JP5150199B2 - Sludge treatment system - Google Patents

Description

  The present invention relates to a sludge treatment system that reduces the volume by heat-treating sludge containing a large amount of organic matter.

  In recent years, many treatment methods have been used in which sludge containing a large amount of organic matter is subjected to anaerobic fermentation by the action of anaerobic microorganisms such as methanogens and digestion gas is recovered. In this case, the treatment target of anaerobic microorganisms is mainly relatively low-molecular organic matter, so if an attempt is made to treat hardly decomposed organic sludge such as excess sludge generated by sewage treatment by anaerobic treatment, the sludge It took a long time to dissolve, leading to an increase in the size of the apparatus and a deterioration in processing efficiency.

  Therefore, a method has been proposed in which a solubilization process is performed in advance when digesting a hardly decomposable organic sludge such as surplus sludge so that digestion with anaerobic microorganisms can be efficiently performed in a short time. As the solubilization treatment, a hydrothermal treatment method utilizing extremely high reactivity of high-temperature high-pressure water has attracted attention, and a technique for that purpose has been proposed (for example, see Patent Document 1).

  The hydrothermal solubilization treatment apparatus in the above proposal has a first heat exchanger and a second heat exchanger, and these heat exchangers each have a liquid retention part and a heat exchange part. . The heat exchanging part has a structure in which a plurality of tubes and heat radiating fins are laminated, and the liquid retaining part has a capacity capable of retaining the organic sludge for the time required for the hydrothermal reaction treatment. The organic sludge is sent to the heat exchange part of the first heat exchanger and preheated. The sludge having a medium temperature and high pressure due to the preheating is introduced into the heat exchange part of the second heat exchanger, and is heated by the heating gas in this heat exchange part. The heated sludge is discharged as a high-temperature and high-pressure hydrothermal solubilized sludge and introduced into the hydrothermal reaction space (consisting of a heat exchange part and a liquid retention part) of the first heat exchanger. Sludge that has undergone hydrothermal solubilization reaction in this hydrothermal reaction space is cooled in a heat exchange section and discharged as low-temperature and high-pressure hydrothermal solubilization sludge. That is, in the hydrothermal reaction space of the second heat exchanger and the hydrothermal reaction space of the first heat exchanger, the organic sludge is exposed to high temperature and high pressure conditions, and hydrothermal solubilization reaction occurs.

In such an apparatus, in the first heat exchanger, the sludge before the heat treatment and the sludge after the heat treatment are heated via the heat transfer surface (a plurality of tubes, heat radiating fins, etc.) at a high pressure in the heat exchange section. Exchange. The sludge preheated in the first heat exchanger is heated by the heating gas in the heat exchange section in the second heat exchanger, and the sludge is solubilized in the hydrothermal reaction section including the heat exchange section. It was that.
JP 2005-254165 A

  In the prior art described above, heat exchange between the pre-heated sludge and the post-heated sludge is performed via a heat transfer surface formed by heat dissipating fins stacked with a plurality of tubes in the heat exchange section. For this reason, for example, if a protein coagulate or sludge such as calcium carbonate due to sludge adheres to the heat transfer surface, the heat exchange efficiency decreases. There is also concern about clogging of the flow path due to sludge.

  An object of the present invention is to make sludge capable of effectively heat-treating sludge without causing deterioration in heat exchange efficiency due to adhesion of sludge components to the heat transfer surface and without causing clogging of the flow path due to sludge. To provide a processing system.

  The sludge treatment system according to the present invention includes a reactor for heating and treating heat sludge under a predetermined pressure, a direct heat exchanger connected to a sludge supply path to the reactor, and a heat treatment from the reactor. The evaporator unit connected on the sludge discharge path is integrated, and the inside thereof is maintained at a lower pressure than that in the reactor, and the sludge before heat treatment introduced into the direct heat exchanger unit is And a preheating device that directly heats the steam generated from the sludge after heat treatment introduced into the evaporator section through a discharge path.

  In the present invention, the preheating device is connected in a plurality of stages in series on the sludge supply path and the post-heat treatment sludge discharge path, and the internal pressures of the plurality of preheating apparatuses are sequentially increased in the downstream direction when viewed from the reactor. It is good also as a structure set low.

  The present invention is installed between any two preheating devices on the sludge discharge path after heat treatment in which preheating devices are connected in series in a plurality of stages, and the internal pressure is self-generated from the upstream preheating device as viewed from the reactor. Is set so as to be lowered sequentially toward the preheating device on the downstream side, and steam is generated from the post-heat treatment sludge introduced from the upstream preheating device by the pressure difference with the upstream side, and the steam is The structure provided with the evaporator which has piping for supplying to the direct heat exchanger part of an upstream preheating apparatus may be sufficient.

  The present invention may have a configuration provided with an anaerobic treatment device for anaerobically treating the sludge after heat treatment which is heat-treated by the reactor and discharged through the evaporator section of the preheating device.

  In the present invention, the digestion gas generated from the anaerobic treatment device may be used as fuel for the heating source equipment for the reaction tank.

  The present invention may include a temperature adjustment device that adjusts the post-heat treatment sludge discharged through the evaporator section of the preheating device to a temperature suitable for anaerobic treatment.

  In the present invention, the temperature adjustment device is set to an internal pressure lower than that of the preheating device, introduces the sludge after heat treatment discharged through the evaporator part of the preheating device, and generates steam due to the internal pressure difference with the preheating device. It is good to comprise with the evaporator which is made to reduce sludge temperature.

  In the present invention, the temperature adjustment device is connected to a pipe line from the sludge discharge section after heat treatment of the preheating device to the anaerobic treatment apparatus, and is an apparatus that mixes sludge that has not been heat-treated with respect to the discharged sludge flowing through this pipe line. Good.

  In this invention, you may comprise a reactor so that the liquid component from which solid content was isolate | separated from the heat-treated sludge may be supplied to the evaporator part of a preheating apparatus through the said discharge path.

  The present invention may have a configuration having a pipe for supplying the solid content of the sludge after heat treatment separated from the liquid to an anaerobic treatment apparatus.

