CN115950982A - High-time-resolution non-methane total hydrocarbon detection method and device - Google Patents
High-time-resolution non-methane total hydrocarbon detection method and device Download PDFInfo
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Abstract
The invention discloses a high-time-resolution non-methane total hydrocarbon detection device and a method, which mainly comprises a metal sintering filter, a sampling probe rod, a heat tracing pipe sampling pump, a heat tracing pipe, a catalytic furnace, a total hydrocarbon column, a first electronic mass flow controller, a second electronic mass flow controller, a proportional valve, a total hydrocarbon FID detector, a methane FID detector, a first micro-current signal processor and a second micro-current signal processor; according to the invention, the total hydrocarbon response time and the methane response time are redefined, so that the total hydrocarbon response time and the methane response time are the same, and the non-methane total hydrocarbon detection precision is improved.
Description
Technical Field
The invention mainly relates to the field of environment-friendly equipment, in particular to a high-time-resolution non-methane total hydrocarbon detection method and device.
Background
Volatile Organic Compounds (VOCs) are important precursors for forming secondary pollutants such as fine particulate matters (PM 2.5) and ozone (O3), and further cause atmospheric environmental problems such as dust haze and photochemical smog. Because hydrogen Flame Ionization Detector (FID) has the sensitivity height, the wide characteristics of linear range to the organic matter detector, consequently gas chromatograph method (GC-FID) is the present main monitoring VOCs method, wide application in on-line monitoring equipment, but because on-line monitoring equipment lacks the comparison equipment, traditional laboratory gas chromatograph is bulky, heavy, be difficult for going out at the platform and detect, detect the laboratory through sampling bag or suma jar with the sample collection, the intermediate process can cause sample loss, the condensation, the analysis result is great with on-line monitoring equipment difference. Therefore, the portable gas chromatograph has come to the end, can ensure the timeliness of the measuring result, and has small volume, light weight and easy field monitoring.
Due to the characteristics of the GC-FID method, through quantitative analysis of a quantitative ring, the analysis period of non-methane total hydrocarbon (NMHC) is usually 2min, the change trend of the current monitoring point position cannot be fed back in real time, the defect is effectively made up by the catalytic-FID method, the output number of the catalytic-FID method can be in second level, but the response time (T90) of the total hydrocarbon and methane system has 3-5s time difference, generally speaking, the internal resistance of the total hydrocarbon gas path is small, the response is fast, the methane gas path passes through a catalytic furnace and a filtering device, the response speed is slow, the concentration of the sample gas in the same time period cannot be accurately measured, and the measured concentration of the non-methane total hydrocarbon and the actual concentration have difference. According to the test result of the research team, the method of enabling the total hydrocarbon and the methane T90 to be the same simply by adjusting the length of the pipeline cannot completely eliminate the delay in the rapid change process of the total hydrocarbon and the methane, so that the problem that the concentration of the non-methane total hydrocarbon calculated by the difference value of the total hydrocarbon and the methane often has a negative value and the like is solved.
Disclosure of Invention
The invention provides a high-time-resolution non-methane total hydrocarbon detection method and a high-time-resolution non-methane total hydrocarbon detection device, which solve the technical problems in the prior art.
The invention provides a high-time-resolution non-methane total hydrocarbon detection device, which comprises a sample collection unit and a host;
the host machine comprises an air source supply unit, a catalytic furnace, a flow control unit, a detection unit and a signal processing unit; the sample collection unit comprises a sampling pump, a heat tracing pipe and a sampling probe rod; a metal sintering filter is arranged at the sampling probe rod; the catalytic furnace comprises a catalyst and a heating and heat-insulating material; the flow control unit comprises a first electronic mass flow controller and a second electronic mass flow controller; the detection unit comprises a total hydrocarbon FID detector and a methane FID detector; the signal processing unit comprises a micro-current signal processor I and a micro-current signal processor II; the gas source supply unit comprises a low-pressure hydrogen storage bottle, a sample gas pipeline and an air pipeline; the sample gas pipeline comprises a total hydrocarbon gas circuit and a methane gas circuit; a proportional valve is arranged in the total hydrocarbon gas circuit;
wherein, the sampling pump is arranged at the tail end of the heat tracing pipe; the head end of the heat tracing pipe is connected with the tail end of the sampling probe rod; a metal sintering filter is arranged at the sampling probe rod; the gas outlet end of the sampling pump is respectively connected with the head end of the total hydrocarbon gas circuit and the head end of the methane gas circuit through a tee; a first electronic mass flow controller and a total hydrocarbon column are arranged in the total hydrocarbon gas path; wherein the electron mass flow controller is connected with the head end of the main hydrocarbon column; a total hydrocarbon FID detector and a micro-current signal processor I are arranged in the total hydrocarbon gas circuit; and the micro-current signal processor is electrically connected with the total hydrocarbon FID detector. The head end of the air pipeline is provided with a high-efficiency hydrocarbon removing filter; a catalytic furnace and an electronic mass flow controller II are arranged in the methane gas path; the tail end of the catalytic furnace is connected with the head end of the methane column through a second electronic mass flow controller; a methane FID detector and a micro-current signal processor II are arranged in the methane column; and the methane FID detector is electrically connected with the second microcurrent signal processor.
