Dust pumping piping in asphalt plants

Abstract

To provide force feed piping for asphalt plant dust which allows stable and accurate detection and suitable maintenance even when a hole is formed in a pipe wall of a curved pipe section of the force feed piping for dust.SOLUTION: A straight pipe section 25a of a prescribed length is connected and integrally formed on at least the upstream side of a curved pipe section 24 in the middle of force feed piping for dust 17. A double structure is formed by covering the integrally formed curved pipe section 24 and straight pipe section 25a with a cover body 28 with a gap 27 left therebetween. Further, a pressure sensor 29 for detecting pressure changes in the gap 27 is provided at the section of the cover body 28 that covers the straight pipe section 25a. Alarm issuing means 30 is provided for issuing an alarm when the pressure sensor 29 detects a pressure change.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to an asphalt plant that produces asphalt mixtures for road paving, and in particular to a dust pressure transfer piping in an asphalt plant that pressure transfers dust collected by the plant's dust collector to a stone powder storage and supply facility within the plant. [Background technology]

[0002] An asphalt plant which manufactures asphalt mixture for road paving consists of the plant main body which is made up of a tiered arrangement of vibrating sieves, aggregate storage bins, measuring tanks and mixers, a dryer which heats and dries the aggregate, a dust collector which captures the dust in the exhaust gas, an asphalt tank which stores the molten asphalt, and stone powder storage and supply equipment which consists of a stone powder silo which stores the stone powder used as a filler, and a supply device which transports and supplies stone powder from the stone powder silo to the measuring tank.

[0003] When producing an asphalt mixture in the asphalt plant, first, the aggregate is heated and dried in the dryer, and this heated aggregate is sieved using a vibrating sieve at the top of the plant body and stored by particle size in an aggregate storage bin below. Depending on the composition of the asphalt mixture to be produced, predetermined amounts of heated aggregate of each particle size, molten asphalt, stone powder, etc. are measured out and mixed in the mixer below to produce the desired asphalt mixture.

[0004] On the other hand, the exhaust gas discharged from the dryer contains dust that has been dispersed and separated from the aggregate, and this dust is collected by the dust collector installed downstream of the exhaust flue. The dust collected by the dust collector can be effectively used as a filler equivalent to the stone powder, so for example, it is compressed by air through a dust compression pipe to the stone powder storage and supply facility, where it is mixed with stone powder that is being stored or supplied and used as a material for asphalt mixture.

[0005] Incidentally, there are a number of bends in the dust pressure transport piping, and at each of these bends, the dust being pressure transported by air repeatedly collides with the inner wall of the bend, gradually wearing away the pipe wall and causing it to become thinner. As a result, in some cases, holes may appear in the pipe wall during plant operation, allowing the dust being pressure transported by air to escape, causing damage to the inside of the plant equipment.

[0006] To address the above problem, for example, as described in Patent Document 1, the outer periphery of a curved pipe part of a transport pipe for pneumatically feeding powder or granular material is covered with a casing with a small gap therebetween to form a double structure, and a pressure sensor for detecting the pressure in the gap is installed in the casing. With this, even if the pipe wall of the curved pipe part wears away and a hole is formed, the casing prevents the powder or granular material from blowing out, while the pressure sensor detects the pressure change in the gap, allowing the worker to know that a hole has formed in the pipe wall, and to replace the curved pipe part at an appropriate time. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Publication No. 5-34140 Summary of the Invention [Problem to be solved by the invention]

[0008] However, in the transport piping of the above-mentioned Patent Document 1, since the pressure sensor is installed on the casing at the outer periphery of the bent pipe, when a hole is formed in the pipe wall of the bent pipe due to wear, some of the powder and granular material ejected from the hole may be ejected directly and forcefully onto the pressure sensor. In this case, if the transported material contains relatively hard material such as dust scattered and separated from the aggregate, which is the raw material of the asphalt mixture, the pressure sensor itself may be worn out in some cases, causing false detection or detection failure, etc., and as a result, it is expected that the bent pipe cannot be replaced at an appropriate time, which may cause problems in terms of maintenance.