  The present invention has a concentrator for concentrating the solid content of sludge after heat treatment separated from the liquid component, and a pipe for supplying the liquid component resulting from the concentration to the anaerobic treatment device through an evaporator for temperature control You may comprise so that it may have.

  In the present invention, the heat treatment in the reactor may be a heat treatment or a heat pressure treatment between 60 ° C. and 374 ° C.

  According to the present invention, the structure is simple, the heat exchange efficiency is reduced due to the adhesion of sludge, the flow path is clogged, and the failure is not easily caused, and the sludge can be effectively heat treated.

  Hereinafter, an embodiment of a sludge treatment system according to the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a block diagram showing the configuration of this embodiment. The sludge treatment system shown in FIG. 1 is a concentrator 12 that concentrates sludge 11 that contains a large amount of organic matter to be treated, a preheater 13 for concentrated sludge, and a reaction that heats and heats the preheated sludge under a predetermined pressure. A container 14.

  For example, as shown in Japanese Patent Application Laid-Open No. 2007-21300, the preheating device 13 arranges the heat exchanger unit 15 directly in the upper part of the common container and arranges the evaporator unit 16 in the lower part to integrate them, The high temperature steam generated in the lower evaporator section 16 is brought into direct contact with the sludge introduced into the upper direct heat exchanger section 15 to heat and preheat.

  The inlet of the direct heat exchanger 15 is connected to the concentrator 12 via a transfer pump 18, and the outlet is connected to the reactor 14 via a transfer pump 19. That is, the direct heat exchanger section 15 is connected to the sludge supply path to the reactor 14. Further, the inlet portion of the evaporator section 16 is connected to the post-heat treatment sludge discharge section of the reactor 14 via the transfer valve 20, and the outlet section is connected to a pipe leading to the subsequent anaerobic treatment device 22. That is, the evaporator section 16 is connected to the sludge discharge path after the heat treatment from the reactor 14.

  The preheating device 13 is provided with a pressurizing compressor 24 and a relief valve 25 (a pressure adjusting valve with a mechanism that opens when the pressure exceeds a set pressure), and the internal pressure of the preheating device 13 (direct heat exchanger section 15 and evaporation). The internal pressure common to the reactor section 16) is maintained at a lower pressure than in the reactor 14. Therefore, the sludge before heat treatment introduced into the direct heat exchanger section 15 of the preheating device 13 is directly heated by the steam generated from the sludge after heat treatment introduced into the evaporator section 16 from the discharge path.

  The reactor 14 heats and heat-treats the sludge after preheating introduced from the preheating device 13 under a predetermined pressure, and liquefies it. For this purpose, the reactor 14 is supplied with high-temperature steam generated from the boiler 27, which is a heating source equipment, by being pressurized to a predetermined pressure by the pressure raising equipment 28, and heats and pressurizes sludge. In addition, a heater 23 is provided for heating. As the fuel for the boiler 27, biogas (digestion gas) containing methane generated by the digestion reaction from an anaerobic treatment device (hereinafter described as a digestion tank) 22 may be used. In this case, the biogas is desulfurized by the desulfurizer 29 and supplied to the boiler 27 for combustion.

  The digestion tank 22 converts the introduced sludge into biogas by the action of anaerobic bacteria, and its inlet is at the outlet of the evaporator section 16 in order to introduce the discharged sludge discharged through the preheating device 13. And a transfer valve 30, an evaporator 31 as a temperature adjusting device, and a transfer pump 32. The evaporator 31 serving as the temperature adjusting device adjusts the discharged sludge discharged through the preheating device 13 to a temperature suitable for anaerobic treatment, and is set to an internal pressure lower than that of the preheating device 13. The high-temperature sludge discharged after passing through is introduced, and steam is generated by the internal pressure difference with the preheating device 13 to lower the sludge temperature to an appropriate temperature. The generated steam may be led out by the vacuum pump 34 via the pressure regulating valve 33 and used as a heat source in the station.

  The remaining solid content of the sludge introduced into the digestion tank 22 and converted into biogas is dehydrated by the dehydrator 35 and then incinerated or landfilled.

  In the above configuration, the sludge 11 is introduced into the heat treatment reactor 14 through the direct heat exchanger section 15 of the preheating device 13. The sludge after the heat treatment is introduced into the evaporator section 16 of the preheating device 13, and the sludge that has passed through the evaporator section 16 is introduced into the subsequent digestion tank 22. A gas component containing a large amount of methane gas generated in the digestion tank 22 is supplied to the boiler 27 after passing through the desulfurization equipment 29 through the gas pipe and burned. The remaining solid content of the sludge treated in the digestion tank 22 is discarded after dehydration.

  Details will be described below. Sludge 11 (temperature 20 ° C.) is first concentrated to a moisture content of 97% or less by the concentrator 12. This concentrated sludge is introduced by the transfer pump 18 into the direct heat exchanger section 15 formed at the top of the preheating device 13. On the other hand, the sludge after the heat treatment that has become a high temperature and a high pressure by the heat treatment described later is introduced from the reactor 14 into the evaporator portion 16 that is integrated with the direct heat exchanger portion 15 and the lower portion.

  Here, the internal pressure of the integrated container of the preheating device 13 is set to 202 kPa by the compressor 24 and the relief valve 25. That is, the relief valve 25 is a valve that opens when the pressure exceeds the set pressure. Therefore, the internal pressure can be easily adjusted by setting the set pressure to 202 kPa. This internal pressure is set lower than the internal pressure of the reactor 14. As is well known, there is a relationship as shown in FIG. 8 between the saturated vapor pressure and the water temperature. For this reason, the sludge after heat treatment at a high temperature (220 ° C.) introduced into the evaporator section 16 and having a pressure higher than the internal pressure of the evaporator section 16 generates steam until the ambient pressure reaches 120 ° C. due to a decrease in the ambient pressure. Reduce the temperature. This heat of evaporation is brought into direct contact with the sludge before heat treatment in the upper direct heat exchanger section 15. By this, the sludge before heat processing is heated from 20 degreeC to (120- (alpha)) degreeC ((alpha) is about 1-5 degreeC by a heat loss part), and is preheated.

