Direct sample injection gas chromatograph calibration device

Abstract

The utility model discloses a direct sample injection gas chromatograph calibration device, which relates to the technical field of dilution gas distribution, and comprises a standard gas inlet and a diluted gas inlet, the standard gas inlet is sequentially connected with a first electromagnetic valve, a first proportional valve and a first gas flow sensor, and the diluted gas inlet is sequentially connected with a second electromagnetic valve, a second proportional valve and a second gas flow sensor. The diluted gas inlet is sequentially connected with a second electromagnetic valve, a second proportional valve and a second gas flow sensor, the outlet end of the first gas flow sensor and the outlet end of the second gas flow sensor are connected to the inlet end of the mixing chamber, and the outlet of the mixing chamber is connected with a gas pressure sensor, a proportional valve and an adjustable gas resistor. The components are connected in parallel to adjust gas pressure. The adjustable gas resistor is connected to a sample gas outlet and a chromatographic instrument sample introduction module, so that automatic dilution and constant-pressure sample introduction are realized. The device reduces errors of a traditional method and is particularly suitable for treating toxic gas. And standard gas can be continuously and stably output, full-automatic work of single-time gas inlet or multiple-time gas inlet according to a set program can be achieved, and the calibration efficiency is improved.

Description

TECHNICAL FIELD

[0001] The utility model relates to the technical field of dilution gas distribution, and specifically relates to a direct sampling gas chromatograph calibration device. BACKGROUND

[0002] In the field of environmental detection, the detection of volatile organic compounds in fixed pollution source waste gas and environmental air is increasingly concerned. Volatile organic compounds (VOCs) are organic compounds that can volatilize into a gaseous state at room temperature. They exist widely in industrial waste gas, automobile exhaust and indoor air, and pose potential threats to human health and the environment. In order to accurately detect these organic compounds, gas chromatography technology is widely used. For example, "Fixed Pollution Source Waste Gas-Volatile Halogenated Hydrocarbons Determination Gas Bag Sampling-Gas Chromatography Method (HJ1006-2018)", "Environmental Air Total Hydrocarbon, Methane and Non-Methane Total Hydrocarbon Determination Direct Sampling-Gas Chromatography Method (HJ 604-2017)", "Fixed Pollution Source Waste Gas Benzene Series Determination Gas Bag Sampling / Direct Sampling-Gas Chromatography Method (HJ 1261-2022)" and other environmental monitoring standards are currently commonly used. The volatile organic compound testing methods mentioned in these standards all require a certain volume of sample to be directly injected into a gas chromatograph for separation and analysis.

[0003] In order to ensure the accuracy and reliability of the analysis data, the periodic calibration of the gas chromatograph is particularly important. There are two common methods for the injection of standard gas: injection through a syringe or injection through a multi-port valve. When using a multi-port valve for injection, the hand-squeezing gas bag method is usually chosen. When the instrument uses multi-point calibration, it is generally necessary to use high-concentration standard gas to prepare standard gas with different concentration gradients. Taking the direct sampling test of benzene series as an example, the "HJ 1261-2022 Fixed Pollution Source Waste Gas Benzene Series Determination Gas Bag Sampling / Direct Sampling-Gas Chromatography Method" standard mentions that at least five concentration points should be prepared for the standard curve. If a six-port valve is used for injection, the sampling gas bag should be squeezed for more than 45s to complete the injection. This manual operation process is usually time-consuming and labor-intensive, and requires high skills and patience from the operator. For the testing of samples of toxic and harmful gases, the use of a syringe or a squeezed gas bag for injection also poses potential occupational hazards.

[0004] In order to reduce the amount of manual operation, some equipment manufacturers use a diaphragm pump as a power source to suck the sample from the gas bag and then inject it for analysis. Despite this, the standard gas still needs to be prepared in a gas bag in advance, and this process requires strict operation and control. There are many uncertain factors in the transfer process of the standard gas, such as the adsorption and sealing properties of the gas bag, which can affect the accuracy of the results and the reliability of the analysis, so a direct sampling gas chromatograph calibration device is proposed. SUMMARY

[0005] In order to solve the above problems, that is, to solve the problems proposed in the above background technology, the utility model provides a kind of direct sample gas chromatograph calibration device, it includes standard gas inlet and dilution gas inlet, the standard gas inlet is sequentially connected with first electromagnetic valve, first proportional valve and first gas flow sensor, the dilution gas inlet is sequentially connected with second electromagnetic valve, second proportional valve and second gas flow sensor, the second gas flow sensor of first gas flow sensor is respectively connected to the import end of mixing chamber, the outlet end of mixing chamber is sequentially connected adjustable gas resistance, sample gas outlet and chromatograph sample module, the outlet end of mixing chamber is also connected with gas pressure sensor and third proportional valve in parallel, the output end of third proportional valve is sequentially connected with float flowmeter and waste gas treatment module.

