JP4811728B2 - Slurry dewatering method and apparatus, and suspension processing system - Google Patents

Description

  TECHNICAL FIELD The present invention relates to water treatment technology, and in particular, a slurry dewatering treatment method and an apparatus therefor in a treatment process for various types of suspensions, drainage, mud water, mud, sludge, contaminated soil, and suspensions using the same. The present invention relates to a liquid processing system.

For example, the treatment of a large amount of construction wastewater generated during the construction of dams and tunnels, the treatment of mud used in various civil engineering methods such as the mud shield method, the treatment of washing water generated by washing treatment of contaminated soil, or the contaminated water area In various water treatment processes such as purification of bottom sediment (sludge), dehydration treatment for agglomerated sedimentation slurry is performed.
Filter slurry, belt press, vacuum dewatering, centrifugal dewatering, screw press, etc. are common methods for such slurry dehydration. Among these, filter presses have a moisture content of cake after dehydration compared to other methods. The large filter press apparatus is effective in that a large amount of slurry can be processed at a time, and is widely used in large-scale processing facilities.

FIG. 7 shows the most common dehydration process for slurry by a filter press apparatus. This is an example of application to a treatment process for a suspension having a solid matter concentration (SS) of about 0.1 to 5% by weight, and the solid matter is settled and separated from the suspension to be treated. The main purpose is to recover the separated water, and firstly, a flocculant (inorganic flocculant or polymer flocculant) is added to the suspension to promote solid sedimentation in the flocculent sedimentation tank 1, and the supernatant liquid Is recovered by the pump 2 as separated water and used for circulation or drainage as drainage.
Then, in order to dehydrate the solid matter that has settled and slurried to the bottom by the sedimentation process in the coagulation sedimentation tank 1 as described above, it is sent to the slurry tank 4 by the slurry pump 3 and stirred while being stored there. While preparing a slurry of a certain concentration (for example, a solid concentration of about 10 to 20%, in other words, a moisture content of about 90 to 80%), when a predetermined amount of slurry is stored, the slurry is pumped to the filter press device 6 by the slurry pump 5. Thus, the pressure dehydration treatment is performed, whereby the water content of the dehydrated cake is set to about 35 to 45% by weight and transferred to the next step to be disposed of appropriately. Normally, the separated water separated by the filter press device 6 is collected in the separated water tank 7, mixed with the suspension, returned to the coagulation sedimentation tank, and reprocessed.

In addition, for example, Patent Document 1 discloses a dehydration process using a high-pressure filter press when treating clay, and in that case, slurry is obtained through a receiving tank and a mud storage tank in which water is added to the clay and stirred. A slurry having a predetermined concentration is prepared by a tank, and the slurry is pumped to a high-pressure filter press by a high-pressure driving pump.
JP 2005-74334 A

By the way, the dehydration process by the filter press apparatus is performed in a batch system, and it is said that slurry supply (plunging) to a large number of filter chambers, pressing process, unpacking and cake peeling, filter cloth washing and resetting. A series of operations are repeated as one cycle. In the conventional general filter press apparatus, each of the above steps requires a considerable amount of time. For example, about 30 to 100 minutes for the slurry driving step, about 30 to 60 minutes for the pressing step, It usually takes about 10 to 30 minutes for the peeling process and about 10 to 20 minutes for cleaning and resetting the filter cloth, and generally takes a long time of 1.5 to 3 hours per cycle.
Therefore, in the past, the operation of 2 to 3 cycles per day is the limit, and even with a large filter press apparatus, the total treatment capacity is not necessarily sufficient, and large-scale water treatment In order to secure the required processing capacity at the facility, a large number of large filter press devices must be installed side by side, which requires a large amount of equipment and operation costs, and this type of facility reduces costs. It is an obstacle to plan.

  In view of the above circumstances, the present invention provides an effective and appropriate treatment method that can greatly improve the efficiency of dewatering treatment of slurry by a filter press device, and an apparatus therefor. It is an object of the present invention to provide an effective and appropriate processing system that can be processed.

