JP4528173B2 - Residue recovery method in high temperature and high pressure treatment equipment for organic waste - Google Patents

Description

  The present invention relates to a residue recovery method in a high-temperature and high-pressure treatment apparatus that oxidatively decomposes organic waste in a reactor having a critical temperature that is not lower than the critical temperature.

  At present, incineration is the main method for treating organic waste. However, incineration is not suitable in areas where a large amount of waste is not discharged because a large plant is required for incineration. Therefore, development of high-temperature and high-pressure treatment of organic waste is being promoted as a treatment technique to replace incineration.

  A typical technique for high-temperature and high-pressure processing is supercritical processing. Supercritical processing is a technique that uses supercritical water at 374 ° C. or higher and 22 MPa or higher as a reaction field for oxidation treatment. In this technique, organic waste is oxidized at a temperature of, for example, 22 to 25 MPa and a temperature of 600 to 650 ° C. However, since the discharge pressure of the pump for feeding the organic waste into the reactor must be 25 MPa or more, the solid content concentration However, it is difficult to treat 10% or more organic waste. In addition to this, there are problems such as corrosion of the apparatus due to severe reaction conditions, and a large amount of cost for pressurization of oxygen and air as oxidants.

  There is a wet oxidation process as another technique of the high temperature and high pressure process. This wet oxidation treatment is a technique for oxidizing organic substances under liquid phase conditions that are below the critical point for both temperature and pressure. However, this treatment has a problem in the degree of oxidation, and in particular, nitrogen is converted into ammonia under these conditions, and this ammonia can hardly be decomposed, so that ammonia is discharged into the waste water.

  In addition, a technique for oxidizing and decomposing organic substances under a condition of a critical temperature or higher and a critical pressure or lower has been proposed. In this technique, as shown in Patent Document 1, an organic substance is moved to a reaction field using a water flow, and is oxidatively decomposed at, for example, 10 MPa and 600 ° C. However, in the method disclosed in Patent Document 1, wastes having a low solid content concentration can only be processed in order to use the water flow, and there is a problem that the solid content that can be processed is small relative to the volume of the apparatus.

  Therefore, the present inventor is developing a technique for oxidatively decomposing an organic substance having a high solid content concentration (10% or more) under conditions of a critical temperature or higher and a critical pressure or lower. In this technique, organic waste is heated by a preheater, oxidized and decomposed by a reactor, and mineralized. Because of the high solid content in the reactor, it burns itself using the heat of reaction. The reactor separates and discharges the residue and exhaust gas, and the exhaust gas is used as a heat source for the preheater. The residue is a powdered inorganic content.

The reactor is provided with a vertical residue discharge line with a double valve, first opening the first valve close to the reactor to drop the residue to the position of the second valve below, then closing the first valve In addition, the second valve is opened, and the residue is discharged out of the system and collected. However, since the residue moves from the reactor to the residue discharge line by mere gravity drop, the residue is blocked in the residue discharge line (particularly above the first valve and below the second valve) in the above-described residue recovery method. This has hindered the practical application of the technology for oxidative decomposition treatment of organic waste having a high solid content concentration.
Japanese Patent Laid-Open No. 10-137774

  Accordingly, an object of the present invention is to provide a residue recovery method capable of discharging a residue having a high solid content under oxidative decomposition under a condition of a critical temperature or higher and a critical pressure or lower without clogging the residue. That is.

In order to solve the above problems, the present invention is directed to oxidatively decomposing organic waste by a reactor having a critical temperature or higher and a critical pressure or lower, and the residue is first valve, second valve, first drain tank, first drain, This is a method of recovering via a residue discharge line equipped with a 3-valve and a second drain tank in series, and in a state where the fourth valve of the line leading the reactor internal pressure is opened below the second valve, The drain tank is increased to a predetermined pressure lower than the reactor internal pressure, the first valve is closed, the second valve is opened, the fourth valve is closed, and the region from the first valve to the third valve is used as the reactor internal pressure. The third valve is opened and the residue below the first valve is collected in the first drain tank and the second drain tank using the differential pressure, and then the first valve is opened and the second valve is closed. Reactor pressure is applied to the upper region After moving the residue to a second valve Te, the first valve closed, it is characterized in that recovering the residue second valve is opened to the first drain tank and the second drain tank.

