JP3521073B2 - Freeze-thaw method and freeze-thaw device - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a freeze-thaw method and a freeze-thaw apparatus, and more particularly to a freeze-thaw method mainly used as a pretreatment for a sludge dewatering process and a freeze-thaw apparatus used therefor.

[0002]

2. Description of the Related Art In order to purify waste water, solid contents such as sludge are mixed in the waste water, so that sludge needs to be separated from water, that is, solid-liquid separation. However, the properties of sludge vary depending on the condition of raw water and the coagulant used.
Its constituents are generally composed of aluminum hydroxide, clays, colloids, micro-organisms and other organic and inorganic substances, which are watery and gelatinous. Therefore,
Poor filterability and the high water content of the separated sludge impose a considerable burden on post-treatment such as transportation costs and landfill incineration. Therefore, a method of utilizing the aggregating action by chemical injection before post-treatment is used. When using inorganic coagulant lime, ferric chloride as injection chemical,
Although the filterability is improved, there is a problem that the amount of sludge to be disposed of is increased by injecting chemicals.

On the other hand, the organic polymer flocculants inevitably contain modified polymers, so if they leak into the environment, they may act as environmental hormones that inhibit biological growth, especially in the field of water purification. Its use is limited.

Therefore, as a method for dewatering sludge, a non-chemical injection method is preferable, and a freezing and thawing method, which has good filtration performance and does not significantly affect the environment, is particularly preferable. This freeze-thaw method can be applied to all sludge,
Dehydrated sludge with a low water content can be obtained, and since it does not use chemicals, it does not increase the amount of sludge that has been disposed of, and it has excellent characteristics such as no problems during soil reduction.

The principle of the freeze-thaw method is to pay attention to the existence of water contained in sludge and water adhering to the surface of the sludge,
By being frozen, the water grows as ice crystals,
At that time, the sludge is pushed to the unfrozen zone and the fine particles are concentrated while being combined and combined into a large block to improve the filtration characteristics. Furthermore, when the whole is frozen, the expansive force of ice formation gives a strong compressive force to the sludge, which destroys the sludge structure (protein or carbohydrate micelle structure or gel-like structure of gel-like substance) and The contained water flows out, and the dehydration effect becomes higher.

[0006]

However, the freeze-thaw method requires a large amount of energy for freezing the sludge, and the energy cost is high, and the dehydration property is higher than that when a polymer flocculant is used. There is a problem such as low.

In view of the above-mentioned problems of the prior art, therefore, the object of the present invention is to efficiently freeze an object to be treated such as sludge, thereby reducing the energy required for freezing and having good dehydration property. Another object of the present invention is to provide a freeze-thaw method and a freeze-thaw apparatus that can be used.

[0008]

The above objects can be achieved by the inventions described in the claims. That is, the characteristic configuration of the freeze-thaw method according to the present invention is a freeze-thaw method of freezing the object to be processed, melting and dehydrating the frozen object to be processed, when freezing the object to be processed. , Concentrate the object to be treated
At the same time, freeze and thaw the concentrated product to be treated.
Before mixing, the pre-prepared material to be treated and the ice nucleation active proteinaceous substance are sufficiently stirred so that they can be uniformly dispersed to prepare a pre-mixture.
Form, then put the premix to freeze molten bath, which
When they are frozen and thawed by an ammonia absorption refrigerator,
Together, the cooling of the absorber that constitutes the ammonia absorption refrigerator
Of the cold heat source generated when the frozen processed material is thawed.
To do it.

