JPS63185500A - Formation of sludge cake - Google Patents

Abstract

PURPOSE:To efficiently form the title cake having a low content of water by carrying out freezing and melting of sludge along with the dehydration and filtration of sludge in the same caking chamber. CONSTITUTION:The caking chamber 13 is formed between two parallel first and second plate members 11 and 12, a filter cloth 14 is laid over the inner surface of the member 11, sludge is forced in from the member 12 side, the member 12 is cooled, cooling proceeds from the whole surface on the member 12 side to the whole surface on the member 11 side, and the cake dehydrated in the chamber 13 is frozen in the chamber 13. The frozen cake is heated by the member 12 in the chamber 13, fresh sludge is forced in from the member 12 and dehydrated, and the frozen and melted first cake layer and the second cake layer dehydrated thereafter are laminated in the chamber 13. The dehydration and filtration efficiency can be increased with this simple structure without necessitating space, the cake can be efficiently discharged, and a cake having a low content of water can be efficiently formed.

Description

[Detailed Description of the Invention] [Field of the Invention] The present invention relates to a sludge cake for producing a sludge cake by dewatering sludge discharged from a sewage treatment equipment or an industrial wastewater treatment equipment containing plating waste liquid, etc. Regarding the generation method.

[Background of the Invention] In industrial wastewater treatment equipment, solid matter (sludge) contained in wastewater is precipitated in a settling tank, and this precipitate is dehydrated and filtered using a filter press to form a cake. . This cake is a non-flowing sludge that typically contains 70% to 80% or more moisture, is soft and inconvenient to handle for disposal, and is not suitable for landfill use or should be incinerated. However, there are many inconveniences such as the need for a large furnace.

Therefore, if the moisture content of such a cake is reduced, for example, from 40% to 50% or less, the cake becomes fine sand-like lumps that are easier to handle and dry in the atmosphere, and the volume is reduced by less than half. This makes it easy to dispose of and incinerate.

Therefore, there is a need for a method and apparatus capable of producing a cake with a sufficiently low moisture content. Furthermore, after the cake is formed, it is desired to efficiently discharge the cake and shorten the overall sludge treatment time.

[Prior Art] FIG. 5 shows the configuration of a filter press used in a conventional cake production method. A drainage conduit 1 is connected to a settling tank 2. The wastewater introduced into the settling tank 2 is separated into clear water 40 in the upper part and sediment (sludge) 41 in the lower part. The clear water 40 is discharged to a drain through a drain pipe 42. sludge 41
is passed through the mud feeding pipe 5 by the pump 4 to the filter press 6.
is pumped to. The filter press 6 consists of a pair of filter frames 61 facing each other and a filter cloth 62 fixed to the inner surface of each filter frame 61, and a cake production chamber 60 is formed between the filter frames 81 and 61. The mud feeding pipe 5 is connected to a mud feeding port (not shown) provided in the filter frame 61. Therefore, a hole (not shown) is also formed in the filter cloth 62 corresponding to this mud feeding port, and the filter cloth 62 is fixed to the inner surface of the filter frame 61 with the hole aligned.

The sludge forced into the cake production chamber 60 is dehydrated and filtered through a filter cloth 62. The dehydrated water is led to a conduit 7 through a groove (not shown) formed in the filter frame on the back side of the filter cloth, and is discharged to a drain pipe 8. The sludge after dehydration remains as a solid cake in the cake generation chamber 6o, and when the cake is filled in the chamber, the filter frame 61 is opened and the cake is discharged for disposal or incineration.

In such a conventional cake production method using a filter press, the dehydration filtration capacity is limited, and the moisture content of the produced cake cannot be lowered to 50% or less as described above. Furthermore, since the filter cloth was fixed to the filter frame, it was troublesome to replace the filter cloth, and cleaning work had to be carried out frequently to prevent clogging. Furthermore, this structure in which the filter cloth is fixed to the filter frame is also a constraint when an automatic cake discharge device is added. That is, in the conventional cake discharge device, the upper ends of both filter cloths facing each other are fixed to a support material above the filter frame.
With the filter frame open, this supporting material was vibrated up and down to shake off the cake adhering to the filter cloth. in this case,
The filter frame must be opened wide when discharging the cake, which requires a large opening space, and especially in a filter press configured with multiple cake production chambers arranged in parallel, it is difficult to open the filter frames of multiple cake production chambers at the same time. However, it was difficult due to space constraints, and it took a lot of time to discharge the cake.

