All this, even to non-engineers, probably seems absurdly simple, and it is. The reason for
explaining it in this way, however, is to show, by means of the simplest kind of equipment,
how engineers go about improving the efficiency of any system. Step by step, adding
something here, saving something there, establishing closer supervision over everything
gradually improves the effectiveness and the efficiency of almost any kind of system. These
are the kind of things engineers are concerned with. Nearly all of them are more or less
complex and require a great deal of specific as well as general knowledge. In the example
just described, for example, just how much surface should the heater in the stack have to
Consider the last question, for example, that of cooling the flue gases too much. What
happens? Well, there is always a certain amount of water vapor in the flue gases, from the
air and from the hydrogen in the fuel. As the temperature of the gases is lowered, there
comes a time when the saturation point is reached and the moisture condenses. If, at the
same time there happens to be any sulfur in the gas, (and there usually is) sulfuric acid will
be formed resulting in the spread of a thin but extremely corrosive layer of liquid on the
inside surfaces of the flues.