Modern Gasworks Practice

THE HORIZONTAL RETORT BENCH 81 price, the additional cost of labour involved is trifling in comparison with. the gain. in other directions. A simple and efiective means of preventing the dropping of the iniiiost ring is to stay up the soffit of the arch by means of tiles supported from the cross-walls of the setting (Fig. 31). It should, however, be seen that expansion of the work below is allowed for, by leaving a space between the top of the tiles and the soffit of the arch. Two indies will usually answer the purpose. The difficulty, however, lies in gauging the amount of expansion, so that wh.cn the setting is heated up the soffit just rests on the tiles. Obviously, if there is a space between the two the tiles are useless, whilst if over-expansion takes place they are actually harmful. In America, some attempt has been made to reduce the losses of heat from radiation by leaving cavities around the main arches, or by employing special ch.an.nel blocks (Fig. 32). The practice, however, camiot be recommended, as the stabil!ty of the work is seriously affected, and radiation losses will not be excessive if the brickwork is carried up at least 18 inches above the top of the arch rings. As a further precaution, the top of the beuch, is frequently plastered with a thin layer (2 inches) of some non-conducting material. This can be effectively made from waste rope dust and rough asbestos com-position composed of ten parts of the former to one part of asbest.os. Such work, including the labour, can be carried out for about 7s. Gd. per square yard. An objectionable practice, which is happily dying out, is tliat of filling up the spandrils of the main Fig. 32.—Segmental Akch with1 Air Channels. arches with. sand, and putting a paving of bricks on the top of this. Far from preventing radiation, the sand, owing to its close-lying nature, is always accompanied by excessive losses in this respect; and in time, when the work gets old, it is likely to dram through crevices, leaving hollow spaces in the spandrils and giving trouble in the settings owing to its low fusing point. (6) The Producer Through retort bench.es should in all cases be fired with the single rather than the double furnace, as in this way a saving of from 10 to 15 per cent, in fuel consump-tion can be looked for. The primary consideration is that of ensuring ampie depth of fuel-bed, so that the reduction of carbon dioxide to carbon monoxide may effectively take place. In the larger regenerative settings of 8’s and 10’s it is preferable to allow for not less than 8 feet from the base of the producer to the springing of the producer arch, although in the smaller units this will often be no more than 6 feet. As regards shape, the internal producer is always rectangular. Although. on certain scientific grounds it should be square (due to the faet that of rectangular figures the square has the smallest perimeter for a given area, thus exposing the minimum amount of wall surface), it is commonly constructed with the front width. about half the distance which it extends backwards at the base. The reason for this is that construction is facilitated, a better distribution of producer gas results, G