Correspondingly, the invention provides a high-time resolution non-methane total hydrocarbon detection method, which comprises the following steps:
a sampling pump negative pressure extracts initial sample gas from the external environment, and the initial sample gas is completely vaporized by stabilizing high temperature through a heat tracing pipe;
the completely vaporized initial sample gas passes through a metal sintering filter at the sampling probe rod to obtain pure sample gas;
after being processed by positive pressure, the pure sample gas is equivalently conveyed to a total hydrocarbon gas circuit and a methane gas circuit through a tee joint; the total hydrocarbon FID response time is made to be the same as the methane FID response time by varying the length of the total hydrocarbon column;
after the pure sample gas in the total hydrocarbon gas circuit is conveyed to the total hydrocarbon column through the first electronic mass flow controller, a total hydrocarbon FID detector in the total hydrocarbon column senses the total hydrocarbon in the pure sample gas in the total hydrocarbon column to generate a total hydrocarbon FID micro-current signal; the first micro-current signal processor acquires a total hydrocarbon FID micro-current signal, and calculates to obtain the total hydrocarbon concentration;
processing the sample gas in the methane gas path through a catalytic furnace to obtain catalyzed sample gas, enabling the catalyzed sample gas to enter a methane FID detector through an electronic mass flow controller II, and inducing methane in the catalyzed sample gas to generate a methane FID micro-current signal; the second micro-current signal processor acquires a methane FID micro-current signal, and calculates to obtain the methane concentration;
the non-methane total hydrocarbon concentration C (NMHC) is calculated from the methane concentration C (CH 4) and the total hydrocarbon concentration C (THC) by:
C(NMHC)＝C(THC)-C(CH4)。
compared with the prior art, the embodiment of the invention has at least the following technical advantages:
the high-time-resolution non-methane total hydrocarbon detection method provided by the invention is analyzed, and mainly comprises a sampling pump, a heat tracing pipe, a sampling probe rod, a metal sintering filter, a catalytic furnace, a catalyst, a heating and heat insulating material, a first electronic mass flow controller, a second electronic mass flow controller, a total hydrocarbon gas circuit, a methane gas circuit, a total hydrocarbon column, a proportional valve, a total hydrocarbon FID detector, a methane FID detector, a micro-current signal processor I and a micro-current signal processor II;
when the sampling probe rod is used in concrete application, the heat tracing pipe is used for stably heating quantitative initial sample gas obtained by negative pressure of the sampling pump at high temperature so as to prevent the sample gas from condensing, and the metal sintering filter arranged at the sampling probe rod is used for filtering particles of the initial sample gas to obtain purer sample gas; according to the embodiment of the invention, a large amount of particles contained in the initial sample gas are fully considered, the sample is heated at a high temperature stably through the heat tracing pipe to prevent the sample from being condensed, and the particles in the initial sample gas are separated through the metal sintering filter at the top end of the sampling probe rod, so that a relatively pure sample gas is obtained.
The filtered pure sample gas is processed by positive pressure and is conveyed to a total hydrocarbon gas circuit and a methane gas circuit in an equivalent manner through a tee joint, the pure sample gas in the total hydrocarbon gas circuit of the total hydrocarbon gas circuit enters a total hydrocarbon column and is responded by a total hydrocarbon FID detector at the tail end of the total hydrocarbon column to generate a real-time continuous total hydrocarbon FID micro-current signal, a micro-current signal processor acquires the amplified total hydrocarbon FID micro-current signal and carries out integral quantitative analysis on the signal to calculate the total hydrocarbon concentration C (THC), the pure sample gas in the methane gas circuit is catalyzed by a catalytic furnace in the methane gas circuit to obtain a catalyzed sample gas only containing methane, the catalyzed sample gas enters the methane FID detector to respond, a real-time continuous methane FID micro-current signal processor II acquires the amplified methane FID micro-current signal and carries out integral quantitative analysis on the signal to calculate the methane concentration C (CH 4), and the non-methane total hydrocarbon concentration C (NMHC) is calculated and measured by differential subtraction.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the structures shown in the drawings without creative efforts.
The implementation, functional features and advantages of the present invention will be further described with reference to the accompanying drawings.
