[Field of the Invention]
The present invention is a technology for producing a combustible gas containing hydrogen, methane, and the like by treating organic substances such as sewage sludge having a relatively large content of inorganic salts in supercritical water, particularly prior to decomposition and gasification of organic substances. The present invention relates to a pretreatment for removing inorganic salts.
Several treatment techniques for oxidizing organic sludge containing inorganic substances, such as sewage sludge, in supercritical water with air or oxygen-enriched air to decompose it into carbon dioxide, water, and ash have been disclosed (for example, see Japanese Patent Laid-Open Publication No. H11-163,837). JP-A-6-511190 (Japanese Patent No. 3036077), JP-A-11-90494, JP-A-11-138198, and the like. In such a process, for the purpose of conveniently supplying an object to be processed to a processing container by a transport means such as a pump, the object is generally supplied as a slurry in which water is suspended in water.
In the process of treating the object to be treated with supercritical water, it is necessary to pressurize and heat the slurry of the object to be treated to a supercritical state of water (temperature 374.15 ° C., pressure 22.1 MPa) or higher. Conventionally, this heating is generally performed by heating an elongated tubular reactor using an electric resistance heating element, or by passing a high-temperature heat medium or a treated high-temperature fluid as a heat source through a double-tube heat exchanger. Is being done.
However, the inorganic substances contained or entrained in the object are dissolved in the water in the slurry while the object is suspended in water, and the organic matter to be processed is decomposed or dissolved in water by heating. At the same time, the inorganic salts contained therein dissolve in water. The solubility of the dissolved inorganic salts significantly decreases as the water reaches the supercritical state. Therefore, in the process of increasing the temperature by heating or the gasification reaction process, the dissolved inorganic salts are in the supercritical fluid and / or the heat transfer surface or the reactor wall. Precipitates as a solid.
When inorganic salts precipitate as solid particles in the supercritical fluid, when using a fixed bed catalyst for gasification reaction, solid particles close the gap between the filled catalysts, so that long-term stable processing can be continued. Becomes difficult. In addition, when a fluidized bed catalyst is used for the gasification reaction, the inorganic salts precipitate on the surface or in the pores of the catalyst, causing a loss of activity or a decrease in activity of the catalyst, generating agglomerates of the catalyst, and the like. An obstacle to the continuation of smooth processing.
Even when the catalyst is not used in the reactor, the precipitated inorganic salts may block the outlet of the reaction product stream of the reactor, or the supercritical fluid containing solid fine particles of the precipitated inorganic salts may be converted into gas, water, and ash. During the separation process, smooth processing is hindered, for example, solid fine particles adhere to the wall of a separator such as a cyclone used.
In addition, during the preheating of the object to be treated in the heat exchanger or the heating process in the reactor, if inorganic salts precipitate as solids on the heat transfer surface, the reactor wall, or the char attached to these surfaces, the transfer may occur. The heat conduction on the hot surface is reduced, and the fluid flow path in the heat exchanger is blocked due to the compound of the inorganic salt solid and the char. As a result, it is necessary to temporarily stop the operation of the apparatus to remove the inorganic salts and chars, resulting in a reduction in the processing capacity, an increase in the removal work cost, and an increase in the heat loss.
[Problems to be solved by the invention]
The present invention, when treating organic matter such as sewage sludge containing inorganic salts in supercritical water, to prevent the obstacles caused by the precipitation of inorganic salts as described above, to smoothly continue stable treatment for a long period of time With the goal. That is, in the treatment of supercritical water such as organic sludge, in order to prevent a decrease in heat transfer, blockage of a fluid passage, deactivation of a catalyst, etc. caused by precipitation of inorganic salts contained in a treatment object during treatment. It is an object of the present invention to provide a processing method and a device used for implementing the processing method.
[Means for Solving the Problems]
According to the present invention, before performing the decomposition / gasification treatment of the organic matter, a pretreatment for removing the inorganic salts contained in the object to be treated and precipitated near the supercritical state is performed, and such inorganic salts are almost completely removed. The above object is achieved by subjecting the removed supercritical fluid to a decomposition / gasification treatment. At the same time as this pretreatment, organic substances are decomposed and converted into low molecular weight components, and some of them may be gasified.However, the purpose of the pretreatment is to prolong the gasification of the organic substances to be treated in a supercritical fluid for a long time. In order to continue smoothly, most of the inorganic salts are removed in advance.
