Method for controlling constant water content in a continuous solid-liquid separation apparatus

Abstract

To provide a method for the operational control of a solid-liquid separation apparatus, specifically, a method for controlling the moisture content at a constant level in a continuous solid-liquid separation apparatus, characterized by controlling air blow into a filtration chamber, a dewatering aid, and a coagulant injection rate to maintain the moisture content of the dewatered cake within a predetermined range.SOLUTION: The moisture content of dewatered cake discharged from a solid-liquid separation apparatus is measured in real-time, and according to the measured moisture content, a dewatering aid, air blow, and a chemical injection rate are increased in that order, or the chemical injection rate, the air blow, and the dewatering aid are decreased in that order. This makes it possible to maintain stable operation of the continuous solid-liquid separation apparatus while prioritizing the reduction of the usage of coagulants with high fixed costs and high-pressure air with high running costs.SELECTED DRAWING: Figure 4

Description

Technical Field

[0006] ,

[0001] The present invention relates to a method for controlling the operation of a continuous solid-liquid separation device, and particularly to a method for controlling the constant moisture content in a continuous solid-liquid separation device that controls the constant moisture content of the dewatered cake discharged by adjusting air blowing into the filtration chamber, the amount of dewatering aid, and the dosing rate of the flocculant.

Background Art

[0002] Conventionally, as a solid-liquid separation device for continuously concentrating and dewatering organic sludge such as sewage, night soil, or food production and processing wastewater, for example, a screw press or a belt press is generally known. Since the properties of the sludge supplied to the solid-liquid separation device vary depending on season, time, weather, etc., various controls (transport speed, pressing pressure, flocculant supply amount, etc.) of the solid-liquid separation device are required to stably produce dewatered cake.

[0003] In particular, a control method for a screw press that reduces the amount of flocculant used by increasing or decreasing the amount of dewatering aid (biomass) added is described in Patent Document 1.

[0004] Also, in the structure of a screw press, a screw press that sends compressed air from a large number of micropores provided in a hollow screw shaft to the filtration chamber and discharges the moisture of the cake to the outside in a short time is described in Patent Document 2.

Prior Art Documents

Patent Documents

[0005] <000002]2>

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] Organic sludge from sewage, human waste, or food processing wastewater fluctuates constantly depending on the season, weather, and time of day, requiring various controls for the operation of solid-liquid separators and sludge conditioning. Generally, sludge conditioning is performed by adjusting the amount of coagulant added, but to suppress the cost increase caused by using large amounts of expensive coagulants for operational control, there is also a technique that combines this with controlling the supply amount of dewatering aids (biomass), as described in prior art 2. However, there was a concern that supplying large amounts of dewatering aids (biomass) would increase the amount of cake discharged, raising the load on downstream equipment.

[0007] Furthermore, the technique of removing moisture by sending compressed air to the dewatered cake in the filtration chamber is effective for inorganic slurries with low compressibility and coarse particles, but less effective for organic slurries with high compressibility.

[0008] The present invention provides a method for controlling the moisture content of a continuous solid-liquid separation apparatus in response to variations in the properties of incoming sewage sludge, by controlling the rate of air blowing into the filtration chamber, the rate of chemical injection of dewatering aids and coagulants so that the moisture content of the dewatered cake remains within a predetermined range. [Means for solving the problem]

