Method and system for controlling supply amount of stored material

Abstract

To provide a supply amount control method of a stored material capable of controlling the supply amount in relation to a discharge amount of the stored material with good followability, and a system.SOLUTION: In a facility having a storage part 2 storing a stored material D, a supply part 4 supplying the stored material D to the storage part 2, and a discharge part 5 discharging the stored material D from the storage part 2, the supply amount of the stored material D in the supply part 4 is controlled corresponding to the discharge amount of the stored material D at the discharge part 5. The supply amount of the stored material D at the supply part 4 can be defined as a function of the discharge amount of the stored material D at the discharge part 5, and the function can be set as a linear function. Furthermore, a correction value C can be added to the function corresponding to an operation state of the facility.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method for controlling the supply amount of stored material in a facility, such as a sludge treatment facility, that has a storage section for storing stored material and where it is necessary to control the amount of stored material in the storage section, and a system for carrying out this method. [Background technology]

[0002] For example, in a sludge treatment facility, a feeder for temporarily storing dehydrated cake to be fed to the incinerator is provided between a storage tank for storing dehydrated cake and an incinerator for incinerating the dehydrated cake, and the dehydrated cake is supplied from the storage tank to the supply port of the feeder by a first pump, and the dehydrated cake is discharged from the discharge port of the feeder by a second pump and fed into the incinerator.

[0003] In the feeder, the amount of dehydrated cake stored must be kept substantially constant so that the stored dehydrated cake does not exceed the capacity and overflow, or the feeder does not become empty and interfere with the operation of the second pump. To achieve this, the first and second pumps are operated so that the amount of dehydrated cake supplied from the first pump to the feeder and the amount of dehydrated cake discharged from the feeder to the second pump are balanced.

[0004] Prior art documents describing technology relating to control of the supply amount of stored material in such facilities include, for example, Patent Document 1 listed below. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2-249812 Summary of the Invention [Problem to be solved by the invention]

[0006] In the past, in order to control the amount of stored material in the feeder in such facilities, the general method was to monitor the amount of stored material in the feeder and adjust the operation of the first pump accordingly. If the amount of stored material is less than the target value or is decreasing, the rotation speed of the first pump is increased to increase the amount of stored material supplied per hour, and if the amount of stored material is more than the target value or is increasing, the rotation speed is decreased to decrease the amount of stored material supplied per hour.

[0007] However, this method has a problem that the control of the supply amount is poor in response to the fluctuation of the supply amount in the first pump. For example, when the discharge amount in the second pump is increased significantly in a short time, the rotation speed of the first pump is increased after the decrease in the storage amount in the feeder is measured, and as a result, when the storage amount in the feeder rises above the target value, the rotation speed of the first pump is decreased, and when the storage amount falls below the target value again, the rotation speed of the first pump is increased again. By repeating this control, the storage amount fluctuates up and down and gradually converges to the target value. In other words, because the supply amount is poor in response to the fluctuation of the discharge amount, the storage amount in the feeder becomes temporarily unstable.

[0008] In view of the above circumstances, the present invention provides a method and system for controlling the supply amount of a stored material, which is capable of controlling the supply amount with good tracking ability with respect to the discharge amount of the stored material. [Means for solving the problem]

[0009] The present invention relates to an equipment including a storage section for storing a stored material, a supply section for supplying the stored material to the storage section, and a discharge section for discharging the stored material from the storage section, The supply amount of the stored material in the supply unit or a value related thereto, and the discharge amount of the stored material in the discharge unit or a value related thereto. primary Define it as a function, and primary The function takes into account the correction value C according to the operating status of the equipment. In order to achieve this, a relational equation is set in which the discharge amount of the stored material in the discharge portion or a value related thereto is multiplied by the correction value C as a coefficient, the supply unit is a first pump that supplies a substance to the storage unit, The correction value is based on C=1, The correction value is set to a value C>1 under at least one of the following conditions: when the amount of the stored material is less than the target value, when the amount of the stored material is decreasing, and when the amount of the transported material in the first pump is small; This relates to a method for controlling the supply volume of stored material, characterized in that the correction value is set to a value of C<1 under at least one of the following conditions: when the amount of stored material is greater than a target value, when the amount of stored material is on the rise, and when the amount of material transported by the first pump is large.

[0011] In the method for controlling the supply amount of a stored material of the present invention, the function may be a linear function.

