JP4133213B2 - Sludge freezing and thawing treatment method and apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The effect of freezing and thawing before filtering and dewatering sludge in the treatment of wastewater sludge, sewage sludge, septic tank sludge, human waste, or sludge discharged when processing industrial wastewater or landfill wastewater. It is getting attention. The present invention relates to the sludge freezing and thawing treatment method and the apparatus used therefor, and particularly effective in combination with the activated sludge treatment method.
[0002]
[Prior art]
Usually, since the sludge contains a large amount of water, the sludge is concentrated and dehydrated using solid-liquid separation means such as sedimentation, filtration, and dehydration, and the final solid is composted. Or final disposal such as landfill and incineration. However, these sludges have extremely poor filtration and dehydration properties, requiring labor for replacement and washing of the filter cloth, and a long time for filtration and dehydration. Conventionally, a filter aid such as slaked lime has been added to the sludge for dehydration. However, there are disadvantages such as an increase in the amount of sludge due to the addition of chemicals and secondary contamination with chemicals.
[0003]
Recently, as one means for solving the above problems, a freezing / thawing treatment method in which sludge is frozen and thawed and then filtered and dehydrated has been proposed, and its effect has been recognized. This is because the freeze / thaw treatment method is a non-drug treatment method that does not use a drug, and for the following reason. Sludge contains internal moisture in the sludge particles and moisture adhering to the sludge particle surface. By applying freezing and thawing treatment, the adhering water grows as ice crystals, and the sludge is concentrated in the unfrozen part and the sludge grains become coarse. Furthermore, in the sludge freezing process, compressive force acts on the sludge due to volume expansion due to freezing, resulting in destruction of part of the sludge structure and outflow of internal moisture, facilitating filtration and dehydration operations.
[0004]
For reference, an example of a sludge dewatering system using freezing / thawing treatment is shown in a flow sheet in FIG. According to this example, water to be treated (pipe 21) containing sludge is guided to the settling basin 22 and the sludge is settled and separated, and then the settled sludge (pipe 23) is fed into the concentration tank 24 and separated and concentrated. Then, the concentrated sludge (pipe 25) is fed into the freezing / thawing tank 26, the refrigerant is flowed through the heat transfer tube 27 provided in the tank 26 to freeze the sludge, and then the refrigerant is switched to the heat medium to remove the sludge. Melt. The supernatant water (pipe 28) of the molten sludge is separated, and the remaining sludge (pipe 29) with improved dewaterability is sent to a dehydrator 30 (for example, a pressure filter) for dehydration. The refrigerant and the heat medium are alternately passed through the heat transfer tube 27 to freeze and thaw the sludge, and is generally carried out by a one-cycle batch process.
[0005]
[Problems to be solved by the invention]
Despite the fact that no chemicals are used, the effect of freezing and thawing before treatment in sludge filtration and dewatering operations is large, but sewage sludge containing organic substances has a lower coagulation effect due to freezing and thawing than inorganic water purification sludge. However, the time required for the freezing / thawing process is long, and there is a problem that the equipment cost and the operating cost are increased. The present invention has been completed as a result of earnestly researching the means for reducing the equipment cost and the operating cost while the operation is completed in a short time in order to effectively execute the freezing / thawing process.
[0006]
[Means for Solving the Problems]
The present invention uses a tubular sludge treatment container provided with cooling and heating means from the outside as means for solving the above-mentioned problems, and the treatment container is filled with the sludge to be treated, and the treatment container is filled with the outside. The sludge in the vicinity of the opening leading to is cooled and frozen, and the treated sludge is enclosed in the treatment container.Then, the enclosed sludge is cooled and frozen to freeze the filled sludge. Provided is a method for freezing and thawing sludge, which is characterized by being melted and taken out of the processing container.
[0007]
The present invention also includes a sludge treatment container for filling the sludge to be treated for freezing and thawing treatment, and cooling and freezing the sludge filled from the outside of the filled sludge treatment container, and heating and melting. And a jacket for circulating the heat medium, and the jacket includes a jacket for selectively freezing the sludge filled in the vicinity of the opening from the sludge treatment container to the outside. A sludge freezing and thawing device is provided.
