Fire-brick Shapes.—The wants of consumers of fire-brick de mand an improved form in presenting the lines of goods carried by manufacturers, and to meet this demand there will be found illustrated in Figs. 92 to t01, shapes carried in stock by the well-known firm of Messrs. Fredericks, Monroe & Co., Far randsville, Pa., from whose catalogue the illustrations are selected.
Refractory Brick-Work of Blast-Furnaces, and its Preserva tion.*—Blast furnaces are large gas generators, in which the gases generated reduce the iron ore and carbonize the iron thus produced, whilst the heat liberated by the gasification of the carbon melts the crude iron and the accompanying con stituents of slag, the latter being presently separated from the crude iron. In these few words is expressed the diversity of objects the blast-furnace has to serve. It will, however, be seen later on, that besides the above-mentioned processes, many other chemical processes take place in the blast-furnace. Moreover, a blast-furnace has to be worked day and night for many years in succession, so that there is but little opportunity for thorough repair of damages.
On the other hand, a kiln, for instance, has to serve but one purpose, and hence its interior can every few days be thor oughly inspected and, if necessary, repaired. Moreover, the arrangement and producing capacity of the blast-furnace have for the last forty years been constantly changed. The first coke blast-furnace in Westphalia was built forty- three years ago, but the size and arrangements of those blast-furnaces can not be compared with the present ones.
A daily out-put of 40,000 pounds of pig-iron was at that time considered something enormous, whilst the present blast furnaces of the different German iron districts produce on an average ten times that quantity.
The various purposes which a blast-furnace has to serve, the many chemical processes which take place in it, and the long continued and enormously increased work expected from it, will sufficiently explain the difficulties of procuring a refractory material for the brick-work which will answer all demands. In regard to blast-furnaces, the term " refractory," as generally applied to brick, means a great deal more. The exposure of a so-called refractory material to the action of heat alone is some thing entirely different from its being at the same time exposed to various other influences. Now, in the blast-furnace, besides
heat, slag and other hot liquid and gaseous combinations, sim ultaneously exert a dissolving influence upon the refractory material.
Thanks to the constant improvement in the manufacture of refractory material, there is no difficulty in procuring brick capable of resisting the highest degree of heat at present at tainable. But as regards resistance against the dissolving in fluences upon the brick-work of the blast-furnace, there is no material known at the present time which can successfully with stand these influences.
Quartz, as well as the best refractory brick, withstands the dissolving action of slag, etc., as little as ordinary brick, because the principal constituents—silica and alumina—of all these materials are with avidity dissolved by the slag, no matter in what proportions to one another they may occur in them. The dissolution may be slightly retarded if the brick possesses great density—hence mechanical strength—without brittleness. But dense or loose, all so-called refractory brick are finally dis solved, just as sure as sugar is in coffee.
That a material need not be refractory, adcording to,the or dinary understanding of the term in order to resist the:4issolv ing action of the slag, etc., is proved by the use of carbon brick.
The best means of preserving the walls of blast-furnaces without regard to the material used in their construction is to cool them with water.
The carbon brick, which have now been largely introduced, have, since 1876, been used in France for constructing the walls of the hearths of blast-furnaces, and at first appeared to be very suitable for that purpose.
These carbon brick are not dissolved by the slag, and if the latter alone were present in the hearth of a blast-furnace,' they would prove to be of great durability.
However, in the hearth, and always upon the bottom of it, is also the crude iron. Now, in the blast-furnace, iron is 'pro ) duced which is not yet saturated with carbon, and, therdore, absorbs the latter with avidity when it comes in contact with coke, and, hence, also when in contact with the carbon-brick.