GB/T 17475-2020 Distillation test for heavy hydrocarbon mixtures—Vacuum kettle distillation method

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Card type: Test method

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

• Standard number: GB/T 17475—2020
• Chinese full title: Distillation test for heavy hydrocarbon mixtures—Vacuum kettle distillation method
• English name: Standard test method for distillation of heavy hydrocarbon mixtures—Vacuum potstill method
• Replacement relationship: replaces GB/T 17475—1998 "Distillation test method for heavy hydrocarbon mixtures (vacuum kettle distillation method)"
• Issued/implemented: issued on 2020-03-31, implemented on 2020-10-01
• Custodian: National Technical Committee for Standardization of Petroleum Products and Lubricants (SAC/TC 280)
• Drafting organizations: Sinopec Research Institute of Petroleum Processing, Daqing Oilfield Engineering Co., Ltd., Sinopec Engineering (Group) Co., Ltd. Luoyang Technology R&D Center, CNOOC Refining and Chemical Research Institute, Sinopec Tianjin Branch, China Petroleum Fuel Oil Co., Ltd. Research Institute
• Main drafters: Zhu Xinyu, Fan Dengli, Song Shouguo, She Qinglong, Hu Yanfang, Huang Shaokai, Zhong Guangwen, Duan Yongsheng
• Previous versions: GB/T 17475—1998

2. Scope of application and non-applicability

• Applicable to: heavy hydrocarbon mixtures with initial boiling point higher than 150 °C and final boiling point lower than 565 °C, such as the distillation process of heavy crude oil, petroleum fractions, residual oil, and synthetic oil.
• Reference implementation: preparation of gas oil and lubricating oil fraction samples may refer to this standard for implementation.
• It may be used to prepare residual oil for asphalt production, but it is not always suitable; prolonged thermal cracking in this test may change some of its properties.
• Note 1: The maximum cut temperature is related to the heating limit of the sample. For most samples, 565 °C is the highest cut temperature that can be reached; for heat-sensitive samples, the maximum cut temperature will be significantly lower than 565 °C; for heat-insensitive samples, it may be slightly higher than 565 °C.
• Note 2: For distillation of crude oil with a cut point before 400 °C, the test method specified in GB/T 17280 may also be used, but the distillation curve and fraction properties obtained cannot be directly compared with those obtained using this standard.

3. Method principle

• 4.1 Distill a certain volume of sample under an absolute pressure of 6.6 kPa–0.013 kPa (50 mmHg–0.1 mmHg) and a specified distillation rate, cutting fractions according to preselected temperatures; record the vapor temperature, operating pressure, and other variables at each cut point.
• 4.2 Weigh the mass of each fraction, and calculate the mass yield of each fraction based on the mass of each fraction and the total recovered mass.
• 4.3 Measure the density of each fraction, calculate the volume of each fraction at 15 °C or 20 °C, and calculate the volume yield.
• 4.4 Based on the results of 4.2 and 4.3, plot the distillation curve of cut temperature versus the mass percentage yield or volume percentage yield (or both) of the fractions.

4. Reagents and materials (purity / preparation)

• Reference substances (melting point calibration, Table B.1): tin-lead-cadmium alloy (mass ratio 50:32:18) 145.0 °C; tin 231.9 °C; lead 327.4 °C.
• Reference substances (atmospheric boiling point calibration, Table B.2): water 100.0 °C; n-heptane 98.5 °C; tetralin 207.2 °C; n-tetradecane 252.5 °C. Purity requirement is 99.9% or above and the accurate boiling point must be known.
• Silicone oil or other inert liquid: used for the bottom of the melting point bath thermal sleeve, 0.5 mL (B.2.2.1).
• Dry ice: crushed dry ice for cold trap (5.5.5, 5.7.4).
• Toluene: for net holdup determination in Appendix E (E.4.1).
• Ethanol or acetone: for cleaning adhering water droplets in Appendix C (C.5.7).
• Nitrogen: for dehydration in Appendix C (C.5.2).
• Mercury: for McLeod vacuum gauge and mercury manometer (5.5.6, B.3.1.3).
• Vacuum grease: for applying to joints (7.1).
• Other purity/preparation details: not provided in the available source.

