Method for analyzing rough nitrogen trifluoride gas by gas chromatography and valve system thereof
Technical Field
The present invention relates to a method for analyzing crude nitrogen trifluoride gas, and more particularly to a method for analyzing by a gas chromatograph.
Background
The existing production method is mainly an electrolytic method, and a plurality of impurity gases, wherein H is contained in the crude nitrogen trifluoride gas produced by electrolysis2Particular attention is paid to the use of the composition as a flammable and explosive component. The prior art scheme for analyzing crude nitrogen trifluoride gas mainly employs a gas chromatography method: helium is used as carrier gas, and nitrogen trifluoride sample gas enters a thermal conductivity detector through a chromatographic column by switching of a sample injection valve for analysis and detection. The disadvantages of this solution are first: the hydrogen has small peak area on a chromatogram taking helium as carrier gas, has low sensitivity and is not beneficial to the on-line monitoring of personnel. Secondly, the method comprises the following steps: because the content of hydrogen in the production process of nitrogen trifluoride gas is not fixed, along with the fluctuation of the content of hydrogen, the chromatographic peak of hydrogen on a thermal conductivity detector using helium as carrier gas can present a positive peak and a negative peak, monitoring personnel need to distinguish the positive and negative of the hydrogen peak, the monitoring is very inconvenient, and even misjudgment and the like can be caused.
Disclosure of Invention
The first technical problem to be solved by the invention is to provide a method for analyzing crude nitrogen trifluoride gas by gas chromatography, which is convenient to monitor and accurate in analysis.
The second technical problem to be solved by the present invention is to provide a valve system for use in a method for analyzing crude nitrogen trifluoride gas by gas chromatography.
For solving the problem that the prior art uses helium as carrier gas in a system H2Small peak response area, and H2The invention has the technical scheme that the method has the following problems that positive and negative peaks appear: a method for analyzing crude nitrogen trifluoride gas by gas chromatography comprises analyzing with a two-valve two-column valve system comprising 1 ten-way valve, 1 six-way valve, 2 quantitative rings, 2 chromatographic columns,2 detectors, 2 electronic gas circuit control modules (EPC) and 2 Pressure Control Modules (PCM).
EPC: (electric pneumatic control) electronic air circuit control module.
PCM: (pressure control model) pressure control module.
The method comprises the following steps:
(1) setting a valve event on gas chromatography operation software for 0min, wherein the states of the ten-way valve and the six-way valve are off, and nitrogen trifluoride sample gas enters a 6 th interface, a 1 st interface, a second quantitative ring, a 4 th interface and a 5 th interface on the six-way valve through a sample inlet and a 7 th interface, an 8 th interface, a first quantitative ring 3, a 5 th interface and a 6 th interface on the ten-way valve and finally enters a recovery pipeline through a sample outlet.
(2) Setting a valve event on gas chromatography operating software for 0.03min, wherein the states of the ten-way valve 1 and the six-way valve are 'on', and after nitrogen carrier gas passes through a PCM (pulse code modulation) module and then passes through a 4 th interface, a 5 th interface, a first quantitative ring, an 8 th interface, a 9 th interface, a first chromatographic column, a 3 rd interface and a 2 nd interface on the ten-way valve, carrying nitrogen trifluoride sample gas in the first quantitative ring into a front detector for analysis and peak appearance; at the moment, helium carrier gas passes through a helium PCM module and then enters a back detector through a 2 nd interface, a 1 st interface, a second quantitative ring, a 4 th interface, a 3 rd interface and a second chromatographic column on the six-way valve to carry nitrogen trifluoride sample gas in the second quantitative ring into the back detector for analysis and peak generation; the remaining components in the nitrogen trifluoride sample gas were successively peaked on the back detector.
(3) Setting a valve event on gas chromatography operation software for 2.5min, wherein the states of the ten-way valve and the six-way valve are off, and the PCM module reversely blows the first chromatographic column to an emptying port through a 4 th interface, a 3 rd interface, a first chromatographic column, a 9 th interface and a 10 th interface on the ten-way valve after nitrogen passes through the nitrogen and then enters a recovery pipeline; and the helium passes through the helium PCM module, and sweeps the components in the second chromatographic column into the rear detector through the interface 2, the interface 3 and the second chromatographic column on the six-way valve for sample analysis.
In order to solve the second technical problem, the invention provides a valve system used in a method for analyzing crude nitrogen trifluoride gas by gas chromatography, which adopts the technical scheme that: a gas chromatography valve system for analyzing crude nitrogen trifluoride gas adopts a two-valve two-column valve system, and comprises 1 ten-way valve, 1 six-way valve, 2 quantitative rings, 2 chromatographic columns, 2 detectors, 2 electronic gas circuit control modules (EPC) and 2 Pressure Control Modules (PCM).