  The sludge preheated by the preheating device 13 is introduced into the reactor 14 by the transfer pump 19. High-temperature steam obtained from the boiler 27 is boosted by a booster 28 and supplied to the reactor 14. Further, by heating with the heater 29 as another heat source, the temperature in the reactor 14 is increased to 220 ° C. and 2.3 MPa. By such pressurized hot water treatment (hereinafter referred to as hydrothermal treatment) in a high-temperature and high-pressure environment, the polymer solid organic material is reduced in molecular weight and liquefied. For example, when surplus sludge, which is drawn sludge from a biological reaction tank in a sewage treatment plant, is targeted, 70 to 80% of the solid content of the sludge is converted into liquid by hydrothermal treatment.

  The liquefied high-temperature sludge at 220 ° C. after the heat treatment is transferred by opening the transfer valve 20 due to the internal pressure difference between the reactor 14 and the preheating device 13 and introduced into the evaporator section 16. . The sludge introduced into the evaporator section 16 is vaporized by being depressurized from 2.3 MPa to 202 kPa, deprived of heat, and reduced in temperature from 220 ° C. to 120 ° C. as described above. This temperature reduction becomes high-temperature steam and, as described above, directly contacts the sludge before heat treatment in the direct heat exchanger section 15 to heat the sludge to (120-α) ° C. and preheat it.

  The sludge whose temperature has been reduced to 120 ° C. in the evaporator section 16 is opened by opening the transfer valve 30 due to a pressure difference between the evaporator section 16 and another evaporator 31 connected to the discharge side thereof. 31. The evaporator 31 is depressurized to 74 kPa by the vacuum pump 34 and the pressure adjustment valve 33. For this reason, the 120 degreeC sludge introduced into the evaporator 31 is temperature-reduced to 40 degreeC suitable for the anaerobic process in the subsequent digestion tank 22 by the said pressure difference.

  The sludge whose temperature has been reduced to 40 ° C. is transferred from the evaporator 31 by the transfer pump 32 and is put into the digestion tank 32. And it is converted into biogas by the action of anaerobic bacteria in the digestion tank 32. The biogas containing 60% or more of methane generated in the digestion tank 32 in this way is burned in the boiler 27 after the hydrogen sulfide is removed by the desulfurization equipment 29. At least a part of the steam generated in the boiler 27 is used for heating of the sludge heat treatment as described above. Of course, it can also be used as another heat source. The remaining solid content after being converted into biogas is dehydrated by the dehydrator 35 and then incinerated or landfilled.

  In this way, the steam when the sludge after heat treatment vaporizes and the sludge before heat treatment are brought into direct contact without going through the heat transfer surface, so that the conventional sludge before heat treatment and the sludge after heat treatment are passed through the heat transfer surface. Compared to heat exchangers that exchange heat, high heat exchange efficiency can be obtained. In this case, as the amount of heat supplied from the outside, only the amount of heat necessary for raising the sludge to 100 ° C. from (120−α) ° C. to 220 ° C. in the reactor 14 can be used. It is. In addition, it is possible to provide a heat exchange device that has a simple structure and is less likely to fail.

  Further, since the sludge is reduced in molecular weight by heat treatment and becomes a component that can be easily used by microorganisms, the amount of methane gas generated can be increased as compared with the case where heat treatment is not performed. In addition, since the molecular weight is reduced, the decomposition rate is increased, so that the number of days of digestion (digestion tank residence time) can be reduced to about 1/3 of the conventional one. That is, processing can be performed with a volume of about 1/3 that of a conventional digester. In addition, the heat treatment at 220 ° C. makes it easier for the sludge to be dehydrated and the solid content is decomposed into a liquid component, so that the amount of generated sludge is reduced by 70 to 80% compared to the case without heat treatment, The amount generated can be greatly reduced.

  In addition, the sludge temperature of each part is not limited to the said embodiment, What is necessary is just the sludge before heat processing heated by the vaporization heat which generate | occur | produces from the sludge after heat processing. That is, any temperature may be used as long as it is in a subcritical state temperature range of 374 ° C. or lower.

  Also, steam for hydrothermal treatment is not directly blown into the reactor 14 from the booster 28, but steam is blown directly into the piping from the heat exchanger section 15 to the reactor 14 (downstream of the transfer pump 19). The structure which heats the sludge in the middle of transfer may be sufficient.

  Further, the heat source for the reactor 14 is not limited to the steam generated when the digested gas is burned by the boiler 27, but may be exhaust heat generated when the generator is operated by biogas, for example, exhaust of a gas turbine. In addition, when the dewatered sludge is incinerated, the gas from the incinerator may be used.

  Next, the embodiment shown in FIG. 2 will be described.

  In this embodiment, the internal pressure adjustment portion in the preheating device 13 is different from the embodiment of FIG. That is, instead of adjusting the internal pressure in the preheating device 13 as shown in FIG. 1 by the compressor 24 and the relief valve 25, as shown in FIG. 2, a pressure adjusting valve 37 is provided and opened. The internal pressure in the preheating device 13 was atmospheric pressure. For this reason, in the evaporator section 16, the heat-treated sludge introduced from the reactor 14 is reduced to 100 ° C. based on the atmospheric pressure, and the steam generated at that time is directly heated in the heat exchanger section 15 before the heat treatment. Directly heated to (100-α) ° C. and preheated.

  The sludge preheated by the preheating device 13 is introduced into the reactor 14 by the transfer pump 19. The sludge introduced into the reactor 14 is hydrothermally treated in a high-temperature and high-pressure environment, and the high-molecular solid organic matter is reduced in molecular weight to become liquefied sludge at 180 ° C. The 180 ° C. high-temperature sludge liquefied by the heat treatment in this way is introduced into the evaporator section 16 due to the internal pressure difference between the reactor 14 and the preheating device 13, vaporized, and deprived of heat as described above. The temperature is reduced to 100 ° C. based on atmospheric pressure. This temperature reduction becomes high-temperature steam and, as described above, directly contacts the sludge before heat treatment in the direct heat exchanger section 15 and warms it to (100-α) ° C. to preheat it.

