxyl chloride detection instrument 202 may be a CIMS instrument.

It can be understood that by controlling the flow of chlorine gas, a plurality of groups of nitroxyl chloride concentration values and corresponding nitroxyl chloride concentration signal values are generated, and the mathematical relationship of the nitroxyl chloride concentration values of the chemical ionization mass spectrometry device can be obtained by analysis, so as to complete calibration.

As shown in fig. 2, a schematic structural diagram of a calibration system of the nitroxyl chloride detection instrument 202 of one embodiment of the present disclosure is shown.

In contrast to fig. 1, the calibration system of fig. 2 may include a chlorine dilution subsystem in addition to the nitroxyl generation subsystem and the detection subsystem.

The chlorine dilution subsystem includes: a chlorine mass flow controller 301 in communication with the chlorine source via a line, at least one nitrogen mass flow controller in communication with the nitrogen source via a line, and a mixing space for mixing nitrogen into chlorine for diluting the chlorine.

The output ends of the chlorine gas mass flow controller 301 and the at least one nitrogen gas mass flow controller are communicated with a chlorine gas port through a mixing space, and the chlorine gas port is communicated with the reaction vessel 101 to output a mixed gas obtained by diluting the chlorine gas with nitrogen gas. The chlorine flow is controlled by the chlorine mass flow controller 301 and the nitrogen flow is controlled by at least one nitrogen mass flow controller so that the chlorine flow, concentration are controllable.

Illustratively, the at least one nitrogen mass flow controller comprises: a first nitrogen mass flow controller 302 and a second nitrogen mass flow controller 303. The first nitrogen mass flow controller 302 is in pipeline communication with a nitrogen source and the mixing space, and is used for controlling the flow of the first nitrogen which is preliminarily diluted with chlorine. The second nitrogen mass flow controller 303 is connected to the nitrogen source and the mixing space through a pipeline, and is used for controlling the flow of the second nitrogen for secondarily diluting the primarily diluted chlorine. The flow rate of the second path of nitrogen is higher than that of the first path of nitrogen. In some embodiments, the flow rate of the chlorine gas delivered under the control of the chlorine gas mass flow controller 301 is 10ml/min, the flow rate of the first nitrogen gas primarily diluted with the chlorine gas is controlled to be 200ml/min by the first nitrogen gas mass flow controller 302, and the flow rate of the second nitrogen gas secondarily diluted with the primarily diluted gas is controlled to be 4l/min to 5l/min by the second nitrogen gas mass flow controller 303. In some examples, the nitrogen source is usually pure N2, and the flow control range of the first nitrogen mass flow controller 302 is 0-500 ml/min. The flow control range of the second nitrogen mass flow controller 303 is 0-10 l/min. The chlorine gas source provides chlorine gas with a concentration of 9.98ppm, and the flow control range of the chlorine gas mass flow controller 301 is 0-500 ml/min.

In some examples, the mixing space includes: a first mixing chamber 304 and a second mixing chamber 306.

The first mixing chamber 304 is used for introducing chlorine and nitrogen to generate mixed gas. Illustratively, the first nitrogen-to-chlorine preliminary dilution may occur at a line prior to the first mixing chamber 304. The primarily diluted chlorine gas is introduced into the first mixing chamber 304, and the second nitrogen gas is also introduced into the first mixing chamber 304 to complete the secondary dilution of the chlorine gas. For example, the first mixing chamber 304 may be provided with a pressure gauge 305, the pressure gauge 305 being adapted to monitor the pressure change in the first mixing chamber 304 and to observe the line stability.

The second mixing chamber 306 communicates between the first mixing chamber 304 and a chlorine port. One of the functions of the second mixing chamber 306 is to adjust the pressure of the mixed gas outputted to the first communication pipe. As an example, the second mixing chamber 306 is further connected to an air pump 308 through an air pump mass flow controller 307, and the air pump 308 pumps air based on the air pump flow set by the air pump mass flow controller 307, so that the mixed gas delivered by the chlorine port is at a preset flow.

In some embodiments, the first mixing chamber 304 and the second mixing chamber 306 may be implemented as lumens within a conduit or as chambers. As an example, the first mixing chamber 304 and the second mixing chamber 306 may be formed of teflon pipes having a predetermined diameter so as to uniformly mix the mixed gas. Further example, the first mixing chamber 304 and the second mixing chamber 306 may be selected from a 10cm length of 1/2 inch Teflon tubing to provide uniform mixing of the gases.

