JP4588442B2 - Mud dehydration method and system - Google Patents

Description

  The present invention relates to a method and system for dewatering a mud that can be stably and efficiently dewatered.

  One of the technologies to effectively use the mixture of water, clay, silt, sand, gravel, etc. (hereinafter referred to as “mud”) generated by dredging sediments in dam lakes and tunnel excavation There is dehydration technology. Among these, mechanical dehydration using a machine such as a screw press is a technique for reducing the volume and increasing the strength of the mud and making it easy to carry and effectively use. As a technique for performing a dehydration treatment of a mud using a screw press, for example, one disclosed in Patent Document 1 is known.

  Patent document 1 is a technology related to recycling sludge generated by dredging. First, mud dredged by a high-concentration dredger is first screened to remove gravel and impurities, and then reacted with a flocculant to floc. After making a dehydrated undiluted solution in which (agglomerated mud) is produced, it is dehydrated by a screw press to separate the drainage to obtain a dehydrated cake. Furthermore, a method is disclosed in which a solidifying agent is added to and mixed with the dewatered cake to form a granular soil.

A screw press is generally composed of a cylindrical or conical outer cylinder (screen) having drainage permeability and a screw shaft in which blades are attached in a spiral shape. The screw shaft is provided at both end faces of the outer cylinder. It is pivotally supported. The volume of the space between the screw shaft and the outer cylinder is such that the shaft diameter of the screw shaft gradually increases from the dehydrating stock solution inlet side toward the dehydrated cake outlet side, or the outer cylinder diameter gradually decreases. By gradually reducing. As a result, the mud is gradually squeezed with strong pressure while being sent to the outlet side by the blades, and finally discharged as a dehydrated cake and discharged from the cake outlet while discharging the drainage through the outer cylinder.
JP 2002-192200 A

  By the way, in the above-mentioned conventional technology, since the properties of the collected mud vary depending on the location, etc., it is possible to stably dewater the dehydrated stock solution generated from the mud with a screw press. There was a problem that it could not be done efficiently.

  Specifically, the content of sand in the dehydrated stock solution, the concentration of mud water (a component obtained by removing sand from the dehydrated stock solution, that is, a mixture of water, clay, and silt), that is, the fine particles contained in the mud water (clay, For example, when the content of sand in the dehydrated stock solution is large (low muddy water content) and the muddy water concentration is high, the rotational speed is too low and clogging occurs in the screw press ( On the other hand, when the content of sand in the dehydrated stock solution is low (high content of muddy water) and the concentration of muddy water is low, the rotational speed is too high and the dewatering is incomplete (incomplete dehydration). Efficiency).

  The present invention has been made in view of the above-described conventional problems, and an object of the present invention is to provide a method and system for dewatering a mud that can stably and efficiently perform dehydration.

  A method for dewatering a mud according to the present invention is a method for dewatering a mud containing sand and muddy water, a separation step for separating the muddy material into sand and muddy water, and the separated separation. A concentration adjusting step for adjusting the muddy water to a predetermined concentration to generate a concentration adjusted muddy water, a mixing step for mixing the separated sand and the concentration adjusted muddy water to generate a mixed dehydrated undiluted solution, and the mixed dehydrated undiluted solution The mixed dehydration stock solution is dehydrated by a screw press while controlling the rotation speed of the screw press based on the sand content detecting step for detecting the sand content ratio and the sand content detected in the sand ratio detecting step. And a dehydration step.

  The generation of the concentration-adjusted mud in the concentration adjustment step is performed based on the specific gravity of the muddy water.

  Moreover, the detection of the sand content ratio in the sand ratio detection step is performed based on the specific gravity of the mixed dehydrated undiluted solution.

  In addition, the detection of the sand content ratio in the sand ratio detection step is performed based on a correlation between the specific gravity of the mixed dehydrated stock solution measured in advance and the sand content ratio in the mixed dehydrated stock solution.

  In addition, the control of the rotation speed of the screw press in the dehydration step is performed based on the correlation between the sand content ratio in the mixed dehydration stock solution measured in advance and the optimum rotation speed of the screw press.

  Further, the present invention has a coagulation and separation step of coagulating and precipitating the waste water discharged in the dehydration step and taking out the coagulated mud water, and mixing the coagulated mud water with the separated mud water.