  The sludge reduced to 100 ° C. is introduced into the evaporator 31 connected to the discharge side of the evaporator section 16, and is heated to a temperature of 40 ° C. suitable for anaerobic treatment in the subsequent digestion tank 22 due to the pressure difference. Reduced temperature. The subsequent operation is the same as that of the embodiment shown in FIG.

  As described above, the configuration shown in FIG. 2 eliminates the need for an extra device and can provide a system with fewer failures.

  Note that the temperature reduction to 40 ° C. suitable for anaerobic treatment in the digestion tank 22 is to reduce the temperature by reducing the pressure using the vacuum pump 34, but the temperature is reduced by providing a separate cooler. It may also be one that performs heat exchange with cooler water.

  Next, the embodiment shown in FIG. 3 will be described.

  This embodiment is different from the embodiment shown in FIG. 1 in that the solid content of the heat-treated sludge is taken out from the reactor 14. That is, since the solid content of the heat-treated sludge is accumulated at the bottom of the reactor 14, a solid content extraction device 39 having an extraction valve 38 is connected to the bottom of the reactor 14 so that the reactor 14 has a solid-liquid separation function. . The solid content of the post-heat treatment sludge that has been solid-liquid separated and extracted from the reactor 14 by the solid content extracting device 39 is supplied to the digestion tank 22 through a pipe having a transfer pump 40. Further, the liquid component of the sludge after heat treatment separated from the solid and the liquid is supplied to the evaporator section 16 of the preheating device 13 through the discharge pipe. That is, the configuration of FIG. 3 is provided with mechanisms 38 and 39 for extracting the solid content from below the reactor 14, and the liquid content is introduced into the evaporator section 16 of the preheating device 13.

  Here, the solid-liquid separation of the sludge after the heat treatment is performed by intermittently withdrawing the solid content by a withdrawal valve 38 connected to the bottom of the reactor 14. The settleability of heat-treated sludge is good, and the solid content settles downward. The liquid component that is the supernatant of the reactor 14 is introduced into the evaporator section 16 of the preheating device 13. The pressure in the container of the preheating device 13 including the evaporator unit 16 is adjusted to 202 kPa. As a result, the liquid content of the sludge after heat treatment is reduced to 120 ° C.

  The liquid content of the sludge after heat treatment introduced into the evaporator section 16 of the preheating device 13 is only the volume of the solid content reduced by solid-liquid separation (the reduced volume is β: 0.2 to 0.3), The amount of steam for the temperature rise when the pressure is reduced in the evaporator section 16 is reduced, and the amount of preheating in the direct heat exchanger section 15 with respect to the sludge before heat treatment is reduced. For this reason, the temperature rise of the sludge which flows out directly from the heat exchanger part 15 becomes small compared with the case of embodiment of FIG. That is, the temperature of the sludge flowing out from the direct heat exchanger section 15 is (120−α) × (1−β) ° C. For this reason, the amount of heat required to be supplied to the reactor 14 from the outside increases. However, clogging of the discharge flow path from the reactor 14 to the evaporator section 16 of the preheating device 13 is reduced, and a stable system can be obtained.

  The liquid component flowing out from the evaporator section 16 of the preheating device 13 is introduced into the evaporator 31, reduced in temperature to around 40 ° C., and then introduced into the digestion tank 22. The solid content extracted from the reactor 14 by the solid-liquid separation is charged into the digestion tank 22 as described above together with the liquid temperature reduced to around 40 ° C. Other operations are the same as those of the embodiment of FIG.

  According to this embodiment, since the vapor when the solution after the heat treatment is vaporized is brought into direct contact with the sludge before the heat treatment without using the heat transfer surface, the heat exchange efficiency is higher than that of the conventional heat exchanger. Thus, heating can be performed for 200 ° C. with only the amount of heat necessary to raise the temperature by about 100 ° C. In addition, since the solid content of the sludge after heat treatment discharged through the evaporator section 16 for preheating is removed in advance, a system configuration with less clogging of flow paths such as transfer pipes and transfer valves may be adopted. it can.

  Solid-liquid separation can be achieved only by gravity sedimentation, and since a new apparatus (membrane, centrifugal concentration) and chemicals such as a polymer flocculant are not added, it can be realized at low cost. Of course, solid-liquid separation may be performed by centrifugation or membrane separation. However, the membrane used for membrane separation must be a high temperature resistant membrane such as a metal membrane. Further, the solid content separated by solid-liquid is not limited to being charged into the digestion tank 22, and may be returned to the subsequent stage of the concentrator 12 installed in the previous stage in order to heat-treat a part thereof. Further, dehydration may be performed as it is without being processed in the digestion tank 22.

  Next, the embodiment shown in FIG. 4 will be described.

  In this embodiment, the preheating device 13 in which the direct heat exchanger section 15 and the evaporator section 16 are integrally configured is installed in multiple stages (three stages in the example in the figure). That is, in the plurality of preheating devices (three preheating devices 13A, 13B, and 13C), their direct heat exchanger portions 15A, 15B, and 15C are connected from the outlet portion of the concentrator 12 to the inlet portion of the reactor 14. The evaporator sections 16A, 16B, and 16C are connected in series on the incoming sludge supply path, and the plurality of evaporator sections 16A, 16B, and 16C are disposed on the post-heat treatment sludge discharge path from the outlet section of the reactor 14 to the inlet section of the evaporator 31. They are connected in series.