5. Apparatus and equipment

• 5.1 Overview: 4 sizes of apparatus, distinguished by distillation head inner diameter 25 mm, 36 mm, 50 mm, 70 mm. The main body of the apparatus consists of the distillation kettle, distillation head with entrainment separator and insulation jacket, condenser, vapor temperature sensor, vacuum gauge connector, fraction withdrawal line, fraction receiver, vacuum pump line, and vacuum pump (Figure 2).
• 5.2 Distillation kettle: volume at least 50% larger than the charge volume; recommended loading factor is a charge amount of 200 mL~400 mL per square centimeter of distillation head neck cross-sectional area. Made of hard borosilicate glass; if volume is greater than 10 L, stainless steel should be used. Equipped with a thermocouple well 6 mm from the bottom, off-center; stainless steel kettles should be equipped with a cooling coil (Figure 3, Table 3).
• Table 2 Standard charge amount and distillation kettle dimensions:
  • 25 mm: neck cross-sectional area 5 cm², charge amount 1–2 L, distillation kettle volume 2–3 L
  • 36 mm: 20 cm², 2–4 L, 3–6 L
  • 50 mm: 40 cm², 4–8 L, 6–12 L
  • 70 mm: the neck cross-sectional area value in this row of the original table requires confirmation against the source standard (source-text extraction), charge amount 8–16 L, distillation kettle volume 12–24 L
• Table 3 Distillation kettle dimensions (A ground joint, B volume): 25 mm: 35/25, 3 L; 36 mm: 65/40, 6 L; 50 mm: 75/50, 12 L; 70 mm: 102/75, 24 L.
• 5.3 Stirring system: the magnetic stir bar for glass kettles should have a diameter of 3 mm and a length of 20 mm; the stir bar for stainless steel kettles should have a diameter of 6 mm and a length of 50 mm; edges should be rounded and smooth; the external magnetic drive should be able to rotate the stir bar at the bottom of the kettle, with the lower part close against the heating mantle.
• 5.4 Heating system: the distillation kettle is heated by a quartz glass fiber heating mantle with reinforcing ribs on the lower half, maintaining an evaporation rate of 150 mL/(h·cm²) neck cross-sectional area, with a heating density of 0.5 W/cm²; usually two or more sets of heating furnace wires are used. The temperature sensor is placed between the distillation kettle and the heating mantle. The upper half of the distillation kettle is covered with a heat loss compensation heating mantle, with a heating density of 0.2 W/cm².
• 5.5 Distillation head: made of hard borosilicate glass, externally covered with a vacuum silver-plated jacket, and the vacuum degree inside the jacket should reach 0.000 1 kPa (0.000 75 mmHg). A glass fiber insulating heating mantle maintains the outer wall temperature of the vacuum jacket at 5 °C lower than the central vapor temperature. The vapor temperature sensor is placed at the center of the distillation head neck, with the top of the sensitive end below the overflow point by 3 mm±1 mm. Figure 1 and Table 1 give the distillation head dimensions.
• 5.5.4 Vapor temperature sensor: platinum resistance, sheathed thermocouple, or other equipment meeting the requirements may be used; response time less than 60 s (Appendix A); reading accuracy at least 0.5 °C, resolution at least 0.1 °C; full-range calibration should be performed on first use, and calibration should be performed at least once a year according to B.2.2; certified sensors should be traceable to the original temperature standard; recalibration should be performed after repair or maintenance; calibration should be performed at least once a month (accurate resistance method or distillation of pure compounds with known accurate boiling points according to B.2.3).
