JP2008032299A - Tar removing method of external heating type rotary kiln - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve efficiency in furnace operation by dispensing with periodical tar scraping-off work. <P>SOLUTION: Sludge M is supplied into a rotating cylindrical retort 2, and the carbonized by heating from an external heating chamber 11 receiving the retort 2. By temporarily raising a temperature of the external heating chamber 11, a temperature in the retort 2 is temporarily raised to a temperature necessary for separating tar over a normal operation temperature for inhibiting volatilization elimination of an organic flammable component. The separated tar is discharged from the retort 2 with the carbonized sludge M. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a tar removal method for an external heating rotary kiln provided with an external heat chamber for heating a rotating retort from the outside.

  Externally heated rotary kilns are used for applications such as the thermal decomposition (carbonization) of organic waste such as dried sludge from sewage in an oxygen-free or low-oxygen state to produce useful carbides that can be used for biomass fuel. An example thereof is shown in FIG. In FIG. 3, an external heat chamber 11 formed in the upper half of the furnace body 1 of the external heat type rotary kiln is provided with a cylindrical retort 2 penetrating therethrough. In the retort 2, ring bodies 21 provided on the outer periphery of the one end portion 25 and the other end portion 26 are respectively supported by a roller (not shown), and a drive chain is suspended on a sprocket 22 provided on the outer periphery of the one end portion 25. It is rotated.

  A screw conveyor 14 extending from the bottom of the hopper 13 is located in the upstream end 23 of the retort 2 located in the furnace body 1, and the sludge M stored in the hopper 13 is carried into the retort 2. The sludge M carried into the retort 2 is transferred toward the other end 26 along with the rotation of the slightly inclined retort 2, and is heated and carbonized by the high temperature of the external heat chamber 11 in this process. The retort discharge port 16 that opens is discharged. Gas jet pipes 4 are provided on the cylindrical wall of the retort 2 at a plurality of positions in the longitudinal direction, and dry distillation gas released from the sludge M during the carbonization process is jetted to the external heat chamber 11 through the gas jet pipe 4. And is ignited by the auxiliary burner 51 disposed on the hearth 17 of the external heat chamber 11. Thereafter, the dry distillation gas ejected from the gas ejection pipe 4 is in a self-combustion state, and the auxiliary burner is extinguished or the combustion state is reduced. The combustion exhaust gas reaches the secondary combustion chamber 12 provided with the burner 52 through the vent 18 provided in the hearth 17 portion of the external heat chamber 11 facing the downstream end portion 24 of the retort 2, and from the opening 19. It goes to the chimney through a smoke exhaust duct (not shown).

  By the way, the organic waste contains a lot of low-temperature decomposable organic combustible components, but in the conventional rotary kiln, the heat of the external heat chamber that reaches a high temperature of about 800 ° C. reaches the retort 2, There was a problem that most of the organic combustible component was gasified and volatilized and disappeared, and the fuel value of the generated carbide was reduced.

Therefore, for example, in the rotary kiln disclosed in Patent Document 1, a heat insulating material is laid on the entire tubular wall of the retort to keep the temperature rise in the retort below 450 ° C., thereby suppressing the loss of volatilization of the low temperature decomposable organic combustible component is doing.
JP-A-11-304364

  However, according to experiments by the inventors, when the internal temperature of the retort is set to a low temperature of about 400 ° C. and the volatilization disappearance of the organic combustible component is suppressed, tar content adheres to the inner wall of the retort, If the inner wall is provided with spiral protrusions that prevent steady air intrusion and allow quantitative discharge of the carbonized material, there is a risk that tar will adhere to it and carbonized material cannot be discharged. there were. For this reason, operations such as periodically stopping the operation of the furnace and scraping off the tar adhered in the retort are necessary.

  Accordingly, the present invention solves such a problem, and an externally heated rotary shaft that improves the efficiency of the furnace operation by minimizing the volatilization loss of organic combustible components and eliminating the need for periodic tar scraping work. It aims at providing the tar removal method of a kiln.