According to this structure, since the mixture of the object to be treated and the ice nucleation active proteinaceous substance is prepared in advance, they are mixed uniformly and mixed, and when this is put into the freeze-thaw tank, the ice nucleation activity is The presence of the protein-like substance raises the freezing start temperature of the object to be treated, and freezing starts around the uniformly dispersed ice nuclei active protein-like substance, and many fine objects to be frozen are used as nuclei. The freezing and thawing tank can be efficiently grown without causing unevenness in freezing of the object to be processed, and the freezing efficiency can be made extremely high. Therefore, the filtration specific resistance during dehydration becomes small,
It becomes easier to remove water, and the dehydration process can be performed efficiently. In addition, since the ice nucleation active protein-like substance used is obtained from ice nucleation active bacteria and does not remain viable, it does not cause contamination or other problems, is easy to handle, and has high work efficiency. Is. Moreover, the subject
Refrigeration cycle by heat drive as a pretreatment for physical dehydration
Since it can be operated, the burden of power consumption is small
Ammonia absorption refrigerator is used, resulting in power saving effect.
In addition to being able to volatilize, if the object to be treated is sludge,
It can be applied to mud, and dehydrated sludge with low water content can be obtained.
Since it is a chemical injection system, there is no increase in the amount of sludge that has been
Advantages of an excellent absorption refrigerator that does not cause problems during reduction
Can be used as is, and ammonia absorption cooling
The cold heat generated when the sludge is thawed by freezing and thawing by a freezer is absorbed.
Since it is partially used as a cooling heat source for the absorber of the refrigerator / freezer,
Lowering the driving energy of the machine and increasing the coefficient of performance,
It is possible to achieve further energy saving and power saving.
It's convenient to come.

As a result, the freezing and thawing method can efficiently reduce the energy required for freezing by efficiently freezing an object to be treated such as sludge, and further improve the efficiency of the dehydration treatment in the next step to improve the dehydration property. Could be provided.

The sludge referred to in the present invention includes all kinds of sludge such as sludge generated in water purification plants and sewage treatment plants, industrial wastewater treatment sludge, landfill wastewater treatment sludge, and human waste treatment sludge.

The pre-mixture of the substance to be treated and the ice-nucleus active protein-like substance is preferably prepared by mixing the concentrated substance to be treated with the powdery ice-nucleus active protein-like substance.

According to this structure, the object to be treated is concentrated, so that the freezing efficiency is enhanced, and the ice-nucleus active protein-like substance is in powder form, so that it is easy to handle, and the start of freezing of the object to be treated is started. It is convenient that many nuclei as points can be uniformly generated.

Connected to the ammonia absorption refrigerator
It is preferable to utilize a heat storage tank. With this configuration
In this way, effective use of heat leads to reduction of power consumption and
Good match.

With respect to the object to be treated,
It is possible to mix 0.01-0.1 g / L of proteinaceous substance.
preferable. If the ice nucleation active protein-like substance is less than 0.01 g / L with respect to the object to be treated, the freezing efficiency is low and
This is because mixing more than 1 g / L is not preferable because the effect is small relative to the added amount.

[0016] It is preferable that the ice-nucleus active protein-like substance is used by filtering and extracting live cultured bacteria with a filter having a diameter of 0.2 µm.

According to this structure, the ice nucleus-activating portion of the ice-nucleating bacteria is formed outside the cell wall of the ice-nucleating bacteria. 5
Since it is a blistering vesicle component with a size of about 0 to 200 nm (consisting of a high-concentration chain of amino groups containing phospholipid phosphatidylinositol), these are filtered and extracted to extract a proteinaceous substance for use. By doing so, the freezing efficiency can be further increased. Examples of ice-nucleating bacteria include Erwinia herbicola, Pseudomonus fl
Uorescens, Pseudomonas syringage fungus, etc. can be used.

Further, the characteristic constitution of the freeze-thaw apparatus according to the present invention is that the object to be treated can be stored and the stored object to be treated is stored.
A freeze-thaw tank for freezing and thawing with an absorption refrigerator,
Including a cooling tower for cooling the absorption refrigerator,
The object to be treated and the ice nucleation active protein-like substance were uniformly dispersed
A premixing tank with a stirring function to create a premix,
Charge the premix into the freeze-thaw tank from a premix tank
The absorption refrigerator has a mechanism and
Absorption refrigerator, which constitutes this ammonia absorption refrigerator
Cooling of the absorber during melting of the frozen processed material
This is done by using the cold heat source that is generated .

