JP5176625B2 - Constant moisture content control method and moisture content constant control device in screw press - Google Patents

Description

  The present invention relates to an improvement of a screw press that concentrates and dehydrates while controlling the supply pressure and flow rate of an agglomerated slurry obtained by adding a flocculant to organic sludge, and in particular, a purified water sludge, a polymer flocculant, and waste paper are added to the organic sludge. The present invention relates to a constant moisture content control method and a moisture content constant control device for a screw press that performs concentration and dewatering.

Conventionally, sludge such as sewage containing difficult-to-filter organic substances is subjected to solid-liquid separation by adding flocculants to form flocs of suspended solids to reduce the moisture content of the dehydrated cake. As a device for concentrating and dewatering this difficult-to-filter sludge, a screw press that concentrates and dewaters while rotating the screw shaft installed in the outer cylinder screen to regenerate the filtration surface that is easily clogged is well known. Yes. In order to improve the dewaterability, a screw press that dehydrates the sludge by coagulating sludge by mixing a slurry liquid of old paper such as newspaper and a polymer flocculant into the concentrated sludge, as described in Patent Document 1. It is known. Also, Patent Document 2 discloses a sludge treatment method in which purified water sludge is mixed into sewage sludge, soluble phosphorus contained in the sewage is fixed to non-soluble phosphorus compounds with slaked lime or PAC in the purified water sludge, and dehydrated. Known as described.
JP 61-293600 (Claims, Fig. 1) Japanese Patent Laid-Open No. 6-269799 (Summary of Objective and Configuration, FIG. 1)

  The conventional screw press is capable of preventing overload and obtaining a cake with a uniform moisture content by controlling the rotation speed of the screw shaft for sludge with low viscosity and good filterability. When the sludge is concentrated and dehydrated by reducing the volume of the filtration chamber, the filtration surface of the outer cylinder screen is clogged at an early stage. Moreover, if it squeezes rapidly, sludge will be discharged | emitted from an outer cylinder screen with a filtrate, and there exists a possibility of suspending a filtrate. If used paper is used as a filter aid as a means for improving filterability, the amount of the polymer flocculant used can be reduced and the water content can be reduced. And the treatment method of the sludge which injects the purified water sludge into the conventional sewage sludge and dehydrates, the slaked lime and PAC in the purified water sludge fix the soluble phosphorus in the sewage to the insoluble phosphorus compound, and the dehydrated cake Therefore, there is an advantage that the running cost and equipment cost of adding metal salts can be reduced, and the efficiency of the sludge treatment equipment can be improved. This invention uses a combination of conventional techniques while controlling the supply pressure and flow rate of the agglomerated slurry, and depending on the sludge concentration and cake moisture variation of the inflowing sewage sludge, purified water sludge, polymer flocculant, The present invention provides a constant moisture content control method and a constant moisture content control device in a screw press that concentrates and dehydrates the produced agglomerated slurry by devising a means for adding waste paper and realizes a uniform dehydrated cake having a low moisture content.

The constant moisture content control method in the screw press according to the present invention includes a pressure controller of a raw liquid supply pump that supplies the aggregated slurry to the screw press, and a constant flow rate control that controls the flow rate of the aggregated slurry by adjusting the rotational speed of the screw shaft. In a screw press with a vessel,
{A} Inject the purified water sludge with the initial water purification sludge injection rate into the sewage sludge with the initial flow rate supplied to the screw press, and add the waste paper with the initial waste paper addition rate and the polymer flocculant with the initial chemical injection rate into the sewage water purification sludge. I started to drive with drugs,
{B} After the start of operation, continuously measure the sludge concentration and sludge flow rate of sewage sludge, and after injecting purified water sludge with a reference clean water sludge injection rate according to the sewage sludge concentration and sewage sludge flow rate ,
{C} Continue operation while adding wastepaper with a standard wastepaper addition rate and a polymer flocculant with a standard chemical injection rate to the sewage sludge mixed sludge, which is compatible with the sewage sludge concentration and sewage sludge flow rate ,
{D} After a predetermined time, the cake moisture concentrated and dehydrated with a screw press is measured. If the cake moisture is higher than the target cake moisture, the pouring rate is increased. Even if the pouring rate is changed, the cake moisture is more than the target cake moisture. If it is high, increase the waste paper addition rate,
{E} Conversely, if the cake moisture to be measured is lower than the target cake moisture, the chemical injection rate is decreased. If the cake moisture is lower than the target cake moisture even if the chemical injection rate is changed, the waste paper addition rate is decreased.
{F} When the used paper addition rate reaches the used paper addition upper limit value or the used paper addition lower limit value, it is a moisture content constant control method that issues a warning while continuing operation,
The amount of sewage sludge is treated by injecting purified water sludge in response to fluctuations in the sludge concentration of the sewage sludge and adjusting the chemical injection rate of the flocculant and the addition rate of waste paper to ensure a stable dehydrated cake with a low moisture content. It is possible to suppress the change of water content and to control the water content constant.