• 5.5.5 Distillation head cold trap and temperature sensor components (Figure 4): the interior of the cold trap should be filled with crushed dry ice throughout the entire distillation process.
• 5.5.6 Vacuum sensor: connected to the cold trap branch tube, should be able to measure pressures less than or equal to 0.001 33 kPa (0.01 mmHg); a non-tilting McLeod vacuum gauge or other reference instrument may be used; when pressure is only reduced to about 1 kPa, a mercury manometer may be used for calibration; diaphragm-type electronic sensors may also be used; sensors based on hot wire, radioactive, or conductivity detectors are not suitable. Uncertified sensors should be calibrated according to B.3; recalibration should be performed after repair or maintenance; pressure sensors should be checked at least once a week.
• 5.6 Condenser: made of hard borosilicate glass, connected to the outlet of the distillation head branch tube (Figure 5, Table 4). The condensate temperature should be able to reach 70 °C to prevent wax solidification.
• Table 4 Condenser dimensions table: 25 mm: A 51, B 28, C 300, D 35/25; 36 mm: A 75, B 45, C 300, D 65/40; 50 mm: A 80, B 54, C 400, D 75/50; 70 mm: A 120, B 80, C 400, D 102/75 (unit mm).
• 5.7 Vacuum pump line: thick-walled rubber tubing or light metal tubing, with an inner diameter at least equal to half the inner diameter of the condenser, and a length not exceeding 2 m; near the vacuum pump, connect a buffer tank with a volume at least equal to the flask volume; place a dry ice cold trap before the buffer tank; install an isolation valve between the buffer tank and the vacuum pump, with an inner diameter at least equal to the line inner diameter; between the upper part of the distillation head and the vacuum sensor, place the hard borosilicate glass distillation head cold trap shown in Figure 4, filled with crushed dry ice throughout.
• 5.8 Vacuum source: a single-stage mechanical vacuum pump capable of stably maintaining the system pressure.
• 5.9 Receiving system: connected at the low-end outlet of the product condenser, consisting of a vacuum adapter that can discharge fractions without disturbing the system pressure (Figure 6, Table 5). The fraction receiver is made of hard borosilicate glass, with a total volume comparable to the components to be received, and is calibrated from the bottom up to 1% of full scale. A device capable of collecting fractions stepwise or simultaneously may be used, but it should allow the system operating pressure to remain stable throughout the distillation process; if the product is to be kept liquid, a heating device should be provided.
• Table 5 Fraction receiver size table: 25 mm: A 45, B 120, C 35/25; 36 mm: A 51, B 120, C 35/25; 50 mm: A 64, B 150, C 50/30; 70 mm: A 75, B 150, C 50/30 (unit mm).
• Warning: The apparatus is operated under high vacuum and high temperature; the vessel and tank should be covered; the front protective device should be transparent and easy to open; automatically operated apparatus should be equipped with an automatic fire extinguisher, cooling water, and an alarm system.

