JP3333687B2 - Supercritical water oxidation treatment equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a supercritical water oxidation treatment apparatus used for decomposing various polymer substances and the like by supercritical water oxidation (SCWO).

[0002]

2. Description of the Related Art As a physicochemical method for decomposing organic wastewater, a chemical oxidation method, a photo-oxidation method, a direct combustion method and the like are known.
15 to 100 atm) and high concentration (about 1%) of organic wastewater is energetically advantageous and NO
_The wet oxidation method is known as a method that does not generate _X and SO _X. However, all of them have a limit in the decomposability of organic substances (accumulation of lower carboxylic acid and residual ammonia), and biological treatment equipment is provided at a later stage. There is a problem that it becomes necessary.

As an alternative method, wastewater containing various polymer substances such as hardly decomposable organic substances and harmful organic substances, or substances which cannot be biologically treated because they contain chlorine compounds, nitrogen compounds, sulfur compounds, etc. It has been proposed to decompose by supercritical water oxidation (Japanese Patent Publication No. 1-38532). This supercritical water oxidation method is basically performed according to the following flow. That is, the fluid containing the decomposition target,
An oxidizing agent fluid such as oxygen and supercritical water are supplied in a premixed or partially mixed state to a reaction vessel for supercritical oxidation reaction, and are decomposed under water supercritical conditions. The substance is oxidatively decomposed. This separates the decomposed products of water and gas (mainly carbon dioxide and some volatile substances), releases the gas under atmospheric pressure through decompression means, and includes water as necessary. To remove salts and inorganic substances.

According to this method, the polarity of water (supercritical water) under the critical conditions of water, that is, under a condition of exceeding a critical temperature of 374 ° C. and a critical pressure of 220 atm, can be controlled by the temperature and the pressure, so that paraffin hydrocarbons and It can also dissolve non-polar substances such as benzene, and can be mixed with a gas such as oxygen in a single phase at an arbitrary ratio. If the content is a few percent, the temperature can be raised to the critical temperature or higher only by the heat of oxidation, so that it is very excellent in thermal energy. Furthermore, it is difficult to decompose organic substances by hydrolysis or thermal decomposition in supercritical water. There is an extremely excellent advantage that toxic organic substances can be almost completely decomposed.

[0005] By the way, the decomposition of organic wastewater by supercritical water oxidation is carried out in industrial scale facilities, although laboratory and pilot scale studies have already confirmed the effectiveness of safe and clean processes. Therefore, technical problems to be solved are pointed out. One of the problems is that salt adheres to the wall surface of the reaction vessel, causing blockage and corrosion of the wall surface. That is, if frequent replacement of the reaction vessel is required due to the adhesion, the running cost is increased, and the efficiency is reduced due to interruption of the processing.

[0006] The problem of salt adhesion to the reaction vessel wall is as follows.
The solubility of inorganic substances and salts in supercritical water is extremely smaller than that in subcritical water (for example, CaCl ₂ is 500 ° C., 25
Only a few ppm are dissolved in supercritical water at 0 atm), and the salt or the salt-forming substance contained in the decomposition target is brought into the reaction vessel and the reaction is under supercritical water oxidation conditions. It appears as a phenomenon that it precipitates as salt in the container and adheres to the wall surface.

For example, when supercritical water oxidation is performed by introducing an organic substance containing a salt-forming substance such as chlorine or sulfur into a reaction vessel, the pH in the reaction vessel drops due to the generated chlorine ions or sulfate ions. Therefore, there is a problem that the reaction vessel is corroded. Therefore, in order to prevent the pH from dropping, it has been considered that a neutralizing agent is added to the liquid to be treated to be introduced into the reaction vessel to neutralize the solution. As a result, salts that are hardly dissolved in supercritical water are considered. Precipitates and adheres to the wall surface of the reaction vessel, which in extreme cases causes a problem of clogging.

