JPH108076A - Deep-layer hydrothermal reaction processing of organic waste - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the subject processing method designed both to cool slurry after reaction and raise the temperature of the fed slurry, without the need of any special pump and any heat exchanger. SOLUTION: This hydrothermal reaction processing method is so designed that organic wastes are exposed to a high-temperature and high-pressure atmosphere in such a slurried state as to be suspended as solid fine granules in an aqueous phase to decrease the ratio of oxygen to carbon in the chemical bonds in the organic matter and produce both carbon dioxide and a combustible gas by causing reductive reaction so as to transfer halogen elements containing the chemical bonds into the aqueous phase. In this case, by using a reactor 1 having a difference of altitude in the vertical direction and having a reciprocating flow channel connected to the bottom. the slurry (a) is fed from above the upper part of the forward channel 2 of the reactor, passed through the bottom of the flow channel, discharged through the upper part of the backward channel 3, and treated. At this time, the reactor affords high pressure at the lower part of the flow channel by applying pressure produced by slurry weight due to the pressure difference between feed and discharge on the upper part of the flow channel and the difference of altitude of the flow channel and raises the temperature of the slurry through heat exchange by partitioning the reciprocating flow channel with a metallic partition wall.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydrothermal treatment method for organic waste, and more particularly to waste containing organic solids such as municipal waste, human waste, sewage sludge, and industrial waste of solid to sludge to waste liquid. The present invention relates to a hydrothermal treatment method in which a substance is heat-treated at a high temperature and a high pressure in the presence of water to convert it into a fuel.

[0002]

2. Description of the Related Art Conventionally, wastes are treated by a hydrothermal reaction as follows. In other words, in the case of waste mainly composed of coarse solids, it is finely crushed to remove inorganic components such as glass, rubble, and metals as much as possible, and is converted into a slurry containing water and having fluidity. In the case of solids that are originally fine and do not need to be crushed, such as waste liquids, or waste that contains almost no solids, if necessary, form a slurry that passes through a screen so that coarse solids are not mixed, and oxidize by pressing. 250% depending on the type of waste with the agent turned off
The temperature is raised to an appropriate temperature of 350 ° C., and usually maintained for several tens minutes to cause a hydrothermal reaction. In the course of this hydrothermal reaction,
Dissolved oxygen and chemically bonded oxygen react to generate carbon dioxide gas, and also release chemically bound halogen elements such as chlorine and bromine, and migrate to the water side to reduce some reducibility. A reduction reaction that also produces gas proceeds.

[0003] For this reason, the remaining organic components which are not changed to gas or water-soluble components are also modified into solids or oils, which are chars or oils called chars, by dehalogenation or decarboxylation. After the reaction, a flash operation for finally reducing the pressure to atmospheric pressure is carried out to degas and simultaneously lower the temperature, and at the same time, remove the halogen by washing with dehydrated water to obtain a solid content or oil content. Here, by performing the hydrothermal reduction reaction, the calorific value of the solid component or the oil component becomes brittle at the same time as the calorific value increases due to the desorption of oxygen that is chemically bonded. In addition, the molecules are divided by the hydrothermal reduction reaction, the viscosity disappears, and dehydration becomes easy. Therefore, the obtained solid content or oil content can be easily pulverized with a low heat content and a low moisture content from which halogen is removed. In this way, there is a research and development process in which the waste is used as a solid or oil fuel or a raw material for a fuel such as CWM.

[0004] In the above, the oil component is extracted with an organic solvent such as hexane or dichlorobenzene, and the cake obtained by filtering the remainder is a solid component. Oils include those that solidify at room temperature, such as tar and pitch, and those that have water solubility. The finely crushed particle size for the hydrothermal reaction is usually set to several mm or less, which does not hinder the heat transfer and the transfer of the reaction product to the water side and almost eliminates the possibility of closing the flow path. FIG. 2 shows a schematic configuration diagram of the above-described conventional treatment by hydrothermal reaction. In FIG. 2, the waste slurry a is pressurized by a high-pressure pump 20, passes through heat exchangers 21 and 22 with the product, is heated by a heating medium heater 23 using a heating medium f, and is introduced into a reactor 24. Is heated by the heat medium f from the heat medium boiler 25 to cause the hydrothermal reduction reaction to proceed. After the reaction, the temperature of the reaction product is reduced by heat exchangers 22 and 21.
A flash operation for reducing the pressure to the atmospheric pressure in the flash tank 26 is performed to degas, and at the same time, the temperature is lowered to separate the slurry into the processing slurry b and the exhaust gas c.

