JP7838430B2 - Switching control method for silos and silo discharge - Google Patents

Description

This invention relates to a method for controlling the switching of silos and silo discharge.

Conventionally, a technique has been known for measuring the height of granular material (powder) stored in a silo (powder supply device) and controlling the silo based on that height. Patent Document 1 is an example of this type of technique. Patent Document 1 describes a powder supply device comprising a main body having a storage space for containing powder and an opening for discharging the powder, and a plurality of powder supply units that supply powder into the storage space from above. The technique describes adjusting the amount of powder supplied from the plurality of powder supply units so that the average storage height of the powder in the storage space is 60% or more of the height of the storage space, and the variation in the storage height of the powder in the storage space is within ±20%.

Japanese Patent Publication No. 2019-89584

Incidentally, one method for measuring the height of the stored powder (granular material) deposits in silos (powder supply devices) involves emitting waves such as microwaves, reflecting them off the deposits, and receiving the reflected waves. However, with this method, the accuracy of the measurement can vary depending on the surface shape of the deposits, potentially making stable silo control impossible.

The present invention aims to provide a silo and a silo discharge switching control method that enables more stable silo control.

(1) The silo according to the present invention comprises a plurality of hoppers, each having a storage section capable of storing powdered or granular material, a discharge section having a discharge opening at the bottom of the storage section and capable of discharging the powdered or granular material stored in the storage section by opening and closing the discharge opening, and a height measuring section provided approximately directly above the discharge opening for measuring the height of the accumulated powdered or granular material stored in the storage section; and a control unit capable of controlling the opening and closing operation of the discharge sections of the plurality of hoppers. The height measuring section comprises a transmitting unit capable of emitting waves and a receiving unit capable of receiving waves. The height of the accumulated material is measured by the wave emitted by the transmitting unit being reflected by the accumulated material and received by the receiving unit. The control unit, when the difference between the multiple measurement values of two adjacent hoppers among the multiple measurement values measured by the plurality of height measuring sections exceeds a predetermined threshold, performs at least one of the following operations: opening the discharge section of the hopper with the larger measurement value, and closing the discharge section of the hopper with the smaller measurement value.

(1) The silo allows for more stable silo control.

(2) In the silo according to the present invention, it is preferable that the control unit, when the difference between the multiple measurement values of two adjacent hoppers among the multiple measurement values measured by the multiple height measuring units exceeds the predetermined threshold, performs the operation of opening the discharge outlet of the hopper with the larger measurement value and closing the discharge outlet of the hopper with the smaller measurement value.

In silo (2), the shape of the granular material deposits can change more rapidly to a shape that is less prone to a decrease in the level gauge's received signal intensity, thus enabling more stable silo control.

(3) In the silo according to the present invention, the wave is preferably a microwave, and the height measuring unit is preferably a microwave level meter that emits microwaves toward the sediment and measures the height of the sediment by receiving the microwaves reflected by the sediment.

(3) The silo is easy to install and maintain, allowing for more cost-effective and stable silo control.

(4) In the silo according to the present invention, the granular material is preferably limestone.

The silo described in (4) can be applied to large-scale silos, such as those used for storing limestone, and stable silo control can mitigate significant losses due to silo shutdowns.

(5) The silo outlet switching control method according to the present invention comprises a plurality of hoppers having a storage section capable of storing powdered or granular material, an outlet opening at the bottom of the storage section and capable of opening and closing the outlet to discharge the powdered or granular material stored in the storage section, a height measuring section provided approximately directly above the outlet and measuring the height of the accumulated powdered or granular material stored in the storage section, and a control unit capable of controlling the opening and closing operation of the outlets of the plurality of hoppers, wherein the height measuring section has a transmitting section capable of transmitting waves and a receiving section capable of receiving waves, and the waves transmitted by the transmitting section are reflected by the accumulated material and received by the receiving section A method for controlling the switching of silo discharge, which is performed by a silo that measures the height of the accumulated material, includes: a measurement value acquisition step of acquiring measurement values measured by the height measuring units in a plurality of hoppers; and a discharge outlet switching step of performing at least one of the following actions when the difference between the measurement values of two adjacent hoppers among the plurality of measurement values measured by the plurality of height measuring units exceeds a predetermined threshold: opening the discharge outlet of the hopper with the larger measurement value, and closing the discharge outlet of the hopper with the smaller measurement value.