As a countermeasure for preventing such salt adhesion to the wall surface of the reaction vessel, for example, in WO92 / 21621, as shown in FIG. 3, a structure having a subcritical region 103 at the bottom for recovering salt is used. Subcritical water flows from the upper supercritical region (reaction region) 102 of the reaction vessel 101 along a wall surface 104 to form a water wall 105, and a salt is dissolved in the subcritical water film 105. Subcritical region 1
A method for preventing the salt from adhering to the wall surface 104 by flowing down to 03 is proposed.

Also, in US Pat. No. 5,388,398,
As shown in FIG. 4, the reaction vessel 201 has a double tube structure of an outer tube (for example, a stainless steel tube) 202 having a pressure tight structure and an inner tube (for example, a sintered metal tube and a ceramic tube) 203 made of a porous material. Provide a reaction area inside the inner tube (supercritical area)
The supercritical water 205 is supplied to the gap 206 between the outer pipe 202 and the inner pipe 203 at a pressure higher than the pressure in the reaction vessel.
A method has been proposed in which the salt deposited in the reaction region 204 is prevented from adhering to the inner tube 203 by ejecting 05 into the reaction vessel 201. Further, in U.S. Pat. No. 5,100,560, as shown in FIG. 5, inside a reaction vessel 301, a U-shaped wall-adhering substance which rotates close to and along the wall surface from a subcritical region 303 to a supercritical region 302 is scraped. A proposal has been made to provide a scraper for dropping. In addition, 305 is a rotation drive unit about the vertical axis of the scraper 304, 306 is a water supply pipe to the subcritical area 303, and 307 is a drain pipe from the subcritical area 303.

[0010]

However, in the above-mentioned method of forming a subcritical water film along the wall surface of the reaction vessel, the supercritical region 102 inside the reaction vessel is maintained at the supercritical condition of water. It is difficult to always form a uniform water film 105 of the subcritical water in which the salt dissolves on the entire inner wall 104, and the salt is deposited and adhered to the cut portion of the water film. In addition, there is a difficulty that prevention of clogging and corrosion cannot be ensured.

In the method in which the reaction vessel 201 has a double-tube structure and the supercritical water 205 is jetted from the outside to the inside of the porous inner tube 203, a larger amount of supercritical water is required than the supercritical water required for the reaction. And the reaction region (supercritical region) 20
Since the pressure of the supercritical water supplied between the outer pipe and the inner pipe must be higher than that of the supercritical water supplied to 4, the energy consumption is increased, and there is a difficulty in increasing the running cost.

Further, the method using the U-shaped scraper 304 is excellent in that the adhered substances on the wall surface can be mechanically and surely scraped off. However, the scraped salt substance adheres and accumulates on the surface of the scraper 304 itself to be scraped off. There is a possibility that the smooth rotation of the vehicle may be hindered, and there is a problem that the burden of maintenance and inspection is large.

The inventor of the present invention has been made in view of the above-mentioned state of the art, and is capable of effectively preventing salt from adhering to the wall surface of the reaction vessel.
An object of the present invention is to provide a supercritical water oxidation treatment apparatus that is effective in preventing corrosion, can reduce the frequency of replacement of a reaction vessel, and can reduce running costs.

Another object of the present invention is to provide a supercritical water oxidation treatment that can reduce the amount of energy consumption for preventing salt from adhering to the inner wall surface of the reaction vessel, reduce the burden of maintenance and inspection, and reduce the running cost. Equipment.

[0015]

In order to achieve the above object, the invention of a supercritical water oxidation treatment apparatus according to claim 1 of the present application has a supercritical region in which a supercritical water oxidation reaction is performed is formed on the upper side in a vessel. And a vertical cylindrical reaction vessel in which a subcritical region is formed on the lower side of the vessel, and water or supercritical water, an organic substance, and a fluid containing an oxidant are supercritically treated with water from the upper end side of the reaction vessel. Fluid supply means for supplying the reaction product into the reaction vessel, first discharge means for discharging the decomposition product by supercritical water oxidation from the subcritical region to the outside of the reaction vessel, and decomposition by supercritical water oxidation from the supercritical region. A supercritical water oxidation treatment apparatus provided with a second discharge means for discharging the generated fluid to the outside of the reaction vessel; And an annular scraper that scrapes off A drive control means for performing the above-described vertical movement of moving the annular scraper to the supercritical region and scraping off the adhering material on the wall surface when necessary is provided so that the annular scraper is always located in the subcritical region. I do.