According to this structure, since the premixing tank for preparing the mixture of the object to be treated and the ice nucleation active protein-like substance is provided, the mixture mixed by the premixing tank is put into the freeze-thaw tank. As a result, the freezing start temperature of the object to be treated rises and freezing starts around the uniformly dispersed ice nuclei active proteinaceous substance. The freezing of the object to be processed can be efficiently grown without causing unevenness, and the freezing efficiency can be made extremely high. As a result, it was possible to provide a freeze-thaw apparatus which can reduce the energy required for freezing by efficiently freezing an object to be treated such as sludge, and can improve the dehydration property. Only
Also, it is frozen by heat drive as a pretreatment for dehydration of the object to be treated
Power consumption due to the ability to operate the cycle
Uses an ammonia absorption refrigerator with less energy consumption
In addition to being able to exert the effect, when the object to be treated is sludge,
Applicable to all types of sludge and obtains dehydrated sludge with low water content
The non-chemical injection method does not increase the amount of sludge that has been disposed.
And excellent absorption refrigeration that does not cause problems during soil reduction
You can use the advantages of the machine as it is,
A) Freezing and thawing by an absorption chiller and cooling that occurs when the sludge is thawed
Part of the heat is used as a cooling heat source for the absorption refrigerator's absorber
Therefore, lowering the driving energy of the refrigerator and the coefficient of performance
To further reduce energy consumption and power consumption
It is convenient to be able to.

A heat storage tank is connected to the ammonia absorption refrigerator.
It is preferable to have been.

According to this structure, heat can be effectively utilized and consumed.
This is convenient because it leads to a reduction in power consumption.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 shows a schematic overall structure when the sludge freeze-thaw treatment system is used for an ice heat storage system. This freeze-thaw apparatus comprises a cooling tower 1 as a cooling source and a freeze-thaw tank 2 for freezing or thawing sludge as an object to be treated.
And an absorption refrigerator 3. The cooling tower 1 is an absorption refrigerator 3.
It is provided to cool the cooling water that cools the ammonia used as the refrigerant. The freeze-thaw tank 2 is 1 in FIG.
Although only a stand is shown, a plurality of stands are usually installed in parallel. When ammonia is used as the refrigerant used in the absorption refrigerator 3, the burden of power consumption is small so that not only the power saving effect can be exhibited but also it can be applied to all sludges, and a dehydrated sludge with a low water content can be obtained. Since it is a non-chemical injection method, there is no increase in the amount of sludge that has been disposed, and there is no problem in soil reduction.

Sludge is put in the freeze-thaw tank 2 according to the process shown in FIG. That is, the raw water containing sludge is once introduced into the sludge basin 15 and stored until it reaches a certain amount, and is sequentially sent from the sludge basin 15 to the concentration tank 16 by the pump P, where the sludge is driven by the motor M. After being agitated by the agitator 21 and being concentrated to about several%, the concentrated sludge is stored in the sludge storage tank 17, and the agitator 22 driven by the motor M also sufficiently agitates the sludge. Next, the stirred concentrated sludge is sequentially fed to the centrifugal separator 18, the sludge is further concentrated, and the concentrated sludge is sequentially fed to the concentrated sludge tank 19. Even in the concentrated sludge tank 19, the agitator 23 driven by the motor M sufficiently agitates the sludge. Then, before sending the sludge concentrated in the thickened sludge tank 19 to the freeze-thaw tank 2, a relatively small capacity premixing tank 20 is arranged, and the thickened sludge sent to this premixing tank 20 is Then, an appropriate amount of powdery ice-nucleus active protein-like substance is added and sufficiently stirred using a stirring device 24 so that both are uniformly dispersed. The concentrated sludge thus uniformly dispersed and the ice nucleus active protein-like substance are put into the freeze-thaw tank 2 to separate the water contained in the sludge and agglomerate the solid matter. Usually, the sludge frozen in the freeze-thaw tank 2 is-
It needs to be cooled to 10 ℃ or less, but because ice-nucleus active protein-like substance is mixed, freezing starts at -2 to -5 ℃ and it freezes at about -10 ℃, depending on the amount of sludge. All the sludge put into the melting tank is surely frozen. Therefore, the energy cost required for cooling in the freeze-thaw tank can be significantly reduced as compared with the prior art.