That is, the first aspect of the present invention is to continuously supply a slurry in which an organic substance to be treated is suspended in water to a pretreatment vessel, to retain the ground particles in a floating fluid state in the vessel, and to heat the supercritical water by heating. By maintaining a critical or subcritical state, the inorganic salts contained in the object to be treated are precipitated in a supercritical fluid as solid fine particles, and the precipitates are discharged out of the vessel and separated to substantially separate the inorganic salts. The present invention relates to a pretreatment method for supercritical water treatment of an organic substance, characterized by obtaining a supercritical fluid not contained in water. Grinding particles referred to here are solid particles that are insoluble and inert in water, and do not damage the reactor walls and the heat transfer surface of the heat exchanger unlike roughening by grit blasting. The fine particles are hard and preferably have an average particle diameter of 0.01 to 1 mm.
The ground particles flow in the container while floating in a fluid near the supercritical state in the pretreatment container, and furthermore, stay in the container. The floating fluid state referred to herein is a state in which particles circulate in a certain partial space in the container by flowing in the container while floating without flowing out from the container, like a fluidized bed catalyst in a catalytic cracking device. . The streamline in which the abrasive particles flow in the container in this manner is schematically shown by a dashed line in FIG. The inorganic salts contained in the object to be treated and dissolved in water are rapidly reduced in solubility when they change to a supercritical state. It is also deposited on the surface of the char adhering to the vessel wall and also on the surface of the abrasive particles themselves.
Under the condition that the solid particles of the inorganic salts float and flow the ground particles whose apparent specific gravity is heavier than the inorganic salt precipitates, the floating particles flow relatively high in the container as schematically shown by the solid lines in FIG. It is discharged to the outside of the container. As the abrasive particles float and flow, not only do the inorganic salts precipitate on the walls and chars of the vessel, but they also work to scrape off the solids generated.In addition, the abrasive particles also remove the solid inorganic salts that have precipitated on the surface of the abrasive particles themselves. It acts to scrape off by friction generated by mutual collision.
A second aspect of the present invention is a pretreatment method for discharging and separating not only solid fine particles of inorganic salts but also ground particles from the pretreatment container. That is, a slurry in which the organic material to be treated is suspended in water is continuously supplied to a pretreatment vessel, the grinding particles are maintained in a floating fluid state in the vessel, and the supercritical, critical or subcritical state of water is heated by heating. Inorganic salts contained in the object to be treated are precipitated as solid fine particles in a supercritical fluid by maintaining the particles, and the precipitates and the ground particles are substantially discharged and separated from the vessel to substantially contain the inorganic salts. The present invention is directed to a pretreatment method for supercritical water treatment of organic matter, characterized in that a supercritical fluid is obtained.
By using abrasive particles including particles having a particle size close to solid fine particles of inorganic salt precipitates, there is no spatial distinction between the two streamlines floating and flowing in the container, and both are discharged from the container. Grinding particles that are insufficient in quantity due to discharge are supplied to the pretreatment container continuously or intermittently from the supply port, or supplied to the pretreatment container together with the slurry by being added to the workpiece slurry. You.
The third aspect of the present invention relates to an organic substance which decomposes and gasifies a fluid containing water and an organic substance in a supercritical state after previously removing inorganic salts contained in the substance to be treated by supercritical water treatment as described above. It is an invention of a supercritical water treatment method. That is, a fluid substantially free of inorganic salts is obtained by performing the above-described pretreatment of the organic material to be treated in the first treatment zone, and then the fluid is introduced into the second treatment zone, and the fluid is introduced in the presence of a catalyst. Alternatively, the present invention is directed to a method for treating a supercritical water with an organic substance, wherein the organic substance is decomposed into a combustible gas and water by maintaining the supercritical, critical or subcritical state of water in the absence.
By introducing the fluid to be treated, from which inorganic salts have been sufficiently removed in the first treatment zone, to the second treatment zone, it is optimal for decomposition and gasification in the second treatment zone without being hindered by the failure of inorganic salts precipitation. Since such reaction conditions can be selected, it is possible to select the composition of the generated gas and to improve the reaction efficiency. Here, in the second treatment zone, a catalyst is not necessarily used. However, if a catalyst such as activated carbon is used as a fluidized bed in a floating state or as a fixed packed bed, a flammable gas containing hydrogen or methane is used. Is preferred because it can be effectively obtained.