6. Recommended operating conditions

• Operating pressure range: 6.6 kPa–0.013 kPa (50 mmHg–0.1 mmHg) (4.1).
• Table 6 Operating pressure and distillation rate:
  • Operating pressure 6.7 kPa (50 mmHg): evaporation rate 90–150 mL/(h·cm²); distillation rate 25 mm 450–750 mL/h, 36 mm 900–1 500 mL/h, 50 mm 1 800–3 000 mL/h, 70 mm 3 600~6 000 mL/h
  • 1.3 kPa (10 mmHg): 75–125 mL/(h·cm²); 25 mm 375–625, 36 mm 750–1 250, 50 mm 1 500–2 500, 70 mm 3 000~5 000 mL/h
  • 0.33 kPa (1 mmHg): 45–75 mL/(h·cm²); 25 mm 225–375, 36 mm 450–750, 50 mm 900–1 500, 70 mm 1 800~3 000 mL/h
  • 0.040 0 kPa (0.3 mmHg): 30–50 mL/(h·cm²); 25 mm 150–250, 36 mm 300–500, 50 mm 600–1 000, 70 mm 1 200~2 000 mL/h
  • 0.013 3 kPa (0.1 mmHg): 10–20 mL/(h·cm²); 25 mm 50–100, 36 mm 100–200, 50 mm 200–400, 70 mm 400~800 mL/h
• Heating: The distillation vessel temperature rises rapidly but should not exceed 300 °C/h; the distillation vessel surface temperature should not exceed 400 °C (8.7).
• Distillation head compensating heating mantle: maintain the outer wall temperature of the distillation head about 40 °C lower than the liquid temperature in the distillation vessel (8.8); after distillation begins, adjust the compensating heater to maintain the outer wall temperature of the distillation head glass jacket 5 °C lower than the vapor temperature (8.10).
• Initial pressure selection: According to Figure 7 and Table 6, select the highest pressure consistent with the expected initial boiling point and the lowest pressure consistent with the expected final boiling point; for samples with an initial boiling point around 343 °C (such as residue obtained from the GB/T 17280 test), a pressure of 0.133 kPa (1.0 mmHg) should be selected (8.9).
• Distillation rate recommended at 80% of the maximum allowable value (8.10 Note).
• Stabilization before final cut point: stabilize for at least 2 min before reaching the cut point (8.12).
• Experience: usually at a pressure of 0.133 kPa, when the crude oil sample distillation is running well, the distillate amount can reach 25%~30% of the initial sample volume (8.12).
• Stepwise pressure reduction: continue distilling the product until the final cut point, or until the liquid temperature in the distillation vessel reaches approximately 290 °C (8.16).
• If it is expected that the liquid phase temperature in the distillation vessel will exceed 320 °C when the final cut point is reached, slow down until heating stops, until the distillation rate slows or stops, requiring 2 min~10 min; then slowly reduce the pressure; reducing the pressure by 1/5 or 1/6 can produce an appropriate amount of distillate at the column head (8.17).
• Restore the original heating rate to 90%, adjust the distillation rate to a lower level (see Table 6); after the pressure stabilizes at this rate, no fraction should be cut within 2 min (8.18).
• When the liquid temperature in the distillation vessel reaches above 310 °C, the final cut point should be reached within 1 h (8.19).
• Stopping conditions: reaching the final cut point, or after distilling off 90% of the sample volume fraction, or upon the onset of initial cracking (8.21).
• Cooling: stop heating, slowly increase the pressure, continue stirring to cool the residue in the distillation vessel; open the insulation jacket of the distillation vessel; for the stainless steel distillation vessel, pass air through the cooling coil (8.21, 8.22).
• When the residue temperature drops to 150 °C, remove and weigh the distillation vessel (8.23).

7. Sampling and sample preparation

• 6.1 Sampling may be performed according to GB/T 4756, or the sample may be obtained from the GB/T 17280 test.
• 6.2 When receiving the sample, the sample should be sealed in an airtight container and should not leak.
• 6.3 If the sample has waxed or solidified, it should be heated to a liquid to ensure uniform mixing before use.
• 6.4 If the sample is found to contain water, pre-distillation should be carried out as described in Appendix C to remove water.
• Appendix C Dehydration of water-containing oil samples (>0.1% water): distill at atmospheric pressure to 150 °C, combine the dehydrated distillate oil with the bottom oil, and calculate the percentage of water. The apparatus requirements are as shown in Figure 2; a capillary tube is placed in the distillation vessel and nitrogen is introduced. Procedure: C.5.1 Pour off the settled water, weigh the distillation vessel and sample (to the nearest 1 g); C.5.2 After installation, introduce nitrogen through the capillary tube (8 cm³/s), and use dry ice to lower the temperature of the cold trap at the condenser outlet to -70 °C; C.5.3 Heat gently to distill out the distillate until water stops flowing out, then continue heating to additionally distill 3%~5% of the fraction; C.5.4 Turn off the heat and cool to below 175 °C; C.5.5 Weigh the distillate and the bottom oil; C.5.6 Separate the fraction below -5 °C and weigh the mass of water; C.5.7 Remove the distillation head and condenser, clean adhering water droplets with ethanol or acetone, dry, and reinstall; C.5.8 Mix the cut fraction with the bottom oil; the fraction in the cold trap is no longer mixed in; C.5.9 Record the mass of oil after dehydration.
• Appendix C Calculation: w = A/B × 100% (Equation C.1), where A is the mass of water collected (g), B is the sample mass (g), and w is the mass fraction of water.
• Appendix C Precision and bias: not provided in the available source.