The reaction of supercritical water oxidation in the above invention is as follows:
Critical temperature of water (374 ° C) and critical pressure (220 atm)
Since the reaction is carried out under high temperature and high pressure conditions, the vertical cylindrical reaction vessel used is made of a material such as stainless steel, carbon steel or the like in a pressure tight closed type, and is generally used. Is used, but is not limited to this. Further, in consideration of corrosion resistance, a vertical reaction vessel using a corrosion-resistant material such as a titanium alloy may be used. In the above description, “vertical” means that the axial direction of the cylindrical reaction vessel is the vertical direction.

The supercritical region formed on the upper side of the vertical reaction vessel is a reaction region for performing supercritical water oxidation, and the temperature and pressure are maintained at the above-mentioned supercritical condition of water.
The subcritical region formed on the lower side of the vertical reaction vessel is a liquid phase region in which the pressure exceeds the critical pressure but the temperature is maintained at a temperature lower than the critical temperature of water, thereby storing subcritical water. . This subcritical water is preferably maintained at a predetermined amount by absorbing and draining water from outside the reaction vessel. A slight diffusion region is formed between the supercritical region and the subcritical region.

In the above description, the term "water or supercritical water, an organic substance, or a fluid containing an oxidizing agent" supplied to the reaction vessel refers to a case where it further contains an inorganic substance, an auxiliary fuel, and other substances that do not interfere with supercritical water oxidation. Not excluded. Examples of the organic substance include, but are not limited to, organic substances such as organic wastewater and toxic organic substances. As the oxidizing agent, oxygen-containing gas such as oxygen and air can be generally mentioned as a preferable example. When an inorganic anion such as a chloride ion is chemically bonded to an organic substance, this is decomposed into hydrochloric acid. Therefore, an alkali (neutralizing agent) may be added to the organic substance in advance. The term “fluid” refers to a substance having appropriate fluidity to supply the above-mentioned substance or the like to the reaction zone, and each substance may be in a gas, liquid, or solid phase at room temperature.

The fluid containing organic matter supplied to the supercritical region is hydrolyzed and oxidatively decomposed by the supercritical water oxidation reaction. In the treatment method using the vertical reaction vessel of the present invention, the decomposition product having a low density is produced. Is discharged from the upper side of the supercritical region (upper side of the reaction vessel) to the outside of the vessel, and is discharged under atmospheric pressure as gas and condensed water through predetermined cooling, decompression, and the like. Examples of such a gas include carbon dioxide gas and nitrogen gas. In consideration of the fact that this gas and condensed water discharge system may contain a substance that is not desirable to discharge as it is, it is preferable to discharge the gas and condensed water to the outside after being brought into contact with an adsorbent such as activated carbon.

In addition, a substance having a high density, such as a salt, among the decomposition products generated by the reaction of the supercritical hydroxylation falls into a subcritical region in the reaction vessel, and the salt is dissolved in the subcritical water to form the subcritical water. The water is discharged out of the container from the lower side as effluent, and is discharged out of the system as a processing liquid through predetermined cooling, decompression, and the like.

The scraper for scraping off the deposits of the inner wall surface of the reaction vessel having the above-described structure causes at a smallest possible clearance to the cylindrical inner wall peripheral surface of the reaction vessel for example, a ring-shaped ring proximate over its entire circumference Can be exemplified. The opposing portion of the reaction vessel wall surface of the ring-shaped scraper, it is preferable to provide a blade (edge) of appropriate shape suitable for scraping. Since the scraper has an annular configuration, it is possible to scrape off the adhering matter all around the inner wall only by vertical movement, and there is no need to perform a rotational movement in the circumferential direction. The pressure seal mechanism can be simplified because it can be formed only, and the pressure seal mechanism is a sliding contact portion only in the axial direction without rotation, which is advantageous in securing the stability and durability of the seal. In general, the annular scraper can be formed using the same material as the reaction vessel such as stainless steel and carbon steel.