On the other hand, in order to reduce the water content of the sludge cake, a method has been proposed in which the sludge after dehydration is once frozen, thawed, and dehydrated again (JP-A-55-131flT
Publication No.). However, in order to carry out such conventional freezing and thawing processing, the cake produced by the filter press must be discharged and then fed to a freezing (thawing) device, which is inefficient and takes a long time. It was necessary.

[Object of the Invention] The present invention has been made in view of the drawbacks of the prior art described above, and has a simple structure that does not require space, increases dehydration filtration efficiency, and efficiently discharges cake to achieve low water content. To provide a method for producing a sludge cake capable of producing a cake with a low moisture content by performing dehydration treatment, freezing and melting treatment in one device using a filter press equipped with cooling and heating means capable of efficiently producing the cake.

[Example] Fig. 1 shows the configuration of a filter press used for carrying out the cake production method according to the present invention. 1 pair of plate filter frames 1
A center plate 12 is arranged parallel to each filter frame between the filter frames. Recesses 24 are formed on both sides of the filter frame 11. Filter frame 11
A projecting edge portion 25 is formed on the periphery of the recess 24 and surrounds the recess 24 to form this recess. By bringing each filter frame 11 close to the center plate 12 and bringing the protruding edge 25 into pressure contact with the center plate 12, the recess 24 is sealed and a cake production chamber 13 is formed between each filter frame 11 and the center plate 12. .

A filter cloth 14 is disposed between each filter frame 11 and the center plate 12. Each filter frame 11 is arranged vertically and movable horizontally, and has a cake production position (the state shown in FIG. 1) close to the center plate 12 and a cake discharge position (the state shown in FIG. It is possible to move between the states shown in Figure 2).

The center plate 12 is provided with mud feeding ports 15 that are open on both sides. The mud feeding port 15 is connected to the mud feeding pump 16 via the mud feeding pipe 26.
It is connected with. A cake scraping device 17 is provided above the center plate 12. This cake scraping device 1
7 includes an arm 18 and a blade 19 provided at the tip of the arm 18, and the arm 18 is connected to a piston 21 of an air cylinder 20. By driving the air cylinder 20, the arm 18 and the blade 19 slide vertically along both sides of the center plate 12. The upper end of the filter cloth 14 is connected to the arm 18 via a support member 27. Filter cloth 1
A weight 22 is attached to the lower end of 4. A stainless steel wire 23 is stretched below the filter frame 11 for bending the filter cloth 14 and bringing it into sliding contact.

A cooling medium passage 32 is provided in the center plate 12, and a cooling medium passage 32 is provided in the central plate 12.
It is connected to the refrigeration device 29 via. A heating medium passage 33 is further provided in the center plate 12 and connected to a heating device 31 via a heating medium pipe 30. As a refrigerant, for example, Freon (product name: E, 1.du Pant de Ne
Mours & Co, Inc.) is used, and the heating medium is, for example, hot water mixed with antifreeze. The center plate 12 is made of a metal material (for example, copper) with high thermal conductivity. In addition, here, the center plate 12 is made of freon from the refrigerator.
However, an indirect cooling method may be adopted in which a solution commonly called brine, such as water mixed with antifreeze, is used as the refrigerant flowing through the center plate 12, and this is cooled with a refrigerator.

FIG. 4 shows a flowchart of a method for producing a sludge cake using the filter press configured as described above. First, the cake production position (with the filter frame 11 close to the center plate 12 and closed)
The filter frame 11 is fixed in the position shown in FIG. 1 (step a).