In some embodiments, the preset flow is in a range of 100ml/min to 200ml/min. By way of example, the suction flow of the suction pump 308 is in the range of 5l/min to 20 l/min. As an example, the flow range of the air extraction mass flow controller 307 may be 0-10 l/min, for precisely controlling the air extraction flow. In one example scenario, the pump 308 may pump out a majority of the gas in the second mixing chamber 306, maintaining a small flow of gas into the reaction vessel 101 to facilitate precise control of the nitroxyl chloride generation reaction.

To allow the pre-pyrolysis gas and post-pyrolysis gas output from the source ports of the nitroxyl radical generation subsystem to be processed as more analytical standard gases, in some examples, the calibration system of the nitroxyl radical detection instrument 202 may further comprise a section for controlling the humidity of the pre-pyrolysis gas and post-pyrolysis gas.

As shown in fig. 3, a schematic structural diagram of a calibration system of the nitroxyl chloride detection instrument 202 of yet another embodiment of the present disclosure is shown.

In the embodiment of fig. 3, the calibration system includes a chlorine humidity control subsystem in addition to the nitroxyl chloride generation subsystem, the detection subsystem, and the chlorine dilution subsystem. It should be noted that the chlorine dilution subsystem is shown in fig. 3 by way of example only and does not mean that the chlorine dilution subsystem is required to coexist with the chlorine humidity control subsystem. That is, in other embodiments, the chlorine dilution subsystem may be omitted from the calibration system, and the required flow of chlorine (e.g., diluted) may be directly input to the nitroxyl chloride generation subsystem from the outside, not by way of limitation.

The chlorine humidity control subsystem includes a third nitrogen mass flow controller 401, a humidification channel 402, and a non-humidification channel 403.

The third nitrogen mass flow controller 401 is connected to a nitrogen source through a pipeline and is used for controlling the flow of the output third nitrogen. It should be noted that, the nitrogen sources connected to the first nitrogen mass flow controller 302, the second nitrogen mass flow controller 303, and the third nitrogen mass flow controller 401 may be the same, or each nitrogen mass flow controller may be respectively connected to one nitrogen source. The nitrogen flow controlled by the third nitrogen mass flow controller 401 is, for example, 4l to 5l/min.

The humidifying channel 402 and the non-humidifying channel 403 are connected between the third nitrogen mass flow controller 401 and the humidifying port through pipelines, so that third nitrogen is output at the humidifying port after being humidified and non-humidified respectively. Wherein, a first humidity control valve 422 and a humidifying device 421 are disposed in the humidifying channel 402; a second humidity control valve 431 is provided in the non-humidifying passage 403. The opening and closing degree of the first humidity control valve 422 and the second humidity control valve 431 are used for adjusting the humidity of the third nitrogen in the humidifying port. In some examples, the first humidity control valve 422 and the second humidity control valve 431 may be needle valves and the humidifying device 421 may be a humidifying bottle. Illustratively, by adjusting the second humidity control valve 431 and the second humidity control valve 431 to control the flow of gas through the humidifying device 421, the relative humidity can be controlled to be about 45% of the atmospheric normal humidity.

The humidifying port is communicated with the generating source port so as to output the third nitrogen to be mixed with the pre-pyrolysis gas to form a first standard gas and the post-pyrolysis gas to form a second standard gas, and the second standard gas is output to the detection subsystem.

Correspondingly, to detect a humidity condition, in some embodiments, the detection subsystem further comprises: and the pipeline is communicated with the hygrometer of the generating source port. Due to the presence of the pyrolysis device, it is also possible to detect the gas temperature, so that the hygrometer may be replaced by a hygrothermograph 204', as shown in fig. 3. Of course, in the case where the chlorine gas humidity control subsystem is not included, only the thermometer 203 may be provided.

Thus, as shown in fig. 3, the nitroxyl chloride detection instrument 201, the nitrogen dioxide measurement instrument 202, the hygrothermograph 204', and the exhaust gas line 203 are connected to each other to form a four-way joint.