The apparatus for carrying out the constant moisture content control method includes a pressure controller of a stock solution supply pump for supplying the agglomerated slurry to the screw press, and a constant flow rate controller for controlling the flow rate of the agglomerated slurry by adjusting the rotational speed of the screw shaft. In a screw press provided with
{A} A sewage water purification tank for injecting purified water sludge into the sewage sludge to be supplied to the screw press, a sludge adjustment tank for adding waste paper to the sewage water purification sludge, and a coagulation admixture tank for pouring a polymer flocculant into the adjusted sludge Install
{B} A purified water sludge injection controller that increases or decreases the purified water sludge injection amount in response to fluctuations in sludge concentration and sludge flow rate of sewage sludge,
{C} Calculate the waste paper standard waste paper addition rate and the polymer flocculant reference chemical injection rate corresponding to the changes in the measured sludge concentration and sludge flow rate of the sewage sludge. If the cake moisture is higher than the target cake moisture, the chemical injection rate If the cake moisture is higher than the target cake moisture even if the dose rate is changed, the waste paper addition rate is increased. Conversely, if the cake moisture is lower than the target cake moisture, the dose rate is decreased and the Even if the pouring rate is changed, if the cake moisture is lower than the target cake moisture, it is equipped with a waste paper / chemical injection controller that reduces the rate of waste paper addition . Addition improves the dehydrating property, reduces the amount of expensive polymer flocculant used, and reduces the running cost.

Specific means of the moisture content constant control device are:
{A} The initial flow rate and target cake moisture of the sewage sludge supplied to the screw press are set, the initial flow rate is previously input to the pressure controller and the constant flow rate controller, and the target cake moisture is input to the moisture content controller. And
{B} Decide the standard clean water sludge injection rate of the purified water sludge that matches the sludge concentration and sludge flow rate of the changing sewage sludge, and input it to the purified water sludge injection controller in advance,
{C} Initial waste paper addition rate, standard waste paper addition rate, waste paper addition rate, waste paper addition upper limit value and waste paper addition lower limit value of waste paper to be added to sewage water purification mixed sludge, and polymer flocculant added to adjusted sludge to which waste paper is added Decide the initial chemical injection rate, standard chemical injection rate, chemical injection rate, chemical injection upper limit value and chemical injection lower limit value to be injected, and input them to the waste paper / chemical injection controller in advance.
{D} Inject the purified water sludge with the initial purified water sludge injection rate into the initial flow rate of the sewage sludge supplied to the screw press, continuously measure the sludge concentration and sludge flow rate of the sewage sludge and send it to the purified water sludge injection controller, Calculate the reference clean water sludge injection rate with the purified water sludge injection controller according to the concentration fluctuation of the incoming sewage sludge, control the rotation speed of the purified water sludge supply pump and inject the purified water sludge,
{E} Add the waste paper of the standard waste paper addition rate that matches the inflowing sewage sludge and the polymer flocculant of the standard chemical injection rate to the sewage water purification sludge ,
{F} The condensed slurry is concentrated and dehydrated with a screw press, and after a predetermined time, the moisture content of the cake is measured with a moisture content meter, and the difference between the cake moisture and the target cake moisture is calculated with a moisture content controller.
{G} Send the calculated data to the used paper / chemical injection controller, and control the rotation speed of the flocculant supply pump with the used paper / chemical injection controller.
{H} If the cake moisture is higher than the target cake moisture, the chemical injection rate is increased. If the cake moisture is higher than the target cake moisture even if the chemical injection rate is changed, the used paper / chemical injection controller rotates the used paper supply pump. Control the number to increase the waste paper addition rate,
{I} Conversely, if the cake moisture is lower than the target cake moisture, the chemical injection rate is decreased. If the cake moisture is lower than the target cake moisture even if the chemical injection rate is changed, the waste paper addition rate is decreased,
{J} When the waste paper addition rate reaches the waste paper addition upper limit value or the waste paper addition lower limit value, the waste paper / chemical injection controller issues an alarm while continuing operation.
Even if the sludge concentration fluctuates, the operation can be continued with a small fluctuation in the stock solution treatment amount within a certain range, and a cake having a uniform low water content can be obtained.
The purified water sludge injected into the sewage sludge may be carbonized sludge, and the relative concentration can be increased and the relative cake moisture can be decreased by adding an inorganic substance.

The present invention is configured as described above, and the purified water sludge injected into the sewage sludge reduces the relative cake moisture, and the polymer flocculant to be poured and the waste paper fibers to be added cooperate to adsorb the sludge particles. The flocs can be formed to reduce the water content. Corresponding to the concentration fluctuation of the sewage sludge, a dehydrated cake having a target low water content can be obtained by adjusting the purified water sludge, the flocculant, and the waste paper, and the cake moisture can be controlled constantly. Purified water sludge and waste paper are less expensive than polymer flocculants, and the amount of polymer flocculant used can be reduced by adding waste paper, thereby reducing running costs.