The interface 1 of the ten-way valve is connected to a nitrogen source through PCM before nitrogen, the interface 2 is connected with a front detector and then connected to the nitrogen source through EPC, a first chromatographic column is connected between the interface 3 and the interface 9, the interface 9 is connected with a vent through an interface 10, the interface 4 is connected to the nitrogen source through PCM after nitrogen, a first quantitative ring is connected between the interface 5 and the interface 8, the interface 5 is connected with the interface 6 on the six-way valve through the interface 6, and the interface 8 is connected with a sample inlet through an interface 7;
a second quantitative ring is connected between a 1 st interface and a 4 th interface of the six-way valve, the 2 nd interface is connected to a helium source through helium PCM, the 2 nd interface is connected to the helium source sequentially through a 3 rd interface, a second chromatographic column, a post detector and helium EPC, and the 4 th interface is connected to a sample outlet through a 5 th interface.
The first chromatographic column is preferably a Hayesep Q chromatographic column; the second column is preferably a Shincabon column. The capacity of both the first dosing ring and the second dosing ring is preferably 1 ml.
The front and rear detectors are preferably Thermal Conductivity Detectors (TCDs).
Further, the sample outlet is connected with an external rotor flow meter and then enters a tail gas recovery pipeline.
The flow rate and pressure control of the whole carrier gas system adopts electronic gas circuit control.
When the whole chromatographic system is in an initial state of analysis and detection, the paths of the carrier gas and the nitrogen trifluoride sample gas flowing on the valve circuit are as follows: in a ten-way valve 1-front detector flow path with nitrogen as a carrier gas, the nitrogen carrier gas is controlled by a nitrogen EPC, a nitrogen front PCM and a nitrogen rear PCM module; nitrogen controlled by nitrogen EPC is used as reference gas and tail gas is blown to directly enter a front detector; one path of nitrogen controlled by PCM before nitrogen enters a front detector after passing through a 1 st interface and a 2 nd interface on the ten-way valve, and one path of nitrogen controlled by PCM after nitrogen enters a recovery pipeline through a vent after passing through a 4 th interface, a 3 rd interface, a first chromatographic column, a 9 th interface and a 10 th interface on the ten-way valve. And the nitrogen trifluoride sample gas passes through a sample inlet, passes through a 7 th interface, an 8 th interface, a first quantitative ring, a 5 th interface and a 6 th interface on the ten-way valve, then passes through a 6 th interface, a 1 st interface, a second quantitative ring, a 4 th interface and a 5 th interface on the six-way valve, and finally enters a recovery pipeline through a sample outlet.
In a six-way valve-post detector flow path with helium as a carrier gas, the helium carrier gas is controlled by helium PCM and helium EPC modules. One path of helium controlled by helium EPC is used as reference gas and tail gas blow directly enters the rear detector; one path of helium controlled by the helium PCM enters the rear detector after passing through the 2 nd interface, the 3 rd interface and the second chromatographic column on the six-way valve.
When the whole chromatographic system is in an analysis detection state, the paths of the carrier gas and the nitrogen trifluoride sample gas flowing on the valve circuit are as follows: in a ten-way valve-front detector flow path with nitrogen as carrier gas, nitrogen controlled by nitrogen EPC is used as reference gas and tail gas is blown to directly enter a front detector; one path of nitrogen controlled by PCM before nitrogen enters a recovery pipeline through a 1 st interface and a 10 th interface on the ten-way valve and then through a vent; after the nitrogen enters the front detector, the nitrogen controlled by the PCM enters a front detector through a 4 th interface, a 5 th interface, a first quantitative ring, an 8 th interface, a 9 th interface, a first chromatographic column, a 3 rd interface and a 2 nd interface on the ten-way valve; and the nitrogen trifluoride sample gas passes through a sample inlet, passes through a 7 th interface and a 6 th interface on the ten-way valve, then passes through a 6 th interface and a 5 th interface on the six-way valve, and then enters a recovery pipeline through a sample outlet.
In a six-way valve-post detector flow path with helium as a carrier gas, the helium carrier gas is controlled by helium PCM and helium EPC modules. One path of helium controlled by helium EPC is used as reference gas and tail gas blow directly enters the rear detector; one path of helium controlled by the helium PCM enters the rear detector after passing through a 2 nd interface, a 1 st interface, a second quantitative ring, a 4 th interface, a 3 rd interface and a second chromatographic column on the six-way valve.