In this state, the sludge pump 16 is driven to force the sludge into the cake production chambers 13 on both sides of the central plate 12 through the sludge ports 15 (step b). - in this step b, the refrigeration device 29 is simultaneously activated to circulate the refrigerant through the cooling medium passages 32 of the central plate 12 to cool the cake being formed; Next, the pump is stopped (step C) and the freezing action of the cake in the cake production chamber is allowed to proceed (step d).

In this step d, the entire center plate 12 becomes a cooling source (heat sink), and the freezing action progresses from the entire surface of both sides of the center plate to the entire opposing surface of each filter frame 11, so that frost-shaped icicles are formed inside the cake on the center plate. It is formed perpendicularly to this. Once the cake is completely frozen, stop the freezing device (step e).

Start heating after some time to stabilize the condition (
Step f). In this step f, hot water circulates through the heating medium passage 33 of the center plate 12, melting the portion of the frozen cake in contact with the center plate 12, and melting the icicles. Now operate the pump again and pressurize new sludge (step g)
. Then, the water in the sludge passes vertically through the gaps between the frost-shaped icicles, and the icicles melt. When the cake melting is complete, stop heating while keeping the pump running (step h)
.

At this time, new sludge is deposited on the inner surface of the frozen and thawed cake (
Since it is press-fitted from the center plate side), the frozen and thawed cake is pressed against the outer surface side (filter frame side). Therefore, a cake is produced in the cake production chamber, consisting of the first cake layer that was first press-fitted and subjected to freezing and thawing operations, and a new cake layer of fS2 on its inner surface. Icicles are formed in countless numbers from the center plate toward the filter cloth, just like frost columns, so they have the property of allowing water to pass through in the vertical direction. For this reason, the dewatering and filtration action for the sludge that is press-ined later is first performed using the icicles, and then the cake layer, which has been frozen and has improved filterability, performs the dewatering process with high filtration efficiency.

FIG. 3(a) shows the cake formation state when the cake is once frozen and thawed and then subjected to dehydration treatment again. In the cake formation chamber, there are the first layer 50a that was first press-fitted and frozen and thawed, and the molten layer 50a. A cake 5o consisting of the second layer 50b which was press-fitted later is produced.

The moisture content of the cake of the first layer 50a has decreased to 20-30%. The moisture content of the cake in the second layer 50b is 70-75
It is about %. The cake can be discharged in this state, or the freeze-thaw process can be repeated again as described below.
As shown in Figure (b), the first layer 5 has been frozen and thawed twice.
By repeating the freezing and thawing process in this way, a three-layer cake 50 may be produced, consisting of the second layer 50b that is frozen and thawed second, and the third layer 50c that is press-fitted last. The lower moisture content cake layers can be increased to produce an overall lower moisture content cake.

When the inside of the frozen and thawed first cake layer is filled with a new second cake layer by a predetermined amount, it is determined in step i whether or not to repeat the freezing action again. The number of repetitions of the freezing and thawing process is set in advance, and this determination is made based on whether the number of times steps C to h have been executed has reached the number of repetitions. The steps are divided depending on the result of this determination. If not repeated, stop the pump and step k) Drain the cake (step 1). On the other hand, if freezing is to be repeated further, the refrigeration system is driven while the pump in step g is kept operating to start cooling again (step j). As a result, the action of forming the second layer of cake proceeds while being cooled. Thereafter, the steps from step C onward are repeated to cool and melt the second layer cake together with the first layer, and further to generate a third layer cake inside the second layer cake (steps C to
h). After forming a predetermined number of cake layers, the pump is stopped and the cake is discharged (step k) (step fL).

When the cake is to be discharged after the dehydration treatment, the filter frame 11 is moved away from the center plate 12 and moved to the open cake discharge position, as shown in FIG. In this state, the air cylinder 26
is driven to push down the arm 18 in the direction of arrow B via the piston 21. As a result, the blade 19 at the tip of the arm 18 slides along both surfaces of the center plate 12 and scrapes off the cake on the surface of the center plate.

