JP2003236594A - Apparatus for treating sludge - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an apparatus for treating sludge wherein fluidity and sticking properties of sludge are improved, thereby reduction of heat transfer efficiency when sludge is preheated and blocking of piping can be prevented, pressure resistant performance of a high pressure pump for supplying the sludge to a hydrothermal reactor can be made simpler and the sludge can be oxidatively decomposed stably and efficiently by a hydrothermal reaction even if the sludge has sticking properties and low fluidity. <P>SOLUTION: Sewage sludge 13 is introduced to an ozone treatment vessel 3 and ozone is blown into the ozone treatment vessel 3 through an ozone supplying passage 15 to be brought into contact with the sludge and matters having sticking properties in the sludge is decomposed to improve fluidity and sticking properties. The resultant sludge is introduced to a heat exchanger 4 using a high pressure pump 21 and then sent to a supplying apparatus 23 of the hydrothermal reactor 5 to be mixed with an oxidizing agent 7 there, the mixed flow thereof is supplied to the hydrothermal reactor 5 in descending flow and a hydrothermal reaction is performed to decompose the sludge. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sludge treatment apparatus for oxidizing and decomposing sludge by hydrothermal reaction in a supercritical or subcritical state of water.

[0002]

2. Description of the Related Art As a method of treating organic sludge such as sewage sludge, a treatment method of oxidizing and decomposing by a hydrothermal reaction in a supercritical state of water has been proposed. The hydrothermal reaction is a method of decomposing waste, generating energy, or producing a chemical substance by subjecting an object to be reacted to an oxidation reaction or a hydrolysis reaction in a supercritical or subcritical state of water. In the case of organic sludge such as sewage sludge, the reaction product containing the organic matter in the supercritical or subcritical state of water causes an oxidation reaction by reacting the oxidizing agent, and the organic matter in the reaction subject can be removed in a short time. , Can be decomposed almost completely.

When oxidatively decomposing the organic matter in the reaction product by the hydrothermal reaction as described above, the reaction product, the oxidant and water are heated by the heating device and pressurized by the high pressure pump and supplied to the reactor, Oxidize. In this case, if the substance to be reacted contains an appropriate amount of water in advance, it is not necessary to supply water.

As a result of the reaction, the organic matter is oxidatively decomposed to obtain a reaction product containing a liquid of water and carbon dioxide at high temperature and high pressure and a solid such as ash and salts in a dried or slurry state. Solids of the reaction product are separated by a solid-liquid separator. The fluid from which the solid has been separated is subjected to energy recovery or cooled and decompressed to be separated into a gas component and a liquid component.

The sewage sludge contains a large amount of proteins, acidic polysaccharides, neutral polysaccharides, nucleic acids, etc., which are said to be mucilages, and therefore has high viscosity and low fluidity, and also on the wall surface of the device. Easy to attach. When such sludge is supplied to the reactor for processing, it tends to adhere to and remain on the heat transfer surfaces of heating devices such as heat exchangers and piping, which lowers heat transfer efficiency and causes clogging of piping. There is a problem. Also, since the pressure loss when supplying to the reactor is large,
In order to continuously raise the pressure above the critical pressure and stably supply it to the reactor, a high-pressure pump with a high discharge capacity is required. Further, even when the high-pressure pump discharges at high pressure and supplies it to the reactor, it is difficult to supply high-concentration sludge to the hydrothermal reaction device because the higher concentration of sludge tends to have lower fluidity. The amount of organic substances supplied is reduced, and auxiliary fuel is required.

As a method for treating sludge having low fluidity by a hydrothermal reaction in a supercritical state of water, JP-A-11-9049 is known.
For No. 4, the sludge concentration was adjusted to 5 to 15% by weight, and 250
A method of preheating to ~ 450 ° C is described. Further, in JP-A No. 11-33568, 5 to 15 MPa, 200 ° C.
By pretreating the sludge under the above high temperature and high pressure conditions, the fluidity is improved, the pressurization operation of the high pressure pump above the critical pressure of water is facilitated, and the sludge is stably supplied to the reactor. Have been described.

In the above-mentioned conventional method, the fluidity of the sludge introduced into the reactor is improved, but the problems of the decrease of heat transfer efficiency due to the adherence of mucus when preheating the sludge and the clogging of the pipe still remain. Has been done.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to improve the fluidity and adhesion of sludge, thereby preventing a decrease in heat transfer efficiency during preheating and preventing clogging of pipes. Moreover, the pressure resistance of the high-pressure pump that supplies sludge to the hydrothermal reaction device can be simplified.
Further, it is an object of the present invention to provide a sludge treatment device capable of oxidatively decomposing stably and efficiently by a hydrothermal reaction even when treating sludge which has low fluidity and tends to adhere.