(5) The silo discharge switching control method allows for more stable and accurate height measurement of the stored powder and granular material.

This is a schematic diagram showing an example of a limestone receiving and transporting system S according to one embodiment of the present invention. This is a schematic diagram showing an example of a silo related to one embodiment of the present invention. A block diagram showing the hardware configuration of a silo related to one embodiment of the present invention. This is a schematic diagram of a silo according to one embodiment of the present invention, in which adjacent hoppers dispense equally. This is a schematic diagram of a silo according to one embodiment of the present invention, in which only one of the adjacent hoppers is dispensing. This is a flowchart illustrating an example of outlet switching control performed by a silo according to one embodiment of the present invention.

Below, an example of a limestone receiving and conveying system S equipped with a silo 1 according to one embodiment of the present invention will be described with reference to Figure 1. The limestone receiving and conveying system S according to one embodiment of the present invention is a system that receives limestone as a granular material and conveys it to a slurry tank located downstream. The arrows in Figure 1 indicate the direction in which the limestone is conveyed. Although the granular material according to this embodiment will be described as limestone below, it is not limited to limestone, and the granular material may be other granular materials besides limestone.

The limestone receiving and transporting system S comprises a receiving and transporting section F, a silo 1 according to one embodiment of the present invention, an auxiliary silo 2, and a dispensing and transporting section C.

The receiving and transporting section F is configured to receive limestone transported by sea and transport it to silo 1. The receiving and transporting section F is composed of, for example, a conveyor.

Silo 1 is configured to store limestone brought in from the receiving and conveying unit F and to dispense the required amount of limestone from the stored limestone. Silo 1 has four hoppers 10a, 10b, 10c, and 10d. In Figure 1, the four hoppers 10a, 10b, 10c, and 10d of Silo 1 are shown side by side for convenience, but in reality, hoppers 10c and 10d are located behind hoppers 10a and 10b when viewed from the front of the page in Figure 1. Similarly, the dispensing conveyors C1 and C2, which will be described later, are also shown side by side for convenience, but in reality, dispensing conveyor C2 is located behind dispensing conveyor C1 when viewed from the front of the page in Figure 1. Further details about Silo 1 will be described later.

Auxiliary silo 2 is configured to store limestone that is fed in from the vertical conveyor C4 (described later) and then into a slurry tank (not shown) located downstream. The slurry tank (not shown) is configured to process the limestone discharged from auxiliary silo 2 into a slurry and feed it into a desulfurization unit (not shown) located downstream.

The discharge and transport section C is configured to transport limestone discharged from silo 1 to auxiliary silo 2. The discharge and transport section C includes a discharge conveyor C1, a discharge conveyor C2, a collection conveyor C3, and a vertical transport conveyor C4.

Discharge conveyor C1 transports limestone discharged from the two hoppers 10a and 10b on the front side of silo 1 and feeds it into the collection conveyor C3, which will be described later. Discharge conveyor C2 transports limestone discharged from the two hoppers 10c and 10d on the back side of silo 1 and feeds it into the collection conveyor C3, which will be described later. Collection conveyor C3 transports the limestone fed in from discharge conveyors C1 and C2 and feeds it into the vertical transport conveyor C4, which will be described later. Vertical transport conveyor C4 transports the limestone fed in from collection conveyor C3 and feeds it into auxiliary silo 2.

<Silo>
Next, a silo 1 according to one embodiment of the present invention will be described with reference to Figures 2 and 3. The silo 1 has the four hoppers 10a to 10d described above, an inlet 20, and a control device 30. Each of the four hoppers 10a to 10d has a storage section 100a to 100d, a slide gate 110a to 110d as a discharge section, and a height measuring section 120a to 120d. In this embodiment, unless otherwise distinguished, the hoppers 10a to 10d, storage sections 100a to 100d, slide gates 110a to 110d, and height measuring sections 120a to 120d will be described as hopper 10, storage section 100, slide gate 110, and height measuring section 120, respectively.

The storage unit 100 is a container capable of storing limestone in powder form. The slide gate 110 has a discharge port 111 opening at the bottom of the hopper 10, and a slide gate valve 112 (shown in Figure 3) that opens and closes the discharge port 111 to discharge the limestone stored in the storage unit 100. The slide gate valve 112 is a valve that can move between an open position (opening the discharge port 111) and a closed position (closing the discharge port 111).

