US3171878A

US3171878A - Metallurgical apparatus

Info

Publication number: US3171878A
Application number: US44770A
Authority: US
Inventors: James J Burke
Original assignee: Independence Foundation; Koppers Co Inc
Current assignee: Independence Foundation; Beazer East Inc
Priority date: 1960-07-22
Filing date: 1960-07-22
Publication date: 1965-03-02
Anticipated expiration: 1982-03-02

Description

3 Sheets-Sheet 1 J. J. BURKE METALLURGICAL APPARATUS March 2., 1965 Filed July 22, 1960 lNvENToR James J. Burke March 2, 1965 J. J. BURKE METALLURGICAL APPARATUS 3 Sheets-Sheet 2 Filed July 22.' 1960 lNvENroR James J. Burke March 2, 1965 J. J; BURKE 3,171,878

' METALLURGICAL APPARATUS Filed July 22. 1960 5 Sheets-Sheet 5 Fig. 3.

\ Y James J. Burke @LM @M 0 RNEY "D United States Patent O 3,171,878 METALLURGICAL APPARATUS James J. Burke, New York, N.Y., assignor, by mesne assignments, to Independence Foundation, Philadelphia, Pa., a corporation of Delaware, and Koppers Company, Inc., Pittsburgh, Pa., a corporation of Delaware Filed July 22, 1960, Ser. No. 44,770

4 Claims, (Cl. 13-10) This invention relates to metallurgy in general and more particularly to direct reduction processes. The invention has for a principal `object the provision of a process for the continuous and direct reduction of metallurgical ores.

In the development of the now quite-diverse Strategic- Udy processes, rotating kilns have played a significant part in the overall eiciency and economics of the process as applied to diverse starting materials. In copending U.S. application of Frank C. Senior, Serial Number, 36,026 filed June 14, 1960, there is described and claimed a unique rotary kiln operation in which it is possible, in one continuous operation to dehydrate ore, calcine fluxes, sintet and agglomerate fines, oxidize sulfur and arsenic, partially reduce metallic oxide values; delivering at the discharge end of the kiln a hot, substantially complete furnace burden including ore, fluxes and carbonaceous reductant in a form suitable for rapid and efficient reduction in an electric furnace. The process operates with high thermal efficiency and is amenable to use in the treatment of a broad range of normal and low-grade ores, uxes and reductants.

Ideally, the process of said copending application is designed for use in conjunction with a rotating-hearth electric furnace, into which the kiln discharge is continuously fed on a substantially uninterrupted basis. The stirring action imparted by the rotating hearth insures intimate admixture of ore and reductant, which speeds the reduction process and conserves thermal energy. With the output of the kiln geared t-o the production rate of the furnace, the process becomes a continuous one, it being necessary to interrupt rotation of the furnace only Vto tap metal and slag from time to time, and to make periodic repairs on refractories and the like.

The process of the present invention is grounded in the basic observation that the operation of a rotating kiln and a'rotating hearth furnace could be advantageously combined into a single unit by rotating both units about the same axis. This has the advantage of reducing appreciably capital investment for the necessary mechanical rotating equipment, eliminating the problem of operating a rotating hearth under a stationary roof, and generally results in a very substantial increase in the thermal efficiency of the overall smelting process.

Briefly, my invention contemplates a rotating kiln substantially as described in the aforementioned copending application of Frank C. Senior, to which is added a furnace section located at the discharge end of the kiln. The furnace section is provided in the shape of a truncated cone rotating about the same axis as the rotating kiln. In essence, the furnace forms an integral part of the kiln, but has a diameter substantially larger than the kiln at the point of junction between the two sections. The slope of the Walls of the cone-shaped furnace section is just adequate to compensate for the slight tilt of the kiln structure, so that the bottom of the furnace section is at all times substantially parallel to the ground line. The truncated end of the furnace section (opposite the kiln side) is normal to the axis yof rotation ice and is supplied with an annular ring and lip-structure which has an inside diameter approximately the same as that of the kiln section. This provides a volumetric capacity in the bottom of the furnace section which is capable of containing molten materials as the unit rotates; this area forming the hearth of the furnace.