  Further, the internal pressures of the plurality of preheating devices 13A, 13B, and 13C were sequentially set to be lower in the downstream direction as viewed from the reactor 14 (from the right side to the left side in the figure). That is, the most downstream preheating device 13A as viewed from the reactor 14 (hereinafter referred to as the first preheating device, and the second and third preheating devices in order toward the right side) has the lowest internal pressure. Adjust the pressure. For example, the internal pressure of the first preheating device 13 </ b> A is controlled to 19.9 kPa by a vacuum pump 3 4 that is common to the pressure regulating valve 42 and the evaporator 31. The internal pressure of the second preheating device 13 </ b> B is controlled to 100 kPa by opening the atmosphere with the pressure regulating valve 37. The internal pressure of the third preheating device 13C is controlled to 360 kPa by the compressor 24 and the relief valve 25. With these pressure controls, the sludge temperatures after evaporation supplied from the reactor 14 and flowing out from the preheating devices 13A, 13B, and 13C can be controlled to 60 ° C, 100 ° C, and 140 ° C, respectively.

  In the above configuration, the sludge 11 (with a temperature of 20 ° C.) is concentrated to a moisture content of 97% or less by the concentrator 12 and is transferred to the transfer valve 41 due to a pressure difference with the first preheating device 13A that is reduced to an atmospheric pressure or less. Is introduced directly into the heat exchanger section 15A. The sludge before heat treatment introduced into the direct heat exchanger section 15A is heated by steam generated in the lower evaporator section 16A as will be described later, and from 20 ° C. to (60−α1) ° C. (α1 is the first Is preheated up to the heat loss of the preheating device 13A).

  The sludge before heat treatment preheated by the first preheating device 13A is introduced into the direct heat exchanger portion 15B of the second preheating device 13B by the first transfer pump 19A and, as will be described later, the lower evaporator portion 16B. And is preheated to (100−α1−α2) ° C. (α2 is a heat loss of the second preheating device 13B).

  Similarly, the sludge before heat treatment preheated by the second preheating device 13B is introduced into the direct heat exchanger section 15C of the third preheating device 13C by the second transfer pump 19B and is evaporated at the lower portion as will be described later. Heated by the steam generated in the vessel section 16C, preheated to (140−α1−α2−α3≈136) ° C. (α3 is a heat loss of the third preheating device 13C).

  Further, the sludge before heat treatment preheated by the third preheating device 13C is introduced into the reactor 14 by the third transfer pump 19C. In the reactor 14, high-temperature exhaust heat from the power generation equipment 43 using the biogas generated from the subsequent digestion tank 22 as fuel via the desulfurization device 29 and the siloxane removal device 42 is boosted to about 1 MPa by the booster 28. Has been added. Moreover, it heats with the heater 29 as another heat source. Thus, the reactor 14 can hydrothermally heat the introduced sludge by raising the temperature to 180 ° C. By this hydrothermal treatment, the polymer solid organic material is reduced in molecular weight and liquefied. For example, when surplus sludge in a sewage treatment plant is targeted, 40 to 50% of the solid content of the sludge is converted into liquid by hydrothermal treatment.

  The liquefied 180 ° C. high-temperature sludge after the heat treatment is transferred by opening the transfer valve 20C due to the internal pressure difference between the reactor 14 and the third preheating device 13C, and is transferred to the evaporator section 16C. be introduced. The sludge introduced into the evaporator section 16C is vaporized by being depressurized from 1 MPa to 360 kPa, deprived of heat, and reduced in temperature to 140 ° C. as described above. This reduced temperature becomes high-temperature steam and, as described above, directly contacts the sludge before heat treatment in the direct heat exchanger section 15C, warms it to (140−α1−α2−α3≈136) ° C., and preheats.

  The sludge whose temperature has been reduced to 140 ° C. is transferred by opening the transfer valve 20B due to an internal pressure difference between the third preheating device 13C and the second preheating device 13B, and is introduced into the evaporator section 16B. . The sludge introduced into the evaporator section 16B is vaporized by being depressurized from 360 kPa to 100 kPa, deprived of heat, and reduced in temperature to 100 ° C. as described above. This temperature reduction becomes high-temperature steam, and as described above, directly contacts the sludge before heat treatment in the direct heat exchanger section 15B, warms up to (100-α1-α2) ° C., and preheats.

  The sludge whose temperature has been reduced to 100 ° C. is transferred by opening the transfer valve 20A due to an internal pressure difference between the second preheating device 13B and the first preheating device 13A, and is introduced into the evaporator section 16A. . The sludge introduced into the evaporator section 16A is vaporized by being depressurized from 100 kPa to 19.9 kPa, and the temperature is reduced to 60 ° C. as described above. This temperature reduction becomes high-temperature steam and, as described above, directly contacts the sludge before heat treatment in the direct heat exchanger section 15B, warms it to (60-α1) ° C., and preheats it.

  The sludge reduced in temperature to 60 ° C. is introduced into the evaporator 31 by opening the transfer valve 30 due to the pressure difference between the evaporator section 16A and another evaporator 31 connected to the discharge side thereof, The temperature is reduced to a temperature of 40 ° C. suitable for anaerobic treatment in the subsequent digester 22. Subsequent operations are the same as those in the above-described embodiments, and a description thereof will be omitted.

  In this embodiment, the sludge before heat treatment can be preheated to about 136 ° C. by connecting the direct heat exchanger portions 15A, 15B, and 15C of the plurality of preheating devices 13A, 13B, and 13C in series. In the vessel 14, it is only necessary to input heat for 44 ° C. to raise the temperature to 180 ° C. from the outside. Although the solubilization rate by the heat treatment heated up to 180 ° C. is lower than that when the temperature is increased to 220 ° C., the final solubilization rate (reduction of sludge volume) by the treatment in the digester 22 at the latter stage is performed. The rate can be expected to be 80% or more. Further, the chromaticity which becomes a problem when the temperature is raised is also better than the case where the temperature is raised to 220 ° C.

  Moreover, the pressure adjustment of each preheating apparatus 13A, 13B, 13C should just depressurize with the one vacuum pump 34 shared with the evaporator 1 regarding the 1st preheating apparatus 13A which obtains the temperature of 100 degrees C or less, 100 With respect to the second preheating device 13B that obtains the temperature of ° C., the pressure is adjusted by releasing it to the atmospheric pressure, so the initial investment of the pressure adjusting pump is low.