According to a fourth aspect of the present invention, a gaseous oxidizing agent and / or a part of a generated gas are introduced again into the first processing zone and / or the second processing zone where a slurry or a fluid to be processed is present in the processing method. And a treatment method for maintaining water in a supercritical, critical or subcritical state in the presence or absence of a catalyst. This generated gas can be obtained by gas / liquid separation after the reaction product generated by the gasification reaction is allowed to flow out of the second treatment zone. That is, there are four types of combinations for introducing either the gaseous oxidant or the product gas into either the pretreatment vessel or the gasification reactor, and the gaseous oxidant or the product gas is supplied to the pretreatment vessel. There are four types of combinations in which either the gaseous oxidizing agent or the product gas is introduced into the gasification reactor, including the case where the gaseous oxidizing agent and the product gas are simultaneously introduced. Any of these eight combinations is effective, and the selection of the combination to be introduced is determined in consideration of the type of the organic substance to be treated, the composition of the desired generated gas, the stability of the treatment, and the like. Thereby, generation of carbides such as char and tar is suppressed, and effective decomposition and gasification of the organic matter to be treated are stably continued.
The fifth invention is an apparatus for removing inorganic salts contained in an object to be treated by supercritical water treatment, wherein at least (a) a supply port for introducing a slurry in which an organic substance to be treated is suspended in water; A means for heating the slurry to a supercritical state of water, an outlet for discharging the treated supercritical fluid, and a means for continuously discharging solid fine particles of inorganic salts precipitated in the supercritical fluid to the outside of the container And (b) a means for maintaining the abrasive particles in a floating fluid state in the pretreatment vessel, the invention comprising a pretreatment apparatus for supercritical water treatment of organic matter. It is.
Further, as a specific means for continuously discharging the solid fine particles of the precipitated inorganic salts out of the pretreatment vessel, a vertical hollow tube having an opening in a relatively upper space in the vessel, A discharge pipe provided to conduct vertically from the container bottom to the outside of the container has a simple configuration and is preferable. By providing the dust collecting edge forming an inclined surface descending toward the opening of the vertical hollow tube, the solid fine particles of the inorganic salts which flow can be more easily collected in the opening, and are not an essential element, but are preferable.
A sixth aspect of the present invention is an apparatus for removing inorganic salts contained in an object to be treated by supercritical water treatment, wherein at least (a) a supply port for supplying a slurry in which an organic substance to be treated is suspended in water; A pressure-resistant device comprising means for heating the slurry to a supercritical state of water, and an outlet for continuously discharging the treated supercritical fluid together with the abrasive particles and solid fine particles of inorganic salts precipitated in the supercritical fluid. (B) means for maintaining the abrasive particles in a floating fluid state in the container, and (c) solid fine particles of inorganic salts and the abrasive particles discharged from the outlet out of the container and supercritical It is an invention of a pretreatment device in supercritical water treatment of organic matter, characterized by comprising a fluid / solid separation means for continuously separating a fluid. Various dust collectors and the like can be used as the fluid / solid separating means, but a cyclone separator is mechanically simple and preferable.
Further, as a specific means for maintaining the abrasive particles in a floating fluid state in the pretreatment vessel, various stirring mechanisms can be used, but a slurry obtained by suspending the organic material to be treated in water is used. It is mechanically simple and preferable to use an orifice capable of adjusting the linear velocity when introducing the slurry into the pretreatment vessel from the supply port and a slurry pump capable of adjusting the supply amount of the slurry.
Further, a seventh aspect of the present invention is an apparatus for treating an organic substance to be treated with supercritical water, comprising: (d) a preheater for preheating an organic substance slurry to be treated; (e) a pretreatment apparatus as described above; A) A pressure-resistant reactor having at least an inlet for introducing a fluid flowing out of the pretreatment device and an outlet for a reaction product stream, which is an invention of a treatment device for supercritical water treatment of organic matter. The slurry to be treated is heated to a high temperature immediately before being introduced into the pretreatment device (e) so that the fluid from which the inorganic salts have been sufficiently removed flows into the pressure-resistant reactor (f). In order to sufficiently precipitate the inorganic salts therein, a slurry preheater (d) is required.
Further, an eighth aspect of the present invention provides the supercritical water treatment apparatus as described above, wherein (g) an organic substance comprising means for heating the fluid after pretreatment by the pretreatment apparatus before introducing the fluid into the pressure-resistant reactor. It is an invention of a supercritical water treatment device. This has a function of reheating the fluid to be treated in the reaction vessel to a temperature required for the decomposition / gasification reaction.
