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CDU Tutorial


CDU/VDU Simulation

Envision Systems CDU Tutorial
Copyright © 2009 by EnVision Systems Inc. All rights reserved worldwide.

CDU Tutorial

The interactive CDU/VDU tutorial provides an overview, fundamental principles, control principles and operating principles for an atmospheric crude distillation unit, using voice, video, animation and graphics.

The principles taught here are also applicable to a vacuum distillation unit.

The topics covered are:


  • Introduction
  • Crude Oil
  • Process Overview
  • Downstream Refinery Units    

CDU Process Components   

  • Crude Preparation
  • Desalter    
  • Preheat Train
  • Preflash Unit
  • Crude Heater    
  • Distillation System

Key Performance and Operating Variables

  • Introduction    
  • Product Specification
  • Desalter
  • Crude Heater Outlet Temperature
  • Tower Pressures    
  • Tower Temperatures
  • Pumparound Rates
  • Overflash Flow
  • Product Rates
  • Main Tower Stripping Steam Rate
  • Side Stripper Stripping Steam Rates

Operating Examples

  • Change in Crude Characteristics    
  • Increase Kerosene Production Rate
  • Decrease Initial Boiling Point of Light Gas Oil (IBP of LGO)

Envision Systems CDU / VDU Simulation
Copyright © 2009 by EnVision Systems Inc. All rights reserved worldwide.

CDU/VDU Simulation

The CDU/VDU simulation is a rigorous and high-fidelity mathematical process model that provides a realistic dynamic response for an atmospheric and vacuum fractionation unit.

Process Overview:

The atmospheric and vacuum fractionation unit separates crude into following product fractions: off gas, naphtha, kerosene, light gas oil (LGO), heavy gas oil (HGO), light vacuum gas oil (LVGO), heavy vacuum gas oil (HVGO), and vacuum residue.



Major Sections:

  • Desalter and Preheat Train
  • Preflash Drum
  • Atmospheric Furnace
  • Atmospheric Tower and Side Strippers
  • Vacuum Furnace
  • Vacuum Tower with Vacuum System


Major Operations for Trainee Practice:

  • Startup and Shutdown Operations
  • Normal Operations
  • Emergency Shutdown Operations
  • Troubleshooting Equipment, Instrument and Control Valve Malfunctions
  • Malfunction Recovery Actions


Simulation Features:

  • Detailed Tray-by-Tray Simulation of Crude Tower and Pre-Flasher
  • Detailed Simulation of Water-Oil Separation at Desalter
    • Effect of Pressure Drop across Mixing Valve
    • Effect of Voltage
  • Crude Characteristic Changes Tracked by TBP/ASTM Curve

  • TBP/ASTM Analysis of Product Fractions
  • Simulation of Physical Properties for Products
    • Flash Point
    • RVP
    • Pour Point
    • IBP, EBP
  • Interlock/Safeguard System
  • Equipment Details
  • Effect of Pumparound Flows on Tower Performance
  • Effect of Product Draw Rates on Tower Performance
  • Dynamic Tray Animation with Detailed Information
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