A device and method for quantitatively analyzing non-methane total hydrocarbons

Abstract

The present invention relates to a device and method for quantitatively analyzing non-methane total hydrocarbons, and belongs to the field of gas analysis and detection. The device of the present invention comprises a non-methane cutter; the non-methane cutter comprises a catalytic oxidizer and a methane separator; the catalytic oxidizer is connected to the methane separator. When the sample gas contains ethane, the catalytic oxidizer oxidizes the ethane to the maximum extent under the premise that all methane is retained, and all other organic compounds are oxidized, and the methane separator then separates the methane from the unoxidized ethane, so that the methane can be accurately quantified, and then the non-methane total hydrocarbons can be accurately quantified. In addition, the high-boiling point organic compounds are all oxidized into carbon dioxide and water, and there is no residue in the device, which will not interfere with the next analysis cycle.

Description

Technical Field

[0001] The invention relates to a device and a method for quantitatively analyzing non-methane total hydrocarbons, belonging to the field of gas analysis and detection. Background Art

[0002] Total hydrocarbons refer to all hydrocarbons and their derivatives. The main part that pollutes the ambient air is the gaseous and liquid part at room temperature but has high volatility. Non-methane total hydrocarbons usually refer to all volatile hydrocarbons and their derivatives (mainly C2-C8) except methane. Under experimental conditions, the total amount of gaseous hydrocarbons and their heteroatom-substituted compounds measured by a hydrogen flame ionization detector (FID) minus the content of the methane part is the non-methane total hydrocarbons. A high concentration of non-methane total hydrocarbons generally indicates a high content of organic pollutants in the air or exhaust gas. In addition to being directly harmful to human health, under certain conditions, hydrocarbons and nitrogen oxides in the atmosphere produce a series of photochemical reactions under sunlight to form photochemical smog, which causes further harm to the environment and humans. Therefore, the maximum allowable emission concentration, maximum allowable emission rate and unorganized emission limit of non-methane total hydrocarbons are clearly stipulated in the comprehensive emission standards for atmospheric pollutants.

[0003] The generally accepted method for determining non-methane total hydrocarbons is to determine the total hydrocarbon and methane content separately, and then subtract the two to obtain the non-methane total hydrocarbon content. For total hydrocarbon determination, the sample gas is usually continuously flowed into the FID detector at a fixed flow rate, or a carrier gas (zero gas) is used to bring a fixed volume of sample gas into the FID detector. This is the standard method for total hydrocarbon determination. At present, there are three main methods for methane determination: infrared analysis, gas chromatography-FID, and catalytic oxidation-FID. Among them, infrared analysis is the simplest, but its sensitivity is one order of magnitude lower than that of the FID method, and it is easily affected by the temperature and water content of the sample gas, which reduces its stability.

[0004] The National Environmental Protection Standard of the People's Republic of China "Gas Chromatography Method for Determination of Total Hydrocarbons, Methane and Non-methane Total Hydrocarbons in Waste Gas from Stationary Pollution Sources" (HJ 38-2017) recommends a gas chromatography analysis method for methane, which is to first separate methane from other organic matter using a porous polymer gas-solid chromatography column, and then use an FID detector for integration and quantification. In addition, Chinese patents with publication numbers CN105987967B, CN104849374B, and CN205426869U also use a gas-solid chromatography column separation-FID quantification method to analyze methane. Although this type of method can completely separate methane from other organic matter and obtain undisturbed analysis results, the gas-solid chromatography column has a strong retention of high-boiling point organic matter. Although the column can be regenerated to a certain extent by backflushing the column, there is a high probability that high-boiling point organic matter will still remain, and it is difficult to return to the ideal state under mild conditions.

[0005] Chinese patent applications with publication numbers CN106053652A and CN110411973A disclose a device for analyzing methane by catalytic oxidation, i.e., using a catalytic oxidation catalyst to oxidize organic matter other than methane into carbon dioxide and water and other substances that do not respond to the FID detector, and the effective component of the catalyst used is usually transition metal oxides such as copper, manganese, cobalt, nickel, or precious metals such as platinum and palladium. This method can avoid the pollution problem of high-boiling point organic matter in the gas chromatography-FID method. Ideally, it should be ensured that other organic matter is completely reacted without loss of methane content, but the main problem is that when the sample gas contains ethane, since the oxidation reaction temperatures of ethane and methane are very close, when ethane is completely catalytically burned, the methane loss is usually more than 10%, and as the use time increases, the catalyst activity will decrease, resulting in an increase in the amount of ethane remaining, thereby affecting the accuracy of the determination of non-methane total hydrocarbons. Summary of the invention

[0006] The present invention solves the above problems by using a device with a new structure to quantitatively analyze non-methane total hydrocarbons.

