CHAPTER XVI

FUEL OIL AND SPECIFICATIONS FOR PURCHASE

FIG. 73.-The Saybolt elec

tests.

ETROLEUM has been known in the United States from prehistoric times. It is certain that the mound builders had wells from which petroleum was obtained. These are still in existence along with the most modern of our own times.

Petroleum was used as a medicine by many tribes of Indians. It was supposed to have many magical as well as medicinal properties. Its inflammable nature seems also to have been known.

No use was discovered for petroleum other than as a medicine until in 1852, when a chemist, by the name of Kier, bethought himself of trical equipment for flash and fire distilling it and extracting from it the more volatile portions. The American people took readily to the use of these oils as illuminating agents from the fact that for some time previously the mineral oils, extracted from lignites and anthracites, according to the process of Sellegries, the Swiss chemist, were in current use.

Enormous Consumption of Fuel Oil in the Industries.-The use of crude petroleum as a fuel for steam generation and power production has now an established position in all parts of the industrial world. Especially is this true of the Pacific Coast and in the southwestern section of the United States where the enormous yield of this product in Oklahoma, Texas and California now constitutes an ever-increasing factor in the total production of the world. Indeed, California alone with her yield of over one hundred million barrels in 1919 produced over 25 per cent. of the world's output.

At its first incipiency it was thought that the probable production of crude petroleum would be limited to but a few years. Due to this factor many power plants on the Pacific Coast were constructed so that an easy change over to operation by coal could be made should this time ever arrive. It is now recognized by many that the probable yield of oil will last as long as the coal fields of the world. Hence this uncertainty is largely dispelled in the industrial production of power.

Advantages of Crude Petroleum as a Fuel.-Oil has many distinct advantages over coal. Due to the simple mechanisms that are involved the cost for handling fuel oil is far less than for coal. By the elimination of stokers an important labor item is found unnecessary. Again for equal heat value oil occupies much less space than coal. Hence for ocean-going vessels it is especially applicable. Combustion too is more perfect so that the quantity of excess air required is reduced to a minimum. The furnace temperature may be kept practically constant as the furnace doors need not be opened for cleaning or working the fires. Smoke may to a large measure be eliminated with the consequent cleanliness of heating surfaces. Again, the intensity of the fire is subject to delicate regulation and sudden load fluctuations are easily handled. Oil does not disintegrate or lose its calorific value when stored. In the boiler room the cleanliness and freedom from dust and ashes results in a saving in wear and tear in machinery. Hence it is clearly evident that the efficiency and the steaming capacity of a boiler, oil fired, is increased in a marked manner.

The disadvantages of fuel oil are of comparatively small moment. For this reason wherever oil can be obtained at a reasonable figure as compared to the prevailing market price of coal it has attained a marked popularity in steam generation and in the industries.

Let us then look into some of the physical properties of this new and important source of heat generation.

Liquid Fuels Classified.-Petroleum is practically the only liquid fuel sufficiently abundant and cheap to be used for the generation of steam. There are three kinds of petroleum in use, namely, those yielding on distillation paraffin, asphalt and olefine. To the first group belong the oils of the Appalachian Range and the Middle West of the United States. These are a dark brown in color with a greenish tinge. Upon their distillation such a variety

of valuable light oils are obtained that their use as a fuel is prohibitive because of price. To the second group belong the oils found in Texas and California. These vary in color from reddish brown to a jet black. Since they are used extensively as a fuel in the United States, our discussion in this chapter shall largely be concerned with this class of oils. The third group compr ses the oils from Russia, which like the second group are used largely for fuel purposes.

Physical and Chemical Properties of Oil.-Mineral oils as found in nature, are a mixture in indefinite proportions of several combinations of hydrogen and carbon designated as hydrocarbons. Oxygen and sulphur are found in very small amounts. Nitrogen is found in a smaller proportion than the latter.

On account of the complexity of their composition, mineral oils differ considerably both physically and chemically.

