SY/T 7508-1997 Determination of total sulfur in liquefied petroleum gas from oil and gas fields - Oxidative microcoulometric method
Some standard content:
ICS 75.160.30
Registration No.: 1126--1998
Petroleum and Natural Gas Industry Standard of the People's Republic of ChinaSY/T 7508--1997
Liguefied petroleum gas of oil and gas ficilddeterminationof total sulfur
Oxidative microcoulombic methodPublished on December 28, 1997
China National Petroleum Corporation
Implemented on June 1, 1998
SY/T 75081997
Referenced Standards
Method Summary
Reagents and Materials
Instruments and Equipment
Test Preparation
Test Procedures
Permissible Error of Determination Result
SY/T7508-1997
This standard was first issued on December 16, 1987. After more than ten years of application, it has been proved that this standard can basically meet the production requirements. According to the 1997 National Standard for Oil and Gas Industry issued by China National Petroleum Corporation (97) Zhongyou Jijianzi No. 42, SY7508-87 was revised. The main changes of this revision are as follows:
1. Added the content of determining the total sulfur content in FLP gas by gas sampler. 2. The Appendix A of 5Y750887 is used as Chapter 8 of this standard. This standard will replace SY7508-87 from the date of implementation. This standard is proposed and managed by the Petroleum Planning and Design Institute of China National Petroleum Corporation. This standard is established by: Sichuan Oil and Gas Research Institute. Who is the main drafter of this standard? He Yong
1 Scope
Petroleum and natural gas industry standard of the People's Republic of China
Determination of total sulfur in liquefied petroleum gas of oil and gas fields
Oxidative microcoulombic method
SY/ T 7508-1997
Replaces SY 7508-87
Liquefied petroleum gas of oil and gas field- determination of total sulfur--Oxidative microcoulombic method This standard specifies the test method for determining the total sulfur content in liquefied petroleum gas of oil and gas fields by oxidative microcoulombic method. This standard is applicable to the determination of total sulfur content in liquefied petroleum gas of oil and gas fields, and the determination range is 1-400mg/2 Referenced standards
The provisions contained in the following standards constitute the provisions of this standard through reference in this standard. When this standard was published, the versions shown were all valid. All standards will be revised. All parties using this standard should explore the possibility of using the latest version of the following standards. SH/T0230--92 Determination of liquefied petroleum gas composition (chromatographic method) SH0233-92 Sampling method for liquefied petroleum gas
3 Method Summary
The sample is carried by nitrogen flow into a cracking tube heated to a certain temperature. After mixing with oxygen and burning, sulfur is converted into sulfur dioxide, and enters the titration cell with nitrogen to react with triiodide ions. The consumed triiodide ions are replenished by electrolytic potassium iodide. According to Faraday's law of electrolysis, the sulfur content of the sample can be calculated from the amount of electricity consumed by electrolysis. 4 Reagents and materials
4.1 Reagents
a) Deionized water or water of equivalent purity;
b) Ice art: 99%:
c Potassium iodide;
Thiophene or dimethyl disulfide;
Petroleum ether (90-120°C) or n-heptane:
Potassium chloride;
9) Carrier gas: purity not less than 99%;
h) Nitrogen: purity not less than 99.99%.
4.2 Materials
Volume flask: 50mL;
b) Micro-injector: 10uL;
Liquid petroleum gas sampler: 500~10001mLc
d) Dilution tube: glass, volume is SmL China National Petroleum Corporation Approved on December 28, 1997 and implemented on June 1, 1998
5 Instruments and equipment
5.1 Microcoulometer
It consists of the following eight parts;
a) Cracking furnace:
b) Cracking tube: Made of quartz:
SY/ T 7508-1997
c) Titration cell: a pair of indicator electrodes and a pair of electrolytic electrodes are inserted into the cell: the indicator electrode is used to indicate the change of diiodide ion concentration, and the electrolytic electrode is used to maintain the concentration of triiodide ions; d) Microcoulomb meter: when sulfur dioxide enters the titration cell to reduce the concentration of triiodide ions, it can automatically (or manually) turn on the electrolysis. The triiodide ions are restored to their original concentration, and the electrolysis time and current can be automatically (or manually) recorded, and the sulfur content can be directly displayed (or calculated) at last:
e) Adjustable speed automatic trace sampler:
↑) Temperature controller: composed of three groups of silicon temperature control circuits, which respectively control the temperature of the preheating zone, combustion zone and outlet zone of the cracking furnace;
Flow controller: control the flow of airflow entering the cracking tube: g)
h) Stirrer: electromagnetic stirrer with adjustable speed. 5.2 Liquid sampler
Use liquid injection valve or pressure syringe of known volume to inject microliter liquefied sample. 5.3 Gas sampler
Composed of quantitative injection six-way valve and gasification device: used for quantitative injection of gasified liquefied petroleum gas. 6 Test preparation
6.1 Sampling
Sampling according to SH0233.
