JP7487621B2 - Air-floated belt conveyor - Google Patents

Description

The present invention relates to a belt conveyor capable of continuously transporting bulk materials such as coal, limestone, and grain, and a method for operating the same.

The goods are transported by conveyor belt and stored in storage tanks such as silos.
Among belt conveyors, air-floating conveyors, which transport materials by floating the belt with air, are widely used due to their advantages over roller-type conveyors, such as lower noise and less energy consumption, and no risk of dust generation due to their completely sealed structure.
In recent years, air-floating belt conveyors equipped with a reversing device that reverses the belt on the return side have been adopted in order to reduce the labor required for cleaning.

An air-floating belt conveyor device is configured such that a conveyor belt is passed through a cylindrical trough pipe between a drive pulley (head pulley) and a driven pulley (tail pulley) that are arranged to rotate freely, and is looped around in an endless manner.
The transported material received by the air floating conveyor on the carrier side belt from an unloader facility or the like is transported toward the discharge section of the conveyor and passed through a hopper to a storage tank such as a silo, or transferred to the next transport device.
A curved trough pipe extends from the carrier side belt and the return side belt, and air is supplied from the bottom to the top side of the trough pipe to float each belt and make the belts run in the axial direction of the cylindrical pipe.
In a typical structure of an air floating conveyor, the cylindrical tube containing the belt on the carrier side is called the upper trough pipe, and the cylindrical tube containing the belt on the return side is called the lower trough pipe, and the upper trough pipe and the lower trough pipe are arranged at a specified distance above and below.

Typically, compressed air is supplied uniformly from multiple air supply ports spaced equally along the length of the trough pipe of an air floating conveyor, so the amount and pressure of air supplied to the multiple air supply ports is uniform and constant.
However, in an air-floating conveyor, the unbalanced load caused by a local increase or decrease in the amount of material received from the inlet moves with the material being conveyed, making it difficult to obtain an optimal gap between the belt and the trough tube over the entire length of the belt.

In addition, if the amount of material received from the inlet varies, the load increases locally, causing contact between the belt and the bottom of the trough pipe (or the inner wall of the trough pipe) and creating resistance to transport, which can lead to problems such as damage to the belt or equipment stoppage. Furthermore, there is also the problem of noise caused by the sliding noise generated by the belt coming into contact with the bottom of the trough pipe (or the inner wall of the trough pipe).

In consideration of these problems, as disclosed in Prior Art Document 1, for example, there is a configuration in which the amount of levitation of the belt of an air-levitation belt conveyor is detected, and the amount of levitation of the belt is controlled to an optimal value even if the load of transported goods on the belt fluctuates, thereby maintaining the supply pressure and enabling stable operation.

In addition, when air-floating conveyors transport flammable materials such as coal, fires can occur inside the trough pipe due to frictional heat or dust generation, and so fire extinguishing equipment is generally installed using a water sprinkler system. However, when using existing water sprinkler systems in the event of a fire, the trough pipe becomes flooded during the fire-fighting operation, and recovery work is time-consuming and costly.

In consideration of this problem, as disclosed in Prior Art Document 2, there is a technology that, in the event of a fire, partition plates are installed inside the conveyor trough pipe to divide it into sections in the longitudinal direction, and inert gas is supplied into the sections to prevent the fire from spreading and extinguish the fire, thereby reducing the amount of recovery work required after a fire breaks out.

Japanese Patent Application Laid-Open No. 8-268524 JP 2016-124633 A

However, when the transported material is a material with high moisture retention, such as coal or woody biomass, the materials tend to adhere to each other and form clumps, which causes uneven movement on the belt and affects stable transport. Therefore, stable transport is difficult to achieve simply by controlling the load fluctuations of the transported material, as in Prior Art 1.

In addition, as in Prior Art Document 2, a structure in which new partitions are installed across the entire conveyor as a means of extinguishing dust fires within the trough pipe requires major design changes from the existing equipment. Furthermore, this structure is a technology that reduces the amount of recovery work required after a fire breaks out, but is not a technology that prevents fires, so interruptions to transport and loss of transported goods due to fire breaks out remain problems.

The present invention aims to provide an air-floating belt conveyor that provides stable transport unaffected by the amount or physical properties of the transported material and prevents fires inside the trough pipe.

As a first means for solving the above problems, the present invention provides
The object of the present invention is to provide an air floating belt conveyor having an endless belt rotated via a head pulley and a tail pulley inside a cylindrical trough pipe, the belt being floated by compressed air supplied from an air supply port at the bottom of the trough pipe, and the belt on the carrier side carrying an article running toward the head pulley, characterized in that a two-fluid nozzle is connected to the air supply port for spraying water droplets together with the compressed air in the form of a fine mist with a particle size of 30 μm or less .
According to the first means described above, the fine mist of water particles sprayed from the two-fluid nozzle acts like a rolling element in a bearing between the inner wall surface of the trough pipe and the conveyor belt, reducing the sliding resistance of the conveyor belt and enabling smooth and stable transportation.
In addition, the fine mist can suppress static electricity and dust inside the trough pipe, preventing fires.

