80. Composition of Producer Gas. — The composition of producer gas is indicated in Table XI, which gives the average percentage, by volume, of the various constituents of producer gas made from bituminous and anthracite coal.
81. Calorific Value of Producer Gas. — Producer gas has a calorific value of from 110 to 160 British thermal units per cubic foot. About 80 cubic feet of gas should be produced per pound of coal.
BLAST-FURNACE GAS
82. Carbon Monoxide. — In the reduction of iron ore, it is necessary to use a considerably greater quantity of coke than the oxygen supplied by the blast will consume, in order to prevent the oxidation of the iron. The result is that a large proportion of the gas from the stack is not carbon dioxide, CO2 but carbon monoxide, CO. Ordinarily, this gas goes to waste at the top of the stack, burning with the familiar blue flame.
83. Use of Blast-Furnace Gas. — Although blast-furnace gas is very poor in heating value, having only about 100 British thermal units per cubic foot, or two-thirds as much as good producer gas, it has been found possible to utilize it in large engines. To accomplish this, the gas is led through a series of scrubbers to purify it and settle the dust, and is then supplied to the engine in much the same manner as is producer gas, except that the proportion of gas to air must be larger. The composition of average blast-furnace gas is shown in Table XIII, from which it will be seen that only about 30 per cent, of the gas is combustible, the remaining 70 per cent, being nitrogen and carbon dioxide.
84. A calculation of the heating values of the carbon, the limestone flux, and the coal shows that the gas produced in the course of smelting a ton of pig iron represents over 13,000,000 British thermal units, of which 25 per cent, can be utilized in an engine of average efficiency. This would be equivalent to about 1,000 available horsepower per ton of