In some embodiments, the "pipeline" referred to herein is a structural unit for a low-concentration nitroxyl standard gas generator, and a channel for conveying gas, and may include a pipeline, a joint, and the like, and the material may be one or more of fluoroplastic, stainless steel, and the like, preferably one of polytetrafluoroethylene and polyperfluoro-alkoxy resin.

Illustratively, in the chlorine dilution subsystem shown in FIG. 3, the units may be connected by Teflon tubing. For example, the piping connection between the chlorine source and the chlorine mass flow controller 301, the piping connection between the nitrogen source and the first nitrogen mass flow controller 302, the piping connection between the chlorine mass flow controller 301, the first nitrogen mass flow controller 302, the second nitrogen mass flow controller 303, the manometer 305 and the first mixing chamber 304, the piping connection between the first mixing chamber 304 and the second mixing chamber 306, the piping connection between the second mixing chamber 306, the pumping mass flow controller 307, the pumping pump 308, etc. may be 1/4 inch teflon piping.

Based on the calibration system in the foregoing embodiments, the present disclosure may also provide a corresponding calibration method in an embodiment. Referring to fig. 4, a flow chart of a method for calibrating the nitroxyl chloride detection instrument 202 of one embodiment of the present disclosure is shown.

In fig. 4, the calibration method of the nitroxyl chloride detection instrument 202 comprises:

step S401: a wet sodium chloride and sodium nitrite powder mixture is provided in the reaction vessel 101.

In some examples, a mixture of Na nitrogen dioxide and NaCl may be placed into the reaction vessel 101 and dissolved with the addition of pure water to formulate a wet sodium chloride and sodium nitrite powder mixture.

Step S402: chlorine gas is passed into the reaction vessel 101 to produce nitroxyl chloride.

In some examples, a desired flow of chlorine output may be controlled by the chlorine dilution subsystem to pass into the reaction vessel 101.

Specifically, based on the embodiment of fig. 2, the first nitrogen source can be controlled by the first nitrogen mass flow controller 302 to output a corresponding flow of the first nitrogen and the chlorine for preliminary dilution; the nitrogen source is controlled by a second nitrogen mass flow controller 303 to output a second path of nitrogen with corresponding flow so as to output the primarily diluted chlorine after secondary dilution; the evacuation is performed based on the evacuation flow rate set by the evacuation mass flow controller 307 so that the secondarily diluted chlorine gas is output to the reaction vessel 101 at a preset flow rate.

In some examples, before the preliminary dilution is performed, 5sccm to 10sccm of chlorine is continuously introduced into the nitroxyl chloride generation subsystem and maintained for a preset period of time, so as to keep the chlorine in the pipeline stable.

Step S403: the output gas of the reaction vessel 101 is passed through a non-heating passage 103 and a heating passage 102, respectively, to obtain a pre-pyrolysis gas and a post-pyrolysis gas, respectively.

The output gas has a uniform concentration of nitroxyl chloride, and the pyrolysis gas for decomposing nitroxyl chloride is obtained through the heating channel 102 and the pyrolysis gas for retaining nitroxyl chloride through the non-heating channel 103 for comparison.

Step S404: a first nitrogen dioxide concentration is obtained by the nitrogen dioxide measuring instrument 201 based on the pre-pyrolysis gas measurement and a second nitrogen dioxide concentration is obtained based on the post-pyrolysis gas measurement to obtain the nitroxyl chloride concentration value of the generated nitroxyl chloride from the difference between the first and second nitrogen dioxide concentrations.

Step S405: a first detection response signal is obtained by the nitroxyl chloride detection instrument 202 based on the pre-pyrolysis gas measurement and a second detection response signal is obtained based on the post-pyrolysis gas measurement to obtain a nitroxyl chloride concentration signal value corresponding to the nitroxyl chloride concentration value based on the difference between the first detection response signal and the second detection response signal.

Step S406: the nitroxyl radical detection instrument 202 is calibrated based on the nitroxyl radical concentration signal value and the concentration relationship.

In some embodiments, the relation between the nitroxyl chloride concentration signal value and the nitroxyl chloride concentration value of the nitroxyl chloride detection instrument can be calibrated by changing the flow rate of the chlorine gas (such as controlling the flow rate of the chlorine gas based on the chlorine gas mass flow controller 301 and each nitrogen gas mass flow controller) to generate different low-concentration nitroxyl chlorides and obtaining multiple groups of the nitroxyl chloride concentration signal values and the corresponding nitroxyl chloride concentration values.

