JP5405332B2 - Asphalt plant - Google Patents

Description

  The present invention relates to an asphalt plant for producing an asphalt mixture that is a road pavement material.

  The asphalt plant that produces the asphalt mixture is equipped with a dryer that heats and drys the aggregate, which is the raw material of the asphalt mixture, to the hot air from the burner. The exhaust gas derived from the dryer is a cyclone, bag filter, etc. After being collected through a dust collector, it is discharged from the chimney into the atmosphere. As described above, in the asphalt plant, much heat energy is used when the aggregate is heat-dried by a dryer, but a part of it is released into the atmosphere together with the exhaust gas, from the viewpoint of energy saving. In order to reduce the amount as much as possible, heat recovery has been attempted by using various methods and means.

  For example, in Patent Document 1 (Japanese Patent Laid-Open No. 2009-1996), a virgin dryer that heats a new aggregate, a recycle dryer that heats asphalt pavement waste, and a deodorization furnace that deodorizes exhaust gas discharged from the recycle dryer. In an asphalt composite material production facility comprising: a device for supplying a part of exhaust gas derived from a deodorizing furnace to a virgin dryer for heat recovery. Moreover, in patent document 2 (Unexamined-Japanese-Patent No. 2009-179935), while supplying a part of exhaust gas derived | led-out from a deodorizing furnace to a virgin dryer similarly to the said document, it is for combustion to each dryer and the burner of a deodorizing furnace. An apparatus is described which is supplied as air for heat recovery.

JP 2009-1996 A JP 2009-179935 A

  As described above, in the asphalt plant, various methods and means have been used to recover heat from the exhaust gas so that it can be effectively used. However, exhaust gas of 100 ° C. or more is still emitted from the chimney. The present inventors thought that there was still room for heat recovery.

  In view of the above points, an object of the present invention is to provide an asphalt plant that can effectively recover heat from an exhaust gas discharged from a chimney and can be effectively used.

  In order to solve the above-described problems, in the asphalt plant according to claim 1 of the present invention, a chimney is connected to an aggregate heating dryer via an exhaust flue for exhaust gas exhaustion, and a heat insulation is provided in the vicinity of the chimney. A water tank having a function is provided, and a water circulation pipe is connected to the water tank so that the water in the tank is supplied along the chimney and circulated to the water tank while the temperature is raised by heat exchange with the exhaust gas. On the other hand, it has a heat pump unit that heats the outside air using the hot water in the water storage tank that has been heated to a predetermined temperature as a heat source, and a supply duct that supplies the outside air heated by the heat pump unit to a dryer. .

  Further, in the asphalt plant according to claim 2, the vertical conveying device downstream of the dryer is provided with a branch chute having a path changing means, and the aggregate discharged to the branch chute side is disposed downstream of the branch chute upstream of the dryer. It is characterized by having a transport device that sends it back to the aggregate storage silo.

  According to the asphalt plant of the first aspect of the present invention, a chimney is connected to an aggregate heating dryer through an exhaust flue for exhaust gas exhaust, and a water storage tank having a heat retaining function in the vicinity of the chimney The water tank is connected to a water circulation pipe that supplies water in the tank along the chimney and circulates to the water tank while raising the temperature by heat exchange with the exhaust gas, while increasing the temperature to a predetermined temperature. Equipped with a heat pump unit that heats the outside air using hot water in the warmed water storage tank as a heat source, and a supply duct that supplies the outside air heated by the heat pump unit to the dryer, which is more effective than the exhaust gas emitted from the chimney Heat recovery can be achieved, and by supplying the outside air heated based on this recovered heat to the dryer, the aggregate can be pre-dried and the exhaust gas heat can be used effectively. It is possible.

  According to the asphalt plant of claim 2, the vertical conveying device downstream of the dryer is provided with a branch chute having a path changing means, and the aggregate discharged to the branch chute side is disposed below the branch chute. Because it is equipped with a transport device that sends it back to the upstream aggregate storage silo, when the dryer is stopped, any aggregate is cut out from the aggregate storage silo, and the dryer only rotates the drum without burning the burner, vertical transport device, Arbitrary aggregate can be preliminarily dried by supplying the outside air heated based on the recovered heat recovered from the exhaust gas in this state to the dryer while circulating through the branch chute and the conveying device.

