How to operate a centrifugal dehydrator

Abstract

To provide an operation method of a centrifugal dehydrator in which spill of solid content into dewatered / separated liquid is suppressed when dehydrating an object to be dehydrated, and moisture percentage of an obtained dehydration product is reduced so as to get the dehydration products whose fluctuation of moisture percentage is small.SOLUTION: An operation method of a centrifugal dehydrator uses a centrifugal dehydrator with an outer casing and a screw conveyor and repeatedly performs load adjustment process n times to determine load value X of the screw conveyor. The load adjustment process includes: dehydration process; and measurement process. The k time dehydration process (k is an integer of 1 to n) includes the steps of: supplying the centrifugal dehydrator with an object to be dehydrated; rotating the outer casing at a constant rotation number; and adjusting rotation number of the screw conveyor so that the load is to be the load value Xk and rotating for dehydration to get dewatered / separated liquid. The k time measurement process is performed to get solid content concentration Sk or turbidity Tk of the dewatered / separated liquid acquired at the k time dehydration process. The load value Xk is defined according to a prescribed regulation and the load value X is defined based on the load value Xn of the n time load adjustment process.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a method for operating a centrifugal dehydrator. [Background technology]

[0002] Conventionally, a method of dewatering materials using a centrifugal dewatering machine is known. In dewatering using a centrifugal dewatering machine, it is desirable that solid-liquid separation be performed appropriately and that the water content of the resulting dewatered material be reduced as much as possible, and for this purpose, it is necessary to set the operating conditions of the centrifugal dewatering machine appropriately. For example, Patent Document 1 discloses a control method for a centrifugal dewatering machine in which a screw conveyor rotating at a relative speed difference with respect to the outer cylinder is housed inside a high-speed rotating outer cylinder to perform solid-liquid separation of sludge, and the turbidity of the separated liquid discharged from the centrifugal dewatering machine is measured, and based on the measured value, the rotation of a hydraulic motor that supplies oil to a differential speed device that applies a relative speed difference to the screw conveyor is automatically controlled. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 10-151370 [Overview of the project] [Problems that the invention aims to solve]

[0004] According to the above-described control method for centrifugal dewatering machines, the turbidity of the separated liquid discharged from the centrifugal dewatering machine is detected, and based on the measurement result, the hydraulic motor supplying oil to the differential speed device is controlled, thereby maintaining a low moisture content in the dewatered material and keeping the turbidity of the separated liquid low. In this case, it is desirable that the moisture content of the resulting dewatered material fluctuates little, thereby stabilizing the processing of the dewatered material after dewatering. For example, when the dewatered material is further incinerated or calcined, stable incineration or calcination can be achieved.

[0005] The present invention has been made in view of the above circumstances, and its object is to provide a method for operating a centrifugal dehydrator that, when dehydrating an object to be dehydrated, sufficiently suppresses the outflow of solids into the dehydration separation liquid, reduces the water content of the resulting dehydrated product as much as possible, and allows for the production of dehydrated products with minimal fluctuations in water content. [Means for solving the problem]

