JP2004125349A - External heating rotary kiln - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an external heating rotary kiln capable of stably operating for a long time when carrying out a dry distillation process of an object to be heated containing a massive amount of high polymer organic matter. <P>SOLUTION: The external heating rotary kiln is composed of a shell rotating around an axis having a supply port of the object to be heated in one end side and a delivery opening for delivering the object in another end side, a heating furnace heating an outer side part of the shell, an exhaust tube fixed by piercing a circumferential wall of the shell and exhausting gas generated in the shell into the heating furnace, and an peeling body interlocking with rotation of the shell in the exhaust tube to peel deposits adhered to an inner face of the exhaust tube. The exhaust tube has in its both ends stoppers with bleeders holding the peeling body in the exhaust tube. The peeling body can coaxially rotate/move with the exhaust tube housing it, and it is formed by a hollow body having vent holes coaxial with the exhaust tube and ventilating dry distillation gas. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an externally heated rotary kiln.
[0002]
[Prior art]
The rotary kiln is an apparatus that performs various heat treatments such as drying, baking, and carbonization by heating an object to be heated supplied into a rotating cylindrical shell. Since the shell is provided slightly inclined from the horizontal, the object to be heated sequentially moves in the axial direction as the shell rotates. An externally heated rotary kiln that indirectly heats an object to be heated from the outside of the shell is frequently used, in addition to a method of directly heating the object to be heated by blowing a flame directly into the shell.
[0003]
Such externally heated rotary kilns have several advantages over direct heating. That is, since there is almost no temperature unevenness due to the flame or hot air directly hitting the object to be heated, the object to be heated can be subjected to a uniform heat treatment. Further, the atmosphere for the heat treatment of the object to be heated can be freely determined regardless of the type of the heating means and the combustion gas. Further, a combustible gas such as carbon monoxide and hydrogen generated by carbonizing a heated object can be discharged into a heating furnace and burned to make the discharged gas harmless.
[0004]
When the heating target containing a large amount of high molecular organic matter such as oils and fats and synthetic resins is carbonized, the generated carbonized gas contains, in addition to the combustible gas such as carbon monoxide and hydrogen, tar. And soot are often contained in large quantities. Then, a part of the tar-like substance or soot may adhere to the inner surface of the exhaust stack and gradually accumulate to reduce the effective area of the exhaust stack. When the deposition further proceeds, the exhaust stack is closed, so that the normal operation of the rotary kiln becomes impossible, and the operation has to be stopped in some cases.
[0005]
In order to solve such a problem, the inventors have proposed to accommodate a sliding body that slides between both ends of the exhaust pipe with rotation of the shell in the exhaust pipe (for example, see Patent Document 1). . That is, while the shell makes one revolution, the sliding body reciprocates in the exhaust cylinder to remove the tar-like substances and soot that have adhered thereto, so that the exhaust cylinder can be prevented from being blocked, and the normal operation of the rotary kiln can be prevented. It can be maintained for a long time. One example of this proposal is shown in FIG. An exhaust pipe 27 is provided in a heated portion of the shell 3 so as to penetrate the peripheral wall of the shell. Both ends of the exhaust pipe 27 are closed by stoppers 31, and four vents 32 are formed near the both ends, respectively. A refractory sliding body 33 is fitted into the exhaust pipe 27 with a slight gap therebetween, and makes one reciprocation in the exhaust pipe 27 while the shell 3 makes one rotation. Tar-like substances, soot and the like adhering to the surface are scraped and released into the heating chamber by the flow of the carbonization gas for incineration.
[0006]
[Patent Document 1]
JP 2002-98479 A
[Problems to be solved by the invention]
However, when heating and heating a high-molecular-weight organic substance, such as RDF or rice bran, which is solid trash, the shape of the exhaust pipe and the sliding body is not always sufficient. Momentarily during the movement in the exhaust pipe 27, the vent 32 is closed. In some cases, it was found that the movement of the exfoliated body was hindered by tar-like substances or soot, and as a result, the exhaust stack was closed. That is, an object of the present invention is to provide an externally heated rotary kiln capable of performing a long-time stable operation when subjecting a heated object containing a large amount of a high molecular organic substance to dry distillation.