[0007] The invention provides a device for quantitatively analyzing non-methane total hydrocarbons, the device comprising a non-methane cutter; the non-methane cutter comprising a catalytic oxidizer and a methane separator; the catalytic oxidizer is connected to the methane separator.

[0008] The function of the catalytic oxidizer in the present invention is: when the sample gas contains ethane, only part of the ethane is oxidized into carbon dioxide and water to retain all the methane, while the remaining organic compounds are all oxidized into carbon dioxide and water.

[0009] The methane separator of the present invention has the function of separating methane from the remaining unoxidized ethane.

[0010] In the present invention, the methane separator is preferably a packed column.

[0011] In the present invention, the filler of the filling column is preferably zeolite molecular sieve or porous silica gel.

[0012] The filler of the present invention is preferably zeolite molecular sieve or porous silica gel for the purpose of preventing performance degradation due to air oxidation and maintaining water content balance at a certain temperature to achieve stable performance.

[0013] In the present invention, the particle size of the zeolite molecular sieve is preferably 100-600 μm and the effective pore size is 0.5-1.3 nm.

[0014] In the present invention, the mesh size of the porous silica gel is preferably 20-100 mesh and the pore size is 15-30 nm. The mesh size of the porous silica gel is further preferably 60-80 mesh or 80-100 mesh.

[0015] In the present invention, the column length of the packed column is preferably 0.5-2 m and the inner diameter is 1-5 mm.

[0016] The present invention preferably comprises an injector I, a total unretained hydrocarbon column, a hydrogen flame ionization detector, and an injector II; the injector I is connected to the hydrogen flame ionization detector via the total unretained hydrocarbon column; the injector II is connected to the hydrogen flame ionization detector via a catalytic oxidizer and a methane separator in sequence.

[0017] The present invention preferably comprises the injector I comprising a two-position three-way valve I, a quantitative ring I, a two-position three-way valve II, and a two-position three-way valve III; the outlet of the two-position three-way valve I is connected to the inlet of the two-position three-way valve II through the quantitative ring I, the outlet II of the two-position three-way valve II is connected to the inlet II of the two-position three-way valve III, and the outlet of the two-position three-way valve III is connected to a hydrogen flame ionization detector through an unretained total hydrocarbon column; the injector II comprises a two-position three-way valve IV, a quantitative ring II, a two-position three-way valve V, and a two-position three-way valve VI; the outlet of the two-position three-way valve IV is connected to the inlet of the two-position three-way valve V through the quantitative ring II, the outlet II of the two-position three-way valve V is connected to the inlet II of the two-position three-way valve VI, and the outlet of the two-position three-way valve VI is connected to a hydrogen flame ionization detector through a catalytic oxidizer and a methane separator in sequence.

[0018] The present invention preferably comprises a flow controller I and a flow controller II; the flow controller I is connected to the inlet I of the two-position three-way valve III, and the inlet II of the two-position three-way valve I is connected between the flow controller I and the inlet I of the two-position three-way valve III; the flow controller II is connected to the inlet I of the two-position three-way valve VI, and the inlet II of the two-position three-way valve IV is connected between the flow controller II and the inlet I of the two-position three-way valve VI.

[0019] Another object of the present invention is to provide a method for quantitatively analyzing non-methane total hydrocarbons using the above-mentioned device, and the method includes the following steps: zero gas I carries sample gas I through an unretained total hydrocarbon column and then enters a hydrogen flame ionization detector to obtain a signal peak of total hydrocarbons, and the signal peak of total hydrocarbons is integrated to obtain the concentration value of total hydrocarbons; zero gas II carries sample gas II through a catalytic oxidizer first, and when sample gas II contains ethane, ethane is oxidized to the maximum extent while retaining all methane, and all other organic compounds are oxidized, and then methane is separated from unoxidized ethane through a methane separator, and then enters a hydrogen flame ionization detector to obtain a signal peak of methane, and the signal peak of methane is integrated to obtain the concentration value of methane, zero gas II is the same as zero gas I, and sample gas II is the same as sample gas I; the concentration value of total hydrocarbons is subtracted from the concentration value of methane, and finally the concentration value of non-methane total hydrocarbons is obtained.

[0020] In order to oxidize ethane to the maximum extent while retaining all methane and completely oxidize the remaining organic compounds, the flow rate of Zero Gas II is controlled at 10-80mL / min and the temperature of the catalytic oxidizer is controlled at 150-300℃ according to different catalytic oxidizers.