8. Analysis procedure

• 8.1 Determine the sample density according to GB/T 13377 or GB/T 1884, and correct it to the density at 15 °C or 20 °C according to GB/T 1885.
• 8.2 Place a stir bar.
• 8.3 According to Table 2, find the sample volume that can be loaded, and calculate the sample mass from the loaded sample volume and density.
• 8.4 Weigh the test sample accurately to 0.1% of the charge amount. When the distillation still is too large, the distillation still may be lowered, and the test sample may be pressed into the distillation still using 90 kPa~95 kPa positive pressure (weigh the transfer tube mass); if the test sample is viscous or solidified, it may be heated appropriately; the mass may be calculated by the difference method.
• 8.5 Install the distillation still on the distillation column (referring to a small distillation still), fasten all heating mantles, place and start the stirring device.
• 8.6 Two methods of continuous cutting: the dynamic method (gradually reducing pressure during distillation) or stepwise pressure reduction (slowing or stopping the distillation rate to carry out pressure reduction operation to reach the final cut point). In both cases, stopping of the distillate caused by reducing the distillation rate should be avoided, and fraction entrainment caused by too rapid pressure reduction should also be avoided.
• 8.7 Heat the distillation still so that the test sample temperature rises rapidly, but it should not exceed 300 °C/h; the surface temperature of the distillation still should not exceed 400 °C, otherwise the test sample near the wall of the distillation still will undergo cracking. Warning: some hydrocarbon mixtures cannot withstand 400 °C high temperature for a long time; in this case, the surface temperature should be reduced.
• 8.8 Energize the compensation heating mantle of the distillation head to maintain the outer wall temperature of the distillation head about 40 °C lower than the liquid temperature in the distillation still.
• 8.9 Gradually reduce the pressure to an appropriate initial pressure. According to Figure 7 and Table 6, select the highest pressure consistent with the expected initial boiling point and the lowest pressure consistent with the expected final boiling point; for a test sample with an initial boiling point of about 343 °C (such as residual oil obtained from a GB/T 17280 test), it is advisable to select a pressure of 0.133 kPa (1.0 mmHg). Note: sometimes before actual distillation begins, the test sample may undergo obvious degassing, characterized by foaming but not producing condensable vapor.
• 8.10 At the start of distillation, vapor can be seen entering the neck of the distillation still. Reduce the heating amount to a certain value, maintain the distillation rate selected in Table 6, adjust the compensation heater, and maintain the outer wall temperature of the glass jacket of the distillation head about 5 °C lower than the vapor temperature. Note: 80% of the recommended maximum allowable value.
• 8.11 When the observed initial vapor temperature is lower than or reaches 150 °C, start the refrigerator to cool the first fraction receiver to ensure recovery. When solid wax appears on the receiver wall, the receiver may be heated with an infrared lamp or an electric hair dryer to liquefy the fraction. Automated instruments should heat the receiver sufficiently to liquefy the fraction, but not too high, so as to avoid volatilization of light fractions.
• 8.12 Dynamic method pressure reduction: calculate the final boiling point temperature based on the difference between operating pressure and temperature (the temperature difference is the difference between the vapor and the still temperature). Assuming that the temperature difference between the vapor and the still remains relatively constant, judge whether the final vapor temperature can reach the final cut point at the current operating pressure while ensuring that the still temperature does not exceed the limit (see 8.17). If the vapor temperature at the initial pressure cannot reach the final cut point temperature, the pressure should be gradually reduced to a pressure that can reach the final cut point. During pressure reduction, attention should be paid to ensuring a suitable distillation rate (see Table 6) and the still temperature limit. The pressure should be reduced low enough to ensure that the distillation rate increases slightly, while avoiding fraction entrainment. The distillation rate should comply with the provisions of Table 6, and it should be ensured that it is stable for at least 2 min before reaching the cut point. Experience shows that usually under a pressure of 0.133 kPa, when the crude oil sample distills well, the distillate amount can reach 25%~30% of the initial sample volume. Repeat the above operation to distill the remaining test sample until an operating pressure satisfying the distillation final cut point temperature is obtained, while noting that the temperature of the entire distillation apparatus should not exceed the maximum value, and the still temperature should not exceed the temperature and time limits (see 8.17).
• 8.13 If the fraction fills the receiver, or the cut temperature is reached, remove the receiver or switch the receiver. Manual instrument: use a vacuum adapter to cut the fraction, vent, replace with another empty receiver, evacuate the new receiver to close to the system pressure, and then connect it to the system; automated instrument: receiver switching is automatic, no special attention is needed.