[0006] The utility model further provides: the gas pressure sensor and third proportional valve are used for monitoring and adjusting the output pressure of sample gas, and gas pressure sensor is located third proportional valve front end.

[0007] The utility model further provides: first electromagnetic valve, first proportional valve, first gas flow sensor, chromatograph sample module, second electromagnetic valve, second proportional valve, second gas flow sensor, gas pressure sensor and third proportional valve are electrically connected intelligent control system.

[0008] The utility model further provides: the intelligent control system includes the circuit control module for controlling valve state, signal processing and transmission module for gathering sensor data, communication module and display operation module for start-stop control, which are connected with each other.

[0009] The utility model further provides: adjustable gas resistance is precision stainless steel needle type valve with scale, and valve body is treated by silanization inert.

[0010] The beneficial technical effect of the utility model discloses: mixed chamber export connects gas pressure sensor, proportional valve and adjustable air resistance, three parallelly arranged, for adjusting and stabilizing the pressure of output gas.Adjustable air resistance connects sample gas export, chromatograph sample module.This device cleverly realizes the function of automatic dilution of gas, constant pressure sampling and starting analysis, effectively avoids the error and uncertainty caused by standard gas transfer storage and manual sampling in traditional method, especially suitable for the safe operation demand of toxic and harmful gas.The device is designed with float flowmeter and waste gas treatment module, can monitor the emission of waste gas in real time, and handles the waste gas generated in the experiment, reduces environmental pollution, and the operator does not need to directly contact standard gas, greatly reduces the operation risk.In addition, the device can realize continuous and stable standard sample gas output, can single automatic air intake or automatic work according to the preset program, improves the calibration efficiency, reduces the tediousness of manual operation and possible human error.Suitable for single point and multi-point calibration of gas analyzer, can meet different calibration requirements, can be used for benzene series, halogenated hydrocarbon, non-methane total hydrocarbon and other gas analysis test, has wide application range. BRIEF DESCRIPTION OF DRAWINGS

[0011] Figure 1 It is the structure schematic diagram of the utility model.

[0012] Figure 2 It is the multi-point calibration curve of hydrogen flame ionization gas chromatograph instrument methane sample of the utility model.

[0013] Figure 3 It is the superimposed spectrum of different concentration points of hydrogen flame ionization gas chromatograph instrument methane sample of the utility model.

[0014] The figure sign: 1, intelligent control system, 2, standard gas inlet, 3, first electromagnetic valve, 4, first proportional valve, 5, first gas flow sensor, 6, mixed chamber, 7, adjustable air resistance, 8, sample gas export, 9, chromatograph sample module, 10, dilution gas inlet, 11, second electromagnetic valve, 12, second proportional valve, 13, second gas flow sensor, 14, gas pressure sensor, 15, third proportional valve, 16, float flowmeter, 17, waste gas treatment module. DETAILED DESCRIPTION

[0015] The technical scheme in the embodiments of the utility model will be described clearly and completely in combination with the drawings in the embodiments of the utility model, and obviously, the described embodiments are only part of the embodiments of the utility model, not all the embodiments.Based on the embodiments in the utility model, all other embodiments obtained by the person skilled in the art without making creative labor belong to the protection scope of the utility model.

