JP2018176108A - Method for operating belt type concentrator and belt type concentration apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for operating a belt type concentrator capable of quick and highly reliable response even when the properties of a supplied sludge are changed suddenly or the like.SOLUTION: There is provided a method for operating a belt type concentrator 1 for gravity dewatering while transporting a sludge 8 on an endless belt 5 having water permeability. An injection amount of a coagulant 9 to be injected into the sludge 8 is adjusted on the basis of a flow rate of a filtrate 14 passing through the endless belt 5.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method of operating a belt type concentrator used, for example, in sewage treatment, and a belt type concentrator.

  Conventionally, as a belt type concentrator of this type, for example, as shown in FIG. 6, an endless belt 103 having water permeability is wound between a drive roller 101 and a driven roller 102. A supply chute 104 is provided at the supply side end of the endless belt 103, and an aggregation mixing tank 105 is provided upstream of the supply chute 104. In the aggregation mixing tank 105, stirring and mixing of the supplied sludge 107 into which the polymer coagulant 106 is injected are performed.

  The concentrated sludge 108 discharged from the discharge side end of the endless belt 103 is discharged from the discharge port 109 into the tank 110. In the tank 110, a concentrated sludge concentration meter 111 for measuring the concentration of the concentrated sludge 108 is provided.

  According to this, the supplied sludge 107 into which the polymer flocculant 106 is injected is supplied to the aggregation mixing tank 105 and is stirred and mixed. The supply sludge 107 thus aggregated is supplied from the supply chute 104 to the supply side end portion of the endless belt 103 which rotates and is gravity dewatered while being conveyed to the discharge side. The sludge on the endless belt 103 concentrated by dewatering is discharged as concentrated sludge 108 from the discharge end of the endless belt 103 through the discharge port 109 into the tank 110.

  Thus, the concentration of the concentrated sludge 108 discharged into the tank 110 is measured by the concentrated sludge densitometer 111, and the injection amount of the polymer flocculant 106 is adjusted based on the measured concentration of the concentrated sludge 108.

  A belt type concentrator as described above is described in, for example, Patent Document 1 below.

Patent No. 4267676

  However, in the above-mentioned conventional method, when the concentration of concentrated sludge 108 is measured by the concentrated sludge densitometer 111, the time required from the supply sludge 107 being supplied onto the endless belt 103 to the concentration measurement is long. When the property has suddenly changed, quick response is difficult.

  Also, the reliability of the concentrated sludge densitometer 111 may decrease with respect to a sudden change that deviates from the normal concentration range, and it is reliable when the property of the supplied sludge 107 suddenly changes. There was a risk that it was not possible to respond highly

  An object of the present invention is to provide a belt type concentrator operating method and a belt type concentrator that can respond quickly and reliably even when the property of supplied sludge suddenly changes.

In order to achieve the above object, a first aspect of the present invention is a method of operating a belt type concentrator which carries out gravity dewatering while conveying sludge on a water permeable endless belt,
Based on the flow rate of the filtrate passing through the endless belt, the amount of coagulant injected into the sludge is adjusted.

  According to this, the flow rate of the filtrate passing through the endless belt is measured by the filtrate flow rate measuring means, and the flow rate of the coagulant is adjusted based on the value of the measured flow rate to discharge the endless belt. The concentration of concentrated sludge can be kept within a predetermined range. As described above, since the passage flow rate of the filtrate measured by the filtrate flow rate measuring means is used as an indicator, the supply supplied to the endless belt is made as compared to the conventional case where only the measurement value of the concentrated sludge concentration is used as an indicator. Even when the property of the sludge suddenly changes, it is possible to respond quickly and reliably when adjusting the injection amount of the coagulant.

  In the method of operating the belt type concentrator according to the second aspect of the present invention, when the flow rate of the filtrate is below the first predetermined flow rate, the injection amount of the coagulant is increased and the flow rate of the filtrate is above the second predetermined flow rate When this occurs, the amount of coagulant injected is reduced.

  According to this, when the property of the supplied sludge suddenly changes and the concentration of the supplied sludge rises, the amount of the coagulant injected is relatively short, so that the aggregation failure occurs and the supplied sludge on the endless belt Water drainage becomes worse, the flow rate of filtrate passing through the endless belt decreases, and the concentration of concentrated sludge discharged from the endless belt decreases.

  On the other hand, when the concentration of supplied sludge falls, the amount of flocculant injected becomes relatively excessive, resulting in excessive aggregation and excessive drainage of the supplied sludge on the endless belt and passing through the endless belt Flow rate of the filtrate increases, and the concentration of concentrated sludge discharged from the endless belt increases.