It is a schematic explanatory drawing which shows one Example of the asphalt plant which concerns on this invention. It is a schematic explanatory drawing which shows another Example of the asphalt plant which concerns on this invention.

  The asphalt plant of the present invention is provided with a dryer for heating and drying aggregates such as sand and crushed stone cut from the aggregate storage silo, and a chimney is connected to the dryer via an exhaust flue for exhaust gas exhaustion On the other hand, on the downstream side of the dryer, there are provided a vertical conveying device for sending the aggregate heated and dried by the dryer, and a plant main body comprising a vibrating sieve, an aggregate storage bottle, an aggregate measuring tank, a mixer and the like. Further, in the vicinity of the chimney, for example, a water storage tank having a heat retaining function by covering the outer periphery with a heat insulating material or the like is provided, and the water in the tank is made to follow the outer wall surface of the chimney. A water circulation pipe that circulates to the water storage tank while raising the temperature by exchanging heat with the exhaust gas supplied and discharged from the chimney is connected, while the hot water in the water storage tank thus heated to a predetermined temperature is used as a heat source for the outside air And a supply duct for supplying high-temperature outside air heated by the heat pump unit to the dryer.

  The heat pump unit includes a heat medium circulation pipe for circulating the heat medium, and an evaporator, a compressor, a condenser, and an expansion valve interposed in the heat medium circulation pipe, and flows in the heat medium circulation pipe. The heat medium first evaporates by absorbing heat energy from the hot water that is the heat source in the evaporator, and the heat medium that has become a gas is pressurized by the compressor to become high temperature and pressure, and then heat is released by the condenser and heated. While the outside air supplied as a target is heated, the heat medium cooled by heat radiation is liquefied and then rapidly reduced in pressure by an expansion valve to become a low temperature and low pressure, and is sent to the evaporator again. By repeating the above-described cycle in this manner, the outside air that is the heating target can be efficiently heated based on the recovered heat recovered from the hot water that is the heat source.

  Further, the discharge chute of the vertical conveying device is provided with a branch chute rotatably provided with a switching damper as a path changing means, and the aggregate discharged to the branch chute side is disposed below the branch chute. A belt conveyor is provided as a transfer device to be sent back to the storage silo.

  Then, when producing the asphalt mixture in the asphalt plant, the aggregate such as sand or crushed stone cut out from the aggregate storage silo is supplied to the dryer and exposed to hot air from a burner provided at one end side of the dryer and dried by heating. On the other hand, the exhaust gas derived from the dryer through the exhaust flue is collected by a dust collector provided in the middle of the exhaust, and then discharged from the chimney at the end of the exhaust flue to the atmosphere. At this time, the water in the water storage tank provided in the vicinity of the chimney is circulated along the outer wall surface of the chimney through the water circulation pipe, and the water flowing in the water circulation pipe and the exhaust gas discharged from the chimney are Heat exchange is performed, and the water in the water storage tank is eventually replaced with hot water of about several tens of degrees Celsius. As described above, the water storage tank is covered with a heat insulating material, and the hot water in the tank is kept at a constant temperature for a while.

  On the other hand, when the production of the asphalt mixture is finished and the operation of the dryer is stopped, the dryer burner is stopped and only the drum is rotated, and the switching damper provided for the discharge chute of the downstream vertical conveying device is rotated. The discharge route is switched to the branch chute side, and a belt conveyor extending from the lower part of the branch chute to the aggregate storage silo is operated, and in that state, any aggregate such as sand is cut out and supplied to the dryer. Then, it is circulated so as to be sent back to the original aggregate storage silo via a vertical conveying device, a branch chute, and a belt conveyor. Then, in this state, warm water stored in the water storage tank is used as a heat source to heat the outside air with a heat pump unit, and the heated high temperature outside air is supplied to the dryer through a supply duct, Predry the aggregate.

  In this way, during dryer operation, water is circulated through a water circulation pipe that is provided along the outer wall surface of the chimney to effectively recover heat from the exhaust gas, and the recovered heat energy is stored in the storage tank in the form of hot water. On the other hand, when the dryer is stopped, aggregated air such as sand is circulated and supplied to the dryer, while the hot water stored in the water storage tank is used as a heat source to efficiently heat the outside air with the heat pump unit, and this high temperature outside air is supplied to the supply duct. By supplying to the dryer, the heat recovered from the exhaust gas can be effectively used for preliminary drying of the aggregate, and energy saving in the asphalt plant can be expected.