6.2 Preparation of electrolyte
Weigh 0.5 potassium iodide: dissolve in a brown glass container containing 500ml water, add 0.0.4mL glacial acetic acid, dilute to 1000ml. The electrolyte is valid for 90d, 6.3 Preparation of saturated potassium chloride dropper
Weigh 20g potassium fluoride in a beaker, add 50mL water to dissolve, and store in a dropper bottle. 6.4 Preparation of sulfur standard sample
Use thiophene or dimethyl disulfide as the sulfur standard reagent. Use sulfur-free right oil ether (90-120℃) or n-heptane as the solvent.
Use an alcohol lamp to slightly heat the bulb of the glass ampoule, and then place it in a desiccator to cool to room temperature. Weigh the ampoule with an analytical balance, and after slightly heating the bulb of the ampoule again, immediately insert the capillary mouth of the ampoule into the reagent bottle to absorb thiophene or dimethyl disulfide, and melt the capillary mouth of the ampoule, and weigh it after cooling. The difference between the two weighings is the amount of reagent absorbed. Gently place the ampoule in a volumetric flask pre-filled with about one-third of the solvent, crush it with a glass, and then dilute it to the scale with the solvent: shake well and set aside. Calculate the concentration of the sulfur standard sample according to formula (1):
P=32.06× N×#× pX 10
Wherein: p—--the sulfur content in the sulfur standard sample, mng/; A the number of sulfur atoms in the sulfur compound molecule
the molar mass of sulfur, g/mol:
the mass of the sulfur compound, mg;
the purity of the sulfur compound, %;
V the volume of the volumetric flask, mL;
SY/ T 7508-1997
M the molar mass of the sulfur compound, /mol. The sulfur content of the sulfur standard sample should be basically close to the sulfur content of the test sample. The sulfur standard sample should be prepared on the same day of use, and a new standard sample should be prepared each time the conversion rate is determined.
6.5 Instrument Installation
Install the instrument according to the instrument manual, and connect the power circuit and carrier gas pipeline. 6.6 Adding electrolyte
Drain the old electrolyte used in the previous sample from the titration cell, add fresh electrolyte, and make the liquid level 5~10m11m higher than the electrode. If the sample is made continuously, the electrolyte should be replaced every 4h. 6.7 Current sensitivity determination
6.7.1 Instrument control components
a) Flow rate:
Nitrogen: 160mL/min;
Oxygen: 40mL/min,
b) Furnace temperature:
Preheating zone: 370~420C;
Combustion zone: 710~750℃;
Exit zone: 570~620℃.
6.7.2 Sensitivity measurement
After the instrument is stable, measure the sensitivity according to the instrument manual, once every 4 hours. When the sensitivity index reaches the requirements specified in the instrument manual, the conversion rate can be measured. 6.8 Conversion rate measurement
6.8.1 Control the flow rate and furnace temperature according to 6.7.1. 6.8.2. Use a 10μL syringe to draw the standard sample and wash the syringe three times. Draw 4 to 8L of the standard sample, invert it to expel the bubbles, pull the needle core back so that the concave surface of the liquid falls at the 1 mark, and read V1. Place the syringe flat on the automatic sampler, clamp it, and inject the sample. The injection speed is controlled at 0.1 to 0.2tL/s. Stop the injection when there is about 0.5L of sample left in the syringe. Remove the syringe, pull the needle core back again, so that the concave surface of the liquid falls at the 1uL mark, and read VV. The difference between V and V is the maximum injection of the standard sample. Titrate with a microcoulometer and read the displayed value. A standard sample should be measured at least twice and the average value should be taken. Calculate the sulfur conversion rate according to formula (2):
F=一×100
Sulfur conversion rate, %;
Where: F-
m--the displayed value of sulfur titration by microcoulomb meter, ng; p--the sulfur content in the standard sample, ing/L; V-the injection volume, L.
