In-Depth Notes on Petroleum Refining Processes

Petroleum Refining Overview

  • Petroleum refining processes convert crude oil into useful petroleum products and petrochemicals.
  • Jurong Island in Singapore is a major petrochemical and refining hub, processing over 1.5 million barrels of crude oil daily.

Refining Flowchart

  • The refining process includes:
    • Separation: Techniques to isolate components of crude oil based on physical characteristics.
    • Conversion: Processes that modify the chemical structure of hydrocarbons.
    • Finishing: Final treatment to meet product specifications.

Key Processes in Petroleum Refining

  • Separation:
    • Utilizes physical differences to separate hydrocarbon compounds.
    • Processes include:
    • Desalting
    • Distillation
    • Deasphalting
    • Dewaxing
  • Conversion:
    • Alters the hydrocarbon composition chemically.
    • Includes processes like thermal cracking.
  • Finishing:
    • Involves removing impurities (e.g., S, N, metals) and blending products to meet specifications and regulations.

Desalting Process

  • Purpose: Remove salts that can cause corrosion and catalyst deactivation in downstream processes.
  • Crude oil is mixed with water; salts and impurities are removed, forming a brine layer.

Distillation Process

  • Involves heating crude oil to separate it into different fractions based on boiling points.
  • Crude Distillation Unit (CDU):
    • Heaviest product, atmospheric residue, sent for further processing in the Vacuum Distillation Unit (VDU) to further separate lighter and more valuable molecules.
  • Reflux in distillation improves separation by returning condensed liquid back to the column.
  • Effect of Vacuum:
    • Lower pressure allows separation of heavier fractions at lower temperatures, preventing coking and other operational issues.

Deasphalting and Dewaxing Processes

  • Deasphalting:
    • Removes asphaltenes from vacuum residue using liquid propane as a solvent, yielding deasphalted oil (DAO) suitable for further processing.
  • Dewaxing:
    • Aims to remove waxy components to enhance pourability of lubricant base oil at low temperatures.
    • Can be executed through solvent dewaxing or catalytic dewaxing, which both help to reduce viscosity and improve lubricant characteristics.

Thermal Cracking Overview

  • Thermal cracking breaks down large hydrocarbon molecules into smaller ones using heat.
  • Types of thermal cracking:
    • Visbreaking: Mild thermal cracking to reduce viscosity and produce light products.
    • Coking: Severe cracking that converts vacuum residue into lighter products and solid coke.
    • Steam Cracking: Utilizes steam to convert lighter hydrocarbons into olefins and aromatics, significant for petrochemical production.

ExxonMobil Case Study

  • The Singapore Refinery of ExxonMobil is the largest in the world, processing 592,000 barrels of crude oil per day and producing various fuels and lubricants integrated with a nearby chemical plant.