GB/T 17144-1997 Determination of Carbon Residue of Petroleum Products (Micro Method)

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Card type: Test method

1. Method number / full title / English title / replacement relationship

• Standard number: GB/T 17144-1997
• Chinese full title: Determination of Carbon Residue of Petroleum Products (Micro Method)
• English title: Petroleum products—Determination of carbon residue—Micro method
• Adoption relationship: eqv ISO 10370:1993 (equivalent adoption)
• Replacement relationship: not provided in the available source
• Publication/implementation: issued by 1997-12-11, implemented on 1998-07-01 (State Bureau of Technical Supervision)
• Main differences from ISO 10370:1993: the ISO method uses soda-lime glass for the sample tube, while this standard uses soda-lime glass or borosilicate glass for the sample tube (foreword, adoption note for 7.1)

2. Scope of application and non-applicability

• 1.1 specifies a micro method for determining the carbon residue of petroleum products.
• 1.2 applies to petroleum products, with a carbon residue determination range of 0.10% (m/m) to 30.0% (m/m). For petroleum products with carbon residue exceeding 0.10% (m/m), the results determined by this standard are equivalent to those determined by the Conradson carbon residue method (GB/T 268).
• 1.3 also applies to petroleum products composed of distillate oils with a carbon residue value lower than 0.10% (m/m); for such products, first use GB/T 6536 to prepare a 10% (V/V) distillation residue, then determine it using this standard.
• 1.4 involves hazardous materials, operations, and equipment, but it is not intended to address all safety issues; users should establish appropriate safety and protective measures and determine applicable management systems before use.
• Not applicable: not explicitly listed in the available source.

3. Method principle

Place a weighed test sample into a sample tube, raise the temperature in an inert gas (nitrogen) atmosphere according to the specified temperature program, and heat to 500℃. Volatile substances generated during the reaction are carried away by the nitrogen, and the remaining carbonaceous residue is reported as a percentage of the original sample as the micro carbon residue value (Chapter 5, Method summary).

4. Reagents and materials (purity / preparation)

• Nitrogen: ordinary nitrogen with a purity of 98.5% or above, supplied through a two-stage regulator at a pressure of 0 kPa to 200 kPa; in practical application, the minimum gas flow pressure is 140 kPa (Chapter 6).
• Other reagents: not provided in the available source.

5. Apparatus and equipment

• 7.1 Sample tube: made of soda-lime glass or borosilicate glass, flat-bottomed. Capacity 2 mL, outer diameter 12 mm, height about 35 mm. When determining samples with a carbon residue amount lower than 0.20% (m/m), use a sample tube with a capacity of 4 mL, an outer diameter of 12 mm, a height of about 72 mm, and a wall thickness of 1 mm.
• 7.2 Dropper or glass rod: used for sampling when weighing the sample.
• 7.3 Coking oven: circular combustion chamber, diameter about 85 mm, depth about 100 mm, capable of being heated to 500℃ at a heating rate of 10℃ to 40℃ per minute, with an exhaust hole of inner diameter 13 mm, the inner cavity of the combustion chamber purged with preheated nitrogen (the gas inlet is near the top, and the exhaust hole is at the center of the bottom); a thermocouple or thermal sensing element is placed inside the combustion chamber to detect near but not touching the sample tube wall; equipped with a top cover that can isolate air; most of the vapor condensate flows directly into a removable collector at the bottom of the furnace chamber (see Figure 1).
• 7.4 Sample tube rack: a metal aluminum cylinder, diameter about 76 mm, thickness about 17 mm, evenly distributed with 12 holes (for holding sample tubes), each hole 13 mm deep and 13 mm in diameter, each hole about 3 mm from the periphery, with 6 mm long legs on the rack for positioning at the center of the furnace chamber; a small round hole on the edge serves as a starting arrangement sample position marker (see Figure 2).
• 7.5 Thermocouple: iron-constantan, including an external readout device, range 450℃ to 550℃.
• 7.6 Analytical balance: sensitivity 0.1 mg.
• 7.7 Cooler: desiccator or similar sealed container, without desiccant.

