JP4020486B2 - Externally heated rotary kiln - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an external heating rotary kiln in which dry distillation gas generated in a retort penetrating a heating chamber substantially horizontally is discharged into the heating chamber and burned.
[0002]
[Prior art]
When carbonizing the material to be heat-treated, the externally heated rotary kiln that directs the dry distillation gas generated during heating to the heating chamber and burns it is not necessary for a special dry distillation gas processing chamber, making the device compact, Since a part of the fuel in the heating chamber can be supplemented with dry distillation gas, there is an advantage of high thermal efficiency, and in recent years, it has been generally used.
[0003]
[Problems to be solved by the invention]
However, in order to burn dry distillation gas in the heating chamber, a temperature of at least 650 ° C. is necessary. In the case of an object to be carbonized below this temperature, for example, 450 ° C. or more when carbonizing sewage sludge. Since the carbon decomposes and the yield decreases when heated to a low temperature, the temperature in the heating chamber must be maintained at 500 ° C. However, if this is done, the dry distillation gas flowing in from the retort may burn in the heating chamber. In this case, there is a problem that the heat efficiency must be lowered in a treatment chamber provided integrally with or separately from the heating chamber, and there is a problem that the heat efficiency is reduced. It is obliged to stay at the above temperature for 2 seconds or more, but if the temperature of the heating chamber is low, the secondary combustion chamber must be made large with many burners,備費 there is a problem that is higher.
[0004]
[Means, actions and effects for solving the problems]
As a means for solving such a problem, the invention of claim 1 covers the outer periphery of at least the portion corresponding to the heating chamber of the retort with a heat insulating material, so that the temperature of the heating chamber is sufficient for the combustion of dry distillation gas. Even if it is 650 ° C. or higher, the temperature in the retort can be maintained at 450 ° C., for example, and there is an effect that the yield of carbon can be increased while maintaining high thermal efficiency, and the temperature of the heating chamber is 800 ° C. or higher. Even if the generation of dioxins is suppressed, the temperature in the retort can be kept low.
[0006]
The invention of claim 1, since covering the outer periphery of the retort with a heat insulating material such as ceramic fiber, it is possible to achieve the effect of the heat transfer control by a relatively simple task, can be manufactured at a low cost effective.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
In FIG. 1, reference numeral 1 denotes a furnace body made of a refractory, and a retort 2 made of a metal cylinder penetrates the upper part thereof almost horizontally with a slight gap.
[0008]
As shown in FIG. 2, the retort 2 includes an inner cylinder 3 and an outer cylinder 4 integrally coupled thereto, and a space 5 is formed therebetween.
[0009]
The inner cylinder 3 extends to the outside of the furnace body, the ring 6 is fixed near both ends thereof, and the ring 6 is supported by a roller 7 supported by a stand (not shown), so that the retort 2 is rotationally driven in one direction. In addition, a screw conveyor 9 penetrating the blocking plate 8 is provided on the inlet side of the inner cylinder 3, a workpiece discharge port 10 is formed on the outlet side, and the inner cylinder A workpiece collection cylinder 11 is provided so as to surround the three outlets.
[0010]
A cooling air introducing cylinder 12 is provided at the entrance of the outer cylinder 4, and the outlet is opened in the furnace body 1.
[0011]
In the portion corresponding to the inside of the furnace body 1 of the retort 2, a number of discharge cylinders 13 whose inner ends are bent toward the outlet and whose outer ends protrude outside the retort 2 are provided through the inner cylinder 3 and the outer cylinder 4. It has been.
[0012]
A hearth 14 having a suction hole 15 is provided below the retort 2 of the furnace body 1. The upper side is a heating chamber 18 and the lower side is a secondary combustion chamber 19. The burner 16 is provided with one burner 17 in the secondary combustion chamber 19, and the secondary combustion chamber 19 communicates with a chimney (not shown).
[0013]
In this embodiment, the burner 16 in the heating chamber 18 is burned to heat the inside of the retort 2 and then the organic material to be processed is put into the retort 2 by the screw conveyor 9. Although it is heated while moving to the outlet side, the inside of the retort 2 is almost shut off from the outside air, so that dry distillation gas is generated and flows into the heating chamber 18 from the discharge cylinder 13 and burns by the flame of the burner 16. This contributes to the temperature rise in the heating chamber 18.
[0014]
For this reason, even if some of the burners 16 are turned off, the temperature in the heating chamber 18 can be kept constant.