[0009] In view of the above, an object of the present invention is to provide a dust pumping piping for an asphalt plant that can be stably and accurately detected and appropriately maintained even if a hole is formed in the pipe wall of a curved section of the dust pumping piping. [Means for solving the problem]

[0010] In order to solve the above problems, the present invention provides a dust pressure pipe for an asphalt plant, which is configured to pressure-feed dust collected by a dust collector of the asphalt plant to a stone powder storage and supply facility in the plant, and a bent pipe part in the dust pressure pipe is provided. Dust flow direction At least upstream and downstream for each Straight pipes of a specified length are connected together The straight pipe section is provided with a flange at an upstream end thereof located upstream of the bent pipe section and at a downstream end thereof located downstream of the bent pipe section. The bent pipe portion is integrally formed. The outer periphery of the bending direction and Before and after The straight pipe portion and Tube outer circumference and some The cover body is covered with a gap to form a double structure, and the cover body Upstream A pressure detection means for detecting a pressure change in the gap is provided at a portion covering the straight pipe portion. Easy to put on and take off and a warning means for issuing a warning when the pressure detection means detects a pressure change.

[0011] In addition, in the dust pressure transport piping of an asphalt plant described in claim 2 of the present invention, a predetermined pressure value is set in the alarm issuing means, and the alarm issuing means issues a first stage alarm when the pressure detection means detects a pressure change less than the predetermined pressure value, and issues a second stage alarm when the pressure detection means detects a pressure change equal to or greater than the predetermined pressure value. Effect of the Invention

[0012] According to the dust pressure transport piping of the asphalt plant according to the first aspect of the present invention, Dust flow direction At least upstream and downstream for each Straight pipes of a specified length are connected together The straight pipe section is provided with a flange at an upstream end thereof located upstream of the bent pipe section and at a downstream end thereof located downstream of the bent pipe section.The bent pipe portion is integrally formed. The outer periphery of the bending direction and Before and after The straight pipe portion and Tube outer circumference and some The cover body is covered with a gap to form a double structure, and the cover body Upstream A pressure detection means for detecting a pressure change in the gap is provided at a portion covering the straight pipe portion. Easy to put on and take off The pressure detection means is provided with an alarm means for issuing an alarm when the pressure detection means detects a pressure change. Therefore, even if a hole is formed in the curved pipe portion due to wear, there is little risk that dust will spray into the gap from this hole and directly hit and damage the pressure detection means installed at a distance upstream, and therefore pressure changes in the gap can be detected stably and accurately, making it possible to perform maintenance conveniently.

[0013] Furthermore, in the dust pressure transport piping of an asphalt plant described in claim 2 of the present invention, a predetermined pressure value is set in the alarm issuance means, and the alarm issuance means issues a first stage alarm if the pressure detection means detects a pressure change below the predetermined pressure value, and issues a second stage alarm if the pressure detection means detects a pressure change equal to or greater than the predetermined pressure value.As a result, after the first stage alarm is issued, the plant operator can, for example, continue operating the plant until the more urgent second stage alarm is issued, and can systematically perform replacement work of the curved pipe section during the off-season, thereby enabling more optimal plant maintenance to be handled. [Brief description of the drawings]

[0014] [Figure 1] FIG. 1 is a schematic explanatory diagram showing an embodiment of a dust pressure transfer pipe of an asphalt plant according to the present invention. [Diagram 2] FIG. 2 is an enlarged view of a main portion of FIG. 1 with a portion thereof omitted. [Diagram 3] 3 is an enlarged view of the bent pipe portion in FIG. 2 and the straight pipe portions before and after it. [Figure 4] FIG. 4 is a cross-sectional view of the AA portion of FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] In the dust pressure transport piping of the asphalt plant according to the present invention, a straight pipe section of a predetermined length is connected to at least the upstream side (with respect to the dust flow direction) of a bent pipe section in the dust pressure transport piping, and the bent pipe section and the straight pipe section are integrally formed, and covered with a cover body with a small gap from the outer periphery of the pipe to form a double structure. The inside of the gap is a closed space isolated from the outside air.