6. Recommended operating conditions

• Nitrogen purge: initial flow rate 600 mL/min, purge for at least 10 min; then reduce to 150 mL/min.
• Heating: heat the furnace to 500℃ at a heating rate of 10℃/min to 15℃/min.
• Constant temperature: hold at 500℃±2℃ for 15 min, then automatically turn off the furnace power.
• Cooling: allow to cool naturally under nitrogen flow (600 mL/min) purge; when the furnace temperature drops below 250℃, remove the sample tube rack and place it in a desiccator in the balance room for further cooling.
• Initial furnace temperature: when placing the sample tube rack, the furnace temperature is below 100℃.
• Next test: the next test may be started when the furnace temperature has cooled below 100℃.

7. Sampling and sample preparation

• 8.1 For samples composed of distillate oils, determination may be carried out according to steps 8.2 to 10.4, or a 10% (V/V) distillation residue may be prepared according to the modified procedure specified in 8.1.1 and 8.1.2 using GB/T 6536.
• 8.1.1 Prepare a 10% (V/V) distillation residue according to GB/T 6536; the apparatus is still installed according to GB/T 6536, but the thermometer at the neck of the distillation flask may be omitted, and only a closely fitting cork or silicone rubber stopper is used to tightly seal the mouth of the distillation flask so that it is safe and secure. Note: The key to this test procedure is collecting the volume of distillate, not the distillation temperature, so a thermometer is not necessary.
• 8.1.2 Stop heating when the volume of distillate in the graduated cylinder is 89 mL; when the liquid continues to flow into the graduated cylinder and just reaches 90 mL, remove the graduated cylinder, replace it with a small glass bottle, collect the last distillate flowing out of the condenser, and while hot combine it with the residue in the distillation flask and mix uniformly; this mixed residue represents the 10% (V/V) residue portion of the original sample, and is used in place of the sample described in 8.2 to 10.4.
• 8.2 Thoroughly stir the sample to be tested; for viscous or waxy petroleum products, first heat to reduce viscosity. When the sample is liquid, a small rod may be used to directly drip the sample onto the bottom of the sample tube; solid samples may also be dripped in after heating or frozen with liquid nitrogen, then broken, and a small piece placed at the bottom of the sample tube.

8. Analytical procedure

• 9.1 During sampling and weighing, use tweezers to hold the sample tube to reduce weighing errors; used sample tubes should generally be discarded.
• 9.2 Weigh a clean sample tube, record the mass, weighing to 0.1 mg.
• 9.3 Drip or place an appropriate mass of sample (see Table 1) onto the bottom of the weighed sample tube, avoiding the sample touching the wall, then weigh again, weighing to 0.1 mg, and record; place the sample tube containing the test sample onto the sample tube rack (at most 12), and record the position corresponding to each test sample according to the designated label.
  • Note: Each batch of test samples may include one reference sample. To determine the average percentage and standard deviation of carbon residue, this reference sample should be a typical sample that has been tested at least 20 times on the same instrument, to ensure the accuracy of the tested samples. When the reference sample result falls within ±3 times the standard deviation of the average carbon residue percentage of that sample, the test results of this batch of samples are considered credible; when the reference sample test result is outside the above limit range, it indicates a problem in the test process or instrument, and the test is invalid.
• Table 1 Sample amount:
  • Black viscous or solid, expected carbon residue value ≥5.0% (m/m), sample amount 0.15 g±0.05 g
  • Brown or black opaque fluid, expected carbon residue value ≥1.0% to 5.0% (m/m), sample amount 0.50 g±0.10 g
  • Transparent or translucent object, expected carbon residue value 0.2 to 1.0% (m/m), sample amount 1.50 g±0.50 g
  • Transparent or translucent object, expected carbon residue value ≤0.2% (m/m), sample amount 1.50 g±0.50 g or 3.00 g±0.50 g
• 10.1 When the furnace temperature is below 100℃, place the sample tube rack filled with test samples into the furnace chamber, cover the lid, and purge with nitrogen at a flow rate of 600 mL/min for at least 10 min; then reduce the nitrogen flow rate to 150 mL/min, and heat the furnace to 500℃ at a heating rate of 10℃/min to 15℃/min.
• 10.2 Hold the heating furnace at 500℃±2℃ for 15 min, then automatically turn off the furnace power; allow it to cool naturally under nitrogen flow (600 mL/min) purge. When the furnace temperature drops below 250℃, remove the sample tube rack and place it in a desiccator in the balance room for further cooling.
  • Note 1: After the sample tube rack is removed from the furnace, turn off the nitrogen. If the test sample in the sample tube foams or splashes causing sample loss, that test sample should be discarded and the test repeated.
  • Note 2: The cause of sample splashing may be that the sample contains water. It may be heated slowly under reduced pressure first, then purged with nitrogen to drive off water; another method is to reduce the sample amount.
  • Note 3: When the furnace temperature has cooled below 100℃, the next test may be started.
  • Caution: Introduction of air (oxygen) will form an explosive mixture with volatile coking products, which is unsafe, so the heating furnace lid must not be opened at any time during heating; during cooling, the furnace lid may be opened only when the furnace temperature drops below 250℃; nitrogen flow may be stopped only after the sample tube rack is removed from the furnace. Place the coking oven in a laboratory fume hood to discharge smoke promptly, or connect the heating furnace exhaust pipe to the laboratory exhaust system to remove smoke, taking care that the piping does not create negative pressure.
• 10.3 Use tweezers to hold the sample tube, move it to another desiccator, allow it to cool to room temperature, weigh the sample tube, weighing to 0.1 mg, and record. Used sample tubes should generally be discarded.
• 10.4 Periodically check the waste oil collection bottle at the bottom of the heating furnace, and if necessary, pour out its contents before putting it back.
  • Caution: The condensate in the waste oil collection bottle at the bottom of the heating furnace may contain some carcinogenic substances; contact with it should be avoided, and it should be buried or properly disposed of by feasible methods.