The height measuring unit 120 is located approximately directly above the discharge outlet 111. The height measuring unit 120 is configured to measure the height of the limestone deposited and stored in the storage unit 100. The height measuring unit 120 includes a transmitter 121 capable of emitting waves and a receiver 122 capable of receiving waves. The height measuring unit 120 measures the height of the deposit by receiving waves emitted by the transmitter 121, which are reflected by the limestone deposit and received by the receiver 122.

The wave emitted by the transmitter 121 in this embodiment is preferably, for example, a microwave MW. In this case, the transmitter 121 of the height measuring unit 120 emits microwave MW towards the sediment, and the receiver 122 of the height measuring unit 120 receives the microwave MW reflected from the sediment to measure the height of the sediment. In this case, the height measuring unit 120 is, for example, a microwave level meter.

The input port 20 is an opening for loading limestone transported from the receiving and transporting section F into the silo 1, and is located approximately in the center of the multiple hoppers 10 in a plan view of the upper part of the silo 1.

The control device 30 is configured to control various operations of the silo 1. The control device 30 includes a processor (not shown), and the control of various operations is achieved by the processor executing calculations. Note that the control of various operations of the silo 1 may also be achieved by a control circuit.

As shown in Figure 3, the control device 30 is communicatively connected to the slide gate valve 112 of the slide gate 110, and to the transmitter 121 and receiver 122 of the height measuring unit 120. The control device 30 can control the operation of the slide gate valve 112 based on the measurement results of the height measuring unit 120.

<Silo dispensing operation>
Next, the discharge operation in silo 1 according to this embodiment will be explained using Figures 4 and 5. In silo 1 according to this embodiment, the height measuring unit 120 constantly measures the height of the limestone L deposit in the storage unit 100, and the discharge outlet is switched based on the measurement result. As shown in Figure 4, the transmitter 121 of the height measuring unit 120 irradiates microwaves MW toward the center of the storage unit 100 in a plan view.

As shown in Figure 4, the four storage sections 100a to 100d are positioned so that their respective centers are approximately directly above the corresponding outlets 111a to 111d. As the limestone L deposit is discharged, the amount of limestone L decreases from the position approximately directly above the outlet 111 in a plan view. Therefore, the surface LS of the limestone L deposit becomes concave from the part corresponding to the outlet 111 in a plan view, forming a mortar shape. In other words, the surface LS of the limestone L deposit takes on a mortar shape centered on the central part of the storage section 100.

The height measuring unit 120 measures height by receiving microwaves MW that are reflected from the object being measured, as described above, and then received by the receiving unit 122. Therefore, as the material is dispensed, the portion directly above the dispenser outlet 111 in a plan view becomes concave, and as shown in Figure 5, the angle of the bowl-shaped slope with respect to the horizontal plane increases. When this angle exceeds a predetermined angle, the proportion of microwaves MW reflected towards the height measuring unit 120 decreases, resulting in a decrease in reception strength. The predetermined angle is, for example, 40 degrees, as shown in Figure 5.

On the other hand, the central part of the mortar-shaped section has a small slope even when it is indented by dispensing. Therefore, when microwave MW is irradiated onto the central part of the mortar-shaped section, the proportion of microwave MW reflected towards the height measuring section 120 increases. Accordingly, in this embodiment, the height measuring section 120 is positioned such that the transmitter 121 and receiver 122 are located approximately directly above the central part of the mortar-shaped section, i.e., directly above the dispensing outlet 111.

Incidentally, in the silo 1 according to this embodiment, if the amount of limestone L required in a subsequent process is small, discharge may be performed from only some of the multiple hoppers 10. For example, as shown in Figure 5, if discharge is performed only from hopper 10b, the limestone L is discharged from the discharge port 111b of hopper 10b, and the surface LSb of the limestone L deposit in hopper 10b becomes concave. Then, the bowl-shaped depression caused by the discharge from hopper 10b extends to the surface LSa of the limestone L deposit in the adjacent hopper 10a.

