GB/T 6536-2010Standard test method for distillation of petroleum products at atmospheric pressure (English PDF)

5.1 Basic components of the instrument

5.1.1 The basic components of the distillation instrument are the distillation flask, the condenser and the connected condensation bath, the metal protective cover or enclosure for the distillation flask, the heater, the distillation flask holder and support plate, the temperature measurement device and the receiving cylinder for collecting the distillate.

5.1.2 The manual distillation apparatus is shown in Figure 1 and Figure 2.

14 - Distillation flask stand;

15 - Ground wire;

16 - Electric heater;

17 - Operation hole for adjusting the level of stand platform;

18 - Power cable;

19 - Receiving cylinder;

20 - Cooling bath of receiving cylinder;

21 - Cover of receiving cylinder.

Figure 2 -- Diagram of electric heating type distillation apparatus

5.2 Instrument details

The specific regulations of the instrument are detailed in Annex A.

5.3 Temperature measurement device

5.3.1 Glass mercury thermometer: shall meet the specifications of GB-46 and

GB-47 thermometers in GB/T 514. The GB-46 thermometer is a low temperature range thermometer. The temperature measurement range is -

2°C~300°C. The graduation value is 1°C. The GB-47 thermometer is a high temperature range thermometer. The temperature measurement range is -

2°C~400°C. The graduation value is 1°C.

When the thermometer is continuously exposed to a temperature higher than

370°C for a long time, the thermometer shall be zero-calibrated or verified in accordance with the provisions of GB/T 514 and JJG 50. Otherwise, the thermometer cannot be used again.

NOTE: When the observed thermometer reading is higher than 370°C, the temperature of the thermometer bulb is close to the stable limit range of the bulb glass. The calibration of the thermometer may be invalid.

5.3.2 Except for the glass mercury thermometer specified in 5.3.1, another

temperature measurement system can also be used in this method, as long as it is confirmed that it has the same temperature hysteresis, exposed liquid column influence and accuracy as the glass mercury thermometer.

5.3.2.1 The circuits and/or algorithms used in other temperature measurement

systems shall have the ability to simulate the temperature hysteresis of a glass mercury thermometer.

5.3.2.2 The temperature sensor can also be placed in the casing, so that the tip is covered. In this way, the temperature sensor system has a temperature lag time similar to that of a glass mercury thermometer due to its thermal quality and thermal conductivity have been adjusted.

8.1.2.1 If the temperature reading measured in the relevant instrument used

does not reach the value specified in Table 4 (see 8.1.2.2 Note and Table 4), then it is considered that this temperature measurement device is nonconforming and cannot be used in this method.

NOTE: Use toluene as calibration solution. It cannot give any information on the degree of temperature hysteresis of the electronic temperature measurement system simulating a glass liquid thermometer.

8.1.2.2 Use analytically pure toluene and hexadecane as the calibration fluid.

However, as long as it can ensure that the measurement accuracy of this method will not be reduced, other grades of reagents can also be used.

NOTE: When measuring with a local immersion thermometer, the reference boiling point of toluene at 101.3kPa is 110.6°C. The reference boiling point of hexadecane at 101.3kPa is 287.0°C. Since the thermometer used in this method is calibrated under full immersion conditions, the measurement results will generally be low. Affected by the type of thermometer and measurement conditions, the measurement results of different thermometers will be different.

8.1.3 Refer to Annex B for the steps to determine the temperature hysteresis.

8.1.4 Refer to Annex C for the steps to estimate the impact of the exposed liquid column.

8.1.5 Use hexadecane to verify the high temperature calibration of the

temperature measurement system. At 50% recovery volume, the temperature measurement system shall display a temperature result equivalent to the distillation conditions of Group 4 in Table 4 and the corresponding temperature of the relevant instrument.

NOTE: Due to the high melting point of hexadecane, the Group 4 verification distillation process needs to be carried out under the condition that the condensation temperature is greater than 20°C.

8.2 Automatic method

8.2.1 Level tracker: The level tracker or recording device in the automatic

distillation tester shall have a resolution of 0.1mL or better for each volume between 5mL and 100mL. The maximum error is 0.3mL. The calibration of the instrument shall be verified at an interval of no more than 3 months according to the instrument manual. Calibration is also required after the system has been replaced and repaired.

NOTE: The typical calibration procedure shall include the calibration of the output value when there are 5mL and 100mL of samples in the receiving cylinder, respectively.

9.5 Position the temperature sensor at the center of the neck of the distillation flask through the close-fitting device specified in 5.4. If a thermometer is used, use a silicone rubber stopper or a stopper made of other equivalent polymer materials, so that the thermometer bubble is located in the center of the bottleneck. The bottom end of the thermometer capillary shall be flush with the highest point at the bottom of the inner wall of the distillation flask branch pipe (see Figure 4). If a thermocouple or resistance thermometer is used, it shall be assembled according to the instrument manual (see Figure 5).

NOTE: If vacuum grease is used on the surface that matches the center positioning device, its amount shall be as small as possible.

9.6 Use a close-fitting cork stopper, silicone rubber stopper or stopper made of

other equivalent polymer materials to tightly connect the branch tube of the distillation flask to the condenser tube. Adjust the distillation flask to an upright position. Make the branch pipe of the distillation flask extend into the condenser tube by 25mm~50mm. Raise and adjust the distillation flask support plate to tightly contact the bottom of the distillation flask.

9.7 Put the previously measured specimen and the undried receiving cylinder

into the temperature-controlled cooling bath below the end of the condenser.

The end of the condenser tube shall be located in the center of the receiving cylinder, and extend into the cylinder at least 25mm, but not below the 100mL graduation line of the cylinder.