FIG. 1 is a graph showing the response time difference between total hydrocarbons and methane in the concentration of non-methane total hydrocarbons monitored by the prior art catalytic-FID method;
FIG. 2 is a graphical representation of a prior art catalytic-FID process for monitoring non-methane total hydrocarbon concentration variability;
FIG. 3 is a schematic diagram of monitoring total hydrocarbon concentration and methane concentration by defining T90 response time in an apparatus and method for high time resolution measurement of non-methane total hydrocarbons according to an embodiment of the present invention;
FIG. 4 is a flow chart showing steps in a method for measuring non-methane total hydrocarbons with high time resolution according to an embodiment of the present invention;
FIG. 5 is a flowchart illustrating the specific processing of step S20 in a method for measuring non-methane total hydrocarbons with high time resolution according to an embodiment of the present invention;
fig. 6 is a schematic diagram of an overall architecture of an apparatus for measuring non-methane total hydrocarbons with high time resolution according to an embodiment of the present invention.
Reference numbers: a sampling pump 10; a heat tracing pipe 11; a sampling probe 12; a metal sintered filter 121; a tee 122; a catalytic furnace 13; a first electronic mass flow controller 141; a second electronic mass flow controller 142; a total hydrocarbon gas circuit 15; a methane gas circuit 16; a total hydrocarbon column 151; a proportional valve 152; a total hydrocarbon FID detector 17; a methane FID detector 18; a first microcurrent signal processor 191; and a second microcurrent signal processor 192.
Detailed Description
It should be understood that the specific embodiments described herein are merely illustrative of the invention and do not limit the invention.
Example one
The embodiment of the invention provides a portable gas chromatograph for measuring non-methane total hydrocarbons with high time resolution, which adopts a catalysis-FID principle to provide measurement data of total hydrocarbons, methane and non-methane total hydrocarbons in real time, wherein the time resolution is as low as 1s. Due to the internal characteristics of the equipment, the T90 response time is redefined in the embodiment of the invention, the T90 response time is divided into two stages, namely T1 and T2, and the embodiment of the invention explains how to achieve the same effect of the total hydrocarbon and methane response time in the measurement process by controlling the T1 and T2 times.
Referring to fig. 6, the invention provides a high-time-resolution non-methane total hydrocarbon detection device, which comprises a sampling pump 10, a heat tracing pipe 11, a sampling probe 12, a metal sintering filter 121, a catalytic furnace 13, a catalyst 131, a heating insulation material 132, a first electronic mass flow controller 141, a second electronic mass flow controller 142, a total hydrocarbon gas circuit 15, a methane gas circuit 16, a total hydrocarbon column 151, a proportional valve 152, a total hydrocarbon FID detector 17, a methane FID detector 18, a first micro-current signal processor 191 and a second micro-current signal processor 192;
the tail end of the total hydrocarbon gas circuit 15 is connected with the head end of the total hydrocarbon column 151, the tail end of the total hydrocarbon column is provided with a total hydrocarbon FID detector 17 and a micro-current signal processor one 191, the total hydrocarbon FID detector 17 is connected with the micro-current signal processor one 191, and the tail end of the total hydrocarbon gas circuit 15 is provided with an electronic mass flow controller one 141;
the total hydrocarbon FID detector 17 is used for generating a continuous micro-current signal by responding to the total hydrocarbon in the total hydrocarbon column 151 in real time;
the micro-current signal processor I191 is used for amplifying the micro-current signal generated by the total hydrocarbon FID detector 17 and carrying out integral quantitative analysis on the signal to obtain the total hydrocarbon concentration in the current total hydrocarbon gas circuit 15;
the first electronic mass flow controller 141 is used for controlling the total hydrocarbon flow in the total hydrocarbon gas circuit 15 by adjusting a proportional valve;
a catalytic furnace 13 is arranged on the methane gas circuit 16 (or called as a catalytic furnace 13 is arranged in the methane gas circuit 16), a methane FID detector 18 and a micro-current signal processor II 192 are arranged at the tail end of the methane gas circuit 16, the methane FID detector 18 is connected with the micro-current signal processor II 192, and an electronic mass flow controller II 142 is arranged at the head end of the methane gas circuit 16;
the methane FID detector 18 is used for generating a continuous micro-current signal by responding to the methane in the methane gas circuit 16 in real time;
the second micro-current signal processor 192 is used for amplifying the micro-current signal generated by the methane FID detector 18 and carrying out integral quantitative analysis on the signal to obtain the current methane concentration in the methane gas circuit 16;
and the second electronic mass flow controller 142 is used for controlling the flow rate of methane in the methane gas circuit 16.
In the specific design of the high time resolution non-methane total hydrocarbon detection device, the device comprises a sample acquisition unit: the sample collection unit adopts inert pipelines, the main body of the sample collection unit is composed of a heat tracing pipe 11 with the length of 2m and a sampling probe rod 12, the temperature of the heat tracing pipe 11 is kept at 120 ℃ or 20 ℃ higher than the temperature of actual sample gas, a metal sintering filter which does not react with the sample gas is arranged at the sampling probe rod 12, the filtering precision is usually 0.2 mu m, and particulate matters are prevented from entering equipment to influence detection;
an air source supply unit: mainly an air source required by the FID detector; hydrogen gas: the hydrogen is stored in a low-pressure hydrogen storage bottle, the storage capacity can reach 50L, and the use is safe and convenient; carrier gas: the principle of the portable gas chromatograph is catalysis-FID, and carrier gas is sample gas; air: the filter is used for filtering the ambient air.