The invention provides a method for analyzing crude nitrogen trifluoride gas by gas chromatography and a valve system thereofThe chromatographic valve path system of the sample injection valve solves the problems in the prior art. One-way N2Carrier gas for analyzing H in sample gas2And one path of He carrier gas is used for analyzing the rest components in the sample gas. H2The component is represented by N2The front detector with carrier gas has large response area and negative peak, and the rest components are analyzed on the back detector with He as carrier gas. The valve path system solves the problem of the prior art H2The component response sensitivity is not high, and the peak positive and negative fluctuation is caused, the original accuracy and sensitivity of other component analysis can be ensured, the structure is simple, the valve path is clear, the operation is convenient, and the analysis is accurate.
Drawings
FIG. 1 is a schematic view of the initial detection state of the valve system for chromatography of the present invention.
FIG. 2 is a schematic representation of a chromatographic valve train system in accordance with the present invention during the performance of a detection assay.
Wherein: 1. a ten-way valve; 2. a six-way valve; 3. a first quantity of rings; 4. a second dosing ring; 5. a first chromatographic column; 6. a second chromatography column; 7. nitrogen EPC; 8. PCM before nitrogen; 9. PCM after nitrogen; 10. helium PCM; 11. helium EPC; 12. a front detector; 13. rear detector
Detailed Description
The present invention will be described in detail with reference to examples.
Example 1
A method for analyzing crude nitrogen trifluoride gas by gas chromatography and a valve path system thereof are disclosed, wherein the gas chromatography valve path system adopts a two-valve two-column valve path system and comprises 1 ten-way valve, 1 six-way valve, 2 quantitative rings, 2 chromatographic columns, 2 detectors, 2 electronic gas path control modules (EPCs) and 2 Pressure Control Modules (PCMs). As shown in fig. 1 and fig. 2, fig. 1 is a schematic diagram of an initial sampling state of a chromatography valve path system, and fig. 2 is a schematic diagram of a chromatography valve path system during sampling. For monitoring the change in the contents of the respective components in the crude nitrogen trifluoride gas in real time. The carrier gas adopted by the system is high-purity nitrogen (N) with the purity of more than 99.999 percent2) And high purity helium (He).
The interface 1 of the ten-way valve 1 is connected to a nitrogen source through a nitrogen front PCM8, the interface 2 is connected to a nitrogen source through a nitrogen EPC7 after being connected with a front detector 12, a first chromatographic column 5 is connected between the interface 3 and the interface 9, the interface 9 is connected with a vent through an interface 10, the interface 4 is connected to the nitrogen source through a nitrogen rear PCM9, a first quantitative ring 3 is connected between the interface 5 and the interface 8, the interface 5 is connected with an interface 6 on the six-way valve 2 through an interface 6, and the interface 8 is connected with a sample inlet through an interface 7;
a second quantitative ring 4 is connected between the 1 st interface and the 4 th interface of the six-way valve 2, the 2 nd interface is connected to a helium source through a helium PCM10, the 2 nd interface is connected to the helium source through a 3 rd interface, a second chromatographic column 6, a rear detector 13, helium EPC11 in sequence, and the 4 th interface is connected to a sample outlet through a 5 th interface.
The crude nitrogen trifluoride gas after pretreatment and gas chromatography contains the following components: hydrogen (H)2) Nitrogen (N)2) Carbon tetrafluoride (CF)4) Nitrogen trifluoride (NF)3) Carbon dioxide (CO)2) Nitrous oxide (N)2O), and the like.
A pre-nitrogen PCM8 module and a post-nitrogen PCM9 module were used for pressure flow control of the carrier gas nitrogen. The helium PCM10 module is used for pressure flow control of the carrier gas helium.
The nitrogen EPC7 module is used to control the flow of the reference gas and the tail insufflation gas for the front detector 12, and the helium EPC11 is used to control the flow of the reference gas and the tail insufflation gas for the rear detector 13.
The first column 5 was a 10 foot Hayesep Q column.
The second column 6 was an 8-foot length Shincabon column.
The volumes of the first dosing ring 3 and the second dosing ring 4 are each 1 ml.
The initial state before sample injection is shown in figure 1: at this time, the states of the ten-way valve 1 and the six-way valve 2 are off. At this time, the nitrogen carrier gas controlled by the pre-nitrogen PCM8 directly enters the front detector 12 after passing through the 1 st interface and the 2 nd interface of the ten-way valve 1, and the nitrogen carrier gas controlled by the post-nitrogen PCM9 passes through the 4 th interface and the 3 rd interface of the ten-way valve 1, then flows through the first chromatographic column 5, and then enters the recovery pipeline through the 9 th interface and the 10 th interface of the ten-way valve 1 through the vent. The nitrogen trifluoride sample gas after pretreatment enters a 7 th interface on the ten-way valve 1 through a sample inlet, enters a 6 th interface, a 1 st interface, a quantitative ring 4, a 4 th interface and a 5 th interface on the six-way valve 2 through an 8 th interface, a first quantitative ring 3, a 5 th interface and a 6 th interface, and then enters a recovery pipeline through a sample outlet. And helium carrier gas controlled by helium PCM10 flows through second chromatographic column 6 into rear detector 13 after passing through interface 2 and interface 3 on six-way valve 2.