[0005] A technique of oxidizing sewage sludge by a deep hydrothermal reaction has been put to practical use. FIG. 3 shows a schematic configuration diagram thereof. In FIG. 3, a metal double pipe 27 is vertically installed underground at a depth of about 1200 to 1500 m, and an inner pipe 2 is provided.
8 to feed the treated sludge while mixing the oxygen gas i;
Invert at the bottom of the double tube and return to the ground through the outside 29 of the double tube. During this time, the organic matter in the sludge is oxidatively decomposed by the mixed oxygen gas. In addition, the double pipe 27
Is provided with a heat transfer fluid jacket 30 for introducing the heat transfer fluid j. In this apparatus, the outer surface of the double pipe is cooled by a water-cooling jacket 30 in order to prevent boiling of the double pipe due to reaction heat and disturbance of flow such as backflow. However, the above-mentioned treatment method by the hydrothermal reaction has the following problems. That is, 25
In order to prevent boiling even at 0 to 350 ° C, 40 to 170
The pressure required was atg or more, and it was necessary to increase the pressure using a special positive displacement pump, which required large equipment and operating costs. In addition, heating and cooling required a large heat exchanger, and heating by a heating medium boiler using fossil fuel was indispensable.

[0006]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems of the prior art, and does not require a special pump for increasing the pressure, cools the slurry after the reaction without using a heat exchanger, and supplies the slurry. It is an object of the present invention to provide a deep hydrothermal treatment method for organic waste that can be heated without using fossil fuel.

[0007]

In order to solve the above-mentioned problems, in the present invention, chemical waste in an organic substance is exposed by exposing organic waste to a slurry state in which solid fine particles are suspended in an aqueous phase at a high temperature and a high pressure. Reducing the content of oxygen to carbon in the bond to produce carbon dioxide and flammable gas,
In a hydrothermal reaction method for causing a reduction reaction in which a halogen element containing a chemical bond is transferred to the aqueous phase, a reactor having a vertical difference and a reciprocating flow path connected at the bottom When the slurry is supplied from the upper part of the outward path of the reactor and discharged from the upper part of the return path through the bottom of the flow path for processing, the pressure difference between the supply and discharge at the upper part of the flow path and the flow path The pressure generated by the slurry weight due to the difference in height is applied to obtain a high pressure at the lower part of the flow path, and the reciprocating flow path is partitioned by a metal partition wall to perform heat exchange to increase the slurry temperature. The method is a deep hydrothermal treatment method for organic waste. In the above-mentioned deep hydrothermal reaction method, an oxidizing agent can be added to the slurry on the outward path to partially oxidize organic substances in the slurry to raise the slurry, and the amount of the oxidizing agent can be reduced. It is preferable to detect and adjust the lower temperature of the flow path. The reactor used in the present invention preferably has a double pipe structure in which the inner pipe is a metal partition wall, and the outside of the partition wall is used as a forward path where the slurry descends, and the inside is used as a return path where the slurry rises.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION In the deep-water hydrothermal treatment method for organic waste of the present invention, the slurry moves down the reactor to a deeper position, whereby the pressure of the slurry increases due to the increasing gravity of the slurry itself. At the same time, heat is exchanged with the rising high-temperature slurry after the reaction via the metal flow channel wall extending on the falling side and the rising side of the reactor, and the temperature is raised. The pressure rise is 1 atm every 10 m deeper, but increases or decreases in proportion to the bulk density of the slurry, and therefore becomes smaller when bubbles are mixed. In addition, the heat exchange between the forward and return slurries alone increases the calorific value of the brought-out slurry after the reaction, so that the reaction temperature of the slurry cannot be maintained. So we have to add the heat. For this, pre-heating is performed by directly blowing steam obtained by separating the feed slurry from the slurry after the reaction in advance,
There is a method in which a heater is used to heat the slurry flow path from outside. There is also a method in which an oxidizing agent is added to the supplied slurry to cause an oxidation reaction in the slurry, and the temperature is raised by the reaction heat. This method does not particularly require a heat source, and the final slurry temperature is determined by the oxidizing agent to be added. Depends on the amount of

