Modern Gasworks Practice

THE COMPLETE GASIFICATION OF COAL CO oo Drake’s Mixed Gas Plant Drake’s plant for producing mixed gas is particularly novel in construction. It consists of two or more vertical retorts mounted upon a similar number of horizontal retorts, heated by means of special producers. The inventars state that the plant is capable of yielding any grade of gas, the quality of which may be varied at will from a producer gas to a rich coal gas. The construction of the plant will be followed from the illustrations. Coal is fed con-tiiiuonsly into the top of the vertical retorts which connect at their base with horizontal retorts. Carbonization of the coal is effected in the vertical portion, so that the horizontal portion contains coke only. This coke, when thoroughly carbon-ized, is discharged by a pusher into two producers situated directly beneatli the discharged ends of the horizontal retorts. The part played by the producers is important in that they are operated with alternate runs and blows. While one of the producers is being steamed the otlier is being subjected to an air-blast. Thus ■one producer is generating “ blue ” water gas while the other is yielding producer gas. The blue gas is led through, the coal charge in the vertical retorts, while the blow gases are passed around the combined retort system, secondary air (pre-heated by the waste gases) being admitted at the same time. Carbonization of the coal is partly effected by the sensible heat of the “ blue ” gas, and partly by transmitted heat •of the blow products. If desired, the gases made during the blow may also be admitted to the retorts, in which. case a lower quality mixed gas results. The system •of runs and blows is alternately operated in the two producers. Helps’ Gas Plant In. connection with this process the inventor states that complete gasification presupposes low-grade gas, and inerts are invariably present in comparatively large ■quantities, Helps submits, however. that even nitrogen is not always a disadvantage, because “ a high grade gas diluted with nitrogen may give a better duty than high-grade gas with out it. The effect of nitrogen in flames has not, so far, been thoroughly investigated ; but where nitrogen enables the proper proportion of air to be admitted to the burner tube, through the power it exerts in injecting the necessary primary air, better results are obtained than when such power in the gas at the nipple of an .atmospheric burner is wanting. The presence of nitrogen in the gas not only reduces the air required, but it has the same injective power as the air-requiring constituents cf the gas.” If it is possible to use the sensible heat in the producer gas to carbonize coal or generate steam, or do otlier required work, the heat losses would be reduced in the proportion, of the sensible heat ntilized. There is no difficulty in working when the heat required to carbonize the coal is contaiiied in. the “ blue ” superlieated water gas made ; but if the superheated water gas does not contain sufficient heat for the purpose, such, heat may be augmented by any of the folio wing means separately or in coin bination : (1) The combustion of blue ” water gas or a mixed gas externally to the carbonizing retort; (2) tlie sensible