The slurry dehydration treatment methods of the present invention, by adding a flocculant to the slurry to be processed is flocculated, the flocs comprising performs pressurized dehydration is pumped into a filter press device by flocs pressure pump, in particular processed The flocculant is added to the slurry in two stages before and after, the anionic polymer flocculant is added in the former stage, the cationic polymer flocculant is added in the latter stage, and the cationic polymer flocculant is added. The amount is 1/10 to 1/20 of the addition amount of the anionic polymer flocculant.

A slurry dewatering apparatus of the present invention is an apparatus for performing dehydration processing on a slurry by the above-described slurry dewatering method , and includes a floc generating apparatus that adds flocculant to a slurry to be processed to form a floc, and a floc. a filter press device for pressing圧脱water, a floc pumping pump for pumping the flocs generated in floc generation device in a filter press apparatus, comprising a coagulant addition device before and after the two-stage floc generation device, added preceding coagulant The apparatus is an anionic polymer flocculant addition device, the latter flocculant addition device is a cationic polymer flocculant addition device, and the addition amount of the cationic polymer flocculant by the latter addition device is the former addition device. It is characterized by being 1/10 to 1/20 of the addition amount of the anionic polymer flocculant.
In the slurry dewatering apparatus of the present invention, it is preferable that a flock storage tank for storing the flock generated by the flock generating device and for separating the flock and the separated water is provided at the subsequent stage of the flock generating device.

  The suspension treatment system of the present invention collects clear separated water by adding a flocculant to the suspension and separating water and solids before the slurry dewatering treatment apparatus, and collects solids. A coagulation sedimentation tank is provided for slurrying and sedimenting the slurry, and a slurry pump is provided for sending the slurry settled at the bottom of the coagulation sedimentation tank to the slurry dewatering apparatus.

According to the slurry dewatering treatment method and apparatus of the present invention, the slurry is flocked and sent to the filter press apparatus while being flocked, and dehydrated under pressure to transfer the slurry as a uniformly stirred and mixed slurry as in the prior art. Compared with pressure dehydration, the time required for pressure feeding and pressure dehydration can be greatly shortened, and as a result, the processing efficiency of the filter press apparatus can be remarkably improved.
In particular, when the slurry is flocculated, the anionic polymer flocculant and the cationic polymer flocculant are added in two stages , and the addition amount of the cationic polymer flocculant is adjusted to the anionic polymer flocculant. By adding 1/10 to 1/20 of the amount of added, the flocs produced thereby are most effective because they are difficult to break during pumping and easily dehydrated during pressure dehydration. .
In addition, according to the suspension treatment system of the present invention, it is possible to obtain clear separated water only by providing the slurry dewatering treatment device in the subsequent stage of the conventional general suspension treatment system, and accompanying this, the generation occurs accordingly. It is possible to efficiently dehydrate a large amount of slurry.

  A basic embodiment of the present invention is shown in FIGS. This is a conventional suspension processing system shown in FIG. 7 in which the slurry dewatering apparatus 10 of the present invention is installed, and the same reference numerals are given to the same components as those in the conventional system. Description is omitted.

  The slurry dewatering apparatus 10 of this embodiment is installed between the slurry tank 4 and the filter press apparatus 6 in a conventional general suspension processing system, and is sent from the slurry tank 4 by the slurry pump 5. A floc generator 11 that flocates by adding a flocculant to the coming slurry and stirring and mixing, a flock reservoir 12 that stores the generated floc, and a flock stored in the flock reservoir 12 are pumped to the filter press 6 And a flock pressure pump 13 for this purpose.

As shown in FIG. 2, the floc generator 11 in the present embodiment is added to the slurry sent from the slurry tank 4 through the line mixer 15 by adding a flocculant in the pipe by a screw as shown in FIG. 2. The slurry is agglomerated and flocated while being transferred forward while stirring and mixing.
The floc generating device 11 may be provided with an adding device for adding a known flocculant by an appropriate method. However, as shown in FIG. 2, a two-stage front and rear flocculant adding device 14 (14a, 14b) is installed. To do. In the illustrated example, the anterior polymer flocculant is added to the former flocculant adding device 14a, and most of the flocculant is supplied to the line mixer 15 and a part thereof is directly supplied to the floc generating device 11. It is said that. Further, the latter-stage flocculant adding device 14 b is configured to supply an anionic high-molecular flocculant directly to the floc generating device 11.