The support structure for the annular scraper is not limited, but usually, a scraper shaft extending along the center axis of the reaction container from a bearing provided at the lower end of the reaction container is provided. It is preferable to employ a configuration in which a plurality of support rods are radially extended from the upper end of the scraper shaft to support the annular scraper.

The above-mentioned annular scraper is formed, for example, by extending the above-mentioned scraper shaft through a bearing below the reaction vessel,
At this extension position, the inside of the reaction vessel is connected to drive control means such as a hydraulic cylinder device or a mechanical vertical movement device which is pressure-blocked. The vertical movement range in the supercritical region (which may include a diffusion region) of the annular scraper can be determined by design in relation to the range in which the salt substance may adhere.

The drive control means of the annular scraper according to the present invention controls the supply and discharge of the hydraulic oil to or from the hydraulic cylinder device, or the motor drive / stop of the mechanical vertical movement device, so that the sub-critical device is always operated. The annular scraper immersed in the subcritical water in the region is moved to the supercritical region when it is necessary to scrape off the adhering material on the wall surface, and the scraper is scraped by a predetermined vertical movement. In the above “when necessary”, for example, the scraping operation may be performed at regular intervals, or may be selectively performed as appropriate according to the driving situation.

According to the present invention, when supercritical water oxidation treatment capable of completely decomposing organic substances is carried out on an industrial scale real apparatus, the supercritical water is precipitated in the supercritical region and adheres to the wall surface of the reaction vessel.
The deposited salt material can be scraped off with sub-critical water in which the solubility of salt material is much higher than supercritical water with a scraper in a timely manner, and the annular scraper is buried in sub-critical water during non-scraping operation. Therefore, the scraper itself has an excellent advantage that there is no problem that the salt substance adheres and accumulates on the scraper itself, which is extremely useful for industrialization of the supercritical water oxidation treatment.

[0026]

1 and 2 are diagrams for explaining an embodiment of the present invention. FIGS. 1 (a) and 1 (b)
FIG. 1 is a schematic view for explaining the movement of an annular scraper for scraping salt substances of a supercritical water oxidation treatment apparatus according to the present invention, and FIG. 2 is a specific example of a drive control device for giving the movement of the annular scraper. FIG.

In these figures, reference numeral 1 denotes a reaction vessel of a supercritical water oxidation treatment apparatus. In this embodiment, upper and lower ends are closed using, for example, stainless steel having excellent pressure resistance and corrosion resistance as described above. It is configured as a vertical circular cylindrical reaction vessel.

In the supercritical water oxidation treatment apparatus according to the present embodiment in which the reaction vessel 1 is used as a main apparatus, a supercritical region (reaction region) 2 is formed in the upper part of the vessel and the supercritical region 2 is formed in the lower part. A subcritical region 3 is formed, and a diffusion region 4 is formed between them.

In the supercritical water oxidation treatment performed in the vertical circular cylindrical reaction vessel 1 having such a configuration, the material to be treated (organic substance) is hydrolyzed in the supercritical region 2 on the upper side of the vessel. The supercritical fluid (supercritical water, supercritical CO _2, etc.) having a low specific gravity is oxidatively decomposed and decomposed, through a fluid discharge pipe (second discharge means according to claim 1) 5 to a predetermined level. The substance (inorganic salt) having a high specific gravity falls into the subcritical region 3 and is contained in the subcritical water through the depressurization process, and is discharged from the water supply system 6 through the subcritical region 3 to the drainage system 7. By passing water through, the substance is also discharged out of the system.

Reference numeral 8 denotes an annular scraper, which is, for example, 90 degrees from the upper end of the scraper shaft 9 disposed at the axis of the reaction vessel 1.
And is supported by radially-provided support rods (not shown) at equally-divided positions. Normally, the annular scraper 8 is moved to the subcritical water in the subcritical region 3 as shown in FIG. When it is necessary to scrape it off, it is moved up and down along the inner peripheral wall of the reaction vessel 1 over the supercritical region (reaction region) 2 and the diffusion region 4 as shown in FIG. 1 (b) (see FIG. 1 (b)). (See arrow).