Thus, the nitroxyl chloride concentration value in the atmosphere can be detected by the calibrated nitroxyl chloride detection instrument.

More specific method embodiments are provided below by way of example, which may be applied to a calibration system such as that shown in FIG. 3, the method comprising the following steps.

Step 1, preparing supersaturated solution of sodium nitrite: a mixture of 0.9g of Na nitrogen dioxide and 9.1g of NaCl was added to the reaction vessel, and 5ml of ultrapure water was added for dissolution.

And 2, connecting a second communicating pipe for outputting standard gas to the CIMS instrument and the nitrogen dioxide measuring instrument. That is, a CIMS instrument is exemplarily selected as the nitroxyl chloride detection instrument.

And 3, continuously introducing a small amount of chlorine source (5-10 sccm) into the generating device for more than 2 hours so as to ensure the stability of the chlorine in the pipeline.

And step 4, opening a first nitrogen mass flow controller communicated with a nitrogen source to provide a first path of nitrogen for primarily diluting chlorine.

The chlorine source with the mass flow controller generally selects chlorine with the concentration of 9.98ppm, and the flow range of the mass flow controller is 0-500 ml/min so that the chlorine source can pass through a proper amount of chlorine, and then low-concentration nitroxyl chloride is generated.

The nitrogen source with the mass flow controller is usually pure N2, and the flow rate range of the mass flow controller is 0-500 ml/min for primarily diluting chlorine.

And 5, starting a second nitrogen mass flow controller and flowing the primarily diluted gas into a first mixing chamber with a pressure gauge.

The second nitrogen mass flow controller is used for diluting chlorine, and the flow range is 0-10 l/min.

The pressure gauge is used for monitoring pressure change in the first mixing chamber and observing pipeline stability.

The first mixing chamber was a 1/2 inch Teflon tube 10cm long to allow for uniform mixing of the gases.

And 6, pumping a certain amount of gas from the gas in the second mixing chamber through a gas pumping mass flow controller and a gas pumping pump for controlling the gas pumping flow, so that the flow rate of the gas passing through a reaction container for loading the supersaturated solution of sodium nitrate is 100-200 ml/min.

The second mixing chamber is a 1/2 inch Teflon pipeline with the length of 10cm, so that the gases are uniformly mixed.

The pumping pump is used for pumping out most of the second mixing chamber with a pumping force of 5-20 l/min, and a small amount of gas is kept flowing into the reaction tank container. The air extraction mass flow controller selects the flow range of 0-10l/min for accurately controlling the air extraction flow.

The reaction container is made of PTFE material, glass or other materials, and the diluted chlorine gas passes through the reaction container to generate the nitroxyl chloride.

And 7, setting the heating temperature of the heating device to 350 ℃, and turning on a power supply to wait for stabilization.

And 8, switching the nitroxyl gas generated by the reaction vessel into a heating or non-heating channel by a ball valve A and a ball valve B respectively.

The ball valves A and B are used for controlling the trend of the air path.

The heating device (which can be a pyrolysis tank) in the heating channel is a quartz tube with the length of 30cm and the inner diameter of 1cm wrapped by heat preservation cotton, and the heating device comprises a heating source capable of raising the temperature to 400 ℃ and is used for pyrolyzing and completely converting nitroxyl chloride into nitrogen dioxide at 350 ℃.

Step 9, a third mass flow controller of nitrogen flow is started, and the air flow of the humidifying device is controlled by adjusting the needle valve A and the needle valve B, so that the relative humidity is controlled at the atmospheric normal humidity: about 45%.

The third mass flow controller is used for accurately controlling the flow of the humidifying gas circuit, wherein the flow range is 0-10 l/min. The needle valve A, the needle valve B and the humidifying bottle device are used for controlling the relative humidity of the humidifying channel.

The corresponding hygrothermograph can be used for monitoring the relative humidity of the tail gas circuit.

And step 10, stably generating different low-concentration nitroxyl chlorides by changing the chlorine flow controlled by the first mass flow controller.

And calculating the nitroxyl chloride concentration value and the nitroxyl chloride concentration signal value before and after pyrolysis of each group based on different nitroxyl chlorides with low concentrations respectively so as to calibrate the calculation relation between the nitroxyl chloride concentration signal value and the concentration value of the nitroxyl chloride detected by CIMS.

