Roasting fluidized bed

Fluidized-bed roasting accounts for most of the world zinc production today. Over the last 15 years, several zinc roasters have augmented their calcine production capacities with oxygen enrichment. These roasters typically encounter production increase limitations due to existing blower capacities, requirements for fluidization characteristics of the bed, and downstream gas-handling capacities. Oxygen enrichment provides roaster operators with a tool to increase roaster capacity in a cost-effective way. Several roaster plants utilize oxygen enrichment to improve calcine... 

Luckos A, den Hoed P. Fluidized-bed roasting of ilmenite. In Kwauk M, Li J, Yang WC, eds. Fluidization X. New York Engineering Foundation, 2001, pp 613-620. 

When the solid is one of the reactants, such as in ore roasting, the flow must be continuous and precise in order to maintain constant conditions in the reactor. Feeding of free-flowing granular solids into a fluidized bed is not difficult. Standard commercially available sohds-weighiug and -conveying equipment can be used to control the rate and dehver the solids to the feeder. Screw conveyors, dip pipes, seal legs, and injectors are used to introduce the solids into the reactor... 

Although it is not a catalytic process, the roasting of iron sulfide in fluidized beds at 650 to 1,100°C (1,202 to 2,012°F) is analogous. The pellets are 10-mm (0.39-in) diameter. There are numerous ants, but they are threatened with obsolescence because cheaper sources of sulfur are available for making sulfuric acid. 

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. 

Use suspension or fluidized bed roasters, where appropriate, to achieve high SO2 concentrations when roasting zinc sulfides. 

Several important applications of fluid beds exist outside the petroleum industry. Fluid bed roasting of pyritic ores is widely used in the metallurgical industry. Calcination of lime is a commercial process. There are also fluidization processes for various nuclear processing steps. 

Fluidized bed reactors were first employed on a large scale for the catalytic cracking of petroleum fractions, but in recent years they have been employed for an increasingly large variety of reactions, both catalytic and non-catalytic. The catalytic reactions include the partial oxidation of naphthalene to phthalic anhydride and the formation of acrylonitrile from propylene, ammonia, and air. The noncatalytic applications include the roasting of ores and Tie fluorination of uranium oxide. 

Figure 117 Fluidized-bed reactor for roasting zinc concentrate (after Themelis and Freeman, 1983)...

Roasting furnaces are in a class of reactors used by the metallurgical industry in a preparatory step for the conversion of ores to metals. There are three widely used roasted furnaces multiple hearth, fluidized bed, and flash roasters. In the multiple hearth configuration hot gases pass over beds of ore concentrate. The flash roaster injects pulverized ore with air into a hot combustion chamber. The fluidized bed roaster operates as described in a separate heading. 

All of these roasting furnace reactors operate continuously. They are noncatalytic gas-solid heterogeneous reactors. The multiple hearth has characteristics similar to plug flow operation. The flash roaster approaches CSTR, and the third option is a fluidized bed configuration. 

CFB (2) [Circulating Fluidized Bed] A metallurgical roasting process, developed originally for the aluminum industry and now used for many other, nonferrous ores. Offered by Lurgi. 

Li, Y., and Wang, F. Experiments of hydrodynamics for roasted magnesite in a fast fluidized bed, Research report (in Chinese), Institute of Chemical Metallurgy, Academia Sinica (1983). 

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