[0006] The operating method of the centrifugal dehydrator of the present invention, which has solved the aforementioned problems, is as follows. [1] A method for operating a centrifugal dewatering machine having a rotationally driven outer cylinder and a screw conveyor provided inside the outer cylinder and rotated coaxially with the rotation axis of the outer cylinder, wherein the load adjustment process is repeated n times (where n is an integer of 2 or more) to determine the load value X of the screw conveyor, The load adjustment process includes a dewatering process and a measurement process. The k-th dewatering step (where k is an integer from 1 to n) involves supplying the material to be dewatered to the centrifugal dewatering machine, rotating the outer cylinder at a constant rotational speed, and moving the screw conveyor with a load value X k The rotation speed is adjusted to achieve the above, and the centrifugal dewatering machine is used to dewater the object to be dewatered and to obtain a dewatered liquid. The k-th measurement step is the solid content concentration S of the dehydrated separated liquid obtained in the k-th dehydration step. k or turbidity T k This is what you get. The load value X in the k-th dewatering step, according to the rules (A1) to (A3) below. k Determine, The nth load adjustment step is carried out in accordance with the following rule (A3), and the solid content concentration S n or turbidity T n The value fell below the standard value. Load value X in the nth load adjustment step n A method for operating a centrifugal dewatering machine, characterized by determining the load value X based on the above. (A1) In the first load adjustment process, the load value X1 is arbitrarily determined. In the k-th load adjustment step after the second time, the solid content concentration S in the (k - 1)-th load adjustment step k-1 or the turbidity T k-1 is less than the reference value, a load value X k-1 greater than the load value X k is determined. (A3) In the k-th load adjustment step after the second time, the solid content concentration S in the (k - 1)-th load adjustment step k-1 or the turbidity T k-1 is greater than or equal to the reference value, a load value X k-1 less than the load value X k is determined. [2] The centrifuge has a differential speed device that gives a rotational difference between the outer cylinder and the screw conveyor, and the load value X k is obtained from the hydraulic pressure value when the differential speed device is hydraulic, or the current value when the differential speed device is a gear type. The operation method of the centrifuge according to [1]. [3] Repeating the load adjustment step n times to determine the load value X is performed when the solid content concentration or turbidity of the dewatered separation liquid from the centrifuge becomes greater than or equal to the reference value. The operation method of the centrifuge according to [1] or [2]. [4] Repeating the load adjustment step n times to determine the load value X is performed at least once every 6 hours. The operation method of the centrifuge according to any one of [1] to [3]. [5] After repeating the load adjustment step n times to determine the load value X, the addition rate of the flocculant to the dehydration target is adjusted. The operation method of the centrifuge according to any one of [1] to [4]. [Advantages of the Invention]

[0007] According to the operation method of the centrifuge of the present invention, when dehydrating a dehydration target with a centrifuge, the outflow of solids into the dewatered separation liquid is sufficiently suppressed, appropriate solid-liquid separation can be achieved, the water content of the obtained dehydrated product is reduced, and a dehydrated product with little variation in water content can be obtained. [Brief Description of the Drawings]

[0008] [Figure 1]This diagram shows a schematic representation of the internal structure of a centrifugal dehydrator. [Figure 2] This diagram illustrates the processing flow of the operating method for the centrifugal dehydrator of the present invention. [Figure 3] This shows an example of how to operate a centrifugal dehydrator according to an embodiment of the present invention. [Figure 4] This illustrates another example of how to operate a centrifugal dehydrator according to an embodiment of the present invention. [Modes for carrying out the invention]

[0009] In describing the operating method of the centrifugal dehydrator of the present invention, we will first describe an example of the configuration of the centrifugal dehydrator with reference to Figure 1. Figure 1 shows a schematic diagram of the internal structure of the centrifugal dehydrator. Figure 1 shows a schematic diagram of a straight-drum type centrifugal dehydrator, but the centrifugal dehydrator may be, for example, a decanter type centrifugal dehydrator.

[0010] The centrifugal dewatering machine 1 comprises an outer cylinder 2 extending in the longitudinal direction and a screw conveyor 3 provided inside the outer cylinder 2 and also extending in the longitudinal direction. The outer cylinder 2 is configured to rotate around the longitudinal direction, and the screw conveyor 3 is configured to rotate coaxially with the rotation axis of the outer cylinder 2. The outer cylinder 2 is formed in a shape such as a cylinder, a cone, or a combination thereof. The screw conveyor 3 is configured with a screw 5 extending helically from the outer surface of a screw shaft 4.

[0011] The centrifugal dewatering machine 1 has a space (hereinafter referred to as the "processing space") between the outer cylinder 2 and the screw conveyor 3 in which the material to be dewatered is held. When the outer cylinder 2 is driven to rotate, centrifugal force is applied to the material to be dewatered in the processing space, causing specific gravity separation, and the material to be dewatered is separated into dewatered material and dewatered separation liquid.