[0008]
[Means for Solving the Problems]
The present inventors have studied these phenomena in detail and have conducted intensive studies on the shapes of the exhaust cylinder and the sliding body (hereinafter, referred to as a peeling body) to complete the present invention.
[0009]
That is, the externally heated rotary kiln of the present invention includes a shell rotating around an axis having a supply port for a heated object on one end side and a discharge port for discharging the heated object on the other end side, and an outer portion of the shell. A heating furnace for heating the shell, an exhaust pipe fixedly penetrating through a peripheral wall of the shell for discharging gas generated in the shell into the heating furnace, and an exhaust pipe that floats in the exhaust pipe as the shell rotates. In an externally heated rotary kiln comprising a peeling body for peeling off the deposits adhered to the inner surface of the cylinder, the exhaust cylinder has stoppers at both ends of the exhaust cylinder, each of which has a vent opening for holding the peeling body in the exhaust cylinder. The exfoliated body is characterized in that it is a hollow body that is rotatable and movable coaxially with an exhaust cylinder that houses the exfoliated body and that has a vent hole coaxial with the exhaust cylinder that vents the carbonization gas.
[0010]
Here, the exfoliated body is preferably a cylinder or a polygonal cylinder, and it is desirable to form a streak on the inner surface of the exhaust pipe to facilitate the floating of the exfoliated body.
[0011]
In addition, it is desirable to form a protrusion on the outer surface of the peeling member to peel off the adhered substance by contacting the inner surface of the exhaust pipe, and it is preferable that the peeling member is ceramics or a heat-resistant metal.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
One embodiment of the present invention will be described with reference to the drawings.
[0013]
FIG. 1 schematically shows a longitudinal section of an externally heated rotary kiln according to the present invention. This externally heated rotary kiln includes a shell 3 made of stainless steel or the like having a supply unit 1 for a heated object and a discharge unit 2 for a heated object to be heated, and a heating furnace for heating an outer surface of the shell. 4.
[0014]
The shell 3 is arranged so as to penetrate the heating furnace 4 in the length direction. Annular tires 6 and 7 are integrally provided on the outer peripheral surface of the shell 3 near both ends of the shell 3, and the shell 3 is supported by bearings 8 and 9 at these portions.
[0015]
The heating furnace 4 is formed of an outer shell 10 made of an iron plate and a fire-resistant heat insulating material 11 and is fixed on a base frame 5. The heating furnace 4 is provided with a heating burner 12 and a combustion gas exhaust port 13. The burner 12 is disposed below the shell 3 penetrating in consideration of thermal efficiency. The combustion gas generated inside the heating furnace 4 is sent from a combustion gas exhaust port 13 to a chimney (not shown).
[0016]
A small gap is provided between the outer peripheral surface of the shell 3 and the heating furnace 4 and substantially sealed by a sealing material (not shown) to prevent heat from being dissipated by the burner 12. The temperature in the heating furnace 4 is automatically controlled by an automatic control device (not shown) so that the temperature becomes the set temperature.
[0017]
The shell 3 is provided with a sprocket wheel 15 on the outer peripheral surface of the shell between the roller 9 of the discharge section 2 and the discharge port 26, and the sprocket wheel 15 and the sprocket 17 of the drive motor 16 supported by the base frame 5 are provided. Are connected by a chain 18 and driven to rotate. The axis of the shell 3 is installed so as to be inclined (the gradient is 1/100 to 3/100) so that the discharge side is slightly lowered. However, when the object to be heated is moved by providing a spiral feed blade or the like on the inner peripheral surface of the shell 3, the axis of the shell 3 may be horizontal.
