JP4629883B2 - Oxidation treatment apparatus for organic treatment liquid and scale removal method thereof - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an oxidation treatment apparatus for an organic treatment liquid that decomposes and purifies an organic treatment liquid containing various organic substances by oxidation under high temperature and high pressure, in particular, supercritical water oxidation or subcritical water oxidation, and a scale removal method thereof. It is about.
[0002]
[Prior art]
For example, by utilizing the fact that even difficult-to-decompose harmful organic substances such as PCBs are decomposed quickly and efficiently at high temperatures and pressures, especially in supercritical water, organic processing liquids containing various organic substances can be converted into supercritical water oxidation or sublimation. An oxidation treatment apparatus for organic liquids to be decomposed and purified by critical water oxidation (which is less efficient than supercritical water oxidation and is also called wet oxidation) has been developed. Such a conventional general organic processing liquid oxidation treatment apparatus mainly comprises a reactor, a heating / pressurizing means, a discharging means, and a heat exchanger.
[0003]
This reactor is a cylindrical container or the like that causes an organic reaction liquid to undergo an oxidation reaction under high temperature and high pressure, and includes a vertical type and a horizontal type. The heating / pressurizing means supplies the organic processing liquid in an appropriate state of high temperature and high pressure to the reactor. Specifically, the raw material tank for storing the organic processing liquid, the raw material High-pressure pump that pumps the organic processing liquid in the tank to the reactor at high pressure, heat exchanger that heats the organic processing liquid by heat exchange with the high-temperature processing liquid discharged from the reactor, organic processing Equipped with a temperature controller that controls the liquid to a predetermined temperature. The discharge means discharges the treatment liquid after the oxidation reaction from the reactor. Specifically, the discharge means is equipped with a cooler for cooling the high-temperature and high-pressure treatment liquid after the reactor, a pressure reducing valve for reducing the pressure, and the like. .
[0004]
[Problems to be solved by the invention]
In the organic treatment liquid oxidation treatment apparatus, since the organic treatment liquid to be treated contains various organic substances, salts, etc., the reactor, the heat exchanger, the organic treatment liquid, and the treatment liquid A scale is formed on the inner wall of the main pipe or the like through which organic matter is circulated due to the accumulation of organic substances or the like and the adhesion of char, and there is a risk of clogging. In particular, since the solubility of the salt in the supercritical state is significantly lower than that in the subcritical state, the salt or the like is likely to precipitate with the change of the state of the organic liquid to be processed to the supercritical state, and scale is likely to be generated on the inner wall. This scale is difficult to remove by passing water at room temperature and pressure, compared to organic matter and char.
[0005]
As a method for removing such scale, conventionally, (a) after the operation of the oxidation treatment apparatus is stopped and the temperature / pressure of the reactor or the like is lowered to room temperature / normal pressure, the organic treatment liquid is replaced with nitric acid. A method of chemically washing the inner wall scale by circulating phosphoric acid or the like, and (b) similarly, after stopping the operation completely, periodically or partially decomposing the oxidation treatment apparatus, A method of cleaning by, for example, is employed.
[0006]
In the method (a) above, nitric acid used for cleaning needs to be handled with care, safety measures are required, post-processing of cleaning waste liquid occurs, and the operation of the oxidation processing device needs to be stopped. In addition, there is a disadvantage that the durability of the reactor, main piping and the like is hindered due to large corrosiveness such as nitric acid used for cleaning. On the other hand, in the method (b), since the operation of the oxidation treatment apparatus is completely stopped and disassembled, the work is large and there is a disadvantage that a great amount of cost is generated.
[0007]
The present invention has been made in view of these disadvantages, and it is not necessary to lower the temperature and pressure during operation to room temperature and normal pressure, and it does not impair the durability of the device, and more safely and quickly forms on the inner wall. It is an object of the present invention to provide an organic treatment liquid oxidation treatment apparatus capable of removing the scale and a scale removal method thereof.
[0008]
[Means for Solving the Problems]
The present inventor noticed that the solubility of salts and the like is significantly improved in the subcritical state as compared to the supercritical state, and switched to the organic liquid to be treated in the oxidation treatment apparatus to change the subcritical state cleaning liquid. It was found that the scale formed on the inner wall was effectively removed by the circulation.
[0009]
As a result, the invention made to solve the above-mentioned problems is a method for removing the scale of an oxidation treatment apparatus that decomposes and purifies an organic liquid to be treated by oxidation reaction under high temperature and high pressure. The organic treatment liquid is a cleaning liquid, and this cleaning liquid is circulated in a subcritical state.
