GB/T 17475-2020 in English

This standard replaces GB/T 17475-1998 and specifies the distillation method of heavy hydrocarbon mixtures (crude oil, residual oil, etc.) with an initial distillation point >150℃ and a final distillation point <565℃ under vacuum conditions of 6.6kPa-0.013kPa. The main technical upgrades include:

• Sensor accuracy enhancement: New calibration requirements for temperature sensors (±0.5℃) and pressure sensors (≤0.00133kPa)
• Operation mode expansion: Introducing two schemes: dynamic pressure reduction and step pressure reduction
• Safety control: Clear emergency stop procedures when there are signs of cracking (pressure surge of 10%, black smoke deposition)

The conversion between reduced pressure temperature (observed value) and atmospheric equivalent temperature (AET) is realized through the Maxwell-Bonnell equation:

AET = (T + 273.15) / (1 + 0.3861A - 0.00051606T) - 273.15

The coefficient A selects different calculation formulas according to the operating pressure range:

• ≥0.266kPa: A = (5.143222 - 0.972546lgP) / (T + 273.15)
• <0.266kPa: A = (5.897249 - 0.987672lgP) / (T + 273.15)

Pay attention to the correction of the influence of the Watson characteristic factor K value (default 12.0±0.2).

Typical operation process

1. Pretreatment: When the water content is greater than 0.1%, dehydrate according to Appendix C and measure the water content
2. Loading: Calculate the loading amount according to the cross-sectional area of the distillation head of 200-400mL/cm² (e.g. 4-8L for 50mm inner diameter)
3. Distillation control:
   • Dynamic pressure reduction method: Each time the pressure is reduced by 1/5, it needs to be stable for ≥2 minutes
   • Step pressure reduction method: Pause heating at 290℃ and restore 90% heating power after pressure reduction
4. Termination conditions: Reach the final distillation point, distillation> 90% or signs of cracking appear

Precision requirements

Repeatability: Temperature difference ≤6.1℃ at 30% distillation rate, reproducibility ≤13.5℃ (95% confidence level)

This standard was proposed by SAC/TC 280, mainly to solve the cracking interference problem of heavy oil products at high temperatures. Compared with the 1998 version:

• Added the requirement of temperature sensor response time ≤60s (Appendix A)
• Improved the pressure sensor calibration system (Appendix B)
• Modified the temperature-pressure conversion formula (Appendix D) to improve the calculation accuracy at >400℃

stainless steel still and glass still. Special attention should be paid to the difference in static holdup treatment between stainless steel still and glass still.