  Further, the dewatering treatment system for mud according to the present invention is a dewatering system for mud containing sand and muddy water, a separation unit for separating the muddy material into sand and muddy water, and the separation unit A concentration adjusting unit that adjusts the separated muddy water separated in step 1 to generate a concentration-adjusted muddy water, and a mixing unit that mixes the separated sand and the concentration-adjusted muddy water to generate a mixed dehydrated concentrate. A sand ratio detecting unit for detecting a sand content ratio in the mixed dehydrated undiluted solution, a screw press for dehydrating the mixed dehydrated concentrate solution, and a screw press rotation based on the sand content ratio detected in the sand ratio detecting step. And a rotational speed control unit for controlling the speed.

  The concentration adjusting unit includes a storage tank that receives the separated muddy water separated by the separation unit, a dilution water supply unit that supplies dilution water to the storage tank, and a high concentration that supplies high concentration mud water to the storage tank. A muddy water supply means, and a concentration adjustment control unit that controls the dilution water supply means and the high-concentration muddy water supply means so that the muddy water has a predetermined concentration according to the concentration of muddy water in the storage tank. It is characterized by.

  Further, the present invention is characterized in that it has an agglomerated mud water generating unit for agglomerating and precipitating drainage discharged during dehydration of the mixed dehydrated undiluted solution in the screw press and taking out the agglomerated mud water, and the agglomerated mud water is the high-concentration mud water.

  The concentration adjusting unit includes a muddy water returning unit that returns muddy water in the storage tank to the separation unit, and a muddy water amount control unit that controls the muddy water returning unit according to the amount of muddy water in the storage tank. It is characterized by that.

  In the method and system for dewatering a mud according to the present invention, dewatering can be performed stably and efficiently.

  DESCRIPTION OF EMBODIMENTS Hereinafter, a preferred embodiment of a method and system for dewatering a mud according to the present invention will be described in detail with reference to the accompanying drawings. As shown in FIG. 1, the dewatering treatment system 1 for mud according to the present embodiment basically includes a separation unit 2, a concentration adjustment unit 3, a mixing unit 4, a screw press 5, and a sand ratio detection. The unit 100 and the rotation speed control unit 110 are mainly configured. In the present specification and claims, the “mud” is a muddy substance that is generated by sediments on the bottom of a dam lake, excavation of a tunnel, etc. A mixture containing silt, sand, gravel, etc. The “muddy water” refers to a mixture of water, clay and silt obtained by removing sand and gravel from mud. “Fine granule” refers to particles smaller than sand, that is, clay and silt.

  The separation unit 2 is provided with a vibrating screen 21 that separates the muddy material into gravel, sand, and muddy water. In the illustrated example, a muddy substance collected by a dredger or the like is sent from the bottom of the dam lake and is put into the receiving port 22 of the vibrating screen 21 of the separation unit 2. In the vibrating screen 21, gravel and sand are separated from the introduced mud. The remaining mixture in which the gravel and sand are separated from the mud, that is, the separated mud, is introduced into the cyclone classifier 24 from the mud outlet 23 of the vibrating screen 21 by the pump P1 and centrifuged, and then the concentration adjusting unit. 3 storage tanks 31. In the cyclone classifier 24, the particles adhering to the wall surface by centrifugal separation are returned to the vibrating screen 21 again, thereby more reliably removing gravel and sand remaining in the separated mud water from the separated mud water. In the illustrated example, particles having a diameter of 3 mm or more are classified as gravel, particles having a diameter of 74 μm or more and less than 3 mm are classified as sand, and a mixture of fine particles less than 74 μm and water is classified as muddy water.

  The gravel and sand separated in the separation unit 2 are accumulated in the earth and sand pit 6. In the earth and sand pit 6, gravel is accumulated in the gravel yard 61 and sand is accumulated in the sand yard 62. Of these, the sand is carried by the backhoe 7 and the bulldozer 8 at any time, via a belt conveyor or load cell (not shown), and the like. It is sent to the mixing unit 4.

  A storage tank 31 is provided in the concentration adjusting unit 3. The storage tank 31 is supplied with the separated muddy water separated by the separation unit 2 and its concentration is adjusted. Dilution water supply means 32 and high-concentration mud water supply means 33 are connected to the storage tank 31, and when diluting the concentration of muddy water in the storage tank 31, dilution water is supplied from the dilution water supply means 32, In the case of increasing the concentration, the high-concentration mud water is supplied from the high-concentration mud water supply means 33, and finally, the concentration-adjusted mud water having a predetermined concentration is generated. The operation of each unit relating to the muddy water concentration adjustment as described above is controlled by the concentration adjustment control unit 34. In the illustrated example, the density adjustment control unit 34 is configured as a part of the first control unit 39.

