Modern Gasworks Practice

282 MODERN GASWORKS PRACTICE CHARGING AND DISCHARGING MACHINERY FOR RETORTS The past decade has witnessed a striking change in the design of machinerv used for the filling and emptying of horizontal retorts. The introduction of the heavy charge and the mass system of carbonization bas been responsible for much of this modification, so that discharging apparatus embodying the principle of the rake—at one time a very common type—has almost entirely disappeared. This is due to the necessity for leaving a considerable space above the charge in the retort in which the rake head may travel. Stoking machinery employed in operating the retorts may be primarily classified under the following headings :— 1. Machines designed to minimize the labour of charging or discharging but which require no power other than manual labour for their operation. 2. Machines charging simultaneously from both sides of the bench, such as the Arrol-Foulis, or West’s scoop charger. 3. Machines discharging from both sides of the beuch simultaneously. These include those types worked on the rake principle, and which. are not suitable for heavy charges. 4. Machines charging from one side of the bench only. (a) Projectors. (b) Those embodying the principle of the conveyor chain. 5. Machines discharging from one side only. These are exclusively worked on the principle of the pusher. 6. Discharging chargers, which simultaneously empty and refill the retort. The last-named type, though not altogether satisfactory at the time of its intro-duction, is now reaching a stage of perfection which has resulted in its more general adoption. One of the chief disadvantages attending the use of the earlier types was the impossibility of working heavy charges, owing to the necessity for leaving the upper portion of the retort clear for the return of the conveyor chain. This difficulty has now, however, been surmounted. It would not be possible to describe fully here the details of construction of all the machines now in operation in gasworks for filling and discharging retorts. It is merely proposed to consider some of the most familiär examples and to indicate. briefly the principles upon which they operate. The engineer who is contemplating the introduction of machinery sliould decide. on the type of plant, in conjunction with. the apparatus for conveying coal, before proceeding with the design of the buildings and retort plant. Many makers have, different types of machinery, such as those with or without storage hoppers, measur-ing chambers, etc. It will, therefore, be found advantageous to settle upon the type and make at the outset. Once the machine is decided upon there are many points requiring attention, and at this juncture discussion between. buyer and maker will prove of great assistance in the design of new buildings or alteration to existing ones. The maker sliould furnish a plan showing the over-all dimensions of bis machine, the clearances required at the front, back, and sides, also the total weiglit when.