[0016] Furthermore, a pressure detection means, such as a pressure switch or a pressure sensor, for detecting a pressure change in the gap is provided in a portion of the cover body that covers the straight pipe portion located upstream of the bent pipe portion, preferably in a portion that covers the upstream end of the straight pipe portion. The length of the straight pipe portion is preferably set to a length such that, when a hole is formed in the bent pipe portion due to wear, dust blowing out from the hole does not directly blow onto the pressure detection means located at the upstream end of the cover body, thereby reducing wear and dust adhesion to the pressure detection means and suppressing the occurrence of false detection and detection omission.

[0017] The apparatus further includes an alarm issuing means for issuing an alarm when the pressure detection means detects a pressure change in the gap, which is a closed space, i.e., when it detects that a hole has been opened in the pipe wall of the bent pipe portion and that the gap is in communication with the pressure detection means. The alarm issuing means may issue an alarm, for example, by displaying a warning on an operation screen of a remote plant operation panel together with position information of the bent pipe portion with the hole (position information within the plant), but since a plant operator patrols the plant before and after plant operation to inspect the equipment, for example, rotating lights or the like may be installed near each bent pipe portion of the dust pressure transfer piping, and when the pressure detection means detects a pressure change, an alarm may be issued by turning on the corresponding nearby rotating light, in which case wiring work to the remote plant operation panel is not necessary, which reduces costs and makes the apparatus easier to adopt.

[0018] Also, preferably, a predetermined pressure value is set in the alarm issuing means, and when the pressure detection means detects a pressure change less than the predetermined pressure value (for example, shortly after a hole is opened in the pipe wall, when the size of the hole is relatively small), a first-stage alarm indicating a low-level "caution" state is issued, and when the pressure detection means detects a pressure change equal to or greater than the predetermined pressure value (for example, when the hole in the pipe wall grows and the size of the hole becomes relatively large), a second-stage alarm indicating a high-level "warning" state is issued in stages. This allows the plant operator to, for example, continue the operation of the plant as much as possible after the issuance of a first-stage alarm with a low level of urgency until the issuance of a second-stage alarm with a high level of urgency, and to systematically replace the bent pipe section during off-season periods when there are fewer shipment requests for asphalt mixtures, and this is expected to result in more optimal plant maintenance responses.

[0019] In this way, the curved pipe section of the dust pressure transport piping of an asphalt plant is constructed as one unit with the straight pipe section connected to it on the upstream side, and this curved pipe section and straight pipe section are covered with a cover body with a small gap between them to form a double structure, and the part of the cover body covering the straight pipe section is provided with a pressure detection means that can detect pressure changes in the gap. Therefore, even if a hole is formed in the curved pipe section due to wear, there is little risk that dust will spray into the gap from this hole and directly hit and damage the pressure detection means located upstream, and pressure changes in the gap can be detected stably and accurately, allowing the operator to replace and maintain the curved pipe section and straight pipe section at the appropriate time. EXAMPLES

[0020] An embodiment of the present invention will now be described with reference to the drawings.

[0021] In the figure, reference numeral 1 denotes an asphalt plant that produces asphalt mixture, a material for road paving, and is equipped with a plant body 7 consisting of an elevated platform 2 on which a vibrating sieve 3, aggregate storage bin 4, measuring tank 5, mixer 6, etc. are arranged in layers, a dryer 8 that heats and dries the aggregate, which is the raw material for the asphalt mixture, an aggregate elevator 9 that transports the heated and dried aggregate to the vibrating sieve 3 at the top of the plant body 7, and a bag filter 11, which is a dust collector that captures dust that is separated and scattered from the aggregate in the exhaust gas discharged from an exhaust flue 10 downstream of the dryer 8.

[0022] Also, 12 in the figure is a stone powder silo that stores stone powder, which is a raw material for asphalt mixtures, just like the aggregates, and together with a stone powder elevator 14 that transports the stone powder in the stone powder silo 12 to a stone powder storage bin 13 provided on the top of the plant main body 7, and a screw feeder 15 that transports and supplies stone powder from the stone powder storage bin 13 to the measuring tank 5, etc., this constitutes stone powder storage and supply equipment 16. Although not shown, an asphalt tank that stores molten asphalt, which is a raw material for asphalt mixtures, just like the aggregates and stone powder, is provided adjacent to the plant main body 7.

