JP3878390B2 - In-furnace deposit removal method for rotary kiln reduction furnace - Google Patents

Description

[0001]
[Technical field to which the invention belongs]
The present invention relates to a method for removing deposits in a rotary kiln type reduction furnace.
[0002]
[Prior art]
The metal oxide-containing raw material is put into a rotary kiln type reduction furnace together with a reducing agent, a component adjusting agent, and the like, and is stirred and reduced while being heated by a flame emitted from a burner into the rotary kiln.
[0003]
However, depending on the temperature in the furnace, the softened semi-melt of the object to be processed begins to adhere to the inner wall of the rotary kiln, and the thickness of the object increases with time, forming a weir. Cannot move downstream. Thus, when the deposit becomes thicker than the prescribed thickness, or when the deposit grows and obstructs the flow of raw materials, or the processing capacity of the rotary kiln has declined, the rotary kiln reduction furnace has been conventionally stopped. After the furnace temperature was lowered, the deposits in the furnace were mechanically removed by means of human power or heavy machinery, and the operation was started again.
[0004]
Japanese Utility Model Laid-Open No. 6-2099 and Japanese Patent Laid-Open No. 2000-18830 disclose a method of mechanically removing deposits inside the rotary kiln during operation using a hammer or a screw member. It is impossible to apply such a mechanical deposit removing device to a high temperature rotary kiln with an internal temperature exceeding 1200 ° C. from the viewpoint of thermal durability.
[0005]
In the present specification, the term “metal oxide” includes not only iron oxide but also oxides of non-ferrous metals such as Cu, Ti, Cr, and Ni.
[0006]
[Problems to be solved by the invention]
In the above-mentioned prior art, the downtime due to the temperature reduction / reheating of the rotary kiln type reduction furnace is long, the operation rate of the rotary kiln is lowered, and the deposit removal work is a dangerous work that may cause deposit fall etc. In addition, there are problems such as damage to refractories due to temperature rise and fall.
[0007]
In view of this problem, the present invention has been intensively researched and developed, and the object of the present invention is to remove the deposits in the furnace within a relatively short time without raising or lowering the temperature of the rotary kiln type reduction furnace. Is to provide a new way to do.
[0008]
[Means for Solving the Problems]
The above object is achieved by the method for removing deposits in a rotary kiln type reduction furnace according to claim 1, that is, in a rotary kiln type reduction furnace in which a metal oxide-containing raw material is reduced using a carbonaceous solid reducing agent. When it adheres to the inner wall of the rotary kiln and the deposit exceeds the specified thickness, it stops operation of the metal oxide-containing raw material and operates with the reducing atmosphere in the furnace maintained by introducing only the reducing agent. Specifically, by adjusting the amount of air so that the oxygen concentration in the rotary kiln exhaust gas is 0 to 1% and the carbon monoxide concentration is 1 to 5%, the deposits in the furnace of the rotary kiln are melted and removed. Can do.
[0009]
[Action]
If the metal oxide-containing raw material is stopped and the operation is performed with only the reducing agent and the air supply amount reduced, the metal oxide constituting the adhering substance will reduce the charged reducing agent and the charged air. Due to the coherent effect with the reducing atmosphere due to the reduced effect, it is reduced and melted, whereby the entire deposit is gradually melted and removed.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the accompanying drawings.
[0011]
FIG. 1 is a schematic view showing a front cross section of a rotary kiln according to an embodiment of the present invention.
[0012]
The rotary kiln 1 has a cylindrical shape, the outer surface is covered with a skin steel plate 101, and a refractory brick 102 is lined on the inner side. The upstream opening end 110 (left end in FIG. 1) is slightly higher than the downstream opening end 120 that discharges the object to be processed and the exhaust gas, and the central axis 105 is arranged to be substantially horizontal.
[0013]
Although the upstream opening end 110 is closed by the front wall 103, a heavy oil burner 130 passes through the front wall 103 and radiates a flame 135 of the heavy oil burner 130 into the rotary kiln 1. In addition to the metal oxide-containing raw material charging hopper 106, a reducing agent charging hopper 107 is attached to the front wall 103. Further, an air blowing port 108 is attached to the front wall 103, and the amount of air introduced into the rotary kiln can be adjusted by the adjustment valve 109.
[0014]
The rotary kiln 1 is rotated around the central axis 105, and the metal oxide-containing raw material 2 is heated while being gradually moved from upstream to downstream while being stirred, the metal oxide is reduced, and the downstream opening end It moves toward 120 and finally falls from the lower part of the downstream opening end 120.
[0015]
However, when the thickness of the deposit adhered to the inner wall of the rotary kiln 1 exceeds a predetermined value, the downstream movement of the workpiece is hindered.
[0016]
【Example】
In this example, iron oxide-containing dust was used as the metal oxide, a rotary kiln having a diameter of 4.2 m and a length of 14 m was used, and when the thickness of the deposit reached 600 mm, the above normal operation was stopped and attached. Switch to kimono removal operation. The iron oxide-containing raw material charging hopper 106 was closed, and the iron oxide-containing raw material charging was stopped. On the other hand, the reducing agent charging hopper was opened, and coal having a particle size under 10 mm was continuously charged at about 1 ton / h. The furnace temperature was set to 1300 ° C or higher, and about 50 ° C higher than that during normal operation. Further, the amount of air blown into the rotary kiln 1 is reduced to keep the rotary kiln from becoming an oxidizing atmosphere. If the deposit removal operation is continued, the iron-containing oxide constituting the deposit is reduced and melted, so the entire deposit is gradually removed, and the thickness of the deposit is about 100 mm in about 24 hours. Reduced to If the deposit has such a thickness, it does not become an obstacle to normal operation.
[0017]
【The invention's effect】
According to the in-furnace deposit removal method according to the present invention, deposits can be removed in a relatively short time, the operation can be resumed, the downtime of the rotary kiln reduction furnace can be shortened, and the operation rate of the furnace can be improved. . Further, the refractory due to the temperature rise and fall of the furnace is prevented from being damaged, and the effect of removing the deposit by a person or heavy equipment is obtained.
[Brief description of the drawings]
FIG. 1 is a schematic view showing a front cross section of a rotary kiln according to an embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Rotary kiln 101 Hull steel plate 102 Refractory brick 103 Front wall 105 Center shaft 106 Metal oxide containing raw material introduction popper 107 Reducing agent introduction hopper 110 Upstream opening end 120 Downstream opening end 130 Heavy oil burner 3 Reduced product

Claims (2)

In a rotary kiln type reduction furnace that reduces a metal oxide-containing raw material using a carbonaceous solid reducing agent, when a semi-molten material adheres to the inner wall of the rotary kiln and the deposit exceeds a predetermined thickness, the metal oxide how to stop the introduction of containing raw material is melted removed furnace deposits rotary kiln reducing furnace to operate in a state of to reduce the air supply to maintain a reducing atmosphere in the furnace while introducing only the reducing agent. In a rotary kiln type reduction furnace that reduces a metal oxide-containing raw material using a carbonaceous solid reducing agent, when a semi-molten material adheres to the inner wall of the rotary kiln and the deposit exceeds a predetermined thickness, the metal oxide Furnace so that oxygen content in the rotary kiln type reduction furnace exhaust gas is reduced to 0 to 1% and carbon monoxide concentration to 1 to 5% by stopping the introduction of the contained raw materials and reducing only the reducing agent and reducing the air supply amount. A method of melting and removing deposits in a rotary kiln type reduction furnace that operates in a state in which the reducing atmosphere is maintained.

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