As the heating means, it is possible to use various heating means such as a heat exchanger and a heating furnace, but by using a direct heating heating furnace using a part of the product gas generated in the gasification reaction as fuel, It is possible and preferable to reduce capital investment costs, effectively use processed products, and reduce heat loss in heat transfer. In the supercritical water treatment according to the prior art, the reaction products were carbon dioxide gas and water containing almost no flammable gas. However, according to the treatment method of the present invention, a flammable gas is obtained and the fluid to be gasified is treated. It became possible to use a heating furnace that uses this as fuel for heating.
BEST MODE FOR CARRYING OUT THE INVENTION
The first and fifth aspects of the present invention will be described with reference to FIG. 1, which illustrates an embodiment of the fifth aspect of the pretreatment apparatus according to the present invention. FIG. 1A is a cross-sectional view showing a cross-sectional end portion taken along a central axis of a cylinder in order to show a schematic structure of a pretreatment container having a vertical hollow cylindrical shape. FIG. 1B shows a plan view of the inside of the container. The pretreatment vessel 1 is made of pressure-resistant, has a supply port 8 for supplying slurry at the lower part of the side face, has an outlet 9 at the top of the vessel through which a supercritical fluid after pretreatment flows out, and heats the slurry inside the vessel. The heat transfer tubes 11 and 12 are provided by connecting two rows of inner and outer rings by headers 13 and 14. Further, a precipitate discharge pipe 6 is provided as means for continuously discharging the precipitated solid fine particles of inorganic salts to the outside of the container. This is a vertical hollow tube having a horizontal opening that opens into a relatively upper space in the container, and is provided so as to penetrate the container bottom in the direction of gravity, that is, vertically, and to connect the inside of the container and the outside of the container. ing. It is preferable to provide the dust collecting edge 61 that forms an inclined surface that descends toward the opening of the vertical hollow tube, because the solid fine particles of the inorganic salts that flow can be easily collected in the opening.
The slurry obtained by suspending the finely crushed object in water in a slurry preparation device (not shown) is continuously passed through a slurry pump 3, a preheater 5, and an orifice 4 from a slurry supply port 8 into the pretreatment vessel. And is heated by a heat transfer tube as a heating means. The concentration of the slurry depends on the type of the material to be treated, but in the case of organic sludge, the solid content is preferably 5 to 15% by weight. A high-temperature heat medium flows through the heat transfer tubes 11 and 12 in the processing vessel to serve as a heat source. Alternatively, the reaction product in a supercritical state flowing out of the reactor after the decomposition and gasification treatment may be used as a heat source. When the object to be treated is organic sludge, the heating temperature is preferably about 450 to 650 ° C.
As a heat source of the slurry preheater 5, a reaction product after decomposition and gasification can be used in the same manner as described above, in addition to using a normal heat medium. When the object to be treated is organic sludge, when water reaches a supercritical state in the preheater, precipitation of inorganic salts occurs in the preheater due to a sudden change in solubility. In order to prevent this precipitation, the preheating temperature is preferably equal to or lower than the critical temperature of water (374 ° C.).
In the pretreatment method of the first invention, since the abrasive particles are hardly discharged from the pretreatment vessel, they are charged in the pretreatment vessel in advance or a slurry in which a predetermined amount of the slurry is suspended is introduced into the pretreatment vessel at a predetermined flow rate. . However, when shortage occurs due to long-term operation, it is preferable to replenish from the supply port 10 as necessary.
The ground particles used for carrying out the first invention are solid particles which are insoluble and inert in water, have a higher specific gravity than the inorganic salt precipitates, and have a hardness such that the inner wall of the pretreatment vessel and the surface of the heat transfer tube are not damaged. Fine particles. The material is not particularly limited as long as it satisfies such conditions. For example, various types of alumina, titania, zirconia, and the like generally used as artificial abrasive grains (abrasive) are used. The particle size is sufficient as long as it can form a floating fluid state, but the average particle size is preferably 0.01 to 1 mm, and particularly preferably about 0.05 to 0.5 mm.
As a means for causing the abrasive particles to float and flow, an orifice 4 whose opening degree can be adjusted is provided on the outside of the container with respect to the slurry supply port, and the linear velocity of the slurry at the supply port 8 is adjusted with respect to a constant amount of slurry supplied by the slurry pump 3. By adjusting the flow rate of the slurry introduction so as to be appropriate for the particle size and specific gravity of the used abrasive particles and the viscosity of the slurry, the abrasive particles can be circulated in a floating state in the vessel without flowing out of the pretreatment vessel 1 without flowing out of the vessel. it can.