  Here, the predetermined concentration is the specification of the screw press 5 used in the dehydration processing system 1 (for example, the volume between the outer cylinder of the screw press 5 and the screw shaft), and the operation of the screw press 5. It is the optimum mud concentration (content of fine particles such as clay and silt in the mud) determined according to the rotation speed of the screw shaft, which is one of the conditions. The data is input to the control unit 34 as data.

  Further, the storage tank 31 is provided with a discharge pipe 35 and a discharge pump P2 for discharging the muddy water in the storage tank 31 (concentration-adjusted muddy water when the concentration is adjusted). The operation of each part relating to the discharge and conveyance of these muddy water or concentration-adjusted muddy water is controlled by a muddy water control unit 38 which will be described later.

  Moreover, the specific gravity measuring device 36 is connected to the storage tank 31, and the concentration adjustment of the muddy water in the storage tank 31 is executed based on the specific gravity of the muddy water. Specifically, the muddy water specific gravity measurement value measured by the specific gravity measuring device 36 is output to the concentration adjustment control unit 34 for executing the muddy water concentration adjustment control, and the concentration adjustment control unit 34 inputs the muddy water previously input. Based on the graph data indicating the relationship between the specific gravity and the muddy water concentration, the current muddy water concentration is determined from the input muddy water specific gravity measurement value. When the current mud concentration is higher than a predetermined concentration, the pump P3 of the dilution water supply means 32 is operated to supply the dilution water to the storage tank 31, or the current mud concentration is predetermined. When the concentration is lower than the concentration, the pump P4 of the high concentration mud supply means 33 is operated to supply the high concentration mud to the storage tank 31, and the mud in the storage tank 31 is adjusted to have a predetermined concentration. Ultimately, it becomes the concentration-adjusted mud.

  Moreover, in order to adjust the amount of muddy water in the storage tank 31, the concentration adjusting unit 3 in the present embodiment is provided with a muddy water returning means 37 and a muddy water amount control unit 38. The muddy water amount control unit 38 is configured as a part of the first control unit 39 in the illustrated example. That is, in the illustrated example, the first control unit 39 includes the above-described concentration adjustment control unit 34 and the muddy water amount control unit 38. The muddy water return means 37 is branched from the discharge pipe 35 of the storage tank 31, and is connected to the receiving port 22 of the vibrating screen 21, and a valve V1 that can be opened and closed provided in the middle of the muddy water return pipe 37a. When the amount of muddy water in the storage tank 31 exceeds a reference value, an appropriate amount is returned via the muddy water return means 37. Is returned to the vibrating screen 21 of the separation unit 2. Specifically, first, the muddy water amount measured value measured by the muddy water amount measuring device 37b is output to the muddy water amount control unit 38, and the muddy water amount control unit 38 determines that the muddy water amount measured value has reached the reference value or more. In this case, the muddy water amount control unit 38 opens the valve V1, closes valves V2 and V3 provided in the middle of concentration adjusting muddy water conveyance pipes 9a and 9b, which will be described later, and then discharges the discharge pump of the storage tank 31. Activate P2. As a result, the muddy water in the storage tank 31 is returned to the receiving port 22 for the vibrating screen 21.

  The muddy water amount control unit 38 automatically returns the muddy water after returning the muddy water for a predetermined period. Alternatively, the return may be terminated when the measured amount of muddy water output from the muddy water measuring device 37b has decreased to a predetermined value.

  Concentration adjusting mud transport pipes 9 a and 9 b for sending the concentration adjusting mud water to the subsequent mixing unit 4 are connected to the discharge pipe 35 of the storage tank 31. The concentration adjusting mud transport pipes 9a and 9b are respectively connected to mixing tanks 41a and 41b of the mixing unit 4 described later, and valves V2 and V3 that can be controlled to open and close are provided in the middle. In the above-described muddy water amount control unit 38, when it is determined that the concentration-adjusted muddy water is generated based on the muddy water specific gravity measurement value output from the specific gravity measuring device 36, the concentration-adjusted muddy water is supplied from the storage tank 31 to the mixing unit 4. In order to convey the air to the water, the valves V2 and V3 are opened, and the discharge pump P2 is operated after the valve V1 of the muddy water return means 37 is closed. As a result, the concentration-adjusted mud generated in the storage tank 31 is conveyed to the mixing unit 4.