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

  In the figure, reference numeral 1 denotes an asphalt plant of the present invention, which is a dryer 2 for heating various aggregates, a vertical conveying device 3 for sending aggregates heated by the dryer 2, and a vertical conveying device 3 The plant is composed mainly of a plant main body 4 and the like, in which aggregates are sieved and weighed, and asphalt or stone powder is added and mixed.

  The dryer 2 tilts and supports a cylindrical drum 5 having a large number of scraping blades (not shown) on the inner periphery thereof on a machine base 6, and is predetermined by a driving device (not shown). The hot air is sent into the drum 5 from the burner 7 provided at one end of the drum 5 and the combustion gas is sucked by the exhaust fan 9 downstream of the exhaust flue 8 at the other end of the drum 5. While exhausted, aggregates such as sand and crushed stones cut from the aggregate storage silos 10a, 10b, and 10c are supplied into the drum 5 via the belt conveyor 11, and the temperature is increased to a predetermined temperature while rolling down the drum 5. Heat.

  The heated aggregate is discharged from the discharge unit 12 on one end side of the drum 5 and put into the downstream vertical transfer device 3, and is lifted up to the upper part of the plant body 4 by the vertical transfer device 3. Supply to the main body 4. Further, a dust collector 14 such as a bag filter is provided downstream of the exhaust flue 8, and the exhaust gas purified by capturing dust in the exhaust gas is discharged from the chimney 15 into the atmosphere.

  The plant body 4 includes a vibrating screen 16 that receives and screens aggregate sent from the vertical transfer device 3, an aggregate storage bin 17 that stores the aggregate screened by the vibrating screen 16 according to particle size, and the aggregate Aggregate measuring tank 18 for accumulating the aggregate of each particle size stored in the storage bin 17, stone powder measuring tank 21 for measuring the stone powder supplied from the stone powder storage bottle 19 by the screw feeder 20, and supply pump from the asphalt tank 22 23, an asphalt measuring tank 24 for measuring the asphalt supplied at 23, and a mixer 25 for manufacturing an asphalt mixture by mixing aggregate, stone powder, asphalt and the like measured in each of these measuring tanks.

  Further, the discharge chute 13 of the vertical conveying device 3 is provided with a branch chute 27 rotatably provided with a switching damper 26 as a path changing means, and the lower part of the branch chute 27 is discharged to the branch chute side. A belt conveyor 28 is provided as a conveying device for sending the aggregate back to the original aggregate storage silos 10a to 10c.

  In the present embodiment, the switching damper 26 is used as a path changing means for switching the aggregate path sent out by the vertical conveying device 3 to the branch chute 27 side. However, the present invention is not limited to this. For example, a slide gate can be preferably employed. Further, in this embodiment, the path changing means and the branch chute 27 are provided in the discharge chute 13 on the outlet side of the vertical conveying device 3, but are provided in the dryer 2 discharge unit 12 on the inlet side of the vertical conveying device 3. In this case as well, a conveying device for returning the aggregate to the original aggregate storage silos 10a to 10c is provided below the branch chute.

  In the vicinity of the chimney 15, there is provided a water storage tank 29 having a heat retaining function by covering the outer periphery with a heat insulating material or the like, and water in the tank is placed on the outer wall surface of the chimney 15 in the water storage tank 29. A water circulation pipe 30 is connected to circulate to the water storage tank 29 while raising the temperature by supplying heat along the meandering and exchanging heat with the exhaust gas discharged from the chimney 15. At this time, about 100 to 120 ° C. exhaust gas is released from the chimney 15 during plant operation, and the water in the water storage tank 29 is about 50 ° C. by exchanging heat with the circulating water for a predetermined time. It can be replaced with hot water. In the present embodiment, the water circulation pipe 30 is arranged along the outer wall surface of the chimney 15 to exchange heat with the exhaust gas, but may be arranged inside the chimney 15.

  A return pipe 33 is connected downstream of the supply pump 31 of the water circulation pipe 30 with a flow path switching valve 32 to send water (warm water) in the water circulation pipe 30 back to the water storage tank 29. When the flow path is switched to the return pipe 33 side during 31 driving, the water (warm water) in the water storage tank 29 can be circulated only on the return pipe 33 side without being directed to the chimney 15. In addition, a heat pump unit 34 is provided in the middle of the return pipe 33 to heat outside air using water (warm water) flowing down inside the pipe as a heat source.