[0021] The beneficial effects of the present invention are:

[0022] When the sample gas contains ethane, the catalytic oxidizer will oxidize ethane to the maximum extent while retaining all the methane, and all the other organic compounds will be oxidized. The methane separator will then separate the methane from the unoxidized ethane, so that the methane can be accurately quantified, and then the non-methane total hydrocarbons can be accurately quantified. In addition, the high-boiling point organic compounds are all oxidized to carbon dioxide and water, without any residue in the device, and will not interfere with the next analysis cycle. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The present invention is attached Figure 3 width,

[0024] Figure 1 This is a working principle diagram of the device in Example 1 in the sample loading state;

[0025] Figure 2 This is a working principle diagram of the detection state of the device described in Example 1;

[0026] Figure 3 This is the chromatogram obtained by the method described in Example 2.

[0027] Wherein: 1. flow controller Ⅰ, 2. two-position three-way solenoid valve Ⅰ, 3. quantitative ring Ⅰ, 4. two-position three-way solenoid valve Ⅱ, 5. two-position three-way solenoid valve Ⅲ, 6. unretained total hydrocarbon column, 7. hydrogen flame ionization detector, 8. flow controller Ⅱ, 9. two-position three-way solenoid valve Ⅳ, 10. quantitative ring Ⅱ, 11. two-position three-way solenoid valve Ⅴ, 12. two-position three-way solenoid valve Ⅵ, 13. catalytic oxidizer, 14. methane separator. DETAILED DESCRIPTION

[0028] The following non-limiting embodiments may enable a person skilled in the art to more fully understand the present invention, but are not intended to limit the present invention in any way.

[0029] Example 1

[0030] A device for quantitatively analyzing non-methane total hydrocarbons, the device comprising a flow controller Ⅰ1, an injector Ⅰ, a non-retained total hydrocarbon column 6, a hydrogen flame ionization detector 7, a flow controller Ⅱ8, an injector Ⅱ, and a non-methane cutter;

[0031] The sample injector I comprises a two-position three-way solenoid valve I2, a quantitative ring I3, a two-position three-way solenoid valve II4, and a two-position three-way solenoid valve III5;

[0032] The sample injector II comprises a two-position three-way solenoid valve IV9, a quantitative ring II10 which is completely identical to the quantitative ring I3, a two-position three-way solenoid valve V11, and a two-position three-way solenoid valve VI12;

[0033] The non-methane cutter includes a catalytic oxidizer 13 and a methane separator 14;

[0034] The outlet of the two-position three-way solenoid valve I2 is connected to the inlet of the two-position three-way solenoid valve II4 through the quantitative ring I3, the outlet II of the two-position three-way solenoid valve II4 is connected to the inlet II of the two-position three-way solenoid valve III5, and the outlet of the two-position three-way solenoid valve III5 is connected to the hydrogen flame ionization detector 7 through the unretained total hydrocarbon column 6;

[0035] The inlet I of the two-position three-way solenoid valve I2 is the inlet of the sample gas I, and the outlet I of the two-position three-way solenoid valve II4 is the outlet of the sample gas I;

[0036] The flow controller Ⅰ1 is connected to the inlet Ⅰ of the two-position three-way solenoid valve Ⅲ5, and the inlet Ⅱ of the two-position three-way solenoid valve Ⅰ2 is connected between the flow controller Ⅰ1 and the inlet Ⅰ of the two-position three-way solenoid valve Ⅲ5;

[0037] The outlet of the two-position three-way solenoid valve IV9 is connected to the inlet of the two-position three-way solenoid valve V11 through the quantitative ring II10, the outlet II of the two-position three-way solenoid valve V11 is connected to the inlet II of the two-position three-way solenoid valve VI12, and the outlet of the two-position three-way solenoid valve VI12 is connected to the hydrogen flame ionization detector 7 through the catalytic oxidizer 13 and the methane separator 14 in sequence;

[0038] The inlet I of the two-position three-way solenoid valve IV9 is the inlet of the sample gas II, and the outlet I of the two-position three-way solenoid valve V11 is the outlet of the sample gas II;

[0039] The flow controller II8 is connected to the inlet I of the two-position three-way solenoid valve VI12, and the inlet II of the two-position three-way solenoid valve IV9 is connected between the flow controller II8 and the inlet I of the two-position three-way solenoid valve VI12;

