flow of a refinery is much more intricate. The flowchart on the next page (Figure
2-29) illustrates this complexity.
Items may be shunted from one process to
another, skipping one step, bypassing another.
Use the flowchart as an aid to
visualizing the relationship between processing units during the detailed
discussion of the various refining components.
c. A refinery is a custom-designed installation made to handle a particular type
of crude oil, using certain techniques to produce particular products. A refinery
layout may appear as a random side by side of components with the various important
units scattered throughout the installation.
With careful analysis, however, the
IA can accurately recognize the functional areas of the plant.
d. Refining processes and specific components are discussed in the following
pages.
You should be able to understand the processing flow and specific
identification features belonging to the refining process to help analyze the
industry.
(1) Refining process.
Crude oil is a mixture of a number of different
hydrocarbons, long chains of hydrogen and carbon atoms linked together in various
combinations. Each of these hydrocarbons has unique characteristics and can be put
to a special use once separated from the others and purified.
(2) Petroleum refining is the process of separating and purifying the
individual hydrocarbons in crude oil.
The key to this operations is "boiling
points." Each of the hydrocarbons has a different temperature at which it boils,
thereby turning from a liquid to a vapor.
Some, like the simple hydrocarbons
methane, ethane, propane, and butane, has boiling points below normally atmospheric
temperatures and, therefore, are normally found in the gaseous state. Others, like
the heavy, complex, viscous molecules of asphalt, must be raised above 1,000 F
before they will vaporize.
(3) Primary or crude distillation is the breakdown of crude oil into its basic
hydrocarbon constituents.
This is the first step in the refining of crude oil.
The principal products of primary distillation are: light gases, low-grade
gasoline, kerosene, diesel oil, heavy gas-oil, wax-oil, and a thick hydrocarbon
residue.
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