The embodiment of the present invention will be described in detail with reference to the drawings. First, FIG. 1 is a flow chart of constant moisture control of a dewatering cake of a screw press that adds dewatered sludge, a polymer flocculant, and waste paper to sewage sludge. The sewage sludge inflow pipe 1 provided with the concentration meter D1 and the flow meter F1 and the purified water sludge supply pipe 2 provided with the purified water sludge supply pump JSP are connected to the sewage purified water mixing tank 3. The purified water sludge is stirred and mixed with the sewage sludge flowing into the sewage purified water mixing tank 3 to fix the soluble phosphorus in the sewage sludge with slaked lime and PAC contained in the purified water sludge, thereby reducing the relative cake moisture. A concentration meter D1 and a flow meter F1 provided in the sewage sludge inflow pipe 1 are connected to the purified water sludge injection controller 4 and continuously measure the sludge concentration D and sludge flow rate Q of the sewage sludge, A detection signal is transmitted to the purified water sludge injection controller 4. In the purified water sludge injection controller 4, an initial flow rate Q0 of the incoming sewage sludge is set in advance, and the initial purified water sludge injection rate S0 of the purified water sludge injected into the sludge having the initial flow rate Q0 and the sludge concentration D of the incoming sewage sludge are set. From the reference clean water sludge injection rate S for fluctuations, a purified water sludge injection rate S1 suitable for sewage sludge is set. First, purified water sludge having an initial purified water sludge injection rate S0 is injected into the sewage sludge having an initial flow rate Q0 supplied to the screw press 21. Measure sewage sludge concentration D and sludge flow rate Q continuously after a predetermined time, confirm the presence or absence of purified water sludge, and if there is purified water sludge, control the rotation speed of purified water sludge supply pump JSP, Inject clean water sludge of standard clean water sludge injection rate S suitable for D and sludge flow rate Q. If there is no purified water sludge, the purified water sludge supply pump JSP is stopped. The purified water sludge injected into the sewage sludge may be carbonized sludge, and the relative sludge concentration and sludge capacity can be increased to reduce the relative cake moisture. Carbonized sludge is a dry particle and can be easily added to the stock solution.

  A sewage water purification pipe 5 connected to the sewage water purification tank 3 and a waste paper supply pipe 8 provided with a waste paper supply pump KP connected to the waste paper dissolution tank 7 are connected to the sludge adjustment tank 6 and dissolved in the sewage water purification sludge. Improve the dewaterability of sewage sludge by pouring used waste paper. An adjusted sludge supply pipe 9 for supplying adjusted sludge from the sludge adjustment tank 6 is connected to the coagulation / mixing tank 10, and a raw liquid supply pump SP and a flow meter F 3 are disposed in the adjusted sludge supply pipe 9. The adjusted sludge is press-fitted into the flocculation mixing tank 10 with the stock solution supply pump SP provided in the adjusted sludge supply pipe 9, and the flow rate of the adjusted sludge is measured with the flow meter F3. The flocculant supply pipe 12 connected to the polymer dissolution tank 11 is connected to the adjusted sludge supply pipe 9 behind the flow meter F3, and the polymer flocs to the adjusted sludge prepared by mixing purified water sludge and waste paper into the sewage sludge. The agent is poured into the agglomeration mixing tank 10. The flocculant supply pipe 12 is provided with a flocculant supply pump PP and a flow meter F2, and the amount of the polymer flocculant injected by the flocculant supply pump PP is measured by the flow meter F2. An agglomerated slurry supply pipe 20 connected to the agglomeration mixing tank 10 is connected to a screw press 21, and the agglomerated slurry stirred and mixed in the agglomeration mixing tank 10 is pressed into the screw press 21 by a tank. A pressure gauge PS is provided in the agglomerated slurry supply pipe 20, and the supply pressure of the agglomerated slurry that is press-fitted into the screw press 21 is measured.

  The pressure gauge PS of the aggregate slurry supply pipe 20 is connected to the pressure controller 13, and the supply pressure of the aggregate slurry is measured and transmitted to the pressure controller 13. The pressure controller 13 is connected to the stock solution supply pump SP disposed in the adjusted sludge supply pipe 9, and the pressure controller 13 keeps the supply pressure constant against the pressure fluctuation of the supply pressure of the aggregated slurry in advance. Thus, the rotation speed of the stock solution supply pump SP is set. The supply pressure of the agglomerated slurry is detected by the pressure gauge PS of the agglomerated slurry supply pipe 20 and transmitted to the pressure controller 13. The pressure controller 13 calculates the number of rotations according to the pressure fluctuation, and sends the command signal to the stock solution supply pump. It transmits to SP, adjusts the supply amount of the adjustment sludge to the coagulation mixing tank 10 by increasing / decreasing the rotation speed of the stock solution supply pump SP, and controls the supply pressure of the coagulation slurry press-fitted into the screw press 21.

  A flow meter F3 behind the raw liquid supply pump SP arranged in the adjusted sludge supply pipe 9 is connected to the constant flow rate controller 14, and detects the adjusted sludge flow rate Q1 pumped by the raw liquid supply pump SP, thereby controlling the constant flow rate. To the device 14. In the constant flow rate controller 14, the rotational speed of the drive unit 15 of the screw shaft 21a is set in advance with respect to the fluctuation of the adjusted sludge flow rate Q1, and the adjusted sludge flow rate Q1 supplied from the adjusted sludge supply pipe 9 is kept constant. Thus, the rotation speed of the screw shaft 21a is controlled. A rotation indicator 16 connected to the constant flow rate controller 14 is disposed in the drive unit 15 of the screw shaft 21a provided in the screw press 21, and the detection signal of the adjusted sludge flow rate Q1 detected by the flow meter F3 is constant flow rate. The controller 14 calculates and sends a command signal to the rotation indicator 16. The rotation indicator 16 controls the rotational speed of the drive unit 15 of the screw press 21 to adjust the supplied adjusted sludge flow rate Q1 to a constant flow rate.