The oxidizing agent is preferably hydrogen peroxide, but oxygen gas or a gas containing oxygen gas such as air may be added to the slurry in the form of air bubbles. In this case, the bubbles are prevented from moving by the solid content contained in the slurry,
It descends together with the slurry, and unlike the case of sludge or waste liquid, it is unlikely that bubbles will collectively float and separate from the slurry, and they will be carried deep into the space together with the slurry. Then, it is dissolved in water at a pressure that increases as it becomes deeper, and becomes a form that easily undergoes a wet oxidation reaction. At the addition position, since the bubble volume becomes large at normal pressure or a pressure close to the normal pressure, the gas pressure is easily obtained at a liquid pressure of the slurry of about 4 to 5 atm, and the gas volume is increased to a degree that does not cause a problem. Should be at a compressed pressure. If the amount of the oxidizing agent is too large, the amount of generated heat becomes excessive, bubbles of steam are generated, and the state is not erased even at the deepest part,
This is not preferable because the residence time of the slurry under high temperature and pressure is reduced. In order to prevent this, the final slurry temperature near the lower part is detected, and the oxidizing agent is added so that the temperature at the deepest part becomes lower than the saturated steam pressure. It is desirable to adjust the amount.

Generally, the temperature is high deep underground. If the soil temperature is high, the reactors and flow paths do not need to be particularly heated or externally heated. In particular, where geothermal energy is high, the amount of preheating, heating, and the amount of oxidizing agent added to the slurry are small due to the inflow of geothermal energy.
At the start of operation, the equipment is heated up to start steady operation.Therefore, the slurry to be introduced into the reactor is sufficiently preheated, the oxidizing agent is sufficiently added, the slurry flow rate is reduced, and the temperature rises. Wait for. Once the temperature rises, the temperature can be easily adjusted by adjusting the amount of the oxidizing agent. The temperature at which the reaction changes from the temperature rule to the oxidant rule has a range of about 200 to 350 ° C. depending on the waste.
This temperature is high for cellulose, such as paper, activated sludge, and food residues.
Those containing sugars and proteins are low, and those of oils, organic acids and plastics are generally high. Oils, organic acids and plastics include cellulose, sugars, such as paper, activated sludge, and food residues.
When processed together with protein-containing waste, it becomes possible to control the temperature at a low temperature and thus at a low pressure according to the oxidizing agent rule. Further, in order to stably react to the composition fluctuation of the waste in accordance with the oxidant rule, at least 250 to 350
It is desirable that the temperature be equal to or higher than ° C.

The depth of the flow path is at least 500 m,
Preferably, it is good to be about 1000 to 1500 m.
The deeper, the higher the pressure, the lower the boiling, and the higher the temperature that can be raised. Specifically, the temperature at which the temperature can be raised is about 260 ° C. at a depth of 500 m, about 310 ° C. at a depth of 1000 m, and 15 ° C.
It is about 340 ° C at 00m. The cross-sectional area of the flow passage should be almost uniform on all roads because it is stored in the borehole,
On the other hand, it is preferable to widen the return path (ascending path) and make the outward path and the return path substantially uniform from top to bottom. By widening the return path, it is possible to obtain a longer residence time after the high temperature, and at the same time, it is possible to obtain an effect of increasing the flow velocity so that the mixed gas easily accompanies the slurry in the forward path. The flow rate is 0.3 to an average so that the residence time is 0.5 to 1.5 hours at a reaction temperature of 300 ° C.
It is appropriate to set it to about 1.2 m / s. Naturally, the higher the temperature, the shorter the residence time, and the longer the flow path, so that the flow velocity can be increased. At a depth of 500 m, the average flow rate of reciprocation is 0.08 to 0.3 m / s so that the residence time is about 1 to 3 hours at a temperature rise to about 250 ° C.
It must be lowered to 1500 m, but at a depth of 1500 m 33
By raising the temperature to about 0 ° C., the average flow rate of reciprocation in which the residence time is less than 1 hour can be increased to 1 m / s or more. Specifically, for example, when the depth is 500 m, the waste 400 tons /
Since the daily treatment is diluted five times with water, the total cross-sectional area of the outward and return paths is 0.463 m ² when the average reciprocating flow velocity is 0.1 m / s. In this case, the diameter is less than 0.8 m. Depth 100
If 0.5 m / s is set as 0 m, the diameter may be less than 0.35 m.

