JP4909540B2 - Sludge treatment apparatus and sludge treatment method - Google Patents

Description

  The present invention relates to a sludge treatment apparatus and a sludge treatment method, and more particularly to a sludge treatment apparatus and a sludge treatment method having a freeze-thaw tank to which a cooling medium is fed from an ammonia absorption refrigerator.

  In the case of sludge treatment, since the sludge contains a large amount of moisture, it is necessary to remove the moisture by solid-liquid separation from the sludge. However, since the sludge contains various organic and inorganic substances, most of them are gelatinous and have poor filterability. In particular, in winter, filterability deteriorates and the efficiency of dehydration treatment decreases. In order to improve this, generally, a method is adopted in which steam is injected into sludge and heated to increase the dehydration efficiency.

  On the other hand, there is a method of increasing the filterability by adding an inorganic flocculant, but there is a problem that the amount of disposal sludge is increased by chemical injection, which is not necessarily a preferable method.

  In view of this, it is considered that a freeze-thaw treatment method with high solid-liquid separation efficiency is not required (for example, Patent Document 1). This freezing and thawing process consumes a considerable amount of energy when processing, so it is preferable to use an ammonia absorption refrigerator that has a lower environmental load than conventional refrigerators. Therefore, it has been proposed to implement wastewater treatment with a low environmental load.

  Furthermore, in order to achieve energy saving by reducing the number of freeze-thaw treatments, it has been proposed to employ a precoat dehydration method (for example, Patent Document 2).

JP 2001-252700 A JP 2003-340217 A

  However, in the case of using the above-described conventional technology, particularly in winter, in order to improve the sludge filterability, extra fuel is required to secure the steam necessary for heating the sludge, and the processing cost is reduced. Was causing a rise.

  Accordingly, in view of the above-mentioned problems of the prior art, the object of the present invention is to prevent an increase in processing costs without requiring extra fuel even if the sludge filterability deteriorates in winter. An object is to provide a possible sludge treatment apparatus and a sludge treatment method.

  The above-mentioned subject is achieved by the invention described in each claim. That is, the sludge treatment apparatus according to the present invention has a characteristic configuration in which a freezing and thawing tank to which a cooling medium is fed from an ammonia absorption refrigerator, and heating that can use the waste heat of the ammonia absorption refrigerator and supply sludge. It is in having an apparatus and the dehydration processing apparatus which dehydrates the sludge heated by this heating apparatus.

  According to this configuration, the exhaust heat generated from the ammonia absorption refrigerator that feeds the cold medium to the freezing and thawing tank can be used for heating the sludge fed to the heating device. There is no need to heat the sludge, and therefore, the increase in treatment cost can be suppressed, and even if the sludge filterability deteriorates in winter, it can be efficiently dehydrated.

  As a result, it was possible to provide a sludge treatment apparatus capable of preventing an increase in treatment costs without requiring extra fuel even when the sludge filterability deteriorates in winter.

  It is preferable that the sludge that has been freeze-thawed in the freeze-thaw tank and the sludge that has been heated by the heating device are mixed and fed to the dehydration device.

  According to this configuration, the dehydration process can be performed more efficiently, and the processing cost can be reduced.

  The sludge that has been freeze-thawed in the freeze-thaw tank and the sludge that has not been freeze-thawed are both fed to the heating device, mixed, and heated.

  Also with this configuration, the dehydration process can be performed more efficiently, and the processing cost can be reduced.

  The sludge that has been freeze-thawed in the freeze-thaw tank and the sludge that has been warmed in the warming device are fed to the dehydrator after mixing and are not freeze-thawed in the freeze-thaw tank. The sludge may be heated by the heating device and fed to the dehydration processing device.

  Also with this configuration, the dehydration process can be performed more efficiently, and the processing cost can be reduced.

  The heating device feeds either or both of cooling water fed from a condenser constituting the ammonia absorption refrigerator to a cooling tower and a steam drain discharged from the ammonia absorption refrigerator. It is preferable to receive.