[0023] Reference numeral 17 in the figure denotes a dust pressure transfer pipe for pressure-transferring the dust collected by the bag filter 11 to the stone powder storage bin 13 of the stone powder storage and supply equipment 16, and the base end of the dust pressure transfer pipe 17 is connected to a rotary valve 19 provided at the discharge section of a screw conveyor 18 at the lower end of the bag filter 11, while the other end of the dust pressure transfer pipe 17 is connected to a cyclone type recovery machine 20 provided above the stone powder storage bin 13. Reference numeral 21 in the figure denotes a blower for supplying compressed air for air pressure transfer into the dust pressure transfer pipe 17.

[0024] In the cyclone type recovery machine 20, dust is separated and recovered by centrifugation from the compressed air supplied through the dust compression piping 17, and this separated and recovered dust is sequentially discharged from a rotary valve 22 provided at the lower end of the cyclone type recovery machine 20 into a lower stone powder storage bin 13 and merged with the stone powder supplied from the stone powder silo 12, while the compressed air from which the dust has been separated and recovered is sent back to the bag filter 11 via a return piping 23 connected to the upper end of the cyclone type recovery machine 20.

[0025] In addition, straight pipe sections 25a, 25b of a predetermined length are connected and integrated into the upstream and downstream sides (in the direction of dust flow) of the curved pipe sections 24 present in several places along the dust pressure transport pipe 17, and a flange 26 is provided at the upstream end of the straight pipe section 25a located upstream of the curved pipe section 24 and at the downstream end of the straight pipe section 25b located downstream of the curved pipe section 24, making it possible to replace the curved pipe sections 24 and the straight pipe sections 25a, 25b as a whole for the dust pressure transport pipe 17.

[0026] 3 and 4, the curved pipe section 24 and the straight pipe sections 25a, 25b before and after it are covered with a cover body 28 having a generally U-shaped cross section along the outer periphery of the curved pipe section 24 in the bending direction, with a slight gap 27 between the curved pipe section 24 and the outer periphery of the pipe, forming a double structure. The inside of the gap 27 is surrounded by the curved pipe section 24 and the outer periphery of the straight pipe sections 25a, 25b and the inner wall surface of the cover body 28, forming a closed space isolated from the outside air.

[0027] Furthermore, a pressure sensor 29, which is a pressure detection means for detecting pressure changes within the gap 27, is detachably provided at a portion of the cover body 28 that covers the upstream end of the straight pipe section 25a located upstream of the curved pipe section 24. By making the pressure sensor 29 detachable from the cover body 28, the pressure sensor 29 portion can be easily reused even when the curved pipe section 24 or the cover body 28 is replaced due to wear, which is advantageous in terms of cost.

[0028] The length of the straight pipe section 25a located upstream of the curved pipe section 24 is preferably set to a length (positional relationship) such that, when a hole is formed near the center of the length of the curved pipe section 24 due to wear, dust ejected from the hole together with the compressed air into the gap 27 is not directly ejected onto the pressure sensor 29 located at the upstream end of the cover body 28, thereby reducing wear and dust adhesion to the pressure sensor 29 and suppressing the occurrence of malfunctions such as false detection and missed detection.

[0029] In this embodiment, the straight pipe section 25b is connected to the upstream side of the bent pipe section 24 as well as the downstream side thereof, and is covered with the cover body 28 in a continuous manner, but these configurations do not directly affect the prevention of wear of the pressure sensor 29, and are not necessarily essential. However, according to maintenance data obtained by the inventors at an actual asphalt plant, it has been confirmed that the wear and thinning phenomenon of the pipe wall of the dust pressure transfer pipe 17 occurs not only in the bent pipe section 24, but also to some extent in the vicinity of the downstream side of the bent pipe section 24. Therefore, it is preferable to cover the straight pipe section 25b in a continuous manner with the cover body 28 while assuming that a hole may be formed in that portion, and to construct the straight pipe section 25b in a continuous manner so that it can be replaced together with the bent pipe section 24 when it is replaced.