The heat pump unit 34 includes a heat medium circulation pipe 35 such as a copper pipe having excellent heat conductivity, and a heat medium such as alternative chlorofluorocarbon, ammonia, and CO ₂ is circulated and supplied into the heat medium circulation pipe 35. On the other hand, an evaporator 36, a compressor 37, a condenser 38, and an expansion valve 39 are interposed in the middle of the heat medium circulation pipe 35 in this order. The heat medium flowing in the heat medium circulation pipe 35 first evaporates by absorbing heat energy from the hot water that is the heat source in the evaporator 36 that is the heat exchanger, and the heat medium that has become a gas is a downstream compressor. (Compressor) Pressurized by 37 to become high temperature and pressure, and then heat is dissipated by a condenser 38 which is a downstream heat exchanger to heat the outside air supplied as a heating target, while the heat medium cooled by heat radiation After being liquefied again, the pressure is suddenly reduced by the expansion valve 39 downstream of the liquefaction to become a low temperature and a low pressure, and sent to the evaporator 36 again. By repeating the above-described cycle in this way, it is possible to efficiently heat the outside air to be heated with only a small amount of driving power for the compressor (compressor) based on the recovered heat recovered from the hot water that is the heat source. .

  In addition, the condenser 38 of the heat pump unit 34 is provided with a blower 40 that blows outside air to be heated, and the condenser 38 receives high-temperature outside air that is heated by heat exchange with a heat medium. The supply duct 41 to be supplied to is connected.

  And when manufacturing an asphalt mixture in the asphalt plant 1 of the said structure, aggregates, such as sand and crushed stone cut out from the aggregate storage silos 10a-10c, are supplied to the dryer 2, and it exposes to the hot air from the burner 7, and is predetermined. The heated aggregate is sent to the plant main body 4 from the discharge chute 13 via the downstream vertical conveyance device 3, and the charged aggregate is screened by the vibration sieve 16 in the plant main body 4. Store in the aggregate storage bin 17 according to particle size. Then, the aggregates of each particle size are sequentially discharged from the aggregate storage bin 17 to the lower aggregate measuring tank 18, accumulated and weighed into the mixer 25, and separately measured in the stone powder measuring tank 21 and the asphalt measuring tank 24. Stone powder and asphalt are respectively added to the mixer 25 and mixed for a predetermined time to produce a desired asphalt mixture. Further, the exhaust gas derived from the dryer 2 through the exhaust flue 8 is collected by a dust collector 14 provided in the middle thereof, and then discharged from the chimney 15 at the end of the exhaust flue 8 to the atmosphere.

  At this time, water is supplied from the water storage tank 29 provided in the vicinity of the chimney 15 so as to follow the outer wall surface of the chimney 15 through the water circulation pipe 30, and exhaust gas of about 100 to 120 ° C. discharged from the chimney 15 and The heat is exchanged and circulated to the water storage tank 29 while gradually raising the temperature (see the two-dot chain line arrow A1 in FIG. 1), and the water in the water storage tank 29 is finally replaced with hot water of about 50 ° C. To go. And if manufacture of an asphalt mixture is complete | finished, the supply pump 31 of the water circulation piping 30 will be stopped, and hot water will be stored in the water storage tank 29 which has a heat retention function, maintaining the said temperature.

  On the other hand, when the asphalt mixture has not been manufactured for a while and the operation of the dryer 2 is not performed, only the drum 5 is rotated without burning the burner 7, and the switching damper 26 of the discharge chute 13 of the vertical conveying device 3 is set. The path of the discharge chute 13 is switched to the branch chute 27 side by rotating and the belt conveyor 28 provided below the branch chute 27 is operated, and in that state, for example, sand among the aggregate storage silos 10a to 10c. Sand is cut out from the storage silo 10a for storage, supplied to the dryer 2, and circulated by being sent back to the original storage silo 10a for sand storage via the vertical conveying device 3, the branch chute 27, and the belt conveyor 28 ( (See two-dot chain arrow B in FIG. 1).

