Roasting blast

FIG. 23-43 Reactors for solids, (a) Temperature profiles in a rotary cement lain, (h) A multiple hearth reactor, (c) Vertical lain for lime burning, 55 ton/d. (d) Five-stage fluidized bed lime burner, 4 by 14 m, 100 ton/d. (e) A fluidized bed for roasting iron sulfides. (/) Conditions in a vertical moving bed (blast furnace) for reduction of iron oxides, (g) A mechanical salt cake furnace. To convert ton/d to kg/h, multiply by 907. 

In the blast furnace reduction slag-making materials are also added together with a small amount of iron, the function of which is to reduce any sulphide which remains, to the product of the roasting operation to produce a sinter. The sinter is then reduced with coke in a vertical shaft blast furnace in which air is blown tluough tuyeres at the bottom of tire shaft. The temperature in the heartlr where metal is produced must be controlled to avoid the vaporization of any zinc oxide in the sinter. The products of tlris process are normally quite complex, and can be separated into four phases. Typical compositions of these are shown in Table 13.1. 

Metal.) blast roasting, verblassen, v.i. fade pale. 

Solid effluents arising from metallurgical operations occur principally in two forms fine particulate solids or dusts, and solid wastes. As an example, blast furnace gas may contain up to 170 kg of dust per ton of pig iron produced. Suitable methods must be devised for processing the solid effluents for two reasons (i) to prevent pollution of the environment and (ii) to recover their valuable content, if any. As far as the latter is concerned, reference may be drawn, as an example, to the recovery of rhenium from the exit gas from molybdenite roasting in a multiple-hearth furnace. 

Hybinette A process for extracting nickel from sulfide ores. The nickel ore that occurs in Canada is a mixture of the sulfides of nickel, copper, and iron. Several methods have been used to separate these metals. In the Hybinette process, the ore is first smelted in a blast furnace, yielding a nickel-copper matte (i.e., a mixture of their lower sulfides). This is roasted to remove sulfur and leached with dilute sulfuric acid to remove copper. The resulting crude nickel oxide is used as the anode of an electrochemical cell. The nickel deposits on the cathode, which is contained in a cloth bag. Precious metals collect in the anode slime. The process was invented by N. V Hybinette in 1904 and operated at the Kristiansand refinery, Norway, from 1910. 

Mansfield A process for extracting copper from sulfide ores by roasting with anthracite or coke and a silicious flux in a special blast furnace. 

The lead concentrate must he roasted for effective removal of sulfur and then smelted in a blast furnace. Sulfur is mostly removed hy a sinter process. The galena concentrate or the ore itself, if its impurity content is low, is mixed with silica and other slag-forming reagents and roasted in sinter machines to produce lead oxide, lead silicate, and some metallic lead. The principal reactions are ... 

When roasted in an air blast furnace, basic lead sulfate, Pb0 PbS04 (also known as sublimed white lead), is formed. 

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,... 

The copper sulfide and iron oxide from this reaction are then mixed with limestone, CaC03, and sand, Si02, in a blast furnace, where CuS is converted to Cu2S. The limestone and sand form molten slag, CaSi03, in which the iron oxide dissolves. The copper sulfide melts and sinks to the bottom of the furnace. The less-dense iron-containing slag floats above the molten copper sulfide and is drained off. The isolated copper sulfide is then roasted to copper metal ... 

Tin occurs as oxide (cassiterite, tin stone, stannic oxide, Sn02). obtained commercially in Malaysia, Indonesia, Thailand, and Bolivia. The ore is concentrated and then roasted to oxide (83-88% stannic oxide). The product is treated in a blast furnace and crude tin recovered. Refining is conducted by electrolysis, or by fractional fusion. 

There is a large class of industrially important heterogeneous reactions in which a gas or a liquid is brought into contact with a solid and reacts with the solid transforming it into a product. Among the most important are the reduction of iron oxide to metallic iron in a blast furnace the combustion of coal particles in a pulverised fuel boiler and the incineration of solid wastes. These examples also happen to be some of the most complex chemically. Further simple examples are the roasting of sulphide ores such as zinc blende ... 

Lead is obtained from its ore, galena (PbS), by roasting the sulfide in air and reducing the resulting PbO with carbon monoxide in a blast furnace ... 

Noncatalytic packed bed reactors have been discussed separately in other sections of this article. They include blast furnaces, convertors, roasting furnaces, rotary kilns, and gasifiers. 

Batch sintering to handle fines included roast heaps, blast roasting pots. 

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