Additionally, an experimental example may be provided in embodiments of the present disclosure to illustrate the performance of the calibration systems and methods in embodiments of the present disclosure. It should be noted that some of the above steps may be sequentially changed according to the needs without being limited to the description.

Before the experiment starts, preparing supersaturated solution of sodium nitrite: a mixture of 0.9g of sodium nitrite (Na. Sub.nitrogen dioxide) and 9.1g of sodium chloride (NaCl) was added to the reaction vessel, and 5ml of ultrapure water was added for dissolution.

At the beginning of the experiment, 10ml/min (9.8 ppmv) of chlorine was initially diluted with 200ml/min of nitrogen by means of a chlorine mass flow controller and a first nitrogen mass flow controller. The primarily diluted gas is further secondarily diluted in the first mixing chamber with 4-5l/min of nitrogen gas controlled by the second nitrogen gas mass flow controller. And then accurately extracting diluted gas in the second mixing chamber through an air extraction mass flow controller, so that the gas flow passing through the reaction container is 100-200 ml/min. The diluted gas is switched by two paths of ball valves to enter a heating or non-heating channel. And then controlling the humidity of 4-5l/min nitrogen through a third nitrogen mass flow controller and two metering needle valves, and mixing the nitrogen with pyrolyzed or non-pyrolyzed gas to form final standard gas. The flow of the generation source port is kept at 4l/min, wherein CEAS-nitrogen dioxide (namely a nitrogen dioxide detection instrument) samples 1.5l/min, the flow required by CIMS instrument sampling is reserved for 2l/min, and the evacuation flow is 0.5l/min. By measuring the difference between the concentration of nitrogen dioxide after pyrolysis and that after non-pyrolysis, the generated ClNO is the generation source in the state ₂ Concentration.

The specific operation steps are as follows.

1. And calibrating the theoretical output flow of each MFC and the final output flow of the gas circuit through the TSI gas mass flowmeter so as to prevent gas circuit leakage.

2. The tail gas pipe is connected into a laboratory main exhaust pipe.

3. Opening an MFC controlling the flow of chlorine, three MFCs controlling the flow of nitrogen and an MFC controlling the flow of pumping, respectively to be connected with Cl ₂ The nitrogen for preliminary dilution and the nitrogen flowing into the gas path (first nitrogen and second nitrogen) are respectively controlled at 200ml/min and 4-5l/min by 2 nitrogen MFCs. And then the air pump is turned on, and the flow of the air pump is accurately controlled through the air pumping MFC, so that the flow passing through the reaction container is 100-200 ml/min. Finally, the humidification circuit nitrogen (i.e., the third nitrogen) was turned on and its flow was controlled at 4-5l/min by the third MFC. At this time, the relative humidity was controlled to 45% of the atmospheric normal humidity by adjusting two metering needle valves.

4. The connection standard is discharged from CIMS and nitrogen dioxide measuring instrument.

5. Setting the heating temperature of the heating device to 350 ℃, and starting the power supply to wait for stabilization.

6. The background signal (no chlorine, nitrogen only) was measured.

7. The wet sodium chloride and sodium nitrite powder mixture after the preparation is added into a reaction tank.

8. Using small amounts of Cl ₂ (5-10 sccm) continuously introducing the chlorine into the pipeline for more than 2 hours so as to ensure the stability of the chlorine in the pipeline.

9. Changing Cl by MFC ₂ The generation source stably generates ClNO with different concentrations ₂ 。

10. Specific concentration calibration experiment record table is shown in table 1, chlorine flow is changed by changing the scale of the mass flowmeter, and then the nitroxyl gas is obtained by switching the pyrolysis furnace.