  The floc storage tank 12 is installed in the lower stage of the flock generation device 11, receives the flock generated and dropped by the flock generation device 11 as it is, stores the flock, and the supernatant liquid is sent to the separation water tank 7 as separated water. It has become. In addition, the capacity | capacitance of the flock storage tank 12 shall be a thing which can store the flock for 1 batch of the filter press apparatus 6 at least.

  The flock pressure feed pump 13 is a pump that pulls out the flock from the bottom of the flock storage tank 12 and pumps it to the filter press device 6, and can be driven into the filter press device 6 without breaking the flock. The form of the floc pump 13 is not particularly limited as long as the floc can be pumped as statically as possible. Conventionally, the means for feeding sludge, fresh concrete (raw concrete), pasty food, etc. For example, a tube pump with a structure that pushes out a floc in the tube by crushing a special rubber formed tube with a pressing roller, and a structure that pushes out the floc by rotating the screw rod. A screw pump, a cylinder pump configured to push out a flock stored in the cylinder by a piston, and the like can be suitably used.

  The processing steps in the suspension processing system provided with the above-described flock generation device 11 are basically the same as the conventional processing system shown in FIG. A flocculant is added to separate the separated water and solid matter in the coagulation sedimentation tank 1, and the clear separation water is collected by the pump 2 for circulation or drainage (discharge), and settles at the bottom of the coagulation sedimentation tank 1. The slurry is sent to the slurry tank 4 by the slurry pump 3, where a slurry having a constant concentration is prepared and stored.

Conventionally, the slurry prepared in the slurry tank 4 is directly transferred to the filter press device 6 by the slurry pump 5 and dehydrated under pressure as it is, but in the present embodiment, the slurry tank 4 The prepared slurry is pumped to the floc generator 11 by the slurry pump 5, where a flocculant is further added and sufficiently stirred and mixed to further agglomerate the slurry to generate floc.
At this time, as described above, the flocculant is added in two stages by the front and rear two-stage flocculant addition apparatuses 14, and in particular, the anionic polymer flocculant is added by the front-stage addition apparatus 14a, and the latter-stage addition apparatus. Cationic polymer flocculant is added by 14b .

In addition, the addition of the anionic polymer flocculant by the former addition device 14a at that time uses a primary solution having a high concentration of about 0.2 to 1.0% by weight, preferably about 0.5% by weight, It is preferable to supply most of the added amount to the line mixer 15 and sufficiently agitate and mix, and in addition to that, a small amount is also added directly to the floc generating device 11, and the total added amount depends on the properties of the slurry. When the slurry concentration is about 10 to 20% by weight, about 50 to 250 ppm is preferable.
Further, the addition amount of the cationic polymer flocculant by the subsequent addition device 14b may be appropriately set according to the addition amount of the anionic polymer flocculant, and the primary solution of the flocculant in this case is also 0.2. A liquid of about -1.0% by weight, particularly 0.3-0.5% by weight is preferred. The addition amount of the cationic polymer flocculant is 1/20 to 1/10 of the addition amount of the anionic polymer flocculant .

  The concentration of the primary solution of the flocculant of about 0.2 to 1.0% by weight is 0.05 to 0.00 which is a general concentration of the primary solution when added for the purpose of normal coagulation sedimentation. The concentration is considerably higher than about 2% by weight. The reason is that when a primary solution having a low concentration similar to the conventional one is used, it becomes close to the floc generation process for the purpose of coagulation sedimentation separation, and the solid matter in the slurry is added when the coagulant is added to the slurry. This is because the concentration decreases and the water content of the slurry increases, which is counterproductive to the subsequent dehydration process. Therefore, when flocs are generated on a slurry concentrated by coagulation sedimentation separation, the primary solution concentration of the coagulant used in the slurry is set as high as possible within the range of high concentrations as exemplified above, and the water is increased. It is preferable to increase the removal efficiency.

As described above, the floc generated by the flock generator 11 is dropped and stored in the flock storage tank 12, and when at least one batch of floc is stored, the flock is pulled out from the bottom of the flock storage tank 12 by the flock pumping pump 13. Then, it is driven into the filter press device 6 while keeping the flock and subjected to pressure dehydration. Since the dehydrated cake after dehydration has a water content of about 35 to 45% by weight, it is transferred to the next step and disposed of as appropriate.
The separated water separated from the floc in the filter press device 6 is collected in the separated water layer 7 together with the separated water separated as a supernatant in the floc storage tank 12, and disposed of or used as appropriate if possible. If further processing is necessary, the material is returned to the coagulation sedimentation tank 1 and reprocessed.

