Some standard content:
National Standard of the People's Republic of China
High purity hydrogen
High purity helium
Subject content and scope of application
GB/T 4844.3-1995
Replaces GB4844～4845-84
This standard specifies the technical requirements, inspection methods, inspection rules, and packaging, marking, storage and transportation of high purity nitrogen products.
This standard applies to bottled high purity gaseous nitrogen extracted from natural gas, air or factory vent gas by cryogenic method. Mainly used for the preparation of standard mixed gas, low temperature superconductivity, scientific research, chromatographic analysis carrier gas, etc. Molecular formula: He.
Relative molecular mass: 4.00260 (according to the international relative atomic mass in 1991). 2
Cited standards
GB/T4844.1 Industrial ammonia
GB4844.2 Pure nitrogen
GB/T5832.1 Determination of trace moisture in gas-Electrolytic method GB/T8984 Determination of carbon monoxide, carbon dioxide and methane in gas-Gas chromatography
GB/T5274 Preparation of mixed gas for gas analysis calibration-Weighing method GB/T 10627
GB/T 10628
3 Technical requirements
Preparation of standard mixed gas for gas analysis-Static volume method Determination of composition of standard mixed gas for gas analysis-Comparative method The quality of high-purity ammonia products shall meet the requirements in the following table. "Purity" and "content" in the table are volume fraction (V/V) items
Ammonia purity, 102
Chlorine content, 106
Hydrogen radical content, 10°6
Oxygen (fluorine) content. 10~6
Nitrogen content, 10-5
Carbon monoxide content, 10\6
Carbon dioxide content, 10°s
Methane content, 10-6
Water content, 10-6
Approved by the State Administration of Technical Supervision on December 20, 1995 6n
Superior product
First-class product
Qualified product
Implemented on August 1, 1996
4 Inspection method
4.1 Ammonia purity
GB/T 4844.3--1995
Nitrogen purity is expressed in volume fraction and is calculated according to formula (1): @100→Φ+++Φ+Φ+更++)×10-4 Wherein: Φ-
Ammonia purity, 10-2 (V/V);
Φ, —Nitrogen content (volume fraction), 10~6 (V/V); d
Hydrogen content (volume fraction), 10-' (V/V), oxygen (argon) content (volume fraction), 10-6 (V/V), nitrogen content (volume fraction), 10- (V/V), --Carbon dioxide content (volume fraction), 10-6 (V/V); Carbon dioxide content (volume fraction), 10-6 (V/V), -Methane content (volume fraction), 10-6 (V/V); Φ: --Water content (volume fraction), 10-6 (V/V). 4.2 Determination of hydrogen, oxygen (fluorine) and nitrogen content 4.2.1 Method summary
Use variable temperature concentration technology and thermal conductivity chromatography for determination. This method quantitatively adsorbs the measured component on an adsorption column at liquid nitrogen temperature, and then quantitatively desorbs it at room temperature (water bath), so that the trace measured component in the sample is pre-concentrated, and after separation by a chromatographic column, it is detected by a thermal conductivity cell detector. 4.2.2 Instrument
This standard uses a laboratory chromatograph with a pre-concentration system, and the chromatographic flow chart is 1. Other conditions of the instrument, such as the voltage-stabilized power supply, the measuring bridge, etc., are the same as those of a general chromatograph. The recorder range is 0-1mV, the detector is a four-arm tungsten filament thermal conductivity cell, and the S value is greater than 1000. F
Figure 1 Flow chart of variable temperature concentration chromatography
1—Nitrogen carrier gas bottle; 2—Pressure reducing valve; 3.8—Needle valve; 4—Detector; 5—Chromatographic column; 6—X-shaped four-way piston; 7—Sample gas bottle; 9—Screw clamp; 10, 15—Bubbler; 11, 12—Three-way two-way piston; 13—Concentration column, 14—Liquid nitrogen bath or water bath; 16—Wet flowmeter; 17—Rotameter; F—Sampling valve 4.2.3 Determination conditions
Carrier gas: High purity nitrogen, in accordance with the requirements of this standard, flow rate 40~60mL/min. a.
GB/T4844.3--1995
b. Concentration column: about 40~50cm long, inner diameter about 4mm, filled with 3~4g of 601 or TDX-01 carbon molecular sieve with a particle size of 0.25~0.40mm.
