THE HORIZONTAL RETORT BENCH 75
(a) The furnace linings should be isolated from the remainder of the brickwork, and not bonded in in any way. The wear and tear with. this type of furnace is extremely heavy, and the furnace requires frequent re-lining.
(k) The stop end of the retort frequently breaks away after the bench. has been. working for some time, and as bricks will then have to be inserted, it is as well to brick up the end (4| inches) before the retort is put to work in the first place.
(l) When starting up settings care must be taken to avoid explosions. The chances of explosions occurring in. direct settings are remote, but the experience is by no means unknown. (For further information, see page 132 et seq.)
GENERATOR AND REGENERATOR SETTINGS
The essential difference between generator and regenerator settings is in the means employed for circulating the waste gases and, in the latter type, for extracting th.e maximum quantity of sensible heat from them before their escape. In the
Fig. 23.—Double Fubnaob. Fig. 24.—Single Fuknace.
generator type the main waste-gas flue travels along the top of the main arch.es, with the cliimneys carried up at intervals, whilst in the regenerator system the waste flue generally runs longitudinally through the entire bench, just above foundation-level. Anotlier important distinction is that with generator settings a double furnace (Fig. 23) is frequently employed, whilst the single furnace (Fig. 24) is now exclusively used with the regenerator bench. The latter embraces the advantages of reduced labour in charging and clinkering, more effectual control of lieats, less wear and tear, and considerably improved working conditions for the men. Generator settings are now seldom used in coniunction with “ through ” retorts. It is interesting to note, however, that the South. Metropolitan Gas Company still employs generator settings to a very large extent. In this case a special arrangement of producers is employed, in which each. producer supplies gas to one-half of each. of three retort settings of the 20-feet “ through ” type. The result of employing the generator principle in lieu of the regenerator is seen by a comparison of the figures of coke used for fuel by this Company with. the same figures of the Commercial Gas Company in which. regenerators alone are employed :—