[0018]
The supply section 1 of the shell includes a supply section hood 19 and a supply hopper 20 for the object to be heated M, and is fixed on the base frame 5. The supply unit hood 19 is for preventing outside air from directly entering the shell or for sucking a part of gas generated from the inside of the shell, and has a supply unit hood exhaust port 21 provided at an upper portion. . The supply hopper 20 for the object to be heated M is provided so as to penetrate the supply unit hood 19 so that the chute 23 supplies the object to be heated M to the inside of the shell. The tip of the chute 23 projects from the supply port 24 opened on the side surface of the shell into the inside of the shell, so that the supplied heated object M does not fall into the supply unit hood 19. The shell 3 and the supply unit hood 19 are provided with a slight clearance, and are substantially sealed with a sealing material (not shown).
[0019]
The discharge part 2 is composed of a discharge part hood 25 for preventing outside air from entering the shell. The shell 3 and the discharge part hood 25 are provided with a slight clearance and are substantially sealed with a sealing material (not shown). Have been. A chute (not shown) for taking out the object to be heated M discharged from the discharge port 26 of the shell is provided below the discharge unit hood 25. A rotary valve (not shown) is provided in the middle of the chute to prevent outside air from entering.
[0020]
An exhaust pipe 27 that penetrates the peripheral wall of the shell 3 and communicates the inside of the shell with the inside of the heating furnace is fixed to the shell outer portion 14 heated by the heating furnace of the shell 3. In each exhaust cylinder, a peeling body 28 that peels off tar-like substances, soot, and the like that adhere to the inner surface of the exhaust cylinder is movably held. Here, it is desirable that the exhaust pipe 27 is detachably attached to the peripheral wall of the shell 3 with bolts or the like. This is for enabling cleaning and repair work of the exhaust pipe 27 and the peeling body 28 as necessary.
[0021]
In the operation of the externally heated rotary kiln having the above-described configuration, first, a fixed amount of the heated object M is supplied from the supply hopper 20 into the shell 3 rotated by the drive motor 16. The object to be heated M gradually flows toward the heating section with the rotation of the shell 3 because the shell 3 is installed at a slightly lower inclination toward the discharge section 2, and the outer periphery of the shell 3 is heated by the heating furnace 4. The surface is heated to a predetermined temperature by being heated. At this time, a large amount of combustible gas such as carbon monoxide and hydrogen, water vapor, and a large amount of carbonized gas including tar-like substances and soot is generated from the material to be heated M, and the material to be heated M is carbonized and carbonized. Thereafter, the heating target M carbonized in this manner flows to the discharge port 26, is cooled by a small amount of infiltrating air flowing from the discharge part 2 and heat radiation escaping from the surface of the shell 3, and is cooled from the discharge port 26 of the shell. It is discharged and discharged out of the furnace from a chute under the discharge unit hood 25.
[0022]
Most of the carbonization gas generated inside the shell 3 is discharged into the heating furnace 4 from an exhaust pipe 27 fixedly provided through the peripheral wall of the shell.
[0023]
Then, the combustible gas such as carbon monoxide and hydrogen among the discharged carbonized gas, and the tar-like substances and soot separated and removed by the separating body 28 are discharged into a heating furnace and burned or incinerated, and heated. The gas is discharged from the exhaust port 13 of the furnace 4 to the chimney. As described above, tar-like substances, soot and the like adhere to the inner surface of the exhaust pipe 27 due to the ventilation of the dry distillation gas, but the exfoliated body 28 accommodated in the exhaust pipe floats in the exhaust pipe as the shell 3 rotates. By doing so, it is possible to prevent tar-like substances and soot from adhering and depositing.
