JPS59173153A - Controlling device for centrifuge - Google Patents

Abstract

PURPOSE:To stabilize the concn. of concentrated cake obtd. by centrifuging by controlling the position of the skimmer nozzle and the number of revolutions of the screw so as to obtain an optimum balanced value for discharging head of the filtrate and discharging head for cake. CONSTITUTION:A signal corresponding to supplied solid matters in the slurry is obtd. from each detection signal of slurry flow rate detector 27 and slurry concn. detector 28. Each concentration signal of slurry and filtrate from detectors 28, 29 and cake concn. signal from a settor 36 are operated using a formula to obtain a signal corresponding to the rate of recovery of solid matters. From these operation signals, a signal corresponding to cake discharge amt. and similarly a filtrate discharge amt. signal are obtd. From above-described signals, a filtrate discharging head signal is operated by further operation, which is inputted into a controller 34 to change the position of the skimmer nozzle 21, and the number of revolutions of the screw is controlled by a controller 38 basing on the comparison of signals from detectors 30, 40. Thus, the concn. of the concentrated cake is maintained at a fixed level.

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates to an improvement in a centrifugal separator that eliminates the instability of the present invention.

It is well known that screw type centrifuges are used to separate a mixed state of various solids and liquids, so-called slurry, into solids and liquids, and also for concentration and dehydration operations to minimize the amount of liquid that accompanies the solids. It is shi. There are two types of screw type centrifuges: a countercurrent type, in which the solids sedimented and separated under centrifugal force and a filtrate flow in opposite directions, as shown in Figure 1, and a countercurrent type, in which the flow directions of the solids and filtrate are opposite to each other, as shown in Figure 2. In either case, the slurry fed into the inner surface of the bowl 1 through the slurry supply pipe 3 in the case 7 and the slurry supply port 16 provided in the screw 2 is The filtrate, which has become clear as solids are precipitated and removed while flowing through the cylindrical pool 18 due to centrifugal force, overflows from the side plate 4 formed at one end of the bowl 1 and is discharged from the bowl 1. The cake that has settled on the outer circumferential side of the machine is transported inside the sibule 18 by the hydraulic pressure and the scraping action of the screw 2 which rotates while being supported by the main bearing 5, and is discharged to the outside of the machine through the cake discharge port 12. It has become. 1 and 2, 6 is a gear unit, 8 is a main sheave, 9 is a back drive sheave, 10 is a base, 11 is an overload protection device, 13 is a blade, and 14 is a filtrate return pipe.

On the other hand, when centrifugally concentrating a slurry in which poorly compacted solids are suspended, the compacted solids (hereinafter referred to as cake) have fluidity, so the cake is discharged from the machine using a screwdriver. Usually, the cake is not primarily scraped out, but the cake is caused to overflow from one end of the bowl using hydraulic pressure. FIG. 3 shows this state horizontally, taking as an example the case of the countercurrent type shown in FIG. 1, and 15 is a dipware. As mentioned above, the slurry 17 introduced into the inner surface of the bowl l through the slurry supply pipe 3 and the slurry supply port 16 provided in the screw 2 flows through the cylindrical pool 18 due to centrifugal force. The filtrate 19, which has become clear after the solid matter has been precipitated and removed, overflows and is discharged from the separating plate 4 on one end side of the bowl 1, and the cake 20 that has settled on the outer circumferential side of the bowl 1 is removed by the liquid pressure and the scraping action of the screw. The cake is then transferred and discharged outside the machine through the cake discharge port 12. The discharge amounts of the filtrate 19 and the cake 20 are each determined to be constant values depending on the operating conditions. To transfer and discharge the filtrate 19 and the cake 20 that controls fluidity, a water head commensurate with the flow resistance is required. He is the water head for discharging the filtrate, Hb is the water head for the cake to pass through the dipware 15, and He is This is the water head for cake discharge.

In order to overflow and discharge the cake 20, a water head Hc corresponding to the specified discharge amount is required, and this water head He is determined by the height of the shelving plate 4. On the other hand, the height of the plate 4 is the filtrate 1
There is only one position of the plate 4 that determines the water head He corresponding to the specified discharge amount of filtrate 19 and cake 20 at the same time. 500 to 2000, which is the operating condition of a centrifuge used for normal concentration applications.
Under the centrifugal force of the filtrate G, the respective water heads are small, for example, around 1 for He and a few for He, so the height of the separating plate 4 must be precisely adjusted according to the specified discharge amount of the filtrate 19 and cake 20. required, but not controlled by conventional centrifuges. Further, if there is a fluctuation in the supply amount of slurry, this causes a change in the water head He and the water head He 2 , sensitively affecting the separation and concentration performance, resulting in a disadvantage that the concentration cake concentration becomes unstable. Therefore, conventional centrifugal separators used for concentration applications either do not automatically control the concentrated cake concentration, or simply control the screw rotation speed according to the deviation between the measured cake concentration value and the set value. However, controlling the cake concentration resulted in increased fluctuations in the solids recovery rate, making it impractical.