Chromatographic column: about 3m long, inner diameter about 4mm, filled with about 1m long 5A molecular sieve (particle size: 0.25~0.40mm) and about 2mc
long coconut shell activated carbon (particle size: 0.25~~0.40mm). After activation treatment, the separation (R) between the components to be measured should be greater than 1d. Adsorption temperature: -196℃ (liquid nitrogen temperature). Desorption temperature: room temperature (water bath). 4.2.4 Preparation
4.2.4.1 Pass dry gas through the concentration column and the chromatographic column (oxygen is prohibited for the concentration column) and heat and activate it. 4.2.4.2 Carefully apply piston oil to all pistons and check that there is no leakage in the chromatographic system. 4.2.4.3 Turn on the carrier gas, adjust the flow rate to 40-60mL, purge the chromatographic system for about 2 hours, turn on the instrument power, and wait for the instrument to work stably. 4.2.4.4 Turn the piston, close the concentrator column, put on the liquid nitrogen bath, and after 5 minutes, remove the liquid nitrogen bath and put on the room temperature water bath. If there is no chromatographic peak on the recorder, it is normal.
4.2.4.5 Turn the piston to allow the carrier gas to pass through the concentrator column. While carefully preventing air backflow, concentrate the carrier gas for 5 minutes and measure the blank value of the chromatographic system. The requirements of 4.2.3 a should be met. 4.2.5 Operation steps
4.2.5.1 Samplingbzxz.net
Connect the sample gas bottle to be tested to the instrument tightly through the needle pressure reducing valve and metal pipe, open the spiral clamp, bottle valve, and needle valve, and use the sample gas to fully replace the valve body and pipe by increasing and decreasing the pressure at least 3 times to make the sample representative. 4.2.5.2 Concentration
Turn pistons 6, 11, and 12 to cut off the carrier gas to the concentrator column. At the same time, pass the sample gas through the concentrator column at a flow rate not higher than 1000mL/min. After purging for 3 to 5 minutes, close piston 12, put a liquid nitrogen bath on the concentrator column, open piston 12, and let the sample gas flow through the bubbler 15. After being measured by the wet flow meter, it is vented.
The concentration operation should always be carried out under the condition of bubbling by the bubbler 10. The concentrated volume of the sample gas is selected by the detection limit of the instrument and the content of the component to be measured.
4.2.5.3 Desorption
After the concentration is completed, close piston 11, remove the liquid nitrogen bath, wait for 20 to 50 seconds, release the adsorbed nitrogen, close piston 12, and then put a water bath on the concentrator column. Rotate pistons 11, 12, and 6 to let the carrier gas pass through the concentrator column and then enter the chromatographic column. Read the concentrated volume (V). Record the chromatographic elution curve of each component to be tested. Measure the chromatographic peak area (A1). 4.2.5.4 Calibration
Connect the standard mixed gas bottle to the instrument through the needle valve and metal pipe, open the bottle valve and needle valve, and fully replace it with the standard gas by increasing and decreasing the pressure at least 3 times. After obtaining the representative sample, switch the six-way valve (F) to inject the sample. Record and measure the chromatographic peak area (A2) of each component. The standard mixed gas uses ammonia as the base gas and is prepared in accordance with GB/T5274 or GB/T10627 or GB/T10628. Among them, the content of each component is about K times the content of the component to be tested (K is the ratio of the concentrated volume V, to the volume V, of the six-way valve measuring tube). When the content of each component in the standard mixed gas is similar to the content of the component to be tested, use the same method as the sample gas, concentrate and inject and calibrate.
4.2.6 Result processing
4.2.6.1 The content of each component to be measured is calculated according to formula (2): Φ × A, × V2
Wherein: Φ--the content of the component i to be measured in the sample gas (volume fraction), 10-6 (V/V); Φ. The content of component i in the standard gas (volume fraction), 10-s (V/V); Vi——the concentrated volume of the sample gas, mL,
V, the injection volume or concentrated volume of the standard gas, mLA—the peak area of component i in the sample gas, mm; 162
（2）
GB/T 4844.3—1995
A The peak area of component i in the standard gas, mm\-representative components nitrogen, hydrogen, oxygen (fluorine), nitrogen. 4.2.6.2 The arithmetic mean of two parallel determinations is taken as the determination result, and the relative deviation of parallel determinations shall not exceed 10%. 4.3-Determination of carbon dioxide, carbon dioxide and methane content 4.3.1 Method Summary
The trace carbon monoxide, carbon dioxide and methane content in nitrogen are determined by variable temperature concentration technology and conversion chromatography. This method pre-concentrates the components to be tested by a concentration column, separates them by a chromatographic column, and then converts carbon monoxide and carbon dioxide into methane, which is detected by a hydrogen flame ionization detector.