  A moisture content measuring device 17 disposed at the discharge port 21 b of the screw press 21 is connected to the moisture content controller 18, and a detection signal obtained by measuring the cake moisture W by the moisture content measuring device 17 is transmitted to the moisture content controller 18. To do. A target cake moisture W0 is set in the moisture content controller 18 in advance, the difference between the detected cake moisture W and the target cake moisture W0 is calculated, and the used paper / chemical injection controller 19 connected to the moisture content controller 18 is calculated. The difference between the cake moisture W and the target cake moisture W0 is transmitted to. A concentration meter D1 and a flow meter F1 arranged in the sewage sludge inflow pipe 1 are also connected to a used paper / chemical injection controller 19, and the used paper / chemical injection controller 19 is disposed in the used paper supply pipe 8. Connected to KP. The used paper / chemical injection controller 19 includes an initial used paper addition rate P0, a used waste paper addition rate P and a used paper addition rate P1, and a used paper addition upper limit value Pu for adding waste paper to the sewage purified water mixed sludge obtained by injecting purified water sludge into sewage sludge. The used paper addition lower limit Pd is determined and inputted. In the present invention, an initial flow rate Q0 of the sewage sludge is set, and the reference waste paper added to the sewage clean water mixed sludge according to the fluctuation of the initial waste paper addition rate P0, the sludge concentration D of the sewage sludge, and the sludge flow rate Q with respect to the initial flow rate Q0. An addition rate P is set, and a used paper addition rate P1, a used paper addition upper limit Pu, and a used paper addition lower limit Pd that are increased or decreased based on the cake water W concentrated and dehydrated by the screw press 21 are set.

  The flocculant supply pump PP and the flow meter F2 disposed in the flocculant supply pipe 12 are also connected to the waste paper / chemical injection controller 19, and the polymer flocculant is added to the adjusted sludge obtained by adding waste paper to the sewage water purification sludge mixed sludge. The initial chemical injection rate A0, the standard chemical injection rate A, the chemical injection rate A1, the chemical injection upper limit value Au, and the chemical injection lower limit value Ad are set and input to the used paper / chemical injection controller 19. In the present invention, purified water sludge having an initial purified water sludge injection rate S0 is injected into the sewage sludge with an initial flow rate Q0, and a polymer flocculant with an initial chemical injection rate A0 is injected into the adjusted sludge to which waste paper having the initial waste paper addition rate P0 is added. I have to do it. Based on fluctuations in the sludge concentration D and sludge flow rate Q of the sewage sludge, the reference chemical injection rate A of the polymer flocculant to be poured into the adjusted sludge with added waste paper is set, and the cake moisture W concentrated and dehydrated with the screw press 21 is set. The chemical injection rate A1 to be increased or decreased based on the above, the chemical injection upper limit value Au of the polymer flocculant to be injected, and the chemical injection lower limit value Ad are set and input in advance to the used paper / chemical injection controller 19.

FIG. 2 is a block diagram of the moisture content constant control method in the screw press, and the moisture content constant control method will be described based on the control block.
{A} “Initial setting values: initial purified water sludge injection rate S0, initial flow rate Q0 of sewage sludge, initial chemical injection rate A0, chemical injection upper limit value Au, chemical injection lower limit value Ad, initial used paper addition rate P0, used paper addition upper limit value Pu, target cake moisture W0 "
As preparation for the start of operation, an initial flow rate Q0 of sewage sludge supplied to the screw press 21 and a target cake moisture W0 are set, and the initial flow rate Q0 of sewage sludge is input to the pressure controller 13 and the constant flow rate controller 14 in advance. The target cake moisture W0 is input to the moisture content controller 18. The initial purified water sludge injection rate S0 of the purified water sludge to be injected into the sludge having the initial flow rate Q0 of the sewage sludge is determined and input to the purified water sludge injection controller 4 in advance. The initial waste paper addition rate P0 and the used paper addition upper limit Pu of the waste paper to be added to the sewage-purified mixed sludge at the start of operation are determined. In addition, the initial chemical injection rate A0, the chemical injection upper limit value Au, and the chemical injection lower limit value Ad for injecting the polymer flocculant into the adjusted sludge to which the waste paper has been added are determined, and the addition rate data of the waste paper and the polymer flocculant is previously determined. Input to the used paper / chemical injection controller 19.

{B} "Driving"
The screw press 21 is driven to start the operation. Check the presence or absence of purified water sludge, inject the purified water sludge with the initial purified water sludge injection rate S0 into the incoming sewage sludge with the initial flow rate Q0, add the waste paper with the initial waste paper addition rate P0 to the sewage purified water mixed sludge, and then the initial chemical injection A polymer flocculant having a rate A0 is poured into the screw press 21.
{C} "Drug concentration detection"
After elapse of a predetermined time from the start, the sludge concentration D and sludge flow rate Q of the inflowing sewage sludge are continuously detected, and a fluctuating sewage sludge detection signal is transmitted to the purified water sludge injection controller 4.
{D} “Calculation: Standard clean water sludge injection rate S”
Based on the sludge concentration D and sludge flow rate Q of the sewage sludge, the purified water sludge injection controller 4 calculates the purified water sludge injection rate S1 that matches the sewage sludge concentration from the reference purified water sludge injection rate S.
{E} "Determine the water purification sludge injection rate S1"
The rotational speed of the purified water sludge supply pump JSP is controlled by the purified water sludge injection controller 4 to determine the purified water sludge injection rate S1 suitable for the sewage sludge having a varying sludge concentration D.