[0009]

The present invention is the following sludge treatment device. (1) Sludge having a decomposing device for decomposing mucilage in sludge, and a hydrothermal reaction device for oxidatively decomposing sludge decomposing mucus in the sludge by hydrothermal reaction in a supercritical or subcritical state of water Processing equipment. (2) The sludge treatment device according to (1) above, wherein the decomposing device is an ozone treatment device that brings the sludge into contact with ozone to decompose the mucilage. (3) The sludge treatment device according to (1) or (2) above, which has a heating device for preheating sludge in the latter stage of the decomposition device.

The sludge to be treated in the present invention is
There is no limitation as long as it is an organic sludge, but sludge with low fluidity, particularly sewage sludge generated from sewage treatment is suitable.
Sewage sludge increases the amount of proteins, acidic polysaccharides, neutral polysaccharides, nucleic acids, etc., which are said to be mucilages, due to the action of microorganisms, usually has high viscosity and low fluidity, and often adheres to the wall surface of equipment. However, in the present invention, such sewage sludge can be efficiently treated. The sewage sludge includes first settling sludge and surplus sludge of biological treatment, and may be in a slurry form before dehydration or in a dehydrated cake form.

The sewage sludge is preferably crushed in advance. The crushing means is not limited. For example, when the sewage sludge is in a solid state called dewatered cake (concentration is usually 15% by weight to 20% by weight or more), a crusher is used, and if necessary, a pump is circulated to the crusher. By passing it multiple times, or mashing with a mill,
It is preferable to crush it to about 1 mm. If the concentration of sewage sludge is not so high and it is in a so-called slurry state, a crusher or a mill may be used in the same manner. Good.

The sludge concentration is 5 to 20% by weight, preferably 1
0 to 20% by weight, or COD concentration of 200,000 to
500,000 mg / L, preferably 300,000-
It is preferably 400,000 mg / L. When the sludge having such a concentration is treated by the apparatus of the present invention, the temperature of the hydrothermal reaction can be maintained by the amount of heat of the organic component in the sludge. When the sludge concentration is out of the above range, the concentration can be adjusted by means such as concentration, dilution or mixing with other sludge in the former stage or the latter stage of the decomposition apparatus.

The decomposing device in the present invention is a device for decomposing viscous matter in sludge, and the decomposing means or the decomposing method is not limited, but an ozone treating device is preferable. As the ozone treatment device, any device having any configuration can be used as long as it is a device capable of bringing ozone into contact with sludge and decomposing viscous substances. As the contact method in this case,
A method of introducing sludge into the ozone treatment tank and blowing ozone, a method of mechanical stirring, a method of utilizing a packed bed, and the like can be adopted.

As ozone, ozone-containing gas such as ozone-containing air or ozonized air can be used in addition to ozone gas. The amount of ozone 0.02g-O ₃ / g-SS or more, preferably it is desirable to 0.05g-O ₃ / g-SS more. These ozone-containing gases are consumed for decomposing the mucilage of sludge, but when ozone and oxygen remain, they function as an oxidant, so it is possible to reduce the total amount of oxidant used. .

The decomposition treatment such as ozone treatment decomposes the viscous matter in the sludge and improves the fluidity and / or the adhesiveness of the sludge, but the degree to which the viscosity of the sludge is treated is determined by the high pressure used. It may be set appropriately according to the performance of the pump. Specifically, the maximum allowable viscosity of the high-pressure pump used at a certain pump flow rate is determined by the performance of the high-pressure pump used, so decomposition processing such as ozone treatment is performed until the maximum allowable viscosity at the set flow rate falls below the maximum allowable viscosity. .

The decomposition treatment such as ozone treatment decomposes the viscous substance in the sludge and improves the fluidity and / or the adhesiveness of the sludge. Therefore, the sludge is prevented from adhering to the heat transfer surface of the heating device such as the heat exchanger and the pipes, and the heat transfer efficiency is not reduced and the pipes are not blocked. Further, the pressure resistance of the high-pressure pump used for supplying the sludge to the hydrothermal reaction device can be made simpler. Furthermore, since it becomes possible to treat high-concentration sludge, the auxiliary fuel becomes unnecessary, or the amount used can be reduced even when used.

In the present invention, it is preferable to provide a heating device for preheating sludge in the latter stage of the decomposition device. A heat exchanger or the like can be used as the heating device. The heat exchanger can also be configured to use the reactant discharged from the hydrothermal reactor as the heating medium. In the heating device, the viscous substance in the sludge is decomposed by the decomposition device in the previous stage, so that it is prevented from adhering to the heat transfer surface and the like and can be efficiently heated.