[0012] The centrifugal dewatering machine 1 has an introduction section 6 for supplying the material to be dewatered into the processing space, a dewatered material discharge section 7 for discharging the dewatered material from the processing space, and a separation liquid discharge section 8 for discharging the dewatered separation liquid from the processing space. In the centrifugal dewatering machine 1, it is preferable that the dewatered material discharge section 7 is provided on one side in the longitudinal direction of the outer cylinder 2, the separation liquid discharge section 8 is provided on the other side in the longitudinal direction of the outer cylinder 2, and the introduction section 6 is provided so as to be located between the dewatered material discharge section 7 and the separation liquid discharge section 8 in the longitudinal direction. It is preferable that the introduction section 6 for supplying the material to be dewatered into the processing space is formed on the screw shaft 4 of the screw conveyor 3, and it is preferable that the screw shaft 4 has a lumen that communicates with the introduction section 6 and the outside of the outer cylinder 2. It is preferable that the screw shaft 4 extends to the outside of the outer cylinder 2 and is configured so that the material to be dewatered can be transported from the outside of the outer cylinder 2 to the introduction section 6 through the lumen of the screw shaft 4.

[0013] The outer cylinder 2 and the screw conveyor 3 are configured to allow control of their respective rotational speeds. The outer cylinder 2 and the screw conveyor 3 rotate at a rotational speed of, for example, 2000 rpm to 5000 rpm. The centrifugal dewatering machine 1 preferably has a differential speed device 9 that gives a rotational difference between the outer cylinder 2 and the screw conveyor 3. By rotating both the outer cylinder 2 and the screw conveyor 3 together and controlling the rotational speed of the screw conveyor 3 to be different from the rotational speed of the outer cylinder 2 using the differential speed device 9 provided in the centrifugal dewatering machine 1, the rotational speeds of the outer cylinder 2 and the screw conveyor 3 can be adjusted.

[0014] Examples of differential speed devices 9 include hydraulic differential speed devices using a hydraulic motor and gear-type differential speed devices using a gear motor. A hydraulic differential speed device can be controlled so that the rotational speed of the screw conveyor 3 is greater than the rotational speed of the outer cylinder 2. A gear-type differential speed device can be controlled so that the rotational speed of the screw conveyor 3 is less than the rotational speed of the outer cylinder 2.

[0015] When the centrifugal dewatering machine 1 dewaters an object, the rotation of the outer cylinder 2 and the screw conveyor 3 is controlled so that they rotate in the same direction and the screw 5 of the screw conveyor 3 moves toward the dewatered material discharge section 7. As a result, the object to be dewatered is transported toward the dewatered material discharge section 7 by the screw 5, and dewatering progresses as the object is transported. The dewatered object is discharged out of the outer cylinder 2 from the dewatered material discharge section 7. The dewatered liquid is not transported by the screw 5 and is discharged out of the outer cylinder 2 from the liquid discharge section 8.

[0016] In the centrifugal dewatering machine 1 shown in Figure 1, the diameter of the screw shaft 4 of the screw conveyor 3 is configured to increase towards the dewatered material discharge section 7. This improves the dewatering performance when the material to be dewatered is conveyed towards the dewatered material discharge section 7.

[0017] Examples of materials to be dewatered by the centrifugal dewaterer 1 include inorganic slurries and organic slurries. Examples of inorganic slurries include slurries containing metal powder, ceramic powder, mineral powder, abrasive powder, etc. Examples of organic slurries include slurries containing pulp and food waste, and sludge. Examples of sludge include sludge generated from sewage treatment, human waste treatment, treatment of industrial wastewater from food factories, paper and pulp factories, chemical plants, etc., and treatment of livestock waste such as livestock manure. The source of sludge in the treatment process is not particularly limited, and for example, primary sedimentation sludge, excess sludge, mixed raw sludge, activated sludge, digested sludge, etc. can be used. The sludge may be sludge obtained by aerobic treatment (aerobic sludge) or sludge obtained by anaerobic treatment (anaerobic sludge).