[0010]
According to the scale removal method of the oxidation treatment apparatus, the organic liquid to be treated is switched to the cleaning liquid, and this cleaning liquid is circulated in a subcritical state, so that it is formed on the inner wall due to the remarkably high solubility of the cleaning liquid in the subcritical state. The scale can be removed easily and quickly. In addition, the oxidation treatment equipment for organic treatment liquid generally decomposes and purifies the organic treatment liquid by supercritical water oxidation or subcritical water oxidation at a slightly lower temperature and lower pressure. Unlike the method, it is not necessary to change the temperature and pressure so much to distribute the cleaning liquid in the subcritical state. As a result, the time required for scale removal is shortened, and the temperature and pressure are required to increase and decrease. Energy and cost can be reduced.
[0011]
The temperature and pressure of the cleaning liquid to be circulated are preferably 200 ° C., 5 MPa to 374 ° C., and 22 MPa or less. Since this water has high handleability and solubility, it is suitable for the scale removal. In addition, by setting the temperature and pressure of the water to be circulated within the above range, the solubility in salts and the like is increased, the rise and fall from the temperature and pressure during operation of the oxidation treatment apparatus is reduced, and the scale removal work by the scale removal method is performed. Reduction of required energy and cost can be promoted.
[0012]
The cleaning liquid may be heated and pressurized to a subcritical state using the heating / pressurizing means of the oxidation treatment apparatus that heats and pressurizes the organic processing liquid. According to this means, the existing heating / pressurizing means can be used to bring the cleaning liquid into a subcritical state, and it is not necessary to separately add heating / pressurizing means for the scale removal method. Increase in cost can be suppressed. In addition, since the heating / pressurizing means of the oxidation processing apparatus is used to bring the cleaning liquid into a subcritical state, an operation of simply switching the organic processing liquid to the cleaning liquid during operation of the oxidation processing apparatus and heating of the oxidation processing apparatus are performed.・ Scaling and removing the scale can be performed continuously from the operation of the oxidation treatment device by a little temperature / pressure control by the pressurizing means, and the oxidation treatment device can be operated continuously from the scale removal work by the reverse operation. It can be performed. Therefore, according to the means, the operation stop time for the scale removal work is further shortened, which contributes to the improvement of the operating rate.
[0013]
As the oxidation reaction in the oxidation treatment apparatus, supercritical water oxidation or subcritical water oxidation is preferable. According to such supercritical water oxidation (SCWO) and subcritical water oxidation, it is possible to quickly and completely decompose and purify organic processing liquids containing various organic substances. However, as described above, the difference in solubility of salts Therefore, the scale removal method is effective because salts are likely to be deposited along with the state change from the subcritical state to the supercritical state, and scale is easily formed on the inner wall.
[0014]
The invention of an apparatus for solving the above-mentioned problems includes a reactor for decomposing and purifying an organic processing liquid by an oxidation reaction at high temperature and high pressure, and heating and heating the organic processing liquid in the reactor. An organic treatment liquid oxidation treatment apparatus comprising heating / pressurization means for supplying under pressure and discharge means for discharging the treatment liquid after the oxidation reaction from the reactor, wherein the organic treatment liquid is washed And a scale removing means for circulating the cleaning liquid in a subcritical state.
[0015]
According to the oxidation treatment apparatus for the organic treatment liquid, similarly to the scale removal method of the oxidation treatment apparatus, the organic treatment liquid to be treated is switched to the cleaning liquid by the scale removing unit, and the cleaning liquid is subcritical. Since it is circulated in a state, the scale formed on the inner wall can be easily and quickly removed due to the remarkably high solubility of the cleaning liquid in the subcritical state. In addition, the organic treatment liquid oxidation treatment apparatus can perform scale removal work continuously in the processing operation, and it is not necessary to fluctuate temperature and pressure so much. Is achieved.
[0016]
Furthermore, for the same reason as the scale removal method of the oxidation treatment apparatus, (a) in the scale removal means, the cleaning liquid is water, and the temperature and pressure of the cleaning liquid to be circulated are 200 ° C., 5 MPa to 374 ° C., and 22 MPa or less. Well, (b) In the scale removing means, the cleaning liquid may be heated and pressurized to a subcritical state by the heating and pressurizing means, and (c) supercritical water oxidation or oxidation may be performed as the oxidation reaction at the high temperature and high pressure. Subcritical water oxidation is preferred.
