Process Engineering Beginner's Guide

CHAPTER SIXPITFALLS IN COMPUTER MODELING

A refinery model, based on the operating characteristics of process equipment including:

• Distillation Trays
• Packed Towers
• Heat Exchangers
• Air Coolers
• Fired Heaters
• Steam Turbines & Surface Condensers
• Centrifugal Pumps – NPSH
• Compressors
• Piping Systems

can be created by computer simulation calculations. Superficially, the use of computerized calculation methods are more accurate in representing actual equipment functions than the older methods that have now been largely displaced by modern computer calculation process engineering techniques.

BASIS FOR PROCESS ENGINEERING CALCULATIONS

In the early 1960s, methods of executing process engineering calculations were gradually replaced by current methods. These rely on numerous iterative calculations that could never be done using manual calculation tools. In the early 1960s process engineering calculations were based largely on:

• Rules of thumb.
• Extrapolating from operating prototypes.
• Data obtained from performances testing.
• Charts and graphs extracted from plant testing.
• Shortcut methods derived from observations of plant data.
• Application of heat and material balance.
• Vapor-liquid equilibrium calculation.
• Application of the ideal gas law.

These 1960s methods were not suitable for any completely new process. But in the refinery industry, we have no new processes. Refinery process units are rather the same in 2017 as they were in 1960.

Thus we pose the question: which method of process engineering ...