A catalytic furnace: the catalytic furnace consists of catalyst and heating and heat insulating material, the catalyst is non-methane hydrocarbon catalyst and consists of Pd, pt and other noble metals, and the Pt content is 0.1-5%. It is in the form of granule with a diameter of 3mm (spherical). The using temperature of the catalytic furnace is 280 ℃, the catalytic flow is about 50ml/min, and the catalytic efficiency is more than 98%.
A flow control unit: hydrogen and air were controlled using electronic mass flow controllers. The sample gas is extracted from the external environment by the negative pressure of a sampling pump, then the sample gas is positively pumped to a total hydrocarbon and methane gas path for analysis, and in order to achieve the same T90 response time of total hydrocarbon and methane detection, the flow control unit makes the following implementation scheme:
defining total hydrocarbon response time T90= T11+ T12 units: s
Defining methane response time T90= T21+ T22 units: s is
The T1 and T2 times are defined as: when the pure sample gas after the same amount of physical filtration is introduced, after the calibration of the equipment is completed, the total hydrocarbon rate responds, when the total hydrocarbon and the methane concentration are measured to be the same, the value is defined as T1 before the moment, and after the total hydrocarbon and the methane concentration are the same, the value is defined as T2 until the reading is stable.
Defining Q1 as the total hydrocarbon gas path flow, unit: ml/min
Defining Q2 as methane gas path flow, unit: ml/min
T1: if the response time of the first stage of the total hydrocarbon and methane is ensured to be the same as the time of T1, namely T11= T21, the same flow of the sample gas needs to be ensured, namely Q1= Q2, but because the apertures of the catalytic furnace and the nozzle of the FID detector in the methane gas path are influenced, the rear-end air resistance is not completely the same, namely the flow Q1 of the total hydrocarbon gas path is equal to the flow Q2 of the methane gas path under the same pressure, so that the time of T1 cannot be defined to be the same.
T2: the response time of the second stage of the total hydrocarbons and the methane is verified to ensure that the time T1 is the same, the time of the total hydrocarbons T12 and the time of the methane T22 are determined, the second response time T12 of the total hydrocarbons is equal to the second response time T22 of the methane by the methane standard gas and the adjustment of the sampling flow, and the response time T11 of the first stage of the total hydrocarbons and the response time T21 of the first stage of the methane under the condition that the response time of the second stage of the two gas paths is the same are recorded.
And the total hydrocarbon gas path and the methane gas path are respectively connected in series with an electronic mass flow controller, and the total hydrocarbon gas path flow Q1 and the methane gas path flow Q2 are respectively controlled and recorded.
Because the second response time T2 of the total hydrocarbon and the methane is the same, the length of the total hydrocarbon column can be changed to achieve the same effect of the first response time of the total hydrocarbon and the methane, and the specific implementation mode is that the length delta L (mm) of the total hydrocarbon column is changed, the cross section area of a pipeline is S (cm) 2 )
ΔL＝(T11-T21)÷60*Q1÷S
After the length of the total hydrocarbon column is changed, the flow Q1 of the whole gas circuit can be changed, and at the moment, the gas resistance of the pipeline is adjusted through a built-in proportional valve of the total hydrocarbon gas circuit, so that the flow after the length of the total hydrocarbon column is adjusted is the same as the flow before Q1, and the T90 response time of the total hydrocarbon and the T90 response time of methane can be ensured to be the same.
A detection unit: two special miniature FID detectors are arranged and are respectively used for detecting the concentration of total hydrocarbon and methane in the sample gas;
a signal processing unit: the concentration of total hydrocarbon and methane is calculated by collecting FID micro-current signals, amplifying the micro-current signals, and carrying out integral quantitative analysis on the signals.
Example two
Referring to fig. 4, the present invention also provides a high time resolution non-methane total hydrocarbon detection method, comprising the steps of:
step S10: the sample gas is extracted from the external environment by the negative pressure of the sampling pump 10, and the sample gas is completely vaporized by stabilizing the high temperature through the heat tracing pipe 11. The method for extracting the sample gas under the negative pressure adopted by the embodiment of the invention can stably extract a certain amount of sample gas, the heat tracing pipe 11 is stabilized at high temperature to vaporize the sample gas, and the heat tracing pipe 11 is kept at 120 ℃ (namely the stabilized high temperature stated in the scheme), so that the influence of the condensation of components in the sample gas on the sampling result is avoided.