The hydrothermal reaction apparatus in the present invention is an apparatus for hydrothermally reacting sludge treated by the above-mentioned decomposition apparatus or sludge preheated by a heating apparatus to oxidize and decompose organic substances.
The hydrothermal reactor is configured to oxidatively decompose sludge in the presence of an oxidant in a supercritical or subcritical state of water by a hydrothermal reaction.

The hydrothermal reaction is a reaction of oxidatively decomposing sludge by an oxidative reaction in the presence of supercritical or subcritical water at high temperature and high pressure and an oxidizing agent. What is a supercritical state?
The state is 4 ° C. or higher and 22 MPa or higher. The subcritical state is, for example, 374 ° C. or higher, 2.5 MPa or higher and 22 MP.
less than a or less than 374 ° C., 22 MPa or more,
Alternatively, it means a state of high temperature and high pressure close to the critical point even at 374 ° C. or lower and less than 22 MPa.

Such a hydrothermal reaction is carried out in a hydrothermal reaction apparatus in a state where sludge, which is a reaction target, is mixed with an oxidant, and these mixtures undergo a hydrothermal reaction inside the reactor of the hydrothermal reaction apparatus. . As the oxidant, air, oxygen, liquid oxygen, hydrogen peroxide solution, ozone, nitric acid, nitrous acid, nitrate, nitrite or the like can be used. The oxidant may be mixed with the sludge and supplied, or may be supplied as a multi-layered flow with a double pipe nozzle as the supply port. If necessary, a catalyst, a neutralizing agent, etc. may be added, and these may be mixed with sludge or supplied separately to the reactor.

The hydrothermal reactor used in the present invention is made of a heat-resistant and pressure-resistant material in a cylindrical reactor arranged substantially vertically so as to carry out hydrothermal reaction in a supercritical or subcritical state. . If the reaction heat alone does not reach the supercritical or subcritical state, an external heating means can be provided.
The reactor may have a cylindrical shape, an elliptic shape, or a polygonal shape, and the lower end portion may have a cone shape. When a hydrothermal reaction is carried out in a supercritical or subcritical state by such a hydrothermal reactor, the organic substance of the reaction product is oxidized by an oxidant and is finally decomposed into water and carbon dioxide, or is hydrolyzed to a low level. The substance is polymerized and the inorganic substance is separated in a solid or molten state. After separating the solid matter, the reaction product is cooled and depressurized to be separated into gas and liquid.

As the above-mentioned hydrothermal reaction apparatus, those conventionally used for hydrothermal reaction can be used as they are,
As shown in JP-A-11-156186, a substantially vertical reactor having a mixed reaction zone with backflow in the upper part and a plug flow reaction zone in the lower part, and an injection device further provided on the upper part. , The mixed flow of the reaction product and the oxidant is injected in a downward flow to form a mixed flow accompanied by backflow in the upper mixing reaction region to cause hydrothermal reaction, and in the lower plug-like reaction region, a parallel downward flow is generated. A structure in which a plug flow is formed to perform an additional hydrothermal reaction is preferable.

The material of the hydrothermal reactor is not limited, but is preferably a corrosion resistant material such as Hastelloy, Inconel or stainless steel. The hydrothermal reactor is preferably provided with a corrosion resistant liner. The corrosion-resistant liner is not particularly limited, and a corrosion-resistant liner having a gap between the corrosion-resistant liner and the pressure load wall as disclosed in JP-A-11-156186 can be used.

The hydrothermal reactor may be provided with cooling means for cooling the reaction mixture before it is discharged from the outlet. The cooling means is not particularly limited, but water can be introduced into the reactor to cool it, and the inorganic salt can be dissolved to accelerate its discharge. Further, water containing an acid or an alkali may be introduced into the reactor and cooled to neutralize the alkali or the acid. When the adherence of solids is significant, a mechanical removal device for removing solids adhering to the inner wall of the reactor can be provided. The mechanical removing device for removing solids is not particularly limited, but a substantially cylindrical scraper including a notched window portion disclosed in JP-A-11-156186 is suitable.

Separation means for separating solids in the reaction fluid discharged from the hydrothermal reactor can be provided. In particular, since inorganic salts are not dissolved in the reaction fluid in a supercritical state but are contained as a solid, separation of insolubilized inorganic substances facilitates reuse of treated water. The solid matter separating means is not particularly limited, and a container having an inlet for introducing the reaction fluid from the hydrothermal reaction device and an outlet for discharging the fluid from which the solid has been removed, and the reaction fluid disposed in the container to the reaction fluid. A means provided with a means for removing and discharging the contained solid can be used. In addition, a means for solid separation or gas-liquid separation can be included in the cooling and depressurizing steps.