In the above state, the organic matter in the object to be treated is completely dissolved in the supercritical water, a part thereof is decomposed and converted into a low molecular weight component, and the pretreated object, that is, the inorganic substance is discharged from the outlet 9 provided at the top of the container. The supercritical fluid from which the salts have been removed flows continuously. On the other hand, the inorganic substance flows while floating in the pretreatment container together with the abrasive particles as solid fine particles which are not dissolved while suspended in the slurry, or solid fine particles which are once dissolved and precipitated by the rapid change in solubility as described above. .
In the method of the first aspect of the present invention, ground particles of a material having a specific gravity sufficiently higher than that of inorganic salts are selected and used, and the linear velocity of the slurry introduced from the supply port is adjusted so that the ground particles are sufficiently suspended and flow, but the specific gravity is light. By adjusting the inorganic salt solid particles so that they do not flow out of the outlet 9, neither the solid precipitate particles nor the abrasive particles flow out of the container, and flow while floating in the partial space separated according to their specific gravities in the container. Can be realized. FIG. 2 schematically shows the movement of such inorganic salt solid particles by a dashed-dotted arrow streamline, and the movement of ground particles by a solid-line arrow streamline. In this way, the solid precipitate fine particles and the ground particles are consequently cleverly separated in the pretreatment vessel.
In FIG. 1, the precipitate discharge pipe 6 is provided vertically, penetrates vertically through the bottom surface of the pretreatment vessel 1, and connects the inside of the vessel and the outside of the vessel. The precipitate solid particles floating and flowing above the opening of the precipitate discharge pipe settle toward the opening by gravity, are taken into the discharge pipe, and are discharged to the outside of the pretreatment vessel through the discharge pipe 6 by gravity. Is done. A precipitate discharger 62 is connected to the lower end of the discharge pipe as a container for storing the precipitate that precipitates outside the pretreatment container. The deposit discharger is a small-capacity pressure-resistant container, and has a discharge valve 65 that opens and closes to connect a lock hopper system or the like to a bottom portion.
Two typical modes of an apparatus for extracting solid fine particles accommodated in a deposit discharger will be described. FIG. 1A shows a lock hopper system. Since the deposit discharger 62 is in communication with the pretreatment container, the discharge valve A65 connected to the lock hopper system is always closed. A piping 68 for introducing a generated gas or other high-pressure gas is connected to the pressure-resistant container A63 via a valve C67, so that the internal pressure of the container A63 can be increased. Further, a facility is provided which can release gas through the pipe 68 to lower the internal pressure of the container A63 to atmospheric pressure. Further, it is connected via a valve B66 to a container B64 (transport container) that stores the precipitate under the atmosphere.
First, the valve C67 is opened in a state where the valves A, B, and C are closed, and the internal pressure of the container A63 is made equal to the internal pressure of the discharger 62. Next, after closing the valve C67, the valve A65 is opened, and the precipitate is transferred from the discharger 62 to the container A63 by gravity. After transferring a predetermined amount of deposits, the valve A65 is closed and the valve C67 is opened to discharge gas to a discharge line (not shown). Next, the precipitate in the container A63 is transferred to the container B64 by gravity, each valve is closed, and a series of operations is completed. This operation is automated and performed intermittently.
The mode of extracting solid particles shown in FIG. 4 uses an apparatus which dissolves and extracts in water. A container A63 is connected to the discharger 62 via a valve A65, and a pipe 69 through which room-temperature or heated high-pressure water can be introduced is connected to the container A63 via a valve C67. First, the valve A65 is opened from a state where the valves A, B and C are closed, and the deposit is transferred to the container A63 by the internal pressure of the discharger 62. After extracting a predetermined amount of deposits, the valve A65 was closed, then the valve C67 was opened to introduce high-pressure water, and while dissolving the deposits, the valve B66 was opened and discharged out of the apparatus, and each valve was closed. End the operation. This operation is automated and performed intermittently.
Using the pretreatment apparatus according to the fifth invention shown in FIG. 1, the second invention can be implemented with respect to a method for extracting a precipitate. That is, by using the abrasive particles containing particles having a particle size close to the solid particles of the inorganic salt precipitates, there is no spatial distinction between the streamlines of the two particles floating and flowing in the pretreatment vessel, and both of them discharge the precipitates. It is taken into the tube 6 and discharged from the pretreatment container 1. Grinding particles that are insufficient in quantity due to discharge may be continuously or intermittently supplied to the pretreatment container from the supply port 10, but a method of mixing and supplying them to the organic slurry to be processed is preferable.