  According to this configuration, the amount of cooling water fed from the condenser constituting the ammonia absorption refrigerator to the cooling tower is sufficient, so that the sludge temperature is about 5 ° C. as in winter. However, it can be reliably heated, for example, when about 5 ° C sludge, which is about 5 times the amount of freezing and thawing, can be heated to about 28-30 ° C. Can ensure a fast filtration rate. Furthermore, by using the steam drain discharged from the ammonia absorption refrigerator, it is possible to warm to a higher temperature and to secure a faster filtration rate.

  Further, the sludge treatment method according to the present invention is characterized in that the cooling medium is fed from the ammonia absorption refrigerator to the freeze-thaw tank, and the exhaust heat of the ammonia absorption refrigerator is fed to the heating device for use. The sludge is supplied to the heating device, and the sludge heated by the heating device is dehydrated by the dehydration processing device.

  According to this configuration, it is possible to provide a sludge treatment method capable of preventing an increase in treatment costs without requiring extra fuel even when the sludge filterability is deteriorated in winter.

  It is preferable that the sludge frozen and thawed in the freeze-thaw tank and the sludge heated by the heating device are mixed and fed to the dehydration device.

  According to this configuration, the dehydration process can be performed more efficiently, and the processing cost can be reduced.

  The sludge that has been freeze-thawed in the freeze-thaw tank may be fed to the heating device together with the sludge that has not been freeze-thawed, mixed, and heated.

  Also with this configuration, highly efficient dehydration processing can be performed, and processing costs can be reduced.

  The sludge that has been freeze-thawed in the freeze-thaw tank and the sludge that has been heated in the heating device are mixed and fed to the dehydration apparatus, and sludge that is not freeze-thawed in the freeze-thaw tank, It may be heated by the heating device and fed to the dehydration processing device.

  Also with this configuration, highly efficient dehydration processing can be performed, and processing costs can be reduced.

  Either one or both of the cooling water supplied from the condenser constituting the ammonia absorption refrigerator to the cooling tower and the steam drain discharged from the ammonia absorption refrigerator are supplied to the heating device. It is preferable.

  Even when the temperature of the sludge is about 5 ° C. as in the winter, it can be surely heated and the dehydration rate can be increased.

  Embodiments of the present invention will be described in detail with reference to the drawings.

<First Embodiment>
FIG. 1 shows a schematic main configuration of an apparatus used in the freeze-thaw processing method according to the first embodiment, and FIG. 2 shows a schematic overall configuration of the freeze-thaw apparatus. First, the sludge 1 to be dehydrated is once stored and settled in the sludge storage tank 2, where it is gravity precipitated and concentrated. This precipitated sludge may be further fed to a concentration tank (not shown) to promote concentration. The concentrated sludge is sent to the freezing and thawing tank 3 that receives the supply of the cooling medium, and the freezing and thawing are repeated to separate the solid and the liquid and dehydrate. However, as described later, By switching the valve 4, a part of the concentrated sludge is heated by being fed to the heating device 7 and mixed with the sludge that has been freeze-thawed. Of course, depending on the properties of the sludge, it may be fed directly to the freeze / thaw tank 3 or the heating device 7 without going through the sludge storage tank 2.

  The concentrated sludge fed to the freezing and thawing tank 3 is effectively solid-liquid separated. In that case, the dewatering efficiency of the dewatering device 6 in the subsequent process can be increased by discharging the supernatant. . Inside the freeze / thaw tank 3, heat transfer tubes 3a connected to the ammonia absorption refrigerator 16 shown in FIG. 2 and through which a refrigerant (an antifreeze liquid cooled to about −10 to −30 ° C.) flows are densely arranged. The sludge is frozen through the heat transfer tube 3a. After the freezing, the heated heat medium is passed through the heat transfer tube 3a for melting and sludge solid-liquid separation. These freezing and thawing processes may be performed sequentially using a single freezing and thawing tank, or a pair of freezing and thawing tanks and sludge freezing treatment in one freezing and thawing tank while the other freeze and thawed. You may make it melt | dissolve the sludge frozen in the tank.