The thawed sludge is further made into a dehydrated cake by a dehydrating device 25 such as a vacuum dehydrator and dried and processed. However, since the sludge is granulated, it is easily dehydrated. As the dehydrator, a vacuum separator, a centrifugal separator, a pressure dehydrator, or the like can be used. The dried sludge cake is incinerated in an incinerator or the like. The exhaust heat is
It can be used as a drive source for the absorption refrigerator 3.

As the ice nucleation active protein-like substance,
Erwinia herbicola and Pseudomonus fl are ice-nucleating bacteria
Uorescens, Pseudomonas syringage, etc. were cultivated in L medium or the like to collect the bacteria, physically destroy them to sterilize, freeze-dry this, and then pulverize into powder.

Next, the freeze-thaw apparatus will be described in more detail with reference to FIG. The absorption refrigerator 3 includes a condenser 4 that liquefies a refrigerant such as ammonia by heat radiation, an evaporator 5 that evaporates ammonia, and an absorber 6 that absorbs the ammonia vapor evaporated by the evaporator 5 into water that is an absorbent. It is configured with. However, a generator that pressurizes and feeds an aqueous ammonia solution containing a sufficient amount of refrigerant with a solution pump (not shown) by the absorber 6, and a rectifier that raises the ammonia concentration and sends it to the condenser 4. May be provided. Further, as a drive source for operating the absorption refrigerator 3, although not shown, waste heat energy such as incineration of sludge and cogeneration is supplied.

The high-pressure, high-concentration ammonia vapor is sent to the condenser 4, where it is heat-exchanged with the cooling water from the cooling tower 1 to be condensed and liquefied. The condenser 4 may be provided with an extraction device that removes a gas component that does not condense. Since the non-condensable gas deteriorates the heat transfer characteristics such as condensation or absorption, it is convenient to remove the non-condensed gas because the heat transfer characteristics can be maintained well. Incidentally, FIG.
Reference number 14 is a cooling water pump for sending cooling water.

Further, a brine circuit is connected to the evaporator 5 and the absorber 6. This brine circuit includes a cold brine circuit B1 including a low temperature cold brine tank 11 and a cold brine pump 12 that feeds cold brine, a hot brine tank 9 and a hot brine pump 10 that feeds warm brine. And a pair of cold temperature switching valves 13 and 13 'for switching between the hot brine circuit B2 and the cold brine circuit B1. A cold brine circuit B1 is connected to the evaporator 5, and a warm brine circuit B2 is connected to the absorber 6.
Are connected. When the sludge sent to the freeze-thaw tank 2 is frozen, the cold brine cooled by the evaporator 5 of the absorption refrigerator 3 is directly sent to the freeze-thaw tank 2 to freeze the sludge. It should be noted that FIG. 7 is a heat storage tank, and for example, it is used to guide cold heat to this heat storage tank at night in summer to perform ice heat storage, and to guide warm heat to the heat storage tank at night in winter to store heat as hot water. Of course, the heat storage tank 7 is not always necessary in the present embodiment, but if it is provided, the heat can be effectively used and the power consumption can be reduced, which is convenient. The reference numbers 8 and 8 ′ are switching valves for using the heat storage tank 7.

[0029]

Example 1 Freezing temperature when the above ice nucleation active protein-like substance and sludge were placed in a small mixing tank in advance and stirred and mixed, and then sequentially charged into a freeze-thaw tank,
Table 1 shows the results of measuring the filtration specific resistance and the water content. The filtration resistivity was measured by carrying out a Nutsche test for dehydration treatment of sludge (according to "Sewer Test Method" stipulated by the Japan Sewer Association).

