972 



IRON 



give a blast-furnace, of any determinate height fixed upon, the largest possible capacity 

 it is capable of receiving, while remaining free from any distortion of form, likely 

 to give a place for minerals to lie out of the way of the action of the upward gaseous 

 current ; when the height exceeds the proportion to its greatest diameter indicated 

 in the figure, an unnecessary sacrifice in its capacity is the only loss entailed. The 

 height above the mouth must be regulated by the kind of hopper used for charging, 

 where it is intended to carry off the gases. 



Doubtless when the true principle of collecting these gases without injury to the 

 blast-furnace becomes more generally known, attention will be directed to the easiest 

 and most convenient mode of introducing the minerals. The conical charger has only 

 one disadvantage, that namely of allowing a great waste of gas during the charging ; 

 probably some kind of revolving hopper may be contrived to remedy this defect. It 

 is of course assumed that the furnace is supplied with a proper quantity of blast, and 

 of a density proportionable to the diameter across the tuyeres, so as to maintain a 

 vigorous combustion of the fuel to the very centre of the hearth, the top of which is 

 indicated by the letters e e, for unless this is attained, a cold cone of minerals will 

 remain in the centre, and produce derangements which no degree of perfection in the 

 form of the furnace in the higher region can remove. 



Theory of the Blast-furnace. Analyses of the gases from a furnace at Alfreton, in 

 Derbyshire, at various depths below the surface, gave to Messrs. Bunson and Playfair 

 the results embodied in the subjoined Table. The furnace was supplied with 80 

 charges in the course of 24 hours, each charge consisting of 390 Ibs. of coal, 420 Ibs. 

 of calcined ironstone, and 170 Ibs. of limestone, the product being 140 Ibs. of pig-iron. 

 The gases were collected through a system of tubes of malleable iron, 1 inch in 

 diameter, and were received in glass tubes 4 inches long, and f of an inch in diameter. 

 The well-known skill of M. Bunsen as a gas analyst is a guarantee of the accuracy of 

 the determinations. 



Composition of the Gases taken from different depths in the Furnace. 



From these analyses it appears : 



1. That at a depth of 34 feet from the top, within 2 feet 9 inches of the tuyere, the 

 gas was entirely free from carbonic acid, but contained an appreciable quantity of 

 cyanogen. 



2. That the nitrogen is at a minimum at 14 feet. 



3. That carburetted hydrogen is found so low as 24 feet, indicating that at tbat 

 depth coal must be undergoing the process of coking. 



4. That hydrogen and olefiant gases are at a maximum at 14 feet. 



5. That the proportions between the carbonic acid and carbonic oxide are irre- 

 gular, which is probably to bo explained by the fact that water is decomposed as its 

 vapour passes through the layers of hot coal. 



The average composition of the gases evolved from the materials used in the blast- 

 furnace is somewhere between the two following numbers : 



Nitrogen 60-907 



Carbonic acid 8'370 



Carbonic oxide 26'846 



Light carburetted hydrogen .... 2'536 



Hydrogen M26 



Olefiant gas 0-112 



Sulphuretted hydrogen 0-046 



Ammonia . . 0-058 



57-878 

 9-823 



24-042 

 2.743 

 4-972 

 0-392 

 0-035 

 0-115 



100-000 



100-000 