  In order to achieve the above-mentioned object, the present invention supplies the material to be treated (M) into the rotating cylindrical retort (2) and heats it from the external heat chamber (11) that houses the retort (2). A tar removal method for an externally heated rotary kiln that carbonizes a material to be treated (M), wherein the temperature in the retort (2) exceeds the normal operating temperature that suppresses the volatilization loss of organic combustible components. It is characterized by being temporarily raised to a temperature necessary for peeling. Here, the temperature increase in the retort can be performed by temporarily increasing the room temperature of the external heat chamber (11), or can be performed by temporarily blowing air into the retort (2). Furthermore, it can be performed by temporarily reducing the moisture content of the material to be treated (M). In the present invention, the peeling of tar from the inner wall of the retort is promoted by temporarily raising the temperature inside the retort to a temperature necessary for peeling of the tar. The peeled tar is discharged from the retort together with the carbonized workpiece. This eliminates the need for periodic tar scraping work.

  As described above, according to the externally heated rotary kiln of the present invention, it is possible to suppress the volatilization and disappearance of the organic combustible component, and to realize the efficiency of the furnace operation because the periodic tar scraping work is unnecessary. Can do.

(First embodiment)
FIG. 1 is a schematic cross-sectional view of an externally heated rotary kiln according to the present invention. In FIG. 1, an external heat chamber 11 is formed in the upper half of a furnace body 1 of a rotary kiln, and a lower half of the furnace body 1 partitioned by a hearth 17 is a secondary combustion chamber 12. A cylindrical retort 2 is provided through the external heat chamber 11, and the retort 2 includes a ring body 21 provided at one end portion 25 and the other end portion 26, supported by a roller (not shown), and one end A drive chain is suspended and rotated by a sprocket 22 provided on the outer periphery of the portion 25. A screw conveyor 14 extending from the bottom of the hopper 13 is positioned in the upstream end 23 of the retort 2, and the sludge M stored in the hopper 13 is carried into the retort 2. The other end portion 26 of the retort 2 reaches the inside of the discharge cylinder 15, and the discharge port 16 is provided here.

  A gas jet pipe 4 penetrating inward and outward is provided only in the upstream end 23 on the cylindrical wall of the retort 2. Thermocouples 61 and 62 are provided at two locations in the retort longitudinal direction on the top wall of the furnace body 1 to detect the room temperature of the external heat chamber 11 at two locations. Burners 7 are provided at four locations in the longitudinal direction of the retort on the furnace wall near the hearth 17, and these burners 7 are temperatures at which a pair located in the first zone Z 1 on the upstream side feeds back a detection signal of the thermocouple 61. Combustion is controlled by a controller (not shown), and the pair located in the downstream second zone Z2 is controlled by a temperature controller (not shown) that feeds back a detection signal of the thermocouple 62. Yes. The hearth 17 is provided with a vent 18 that communicates with the secondary combustion chamber 12 at a position corresponding to the upstream end 23 of the retort 2. A burner 52 is provided in the secondary combustion chamber 12, and the secondary combustion chamber 12 communicates with the smoke exhaust duct through an opening 19 provided in the downstream furnace wall.

  In the externally heated rotary kiln having such a structure, the sludge M stored in the hopper 13 is carried into the retort 2 and transferred in the downstream direction as the retort 2 is slightly inclined. Then, it is carbonized by the heat from the external heat chamber 11, reaches the retort discharge port 16 opened in the discharge cylinder 15, and is discharged. Particularly in the initial stage when the sludge M is carbonized, a large amount of dry distillation gas is generated, which is discharged from the gas ejection pipe 4 provided at the upstream end 23 of the retort 2 cylindrical wall to the outside of the retort 2 and opened in the vicinity thereof. Through the vent 18, the air is quickly introduced into the secondary combustion chamber 12 without staying in the external heat chamber 11 and burning itself. Then, after the odor component is burned and decomposed by the burner 52, it is discharged from the chimney through the smoke exhaust duct from the opening 19.