[0030]

[Table 1] As can be seen from Table 1, when the ice nucleation active protein-like substance is added in an amount of 0.01 g / L or more, the freezing start temperature is certainly increased, the filtration resistivity is remarkably reduced, and the water content is reduced. To be

(Example 2) Next, 0.04 g / L of ice nucleus active protein-like substance was added to sludge previously stored in a small mixing tank.
When the mixture prepared by adding and stirring for 5 to 15 minutes is put into a freeze-thaw tank a, sludge and an ice nucleus active protein-like substance (added amount 0.0
4 g / L), the time when the entire charge was frozen was compared for each of b and b. The result is shown in FIG.
As is clear from FIG. 3, in the case of the pre-mixing treatment a, the temperature at which the entire input material freezes (about -10 ° C.) is faster than that in the case where the pre-mixing treatment is not performed, and the freezing time is about 2 /
I was able to shorten to 3.

[0032]

( 1 ) The hot brine circuit and the cold brine circuit may be always operated for a plurality of freeze-thaw tanks. That is, the cold brine circuit is operated to freeze the sludge in one freeze-thaw tank, while the warm brine circuit is operated to thaw the sludge already frozen in the other freeze-thaw tank. By sequentially performing such an operation on a plurality of freeze-thaw tanks, the pre-dewatering treatment of sludge can be efficiently performed, and the treatment efficiency can be increased.

[Brief description of drawings]

FIG. 1 is a schematic overall configuration diagram of a freeze-thaw device according to an embodiment of the present invention.

FIG. 2 is a schematic process diagram showing the treatment of the object to be treated, which is put into a freeze-thaw tank constituting the freeze-thaw apparatus of FIG.

FIG. 3 is a graph showing the results of freezing with and without premixing of sludge and ice nucleation active proteinaceous substance.

[Explanation of symbols]

2 Freeze-thaw tank 3 absorption refrigerator 6 absorber 20 premixing tank

─────────────────────────────────────────────────── ─── Continued Front Page (51) Int.Cl. ⁷ Identification Code FI (C12N 1/00 C12R 1:39 C12R 1:38) (C12N 1/00 C12R 1:39) (C12N 1/20 C12R 1: 18) (C12N 1/20 C12R 1:38) (C12N 1/20 C12R 1:39) (56) References JP-A-4-126600 (JP, A) JP-A-2-76595 (JP, A) Kai 52-86257 (JP, A) JP-A-9-264629 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) C02F 11/00-11/20 C12N 1/00, 1/20

Claims (5)

(57) [Claims] 1. A freeze-thaw method for freezing an object to be processed, thawing the frozen object to be processed and dehydrating the same, wherein the object to be processed is concentrated when the object to be processed is frozen.
Before freeze-thawing the concentrated product to be treated,
The pre-prepared object to be treated and the ice nucleation active proteinaceous substance are sufficiently stirred so that they can be uniformly dispersed to prepare a pre-mixture.
Pour this premix into a freeze-thaw bath and unload them.
Freezing and thawing with a monia absorption refrigerator,
Freeze the cooling of the absorber that constitutes the ammonia absorption refrigerator.
Using the cold heat source that is generated when the bonded objects are melted
Freeze-thaw method, characterized in that the cormorant. 2. The freeze-thaw method according to claim 1, wherein the pre-mixture of the substance to be treated and the ice-nucleus active protein-like substance is prepared by mixing the concentrated substance to be treated with the powdery ice-nucleus active protein-like substance. . 3. Connected to the ammonia absorption refrigerator
The freezing and thawing method according to claim 1 or 2, which utilizes a heat storage tank . 4. An object to be processed can be stored, and the stored object
Freezing and thawing that freezes and thaws the object to be processed with an absorption refrigerator.
Freezing provided with a thaw tank and a cooling tower for cooling the absorption refrigerator.
It is a melting and melting device, and the object to be treated and the ice nucleation active protein are previously prepared.
Stirring function to create a pre-mixture in which a substance like substance is uniformly dispersed
And a premixing tank equipped with
In addition to having a mechanism to put in the freeze-thaw tank,
If the absorption refrigerator is an ammonia absorption refrigerator,
Freeze the cooling of the absorber that constitutes the
In addition, the cold heat source generated when the processed material is melted is used.
Freezing and thawing device characterized by: 5. A heat storage tank is connected to the ammonia absorption refrigerator.
The freeze-thaw apparatus according to claim 4, which is continued.