[0030] Reference numeral 30 in the drawing denotes an alarm issuing means for issuing an alarm to an operator when the pressure sensor 29 detects a pressure change in the gap 27, i.e., when it detects that a hole has opened in the pipe wall of the bent pipe section 24 and is in communication with the gap 27. The alarm issuing means 30 can take various forms, but in this embodiment, a rotating light 31 and a plant operation panel 32 are used in combination.

[0031] The rotating lights 31 are provided near each of the multiple bent pipe sections 24 present in the dust pressure transfer pipe 17, and are installed in positions that are easily visible at least to an operator making a patrol inspection of the plant, and when the pressure sensor 29 detects a pressure change in the gap 27, the rotating lights 31 light up and rotate to issue an alarm. In addition, a signal line 33 from the pressure sensor 29 is connected to the remote plant operation panel 32, and when the pressure sensor 29 detects a pressure change in the gap 27, an alarm is issued by displaying a warning on the operation screen of the plant operation panel 32 together with position information of the bent pipe section 24 with a hole in the pipe wall (position information within the plant).

[0032] In this embodiment, when the pressure sensor 29 detects a pressure change, the rotating light 31 is turned on and rotated, and a warning is also displayed on the plant operation panel 32, but an alarm may be issued by only one of them. In particular, by limiting the use to the rotating light 31 only, wiring work for the signal line 33 to the remote plant operation panel 32 is not required, which reduces costs and makes the system easy to install and adopt in existing plants.

[0033] The rotating light 31 and the plant operation panel 32 of the alarm issuing means 30 are provided with a setting unit for setting a predetermined pressure value in advance, and when the pressure sensor 29 detects a pressure change less than the predetermined pressure value (for example, a stage in which a hole is relatively small soon after a hole is made in the pipe wall: the amount of pressure change is relatively small at this time), the alarm issuing means 30 issues a first-stage alarm indicating a low-urgency "Caution" state, and when the pressure change is greater than the predetermined pressure value (for example, a stage in which a hole in the pipe wall grows and the size of the hole becomes relatively large: the amount of pressure change is relatively large at this time), the alarm issuing means 30 issues a second-stage alarm indicating a higher urgency "Warning" state. The predetermined pressure value set in the alarm issuing means 30 may be set based on, for example, experimental data, but it is preferable to reset the value as appropriate if actual data, such as data on the opening of a hole in the bent pipe section 24 during actual plant operation, is obtained.

[0034] In addition, when the first and second stage alarms are issued in stages on the plant operation panel 32, for example, the color of the characters on the display screen may be yellow in the first stage, and the color of the characters may be changed to red in the second stage, and an alarm may be sounded at the same time. In addition, in the rotating light 31, for example, the interval at which the rotating light 31 is turned on may be shorter in the second stage than in the first stage, the color of the light may be changed from yellow to red, and a separate speaker or the like may be provided to sound an alarm at the same time, so that the operator can easily intuitively grasp the degree of urgency.

[0035] When the asphalt plant 1 equipped with the dust pressure transfer pipe 17 is operated to produce an asphalt mixture, the aggregate is heated and dried in the dryer 8, and the exhaust gas generated during this process is led to the downstream bag filter 11, which collects the dust contained in the exhaust gas that has been scattered and separated from the aggregate. The collected dust is air-pressurized via the dust pressure transfer pipe 17 to the stone powder storage bin 13 on the top of the plant main body 7, where it is combined with stone powder supplied from the stone powder silo 12 and used as a raw material for the asphalt mixture.

[0036] At this time, in the dust pressure transport pipe 17, the dust pressure-transported by air repeatedly collides with the inner wall surface of the curved pipe section 24, gradually wearing away the pipe wall and thinning it. Therefore, in anticipation of a hole being formed in the pipe wall, the outer periphery of the curved pipe section 24 is covered with a cover body 28 with a gap 27 left thereon to form a double structure, and a pressure sensor 29 is provided to detect pressure changes within the gap 27. Even if a hole is formed in the curved pipe section 24, the cover body 28 prevents dust from escaping, and the pressure sensor 29 detects the pressure change so that the operator can know that a hole has been formed in the curved pipe section 24.