  As described above, the slurry settled and separated in the coagulation sedimentation tank 1 is further flocked by the flock generation device 11 and then pumped to the filter press device 6 to perform pressure dehydration, thereby obtaining a conventional uniformly stirred and mixed slurry. Compared with the case of dehydrating under pressure, the processing efficiency in the filter press device 6 can be greatly improved. In the past, it took 1.5 to 3 hours for one cycle. In this embodiment, one cycle can be shortened to about 1 hour or less.

  That is, in this embodiment, only the floc obtained by removing the separated water from the bottom of the floc storage tank 12 may be pumped to the filter press device 6 by the flock pumping pump 13, and the floc pumping pump 13 is a large capacity tube pump. Since a screw pump, a cylinder pump, or the like can be employed, the flock driving process from the flock storage tank 12 to the filter press device 6 can be efficiently performed in a short time (for example, only about 10 minutes).

Further, by flocking the slurry and dehydrating under pressure, the amount of flock processing per cycle in the filter press device 6 is equivalent to the conventional one, but the time required for the squeezing process in the filter press device 6 is shortened compared to the conventional one. For example, the pressure dehydration process can be performed in only about 20 minutes.
The main reason is that, in the past, uniform stirring and mixing slurry mainly composed of fine particles is subjected to pressure dehydration as it is, so that clogging with filter cloth is likely to occur, and therefore rapid pressure dehydration is performed in a short time. However, in this embodiment, the flocs are formed as larger particles, so that clogging is not likely to occur during pressure dehydration, and rapid pressure dehydration in a short time is hindered. Because it is done without.

In addition, as described above, when the slurry is flocculated, the anionic and cationic polymer flocculants are added in two stages, and the amount of the cationic polymer flocculant added is added to the anionic polymer flocculant. By setting the amount to 1/20 to 1/10 , not only can the flocs sufficiently strong and hard to break be formed, but the flocs can easily separate moisture, and as a result, when the floc pump 13 is pumped. In addition, it is possible to form a floc having a very preferable structure in which the floc is not easily broken and moisture is easily separated from the floc in the pressure dehydration process.
That is, the floc generated by adding the anionic polymer flocculant by the addition device 14a in the previous stage entangles the polymer and the soil particles to form a strong floc, and therefore the floc is a floc pump 13. It is not easily broken even when the pressure is fed by the pressure, and the pressure can be fed to the filter press device 6 without any trouble in the flock state. However, such a floc is a water-containing floc that is firmly agglomerated by taking moisture into the inside, and is sufficiently strong, so that it is extremely difficult to dehydrate in the pressure dehydration process in the filter press device 6 as it is. It is in a state. Therefore, a small amount of cationic polymer flocculant is further added by the subsequent addition device 14b and the mixture is slowly stirred and mixed, whereby the polymer chains in the floc are partially removed and the moisture taken into the inside thereof. Is easily discharged, and can be easily dewatered by the pressure dehydration step in the filter press device 6.

In the conventional general suspension treatment system, when the solid matter is coagulated and settled as a slurry in the coagulation sedimentation tank 1, the solid particles are flocated as they are. It is weak and will naturally break with the passage of time, and even when it is pumped to the slurry tank 4 by the slurry pump 3, the floc breaks and returns to the slurry dispersed in the fine soil particles. It is not something that can be pumped downstream. In addition, if the slurry is actively flocked in the coagulation sedimentation tank 1, clear separation water which is the original purpose cannot be easily obtained, and such is not realistic.
Therefore, in order to make it possible to improve the efficiency of the dehydration treatment for the slurry generated with the treatment for clarifying the suspension, the slurry is actively flocked at the subsequent stage of the coagulation sedimentation tank 1. And a step of pumping the generated floc as it is indispensable, adding a special flocking processing step by the flock generating device 11 as in this embodiment, and the generated flock as a tube It is indispensable to perform static pressure feeding by a flock pressure feeding pump 13 such as a pump, a screw pump, a cylinder pump, etc., so that the efficiency improvement of the pressure dehydration process can be realized for the first time.
In particular, as described above, two types of polymer flocculants, anionic and cationic, are added in two stages, and the addition amount of the cationic polymer flocculant is set to 1 of the addition amount of the anionic polymer flocculant. By setting the ratio to / 20 to 1/10, it is possible to form a floc having an optimum structure suitable for the processing as described above. Therefore, it is optimal to do so.