Step S11: filtering the particles in the completely vaporized sample gas through a metal sintering filter at the sampling probe rod 12 to obtain pure sample gas; the particles generally refer to some dust particles in the air; it should be noted that the heat tracing pipe 11 and the sampling probe rod 12 are all inert pipelines, the metal sintering filter does not react with the sample gas, the sample gas detection error caused by the reaction with the sample gas under the high-temperature condition is prevented, the filtering precision of the metal sintering filter is 0.2 μm, the particles are fully filtered, and the particles are prevented from entering the equipment to influence the detection precision. The metal sintering filter adopted in the embodiment of the invention does not react with the sample gas and has high filtering precision, particulate matters in the initial sample gas can be fully filtered, the particulate matters are prevented from entering equipment to influence the detection precision, and the sampling probe rod 12 and the heat tracing pipe 11 are inert pipelines, so that the initial sample gas cannot react with the sampling probe rod when passing through the inert pipelines, and the precision of a detection result is further influenced;
step S20: after being processed by positive pressure, the filtered pure sample gas is equally conveyed to a total hydrocarbon gas path 15 and a methane gas path 16 through a tee joint (it needs to be noted that the sample gas enters from a sampling pump under negative pressure and then is output under positive pressure after passing through the tee joint); the total hydrocarbon FID response time is made the same as the methane FID response time by varying the length of the total hydrocarbon column;
step S21: the branched pure sample gas in the total hydrocarbon gas circuit 15 enters the total hydrocarbon FID detector 17 through the total hydrocarbon column 151, and the total hydrocarbon FID detector 17 responds to the total hydrocarbon in the pure sample gas in the total hydrocarbon column 151 to generate a total hydrocarbon FID micro-current signal (the signal refers to a real-time continuous total hydrocarbon FID micro-current signal obtained by real-time detection);
the first micro-current signal processor 191 acquires a total hydrocarbon FID micro-current signal, amplifies the total hydrocarbon FID micro-current signal, performs integral quantitative analysis on the signal (the work of the first micro-current signal processor 191 is the prior art and is not repeated), and calculates the total hydrocarbon concentration;
step S22: the branched pure sample gas in the methane gas path 16 is subjected to catalytic treatment through a catalytic furnace 13 in the methane gas path 16, and the sample gas after catalysis is a sample gas formed after organic matters except methane in the pure sample gas in the methane gas path 16 are catalyzed into inorganic matters (the sample gas after catalysis only contains methane which is a single gas);
the sample gas after catalysis enters a methane FID detector 18, the methane FID detector 18 responds to the residual organic matters in the sample gas after catalysis (at the moment, inorganic matters in the sample gas do not respond to the methane FID, and the organic matters in the sample gas are only methane), and a methane FID micro-current signal is generated;
and the second micro-current signal processor 192 acquires a methane FID micro-current signal, amplifies the methane FID micro-current signal, performs integral quantitative analysis on the signal and calculates the methane concentration.
Preferably, the catalytic furnace 13 performs catalytic treatment to the catalyzed sample gas, and specifically includes: setting the working temperature of the catalytic furnace 13, controlling the working temperature to be a high temperature of 280 ℃ (generally, the temperature for methane combustion is 538 ℃) and controlling the catalytic flow to be 50ml/min for carrying out fine catalysis, so as to catalyze organic matters (or called organic matter gas) except methane in the pure sample gas in the methane gas circuit 16 into inorganic matters;
step S23: the concentration of non-methane total hydrocarbons was measured by differential subtraction: c (NMHC) = C (THC) -C (CH 4);
wherein C (NMHC) is the non-methane total hydrocarbon concentration; c (THC) is the total hydrocarbon concentration; c (CH 4) is methane concentration;
referring to fig. 5, in the step S20, during the process, pure sample gases with the same quantity are introduced into the total hydrocarbon gas circuit 15 and the methane gas circuit 16, and when the total hydrocarbon concentration and the methane concentration are obtained, in order to ensure that the response time of the total hydrocarbon FID detector of the total hydrocarbon gas circuit is consistent with the response time of the methane FID detector of the methane gas circuit, and the total hydrocarbon flow of the total hydrocarbon gas circuit is also consistent with the methane flow of the methane gas circuit, the flow controller executes the following steps:
step S201: the flow controller obtains the response time of a total hydrocarbon FID detector 17 in the total hydrocarbon gas circuit 15 and the response time of a methane FID detector 18 in the methane gas circuit 16, and then calculates the total hydrocarbon concentration (namely, the response time is recorded as the response time) obtained when the total hydrocarbon FID detector 17 in the total hydrocarbon gas circuit 15 responds to the total hydrocarbon and the methane concentration obtained when the methane FID detector 18 in the methane gas circuit 16 responds to the methane according to the total hydrocarbon concentration obtained by calculation;
defining a total hydrocarbon response time T90= T11+ T12; unit: s;
defining a methane response time T90= T21+ T22; unit: s;
wherein the first response time of the total hydrocarbons is recorded as T11, and the time of the stabilization moment after the second response of the total hydrocarbons is recorded as T12;
wherein, the first response time of the methane is recorded as T21, and the time of the stable moment after the second response of the methane is recorded as T22;