[0009] The present invention relates to a continuous solid-liquid separation apparatus that separates filtrate by supplying tempered sludge, which is obtained by adding a dewatering aid and a coagulant to raw sludge, and adjusts the moisture content by injecting compressed air into the dewatered cake in the solid-liquid separation apparatus, wherein the present invention provides a predetermined range of standard moisture content for the dewatered cake, a standard supply amount of the dewatering aid, a maximum supply amount which is the maximum value of the standard supply amount, a minimum supply amount which is the minimum value of the standard supply amount, a range of supply amounts which are increased or decreased in stages, a standard supply amount of compressed air, a maximum supply amount which is the maximum value of the standard supply amount, and a minimum supply amount which is the minimum value of the standard supply amount. The following parameters are set: the supply amount, a range of supply amounts to be increased or decreased in stages, a standard supply amount of coagulant, a maximum supply amount (the maximum value of the standard supply amount), a minimum supply amount (the minimum value of the standard supply amount), and a range of supply amounts to be increased or decreased in stages. The moisture content of the dewatered cake is measured, and if the measured moisture content is within the range of the standard moisture content, the operation of the solid-liquid separator is continued. If the measured moisture content is higher than the preset standard moisture content, the supply amount of the dewatering aid is increased by the supply amount range, and this operation is repeated until the moisture content of the dewatered cake falls within the range of the standard moisture content. When the supply of auxiliary material reaches its maximum, the supply of compressed air is increased by the supply amount range, and this operation is repeated until the moisture content of the dewatered cake falls within the range of the standard moisture content. When the supply of compressed air reaches its maximum, the supply of coagulant is increased by the supply amount range, and this operation is repeated until the moisture content of the dewatered cake falls within the range of the standard moisture content. If the measured moisture content is lower than the preset standard moisture content, the supply of coagulant is decreased by the supply amount range, and this operation is repeated until the moisture content of the dewatered cake rises within the range of the standard moisture content. The operation is repeated until the coagulant supply reaches the minimum amount, at which point the compressed air supply is reduced by the supply range, and this operation is repeated until the moisture content of the dewatered cake rises within the range of the standard moisture content. When the compressed air supply reaches the minimum amount, the supply of the dewatering aid is reduced by the supply range, and this operation is repeated until the moisture content of the dewatered cake rises within the range of the standard moisture content. This method controls the moisture content of the dewatered cake to be constant, enabling the discharge of a stable dewatered cake that is resistant to fluctuations in sludge properties, and also contributes to cost-effective operation management. [Effects of the Invention]

[0010] This invention controls the moisture content of dewatered cake discharged from a continuous solid-liquid separator to a constant level. When increasing the moisture content, it prioritizes reducing the amount of coagulant (which has high fixed costs) and the amount of high-pressure air (which has high running costs). When decreasing the moisture content, it prioritizes reducing the amount of coagulant (which has high fixed costs), and then prioritizes reducing the amount of high-pressure air (which has high running costs). This prevents abrupt changes in the operation of the solid-liquid separator, allows for dewatering operation in an optimal state for sludge properties in the filtration chamber even for slurries with low compressibility, and contributes to cost-effective operation management. [Brief explanation of the drawing]

[0011] [Figure 1] This is a schematic diagram illustrating the screw press according to this invention. [Figure 2] Similarly, this is a schematic diagram of a belt press. [Figure 3] Similarly, this is an operation control system for a solid-liquid separation device. [Figure 4] Similarly, this is a flowchart of the driving control system. [Modes for carrying out the invention]

[0012] Figure 1 is a schematic diagram of a screw press, in which a screw shaft 4 with spiral screw blades 3 wound around a cylindrical screen 2 is inserted to form a filtration chamber 5. The raw sludge supplied to the starting end of the screen 2 is conveyed by the screw shaft 4, and the liquid passes through the screen 2 and is discharged outside the machine. Dewatered cake with reduced moisture content is discharged from the end of the screen 2. The screw shaft 4 has a hollow interior and has numerous micropores 6 that connect the interior to the filtration chamber 5. During the filtration process, compressed air is supplied to the inside of the screw shaft 4 and released into the filtration chamber 5 through the micropores 6. Moisture is carried along as it passes through the gaps in the dewatered cake in the filtration chamber 5 and discharged to the outside through the screen 2. The micropores 6 on the screw shaft 4 are preferably located in the later stages where the solid content of the dewatered cake increases.

[0013] Figure 2 is a schematic diagram of a belt press, which comprises a pair of upper and lower filter cloths 9,9 and a plurality of rolls 10... that stretch the pair of filter cloths 9,9 in an endless manner. Raw sludge is supplied between the pair of filter cloths 9,9, and while each roll 10 is rotated with the cloths held in place, the liquid is discharged outside the machine by passing through the filter cloths 9. At the discharge section, the pair of filter cloths 9,9 open up and the dewatered cake is discharged. A nozzle 11 for injecting compressed air is provided in front of the discharge section, facing the filter cloth 9. As the compressed air passes through the gap between the dewatered cake sandwiched between the filter cloths 9, 9, it carries moisture with it and discharges it to the outside.

