JP2005052707A - Waste treatment method and apparatus therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent the clogging of piping by preventing the adhesion of a soft foreign matter consisting of an organic matter to the inside of the piping and to also prevent an increase in the amount of the discharge liquid discharged from a waste treatment apparatus. <P>SOLUTION: The waste treatment method has a hydrothermal reaction process of liquefying organic waste X held to a high-pressure/high-temperature state to obtain a treated liquid Y and a pressure reducing process for reducing the pressure of the treated liquid Y and also has a cooling process of cooling a part of or the whole of the treated liquid Y after the pressure reducing process to obtain cooling water Y' and feeding back this cooling water Y' to the treated liquid Y to cool the treated liquid Y. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a waste treatment method and apparatus.
[0002]
[Prior art]
In recent years, as a method for treating organic waste such as excess sludge, a treatment method using a subcritical hydrothermal reaction has been proposed. The organic waste treatment method utilizing hydrothermal reaction (hereinafter referred to as hydrothermal reaction method) is a method of treating organic waste in a liquid state by hydrothermal reaction treatment of subcritical high-temperature / high-pressure organic waste. The processed liquid is converted into a processed liquid, and the processed liquid is decompressed and then discharged to the outside.
A hydrothermal reaction apparatus (waste treatment apparatus) that employs such a hydrothermal reaction method is usually composed of a hydrothermal reactor for hydrothermal reaction treatment of organic waste in a high temperature and high pressure state, and the hydrothermal reactor. A preheater that cools the treated liquid by indirectly exchanging the discharged treated liquid and the organic waste and preheats the organic waste, and the treated liquid indirectly by a cooling medium such as cooling water A cooler for cooling and a pressure reducing valve for reducing the pressure of the treated liquid are provided.
[0003]
[Patent Document 1]
Japanese Patent Laid-Open No. 2001-145860
[Problems to be solved by the invention]
However, it has been found that piping clogging occurs in the preheater and the cooler while the hydrothermal reactor is actually in operation. When these preheaters and coolers were disassembled, it was found that soft foreign substances made of organic matter adhered to the inner wall of the pipe. Since such a soft foreign substance adheres only to the inner wall of the preheater and the cooler pipe, it is generated in the process where the treated liquid comes into contact with the inner wall of the preheater and the cooler pipe and is gradually cooled. It is thought to be a thing.
In response to this problem, mixing a large amount of cooling medium and cooling reduces the temperature difference between the treated liquid and the inner wall of the pipe during the cooling process, and soft foreign substances made of organic matter adhere to the inner wall of the pipe. It is conceivable not to do so. However, in such a case, the amount of effluent discharged from the hydrothermal reactor increases.
In addition, it is conceivable to use a heat exchanger or the like, in which foreign matter hardly adheres in the piping, as a preheater and a cooler, but such a heat exchanger is difficult to use in a pressurized state.
[0005]
The present invention has been made in view of the above-mentioned problems, and prevents clogging of piping by preventing adhesion of soft foreign substances made of organic matter in the piping, and discharge discharged from the waste treatment apparatus. The purpose is to prevent an increase in the amount of liquid.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, in the present invention, as a first means related to a waste treatment method, a hydrothermal reaction step of liquefying organic waste under a high temperature and high pressure to obtain a treated liquid, and the above treatment A waste disposal method having a decompression step of decompressing the spent solution, wherein the treatment is performed by cooling a part or all of the treated solution after the decompression step and feeding back to the treated solution as cooling water. A configuration is adopted in which a cooling process for cooling the spent solution is provided.
[0007]
As a second means related to the waste treatment method, in the first embodiment, a configuration is adopted in which the cooling water is fed back to the treated liquid immediately after the decompression step.
[0008]
As the third means related to the waste treatment method, the second means adopts a configuration in which the treated liquid is cooled by directly flowing into the vicinity of the central portion of the cross section of the pipe through which the cooling water flows. .
[0009]
As a fourth means related to the waste treatment method, there is an auxiliary cooling step for cooling the treated liquid before the depressurizing step to a temperature at which a soft foreign substance made of organic matter does not precipitate in the treated liquid. The decompression step includes a first decompression step for decompressing the treated liquid after the auxiliary cooling step to a saturated water vapor pressure, and a second decompression step for further decompressing the treated liquid after the first decompression step; The cooling water is press-fitted into the treated liquid between the first decompression step and the second decompression step.
[0010]
As a fifth means related to the waste treatment method, in any one of the first to fourth means, the flow rate of the cooling water is defined so that the treated liquid is equal to or lower than a saturated water vapor temperature after the decompression step. Adopted a configuration that is.