The valve circuit state shown in fig. 1 is "closed", the valve circuit state shown in fig. 2 is "open", and the valve circuit state can be switched from the state shown in fig. 1 to the state shown in fig. 2 by only clicking a "start" button on the gas chromatograph during gas chromatography sample injection.
The sampling state in the sample injection is shown in figure 2: at this time, the states of the ten-way valve 1 and the six-way valve 2 are "on". At this time, the nitrogen carrier gas controlled by PCM8 enters the recovery pipeline through the 1 st interface and the 10 th interface on the ten-way valve 1 through the vent. The nitrogen carrier gas controlled by the PCM9 after passing through the 4 th interface, the 5 th interface, the first quantitative ring 3, the 8 th interface and the 9 th interface of the ten-way valve 1 passes through the first chromatographic column 5 and then passes through the 3 rd interface and the 2 nd interface and finally enters the front detector 12 for sample analysis. At the moment, nitrogen trifluoride sample gas enters a 6 th interface on the six-way valve 2 after passing through a sample inlet, a 7 th interface and a 6 th interface on the ten-way valve 1, and a 5 th interface enters a recovery pipeline through a sample outlet. Helium carrier gas controlled by helium PCM10 passes through port 2, port 1, quantification ring 4, port 3 and second chromatographic column 6 on six-way valve 2 and brings the sample into rear detector 13 for analysis.
The nitrogen gas is taken as carrier gas and enters the front detector 12 through the ten-way valve 1 to mainly analyze and monitor the hydrogen component in the nitrogen trifluoride sample gas, the peak of the hydrogen component on the thermal conductivity detector taking the nitrogen gas as the carrier gas is negative, and the response area on the thermal conductivity detector taking the hydrogen gas as the carrier gas is close to 1000: 1 with the response area on the thermal conductivity detector taking the helium gas as the carrier gas, namely H in the crude nitrogen trifluoride gas in the monitoring process2The response area of the components on the thermal conductivity detector with helium as the carrier gas was 20, and the response area on the thermal conductivity detector with nitrogen as the carrier gas was 20,000. Therefore, is atAfter the hydrogen spike on the front detector 12 is completed, the ten-way valve 1 can be switched from "on" to "off", i.e. back to the initial state of the analysis, at which time the first chromatographic column 5 is reversely purged by the nitrogen carrier gas controlled by the nitrogen post-PCM 9 in the initial state of the analysis, and the other components in the chromatographic column except hydrogen are purged to the recovery line through the vent and wait for the start of the next sample preparation. Helium is used as carrier gas, the sample gas enters the rear detector 13 through the six-way valve 2 mainly for analyzing and monitoring other components except hydrogen in nitrogen trifluoride, so the whole sampling time is long, the state of the six-way valve 2 can be switched from 'on' to 'off' after all chromatographic peaks on the rear detector 13 are completely appeared, namely the six-way valve returns to the initial state of analysis, at the moment, the helium carrier gas controlled by helium PCM10 performs forward purging on the second chromatographic column 6 in the initial state of analysis and passes through the rear detector 13 until the chromatographic baseline on the rear detector 13 is stable, and the next sample injection can be prepared. The duration of the entire analysis procedure was about 8 minutes, where H2The peak-out time on the front detector 12 is 2.1min, N2The peak-off time on the rear detector 13 is 2.4min, CF4The peak-off time on the rear detector 13 is 3.2min, NF3The peak-off time on the rear detector 13 is 3.5min, CO2The peak-off time on the rear detector 13 is 6.2min, N2The peak out time of O on the post detector 13 was 7.3 min. The chromatogram was set to a period of 11min for one analysis of crude nitrogen trifluoride gas, i.e.in the last component N2After the O peak is over, the helium source still has time to fully purge the second column 6 for approximately 4 min. The valve path diagram of the patent is adopted to firstly carry out H on the experimental result of sample making2The response area of (2) is more than 20,000, the peak area is larger, and the monitoring is easier. Second H2The peak is negative because nitrogen is used as carrier gas, and the fluctuation of positive peak and negative peak is not generated. Finally, the peak-off time of the rest components in the crude nitrogen trifluoride gas on the post detector 13 is shortened to be within 8min, and the requirement of an analysis period of 11min can be met.
In conclusion, the method and the valve path system solve the problem of the prior art H2Component response sensitivityThe method has the advantages of low degree and positive and negative fluctuation of peaks, can also ensure the accuracy and sensitivity of the analysis of other original components, is convenient to operate and accurate in analysis, and can be applied to the effective monitoring of each component of rough nitrogen trifluoride gas.