[0014] Screw presses and belt presses can continuously dewater agglomerated slurries. Compared to conventional batch-type dewatering machines such as filter presses, they are smaller, more compact, and require less power from the motor. Furthermore, continuous solid-liquid separation devices can achieve stable filtration by optimally adjusting the conveying speed, enabling continuous dewatering at the optimal moisture content. Furthermore, any continuous solid-liquid separation apparatus that can reduce the moisture content of the dewatered cake by supplying compressed air to the filtration chamber can be used in addition to screw presses and belt presses.

[0015] Figure 3 is a schematic diagram of the constant water content control method in a continuous solid-liquid separation apparatus according to this invention, and its operation control system will be explained below. The raw material supply pipe 31 and the dewatering aid supply pipe 32 are connected to the raw material adjustment tank 33. The raw material adjustment tank 33 is equipped with a stirring device 34 for stirring and mixing the treatment raw material such as sludge supplied from the raw material supply pipe 31 and the dewatering aid supplied from the dewatering aid supply pipe 32.

[0016] The dewatering aid is crushed and stored in the dewatering aid storage tank 35, and is supplied to the raw liquid preparation tank 33 via the dewatering aid supply pipe 32 by the supply device 36 as needed. The dewatering aid may also be supplied to the coagulation mixing tank 39, which will be described later. The supply device 36 may be appropriately selected as a belt type, screw type, etc., depending on the equipment and the dewatering aid.

[0017] In this embodiment, unused biomass is used as a dewatering aid. Unused biomass has low utility value in its original state and is usually disposed of as waste. Specifically, there are plant-based wastes such as lignocellulosic rice husks, thinned wood, etc., and food-based tea seed cakes, plant residues, etc.

[0018] Also, depending on the biomass to be added, pretreatment may be performed to make it have a shape and properties that are easy to adapt to the stock solution before supplying it to the stock solution adjustment tank 33. Especially in the case of biomass with high hardness, after performing an expansion softening treatment, a cotton-like treatment may be further performed. By subdividing the plant fibers of the biomass, the fibers can be more easily adapted to the stock solution, and it is possible to reduce the true moisture content.

[0019] Since the specific gravity of the biomass is lighter than the stock solution, the biomass and the stock solution are stirred and mixed in the stock solution adjustment tank 33. In the stock solution adjustment tank 33, the biomass and the stock solution become a conditioned stock solution that is evenly mixed. The stirring device 34 may be anything as long as it can stir and mix the biomass and the stock solution evenly. In this embodiment, a stirring blade is used.

[0020] The conditioned stock solution mixed with the dewatering aid in the stock solution adjustment tank 33 is pumped to the coagulation mixing tank 39 through the conditioned stock solution supply pipe 38 by the injection pump 37. A measuring instrument 40 (flow meter, concentration meter) is arranged at the rear stage of the injection pump 37. An aggregating agent supply pipe 41 is connected to the conditioned stock solution supply pipe 38, and an aggregating agent (polymer aggregating agent, inorganic aggregating agent) is supplied from the aggregating agent dissolution tank 42 by the aggregating agent supply pump 43. A flow meter 44 for measuring the supply amount of the aggregating agent is arranged at the rear stage of the aggregating agent supply pump 43. Note that the aggregating agent supply pipe 41 may be connected to the coagulation mixing tank 39.

[0021] The coagulation mixing tank 39 is equipped with a stirring device 45 for stirring and mixing the tempering stock solution and the coagulant. The tempering stock solution and the coagulant are stirred and mixed in the coagulation mixing tank 39 to generate strong flocs. The dewatering aid connects the coagulated flocs together to form a coagulation slurry, which is then supplied to the solid-liquid separator 1 via the coagulation slurry supply pipe 46. The coagulation slurry supply pipe 46 is equipped with a pressure gauge 47 for measuring the pressure of the coagulation slurry supplied to the solid-liquid separator 1.

[0022] A compressed air supply pipe 48 is connected to the solid-liquid separation device 1, and compressed air is supplied to the solid-liquid separation device 1 from a compressed air supply source 49 via a control valve 50 and a flow meter 51. The compressed air supplied to the dewatered cake during transport discharges the moisture in the dewatered cake from the filter media to the outside.