[0011]
As a first means related to the waste treatment apparatus, a hydrothermal reactor that liquefies organic waste in a high temperature / high pressure state and discharges it as a treated liquid, and a pressure reducing valve that decompresses and discharges the treated liquid are provided. The waste treatment apparatus includes a cooling circulation mechanism that cools the treated liquid discharged from the pressure reducing valve and feeds back the treated liquid to the treated liquid.
[0012]
As a second means related to the waste treatment apparatus, a configuration is adopted in which, in the first means, the cooling circulation mechanism is connected to a pipe immediately after the pressure reducing valve.
[0013]
As a third means related to the waste treatment apparatus, in the first means, the treated liquid is supplementarily cooled by exchanging heat between the treated liquid before the pressure reducing valve and the organic waste. A preheating device, and the decompression valve comprises a first decompression valve that decompresses the treated liquid discharged from the preheater to a saturated water vapor pressure, and the treated liquid discharged from the first decompression valve. And a second pressure reducing valve for reducing pressure, wherein the cooling circulation mechanism includes a heat exchanger for cooling a part of the treated liquid discharged from the pressure reducing valve and the processed liquid discharged from the heat exchanger. And a pressurizing pump for pressurizing the pressure sensor and connected between the first pressure reducing valve and the second pressure reducing valve.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of a waste treatment method and apparatus according to the present invention will be described with reference to the drawings.
[0015]
(First embodiment)
FIG. 1 is a schematic configuration diagram of a hydrothermal reaction apparatus (waste treatment apparatus) according to this embodiment. In this figure, reference numeral 1 is a hopper, 2 is a discharge pump, 3 is a pressurizing pump, 5 is a circulation pump for a hydrothermal reactor, 6 is a hydrothermal reactor, 7 is a cooling circulation mechanism, 8 is a pressure reducing valve, and 9 is a reservoir. The tank, X is excess sludge (organic waste), Y is a treated liquid, and Y ′ is cooling water.
[0016]
The hopper 1 temporarily stores surplus sludge X supplied from the outside. The lower end of the hopper 1 is formed as an open end, and a discharge pump 2 is connected thereto. This discharge pump 2 regulates the discharge amount of the excess sludge X, and supplies the excess sludge X stored in the hopper 1 to the pressurizing pump 3 via the pipe a.
[0017]
The pressurizing pump 3 pressurizes the excess sludge X supplied from the dispensing pump 2 to a predetermined pressure and discharges it to the subsequent stage through the pipe b.
As shown in the drawing, a circulation path including a hydrothermal reactor circulation pump 5, a hydrothermal reactor 6, and a pipe c is disposed at the subsequent stage of the pressurizing pump 3.
The hydrothermal reactor 6 liquefies surplus sludge X supplied to itself by hydrothermal reaction treatment in a subcritical high temperature and high pressure state (150 to 300 ° C. and a pressure higher than the saturated water vapor pressure at that temperature). And discharged as processed liquid Y.
Further, the hydrothermal reactor circulation pump 5 circulates the treated liquid Y and the excess sludge X in a mixed state in the direction of the arrow through the pipe c.
[0018]
The decompression valve 8 decompresses the treated liquid Y and discharges it through the pipe f. The pipe f is connected to a pipe h of a cooling circulation mechanism 7 described later immediately after the pressure reducing valve 8.
FIG. 2 is an enlarged cross-sectional view of a connection portion between the pipe f and the pipe h. As shown in this figure, the pipe f is arranged in an inserted state in the pipe h so that the end of the pipe f is located in the vicinity of the center of the cross section of the pipe h.
[0019]
Returning to FIG. 1, a storage tank 9 for storing the treated liquid Y supplied through the pipe h at a height of, for example, 20 m is disposed at the subsequent stage of the pressure reducing valve 8. Is connected to the lower part of the storage tank 9.
[0020]
The cooling circulation mechanism 7 cools a part of the treated liquid Y discharged to the outside through the pipe g connected to the upper part of the storage tank 9 to form cooling water Y ′, and treats the treated liquid through the pipe h. This is fed back to Y and mixed. The cooling circulation mechanism 7 cools the intake liquid 71 for taking a part of the treated liquid Y from the pipe g into the pipe h, and the treated liquid Y supplied from the intake pump 71 to cool the cooling water Y ′. The heat exchanger 72 is provided. As the heat exchanger 72, a spiral heat exchanger or the like in which piping is not easily clogged, that is, foreign matter is not easily attached to the inner wall of the piping is used.