wherein, in the case of not changing the length of the total hydrocarbon column 151, T12 and T22 are the same second response time of the total hydrocarbon and methane, i.e. T12= T22, and the subsequent operation is to change the length of the total hydrocarbon column 151 to realize T11 and T21;
step S202: the flow control unit defines the moment when the measured total hydrocarbon concentration is the same as the methane concentration as T1 and defines the moment when the measured total hydrocarbon concentration is stable as T2 after the measured total hydrocarbon concentration is the same as the methane concentration as T1 according to the total hydrocarbon concentration of the response time of the total hydrocarbon FID detector 17 and the methane concentration of the response time of the methane FID detector 18, and at the moment, T12= T22;
step S203: the flow control unit controls the total hydrocarbon gas circuit 15 flow rate Q1 to be the same as the methane gas circuit 16 flow rate Q2 by changing the length of the total hydrocarbon column 151, so that the total hydrocarbon first response time is the same as the methane first response time (i.e. T11 and T21 are achieved to be the same), and the length formula is changed with respect to the total hydrocarbon column 151 as follows:
ΔL＝(T11-T21)÷60*Q1÷S；
wherein Δ L (mm) is the total hydrocarbon column 151 change length;
S(cm 2 ) Is the cross-sectional area of the pipeline;
t11 is total hydrocarbon first response time;
t21 is the methane first response time;
q1 (ml/min) is the total hydrocarbon gas circuit 15 flow.
After the length of the total hydrocarbon column 151 is changed, the flow Q1 of the total hydrocarbon gas path is changed, the gas resistance of the pipeline is adjusted through a built-in proportional valve of the total hydrocarbon gas path, so that the flow after the total hydrocarbon column 151 is adjusted is the same as the flow before Q1, the T90 of the total hydrocarbon can be ensured to have the same response time with the T90 of the methane, and the accuracy of the measured concentration of the sample is further ensured; it should be noted that, in general, the first response time of the total hydrocarbons is relatively earlier, so that it is important to increase the length of the total hydrocarbon column 151, and by increasing the length of the total hydrocarbon column 151, the numerical value of the total hydrocarbon first response time recorded as T11 can be increased, so that the total hydrocarbon first response time T11 is finally equal to the methane first response time T21, and since T12 (the time of the stabilization instant after the total hydrocarbon second response) is always equal to T22 (the time of the stabilization instant after the methane second response), the technical purpose of the T90 of the total hydrocarbons being equal to the T90 response time of the methane can be finally achieved by changing the length of the total hydrocarbon column 151, and the accuracy of the measured concentration of the sample can be further ensured.
In summary, the embodiment of the present invention provides a portable gas chromatograph for measuring non-methane total hydrocarbons with high time resolution, the apparatus adopts a catalysis-FID principle, collects a sample under negative pressure by a high temperature sampling pump, and then divides the sample gas into two paths by a tee joint, wherein one path of the sample gas enters a total hydrocarbon FID detector to measure the Total Hydrocarbon Concentration (THC) in the sample gas; the other path of sample gas enters a methane FID detector through a catalytic furnace, the catalytic furnace is used for catalyzing organic matters in the sample gas except methane into inorganic matters, and the inorganic matters do not respond on the methane FID detector, so that the concentration (CH 4) of the methane in the sample gas is measured; the non-methane total hydrocarbon concentration was then determined by subtraction: c (NMHC) = C (THC) -C (CH 4), time resolution as low as 1s. Due to the internal characteristics of the equipment, the T90 response time is redefined in the embodiment of the invention, the T90 response time is divided into two stages, namely T1 and T2 (shown in figure 3), and the embodiment of the invention illustrates how the T1 and T2 time is controlled to achieve the same effect of the total hydrocarbon and methane response time in the measurement process.
In summary, the technical scheme of the embodiment of the invention has the following beneficial effects: 1. the portable gas chromatograph can realize on-site monitoring and can realize high-time resolution detection of the content of non-methane total hydrocarbons in the sample gas; 2. the portable chromatograph can effectively solve the problem of large data deviation caused by sample timeliness caused by third-party detection. 3. The system response time of the total hydrocarbons and the methane is the same, so that the accuracy of the measured data can be ensured, that is, the concentrations of the total hydrocarbons and the methane at the same time point are obtained, and the accurate concentration of the non-methane total hydrocarbons in the sample gas at the same time period is calculated. 4. The catalysis method-FID method can be used in the fields of factories and aviation vehicles, can capture the concentration value of non-methane total hydrocarbons in real time, and can draw a concentration trend curve. 5. Non-methane total hydrocarbon is measured with high time resolution, and second-level measurement is realized; the response time of the total hydrocarbon and the methane is kept the same at all times, so that the difference of the measured concentration caused by the difference of the response time is avoided
Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; the technical solutions described in the foregoing embodiments can be modified by those skilled in the art, or some or all of the technical features can be equivalently replaced; and these modifications or substitutions do not depart from the spirit of the corresponding technical solutions of the embodiments of the present invention.