[0023] The solid-liquid separator 1 is equipped with a dewatered cake tank 52 at its discharge section to temporarily store the discharged dewatered cake. A moisture content meter 53 is installed in the dewatered cake tank 52 to measure the moisture content of the dewatered cake, which increases or decreases depending on the properties of the raw liquid. The moisture content W measured by the moisture content meter 53 is compared with a preset standard moisture content W0, and the load on the solid-liquid separator 1 is adjusted so that the moisture content reaches the standard moisture content W0. The moisture content is measured using a known method, and may be measured near the discharge section of the solid-liquid separation device 1 or in the conveying device to the next process.

[0024] Specifically, commands are given to the supply device 36, the coagulant supply pump 43, or the control valve 50 to increase or decrease the supply amount of dewatering aid, coagulant, or compressed air, respectively, in order to perform constant moisture content control operation. In practice, the detection signal measured by the moisture content meter 53 is transmitted to the control device 54, which compares and judges the results, and then issues commands to the supply device 36, the coagulant supply pump 43, or the control valve 50.

[0025] In addition, other control methods (such as constant injection pressure control or transport speed control) may be implemented simultaneously to ensure stable operation of the solid-liquid separation device 1.

[0026] The operation control method according to the present invention is based on controlling the water content of the solid-liquid separation device 1 to a constant level in order to operate the solid-liquid separation device 1 stably. Therefore, in order to keep the water content constant, the amount of dewatering aid supplied to the solid-liquid separation device 1, the amount of coagulant supplied, or the amount of compressed air supplied is controlled.

[0027] When the solid-liquid separation device 1 is started, the moisture content of the dewatered cake discharged from the discharge section of the solid-liquid separation device 1 is measured in real time by the moisture content meter 53 and sent to the control device 54.

[0028] Therefore, the control device of the present invention compares the measured value W of the moisture content meter 53 with a preset standard moisture content W0, and if the measured value W is outside the standard moisture content W0, it issues a command to the supply device 36, the coagulant supply pump 43, or the control valve 50 to control the amount of dewatering aid supplied, the amount of coagulant supplied, or the amount of compressed air supplied, thereby adjusting the operating load on the solid-liquid separation device 1. By adjusting the load in this way, the moisture content discharged from the solid-liquid separation device 1 can be easily maintained at the standard moisture content W0. The standard moisture content W0 can be set within a certain range, and when the measured moisture content W is within that range, normal operation continues while maintaining the current state.

[0029] More specifically, if the measured moisture content W is higher than the standard moisture content W0, the control device 54 commands the supply device 36 to increase the amount of solids in the coagulated slurry. By supplying the tempered slurry with the increased amount of solids to the solid-liquid separator 1, the moisture content of the dewatered cake can be reduced.

[0030] Furthermore, if the measured moisture content W does not return to the standard moisture content W0 even when the supply amount of the dewatering aid is increased, the control device 54 issues a command to the control valve 50 to increase the supply amount of compressed air. This increases the amount of compressed air injected into the dewatered cake during transport, thereby lowering the moisture content of the dewatered cake.

[0031] Furthermore, if the measured moisture content W does not return to the standard moisture content W0 even after increasing the compressed air supply, the control device 54 issues a command to the coagulant supply pump 43 to increase the amount of coagulant supplied. By supplying the tempered stock solution, in which the coagulation flocculation strength has been increased, to the solid-liquid separation device 1, the moisture content of the dewatered cake can be reduced.

[0032] On the other hand, if the measured moisture content W is lower than the standard moisture content W0, the control device 54 commands the coagulant supply pump 43 to reduce the amount of coagulant supplied. By supplying the tempered stock solution, in which the strength of the coagulated flocs has been weakened, to the solid-liquid separation device 1, the moisture content of the dewatered cake can be increased.

[0033] Furthermore, if the measured moisture content W does not return to the standard moisture content W0 even after reducing the supply of the coagulant, the control device 54 issues a command to the control valve 50 to reduce the supply of compressed air. This reduces the amount of compressed air injected into the dewatered cake during transport, thereby increasing the moisture content of the dewatered cake.

