JP2002538401A - Furnace discharge system and method of operation for rotary hearth furnace - Google Patents

Abstract

(57) Abstract: A furnace discharge system and method for removing material from a hearth 18 of a rotary hearth furnace 10 is provided. The system includes at least two discharge augers 28, 30 located above the hearth 18 of the rotary hearth furnace 10. Each discharge auger 28, 30 is operatively mounted to allow the height of the discharge augers 28, 30 in an alternating sequence from a material removal position to an elevated material bypass position.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[Industrial applications]

The present invention relates to a furnace discharge system and a rotary hearth furnace.
(n.) operation method. In particular, the present invention relates to a furnace discharge for a rotary hearth furnace with at least two helical augers for cooperatively transferring material from continuous processing in the rotary hearth furnace to discontinuous processing outside the rotary hearth furnace. System (furnace dis
charge system).

[0002]

[Prior art]

Briefly stated, a rotary hearth furnace (RHF) is a continuous reheating furnace that generally has an annular inner wall surrounded by spaced annular outer walls. The space between the inner and outer walls has a circular rotary hearth. Burners are attached to the inner and outer walls and the ceiling. Exhaust gases from the combustion and treatment escape through a flue located on the ceiling or side wall.

[0003] The rotary hearth is typically used for heating each metal section for downstream mechanical forming or forging or rolling. Another use is found where the solid material is heated in an internal gaseous furnace atmosphere suitable for preventing metal oxidation and / or reducing metal oxides present in the solid material. Rotary hearth furnaces include internal and external water seals that make the furnace ideal for containment of internal gases required for high temperature oxidation prevention and / or reduction.

In general, materials such as pellets, briquettes, bulk mixtures and agglomerates are evenly distributed (dropped) on a rotating hearth by a conveyor or chute for processing in a furnace. After the material is transported along the hearth path and processed in the furnace, the material is in the form of pellets, briquettes, a mixture of looses, agglomerates or melts and is discharged from the furnace using a single material discharge auger. The discharge auger typically comprises a central axis and a solid metal helical flight welded or bolted to the central axis so as to project outwardly from the axis. The discharge auger extends across the width of the circular hearth and is rotatably connected to an external motor. The discharge auger continuously transports the material from the hearth down the refractory chute and into the transfer canister.

[0005] In applications where material from the RHF is used for discontinuous batch processing downstream, a single auger facility may be used to control the delivery of material into the transfer canister first by a discharge chute.
A sophisticated structure with a discharge chute valve arrangement and / or multiple canisters and arc gates (release valves) is required. Obviously, the canister receiving the material from the furnace must be located on a swivel base and indexed into and out of the loading position below the canister and the arc gate. During this indexing, the continuous release material is delivered to the canister and the full canister is indexed to make room for a new transfer canister.

[0006] Alternatively, a single discharge auger can be placed to deliver hot product into a branch chute suitable for alternating discharge into multiple transfer canisters. This construction is a two-way valve or arc valve that directs the material flow to the outgoing transfer canister.
Requires a gate. Each leg of the branch chute must have a gate valve located at the lower end. Obviously, considerable height is required to accept the branch chute structure.

[0007] In addition to complex equipment, a single material ejection auger structure may cause operational problems and problems due to the inability to properly open and close potential bridges and / or ejection valves (arc gates) of material in the hopper. This causes undesirable downtime. Obviously, the closing of the gate is hindered by materials that interfere with the sufficient rotation of the gate. In addition, due to the incomplete closing of the gate valve, extremely hot material is continuously discharged from the furnace, allowing air (oxygen) to flow into the furnace, thereby allowing highly reducing atmospheres (CO and H ₂ ) to enter the RHF. Obviously, it creates a very dangerous condition for automatic combustion when present.

[0008] The present invention is directed to an improved RHF release system that addresses the problems associated with single material auger release. The present invention also facilitates the transition from continuous processing of RHF to discontinuous processing downstream of RHF. The dual material auger arrangement of the present invention allows the material transfer canister movement to proceed without the need for an intermediate holding hopper and a material supporting arc gate. The simplicity of the discharge assembly of the present invention also simplifies the layout of the RHF treatment facility.

In summary, the present invention relates to a furnace discharge system for removing material from the hearth of a rotary hearth furnace. The system includes at least two material discharge augers located above the hearth of a rotary hearth furnace. Each discharge auger is operatively mounted so that the height of the discharge auger can be raised in an alternating sequence from a material removal position to a material bypass position.

[0010] Material is discharged from the rotary hearth furnace by lowering at least one discharge auger to a material removal position and raising at least one discharge auger to an elevated material bypass position. The material transfer canister is operatively attached to the discharge chute, closing the discharge chute valve of the raised discharge auger and opening the lowered discharge auger valve. The material from the rotary hearth furnace is then conveyed into a material transfer canister.

