Heating – Shaft type
Patent
1982-07-16
1985-01-22
Yuen, Henry C.
Heating
Shaft type
34174, 34168, 432 96, 432102, F27B 1510, F27D 108
Patent
active
044949308
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention relates to metallurgical and chemical technology and, in particular, to shaft furnaces for heat treatment of finely dispersed materials.
DESCRIPTION OF THE PRIOR ART
Currently, powder-like materials are treated mostly in multiple-hearth mechanically rabbled furnaces. These furnaces have several annular hearths placed one above another and enclosed in a metallic cylindrical casing lined on the inside with a refractory material. The material is moved from one hearth to another by rabbles attached to a central cooled driving shaft. Modern furnaces have up to 16 hearths. The furnaces are heated by combustion gases and burners provided additionally on some hearths. Gases are drawn off through a gas outlet in the top part of the furnace.
This type of furnace is employed for drying and calcining limestone, limestone slimes, and magnesite, and for oxidizing roasting of sulfide materials. The furnace is bulky, and mechanical rabblers inside the furnace complicate its construction and sealing, which renders a multiple-hearth mechanically rabbled furnace practically unsuitable for heat-treatment of powdery and pasty materials without access of air.
Rotary kilns are widely employed for calcining or roasting pasty materials. These kilns have a horizontally arranged metallic casing lined on the inside with a refractory material. The heating arrangements of the rotary kiln include a fire hood and a gas discharge end. Also provided are devices for supplying fuel and discharging calcined (roasted) material. Sealing devices at joints of rotating and stationary parts of the kilns greatly complicate the design thereof. These kilns are used for sintering pasty bauxite or nepheline materials and for oxidizing roasting of sulfide materials. No effective sealing of rotary kilns is practically possible, so that they are not employed for thermal treatment without access of air of powdery or pasty materials.
In addition, treatment of powdery materials in rotary kilns and multiple-hearth furnaces involves substantial dusting, which adversely affects the good repair and service life of units and component parts of the kilns and furnaces.
Materials can also be heat-treated in a protective atmosphere in electrical resistor-drum-type rotary kilns which are intended for treating non-caking and non-sticking loose materials.
These kilns are suited for heat-treatment of materials that give off little dust, as then only it proves advantageous to circulate the costly inert gas.
However, electrical resistor-type rotary kilns cannot be used for thermal processing of flotation concentrates which are fine dusting materials. Another obstacle for treating flotation concentrates is the attendant evolution of moisture, of products from the pyrolysis of flotation reagents and of sulfur.
Finely dispersed dusting materials can also be treated thermally in fluidized bed furnaces. These furnaces comprise a bottom through which hot air is supplied under pressure to fluidize the material being treated. An important component part of the furnace is the bottom which is a slab of refractory concrete with many orifices that are protected against ingress of the material by "mushroom"-shaped nozzles. The treated material is discharged from the furnace by gravity through devices situated level with the fluidized bed.
These furnaces are employed for oxidizing, reducing, sulfidizing, chloridizing and other kinds of roasting of various concentrates and ores, for drying granula, pasty, and liquid materials.
However, these furnaces suffer from a considerable entrainment of dust, the amount of which may attain 50% of the charge fed to the furnace. This complicates and raises the cost of a dust cleaning system for collecting entrained particles. The recovered material requires re-roasting in muffle furnaces and a subsequent individual treatment for extraction of valuable components therefrom.
The devices for collecting entrained particles substantially complicate furnace design and raise the cost of furnace operation. To obviate th
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Abdulkhairov Vakhit T.
Abishev Dzhantore N.
Alipchenko Elena S.
Baltynova Nazymkul
Bauer Ivan K.
Khimiko-Metallurgichesky Institut
Yuen Henry C.
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