[0024]
In addition to the conventional configuration of the externally heated rotary kiln as described above, a feature of the present invention is that, in the rotary kiln of FIG. The use of a hollow body having the same allows the exfoliated body itself to ventilate the carbonized gas. That is, since the exfoliated body according to the prior art was a spherical or short cylindrical solid body fitted with a small gap in the exhaust cylinder, a short period of time is required for the floating body to float in the exhaust cylinder with the rotation of the shell. However, the vent provided in the exhaust pipe was sometimes blocked. However, in the present invention, the vent holes are opened at the stoppers on both ends of the exhaust pipe, and the exfoliated body is a cylindrical or polygonal hollow body, so that the dry distillation gas can always be ventilated through the internal space of the exfoliated body. Therefore, the vent hole is not blocked by the peeling body. For example, FIG. 7 is a schematic cross-sectional view in which a cylindrical exfoliated body 27 having an outer diameter smaller than the inner diameter of the exhaust cylinder 27 is accommodated in a cylindrical exhaust cylinder 27. Here, a circle 29 indicates a vent opening to the stopper at both ends of the exhaust pipe. That is, with the rotation of the shell, tar-like substances and soot adhering to the inner wall surface of the exhaust pipe 27 due to the upper and lower edges and the outer peripheral surface of the peeling body 28 coming into random contact with the inner wall of the exhaust pipe 27. Exfoliation can be prevented from accumulating. Further, since the exfoliated body 28 reciprocates while colliding with the stoppers 31 at both ends of the exhaust cylinder 27 due to gravity, soot and the like adhering to the inner wall surface of the exhaust cylinder 27 due to the impact of this collision are exfoliated, and together with the dry distillation gas. It can be discharged to the heating furnace and incinerated.
[0025]
As shown in FIG. 7, when the exhaust cylinder 27 and the exfoliated body 28 have the same shape and a large amount of tar-like substance is generated, the contact area between the inner surface of the exhaust cylinder 27 and the side surface of the exfoliated body 28 is large. For this reason, smooth running of the exfoliated body 28 may become difficult as the operation time of the rotary kiln elapses. Therefore, it is also preferable that the shape of the exfoliated body be a rectangular tube as shown in FIG. In this case, the rectangular cylindrical exfoliated body 28 and the inner surface of the exhaust cylinder 27 are in contact only with the four ridge lines 28a of the exfoliated body 28. Therefore, the contact area between the exhaust cylinder and the peeling body is extremely small, and smooth running of the peeling body 28 does not become difficult as the operation time of the rotary kiln elapses.
[0026]
Further, it is preferable that a strip such as a round bar be attached to the inner wall surface of the exhaust pipe to reduce the contact area with the peeling body. Examples of these are shown in FIGS. FIG. 2 is a schematic longitudinal sectional view of a round exhaust cylinder 27 holding a strip 30 on the inner surface and holding a cylindrical exfoliated body 28. The exhaust pipe 27 is fixedly provided through the peripheral wall of the shell 3, and stoppers 31 are provided at both ends so that the peeling body 28 can be held inside. Each stopper 31 is provided with a vent 32 for venting the carbonized gas. FIG. 3 is an AA cross section of FIG. That is, the exhaust pipe 27 is provided with three rods 30 each formed of a rod or a line having a circular cross section on the inner wall surface at an interval of about 120 °. In the exhaust pipe 27, a stripped body 28 formed of a short cylinder having an outer diameter that maintains a small gap with each strip 30 is held coaxially with the exhaust pipe 27 so as to be rotatable and movable.
[0027]
As described above, since the exfoliated body 28 is a hollow body that can be ventilated coaxially with the vent 32 of the exhaust pipe 27, the vent 32 is closed even if the exfoliated body contacts the stopper in the heating furnace of the exhaust pipe. I can't. Therefore, the deposition of tar-like substances and soot on the inner surface of the exhaust cylinder due to the stagnant flow of the carbonized gas in the exhaust cylinder is not promoted. In addition, the short cylindrical exfoliated body 28 is always floating, and the collision always occurs once per rotation of the stopper 3 and the shell 3 at both ends of the exhaust pipe 27, so that tar or soot adheres to the inner surface thereof. Is less. FIG. 4 is a schematic cross-sectional view showing a case where both the exhaust pipe 27 and the peeling body 28 have a rectangular cross section and the strip 30 is attached to the inner surface of the exhaust pipe. In this case, the strip 30 may be provided one at the center of each surface. There is no particular limitation on the size and shape of the strip, but in order to reduce the contact area and smooth the movement of the exfoliated body, a circular cross section is desirable, and it is provided linearly in the axial direction of the exhaust pipe. Good.