FIG. 3 shows that when the slurry is dehydrated as in the conventional case, when various flocculants are added to the slurry to be dehydrated by flocking as in the present invention, the slurry is further flocked and deliberately destroyed. The experimental results showing the relationship between the dehydration time and the amount of dehydration are shown for each of the cases where the dehydration is performed thereafter. In this experiment, 500 ml of the original slurry is used. The slurry was dewatered by a vacuum dewatering Nutsche test.
From this result, when the slurry is dehydrated as in the conventional case, the dehydration amount is only about 100 ml even if the dehydration time is 600 seconds (10 minutes), whereas the anionic or cationic agglomeration When the agent is added alone or both of them are added, a dehydration amount of 300 ml or more is obtained in 100 seconds (less than 2 minutes), and the dehydration efficiency is remarkably improved. It can be seen that the addition of both cationic flocculants is most effective.
In addition, when the flock is intentionally destroyed after the generation of flocs, the efficiency is slightly lower than when the flocs are processed, but it is sufficient as compared with the case where the flocs are processed without using the flocs. Improvement effect is obtained. For this reason, when flock pumping, the flock should be pumped as statically as possible so that the flock is not destroyed, but even if it is broken somewhat by the flock pump, sufficient processing efficiency is obtained compared to the conventional one. I understand that

As described above, according to the slurry dehydration processing apparatus 10 and the suspension processing system including the slurry dehydration processing apparatus according to the present embodiment, by performing pressure dehydration with the filter press apparatus 6 after flocking the slurry, Compared with the conventional case where pressure dehydration is performed in the form of slurry, the dewatering efficiency can be remarkably improved. Therefore, the required number of filter press devices 6 can be reduced to half or less.
Of course, the floc generator 11 is not complicated as long as the flocculant is simply added to the slurry and stirred and mixed, and the floc storage tank 12 and the floc pump 13 are not special. The increase in cost required to install them is insignificant, and since it does not take a long time to generate flocs, it is possible to greatly reduce both the equipment cost and the operating cost, and it is sufficient Can be improved.

  The basic embodiment of the present invention has been described above. However, the present invention is not limited to the above-described embodiment. In short, the slurry to be treated is flocked and the floc remains in the floc filter. What is necessary is just to pressure-dehydrate and press-dehydrate to a press apparatus, and as long as it is concrete, a specific process and apparatus structure can be changed suitably, for example, the following deformation | transformation and application are considered.

  In the basic embodiment shown in FIG. 4, the slurry tank 4 installed in the subsequent stage of the coagulation sedimentation tank 1 is omitted, and the slurry to be treated is transferred from the coagulation sedimentation tank 1 to the slurry pump 5. Is sent directly to the floc generator 11. According to this, it is possible to save space by omitting the large-capacity slurry tank 4 and shorten processing time by omitting the time required for slurry preparation and storage in the slurry tank 4.

  In the basic embodiment shown in FIG. 1, the one shown in FIG. 5 omits the flock storage tank 12 attached to the subsequent stage of the flock generator 11, and the flock generated by the flock generator 11 is used as a flock pump. 13 is configured to be directly pumped to the filter press device 6 almost continuously. According to this, simplification and space saving of the entire apparatus can be achieved, and the time required for flock storage can be omitted, and the processing time can be further shortened.

  6 is based on the one shown in FIG. 4, and a plurality of (two in the illustrated example) filter press devices 6 are juxtaposed in the subsequent stage of the flock storage tank 12. The flock is pumped sequentially or alternately from the storage tank 12. According to this, the flock generation device 11 can be operated almost continuously independently of the batch processing step of each filter press device 6, and the processing efficiency of the entire system can be further improved. Of course, in this case as well, the floc storage tank 12 may be omitted as in the embodiment shown in FIG. 5, and the floc may be directly pumped from the flock generating device 11 to each filter press device 6.