TABLE 1 ClNO ₂ Concentration calibration record table

Sequence number	Chlorine mass flowmeter (%)	Chlorine actual flow (sccm)	Heating device
				1	0	0
2	20	40
				3	20	40	√
4	30	60
				5	30	60	√
6	40	80
				7	40	80	√
8	60	120
				9	60	120	√
10	80	160
				11	80	160	√

11. The results of the calibration experiments are shown in table 2, and the nitrogen dioxide concentration values (unit ppb) of the gases before and after pyrolysis, the nitrogen dioxide concentration difference between each other, the variance of the concentration difference, the nitroxyl chloride concentration signal values (response, unit counts) of the CIMS instrument before and after pyrolysis of nitroxyl chloride, the detection response signal difference, and the variance of the signal difference are recorded, respectively. Wherein the concentration difference before and after pyrolysis of nitrogen dioxide is the generated ClNO ₂ The concentration is 0.15-1.43 ppb, and the performance is good. 11. The results of the calibration experiments are shown in Table 2, and the nitrogen dioxide concentration values of the gases before and after pyrolysis (singlyPpb), the difference in nitrogen dioxide concentration between each other, the variance of the difference in concentration, the nitroxyl chloride concentration signal value (response, counts) of the CIMS instrument before and after pyrolysis of nitroxyl gas, the difference in detection response signal, and the variance of the difference in signal. Wherein the concentration difference before and after pyrolysis of nitrogen dioxide is the generated ClNO ₂ The concentration is 0.15-1.43 ppb, and the performance is good.

TABLE 2 data recording table

Based on data records similar to table 2, mathematical relationships between nitroxyl chloride concentration values and nitroxyl chloride concentration signal values were analyzed. Reference may be made to fig. 5, which shows that in an experiment, by implementing a calibration method in a calibration system, a signal response curve of the CIMS instrument to the nitroxyl gas concentration is obtained, which curve represents the mathematical relationship. The abscissa in fig. 5 represents the nitroxyl gas concentration in ppb; the ordinate is the signal response of the CIMS instrument in counts. Using this signal response curve, the CIMS instrument response to the nitroxyl chloride signal can be converted to a concentration.

The embodiment of the disclosure also provides a method for detecting nitroxyl chloride, which comprises the following steps: the detection of the nitroxyl chloride of the gas to be detected is performed by the nitroxyl chloride detection instrument calibrated by the calibration method of the nitroxyl chloride detection instrument described in the above embodiments, and the corresponding nitroxyl chloride concentration value is obtained based on the detected nitroxyl chloride concentration signal value conversion, such as by using the signal response curve shown in fig. 5.

For example, fig. 6 is the atmospheric concentration of nitroxyl chloride observed by applicant at the experimental site using CIMS apparatus from 9 to 10 months 2022, with time resolution of minutes, the abscissa representing the measurement time and the ordinate representing the nitroxyl gas concentration.

The above embodiments are merely illustrative of the principles of the present disclosure and its efficacy, and are not intended to limit the disclosure. Modifications and variations may be made to the above-described embodiments by those of ordinary skill in the art without departing from the spirit and scope of the present disclosure. Accordingly, it is intended that all equivalent modifications and variations which a person having ordinary skill in the art would accomplish without departing from the spirit and technical spirit of the present disclosure be covered by the claims of the present disclosure.

Claims

1. A calibration system for a nitroxyl chloride detection instrument, comprising:

a nitroxyl chloride generation subsystem comprising: the reaction vessel is used for receiving the introduction of chlorine, and the input end of the reaction vessel is communicated with a heating channel and a non-heating channel of the reaction vessel; the output end of the heating channel or the non-heating channel is communicated with the generation source port, and the heating channel and the non-heating channel are alternatively conducted; wherein the reaction vessel is provided with a wet sodium chloride and sodium nitrite powder mixture for reaction with chlorine gas to form nitroxyl chloride; the output gas of the reaction vessel passes through the non-heating channel when being conducted so as to output the gas before pyrolysis at the generation source port, and the output gas of the reaction vessel passes through the heating channel when being conducted so as to output the gas after pyrolysis at the generation source port; the nitroxyl chloride is pyrolyzed in the heating channel to form nitrogen dioxide;

a detection subsystem, comprising:

the nitrogen dioxide measuring instrument is communicated with the generation source port through a pipeline and is used for obtaining a first nitrogen dioxide concentration based on the gas measurement before pyrolysis and a second nitrogen dioxide concentration based on the gas measurement after pyrolysis so as to obtain a nitroxyl chloride concentration value of the generated nitroxyl chloride according to the difference between the first nitrogen dioxide concentration and the second nitrogen dioxide concentration;

The pipeline is communicated with the nitroxyl chloride detection instrument of the generation source port and is used for obtaining a first detection response signal based on the gas measurement before pyrolysis and obtaining a second detection response signal based on the gas measurement after pyrolysis so as to obtain a nitroxyl chloride concentration signal value corresponding to the nitroxyl chloride concentration value according to the difference between the first detection response signal and the second detection response signal;

the relation between the nitroxyl chloride concentration signal value and the corresponding nitroxyl chloride concentration value is used for calibrating the nitroxyl chloride detection instrument.