The means for starting the reaction by the hydrothermal reaction device is not particularly limited. Usually, the reactor is preheated to around a predetermined reaction temperature at the start of the reaction. The preheating can be performed by providing a heating device in the reactor or by introducing heated water or air provided in the sludge and / or oxidant supply passage. Further, normally, water or an oxidant is supplied to the reactor, and the pressure is adjusted to a predetermined pressure by a pressure adjusting valve that is usually provided. After the temperature and pressure are adjusted to predetermined values, a fluid containing sludge, which is a reaction target, is supplied to start a hydrothermal reaction. Organic substances are decomposed by the reaction, and heat of reaction is generated. When a mixing reaction zone involving backflow is provided in the upper part of the hydrothermal reaction device (upper part of the reactor), the reactant, oxidant, reactor contents, etc. are sufficiently mixed by the mixing action involving backflow. The fluid temperature rises. The reactant to be supplied thereby rapidly starts the hydrothermal reaction and the stable reaction is continued. The reaction fluid moves downward in the reactor, continuously reacts in the plug flow reaction region, and is then discharged from the discharge port. The length: diameter ratio of the reactor is preferably 1: 1 to 100: 1.

The reaction fluid discharged from the hydrothermal reactor is separated into solids, then cooled and decompressed to be gas-liquid separated. When a liquid is produced by cooling in the reactor, it is separated from the liquid together with the solid at the stage of leaving the reactor, and further cooled and gas-liquid separated if necessary. The finally produced water, gas, and solid are directly recovered as energy, reused as a substance, or directly or additionally treated and disposed of. The reaction fluid discharged from the hydrothermal reaction device can also be used as a heating medium of a heating device for preheating sludge.

[0028]

As described above, according to the present invention, a decomposing device and a hydrothermal reaction device are provided, and mucus in sludge is decomposed by the decomposing device, and then in a supercritical or subcritical state in the hydrothermal reaction device. Since it is oxidatively decomposed by a hydrothermal reaction, the sludge's fluidity and adhesiveness are improved in the decomposition device, which prevents a decrease in heat transfer efficiency during preheating, and
It is possible to prevent the clogging of the pipes, and to simplify the pressure resistance of the high-pressure pump that supplies the sludge to the hydrothermal reactor, and to stabilize the sludge even when treating sludge that has low fluidity and tends to adhere. Can be processed efficiently.

[0029]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a system diagram of a sludge treatment device according to an embodiment. In FIG. 1, 1 is a sludge storage tank, 2 is a sludge crushing device, 3 is an ozone treatment tank as a decomposition device, 4 is a heat exchanger, 5 is a hydrothermal reaction device, 6 is a solid separator, 7 is an oxidizer tank, 8 is a gas-liquid separator.

A sludge supply passage 10 for introducing sewage sludge is connected to the sludge storage tank 1, and a system passage 12 having a pump 11 is connected from the sludge storage tank 1 to the sludge crushing device 2. The ozone treatment tank 3 is connected to a system path 13 that communicates with the sludge crushing device 2, an ozone supply path 15 that introduces ozone generated by the ozone generator 14, and an ozone discharge path 16 that discharges waste ozone. The ozone treatment tank 3 introduces the sewage sludge crushed by the sludge crushing device 2, blows the ozonized air generated by the ozone generator 14 from the ozone supply passage 15 to contact the sewage sludge, and removes the viscous matter in the sewage sludge. It is configured to disassemble.

A system path 22 having a high-pressure pump 21 for supplying sewage sludge decomposing mucilages is connected to a supply device 23 provided above the hydrothermal reaction device 5 from the ozone treatment tank 3 via the heat exchanger 4. I am in touch. In the supply device 23, the system passage 2 including the high pressure pump 24 from the oxidant tank 7 for supplying the oxidant
5 is in touch. This supply device 23 is attached so as to supply a mixed flow of an oxidant and sewage sludge to the hydrothermal reaction device 5 as a downward flow.

The hydrothermal reactor 5 has a hollow reactor having a mixing reaction zone accompanied by backflow in the upper part and a plug flow reaction zone in the lower part. The hydrothermal reaction device 5 is optionally provided with a heating device. From the lower part of the hydrothermal reactor 5 to the line 26
Communicate with the heat exchanger 4 via the solid separator 6, and the system path 27 communicates with the gas-liquid separator 8 from the heat exchanger 4. A gas discharge passage 32 having a pressure reducing valve 31 and a liquid discharge passage 34 having a pressure reducing valve 33 communicate with the outside of the system from the gas-liquid separator 8. Although a pump, a valve and the like are required in the above device, they are omitted in the drawing.