[0034] Furthermore, if the measured moisture content W does not return to the standard moisture content W0 even when the compressed air supply is reduced, the control device 54 issues a command to the supply device 36 to reduce the amount of solid matter in the agglomerated slurry. By supplying the tempered raw liquid with reduced solid matter content to the solid-liquid separator 1, the moisture content of the dewatered cake can be increased.

[0035] When reducing moisture content, priority should be given to reducing the amount of coagulant used, which has high fixed costs, and the amount of high-pressure air used, which has high running costs. Conversely, when increasing moisture content, priority should be given to reducing the amount of coagulant used, which has high fixed costs, and then to reducing the amount of high-pressure air used, which has high running costs. By controlling it in this way, the moisture content of the dewatered cake can be easily controlled to within the standard value, allowing for continued stable operation of the solid-liquid separation device 1, and contributing to cost-effective operational management.

[0036] Once the supply amount of the supply device 36, the coagulant supply pump 43, or the control valve 50 is changed, the moisture content is measured again after a certain period of time has elapsed, and the above operation is repeated until the measured value W returns to within the standard moisture content W0.

[0037] The supply range for gradually increasing or decreasing the supply of dewatering aid, coagulant, or compressed air is predetermined. Upper and lower limits can be set for each, and an alarm may be issued or the operation may be automatically stopped to allow for investigation when the upper or lower limit is reached. [Examples]

[0038] Figure 4 is a flowchart of the operation control system according to this embodiment. A. Initial settings The standard moisture content W0 of the dehydrated cake (maximum standard moisture content Wmax, minimum standard moisture content Wmin) is set. In this example, the standard moisture content W0 is set as a range between the maximum standard moisture content Wmax and the minimum standard moisture content Wmin. Set the standard supply amount A0, the maximum supply amount Amax, the minimum supply amount Amin, and the supply amount range a for gradually increasing or decreasing the dehydration aid. Set the standard supply amount B0, the maximum supply amount Bmax, the minimum supply amount Bmin, and the supply amount range b to be increased or decreased in stages for compressed air. The standard supply amount C0, maximum supply amount Cmax, minimum supply amount Cmin, and the supply amount range c for gradually increasing or decreasing the amount of the flocculant are set.

[0039] B. Start of operation Each device will be operated at the above reference values ​​W0, A0, B0, and C0.

[0040] C. Moisture content comparison The moisture content of the dewatered cake discharged from the solid-liquid separation device 1 is measured and compared with the standard moisture content W0. If the measured moisture content W is within the standard moisture content W0, the operation of each device will be maintained in its current state. If the measured value W is greater than the standard moisture content W0, the process moves to step D in the flowchart, and control is performed to gradually increase the amount of dewatering aid, coagulant, or compressed air supplied to the solid-liquid separation device 1. If the measured value W is less than the moisture content W0, the process moves to L in the flowchart and controls the supply of coagulant, compressed air, or dewatering aid in stages.

[0041] D. Comparison of maximum supply amounts of dehydration aids In flowchart C above, if the measured moisture content W is greater than the standard moisture content W0, the supply amount A, which takes into account a supply amount range a that increases the amount of dewatering aid in stages, is compared with the maximum supply amount Amax. If the supply amount A of the dewatering aid after the change is less than the maximum supply amount Amax, the process moves to E in the flowchart and controls the supply amount of the dewatering aid to increase in stages. If the supply amount A of the dewatering aid after the change is greater than or equal to the maximum supply amount Amax, the process moves to F in the flowchart and controls the supply amount of compressed air to be increased in stages.

[0042] E. Dehydration aid (increased) In the flowchart D above, if the supply amount A of the dewatering aid after the change is less than the maximum supply amount Amax, the supply device 36 is adjusted to increase the supply amount of the dewatering aid by a preset supply amount width a.

[0043] F. Comparison of maximum compressed air supply rates In the flowchart D above, if the supply amount A of the dewatering aid exceeds the maximum supply amount Amax, the supply amount B, which takes into account a supply amount range b that increases in stages to increase compressed air, is compared with the maximum supply amount Bmax. If the modified compressed air supply amount B is less than the maximum supply amount Bmax, the process moves to step G in the flowchart and controls the compressed air supply amount to increase gradually. If the modified compressed air supply rate B exceeds the maximum supply rate Bmax, the process moves to step H in the flowchart, where the flocculant supply rate is gradually increased.

