386
��Popular Science Monthly
��AERIAL CONDENSER
NAPHTHAS & FIXED GASES
��A - COr<DE NSE R TUBES B- COLLECTOR PANS C- COOLING COILS 0-COOLINS TANK E- RUNNING TANKS r - GAS TRAP
���#1 #1 ^t -tb^fii
��CYLINDER STOCR HEAVY LU6Hll«e LIGHT LUBtfTING GAS OIL
RESIDUUM DISTILLATE DISTILLATE DISTILLATE
��ILLUMINATING OIL NAPHTHA DISTILLATE DISTILLATE
��Fig. 1. First Separation of Crude Petroleum Into Groups by Distillation
��and other spi-cially distinguishing char- acteristics.
As cream, butter, cheese, casein, and other products are derived from milk, so are hundreds of different hydro-carbon compounds lying between the extreme limits of gasoline and cylinder stocks or coke, separated from crude oil by frac- tional distillation. These products are divided into many different grades, according to their physical and chemical characteristics, and to the purpose for which they are used and shipped to all parts of the world, wherever an internal combustion engine is run, a lamp burned, or a wheel turned.
Crude oils ma>- l)e divided into three main families: lliose of paraffin, asphaltic and cycIo-na|)hl!u>ne base. There is no sharp line of separation fjetween these groups, since most crude oils found in all fields may contain mi.xtures in variable percentages of hydro-carbons, belonging to two or more fain il its.
When the crude petroleum arrives ilirough the pipe line and is deijosited into storage tanks of large cajiacit)-, a certain settling takes place. The semi- solids which settle out consist of amor- |)hous paraffin wax, mud or other earth>- foreign matter antl impurities.
��First Stai^e — Separation into Groups by Distillation
From the storage tanks the crude oil is pumped into a large cylindrical boiler, called a "crude still."
Distillation as applied to hydro-carbon oil, is the separation of the more volatile portions from the less volatile portions by vaporization, and later condensing them by passing the hot vapors through a cooled tube. Light hydro-carbons like gasoline, vaporize very readily, whereas heavy oils form practically no vapors at atmospheric pressure and temperature; therefore, it is necessary to heat and boil crude petroleum in a closed vessel, in order to accomjilish complete vaporiza- tion and separation of the ditTcrent hydro-carbons. Since crude oil is a complex mixture of hydro-carbons, each of which has a different boiling point, a different temperature is required for the \aporization of each compound. Dis- soKed gas and the lightest h>dro-carbons pa.ss o\cr first, and as the temperature is increased, heaxier and heaxier hydro- carbons are xaporizcd.
Re\erling to Figure I : llu' \apors formed are led through a pipe from the still and discharged into the base of an aerial tower condenser. From there they
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