Claims (7)
1. A high time resolution non-methane total hydrocarbon detection device is characterized by comprising a sample collection unit and a host;
the host machine comprises an air source supply unit, a catalytic furnace, a flow control unit, a detection unit and a signal processing unit; the sample collection unit comprises a sampling pump, a heat tracing pipe and a sampling probe rod; a metal sintering filter is arranged at the sampling probe rod; the catalytic furnace comprises a catalyst and a heating and heat-insulating material; the flow control unit comprises a first electronic mass flow controller and a second electronic mass flow controller; the detection unit comprises a total hydrocarbon FID detector and a methane FID detector; the signal processing unit comprises a micro-current signal processor I and a micro-current signal processor II; the gas source supply unit comprises a low-pressure hydrogen storage bottle, a sample gas pipeline and an air pipeline; the sample gas pipeline comprises a total hydrocarbon gas circuit and a methane gas circuit;
wherein, the sampling pump is arranged at the tail end of the heat tracing pipe; the head end of the heat tracing pipe is connected with the tail end of the sampling probe rod; a metal sintering filter is arranged at the sampling probe rod; the gas outlet end of the sampling pump is respectively connected with the head end of the total hydrocarbon gas circuit and the head end of the methane gas circuit through a tee joint; the total hydrocarbon gas circuit is internally provided with a first electronic mass flow controller, a total hydrocarbon column and a proportional valve; wherein, the electronic mass flow controller is connected with the head end of the total hydrocarbon column; the proportional valve is connected with the tail end of the total hydrocarbon column; the total hydrocarbon gas circuit is provided with a total hydrocarbon FID detector and a micro-current signal processor I; the micro-current signal processor is electrically connected with the total hydrocarbon FID detector; the head end of the air pipeline is provided with a high-efficiency hydrocarbon removing filter; a catalytic furnace and an electronic mass flow controller II are arranged in the methane gas path; the tail end of the catalytic furnace is connected with a second electronic mass flow controller; a methane FID detector and a micro-current signal processor II are arranged in the methane gas circuit; the methane FID detector is electrically connected with the second micro-current signal processor;
the proportional valve is used for regulating the air resistance of the pipeline so as to regulate the total hydrocarbon flow in the total hydrocarbon column;
the total hydrocarbon FID detector is used for generating a continuous micro-current signal by responding to the total hydrocarbon in the total hydrocarbon gas circuit in real time;
the first micro-current signal processor is used for amplifying micro-current signals generated by the total hydrocarbon FID detector and performing integral quantitative analysis on the signals to obtain the total hydrocarbon concentration in the current total hydrocarbon gas circuit;
the first electronic mass flow controller is used for adjusting the total hydrocarbon flow in the total hydrocarbon gas circuit;
a catalytic furnace is arranged in the methane gas circuit, the tail end of the methane gas circuit is connected with the head end of the catalytic furnace, a methane FID detector and a micro-current signal processor II are mounted at the tail end of the catalytic furnace, the methane FID detector is connected with the micro-current signal processor II, and an electronic mass flow controller II is arranged at the head end of the methane gas circuit;
the methane FID detector is used for generating a continuous micro-current signal by responding to methane in the methane gas circuit in real time;
the second micro-current signal processor is used for amplifying the micro-current signals generated by the methane FID detector and carrying out integral quantitative analysis on the signals to obtain the current methane concentration in the methane gas circuit;
and the second electronic mass flow controller is used for adjusting the methane flow in the methane gas circuit.