The cooling circulation mechanism according to the present invention is configured by the intake pump 71, the heat exchanger 72, and the pipe h in the first embodiment.
[0021]
Next, a waste processing method in the waste processing apparatus according to the first embodiment configured as described above will be described.
[0022]
The surplus sludge X supplied to the hopper 1 is temporarily stored by the hopper 1, and then a predetermined amount is continuously supplied to the subsequent pressurizing pump 3 through the pipe a by the discharge pump 2. The excess sludge X is pressurized to a predetermined pressure by the pressurizing pump 3 and further supplied to a circulation path composed of the hydrothermal reactor circulation pump 5, the hydrothermal reactor 6, and the piping c through the piping b. The
[0023]
In this circulation path, the treated liquid Y previously hydrothermally treated by the hydrothermal reactor 6 is circulated by the hydrothermal reaction circulation pump 5. Excess sludge X is mixed with the treated liquid Y circulating in this circulation path and supplied to the hydrothermal reactor 6. The surplus sludge X is liquefied by being hydrothermally treated in a subcritical state in the hydrothermal reactor 6 and discharged from the hydrothermal reactor 6 as a treated liquid Y (hydrothermal reaction step).
[0024]
A part of the treated liquid Y discharged from the hydrothermal reactor 6 is discharged from the circulation path through the pipe d. And the processed liquid Y is discharged | emitted via the piping f, after being pressure-reduced by the pressure-reduction valve 8 (pressure reduction process).
And the processed liquid Y discharged | emitted via the piping f flows in into the piping h through which cooling water Y 'flows, and the processed liquid Y and cooling water Y' are mixed. Thereby, the processed liquid Y is cooled (cooling process). Usually, the treated liquid Y flowing through the pipe d is heated to about 280 ° C. in the above-described hydrothermal reaction step, and a pressure of about 6 MPa is applied. For this reason, the treated liquid Y is instantaneously flushed (sudden boiling) by being temporarily depressurized by the pressure reducing valve 8, but the pipe f is connected to the pipe h immediately after the pressure reducing valve 8. Immediately cooled to liquid phase. Further, as shown in FIG. 2, the pipe f is arranged in an inserted state through the pipe h so that the end of the pipe f is located near the center of the cross section of the pipe h. The foreign matter deposited by instantaneous flushing is allowed to flow with the treated liquid Y without adhering to the inner walls of the pipes f and h. Therefore, the pipe f and the pipe h are not clogged.
In addition, it is preferable that the piping f and the piping h are formed of the member which has the rigidity which can endure the above-mentioned flash.
In this way, since the cooling liquid Y ′ and the processed liquid Y discharged from the pressure reducing valve 8 are mixed, the processed liquid Y is cooled at a stretch, and thus generated in the process of cooling the processed liquid Y. It is difficult for soft foreign substances made of organic matter to be generated. Therefore, it is possible to prevent soft foreign substances made of organic matter from adhering to the pipe.
[0025]
As for the cooling water Y ′, a part of the treated liquid Y discharged from the storage tank 9 through the pipe g is taken into the pipe h by the intake pump 71, and the taken processed liquid Y is taken in by the heat exchanger 72. Produced by cooling. In this case, the processed liquid Y is indirectly cooled by the heat exchanger 72. However, since a spiral heat exchanger or the like in which piping clogging is unlikely to occur is used as the heat exchanger 72, heat exchange is performed. The pipe 72 is also prevented from clogging. The reason why the spiral heat exchanger or the like in which pipe clogging hardly occurs can be used as the heat exchanger 72 is that the treated liquid Y in the pipe h is decompressed by the pressure reducing valve 8.
The flow rate of the processed liquid Y taken from the pipe g, that is, the flow rate of the cooling water Y ′ is defined so that the processed liquid Y after the pressure reducing valve 8 is equal to or lower than the saturated water vapor temperature. Therefore, for example, when the above-described treated liquid Y at 280 ° C. is cooled to 75 ° C. with the cooling water Y ′ at 50 ° C., the flow rate of the cooling water Y ′ is the processed amount discharged from the pipe f. About 8 times the flow rate of the liquid Y.
[0026]
As described above, according to the waste processing method and apparatus according to the present embodiment, it is possible to prevent soft foreign substances made of organic matter from adhering to the pipe and to treat the processed liquid discharged from the storage tank 9. Since a part of Y is used as the cooling water Y ′, it is possible to prevent an increase in the amount of the processed liquid Y (discharged liquid) discharged from the waste treatment apparatus.