  The mixing unit 4 includes a belt conveyor 42 that receives sand conveyed from the sand storage place 62 of the earth and sand pit 6, and two mixing tanks 41a and 41b connected in parallel to the belt conveyor. The belt conveyor 42 capable of reversing forward and reverse throws the received sand into the mixing tank 41a or the mixing tank 41b. Moreover, each mixing tank 41a, 41b is connected to the density | concentration adjustment muddy water conveyance pipe | tube 9a, 9b which receives muddy water from the storage tank 31, and in each mixing tank 41a, 41b from said sand and concentration adjustment muddy water conveyance pipe | tube 9a, 9b. A mixed dehydrated undiluted solution is produced by mixing with the concentration-adjusted mud.

  Moreover, the sand ratio detection part 100 is connected to each mixing tank 41a, 41b, and the content rate (= mixing of sand and density | concentration adjustment mud water) contained in the mixing dehydration stock solution in each mixing tank 41a, 41b. Ratio) is detected. Specifically, the specific gravity measurement value of the mixed dehydrated stock solution is measured by the specific gravity measuring devices 44 a and 44 b respectively connected to the mixing tanks 41 a and 41 b, and this specific gravity measurement value is output to the sand ratio detection unit 100. Based on the measured specific gravity value and the data indicating the correlation between the specific gravity of the mixed dehydrated stock solution and the content ratio of the sand in the mixed dehydrated stock solution, the sand ratio detecting unit 100 preliminarily measures the sand in the mixed dehydrated stock solution. Determine the content.

  The correlation between the specific gravity of the mixed dehydrated undiluted solution and the content ratio of sand in the mixed dehydrated undiluted solution is represented by a graph as shown in FIG. 2, for example. That is, since the specific gravity of sand is larger than that of muddy water, the higher the content ratio of sand, the larger the specific gravity of the mixed dehydrated stock solution containing sand (as a result, the graph goes up to the right). As an example showing actual detection, when the specific gravity measurement value of the mixed dehydrated stock solution measured by the specific gravity measuring devices 44a and 44b is a point indicated by a circled number 1 in the figure, the sand ratio detection unit 100 displays this graph. Based on the above, the sand content is determined to be α (%).

  If the muddy water concentration in the mixed dehydrated undiluted solution is different, the shape of the graph in FIG. 2 is different. In this dehydration processing system, the concentration adjusting muddy water adjusted to have a constant concentration is used in the concentration adjusting step described above. Since the mixed dehydrated stock solution is produced, the shape of the graph is always constant.

  In the two parallel mixing tanks 41a and 41b, the generation of the mixed dehydrated stock solution and the detection of the sand ratio in the mixed dehydrated stock solution are alternately performed, and the detected mixed dehydrated stock solution is sequentially transferred to the paddle reactor 10 at the subsequent stage. Sent.

  The mixed dehydrated stock solution charged into the paddle reactor 10 is reacted with one or more suitable flocculants 11 such as anions and cations to generate flocs, and the particles in the mixed dehydrated stock solution are contained in the screw press 5. After adjusting so that it is difficult to be discharged from the outer cylinder, it is put into the screw press 5.

  The screw press 5 includes a cylindrical or conical outer cylinder (screen) having drainage permeability, and a screw shaft on which blades are spirally attached. The screw shaft is freely rotatable on both end faces of the outer cylinder. Is pivotally supported. The volume of the space between the screw shaft and the outer cylinder is such that the shaft diameter of the screw shaft gradually increases from the mixed dehydrating stock solution inlet 51 side toward the dehydrated cake outlet 52 side, or the outer cylinder diameter increases. Reduce gradually by gradually reducing. As a result, the mixed dehydrated undiluted solution is gradually squeezed with a strong pressure while being sent to the outlet 52 side by the blades, and finally discharged as a dehydrated cake and discharged from the cake outlet 52 while discharging the drainage through the outer cylinder. .

  At that time, the rotational speed of the screw shaft of the screw press 5 is controlled by the rotational speed control unit 110 connected to the screw press 5 so as to be always the optimum rotational speed. Specifically, the rotational speed control unit 110 detects the sand content ratio in the mixed dehydrated stock solution detected by the sand ratio detection unit 100, the sand content ratio and screw in the mixed dehydrated stock solution measured in advance. The optimum rotation speed of the screw press 5 is determined based on the data indicating the correlation with the optimum rotation speed of the press.