  In order to suppress such fluctuation of the concentration of concentrated sludge, the amount of coagulant injected is increased when the flow rate of the filtrate measured by the flow meter becomes equal to or less than the first predetermined flow rate. As a result, an appropriate amount of coagulant is injected, aggregation failure is eliminated, drainage of supplied sludge on the endless belt becomes appropriate, and the flow rate of filtrate passing through the endless belt increases, so that the endless belt is endless. Concentration of concentrated sludge discharged from

  Conversely, when the flow rate of the filtrate measured by the flow meter is equal to or higher than the second predetermined flow rate, the amount of coagulant injected is decreased. As a result, an appropriate amount of coagulant is injected, aggregation failure is eliminated, drainage of supplied sludge on the endless belt becomes appropriate, and the flow rate of filtrate passing through the endless belt decreases, so that the endless belt is endless. Concentration of concentrated sludge discharged from

  Thus, using the flow rate of the filtrate measured by the flow meter as an index, the concentration of the concentrated sludge is adjusted by adjusting the injection amount of the coagulant, so that the property of the supplied sludge supplied to the endless belt is sudden Even in the case of changing the amount of coagulant, it is possible to respond quickly and reliably when adjusting the injection amount of the coagulant.

The method for operating a belt type concentrator according to the third aspect of the present invention comprises: a first control system for adjusting the injection amount of a coagulant to be injected into sludge based on the flow rate of filtrate passing through the endless belt;
And a second control system for adjusting the amount of coagulant injected into the sludge based on the concentration of concentrated sludge discharged from the endless belt,
Execute the first control system and the second control system in parallel,
The second increase / decrease value of the injection amount of coagulant based on the concentration of concentrated sludge in the second control system, and the injection amount of coagulant based on the flow rate of the filtrate in the first control system The value is set smaller than the first increase / decrease value per time.

  According to this, by executing the first control system and the second control system in parallel, in addition to adjusting the injection amount of the coagulant using the concentration of concentrated sludge measured by the concentrated sludge densitometer as an index Thus, the amount of coagulant injected can be adjusted using the flow rate of the filtrate measured by the flow meter as an index.

  At this time, the second increase / decrease value per injection amount of coagulant based on the concentration of concentrated sludge, and the 1st increase / decrease value per injection amount of coagulant based on the flow rate of filtrate Because it is set smaller than the above, even if a sudden change occurs in the supplied sludge concentration to such an extent that the reliability of the measurement value of the concentrated sludge densitometer decreases, the filtrate which is a more direct indicator By using the measured value of the passing flow rate, it is possible to prevent the possibility that the concentration concentration of sludge will be greatly reduced when adjusting the injection amount of the coagulant, and quick response with maintaining the concentration concentration of sludge good to a certain extent. Is possible.

  In the method of operating the belt type concentrator according to the fourth aspect of the present invention, when the supply flow rate of the supplied sludge supplied to the endless belt is increased or decreased from the standard sludge supply flow rate, the ratio of the supplied sludge flow rate to the standard sludge supply flow rate The amount of coagulant injected is corrected accordingly.

  According to this, even when the supply flow rate of supply sludge is increased or decreased from the standard sludge supply flow rate, it is supplied to the endless belt as compared to the conventional case where only the measured value of concentrated sludge concentration is used as an index Even if the properties of the supplied sludge suddenly change, it is possible to respond quickly and reliably by correcting the injection amount of the coagulant.

A fifth aspect of the present invention is a belt type concentrator that carries out gravity dewatering while conveying sludge on a water permeable endless belt,
Flocculant injection means for injecting a flocculant into sludge before being supplied onto the endless belt;
Filtrate flow rate measuring means for measuring the flow rate of filtrate passing through the endless belt;
And control means for adjusting the injection amount of the coagulant by the coagulant injection means based on the measurement value from the filtrate flow rate measurement means.

  According to this, the sludge into which the coagulant is injected by the coagulant injection means is supplied onto the endless belt and gravity dewatered while being conveyed by the endless belt. At this time, the flow rate of the filtrate passing through the endless belt is measured by the filtrate flow rate measuring means, and based on the measured value, the injection amount of the coagulant by the flocculant injection means is adjusted. Thus, the concentration of concentrated sludge discharged from the endless belt can be maintained within a predetermined range.