[0016] Please refer toFigures 1-3 The utility model provides a technical scheme: a kind of direct sample introduction gas chromatograph calibration device, including standard gas inlet 2 and dilution gas inlet 10, standard gas inlet 2 is sequentially connected with first electromagnetic valve 3, first proportional valve 4 and first gas flow sensor 5, dilution gas inlet 10 is sequentially connected with second electromagnetic valve 11, second proportional valve 12 and second gas flow sensor 13, the present application scheme mainly discusses two dilution gas distribution, this device can also be expanded multiple dilution gas distribution according to demand, gas flow sensor and proportional valve are used to adjust the flow of standard gas and dilution gas.Gas flow sensor and proportional valve feedback regulation, closed loop control gas flow through proportional valve.By changing the flow of standard gas and dilution gas, continuously output certain concentration gas sample, its concentration interval is 0%~100% of standard gas concentration, the outlet end of first gas flow sensor 5 and second gas flow sensor 13 is connected to the inlet end of mixing chamber 6 respectively, the outlet end of mixing chamber 6 is sequentially connected adjustable gas resistance 7, sample gas outlet 8 and chromatograph sample introduction module 9, the outlet end of mixing chamber 6 is also connected with gas pressure sensor 14 and third proportional valve 15 in parallel, the output end of third proportional valve 15 is sequentially connected with float flowmeter 16 and waste gas treatment module 17.

[0017] First electromagnetic valve 3, first proportional valve 4, first gas flow sensor 5, chromatograph sample introduction module 9, second electromagnetic valve 11, second proportional valve 12, second gas flow sensor 13, gas pressure sensor 14 and third proportional valve 15 are electrically connected with intelligent control system 1.

[0018] Intelligent control system 1 includes circuit control module for controlling valve state, signal processing and transmission module for collecting sensor data, communication module for communicating with chromatograph and display operation module, and is connected with each other, intelligent control system 1 can realize single or sequence automatic dilution gas distribution by inputting existing preparation method, and can edit, store, call etc. Operation to sequence, can record data or output through display operation module, and has the function of communicating with chromatograph.Sequence is different concentration standard gas sample preparation method arranged in order, including gas type, gas concentration, duration, running interval, output gas concentration, output gas total flow, execution times etc. Parameters.Running interval is greater than the cycle time of chromatograph sample analysis.Cycle time is the time when chromatograph sample analysis is completed and reaches ready state.Communication module is the function of sending start analysis signal after gas distribution is completed and receiving stop analysis signal to start next gas distribution.Sequence gas distribution, stop gas distribution in running interval, after receiving analysis completion signal, automatically cut into next step dilution gas distribution.

[0019] Gas pressure sensor 14 and third proportional valve 15 are used to monitor and adjust the output pressure of sample gas, and gas pressure sensor 14 is located at the front end of third proportional valve 15 to provide real-time feedback of upstream pressure, and according to the threshold value between the measured value and the set value, the third proportional valve 15 is adjusted in real time.

[0020] Adjustable gas resistance 7 is a precision stainless steel needle valve with scale and the valve body is inert treated by silanization, which is used to form stable output pressure and adjust the size of gas resistance according to the demand.

[0021] The detailed connection means is a well-known technology in the art, and the working principle and process are mainly introduced below.

[0022] The calculation principle of the gas distribution of the present calibration device is as follows: the concentration of the standard component gas, the target concentration of the output sample gas, and the total output flow of the system are input in the intelligent control system 1 display operation module, the system automatically calculates the target flow of the standard component gas channel and the dilution gas channel, and outputs the real-time output concentration of the sample gas component. The specific calculation formula is as follows:

[0023]

[0024] In the formula:

[0025] q c — the input flow of the standard component gas channel, mL / min;

[0026] c i — the target concentration of the diluted standard component gas;

[0027] q t — the set total output flow of the system;

[0028] c o — the initial concentration of the standard component gas.

[0029]

[0030] c (rt)i — the real-time output concentration of the diluted standard component gas;

[0031] q (rt)i — the real-time flow of the standard component gas channel, mL / min;

[0032] q (rt)t — the sum of the real-time input flow of the dilution gas and all standard component gas channels, mL / min;

[0033] Further, the intelligent operation system of the present calibration device also includes the calculation result of the standard uncertainty of dilution ratio, and the calculation method is as follows:

[0034] The dilution ratio of the present calibration device is calculated according to formula (3):

[0035]

[0036] In the formula:

[0037] Dilution ratio, %;

[0038] q c Flow rate of standard gas channel, mL / min;

[0039] q d Flow rate of dilution gas channel, mL / min.

[0040] Differentiating formula (3), we have:

[0041]

[0042] The standard uncertainty of the dilution ratio can be expressed as:

[0043]

[0044] Substituting formula (4) and (5) into formula (6), the relative uncertainty of the dilution ratio of the present calibration device can be expressed as:

[0045]

[0046] That is:

[0047]

[0048] Example 1: Taking the methane multi-point calibration in a non-methane total hydrocarbon test experiment with a gas chromatograph instrument with a hydrogen flame ionization detector as an example, the working process of the gas calibration device in the figure is briefly described.