  Note that the number of connected preheating devices 13 is not limited to three, and may be any number as long as it is two or more. As the number of stages increases to a certain level, the input energy from the outside becomes smaller and the heat recovery rate of the entire system improves. However, since a plurality of containers, pumps, valves, and the like are required and the configuration becomes more complicated, it is desirable to select a balanced number of both.

  Further, the means for reducing the temperature of the sludge after heat treatment from 60 ° C. to 40 ° C. suitable for treatment in the digestion tank 22 is not limited to the one in which the evaporator 31 is depressurized by the vacuum pump 34, but is cooled by a separate cooler. It may be. Further, heat exchange between the 20 ° C. sludge before heat treatment and the sludge after heat treatment may be performed by a normal heat exchange method via a heat transfer surface.

  Next, the embodiment shown in FIG. 5 will be described.

  This embodiment has a configuration in which a plurality (three in this case) of preheating devices 13A, 13B, and 13C are connected in series as in the embodiment of FIG. (In the example shown in the figure, the second stage preheating device 13B) is configured to raise the temperature of sludge before heat treatment at once. For this purpose, an evaporator 45 is installed on the sludge discharge path after heat treatment between any two preheating devices (in this case, between 13A and 13B), and the steam generated by the evaporator 45 and the exhaust generated from the power generation equipment 43 are disposed. The piping is connected so that heat is blown into the direct heat exchanger section 15B of the second stage preheating device 13B.

  Here, the internal pressure of the evaporator 45 is set so as to decrease sequentially from the preheating device 13B on the upstream side when viewed from the reactor 14 toward the preheating device 13A on the downstream side including itself. And the pipe | tube for supplying the vapor | steam produced by the pressure difference with an upstream from the post-heat-treatment sludge introduced from the upstream evaporator part 16B to the direct heat exchanger part 15B of the preheating apparatus 13B as mentioned above is provided. ing.

  Here, the internal pressure with the evaporator 45 installed between the 1st, 2nd, 3rd preheating apparatus 13A, 13B, 13C and the preheating apparatuses 13A, 13B is set as follows. For example, the first preheating device 13A has an internal pressure of 19.9 kPa by the vacuum pump 34 and the pressure regulating valve 42, an internal pressure of the evaporator 45 is 100 kPa by opening to the atmosphere, and the second and third preheating devices 13B, The internal pressure of 13C is controlled to around 360 kPa and 1 MPa by the common compressor 24 and relief valves 25 and 46 set to different pressures, respectively. By this, the temperature of the sludge after heat processing can be controlled to 60 degreeC, 100 degreeC, 140 degreeC, and 180 degreeC, respectively.

  In the reactor 14, the high-temperature exhaust heat from the power generation equipment 43 is raised to around 22 MPa by the booster 28, so that the temperature is raised to 220 ° C., and the introduced sludge is hydrothermally treated.

  In the above configuration, the 20 ° C. sludge 11 concentrated to a water content of 97% or less by the concentrator 12 is introduced into the direct heat exchanger section 15A of the first preheating device 13A and generated in the lower evaporator section 16A. It is heated by steam and preheated from 20 ° C. to (60−α1) ° C. (α1 is the heat loss of the first preheating device 13A).

  The sludge before heat treatment preheated by the first preheating device 13A is introduced into the direct heat exchanger section 15B of the second preheating device 13B. As described above, exhaust heat generated from the power generation equipment 43 and steam generated in the evaporator 45 are injected into the direct heat exchanger section 15B, and steam generated in the lower evaporator section 16B is in direct contact with sludge. As a result, the temperature is raised from (60-α1) ° C. to 140 ° C. at once.

  Thus, the sludge before heat treatment preheated to 140 ° C. by the second preheating device 13B is introduced into the direct heat exchanger portion 15C of the third preheating device 13C and heated by the steam generated in the lower evaporator portion 16C. And is preheated to (180−α3) ° C. (α3 is the heat loss of the third preheating device 13C).

  Further, the sludge before heat treatment that has been preheated to (180−α3) ° C. by the third preheater 13 </ b> C is introduced into the reactor 14. Since the pressure inside the reactor 14 is increased to around 22 MPa as described above, the introduced sludge is heated to 220 ° C. and hydrothermally treated. By this hydrothermal treatment, the polymer solid organic material is reduced in molecular weight and liquefied.

  The liquefied high-temperature sludge at 220 ° C. after the heat treatment is introduced into the evaporator section 16C due to the internal pressure difference between the reactor 14 and the third preheating device 13C, and the pressure is reduced from 22 MPa to 1 MPa. Vaporize and reduce to 180 ° C. This reduced temperature becomes high-temperature steam, directly contacts with the sludge before heat treatment in the direct heat exchanger section 15C, and is heated to (180-α3) ° C. and preheated as described above.

  The sludge reduced to 180 ° C. is vaporized by being introduced into the evaporator section 16B due to an internal pressure difference between the third preheating device 13C and the second preheating device 13B, and depressurizing from 1 MPa to 360 kPa, The temperature is reduced to 140 ° C. This reduced temperature becomes high-temperature steam, and in the direct heat exchanger section 15B, it preheats in direct contact with the sludge before heat treatment together with the steam from the evaporator 45 and the exhaust heat from the power generation equipment 43.

  The sludge whose temperature has been reduced to 140 ° C. is introduced into the evaporator 45 due to the internal pressure difference between the second preheating device 13B and the evaporator 45, and is vaporized by reducing the pressure from 360 kPa to 100 kPa. Is done. This reduced temperature becomes high-temperature steam and is blown into the second direct heat exchanger section 15B on the upstream side when viewed from the reactor 14, and as described above, the steam from the lower evaporator section 16B and the power generation equipment 43 Preheated by heating directly to 140 ° C. in direct contact with the sludge before heat treatment together with the exhaust heat from the heat treatment.

  The sludge reduced in temperature to 100 ° C. is introduced into the evaporator section 16A due to an internal pressure difference between the evaporator 45 and the first preheating device 13A, and is vaporized by reducing the pressure from 100 kPa to 19.9 kPa. The temperature is reduced to ° C. This reduced temperature becomes high-temperature steam, directly contacts the sludge before heat treatment in the direct heat exchanger section 15B, warms to (60-α1) ° C., and preheats.

