Modern Gasworks Practice

REFRACTORIES FOR GASWORKS PURPOSES 219 Segmental Retorts From the point of view of working life, segmental or built-up retorts are far superior to the common moulded type, but, chiefly owing to the preliminary expense incurred, they have not been very generally adopted in this country. Built-up retorts may be classified under two headings, namely, those composed. of large segments and those constructed from special small blocks about the size of an ordinary brick. It has been said that retorts built up from small tongued and grooved segments can be worked continuously for five years without requiring repairs, the explanation being that the flexible units give and take with the expansion and contraction caused. by the variation, of temperature in the setting. In. the case of a brick retort, the line of fracture necessarily foliows along the joint-lines, whereas in the case of a moulded retort the line of cleavage is indefinite, and cross-stresses are set up. Under local Hearing, it is impossible to expect perfectly uniform movement; thus, when the retort is composed of one single piece, cracks and fissures result. In these days of the “ pusher,” moreover, distortion must be avoided if the charge is not to j am up. In. this respect, the built-up retorts composed of small units are probably to be preferred to those in wliich large sections are employed, although opinion in this respect difEers considerably. The retort built up of small units is extremely flexible, and yet (owing to the tongued and grooved joint) lifrtle or no leakage takes place. A difficulty, however, arises wlien “ scurfing ” is considered, for, owing to their delicate adjustment, the separate units are l'able to be damaged with. the heavy tool employed and the rough. handling they receive. Furthermore, there is the possibility of the carbon getting into the joints and opening out the bricks in this way. Segmental retorts require, of course, substantial and at the same time flexible supports, this being another factor which adds to the expense. With regard to the relative “ gastight-ness ” of the two types of retort, there appears to be some divergence of opinion. It may be generally taken, however, that, so long as the segments are carefully made and laid together, the gas leakage will, in the long run, be less than with the moulded retort, in spite of the number of joints necessitated. Some aut.horities attribute the tightness of the segmental retort to the faet that when ä line of cleavage occurs, it runs along the joints and is quickly sealed by the formation of scurf. With the moulded retort, on the other hånd, the cracks may be anything from | inch to 1 inch, or even. greater. built-up retort, moreover, lends to effeetive repair. A typical briok-built retort tiled bottom, of a somewhat fashioned type, is shown in Fig. whilst the more common forms of mented retorts are illustrated in Fig. 115.—Brick Rbtokt with Tilbd Base.. The itself with old-115, seg-Fig.