Further features, objects, and advantages of the present invention are described in detail below with reference to the accompanying drawings.

[0012]

【Example】

In the following description, similar or corresponding parts are denoted by similar reference numerals. FIG. 1 is a simplified horizontal sectional view of a rotary hearth furnace (RHF) 10 according to the present invention. In the illustrated RHF 10, the structure is merely diagrammatic and some details of the structure have been omitted for simplicity. Such details will be apparent to one skilled in the art in describing the present invention.

As shown in FIG. 1, the RHF 10 includes an annular refractory insulating outer wall 12, a spaced annular refractory insulating inner wall 14, and a ceiling 16 connecting the tops of the outer wall 12 and the inner wall 14 to each other. . The circular hearth 18 rotates in the space between the outer wall 12 and the inner wall 14 in the RHF 10. A plurality of burners (not shown) are located around the perimeter of the RHF 10 to create combustion in a closed space between the outer wall 12, the inner wall 14, the ceiling 16 and the hearth 18. Material 20 from the feed conveyor 13 is fed to a feeder mounted below the feeder hood 15 or down the ceiling section 17 via the outer wall (not shown) of the RHF 10 as is well known in the art. Hearth 1 by 19
8 on. The removable auger and hood 37 are provided to facilitate removal of the auger during the maintenance period.

The depth of the material 20 on the hearth 18 is controlled to allow for maximum heating and maximum exposure to the furnace environment. The hearth 18 may be, for example, as disclosed in U.S. Pat.
It is suitably sealed to the hearth enclosure by a water seal (not shown) as described in US Pat. No. 452,972. The hearth 18 can be driven by any conventional drive means, for example, as shown in U.S. Pat. No. 3,452,972 or U.S. Pat. No. 4,597,564 referred to in this description. It is supported by the attached member 24.

After finishing the processing of material 20, typically after approximately one revolution of hearth 18,
Is removed by the furnace discharge system 26 according to the present invention for subsequent processing or downstream use of the RHF 10.

In a preferred embodiment, the furnace discharge system 26 includes at least two discharge augers 2 sequentially positioned around the periphery of the RHF 10.
8 and 30 are provided. Each discharge auger 28, 30 is operatively mounted on a trunnion (not shown) so that the height of the retracted position 1 can be adjusted from the discharge auger material removal position above the surface of the hearth 18. In the preferred embodiment, at least two discharge augers 18, 30 are operatively mounted transverse to the direction of movement of the rotary hearth 18. In another embodiment, at least two discharge augers 28, 30 are actuated at an angle from the radial direction to act as a composite auger and plow so that material removal from rotary hearth 18 is easier. Attach it.

Each discharge auger 28, 30 comprises a central cylindrical shaft 32 to which at least one helical flight 34 is mounted. The helical flight 34 surrounds the central axis 32 and projects radially outward from the central axis 32. Each flight 34 extends radially outward from shaft 32 by about 1 to 12 inches, preferably by 6 inches, and has a thickness of about 3/4 to 11/2 inches. The shaft 32 may be insulated between each flight 34 to reduce heat loss and may be fluid cooled as is well known in the art. A more detailed description of the discharge auger may be found in U.S. patent application Ser.
No. 9 is described.

FIGS. 2 and 3 show the first discharge auger 28 in its lowered material removal position. The material 20 is removed from the hearth 18 by a rotating helical auger and transferred to a closed inert material discharge chute 36. The material 20 is transported downwardly through a discharge chute 36 into a movable material canister.
canister) 38. The flow of material 20 and entry through chute 36 is controlled by a valve 40, such as a seal valve of the type well known in the art. Obviously, the valve 40 acts primarily to seal the furnace atmosphere from the outer atmosphere. Valve 40 is operatively controlled to open only when material canister 38 is operatively attached to discharge chute 36.

As used herein, the term “inert” refers to non-reactive atmosphere within a sealed enclosure. As shown, the transport canister (transport canis)
ter) 38 is a closed and insulated inert atmosphere container having a removable top adapted to receive the lower end of discharge chute 36. Transfer canister 38
Is mounted on wheels 42 for easy transfer via a transfer carriage along a transfer path 44 located within a charging pit 48 between the RHF 10 and downstream processing operations, such as iron and steel making operations. R supported on the abutment 46 by the structure of the furnace discharge assembly
A relatively low headroom requirement between the HF 10 and the material receiving canister 38 may be met.