  In this state, after switching the flow path switching valve 32 in the middle of the water circulation pipe 30 connected to the water storage tank 29 to switch the flow path to the return pipe 33 side, the supply pump 31 is driven to drive the inside of the water storage tank 29. 1 is circulated through the return pipe 33 (see the two-dot chain line arrow A2 in FIG. 1), and at the same time, the heat medium in the heat medium circulation pipe 35 of the heat pump unit 34 is also circulated. At this time, the heat medium first evaporates by absorbing heat energy from hot water as a heat source in the evaporator 36, and the heat medium that has become a gas is pressurized by the downstream compressor 37 (compressor) to become high temperature and high pressure. Further, the outside air that is radiated by the downstream condenser 38 and heated from the blower 40 is heated by heat exchange, while the heat medium cooled and liquefied by the radiation is suddenly decompressed by the downstream expansion valve 39 to become low temperature and low pressure. Then, it is sent again to the evaporator 36 and circulates (see the two-dot chain line arrow C in FIG. 1). The heated high-temperature outside air is supplied into the drum 5 of the dryer 2 through the supply duct 41, and is effectively used for pre-drying the circulating sand. Further, the pre-dried sand is discharged from the discharge chute 13 of the vertical conveying device 3, but is discharged to the branch chute 27 side in the middle and sent back to the original storage silo 10a for storing sand by the belt conveyor 28. Stored again.

  Although the temperature of the hot water circulating in the return pipe 33 is not so high as about 50 ° C., the heat pump unit 34 can heat the outside air to be heated to a sufficiently high temperature using this level of hot water as a heat source. The sand flowing down in the drum 5 can be suitably dried by blowing such high temperature outside air into the drum 5.

  Thus, when producing the asphalt mixture in the asphalt plant 1, that is, during the operation of the dryer 2, the effect is obtained by exchanging heat between the exhaust gas discharged from the chimney 15 and the water in the water circulation pipe 30 around the chimney 15. The collected heat can be stored in the water storage tank 29 having a heat retaining function as hot water while the heat recovery is performed, while the aggregate storage silos 10a to 10c are used when the asphalt mixture has not been manufactured for a while, that is, when the dryer 2 is stopped. Arbitrary aggregate to be cut is circulated and supplied through the dryer 2, the vertical conveying device 3, the branch chute 27, and the conveying device 28, and the outside air is efficiently used by the heat pump unit 34 using the hot water stored in the water storage tank 29 as a heat source By heating well and supplying this high temperature outside air to the dryer 2 via the supply duct 41 Material can predrying processes, it is possible to suitably effective use of recovered heat from the exhaust gas.

  In this embodiment, water is used as a medium for recovering heat from the exhaust gas discharged from the chimney 15. However, it is possible to recover heat with other liquid media such as oil. However, since the exhaust gas temperature derived from the aggregate heating dryer 2 is at most about 100 to 120 ° C., it can be adequately handled without boiling with water. It is considered preferable to adopt.

  The aggregate to be circulated and preliminarily dried when the dryer 2 is stopped may be arbitrary. However, as in this embodiment, the moisture content ratio can be increased by preliminarily drying sand having a relatively high moisture content and a large variation. The asphalt mixture to be produced can be expected to improve quality.

  In this embodiment, the dried aggregate discharged from the dryer 2 is returned to the original aggregate storage silos 10a to 10c by the transport device such as the belt conveyor 28. However, this is not necessarily the case. There is no need, for example, it may be extracted once by the dryer 2 discharge section 12, and may be appropriately transported by a heavy machine such as a shovel car and returned to the silos 10a to 10c. Easy to adopt.

  In the present embodiment, when heat is recovered from the exhaust gas heat released from the dryer 2, heat recovery is performed by the chimney 15. For example, the outer peripheral surface of the exhaust flue 8 upstream from the chimney 15. It is also possible to recover heat in the exhaust flue 8 by arranging the water circulation pipe 30 so as to extend along the line.

  Furthermore, in this embodiment, in the asphalt plant 1 having only the dryer 2 for heating the new aggregate, a case is shown in which heat recovery is performed from the exhaust gas at the chimney 15 that releases the exhaust gas of the dryer 2. For example, in an asphalt plant equipped with a waste dryer for heating asphalt pavement waste in addition to a new aggregate dryer 2, the exhaust gas from the dryer 2 and the exhaust gas from the waste dryer are combined and released together. You may make it aim at heat recovery with a chimney. In this case, when there is no heat treatment of the new aggregate and only the heat treatment of the asphalt pavement waste material is performed, the heat pump unit 34 uses the recovered heat as a heat source while recovering heat from the exhaust gas derived from the waste material dryer. It is also possible to perform an operation in which the outside air is supplied to the new aggregate dryer 2 being stopped, and the aggregate such as sand is pre-dried by this dryer.