[0017]
In addition, it is preferable that the oxidation treatment apparatus for the organic treatment liquid further includes a scale monitoring unit that monitors the formation of scale. If the scale monitoring means can monitor the presence and degree of scale formation on the inner wall, the appropriate timing for removing the scale by the scale removing means and the time required for the removal work can be known. It is possible to further promote the improvement of the operation rate and the reduction of the cost required for scale removal.
[0018]
As this scale monitoring means, it is preferable to adopt means for measuring the pressure at the entrance and exit, and determining the presence and degree of scale formation based on the pressure difference. According to the scale removal means in the oxidation treatment apparatus for the organic treatment liquid, since almost the entire oxidation treatment apparatus can be washed by circulating the subcritical cleaning liquid switched from the organic treatment liquid, an accurate scale can be obtained. It is not necessary to detect the formation position, and it is only necessary to detect whether or not a scale of a predetermined level or more has been formed as a whole apparatus. Therefore, the scale monitoring means is based on the increase in the pressure difference at the inlet / outlet as a reference. It is sufficient to determine the presence and degree of formation.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings as appropriate. FIG. 1 is a schematic configuration diagram showing an organic treatment liquid oxidation treatment apparatus according to an embodiment of the present invention.
[0020]
The organic treatment liquid oxidation treatment apparatus 1 in FIG. 1 includes a reactor 2, a high-pressure pump 3, a heat exchanger 4, a temperature controller 5, an oxidant supply means 6, a cooler 7, a decompressor 8, and gas-liquid separation. A tank 9 is provided, and in addition, a scale removing means 10 is provided. Among these, the high pressure pump 3, the heat exchanger 4 and the temperature controller 5 correspond to the heating / pressurizing means, and the cooler 7, the decompressor 8 and the gas-liquid separation tank 9 correspond to the discharging means.
[0021]
The high-pressure pump 3 pumps the organic processing liquid A stored in a raw material tank or the like to the reactor 2, and for example, a plunger pump, a diaphragm pump, a screw pump, or the like is used.
[0022]
The heat exchanger 4 exchanges heat between the processing liquid discharged from the reactor 2 and the organic processing liquid A, and preheats the organic processing liquid A with a high-temperature and high-pressure processing liquid. As this heat exchanger 4, a general heat exchanger for high temperature resistance and high pressure resistance can be used, but in consideration of using a high-temperature / high-pressure and high-concentration liquid as a working fluid, a double pipe type A heat exchanger is preferred.
[0023]
The temperature controller 5 is for controlling the organic liquid A to be sent to the reactor 2 to a predetermined oxidation reaction temperature, and requires contradictory functions of heating and cooling. For this reason, as the temperature controller 5, there are a case where separate devices such as a heater and a cooler are provided, and a case where both devices are provided. The heating means and the cooling means in the temperature controller 5 are not particularly limited, and general means can be used.
[0024]
The reactor 2 is for decomposing and purifying an organic substance in the organic liquid A to be treated under high temperature and high pressure (for example, a supercritical state or a subcritical state). The type of the reactor 2 is not particularly limited, and a general reactor for high temperature resistance and high pressure resistance can be used, but the organic treatment liquid A is continuously decomposed. In view of the above, a tubular reactor is preferable. The temperature and pressure in the reactor 2 are preferably 200 ° C. to 650 ° C., 5 MPa to 30 MPa, and supercritical water oxidation at 400 ° C. to 600 ° C. and 22 MPa to 30 MPa is preferred in terms of rapidity and completeness of the reaction. Particularly preferred.
[0025]
The oxidant supply means 6 is for injecting an oxidant into the organic treatment liquid A in order to cause an oxidation reaction to the organic matter in the organic treatment liquid A in the reactor 2. As the oxidant used in the oxidant supply means 6, for example, oxygen is used, but air having an oxidizing power with respect to organic substances, hydrogen peroxide water, and the like can also be used. Further, as the supply point of the oxidant by the oxidant supply means 6, all the amount necessary for the decomposition of the organic matter in the organic liquid A to be treated may be injected immediately before the reactor 2, or immediately before the reactor 2. You may divide and supply to the suitable position of the reactor 2. FIG.
[0026]
The cooler 7 is for cooling the high-temperature and high-pressure processing liquid discharged from the reactor 2, and a general cooler such as an air cooler can be used. It is also conceivable to use waste heat effectively by cooling with a refrigerant.
