COKE 889 



them on a large scale for coking coal. The result has been that in the course of a 

 few months the original idea has been so satisfactorily matured and developed, that 

 instead of coking 6 tons of coal in an oven costing 80/. 150 tons of coal are now 

 being coked at once in a kiln costing less than the former single oven. 



' Figs. 497 and 498 are a side elevation and plan of one of the new coking kilns 

 to a small scale ; jig. 499 is an enlarged transverse section. 



' D D are the walls of the kiln, which are provided with horizontal flues, E, r, 

 which open into the side or bottom of the mass of coal. Connected with each of these 

 flues are the vertical chimneys G, H. The dotted lines 1 1, fig. 498, represent a moveable 

 railway, by which the coal may be brought into the kiln and the coke removed from 

 it. In filling the kiln with coal, care is taken to preserve transverse passages or flues 

 for the air and gases between the corresponding flues E F in the opposite walls. This 

 is effected by building or constructing the passages at the time with the larger pieces 

 of coal, or else by means of channels or flues permanently formed in the bed of the 

 kiln. When the coal is of different sizes, it is also advantageous to let the size of the 

 pieces diminish towards the top of the mass. The surface of the coal when filled in is 

 covered with small coal, ashes, and other suitable material. 



' When the kiln is filled the openings K at the ends are built up with bricks, as 

 shown dotted ; the kiln is not covered by an arch, but left entirely open at the top. 

 The apertures of the flues F and the chimneys G are then closed, as shown in fig. 499, 

 and the coal is ignited through the flues E ; the air then enters the flues E, and passes 

 through the coal, and then ascends the chimneys H, as shown by the arrows. When 

 the current of air has proceeded in this direction for some hours, the flues E and 

 chimneys H are closed, and F and G are opened, which reverses the direction of the 

 current of air through the mass. This alteration of the current is repeated as often 

 as may be required. At the same time air descends through the upper surface of the 

 mass of coal. When the mass is well ignited, which takes place in from 24 to 36 

 hours, the external apertures of the flues E and F are closed, and the chimneys G and 

 H opened : the air now enters through the upper surface of the coal only, and descends 

 through the mass of the coal, the products of combustion passing up the chimneys. 



' The coking gradually ascends from the bottom of the mass to the top, and can be 

 easily regulated or equalised by opening or closing wholly or partially the apertures 

 of the flues or chimneys. The top surface of the coal being kept cool by the descend- 

 ing current of air, the workman is enabled to walk over it during the operation ; he 

 inserts from time to time at different parts of the surface an iron bar, which is easily 

 pushed down until it reaches the mass of coke, by which its further descent is pre- 

 vented. In this way the workman gauges the depth at which the coking process is 

 taking place, and if he finds it to have progressed higher at one part than at another, 

 he closes the chimneys communicating with that part, and thus retards the progress 

 there. This gauging of the surface is carried on without difficulty until the coking 

 process has arrived close to the top. The gases and tarry vapours produced by the 

 distillation or combustion descend through the interstices of the incandescent mass 

 below, and there deposit a portion of the carbon contained in them, the residual 

 gases passing up the chimneys. The coke at the lower part of the kiln is effectually 

 protected from the action of the air, by being surrounded and enveloped in the gases 

 and vapours which descend through it, and ape non-supporters of combustion. 



' When the mass of coal has been coked up to the top, which takes place in about 

 seven days, it is quenched with water, the walls closing the end openings, K, are taken 

 down, and the coke is removed. When a portion has been removed, a moveable 

 railway is laid in the kiln, so as to facilitate the removal of the remainder of the 

 coke. 



' The flues E and F may enter at the bottom of the kiln, or at the sides above the 

 bottom, as in fig. 499 ; in the latter case the space below, up to the level of the 

 bottom of the flues, may be filled with small coal, which becomes coked by the 

 radiated heat from the incandescent mass above. The transverse passages through 

 the mass are then constructed upon this bed of small coal with the larger lumps 

 of coal, as before mentioned. The flues and chimneys need not necessarily be 

 horizontal and vertical ; and instead of connecting a separate chimney with each 

 transverse flue, flues may be constructed longitudinally in the walls of the kiln, so as 

 to connect two or more of the transverse flues, which are then regulated by dampers, 

 conveying the gaseous products from them into chimneys of any convenient height ; 

 the arrangement first described, however, and shown in the drawings is preferred. 

 The gaseous products may be collected, and tar and ammonia and other chemical 

 compounds manufactured from them by the usual modes. The coking or charring of 

 peat and wood may be effected in a similar manner to that already described with 

 regard to coal. 



' The new kilns have proved entirely successful ; they are already in use at some of 