  The correlation between the content ratio of sand in the mixed dehydrated stock solution and the optimum rotation speed of the screw press is represented by a graph as shown in FIG. 3, for example. In other words, the higher the content ratio of sand in the mixed dehydrated stock solution, the faster the dehydration is completed. Therefore, if the screw press 5 is not rotated at a high speed, the dehydrated and reduced fluidity will clog in the middle. . Accordingly, the higher the sand content ratio, the higher the optimum rotation speed of the screw press 5 (as a result, the graph increases to the right).

  As an example of actually determining the optimum rotation speed, when the value of the sand content ratio in the mixed dehydrated stock solution determined by the sand ratio detection unit 100 is a point indicated by a circled numeral 2 in the figure, the rotation speed In the control part 110, the optimal rotational speed of the screw press 5 is determined as (beta) based on a graph.

  If the muddy water concentration in the mixed dehydrated undiluted solution is different, the shape of the graph in FIG. 3 is different. In this dehydration processing system, the concentration adjusting muddy water adjusted to have a constant concentration is used in the concentration adjusting step described above. Since the mixed dehydrated stock solution is produced, the shape of the graph is always constant.

  In the subsequent stage of the screw press 5, a sludge storage 14 is provided via a thickener 12 a as a condensed mud water generating unit 12 and a belt conveyor 13. The dewatered cake is accumulated in the sludge storage 14.

  In the thickener 12a, the waste water discharged from the outer cylinder of the screw press 5 is received and subjected to agglomeration treatment with one or more kinds of suitable aggregating agents 15 such as polysodium chloride (PAC) and organic polymer type aggregating agent. As a result, fine particles such as clay and silica slightly remaining in the wastewater agglomerate and settle, and the liquid containing the precipitate is taken out from the discharge port 12b below the thickener 12a. In the illustrated example, this liquid (aggregated muddy water) is muddy water having a higher concentration than the concentration adjusted muddy water generated in the concentration adjusting unit 3, and the discharge port 12 b of the thickener is connected to the high concentration muddy water supply means 33. It is connected and this agglomerated mud is used as the high-concentration mud supplied by the high-concentration mud supply means 33 of the concentration adjusting unit 3. That is, when the concentration of the muddy water in the storage tank 31 is increased, the muddy water is mixed with the muddy water. In addition, the supernatant liquid which is the remainder of the aggregation process in the thickener 12a is discharged | emitted suitably, such as returning to a dam lake.

  Next, a method for dewatering such a mud will be described using the dewatering system 1 as an example. The mud collected from the dam lake is put into the receiving port 22 of the vibrating screen 21 of the separation unit 2 and a separation step is performed. That is, it is screened by the vibration sieve 21 and separated from gravel, sand, and other muddy water. Among these, gravel and sand are accumulated in the gravel place 61 and the sand place 62 of the earth and sand pit 6, respectively. The separated muddy water is centrifuged in the cyclone classifier 24, and the separated particles are returned to the vibrating screen 21 again.

  Next, the separated muddy water that has passed through the cyclone classifier 24 is charged into the storage tank 31 of the concentration adjusting unit 3 and adjusted to a predetermined concentration. In the density adjusting unit 3, a density adjusting step is performed. That is, when the concentration of the muddy water in the storage tank 31 is higher than a predetermined concentration, the dilution water is supplied from the dilution water supply means 32, and when the concentration is lower than the predetermined concentration, the thickener 12a. Aggregated mud water, which is high-concentration mud water, is supplied from the high-concentration mud water supply means 33 connected to the discharge port 12b.

  Such muddy water concentration adjustment is performed based on the specific gravity of the muddy water in the storage tank 31. The operations of the dilution water supply means 32 and the high-concentration mud water supply means 33 are controlled by the concentration adjustment control unit 34 included in the first control unit 39. Specifically, the concentration adjustment control unit 34 first determines the current mud concentration based on the measured mud specific gravity output from the specific gravity measuring device 36 connected to the storage tank 31, and then determines the concentration in advance. Compared with the determined concentration, it is judged whether the current mud concentration should be increased or decreased. In the case of increasing the concentration, the pump P4 of the high-concentration mud supply means 33 is operated to supply the aggregated mud water, and in the case of reducing the thickness, the pump P3 of the dilution water supply means 32 is operated to supply the dilution water. And the density | concentration of the present muddy water corresponds with the density | concentration decided beforehand, and those supply will be stopped when density | concentration adjustment muddy water is produced | generated.

