JP4016898B2 - Freezing and thawing equipment - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a sludge dewatering apparatus in which the dewaterability of sludge is improved by using freezing and thawing treatment in the dewatering treatment of wastewater sludge and industrial wastewater sludge in a water purification plant.
[0002]
[Prior art]
The amount of generated water and sewage treatment plant sludge and industrial wastewater sludge tends to increase year by year, and a shortage of dewatered sludge disposal sites is a major problem. Recently, effective utilization of dewatered sludge has been promoted for environmental conservation or the establishment of a recycling society. In this disposal and effective use, it is important to efficiently concentrate and dehydrate the raw sludge to a low water content without adding chemicals.
One of the sludge dewatering apparatuses is a freeze-thaw processing apparatus. The freeze-thaw treatment apparatus is a non-chemical injection method, and is used when dewatering raw sludge such as purified water sludge is modified into coarse particles by freeze-thaw treatment and dehydrated to a low water content state at a high filtration rate.
[0003]
The freezing and thawing principle is applied to the dehydration phenomenon of solid and liquid by freezing, as seen in the growth of frost pillars and the production of frozen tofu. Micrograph of sludge to explain the principle of freezing and thawing A diagram illustrating an example is shown in FIG. As shown in FIG. 5 (a), raw sludge generated in water treatment facilities such as water purification plants is composed of cotton-like aluminum hydroxide, fine soil particles, plant matter, It is a sedimentation concentrate of flocculated flocs such as algae. In the freezing and thawing process, when this raw sludge is first cooled and frozen, the sludge grows in the form of needles in the frozen state as shown in FIG. 5 (b), and the sludge particles are ice and ice. The particles are moved to be compressed and are strongly bonded to form coarse particles. Next, when this frozen sludge is heated and melted, as shown in FIG. 5 (c), the sludge in the melted state retains the sludge particles even when the ice melts. Solids settle and water separates as supernatant.
[0004]
Because of this principle, dehydration is very difficult with devices that pressurize and dewater sludge, such as centrifugal separation, but freeze-thaw treatment devices can be applied to many types of sludge that can be easily dehydrated to low water content. is there. Examples of sludge that are particularly effective in application include the following.
1) Coagulated sediment sludge generated from raw water containing organic matter, 2) Eutrophied dam water, sludge generated from raw water rich in algae such as lake water, 3) River surface water and dam water during drought and snowfall 4) Sludge containing a lot of aluminum hydroxide generated from coagulation sedimentation with low water content such as 4) Coagulation sedimentation sludge generated by injection of a large amount of aluminum coagulant into raw water to remove Cryptosporidium, 5) Well Sludge containing a lot of iron hydroxide and manganese dioxide generated by oxidation treatment of water (groundwater).
[0005]
FIG. 6 shows a basic method of sludge treatment using freeze-thaw treatment. In this figure, the raw sludge (purified water sludge) generated in the water treatment facility is concentrated in a gravity concentration tank and a filtration concentration device to become concentrated sludge, which is reformed into coarse particles by the above-mentioned principle in the freeze-thaw treatment device, It is separated into dewatered sludge and treated water by a dehydrator and sludge treatment is performed.
An example of a conventional freeze-thaw type sludge treatment system including the above-described filtration concentration apparatus, freeze-thaw treatment apparatus, and dehydrator is shown in FIG. In this figure, first, raw sludge enters a siphon type filtration and concentration device 31 from the raw sludge tank 5, where the siphon action produced by opening the filter cloth 31a and the switching valve 37b in the filtration concentration device 31 and the filter cloth 31a. The filtrate is discharged using the suction action of the filtrate drainage pump 36. The concentrated sludge concentrated by this filtrate discharge is stored in the concentrated sludge storage tank 32 using the transfer pump 35a. The concentrated sludge is then sent to the freeze / thaw treatment tanks 33a and 33b by the transfer pump 35b, and is reformed into freeze-thaw sludge of coarse particles by freeze-thaw treatment here. The freeze-thawed sludge is discharged below the freeze-thaw treatment tanks 33a and 33b, and separated into dehydrated sludge and treated water by a dehydrator 34 using vacuum dehydration or the like, and the sludge treatment is completed.