As a second means for solving the above problems, the present invention provides
The two-fluid nozzle is equipped with an air flow control valve and a water flow control valve that respectively adjust the flow rates of the compressed air and water supplied to the trough pipe.
The object of the present invention is to provide an air floating type belt conveyor according to the first aspect, characterized in that the air-water ratio of the fine mist sprayed out from the two-fluid nozzle is adjusted.
According to the second means described above, the air-to-water ratio of the fine mist generated from the two-fluid nozzle refers to the ratio of compressed air to water, and this air-to-water ratio is adjusted to an optimal ratio by an air flow regulating valve that adjusts the flow rate of compressed air and a water flow regulating valve that adjusts the flow rate of water.
In this way, the fine mist of water particles sprayed from the two-fluid nozzle, with the air-water ratio adjusted to an optimum level, acts like a rolling element in a bearing between the inner wall surface of the trough pipe and the conveyor belt, reducing the sliding resistance of the conveyor belt and enabling smooth, stable transportation.
In addition, the fine mist adjusted to an optimal air-water ratio can suppress static electricity and dust inside the trough pipe, preventing fires.

The present invention provides a third means for solving the above problems,
The air flow control valve and the water flow control valve are provided with a control device,
The object of the present invention is to provide an air floating belt conveyor according to the second means, characterized in that the control device controls the opening of the air flow control valve and the water flow control valve based on the temperature in the trough pipe of the air floating belt conveyor and changing parameters in the belt drive.
According to the third means, when the temperature inside the trough pipe reaches or exceeds a predetermined warning temperature, it is highly likely that a fire will break out, and when the threshold value of the change parameter in the belt drive is exceeded, it is presumed that the sliding resistance of the belt is high, so that adjustments can be made to increase the amount of fine mist ejected or the proportion of water in the fine mist. Here, the change parameter in the belt drive is the drive current value, torque value, or vibration value of the motor that drives the belt.
In this way, by spraying a fine mist adjusted to an optimal air-water ratio from the two-fluid nozzle, the temperature inside the trough pipe is lowered to prevent it from reaching an ignition temperature, and static electricity and dust are suppressed, preventing fires.
In addition, the fine mist particles, adjusted to an optimal air-water ratio, act like rolling elements in a bearing between the inner wall surface of the trough pipe and the conveyor belt, reducing the sliding resistance of the conveyor belt and enabling smooth, stable transportation.

The present invention has the above-described configuration, and has the effect of providing an air-floating belt conveyor that can transport goods stably without being affected by the amount or physical properties of the goods, and can prevent fires by suppressing static electricity and dust in the trough pipe.

1 is a block diagram showing a schematic system configuration of an embodiment of the present invention; 4 is a cross-sectional view taken along line AA in FIG. 3. 1 is a simplified side view of a conventional air floating conveyor.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail with reference to the drawings.
Hereinafter, the configuration of a conventional air floating type belt conveyor will be described with reference to the accompanying Figs. 2 and 3, and then the configuration of the air floating type belt conveyor of the present invention will be described with reference to Fig. 1.

[Conventional air-floating belt conveyor]
As shown in Fig. 3, the air floating belt conveyor 1 is configured by looping an endless belt between a head pulley 6 and a tail pulley 5. The carrier side belt 7 and the return side belt 8 are housed in a trough pipe 14, and compressed air is sent from the blower 4 through a pipe 9 to float the carrier side belt 7 and the return side belt 8, causing them to run in the axial direction of the cylindrical trough pipe 14.

The transported material is fed from the inlet 3 onto the belt 7 on the carrier side, and is transported toward the cover 12 containing the head pulley 6. After reaching the inside of the cover 12, the material is received into the storage tank through the outlet 13 and stored there. Dust generated during this receiving process is collected and removed by the dust collector 10.
Thereafter, the return side belt 8, which no longer has any transported goods, passes through a belt reversal area and travels toward the cover 2 containing the tail pulley 5.

Figure 2 is a cross-sectional view taken along the line A-A in Figure 3, and the upper trough pipe 14a and the lower trough pipe 14b incorporate a carrier-side belt 17 and a return-side belt 18. The air duct 16 is also connected to the pipe 9 from the blower 4 shown in Figure 3.

