COPPER 



explaining that tho furnace should bo of considerable length. Fig. 531 represents 

 a cross-section ; and in describing the apparatus in tho first instance \ve suppose that 

 the manufacture of sulphuric acid is tho object in view. 



630 



Spence's Furnace for Calcining Copper Ores. 



At a are the fire-bars of the furnace, and at b tho fire-chamber, formed by channels, 

 as seen in fig. 531, extending under a partition c, of fire brick, which partition forms 



tho bottom of another and distinct chamber 

 d, furnished at one or both sides with a 

 number of doors e l , e 2 , &c. At / is an aper- 

 ture formed through the brickwork, and 

 constituting a communication from the ex- 

 ternal atmosphere to the chamber d. The 

 ores from which sulphuric acid is to be ob- 

 tained are passed through the door e 1 into 

 the chamber d in sufficient quantity to lio 

 about two or three inches in thickness upon 

 the bed c, and to extend, say, halfway to- 

 wards the door (P. This batch having been 

 submitted to heat, passing from the fire- 



Spence's Furnace for calcining Copper 

 Ores. 



chamber 6 for the required time, is pushed forward by any convenient instrument, 

 so as to be brought opposite the door e 2 , and another batch is introduced through the 

 door e 1 ; then the first charge is removed from e 2 to e 3 , and the second from c 1 to c-, 

 and so on until the first-deposited batch shall have arrived at the .other end of 

 the furnace at e 12 , and it is then pushed through the aperture /into any receptacle 

 placed to receive it. During this transference of the material, it has gradually become 

 heated, and a current of air entering at /has been passing over it, and the operation 

 has caused the sulphur to be driven off from the ore and conveyed through the 

 channel g to the ordinary sulphuric acid apparatus. The end of tho fire-chamber 

 d leads to a flue at i. The degree of roasting to be effected, and so as to secure tho 

 best results, can be ascertained only by experience ; but working with a furnace 

 fifty feet long and with twelve doors, the first charge is allowed to remain for one 

 hour, then transferred to the second position, and a fresh charge put into the first, 

 and so on, waiting an hour between each charge. 



An advantage arising from this invention is its capability of being applied to the 

 manufacture of sulphuric acid from any description of ores. It is well known to those 

 engaged in the extraction of copper from ores that the sulphur thereof is frequently 

 wasted from the impracticability of roasting certain mixed ores so as to render them 

 into a fit condition for reduction, and also for the manufacture of sulphuric acid ; but 

 by this improved method, ores of any description, large or small, may be roasted so 

 as to produce sulphuric acid with economical results. In calcining the mixed copper 

 ores preparatory to smelting, as practised at the Swansea and other copper works, 

 and with the view of economising the manufacture of sulphuric acid, the process of 

 calcination by this method is effected with equal advantage as by the modes now 

 practised, as the heat is made to act on a large body of ore without an exhaxistive, 

 but with an accumulative effect, so that the heat which has calcined or driven off 

 nearly the last portion of sulphur from the ore which lies at the exit of the furnace 

 then passes on, heating every successive charge, and gaining strength from the com- 

 bustion of the sulphur until it comes into contact with the cold charge, which it 

 rapidly heats to ignition, partly from the iinder heat of the bed derived from the fire, 

 which, after leaving the furnace, is passed to a chimney, and partly from all the hot 

 gases passing over it on their way out of the furnace to the vitriol chamber, into 

 which they are conveyed after being mixed with nitrous gases, as is well known. 