[0006]
Here, as shown in FIG. 7, the above-mentioned freeze-thaw treatment tank is a set of two tanks 33a and 33b. Inside each tank is a serpentine heat exchanger 33h, and the raw sludge is cooled and heated. The apparatus 22 and the heat exchanger 33h are used to perform freezing in one tank (33a in this figure) and thawing in the other tank (33b in this figure).
There is a system in which cold brine and warm brine circulate in the heat exchanger (heat transfer body) 33h of the freeze / thaw treatment tanks 33a and 33b by the cooling and heating device 22 that performs cooling and heating. The cooling side system is a cooling circuit that circulates through the cold brine tank 11a, the brine cooling pump 12a, the brine cooling heat exchanger 13a, the heat exchanger of the freeze / thaw processing tank 33a, etc. Heating circuits that circulate through the tank 11b, the brine heating pump 12b, the brine heating heat exchanger 13b, the heat exchanger of the freeze-thaw processing tank 33b, and the like are configured. Further, in order to switch between cooling and heating of the heat exchangers of the freeze / thaw treatment tanks 33a and 33b, cold / heat switchers 38a and 38b are provided.
[0007]
In this configuration, one of the freeze-thaw processing tanks 33a is cooled by supplying cold brine cooled by the cold heat of the refrigerator to the heat exchanger 33h to cool and freeze the concentrated sludge, and predetermined holding determined by the freezing conditions of the tanks Hold the time (for example, 1.5 hours), and then heat the freezing and thawing treatment tank 33a by switching the cold / hot switch 38a, 38b, and supply hot brine heated by the exhaust heat of the refrigerator to the heat exchanger 33h. The sludge is heated and melted and held for a predetermined holding time (for example, 1.2 hours) determined by the melting conditions of the tank. The dewatered sludge that has been modified into coarse particles within the difference between the freeze holding time and the melting hold time (here 0.3 hours) opens a discharge gate (not shown) at the bottom of the freeze thaw tank 33a. It is discharged to the dehydrator 34 and the next concentrated sludge is filled from the concentrated sludge storage tank 32. In the other freeze / thaw treatment tank 33b, the cooling and heating processes described above are executed with a half cycle delay from the freeze / thaw treatment tank 33a.
[0008]
In the conventional freeze-thaw treatment apparatus, in addition to the above-described apparatus, an apparatus provided with a vibration means that vibrates sludge in the freeze-thaw treatment tank in order to increase the dehydration effect by making uniform freezing difficult to cause overcooling (patent) Document 1), and a device (see Patent Document 2) that provides a mixing tank for mixing sludge frozen and thawed in a freeze-thaw treatment apparatus and untreated raw water to dewater the sludge in this mixing tank has been proposed. However, in both cases, the concentration tank and the freeze-thaw treatment tank are connected by piping, and the concentrated sludge is transferred.
[0009]
[Patent Document 1]
JP 2001-334300 A
[Patent Document 2]
JP 2002-205100 A
[0010]
[Problems to be solved by the invention]
In conventional freeze-thaw treatment equipment, which can be processed without these chemical injections and can treat even sludge that is difficult to dehydrate with ordinary pressure dehydration equipment, much power is consumed to freeze the water in the sludge. There is a problem that it is necessary.
Conventionally, in order to reduce power consumption, as previously mentioned, concentrated sludge with reduced sludge volume (weight) by removing water from the original sludge using a centrifuge or filtration concentrator is supplied to the freeze-thaw processor. This method is used. In this method, the amount of water that needs to be frozen is reduced because the volume of sludge is reduced, and the power consumption is considerably reduced.However, as the concentration of concentrated sludge increases, the fluidity decreases, and the sludge is frozen and thawed. It becomes difficult to uniformly fill the space between the heat exchangers in the tank and the freeze-thaw treatment tank. For this reason, since sludge can be concentrated only to a state where fluidity is still sufficient in practical use, power consumption cannot be sufficiently reduced. Moreover, it is necessary to send the sludge after the melting treatment to an external dehydrator for dehydration.
[0011]
Therefore, in the freeze-thaw treatment apparatus, in addition to the freeze-thaw treatment tank, a raw sludge concentrator and a melt-treated sludge dehydrator are necessary, and there is a problem that the cost of the freeze-thaw treatment equipment becomes expensive.