[0008]
As a preferred specific example of the sludge freezing and thawing device, a sludge treatment tube 1 bundle of sludge to be treated is filled from the inlet 2 at the upper end and the treated sludge is taken out from the outlet 3 at the lower end. A treatment vessel, in which the sludge treatment tube bundle is vertically installed, an upper section 4 for cooling or heating the vicinity of the inlet 2 at the top of the sludge treatment pipe, a central section 5 for cooling or heating the central portion, The jacket 7 is divided into at least three sections, ie, a lower section 6 that cools or heats the vicinity of the discharge port, and each of them independently circulates a heat medium for cooling or heating. A sludge freezing and thawing device is preferably used, in which a top plate 10 provided with a sludge supply port 8 is attached to the upper end and a end plate 11 provided with an outlet 9 is attached to the lower end. It can be. The sludge treatment tube 1 is preferably a grooved tube whose inner surface is ring-shaped or helically grooved.
[0009]
In the present invention, by using the sludge freezing and thawing apparatus of the preferred embodiment described above, first, each sludge treatment tube is filled with the sludge to be treated, and then the refrigerant is allowed to flow through the upper and lower sections of the jacket. After freezing the sludge near the inlet and outlet and enclosing the sludge in the central compartment, the refrigerant is poured into the central compartment to freeze the sludge enclosed, freezing treatment is finished, and the refrigerant flowing in the jacket is removed. It can be easily carried out by switching to the heat medium and discharging the sludge melted and discharged from the outlet.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Further, the present invention will be specifically described with reference to the embodiments. The conventional freezing / thawing means is a method in which sludge is put into a freezing / thawing tank, a refrigerant is flown through a heat transfer tube attached inside, the sludge is frozen under open air, and the refrigerant is switched to a heat medium after a predetermined freezing treatment. The frozen sludge was melted and the sludge was frozen and thawed. On the other hand, in the present invention, the sludge to be treated is filled into the treatment container using a tubular sludge treatment container provided with cooling and heating means from the outside, and subjected to freezing / thawing treatment. Since a considerable internal pressure is applied to the sludge treatment container in the present invention, a circular pipe is usually used. Further, in order to adopt an external heating method to shorten the cooling and heating time, preferably a sludge treatment tube having a relatively small diameter is bundled and used as a sludge treatment container.
[0011]
In the freezing / thawing process of the present invention, the sludge in the vicinity of the opening communicating from the sludge treatment container to the outside of the container is first cooled and frozen, and the sludge filled with the frozen sludge is enclosed in the treatment container. Next, the enclosed sludge is cooled and frozen to carry out a freezing treatment. When the freezing process is completed, the refrigerant is switched to the heat medium, and the sludge is melted and discharged out of the container. The unfrozen sludge enclosed by the above operation expands with freezing, but since the sludge in the opening communicating with the outside of the container is frozen, it is frozen under a higher pressure than conventional means for freezing in an open system. . As a result, when used in combination with the activated sludge method, the cell membrane of the bacterial cells in the sludge is easily broken, the internal water can easily flow out, the dehydration time is shortened, and the residual moisture can be reduced.
[0012]
The freezing / thawing treatment of the present invention includes a sludge treatment container for filling and treating the sludge to be treated, and a purpose of melting the frozen sludge by cooling or freezing the filled sludge from the outside of the treatment container. Then, a freezing / thawing apparatus including a cooling / heating jacket for switching and circulating both the cooling and heating heat media is used. The purpose is to selectively freeze the sludge filled near the opening of the processing vessel in order to cool and freeze the sludge near the opening and enclose the filled unfrozen sludge in the processing vessel. A freezing / thawing device in which the flow path is provided in the jacket is suitable.
[0013]
Next, the present invention will be described with reference to the drawings with specific preferred embodiments. FIG. 1 is an explanatory view showing a preferred embodiment of a sludge freezing / thawing apparatus according to the present invention. The freezing and thawing apparatus shown in FIG. 1 is similar in structure to a vertical multitubular heat exchanger.
[0014]
In the freezing / thawing apparatus of the present embodiment, a bundle of circular containers 1 is used as a sludge treatment container. The upper end of the sludge treatment pipe 1 is the sludge inlet 2 and the lower end is the treated sludge outlet 3. A plurality of sludge treatment tubes are generally arranged regularly at a predetermined interval, and both upper and lower end portions are attached to the tube plate 14, and the tube jacket 14 (also referred to as a trunk) is inserted through the tube plate 14. , Attached in the vertical axis direction. The sludge treatment tube 1 side is configured in one pass in one direction in the up and down direction to fill the sludge to be cooled and heated. Preferably, as the sludge treatment tube 1, a grooved tube whose inner surface is ring-shaped or spiral-shaped uneven groove processing is used. It has the effect of preventing slippage between the inner surface of the tube 1 and the frozen sludge and increasing the pressure applied to the frozen sludge. A heat transfer tube is preferably used for the sludge treatment tube 1.