[0049] (1) Methane gas standard in nitrogen: 512 μmol / mol.

[0050] (2) Working process: Connect the methane standard gas and high-purity nitrogen into the standard gas inlet 2 and the dilution gas inlet 10 respectively, and connect the sample gas outlet 8 to the sample injection module of the gas chromatograph instrument with a hydrogen flame ionization detector. Set the information of the input gas source in the display operation module, and output the gas concentration, flow rate, pressure, sequence information and other parameters. The sequence is dilution gas preparation with 5 concentration points, the instrument starts to prepare gas, the first solenoid valve 3 and the second solenoid valve 11 are opened at the same time, the proportional valve and the gas flow sensor adjust the flow rate according to the dilution ratio, and the mixed gas is output after being mixed uniformly in the mixing chamber 6.

[0051] (3) Gas chromatograph analysis conditions:

[0052] Column temperature: 80°C, detector temperature: 200°C, carrier gas: nitrogen, column flow: 30 ml / min, hydrogen: 30 ml / min, auxiliary gas: 300 ml / min.

[0053] The applicant has carried out the drawing of the methane multi-point calibration curve by the device of the accompanying drawings and the method of the specification, and the result data is shown in Table 1.

[0054] Table 1: Calibration curve concentration and response value

[0055] Target concentration (pmol / mol) Peak area (mV) Standard point 1 32 11.120 Standard point 2 64 22.812 Standard point 3 128 46.495 Standard point 4 256 93.354 Standard point 5 512 188.143

[0056] Although the embodiments of the present application have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions and alterations can be made thereto without departing from the principles and spirit of the present application, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A gas chromatograph calibration device for direct injection, comprising a standard gas inlet (2) and a dilution gas inlet (10), characterized in that: The standard gas inlet (2) is connected in sequence to a first electromagnetic valve (3), a first proportional valve (4) and a first gas flow sensor (5); the dilution gas inlet (10) is connected in sequence to a second electromagnetic valve (11), a second proportional valve (12) and a second gas flow sensor (13); the outlet ends of the first gas flow sensor (5) and the second gas flow sensor (13) are respectively connected to the inlet end of the mixing chamber (6); the outlet end of the mixing chamber (6) is connected in sequence to an adjustable gas resistance (7) and a sample gas outlet (8); the outlet end of the mixing chamber (6) is also connected in parallel to a gas pressure sensor (14) and a third proportional valve (15); the output end of the third proportional valve (15) is connected in sequence to a float flowmeter (16) and an exhaust gas treatment module (17).

2. The gas chromatograph calibration device for direct injection according to claim 1, characterized in that: The gas pressure sensor (14) and the third proportional valve (15) are used to monitor and adjust the output pressure of the sample gas, and the gas pressure sensor (14) is located at the front end of the third proportional valve (15).

3. The gas chromatograph calibration device for direct injection according to claim 1, characterized in that: The first solenoid valve (3), the first proportional valve (4), the first gas flow sensor (5), the second solenoid valve (11), the second proportional valve (12), the second gas flow sensor (13), the gas pressure sensor (14) and the third proportional valve (15) are all electrically connected to the intelligent control system (1).

4. The gas chromatograph calibration device for direct injection according to claim 3, characterized in that: The intelligent control system (1) comprises a circuit control module for controlling valve status, a signal processing and transmission module for collecting sensor data, a communication module for communicating with a gas chromatograph and controlling an operation interval, and a display operation module, which are interconnected. The intelligent control system (1) is used for single or sequential automatic dilution and gas preparation; the sequence is a method for preparing standard gas samples of different concentrations arranged in sequence and set in advance, specifically including standard gas type, standard gas concentration, duration, operation interval, output gas concentration, output gas total flow rate, and execution times; the operation interval is greater than the cycle time of sample analysis of the chromatograph; The cycle time is the time it takes for the chromatograph to complete sample analysis and reach a ready state. The communication module is used to send a start analysis signal after gas distribution is completed and receive a stop analysis signal to start the next gas distribution.

5. The gas chromatograph calibration device with direct injection according to claim 1, characterized in that: The adjustable air resistance (7) is a precision stainless steel needle valve with a scale, and the valve body has been subjected to silanization inert treatment.

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