  The sludge whose temperature has been reduced to 60 ° C. is introduced into a high-temperature digestion tank (digestion with high-temperature bacteria at 60 ° C.) and further reduced in volume. Subsequent operations are the same as those in the above-described embodiments, and a description thereof will be omitted.

  According to this embodiment, the sludge before heat treatment is heated from 60 ° C. to 140 ° C. at a stretch in the direct heat exchanger section 15B of the second preheating device 13B. The temperature in the region of 0 ° C. is increased all at once, so that the system is less likely to block the piping and adhere to the container due to protein coagulum.

  In addition, since the steam generated in the evaporator 45 is blown into the second direct heat exchanger section 15B, the heat generated when the evaporator 45 is depressurized can be used effectively.

  Furthermore, since the subsequent digestion tank 22 is a high-temperature digestion tank, it is not necessary to reduce the temperature of sludge at 60 ° C. to 40 ° C. Therefore, no equipment for reducing the temperature to 40 ° C. is required and the configuration is simplified. it can.

  In addition, when not using a high-temperature digester for the latter digester 22, it is necessary to reduce 60 degreeC sludge to 40 degreeC, but in that case, as shown in FIG. 6, it is comparatively low temperature (20 degreeC). The raw sludge 111 may be mixed with the heat-treated sludge supplied to the digestion tank 22. That is, as a temperature adjusting device for the heat treatment sludge, it is connected to a pipe line from the post-heat treatment sludge discharge part of the preheating device 13A to the digestion tank 22, and the sludge that has not been heat-treated is mixed with the discharged sludge flowing through this pipe line. An apparatus may be used.

  Here, when the sludge 11 to be heat treated is sludge generated from the biological reaction tank of the sewage treatment plant (referred to as surplus sludge), the sludge 111 generated from the sedimentation basin before the biological treatment of the sewage treatment plant is referred to as raw sludge. The generation amount of raw sludge and surplus sludge is approximately 1: 1, and the heat treatment sludge of surplus sludge flowing out from the sludge discharge section after heat treatment of the preheating device 13A and the raw sludge after concentration are mixed in the pipe.

  In the embodiment of FIG. 6, the heat treatment part of the excess sludge is the same as that of the embodiment of FIG. In the embodiment of FIG. 6, by mixing the sludge after heat treatment at 60 ° C. flowing out from the sludge discharge section after heat treatment of the preheating device 13A with the raw sludge 111 at 20 ° C. not subjected to heat treatment in a one-to-one ratio. The temperature is reduced to 40 ° C. suitable for treatment in the digestion tank 22. That is, mixed sludge (40 ° C.) of raw sludge and excess sludge is introduced into the digestion tank 22.

The effects are as follows.

  According to the embodiment of FIG. 6, surplus sludge having a relatively low biodegradability in the digestion tank 22 is heat-treated, and raw sludge having a relatively high biodegradability is added without heat treatment, so that the raw sludge can be increased. Because it does not require equipment and energy to heat, it is more economical than when both sludges are heated. Moreover, the surplus sludge with low biodegradability is heat-processed, Therefore The increase in the gas generation amount in the digestion tank 22, reduction of digestion tank capacity, and volume reduction of a waste sludge amount can be achieved.

  Moreover, since the temperature is reduced from 60 ° C to 40 ° C by mixing raw sludge and excess sludge, no special equipment is required to reduce the excess sludge from 60 ° C to 40 ° C. A digester (digestion with mesophilic bacteria at 40 ° C) can be used.

  The target sludge does not have to be a mixture of raw sludge and excess sludge as described above.For example, half of the sludge is heat-treated and half is not heat-treated.By mixing the heat-treated sludge and the sludge not heat-treated, The temperature of sludge may be reduced. Further, the mixing ratio is not limited to 1: 1, and any ratio may be used. Moreover, in the said embodiment, although mixing shall be performed in piping, the mixing tank in which the stirrer was installed may be provided and it may mix in the mixing tank.

  The steam generated from the evaporator 31 shown in FIG. 1 to FIG. 4 is not simply discharged to the outside, but may be configured to be used as a heat source for hot water supply equipment, for example. If comprised in this way, an excess heat source will be used effectively and it will lead to the energy saving of the whole plant. Of course, not only hot water supply equipment, but also steam used from the evaporator 31 and steam multiplied when the heated sludge is depressurized are used for heating and reducing the temperature of ancillary equipment such as air conditioning equipment. Anything may be used.

  Next, the embodiment of FIG. 7 will be described.

  In this embodiment, in the heat treatment including solid-liquid separation shown in FIG. 3, the liquid is processed by the high-speed anaerobic reactor 46, for example, by the UASB (Upflow Anearobic Sludge Blanket) method. The solid content is a process flow for dehydration.

  In the above configuration, the reactor 14 is hydrothermally treated at 220 ° C., so that 70 to 80% of the solid content is solubilized if the excess sludge is in the sewage treatment plant. 30%. After this hydrothermal treatment, the solid content of the sludge is extracted by the extraction valve 38 and is separated into solid and liquid. The solid content is further concentrated without chemical injection by the concentrator 48, then dehydrated by the dehydrator 35 and discarded.

  Since heat-treated sludge has a high sedimentation property, high concentration can be obtained by centrifugal concentration without chemical injection, and the moisture content of the solid content can be lowered, so that the volume of the solid content can be further reduced. Further, the concentrated liquid component generated in the concentrator 48 is introduced into the evaporator 31, and after being reduced in temperature by the evaporator 31, UASB processing is performed in the reactor 46. On the other hand, the liquid component flowing out from the reactor 14 to the preheating device 13 is treated by a UASB process in which sludge is hardly generated after the temperature is reduced in the evaporator section 16 and the evaporator 31. In the UASB process, since the treatment is performed with granular granules in which methanogens are accumulated, the solubilized liquid can be processed in a processing tank having a short residence time (volume) compared to a general digestion tank. The treated water of UASB is treated in a water treatment process (for example, if it is a sewage treatment plant, it is returned before a biological treatment tank (aeration tank)), and finally discharged into a river.