[0037] In addition to the above configuration, in the present invention, a straight pipe section 25a of a predetermined length is connected to the upstream side of the curved pipe section 24 to form an integral structure, and the curved pipe section 24 and the straight pipe section 25a which are integrally formed are covered with the cover body 28, and the pressure sensor 29 is attached to a portion of the cover body 28 which covers the upstream end of the straight pipe section 25a. Therefore, even if a hole is formed in the curved pipe section 24 due to wear, there is little risk that dust blowing out from this hole will directly blow onto the pressure sensor 29 located at a distance upstream thereof, causing wear or adhesion of dust, and pressure changes in the gap 27 during plant operation can be detected stably and accurately, and an operator can replace and maintain the curved pipe section 24 and the straight pipe section 25a at an appropriate time.

[0038] In this embodiment, the dust collected by the bag filter 11 is compressed by air through the dust compression pipe 17, and the destination of the compressed air is assumed to be the stone powder storage bin 13 of the stone powder storage and supply equipment 16. However, this is not limited to this, and for example, the stone powder silo 12 of the stone powder storage and supply equipment 16 may also be the destination of the compressed air. In this case, the curved pipe section 24 of the dust compression pipe 17 may have a similar configuration to that described above.

[0039] In addition, in this embodiment, a pressure sensor 29 is used to detect pressure changes within the gap 27, but this is not necessarily limited to this, and it is sufficient if the pressure changes within the gap 27 can be detected. For example, various modifications can be made within the scope of the gist of the present invention, such as adopting a simpler configuration and less expensive pressure switch, etc. [Industrial Applicability]

[0040] The present invention can be widely used not only in asphalt plants but also in various dust pressure-transport piping for pressure-transporting abrasive dust by air. [Explanation of symbols]

[0041] 1... Asphalt plant 7... Plant body 8... Dryer 11... Bag filter (dust collector) 12...Stone powder silo 13...Stone powder storage bin 16...Stone powder storage and supply equipment 17...Dust pressure transfer device 20...Cyclone type recovery machine 23...Return piping 24...Bent pipe section 25a...Straight pipe section (upstream side) 25b...straight pipe section (downstream side) 26...flange 27: Gap 28: Cover body 29... Pressure sensor (pressure detection means) 30... Alarm issuing means 31... Rotating light (alarm means) 32...Plant operation panel (alarm issuing means)

Claims

1. 1. A dust pressure transfer piping for pressure-transferring dust collected by a dust collector of an asphalt plant to a stone powder storage and supply facility within the plant, comprising a bent pipe section in the dust pressure transfer piping, at least on the upstream and downstream sides in the dust downstream flow direction, straight pipe sections of a predetermined length are connected to each other, and a flange is provided at the upstream end of the straight pipe section located upstream of the bent pipe section and the downstream end of the straight pipe section located downstream of the bent pipe section are each provided with a flange and formed as an integral unit, the outer periphery of the bent pipe section and the straight pipe sections before and after it are covered with a cover body with a small gap from the outer periphery of the pipe, and a double structure is formed by covering the outer periphery of the pipe from the outer periphery of the pipe over the outer periphery of the bent pipe section and the straight pipe sections before and after it, and a pressure detection means is provided in a detachable manner at a portion of the cover body covering the straight pipe section on the upstream side, and an alarm issuance means is provided for issuing an alarm when the pressure detection means detects a pressure change.

2. 2. The dust pressure transfer piping of an asphalt plant as described in claim 1, characterized in that a predetermined pressure value is set in the alarm issuing means, and when the pressure detection means detects a pressure change less than the predetermined pressure value, the alarm issuing means issues a first stage alarm, and when the pressure detection means detects a pressure change equal to or greater than the predetermined pressure value, the alarm issuing means issues a second stage alarm.

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