In the method of the second aspect of the invention, there is no need to provide any particular difference in the size of the pretreatment container, the type of the abrasive particles, and the like from the case of the first aspect of the invention. Regarding which method is selected, the diameter of the pretreatment vessel, the amount of slurry introduced, the specific gravity and the particle size of the abrasive particles, etc. are taken into consideration. However, as for the extraction of the precipitate from the discharger 62, since the abrasive particles discharged together with the inorganic salts are insoluble in water, a rock hopper system is suitable, and the apparatus for dissolving and extracting in water shown in FIG. 4 cannot be used. .
The second and sixth aspects of the present invention will be described with reference to FIG. 3, which illustrates one embodiment of the sixth aspect of the pretreatment apparatus according to the present invention. FIG. 3 is a system diagram relating to the pretreatment device. In the figure, a schematic cross-section taken along the central axis of the cylinder of the pretreatment container 1 which is a vertical hollow cylindrical shape, solid fine particles of precipitated inorganic salts are continuously discharged out of the container through the outlet 9 together with the abrasive particles. Thereafter, a schematic longitudinal section of a cyclone separator 7 which is a means for separating fluid and solid from a supercritical fluid, a lock hopper system for extracting fine particles collected by the cyclone 7 and accumulated in a lower portion 71 of the cyclone (for details, see the description of FIG. 1) ), A slurry pump 3 and an orifice 4, which are means for supplying a slurry of the organic substance to be treated to the pretreatment vessel 1, and for appropriately suspending and flowing solid fine particles and ground particles of the precipitate in the vessel to flow out of the vessel; A connection relation of a preheater 5 for heating the slurry before supplying the slurry to the container 1 is illustrated.
In FIG. 3, the inside of the pretreatment vessel 1 is provided with a heat transfer surface such as a heat transfer tube 11 for heating the slurry to a supercritical temperature. In the second invention, since the ground particles containing particles having a particle size close to the solid particles of the inorganic salt precipitates are used, the flow lines of the two particles floating and flowing in the pretreatment vessel are as shown by solid lines in FIG. And both are discharged from the outlet 9 of the pretreatment container 1. Grinding particles deficient due to discharge may be continuously or intermittently supplied to the container 1 from a supply port (not shown), but a method of mixing and supplying to the slurry of the organic matter to be treated is preferable.
In FIG. 3, a mixture of solid fine particles and ground particles collected by the cyclone and collected in the cyclone lower part 71 is supplied to the lock hopper system connected to the high pressure gas and the atmospheric pressure release line piping by the operation method described in the extraction method. And is taken out of the cyclone and stored in the transport container 64. The abrasive particles are insoluble in water and the extraction device using high-pressure water cannot be connected to a cyclone.
Embodiments of the third invention and the seventh invention will be described with reference to FIG. 4 illustrating one embodiment of the seventh invention relating to the apparatus for treating organic supercritical water. FIG. 4 is a system diagram relating to the supercritical water treatment apparatus, wherein the pretreatment according to the fifth invention is provided with a precipitate discharge pipe 6 for continuously discharging solid fine particles of inorganic salts precipitated in the pretreatment to the outside of the container. Ancillary equipment such as a vessel 1 and a slurry pump 3, an extraction device for discharging precipitates from a precipitate discharger 62, a reactor 2 for decomposing and gasifying a pretreated supercritical fluid, a pretreatment container 1 and a reactor 2 shows a connection relationship between a pipe 24 for introducing a part of the generated gas to the reactor 2 and a pipe 25 for introducing a gaseous oxidant to the pretreatment vessel 1 and the reactor 2. However, in the embodiment of the third invention, any of the pretreatment device, the attached solid particle discharging / extracting device, and the processing operation described above may be used.
The present invention is not limited by the type of reactor used. As the type of the reactor 2, a tubular reactor used in the prior art can be used, and a vertical cylindrical reaction tower which the present inventors previously applied for a patent (Japanese Patent Application No. 2002-296409). Etc. can be used. The gasification reaction of organic substances in supercritical water according to the present invention may be carried out without a catalyst depending on the properties of the material to be treated, or a carbon-based catalyst such as activated carbon or another known catalyst may be used. In the present invention, since the organic substances dissolved in the supercritical fluid from which the inorganic salts have been removed by the pretreatment are decomposed, solid particles of inorganic salt precipitates which are conventionally generated even when the catalyst is used in a fixed bed. There is no trouble such as blockage of the catalyst layer due to the above. Since deactivation due to precipitation of inorganic salts on the catalyst does not occur, the treatment can be smoothly continued for a long time even when the catalyst is used in a floating state as a fluidized bed.