• 8.14 Record the following observed values: time (h or min); distillate volume (mL); vapor temperature (accurate to 0.5 °C); liquid temperature in the distillation still (°C); distillation pressure (accurate to 1%); temperature at atmospheric pressure calculated according to Appendix D.
• 8.15 Proceed to 8.19.
• 8.16 Stepwise pressure reduction method: achieved by initializing distillation and operating at a stable distillation pressure (see 8.9). Continue distilling the product until the final cut point, or the liquid temperature in the distillation still reaches about 290 °C.
• 8.17 If it is expected that when the final cut point is reached, the liquid phase temperature in the distillation still exceeds 320 °C, then slow down until heating stops, until the distillation rate slows or stops; this process depends on the amount of test sample in the distillation still and requires 2 min~10 min. Then slowly reduce the pressure until an appropriate amount of distillate can be produced; reducing the pressure by 1/5 or 1/6 can produce an appropriate amount of distillate at the column head.
• 8.18 Restore the original heating rate of 90%, adjust the distillation rate to a lower level (see Table 6); after the pressure is stable at this rate, no fraction should be cut within 2 min. Repeat the operations of 8.16 and 8.17 until the pressure reaches a level at which distillation can reach the final cut point before the liquid temperature reaches 320 °C.
• 8.19 If no sign of the test sample beginning to crack is found, continue distillation, carefully heating the distillation still to maintain the fraction outflow rate. When the liquid temperature in the distillation still reaches above 310 °C, the final cut point should be reached within 1 h.
• 8.20 When signs of beginning cracking are observed, stop distillation immediately. Note 1: cracking has a great influence on the properties of the cut fractions and the residue in the distillation still; for example, the density and viscosity of cracked products are significantly lower than those of uncracked products. Note 2: the initial sign of cracking is usually the observation of an obvious and persistent pressure rise (for example, exceeding 10% of the pressure set value), or the observation of an increased working load of the vacuum pump; automatic vacuum controllers sometimes mask the initial pressure rise at the beginning of cracking; other initial signs of cracking include thin black deposits accumulating on the distillation column, or smoky vapor appearing in the system after condensation.
• 8.21 When the final cut point is reached, or after a volume fraction of 90% of the test sample has been distilled, or when initial cracking occurs, stop distillation. Stop heating, slowly increase the pressure, and continue stirring to cool the residue in the distillation still. Note: if the distillate exceeds a volume fraction of 90% of the test sample, the distillation still is close to being distilled to dryness, which is unfavorable for safety.
• 8.22 Open the insulation cover of the distillation still; for a stainless steel distillation still, pass air through the cooling coil.
• 8.23 When the temperature of the residue in the distillation still drops to 150 °C, remove and weigh the distillation still, and calculate the mass of the residue. For a larger distillation still, use a positive pressure of about 10 kPa to press the residue out from the oil charging tube.
• 8.24 Weigh all fractions, accurate to 0.1% of the test sample mass.
• 8.25 Determine the density of all fractions according to GB/T 1884 or GB/T 13377, and use GB/T 1885 to convert to the density at 15 °C or 20 °C.
• 8.26 Small distillation still: use another distillation still and a solvent such as toluene for distillation, wash the distillation head and condenser tube; then blow dry the solvent with air, and determine the amount of adhering matter. The adhering matter may be treated as a separate fraction (estimate its density), or may be mixed into the residue; if other properties of the residue besides density need to be analyzed, the adhering matter should be mixed into the residue. Large distillation still: determine the adhering amount according to Appendix E; the adhering matter of a large distillation still includes adhering matter from both the distillation head and the distillation still, and these adhering matters should be taken as a separate fraction and their density determined.
• Appendix E Determination of net holdup: E.3.1 After the distillation process is completed, the residual amount on the inner wall of the distillation apparatus is greater than 0.5%; E.3.2 static holdup includes adhering matter in the distillation still. Operation: E.4.1 Charge toluene equivalent to 10%~20% of the normal charge amount; E.4.2 heat to boiling, wash all components (about 3 min), then stop heating; E.4.3 after the distillation flask cools, recover the solvent in the distillation still and the distilled solvent in a fume hood, and pass gentle air to blow away the last trace of solvent; E.4.4 weigh the static holdup and determine its density; E.4.5 treat the static holdup as a separate fraction. E.5 Precision and bias: not provided in the available source.