  Here, when the amount of muddy water in the storage tank 31 exceeds the reference value and is likely to increase too much, an appropriate amount of muddy water is returned to the separation unit 2 by the muddy water returning means 37. That is, in the muddy water amount control unit 38 included in the first control unit 39, the current muddy water amount is first determined based on the muddy water amount measurement value output from the muddy water amount measuring device 37b connected to the storage tank 31, The amount is then compared with a predetermined reference value to determine whether the current amount of mud should be reduced. If it is determined that the value is to be decreased, the valve V1 provided in the middle of the mud return pipe 37a is opened, and the valves V2 and V3 provided in the middle of the concentration adjusting mud transport pipes 9a and 9b are closed. Then, the discharge pump P2 of the storage tank 31 is operated, and the return is stopped after a predetermined period has elapsed or when the muddy water measurement value has decreased to a predetermined value. As a result, an appropriate amount of muddy water is returned to the receiving port 22 of the vibrating screen 21 through the muddy water return pipe 37a.

  When muddy water having a concentration that matches a predetermined concentration, that is, concentration-adjusted muddy water is generated, it is conveyed to the mixing tanks 41a and 41b of the mixing unit 4 via the concentration-adjusted muddy water conveying pipes 9a and 9b. At that time, the muddy water amount control unit 38 opens the valves V2 and V3 provided in the middle of the concentration adjusting muddy water transport pipes 9a and 9b, and closes the valve V1 provided in the middle of the muddy water return pipe 37a. Then, the discharge pump P2 of the storage tank 31 is operated. As a result, the concentration-adjusted mud generated in the storage tank 31 is sent to the mixing unit 4.

  Next, a mixing step is performed in the mixing unit 4. That is, the concentration-adjusted mud water and the sand separated in the separation unit 2 are introduced into the mixing tanks 41a and 41b of the mixing unit 4 from the belt conveyor 42 and mixed to generate a mixed dehydrated stock solution.

  Next, the sand ratio detection unit 100 executes a sand ratio detection step to detect the content ratio of sand in the mixed dehydrated stock solution. In the sand ratio detection step, first, the specific gravity of the mixed dehydrated stock solution is measured, and based on the measured value of the specific gravity and the correlation between the specific gravity of the mixed dehydrated stock solution and the content of sand in the mixed dehydrated stock solution measured in advance. Determine the sand content.

  Next, the mixed dehydrated stock solution is charged into the paddle reactor 10. In the paddle reactor 10, the mixed dehydrated stock solution is reacted with the flocculant 11 to generate floc.

  Next, the mixed dehydrated stock solution in which flocks are generated is put into the screw press 5 and a dehydration step is performed. At that time, the rotation speed control unit 110 determines the rotation speed of the screw press 5 from the sand content ratio detected in the sand ratio detection step, and performs control so that the rotation speed of the screw press 5 is always optimum. The determination of the rotational speed is performed based on the correlation between the sand content ratio in the mixed dehydrated stock solution and the optimum rotational speed of the screw press measured in advance. As a result, in the screw press 5, the charged mixed dehydrated stock solution is sent to the cake outlet 52 side while being compressed by the rotation of the screw shaft, and the dehydrated cake is discharged from the cake outlet 52.

  In the dehydration step, the drainage discharged from the outer cylinder of the screw press 5 is sent to a thickener 12a as the agglomerated muddy water generating unit 12. In the thickener 12a, a coagulation separation step is performed. That is, in the thickener 12a, the flocculant 15 is added to and mixed with the above-mentioned wastewater to perform the agglomeration treatment. As a result, the fine particles remaining in the wastewater are agglomerated and precipitated, and a liquid (aggregated muddy water) containing this precipitate is taken out from the discharge port 12b of the thickener 12a and connected to the discharge port 12b. 33 is sent to the density adjusting unit 3. In the concentration adjusting unit 3, when increasing the concentration of the separated mud stored in the storage tank 31, this aggregated mud is used as the high concentration mud and mixed with the mud in the storage tank 31.