[0040] The specification of the unretained total hydrocarbon column 6 is 1m (column length)*2.03mm (inner diameter), and the filler of the unretained total hydrocarbon column 6 is silanized quartz sand with a particle size of 0.15-0.18mm;

[0041] The catalytic oxidizer 13 is a catalytic oxidation column, the specification of the catalytic oxidation column is 1.5m (column length)*2.03mm (inner diameter), the filler of the catalytic oxidation column is catalyst particles with a particle size of 0.42-0.85mm, the catalyst carrier is α-alumina, and the carrier is loaded with 10% (w / w) palladium;

[0042] The methane separator 14 is a methane separation column, the specification of which is 1m (column length)*2.03mm (inner diameter), the filler of which is porous silica gel with a mesh size of 80-100 meshes, and the pore size of the porous silica gel is 20-25nm.

[0043] Example 2

[0044] A method for quantitatively analyzing non-methane total hydrocarbons using the device described in Example 1, the method comprising the following steps:

[0045] Condition settings:

[0046] Zero gas I is composed of 20% (v / v) oxygen and 80% (v / v) nitrogen, and zero gas II has the same composition as zero gas I;

[0047] The composition of sample gas I is: methane 1001ppmC, ethane 1996ppmC, propane 3006ppmC, oxygen 20% (v / v), nitrogen 80% (v / v), and the composition of sample gas II is the same as that of sample gas I;

[0048] The temperature of both injector I and injector II is 120°C;

[0049] The temperature of the unretained total hydrocarbon column 6, the hydrogen flame ionization detector 7 and the methane separator 14 are all 180°C;

[0050] In order to oxidize ethane to the maximum extent while retaining all methane and oxidize all propane, according to the catalytic oxidation column, the flow rate of zero gas II is preferably 30 mL / min, and the temperature of the catalytic oxidizer 13 is preferably 180°C;

[0051] The flow rate of zero gas I and zero gas II is the same;

[0052] Loading:

[0053] When the two-position three-way solenoid valve Ⅰ2, two-position three-way solenoid valve Ⅱ4, two-position three-way solenoid valve Ⅲ5, two-position three-way solenoid valve Ⅳ9, two-position three-way solenoid valve Ⅴ11 and two-position three-way solenoid valve Ⅵ12 are powered off, Figure 1 As shown, the inlet I of the two-position three-way solenoid valve I2 is connected to its outlet, the inlet of the two-position three-way solenoid valve II4 is connected to its outlet I, the inlet I of the two-position three-way solenoid valve III5 is connected to its outlet, the inlet I of the two-position three-way solenoid valve IV9 is connected to its outlet, the inlet of the two-position three-way solenoid valve V11 is connected to its outlet I, and the inlet I of the two-position three-way solenoid valve VI12 is connected to its outlet;

[0054] The sample gas I enters from the inlet I of the two-position three-way solenoid valve I2, passes through the outlet of the two-position three-way solenoid valve I2, the quantitative ring I3, the inlet of the two-position three-way solenoid valve II4, and then flows out from the outlet I of the two-position three-way solenoid valve II4. The sample gas I is filled into the quantitative ring I3.

[0055] The sample gas II enters from the inlet I of the two-position three-way solenoid valve IV9, passes through the outlet of the two-position three-way solenoid valve IV9, the quantitative ring II10, the inlet of the two-position three-way solenoid valve V11, and then flows out from the outlet I of the two-position three-way solenoid valve V11, and the sample gas II is filled into the quantitative ring II10;

[0056] Detection:

[0057] When two-position three-way solenoid valve Ⅰ2, two-position three-way solenoid valve Ⅱ4, two-position three-way solenoid valve Ⅲ5, two-position three-way solenoid valve Ⅳ9, two-position three-way solenoid valve Ⅴ11 and two-position three-way solenoid valve Ⅵ12 are energized, Figure 2 As shown, the inlet II of the two-position three-way solenoid valve Ⅰ2 is connected to its outlet, the inlet of the two-position three-way solenoid valve Ⅱ4 is connected to its outlet II, the inlet II of the two-position three-way solenoid valve Ⅲ5 is connected to its outlet, the inlet II of the two-position three-way solenoid valve Ⅳ9 is connected to its outlet, the inlet of the two-position three-way solenoid valve Ⅴ11 is connected to its outlet II, and the inlet II of the two-position three-way solenoid valve Ⅵ12 is connected to its outlet;