[0012] The slurry, which is cooled by lowering the reactor and heated, gradually consumes the oxidant by the hydrothermal oxidation reaction, including the case where the oxidant is added, and the temperature rise due to generation of reaction heat slows down. Exhaustion, the hydrothermal reduction reaction proceeds, the reversal occurs at the deepest point, and the heat exchanges with the descending slurry through the metal partition walls, thereby increasing the temperature while decreasing the temperature and reducing the pressure. Go on. The hydrothermal reduction reaction continues until the temperature drops sufficiently to make it impossible to proceed. Here, since a temperature gradient is required for heat exchange, the temperature of the return path on the ascending side is higher than that of the outward path on the descending side. Therefore, the saturated vapor pressure at the temperature of the slurry becomes higher than the pressure of the slurry on the way, and the water in the slurry boils by that amount, so that the pressure of the slurry falls to a temperature at which the saturated vapor pressure is almost saturated, and rises. As the temperature decreases, the gas content is increased while the temperature is reduced. The ascending slurry becomes a solid-gas-liquid three-phase flow due to the generated gas containing saturated steam, and loses weight as compared to the descending slurry to generate buoyancy, thereby generating a force for sucking the descending slurry. No special power is required. Conversely, it is preferable to restrict the discharge at the slurry discharge section so that the slurry supply section does not become excessively unpressurized so as to have a pressure. This pressure may be controlled by the pressure of the slurry supply unit.

When a gas such as oxygen gas or air is used as the oxidizing agent, it is desirable to increase the set pressure in order to reduce the volume of added gas and promote dissolution. Of course, by setting the pressure to be high, the gas volume in the slurry can be made small, and the cross section of the flow path for raising or lowering the slurry can be made small. Generally, it is desirable that the pressure of the slurry supply unit be about 2 to 3 atm. As described above, the organic waste is converted into a slurry state in which solid fine particles are suspended in an aqueous phase, and is reacted at a high pressure and a high temperature at a saturated steam pressure equal to or lower than the high pressure. By reducing the content of oxygen to carbon in the chemical bond,
At the same time that the carbon dioxide gas and the combustible gas are generated, a hydrothermal reduction reaction in which the contained halogen element containing a chemical bond is transferred to the aqueous phase proceeds. If this is cooled to 100 ° C. or lower and dehydrated to separate an oil component and a solid component, a brittle solid having a low moisture content and a high calorific value can be obtained. It can be used as a fuel as it is, or it can be pulverized in water and stabilized in an emulsion state by a surfactant to make it similar to a liquid fuel similar to CWM.

The flow path for descending and ascending with the slurry of the reactor has a double-pipe structure reverse to the known deep-water hydrothermal oxidation of sludge, the inner pipe is a metal partition wall, and the outside is the descending side of the outward path. It is good to set the inside as the rising side of the return path. this is,
Eliminating the horizontal temperature distribution in each channel wall almost eliminates the distortion, bending, and stress generation of the channel due to the difference in thermal expansion due to the temperature difference, and the action of the viscous and solid slurry contained inside the slurry The slurry descending side of the outward path, in which mixing is less likely to occur and the content of gas is small, is defined as a hollow circular flow path cross section, and the slurry rising side of the low viscosity return path, which has a high content of gas, is defined as a simple circular cross section. This is to suppress backflow and stagnation of the flow in the cross-sectional direction of the liquid-solid multiphase flow. In addition, by bringing the slurry on the low temperature side to the outside, it has various advantages such as suppressing heat dissipation, increasing the amount of geothermal inflow, and preventing burns. Further, since the temperature rise due to the oxidation reaction occurs on the lower side of the slurry, it is easier to detect the temperature for adding the oxidizing agent, control the temperature, and measure the progress of the reaction by setting the lower side of the slurry to the outside.

[0015] Even if the temperature of the slurry rises before the slurry reaches a deep portion because the oxidation reaction proceeds rapidly,
Boiling removes heat in the form of latent heat of vaporization, stays at a temperature of saturated steam pressure corresponding to the pressure at that depth, and moves in a direction to control the reaction. In addition, the generated steam is stopped by the solid content contained in the slurry,
It is held in the slurry without being separated or floated, and at a pressure increasing as it goes deeper, the steam condenses while releasing its latent heat of vaporization and returns to water again, so this is not a problem. At the slurry outlet of the reactor, the entrained gas containing water vapor is separated from the slurry after the reaction, and then blown into the supply slurry to reduce the amount by condensation of water vapor and the like, and at the same time, preheat the supply slurry.