An object of the present invention is to provide a freeze-thaw treatment apparatus that solves the above-described problems, has low power consumption, and has low utility costs and high practicality.
[0012]
[Means for Solving the Problems]
In order to solve the above problems, in the present invention, in a freeze-thaw treatment apparatus that performs dewatering treatment of purified water sludge and industrial wastewater sludge using the principle of freeze-thaw, the raw sludge supply means and the supplied raw sludge Storage means for storing; heat transfer means for cooling and heating the stored raw sludge; sludge concentration means for filtering the moisture of the stored raw sludge; means for discharging the filtered treated water; The dewatering sludge discharging means is provided in the freeze-thaw treatment tank (Claim 1). In the conventional freeze-thaw treatment apparatus, the concentration means, the freeze-thaw treatment means, and the dewatering means are configured as separate devices, and it is necessary to transport sludge for each of these devices. It is characterized in that the means necessary for processing is integrated with the freeze-thaw processing tank.
[0013]
Further, in the above freeze-thaw treatment apparatus, the dewatering sludge discharging means is configured as a part of the wall surface of the freeze-thawing treatment tank as a discharging means having a movable portion, and a filter is provided on the wall surface side of the freeze-thawing treatment tank. In addition, an outlet for filtered water is provided on the outside, and filtered water is discharged from this outlet during filtration and concentration, and sludge is discharged by moving the moving part of this discharging means when discharging dewatered sludge. (Claim 2).
Furthermore, in the freeze-thaw treatment apparatus according to claim 1 or 2, the freeze-thaw treatment tank is hermetically sealed so as to be a pressurizable container, and a pressurizing pump is provided in the raw sludge supply means so that the raw sludge is supplied. During filtration and concentration, the raw sludge is pressurized to promote the discharge of the filtrate (claim 3).
[0014]
In addition to this, in the freeze-thaw treatment apparatus according to any one of claims 1 to 3, the freeze-thaw treatment tank is hermetically sealed to be a pressurizable container, and a compressed air tank and air for promoting concentration of raw sludge are used. A compressor is provided, and when the raw sludge is filtered and concentrated, the raw sludge is pressurized with compressed air to promote the discharge of the filtrate (claim 4).
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, two embodiments of the present invention will be described with reference to the drawings.
[Example 1]
An embodiment of a freeze-thaw processing apparatus including claims 1, 2, and 3 of the present invention is shown in FIG. As can be seen from this figure, the freeze / thaw treatment apparatus is composed of a raw sludge tank 5, a freeze / thaw treatment tank 21, and a cooling / heating apparatus 22. The freezing and thawing treatment tank 21 includes raw sludge supply and pressurization means (sludge supply pump 6 and sludge supply valve 6a), raw sludge storage means for treatment (sludge treatment tank 1), The heat transfer means (heat transfer body 2) that exchanges the cooling and heating heat with the raw sludge by flowing the cold and warm brine of the cooling and heating device 22, the sludge concentration means that filters the moisture of the raw sludge, and the filtered water The discharge means (filter cloth 3, drainage net 4, filtrate drain pipe 9a) and the dewatered sludge discharge means (dehydrated sludge drainage device 9) provided with a movable part are provided integrally.
[0016]
The cooling and heating device 22 is the same as the conventional device, the compression refrigerator 10, the cold (warm) brine tanks 11a and 11b, the brine cooling (heating) pumps 12a and 12b, the brine cooling (heating) heat exchanger 13a, 13b, the refrigerant container 14, the expansion valve 15, and the switching valves 16a, 16b, 17a, 17b.
FIG. 3 is a cross-sectional view showing an actual arrangement example of the heat transfer body (heat exchanger) 2, the filter cloth 3, and the drainage net 4 in the freeze / thaw treatment tank 21. In FIG. 1, the sludge treatment tank 1, the heat transfer body 2, the filter cloth 3, and the drainage net 4 in the freeze / thaw treatment tank 21 are shown at the center, right side, and left side, respectively, for the sake of simplicity. In order to improve the effect of water removal and cooling / heating of the raw sludge, it is necessary to increase the contact area with the raw sludge. Actually, multiple serpentine tubes and flat tubes are alternately arranged as shown in FIG. The structure to be used is available. However, this arrangement is not limited to this example as long as various deformation structures are possible and the heat transfer means and the concentration means for the raw sludge are provided in the sludge treatment tank. Further, as the material of the heat transfer body 2 at that time, stainless steel, galvanized iron or the like can be used, and the drainage net 4 can be a metal or plastic coarse net.