[0044] G. Compressed air (increased) In the flowchart F above, if the modified compressed air supply amount B is less than the maximum supply amount Bmax, the control valve 50 is adjusted to increase the compressed air supply amount by a preset supply amount range b.

[0045] H. Comparison of maximum supply amounts of flocculants In the flowchart F above, if the compressed air supply amount B is greater than or equal to the maximum supply amount Bmax, the supply amount C, which takes into account the supply amount range c that is gradually increased in order to increase the amount of coagulant, is compared with the maximum supply amount Cmax. If the changed flocculant supply amount C is less than the maximum supply amount Cmax, the process moves to step J in the flowchart and controls the flocculant supply amount to be increased in stages. If the supply amount C of the flocculant after the change exceeds the maximum supply amount Cmax, the process proceeds to K in the flowchart, where an alarm is issued or control is performed to automatically stop the operation of the solid-liquid separator 1.

[0046] J. Flocculant (increased) In the flowchart G above, if the changed flocculant supply amount C is less than the maximum supply amount Cmax, the flocculant supply pump 43 is adjusted to increase the flocculant supply amount by a preset supply amount width a.

[0047] K. Alarm / Operation Stop After a certain period of time has elapsed, the moisture content is measured again, and the above operation is repeated until the measured value W returns to within the standard moisture content W0. If the measured moisture content W does not return to within the standard value W0 even when the coagulant reaches the maximum supply amount, an alarm is issued or the operation of the solid-liquid separator 1 is automatically stopped.

[0048] L. Comparison of minimum supply amounts of flocculants In the flowchart C above, if the measured moisture content W is less than the standard moisture content W0, the supply amount C, which takes into account a supply amount range c that gradually reduces the amount of flocculant supplied, is compared with the minimum supply amount Cmin. If the changed flocculant supply amount C is greater than the minimum supply amount Cmin, the process moves to M in the flowchart and controls the flocculant supply amount to be reduced in stages. If the supply amount C of the flocculant after the change falls below the minimum supply amount Cmin, the process moves to N in the flowchart, and control is performed to gradually reduce the supply amount of compressed air.

[0049] M. Flocculant (reduced) In the flowchart L above, if the changed amount of flocculant supplied C is greater than the maximum supply amount Cmin, the flocculant supply pump 43 is adjusted to reduce the amount of flocculant supplied by a preset supply amount width a.

[0050] N. Comparison of minimum supply rates of compressed air In the flowchart L above, if the supply amount C of the coagulant is less than or equal to the minimum supply amount Cmin, the supply amount B, which takes into account a supply amount range b that gradually reduces the amount of compressed air, is compared with the minimum supply amount Bmin. If the modified compressed air supply rate B is greater than the minimum supply rate Bmin, the process moves to P in the flowchart and controls the compressed air supply rate to decrease gradually. If the compressed air supply amount B after the change falls below the minimum supply amount Bmin, the process moves to Q in the flowchart, and control is performed to gradually reduce the supply amount of the dewatering aid.

[0051] P. Compressed air (reduced) In the flowchart N above, if the modified compressed air supply amount B is greater than the minimum supply amount Bmin, the control valve 50 is adjusted to increase the compressed air supply amount by a preset supply amount range b.

[0052] Q. Comparison of minimum supply amounts of dehydration aids In the flowchart N above, if the compressed air supply amount B is less than or equal to the minimum supply amount Bmin, the supply amount A, which takes into account a supply amount range a that gradually decreases the supply amount of the dewatering aid, is compared with the minimum supply amount Amin. If the supply amount A of the dewatering aid after the change is greater than the minimum supply amount Amin, the process moves to R in the flowchart and controls the supply amount of the dewatering aid to be reduced in stages. If the supply amount A of the dewatering aid after the change falls below the minimum supply amount Amin, the system proceeds to step S in the flowchart and either issues an alarm or automatically stops the operation of the solid-liquid separator 1.

[0053] R. Dehydration aid (reduced) In the flowchart Q above, if the supply amount A of the dewatering aid after the change is greater than the minimum supply amount Amin, the supply device 36 is adjusted to reduce the supply amount of the dewatering aid by a preset supply amount width a.

