GAS PRODUCER. The preliminary re quirement in using any form of fuel is its con version into a gas in order that it may com bine more readily with the oxygen in the com bustion process. Whether the gas thus ob tained is combustible, i.e., whether it enters into combination with oxygen with the production of heat, or otherwise, depends upon the nature of the fuel from which it is derived and upon the method of gasification employed.
In most fuels, the chief combustible ele ments are carbon (C) and hydrogen (H), which are present in a great variety of chemical com binations with varying physical characteristics. When these fuels are completely burned, the products of combustion contain only carbonic acid (CO3)• and water (ILO), with nitrogen (N) and some of the oxygen (0) of the air supplied for combustion, all of which are in combustible. But when the fuel is incompletely or partially burned, the products of combustion will also contain varying quantities of carbon monoxide (CO), various forms of hydrocar bons (CH.), hydrogen, and sometimes tar and smoke as the products of distillation, all of which are combustible or have a heating value, which is wasted if not oxidized in the combus tion processes.
Fuels may be burned by either direct firing on a grate or after conversion into gaseous form. The ultimate object of direct firing is the at tainment of complete combustion in close prox imity to the fuel bed, by vaporizing, distilling, gasifying and completely burning the fuel ele ments within the that chamber. It is well known, however, that the processes of vaporiza tion and distillation do not produce heat but, on the contrary, absorb it, and, therefore, it is advantageous to separate them from the point at which the combustion of the gases takes place, and where high temperatures are devel oped by the heat evolved, as is accomplished by the use of a gas producer or generator.
Generation of Producer In the gas producer, the processes•of vaporization, distilla tion and gasification result in the generation of combustible gas, which is led away to a sep arate combustion chamber in which it is subse quently burned under conditions more favorable to a full realization of the heat value of the fuel, and the high temperatures absolutely un attainable by any other method of firing.
It should be clearly understood, however, that the use of a gas producer does not enable the generation of a greater quantity of heat than may be obtained by direct firing. Even when the producer is closely connected to the furnace so as to utilize the sensible heat of the gas, a loss of energy of from 15 to 20 per cent of the calorific value of the fuel is sustained; but notwithstanding this loss, practical experience has demonstrated that the gas producer accom plishes, with much less fuel, practical results equal to those obtained by direct firing and has made possible metallurgical operations imprac ticable by the latter method.
The advantages of gas firing over direct fir ing will be better understood by a brief discus sion of the manner in which producer gas is generated.
As already stated, the products of the in complete combustion of a fuel contain various combustible elements which are susceptible of being burned at a higher temperature than that of the original combustion, and producer gas is simply the product of an incomplete combustion or, more exactly, a distillation of a fuel in the generator.
The oxygen of the air admitted to the pro ducer comes in contact with the incandescent carbon of the fuel and forms a certain amount of incombustible carbonic acid gas or carbon dioxide (CO,). The heat evolved by this re action is absorbed by the CO, thus formed and by the nitrogen of the air supplied. These gases ascend and yield their heat to the fuel above and bring it to the point of incandescence, so that the CO, first formed is brought in con tact with this glowing carbon, and taking up an additional quantity of carbon is converted into the combustible carbon monoxide (CO). In a word, then, the primary object of the gas pro ducer is to convert carbonaceous fuel into car bon monoxide gas.