Modern Gasworks Practice

CO MODERN GASWORKS PRACTICE modus operandi, however, is by no means as simple as might be supposed, particularly as far as the maintenance of quality is concerned, also the needless “ blowing-ofE ” and waste of moderately good gas. The responsibility is, of course, increased owing to the continuity of the process being broken. In some cases vertical retort installations have facilitated matters, as has also the adoption of heavy charges in conjunc-tion with the horizontal retort. Needless to say, the latter practice (that is, twelve-hour or ten-hour charges) has greatly facilitated the work of temporary shutting-down. Regulation of the Charges No hard and fast rules can be laid down as to the line of action to be followed during a temporary stop. Much must necessarily depend upon the conditions and facilities prevailing at the works—such as ampie storage capacity, the type of retort settings to be dealt with, and whether enrichment by carburetted water-gas or other means is available. The most general practice is to commence the non-gasmaking period at 6 a.m. and to continue it until 6 p.m., but in some instances, under favourable circumstances, a restart is not made until 10 p.m. It is proposed to describe here a method which will be found satisfactory from every point of view, and which has the primary advantage of being extremely simple. Though the method may be applied in all cases (whatever duration the stopping period may be) it will be assumed, for the sake of simplifying the illustration, thai no retort-house work is desired between the hours of 6 a.m. and 6 p.m. In this case the last row of retorts is charged so as to be completed by 6 a.m.; thus for some time the normal volume of gas is coming away. As this gradually decreases, however, some little precaution is necessary in the regulation of the ex-hauster and retort-house governor. The method of operating these will be best followed by referring to the two charts shown in Figs. 68 and 69. In faet, the whole idea can readily be grasped by keeping these diagrams in mind. Fig. 68 is a vaeuum chart showing the “ pull ” exerted by the exhauster throughout the twenty-four hours, whilst in Fig. 69 is shown the vaeuum on the foul main for the corresponding period.. ReGULATING THE “ ÜRAW ” For the first hour and half, i.e., until 7.30 a.m., the quantity of gas driven off will permit the use of the full average “ draw.” Folio wing this period the volume of gas evolved gradually becomes smaller and smaller, and the “draw” at the exhauster is reduced by degrees, until it is in average cases no more than about 10 per cent, of the normal or, say, lialf an inch about three hours atter the retorts were last charged, i.e., about 9 a.m. Meanwhile, as will be seen from the second chart, the retort-house governor is ad] usted so as to give “ level gauge ” on the hydraulic main; this continuing until 6 p.m. in the evening, when the retorts are charged-up once more. Similarly, the half-inch “ draw ” is maintained at the exhausters until shortly after 6 p.m., when it is raised gradually to the usual amount. When the exhauster is working at so low a vaeuum as half an inch it must necessarily