  As described above, since the passage flow rate of the filtrate measured by the filtrate flow rate measuring means is used as an indicator, the supply supplied to the endless belt is made as compared to the conventional case where only the measurement value of the concentrated sludge concentration is used as an indicator. Even when the property of the sludge suddenly changes, it is possible to respond quickly and reliably when adjusting the injection amount of the coagulant.

  As described above, according to the present invention, since the passage flow rate of filtrate measured by the filtrate flow rate measuring means is used as an index, endless belts are used as compared with the conventional case where only the measured value of concentrated sludge concentration is used as an index. Even when the properties of the supplied sludge to be supplied to the water suddenly change, it is possible to respond quickly and reliably when adjusting the injection amount of the coagulant.

It is a figure of the belt type concentrator in embodiment of this invention. It is a graph which shows the relationship between the supply sludge density | concentration of the belt type concentration apparatus in embodiment of this invention, concentration sludge density | concentration, the passage flow rate of filtrate, and the injection amount of a coagulant | flocculant. It is a graph which shows the relationship between the supply sludge density | concentration of the belt type concentration apparatus in embodiment of this invention, concentration sludge density | concentration, the passage flow rate of filtrate, and the injection amount of a coagulant | flocculant. It is a flowchart of the 1st control system of the belt type concentration apparatus in embodiment of this invention. It is a flow chart of the 2nd control system of the belt type concentration device in an embodiment of the invention. It is a figure of the conventional belt type concentrator.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

First Embodiment
In the first embodiment, as shown in FIG. 1, 1 is a belt type concentrator that carries out gravity dewatering while conveying sludge. The belt type concentrator 1 includes a rotatable first roller 2 disposed on the sludge supply side, a rotatable second roller 3 disposed on the sludge discharge side, and a motor 4 for driving the second roller 3 to rotate. , A rotatable endless belt 5 wound between the rollers 2 and 3, a cleaning device 6 for cleaning the endless belt 5, a body cover 7, and supply sludge 8 before being supplied onto the endless belt 5 The coagulant injection means 10 for injecting the coagulant 9 into the mixture, the coagulation mixing tank 11 for stirring and mixing the supplied sludge 8 and the coagulant 9, and the flow rate of the filtrate 14 (separation liquid) passing through the endless belt 5 It has a flow meter 15 (an example of filtrate flow rate measuring means), a concentrated sludge densitometer 18 for measuring the concentration of concentrated sludge 17 discharged from the endless belt 5, a control means 20 and the like.

  The endless belt 5 has water permeability. A sludge supply pipeline 22 for supplying the supply sludge 8 is connected to the aggregation mixing tank 11.

  The coagulant injection means 10 includes a coagulant injection line 23 connected to the sludge supply line 22 and a coagulant injection pump 24 provided in the coagulant injection line 23. As the coagulant 9, a polymer coagulant or the like is used.

  Both the rollers 2 and 3, the endless belt 5 and the cleaning device 6 are accommodated in the main body cover 7. The endless belt 5 further includes a forward path 27 moving along the sludge conveyance path 26 from the sludge supply side to the sludge discharge side, and a return path 28 returning from the sludge discharge side to the sludge supply side.

  Below the forward path portion 27 of the endless belt 5, a first tray 30 for receiving the filtrate 14 which has permeated the endless belt 5 is provided. A first filtrate discharge conduit 37 is connected to the first receptacle 30. Below the return path portion 28 of the endless belt 5, a second tray 32 is provided which receives the filtrate 14 discharged from the first tray 30 through the first filtrate discharge pipe line 37. The second tray 32 has a small tank 33.

  The cleaning device 6 includes a plurality of injection nozzles 34 for injecting the filtrate 14 collected in the tank 33 to the return path 28 of the endless belt 5 and a cleaning pipe for supplying the filtrate 14 in the tank 33 to each injection nozzle 34. It has 35 and the pump 36 for washing | cleaning provided in the piping 35 for washing | cleaning.

  A second filtrate discharge line 38 for discharging the filtrate 14 to the outside of the belt type concentrator 1 is connected to the second receiving tray 32. A flow meter 15 is provided in the second filtrate discharge line 38.

  The main body cover 7 is formed with a discharge port 44 for discharging the concentrated sludge 17 discharged from the endless belt 5 to the external discharge pipeline 43. In the discharge pipeline 43, a removal pipeline 46 which takes out a part of the concentrated sludge 17 discharged and supplies it to the stirring device 45, and a return pipe which returns the concentrated sludge 17 stirred by the stirring device 45 to the discharge pipeline 43 The path 47 is connected.