The processing in the above apparatus is performed as follows. First, the system path 12 from the sludge storage tank 1 by the pump 11
The sewage sludge is introduced into the sludge crushing device 2 through the sewage sludge to crush the sewage sludge. The crushed sewage sludge is introduced into the ozonization tank 3 through the system line 13, the ozonized air generated by the ozone generator 14 is blown from the ozone supply line 15 and brought into contact with the sewage sludge, and the mucilage in the sewage sludge Disassemble. This improves the fluidity and / or the adhesion of the sewage sludge. For this reason, sewage sludge is prevented from adhering to the heat transfer surface of the heat exchanger 4, the system passages 22 and the like, and the heat transfer efficiency is not reduced and the piping is not blocked. Further, the pressure resistance of the high-pressure pump 21 used for supplying the sewage sludge to the hydrothermal reaction device 5 can be more simplified, and a stable supply can be achieved. Further, since it becomes possible to treat high-concentration sewage sludge, auxiliary fuel becomes unnecessary, or the amount used can be reduced even when used. Waste ozone is ozone discharge channel 1
Discharge from 6 to the outside of the system.

The sewage sludge decomposing mucus is a high-pressure pump 2
After being introduced into the heat exchanger 4 from the system line 22 by 1 and preheated, it is sent to the supply device 23 of the hydrothermal reaction device 5. Here, the high pressure pump 24 mixes with the oxidant (for example, air, hydrogen peroxide solution) sent from the oxidizer tank 7 and the mixed flow is supplied to the hydrothermal reaction device 5 in a downward flow to generate hydrothermal heat. Perform the reaction. In the hydrothermal reaction apparatus 5, the hydrothermal reaction is carried out while keeping the water in a supercritical or subcritical state.

The mixed flow supplied from the supply device 23 forms a mixed reaction zone accompanied by a reverse flow in the upper part of the hydrothermal reaction device 5 to undergo oxidative decomposition, and the turbulent flow is eliminated in the lower part to form a plug flow reaction region. To form an additional reaction. Since the high-concentration sewage sludge can be supplied to the hydrothermal reaction device 5, the temperature of the hydrothermal reaction can be maintained only with the heat amount of the organic component in the sewage sludge or with a small amount of auxiliary fuel. For example, the reaction temperature is 6
The temperature can be maintained at 00 ° C. or higher, and therefore, the reaction can be performed at a high temperature to decompose ammonia at a high decomposition rate.

The reaction product of the hydrothermal reaction apparatus 5 is introduced into the solid separator 6 from the system path 26 to separate solids, and the separated solids are discharged from the solid discharge path 35. The separated reaction product is introduced into the heat exchanger 4 to heat the sewage sludge to cool itself, and then the gas-liquid separator 8 separates the gas into a gas discharge path 3
The gas is discharged from 2 and the treated water is discharged from the liquid discharge path 34.

As the hydrothermal reaction apparatus 5, Japanese Patent Laid-Open No. 11-15
The device shown in 6186 is preferred, but other devices may be used. A compressor may be used instead of the high pressure pump 24.

[Brief description of drawings]

FIG. 1 is a system diagram of a sludge treatment device according to an embodiment.

[Explanation of symbols]

1 sludge storage tank 2 Sludge crusher 3 Ozone treatment tank 4 heat exchanger 5 Hydrothermal reactor 6 Solid separator 7 Oxidizer tank 8 gas-liquid separator 10 Sludge supply channel 11 pumps 12, 13, 22, 25, 26, 27 route 14 Ozone generator 15 Ozone supply path 16 Ozone discharge channel 21, 24 High pressure pump 23 Feeder 31, 33 Pressure reducing valve 32 gas discharge path 34 Liquid discharge path 35 Solid discharge path

Claims (3)

[Claims] 1. A decomposing device for decomposing mucilage in sludge, and a hydrothermal reaction device for oxidatively decomposing sludge decomposing mucus in sludge by hydrothermal reaction in a supercritical or subcritical state of water. Sludge treatment equipment. 2. The sludge treatment device according to claim 1, wherein the decomposing device is an ozone treatment device for decomposing viscous matter by bringing ozone into contact with sludge. 3. The sludge treatment device according to claim 1, further comprising a heating device for preheating the sludge at a stage subsequent to the decomposition device.