9.8 Determination of initial boiling point

9.8.1 Manual method: Use a piece of absorbent paper or similar material to

cover the receiving cylinder, so as to reduce evaporation loss in distillation. The paper or material used for covering shall be cut close to the condenser tube so that the cylinder can be tightly covered. If a receiving deflector is used, make the tip of the deflector just touch the inner wall of the receiving cylinder. If the receiving deflector is not used, the drip tip of the condenser tube shall not touch the inner wall of the receiving cylinder. Start distilling. Indicate the start time of distillation. Observe and record the initial boiling point, to the nearest of 0.5°C.

If the receiving deflector is not used, when the initial boiling point is observed, the receiving cylinder shall be moved immediately so that the drip tip of the condenser tube touches the inner wall of the cylinder.

9.8.2 Automatic method: Use the device provided by the instrument

manufacturer to reduce the evaporation loss during the distillation process.

Make the tip of the receiving deflector just touch the inner wall of the receiving cylinder. Start heating the distillation flask and specimen. Indicate the start time of distillation. Record the initial boiling point, to the nearest of 0.1°C.

9.9 Adjust the heating so that the time interval from the start of heating to the

WARNING: Due to the structure and test conditions of the distillation flask, if the vapor and liquid around the temperature sensor do not reach thermodynamic equilibrium, the distillation rate will affect the measured vapor temperature. Therefore, the distillation rate shall be kept as uniform as possible throughout the test.

NOTE: When measuring gasoline specimens, when the steam temperature reaches 160°C, sometimes it is found that the condensate suddenly forms an insoluble liquid phase and accumulates (bubbles) on the temperature measurement device and the neck of the distillation flask. This phenomenon will be accompanied by a rapid drop in steam temperature (about 3°C) and a drop in recovery rate. This phenomenon may be caused by traces of water in the specimen. Generally, it lasts about 10s~30s. Then the temperature rises again and the condensate starts to flow smoothly again. This point is commonly referred to as the "pause point".

9.12 If the distillation process fails to meet the requirements of 9.9, 9.10 and

9.11, the distillation shall be repeated.

9.13 If the decomposition point as described in 3.3 is observed, the heating shall be stopped and the step 9.17 shall be followed.

9.14 Between the initial boiling point and the final boiling point, observe and

record the calculation and report the data required by the specifications or the test results determined in advance. These observed data can include temperature readings at specified percent recovery and/or percent recovery at specified temperature readings.

9.14.1 Manual method: Record the volume reading of the receiving cylinder, to

the nearest of 0.5mL. Record the temperature reading, to the nearest 0.5°C.

9.14.2 Automatic method: Record the volume reading of the receiving cylinder, to the nearest of 0.1mL. Record the temperature reading, to the nearest 0.1°C.

9.14.3 Group 0: If no special data requirements are specified, record the initial boiling point, final boiling point and the temperature readings at every 10% recovery volume multiple between 10%~90% recovery volume.

9.14.4 Group 1, Group 2, Group 3 and Group 4: If no special data requirements are specified, record initial boiling point, final boiling point and/or dry point, temperature readings at 5%, 15%, 85% and 95% recovery volume, as well as the temperature reading at every 10% recovery volume multiple between

10%~90% recovery volume.

Group 4: When measuring jet fuel or similar products with a high temperature range thermometer, the relevant thermometer readings may be obscured by the central positioning device. If these data are needed, another distillation test shall be done according to the regulations of If these data are needed, another

If the actual front end loss differs from the estimated value by more than 2mL, the test shall be repeated.

9.16 Observe and record the final boiling point and/or dry point as needed. Stop heating.

9.17 After the heating is stopped, the distillate is completely dropped into the receiving cylinder.

9.17.1 Manual method: When there are continuous drops in the condenser tube dripping into the receiving cylinder, observe and record the condensate volume every 2min, to the nearest of 0.5mL, until the volume of two consecutive observations is the same. Accurately measure the volume of liquid in the receiving cylinder. Record it to the nearest of 0.5mL.

9.17.2 Automatic method: The instrument will continuously monitor the recovery

volume until the change in the recovery volume is less than 0.1mL within 2min.

Accurately record the volume of liquid in the receiving cylinder to the nearest

0.1mL.

9.18 Record the percent recovery corresponding to the volume of liquid in the

receiving cylinder. If the distillation is terminated prematurely due to the occurrence of a decomposition point, then subtract the percent recovery from

100%. Report this difference as the sum of the percent residue and the percent loss, and omit step 9.19.

9.19 After the distillation flask is cooled, and no more steam is observed, remove the distillation flask from the condenser. Pour its contents (except zeolite) into a 5mL graduated cylinder. Hang the distillation flask upside down on the cylinder. Let the liquid in the distillation flask drip until the volume of the liquid in the cylinder does not increase significantly. Measure the volume of the liquid in the cylinder to the nearest 0.1mL. Record it as the percent residue.

9.19.1 If the 5mL cylinder has no scale below 1mL, and the liquid volume is less than 1mL, then add 1mL of heavier oil to the pilot cylinder to better measure the volume of the recovered liquid.

If more residue is obtained than expected and the distillation is not artificially terminated before the final boiling point, check whether the heating during the distillation process is sufficient, and whether the conditions during the test meet the requirements of Table 5. If not, the test shall be repeated.

NOTE 1: The typical values of the volume fraction of distillation residues obtained from the determination of gasoline, kerosene and diesel fractions by this method are 0.9%~1.2%,

0.9%~1.3%, and 1.0%~1.4%, respectively.

NOTE 2: This method is not suitable for the analysis of distillate fuels containing more

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