[0058] The zero gas I first passes through the flow controller I1, the inlet II of the two-position three-way solenoid valve I2, the outlet of the two-position three-way solenoid valve I2, and the quantitative ring I3 in sequence, and then carries the sample gas I through the inlet of the two-position three-way solenoid valve II4, the outlet II of the two-position three-way solenoid valve II4, the inlet II of the two-position three-way solenoid valve III5, the outlet of the two-position three-way solenoid valve III5, the unretained total hydrocarbon column 6, and the hydrogen flame ionization detector 7 in sequence to obtain the signal peak of the total hydrocarbon, and the signal peak of the total hydrocarbon is integrated to obtain the concentration value of the total hydrocarbon;

[0059] The zero gas II first passes through the flow controller II8, the inlet II of the two-position three-way solenoid valve IV9, the outlet of the two-position three-way solenoid valve IV9, and the quantitative ring II10, and then carries the sample gas II through the inlet of the two-position three-way solenoid valve V11, the outlet II of the two-position three-way solenoid valve V11, the inlet II of the two-position three-way solenoid valve VI12, the outlet of the two-position three-way solenoid valve VI12, the catalytic oxidizer 13, the methane separator 14, and the hydrogen flame ionization detector 7 to obtain the signal peaks of methane and ethane. The signal peaks of methane and ethane are integrated to obtain the concentration values ​​of methane and ethane respectively. After calculation, the recovery rate of methane is 98%, the recovery rate of ethane is 13%, and the propane is completely oxidized.

Claims

1. A device for quantitatively analyzing non-methane total hydrocarbons, characterized in that: The apparatus includes a non-methane cutter; The non-methane cutter includes a catalytic oxidizer and a methane separator; The catalytic oxidizer is connected to the methane separator; The methane separator is a packed column; The filler of the filling column is zeolite molecular sieve or porous silica gel; The particle size of the zeolite molecular sieve is 100-600 μm and its effective pore size is 0.5-1.3 nm; The mesh size of the porous silica gel is 20-100 mesh and the pore size is 15-30 nm; The column length of the packed column is 0.5-2m and the inner diameter thereof is 1-5mm; The device comprises a sample injector I, a total hydrocarbon column without retention, a hydrogen flame ionization detector, and a sample injector II; The injector I is connected to a hydrogen flame ionization detector via a non-retained total hydrocarbon column; The sample injector II is connected to a hydrogen flame ionization detector via a catalytic oxidizer and a methane separator in sequence; The sample injector I comprises a two-position three-way valve I, a quantitative ring I, a two-position three-way valve II, and a two-position three-way valve III; The outlet of the two-position three-way valve I is connected to the inlet of the two-position three-way valve II through the quantitative loop I, the outlet II of the two-position three-way valve II is connected to the inlet II of the two-position three-way valve III, and the outlet of the two-position three-way valve III is connected to the hydrogen flame ionization detector through the unretained total hydrocarbon column; The sample injector II comprises a two-position three-way valve IV, a quantitative ring II, a two-position three-way valve V, and a two-position three-way valve VI; The outlet of the two-position three-way valve IV is connected to the inlet of the two-position three-way valve V through the quantitative ring II, the outlet II of the two-position three-way valve V is connected to the inlet II of the two-position three-way valve VI, and the outlet of the two-position three-way valve VI is connected to the hydrogen flame ionization detector through the catalytic oxidizer and the methane separator in sequence; The device comprises a flow controller I and a flow controller II; The flow controller I is connected to the inlet I of the two-position three-way valve III, and the inlet II of the two-position three-way valve I is connected between the flow controller I and the inlet I of the two-position three-way valve III; The flow controller II is connected to the inlet I of the two-position three-way valve VI, and the inlet II of the two-position three-way valve IV is connected between the flow controller II and the inlet I of the two-position three-way valve VI.

2. A method for quantitatively analyzing non-methane total hydrocarbons using the device of claim 1, characterized in that: The method comprises the following steps: Sample gas I is filled into quantitative loop I, and sample gas II is filled into quantitative loop II; Zero gas I carries sample gas I through the unretained total hydrocarbon column and enters the hydrogen flame ionization detector to obtain the signal peak of total hydrocarbons. The signal peak of total hydrocarbons is integrated to obtain the concentration value of total hydrocarbons. Zero gas II carries sample gas II through the catalytic oxidizer and methane separator in turn and then enters the hydrogen flame ionization detector to obtain the signal peak of methane. The signal peak of methane is integrated to obtain the concentration value of methane. Zero gas II is the same as zero gas I, and sample gas II is the same as sample gas I. The concentration value of non-methane total hydrocarbons was obtained by subtracting the concentration value of methane from the concentration value of total hydrocarbons.

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