The hole left by the aforementioned annular ring and lip is blocked by a removable end-wall similar in function to the wall at the discharge end of the kiln in the copending application of Frank C. Senior, but adapted to carry electrode holders and also adapted to be moved away from the opening for the purpose of changing electrodes, etc.

A carbon electrode (or electrodes) of substantially shorter overall length than those normally found in conventional electric furnaces is mounted in water-cooled holders which extend through the endiwall and into the furnace section. The electrode holder may be adjusted in a vertical sense as in conventional electric furnaces to keep the tip of the electrode or electrodes at any desired operating level with respect to the bath. The end-wall is also preferably provided with an opening for the continuous kiln-charging device described and claimed in the above-identified application of Frank C. Senior, but a gasor oil-burner, as found in conventional rotating kilns, becomes unnecessary in the unique structure of my invention.

The entire unit is lined with suitable refractories, the type and composition -of refractories in each section being chosen for the temperatures and reaction conditions prevailing in that particular section. The unit is rotated by motor-driven trunnions in the same manner as conventional rotating kilns, With the exception that the trunnions under the furnace section are adapted to engage the coneshaped exterior surface of that section.

It is believed that a more detailed understanding of the process and apparatus of my invention will be gained by referring to the following drawings of one embodiment thereof which are meant to be illustrative only and are not intended to limit the invention as claimed hereinafter, and in which:

FIG. 1 is a simplified plant view of the kiln-furnace structure of the invention, partially in section;

FIG. 2 is a top view of the furnace section and endwall of the unit showing the track arrangement; and

FIG. 3 a perspective view, partially in section, showing the relation of the overall kiln-furnace unit to auxiliary equipment.

With reference to FIGURE 1, a tubular steel shell 1 as'found in conventional rotary kilns is integrally attached to a slightly cone-shaped furnace section 2. The entire unit is adapted to be rotated on motor-driven trunnions 37 and is lined with suitable refractories 3. The end-wall at the charge-end of the kiln 4 is equipped with ports for charging ore, ux, and reductant 5 and for drawing-olf effluent gases 6. The kiln portion is equipped with pipes 7 for introducing combustion gas into the kiln, thereby controlling the kiln atmosphere, and enabling both oxidizing and reducing zones to be maintained in separate portions of the kiln section. These pipes are connected to a motor-driven fan. A continuous charging device 8 for feeding reductant, fine ore, and recycled fines is located about mid-way in the kiln section and is fed by a trough 9. Another such charging device 10:is locatedat the end of the kiln section, fed by its own trough 11, and is adapted to feed materials directly to the furnace section.

The end-wall at the discharge end 12 has a slot 13 or slots which allow the electrode holder 18 to be moved vertically. The end-wall is also equipped with a port 14 for inserting a charge-gun 3f) for feeding solid reductant into the reducing portion of the kiln. The port is positioned slightly ofi-center so as to avoid hitting the electrode.

The end-wall is provided with two discharge holes, 16 and 25, which may be used for tapping intermittently through tap-hole 15, which is otherwise closed, or for continuous tapping over the lip structure defining a circular opening and into discharge hole 25. Both methods may be conveniently used by periodically tapping metal through tap-hole 15 and discharge hole 16, while the liquid slag is allowed to accumulate until it runs over the lipstructure and out through discharge hole 25. The entire end-wall structure 12 is mounted on a movable truck 17 constructed of I-beams or the like, this truck also carries the electrode holder 18, the electrode support 23, the electrode itself 20, and motors or other suitable driving means 19 f-or raising and lowering the electrodes, the mechanism for so doing being located in housing 36. When it is necessary to change electrodes the entire structure is rolled back, being mounted on suitable tracks (see FIG- URE '2), and access to the electrodes becomes a simple matter.