[0013] The present invention also relates to a system for controlling the supply amount of a stored material, characterized in that the system is configured to be able to execute the above-mentioned method for controlling the supply amount of a stored material. Effect of the Invention

[0014] According to the method and system for controlling the supply amount of a stored material of the present invention, it is possible to obtain the excellent effect of controlling the supply amount with good tracking ability with respect to the discharge amount of the stored material. [Brief description of the drawings]

[0015] [Figure 1] 1 is a schematic diagram showing an example of the configuration of a supply amount control system for a stored material according to an embodiment of the present invention. [Diagram 2] 11 is a graph showing an example of a relationship between a value related to a supply amount and a value related to a discharge amount, and illustrating correction of a proportionality coefficient. [Diagram 3] 11 is a graph showing an example of fluctuations in supply amount and storage amount relative to fluctuations in discharge amount assumed when control according to the present invention is performed. [Figure 4] 11 is a graph showing an example of fluctuations in supply amount and storage amount with respect to fluctuations in discharge amount assumed when control is performed by a conventional method, as a reference example of the present invention. [Diagram 5] 11 is a graph showing the variation in supply amount and storage amount with respect to the variation in discharge amount observed when control according to the present invention is implemented. [Figure 6] 1 is a flowchart illustrating an example of the procedure of a method for controlling the supply amount of stored material according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.

[0017] FIG. 1 shows an example of the configuration of a system capable of implementing the method for controlling the supply amount of a stored material of the present invention, and assumes the case where the present invention is applied to a sludge treatment facility. In a storage tank 1, a dehydrated cake D is stored as a stored material, and the dehydrated cake D in the storage tank 1 is transferred to a feeder 2 as a storage section for temporarily storing the dehydrated cake D, and then fed into an incinerator 3. A first pump 4 as a feed section and a second pump 5 as a discharge section are provided between the storage tank 1 and the feeder 2, and between the feeder 2 and the incinerator 3, respectively, and the dehydrated cake D is supplied from the storage tank 1 to the feeder 2 by the first pump 4, and is discharged from the feeder 2 by the second pump 5 as a discharge section, and fed into the incinerator 3. The first pump 4 is, for example, a screw pump, and the second pump 5 is, for example, a single-shaft eccentric pump.

[0018] The operation of the first pump 4, the second pump 5, and the incinerator 3 is controlled by a control unit 6. The control unit 6 is a device that monitors and controls the operation of each part of the facility, and controls the on / off and rotation speed of the first and second pumps 4, 5 by inputting operation signals to the motors 4a, 5a of the first and second pumps 4, 5. In addition, signals indicating the rotation speed are input to the control unit 6 from the motors 4a, 5a at any time.

[0019] The feeder 2 is provided with a level meter 7 as a storage amount measuring unit that measures the storage amount of the dehydrated cake D stored therein. The storage amount measuring unit (level meter) 7 is, for example, an ultrasonic distance sensor. The measured storage amount of the dehydrated cake D is inputted from the level meter 7 to the control unit 6 as a measurement signal. Note that any device may be adopted as the storage amount measuring unit or level meter as long as it is a device capable of measuring the storage amount of the dehydrated cake D. The level meter may be, for example, a laser type in addition to an ultrasonic type. In the case of a level meter, the storage amount is measured as a height, but a device other than a level meter may be used as the storage amount measuring unit, and the storage amount may be measured as, for example, a weight or a volume.

[0020] The storage tank 1 is provided with a moisture content meter 8 as a property measuring unit for measuring the property of the dehydrated cake D supplied from the first pump 4 to the feeder 2. The connection between the storage tank 1 and the first pump 4 is provided with a load cell 9 as a weight measuring unit for measuring the weight of the dehydrated cake D in the storage tank 1 to be added to the inlet of the first pump 4. The measured values ​​of the moisture content meter 8 and the load cell 9 are input to the control unit 6 as measurement signals. These values ​​are used to control the supply amount of the dehydrated cake D, which will be described later, as values ​​that may affect the supply amount. Note that, as the property measuring unit and the weight measuring unit, various devices other than the moisture content meter and the load cell may be used as long as the property and weight of the dehydrated cake D can be appropriately measured. For example, a viscometer may be used instead of the moisture content meter to measure the viscosity as a property of the dehydrated cake D.

[0021] The greatest feature of the present invention is, as described below, to control the supply amount of the stored material D in the supply unit (first pump) 4 according to the discharge amount of the stored material D in the discharge unit (second pump) 5 in order to keep the amount of the stored material (dehydrated cake D) in the storage unit (feeder) 2 close to a target value, and more specifically, to define the supply amount of the stored material by the supply unit 4 or a value related thereto (e.g., the rotation speed of the first pump 4 or the output of the motor 4a) as a function of the discharge amount by the discharge unit 5 or a value related thereto (e.g., the rotation speed of the second pump 5 or the output of the motor 5a). In other words, the supply amount is directly correlated with the discharge amount rather than being controlled by feedback of the stored amount, and the largest factor to be considered in determining the supply amount is the discharge amount rather than the stored amount.