  According to the embodiment of FIG. 7, since the solution is processed by the UASB method, the volume can be reduced to about 1/30 compared to a normal digestion tank (retention time 30 days), and space-saving sludge is obtained. A processing process can be realized. In addition, the amount of waste sludge generated can be reduced by 80 to 90% on a volume basis by heat treatment of sludge and by solubilization and sedimentation improvement by heat treatment, compared to the case where heat treatment is not performed. Further, by concentrating the sludge from the reactor 14 with no chemical injection, the amount of chemicals used is low, the running cost is low, and the amount of inorganic sludge generated is small.

  In addition, you may provide the chromaticity processing process by activated carbon in the back | latter stage of the UASB processing process by the reactor 46. FIG. In addition, the chromaticity treatment process may be performed before the UASB treatment, and is not limited to the activated carbon treatment, and the chromaticity treatment process can be performed alone or in combination such as activated carbon, a flocculant (iron-based flocculant), OH radical, or electrolysis treatment. It may be. Moreover, the process of carrying out chromaticity treatment together with the desorbed liquid after sludge dehydration may be used. Thereby, the chromaticity which becomes a problem when heat-treating can be improved.

  The high-speed anaerobic treatment process reactor 46 is not limited to the UASB process, but can be any high-speed reactor capable of treating high-load organic matter such as an EGSB (Expanded Granular Sludge Bed) reactor or an IC (Internal Circulation) reactor. It may be an anaerobic treatment process. In addition, the solid content from the reactor 14 may not be dehydrated after concentration as shown in FIG. 7, but may be dehydrated after concentration and after anaerobic treatment in a digestion tank. .

1 is a system configuration diagram showing an embodiment of a sludge treatment system according to the present invention. It is a system block diagram which shows embodiment which changed the pressure adjustment mechanism of the preheating apparatus in this invention. It is a system block diagram which shows embodiment which gave the solid-liquid separation function to the reactor in this invention. It is a system configuration figure showing an embodiment which constituted a preheating device in the present invention in multiple stages. 1 is a system configuration diagram showing an embodiment in which a preheating device according to the present invention is configured in multiple stages and a configuration for raising the temperature at a stretch by a specific preheating device is adopted. FIG. It is a system configuration | structure figure of embodiment which shows the other example of the temperature control apparatus in this invention. 1 is a system configuration diagram showing an embodiment in which a reactor according to the present invention is provided with a solid-liquid separation function and its liquid content is processed in a high-speed anaerobic reactor. It is a characteristic view which shows the relationship between saturated vapor pressure and water temperature.

Explanation of symbols

11 Sludge to be treated 13 Preheating device 14 Reactor 15 Direct heat exchanger part 16 Evaporator part 22 Anaerobic treatment device (digestion tank)

Claims (12)

A reactor for heating and treating the sludge under a predetermined pressure;
The direct heat exchanger part connected on the sludge supply path to the reactor and the evaporator part connected on the sludge discharge path after the heat treatment from the reactor are integrated, and the inside thereof is the reaction The sludge before heat treatment, which is held at a lower pressure than the inside of the vessel and introduced into the direct heat exchanger section, is directly brought into contact with the steam generated from the sludge after heat treatment introduced into the evaporator section through the discharge path. And a preheating device for heating.   The preheating device is connected in series in a plurality of stages on the sludge supply path and the heat treatment sludge discharge path, and the internal pressures of the plurality of preheating apparatuses are sequentially set lower as they go downstream as viewed from the reactor. The sludge treatment system according to claim 1 characterized by things.   The preheater is installed between any two preheaters on the sludge discharge path after heat treatment in which a plurality of stages of the preheater are connected in series, and the internal pressure is lower than the preheater upstream from the reactor, including itself. The steam is generated from the sludge after heat treatment introduced from the upstream side preheating device by a pressure difference with the upstream side, and the steam is preheated to the upstream side preheating device. The sludge treatment system according to claim 2, further comprising an evaporator having a pipe for supplying to a direct heat exchanger part of the apparatus.   4. The apparatus according to claim 1, further comprising an anaerobic treatment device that anaerobically treats the sludge after heat treatment that is heat-treated by the reactor and discharged through the evaporator section of the preheating device. The described sludge treatment system.   The sludge treatment system according to claim 4, wherein digestion gas generated from the anaerobic treatment device is used as fuel for a heating source facility for the reaction tank.   The sludge treatment system according to claim 4, further comprising a temperature adjusting device for adjusting the post-heat treatment sludge discharged through the evaporator section of the preheating device to a temperature suitable for anaerobic treatment.   The temperature adjusting device is set to an internal pressure lower than that of the preheating device, introduces heat-treated sludge discharged through an evaporator section of the preheating device, and generates steam by an internal pressure difference with the preheating device. 7. The sludge treatment system according to claim 6, wherein an evaporator that lowers the sludge temperature is used.   The temperature adjusting device is connected to a pipe line from the sludge discharge part after heat treatment of the preheating device to the anaerobic treatment apparatus, and mixes sludge that has not been heat-treated with the discharged sludge flowing through the pipe line. The sludge treatment system according to claim 6.   9. The reactor according to claim 1, wherein a liquid component obtained by separating a solid content from heat-treated sludge is supplied to the evaporator section of the preheating device through the discharge path. The sludge treatment system described in 1.   The sludge treatment system according to claim 9, further comprising a pipe for supplying the solid content of the sludge after heat treatment separated from the liquid to an anaerobic treatment apparatus.   It has a concentrator that concentrates the solid content of the sludge after heat treatment separated from the liquid component, and has a pipe that supplies the liquid component generated by the concentration to the anaerobic treatment device through an evaporator for temperature control. The sludge treatment system according to claim 9, wherein   The sludge treatment system according to any one of claims 1 to 11, wherein the heat treatment in the reactor is a heat treatment or a heat pressure treatment between 60 ° C and 374 ° C.

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