[0018] A dewatering aid may be supplied to the centrifugal dewaterer 1 along with the material to be dewatered. This can improve the dewatering properties of the material to be dewatered. Examples of dewatering aids include inorganic flocculants and organic flocculants. Examples of inorganic flocculants include iron-based flocculants such as ferric chloride, ferric sulfate, and polyferric sulfate (polyiron); and aluminum-based flocculants such as aluminum chloride and aluminum sulfate (aluminum sulfate). Examples of organic flocculants include polymer flocculants such as anionic, cationic, amphoteric, and nonionic types.

[0019] In the centrifugal dewatering machine 1, a correlation is observed between the load on the screw conveyor 3 and the dewatering properties of the dewatered material. When the dewatering properties increase, i.e., when the moisture content of the dewatered material decreases, the load on the screw conveyor 3 tends to increase, and when the dewatering properties decrease, i.e., when the moisture content of the dewatered material increases, the load on the screw conveyor 3 tends to decrease. It is preferable that the dewatered material obtained by dewatering the object to be dewatered in the centrifugal dewatering machine 1 has as constant a moisture content as possible, thereby improving the stability of the processing of the dewatered material and improving the handling of the dewatered material. From this viewpoint, in the operating method of the centrifugal dewatering machine of the present invention, the operating conditions are set so that the load on the screw conveyor 3 takes a constant value, i.e., a constant load value X. On the other hand, if the load on the screw conveyor 3 is not controlled to take a constant value, and instead the differential speed of the screw conveyor 3 is changed as needed according to the solid content concentration or turbidity of the dewatered separation liquid, the moisture content of the dewatered material will not be stable, and the properties of the resulting dewatered material will vary greatly.

[0020] The load on the screw conveyor 3 can be adjusted by controlling the differential speed of the screw conveyor 3 (the difference in rotational speed of the screw conveyor 3 relative to the rotational speed of the outer cylinder 2). If the supply amount of material to be dewatered is kept constant and the differential speed of the screw conveyor 3 is increased, the moisture content of the dewatered material increases (dehydrability decreases), and the load on the screw conveyor 3 tends to decrease. If the supply amount of material to be dewatered is kept constant and the differential speed of the screw conveyor 3 is decreased, the moisture content of the dewatered material decreases (dehydrability increases), and the load on the screw conveyor 3 tends to increase.

[0021] The load on the screw conveyor 3 can be measured from the torque of the screw conveyor 3 and the torque of the differential speed device 9. The torque of the differential speed device 9 changes in conjunction with the torque of the screw conveyor 3. The load on the screw conveyor 3 can be determined, for example, from the hydraulic pressure value if the differential speed device 9 is hydraulic, or from the current value if the differential speed device 9 is gear-type.

[0022] In centrifugal dewatering, as dewatering efficiency increases, the solid content concentration or turbidity of the dewatered liquid tends to decrease, and as dewatering efficiency decreases, the solid content concentration or turbidity of the dewatered liquid tends to increase. However, if the differential speed of the screw conveyor is reduced too much, i.e., if the load on the screw conveyor is increased too much, the supplied material to be dewatered will not be sufficiently separated into solid and liquid, and the solid content will easily migrate to the dewatered liquid. As a result, the properties of the dewatered liquid will deteriorate, i.e., the solid content concentration in the dewatered liquid will increase. Therefore, in centrifugal dewatering, it is desirable to appropriately set the operating conditions to maximize the dewatering efficiency of the dewatered material without significantly deteriorating the properties of the dewatered liquid.

[0023] To this end, the centrifugal dewatering machine operation method of the present invention includes a load adjustment step for appropriately setting the load on the screw conveyor. In the centrifugal dewatering machine operation method of the present invention, the load adjustment step is repeated n times (where n is an integer of 2 or more) to determine the load value X of the screw conveyor. According to the present invention, it is possible to set operating conditions for a centrifugal dewatering machine that can increase dewatering efficiency and lower the moisture content of the dewatered product while sufficiently suppressing the outflow of solids into the dewatered separation liquid, and that can produce dewatered product with little fluctuation in moisture content. As a result, efficient dewatering by the centrifugal dewatering machine can be realized, and stabilization of the processing of the dewatered product after dewatering can be expected. Hereinafter, any load adjustment step from the 1st to the nth time will be generalized and referred to as the kth load adjustment step, where k is an integer from 1 to n.