[0015]
The jacket side includes an upper section 4 that cools or heats the vicinity of the inlet 2 of the sludge treatment tube 1, a central section 5 that cools or heats the center, and a lower section 6 that cools or heats the vicinity of the discharge port. It is partitioned into at least three sections. And in the said division, the heat carrier for cooling or heating can be independently passed through each. Reference numerals 15, 16, and 17 denote heat medium flow paths in the upper, middle, and lower sections.
[0016]
The number of partitions may be increased if necessary. An end plate 10 provided with a sludge supply port 8 is attached to the upper end of the jacket 7, and an end plate 11 provided with an outlet 9 is attached to the lower end to form a sludge flow path or an area for temporarily storing sludge. ing. Normally, the jacket 7 is less likely to receive a load other than the pressure due to the heat medium, and may be a cylinder or a square tube on the premise of ensuring safety.
[0017]
When using the sludge freezing and thawing device of this embodiment, first, sludge is filled in each sludge treatment tube. The sludge filling is performed, for example, by operating the gate valve 12 attached to the sludge supply port 8 side pipe and the gate valve 13 attached to the outlet 9 side pipe, and the sludge for each batch of the sludge treatment container as an extrusion flow. Intermittent supply, or the sludge removal level after the end of the treatment may be maintained near the lower end of the sludge treatment tube 1 to intermittently supply and fill one batch processing amount. It is convenient to connect the sludge weighing hopper to the sludge intake side and supply one batch of processing amount.
[0018]
After filling the sludge, in order to cool the vicinity of the sludge inlet 2 and the outlet 3, the refrigerant is flown to the jacket side of the upper and lower compartments 4, 6, and the sludge at both ends of the filled sludge is frozen. Enclose sludge. Then, the refrigerant is circulated through the central section 5 to freeze the enclosed sludge. Unfrozen encapsulated sludge undergoes freezing treatment under high pressure rather than volume expansion with freezing and freezing in an open system. Unfrozen intermediate sludge expands in volume with freezing, but both ends are frozen, so it freezes under high pressure rather than freezing in an open system, and the cell membrane of the bacterial cells in the sludge is destroyed and internal water flows out. To do. After the charged sludge is lowered to a predetermined freezing temperature and a predetermined holding time is passed, the refrigerant flowing on the jacket side is switched to the heat medium, and the sludge is melted and discharged. The temperature of the refrigerant used is generally about −10 to −20 ° C. depending on the conditions.
[0019]
【Example】
In order to understand the present invention in detail, the conventional freezing / thawing tank will be described in detail with reference to an example in which the freezing / thawing tank according to the present invention is modified. It is not limited.
[0020]
Conventional Example The conventional freezing / thawing tank has an upper shape in the shape of a square tube, and the bottom is valley-shaped so that the freezing / thawing tank sludge can be easily discharged. In the tank, a heat transfer tube of SB340 material having a normal outer diameter of 25.4 mm, in which a refrigerant and a heat medium are passed in order to freeze and thaw sludge, is vertically installed in a grid arrangement with a pitch of 50 mm. The structure of the tank body is made of carbon steel, and the surface of the tank is affixed to the inner surface of the tank with anti-corrosion foam rubber as a cushioning material to prevent corrosion, keep cold insulation, and prevent damage to the tank due to volume expansion when sludge freezes. It has become.
[0021]
Then, only moisture from the vicinity of the heat transfer tube is frozen, solid sludge is removed from the ice and moved to the unfrozen part, and finally the solid sludge is concentrated near the center of the heat transfer tube However, because of the open system, the pressure due to the volume expansion force of ice due to freezing escapes when the cushion material and the upper water surface rise, and the sludge aggregates are not pressurized, so the treatment is finished in a soft state.