Odor and Color.-Oil is generally found in a very fluid condition in North and South America, while in Russia and East India it is found in a very dense and syrupy condition. They all possess a characteristic odor while their color varies from amber or greenish yellow to dark brown. By reflection they are all greenish.

Effect of Heat.-Heat will separate the different hydrocarbons successively according to their volatility and cause them to dissociate at higher temperatures. Low temperatures will solidify these products, the highest freezing at a lower temperature.

Density of Various Oils.-The density varies from 0.765 to 0.970. compared with water at 4°C., as found in nature (crude). Distillates will be much lighter.

Physical Properties of California Oils.-We shall now consider as a typical example a sample of California crude petroleum taken from an average of forty samples drawn from the Kern River oil field by representatives of the U. S. Bureau of Mines.

The specific gravity or density of fuel oil is an important factor to be known and is the ratio of the weight of an oil sample as compared with the weight of an equal volume of water. The average oil sample is found to have a specific gravity of 0.9645, which on the Baume scale at 60°F. is 15.16°. Hence, the average gallon of fuel oil weighs 8.03 lbs.

The determination of the gravity of fuel oil and the relationship of specific gravity with gravities expressed on the Baume scale are of such importance that a subsequent chapter has been set aside for detailed discussion and analysis.

The Calorific Value of Fuel Oil.-In steam boiler economy the heat producing value of the fuel per pound consumed in the

FIG. 74.-Laboratory equipment for fuel oil testing.

In the gathering of fuel oil data for boiler tests the three things to be ascertained accurately are the specific gravity, the moisture content, and the calorific value of the oil sample. The principal pieces of apparatus necessary are the Westphal Balance, the chemist's scales, a Parr calorimeter, and a still with their accessories as shown. In the text of this article these physical characteristics of fuel oil are set forth. In later discussions the laboratory procedure in order to ascertain each of these points will be discussed in separate chapters.

furnace is of utmost importance. The average sample of Kern River oil generates or gives out 10,307 calories per gram, which transferred to steam engineering units is found to be 18,553 B.t.u. per pound or 148,980 B.t.u. per gallon of oil.

Oil, like water, requires the actual absorption of a large quantity of heat in its conversion into the gaseous state. Indeed the latent heat of evaporation for fuel oil is approximately

130-150 B.t.u. per pound under atmospheric pressure, as compared with 970.4 for the latent heat of evaporation of water as set forth in previous discussions. Hence, the actual heat given out by the average sample above referred to is approximately 18,700 B.t.u. per pound, but since we must gasify the oil to make use of its heat generating characteristics in the furnace the net value of 18,553 is solely of commercial importance.

The determination of the calorific value of fuel oil and the many computations involved are of such vast importance that several chapters have been set aside for future discussions of these various factors.

The Flash Test and the Burning Point of Oil.-The flash test of an oil is the temperature at which it gives off inflammable vapors. For the purpose of safety in handling, fuel oils should not give off inflammable vapors below 150°F. The flash point of an oil is determined by heating the oil in a vessel adjacent to which is a small flame. When the oil has been heated to a point where vapor rises and ignites from the flame, this temperature is called the flash point. The flash point of the average California oils is 108°C. or 226.4°F.

The burning point of oil is the temperature at which its ingredients will permanently ignite. This is determined by continuing the heating of the oil after the flash point has been ascertained until the "flash" becomes permanent, that is, until the oil ignites and continues to burn quietly. For the average Kern River oil sample the burning point is found by the open cup test to be 130°C. or 266°F.

Viscosity. Some oils are more fluid or mobile than others. All are familiar with the difference between "cold molasses" and "hot molasses." And so in oil flow we have a similar phenomenon. This tendency for the particles of oil to cohere to one another is known as viscosity. Viscosity is determined by measuring the time it takes oil to flow through a standard sized tube under standard conditions. On the so-called Engler scale the average viscosity of Kern River oil at 20°C. is found to be 915.6. The viscosity is very materially lessened as the temperature is increased. Hence at once is seen the advantages of oil heating both for efficiency in transmission through long pipe lines, and for feeding the oil to the burners. In power plants the oil is heated to a temperature of 160°F. before reaching the burners.