[0024] The load adjustment process includes a dewatering process and a measurement process; therefore, the kth load adjustment process includes the kth dewatering process and the kth measurement process. In the kth dewatering process, the material to be dewatered is supplied to the centrifugal dewatering machine, and the screw conveyor is set to a load value X k The rotation speed is adjusted to achieve the desired result, and the material to be dewatered is dewatered using a centrifugal dehydrator. By dewatering the material, a dewatered separation liquid is obtained. In the k-th dewatering step, it is preferable to keep the amount of material to be dewatered supplied to the centrifugal dehydrator constant (supply amount per unit time), and it is also preferable to continuously supply the material to the centrifugal dehydrator. In the k-th measurement step, the solid content concentration S of the dewatered separation liquid obtained in the k-th dewatering step is measured. k or turbidity T k To obtain.

[0025] Load value X in the kth dewatering step k This is determined according to the following rules (A1) to (A3). (A1) In the first load adjustment process, the load value X1 is arbitrarily determined. (A2) In the kth load adjustment step from the second step onward, the solid content concentration S of the k-1 load adjustment step is used. k-1 or turbidity T k-1 If the load value X is below the standard value, k-1 Larger load value X k To define. (A3) In the kth load adjustment process from the second time onward, the solid content concentration S of the k-1 load adjustment process k-1 or turbidity T k-1 If the load value X is above the standard value, k-1 Smaller load value X k To define.

[0026] In the dewatering process of the load adjustment process, the outer cylinder is rotated at a constant speed. The screw conveyor rotates in the same direction as the outer cylinder, and its rotational speed relative to the outer cylinder is adjusted so that the screw moves towards the dewatered material discharge section. At this time, the load on the screw conveyor is a constant load value X. kThe rotational speed of the screw conveyor is adjusted accordingly. Generally, increasing the rotational speed (differential velocity) of the screw conveyor tends to decrease the load on the screw conveyor, while decreasing the rotational speed (differential velocity) tends to increase the load on the screw conveyor. In the dewatering process, the load on the screw conveyor is load value X. k If it deviates from the target, the rotation speed of the screw conveyor is adjusted accordingly so that the load on the screw conveyor remains constant at a load value X. k It is preferable to use feedback control to take the desired result.

[0027] Load value X k This is obtained by measuring the load on the screw conveyor. Load value X k This can be determined by directly measuring the load on the screw conveyor, or by taking the load value X from the load on the differential speed device. k It is convenient to determine the load value X from the hydraulic pressure value. For example, if the differential speed device is hydraulic, the load value X k The load value X can be calculated from the current value if the differential speed device is gear-type. k It is possible to find this.

[0028] The method for determining the load value X of the screw conveyor according to the rules (A1) to (A3) above will be explained in detail with reference to Figure 2. The load value X1 in the first load adjustment process can be set as appropriate (rule (A1)). The load value X in the kth load adjustment process from the second onwards... k This is the solid content concentration S in the previous k-1 load adjustment step. k-1 or turbidity T k-1 Determined based on the following: Solid content concentration S of the k-1 load adjustment step. k-1 or turbidity T k-1 If the value is below the standard value, load value X k-1 Larger load value X k The solid content concentration S of the k-1 load adjustment step is determined (Rule (A2)), and the load adjustment step is determined. k-1 or turbidity T k-1 If the value is above the standard value, load value X k-1 Smaller load value X k Establish (Rule (A3)).