  The stirring device 45 has a stirring tank 49, a stirring blade 50 rotatable in the stirring tank 49, and a motor 51 for driving the stirring blade 50 to rotate. The concentrated sludge densitometer 18 is, for example, a scattered light densitometer and is provided in the stirring device 45. A densitometer other than the scattered light type may be used.

  The control means 20 controls the number of rotations of the coagulant injection pump 24 based on the flow rate of the filtrate 14 measured by the flow meter 15 and the concentration of the concentrated sludge 17 measured by the concentrated sludge densitometer 18. Thus, the injection amount of the coagulant 9 is adjusted.

  Hereinafter, the operation in the above configuration will be described.

  By steady operation of the belt type concentrator 1, the coagulant 9 supplied from the coagulant injection pipe 23 is injected into the supplied sludge 8 supplied from the sludge supply pipe 22 to the coagulation mixing tank 11, and the supplied sludge is supplied. 8 and the coagulant 9 are mixed in the aggregation mixing tank 11. The feed sludge 8 thus flocculated is supplied from the flocculating tank 11 to the rotating endless belt 5 and is gravity dewatered while being transported to the discharge side.

  The sludge on the endless belt 5 concentrated by dehydration is discharged as concentrated sludge 17 from the discharge end of the endless belt 5 through the discharge port 44 into the discharge pipeline 43. Thus, a part of the concentrated sludge 17 discharged to the discharge pipe line 43 is supplied from the take-out pipe line 46 to the stirring device 45, stirred by the rotating stirring blade 50, and then returned It is returned to the discharge pipeline 43 via the passage 47. At this time, the concentration of the concentrated sludge 17 in the stirring device 45 is measured by the concentrated sludge densitometer 18.

  The filtrate 14 which has passed through the endless belt 5 is first received by the first tray 30 and then discharged from the first tray 30 through the first filtrate discharge line 37 into the tank 33. . When the belt type concentrator 1 is in steady operation, the inside of the tank 33 is filled with the filtrate 14, and the filtrate 14 in the tank 33 is kept in the overflowed state to the second tray 32. .

  Further, by driving the washing pump 36, a part of the filtrate 14 in the tank 33 flows through the washing pipe 35 and is jetted from the jet nozzles 34 to the endless belt 5. As a result, the endless belt 5 is cleaned, and the filtrate 14 jetted from the jet nozzles 34 is received by the second tray 32.

  The filtrate 14 in the second receiving tray 32 is discharged to the outside through the second filtrate discharge line 38, and at this time, the unit time of the filtrate 14 flowing in the second filtrate discharge line 38 The flow rate per unit is measured by the flow meter 15. Thus, the flow rate per unit time of the filtrate 14 which has passed through the endless belt 5 is measured by the flow meter 15.

  When the control unit 20 is operating the belt type concentrator 1, the flow chart of the first control system 57 shown in FIG. 4 and the flow chart of the second control system 58 shown in FIG. Run. Hereinafter, an operation method of the belt-type concentrator 1 by the control means 20 will be described based on the flowcharts of FIGS. 4 and 5 and the graphs shown in FIGS. 2 and 3.

In both graphs of FIG. 2 and FIG. 3, the horizontal axis shows the time T at which the belt type concentrator 1 is operated, and the graph A shows the supplied sludge 8 supplied from the coagulation mixing tank 11 to the endless belt 5 The graph B shows the concentration [% by weight] of the concentrated sludge 17 measured by the concentrated sludge densitometer 18 and the graph C shows the flow rate of the filtrate 14 measured by the flow meter 15 [m ^{3 /} h] indicates, graph D indicates the injection quantity of the coagulant 9 is injected into the feed sludge 8 from the coagulant injection line 23 [m 3 ^{/ h].}

  Further, in the graph B, the range between the first predetermined concentration D1 and the second predetermined concentration D2 is set as the appropriate concentration range P, and in the graph C, the first predetermined flow rate F1 and the second predetermined flow rate Set the range between F2 and the appropriate flow rate range Q.

  (1) At time t1 in the graph of FIG. 2, as shown in graph A, when the property of the supplied sludge 8 suddenly changes and the concentration of the supplied sludge 8 suddenly increases, Since the injection amount is insufficient, aggregation failure occurs and drainage of the supplied sludge 8 on the endless belt 5 worsens, the flow rate of the filtrate 14 passing through the endless belt 5 decreases, and the endless belt 5 is discharged. Concentration of concentrated sludge 17 decreases. As a result, the flow rate of the filtrate 14 measured by the flow meter 15 rapidly decreases as shown by graph C, and the concentration of concentrated sludge 17 measured by the concentrated sludge concentration meter 18 as shown by graph B descend.