  In the mud dehydration method and system according to the present embodiment described above, the mud is separated into sand and muddy water in the separation step in the separation unit 2, and the concentration in the concentration adjustment unit 3 is obtained. In the adjustment step, the separation mud separated in the separation step is adjusted to a predetermined concentration to generate a concentration adjustment mud, and in the mixing step in the mixing unit 4, the separated sand and the concentration adjustment mud are mixed and mixed. After the dehydrated stock solution is generated, the sand content detection step in the sand rate detection unit 100 detects the content ratio of the sand in the mixed dehydrated stock solution, and based on the detected sand content rate, the rotation speed control unit 110. Therefore, each time the mixed dehydrated stock solution is fed from the mixing unit 4, the screw of the sand in the mixed dehydrated stock solution is controlled. Contains It can be appropriately controlled to be operated at an optimal rotational speed depending on the case. As a result, the screw press 5 can be stably and efficiently dehydrated without causing clogging or incomplete dehydration.

  In addition, in the concentration adjustment step in the concentration adjustment unit 3, since the generation of the concentration adjustment mud is performed based on the specific gravity of the separated muddy water, the concentration adjustment is performed based on the amount of the muddy water in the storage tank 31. In comparison, since it is not necessary to measure the total amount of the muddy water, the concentration judgment and concentration adjustment of the muddy water can be easily performed.

  Moreover, in the sand ratio detection step in the sand ratio detection unit 100, since the detection of the sand content ratio is performed based on the specific gravity of the mixed dehydrated stock solution, the sand and concentration adjustment to be added to the mixing tanks 41a and 41b Compared to the case of mixing based on the amount of muddy water, it is not necessary to measure the total amount of sand or concentration-adjusted muddy water, and the detection can be easily performed.

  In the sand ratio detection step in the sand ratio detection unit 100, the detection of the sand content ratio is performed based on the correlation between the specific gravity of the mixed dehydrated stock solution and the sand content ratio in the mixed dehydrated stock solution measured in advance. Therefore, the specific gravity measurement value of the mixed dehydrated stock solution measured by the specific gravity measuring devices 44a and 44b can be used to determine the sand content ratio in the mixed dehydrated stock solution by a simple and reliable method.

  In the dehydration step, the rotation speed control unit 110 controls the rotation speed of the screw press 5 based on the correlation between the sand content ratio in the mixed dehydration stock solution and the optimum rotation speed of the screw press 5 measured in advance. Therefore, the optimum rotation speed of the screw press 5 is determined by a simple and reliable method using the value of the sand content ratio in the mixed dehydrated stock solution detected by the sand ratio detection unit 100. be able to.

  Further, in the aggregating and separating step in the agglomerated mud water generating unit 12, the drainage discharged from the screw press 5 is agglomerated and precipitated, the agglomerated muddy water is taken out, and the agglomerated muddy water is mixed with the separated muddy water. In the concentration adjustment step in the adjustment unit 3, since it was decided to use as high concentration muddy water to generate concentration adjusted muddy water, by circulating the drainage from the screw press 5 again in the dehydration processing system 1, Some particles remaining in the waste water can be removed more reliably and efficiently, and the configuration of the dehydration treatment system 1 can be simplified and the cost can be reduced as compared with the case where high-concentration mud is procured from the outside. Can be achieved.

  The concentration adjusting unit 3 also receives a storage tank 31 that receives the separated muddy water separated by the separation unit 2, dilution water supply means 32 that supplies the dilution water to the storage tank 31, and supplies high concentration mud water to the storage tank 31. A configuration having a high-concentration mud supply unit 33 and a concentration adjustment control unit 34 for controlling the dilution water supply unit 32 and the high-concentration mud supply unit 33 so as to have a predetermined concentration according to the concentration of the mud in the storage tank 31. Therefore, the concentration of muddy water in the storage tank 31 can be reliably adjusted with a simple configuration.

  Further, the concentration adjusting unit 3 returns the muddy water returning means 37 for returning the muddy water in the storage tank 31 to the separating unit 2, and the muddy water amount control part 38 for controlling the muddy water returning means 37 according to the amount of muddy water in the storage tank 31. Therefore, the muddy water in the storage tank 31 does not overflow and is appropriately suppressed within a certain amount, and the muddy water in the storage tank 31 is circulated again in the dehydration processing system 1. As a result, it is possible to more reliably and efficiently remove sand and gravel slightly remaining in the returned muddy water.

  In addition, in the above-described embodiment, as an example, the mud from the dam lake was described as an example, but is not limited to this, for example, the mud generated by excavation of the tunnel, Applicable to any mud.