[0029] Solid concentration S k-1 or turbidity T k-1 If the value is below the standard value, it can be determined that almost no solid matter from the material to be dewatered is transferred to the dewatering liquid, and that it is possible to further improve the dewatering properties. Therefore, in the k-th load adjustment step, the load value X of the k-1th load adjustment step is used. k-1 Larger load value X k Determine the differential speed of the screw conveyor. Meanwhile, the solid content concentration S of the k-1 load adjustment process. k-1 or turbidity T k-1 If the value exceeds the standard value, it is determined that a certain amount of solid matter from the material to be dewatered has transferred to the dewatered liquid, resulting in a decrease in solid-liquid separation performance. Therefore, in the k-th load adjustment step, the load value X from the k-1th load adjustment step is used. k-1 Smaller load value X k The differential speed of the screw conveyor is increased. As a result, excessive retention of the material to be dewatered in the centrifugal dewaterer is suppressed, and the outflow of solid matter from the material to be dewatered into the dewatering liquid is suppressed.

[0030] In the kth load adjustment process from the second time onward, the load value X k and load value X k-1 The difference can be constant or not, and should be set appropriately based on experience. For example, load value X k load value X k-1 The load value X in the k-1 load adjustment process may be set to have a constant difference. k-1 Or solid content concentration S k-1 or turbidity T k-1 Based on this, load value X k and load value X k-1 You may change the difference as appropriate.

[0031] Solid content concentration S of the dehydrated separated liquid k-1 or turbidity T k-1 The standard value should be set appropriately based on the type of material to be dewatered, the required solid content concentration or turbidity of the dewatered liquid, etc. It is desirable to set a constant (same) standard value in each load adjustment process.

[0032] In the measurement process of the load adjustment process, either the solid content concentration or turbidity of the dewatered separated liquid may be measured, or both may be measured, but measuring only one of them is sufficient. It is preferable to measure the solid content concentration or turbidity on-site, and for example, the solid content concentration or turbidity can be measured using a SS meter or a turbidimeter. When measuring both the solid content concentration and turbidity, the solid content concentration S k-1 and turbidity T k-1 If both are below the standard value, load value X k-1 Larger load value X k Determine the solid content concentration S k-1 and turbidity T k-1 If at least one of the following is above the standard value, the load value X k-1 Smaller load value X k It is preferable to define it.

[0033] Load value X in the kth load adjustment step k It is preferable to set it within a range greater than or equal to a predetermined value. Load value X k If the load value X1 is extremely low, solid-liquid separation of the material to be dewatered in the centrifugal dehydrator may be insufficient, potentially resulting in a higher water content in the dewatered material or an increase in the amount of solids transferred to the dewatering liquid. Therefore, the load value X1 in the first load adjustment step should be set within a range greater than or equal to a predetermined value, and the load value X should also be set in the kth load adjustment step from the second onward. k It is preferable to set the load value X within a range greater than or equal to a predetermined value. k-1 The lower limit of the range above the specified value, i.e., the specified value (or a smaller value), and the solid content concentration S k-1 or turbidity T k-1 If the load value exceeds the standard value, the load value X in the kth load adjustment process will be... k This is from load value X1 to load value X k-1 It is preferable to set a value higher than any of the above.

[0034] The implementation time of one load adjustment process may be appropriately set according to the residence time of the dehydration target in the centrifuge. It is preferable to shift from the (k - 1)-th load adjustment process to the k-th load adjustment process, and after a certain degree of replacement of the dehydration target in the centrifuge and the operation of the centrifuge becomes stable, perform the (k + 1)-th load adjustment process. The implementation time of one load adjustment process may be appropriately set, for example, between 1 minute and 60 minutes, preferably between 3 minutes and 45 minutes.

[0035] The last load adjustment process, that is, the n-th load adjustment process, is performed according to rule (A3), and the solid content concentration S n or the turbidity T n becomes less than the reference value. In other words, when the k-th load adjustment process is performed according to rule (A3) and the solid content concentration S <000008​​​​​​​​​​​​​​​​​​​​​​​​The operating method for the centrifugal dewatering machine of the present invention is preferably performed periodically during operation of the centrifugal dewatering machine. The moisture content and properties of the material to be dewatered supplied to the centrifugal dewatering machine may change as the process continues, and in that case, the load value X that was initially determined may not be the optimal value for subsequent processing. From this viewpoint, it is preferable to repeat the load adjustment process n times to determine the load value X, for example, at least once every 6 hours. The interval between repeating the load adjustment process n times to determine the load value X may be shorter than this. It is preferable that the interval between repeating the load adjustment process n times to determine the load value X is longer than the duration of one load adjustment process, preferably set to be at least twice the duration of one load adjustment process, and more preferably three times or more.