[0027]
The decompressor 8 is for decompressing the high-temperature and high-pressure treatment liquid discharged from the reactor 2, and generally a decompression valve or the like is used.
[0028]
The gas-liquid separation tank 9 is a tank that separates the treated liquid discharged from the reactor 2 into clean water B that has been decomposed and discharged gases C such as carbon dioxide and nitrogen generated by the oxidation reaction of organic matter.
[0029]
The function of the organic treatment liquid oxidation treatment apparatus 1 having the above structure will be described below. First, the organic treatment liquid A is supplied to the reactor 2 by being pressurized and heated by the high-pressure pump 3 of the heating / pressurizing means, the heat exchanger 4 and the temperature controller 5, and organically by the oxidizing agent supplying means 6. When the oxidizing agent is supplied into the oxidizing liquid A, the organic substance is oxidized and decomposed in the reactor 2 by an oxidation reaction between the organic substance and the oxidizing agent in the organic processing liquid A. Thereafter, the processing liquid discharged from the reactor 2 is cooled, depressurized and gas-liquid separated by a cooler 7, a decompressor 8 and a gas-liquid separation tank 9 as discharge means, and discharged to the outside. Through such steps, the organic processing liquid A containing organic matter is decomposed and purified.
[0030]
The organic treatment liquid oxidation treatment apparatus 1 includes a scale removing means 10 for removing scales formed on the inner walls of the reactor 2, the organic treatment liquid A, the main pipe of the treatment liquid, and the like. The scale removing means 10 switches the organic liquid A to be processed by the oxidation treatment apparatus 1 to the cleaning liquid D, and distributes the cleaning liquid D in a subcritical state. In this scale removing means 10, as means for heating and pressurizing the cleaning liquid D to the subcritical state, the high pressure pump 3, the heat exchanger 4, the temperature regulator 5 and the pressure reducing valve of the organic treatment liquid oxidation treatment apparatus 1 are used. 8, that is, by switching to the cleaning liquid D while maintaining the operation state in which the organic processing liquid A is decomposed and purified, and slightly controlling the high pressure pump 3, the heat exchanger 4, the temperature controller 5 and the pressure reducing valve 8. The cleaning liquid D can be brought into a subcritical state.
[0031]
The specific temperature and pressure of the subcritical cleaning liquid D circulated by the scale removing means 10 are 200 ° C. and 5 MPa when safe and highly handleable water (pure water or tap water) is used as the cleaning liquid D. 374 ° C. and 22 MPa or less are preferable, and 300 ° C., 15 MPa and 374 ° C., and 22 MPa or less are particularly preferable. This is because if the temperature and pressure of the cleaning liquid D are smaller than the above ranges, the difference between the temperature and pressure of the organic processing liquid A during operation of the oxidation treatment apparatus 1 is large, and the temperature lowering / decreasing and operation during scale removal work are large. This is because time and energy are required for temperature increase and pressure increase at the time of restart, and scale removal ability is reduced. Conversely, when the temperature and pressure of the cleaning liquid D exceed the above range, a supercritical state is obtained. This is because the solubility decreases and the scale removal ability decreases.
[0032]
For example, when the oxidation treatment apparatus 1 is an apparatus for decomposing and purifying the organic liquid to be treated A by supercritical water oxidation under an operating condition of about 550 ° C. and about 26 MPa, after the scale removal means 10 switches to the cleaning liquid D The pressurizing condition by the high-pressure pump 3 is maintained as it is, and the heating condition by the heat exchanger 4 and the temperature controller 5 is preferably heated so that the cleaning liquid D is about 350 ° C. As a result, the operation of the oxidation treatment apparatus 1 is continued, and in the thermal relationship, cooling to the room temperature and heating to the supercritical temperature are not required for the scale removal work and the resumption of operation, and in the pressure relationship, the scale is reduced. Unnecessary step-down and step-up are not required for the removal operation and the restart of operation. Therefore, the time required for the scale removal operation can be shortened and the cost can be reduced.
[0033]
In addition, the organic treatment liquid oxidation treatment apparatus 1 may include scale monitoring means for monitoring the presence and degree of scale formation. When the scale monitoring unit detects the formation of a scale above a predetermined level, the scale removing unit 10 performs the scale removal operation, and when the scale monitoring unit detects the scale removal, the scale removing unit 10 Then, the scale removal operation is completed, and then the cleaning liquid D is continuously switched to the organic processing liquid A to shift to the normal operation. By providing the scale monitoring means in this way, it is possible to optimize the timing and work time for performing the scale removal work by the scale removal means 10.