At this time, as shown in the flowchart of FIG. 4, the control means 20 controls the flow rate of the filtrate 14 measured by the flow meter 15 in the first control system 57 to the first predetermined flow F1 or lower, which is the lower limit. Then (see S-1), the first increase / decrease value of the injection amount of the coagulant 9 injected from the coagulant injection pipe 23 to the sludge supply pipe 22 is + α [m ³ / h] (S-2 reference). The first increase / decrease value of + α is to increase the injection amount of the coagulant 9 by α [m ³ / h].

Further, as shown in the flowchart of FIG. 5, in the second control system 58, the control unit 20 controls the concentration of the concentrated sludge 17 measured by the concentrated sludge densitometer 18 to a first predetermined concentration D1 or lower, which is the lower limit. (See T-1), the second increase / decrease value of the injection amount of the coagulant 9 injected from the coagulant injection pipe 23 to the sludge supply pipe 22 is + β [m ³ / h] (T − 2). The second increase / decrease value of + β is to increase the injection amount of the aggregating agent 9 by β [m ³ / h].

  Thereby, the control means 20 increases the number of rotations of the coagulant injection pump 24, and the total increase or decrease of the injection amount of the coagulant 9 is the sum of the first increase / decrease value + α and the second increase / decrease value + β. (Ie, α + β). By such control, at time t1 in the graph of FIG. 2, as shown by graph D, the injection amount of coagulant 9 injected from coagulant injection conduit 23 to sludge supply conduit 22 is from the injection amount immediately before. Since the aggregate increase / decrease amount (α + β) is increased and the aggregation failure is eliminated, the drainage of the supplied sludge 8 on the endless belt 5 becomes appropriate, and the flow rate of the filtrate 14 passing through the endless belt 8 increases. As a result, the concentration of concentrated sludge 17 discharged from the endless belt 5 increases.

Then, as shown in the flowchart of FIG. 4, in the first control system 57, the flow rate of the filtrate 14 measured by the flowmeter 15 is appropriate between the first predetermined flow F1 and the second predetermined flow F2. When the flow rate range Q is returned (see S-3), the first increase / decrease value is set to 0 [m ³ / h] (see S-4). The first increase or decrease value of 0 means that the injection amount of the coagulant 9 is not increased or decreased from the injection amount at the present time.

Further, as shown in the flowchart of FIG. 5, in the second control system 58, the concentration of the concentrated sludge 17 measured by the concentrated sludge densitometer 18 is between the first predetermined concentration D1 and the second predetermined concentration D2. When it returns to the appropriate concentration range P of (see T-3), the second increase / decrease value is set to 0 [m ³ / h] (see T-4). The second increase or decrease value of 0 means that the injection amount of the coagulant 9 is not increased or decreased from the injection amount at the present time.

  As a result, since the total increase or decrease amount of the first increase / decrease value and the second increase / decrease value becomes 0, the control means 20 does not raise or lower the number of rotations of the coagulant injection pump 24, and the current rotation Keep in number.

  (2) Also, as shown in graph A, at time t2 in the graph of FIG. 3, when the property of the supplied sludge 8 suddenly changes and the concentration of the supplied sludge 8 suddenly decreases, the coagulant is relatively set. Since the injection amount of 9 becomes excessive, aggregation failure occurs, the drainage of the supplied sludge 8 on the endless belt 5 becomes excessive, and the flow rate of the filtrate 14 passing through the endless belt 5 increases, and the endless belt The concentration of concentrated sludge 17 discharged from 5 is increased. As a result, the flow rate of the filtrate 14 measured by the flow meter 15 rapidly increases as shown by graph C, and the concentration of concentrated sludge 17 measured by the concentrated sludge concentration meter 18 as shown by graph B To rise.

At this time, as shown in the flowchart of FIG. 4, the control means 20 controls the flow rate of the filtrate 14 measured by the flow meter 15 in the first control system 57 to a second predetermined flow rate F2 or more, which is the upper limit value. Then (see S-5), the first increase / decrease value of the injection amount of the coagulant 9 injected from the coagulant injection pipe 23 to the sludge supply pipe 22 is -α [m ³ / h] (S- 6). The first increase / decrease value of -α is to reduce the injection amount of the coagulant 9 by α [m ³ / h].