[0037] The centrifugal dehydrator operation method of the present invention is also preferably performed when the solid content concentration or turbidity of the dewatered liquid exceeds a standard value during operation of the centrifugal dehydrator. In dewatering by centrifugal dehydrator, the water content and properties of the material to be dewatered supplied to the centrifugal dehydrator change as the process continues, which can lead to deterioration of the properties of the dewatered liquid. In this case, it is preferable to monitor the solid content concentration or turbidity of the dewatered liquid discharged from the centrifugal dehydrator, and when the solid content concentration or turbidity of the dewatered liquid exceeds a standard value, repeat the load adjustment process n times to determine the load value X again.

[0038] When changing the addition rate of a coagulant (dewatering aid) to the material to be dewatered, it is preferable to first determine the load value X by repeating the load adjustment process n times, and then adjust the addition rate of the coagulant to the material to be dewatered. Since the load value of the screw conveyor has a greater impact on dewatering performance than the addition rate of the coagulant, it is possible to efficiently determine appropriate dewatering conditions by first converging the load of the screw conveyor to an optimal value by repeating the load adjustment process n times, and then adjusting the addition rate of the coagulant.

[0039] In the above case, when the dehydration performance is improved by increasing the addition rate of the flocculant, it is assumed that the margin of the load value of the screw conveyor increases. Therefore, in this case, after adjusting the addition rate of the flocculant, it is preferable to repeat the load adjustment process n times again to determine the load value X. In this case, the adjustment of the load value X of the screw conveyor, the adjustment of the flocculant addition rate, and the adjustment of the load value X of the screw conveyor are sequentially performed.

[0040] Next, an operation example of the centrifuge will be described with reference to FIGS. 3 and 4. FIGS. 3 and 4 show an example of the relationship between the load value X k and the solid content concentration S k or the turbidity T k when dehydrating the object to be dehydrated by the centrifuge. In FIGS. 3 and 4, the order of the load adjustment process is indicated by circled numbers, and the reference values of the solid content concentration S and the turbidity T are represented by dotted lines.

[0041] In the operation example of FIG. 3, first, the first load adjustment process was performed based on the rule (A1). In the first load adjustment process, since the solid content concentration S1 or the turbidity T1 was less than the reference value, in the second load adjustment process, based on the rule (A2), the load value of the screw conveyor was set to a load value X2 larger than the load value X1 of the first load adjustment process, and the centrifuge was operated.

[0042] Since the solid content concentration S2 or the turbidity T2 was also less than the reference value in the second load adjustment process, in the third load adjustment process, based on the rule (A2), the load value of the screw conveyor was set to a load value X3 larger than the load value X2 of the second load adjustment process, and the centrifuge was operated.

[0043] In the third load adjustment process, the solid content concentration S3 or turbidity T3 exceeded the standard value. Therefore, in the fourth load adjustment process, in accordance with rule (A3), the load value of the screw conveyor was set to a load value X4, which is smaller than the load value X3 from the third load adjustment process, and the centrifugal dewatering machine was operated. In the fourth load adjustment process, the solid content concentration S4 or turbidity T4 was below the standard value. Therefore, the final load value X of the screw conveyor was determined based on the load value X4 from the fourth load adjustment process.

[0044] In the operation example shown in Figure 4, the first load adjustment process was performed based on rule (A1). In the first load adjustment process, the solid content concentration S1 or turbidity T1 was above the standard value, so in the second load adjustment process, based on rule (A3), the load value of the screw conveyor was set to a load value X2 which is smaller than the load value X1 from the first load adjustment process, and the centrifugal dewatering machine was operated.