[0017]
The operation with this device proceeds in the following order. 1) The raw sludge in the raw sludge tank 5 is supplied to the sludge treatment tank 1 using the sludge supply pump 6 and the sludge supply valve 6a. 2) The water contained in the raw sludge is discharged from the filtrate discharge pipe 9a through the gap of the metal drainage net 4 through the filter cloth 3 by pressurization of the sludge supply pump 6 or the like. 3) In the heat transfer body 2 made of a stainless steel container or the like, the switching valves 16a and 17a on the cooling side of the cooling and heating device 22 are opened and cold brine is supplied by the brine cooling pump 12a to reduce the water content of the raw sludge. Cool the concentrated sludge. 4) After cooling the concentrated sludge and freezing is completed, the supply of cold brine is stopped. 5) Close the cooling side switching valves 16a, 17a and open the heating side switching valves 16b, 17b to switch from cold brine to warm brine to supply warm brine to the heat transfer body 2 and heat the frozen sludge. Thaw. 6) The water of the molten sludge passes through the gap between the filter cloth 3 and the drainage net 4 and is discharged from the filtrate discharge pipe 9a. 7) The dewatered sludge is taken out by lowering the lid by the movable part (elevating device) of the dewatered sludge discharge device 9.
[Example 2]
FIG. 2 shows an example of a freeze-thaw processing apparatus in which claim 4 of the present invention is added to Example 1 described above. The difference between this figure and Example 1 is that a compressed air tank 8, an air compressor 7 and a pressurized air gate valve 7a for concentrating raw sludge were added to the freeze / thaw treatment apparatus of Example 1. is there.
[0018]
The operation of this apparatus is obtained by changing and adding a part of the process of Example 1, and the operation sequence of Example 2 is shown in FIG. In this figure, the same constituent elements as those in FIG. 2 are denoted by the same reference numerals. That is, in the process of FIG. 4, 1) The raw sludge in the raw sludge tank 5 is supplied to the sludge treatment tank 1 using the sludge supply pump 6 and the sludge supply valve 6a. At that time, in Example 2, the water contained in the raw sludge is added to the filter cloth 3 by opening the pressurized air gate valve 7a and adding the air pressure of the compressed air tank 8 together with the pressure of the sludge supply pump 6. Through the eyes, the discharge is promoted from the filtrate discharge pipe 9a through the gap of the metal drainage net 4. 2) Cool brine is supplied into the heat transfer body 2 made of a stainless steel container or the like, and the concentrated sludge with reduced moisture in the raw sludge is cooled. After the concentrated sludge is cooled and freezing is completed, the supply of cold brine is stopped. 3) Switch from cold brine to warm brine, supply warm brine to heat transfer body 2, and heat frozen sludge to a molten state. 4) The water of the molten sludge passes through the gap between the filter cloth 3 and the drainage net 4 and is discharged from the filtrate discharge pipe 9a. In that case, in Example 2, the discharge of filtrate can be accelerated | stimulated by opening the pressurized air gate valve 7a and adding the air pressurization of the compressed air tank 8. FIG. 5) The dewatered sludge is taken out by lowering the lid by the movable part (elevating device) of the dewatered sludge discharge device 9.
[0019]
【The invention's effect】
In the present invention, the freeze / thaw treatment apparatus is composed of the raw sludge tank 5, the freeze / thaw treatment tank 21, and the cooling / heating apparatus 22, and the freeze / thaw treatment tank 21 is sludge capable of supplying and pressurizing the raw sludge. Pump 6 for supply, sludge treatment tank 1 of raw sludge, heat transfer body 2 that cools and heats raw sludge, filter cloth 3 that drains and concentrates water of raw sludge, drainage net 4 and filtrate drain pipe 9a and the dewatered sludge drainage device 9 having a movable part are integrated. A compressed air tank 8 and an air compressor 7 are provided for concentrating raw sludge and for dehydrating molten sludge.
