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impounding the heat developed by the combustion of the furnace gas, and later returning it to the blast. Each blast-furnace is now provided. with three or even four off these stoves, which collectively may be nearly thrice as large as the furnace itself. At any given time one of these is “ on wind ” and the others K(77 on gas. The Whitwell stove (fig. IO), by means of the surface of 'several nre-brick walls, catches in one phase the heat evolved by the burning gas as it sweeps with carbon and scoriaceous matter when the furnace is in normal working. Each of these rows, of which five are shown in fig. 7, consists of a- great number of short segmental boxes. 72. Blast-furnace Gas Engines.-When the gas which escapes from the furnace top is used in gas engines it generates about four times as much power as when it is used for raising steam. It has been calculated that the gas from a pair of old-fashioned blast-furnaces making 1600 tons of iron per week would in this way yield some 16,000 horse-power in excess of their own needs, and that all the available blast-furnace gas in the United States would develop about 1,500,000 horse-power, to develop which by raising steam would need about 20,000,000 tons of coal a year. Of this power about half would be used at the blast furnaces them- ” L through, and in the il; other phase returns that heat to the entering blast as it sweeps through from left to right. In the E original Vl/hitwell E stove, which lacks

the chimneys shown

iii afthefopvffig-10, § :1 both the burning gas and the blast pass up and down repeatedly. In the H. g Kennedy modifica§ : 5 tion, shown in fig. ro, the gas and alr in E = one phase enter at QQ I the bottom of all three of the large vertical chambers, burn in passing up* wards, and escape at m once at the top, as 3 shown by the broken

2 $2 i 5 E arrows. In the other

% phase the cold blast, L I ¥orcedinatA, passe§ , ourtimesu an down as 5|-, Gsm by mad 'T the unbroken arrows, and escapes as hot blast at B. This, th@n, iSa“0H@-Pass" stove when on gas U if 52:2 § .3 ut a “ our- ass "

  • E 5 —if one when on wihd.

The Cow er stove (fig. II) diff)ers from the Whitwell (I) in having not a series of flat smooth walls, but a great number of narrow vertical Hues, E, for the alternate absorption and emission of the heat, with the consequence that, for given outside dimensions, it offers about one-half more heating surface than the true Vlfhitwell stove; and (2) in that the gas and the blast pass only once up and once down through lt, instead of twice up and twice down as in the modern true /Vhitwell t ' . A ' ' s owes s regards frlctlonal resistance, this smaller number of reversals of direction com ensates in a measure for the smaller area of the Cowper fiues. The large combustion chamber B permits thorough combustion of the gas. FIG. 10.-Whitwell Hot-Blast Stove, as modified by H. Kenned . When “ on wind, ” the cold blast is forced, in at A, and passes four times up and down, as shown by means of unbroken arrows, escaping as hot-blast at B. When “ on gas, " the gas and air enter at the bottom of each of the three larger vertical chambers, pass once up through the stove, and escape at the top, as shown by means of broken arrows. Hence this is a fourpass Stove when on wind, but a one-pass stove when on gas.

71. Preservation of the Furnace Walls.-The combined fluxing and abrading action of the descending charge tends to wear away the lining of the furnace where it is hottest, which of course is near its lower end, thus changing its shape materially, lessening its efficiency, and in particular increasing its consumption of fuel. The walls, therefore, are now made thin, and are thoroughly cooled by water, which circulates through pipes or boxes bedded in them. James Gayley's method of cooling, shown in fig. 7, is to set in the brick-work walls several horizontal rows of flat water-cooled bronze boxes, RR', extending nearly to the interior of the furnace, and tapered so that they can readily be withdrawn and replaced in case they burn through. The brickwork may wear back to the front edges of these boxes, or even, as is shown at R', a little farther. But in the latter case their edges still determine'the effective profile of the furnace walls because the depressions at the back of these edges become filled selves, leaving @ 750,000 horse- ; power aVailab1e for driving the machinery of t h e rolling mills, &c.

This use of the gas engine - is likely to have far-reaching results. In order to utlllze this power, the ln. w ic the pig lron; is converted in t o steel, and the rolling mills must adjoln t h e blast - furnace. The numerous con- verting mills which treat pig iron made at a lstance will now have the crush- ing burden of pro- in other ways, Zn- power which , their rivals get from the blast-furnace, in addition to the severe /ft" disadvantage under which they already suffer, of wasting the initial heat of the ea: molten cast lron as; It runs from the blast- furnace. Before its, use in the gasenglne, the blast-furnace gas his to be freed care u y rom the large fun. guantity of flne ore ust which It carries ZIIH, ln suspension.

73. Mechanical Afpliances - Mov- ing the raw ma- terlals and the pro- ducts: In order to m ove economically the great quantity of materials which enter and issue from each furnace daily, mechanical appliances have at many works displaced hand labour wholly, FIG. II.-Diagram of Cowper Hot-Blast Stove at Duquesne. (After].Kennedy.) Broken arrows show the path of the gas and all while the stove is “ on gas, " and solid arrows that of the blast while it is “ on wind.” A, Entrance for blast-furnace gas. B, B, Combustion chamber. C, Chimney valve., D, Cold blast main.

and indeed that any E, Hollow bflCkSof the materials should be shovelled by hand is not to be thought of in designing new works.

The arrangement at the Carnegie Company's Duquesne works (fig. I2) may serve as an example of modern methods of handling. The standard-gauge cars which bring the ore and coke to Duquesne

pass over one of three very long rows of bins, A, B, and C (fig. 12), of which A and B receive the materials (ore, coke and limestone)