  Moreover, in the said embodiment, although the process of each step was demonstrated as what is performed batchwise, all are good also as processing continuously. In that case, specifically, for example, the detection of the sand content ratio in the mixed dehydrated undiluted solution in each mixing tank 41a, 41b in the sand ratio detection step is executed every moment, and the rotation control unit 110 receives these information. The feedforward control of the rotational speed of the screw press 5 is performed.

It is explanatory drawing which shows suitable one Embodiment of the dehydration processing system for enforcing the dehydration processing method of the sludge concerning this invention. It is a graph which shows an example of correlation with the specific gravity of mixed dehydration stock solution, and the content rate of the sand in mixed dehydration stock solution used in the sand ratio detection step of the dehydration processing method of FIG. It is a graph which shows an example of the correlation with the content rate of the sand in mixed dehydration stock solution and the optimal rotational speed of a screw press used in the spin-drying | dehydration step of the spin-drying | dehydration processing method of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Dehydration processing system 2 Separation part 3 Concentration adjustment part 4 Mixing part 5 Screw press 12 Agglomerated mud water generation part 31 Reservoir 32 Dilution water supply means 33 High concentration mud water supply means 34 Concentration adjustment control part 37 Mud water return means 38 Mud water amount control part 100 sand ratio detection unit 110 rotation speed control unit

Claims (10)

A method of dewatering a mud containing sand and muddy water,
A separation step for separating the mud into sand and muddy water;
A concentration adjusting step for adjusting the separated separated muddy water to a predetermined concentration to generate a concentration adjusted muddy water;
Mixing the separated sand and the concentration-adjusted mud water to produce a mixed dehydrated stock solution; and
A sand ratio detecting step for detecting a content ratio of sand in the mixed dehydrated undiluted solution;
A dehydration step of dehydrating the mixed dehydration stock solution with a screw press while controlling the rotational speed of the screw press based on the sand content ratio detected in the sand ratio detection step. Processing method.   The method for dewatering a mud according to claim 1, wherein the generation of the concentration-adjusted mud in the concentration adjustment step is performed based on the specific gravity of the muddy water.   The method for dewatering a mud according to claim 1 or 2, wherein the detection of the sand content ratio in the sand ratio detection step is performed based on a specific gravity of the mixed dehydrated stock solution.   4. The detection of the sand content ratio in the sand ratio detection step is performed based on a correlation between a pre-measured specific gravity of the mixed dehydrated stock solution and a sand content ratio in the mixed dehydrated stock solution. Of dehydration treatment of sludge.   The control of the rotational speed of the screw press in the dewatering step is performed based on the correlation between the sand content ratio in the mixed dehydrated stock solution measured in advance and the optimum rotational speed of the screw press. 2. A method for dehydrating a mud according to item 2.   6. The method according to claim 1, further comprising a coagulation separation step of coagulating and sedimenting the waste water discharged in the dehydration step and taking out the coagulated mud water, and mixing the coagulated mud water with the separation mud water. A dehydration method for mud. A dewatering system for mud containing sand and muddy water,
A separation unit for separating the mud into sand and muddy water;
A concentration adjusting unit that adjusts the separated mud separated by the separating unit to a predetermined concentration to generate a concentration-adjusted mud,
Mixing the separated sand and the concentration-adjusted mud water, and generating a mixed dehydrated stock solution; and
A sand ratio detector for detecting the content ratio of sand in the mixed dehydrated undiluted solution;
A screw press for dehydrating the mixed dehydrated stock solution;
And a rotation speed control unit for controlling the rotation speed of the screw press based on the sand content ratio detected in the sand ratio detection step.   The concentration adjusting unit includes a storage tank that receives the separated muddy water separated by the separation unit, a dilution water supply unit that supplies dilution water to the storage tank, and a high concentration muddy water supply that supplies high concentration muddy water to the storage tank. And a concentration adjustment control unit for controlling the dilution water supply means and the high-concentration mud water supply means so that the muddy water has a predetermined concentration according to the concentration of the muddy water in the storage tank. The sludge dehydration system according to claim 7.   9. The agglomerated muddy water generating unit for aggregating and precipitating drainage discharged during dehydration of the mixed dehydrated undiluted solution in the screw press to extract agglomerated muddy water, wherein the agglomerated muddy water is the high-concentration muddy water. The dehydration processing system for the described muddy matter.   The concentration adjusting unit includes a muddy water returning unit that returns muddy water in the storage tank to the separation unit, and a muddy water amount control unit that controls the muddy water returning unit according to the amount of muddy water in the storage tank. The dewatering treatment system for mud according to claim 8 or 9, characterized in that

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