The present invention is a series of tests for the development of a centrifugal thickener for sewage sludge, and as a result of pursuing the cause of instability in the test data, it was found that the discharge head of the filtrate and cake was minute, and both values were adjusted to the operating conditions. This system focuses on the fact that the main cause is that a certain balance is not precisely maintained according to the We discovered that it is important to control the optimal balance between the discharge head and the cake water head, and realized this as an automatic control method.

(2) Measure the concentration of the concentrated cake discharged from the centrifuge by applying the principle of proportionality to the rotational resistance of the loaf, and control the screw rotation speed according to the deviation from the set value.

(3) By combining the controls in (4) and (2) above, the concentrated cake concentration is set to the set value while the solids recovery rate is maintained at a constant level.

It is characterized by

Hereinafter, embodiments of the present invention will be described in detail based on one page. Note that parts that are the same as those in the prior art are given the same numbers and redundant explanations will be omitted.

FIG. 4 shows an implementation 91j of the invention. As shown in the figure, the concentration of the slurry 17 introduced into the bowl L is detected by a production detector 28, and the flow rate is detected by a flow rate detector 27, and the degree of gourage is detected. The preparation signal Cf is sent from the device 28, and the flow rate signal Qf is sent from the flow rate detector 27.
is sent. The bowl 1 is equipped with a skimmer nozzle 21 that arbitrarily sets the water head He for filtrate discharge during operation.
24. The position of the skimmer nozzle 21 is detected by the position detector 31, and the concentration #i of the filtrate 19 flowing out through the skimmer nozzle 21 is detected by the concentration detector 29, and a concentration signal ee corresponding to the detected concentration is sent out. . The screw 2 is connected to a motor 26 via a transmission 23, and is rotated by the motor 26. The rotation speed of the screw 2 is detected by a rotation speed detector 33. On the other hand, the bowl 1 is connected to a motor 25 via a transmission 22, and is rotated by the motor 25. The rotation speed of the bowl 1 is detected by a rotation speed detector 32, and a rotation speed signal Nb corresponding to the bowl rotation speed is sent from the rotation speed detector 32. The concentration of the cake 20 being overflowed and discharged L8 is detected once by the detector 30, and this concentration detector 30 outputs a concentration signal Cc corresponding to each cake.
is sent.

Here, a specific example of the configuration of the concentration detector 30 is shown in FIG. As shown in the figure, the case 7 is equipped with a vat 34 into which the cake 20 flows, and a regulating valve 35 is provided at the bottom of the vat 34. By manually adjusting the opening degree of the valve 35, the amount of cake flowing into the vat 34 and the amount of cake flowing out are balanced.
The liquid level of the cake 20 in the container 4 is kept constant.

A rotor 43 is rotatably provided so as to be immersed in the cake 2° within the vat 34. Therefore, the rotor 43
Since rotational resistance corresponding to the concentration of the cake 2o acts on the rotor 43, l11 degrees is detected by detecting this rotational resistance. Input a signal proportional to rotational resistance into a function generator (not shown),
The concentration signal Cc is obtained by converting the signal according to a preset correlation function. Note that the regulating valve 35 may be automatically adjusted.

FIG. 6 is a block diagram showing an embodiment of concentrated cake concentration control to which the present invention is applied, and 36 is a computing unit; 37.3
8 is a regulator, 39 is a fertility information indicator, 40 is a concentration cake concentration setting device, 41 and 42 are bowl rotation speed and slurry supply amount setting devices, and the instruction/adjustment section is omitted.

In addition, in the embodiment shown in FIGS. 4 and 6, when changing the bowl rotation speed in multiple steps such as by replacing the pulley, the bowl rotation speed change device 22, the rotation speed detector 32, and the bowl rotation speed setting Since the device 41 is not provided, it is sufficient to manually enter the signal in advance into the corresponding rotation speed signal memory of the computing device 36 using some method.

Next, refer to Figures 4 and 6.
Describe the effect of j.

First, the basic functions of the arithmetic unit 36 will be described.

The flow rate signal Qf from the flow rate detector 27 is multiplied by the concentration signal cf from the slurry concentration detector 28 to obtain 1g++Sf of the supplied solids. υ degree detector 28
, 29 (7) Concentration signal (-'f, Ce and setting g
The concentration setting signal Cc,i of 4° or the concentration signal Cc of the concentration detector 3o is calculated using equation (1) described later to obtain an output signal Re corresponding to the solids recovery rate. Obtained output signal S
Multiply f and Re and divide by cake concentration setting signal CC to output signal equivalent to cake discharge amount. Wait for C. Flow rate detector 2
The output signal Qc is subtracted from the flow rate signal Qf of No. 7 to obtain an output signal Qe corresponding to the amount of filtrate discharged. As mentioned above, the filtrate discharge head He, the cake discharge head He, and the dipware passage head Hb.

Note that the filtrate discharge amount Qe and the cake discharge amount Qc are related to the following equations (II), (m), and (+v), respectively, the output signals Qe and Qc, the bowl rotation speed signal Nb, and the dimensions of the centrifuge. Using the specifications and the memory retention signal of 5 proportionality constants, (II) l (ill),
A setting signal He corresponding to a filtrate discharge head that simultaneously satisfies equation (lv) is output.