[0054] S. Alarm / Operation Stop After a certain period of time has elapsed, the moisture content is measured again, and the above operation is repeated until the measured value W returns to within the standard moisture content W0. If the measured moisture content W does not return to within the standard value W0 even after the dewatering aid has reached the minimum supply amount, an alarm is issued or the operation of the solid-liquid separator 1 is automatically stopped.

[0055] If the supply amount of dewatering aid, coagulant, or compressed air is changed, the injection pressure is measured again after a certain period of time, and the above operation is repeated until the measured value W returns to within the standard moisture content W0. [Industrial applicability]

[0056] The present invention provides a method for controlling the constant moisture content in a continuous solid-liquid separator, which involves conditioning the raw sludge either upstream of or within the solid-liquid separator to maintain a constant moisture content and thus maintain stable dewatering performance. Consequently, the load and adjustment of downstream equipment that receives the dewatered cake are simplified, and the method can be applied to various continuous solid-liquid separators that separate sewage sludge, whose properties fluctuate constantly depending on the season and weather. [Explanation of symbols]

[0057] 1 Solid-liquid separator W Moisture content measurement W0 Standard moisture content A0 Standard supply amount of dehydration aid Amax Maximum supply amount Amin minimum supply amount a. A range of supply quantities to be increased or decreased in stages. B0 Standard supply volume of compressed air Bmax Maximum supply amount B-Phase Minimum Supply b. A range of supply quantities to be increased or decreased in stages. Standard supply amount of C0 flocculant Cmax Maximum supply amount Cmin Minimum supply amount c. A range of supply quantities that can be increased or decreased in stages.

Claims

[Claim 1] In a continuous solid-liquid separator that supplies treated sludge (raw sludge to which a dewatering aid and a coagulant have been added) to the raw sludge to separate the filtrate, and adjusts the moisture content by injecting compressed air into the dewatered cake in the solid-liquid separator, The standard moisture content (W0) of the dehydrated cake, which has a predetermined range, The standard supply amount of the dewatering aid (A0), the maximum supply amount (Amax), which is the maximum value of the standard supply amount, the minimum supply amount (Amin), and the range of supply amounts to be increased or decreased in stages (a), The standard supply amount of compressed air (B0), the maximum supply amount (Bmax), which is the maximum value of the standard supply amount, the minimum supply amount (Bmin), and the range of supply amounts to be increased or decreased in stages (b), The standard supply amount of the flocculant (C0), the maximum supply amount (Cmax), which is the maximum value of the standard supply amount, the minimum supply amount (Cmin), and the range of supply amounts to be increased or decreased in stages (c), Set it, The moisture content (W) of the dehydrated cake was measured. When the measured moisture content (W) is within the range of the standard moisture content (W0), the solid-liquid separation device will continue to operate. If the measured moisture content (W) is higher than the preset standard moisture content (W0), the supply amount of the dewatering aid is increased by the supply amount range (a), and this operation is repeated until the moisture content of the dewatered cake falls within the range of the standard moisture content (W0). When the dewatering aid reaches its maximum supply (Amax), the compressed air supply is increased by the supply range (b), and this operation is repeated until the moisture content of the dewatered cake falls within the range of the standard moisture content (W0). When the compressed air supply reaches its maximum amount (Bmax), the supply amount of coagulant is increased by the supply amount range (c), and this operation is repeated until the moisture content of the dewatered cake falls within the range of the standard moisture content (W0). If the measured moisture content (W) is lower than the preset standard moisture content (W0), the amount of flocculant supplied is reduced by the supply range (c), and this operation is repeated until the moisture content of the dewatered cake rises within the range of the standard moisture content (W0). When the flocculant supply reaches the minimum amount (Cmin), the compressed air supply is reduced by the supply range (b), and this operation is repeated until the moisture content of the dewatered cake rises within the range of the standard moisture content (W0). When the compressed air supply reaches the minimum amount (Bmin), the supply amount of the dewatering aid is reduced by the supply amount range (a), and this operation is repeated until the moisture content of the dewatered cake rises to within the range of the standard moisture content (W0). A method for controlling the water content to remain constant in a continuous solid-liquid separation apparatus, characterized by the features described above.

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