First course in chemistry by McPherson William 1864- & Henderson William Edwards b. 1870 joint author

Author:McPherson, William, 1864- & Henderson, William Edwards, b. 1870, joint author
Language: eng
Format: epub
Tags: Chemistry
Publisher: Boston, New York [etc.] Ginn and company
Published: 1915-03-25T05:00:00+00:00

Fig. 100. Plant for the manufacture of coal gas and accompanying products

ton of good gas coal yields approximately 10,000 cu. ft. of gas, 1400 lb. of coke, 120 lb. of tar, and 20 gal. of ammoniacal liquor. Not only is' the ammonia obtained in the manufactur.e of the gas of great importance, but the coal tar is the source of many very useful substances, as will be explained later.

Water gas. Water gas is essentially a mixture of carbon monoxide and hydrogen. It is made by passing steam over very hot anthracite coal or coke, when the reaction shown in the following equation takes place:

C + H^O—J^CO + H^

The process is intermittent. The fuel is burned in a draft of air until it is very hot. The air is then shut off and

steam turned on. The temperature gradually falls, and when it reaches about 1000°, the process is again reversed.

Water gas is very effective as a fuel, since both carbon monoxide and hydrogen bum with very hot flames. It has little odor and is very poisonous. Its use is therefore attended with some risk, since leaks in pipes are very likely to escape notice.

Enriched water gas. When required merely for the production of heat, the gas as prepared above is at once ready for use. When made for illuminating purposes, it must be enriched; that is, illuminants must be added, since both carbon monoxide and hydrogen burn with a nonluminous flame. This is accomplished by passing it into heaters containing highly heated petroleum oils. The gas takes up the gaseous hydrocarbons formed in the decomposition of the petroleum oils, and these hydrocarbons make it burn with a luminous flame.

Producer gas. This is made by burning coal in a limited supply of air so that the product of combustion is largely carbon monoxide. It is used as a fuel in gas engines and in many industrial operations.

Natural gas. In many regions of the United States, as well as in other countries, natural gas is obtained from wells drilled into a stratum holding the gas. While it is variable in composition, it consists largely of methane, many samples containing as much as 95 per cent of this compound. It burns with a rather smoky flame of moderate luminosity, but works well with a gas mantle. It has a high heat of combustion, as shown in the following equation:

CH, + 2 O^ — y CO^ + 2 Hp + 213,500 cal.

It is an ideal fuel and is often conducted through pipes for hundreds of miles from the gas fields to cities.

FUELS; FLAMES; ELECTRIC FURNACES 213

Comparative composition of fuel gases. The following figures are the results of analyses of average samples, but since each kind of fuel gas varies considerably in composition, the values are to be taken as approximate only. The nitrogen and traces of oxygen are derived from the air.

COMPOSITION OF GASES

Constituent

Ohio

Natural

Gas

Coal Gas

Water Gas

Enriched

Water

Gas

Producer Gas

H.

CH4

Celle

CgH^andCgH^ . .

CO

CO2

N.

o.

Other hydrocarbons.

0.9 89.5 9.3 0.3 0.4 0.3 0.2 0.0 0.0

41.3 43.6

3.9 6.4 2.0 1.2 0.3 1.5

52.88 2.16

36.80 3.

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