The conversion rate is measured once every 7 days. The sample can be measured only when the conversion rate index meets the requirements specified in the instrument manual. 7 Test steps
7.1 Test steps using liquid sampler
7.1.1 Process connection
7.1.1.1 Replace the automatic sampler with a liquid sampler, SY/T 75081997
7.1.1.2 Connect the liquid sampler and the liquefied petroleum gas sampler as shown in Figure 1. Connect the No. 9 injection needle to the outlet tube of the liquid sampler and insert it into the injection port of the cracking tube.
Purge gas
Vent air
A group products
Purge point
1.5, 7—needle valve; 2, 4, 11, 13—flow meter 3—sliding injection valve 6—liquefied petroleum gas sampler: 8-dilution tube: 9—quartz cracking tube: 10, 12—steady flow valve; A—filling; B—injection
Figure 1 Liquid filling and injection flow chart
7 .1.2 Control conditions
a) Flow rate:
Purge gas: 35mL/min;
Supplementary carrier gas: 105mL／min
Oxygen: 60mLmin
b) Furnace temperature:
Preheating zone: 370～420℃
Combustion zone: 710～750℃;
Exit zone: 570-620℃.
7.1.3 Filling the sample
Fully open valve 7 and slightly open valve 5 to fully drain until the flow meter 4 is filled with liquid. Pull out the sliding injection valve handle (see A in Figure 1: the sample is filled into the valve core, and the valve core is purged for 10 to 20 seconds. 7.1.4 Injection
Push the sliding reverse sample valve handle (see B in Figure 1). The valve core is aligned with the purge gas, and the sample in the valve core is blown into the dilution tube, and then enters the pyrolysis tube for oxidation and pyrolysis. Titrate with a micro-cupometer: read its displayed value. A sample should be measured at least twice and the average value taken. Note: Whether the dilution tube needs to be connected depends on the carbon deposition of the pyrolysis tube. 7.2 Test steps using a gas sampler
7.2.1 Process connection
7.2.1.1 Replace the automatic sampler with a gas sampler. SY/ T 7508-1997
7.2.1.2 Connect the gas sampler and the liquefied petroleum gas sampler as shown in Figure 2. 7.2.2 Control conditions
Perform as in 7.1.2
7.2.3 Filling the sample
Adjust the temperature of the constant temperature vaporization chamber to 60-80℃, turn the quantitative injection six-way valve to the sampling position: open valve 7: then slowly open the flow regulating valve 8 to fully empty, and be careful to avoid liquid rushing out: the gas discharged from the flushing pipeline should be led out of the case 7.2.4 Injection
Turn the quantitative injection six-way valve to the injection position, and the sample in the quantitative tube is blown into the crack. Tube dissolution: Titrate with a microcoulomb meter, read the displayed value, and record the atmospheric pressure and vaporization chamber temperature. Note: The entire injection system should be tested for leaks before injection. If there is gas, it should be removed and the water can avoid the sample. Release chamber
to cracking tube
1, 7.8-needle valve: 2-flow meter; 3-vaporization chamber; 4-amount of tube: 5-amount of sample six-way valve: 6-liquefied petroleum gas sampler diagram? Gas filling and injection flow chart
&CalculationWww.bzxZ.net
8.1 Calculation of total sulfur content in liquid sample determined by liquid injector 8.1.1 The total sulfur content in the sample expressed as mass fraction is calculated according to formula (3): Vxex F
Wherein: ——total sulfur content in the sample, 10-\, Bn—the displayed value of sulfur titrated by microcoulomb meter, ng; V-injection volume, uL;
sample density, /cm
sulfur conversion rate, %,
SY/ T 75081997
8.1.2 The total sulfur content in the sample when volatilized into gaseous state is calculated according to formula (4): mxM
p= 24.055x V× d× F
In the formula: p-
-total sulfur content in the sample, mg/m;
displayed value of sulfur titration by microcoulombmeter, g;
molar mass of liquefied petroleum gas, gmol;
injection volume, uL;
ddensity of sample, g/cm;
F-sulfur conversion rate, %;
molar volume of gaseous liquefied petroleum gas at 20℃ and 101.325kPa, L/m0l. Note: The molar mass M of liquefied petroleum gas is calculated according to SH/T023h. 8.2 Calculation of total sulfur content in gasified gas sample by gas sampler 8.2.1 The volume of gas is converted according to formula (5): xp
273.15+ t
Wherein: V, - volume of sample at 20°C and 101.325kPa, mL; sampling volume of the six-way valve for a certain amount of injection, mL; atmospheric pressure at the time of sampling, kPa;
temperature of the constant temperature gasification chamber, °C.