[0022] Of course, the variables of the function defining the supply amount may include not only the supply amount but also the stored amount, and may also include various other values ​​that may affect the stored amount or the supply amount. In this embodiment, the supply amount is corrected to a more appropriate value according to the operating conditions by taking into account the properties (values ​​measured by the property measuring section (moisture content meter 8)) of the dehydrated cake D, which is the stored matter, and the weight (values ​​measured by the weight measuring section (load cell 9)) of the dehydrated cake D at the inlet of the first pump 4 when calculating the rotation speed of the first pump 4, and the stored amount is accurately controlled to be kept close to the target value.

[0023] In this way, by defining the supply amount or a value related thereto in advance as an appropriate function, the supply amount can be appropriately calculated by simple calculation processing when control is executed.

[0024] A specific control method will be described. In the case of the sludge treatment facility described above, in order to keep the amount of dehydrated cake D stored in the feeder 2 constant, the amount of dehydrated cake D supplied by the first pump 4, which is the supply section, can be controlled to be equal to the amount discharged by the second pump 5, which is the discharge section. Therefore, a value related to the amount of dehydrated cake D supplied (the rotation speed of the first pump 4) is defined as a function of a value related to the discharge amount (the rotation speed of the second pump 5). In the case of the example shown here, it is sufficient to define this function as a simple linear proportional equation as follows, and an appropriate supply amount according to the discharge amount can be easily calculated using such a calculation equation. (Rotational speed of first pump 4)=A×C×(Rotational speed of second pump 5)

[0025] In the above formula, A is a preset coefficient, and can be determined as a design value such that the supply amount of dehydrated cake D by the first pump 4 is equal to the discharge amount of dehydrated cake D by the second pump 5, taking into consideration, for example, the design relationship between the rotation speed and the conveyance amount of the first pump 4 and the design relationship between the rotation speed and the conveyance amount of the second pump 5. In other words, by operating the first pump 4 with A as the proportionality coefficient of the rotation speed of the first pump 4 to the rotation speed of the second pump 5, the supply amount and discharge amount to the feeder 2 are balanced, and the amount of dehydrated cake D stored can be kept constant.

[0026] However, depending on the actual operating conditions, the first and second pumps 4 and 5 may not match each other just by making the rotational speeds of the pumps proportional to a fixed coefficient. For example, if the first pump 4 is a screw pump and the second pump 5 is a single-shaft eccentric pump, the second pump 5, which is a single-shaft eccentric pump, can transport the amount of dehydrated cake D that is almost proportional to the rotational speed, but the first pump 4, which is a screw pump, may have a variable amount of dehydrated cake D transported per rotational speed depending on the amount and properties of the dehydrated cake D stored in the storage tank 1. For example, when a large amount of dehydrated cake D is stored in the storage tank 1, a large amount of dehydrated cake D is pushed into the first pump 4 by its own weight, so that the transport amount is larger even if the rotational speed is the same, and the supply amount to the storage section (feeder 2) is larger than when the amount of dehydrated cake D stored in the storage tank 1 is small. Also, if the dehydrated cake D is hard, it is difficult for the first pump 4 to cut it out, so the transport amount is smaller, and if the dehydrated cake D is soft, the transport amount is larger.

[0027] Therefore, in this embodiment, a variable C is set on the right side of the above formula as a correction value to be taken into account depending on the operating conditions of the equipment, thereby allowing control to be performed in accordance with the operating conditions at each time. This correction value C is calculated using an appropriate control method such as fuzzy control, PID control, logic control, etc., with the measured values ​​of the property measuring section (moisture content meter 8) and weight measuring section (load cell 9) and the amount of dehydrated cake D stored in the storage section (feeder) 2 as variables (note that the calculation method of the correction value C is not limited to these, and other control methods and calculation methods may also be used as appropriate).

[0028] In addition, the amount of dehydrated cake D stored in the feeder 2 may also be used as a variable in calculating the correction value C. For example, when the stored amount is less than the target value or is on a decreasing trend, the correction value C is set to a larger value, and when the stored amount is more than the target value or is on an increasing trend, the correction value C is set to a smaller value, thereby further improving the tracking ability of the control.