At this time, the filter cloth 14 is simultaneously pulled downward by the weight 22 and descends while being given an appropriate tension. During this downward movement, the filter cloth 14 slides into contact with the protruding edge 25 at the lower end of the filter frame 11 and is bent, and the cake adhering to the filter cloth 14 is peeled off. Roughly, the filter cloth 14 is bent in sliding contact with the stainless steel wire 23,
The cake remaining on the filter cloth 14 is scraped off. Such cake scraping operation may be repeated multiple times by repeating the reciprocating movement of the piston 21.

Note that FIG. 3 shows a configuration in which three filter frames 11 are arranged in parallel and a center plate 12 is disposed between each filter frame to increase the number of cake generation chambers. The number of such filter frames 11 is appropriately selected depending on the installation space, the amount of sludge processed, etc.

When three or more filter frames 11 are arranged in parallel, it is desirable that the center plate 12 and the air cylinder 20 are fixed to each other and configured to be movable in the horizontal direction together with the filter frames 11. This allows a plurality of filter frames to be opened and closed at the same time, improving the operability of the opening and closing operations.

[Effects of the Invention] As described above, in the present invention, a cake with a low moisture content can be efficiently produced because the dehydration filtration and freezing and thawing of sludge are performed in the same cake production chamber. Also,
By disposing a center plate between at least one pair of filter frames and making the entire center plate act as a cooling plate or a heating plate, cakes in cake forming chambers on both sides of the center plate can be efficiently and efficiently treated in the same device. Freezing and thawing operations can be performed with high filtration efficiency, and a frozen cake can be formed into layers to produce a cake with a low moisture content in one device. In addition, by providing a sludge supply port in the center plate, there is no need to fix the filter cloth to the filter frame as in the conventional case, making it easier to install and replace the filter cloth, and to scrape off the cake attached to the filter cloth. It is possible to do this in a narrow space, the device can be made smaller, and a plurality of filter frame opening operations can be performed at the same time, and the cake discharge operation can be accomplished efficiently and in a short time. In addition, since the cake layer can be made thinner, the dehydration filtration efficiency is improved and the processing time is shortened.Furthermore, the layered cake has a thin layer of unprocessed cake attached to the frozen processed cake, and the unprocessed cake is It can also be easily dried through the treated cake, making it easy to incinerate.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of an embodiment of the present invention, FIG. 2 is an explanatory diagram of the cake discharging operation of the embodiment of FIG. 1, FIG. 3 is an explanatory diagram of the cake production state according to the embodiment of the present invention, and FIG. A flowchart showing the procedure of the method of the present invention, and FIG. 5 is an explanatory diagram of the prior art. ll: Filter frame, 12: Center plate, 13: Cake generation chamber, 14
: filter cloth, 15: mud feeding port, 16: mud feeding pump, 29: freezing device, 31: heating device - 32: cooling medium passage, 33: heating medium passage. Figure 1 ・ i″ father (b) Figure 3

Claims (1)

[Scope of Claims] 1. A sludge cake that has been dehydrated in a cake production chamber is frozen in the cake production chamber, and then this frozen cake is heated in the same cake production chamber, and freshly heated from one side of the cake production chamber. sludge is press-injected and dehydrated, and a first cake layer that has been subjected to freeze-thaw treatment is layered in the cake generation chamber, followed by a second cake layer that has been newly dehydrated. A method for producing sludge cake. 2. The cake generation chamber is formed between two parallel first and second plate members, a filter cloth is arranged on the inner surface of the first plate member, and a filter cloth is disposed on the inner surface of the first plate member, and a filter cloth is disposed on the inner surface of the first plate member. A patent claim characterized in that sludge is press-fitted, the second plate-shaped member is cooled, and the cooling action progresses from the entire surface of the second plate-shaped member to the entire surface of the first plate-shaped member. The method for producing a sludge cake according to item 1. 3. After stopping the cooling of the second plate-like member, the frozen cake is partially melted by heating the second plate-like member. sludge cake production method. 4. The process of freezing the cake in the cake production chamber, heating it to melt at least a portion of it, and then pressurizing new sludge for dehydration treatment is repeated two or more times to obtain a freezing effect in the cake production chamber. The method for producing a sludge cake according to any one of claims 1 to 3, characterized in that three or more cake layers are sequentially formed.