8.2.2 The total sulfur content in gasified gas sample is calculated according to formula (6): Appendix
Formula\---The maximum content of total sulfur in gasified gas sample, g/mm
The displayed value of sulfur titrated by microcoulomb meter, ng; The conversion rate, %.
Allowable difference of determination results
For the same operator, the difference between two consecutive determination results shall not exceed the value specified in Table 1. Table 1 Allowable relative error
Measurement range of total sulfur content
Mass fraction W
Mass concentration
Allowable relative error
(the smaller one is taken as the benchmark)4 Injection
Push the handle of the sliding reverse sample valve (see B in Figure 1). The valve core is aligned with the purge gas, and the sample in the valve core is blown into the dilution tube, and then enters the cracking tube for oxidation and cracking. Use a micro-coulometer to titrate: read its displayed value. A sample should be measured at least twice and the average value taken. Note: Whether the dilution tube needs to be connected depends on the carbon deposition of the cracking tube. 7.2 Test steps using a gas sampler
7.2.1 Process connection
7.2.1.1 Replace the automatic sampler with a gas sampler. SY/ T 7508-1997
7.2.1.2 Connect the gas sampler and the liquefied petroleum gas sampler as shown in Figure 2. 7.2.2 Control conditions
Follow 7.1.2
7.2.3 Sample filling
Adjust the temperature of the constant temperature vaporization chamber to 60-80℃, turn the quantitative injection six-way valve to the sampling position: open valve 7: then slowly open the flow control valve 8 to fully empty, and be careful to avoid liquid rushing out: the gas discharged from the flushing pipeline should be led out of the case 7.2.4 Sampling
Turn the quantitative injection six-way valve to the injection position, and the sample in the quantitative tube is blown into the pyrolysis tube: titrate with a microcoulometer, read its display value, and record the atmospheric pressure and vaporization chamber temperature. Note: The entire injection system should be tested for leaks before injection. If there is gas, it should be removed and the water can avoid the sample. Release chamber
to cracking tube
1. 7.8-needle valve: 2-flow meter; 3-vaporization chamber; 4-amount tube: 5-amount sample six-way valve: 6-liquefied petroleum gas sampler diagram? Gas filling and injection flow chart
&Calculation
8.1 Calculation of total sulfur content in liquid sample determined by liquid sampler 8.1.1 The total sulfur content in the sample expressed as mass fraction is calculated according to formula (3): Vxex F
Wherein: ——total sulfur content in the sample, 10-\, ben—the displayed value of sulfur titrated by microcoulomb meter, ng; V-injection volume, uL;
sample density, /cm
sulfur conversion rate, %,
SY/ T 75081997
8.1.2 The total sulfur content in the sample when volatilized into gaseous state is calculated according to formula (4): mxM
p= 24.055x V× d× F
In the formula: p-
-total sulfur content in the sample, mg/m;
displayed value of sulfur titration by microcoulombmeter, g;
molar mass of liquefied petroleum gas, gmol;
injection volume, uL;
ddensity of sample, g/cm;
F-sulfur conversion rate, %;
molar volume of gaseous liquefied petroleum gas at 20℃ and 101.325kPa, L/m0l. Note: The molar mass M of liquefied petroleum gas is calculated according to SH/T023h. 8.2 Calculation of total sulfur content in gasified gas sample by gas sampler 8.2.1 The volume of gas is converted according to formula (5): xp
273.15+ t
Wherein: V, - volume of sample at 20°C and 101.325kPa, mL; sampling volume of the six-way valve for a certain amount of injection, mL; atmospheric pressure at the time of sampling, kPa;
temperature of the constant temperature gasification chamber, °C.
