What is End Point in Refining?
✅ End Point (EP) refers to the highest temperature at which the last fraction of a petroleum product evaporates during distillation. It is measured using ASTM D86 or similar distillation tests.
Why is End Point Important?
✔ Product Quality Control: Ensures that different fuel products (e.g., gasoline, diesel, jet fuel) meet boiling range specifications.
✔ Fraction Purity: Prevents contamination between adjacent fractions (e.g., diesel blending into kerosene).
✔ Performance & Safety: Higher end points in fuels can cause poor combustion, increased emissions, and engine deposits.
Typical End Points of Petroleum Fractions
| Product | End Point (°C) |
|---|---|
| LPG | – |
| Naphtha | 150-200°C |
| Kerosene | 250-300°C |
| Diesel | 350-380°C |
| Gas Oil | 400-450°C |
| Residue | Above 500°C |
Effect of High or Low End Point
✔ Too High End Point:
- Leads to heavier components in the product, affecting its properties (e.g., diesel with a high endpoint may not burn cleanly).
- Causes excessive smoke, poor atomization, and higher emissions.
✔ Too Low End Point:
- Lighter hydrocarbons are removed, leading to lower energy content in the fuel.
- May cause vapor lock in gasoline (fuel turns into vapor in the fuel system).
How to Control End Point in the Crude Distillation Unit (CDU)?
✔ Adjust column temperature to control the final boiling point of products.
✔ Optimize reflux ratio to improve separation.
✔ Use stripping steam to remove lighter hydrocarbons from heavy fractions.
✔ Monitor & adjust pump-around rates to maintain product specifications.