  The ammonia absorption refrigerator 16 can be driven by using steam obtained from the exhaust gas from the adjacent gas turbine cogeneration system or the like, and this is preferable because energy saving can be improved.

  In the treatment by the freeze-thaw tank 3, the sludge has a high solid-liquid separation property, and an interface is formed in a short time (for example, about 30 minutes). Therefore, after the thawing process, it can be easily separated into the supernatant 5 and the concentrated frozen thawed sludge. Concentration by separating and removing the supernatant 5 may be performed in the freeze / thaw tank 3, or a freeze-thaw sludge storage tank (not shown) for temporarily storing the freeze-thawed sludge is provided and separated here. -It may be removed.

  As described above, the sludge treated in the freeze-thaw tank 3 has a high solid-liquid separation property, so that the filtration rate during the dehydration process in the pressure filtration type dehydration apparatus 6 in the next step is increased. . Therefore, as compared with the conventional dehydration apparatus, a smaller dehydration apparatus is sufficient, and the energy load due to the dehydration process can be reduced.

Further, the sludge treated in the freeze / thaw tank 3 is pressure-fed to the surface of the filter cloth of the dehydration processing apparatus 6 and pre-coated. In this case, since the sludge processed in the freeze / thaw tank 3 is aggregated into coarse particles, the filter cloth surface is not clogged. Moreover, since the melted sludge has been heated to some extent, the viscosity is not so low even in winter sludge. For example, 2 m ³ , which is half the amount of sludge that has been frozen and thawed, is pre-coated by feeding it to the dewatering device 6, and then the remaining 2 m ³ and the sludge heated by the heating device 7 are dewatered. By feeding to the apparatus 6, dehydration can be performed at a high filtration rate.

  Next, by switching the three-way valve 4, a part of the concentrated sludge is heated by feeding it to the heating device 7, and the heated sludge is fed to the dehydration processing device 6. Thereby, the viscosity of sludge becomes low also in winter with high viscosity, and the filtration rate in the dehydration processing apparatus 6 is promoted. The heating device 7 heats the sludge using exhaust heat or a steam drain in cooling water from an ammonia absorption refrigerator that supplies a refrigerant or a heat medium to the freeze / thaw tank 3. Therefore, since a new heat source is not required, the processing cost does not increase significantly.

  The use of the exhaust heat of the ammonia absorption refrigerator 16 will be described in detail with reference to FIG. The ammonia absorption refrigerator 16 includes a condenser C that liquefies ammonia serving as a refrigerant, an evaporator E that evaporates ammonia, and an absorber A that absorbs ammonia vapor evaporated in the evaporator E into water as an absorbent. And is configured. A generator for supplying an aqueous ammonia solution sufficiently containing a refrigerant by the absorber A with a solution pump (not shown) and a rectifier for increasing the ammonia concentration and sending it to the condenser C are provided. You may let them.

  The high-pressure, high-concentration ammonia vapor is sent to the condenser C where it is heat-exchanged with the cooling water from the cooling tower T to be condensed and liquefied. The condenser C may be provided with an extraction device that removes a gas component that does not condense. Since non-condensable gas deteriorates heat transfer characteristics such as condensation or absorption, it is convenient to maintain the heat transfer characteristics well if it is removed. In FIG. 2, reference numeral 14 is a cooling water pump for sending cooling water.

