928 



COPPER 



the ore ignites, and afterwards maintains its own combustion, without the aid of fuel, 

 for any length of time; while the ascending current of air becomes charged with sul- 

 phurous acid of sufficient strength and purity to bo conveyed to the vitriol chambers. 

 The annexed figures represent perpendicular transverse sections of M. Gersten- 



hofer's furnace. Fig. 527 is a cross-section 

 parallel with the front ; Jig. 528 represents a 

 section from front to back. The length of the 

 earthen bars is about two feet six inches: 

 twenty rows occupy about twelve feet in height ; 

 a is an iron box or hopper for containing a 

 supply of ground ore, having at bottom two 

 or more cast-iron grooved rollers, which are 

 worked without interruption, at a speed adapted 

 to supply ore equal to a discharge of about 

 10 cwts. of sulphur per twenty-four hours. As 

 the ore sometimes has a tendency to form a 

 cake on the bars, it is necessary to scrape these 

 occasionally, by means of an iron rod, with 

 curved end, which is introduced through plug- 

 holes in cast-iron boxes, shown in Jiff. 528. 

 The calcined ore collects in the cavity b at the 

 bottom, and is raked out when convenient. 

 The necessary amount of air is admitted partly 

 at the back through the flue c, regulated by 

 means of a screw-valve, and partly through 

 the plug-holes in front. After passing upwards 

 through the calciner, the air, now charged with 

 sulphurous acid to the extent of 6 or 8 per 

 cent, in volume, passes over the bridge, and 

 through the flue e in the direction of the ar- 

 rows, Jig. 528. Provision is made at the bottom 

 of these flues for collecting and removing par- 

 ticles of roasted ore carried over by the current ; 

 / is a brick-built chamber for a similar pur- 

 pose, from the back of which the gas passes 

 through the flue g to the vitriol chambers. 

 The latter are supplied with nitric acid in the 

 usual way ; either from a nitrate-pot or oven 

 worked independently, or with liquid nitric 

 acid allowed to percolate a tower and mix 

 with the gas from the calciners before entering 

 the leaden chambers. 



The Gerstenhofer calciner is applicable to all 

 varieties of sulphuretted copper ores, although 

 varying in proportion of sulphur from 16 to 40 

 per cent. ; it is also adapted to the ' coarse- 

 metal ' or regulus obtained as the result of the 

 first reducing operation. 



Cterstenhofer's Furnace for calcining 

 Copper Ores. 



The calcination is conducted with ease, so that no more sulphur remains in the ore 

 than is necessary for the smelting processes. 



As the superiority of this calciner over every other, having a similar object, has 

 been proved, in the Government copper smeltir,<? establishments of Freiberg and 

 Mansfeld, and in this country, in the works of Messrs. Vivian and Sons, near Swansea 

 (who are the proprietors of the English patent), it is expected that their general 

 introduction into copper works will be the means of greatly reducing the smoke 

 arising therefrom and turning it to profitable account. This was written in 1867. 

 Although still used advantageously, its use has not, in 1874, been extended. 



Mr. Peter Spence, of Manchester, has also a calciner which has been four years in 

 operation, and has calcined 20,000 tons of copper ore. Mr. Spence, in his patent of 

 the 3rd July 1861, thus describes his arrangements: 



' The essential feature of invention consists in submitting such ores to the action 

 of a roasting heat as they are passed from one end of a furnace to the other, during 

 which transference a current of air is caused to travel over them in an opposite direc- 

 tion ; to accomplish this, a furnace of considerable length, having several doors for 

 the purpose of introducing apparatus by which the transference may be effected, is 

 used. It will be obvious that by this arrangement the ores may be submitted to heat 

 in a thin stratum, that the amount of roasting may be modified by a quicker or slower 