9. Qualitative and quantitative and calculation formulas

• 9.1 Calculate the sum of all fractions and adhering amounts, and calculate the proportion of the test sample. The resulting mass fraction should be between 99.6%~100.1%. In the report, indicate the actual loss and the proportion of the loss in the total fractions.
• 9.2 Calculate the volume of each fraction based on the relative density and mass of each fraction.
• Appendix D Conversion between observed vacuum vapor temperature and atmospheric pressure temperature (AET):
  • D.3.1 Calculate AET according to formula (D.1): AET = 748.1A / (1/(T+273.15) + 0.386 1A - 0.000 516 06) - 273.15 Where: AET is the corresponding temperature at atmospheric pressure (°C); T is the observed vapor temperature (°C); A is the calculation factor.
  • a) When the operating pressure is greater than or equal to 0.266 kPa (≥2 mmHg), A is calculated according to formula (D.2) or formula (D.3): A = 5.143 222 - 0.972 546 lgP / (2 579.329 - 95.76 lgP) (P unit kPa, formula D.2) A = 5.994 295 - 0.972 546 lgP / (2 663.129 - 95.76 lgP) (P unit mmHg, formula D.3)
  • b) When the operating pressure is less than 0.266 kPa (<2 mmHg), A is calculated according to formula (D.4) or formula (D.5): A = 5.897 249 - 0.987 672 lgP / (2 962.909 - 43.00 lgP) (P unit kPa, formula D.4) A = 6.761 559 - 0.987 672 lgP / (3 000.538 - 43.00 lgP) (P unit mmHg, formula D.5)
  • D.3.2 The above formula is applicable when the distillate Watson K value is 12.0±0.2; or when both parties agree that the effect of the K value is negligible.
  • D.3.3 When correction is required, the K value is calculated according to formula (D.6): K = ∛(1.8(B+273.15)) / D, where B is the mid-average boiling point (°C), and D is the relative density of 15.6 °C. Conventionally, the midpoint temperature of the distillate vapor or the midpoint temperature of gas chromatographic distillation may be used as the mid-average boiling point, but this should be stated when used. Figure D.1 may be used to estimate the K value.
  • D.3.4 The atmospheric temperature correction value is calculated according to formula (D.7): t = -1.4[K-12][lg(p₀/p)], where t is the correction value, p₀ is the atmospheric pressure (kPa), and p is the observed pressure (kPa). Figure D.2 may be used to estimate the atmospheric temperature correction value.
• Appendix C Water mass fraction: w = A/B × 100% (formula C.1).