Next, the processing method of the present invention will be specifically described with reference to the drawings. FIG. 1 shows a schematic configuration diagram of an apparatus used in the deep hydrothermal reaction method of the present invention. In FIG. 1, a reactor 1 has an outer pipe 2 and an inner pipe 3, a gas-liquid separation tank 6 is provided on the upper part of the inner pipe 3, and an air header 4 is provided in the middle of the outer pipe 2. Compressed air d provided as oxidant
Is connected to Waste slurry a is supplied to the preheating tank 5
And is preheated by the steam e separated in the gas-liquid separation tank 6, and the pressure of the slurry supply unit is 2 to 3
The regulating valve 8 is controlled by the pressure regulator 10 so that the pressure becomes the atmospheric pressure. The preheat tank 5 has a level controller 1
2 is provided, and the flow rate in the tank 5 is adjusted by controlling the discharge amount of the exhaust gas c by the adjustment valve 9.

Next, the slurry is introduced from the preheating tank 5 into the upper portion of the outer tube 2 of the reactor 1, descends the outer tube 2, and proceeds with the hydrothermal reduction reaction while increasing the temperature and pressure. At this time, the temperature of the slurry is measured by a monitoring thermometer 15 arranged at the lower part of the outer tube. If the slurry temperature does not rise to a predetermined temperature, the adjustment valve 13 of the compressed air d is controlled by a command from the temperature control instrument 14. Open the outer tube pressure is 4 ~
Air d is introduced from the air header 4 at a position of 5 atm. Thereby, the slurry temperature rises and reaches a predetermined temperature.
Then, the slurry reaches a predetermined temperature and pressure at the lowermost end of the reactor 1, reverses, rises from the inner tube 3, lowers the temperature while exchanging heat with the slurry that descends, and reaches the gas-liquid separation tank 6. In the gas-liquid separation tank 6, the slurry subjected to the hydrothermal reduction reaction is extracted while controlling the regulating valve 7 based on a signal from the level controller 11, while the discharged steam is used for preheating the supplied slurry in the preheating tank 5. Used. The extracted processing slurry is cooled and separated into solid and liquid, and is used as fuel or the like.

[0018]

According to the present invention, a high pressure is obtained without using a high-pressure pump, and the heat of the slurry after the reaction is cooled without using a heat exchanger, and at the same time, the heat is used to raise the temperature of the supplied slurry. The shortage of heat can be compensated only by adding an oxidizing agent such as air to the supply slurry. Therefore, the facility for the hydrothermal treatment of waste is simplified and the energy balance is greatly improved.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing an example of an apparatus used for a deep hydrothermal reaction method of the present invention.

FIG. 2 is a schematic configuration diagram of a conventional hydrothermal reduction reaction processing apparatus.

FIG. 3 is a schematic configuration diagram of a known sludge hydrothermal oxidation treatment apparatus.

[Explanation of symbols]

1: deep-water hydrothermal reactor, 2: outer tube, 3: inner tube, 4: air header, 5: preheating tank, 6: gas-liquid separation tank, 7, 8,
9: regulating valve, 10: pressure regulator, 11, 12: level regulator, 13: regulating valve, 14: temperature control instrument, 15: monitoring thermometer, a: waste slurry, b: treated slurry,
c: exhaust gas, d: compressed air, e: steam,

Claims (4)

[Claims] An organic waste is exposed to a high temperature and a high pressure in a slurry state in which solid fine particles are suspended in an aqueous phase to reduce the content ratio of oxygen to carbon in a chemical bond in an organic substance, thereby reducing carbon dioxide and combustible gas. In a hydrothermal treatment method in which a reactive gas is generated and a halogen element containing a chemical bond contained therein is transferred to the aqueous phase to cause a reduction reaction, the liquid has a vertical difference in height and is connected at the bottom. In a reactor having a reciprocating flow path, the slurry is supplied from the upper part of the outward path of the reactor, and is discharged from the upper part of the return path through the bottom part of the flow path for processing. And the pressure generated by the weight of the slurry due to the height difference of the flow path, thereby obtaining a high pressure at the lower part of the flow path and performing heat exchange by partitioning the reciprocating flow path by a metal partition wall. A deep hydrothermal treatment method for organic waste, characterized in that the temperature is raised to a high temperature. 2. The deep hydrothermal reaction of organic waste according to claim 1, wherein an oxidizing agent is added to the slurry on the outward path to partially oxidize organic substances in the slurry to raise the temperature of the slurry. Processing method. 3. The deep hydrothermal treatment method for organic waste according to claim 2, wherein the amount of the oxidizing agent is adjusted by detecting the lower temperature of the flow path. 4. The reactor according to claim 1, wherein the reactor has a double pipe structure in which an inner pipe is a metal partition wall, the outside of the partition wall is a forward path where slurry descends, and the inside is a return path where slurry rises. Item 3. The method for treating a deep hydrothermal reaction of organic waste according to item 1 or 2.