  The exhaust gas temperature emitted from the chimney 15 is about 100 to 120 ° C. in the case of the dryer 2 alone for heating the new aggregate, whereas it is about 150 to about collective chimney with the waste material dryer. Since the temperature is as high as about 160 ° C., more effective heat recovery can be expected.

  FIG. 2 shows another embodiment of the present invention. In FIG. 2, the same reference numerals as those in FIG. 1 denote the same components, and the description thereof is omitted. In the asphalt plant 1 ′ shown in FIG. 2, an aggregate predrying facility 42 for preliminarily drying the aggregate such as sand is additionally installed, and the predrying is performed separately from the dryer 2 for heating the aggregate. And an equipment such as an aggregate storage silo 44 for storing the aggregate dried by the preliminary drying dryer 43.

  The pre-drying dryer 43 has substantially the same structure as that of the dryer 2, and a cylindrical drum 45 having a large number of scraping blades (not shown) is provided on the inner peripheral portion thereof so as to freely rotate on the machine base 46. It is supported and rotated at a predetermined speed by a driving device (not shown), and the other end of the supply duct 41 connected to the condenser 38 of the heat pump unit 34 is connected to one end of the predrying dryer 43. The high-temperature outside air heated by the condenser 38 is fed into the drum 45, and the exhaust duct 47 at the other end of the preliminary drying dryer 43 is connected to the exhaust flue 8 of the aggregate heating dryer 2. The dust-containing air derived from the predrying dryer 43 is combined with the exhaust gas derived from the dryer 2 and collected together to be discharged from the chimney 15. Then, by supplying aggregate such as sand cut out from the aggregate hopper 48 into the drum 45 via the belt conveyor 49, moisture can be blown off from the aggregate flowing down in the drum 45 so that the drying process can be performed.

  The aggregate hopper 48 may store an arbitrary aggregate. However, as described above, sand having a relatively high moisture content and a large variation is stored and preliminarily dried by the predrying dryer 43. In this case, the water content ratio can be kept constant, and the quality of the asphalt mixture to be produced can be expected to improve. The size of the preliminary drying dryer 43 is relatively smaller than that of the aggregate heating dryer 2, so that a small amount of aggregate cut out from the aggregate hopper 48 can be suitably dried. I am trying.

  In addition, the aggregate dried by the preliminary drying dryer 43 is lifted by the downstream vertical conveying device 50 and temporarily stored in the aggregate storage silo 44. The aggregate stored in the aggregate storage silo 44 is appropriately discharged in accordance with the timing of manufacturing the asphalt mixture, and can be supplied to the aggregate heating dryer 2 by the belt conveyor 51.

  Further, in the water storage tank 29 provided near the chimney 15, the water in the tank is supplied to the chimney 15 by the supply pump 31 and heat-exchanged with the exhaust gas to increase the temperature to the water storage tank 29 as described above. A water circulation pipe 30 to be circulated and a second water circulation pipe 53 that circulates water (hot water) in the tank without being directed to the chimney by the supply pump 52 are connected to the second water circulation pipe 53. In the middle of the water circulation pipe 53, there is provided a heat pump unit 34 for heating the outside air blown from the blower 40 using water (hot water) flowing through the pipe as a heat source in the same manner as described above, and the condenser 38 of the heat pump unit 34 is provided with the heat pump unit 34. Is connected to a supply duct 41 for supplying the heated high temperature outside air to the preliminary drying dryer 43.

  And when manufacturing an asphalt mixture in the asphalt plant 1 'having the above-mentioned configuration, as described above, the aggregate 2 such as crushed stone cut out from the aggregate storage silos 10a to 10c is supplied to the dryer 2 and heat-treated. At the chimney 15 at the end of the flue 8, the exhaust gas and the water circulated and supplied from the water storage tank 29 are subjected to heat exchange to recover heat, and the water in the tank is replaced with hot water and stored (two-dot chain arrows in FIG. 2). A1).

