REFRACTORIES FOR GASWORKS PURPOSES 225
contains a comparatively high proportion of impurities, and these are actually caused to flux during burning, so as to firmly bind the remainder of the material together. A point to remember is that extremely high temperatures and “ Cutting heats ” are not alone responsible for “ running.” Considerable damage from this cause may often be found at the relatively cool zone of the producer linings, and also at the base of water-gas generators. Such occurrences are, of course, due to the adhesion of clinker (having an extremely low fusion-point) to the walls, and its subsequent “ slagging ” action 011 the impurities of the liaing material. The chief precaution is to ensure that the bricks or blocks made use of contain a low proportion. of fusible constituents. The unwelcome results cf “ running ” are very well illustrated in Kg. 125. This photograph shows the consequences of using an unsuitable jointing material, and the manner in wliicli incipient slagging has
Fig. 125.—The Ejtects of “ Running.”
been set up in the brick can be clearly noticed. The brick in this case was taken from a combustion chamber working at a temperature of about 1,400° C.
With regard to fireclays for the making of cement for use in retort bench.es, before making a definite purchase it is advisable to apply a rough test in order to ascertain their suitability. Au excellent rough method for determining their re-fractoriness is to mix up the cement in the usual way, afterwards plastering it on one side of a brick to the depth of about an inch. The brick should tlien, be pushed into the combustion chamber of a retort setting and allowed to remain for about a week. If at the end of that time there is no sign of fusion, the material may be safe]y relied on. The test is, no doubt, severe—particularly in view-of the rapid rate at which the temperature of the sample is increased.
PRODUCERS AND REGENERATORS
As pointed out above, the material employed for the lining of the producer must possess the ability to withstand the slagging action of the low fusing-point Ö