[0029] In actual operation, the supply amount itself, the rotation speed and output of the motor 4a, etc. may be used instead of the rotation speed of the first pump 4 as a value related to the supply amount, and the discharge amount itself, the rotation speed and output of the motor 5a, etc. may be used instead of the rotation speed of the second pump 5 as a value related to the discharge amount. In measuring the discharge amount, for example, a flow meter (not shown) is provided downstream of the second pump 5, and the measured value can be obtained as the discharge amount. In addition, the numerical values ​​used as the "value related to the supply amount" and the "value related to the discharge amount" can be appropriately set other than those described here.

[0030] In addition, other values ​​may be used as variables in place of or in addition to the above-mentioned values ​​(the properties, weight, and storage amount of the dehydrated cake D) in calculating the correction value C. For example, other sensors (not shown) may be provided and their measured values ​​may be used as variables.

[0031] 2 shows an example of a proportional relationship when controlling a value related to the supply amount (the rotation speed of the first pump 4) as a proportional value to a value related to the discharge amount (the rotation speed of the second pump 5) as described above. When C=1, control is performed according to the relationship shown by the solid line in the figure (proportionality coefficient=A). When the amount of dehydrated cake D stored in the feeder 2 is less than the target value, when the amount of storage is on a decreasing trend, when the dehydrated cake D is hard and the amount of transport by the first pump 4 is small, when the weight added to the first pump 4 by the dehydrated cake D in the storage tank 1 is small and the amount of transport by the first pump 4 is small, etc., the correction value C is set to a value greater than 1 (see the dashed line in the figure). On the other hand, when the amount of dehydrated cake D stored in the feeder 2 is greater than the target value, when the amount of storage is increasing, when the dehydrated cake D is soft and the amount of conveyance by the first pump 4 is large, or when the weight of the dehydrated cake D in the storage tank 1 applied to the first pump 4 is large and the amount of conveyance by the first pump 4 is large, the correction value C is set to a value smaller than 1 (see the dashed line in the figure). Note that the specific correction value C is appropriately determined by fuzzy control or the like as described above. Also, the correction value C may be appropriately set to an upper limit value and a lower limit value, or the upper limit value and the lower limit value may be made variable.

[0032] When the supply amount is controlled to vary in accordance with the discharge amount in this manner, the supply amount can be controlled with good tracking to the variation in the discharge amount, for example as shown in Fig. 3. In Fig. 3, it is assumed that the discharge amount of the second pump 5 increases rapidly from time t1 to t2, and then decreases rapidly from time t3 to t4 (see the upper part). By changing the supply amount in accordance with this variation in the discharge amount (see the middle part), it is possible to accurately maintain the storage amount close to the target value even if the discharge amount varies (see the lower part).

[0033] In contrast, in conventional control in which the supply amount varies according to the storage amount, the supply amount has low follow-up ability to the variation in the discharge amount. An example of the variation in the supply amount and the storage amount assumed in such a case is shown as a reference example in FIG. 4. In this reference example, when the discharge amount (upper row) increases from time t1 to t2, the storage amount (lower row) decreases first, and in response to this, control is performed to increase the supply amount (middle row). As a result, the storage amount increases beyond the target value, and in response to this, the supply amount is subsequently decreased. By repeating this, the storage amount gradually approaches the target value while fluctuating up and down. Similarly, from time t3 to t4 (when the discharge amount is decreasing), the storage amount converges to the target value while fluctuating greatly. In this way, in the conventional control method, it takes a long time for the storage amount to stabilize in response to the variation in the discharge amount.

[0034] 5 shows the results of actual measurements of the supply and storage volumes in response to the change in discharge volume in the above embodiment. In this actual operation, the second pump 5 is turned on at time t0, and then the discharge volume increases rapidly from time t5 to time t7, and then decreases rapidly from time t6 to time t7. After that, the discharge volume gradually increases (see the upper dashed line).

[0035] The supply amount of the first pump 4 quickly follows such fluctuations in the discharge amount, fluctuating while generally balancing with the discharge amount (see the solid line in the upper part). The storage amount of the feeder 2 is kept close to the target value after time t0 (see the lower part). Unlike the reference example shown in Figure 4, which once deviates significantly from the target value and then converges over time, the storage amount does not deviate significantly from the target value from the beginning, even if the discharge amount increases or decreases.

[0036] The procedure for executing the above control method in a system can be summarized in a flowchart such as that shown in FIG.

[0037] First, a target value for the amount of stored material (dehydrated cake D) in the storage section (feeder 2) is set (step S1). Next, a coefficient A is set to be used for controlling the supply amount of the stored material relative to the discharge amount (step S2). The actual value of the amount of stored material D in the storage section 2 is obtained from the level meter 7 (step S3), and other values ​​to be used for calculating the correction value C (in the above-mentioned embodiment, the measured values ​​of the moisture content meter 8 and the load cell 9) are obtained (step S4). The correction value C is calculated based on the values ​​obtained in steps S3 and S4 (step S5).