2. A high time resolution non-methane total hydrocarbon detection method, characterized in that, based on the high time resolution non-methane total hydrocarbon detection device of claim 1 to realize detection processing, comprising the following steps:
a sampling pump negative pressure extracts initial sample gas from the external environment, and the initial sample gas is completely vaporized by stabilizing high temperature through a heat tracing pipe;
the completely vaporized initial sample gas passes through a metal sintering filter at the sampling probe rod to obtain pure sample gas; after being processed by positive pressure, the sample gas is equivalently conveyed to a total hydrocarbon gas circuit and a methane gas circuit through a tee joint; the total hydrocarbon FID response time is made the same as the methane FID response time by varying the length of the total hydrocarbon column;
after the sample gas in the total hydrocarbon gas circuit is conveyed to the total hydrocarbon column through the first electronic mass flow controller, a total hydrocarbon FID detector in the total hydrocarbon column senses the total hydrocarbon in the pure sample gas in the total hydrocarbon column to generate a total hydrocarbon FID micro-current signal; the first micro-current signal processor acquires a total hydrocarbon FID micro-current signal, and calculates to obtain the total hydrocarbon concentration;
the sample gas in the methane gas circuit is processed through a catalytic furnace to obtain a catalyzed sample gas, the catalyzed sample gas enters a methane column through a second electronic mass flow controller, and a methane FID detector in the methane gas circuit induces methane in the catalyzed sample gas to generate a methane FID micro-current signal; the second micro-current signal processor acquires methane FID micro-current signals and calculates the methane concentration;
the non-methane total hydrocarbon concentration C (NMHC) is calculated from the methane concentration C (CH 4) and the total hydrocarbon concentration C (THC) by:
C(NMHC)＝C(THC)-C(CH4)。
3. the method of claim 2, wherein the heat tracing pipe is 2m long and the temperature is maintained at 120 ℃.
4. The method as claimed in claim 2, wherein the heat tracing pipe and the sampling probe are inert pipes.
5. The method of claim 2, wherein the metal sintered filter has a filter fineness of 0.2 μm.
6. The method for detecting the non-methane total hydrocarbons with high time resolution according to claim 2, wherein the catalytic furnace carries out catalytic treatment to the catalyzed sample gas, and specifically comprises:
and setting the working temperature of the catalytic furnace, controlling the working temperature to be at a high temperature of 280 ℃ and controlling the catalytic flow to be 50ml/min for high-efficiency catalysis.
7. The method for detecting non-methane total hydrocarbons with high time resolution according to claim 2, wherein the total hydrocarbon FID response time is the same as the methane FID response time by changing the length of the total hydrocarbon column, comprising the following steps:
the flow controller obtains the response time of a total hydrocarbon FID detector in a total hydrocarbon gas circuit and the response time of a methane FID detector in a methane gas circuit, and then calculates the total hydrocarbon concentration obtained when the total hydrocarbon FID detector in the total hydrocarbon gas circuit responds to total hydrocarbons and the methane concentration obtained when the methane FID detector in the methane gas circuit responds to methane according to the total hydrocarbon concentration obtained by calculation;
defining a total hydrocarbon response time T90= T11+ T12; unit: s;
defining a methane response time T90= T21+ T22; unit: s;
wherein the first response time of the total hydrocarbons is recorded as T11, and the time of the stabilization moment after the second response of the total hydrocarbons is recorded as T12;
wherein, the first response time of methane is recorded as T21, and the time of the stable moment after the second response of methane is recorded as T22;
the flow control unit defines the moment when the measured total hydrocarbon concentration is the same as the methane concentration as T1 and defines the moment when the measured total hydrocarbon concentration is the same as the methane concentration as T2 after the measured total hydrocarbon concentration is the same as the methane concentration according to the total hydrocarbon concentration of the response time of the total hydrocarbon FID detector and the methane concentration of the response time of the methane FID detector, and at the moment, T12= T22;
the flow control unit controls the flow Q1 of the total hydrocarbon gas circuit to be the same as the flow Q2 of the methane gas circuit by changing the length of the total hydrocarbon column, so that the first response time of the total hydrocarbon is the same as the first response time of the methane, namely T11= T21; the total hydrocarbon column change length formula is as follows:
ΔL＝(T11-T21)÷60*Q1÷S；
wherein Δ L (mm) is the total hydrocarbon column change length;
s (cm 2) is the cross-sectional area of the pipeline;
t11 is total hydrocarbon first response time;
t21 is the methane first response time;
q1 (ml/min) is the total hydrocarbon gas path flow.
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| CN117054511A (en) * | 2023-10-13 | 2023-11-14 | 杭州盈创环境科技有限公司 | Non-methane total hydrocarbon detection device and method based on double detectors |
| CN117147671A (en) * | 2023-10-30 | 2023-12-01 | 杭州盈创环境科技有限公司 | Non-methane total hydrocarbon detection device and method based on dilution technology |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN117054511A (en) * | 2023-10-13 | 2023-11-14 | 杭州盈创环境科技有限公司 | Non-methane total hydrocarbon detection device and method based on double detectors |
| CN117054511B (en) * | 2023-10-13 | 2024-01-12 | 杭州盈创环境科技有限公司 | Non-methane total hydrocarbon detection device and method based on double detectors |
| CN117147671A (en) * | 2023-10-30 | 2023-12-01 | 杭州盈创环境科技有限公司 | Non-methane total hydrocarbon detection device and method based on dilution technology |
| CN117147671B (en) * | 2023-10-30 | 2024-02-06 | 杭州盈创环境科技有限公司 | Non-methane total hydrocarbon detection device and method based on dilution technology |
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