In other words, the microwave MW emitted from the height measuring unit 120a of hopper 10a, which is adjacent to hopper 10b where dispensing is taking place, is directed towards the bowl-shaped slope created by the dispensing from hopper 10b. In the example shown in Figure 5, the inclination angle of the limestone L deposit in hopper 10b becomes a predetermined angle of 40 degrees.

As described above, when the inclination of the surface LS of the sediment irradiated with microwaves MW is small, the proportion of microwaves MW reflected towards the height measuring unit 120 is large. However, in Figure 5, because the inclination angle of the surface LSa is greater than a predetermined angle, the proportion of microwaves MW reflected from the surface LS of the sediment and directed towards the receiving unit 122a of the height measuring unit 120a becomes small.

Therefore, the way the microwaves MW emitted from the transmitter 121 of the height measuring unit 120 are reflected may change, potentially making accurate height measurement impossible. Specifically, in the state shown in Figure 5, the reception intensity of the receiver 122a of the height measuring unit 120a may decrease, potentially making measurement impossible.

Therefore, in the silo 1 according to one embodiment of the present invention, the control is such that when the difference in the measurement values of two adjacent hoppers 10 measured by the height measuring unit 120 exceeds a predetermined threshold, the discharge outlet is switched. For example, in the silo 1 according to this embodiment, as shown in Figure 5, in the two adjacent hoppers 10a and 10b, the difference between the measurement value measured by the height measuring unit 120a and the measurement value measured by the height measuring unit 120b is 1.1 m, which exceeds the predetermined threshold of 1.0 m. In this case, the control is such that the slide gate 110a of the hopper 10a with the larger measurement value and higher deposit height is opened, and the slide gate 110b of the hopper 10b with the smaller measurement value and lower deposit height is closed.

Furthermore, the control of switching the discharge outlet is not limited to this; it is also possible to simply open the slide gate 110 of the hopper 10 with the higher sediment height, or simply close the slide gate 110 of the hopper 10 with the lower sediment height.

Furthermore, the predetermined threshold is set to a height such that the mortar-shaped structure formed on the surface LS of the sediment in the adjacent hopper 10 extends to the destination of the microwave MW emitted by the height measuring unit 120, as shown in Figure 5. The predetermined threshold is, for example, 1.0 m. However, the setting of the predetermined threshold is not limited to this and may include a margin of safety.

<Dispensing outlet switching control>
Next, the switching control performed by the silo 1 according to this embodiment will be explained using Figure 6. This control is executed when the control device 30 is instructed to start the switching control.

The control device 30 first opens the discharge port 111 at the slide gate 110 of a predetermined hopper 10 among the multiple hoppers 10, thereby initiating the discharge operation (step S10). Next, as a measurement value acquisition step, the control device 30 acquires height information of the limestone L deposits in all hoppers 10 (step S11). Then, it calculates the difference in limestone L deposit heights for all adjacent hopper combinations (step S12).

Next, it is determined whether any of the multiple measurement values measured by the multiple height measuring units 120 exceed a predetermined threshold when comparing adjacent hoppers 10 (step S13). If none of the multiple measurement values measured by the multiple height measuring units 120 exceed the predetermined threshold when comparing adjacent hoppers 10 (step S13: NO), the process proceeds to step S11, and the acquisition and determination of height information for the limestone L deposits in all hoppers 10 is continued.

On the other hand, if, among the multiple height measurement units 120, there is a difference between adjacent hoppers 10 that exceeds a predetermined threshold (step S13: YES), the control device 30, for each combination of hoppers 10 that exceeds the predetermined threshold, opens the slide gate 110 of the hopper 10 with the larger measurement and closes the slide gate 110 of the hopper 10 with the smaller measurement, thereby performing a discharge outlet switching step (step S14).

Next, the control device 30 checks whether the switching control stop operation has been performed (step S15). If the switching control stop operation has not been performed (step S15: NO), the control device 30 proceeds to step S11 and resumes acquiring and determining the height information of the limestone L deposits in all hoppers 10, switching the slide gates 110, etc. On the other hand, if the switching control stop operation has been performed (step S15: YES), the control device 30 terminates the switching control.