FIGURE 3 shows the entire unit in perspective, giving emphasis to the necessary auxiliary equipment. The entire unit is mounted on motor-driven trunnions 37 which are carried on suitable supports. An additional pair of tracks 27 run under the discharge end of the furnace, and conventional ladle cars Z8 carrying suitable ladles 29 are run underneath to tap metal and slag. A suitable launder arrangement can be used to tap metal and slagy into separate ladles. The continuous charging device 3) employing a compressed gas to propel solid reductant from bin 31 is shown inserted through port 14 in the end wall. The continuous charging troughs 9 and 11 are fed from

bins

33 and 32, respectively, supplying, in turn, charging devices 8 and 10 with reductant etc. on each revolution of the kiln. The initial charge of ore, fluxes and reductant enters the kiln section-through bin 34. Effluent gases escape through duct 35 to the dust collecting apparatus (not shown). Other equipment necessary for operation but not shown in the drawings includes flexible power and cooling water connections for the electrodes, a flexible compressed gas connection for the continuous charging *device 30, suiuble means'for electrically grounding the furnace shell where a single electrode is to be usedand Y the lining (carbon or the like) is to complete the circuit in the furnace section, and suitable control means such as thermocouples and the like for monitoring the unit when in operation.

In operation, the kiln section of my invention functions substantially as described and claimed in the aforementioned copending application of Frank C. Senior. Briefly, this involves continuously charging a mixture of ore, flux, andl someA reductant through charge port 5. Roughly, the first half of the kiln is devoted to calcining and dehydrating the charge, sintering and agglomerating fines, and oxiding sulfur and arsenic present in the ore and reductant. The pipes 7 supply combustion air to this section and maintain an oxidizing atmosphere over thebed. At approximately the midpoint of the kiln, reductant is added through continuous charging device 8, the atmosphere is changed from oxidizing to reducing, and pre-reduction of the ore proceeds. vAs the charge nears the end of the kiln section, additional reductant that will be needed to complete the reduction is added bythe charging device located in port 14 in the endwall, and this reductant is so placed on the bed 22 that by the time the charge reaches the end of the kiln section the reductant is coked and the charge `is in every sense a complete furnace burden.v

Under the influence of the agitation imparted by the rotary action of the unit, the bed 22 continuously discharges into the furnace section and distributes itself over the slag-metal bath 21. Rotation of the hearth further serves to continuously mix the incoming charge with the slag and metal, insuring a fast and selective reduction operation. This agitation also prevents cakes of prereduced iron mixed with gangue from building up, and the evolution of gases is free and even, with no chance of puffs or blowing occurring. As would be expected, the entire hearth-wall will become Very hot, as it is dipped under the molten bath on each revolution of the unit. A substantial portion of the heat absorbed by this wall, however, is reverberated into the kiln section, thus contributing, along with the hot gases from the reducing reactions, toward the exceptionally high thermal efficiency of the process.

As smelting in the furnace proceeds, additional materials may be added as required to the bath through the continuous charging device 10. This may conveniently be construed of suitably refractory materials so that hot, or even molten, additions may be made to the bath.

The end-wall 12 is equipped with water cooling, gas seals and other equipment commonly auxiliary to electric furnace operations.

The composition of the metallic product may be controlled as in any electric furnace operation, by making additions of desired elements, raising yor lowering smelting temperature, or otherwise changing the smelting conditions. Control is faster and more accurate than in conventional operations, due to the effect of rapid intermixing of all materials in the hearth area.

Size of the electrode (or electrodes) is naturally limited to that which will fit in the furnace section and can be conveniently inserted. Changing of the electrodes is a very simple and quick operation, however, which does not require that rotation of the unit be interrupted. As shown in FIGURE 2, the entire end-wall assembly is mounted on tracks 26. When it is necessary to change electrodes, the power is turned ofi", the electrode is raised to a position where it will clear the orifice in the furnace, and the whole assembly backs out on one of the two tracks 26a or 26h. A duplicate end-wall unit carrying a new electrode (not shown) is then brought into operating position from the other track, and smelting is resumed in a matter of minutes. By using duplicate end-wall units the process becomes truly continuous, and the spare may be repaired and a new electrode inserted at the convenience of the operator.