  In any of the inventions, it is preferable to increase the pressure of the second drain tank with an inert gas. The area below the first valve is increased to the reactor internal pressure, and the fourth valve is opened to bring the entire pressure to the reactor internal pressure. It is preferable to add a step of returning.

  According to the present invention, a differential pressure is generated inside the residue discharge line directly connected to the reactor, and the residue accumulated in the residue discharge line is discharged to the drain tank. Therefore, it is possible to discharge the organic matter having a high solid content concentration from the reactor for oxidative decomposition treatment without clogging the residue. In this case, the internal pressure of the reactor hardly fluctuates and the reaction system is not disturbed.

  FIG. 1 is a conceptual diagram showing an apparatus configuration, wherein 1 is a preheater, and 2 and 3 are reactors. For example, organic waste such as sewage sludge is pressurized by the slurry injector 4 in a slurry state with a solid content concentration of 10% or more and injected into the preheater 1. The temperature of the reactors 2 and 3 is maintained at a critical temperature of 374 ° C. or higher (600 ° C. or lower), and the preheater 1 preheats the organic waste to this temperature and sends it to the reactor 2. The internal pressures of the preheater 1 and the reactors 2 and 3 are in the range of 4 to 10 MPa below the critical pressure, but these devices are all in the same pressure because they communicate with each other. This is called “reactor internal pressure”. In the present invention, a single reactor may be used.

  The organic waste proceeds inside the reactors 2 and 3 by the feed blades 5 and 6 and is oxidatively decomposed in a reaction field of a critical temperature or higher and a critical pressure or lower, exhaust gas such as carbon dioxide gas, nitrogen gas, etc. It becomes a residue. Oxygen is supplied into the preheater 1 and the reactors 2 and 3 for oxidative decomposition.

  A vertical residue discharge line is directly connected to the lower surface of the rear end portion of the reactor 3. The residue discharge line includes a first valve 11, a second valve 12, a first drain tank 13, a third valve 14, and a second drain tank 15 in series. In addition, there is a line 7 that communicates the preheater 1 with the lower part of the second valve 12 and guides the reactor internal pressure to the residue discharge line. A fourth valve 16 is provided in this line 7. Of the residue discharge line, the portion below the connection point of the line 7 is easy to prevent clogging of the residue using the internal pressure of the reactor, whereas the portion above the portion is the portion where it has been difficult to remove the accumulated residue.

  Hereinafter, the steps of the present invention will be described with reference to FIGS. Here, description will be made assuming that the internal pressure of the reactor is 4 MPa. Further, the square frames in FIG. 2 and subsequent figures are for displaying a range where the pressure is the same. Valves are indicated by open circles and closed circles.

  First, FIG. 2 is a diagram showing a state during normal operation, in which the third valve 14 is closed and the fourth valve 16 is open, and the internal pressure of the second drain tank 15 is 0 MPa. The internal pressure of the residue discharge line is kept at 4 MPa, which is the internal pressure of the reactor because the fourth valve 16 of the line 7 is open, and the first valve 11 and the second valve 12 constituting the double valve are alternately opened and closed. As a result, the residue is dropped into the first drain tank 13. This residue discharge is caused by gravity drop, and as described above, there is a possibility of occurrence of clogging.

  The steps of collecting the residue are as shown in FIG. First, as shown in FIG. 3, the second drain tank 15 is increased to a predetermined pressure lower than the reactor internal pressure. The pressure is increased using an inert gas such as argon gas, and the pressure is increased to 3 MPa, for example. Use of nitrogen gas is not preferable because ammonia may be generated. If the pressure difference with the reactor internal pressure is too small, the residue will not be discharged sufficiently, and if the pressure difference with the reactor internal pressure is too large, the influence on the reaction system will increase, so that the pressure is about 0.5 to 1.5 MPa. The pressure difference is appropriate. Then, the first valve 11 is closed and the second valve 12 is opened.

  Next, the fourth valve 16 in the line 7 is closed as shown in FIG. At this time, the region from the first valve 11 to the third valve 12 is 4 MPa which is the reactor internal pressure, and the portion below the third valve 12 is 3 MPa. Next, the third valve 14 is opened as shown in FIG. At this moment, the residue below the first valve 11 moves downward due to the pressure difference and is collected in the first drain tank 13 and the second drain tank 15. Since the third valve 14 is opened, the pressure in the area below the first valve 11 is intermediate between the reactor internal pressure and the predetermined pressure in the previous period, for example, 3.5 MPa.