2. The system according to claim 1, characterized in that it comprises:

a chlorine dilution subsystem comprising: the pipeline is communicated with a chlorine gas mass flow controller of a chlorine gas source and at least one nitrogen gas mass flow controller of a nitrogen gas source, the output ends of the chlorine gas mass flow controller and the at least one nitrogen gas mass flow controller are communicated to a chlorine gas port through a mixing space, and the chlorine gas port is communicated to the reaction container so as to output mixed gas obtained after the chlorine gas is diluted by nitrogen gas.

3. The system of claim 2, wherein the at least one nitrogen mass flow controller comprises:

The first nitrogen mass flow controller is communicated with a nitrogen source and the mixing space through a pipeline and is used for controlling the flow of the first nitrogen which is preliminarily diluted with chlorine;

the second nitrogen mass flow controller is communicated with a nitrogen source and the mixing space through a pipeline and is used for controlling the flow of second-path nitrogen for secondarily diluting the primarily diluted chlorine; the flow rate of the second path of nitrogen is higher than that of the first path of nitrogen.

4. The system according to claim 1 or 2, characterized in that it comprises:

a chlorine humidity control subsystem comprising:

the third nitrogen mass flow controller is communicated with a nitrogen source through a pipeline and used for controlling the flow of the output third nitrogen;

the pipeline is communicated between the third nitrogen mass flow controller and the humidifying port so as to respectively humidify and non-humidify the third nitrogen and then output the third nitrogen at the humidifying port; wherein, a first humidifying valve and a humidifying device are arranged in the humidifying channel; a second humidifying valve is arranged in the non-humidifying channel; the opening and closing degree of the first humidifying valve and the second humidifying valve is used for adjusting the humidity of third nitrogen in the humidifying port;

5. The system of claim 4, wherein the detection subsystem further comprises: and the pipeline is communicated with the hygrothermograph of the generating source port.

6. The system of claim 2, wherein the mixing space comprises: the first mixing chamber is provided with a pressure gauge and is used for introducing chlorine and nitrogen to generate mixed gas; the second mixing chamber is communicated between the first mixing chamber and the chlorine port; the second mixing chamber is also communicated with an air extracting pump through an air extracting mass flow controller pipeline, and the air extracting pump is used for extracting air based on the air extracting flow set by the air extracting mass flow controller so as to enable the mixed gas conveyed by the chlorine port to be at a preset flow;

and/or a first switch valve and a heating device which are communicated through pipelines are arranged in the heating channel; and a second switch valve is arranged in the non-heating channel.

7. The system of claim 1, comprising at least one of:

the mixing space of the chlorine and the nitrogen comprises at least one mixing chamber, and each mixing chamber is formed by a Teflon pipeline with a preset diameter length so as to uniformly mix the mixed gases;

a tail gas pipeline communicated with the generation source port;

The heating temperature of the heating device in the heating channel is 350 ℃; and/or the heating device comprises a quartz tube wrapped by heat preservation cotton and comprises a heating source with the upper heating limit of 400 ℃;

ball valves for controlling on/off are respectively arranged in the heating channel and the non-heating channel;

the secondary chlorine humidity control subsystem comprises a third nitrogen mass flow controller, a humidifying channel and a non-humidifying channel; needle valves are respectively arranged in the humidifying channel and the non-humidifying channel, and/or the flow range of nitrogen conveyed under the control of the third nitrogen mass flow controller is 4 l/min-5 l/min, and/or the humidity of nitrogen output by a humidifying port of the secondary chlorine humidity control subsystem is 20% -40% or 40% -60%;

the flow rate of the chlorine gas conveyed under the control of the chlorine gas mass flow controller is 10ml/min, the flow rate of the first path of nitrogen gas which is primarily diluted with the chlorine gas is controlled to be 200ml/min by the first nitrogen gas mass flow controller, and the flow rate of the second path of nitrogen gas which secondarily dilutes the primarily diluted gas is controlled to be 4l/min to 5l/min by the second nitrogen gas mass flow controller; and/or the flow control range of the first nitrogen mass flow controller is 0-500 ml/min and/or the flow control range of the second nitrogen mass flow controller is 0-10 l/min; and/or the chlorine concentration provided by the chlorine source is 9.98ppm, and the flow control range of the chlorine mass flow controller is 0-500 ml/min;