[0027]
(Second Embodiment)
Next, a second embodiment of the waste treatment method and apparatus according to the present invention will be described with reference to FIG. In the second embodiment, only parts different from the first embodiment will be described.
FIG. 3 is a schematic configuration diagram of a hydrothermal reaction device (waste treatment device) according to the second embodiment. In this figure, reference numeral 4 is a preheater, 81 is a first pressure reducing valve, 82 is a second pressure reducing valve, and 73 is a second pressure pump.
[0028]
The preheater 4 exchanges heat between the excess sludge X supplied from the pressurizing pump 3 and the treated liquid Y supplied from the hydrothermal reactor 6, thereby heat-treating the treated liquid Y in an auxiliary manner. A pipe b and a pipe d are inserted.
[0029]
The first pressure reducing valve 81 is for reducing the treated liquid Y discharged from the preheater 4 to a saturated water vapor pressure, and is connected to the pipe d. A pipe i extends from the first pressure reducing valve 81, and a second pressure reducing valve 82 is connected to the pipe i. And the piping h through which the cooling water Y 'shown in the said 1st Embodiment flows is connected to this piping i. The second pressure reducing valve 82 is connected to the storage tank 9 through a pipe e.
[0030]
The second pressurizing pump 73 is provided in the subsequent stage of the heat exchanger 72 and has a function of taking the treated liquid Y at a predetermined flow rate from the pipe g and the treated functional liquid Y in the pipe i with the treated liquid Y in the pipe i. It bears the function of pressurizing to the same pressure.
Note that the hydrothermal reaction apparatus according to the second embodiment is not provided with the pressure reducing valve 8 and the intake pump 72 shown in the first embodiment.
Further, the cooling circulation mechanism 7 according to the present invention is configured by the heat exchanger 72, the second pressurizing pump, and the pipe h in the second embodiment.
[0031]
Next, a waste processing method in the waste processing apparatus according to the second embodiment configured as described above will be described.
[0032]
The surplus sludge X is discharged from the pressurizing pump 2 and supplied to the preheater 4 so that the treatment is discharged from the circulation path including the hydrothermal reactor circulation pump 5, the hydrothermal reactor 6 and the pipe c. Heat exchange with the spent solution Y is performed, and preheated thereby, and supplied to the circulation path.
In this way, by preheating the treated liquid Y by the preheater 4, it is possible to reduce the heat energy used in the subsequent hydrothermal reactor 6 and to reduce the burden on the hydrothermal reactor 6. It becomes.
[0033]
And the processed liquid Y discharged | emitted from the circulation path is heat-exchanged with the excess sludge X by supplying to the said preheater 4, and the soft foreign material which consists of organic substance does not precipitate in the processed liquid Y. Cooling in an auxiliary temperature range (auxiliary cooling step). Here, the term “auxiliary” is used to indicate that the preheater 4 is not intended to completely cool the processed liquid Y to a temperature at which the processed liquid Y is not flushed after decompression.
[0034]
Since it has been confirmed that soft foreign substances made of organic substances do not precipitate when the treated liquid Y is 130 ° C. or higher, specifically, the treated liquid Y is cooled to 180 ° C. by the preheater 4.
[0035]
Since the treated liquid Y cooled to 180 ° C. does not flash even at a pressure of about 2 MPa (saturated water top pressure or less), it is decompressed to 2 MPa by the first decompression valve 81 (first decompression). Process). And the processed liquid Y is cooled to 75 degreeC at a stretch by being mixed with the cooling water Y 'press-fit from the pipe h in the pipe i.
[0036]
Therefore, the second pressurizing pump 73 only needs to pressurize the cooling water Y ′ to about 2 MPa, so that the burden on the pressurizing pump 73 can be reduced.
When a pressure pump that can pressurize the cooling water Y ′ up to about 6 MPa can be installed, a single pressure reducing valve is provided, and the treated liquid Y before the pressure reducing valve is provided with the cooling water Y ′. May be supplied.
[0037]
Then, the treated liquid Y cooled by being supplied with the cooling water Y ′ is further decompressed by the second decompression valve 82 (second decompression step). Thereafter, the cooling water Y ′ is supplied to the storage tank 9 through the pipe e.
[0038]
According to the waste treatment method and apparatus according to the second embodiment, the same effects as the waste treatment method and apparatus according to the first embodiment are obtained, and the treated liquid Y is not flushed. Therefore, it is not necessary to provide the pipe with rigidity that can withstand flash.