[0045] In the second load adjustment process, the solid content concentration S2 or turbidity T2 was still above the standard value. Therefore, in the third load adjustment process, in accordance with rule (A3), the load value of the screw conveyor was set to a load value X3 that was smaller than the load value X2 in the second load adjustment process, and the centrifugal dewatering machine was operated. In the third load adjustment process, the solid content concentration S3 or turbidity T3 was below the standard value. Therefore, the final load value X of the screw conveyor was determined based on the load value X3 in the third load adjustment process.

[0046] As shown in the operating examples in Figures 3 and 4, the operating method of the centrifugal dewatering machine of the present invention can increase the dewatering properties during dewatering and reduce the moisture content of the dewatered product while keeping the solid content or turbidity of the dewatered liquid below a standard value. Furthermore, by operating the centrifugal dewatering machine while adjusting the differential speed of the screw conveyor so that the load on the screw conveyor remains constant at load value X, it is possible to obtain dewatered product with less fluctuation in moisture content. Therefore, efficient dewatering by the centrifugal dewatering machine can be achieved, and the processing of the dewatered product after dewatering can also be stabilized. [Explanation of Symbols]

[0047] 1: Centrifugal dehydrator 2: Outer cylinder 3: Screw conveyor 4: Screw shaft 5: Screw 6: Introduction 7: Dehydrated material discharge section 8: Separated liquid discharge part 9: Differential speed device

Claims

1. A method for operating a centrifugal dewatering machine, which has a rotating outer cylinder and a screw conveyor provided inside the outer cylinder and rotating coaxially with the rotation axis of the outer cylinder, wherein the load adjustment process is repeated n times (where n is an integer of 2 or more) to determine the load value X of the screw conveyor, The load adjustment process includes a dewatering process and a measurement process. The kth dewatering step (where k is an integer from 1 to n) involves supplying the material to be dewatered to the centrifugal dewatering machine, rotating the outer cylinder at a constant rotational speed, and moving the screw conveyor with a load value X ｋ The rotation speed is adjusted to achieve the above, and the centrifugal dewatering machine is used to dewater the object to be dewatered and to obtain a dewatered liquid. The k-th measurement step is the solid content concentration S of the dehydrated separated liquid obtained in the k-th dehydration step. ｋ or turbidity T ｋ This is what you get. Load value X in the k-th dewatering step according to the rules (A1) to (A3) below ｋ Determine, The nth load adjustment step is carried out in accordance with the following rule (A3), and the solid content concentration S ｎ or turbidity T ｎ The value fell below the standard value. Load value X in the nth load adjustment process ｎ A method for operating a centrifugal dewatering machine, characterized by determining the load value X based on the above. (A1) In the first load adjustment process, load value X １ The value is determined arbitrarily. In the k-th load adjustment process after the second time (A2), when the solid content concentration S ｋ－１ or the turbidity T ｋ－１ is less than the reference value, a load value X ｋ－１ greater than the load value X ｋ is determined. (A3) In the kth load adjustment step from the second time onward, the solid content concentration S of the k-1 load adjustment step is used. ｋ－１ or turbidity T ｋ－１ If the load value X is above the standard value, ｋ－１ Smaller load value X ｋ To define.

2. The centrifugal dewatering machine has a differential speed device that gives a rotational difference between the outer cylinder and the screw conveyor, The aforementioned load value X ｋ The method for operating a centrifugal dewatering machine according to claim 1, wherein the differential speed device is determined from the hydraulic pressure value when the differential speed device is hydraulic, or from the current value when the differential speed device is gear-type.

3. The method for operating a centrifugal dehydrator according to claim 1, wherein the load adjustment step is repeated n times to determine the load value X when the solid content concentration or turbidity of the dewatered liquid separated from the centrifugal dehydrator exceeds a standard value.

4. The method for operating a centrifugal dehydrator according to claim 1, wherein the load adjustment step is repeated n times to determine the load value X, and this is performed at least once every six hours.

5. A method for operating a centrifugal dewatering machine according to claim 1, wherein the load adjustment step is repeated n times to determine the load value X, and then the rate of addition of a flocculant to the material to be dewatered is adjusted.

Images