Further, as shown in the flowchart of FIG. 5, in the second control system 58, the control means 20 controls the concentration of the concentrated sludge 17 measured by the concentrated sludge densitometer 18 to a second predetermined concentration D2 or higher, which is the upper limit value. (See T-5), the second increase / decrease value of the injection amount of coagulant 9 injected from the coagulant injection pipe 23 to the sludge supply pipe 22 is −β [m ³ / h] (T -6). The second increase / decrease value of -β means that the injection amount of the aggregating agent 9 is reduced by β [m ³ / h].

  Thereby, the control means 20 reduces the number of rotations of the coagulant injection pump 24, and the total increase or decrease of the injection amount of the coagulant 9 is the sum of the first increase / decrease value α and the second increase / decrease value β. (Ie, by α + β). By such control, at time t2 in the graph of FIG. 3, as shown by graph D, the injection amount of coagulant 9 injected from coagulant injection conduit 23 to sludge supply conduit 22 is from the injection amount immediately before. The aggregation loss is reduced by the total increase / decrease amount (α + β) and the aggregation failure is eliminated, so the drainage of the supplied sludge 8 on the endless belt 5 becomes appropriate and the flow rate of the filtrate 14 passing through the endless belt 8 decreases. As a result, the concentration of the concentrated sludge 17 discharged from the endless belt 5 decreases.

Then, as shown in the flowchart of FIG. 4, in the first control system 57, when the flow rate of the filtrate 14 measured by the flowmeter 15 returns to the appropriate flow rate range Q (see S-3), The increase / decrease value of is set to 0 [m ³ / h] (see S-4).

Also, as shown in the flowchart of FIG. 5, when the concentration of concentrated sludge 17 measured by the concentrated sludge densitometer 18 returns to within the appropriate concentration range P in the second control system 58 (see T-3), The second increase / decrease value is set to 0 [m ³ / h] (see T-4).

  As a result, since the total increase or decrease amount of the first increase / decrease value and the second increase / decrease value becomes 0, the control means 20 does not raise or lower the number of rotations of the coagulant injection pump 24, and the current rotation Keep in number.

  As shown in the graphs of FIG. 2 and FIG. 3, the concentration discharged from the endless belt 5 by the processes of S-1 to S-6 shown in FIG. 4 and T-1 to T-6 shown in FIG. The concentration of the sludge 17 can be maintained within the appropriate concentration range P.

  As described above, in the first control system 57 shown in the flowchart of FIG. 4, concentrated sludge 17 is controlled by controlling the injection amount of the coagulant 9 using the flow rate of the filtrate 14 measured by the flow meter 15 as an index. In the second control system 58, the property of the supplied sludge 8 supplied to the endless belt 5 is steeper than in the case where only the measured value of the concentrated sludge concentration is used as an index in order to adjust the concentration of Even in the case where the amount of the coagulant 9 changes, it is possible to respond quickly and reliably when adjusting the injection amount of the coagulant 9.

(3) Also, as shown by graph B, at time t3 in the graph of FIG. 2, the concentration of concentrated sludge 17 measured by concentrated sludge densitometer 18 was lowered to the first predetermined concentration D1 or less (T − 1), as shown by the graph C, when the flow rate of the filtrate 14 measured by the flowmeter 15 is within the appropriate flow rate range Q (see S-3), the control means 20 is shown in the flowchart of FIG. As shown, in the first control system 57, the first increase / decrease value is set to 0 [m ³ / h] (see S-4), and as shown in the flow chart of FIG. , The second increase / decrease value is + β [m ³ / h] (see T-2). As a result, the control means 20 increases the rotational speed of the coagulant injection pump 24 to increase the injection amount of the coagulant 9 by adding the first increase / decrease value 0 and the second increase / decrease value + β. (Ie 0 + β = β) increase.

As a result, the injection amount of the flocculant 9 gradually increases by the total increase / decrease amount β, and when the concentration of the concentrated sludge 17 returns to within the appropriate concentration range P (see T-3), the second increase / decrease value And 0 [m ³ / h] (see T-4). As a result, since the total increase or decrease amount of the first increase / decrease value and the second increase / decrease value becomes 0, the control means 20 does not raise or lower the number of rotations of the coagulant injection pump 24, and the current rotation Keep in number.