{F} “Determination of reference value: reference waste paper addition rate P, reference drug injection rate A”
In accordance with fluctuations in the sludge concentration D and sludge flow rate Q of the inflowing sewage sludge, the waste paper / chemical injection controller 19 determines the waste paper standard waste paper addition rate P added to the sewage water purification sludge and the polymer flocculant reference chemical injection rate. Set A. Waste paper with a reference waste paper addition rate P determined according to changes in the sewage sludge and a polymer flocculant with a reference chemical injection rate A are supplied to the sewage clean water mixed sludge.
{G} “Measurement wait timer”
After changing the waste paper addition rate and chemical injection rate, wait for the cake moisture comparison measurement until the operating condition is stable.
{H} “Detection of cake moisture W”
After a predetermined time, the cake moisture W concentrated and dehydrated by the screw press 21 is measured by the moisture content measuring device 17, the difference between the cake moisture W and the target cake moisture W0 is calculated by the moisture content controller 18, and the used paper / chemical injection controller 19 to send.

{I} “Comparison of current cake moisture W and target cake moisture W0”
The waste paper / chemical injection controller 19 that has received the detection signal of the difference in the cake moisture W with respect to the target cake moisture W0 determines the sludge concentration D of the sewage sludge and the sludge from the relationship between the measurement result of the moisture content measuring device 17 and the target cake moisture W0. The increase / decrease of the chemical injection rate A1 suitable for the flow rate Q is calculated. When the target cake moisture W0 is higher than the current cake moisture W and the difference exceeds the allowable value δ (W0−W> δ), the chemical injection rate A1 is decreased. Further, when the current cake moisture W is higher than the target cake moisture W0 and the difference exceeds the allowable value δ (W−W0> δ), the polymer flocculant injection rate A1 is increased. If the difference between the current cake moisture W and the target cake moisture W0 is within the allowable value δ (−δ ≦ W−W0 ≦ δ), the current situation is maintained and the process waits for another cake moisture measurement.
{J} “Medication rate lower limit Ad or higher”
When the target cake moisture W0 is higher than the current cake moisture W and the difference exceeds the allowable value δ (W0−W> δ), the process shifts to a decrease in the chemical injection rate A1 of the polymer flocculant. The used paper / chemical injection controller 19 confirms whether or not the chemical injection rate A1 of the polymer flocculant is equal to or higher than the chemical injection lower limit value Ad, and if the chemical injection rate A1 is equal to or higher than the chemical injection lower limit value Ad, the high The molecular aggregating agent shifts to a decrease in the injection rate A1. Moreover, if the chemical injection rate A1 of the coagulant is equal to or less than the chemical injection lower limit Ad, the process proceeds to a decrease in the waste paper addition rate P1. If the sludge concentration D fluctuates more than the set value, the set value is canceled even during operation in a closed circuit, and the control block {c} returns to “raw solution concentration detection”, and the sludge flow rate Q of the sewage sludge. And a sludge concentration D is detected, and a feedback circuit for calculating a reference clean water sludge injection rate S suitable for the inflowing sewage sludge is taken.
{K} “Reference drug injection rate A decrease”
The waste paper / chemical injection controller 19 controls the rotational speed of the flocculant supply pump PP to reduce the chemical injection rate A1 if the reference drug injection rate A of the polymer flocculant is equal to or higher than the chemical injection lower limit Ad. . When the proportional injection of the polymer flocculant reaches the drug injection lower limit Ad, the control circuit {g} returns to the “measurement waiting timer” feedback circuit.

{L} “More than the lower limit Pd of waste paper”
In decision control block {j} "chemical feeding, chemical dosing rate limit value Ad above", reference chemical feed rate A of the coagulant is at most chemical feeding, chemical dosing rate limit value Ad, paper-dosing controller 19, the reference paper added It is confirmed whether or not the rate P is equal to or greater than the used paper addition lower limit Pd.
{M} “Recycled paper addition rate P1 reduction”
If the used paper addition rate P1 is equal to or greater than the used paper addition lower limit Pd, the used paper addition rate P1 is decreased stepwise. After a certain period of time has elapsed, the control block {g} returns to the cake moisture detection feedback circuit of the “measurement wait timer”.
{N} "Alarm"
In the determination of “used paper addition lower limit Pd or more” in the block {l}, even if the used paper addition rate P1 reaches the used paper addition lower limit Pd, the target cake moisture W0 is higher than the current cake moisture W, and the difference is an allowable value δ. When exceeding (W0−W> δ), an alarm is issued while continuing operation.

