This invention relates to the transfer of hot feed materials from a preprocessing plant to an electric smelting or melting furnace. The preprocessing plant may be a kiln, a direct reduction facility, or a rotary hearth furnace, in which an ore is calcined, sintered or reduced.
The problems associated with the transportation of hot feed materials arise from their inherent characteristics, which may include some or all of the following:
A typical hot material transfer system might consist of the following:
The transfer process just described is characterized by significant release of pollutants, at the kiln discharge valve, from the container itself while in transit, and at the loading of the feed bin from the container.
The total distance travelled by the container, vertical and horizontal, is, in a typical case, about 60 meters. The provision of an emission control system, large enough to cover the arrangement just described, and consisting of hood, ducting fan, baghouse and controls, imposes a large financial burden, in both capital and operating costs. Systems using drag chain conveyors or other transportation methods have similar problems.
One transfer system which has been widely discussed but not widely employed, consists of placing the kiln at a higher elevation than the furnace and using gravity to transfer the hot material downwards through closed pipes or ducts. This has the following advantages:
The operational advantages of this system are offset by the very high capital cost involved in locating a kiln or a rotary hearth furnace 30 m± above grade elevation, particularly in areas of high seismic risk.
In practical situations, the material may need to be fed to the furnaces at a substantially different, but usually higher, level than that at which it is discharged from the calcining plant. The calcine needs to be distributed in a controlled manner through multiple feed ports into the furnace.
It is an object of the invention to provide a transfer system which addresses the above problems.
According to the invention, apparatus for transferring hot material between a preprocessing plant and an electric furnace comprises an enclosed housing extending between the plant and the furnace and within which a controlled atmosphere is maintained, at least one bin having at least one compartment receiving feedstock material at a delivery station from the plant, mechanism for shuttling the at least one bin along a path within the housing between the delivery station and discharge tubes above and leading into the furnace at distributed locations, and discharge mechanism for dropping material from each compartment into a discharge tube. The path may be horizontal, vertical, or inclined, to suit the relative locations of the preprocessing plant and the battery. Each bin is usually each divided to feed multiple tubes. The shuttling mechanism may be a hoist or a railway or cable span, and the discharge mechanism is typically a means for tipping the bin. The bin should be such that the depth of material therein during transit is sufficiently low to limit coagulation of the material in transit, if this is a problem.
This arrangement enables the entire transfer operation to be carried out in a controlled atmosphere, with transfer time reduced to a minimum, and without any substantial static accumulation of material, while, at the same time, allowing the transfer components to be very simple and robust with a minimum need for maintenance.
Further features of the invention will be apparent from the following description of presently preferred embodiments of the invention with reference to the accompanying drawings.
Referring to
The tower 2 contains two hoists 24 mounted for limited movement on a platform 26 on a horizontal axis perpendicular to the axis of the row of furnace electrodes 14. Pairs of funnel assemblies 28a, 28b, 29a, 29b, 30a, 30b, and 31a, 31b are mounted on the wall of the tower nearest the shed 4 at different levels above the furnaces 6. The funnel assemblies are each divided into four funnels, each of which forms an enlarged opening to one of the tubes through which calcine is delivered to the furnace. The connections of the tubes between the chutes and furnace are illustrated in
Each hoist is connected by cables 42 to a frame 32 supporting a compartmented tray 34 through pivots 36 so that the tray may be tipped as shown in its uppermost depiction in
In the embodiment shown in
The bins 134 in the example shown consist of four compartments in the form of tubular containers which guides 144 cause to tilt to a vertical position to place open ends of the tubes beneath the chute 138 so that each may be wholly or partially filled with calcine. The tubular containers are returned to a near horizontal position for transit (as seen in
In each embodiment, the tower 2 or passages 102 are enclosed to exclude the ambient atmosphere, and the atmosphere inside is controlled, both to avoid release of fumes, and to avoid unwanted reactions with the material being transported. For example, off-gas from the calcining plant or furnace, or waste gas from elsewhere in the plant may be admitted, surplus gas being passed to an appropriate treatment plant. Gas may be admitted at either the top or bottom of the volume to be filled according to whether it is heavier or lighter than ambient air such as to displace air from the volume concerned. Alternatively, the volume may be allowed to fill with gases emitted from the material, suitable treatment facilities again being provided to handle surplus gas. The tower or passages also provide an opportunity for dust from the material to settle. A hopper 48 (
The embodiments described are exemplary only. In the embodiments described, the shuttle path is respectively vertical and horizontal. It should be understood that applications in which the housings (tower or passage) are inclined, either laterally or longitudinally, so as to have both vertical and horizontal extent are also within the scope of the invention, with the shuttle(s) for the tray(s) or bin(s) having suitable guidance to follow the inclined path. Regardless of the arrangement used, a shuttle mechanism within the housing is used to provide rapid transportation of material, as it is delivered, to distributed points within the furnace, without any substantial accumulation of material. Distribution of the material within the furnace can be controlled by controlling the amount of material discharged into each compartment within the shuttle tray or bin, while permitting extremely simple and robust mechanisms to be utilized.
Number | Date | Country | Kind |
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2341772 | Mar 2001 | CA | national |
This application claims the benefit of International Application No. PCT/CA02/00387, which was filed on Mar. 19, 2002 and published under PCT Article 21(2) in English and which claims the benefit of Canadian Patent Application No. 2,341,772 filed on Mar. 22, 2001.
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/CA02/00387 | 3/19/2002 | WO | 00 | 6/3/2004 |
Publishing Document | Publishing Date | Country | Kind |
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WO02/07729 | 10/3/2002 | WO | A |
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Number | Date | Country | |
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20040214125 A1 | Oct 2004 | US |