10. Precision

• 11.1.1 The reliability of results is judged according to the following provisions (95% confidence level). Note: The precision data come from the 1986 annual unified operation experiment (6 samples, 5 laboratories), the 1988 annual unified operation experiment (3 samples, 4 laboratories), and operation experiments by a single laboratory on different samples (5 samples, 3 laboratories). Although these data do not fully meet the statistical test requirements for determining precision, due to time and funding constraints, no additional operation tests will be initiated in the near future.
• 11.1.2 Repeatability: For the same operator, using the same instrument, on the same sample, the difference between two test results obtained shall not exceed the value listed in Table 7.
• 11.1.3 Reproducibility: For different operators, in different laboratories, using different instruments, on the same sample, the difference between two single, independent results obtained shall not exceed the value listed in Table 7.
• Table 7 Repeatability and reproducibility requirements (unit °C):
  • Volume fraction of distilled liquid 10%: repeatability 6.1, reproducibility 16.9
  • 20%: repeatability 4.5, reproducibility 12.8
  • 30%: repeatability 6.1, reproducibility 13.5
  • 40%: repeatability 4.9, reproducibility 11.2
  • 50%: repeatability 5.7, reproducibility 14.2
  • 60%: repeatability 4.1, reproducibility 8.4
  • 80%: repeatability 4.8, reproducibility 11.4
  • 90%: repeatability 4.9, reproducibility 5.1
  • In Table 7, the 70% row: not provided in the available source (the 70% row data does not appear in the source-text extraction table)
• 11.2 Bias: Because there is no suitable sample for determining bias, no bias test of this method was conducted.
• Appendix A Precision and bias: not covered, because the measurement results are only used to determine whether the sensor temperature response time meets the specification requirements.
• Appendix C Precision and bias: not covered, because it is only used to provide samples for the test method of this standard.
• Appendix E Precision and bias: not described, because the results are only used in the test method in the main text of this standard.

11. Report

• 10.1 The report shall include: a) The mass of the sample, in grams (g); b) The density of the sample at 15 °C or 20 °C, in grams per cubic centimeter (g/cm³), retained to four significant figures; c) The volume of the sample at 15 °C or 20 °C, in milliliters (mL); d) The gain or loss of total volume, accurate to 0.1%; e) According to the boiling point list of the fractions, place the residue last; f) The calculated cumulative mass and volume percentages.
• 10.2 List the observed and recorded data described in 8.14 as a second table and attach it. Figure 8 Example distillation report, Figure 9 Example distillation record.
• 10.3 Using the cut temperature (AET, °C) as the ordinate and the mass and volume yields as the abscissa, draw a smooth distillation curve.

12. Normative references

• GB/T 1884 Standard test method for density of crude petroleum and liquid petroleum products (hydrometer method)
• GB/T 1885 Petroleum measurement tables
• GB/T 4756 Standard practice for manual sampling of petroleum liquids
• GB/T 13377 Determination of density or relative density of crude petroleum and liquid or solid petroleum products—Capillary-stoppered pyknometer and graduated bicapillary pyknometer methods
• GB/T 17280 Standard test method for distillation of crude petroleum—15- theoretical plate distillation column
• GB/T 1.1—2009 (mentioned in the foreword, drafting rules)

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 reference for questions and answers