The belt 17 on the carrier side is floated by compressed air supplied from a plurality of air supply ports 20 arranged at equal intervals opposite the air duct 16 arranged in the axial direction at the bottom of the upper trough pipe 14a. The belt 18 on the return side is floated by compressed air supplied from a plurality of air supply ports 20 arranged at equal intervals opposite the air duct 16 arranged in the axial direction at the bottom of the lower trough pipe 14b.

However, the gap 11 formed between the upper trough pipe 14a and the opposite conveying surface of the carrier-side belt 17 may become smaller as the amount of conveyed goods 15 loaded on the carrier-side belt 17 increases, causing the belt to come into contact with the inner wall of the trough pipe. The unbalanced load generated by a local increase or decrease in the load of the conveyed goods 15 in this manner moves as the conveyed goods 15 are conveyed, making it difficult to obtain an optimal gap 11 of the trough pipe over the entire length of the belt.
If the optimum gap 11 is not obtained, the belt will come into contact with the inner wall of the trough pipe, causing sliding resistance, which may lead to problems such as damage to the belt or device stoppage. There is also a problem that the sliding noise generated by the contact between the belt and the inner wall of the trough pipe becomes noise.

Furthermore, this unbalanced load can also occur when the transported materials adhere to each other on the belt and form clumps due to the physical properties of the material, such as high moisture retention, such as coal or woody biomass. In other words, the gaps 11 are smaller where there are large lumps, and the gaps 11 are larger where there are small lumps than where there are large lumps, and the bias caused by the size of the lumps prevents stable transport.

[Air floating belt conveyor of the present invention]
In consideration of these points, as shown in Fig. 1, a two-fluid nozzle 31 is connected to the air duct 26 provided at the bottom of the upper trough pipe 24a incorporating the carrier-side belt 27. Water droplets are sprayed in the form of a fine mist together with compressed air through a pipe 29 from this two-fluid nozzle 31 and from a plurality of air supply ports 30 provided at equal intervals opposite the air duct 26 provided in the axial direction of the upper trough pipe 24a.

Compressed air, the amount of which is adjusted by air flow rate control valve 33 from the air supply source, passes through pipe 39a, and water, the amount of which is adjusted by water flow rate control valve 32 from the water supply source, passes through pipe 39b, and enters two-fluid nozzle 31 where they are mixed to spray a fine mist with an optimal air-to-water ratio. The openings of air flow rate control valve 33 and water flow rate control valve 32 are adjusted to adjust the supply amounts of compressed air and water.
Specifically, when it is desired to increase the supply amount of fine mist, the supply amounts of compressed air and water are increased while keeping the jet pressure of compressed air constant and maintaining the determined optimum air-water ratio, i.e., the openings of the air flow control valve 33 and the water flow control valve 32 are adjusted in the direction of opening, thereby increasing the amount of fine mist sprayed from the bi-fluid nozzle 31. On the other hand, when it is desired to decrease the amount of fine mist sprayed from the bi-fluid nozzle 31, the supply amounts of compressed air and water are decreased while keeping the determined optimum air-water ratio, i.e., the openings of the air flow control valve 33 and the water flow control valve 32 are adjusted in the direction of closing, thereby decreasing the supply amounts of compressed air and water.

[Two-fluid nozzle 31]
In the two-fluid nozzle 31, compressed air is injected from the pipe 39a into the water flowing in from the pipe 39b and mixed with the water, so that the water is atomized and ejected by the shearing action of the compressed air.
The particle size of the fine mist can be adjusted by changing the air-to-water ratio (mixture ratio) of the compressed air and water supplied while keeping the compressed air ejection pressure constant. For example, when the ratio of compressed air to water is 4:6, the particle size of the ejected fine mist will be about 30 μm to 90 μm.
In this embodiment, the particle size of the fine mist sprayed from the two-fluid nozzle 31 is 100 μm or less, and preferably 30 μm or less. A fine mist with a particle size of 30 μm or less is called an ultra-fine mist in a dry state without any wetness.

[Method of controlling two-fluid nozzle 31]
The openings of a water flow rate control valve 32 and an air flow rate control valve 33, which adjust the air-water ratio of the fine mist sprayed from the two-fluid nozzle 31, are adjusted by a control device.
Signals transmitted from a temperature detector 28 and a belt-driven detector (not shown) installed at the top of the upper trough pipe 24a are received by the control device via transmission lines 25a and 25b, respectively. The received signals are calculated within the control device, and based on the calculated air-water ratio and amount of fine mist supplied, the openings of the water flow control valve 32 and the air flow control valve 33 are adjusted via transmission lines 35a and 35b.