  Further, a brine circuit is connected to the evaporator E and the absorber A. This brine circuit is composed of a cold brine circuit B1 composed of a cold cold brine tank 11 and a cold brine pump 12 for feeding cold brine, and a hot brine tank 9 and a warm brine pump 10 for feeding warm brine. And a pair of cold / warm switching valves 13 and 13 ′ for switching between the warm brine circuit B2 and the cold brine circuit B1. A cold brine circuit B1 is connected to the evaporator E, and a warm brine circuit B2 is connected to the absorber A. When the sludge fed to the freeze / thaw tank 2 is frozen, the cold brine cooled by the evaporator E of the absorption refrigerator 16 is directly sent to the freeze / thaw tank 3 to freeze the sludge. In addition, the number 17 is a heat storage tank, for example, cool heat is led to this heat storage tank at the night of summer, and ice heat storage is carried out, and the heat is led to the heat storage tank at night in the winter and used as heat water. However, although the heat storage tank 17 is not necessarily required in the present embodiment, it is convenient to effectively use heat and reduce power consumption. Numbers 8 and 8 'are switching valves for using the heat storage tank 17, and number 15 is a brine heat exchanger.

  Then, the cooling water 18 fed from the condenser C to the cooling tower T and the steam drain 19 discharged from the ammonia absorption refrigerator 16 are concentrated in the sludge storage tank 2 and added to the sludge sent to the freezing and thawing tank 3. The heat is used directly or after heat exchange.

  The amount of cooling water 18 fed from the condenser C to the cooling tower T is sufficient in quantity and easy to take out on the apparatus piping, and is usually about 35 to 40 ° C. About 5 times as much sludge (about 5 ° C in winter) can be heated to about 28-30 ° C. And when dewatering the sludge which carried out the freezing and thawing process with the dehydration processing apparatus 6 as mentioned above, a quick filtration rate is securable.

  The cooling water 18 fed from the condenser C to the cooling tower T releases heat in the cooling tower T and is used to warm the warm brine by the brine heater, but this cooling water has a large flow rate. However, since the outlet temperature of the condenser C is slightly low, it may not be sufficient for heating a large amount of sludge at a low temperature. Therefore, since the steam drain obtained after supplying the steam obtained from the connected gas turbine cogeneration (CGS) to the ammonia absorption refrigerator 16 has a high temperature, it is cooled from the condenser C and the cooling tower T described above. It is preferable to use together with the cooling water 18 fed to the water. However, since this steam drain is generally supplied to a boiler (not shown) via an economizer (not shown), a large amount of water may not be used. ) Even in the winter season, the sludge can be reliably heated to about 30 to 40 ° C. Heating of the sludge exceeding 40 ° C. is not preferable because of the heat resistance problem of the dehydrator filter plate.

  The dewatered sludge that has been dehydrated is crushed to a predetermined size or less by a crusher as necessary, and can be used as a building material or treated as a waste.

Second Embodiment
FIG. 3 shows a schematic main configuration of an apparatus used for the freeze-thaw processing method according to the second embodiment. In this embodiment, both the freeze-thawed sludge and the sludge concentrated in the sludge storage tank 2 are heated in the heating tank 7, and the heated and mixed sludge is dehydrated in the dehydration processing device 6. Like to do. Other configurations are the same as those of the first embodiment. By doing in this way, in the dehydration processing apparatus 6, it is possible to perform dehydration processing with a higher filtration rate.

<Third Embodiment>
FIG. 4 shows a schematic configuration of a main part of an apparatus used for the freeze-thaw processing method according to the third embodiment. In this embodiment, in addition to the apparatus used for the freeze-thaw treatment method according to the first embodiment, a part of the concentrated sludge to be treated is not freeze-thawed in the freeze-thaw tank 3, and the heating device 7 is used. Is heated and fed to the dehydration apparatus 6. Even if it does in this way, a dehydration process can be performed still more efficiently and reduction of processing cost can be aimed at.

<Fourth embodiment>
In this embodiment, as shown in FIG. 5, in addition to the apparatus used for the freeze-thaw treatment method according to the second embodiment, a part of the concentrated sludge to be treated is freeze-thawed in the freeze-thaw tank 3. Instead, it is heated by the heating device 7 and fed to the dehydration processing device 6. Even if it does in this way, a dehydration process can be performed still more efficiently and reduction of processing cost can be aimed at.