The flow of the gas output by the generation source port to the detection subsystem is 4l/min, wherein the sampling flow distributed to the nitrogen dioxide measuring instrument is 1.5l/min, and the sampling flow distributed to the nitroxyl chloride detecting instrument is 2l/min;

the mixing space includes: the first mixing chamber is provided with a pressure gauge and is used for introducing chlorine and nitrogen to generate mixed gas; the second mixing chamber is communicated between the first mixing chamber and the chlorine port; the second mixing chamber is also communicated with an air extracting pump through an air extracting mass flow controller pipeline, and the air extracting pump is used for extracting air based on the air extracting flow set by the air extracting mass flow controller so as to enable the chlorine conveyed by the chlorine port to be at a preset flow;

the mixed gas conveyed by the chlorine port is controlled at a preset flow rate, and the range of the preset flow rate is 100 ml/min-200 ml/min; and/or the suction flow rate of the suction pump is 5l/min-20 l/min;

the reaction vessel is made of polytetrafluoroethylene.

8. A method for calibrating a nitroxyl chloride detection instrument, applied to the system of any one of claims 1 to 7, comprising:

providing a wet sodium chloride and sodium nitrite powder mixture in a reaction vessel;

Introducing chlorine into a reaction vessel to produce nitroxyl chloride;

respectively passing the output gas of the reaction container through a non-heating channel and a heating channel to obtain pre-pyrolysis gas and post-pyrolysis gas respectively;

obtaining a first nitrogen dioxide concentration based on the pre-pyrolysis gas measurement and a second nitrogen dioxide concentration based on the post-pyrolysis gas measurement by a nitrogen dioxide measuring instrument, so as to obtain a nitroxyl chloride concentration value of the generated nitroxyl chloride according to the difference between the first nitrogen dioxide concentration and the second nitrogen dioxide concentration;

obtaining a first detection response signal based on the pre-pyrolysis gas measurement and a second detection response signal based on the post-pyrolysis gas measurement by a nitroxyl chloride detection instrument, so as to obtain a nitroxyl chloride concentration signal value corresponding to the nitroxyl chloride concentration value according to the difference between the first detection response signal and the second detection response signal;

calibrating the nitroxyl radical detection instrument based on the nitroxyl radical concentration signal value and the concentration relation.

9. The method of claim 8, wherein calibrating the nitroxyl radical detection instrument based on the nitroxyl radical concentration signal value and the concentration relationship comprises: and (3) by changing the flow of the chlorine gas to generate different low-concentration nitroxyl chlorides, obtaining a plurality of groups of nitroxyl chloride concentration signal values and corresponding nitroxyl chloride concentration values, and calibrating the relation between the nitroxyl chloride concentration signal values and the nitroxyl chloride concentration values of the nitroxyl chloride detection instrument.

10. The method of claim 8, comprising at least one of:

placing a mixture of Na nitrogen dioxide and NaCl into a reaction vessel and adding pure water for dissolution to prepare a wet sodium chloride and sodium nitrite powder mixture;

the first nitrogen source is controlled by a first nitrogen mass flow controller to output a first path of nitrogen and chlorine with corresponding flow for preliminary dilution;

controlling a nitrogen source to output a second path of nitrogen with corresponding flow through a second nitrogen mass flow controller so as to output the primarily diluted chlorine after secondary dilution;

pumping based on pumping flow set by a pumping mass flow controller so as to output the secondarily diluted chlorine to a reaction container at a preset flow;

before preliminary dilution is carried out, 5-10 sccm of chlorine is continuously introduced into the nitroxyl chloride generation subsystem and maintained for a preset period of time, so that the stability of the chlorine in the pipeline is maintained.

11. A method for detecting nitroxyl chloride, comprising:

the nitroxyl chloride detection instrument calibrated by the calibration method of the nitroxyl chloride detection instrument of any one of claims 8 to 10, performing the detection of the nitroxyl chloride of the gas to be detected, and converting the detected nitroxyl chloride concentration signal value to obtain the corresponding nitroxyl chloride concentration value.