In addition, each input signal and each output signal in the calculation process are outputted to the alarm instruction panel 39 according to the function of the obituary instruction panel 39.

Next, the regulator 37 will be described. The basic function of this regulator 370 is to input the setting signal He'' from the calculator 36 and the position signal Ps from the skimmer nozzle position detector 31, compare the set value of the filtrate discharge head with the actual value, and respond according to the deviation. The skimmer nozzle NU outputs a control signal Ps.

The skimmer nozzle drive 24 receives a control signal Ps to change the position of the skimmer nozzle so as to be equal to the filtrate discharge head setting signal He.

Next, the regulator 38 will be described. The basic function of this regulator 380 is to compare the concentration setting (% Cc) of the setting device 4o with the concentration signal Cc of the concentration detector 3o and output a control signal Ns0 for the screw rotation speed according to the deviation.Screw rotation speed The transmission 23 inputs the control signal Ns,
Change the screw rotation speed to be equal to the set value.

Alarm indication panel 39Vi receives output signals from each detector, calculator, controller, and setting device to perform display and alarm.

Here, formulas (1) to ()V) are shown.

Qa=kI-Nb'[Hc(2R-H'c)]"・
= −(tl)Qe = kg ・Nb' Be 2
−・−,・, ,,, (11) Hc −k3
・Nb”・He ・・・・・・・・・(I
Cutoff Qc: Flow rate of cake discharge (per hour)) Qe: Filtrate discharge (#I) Cf Nissurari concentration Ce: Filtrate concentration Cc: Cake concentration or concentration setting value Nb: Bowl rotation speed He: Filtrate discharge head Hc: Cake discharge head R: Bowl small end diameter (radius) kI*kz, 3: Proportionality constant As is clear from the above explanation, fluctuations in the cake discharge head He are equivalent to fluctuations in the discharge amount of cake 2o. Then, the relationship of equation (-)' holds true.

Qc oc(He (2R-He) 32., , ,
, , , straight 1i)' Qc: Cake overflow discharge (flow rate per hour) Hc: Cake discharge head R: Bowl small end diameter (see Figure 3) On the other hand, cake discharge Qc is a constant solid matter Under the recovery rate, there is a linear relationship with the P4 condensed cake concentration CC, so the relationships between formulas (I+)' to (v) are established between the concentrated cake concentration and the cake discharge head.

ICc oc CHc (2R-He) ]2---(
JCc: Concentrated cake concentration Hc: Cake discharge head R: Firefly small end diameter Therefore, if the above-mentioned control is not performed, for example, if the cake discharge head increases by 0.13 from the condition (11). Then, the concentrated cake concentration decreased to 4%, and the influence of the cake discharge head was extremely large.

Conditions (1) ■ Surplus activated sludge SS], 0% ■ Screw differential speed 10
rpm ■Centrifugal force 1000 Focusing on the fact that the optimal value can be determined by balancing the dominant p and the filtrate discharge head, we applied it to a concentrated cake concentration control device to precisely control the skimmer nozzle and reduce the concentration discharged from the centrifuge. By actually measuring the cake concentration and feedback-controlling the screw rotation speed according to the deviation from the cake concentration set value, the concentrated cake concentration can be controlled to the set value while maintaining the solids recovery rate at a partial level.

[Brief explanation of drawings]

Fig. 1 is a partially cutaway front view showing a horizontal countercurrent centrifuge, Fig. 2 is a partially cutaway front view showing a horizontal concurrent centrifuge, and Fig. 3 explains problems with the prior art. FIG. 4 is a schematic configuration diagram showing an embodiment of the present invention, FIG. 5 is a configuration diagram specifically showing a cake concentration detector, and FIG. FIG. 2 is a block diagram illustrating an exemplary control example. In the drawing, 1 is the bowl, 2 is the screw, 12 is the cake drain, 17 is the stripe, 19 is the filtrate, 20 is the concentrated cake (solid matter), 21 is the skimmer nozzle, 23 is the transmission, 24 is the skimmer nozzle. Drive device. 27 is a slurry flow detector, 28 is a slurry concentration detector, 2911 is a slow liquid concentration detector, 30 is a cake concentration detector, 31 is a skimmer nozzle position detector, 36 is a calculator, 37.38 is an adjustment 40.41.42 is a setting device.

Claims (1)

[Claims] In a centrifugal separator that overflows and discharges solids concentrated by centrifugation using the scraping action of a screw and hydraulic pressure, there is provided a skimmer nozzle for discharging the filtrate, a driving means for changing the position of this skimmer nozzle, and a concentration of the concentrated solids. a calculation means for calculating the optimum filtrate discharge head in accordance with a set value of , an adjustment means for controlling the position of the skimmer nozzle via the drive means so as to achieve the calculated filtrate discharge head, and a control means for controlling the concentration of the concentrated solids. 1. A centrifugal separator control device, comprising: adjusting means for measuring and controlling the rotational speed of a screw according to the deviation between the measured value and a set value.