Chinon(Qianneng) Technology-A Leader in Industrial Oil Purification Machine
Why Hydrotreating Matters
- Environmental regulations: Ultra-low sulfur diesel (ULSD) is required worldwide to reduce harmful emissions like sulfur oxides (SOx).
- Engine protection: Cleaner diesel prevents corrosion and extends the life of fuel injection systems.
- Product quality: Hydrotreating improves fuel stability, color, and cetane index (a measure of combustion quality).
The Basic Principle
A diesel hydrotreater uses hydrogen gas under high pressure and temperature in the presence of a catalyst to react with unwanted compounds. This process converts impurities into stable, easily removable forms:
- Sulfur → hydrogen sulfide (H₂S)
- Nitrogen → ammonia (NH₃)
- Oxygen → water (H₂O)
- Unsaturated hydrocarbons → saturated hydrocarbons (improving stability)
Main Process Steps
Feed Preparation & Mixing
- Diesel-range hydrocarbons from the atmospheric or vacuum distillation unit are mixed with high-purity hydrogen.
- The mixture is preheated in a feed/effluent exchanger.
Heating in the Furnace
- The combined feed passes through a fired heater (furnace) to reach reaction temperature, typically 300–380°C.
Reaction in the Catalyst Bed
- The heated stream enters a fixed-bed reactorfilled with a cobalt-molybdenum (Co-Mo) or nickel-molybdenum (Ni-Mo) catalyst.
- At high pressure (typically 30–70 bar) and temperature, hydrogen reacts with sulfur, nitrogen, and other impurities.
- These reactions produce H₂S, NH₃, and water vapor, while saturating olefins and aromatics.
Cooling and Separation
- The effluent from the reactor is cooled using heat exchangers and air/water coolers.
- It then enters a high-pressure separator, where hydrogen-rich gas is recycled back to the reactor (after purification), and the liquid stream moves forward.
Stripping & Product Recovery
- The liquid stream is sent to a stripper column, where light gases, H₂S, and NH₃ are removed.
- The final product is ultra-low sulfur dieselthat meets modern emission standards.
Key Features of a Diesel Hydrotreater
- Hydrogen recycle loopto maximize hydrogen usage.
- Amine treating & sour water systemsto handle H₂S and NH₃ byproducts.
- Multiple catalyst bedswith interstage quenching to control temperature.
- Safety systemsdue to high pressure and flammable hydrogen handling.
The Bigger Picture
Diesel hydrotreaters are just one part of a refinery’s hydroprocessing units, which also include naphtha hydrotreaters, kerosene hydrotreaters, and hydrocrackers. Together, they ensure that fuels are cleaner, safer, and compliant with environmental standards.
In short, a diesel hydrotreater acts like a “clean-up station” for fuel: it strips out harmful elements and leaves behind a higher-quality, environmentally friendly product.