Pressurization and pressure control means (not shown) commonly used in the art are used to raise and maintain the critical pressure of water in the reactor used to practice the present invention. As a heating means provided in the reactor to raise and maintain the critical temperature of water, for example, in the case of a tubular reactor, electric heating using a conventional electric resistance heating element, or a double tube heat exchange Heating by passing a high-temperature heat medium or a high-temperature fluid after supercritical water treatment into the vessel as a heat source can be used.
An embodiment of the method according to the fourth invention will be described with reference to FIG. In the supercritical water treatment method according to the fourth invention, in addition to the embodiment described in the description of the third invention, a part of the product gas separated from the reaction product flowing out of the reactor is pretreated and / or The gas is introduced into the lower part of the reactor through a recycle gas pipe 24. The ratio of the gas to be introduced to the fluid to be treated flowing into the reactor is preferably about 20 to 150 in terms of the volume ratio of the gas in the standard state to the slurry for the workpiece in the normal temperature state. Of these, 40-80 is particularly preferred. The gaseous oxidizing agent may be introduced alone, but is preferably added simultaneously with the introduction of the gas. When oxygen, oxygen-enriched air or the like is introduced into the lower part of the reactor, the ratio of oxygen introduced to the fluid to be treated flowing into the reactor is preferably about 10 to 50 by volume. By introducing these, there are advantages in that the production of char and tar can be suppressed, the reaction temperature can be easily controlled by stabilizing the catalytic activity, and the composition of the produced gas can be adjusted.
An embodiment of the eighth invention will be described with reference to FIG. FIG. 5 is a system diagram relating to a supercritical water treatment apparatus, in which solid fine particles of inorganic salts precipitated in the pretreatment are continuously flown out of the pretreatment vessel 1 together with the abrasive particles, and then separated into a fluid and a solid from the supercritical fluid. The pretreatment vessel 1 according to the sixth aspect of the invention having the cyclone 7 to be provided, the auxiliary equipment such as the slurry pump 3, and a lock for extracting solid fine particles and ground particles collected in the cyclone lower part 71 by using the internal pressure of the separator and the high-pressure gas. The connection relationship of a hopper system, a heating furnace 23 for raising the temperature of a fluid to be treated after pretreatment to a temperature required for decomposition and gasification, and a reactor 2 for decomposing and gasifying the heated fluid to be treated is illustrated. I have.
However, in the apparatus according to the eighth aspect, any of the apparatuses and processing operations of the pre-processing described above may be used. There is no restriction on the manner in which the fluid to be treated introduced into the reactor 2 is heated because the fluid to be treated does not contain solid fine particles or ground particles. However, it is particularly preferable to use a heating furnace 23 in which part of the generated gas is used as fuel and the heat transfer tube through which the fluid to be processed flows is directly heated by a burner. .
The eighth invention is not restricted by the type of reactor used. That is, in the apparatus according to the eighth invention, the type of the reactor 2 can be the same as that used in the seventh invention, and the reactor used in the prior art can be used. A vertical cylindrical reaction tower (Japanese Patent Application No. 2002-296409) can be used. The gasification reaction of organic substances in supercritical water according to the present invention may be carried out without a catalyst depending on the properties of the material to be treated, or a carbon-based catalyst such as activated carbon or other known catalysts may be used. Further, as described in the method according to the fourth invention, the product gas and / or the gaseous oxidizing agent may be introduced into the pretreatment vessel and / or the reactor by selecting from eight combinations.
Since the representative embodiment of each invention has been clearly described in the above description, the details of the processing results will be described below by way of examples. However, the present invention is not limited by this embodiment.
The slurry to be treated was prepared by suspending organic sludge containing inorganic salts expressed as ash in water at a concentration of 10% by weight on a dry matter basis (dry-kg / h). The processing apparatus shown in FIG. 4 was used, and the method according to the first invention was used as a preprocessing method. The preheating temperature was about 350 ° C and the pretreatment temperature was about 520 ° C. However, as the decomposition / gasification method, the method according to the third invention, that is, the method in which neither product gas nor gaseous oxidizing agent is introduced, was used. The gasification temperature was about 600 ° C. The pretreatment and gasification pressure was maintained at about 35 MPa. The processing continued smoothly for 7 days and was stopped in a state where it was still operable. The treatment results were displayed in the form of a material balance by elemental analysis.