In addition, the present invention is not limited to being applied to the suspension treatment system exemplified in each of the above embodiments, and when pressure dehydration treatment is performed by a filter press device for various slurries in various water treatment processes. Naturally, it can be widely applied in general, and the specific configuration of the processing process and processing equipment has been changed appropriately in consideration of various conditions such as the properties of the slurry to be processed and the required processing performance. Just do it.
For example, the configuration of the floc generating device is not limited to the one in which the flocculant is stirred and mixed while the slurry is transferred by a screw as exemplified in the above embodiment. For example, the muddy water continuous treatment disclosed in Japanese Patent No. 3728647 A configuration in which the slurry is stirred and mixed by a stirrer in a water tank, such as a floc generating tank in equipment, can also be suitably employed. However, it is not preferable to drop the generated floc in the discharge chute as shown in the above publication or to further adjust the particle size of the floc in the subsequent stage. Should be stored in the flock storage 12, or directly from the flock generator 11 to the filter press device 6 as statically as possible by the flock pressure pump 13.
In addition, as described above, the addition of the flocculant for flocking the slurry is performed in two stages, before and after, an anionic polymer flocculant is added in the former stage, and a cationic polymer flocculant is added in the latter stage Although it is optimal to use the anionic or cationic flocculant alone as shown in FIG. 3, it is sufficiently effective. The process is not particularly limited.
Of course, the flocculant is not limited to anionic and cationic polymer flocculants, and natural organic flocculants such as sodium alginate and CMC (carboxymethylcellulose) and, in some cases, inorganic flocculants are used. May be.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a system diagram illustrating a slurry dewatering apparatus and a suspension processing system including the same, which are basic embodiments of the present invention. FIG. It is a figure which shows the improvement effect of the dehydration processing efficiency by flocking. It is a systematic diagram which shows the slurry dehydration processing apparatus which is other embodiment of this invention, and a suspension processing system provided with the same. It is a figure which shows other embodiment same as the above. It is a figure which shows other embodiment same as the above. It is a systematic diagram showing a conventional general suspension processing system.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Coagulation sedimentation tank 2 Pump 3 Slurry pump 4 Slurry tank 5 Slurry pump 6 Filter press apparatus 7 Separation water tank 10 Slurry dehydration apparatus 11 Flock production | generation apparatus 12 Flock storage tank 13 Flock pressure feed pump 14 (14a, 14b) Flocculant addition apparatus 15 Line mixer

Claims (4)

A method for dehydrating a slurry,
A flocculant is added to the slurry to be treated to form a floc, and the floc is pressure-dehydrated by feeding it to a filter press device with a floc pump .
Addition of the flocculant to the slurry to be treated is divided into two stages before and after, an anionic polymer flocculant is added in the former stage, and a cationic polymer flocculant is added in the latter stage ,
A slurry dewatering method, wherein the addition amount of the cationic polymer flocculant is 1/10 to 1/20 of the addition amount of the anionic polymer flocculant . An apparatus for performing a dehydration process on a slurry by the slurry dehydration method according to claim 1 ,
Comprising a floc generator for flocculation by adding an aggregating agent to the slurry to be processed, a filter press apparatus for pressing圧脱water flocks, a flock feed pump that pumps the flocs generated in floc generation device in a filter press apparatus ,
The floc generator is equipped with a front and rear two-stage flocculant addition device, the former flocculant addition device is an anionic polymer flocculant addition device, and the latter flocculant addition device is a cationic polymer flocculant addition device. Device ,
A slurry dewatering apparatus characterized in that the addition amount of the cationic polymer flocculant by the latter addition device is 1/10 to 1/20 of the addition amount of the anionic polymer flocculant by the previous addition device . The slurry dewatering apparatus according to claim 2 ,
A slurry dewatering apparatus, comprising a flock storage tank for storing flocks generated by the flock generation device and separating the flock and separated water at a subsequent stage of the flock generation device. A suspension treatment system comprising the slurry dewatering device according to claim 2 or 3 ,
A flocculant settling tank is added in front of the slurry dewatering equipment to collect clear separated water by adding a flocculant to the suspension and separating water and solids, and slurries and settles solids. And a slurry pump for feeding the slurry settled at the bottom of the coagulation sedimentation tank to the slurry dewatering apparatus.

Images