(4) Also, as shown by graph B, at time t4 in the graph of FIG. 2, the concentration of concentrated sludge 17 measured by the concentrated sludge densitometer 18 has risen to a second predetermined concentration D2 or higher. 5), as shown by the graph C, when the flow rate of the filtrate 14 measured by the flowmeter 15 is within the appropriate flow rate range Q (see S-3), the control means 20 is shown in the flowchart of FIG. As shown, in the first control system 57, the first increase / decrease value is set to 0 [m ³ / h] (see S-4), and as shown in the flow chart of FIG. , The second increase / decrease value is −β [m ³ / h] (see T-6). As a result, the control means 20 lowers the rotational speed of the coagulant injection pump 24, and the total increase or decrease of the injection amount of the coagulant 9 is the sum of the first increase / decrease value 0 and the second increase / decrease value -β. Reduce by an amount (ie β).

As a result, when the concentration of the concentrated sludge 17 returns to within the appropriate concentration range P (see T-3), the second increase / decrease value is set to 0 [m ³ / h] (see T-4). As a result, since the total increase or decrease amount of the first increase / decrease value and the second increase / decrease value becomes 0, the control means 20 does not raise or lower the number of rotations of the coagulant injection pump 24, and the current rotation Keep in number.

(5) Also, at time t5 in the graph of FIG. 3, as shown by graph C, the flow rate of the filtrate 14 measured by the flow meter 15 is reduced to the first predetermined flow rate F1 or less (see S-1 4), when the concentration of the concentrated sludge 17 measured by the concentrated sludge densitometer 18 is within the appropriate concentration range P (see T-3) as shown in the graph B, the control means 20 As shown, in the first control system 57, the first increase / decrease value is + α [m ³ / h] (see S-2), and as shown in the flowchart of FIG. , The second increase / decrease value is 0 [m ³ / h] (see T-4). As a result, the control means 20 increases the rotational speed of the coagulant injection pump 24 to increase the injection amount of the coagulant 9 by adding the first increase / decrease value + α and the second increase / decrease value 0. Increase by (ie α).

Thereby, when the flow rate of the filtrate 14 returns to the appropriate flow rate range Q (see S-3), the first increase / decrease value is set to 0 [m ³ / h] (see S-4). As a result, since the total increase or decrease amount of the first increase / decrease value and the second increase / decrease value becomes 0, the control means 20 does not raise or lower the number of rotations of the coagulant injection pump 24, and the current rotation Keep in number.

(6) Although not shown in the graph, the flow rate of the filtrate 14 measured by the flow meter 15 has risen to the second predetermined flow rate F2 or more (see S-5), but it is measured by the concentrated sludge concentration meter 18 When the concentration of the concentrated sludge 17 is within the appropriate concentration range P (see T-3), the control unit 20 causes the first control system 57 to increase or decrease the first concentration as shown in the flowchart of FIG. While setting the value to -α [m ³ / h] (see S-6), as shown in the flowchart of FIG. 5, in the second control system 58, the second increase / decrease value is 0 [m ³ / h] (See T-4). As a result, the control means 20 lowers the rotational speed of the coagulant injection pump 24, and the total increase or decrease of the injection amount of the coagulant 9 is the sum of the first increase / decrease value -α and the second increase / decrease value 0. Reduce by an amount (ie α).

Thereby, when the flow rate of the filtrate 14 returns to the appropriate flow rate range Q (see S-3), the first increase / decrease value is set to 0 [m ³ / h] (see S-4). As a result, since the total increase or decrease amount of the first increase / decrease value and the second increase / decrease value becomes 0, the control means 20 does not raise or lower the number of rotations of the coagulant injection pump 24, and the current rotation Keep in number.

  As shown in the above (1) to (6), the control means 20 executes the first control system 57 shown in the flowchart of FIG. 4 and the second control system 58 shown in the flowchart of FIG. 5 in parallel. By using the flow rate of the filtrate 14 measured by the flow meter 15 as an indicator, in addition to adjusting the injection amount of the coagulant 9, the concentration of the concentrated sludge 17 measured by the concentrated sludge densitometer 18 as an indicator The injection amount of coagulant 9 can be adjusted.

  Under the present circumstances, as shown to the graph D of FIG. 2 and FIG. 3, the absolute value of 2nd increase / decrease value +/- beta in the 2nd control system 58 is 1st increase / decrease value +/- alpha in the 1st control system 57. It is set smaller than the absolute value. Thereby, with respect to the gradual change of the property of the supplied sludge 8, the concentration of the concentrated sludge 17 in the second control system 58 is used as an index to perform a small adjustment of the injection amount of the coagulant 9. With respect to the rapid and large change of the properties of the above, it is possible to make a large adjustment of the injection amount of the coagulant 9 by using the flow rate of the filtrate 14 in the first control system 57 as an index.