The silo system described above provides the following benefits: The limestone receiving and storage facility may be configured to discharge from multiple hoppers as a measure against blockage in the dead space within the sea transport receiving silo. Furthermore, depending on the specifications of the desulfurization equipment, the limestone receiving and storage facility may have only one inlet for the limestone slurry tank. Additionally, to prevent blockage in the lower hopper of the sea transport silo, the limestone receiving and storage facility may include an auxiliary silo for temporary storage between the sea transport receiving silo and the limestone slurry tank.

In these cases, the limestone receiving and storage facility is configured to supply limestone in the following order: for example, a sea-transport receiving silo with four hoppers, two discharge conveyors, one consolidation conveyor, one vertical conveyor, one auxiliary silo, one discharge conveyor, one limestone slurry tank, and a desulfurization facility.

Such limestone receiving and storage facilities incur significant investment and maintenance costs, and because the conveyors lack backup systems, there remains a risk of disruptions to limestone supply due to malfunctions.

In this case, a possible limestone receiving and storage facility could be configured to supply limestone in the following order: a sea-transport receiving silo with two hoppers, two discharge conveyors, a limestone slurry tank, and a desulfurization unit. This eliminates the need for auxiliary silos, reducing capital investment costs. Furthermore, the reduced number of pieces of equipment minimizes maintenance costs. Additionally, the presence of a backup system for the conveyors allows operation to continue even if one system experiences a supply disruption.

However, in the limestone receiving and storage facility with the above configuration, if discharge is continuously performed on one of the two hopper receiving silos, the tilt angle of the powder inside the silo increases, potentially leading to a decrease in reception strength and detection failure in microwave level measurements. Therefore, in silo 1 according to one embodiment of the present invention, alternating discharge conveyor operation is performed considering the powder angle, enabling more stable control of the silo operation without reducing the reception strength of the level meter.

In other words, the silo 1 according to this embodiment comprises a plurality of hoppers 10 having a storage section 100 capable of storing limestone L, a discharge port 111 opening at the bottom of the storage section 100, a slide gate 110 that can open and close the discharge port 111 to discharge the limestone L stored in the storage section 100, a height measuring section 120 provided approximately directly above the discharge port 111 to measure the height of the deposit of limestone L stored in the storage section 100, and a control device 30 capable of controlling the opening and closing operation of the slide gates 110 of the plurality of hoppers 10, wherein the height measuring section 120 has a transmitter 121 capable of emitting microwaves MW and a receiver for microwaves MW. The system includes a receivable receiving unit 122. Microwaves MW transmitted by the transmitting unit 121 are reflected by the limestone deposit L and received by the receiving unit 122, thereby measuring the height of the limestone deposit L. The control device 30, when the difference between the multiple height measurements taken by the multiple height measuring units 120 between two adjacent hoppers 10 exceeds a predetermined threshold, performs at least one of the following actions: opening the slide gate 110 of the hopper 10 with the larger measurement value, and closing the slide gate 110 of the hopper 10 with the smaller measurement value.

This provides a silo and silo discharge switching control method that enables more stable silo control.

[Variations]
In this embodiment, the silo 1 was configured to determine whether or not to switch based on whether the height difference exceeded a predetermined threshold, but this is not limited to this configuration. For example, the time required for the height difference to exceed the predetermined threshold may be measured in advance, and the decision to switch based on that time may be made. This modified configuration will be described below. Note that configurations that are common or similar to those already described may be given the same name, and detailed explanations may be omitted.

The switching time for limestone receiving silo discharge was examined under the following conditions.
(1) Maximum payout: 11 t/h
(2) Limestone specific gravity 1.0t/m ³
(3) Silo inner diameter 15.7 m
(4) Others The change in the level (height) of limestone inside the silo due to discharge will be calculated only on the side of the discharge system (half of the entire silo).

The level difference of limestone inside the silo caused by continuous discharge from only one system was calculated and evaluated over time.
(1) The rate of decrease in the limestone level inside the silo per hour was calculated. First, the area inside the silo in this embodiment was calculated as shown in equation (1).

... (1)
Next, the amount of level decrease per hour at maximum payout was calculated as shown in equation (2).

... (2)
Next, the amount of level decrease per hour during normal payout was calculated as shown in equation (3).

... (3)
Based on equations (1) to (3), the level reduction during maximum and normal payouts relative to the operating time was calculated and summarized in Table 1.