[0039]
Further, according to the hydrothermal reaction method and apparatus shown in the first and second embodiments, even if a soft foreign substance made of organic matter adheres to the piping and the piping is clogged, the treatment Since the portion where the spent liquid Y is cooled is after the pressure reduction, maintenance can be easily performed.
[0040]
The preferred embodiments of the waste treatment method and apparatus according to the present invention have been described above with reference to the accompanying drawings. Needless to say, the present invention is not limited to the above-described embodiments. Various shapes, combinations, and the like of the constituent members shown in the above-described embodiments are examples, and various modifications can be made based on design requirements and the like without departing from the gist of the present invention.
[0041]
【The invention's effect】
As described above, according to the present invention, a waste having a hydrothermal reaction step that liquefies organic waste under high temperature and high pressure to form a treated liquid, and a decompression step that depressurizes the treated liquid. Since it is a processing method and has a cooling process which cools the above-mentioned processed liquid by cooling a part or all of the above-mentioned processed liquid after the above-mentioned decompression process, and feeding back to the above-mentioned processed liquid as cooling water, piping It is possible to prevent clogging of piping by preventing soft foreign substances made of organic matter from adhering therein, and to prevent an increase in the amount of discharged liquid discharged from the waste treatment apparatus.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of a hydrothermal reaction device (waste treatment device) according to a first embodiment of the present invention.
FIG. 2 is an enlarged cross-sectional view of a connection portion between a pipe f and a pipe h according to the first embodiment of the present invention.
FIG. 3 is a schematic configuration diagram of a hydrothermal reaction device (waste treatment device) according to a second embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Hopper 2 ... Discharge pump 3 ... Pressure pump 4 ... Preheater 5 ... Hydrothermal reactor circulation pump 6 ... Hydrothermal reactor 7 ... Cooling circulation mechanism 8 ... Pressure reducing valve 9 ... Storage tank X ... Surplus sludge (organic waste)
Y …… Processed liquid Y ′ …… Cooling water (cooling medium)

Claims (8)

A waste treatment method comprising a hydrothermal reaction step to liquefy organic waste under high temperature and high pressure to form a treated liquid, and a decompression step to depressurize the treated liquid,
A waste treatment method comprising a cooling step of cooling the treated liquid by cooling a part or all of the treated liquid after the depressurizing step and feeding back to the treated liquid as cooling water. . The waste treatment method according to claim 1, wherein the cooling water is fed back to the treated liquid immediately after the decompression step. The waste treatment method according to claim 2, wherein the treated liquid is cooled by directly flowing into the vicinity of a central portion of a cross section of a pipe through which the cooling water flows. Having an auxiliary cooling step of cooling the treated liquid before the depressurizing step to a temperature at which a soft foreign substance made of organic matter does not precipitate in the treated liquid;
The depressurization step includes a first depressurization step of depressurizing the treated liquid after the auxiliary cooling step to a saturated water vapor pressure, and a second depressurization step of further depressurizing the treated liquid after the first depressurization step. Have
The waste treatment method according to claim 1, wherein the cooling water is press-fitted into the treated liquid between the first decompression step and the second decompression step. The waste treatment method according to any one of claims 1 to 4, wherein the flow rate of the cooling water is defined so that the treated liquid has a temperature equal to or lower than a saturated water vapor temperature after the decompression step. A waste treatment apparatus having a hydrothermal reactor that liquefies organic waste in a high temperature / high pressure state and discharges it as a treated liquid, and a pressure reducing valve that decompresses and discharges the treated liquid,
A waste treatment apparatus comprising a cooling circulation mechanism that cools the treated liquid discharged from the pressure reducing valve and feeds it back to the treated liquid. The waste treatment apparatus according to claim 6, wherein the cooling circulation mechanism is connected to a pipe immediately after the pressure reducing valve. A preheater for assisting cooling of the treated liquid by exchanging heat between the treated liquid and the organic waste before the pressure reducing valve; and the pressure reducing valve was discharged from the preheater A first decompression valve for decompressing the treated liquid to a saturated water vapor pressure; and a second decompression valve for further decompressing the treated liquid discharged from the first decompression valve;
The cooling circulation mechanism includes a heat exchanger that cools a part of the processed liquid discharged from the pressure reducing valve, and a pressure pump that pressurizes the processed liquid discharged from the heat exchanger, and The waste treatment apparatus according to claim 6, wherein the waste treatment apparatus is connected between the first pressure reducing valve and the second pressure reducing valve.

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