{O} "following Kusurichuritsu upper limit Au"
When the current cake moisture W is higher than the target cake moisture W0 and the difference exceeds the allowable value δ (W−W0> δ), the process shifts to an increase in the chemical injection rate A1 of the polymer flocculant. The used paper / chemical injection controller 19 confirms whether or not the chemical injection rate A1 of the polymer flocculant is equal to or lower than the chemical injection upper limit Au, and if the chemical injection rate A1 is equal to or lower than the chemical injection upper limit Au, The molecular aggregating agent shifts to an increase in the drug injection rate A1. Moreover, if the chemical injection rate A1 of the flocculant is equal to or higher than the chemical injection upper limit Au, the process proceeds to an increase in the waste paper addition rate P1. If the sludge concentration D fluctuates more than the set value, the set value is canceled even when operating in a closed circuit, and the control block {c} returns to the “raw solution concentration detection”, and the sludge concentration D of the sewage sludge A sludge flow rate Q is detected, and a feedback circuit for calculating a reference clean water sludge injection rate S suitable for the inflowing sewage sludge is taken.
{P} "Reference drug injection rate A increase"
If the reference drug injection rate A is less than or equal to the drug injection upper limit value Au, the drug injection rate A1 of the polymer flocculant is increased. The waste paper / chemical injection controller 19 controls the rotational speed of the flocculant supply pump PP to increase the chemical injection rate A1 if the reference chemical injection rate A of the polymer flocculant is not more than the chemical injection upper limit Au. . When the proportional injection of the polymer flocculant reaches the chemical injection upper limit Au, the control circuit {g} returns to the “measurement waiting timer” feedback circuit.

{Q} “Up to the upper limit Pu of used paper”
In the determination of "less Kusurichuritsu upper limit Au" of control blocks {o}, reference chemical feed rate A of the coagulant is not less than dosing the upper limit Au, paper-dosing controller 19, the reference paper added It is confirmed whether the rate P is equal to or less than the used paper addition upper limit Pu.
{R} “Increased waste paper addition rate P1”
If the used paper addition rate P1 is equal to or less than the used paper addition upper limit Pu, the used paper addition rate P1 is increased stepwise. After a certain period of time has elapsed, the control block {g} returns to the cake moisture detection feedback circuit of the “measurement wait timer”.
In the determination of “spent paper addition upper limit value Pu or less” in the {s} alarm block {q}, even if the used paper addition rate P1 reaches the used paper addition upper limit Pu, the current cake moisture W is higher than the target cake moisture W0, and there is a difference. When the value exceeds the allowable value δ (W−W0> δ), a warning is issued while continuing the operation.

  Using a screw press with an outer cylinder diameter of Φ300 mm, polymer flocculants with a chemical injection rate of 0.8% and 0.9% were added to the mixed raw sludge, and the agglomerated sludge was pressed into the screw press. Concentrated and dehydrated. The rotational speed of the screw shaft, cake moisture, and dry cake throughput were measured. The experimental results are shown in Tables 1 and 2.

  Table 1 is a comparison table of the rotational speed of the screw shaft and the cake moisture, in which the rotational speed (rpm) of the screw shaft is plotted on the horizontal axis and the cake moisture (%) is plotted on the vertical axis. The mixed raw sludge in which 0.8% of the polymer flocculant was poured had a cake water content of 78% when the rotation speed of the screw shaft was 0.2 rpm and a cake water content of 81.8% when the rotation speed was 0.5 rpm. . The mixed raw sludge to which 0.9% of the polymer flocculant was poured had a cake water content of 78% when the screw shaft rotation speed was 0.3 rpm, and a cake water content of 80.2% when the rotation speed was 0.5 rpm. . From this experimental result, it can be seen that the moisture content of the dewatered cake decreases as the rotational speed of the screw shaft is slower and the drug injection rate is higher.

  Table 2 is a comparison table of the rotational speed and the dry cake processing amount, where the horizontal axis represents the rotational speed (rpm) and the vertical axis represents the dry cake processing amount (kg / hr). Mixed sludge mixed with 0.8% polymer flocculant has a dry cake throughput of 22 kg / hr when the screw shaft rotation speed is 0.2 rpm and a screw shaft rotation speed of 0.5 rpm. The dry cake throughput was 49 kg / hr. Mixed sludge mixed with 0.9% polymer flocculant has a dry cake throughput of 38 kg / hr when the screw shaft rotation speed is 0.3 rpm and a screw shaft rotation speed of 0.5 rpm. The dry cake throughput was 53 kg / hr. From this experimental result, it can be seen that the faster the number of rotations of the screw shaft and the higher the chemical injection rate, the higher the dry cake throughput.

  Table 3 is a comparison table of the dry cake treatment amount and the cake moisture. The horizontal axis represents cake moisture (%), and the vertical axis represents the dry cake treatment amount (kg / hr). Mixed sludge mixed with 0.8% polymer flocculant has a dry cake throughput of 22kg / hr when the cake moisture is 78.4% and a dry cake throughput of 49kg when the cake moisture is 81.8%. / Hr. Mixed sludge mixed with 0.9% polymer flocculant has a dry cake throughput of 37 kg / hr when the cake moisture is 78% and a dry cake throughput of 54 kg / hr when the cake moisture is 80.2%. Met. From this experimental result, it can be seen that the amount of dry cake processing increases as the cake moisture increases.

  As shown in Tables 1 and 2, the cake moisture increases as the number of rotations of the screw shaft increases, and the dry cake processing amount increases. Using a screw press having an outer cylinder diameter of Φ300 mm, the mixed raw sludge added by changing the waste paper is supplied to the screw press, and the rotation speed of the screw shaft is 0.20 rpm, 0.30 rpm, 0.50 rpm,. The cake was dehydrated by rotating at four stages of 75 rpm, and the cake moisture and dry cake throughput with respect to the waste paper addition rate were measured.