In Table 1, the evaluation was based on the assumption that no decrease in the received signal strength of the level meter (height measuring unit) occurs in the range of 1.0 m or more. Specifically, if the level drop range is 1.0 m or less, it is judged as "○" because no decrease in the received signal strength of the level meter occurs; if the level drop range is 1.0 m or more, it is judged as "△" because a decrease in the received signal strength of the level meter occurs; and if the level drop range is 19 m or more, it is judged as "－" because it is outside the silo height limit.

Table 1 shows that, during maximum discharge, the level drop exceeds 1.0 m when the operating time exceeds 9 hours; therefore, the discharge port should be switched when the operating time exceeds 8 hours. Similarly, during normal discharge, the level drop exceeds 1.0 m when the operating time exceeds 22 hours; therefore, the discharge port should be switched when the operating time exceeds 21 hours. Thus, since the discharge switching control can be performed based on a pre-calculated switching time, the control process can be simplified. Note that the switching time is not limited to the above-described modifications; it may also be a time corresponding to the silo's specifications, such as the silo's maximum discharge volume, normal discharge volume, the specific gravity of the stored limestone, and the silo's inner diameter. Furthermore, the switching time may include a margin of safety.

[Variations]
Furthermore, the present invention is not limited to the embodiments described above, and any modifications, improvements, etc., that can achieve the objectives of the present invention are included within the scope of the present invention.

L: Powder/granular material; MW: Microwave (wave motion)
S11 Measurement value acquisition step S14 Dispensing outlet switching step 10 Hopper 30 Control device (control unit)
100 Storage section 110 Slide gate (dispensing section)
111 Discharge outlet 120 Height measuring unit 121 Transmitting unit 122 Receiving unit

Claims (5)

A plurality of hoppers, each having a storage section capable of storing powdered or granular material, a discharge section having a discharge outlet opening at the bottom of the storage section and capable of discharging the powdered or granular material stored in the storage section by opening and closing the discharge outlet, and a height measuring section provided directly above the discharge outlet for measuring the height of the accumulated powdered or granular material stored in the storage section.
The system comprises a control unit capable of controlling the opening and closing operation of the dispensing sections of multiple hoppers,
The height measuring unit comprises a transmitting unit capable of emitting waves and a receiving unit capable of receiving waves, and measures the height of the sediment by having the waves emitted by the transmitting unit reflected by the sediment and received by the receiving unit.
The control unit performs at least one of the following actions when the difference between two adjacent hoppers measured by a plurality of height measuring units exceeds a predetermined threshold: opening the dispensing section of the hopper with the larger measurement value, and closing the dispensing section of the hopper with the smaller measurement value. The silo according to claim 1, wherein the control unit, when the difference between two adjacent hopper measurements among the multiple height measurement units exceeds a predetermined threshold, performs the following operations: opening the outlet of the hopper with the larger measurement value and closing the outlet of the hopper with the smaller measurement value. The aforementioned wave is a microwave,
The silo according to claim 1 or 2, wherein the height measuring unit is a microwave level meter that measures the height of the sediment by transmitting microwaves toward the sediment and receiving microwaves reflected by the sediment. The silo according to claim 1 or 2, wherein the granular material is limestone. A plurality of hoppers, each having a storage section capable of storing powdered or granular material, a discharge section having a discharge outlet opening at the bottom of the storage section and capable of discharging the powdered or granular material stored in the storage section by opening and closing the discharge outlet, and a height measuring section provided directly above the discharge outlet for measuring the height of the accumulated powdered or granular material stored in the storage section.
The system comprises a control unit capable of controlling the opening and closing operation of the discharge outlets of multiple hoppers,
The height measuring unit comprises a transmitting unit capable of transmitting waves and a receiving unit capable of receiving waves, and the height of the sediment is measured by the wave transmitted by the transmitting unit being reflected by the sediment and received by the receiving unit, and the method for controlling the switching of silo discharge to be performed by the silo,
A measurement value acquisition step in which the height measuring unit in a plurality of hoppers acquires the measurement value measured by the height measuring unit,
A silo discharge switching control method, comprising: a discharge port switching step, which, when the difference between two adjacent hoppers among a plurality of height measurements taken by a plurality of height measuring units exceeds a predetermined threshold, performs at least one of the following: opening the discharge port of the hopper with the larger measurement value, and closing the discharge port of the hopper with the smaller measurement value.