FIG. 2 shows a hydraulic cylinder device as drive control means for moving the annular scraper 8 from the subcritical region 3 to the supercritical region 2 and moving the annular scraper 8 up and down over the supercritical region 2 and the diffusion region 4. 1 shows a configuration of a drive control device including a drive control device 10.

The hydraulic cylinder device 10 has a plunger 11 which is fitted to the lower end of the scraper shaft 9 in an uneven manner, and a reciprocating motion of the plunger 11 by hydraulic pressure forms a bearing member forming the bottom of the reaction vessel 1. 20 bearing holes 2
The scraper shaft 9 slidably movably in the axial direction 1 is moved up and down. Reference numeral 22 denotes a high-pressure seal for preventing fluid from leaking from the reaction vessel 1.

The plunger 11 constitutes a hydraulic cylinder device provided so that hydraulic pressure in both directions acts from the upper oil chamber 12 and the lower oil chamber 13 facing the head 11a. , 13 are supplied with pressure oil from a hydraulic source 16 through supply / discharge pipes 14, 15, respectively. Reference numeral 17 denotes a seal ring for preventing pressure oil leakage, and reference numeral 18 denotes a cylinder body.

Numeral 30 denotes a cooling jacket provided between the bearing member 20 and the hydraulic cylinder device 10. The function of preventing boiling and the function of preventing the pressure oil of the hydraulic cylinder device 10 from leaking to the scraper shaft 9 are performed. 31 is a cooling water supply pipe, 32 is a cooling water discharge pipe, and 33 is a water passage around the plunger 11.

The main body member 34 of the cooling jacket 30 is mechanically firmly fastened to the bearing member 20 and the cylinder body 18 of the hydraulic cylinder device by bolts with flanges provided at upper and lower ends, respectively. . 35 to 37 are seal rings.

With the drive control device having the above configuration, when the plunger 11 shown in FIG.
The annular scraper 8 is located at the position shown in FIG. 1A, and when the pressure oil is supplied to the lower oil chamber 13 (the pressure oil is discharged from the upper oil chamber 12) and the plunger 11 moves upward, the annular scraper 8 shown in FIG. After moving to the position, the plunger 11 is moved downward by the supply of the pressurized oil to the upper oil chamber 12 (the discharge of the pressurized oil from the lower oil chamber 13), and the operation of scraping off the deposits on the wall surface is performed.

According to this embodiment, the salt substance adhering to the wall surface of the reaction vessel used for the supercritical water oxidation treatment can be mechanically and securely scraped off, and a mechanism adopted for this scraping is provided. However, since an annular scraper which is always buried in subcritical water is used, there is an excellent effect that there is no possibility that a salt substance adheres or accumulates on the annular scraper. Further, since the mechanism for moving the annular scraper up and down is configured by using a hydraulic cylinder device, the structure is simple and the operation can be easily performed.

[0038]

As described above, the present invention relates to a vertical cylindrical reaction vessel in which a supercritical region is formed in the upper part of the vessel and a subcritical area is formed in the lower part of the vessel. A fluid supply means for supplying a fluid containing water or supercritical water, an organic substance, and an oxidizing agent into the reaction vessel under supercritical conditions of water from the upper end side of the reactor, and reacting a decomposition product by supercritical water oxidation from a subcritical region. In a supercritical water oxidation treatment apparatus comprising: a first discharge means for discharging outside the vessel; and a second discharge means for discharging a fluid generated by decomposition of supercritical water from the supercritical region to outside the reaction vessel. An annular scraper that moves up and down in the direction of the wall generatrix in a state of being close to the entire circumference of the inner wall surface in the container to scrape off the adhering material on the wall surface, and the annular scraper is always positioned in the subcritical region and scraped. If necessary, drop this ring The problem is that supercritical water oxidation treatment that can completely decompose organic substances is carried out on an industrial-scale real device by providing a drive control unit that moves the gas to the supercritical region and moves it up and down. The problem that the salt substance adheres and accumulates on the wall surface of the reaction vessel, which was a point, can be solved by scraping the salt substance into subcritical water. The scraper itself has an excellent advantage that there is no problem that a salt substance adheres and accumulates on the scraper itself, and the effect is extremely useful in industrializing the supercritical water oxidation treatment. .