[0034]
As the scale monitoring means, (1) a pressure gauge 11 for measuring the internal pressure is installed, the pressure at the inlet / outlet of the equipment such as the reactor 2, the heat exchanger 4 and the main pipe is measured, and the judgment is made by increasing the pressure difference. Various means such as (2) means for measuring the external surface temperature of the above-mentioned device and judging from the change over time, (3) means for judging from the flow velocity, etc. According to this, since the scale removal of the entire oxidation treatment apparatus 1 is possible and there is no need to partially detect the scale formation location, the presence / absence and degree of scale formation can be determined by the pressure difference at the inlet / outlet of (1) which is easy to monitor. Means for determining are preferred.
[0035]
The organic treatment liquid oxidation treatment apparatus and the scale removal method thereof according to the present invention are not limited to the above-described embodiment. For example, a means for heating and pressurizing the cleaning liquid D to a subcritical state is separately provided. It is also possible to circulate through the oxidation treatment apparatus 1 as a critical state. Further, the liquid discharged from the gas-liquid separation tank 9 during the scale removing operation by the scale removing means 10 may be circulated in the cleaning liquid D. Further, the scale monitoring means may be periodically performed by the scale removing means 10 without providing the scale monitoring means.
[0036]
【The invention's effect】
As described above, according to the organic treatment liquid oxidation treatment apparatus and scale removal method of the present invention, scales formed on the inner wall of a reactor or the like can be removed easily and quickly. In addition, since the scale removal operation can be performed without significantly changing the temperature and pressure during operation of the oxidation treatment apparatus, energy and cost can be reduced.
Furthermore, the scale formed on the inner wall can be removed safely and quickly without impairing the durability of the oxidation treatment apparatus.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram showing an organic treatment liquid oxidation treatment apparatus according to an embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Oxidation processing apparatus 2 of organic to-be-processed liquid 2 Reactor 3 High pressure pump 4 Heat exchanger 5 Temperature controller 6 Oxidant supply means 7 Cooler 8 Depressurizer 9 Gas-liquid separation tank 10 Scale removal means 11 Pressure gauge

Claims (8)

A method for removing the scale of an oxidation treatment apparatus for decomposing and purifying an organic liquid to be treated by oxidation reaction under high temperature and high pressure,
An organic treatment liquid to be treated by this oxidation treatment apparatus is switched to water , and water is circulated in a subcritical state at a temperature of 200 ° C. to 374 ° C. and a pressure of 5 MPa to 22 MPa . Scale removal method. The oxidation treatment apparatus organic liquid to be treated is provided with a heating and pressurizing means for heating and pressurizing, the oxidation described by this heating and pressing means to claim 1, heating and pressurizing the water in a subcritical state A scale removal method for a processing apparatus. The scale removal method for an oxidation treatment apparatus according to claim 1 or 2 , wherein the oxidation reaction in the oxidation treatment apparatus is supercritical water oxidation or subcritical water oxidation. A reactor for decomposing and purifying organic processing liquid by oxidation reaction under high temperature and high pressure;
An apparatus for oxidizing organic processing liquid, comprising heating / pressurizing means for heating and pressurizing and supplying the organic processing liquid to the reactor, and discharge means for discharging the processing liquid after the oxidation reaction from the reactor Because
Oxidation of the organic processing liquid characterized by comprising scale removing means for switching the organic processing liquid to water and circulating the water in a subcritical state at a temperature of 200 ° C. to 374 ° C. and a pressure of 5 MPa to 22 MPa. Processing equipment. The organic treatment liquid oxidation treatment apparatus according to claim 4 , wherein in the scale removing means, water is heated and pressurized to a subcritical state by the heating and pressurizing means. Oxidizing apparatus of the organic liquid to be treated according to claim 4 or claim 5 oxidation reaction under the high temperature and high pressure is supercritical water or subcritical hydroxide. Oxidizing apparatus of the organic liquid to be treated according to any one of claims 4 to 6 further comprising a scale monitoring means for monitoring the formation of scale. 8. The organic treatment liquid oxidation treatment apparatus according to claim 7 , wherein the scale monitoring means measures the pressure at the entrance and exit, and determines the presence and degree of scale formation based on the pressure difference.

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