[Another embodiment]
(1) In the above embodiment, as a dehydration processing apparatus, in addition to a pressure filtration type in which sludge is placed on a filter cloth and filtered while applying pressure, two filter cloths are incorporated into a number of rolls, and the filter cloth It is possible to use various types of dewatering apparatus such as a belt press method and a centrifugal dewatering method for running and dewatering, and a screw press method and a multi-disc dehydrator.
(2) In the said embodiment, although the refrigerator to be used is an ammonia absorption refrigerator, sludge heating can also be performed using the exhaust heat of an electric compression refrigerator.

FIG. 1 is a schematic configuration diagram illustrating a main part of a sludge treatment method according to a first embodiment of the present invention. Schematic overall configuration diagram of a freeze-thaw device for explaining the use of exhaust heat of an ammonia absorption refrigerator Schematic block diagram for explaining the sludge treatment method according to the second embodiment of the present invention Schematic block diagram for explaining the sludge treatment method according to the third embodiment of the present invention Schematic block diagram explaining the sludge treatment method according to the fourth embodiment of the present invention

Explanation of symbols

3 Freezing and thawing tank 6 Dehydration processing device 7 Heating device 16 Ammonia absorption refrigerator C Condenser T Cooling tower

Claims (8)

A freezing and thawing tank in which a cooling medium is fed from an ammonia absorption refrigerator and freezes and thaws the sludge, a heating device that can use the waste heat of the ammonia absorption refrigerator and supply sludge, and a heating device And a dewatering device for dewatering the heated sludge ,
The heating device feeds either or both of cooling water fed from a condenser constituting the ammonia absorption refrigerator to a cooling tower and a steam drain discharged from the ammonia absorption refrigerator. The sludge treatment equipment that is supposed to receive .   The sludge according to claim 1, wherein the sludge that has been freeze-thawed in the freeze-thaw tank and the sludge that has been heated by the heating device are mixed and fed to the dehydration device. Processing equipment.   The sludge treatment apparatus according to claim 1, wherein both the sludge that has been freeze-thawed in the freeze-thaw tank and the sludge that has not been freeze-thawed are fed to the heating apparatus, mixed, and heated. .   The sludge that has been freeze-thawed in the freeze-thaw tank and the sludge that has been warmed in the warming device are fed to the dehydrator after mixing and are not freeze-thawed in the freeze-thaw tank. The sludge treatment apparatus according to claim 1, wherein the sludge is heated by the heating apparatus and is fed to the dehydration treatment apparatus. The cooling medium from the ammonia absorption refrigerator is fed to a freeze-thaw tank for freezing and thawing sludge, and the waste heat of the ammonia absorption refrigerator is fed to a heating device for use. A sludge treatment method in which sludge is supplied to the sludge and the sludge heated by the heating device is dehydrated by the dehydration treatment device ,
Either one or both of the cooling water supplied from the condenser constituting the ammonia absorption refrigerator to the cooling tower and the steam drain discharged from the ammonia absorption refrigerator are supplied to the heating device. Sludge treatment method. The sludge treatment method according to claim 5 , wherein the sludge frozen and thawed in the freeze thaw tank and the sludge heated by the heating device are mixed and fed to the dehydration device. The sludge treatment method according to claim 5, wherein the sludge that has been freeze-thawed in the freeze-thaw tank is fed to the heating device together with sludge that has not been freeze-thawed, mixed, and heated. The sludge that has been freeze-thawed in the freeze-thaw tank and the sludge that has been heated in the heating device are mixed and fed to the dehydration apparatus, and sludge that is not freeze-thawed in the freeze-thaw tank, The sludge treatment method according to claim 5 , wherein the sludge is heated by the heating device and fed to the dehydration device.

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