  Next, as shown in FIG. 6, both the first valve 11 and the second valve 12 are closed, and the area between the first valve 11 and the second valve 12 is set to 3.5 MPa. At this time, the upper part of the first valve 11 is 4 MPa which is the internal pressure of the reactor, and the lower part of the first valve 11 is 3.5 MPa, so that a pressure difference is formed. In this state, when the first valve 11 is opened as shown in FIG. 7, the high pressure gas from the reactor 6 flows toward the residue discharge line due to the pressure difference at that moment, and accumulates on the top and bottom of the first valve 11. The residue is moved to the second valve 12.

  Next, as shown in FIG. 8, the first valve 11 is closed and the second valve 12 is opened, and the residue that has moved up to the second valve 12 is collected in the first drain tank 13 and the second drain tank 15. 6 to 8 may be repeated several times. Since the second valve 12 is always closed when the first valve 11 is opened, no pressure fluctuation occurs in the reaction system.

  After the residue recovery is completed in this way, as shown in FIG. 9, the area below the first valve 11 is increased to 4 MPa, which is the reactor internal pressure, by an inert gas. And the 4th valve 16 of line 7 is opened, and it returns to normal operation. The residue collected in the first drain tank 13 and the second drain tank 15 is appropriately taken out with the second valve 12 and the fourth valve 16 closed.

  As described above, according to the present invention, an appropriate differential pressure is generated inside the residue discharge line by operating the valve, and the residue accumulated in the residue discharge line can be discharged to the drain tank using this differential pressure. it can. In particular, the residue on the upper portion of the first valve 11 that has been easily blocked can be reliably discharged. Moreover, even in that case, there is an advantage that the reaction system is not disturbed. In addition, when the residue inside a residue discharge line gets wet with the water vapor | steam discharged | emitted from a reaction system, obstruction | occlusion is accelerated | stimulated. For this reason, it is preferable to prevent the wetting by providing a heater on the outer periphery of the residue discharge line.

It is a conceptual diagram which shows an apparatus structure. It is explanatory drawing which shows the valve opening / closing state during normal driving | operation. It is explanatory drawing which shows the state which pressure-rised the 2nd drain tank to predetermined pressure. It is explanatory drawing which shows the state which closed the 4th valve | bulb. It is explanatory drawing which shows the state which opened the 3rd valve | bulb. It is explanatory drawing which shows the state which closed the 1st valve | bulb and the 2nd valve | bulb. It is explanatory drawing which shows the state which opened the 1st valve | bulb. It is explanatory drawing which shows the state which closed the 1st valve and opened the 2nd valve. It is explanatory drawing which shows the state which opened the 4th valve | bulb.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 1 Preheater 2 Reactor 3 Reactor 4 Slurry injector 5 Feed blade 6 Feed blade 7 Line 11 which guides reactor internal pressure 11 1st valve 12 2nd valve 13 1st drain tank 14 3rd valve 15 2nd drain tank 16 4th valve

Claims (3)

  Residue from organic waste oxidatively decomposed by a reactor at a critical temperature or higher and a critical pressure or lower is discharged from the first valve, second valve, first drain tank, third valve, and second drain tank in series. In this method, the second drain tank is raised to a predetermined pressure lower than the reactor internal pressure with the fourth valve of the line leading the reactor internal pressure below the second valve open. The first valve is closed, the second valve is opened, the fourth valve is closed, the region from the first valve to the third valve is used as the reactor internal pressure, and then the third valve is opened and the differential pressure is used. Residues of 1 valve or less are collected in the first drain tank and the second drain tank, then the first valve is opened, the second valve is closed, and the internal pressure of the reactor is applied to the region above the first valve to remove the residue. After moving to the second valve, Closing the valve, the residue recovery method at high pressure treatment apparatus of organic waste and recovering the residue second valve is opened to the first drain tank and the second drain tank. The method for recovering residues in a high-temperature and high-pressure treatment apparatus for organic waste according to claim 1, wherein the second drain tank is pressurized with an inert gas. 2. The high-temperature and high-pressure of organic waste according to claim 1, further comprising the step of increasing the region below the first valve to the reactor internal pressure and opening the fourth valve to restore the whole to the reactor internal pressure. Residue collection method in processing equipment.

Images