Further, since the adhesion of salt to the wall surface of the reaction vessel can be effectively eliminated as described above, it is effective in preventing the clogging and corrosion of the reaction vessel, and the frequency of replacing the reaction vessel can be reduced, and the running cost can be reduced. In addition to this, a sub-critical water flow along the wall surface can be used as a device for scraping salt substances, which uses a low operating energy consumption such as a hydraulic cylinder and has a small maintenance and inspection burden. The instability of the lower method, the difficulty of multi-energy consumption type of jetting supercritical water from the outside of the porous inner tube, the adhesion of salt substance to the scraper itself using the U-shaped scraper
There is an extremely large benefit in realizing a supercritical water oxidation treatment apparatus on an industrial scale, which can solve all the problems of the deposition method.

According to the second aspect of the present invention, wherein the drive control means for moving the annular scraper up and down is constituted by using a hydraulic cylinder device, the structure of the drive control means is simple and the operation can be easily performed. There is also an effect that it can be done.

[Brief description of the drawings]

BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a front view schematically showing an example of a configuration outline of a reaction vessel of a supercritical water oxidation treatment apparatus of the present invention, wherein (a) shows a normal state, and (b) shows a state when a salt substance is scraped off. ing.

FIG. 2 is a longitudinal sectional view showing an example of a drive control device of an annular scraper of the supercritical water oxidation treatment device of FIG.

FIG. 3 is a view showing an example of a conventional method for preventing the attachment of a salt substance.

FIG. 4 is a view showing another example of a conventional method for preventing the adhesion of a salt substance.

FIG. 5 is a view showing still another example of the conventional salt substance adhesion preventing method.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Reaction container, 2 ... Supercritical area, 3 ... Subcritical area, 4 ... Diffusion area, 5 ... Fluid discharge pipe, 6 ...
..Water supply system, 7 ... drainage system, 8 ... annular scraper, 9 ... scraper shaft, 10 ... hydraulic cylinder device, 11 ... plunger, 11a ... head, 1
2, 13 ... oil chamber, 14, 15 ... supply / drain pipe, 16
..Hydraulic pressure source, 17 seal ring, 18 cylinder body, 20 bearing member, 21 bearing hole, 22 high pressure seal, 30 cooling jacket, 31 Cooling water supply pipe, 32 cooling water discharge pipe, 33 water passage, 34 body member, 35-3
7 ... Seal ring.

 ────────────────────────────────────────────────── ─── Continued from the front page Examiner Tadahiro Sanada (56) References JP-A-8-164348 (JP, A) US Patent 5,100,560 (US, A) US Patent 4,338,199 (US, A)

Claims (2)

(57) [Claims] 1. A vertical cylindrical reaction vessel in which a supercritical region in which a supercritical hydroxylation reaction is performed is formed in an upper part of a vessel and a subcritical area is formed in a lower part of the vessel, and the reaction vessel A fluid supply means for supplying a fluid containing water or supercritical water, an organic substance, and an oxidant into the reaction vessel under supercritical conditions of water from an upper end side of the water, and a decomposition product by supercritical water oxidation from the subcritical region. In a supercritical water oxidation treatment apparatus comprising: a first discharge means for discharging outside the reaction vessel; and a second discharge means for discharging a decomposition product fluid by supercritical water oxidation from the supercritical region to outside the reaction vessel. In the above-mentioned reaction vessel, an annular scraper that moves up and down in the direction of the wall generatrix in a state of being close to the entire circumference of the inner wall surface to scrape off the wall adhering matter, and that this annular scraper is always located in the subcritical region, And when necessary, this annular scraper Supercritical water treatment apparatus is characterized by providing a drive control means for causing the vertical movement for scraping off the wall deposits is moved in the supercritical region. 2. The supercritical water oxidation apparatus according to claim 1, wherein the drive control means is a hydraulic cylinder device.