Industrial electric heating furnaces – Resistance furnace device – Charging or discharging
Patent
1981-05-28
1983-12-20
Envall, Jr., Roy N.
Industrial electric heating furnaces
Resistance furnace device
Charging or discharging
432 95, H05B 300
Patent
active
044221746
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to metallurgical and chemical industries, and more particularly, to a shaft furnace for heat treatment of materials.
The invention is readily adapted to application for drying and roasting without air access, of various powdered and pasty materials, such as flotation concentrates and slimes, as well as for driving off volatile and easily disintegrating substances, for instance, mercury, sulphur and flotation agents.
BACKGROUND OF THE INVENTION
In modern practice of heat treatment of powdered materials extensive use is made of multiple-hearth mechanical furnaces. This type of furnace generally comprises several superimposed annular hearths encased in a metallic cylindrical shell lined on the inside with a refractory material. To replace the material being treated from one hearth onto another, there is provided a power-driven cooled shaft formed with rabbles. A modern furnace may comprise up to 16 hearths. It is usually heated by furnace gases or else by burners, which are additionally mounted on some of the hearths. Gases are discharged from the furnace through an outlet pipe provided in the upper portion thereof.
This type of furnace is used for drying and firing lime, lime sludges, magnesite, as well as for oxidizing roasting of sulphide materials. Apart from being cumbersome, the furnace is rather complicated in construction and not sufficiently leak-proof, which is largely due to the presence of mechanical rabbling mechanism mounted within the furnace. Therefore, multiple-hearth mechanical furnaces are unsuitable for heat treatment of powdered or pasty materials without access of air.
Rotary-drum furnaces are now widely employed for sintering or roasting of pasty materials. The furnace of this type generally comprises an upright metallic shell lined on the inside with a refractory material. Burner and gas outlet heads are provided to make possible the furnace heating. To replace the material within the furnace, the latter is furnished with a rabbling mechanism mounted in the furnace interior. There are also provided fuel supply means and means intended to discharge the roasted material. The furnace construction is rendered very much complicated by sealings disposed at the places of connection of the furnace rotatable and fixed members.
The furnaces of the type described above are suitable for effecting sintering of pasty boxite and nepheline materials, as well as for oxidizing roasting of sulphide materials. It is practically impossible to make rotary-drum furnaces 100% leak-proof. Because of this such furnaces are never used for heat treatment of powdered or pasty materials without air access.
Moreover, the treatment of powdered materials in rotary and multiple-hearth furnaces is accompanied by the formation of immense amount of dust, which adversely affects reliability and durability of the furnace units and members.
It is common practice to use drum-type electric resistance furnaces where heat treatment of materials is conducted in the protective atmosphere. These furnaces are intended to perform heat treatment of non-sintering and other loose materials with no tendency to adhere to the furnace walls. Such furnaces are predominantly employed for the treatment of low-dust producing materials, this being important condition for setting up the circulation of an expensive inert gas.
However, the drum-type electric resistance furnaces are unsuitable for treatment of flotation concentrates, which are finely pulverized dust-forming materials. In addition, the heat treatment of flotation concentrates results in the precipitation of moisture, as well as in the separation of decomposition products obtained in the course of pyrolysis of flotation agents, and sulphur.
If heat treatment of finely dispersed dust-forming materials is effected in the protective atmosphere, use is made of furnaces intended for fluidized-bed roasting. The furnace of this type comprises a chamber with a bottom hearth through which heated compressed air is supplied to form fluidiz
REFERENCES:
patent: 2108118 (1938-02-01), Greenawalt
patent: 2337042 (1943-12-01), Gloss
Electrothermic Equipment, Reference Book, Edited by A. N. Altgauzen et al., Publishing House "Energy", Moscow, 1967, p. 365.
Abishev Dzhantore N.
Bauer Ivan K.
Burovoi Isaak A.
Gainutdinov Garifulla K.
Kusainov Temirkhan A.
Envall Jr. Roy N.
Greenspan Myron
Khimiko-metallurgichesky Institut AN Kazakhskoi SSR
Lilling Bruce E.
Lilling Burton L.
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