  Table 4 shows the relationship between the waste paper addition rate and the cake moisture, and the cake moisture when the waste paper is added to the mixed raw sludge by 5%, 10%, and 20% and dehydrated at four stages of rotation speed is shown. . The abscissa represents the waste paper addition rate (% vs. TS), and the ordinate represents the cake moisture (%). The cake moisture when the waste paper addition rate is 5% is approximately 74 to 79%, the cake moisture when the waste paper addition rate is 10% is approximately 72.5 to 77%, and the cake moisture when the waste paper addition rate is 20% is approximately 70. 5-75.5%. From this measurement result, it can be seen that the cake moisture decreases as the amount of used paper increases.

Table 5 shows the relationship between the waste paper addition rate and the amount of dry cake treated. 0.9% of the polymer flocculant was poured into the mixed raw sludge having a stock solution concentration of 5%, and the waste paper addition rate was 0%, 5%. %, 10%, 20%, and 30%, and the cake moisture when dehydrated at four stages of rotation speed is shown. The abscissa represents the waste paper addition rate (% vs. TS), and the ordinate represents the dry cake throughput (kg / h). The dry cake throughput when the waste paper addition rate is 5% is approximately 29 to 60 kg / h, the dry cake throughput when the waste paper addition rate is 10% is approximately 30 to 72 kg / h, and the dry cake throughput when the waste paper addition rate is 20%. The throughput was approximately 30 to 75 kg / h.
When the rotational speed of the screw shaft is 0.75 rpm when the waste paper addition rate is 30%, clogging occurs and dehydration is impossible, and when the rotational speed of the other screw shaft is 0.20 rpm, 0.30 rpm, 0.50 rpm The dry cake processing amount is also 25 to 60 kg / h, and it seems that the processing amount decreases due to clogging. From the test results, it can be seen that 20% is the optimal waste paper addition rate.

The constant moisture content control method and the constant moisture content control device in the screw press according to the present invention adjust the purified water sludge, the polymer flocculant, and the waste paper to the screw press that concentrates and dehydrates while controlling the supply pressure and flow rate of the agglomerated slurry. Concentrated dewatering is performed while the purified water sludge injected into the sewage sludge reduces the relative cake moisture, and the polymer flocculant to be poured and the added waste paper fibers cooperate to adsorb sludge particles, It can be formed to reduce water content and improve dehydration. Corresponding to the concentration fluctuation of the sewage sludge, the purified water sludge, the flocculant, and the waste paper can be adjusted to reduce the relative cake moisture to obtain a target dehydrated cake having a low water content. Purified water sludge and waste paper are cheaper than polymer flocculants, reducing running costs, obtaining a cake with a uniform low moisture content, and facilitating constant cake moisture control. Therefore, when used in a sewage treatment plant or a human waste treatment plant close to the water purification plant, the running cost is reduced and the cake moisture constant control becomes easy.

It is a flowchart of water | moisture-content constant control of the dewatering cake of the screw press which concerns on this invention. Similarly, it is a block diagram of moisture content constant control in a screw press.

Explanation of symbols

3 Sewage water purification tank 4 Clean water sludge injection controller 6 Sludge adjustment tank 10 Coagulation mixing tank 13 Pressure controller 14 Constant flow controller 17 Moisture content measuring device 18 Moisture content controller 19 Used paper / chemical injection controller 21 Screw press 21a Screw Axis A Standard chemical injection rate A0 Initial chemical injection rate A1 Chemical injection rate Ad Lower limit of chemical injection Au Upper limit of chemical injection D Sludge concentration JSP Clean water sludge supply pump KP Waste paper supply pump P Standard waste paper addition rate P0 Initial waste paper addition rate P1 Waste paper addition Rate Pd Waste paper addition lower limit Pu Waste paper addition upper limit PP Coagulant supply pump Q Sludge flow rate Q0 Initial flow rate S Standard water purification sludge injection rate S0 Initial water purification sludge injection rate S1 Water purification sludge injection rate SP Stock solution supply pump W Cake moisture W0 Target cake moisture

Claims (4)