[0038] Once the value relating to the discharge rate (the rotation speed of the second pump 5) is obtained (step S6), it is multiplied by the coefficient A and the correction value C to calculate the value relating to the supply rate (the rotation speed of the first pump 4) (step S7). The first pump 4 is operated based on the value calculated here to control the supply rate (step S8). That is, the motor 4a is controlled so that the rotation speed of the first pump 4 becomes the value calculated in step S7. Returning to step S3, the subsequent steps are repeated.

[0039] The control method described above is merely an example. For example, when controlling the supply amount according to the discharge amount, the function to be set is not limited to the proportional formula as described above. The function can be set appropriately according to the actual situation of the equipment to be controlled. For example, a constant term or other variable term may be provided on the right side of the proportional formula, or a quadratic function, exponential function, or other various functions may be set. In addition, the procedure shown in FIG. 6 is also variable, and the order of steps may be changed appropriately, some steps may be omitted, or other steps may be added.

[0040] In addition, the stored material and equipment to which the control method is applied are not limited to the above-mentioned dehydrated cake and sludge treatment facilities. The present invention can be widely applied to equipment that includes a storage section for storing the stored material, a supply section for supplying the stored material to the storage section, and a discharge section for discharging the stored material from the storage section, when it is necessary to control the amount of the stored material in the storage section.

[0041] As described above, in the method for controlling the supply amount of the stored material of the present embodiment, in an equipment including a storage section (feeder) 2 for storing the stored material (dehydrated cake) D, a supply section (first pump) 4 for supplying the stored material D to the storage section 2, and a discharge section (second pump) 5 for discharging the stored material D from the storage section 2, the supply amount of the stored material D in the supply section 4 is controlled according to the discharge amount of the stored material D in the discharge section 5. In this way, the supply amount can be controlled with good tracking ability with respect to fluctuations in the discharge amount, and even if the discharge amount fluctuates, the stored amount can be accurately maintained near the target value.

[0042] In this embodiment, the supply amount of the stored material D in the supply unit 4 or a value related thereto is defined as a function of the discharge amount of the stored material D in the discharge unit 5 or a value related thereto. In this way, the supply amount can be appropriately calculated by a simple calculation process.

[0043] In this embodiment, the function is a linear function, which allows the supply amount to be calculated appropriately with simpler calculation processing.

[0044] In this embodiment, a correction value C according to the operating conditions of the equipment is added to the function. In this way, control suited to the operating conditions at each time can be performed.

[0045] Furthermore, since the system for controlling the supply amount of a stored material according to the present embodiment is configured to be able to execute the method for controlling the supply amount of a stored material described above, the system can achieve the above-mentioned advantageous effects.

[0046] Therefore, according to the embodiment described above, the supply amount can be controlled with good follow-up to the discharge amount of the stored matter.

[0047] Incidentally, the method and system for controlling the supply amount of stored material of the present invention are not limited to the above-mentioned embodiment, and it goes without saying that various modifications can be made within the scope of the present invention without departing from the gist of the present invention. [Explanation of symbols]

[0048] 2 Storage section (feeder) 4 Supply section (first pump) 5 Supply section (second pump) D Retention material (dehydrated cake)

Claims

1. In an equipment including a storage section for storing a stored material, a supply section for supplying the stored material to the storage section, and a discharge section for discharging the stored material from the storage section, The supply amount of the stored material in the supply section or a value related thereto is defined as a linear function of the discharge amount of the stored material in the discharge section or a value related thereto, and a relational equation is set in which the discharge amount of the stored material in the discharge section or a value related thereto is multiplied by the correction value C as a coefficient so that the linear function takes into account a correction value C according to the operating status of the equipment; the supply unit is a first pump that supplies a substance to the storage unit, The correction value is based on C=1, The correction value is set to a value of C>1 under at least one of the following conditions: when the amount of the stored material is less than the target value, when the amount of the stored material is decreasing, and when the amount of the transported material in the first pump is small; A method for controlling the supply volume of stored material, characterized in that the correction value is set to a value C<1 under at least one of the following conditions: when the amount of stored material is greater than a target value, when the amount of stored material is tending to increase, and when the amount of material transported by the first pump is large.

2. The function is a linear function. The method for controlling the supply amount of a stored material according to claim 1 .

3. A system for controlling the supply amount of stored material, configured to be capable of executing the method for controlling the supply amount of stored material according to claim 1 or 2.

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