[0020]
For this reason, in the conventional freeze-thaw treatment device in which the raw sludge concentrator, the freeze-thaw treatment tank, the dehydrator, and the cooling and heating device are configured separately, if the sludge concentration in the concentrator is high, the fluidity decreases. The problem is that it is difficult to transfer sludge to the freeze-thaw treatment tank and to uniformly fill the space between the heat exchangers in the freeze-thaw treatment tank, and the degree of concentration is limited, so the power consumption cannot be reduced sufficiently. There is an effect that two points of the problem that the cost of the freeze / thaw treatment apparatus becomes expensive due to the combination of the point and the individual apparatus can be solved at once by the integration of the freeze / thaw treatment tank of the present invention. .
[Brief description of the drawings]
FIG. 1 is a diagram showing an embodiment of a freeze-thaw processing apparatus including claims 1, 2, and 3 of the present invention. FIG. 2 is an embodiment of a freeze-thaw processing apparatus in which claim 4 of the present invention is added to the first embodiment. FIG. 3 is a cross-sectional view showing an actual arrangement example of a heat transfer body, a filter cloth, and a drainage net in a sludge treatment tank. FIG. 4 is a diagram showing an operation sequence of Example 2. FIG. Fig. 6 is a diagram showing an example of a micrograph of sludge for explaining the principle. Fig. 6 is a diagram showing a basic method of sludge treatment using a freeze-thaw treatment apparatus. Fig. 7 is a diagram showing an example of a conventional freeze-thaw type sludge treatment system. [Explanation of symbols]
1: Sludge treatment tank 2: Heat transfer body (heat exchanger)
3: Filter cloth 4: Drainage net 5: Raw sludge tank 6: Sludge supply pump 6a: Sludge supply valve 7: Air compressor 7a: Pressurized air gate valve 8: Compressed air tank 9: Dehydrated sludge discharge device 9a: Filter Liquid drain pipe 10: Compression refrigerator 11a: Cold brine tank 11b: Hot brine tank 12a: Brine cooling pump 12b: Brine heating pump 13a: Brine cooling heat exchanger 13b: Brine heating heat exchanger 14: Refrigerant container 15: expansion valves 16a, b: switching valves 17a, b: switching valves 21: freeze-thaw treatment tank 22: cooling and heating device 31: filtration and concentration device 31a: filter cloth 32: concentrated sludge storage tank 33a, b: freeze-thaw treatment tank 33h : Heat exchanger (heat transfer body)
34: Dehydrator 35a, b: Concentrated sludge transfer pump 36: Filtrate discharge pump 37a, b: Switching valve 38a, b: Cold / heat switching device

Claims (4)

In freeze-thaw treatment equipment that performs dewatering treatment of purified water sludge and industrial wastewater sludge using the principle of freeze-thaw, raw sludge supply means, storage means for storing the supplied raw sludge, and cooling of the stored raw sludge・ Freezing and thawing treatment tank is provided with heat transfer means for heating, sludge concentration means for filtering the water of stored raw sludge, means for discharging filtered treated water, and means for discharging dewatered sludge after filtration. A freeze-thaw treatment apparatus characterized by the above. In the freeze thaw processing apparatus according to claim 1, the dewatering sludge discharging means is configured as a part of the wall surface of the freeze thaw processing tank as a discharging means having a movable part, The filter body is provided with an outlet for filtered water on the outside, and the filtered water is discharged from this outlet during filtration concentration, and the sludge is discharged by moving the moving part of this discharge means when discharging the dewatered sludge. A freeze-thaw treatment apparatus characterized by the above. 3. The freeze / thaw treatment apparatus according to claim 1 or 2, wherein the freeze-thaw treatment tank is hermetically sealed to provide a pressurizable container, and a pressurizing pump is provided in the raw sludge supply means to supply and filter the raw sludge. A freezing and thawing device characterized in that the raw sludge is pressurized during concentration to promote the discharge of the filtrate. The freeze / thaw treatment apparatus according to any one of claims 1 to 3, wherein the freeze-thaw treatment tank is hermetically sealed to be a pressurizable container, and a compressed air tank and an air compressor for promoting concentration of raw sludge are provided. A freezing and thawing treatment apparatus characterized in that when the raw sludge is filtered and concentrated, the raw sludge is pressurized with compressed air to accelerate the discharge of the filtrate.

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