A pressure controller (13) of the stock solution supply pump (SP) for supplying the agglomerated slurry to the screw press (21) and a constant flow rate controller for controlling the flow rate of the agglomerated slurry by adjusting the rotational speed of the screw shaft (21a) ( 14) In the screw press provided with
{A} Purified water sludge having an initial purified water sludge injection rate (S0) is injected into the sewage sludge with an initial flow rate (Q0) supplied to the screw press (21), and used paper having an initial waste paper addition rate (P0) to the sewage purified water mixed sludge. Then, the polymer flocculant with the initial chemical injection rate (A0) was injected and the operation was started.
{B} After the start of operation, the sludge concentration (D) and sludge flow rate (Q) of sewage sludge are continuously measured, and the purified water sludge with the reference clean water sludge injection rate (S) according to the sewage sludge concentration and sewage sludge flow rate. After injecting
{C} Continue operation while adding waste paper of standard waste paper addition rate (P) suitable for sewage sludge concentration and sewage sludge flow rate and polymer flocculant of reference chemical injection rate (A) to sewage clean water mixed sludge,
{D} After a predetermined time, the cake moisture (W) concentrated and dehydrated with the screw press (21) is measured, and if the cake moisture (W) is higher than the target cake moisture (W0), the drug injection rate (A1) is increased. If the cake moisture (W) is higher than the target cake moisture (W0) even after changing the chemical injection rate (A1), increase the waste paper addition rate (P1),
{E} Conversely, if the cake moisture (W) to be measured is lower than the target cake moisture (W0), the dosing rate (A1) is decreased, and even if the dosing rate (A1) is changed, the cake moisture (W) is not changed. If it is lower than the target cake moisture (W0), decrease the waste paper addition rate (P1),
{F} When the used paper addition rate (P1) reaches the used paper addition upper limit value (Pu) or the used paper addition lower limit value (Pd), a warning is issued while continuing the operation, and the moisture content constant control in the screw press is provided. Method. A pressure controller (13) of the stock solution supply pump (SP) for supplying the agglomerated slurry to the screw press (21) and a constant flow rate controller for controlling the flow rate of the agglomerated slurry by adjusting the rotational speed of the screw shaft (21a) ( 14) In the screw press provided with
{A} A sewage water purification tank (3) for injecting purified water sludge into the sewage sludge to be supplied to the screw press (21), a sludge adjustment tank (6) for adding waste paper to the sewage water purification sludge, and a polymer for the adjustment sludge A flocculent mixing tank (10) for pouring the flocculant is installed,
{B} A purified water sludge injection controller (4) that increases or decreases the reference purified water sludge injection rate (S) in response to changes in sludge concentration (D) and sludge flow rate (Q) of sewage sludge,
{C} Calculate the waste paper standard waste paper addition rate (P) and the polymer flocculant standard chemical injection rate (A) corresponding to the changes in the measured sludge concentration (D) and sludge flow rate (Q) of the sewage sludge, If the cake moisture (W) is higher than the target cake moisture (W0), the chemical injection rate (A1) is increased, and even if the chemical injection rate (A1) is changed, the cake moisture (W) is higher than the target cake moisture (W0). In this case, the waste paper addition rate (P1) is increased. Conversely, if the cake moisture (W) is lower than the target cake moisture (W0), the chemical injection rate (A1) is decreased and the chemical injection rate (A1) is changed. However, when the cake moisture (W) is lower than the target cake moisture (W0) , the screw press is provided with a used paper / chemical injection controller (19) for reducing the used paper addition rate (P1). Constant moisture content control device.

{A} The initial flow rate (Q0) and target cake moisture (W0) of the sewage sludge supplied to the screw press (21) are set, and the initial flow rate (Q0) is set in advance by the pressure controller (13) and the constant flow rate controller. (14), the target cake moisture (W0) is input to the moisture content controller (18),
{B} Determine the initial purified water sludge injection rate (S0) and the reference purified water sludge injection rate (S) of the purified water sludge that match the sludge concentration (D) and the sludge flow rate (Q) of the changing sewage sludge. Input to the injection controller (4)
{C} Initial waste paper addition rate (P0), standard waste paper addition rate (P), waste paper addition rate (P1), waste paper addition upper limit value (Pu) and waste paper addition lower limit value (Pd) of waste paper added to sewage water purification sludge And initial chemical injection rate (A0), standard chemical injection rate (A), chemical injection rate (A1), chemical injection upper limit (Au) and chemical injection Decide the lower limit value (Ad) and input it to the used paper / chemical injection controller (19) in advance,
{D} The purified water sludge having the initial purified water sludge injection rate (S0) is injected into the initial flow rate (Q0) of the sewage sludge supplied to the screw press (21), and the sludge concentration (D) of the sewage sludge and the sludge flow rate ( Q) is measured and transmitted to the purified water sludge injection controller (4), and the reference purified water sludge injection rate (S) is calculated by the purified water sludge injection controller (4) according to the variation of the incoming sewage sludge. Injecting purified water sludge by controlling the rotation speed of the sludge supply pump (JSP),
{E} Add the waste paper of the standard waste paper addition rate (P) that matches the inflowing sewage sludge and the polymer flocculant of the standard chemical injection rate (A) to the sewage water purification sludge ,
{F} The agglomerated slurry is concentrated and dehydrated with a screw press (21), and after a predetermined time, the cake moisture (W) is measured with a moisture content measuring device (17), and the cake moisture (W) is measured with a moisture content controller (18). And the difference between the target cake moisture (W0)
{G} The calculated data is transmitted to the used paper / chemical injection controller (19), and the rotational speed of the flocculant supply pump (PP) is controlled by the used paper / chemical injection controller (19).
{H} If the cake moisture (W) is higher than the target cake moisture (W0), the dosing rate (A1) is increased,
If the cake moisture (W) is higher than the target cake moisture (W0) even when the chemical injection rate (A1) is changed, the used paper / chemical injection controller (19) controls the rotation speed of the used paper supply pump (KP). Increase the waste paper addition rate (P1)
{I} Conversely, if the cake moisture (W) is lower than the target cake moisture (W0), the dosing rate (A1) is decreased, and even if the dosing rate (A1) is changed, the cake moisture (W) is still the target cake. If it is lower than the water content (W0), decrease the waste paper addition rate (P1),
{J} When the used paper addition rate (P1) reaches the used paper addition upper limit (Pu) or the used paper addition lower limit (Pd), the used paper / chemical injection controller (19) issues an alarm while continuing the operation. The moisture content constant control apparatus in the screw press according to claim 2, characterized in that: 4. The moisture content constant control device in the screw press according to claim 2, wherein carbonized sludge is used instead of the purified water sludge injected into the sewage sludge.