THE GLOBE PLANT OF THE AMERICAN SMELTING AND REFINING COMPANY[58]
By O. Pufahl
(May 5, 1905)
This plant produces 1800 tons of base bullion per month and 200 tons of lead-copper matte containing 45 to 52 per cent. of copper. The ores smelted are mostly from Colorado, but include also galena from the Cœur d’Alene and other supplies. The limestone is quarried 14 miles from Denver; coke and coal are brought from Trinidad, Colo.
All sulphides, except the slimes, concentrates and the rich Idaho ores, are roasted. For roasting there are:
(1) Fifteen reverberatory furnaces, five of which measure 60 × 14 ft., and the other ten 80 × 16 ft. externally. In 24 hours these roast six charges of 4400 lb. (average) of moist ore (2.15 tons of dry ore) from 28 to 30 per cent. down to 3 to 4 per cent. sulphur. Each furnace is attended by three men working in 12-hour shifts; the stoker earns $2.75; the roasters, $2.30.
(2) Two Brown-O’Harra furnaces, 90 ft. long, with two hearths, and a small sintering furnace attached. They have three grates on each long side, and each roasts 26 tons of ore in 24 hours down to ¾ per cent. sulphur.
(3) Twelve Brückner furnaces, each taking 24 tons’ charge, with under-grate blast, the air being fed into the cylinders by a steam jet. According to the zinc content of the ores the roasting operation lasts 70 to 90 hours, the furnace making one revolution per hour. The roasted product from the Brückner furnaces is pressed into briquets, together with fine ore, flue dust and lime.
The smelting is carried out in seven blast furnaces, with 16 tuyeres, blast at 2-lb. pressure, hight of furnace 18 ft. 6 in., section at the tuyeres 42 × 144 in. The charge is 120 to 150 tons exclusive of slag and coke. The slag and the matte are tapped off together into double-bowl Nesmith cars, which are hauled, by an electric locomotive, to a reverberatory furnace (hearth 20 × 12 ft.) in which they are kept liquid, for several hours, in charges of 14 to 15 tons, in order to effect complete separation. A little work-lead is obtained in this operation, while the matte is tapped off into cast-iron pans of one ton capacity, and the slag, 0.5 to 0.6 per cent. lead, 0.6 to 0.7 oz. silver, is removed in 5-ton pots to the dump.
The matte is broken up, crushed to 0.25 in. size, roasted in the reverberatory furnaces, smelted for a 45 to 52 per cent. copper matte, which is shipped to be further worked up into blister copper. The crude matte contains 10 to 12 per cent. copper, 12 to 15 per cent. lead, 40 oz. silver and 0.05 oz. gold.