  On the other hand, the external heat chamber 11 is divided into a burner 7 in the first zone Z1 on the upstream side where the evaporation of water in the retort is active and the amount of heating is required, and in the second zone Z2 where the evaporation of water is relatively small. The combustion temperature control is accurately maintained at 410 to 450 ° C., preferably 420 to 430 ° C., respectively. Thereby, the retort internal temperature is maintained at 390 ° C. to 430 ° C., preferably 390 ° C. to 410 ° C., and volatilization loss of the organic combustible component in the carbonized sludge is suppressed. Here, in the present embodiment, the set temperature of the first zone Z1 and the second zone Z2 is temporarily once a day, from the above-mentioned 420 ° C. to 430 ° C., which is the temperature during normal operation, to, for example, about 600 ° C. temporarily. Increase and then return to the original temperature. Accordingly, the temperature in the retort 2 rises from about 400 ° C. to 470 ° C. to 500 ° C., and then returns to the original temperature again. This time is, for example, 20 minutes to 40 minutes. By temporarily raising the temperature in the retort 2 in this manner, the tar content adhering to the inner wall of the retort 2 is peeled off and discharged out of the retort 2 from the discharge port 16 together with the sludge carbide. Therefore, periodic tar scraping work becomes unnecessary, and the efficiency of the furnace operation is realized. If the temperature is raised to about 500 ° C., the volatilization and disappearance of the organic combustible component in the sludge carbide can be kept small. In addition, the interval of the tar removal work of the present invention differs depending on the operation mode of the furnace (whether it is a continuous operation for 24 hours or a batch operation for only daytime), and in the case of a continuous operation for 24 hours, once a day as described above. If it is only daytime driving, it may be about once every three days.

(Second Embodiment)
In the present embodiment, as shown in FIG. 2, an air inlet 72 that can be opened and closed by a sliding door 71 is provided in the chute of the discharge cylinder 15 in which the other end portion 26 of the retort 2 is positioned. Other configurations are the same as those of the first embodiment.

  In such a configuration, the air inlet 72 is opened at an appropriate interval for 10 to 20 seconds during operation, and external air is fed into the retort 2. If it carries out like this, the dry distillation gas currently generate | occur | produced in the retort 2 will start combustion, and the temperature in a retort will rise temporarily to 480 degreeC-550 degreeC with the combustion heat. Thereby, the tar part adhering to the inner wall of the retort 2 peels off, and is discharged out of the retort 2 from the discharge port 16 together with the sludge carbide. This embodiment also has the same effect as the first embodiment. In addition, since it is a short time of 10 seconds-20 seconds, the volatilization loss of the organic combustible component in sludge carbide is suppressed to the limited part of the whole sludge carbide processed.

(Third embodiment)
With the same configuration as in the first embodiment, the moisture content of the sludge M supplied into the retort 2 is temporarily reduced by 7% to 15% from the value during normal operation (for example, about 50%). As a result, the amount of water evaporation in the retort 2 decreases and the temperature in the retort 2 temporarily rises to 480 ° C. to 550 ° C., and the tar content adhering to the inner wall of the retort 2 is peeled off and discharged together with sludge carbide. 16 is discharged out of the retort 2. Thereby, the same effect as the first embodiment can be obtained. Also in this case, the volatilization and disappearance of the organic combustible component in the sludge carbide is suppressed to a limited portion of the entire sludge carbide to be treated.

(Other embodiments)
The tar removal method of the present invention is not limited to the externally heated rotary kiln having the structure shown in the above embodiment, and an externally heated rotary having the structure shown in the conventional example in which a heat insulating material is laid on the entire cylindrical wall of the retort. Applicable to kilns.

It is a schematic sectional drawing of the external heating type rotary kiln in 1st Embodiment of this invention. It is a schematic sectional drawing of the external heating type rotary kiln in 2nd Embodiment of this invention. It is a schematic sectional drawing of the conventional external heating type rotary kiln.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Furnace body, 11 ... External heat chamber, 18 ... Vent, 2 ... Retort, 23 ... Upstream end part, 25 ... One end part, 26 ... Other end part, 4 ... Gas ejection pipe, 7 ... Burner, M ... Sludge , Z1, Z2 ... zones.

Claims (4)

A tar removal method for an externally heated rotary kiln in which a material to be treated is supplied into a rotating cylindrical retort, and the material to be treated is carbonized by heating from an external heat chamber in which the retort is accommodated. A method for removing tar from an externally heated rotary kiln, characterized in that the temperature inside the chamber is temporarily raised to a temperature necessary for tar separation, exceeding a normal operating temperature at which volatilization of organic combustible components is suppressed. The method for removing tar from an externally heated rotary kiln according to claim 1, wherein the temperature inside the retort is increased by temporarily increasing the room temperature of the external heat chamber. The method for removing tar from an externally heated rotary kiln according to claim 1, wherein the temperature inside the retort is increased by temporarily blowing air into the retort. The method for removing tar from an externally heated rotary kiln according to claim 1, wherein the temperature inside the retort is increased by temporarily reducing the moisture content of the material to be treated.

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