In Table 1, the materials to be treated entering the pretreatment vessel are shown by elemental analysis values for organic substances to be gasified, and ash contents for inorganic substances, and further, the flow rates are shown. It can be seen that the slurry can be processed smoothly at a slurry concentration of 10% by weight on a dry matter basis.
Table 2 shows the composition of the precipitate (ash) discharged from the pretreatment container, the organic components discharged together with the precipitate, and the respective flow rates. From this result, it can be seen that substantially all of the inorganic salts introduced into the pretreatment device are discharged from the precipitate discharger, and that the abrasive particles are not substantially discharged.
Table 3 shows the composition and flow rate of the fluid flowing into the gasification reactor. The results show that organic substances to be treated containing no inorganic salts or ground particles can be introduced into the gasification reactor.
Table 4 shows the components, compositions, and flow rates of the reaction products flowing out of the gasification reactor. Looking at the water mass balance, the outflow weight of 7.10 in Table 4 was 7.75 in comparison with the outflow weight of 7.10 shown in Table 3 above. It is thought that it was converted to carbon dioxide. In addition, the total inflow weight 8.86 of all the substances shown in Table 3 and the total outflow weight 8.86 of all the substances in Table 4 are the same, and are balanced as the material balance. As a result of this practice, substantially all organic substances are decomposed into gas, the generated gas is a flammable gas mainly composed of hydrogen and methane, and the generation of harmful gas components is extremely small. It was shown that the period of stable operation could be greatly extended as compared with the prior art without pretreatment.
【The invention's effect】
In the pretreatment method according to the present invention, almost all of the inorganic salts contained in the material to be treated such as organic sludge precipitate as solid fine particles due to a change in solubility or adhere as solids to the tube wall of a heat transfer tube. The adhered precipitate is scraped off by the abrasive particles to become solid fine particles, and is removed out of the pretreatment vessel. As a result, a fluid to be treated substantially containing no inorganic salts can be obtained, and at the same time, the pretreatment device itself can stably operate for a long time.
When treating organic substances containing inorganic salts with supercritical water, the first zone for performing the pretreatment according to the present invention exclusively for the function of the entire treatment process, and the fluid that has been subjected to this pretreatment in the supercritical state exclusively By sharing the function with the second zone that decomposes and gasifies, the stable operation time of the processing equipment is dramatically increased by about 10 times compared to the conventional one, and the cost of cleaning the equipment is significantly reduced. The practicality of the critical water treatment method has been significantly improved.
This is because, in the present invention, the supercritical fluid flowing into the cracking / gasification reactor does not substantially contain inorganic salts, so that an operational obstacle due to the precipitation of inorganic salts that has conventionally occurred in the reactor is avoided. The result is that the capacity of the processing apparatus is remarkably improved because it hardly occurs.
[Brief description of the drawings]
FIG. 1A is a longitudinal sectional view illustrating an embodiment of a pretreatment device according to the present invention, and FIG. 1B is a plan view showing the inside of a pretreatment container.
FIG. 2 is an explanatory view schematically showing a flow state of solid precipitate particles and a floating flow state of ground particles in a pretreatment vessel according to the present invention.
FIG. 3 is a system diagram illustrating another embodiment of the pretreatment device according to the present invention.
FIG. 4 is a system diagram illustrating an embodiment of a supercritical water treatment apparatus according to the present invention.
FIG. 5 is a system diagram illustrating another embodiment of the supercritical water treatment apparatus according to the present invention.
[Explanation of symbols]
1 Pretreatment container
11, 12 heat transfer tubes
13, 14 header
2 Gasification reactor
21 Inflow port of fluid to be treated
22 Reaction product logistics outlet
23 heating furnace
24 Recycle gas piping
25 gaseous oxidizer piping
26, 27 Recycle gas selection valve
28, 29 Gaseous oxidizer selection valve
3 slurry pump
4 orifice 5 preheater
6 Precipitate discharge pipe
61 dust collecting edge 62 sediment discharger
63 container A 64 container B
65 valve A 66 valve B 67 valve C
68 High pressure gas piping 69 High pressure water piping
71 cyclone bottom
8 Slurry supply port
9 Outlet 10 Supply port