[0022]
EXAMPLE A freezing / thawing tank according to the present invention has a heat transfer tube made of SB410 having an outer diameter of 42.7 mm and is vertically arranged in a triangular arrangement at a pitch of 50 mm, and sludge is frozen in the tube, contrary to the conventional method. Moreover, it has a structure in which a refrigerant and a heat medium for melting are passed. By freezing both ends of the heat transfer tube in the sludge charged into the pipe, and then freezing the entire charged sludge, the pressure due to the volume expansion force of the ice due to freezing cannot escape and the whole sludge is boosted. By pressing the aggregated aggregate of sludge concentrated near the center of the heat transfer tube, the binding force of the aggregate becomes stronger, and by destroying the cell membrane of the bacterial body such as sewage surplus sludge and discharging the body fluid, Dehydration filtration in the subsequent process becomes very easy.
[0023]
In order to maintain the internal pressure, both ends of the heat transfer tube have a closing mechanism such as a valve, but the inner surface of the heat transfer tube is provided with a ring shape, or a spiral shape and a concave / convex groove, so By maintaining the pressure of the frozen sludge in the pipe by suppressing slippage, cost reduction and maintenance become very easy.
[0024]
【The invention's effect】
By utilizing the present invention, the time required for the sludge freezing and thawing treatment can be shortened, or the moisture content in the sludge after dehydration can be reduced, and the equipment cost and the operating cost can be reduced.
[Brief description of the drawings]
FIG. 1 is an explanatory view showing an embodiment of a sludge freezing / thawing apparatus according to the present invention. FIG. 2 is a schematic flow sheet illustrating a conventional sludge treatment using a freezing / thawing treatment method.
1: Sludge treatment pipe 2: Treated sludge inlet 3: Treated sludge outlet 4: Jacket upper compartment 5: Jacket middle compartment 6: Jacket lower compartment 7: Jacket body 8: Treated sludge supply port 9: Treated Sludge outlet 10: Upper end panel 11: Lower end panel 12: Supply port side gate valve 13: Outlet side gate valve 14: Tube plate 15: Upper section heat medium flow path 16: Central section heat medium flow path 17: Lower section Heat medium flow path 21: Water to be treated (pipe) 22: Sedimentation basin 23: Sedimentation sludge (pipe) 24: Concentration tank 25: Concentrated sludge (pipe) 26: Freezing / thawing tank 27: Heat transfer pipe 28: Supernatant water (piping) )
29: Treated sludge (piping) 30: Dehydrator (pressure filter)

Claims (5)

Using a tubular sludge treatment container equipped with cooling and heating means from the outside, the treatment container is filled with the treatment sludge, and the sludge near the opening communicating from the treatment container to the outside is cooled and frozen to be treated. Sludge is sealed in a processing container, then the sealed sludge is cooled and frozen to freeze the filled sludge, and the sludge that has been frozen is melted and taken out of the processing container. Freezing and thawing method. A sludge treatment container for freezing and thawing by filling the sludge to be treated;
A jacket through which a heat medium is circulated to cool and freeze the sludge filled from the outside of the filled sludge treatment container and to melt by heating;
The jacket is provided with a heat medium flow path for selectively freezing the sludge filled in the vicinity of the opening that leads from the sludge treatment container to the outside. apparatus. A bundle of sludge treatment pipes (1) for filling the sludge to be treated from the top inlet (2) and taking out the treated sludge from the bottom outlet (3) is a sludge treatment container,
Inside the sludge treatment tube bundle is installed vertically, an upper section (4) for cooling or heating the vicinity of the inlet of the upper part of the sludge treatment pipe, a central section (5) for cooling or heating the central portion, and A cylindrical body (7) that is divided into at least three sections of a lower section (6) that cools or heats the vicinity of the discharge port and circulates a heat medium for cooling or heating independently of each other, as a jacket,
The end plate (10) provided with the supply port (8) of sludge is attached to the upper end of the jacket body, and the end plate (11) provided with the outlet (9) is attached to the lower end. The sludge freezing and thawing device described in 1. The sludge freezing and thawing device according to claim 2 or 3, wherein the sludge treatment tube is a grooved tube having an inner surface provided with a ring-shaped or spiral groove. Using the sludge freezing and thawing device according to claim 3 or 4,
First, each sludge treatment pipe is filled with the treated sludge,
Next, after flowing the refrigerant in the upper and lower compartments of the jacket to freeze the sludge in the vicinity of the inlet and outlet, and sealing the sludge in the central compartment,
Freeze the sludge encapsulated by flowing a refrigerant in the central compartment and finish the freezing treatment,
A method for freezing and thawing sludge, wherein the refrigerant flowing through the jacket is switched to a heat medium and the sludge melted and melted is discharged from the outlet.

Images