[Temperature detection]
The temperature inside the upper trough pipe 24a can be measured by a temperature detector 28, and if this temperature exceeds a predetermined warning temperature, there is a high possibility of a fire breaking out. In addition, a rise in temperature inside the upper trough pipe 24a may be caused by frictional heat generated when the belt 27 on the carrier side comes into contact with the inner wall of the upper trough pipe 24a.

In such a case, by ejecting fine mist with its water-air ratio and supply amount adjusted by a control device from the two-fluid nozzle 31, the temperature inside the upper trough pipe 24a can be lowered and prevented from reaching the ignition temperature. In this case, the effect of preventing fires can be increased by increasing the proportion of water in the fine mist or by increasing the supply amount of the fine mist. In addition, the fine mist particles adjusted to the optimal water-air ratio act like rolling elements in a bearing between the inner wall surface of the trough pipe and the conveyor belt, reducing the sliding resistance of the conveyor belt and preventing the generation of frictional heat.
Furthermore, while there is a possibility of fire occurring due to static electricity or dust from the transported goods, the humidifying function achieved by spraying a fine mist adjusted to an optimal air-to-water ratio has the effect of suppressing the generation of static electricity and dust in the upper trough pipe 24a and preventing fires.
The present invention makes it possible to predict and prevent fires from occurring in advance.

[Sliding resistance detection]
When the change parameter in the belt drive exceeds a threshold value, it is estimated by a belt drive detector (not shown) that the sliding resistance of the belt is high. In such a case, the gap 21 between the belt 27 on the carrier side and the upper trough pipe 24a is not sufficiently obtained, and there is a possibility that the belt 27 comes into contact with the inner wall of the upper trough pipe 24a, causing sliding resistance. In addition, when the transported material has a high moisture retention rate, such as coal or woody biomass, the transported material adheres to each other and forms a mass, which causes the sliding resistance due to an unbalanced load.
The sliding resistance can cause problems such as belt damage and device stoppage, as well as noise from the sliding.

In such a case, the detection values of change parameters such as the drive current value, torque value, and vibration value of the motor that drives the belt are converted into signals and sent to the control device through the transmission line 25b, and based on the analysis or comprehensive judgment results, the openings of the water flow control valve 32 and the air flow control valve 33 are adjusted to adjust the air-water ratio and supply amount through the transmission lines 35a and 35b, thereby adjusting the fine mist to an optimal air-water ratio. When the fine mist adjusted to an optimal air-water ratio is supplied from the two-fluid nozzle 31 through the pipe 29 to the upper trough pipe 24a, the fine mist particles act like rolling elements in a bearing in the gap 21 between the carrier side belt 27 and the inner wall surface of the upper trough pipe 24a, reducing the sliding resistance of the conveyor belt and enabling smooth and stable transportation.
Furthermore, the embodiment shown in FIG. 1 can reduce sliding resistance, suppress sliding noise, and prevent belt wear, so that it is expected to have the effect of reducing the frequency of belt replacement due to wear.

In addition to the above, it is possible to select and discard the configurations described in the above embodiments or to change them to other configurations as appropriate without departing from the spirit of the present invention.

1 Air floating belt conveyor 2, 12 Cover 3 Input port 4 Blower 5 Tail pulley 6 Head pulley 7, 17, 27 Carrier side belt 8, 18 Return side belt 9, 29, 39a, 39b Pipe 10 Dust collector 11, 21 Gap 13 Discharge port 14 Trough pipe 14a, 24a Upper trough pipe 14b Lower trough pipe 15 Transported object 16, 26 Air duct 20, 30 Air supply port 25a, 25b, 35a, 35b Transmission line 28 Temperature detector 31 Two-fluid nozzle 32 Water flow rate control valve 33 Air flow rate control valve

Claims (3)

In an air floating belt conveyor, an endless belt that rotates via a head pulley and a tail pulley is disposed in a cylindrical trough pipe, and the belt is floated by compressed air supplied from an air supply port at the bottom of the trough pipe, so that the belt on the carrier side carrying the transported object runs toward the head pulley.
An air floating belt conveyor, characterized in that a two-fluid nozzle is connected to the air supply port, which sprays water droplets together with compressed air in the form of a fine mist having a particle size of 30 μm or less . The air-floating belt conveyor of claim 1, characterized in that the two-fluid nozzle is equipped with an air flow control valve and a water flow control valve that respectively adjust the flow rates of compressed air and water supplied into the trough pipe, thereby adjusting the air-water ratio of the fine mist sprayed from the two-fluid nozzle. The air flow rate regulating valve and the water flow rate regulating valve are provided with a control device,
The air floating belt conveyor according to claim 2, characterized in that the control device controls the opening degree of the air flow control valve and the water flow control valve based on a change parameter in the temperature in the trough pipe of the air floating belt conveyor and a change parameter in the belt drive.

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