[0015]
On the other hand, since the air fed from the cooling air introduction cylinder 12 flows in the space 5 formed between the inner cylinder 3 and the outer cylinder 4 of the retort 2, the temperature in the retort 2 is the temperature in the heating chamber 18. Air that is kept lower and heated by heat exchange is supplied from the end of the space 5 into the heating chamber 18 for combustion.
[0016]
The gas in the heating chamber 18 enters the secondary combustion chamber 19 through the suction hole 15 of the hearth 14, is heated by the combustion flame of the burner 17, decomposes odors and harmful substances, and is released from the chimney to the atmosphere. .
[0017]
The carbide generated by the dry distillation is discharged from the workpiece discharge port 10 to the workpiece collection cylinder 11 and collected.
[0018]
Example 1
Twelve channel steel members 21 having a groove depth of 20 mm are welded to the outer periphery of a cylinder 20 having a diameter of 400 mm and an effective length in the furnace of 3.5 m to form a groove-shaped space 22, and approximately 80 The retort 2 having a groove-like double structure occupying a percentage of water is used, and the other structure is the same rotary rotary kiln as the above embodiment, and the sewer sludge adjusted to a moisture of 25% in another drying furnace is 60 kg / h. The cooling air to be introduced into the space 22 is supplied at a rate, the residence time in the furnace is 40 minutes, the temperature in the heating chamber 18 is maintained at 850 ° C., and the maximum temperature in the retort 2 is 450 ° C. The amount was automatically controlled.
[0019]
The flow rate of the cooling air at this time was 2.5 m ³ / min on average.
[0020]
The temperature in the secondary combustion chamber 19 was also maintained at 850 ° C. by the flame of the burner 17, and the combustion gas was exposed to the temperature of 850 ° C. for 2 seconds or more together with the heating chamber 18.
[0021]
As a result, good carbides were obtained, and the amount of dioxin in the exhaust gas was below the reference value.
[0022]
Example 2
As shown in FIG. 4, a rotary kiln having the same structure as that of the above embodiment is used, using a retort 2 having a diameter of 400 mm in which a ceramic fiber layer 23 is formed around a cylinder 20 and an effective length in a furnace of 3.5 m. Separately, the sewage sludge whose water content was adjusted to 25% in a drying furnace was supplied at a rate of 60 kg / h, the residence time in the furnace was 40 minutes, the temperature in the heating chamber 18 was maintained at 850 ° C., and the retort 2 The maximum temperature was 450 ° C.
[0023]
The thickness of the ceramic fiber 23 was set to 12 mm in order to satisfy the above conditions from the result of the preliminary experiment.
[0024]
The dry distillation gas generated in the retort 2 flowed into the heating chamber 18 through the discharge tube 13 and was completely burned in an atmosphere at 850 ° C.
[0025]
The temperature in the secondary combustion chamber 19 was also maintained at 850 ° C. by the flame of the burner 17, and the combustion gas was exposed to the temperature of 850 ° C. for 2 seconds or more together with the heating chamber 18.
[0026]
As a result, good carbides were obtained, and the amount of dioxin in the exhaust gas was below the reference value.
[0027]
Although the control delay was slightly larger than that of Example 1, there was no practical problem.
[0028]
The secondary combustion chamber 19 may be provided separately from the furnace body 1, and the exhaust gas can be used for drying, preheating, or combustion directly or via a heat exchanger.
[0029]
Further, in the case of the second embodiment, the ceramic fiber layer 13 may be attached in a zebra shape with a certain interval in the length direction or the circumferential direction of the cylinder 20, or the thickness may be changed.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of an embodiment of the present invention.
FIG. 2 is a cross-sectional view of the retort.
FIG. 3 is a cross-sectional view of one embodiment of a retort.
FIG. 4 is a cross-sectional view of another embodiment of the retort.
[Explanation of symbols]
1: furnace body 2: retort 3: inner cylinder 4: outer cylinder 5, 22: space 12: cooling air introduction cylinder 13: discharge cylinder 18: heating chamber 21: channel steel material 23: ceramic fiber layer

Claims (3)

In an externally heated rotary kiln in which dry distillation gas generated in a retort penetrating the heating chamber almost horizontally is discharged into the heating chamber and burned.
An externally heated rotary kiln in which the outer periphery of at least a portion corresponding to the heating chamber of the retort is covered with a heat insulating material .   The externally heated rotary kiln according to claim 1, wherein the heat insulating material is a ceramic fiber.   The externally heated rotary kiln according to claim 1 or 2, wherein the heat insulating material is arranged at intervals in a length direction or a circumferential direction of the retort.

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