In the above embodiment, the endless belt 5 is cleaned using the filtrate 14 that has permeated the endless belt 5, but even if the cleaning water such as fresh water is introduced from the outside to clean the endless belt 5 Good. In this case, the flow meter 15 measures the combined flow rate of the filtrate 14 and the wash water, so that the flow rate of the wash water may be subtracted from the measured value to obtain the flow rate of the filtrate 14.
Second Embodiment
In the first embodiment described above, as shown in FIG. 1, the supply flow rate of the supplied sludge 8 supplied from the aggregation and mixing tank 11 onto the endless belt 5 is maintained at the reference sludge supply flow rate (constant amount). ing. On the other hand, in the second embodiment, when the supply flow rate of the supply sludge 8 supplied from the aggregation and mixing tank 11 onto the endless belt 5 increases or decreases from the reference sludge supply flow rate, the supply flow rate of the supply sludge 8 The injection amount of the coagulant 9 is corrected according to the ratio to the reference sludge supply flow rate.

For example, assuming that the supply flow rate of supply sludge 8 is X [m ³ / h] and the standard sludge supply flow rate is K [m ³ / h], the supply flow rate X of supply sludge 8 and the standard sludge supply flow rate K The injection amount of the coagulant 9 is corrected by multiplying the injection amount of the coagulant 9 shown in FIG. 2 and the graph D of FIG. 3 by the ratio R (= X / K).

  As a result, even when the supply flow rate X of the supplied sludge 8 is increased or decreased from the standard sludge supply flow rate K, the endless belt 5 can be compared to the conventional case where only the measured value of the concentrated sludge concentration is used as an index. Even if the property of the supplied sludge 8 is suddenly changed, the correction of the injection amount of the coagulant 9 as described above enables a quick and highly reliable response.

In each of the above embodiments, the graph D in FIG. 2 and FIG. 3 shows the injection amount [m ³ / h] of the coagulant 9, but the injection rate [%] of the coagulant 9 may also be shown.

  In each of the above-described embodiments, as shown in FIG. 1, the flow meter 15 is provided in the second filtrate discharge line 38, but may be provided in the first filtrate discharge line 37.

Reference Signs List 1 belt-type concentrator 5 endless belt 8 supplied sludge 9 coagulant 10 coagulant injection means 14 filtrate 15 flow meter (filtrate flow rate measuring means)
17 concentrated sludge 20 control means 57 first control system 58 second control system F1 first predetermined flow F2 second predetermined flow X supply sludge supply flow K reference sludge supply flow α first increase / decrease value β first Second increase / decrease value

Claims (5)

A method of operating a belt type concentrator which carries out gravity dewatering while conveying sludge on an endless belt having water permeability,
An operation method of a belt-type concentrator characterized in that the injection amount of a coagulant injected into sludge is adjusted based on the flow rate of filtrate passing through the endless belt. When the flow rate of the filtrate is below the first predetermined flow rate, the injection amount of the coagulant is increased, and when the flow rate of the filtrate is above the second predetermined flow rate, the injection amount of the coagulant is decreased. A method of operating a belt type concentrator as claimed in claim 1. A first control system for adjusting the amount of coagulant injected into the sludge based on the flow rate of filtrate passing through the endless belt;
And a second control system for adjusting the amount of coagulant injected into the sludge based on the concentration of concentrated sludge discharged from the endless belt,
Execute the first control system and the second control system in parallel,
The second increase / decrease value of the injection amount of coagulant based on the concentration of concentrated sludge in the second control system, and the injection amount of coagulant based on the flow rate of the filtrate in the first control system The method according to claim 1 or 2, wherein the value is set smaller than the first increase / decrease value per time. If the supply flow rate of the supply sludge supplied to the endless belt increases or decreases from the standard sludge supply flow rate, the injection amount of the coagulant is corrected according to the ratio of the supply sludge supply flow rate to the standard sludge supply flow rate. The operating method of the belt type concentrator according to any one of claims 1 to 3 characterized by the above-mentioned. A belt type concentrator for gravity dewatering while conveying sludge on a permeable endless belt, comprising:
Flocculant injection means for injecting a flocculant into sludge before being supplied onto the endless belt;
Filtrate flow rate measuring means for measuring the flow rate of filtrate passing through the endless belt;
What is claimed is: 1. A belt type concentrator comprising: control means for adjusting the amount of coagulant injected by the coagulant injection means on the basis of the measured value from the filtrate flow rate measurement means.

Images