Modern Gasworks Practice

REFRACTORIES FOR GAS WORKS PURPOSES 215 important respects, viz., mech.an.ical strength, resistance to spalling and abrasion,. and accuracy of shape. thcy were superior. The Effect of Slags Refractories employed in certain. portions of gasworks plant, such as the retort-bench. producers and water-gas generators, are particularly liable to be damaged by the action of low-melting fluxes or slags. The Chemical composition of askes derived from coke fuel is decidedly variable, the iron content ranging between 5 and 40 per cent., wliile lime compounds may be anything between. 2 and 10 per cent. In addition to the action, of slags, portions of the plant have to withstand the corrosive action of the dust suspended in the travelling flue gases. Mellor and Emery 1 have shown that the deep red-coloured dust collected from the top of the retort beuch has the following composition :— Silica ........... 20-40 per cent. Alumina .......... 10-07 „ Ferric oxide ......... 55-86 „ Lime ........... 2-25 „ with. smaller proportions of titanic oxide, magnesia, potasb, soda and sulphur trioxide. At temperatures below 1,300° C. the action of the dust is meclianical rather than Chemical, and it beging to act chemically at some temperature exceeding 1,300° C. At temperatures of 1,400° C., with the above dust, it was found that the surface of the brick becomes glazed and is corroded to some extent. Considerable Cracking was also found, the dust having penetrated completely through the brick. On the other band, the grog particles had suffered but little, although the bond was permeated with. dust. It may be said as a general rule that the finer the texture of the brick the less will be the penetration, and that “ aluminous ” bricks are more susceptible to corrosion than are silica bricks. Much, of course, depends upon. the prevailing conditions of atmosphere, wliether oxidizing or reducing. Texture, however, is of chief importance in the way of effecting meclianical resistance, and where flue-dust corrosion is suspected a high-quality close-grained brick should be utilized. Raymond. Howe,2 in conducting experiments in connection with the rate of penetration of slag, found that in all cases the slag penetrated more deeply at higher temperatures. In many cases an. increase of 10 per cent, in temperature resulted in nearly doubling the penetration. This increased penetration has several effects in practice. One effect concerns the strength of the brick itself, for it is known that bricks when saturated with slag are not so strong at high temperatures as when they are free from slag. This decreases their ability to sustain the weight of the superimposed parts of the structure. Some interesting points in connection with the choice of refractories for water-gas plant have been raised by Fulweiler and Taussig,3 who state that in water-gas. 1 Proc. Ceramic Society, XVIII, 234. 2 American Refractories Manufakturers’ Assoen., November, 1918. 3 J. Eng. and Ind. Chemistry, 1919, 11, p. 1153