The practice of my invention is not limited kto any particular furnace practice of raw materials, and may be advantageously used in any of the Strategic-Udy smelting processes, or other reduction operations.

What I claim is:

l. A rotary kiln-furnace comprising a kiln section and a furnace section, said kiln section comprising a refractory-lined tubular metal shell, means for rotating said shell about its central axis at a slightly declined angle from the horizontal, a refractory lined end-closure member at the upper, charge end of said shell, and combustion control means for establishing and maintaining independent oxidizing and reducing atmospheres throughout separate portions of the interior of said shell, said furnace section being integrally attached to and rotating about the same central axis as the lower, discharge end of said kiln section and comprising a refractory lined truncated-cone shaped metal vessel having a larger end and a smaller end, an annular ring and lip structure mounted inside said smaller end, a cone-shaped ring connecting said larger end with the lower, discharge end of said kiln section, said rings adapted to form a containment area within the periphery of said furnace section, a removable refractory-lined end-closure member adapted to slidably engage said smaller end, arc-electrode means for electrically heating slag and metal Vin said containment area, and means for discharging metal and slag throughsaid end-closure member.

2. Rotary kiln-furnace as described in claim 1, wherein said removable end-closure member is equipped with separate discharge means for said metal and said slag.

3. Rotary kiln-furnace as described in claim 1, wherein a continuous charging device is located in said kiln section near the lower, discharge end, said charging device being adapted to introduce necessary additions directly t'o said furnace section.

4. Rotary kiln furnace as described in claim 1, wherein said electrode means are adjustably mounted on said removable end-closure member, whereby said electrode means can be inserted into said furnace section and placed in contact with slag and metal in said containment area.

References Cited in the le of this patent UNITED STATES PATENTS Tommasini Jan. 14, 1913 Basset Mar. 22, 1921 Driscoll June 27, 1922 Greene Aug. 1, 1933 FOREIGN PATENTS Great Britain of 1911 Great Britain Apr. 5, 1950 Austria Apr. 10, 1926

Claims

1. A ROTARY KILN-FURNACE COMPRISING A KILN SECTION AND A FURNACE SECTION, SAID KILN SECTION COMPRISING A REFRACTORY-LINED TUBULAR METAL SHELL, MEANS FOR ROTATING SAID SHELL ABOUT ITS CENTRAL AXIS AT A SLIGHTLY DECLINED ANGLE FROM THE HORIZONTAL, A REFRACTORY LINED END-CLOSURE MEMBER AT THE UPPER, CHARGE END OF SAID SHELL, AND COMBUSTION CONTROL MEANS FOR ESTABLISHING AND MAINTAINING INDEPENDENT OXIDIZING AND REDUCING ATMOSPHERSES THROUGHOUT SEPARATE PORTIONS OF THE INTERIOR OF SAID SHELL, SAID FURNACE SECTION BEING INTEGRALLY ATTACHED TO AND ROTATING ABOUT THE SAME CENTRAL AXIS AS THE LOWER, DISCHARGE END OF SAID KILN SECTION AND COMPRISING A REFRACTORY LINED TRUNCATED-CONE SHAPED METAL VESSEL HAVING A LARGE END AND A SMALLER END, AN ANNULAR RING AND LIP STRUCTURE MOUNTED INSIDE SAID SMALLER END, A CONE-SHAPED RING CONNECTING SAID LARGER END WITH THE LOWER, DISCHARGE END OF SAID KILN SECTION, SAID RINGS ADAPTED TO FORM A CONTAINMENT AREA WITHIN THE PERIPHERY OF SAID FURNACE SECTION, A REMOVABLE