9. Qualitative and quantitative determination and calculation formulas

• The carbon residue X of the original sample or the distillation residue of 10% (V/V), % (m/m), is calculated according to formula (1):
  • X = (m3 − m1) / (m2 − m1) × 100
  • Where: m1—— mass of the empty sample tube, g; m2—— mass of the empty sample tube plus the mass of the test sample, g; m3—— mass of the empty sample tube plus the amount of carbon residue, g.
  • Note: In the original text, the formula layout of source-text extraction is "X-7 two M × 100", and it has been organized into the above formula according to the context and symbol explanations; requires confirmation against the source standard (source-text extraction).

10. Precision

Judge the reliability of the test results according to the following provisions (95% confidence level).

• 12.1 Repeatability (r): The difference between two results obtained by the same operator on the same sample shall not exceed the value calculated by formula (2) or the repeatability value shown in Figure 3.
  • r = 0.0770 X^(2/3) (formula 2)
  • Where: X—— arithmetic mean of two determination results, % (m/m).
  • Note: In the original text, source-text extraction is "0.0770X3/3", and it has been organized into X^(2/3) according to the context and the values in Figure 3; requires confirmation against the source standard (source-text extraction).
• 12.2 Reproducibility (R): The difference between two independent results for the same sample provided by two laboratories shall not exceed the value calculated by formula (3) or the reproducibility value shown in Figure 3.
  • R = 0.2451 X^(2/3) (formula 3)
  • Where: X—— arithmetic mean of two determination results, % (m/m).
  • Note: In the original text, source-text extraction is "R=0.2451X2/3", and it has been organized into X^(2/3) according to the context; requires confirmation against the source standard (source-text extraction).
• Figure 3 is a precision data chart for carbon residue (micro method), with the horizontal axis being the average carbon residue (micro method) % (m/m) 0~30, and the vertical axis being the precision value; values such as 0.054, 0.02, 0.01, etc. are visible in the figure, and the specific correspondence requires confirmation against the source standard (source-text extraction).

11. Report

Take the arithmetic mean of two repeat determination results as the carbon residue value of the test sample or the distillation residue of 10% (V/V), and report the result to the nearest 0.01% (m/m) (Chapter 13).

12. Normative References

• GB/T 268 Petroleum products — Determination of carbon residue (Conradson method)
• GB/T 508 Petroleum products — Determination of ash
• GB/T 6536 Petroleum products — Determination of distillation
• SH/T 0559 Determination of alkyl nitrate content in diesel fuel (spectrophotometric method)
• Adoption note: ISO 10370:1993 Annex B was adapted as the normative references in Chapter 2 of this standard; ISO 10370:1993 Chapter 1 Scope, paragraph 3 and the note were adapted as Chapter 4 Significance and Use of this standard.

13. Source and verification

This page is an AI translation of the available Chinese method card. Human verification is pending. It is not an official translation of the standard. Check the source standard and product certificate before use.

14. Quick Q&A Reference