Roasting reverberatory

As well as containing iron at around 40 to 45 per cent, matte contained about 12 per cent lead, most of the copper from blast furnace feed, about half the zinc and a substantial proportion of the silver. Matte was initially roasted in open heaps or stalls to remove sulfur and was then recycled to the blast furnace, but later reverberatory roasting furnaces were used. A shaft kiln was used at the Harz smelter in Germany. 

Flintshire An early lead-smelting process in which galena was roasted in a reverberatory furnace. 

Then the roasted ore is combined with sand, powdered limestone, and some unroasted ore (containing copper(II) sulfide), and heated at 1,100°C in a reverberatory furnace. Copper(II) sulfide is reduced to copper(I) sulfide. Calcium carbonate and silica react at this temperature to form calcium silicate, CaSiOs The liquid melt of CaSiOs dissolves iron(II) oxide forming a molten slag of mixed silicate ... 

Smelting in Blast Furnaces.—The use of the blast furnace involves the necessity of a somewhat different treatment. The Scotch furnace or ore-hearth, described at page 465, may be taken as the type of this kind of furnace when adapted to the smelting of lead ores. Generally very rich ores are operated upon where the Scotch furnace is employed end these are subjected before smelting to a preliminary roasting in a furnace of the reverberatory class,... 

In Cornwall and Devon the ores used contain arsenopyrite mixed with iron and copper pyrites, tin ore, zinc blende, galena, etc. Before roasting, the ores are separated as far as possible by hand, and tinstone is removed by washing the finely powdered material. The roasting is conducted in a reverberatory furnace having a revolving floor over which a number of scrapers are fixed. The ore, which contains 10 to 80 per cent. As, is introduced through a hopper on to the floor, which revolves once every 12 minutes or so. It is heated to dull redness for... 

CA Registry No [7440-31-5]. Occurs to the extent of 6 x l0" % in the earth s crust. Found in cassiterite, stannite and tealite. CommI prepn is by roasting the ore (cassiterite) to oxidize sulfates and to remove arsine, then reducing with coal in a reverberatory furnace or by smelting in an electric furnace... 

The speiss is crushed and ground with 20 pex cent, of sodium chloride till it passes a 30-mesh sieve, and then roasted in reverberatory furnaces. The chloridised product is extracted with water to remove unchanged salt and soluble compounds of cobalt, nickel, and copper. The copper is removed from the liquor by treatment with scrap-iron, and the cobalt and nickel are then precipitated with caustic soda, and the precipitate washed, dried, calcined, and ground. It contains about 40 per cent, of cobalt to 3 per cent, of nickel, since the latter is not attacked so readily as the former in chloridising the speiss the mixed oxides also contain about 15 ounces of silver per ton. 

The residue from the chloridised speiss, after extraction of soluble cobalt and nickel salts, is extracted with sodium thiosulphate, to dissolve out silver chloride, which is recovered as the sulphide and reduced to metal. The residue is dried, ground, and smelted with quartz to remove most of the iron as a slag. This slag is reworked with more ore in the blast-furnaces, as it contains silver and cobalt. The new speiss simultaneoiisly produced is treated as described above for recovering cobalt and nickel, copper, and silver. The final residue is dried, mixed with 20 per cent, of sodium nitrate and 10 per cent, of sodium carbonate, and roasted in reverberatory furnace to convert the arsenic into sodium arsenate, which is extracted with hot water. The dried residue has the following average composition ... 

Epitome of Process.—The ore is first dressed, roasted, and then smelted in blast or reverberatory furnaces to a ferruginous matte consisting essentially of sulphides of copper, nickel, and iron. This is then oxidised in a blast of air in a converter in an analogous manner to the production of steel by the basic Bessemer process. By this means practically all the iron is removed, and as much sulphur as possible without excessive loss of nickel. On an average the product contains approximately ... 

Treatment of Arsenical Ores.—Nickel is also obtained on a small scale from its arsenical ores. These are roasted to remove part of the arsenic and sulphur, smelted with silica and coke to remove iron in the slag, and the crude nickel arsenide thus obtained roasted in a reverberatory furnace to oxidise more iron and remove more arsenic. The last two operations are repeated until the product is sufficiently... 

The formation of the chlorides is effected in the dry way by calcination with sodium chloride or in the wet way by interaction with ferrous chloride and hydrochloric acid or with ferric chloride. The wet way is only adopted if fuel is scarce, or the escape of noxious vapours into the atmosphere is not permissible. In the dry method the ore is oxidized by a preliminary roasting, and then chloridized by calcination with sodium chloride or Abraum salts in a furnace of the reverberatory or muffle type, the principal product being cupric chloride. The Dotsch modification of the wet process, worked at Rio Tinto, depends on the action of ferric-chloride solution on a mixture of the ore with sodium sulphate and ferric chloride. The liquid drawn off from the bottom of the heaps of ore contains cuprous chloride in solution as a complex salt. The copper is liberated by the action of iron, the ferrous chloride simultaneously formed being chlorinated in towers to ferric chloride, and the product employed for moistening the heaps of ore. 

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