4.3.2 Instrument
This standard uses a gas chromatograph with a pre-concentration system, a nickel catalyst conversion system and a hydrogen flame ionization detector. The detection limit (volume fraction) of the instrument for methane is not less than 0.5×10-6 (V/V). Other conditions of the instrument are in accordance with GB/T8984. The chromatographic flow is shown in Figure 2. e1
Figure 2 Conversion chromatography flow chart
1--Hydrogen bottle; 2--Nitrogen bottle; 3--Air bottle; 4--Pressure reducing valve; 5--Needle valve; 6--Silica gel drying tube; 7--Molecular sieve drying tube: 8--Rotameter: 9--Detector (FID); 10--Microcurrent amplifier, 11 Recorder; 12--Heating furnace; 13--Nickel catalyst tube; 14--Constant chamber: 15--Chromatographic column; 16--Pressure regulating valve; 17--Pressure gauge; 18--Resistance tube; F--Sampling valve Note: The sample concentration process in the dotted box is the same as that in Figure 1. 4.3.3 Determination conditions
3~4g.
Concentration column: U-shaped column with a length of about 30cm and an inner diameter of about 4mm, filled with color-changing silica gel with a particle size of 0.25~0.40mm. About -163
GB/T 4844.3--1995
Chromatographic column, conversion column, carrier gas, fuel gas, combustion-supporting gas, etc. shall comply with the provisions of GB/T8984. b.
The operating conditions of the instrument can be selected according to the concentration of the component to be measured and the concentration volume. c
d. Concentration adsorption temperature: liquid nitrogen temperature. Desorption temperature: boiling water temperature. 4.3.4 Preparation
4.3.4.1 Activate the concentration column and chromatographic column at about 180℃ with dry gas for 3~~4h. 4.3.4.2 Carefully apply piston oil to all pistons and check that there is no leakage in the system. 4.3.4.3 Turn on the carrier gas, fuel gas and combustion-supporting gas to the required flow rate. 4.3.4.4 Turn on the power of the instrument and select the sensitivity of the instrument until the instrument works stably. 4.3.5 Operation steps
4.3.5.1 Put a boiling water bath on the concentration column to completely desorb the adsorbed components in the concentration column, and remove the water bath. 4.3.5.2 The operation steps for the determination of sample gas shall be in accordance with the provisions of Article 4.2.5. The corresponding relationship between the various parts of the concentration device is shown in Figures 1 and 2. 4.3.6 Result processing
The result processing shall be in accordance with the provisions of Article 4.2.6, where represents the components to be measured carbon monoxide, carbon dioxide, and methane respectively. 4.4 Determination of moisture content
Determine in accordance with the provisions of GB5832.1.
5 Inspection rules
5.1 High-purity nitrogen products shall be inspected by the quality supervision and inspection department of the manufacturer in accordance with the provisions of this standard to ensure that the products leaving the factory meet the requirements of this standard. 5.2 High-purity nitrogen products shall be inspected bottle by bottle. If any of the indicators in the inspection results do not meet the requirements of this standard, the product shall be unqualified.
5.3 Users have the right to conduct inspection and acceptance in accordance with the provisions of this standard. They can be inspected bottle by bottle, or they can be inspected by random sampling in batches in accordance with Article 5.2 of GB4844.2. If any of the indicators in the batch sampling inspection results do not meet the requirements, double sampling should be conducted from the batch of products for re-inspection. If there is still one unqualified indicator, the batch of products shall be unqualified. 5.4 When the supply and demand parties have objections to the product quality, they shall negotiate, or jointly inspect and accept, or submit to arbitration. 6 Packaging, marking, storage and transportation
6.1 The packaging, marking, storage and transportation of high-purity hydrogen products shall comply with the provisions of Chapter 6 of GB4844.1. 6.2 The words "High Purity Nitrogen" shall be printed on the gas cylinder. Additional notes:
This standard is proposed by the Ministry of Chemical Industry of the People's Republic of China. This standard was formulated by the Southwest Chemical Research Institute of the Ministry of Chemical Industry. This standard was drafted by the Southwest Chemical Research Institute of the Ministry of Chemical Industry and the Weiyuan Natural Gas Chemical Plant of the Sichuan Petroleum Administration Bureau. The main drafters of this standard were He Daoshan and Dai Qiwen.
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