When charging of the material transfer canister 38 is completed, the discharge auger 28 is raised from the hearth 18 and the release valve 40 is closed. As the material transfer canister 38 nears full, the material discharge auger 30 is raised from its material removal position and as soon as the material discharge auger 30 is lowered onto the hearth 18 to its material removal position to remove material from the hearth. Begin to. Prior to lowering the auger 30 to the material removal position, the material transfer canister 38 can be positioned at the loading position and the valve 40 opened to discharge material from the hearth 18 through the chute 36 to the transfer canister 38. When the transfer canister 38 is full, it is removed from the area of the RHF 10 via a transfer trolley and sent along the desired transfer path 44 to downstream processing operations. Full transfer canister 3
8 is then unloaded from the transport trolley in a downstream processing operation.
On the transfer truck and return it to the RHF 10 below the appropriate chute 36 of the discharge auger 28 or discharge auger 30.

The above procedure for the transfer canister loading and unloading cycle is as follows:
When processing the material 20 with RHF, it alternates between the first discharge auger 28 and the second discharge auger 30. Obviously, the continuity of the transition from continuous processing to discontinuous processing in the furnace can be easily obtained by the present invention. In such a discontinuous process, the materials are collected batchwise in periodically moving canisters for batch consumption in another downstream process. A material discharge assembly construction that increases the life expectancy of the material discharge assembly discharge auger and reduces furnace downtime and maintenance requirements for periodic auger removal.
What you need for a single auger delivery system. Further, the discharge system of the present invention reduces maintenance requirements and simplifies the RHF structure by using a direct material discharge chute without the need for an intermediate material storage hopper and a support release valve.

Although the above detailed description has been provided with two emission augers 28, 30, it is clear that the invention may comprise more than one emission auger according to the dimensions and / or perimeter of the RHF. It is.

Each of the above documents is referenced in this description.

Although the preferred embodiment of the present invention has been described above, the present invention is capable of various changes and modifications without departing from the spirit thereof.

[Brief description of the drawings]

FIG. 1 is a plan view of a furnace discharge system configured according to the present invention.

FIG. 2 is an enlarged cross-sectional view taken along line AA of FIG. 1 showing a furnace discharge system including a material canister.

FIG. 3 is a side view of FIG. 2;

[Explanation of symbols]

 Reference Signs List 10 rotary hearth furnace 18 hearth 20 material 26 furnace discharge system 28, 30 material discharge auger

Claims (15)

[Claims] 1. A furnace discharge system for removing material from a hearth of a rotary hearth furnace, comprising: at least two material release augers positioned above the hearth of the rotary hearth furnace; A furnace discharge system, wherein the height of the discharge auger is adjusted in an alternating sequence from a material removal position to an elevated material bypass position. 2. The furnace discharge system of claim 1, further comprising at least two discharge chutes adapted to receive material removed from the hearth by the discharge auger and arranged to alternately charge transfer canisters. . 3. The furnace discharge system of claim 1 wherein each of said discharge augers is sequentially positioned around a periphery of said rotary hearth furnace. 4. A furnace discharge system according to claim 2, wherein said material flows downward through said discharge chute and is charged into a movable material transfer canister. 5. The furnace discharge system according to claim 4, wherein a flow and a material entering the rotary hearth furnace by the discharge chute are controlled by a valve. 6. The furnace discharge system according to claim 5, wherein a sealing valve is used as said valve. 7. The furnace discharge system of claim 7, wherein the valve is operatively controlled to open only when a material transfer canister is operatively attached to the discharge chute. 8. The furnace discharge system of claim 7 wherein said transfer canister is a closed insulated container having a removable top adapted to receive said discharge chute. 9. The furnace discharge system of claim 7 wherein said transfer canister is a closed insulated container having a removable bottom suitable for emptying said canister. 10. The furnace discharge system of claim 8 wherein said transfer canister is mounted on wheels. 11. At least two helical mounts positioned sequentially around the perimeter of the rotary hearth furnace and mounted for alternating discharge auger height adjustment from a material removal position to an elevated material bypass position. A method of discharging material from a rotary hearth furnace having an auger and a valve for sealing the rotary hearth furnace and having at least two discharge chutes suitable for receiving material from each of the discharge augers, Lowering at least one discharge auger to a material removal position and raising at least one discharge auger to an elevated material bypass position; operatively attaching a material transfer canister to the discharge chute; Closing the valve of the discharge chute of the raised discharge auger and opening the valve of the lowered discharge auger Filling the material transfer canister with material from the rotary hearth furnace;
Consisting of: 12. As the material transfer canister approaches a full state, the raised discharge auger is lowered onto the hearth as soon as the discharge auger rises from its material discharge position into the material discharge position. 12. The method of claim 11, wherein the method is adapted to begin removing material from the material. 13. The method of claim 12, wherein said filled transfer canister is removed from said RHF section via a transfer trolley for downstream processing operations. 14. The method of claim 13, wherein said filled transfer canister is removed from said transfer trolley in said downstream processing operation and is located on a transfer trolley from an empty transfer canister. 15. The method of claim 14 wherein said transfer canister is operatively attached to said discharge sheet.