[0028]
In addition, the strip may be provided as a protrusion on the side surface of the peeled body. 5 and 6 show examples in which the protrusions are provided on the side surfaces of the peeling body. FIG. 5 is a schematic vertical cross-sectional view in which a peeling body 28 is held in a round exhaust cylinder 27, and shows a state in which a protrusion 30 is attached to an outer surface (side surface) 28b of the peeling body 28. FIG. 6 is a schematic diagram showing a BB cross section of FIG. In this case, the protrusions are not limited to the linear shape, and a plurality of the protrusions may be provided in a dotted shape substantially on the same line in the coaxial direction with the exhaust pipe. By providing such protrusions on the outer surface of the exfoliation body, the exfoliation ability for exfoliating the adhering matter adhering to the inner surface of the exhaust tube is improved, and the smoothness of the exfoliation body can be maintained.
[0029]
Since the exfoliated body will be exposed to a high-temperature dry distillation gas, it is desirable to use a material having high heat resistance such as heat resistant metal or ceramic. Examples of the heat-resistant metal include stainless steel SUS310S and Inconel, and examples of the ceramic include high-strength ceramics such as silicon carbide and silicon nitride.
[0030]
The present invention is not limited by the above embodiments, and it goes without saying that the shape of the exhaust cylinder and the shape of the exfoliated body can be selected without departing from the gist of the present invention.
(Experimental example 1)
The object to be heated (RDF) obtained by solidifying and drying the refuse was supplied to the externally heated rotary kiln of FIG. 1 at a supply rate of 17.2 kg / hour. The dimensions of the main part of the externally heated rotary kiln were as follows. That is, shell inner diameter: 300 mm, shell length: 3 m (effective length in shell: 2.4 m), shell inclination angle: 1%, shell rotation speed: 1.7 rpm, heating temperature: 900 ° C., object to be heated , Which was distilled under a condition of 75 minutes.
[0031]
The exhaust cylinder was an S310S cylinder having an outer diameter of 114.3 mm (inner diameter: 102.3 mm) × length: 190 mm, and the number of attachments to the shell was five. Then, three strips (material: SUS310S, round bar having a diameter of 10 mm) were attached in parallel with the length direction of the exhaust cylinder so as to substantially divide the inner circumference of each exhaust cylinder into three.
[0032]
The exfoliated body was a SUS310S pipe having an outer diameter of 76.3 mm, an inner diameter of 65.9 mm, and a length of 85 mm in order to provide a strip attached to the inner surface of the exhaust cylinder and a slight clearance. This pipe (peeled body) was accommodated in the exhaust cylinder.
[0033]
Under the above conditions, the externally heated rotary kiln was operated for 24 hours, and as a result, a phenomenon in which the pressure inside the shell was increased due to clogging of the exhaust pipe was not recognized. Further, the exhaust stack was inspected after the stoppage, but only a slight amount of carbon had adhered to the inner surface of the exhaust stack, and no deposits that could block the exhaust stack were found.
[0034]
This is because the exfoliated body moves with the rotation of the shell, preventing the adhesion of tar-like substances and soot to the inside of the exhaust pipe, and the soot adhering by knocking where the exfoliated body gently collides with the stopper. This is probably due to exfoliation.
[0035]
On the other hand, in the case where the same object to be heated (solidified and dried garbage) is carbonized in an externally heated rotary kiln according to the prior art using a solid exfoliated body having no vent, it takes 3 to 5 hours. A phenomenon was observed in which a deposit of tar-like substances and soot grew on the inner surface of the exhaust pipe, and the pressure inside the shell increased.
