Bisbee daily review., 1918-09-01

were made by Chalmers & Williams The crushers are cross connected by chutes. are provided with grizzlies and deliver the ore to pair of 20 in. con veyor-belts that take it to the top of the sampling and screening-plant. A new set of bins has just been installed parallel to the older series, and No & gyratory. built by the Allis-Cham- bers Manufacturing company, has been erected at the end of the line or bins. The crushed ore from this ma chine will be handled by new unit of the sampling works. This adsli- tion to the mill is at present only equipped for handling the samples as they are cut from the main stream of reject, and for screening sulphldes, the coarser sulphide being sent to the mixing beds for the blast furnaces, while the remainder is brought down to approximately F in. size for the reverberatcry furnaces. The sulphides go to the Herreshoff furnaces to be roasted, and the oxide ores go direct to the charging bins.
 The handling of the ore through the mill is on a 2-belt system, each belt being capable of carrying the entire product of each unit The arrange ment is in parallel, so that no delay can ever occur on account of needed repairs. The Ain. ore from the pri mary crushers is first delivered to a pair of Snyder samplers, consisting of a shallow cone, like a bowl set on edge, the ore chute delivering to the lower inside rim which is protected by renewable cast-iron liners. At one point in the rim is an open segment the width of the Ore-chute. The bowl revolves and during nine-tenths of the revolution the machine is dischaTging reject to the main ore-stream, while for the remaining one-tenth of the rev olution the whole stream is diverted to the sampling unit of the mill. The Snyder sampler, which is excessive ly simple and efficient, cuts one-tenth of the stream and by such successive reductions the entire volume of 24OO tons per day is accurately sampled, each variety of ore being separately treated and for every 100 tons there results a sample of 160 lbs, which is sent to the bucking room. It is re- duced there to a proper size for the assay office by the usual series of gy- ratories, coffee-mill crushers, and disc grinders. Although every ton of ore entering the shelter passes through the mill and is sampled, there is a by- pass after the first sampler by means of which ore suitable for bedding can go direct to the beds The coarser crushing is done by four 10 by 20-in. Blake crushers made by the Power & Mining Machinery company. The final reduction of the ore to 19 inch size is effected in two Symons vertical disc-crushers. each of which has a ca- pacity of 50 tons per hour. Through out the plant trommels are used for screening.
 From the sampling works conveyor belts take the coarse ore to the Mes sitter beds. the fine siliciOus ore to bins in the reverberatory department, the fine sulphide ore to the roasters, while the calcine from the roasters is transported by acknowledgements trains of larries to the reverberatory charging bins. The roasting practice has been dwelt upon in a previous article describing the sulphuric-acid plant. The furnace used is the latest design of the Herreshoff, built by the Pacific Boundary company of San Francisco. Each furnace has six hearths, exclusive of the drying-pan. 20 feet, ? inches inside diameter, and 21 feet, 2 1-4 inches over all It may be we'll to recall the fact that, of the 24 Herreshoff furnaces, only 5 are running closed" that is, with the gas discharge muffled by being sent through flues into the dust-chamber and thence through the nitre house Glover tower and acid chambers. The remaining 19 are running "open," the gases. which carry from to IS per cent of the weight of the charge, pass ing through a dust chamber l4O feet long and 50 by 2912 feet in vertical section, on their way to the stack Tn walls of the dust-chamber are built of hollow tile. A baffle-wall is placed near the front and rear of the cham Der. The ore for roasting does not need to be reduced to F inch, since disintegration on the hearths brings 1t down to proper size. About 25 to 30 per cent of the ore for the "open" fur mace will remain on F inch screen In the ore roasted in the "closed' furnaces the sulphur content is main tained a little higher. although the difference usually does not exceed to 5 per cent The average is about 29 per cent sulphur. Owing to the coarseness of the material a consider able amount of kernel roasting" is done. The calcine issues from the "open" furnaces with about 10 pel cent sulphur as against 1S per cent from those connected to the aciC plant. The capacities of the "open' and the closed" furnaces are respect
 ively 90 and 70 tons each per diem, al
 though the "open" furnaces can b'
 driven to the extent of handling 12' tons.
 The official figures regarding thu blast furnaces are also given. A:
 previously stated, there are two furn
 aces of the long pattern first develop ed in practice by E. P Matthewson though it had long been pointed ou
 by metalurgists that there was nc
 necessary limit to the length of rect
 angular furnace for copper smelling
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