8.2.2 The total sulfur content in gasified gas sample is calculated according to formula (6): Appendix
Formula\---The maximum content of total sulfur in gasified gas sample, g/mm
The displayed value of sulfur titrated by microcoulomb meter, ng; The conversion rate, %.
Allowable difference of determination results
For the same operator, the difference between two consecutive determination results shall not exceed the value specified in Table 1. Table 1 Allowable relative error
Measurement range of total sulfur content
Mass fraction W
Mass concentration
Allowable relative error
(the smaller one is taken as the benchmark)4 Injection
Push the handle of the sliding reverse sample valve (see B in Figure 1). The valve core is aligned with the purge gas, and the sample in the valve core is blown into the dilution tube, and then enters the cracking tube for oxidation and cracking. Use a micro-coulometer to titrate: read its displayed value. A sample should be measured at least twice and the average value taken. Note: Whether the dilution tube needs to be connected depends on the carbon deposition of the cracking tube. 7.2 Test steps using a gas sampler
7.2.1 Process connection
7.2.1.1 Replace the automatic sampler with a gas sampler. SY/ T 7508-1997
7.2.1.2 Connect the gas sampler and the liquefied petroleum gas sampler as shown in Figure 2. 7.2.2 Control conditions
Follow 7.1.2
7.2.3 Sample filling
Adjust the temperature of the constant temperature vaporization chamber to 60-80℃, turn the quantitative injection six-way valve to the sampling position: open valve 7: then slowly open the flow control valve 8 to fully empty, and be careful to avoid liquid rushing out: the gas discharged from the flushing pipeline should be led out of the case 7.2.4 Sampling
Turn the quantitative injection six-way valve to the injection position, and the sample in the quantitative tube is blown into the pyrolysis tube: titrate with a microcoulometer, read its display value, and record the atmospheric pressure and vaporization chamber temperature. Note: The entire injection system should be tested for leaks before injection. If there is gas, it should be removed and the water can avoid the sample. Release chamber
to cracking tube
1. 7.8-needle valve: 2-flow meter; 3-vaporization chamber; 4-amount tube: 5-amount sample six-way valve: 6-liquefied petroleum gas sampler diagram? Gas filling and injection flow chart
&Calculation
8.1 Calculation of total sulfur content in liquid sample determined by liquid sampler 8.1.1 The total sulfur content in the sample expressed as mass fraction is calculated according to formula (3): Vxex F
Wherein: ——total sulfur content in the sample, 10-\, ben—the displayed value of sulfur titrated by microcoulomb meter, ng; V-injection volume, uL;
sample density, /cm
sulfur conversion rate, %,
SY/ T 75081997
8.1.2 The total sulfur content in the sample when volatilized into gaseous state is calculated according to formula (4): mxM
p= 24.055x V× d× F
In the formula: p-
-total sulfur content in the sample, mg/m;
displayed value of sulfur titration by microcoulombmeter, g;
molar mass of liquefied petroleum gas, gmol;
injection volume, uL;
ddensity of sample, g/cm;
F-sulfur conversion rate, %;
molar volume of gaseous liquefied petroleum gas at 20℃ and 101.325kPa, L/m0l. Note: The molar mass M of liquefied petroleum gas is calculated according to SH/T023h. 8.2 Calculation of total sulfur content in gasified gas sample by gas sampler 8.2.1 The volume of gas is converted according to formula (5): xp
273.15+ t
Wherein: V, - volume of sample at 20°C and 101.325kPa, mL; sampling volume of the six-way valve for a certain amount of injection, mL; atmospheric pressure at the time of sampling, kPa;
temperature of the constant temperature gasification chamber, °C.
8.2.2 The total sulfur content in gasified gas sample is calculated according to formula (6): Appendix
Formula\---The maximum content of total sulfur in gasified gas sample, g/mm
The displayed value of sulfur titrated by microcoulomb meter, ng; The conversion rate, %.
Allowable difference of determination results
For the same operator, the difference between two consecutive determination results shall not exceed the value specified in Table 1. Table 1 Allowable relative error
Measurement range of total sulfur content
Mass fraction W
Mass concentration
Allowable relative error
(the smaller one is taken as the benchmark)
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