[0036]
【The invention's effect】
In the externally heated rotary kiln of the present invention, the vent is opened in the stopper of the exhaust cylinder, and the exfoliated body held in the exhaust cylinder is a hollow body. Does not block vents. Therefore, the dry distillation gas generated by heating is always discharged from the shell into the heating furnace, and does not stay in the exhaust pipe, and deposits of tar-like substances and deposits by soot grow on the inner surface of the exhaust pipe. Nothing. Therefore, a stable operation state of the rotary kiln can be maintained for a long time.
[0037]
This is an externally heated rotary kiln that is suitable for performing carbonization treatment or dry distillation treatment of refuse solids (RDF) or rice bran or the like containing a very large amount of high molecular organic substances such as oils and fats and synthetic resins.
[Brief description of the drawings]
FIG. 1 is a schematic longitudinal sectional view of an embodiment of an externally heated rotary kiln of the present invention.
FIG. 2 is a schematic vertical sectional view showing a relationship among a shell, an exhaust pipe, and a peeling body according to the present invention.
3 is a schematic view showing a cross section taken along line AA of FIG. 2, and is a view showing a relationship between a circular exhaust cylinder having a strip attached to an inner peripheral surface thereof and a cylindrical exfoliated body.
FIG. 4 is a schematic cross-sectional view showing a relationship between a prismatic exhaust pipe having a projection attached to an inner peripheral surface thereof and a prismatic stripper.
FIG. 5 is a schematic view showing a relationship between a round exhaust cylinder and a cylindrical exfoliated body having a strip attached to an outer surface.
6 is a schematic diagram showing a cross section taken along line BB of FIG. 5, and is a diagram showing a relationship between a round exhaust cylinder and a peeled body having a protrusion attached to an outer surface.
FIG. 7 is a schematic cross-sectional view showing one embodiment of the present invention, and is a view showing a state where a cylindrical exfoliated body is in contact with a round exhaust cylinder.
FIG. 8 is a schematic cross-sectional view showing one embodiment of the present invention, and is a view showing a state in which a square tubular exfoliated body is in contact with a round exhaust cylinder.
FIG. 9 is a partially cutaway side view of an embodiment according to the prior art, showing a relationship between an exhaust pipe, a vent, and a sliding body (peeling body).
[Explanation of symbols]
3: Shell 4: Heating furnace 14: Shell outer part 24: Supply port 26: Discharge port 27: Exhaust tube 28: Separated body 30: Projection 31: Stopper 32: Vent 33: Sliding body M: Heated object

Claims (5)

A shell that rotates around an axis having a supply port for the heated object on one end side and a discharge port for discharging the heated object on the other end side,
A heating furnace for heating the outer portion of the shell;
An exhaust pipe fixedly penetrating through the peripheral wall of the shell and discharging gas generated in the shell into the heating furnace;
A peeling body that floats in the exhaust pipe with the rotation of the shell and peels off the attached matter attached to the inner surface of the exhaust pipe,
In an externally heated rotary kiln consisting of
The exhaust pipe has stoppers at both ends of the exhaust pipe, each of which has a vent opening for holding the peeled body in the exhaust pipe, and the peeled body is rotatable and movable coaxially with the exhaust pipe containing the exhaust body. 3. An externally heated rotary kiln, characterized in that it is a hollow body having a ventilation hole coaxial with the exhaust pipe through which the gas is passed. 2. The externally heated rotary kiln according to claim 1, wherein the exfoliated body is a cylinder or a polygonal cylinder. The externally heated rotary kiln according to claim 1 or 2, wherein a strip is formed on an inner surface of the exhaust cylinder to smoothly move the exfoliated body. The externally heated rotary kiln according to claim 1, wherein a protrusion is formed on an outer surface of the peeling member to peel off an attached matter by contacting an inner surface of the exhaust cylinder. The externally heated rotary kiln according to any one of claims 1 to 4, wherein the exfoliated body is a ceramic or a heat-resistant metal.

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