  Then, regardless of whether the asphalt mixture is manufactured or not manufactured, for example, sand is cut out from the aggregate hopper 48 and rotated to the preliminary drying dryer 43 while rotating the drum 45 of the preliminary drying dryer 43 at an appropriate timing. While supplying (refer to the two-dot chain line arrow D in FIG. 2), while circulating the hot water in the second water circulation pipe 53 of the water storage tank 29 in this state (see the two-dot chain line arrow A2 in FIG. 2), at the same time heat pump The heat medium in the heat medium circulation pipe 35 of the unit 34 is also circulated. At this time, similarly to the above, the heat medium first evaporates by absorbing heat energy from the hot water as a heat source in the evaporator 36, and the heat medium turned into a gas is pressurized by the downstream compressor 37 and is heated to a high temperature. While the high pressure is applied, the outside air supplied from the blower 40 is radiated by the downstream condenser 38 and heated by heat exchange. On the other hand, the heat medium cooled and liquefied by the radiated heat is suddenly decompressed by the downstream expansion valve 39 and is cooled to a low temperature. The pressure becomes low, and it is sent again to the evaporator 36 and circulates (see the two-dot chain line arrow C in FIG. 2). Then, the high temperature outside air thus heated is supplied to the preliminary drying dryer 43 through the supply duct 41, and the sand cut out from the aggregate hopper 48 is subjected to a preliminary drying process.

  At this time, the water circulation pipe 30 and the second water circulation pipe 53 connected to the water storage tank 29 have independent paths and are individually provided with supply pumps 31 and 52. Heat is recovered from the exhaust gas derived from the dryer 2 in the water circulation pipe 30 to replace the water in the tank with warm water, and at the same time, the warm water is circulated through the second water circulation pipe 53, and the hot water is used as a heat source. The unit 34 can heat the outside air for preliminarily drying the aggregate, and the aggregate such as sand can be efficiently preliminarily dried without being bound by the production schedule of the asphalt mixture.

  The pre-dried sand is temporarily stored in the aggregate storage silo 44 via the vertical conveyance device 50, and an appropriate amount of sand is cut out from the aggregate storage silo 44 when the dryer 2 is operated, and then passed through the belt conveyor 51. Then, it is supplied to the dryer 2 and heat-treated together with other aggregates such as crushed stone cut out from the aggregate storage silos 10a to 10c.

  As described above, in this embodiment, the dryer 43 for exclusive use for pre-drying the aggregate such as sand is provided separately from the dryer 2 for heating the aggregate, so that the asphalt mixture 1 ′ is manufactured in the asphalt plant 1 ′. Regardless of whether or not there is, the aggregate such as sand can be pre-dried at an appropriate timing, and the recovered heat recovered from the exhaust gas can be used effectively.

  The object to be dried by the dryer may be other than aggregate. For example, construction sludge having a relatively high water content ratio and difficult to handle is supplied to the aggregate heating dryer 2, and the aggregate heating dryer 2 is supplied to the aggregate heating dryer 2. If the outside air heated by the heat pump unit 34 is sent in, the construction sludge and the like can be dried to a state that is relatively easy to handle. In that case, there is no production of the asphalt mixture at the asphalt plant, and the construction heating sludge is supplied and dried at the timing when the aggregate heating dryer 2 is not in operation. Alternatively, if a drying treatment dryer such as construction sludge is installed separately from the aggregate heating dryer 2 as in the preliminary drying dryer 43, when the asphalt mixture is manufactured or not manufactured Regardless, construction sludge and the like can be suitably dried at an appropriate timing.

DESCRIPTION OF SYMBOLS 1 ... Asphalt plant 2 ... Dryer 3 ... Vertical conveyance apparatus 4 ... Plant main body 7 ... Burner 8 ... Exhaust flue 10a, 10b, 10c ... Aggregate storage silo 13 ... Exhaust chute 15 ... Chimney 16 ... Vibrating sieve 17 ... Aggregate storage Bins 18 ... Aggregate measuring tank 25 ... Mixer 26 ... Switching damper (path changing means) 27 ... Branch chute 28 ... Belt conveyor (conveying device) 29 ... Water storage tank 30 ... Water circulation piping 32 ... Flow path switching valve 33 ... Return piping 34 ... Heat pump unit 35 ... Heat medium circulation piping 36 ... Evaporator 37 ... Compressor 38 ... Condenser 39 ... Expansion valve 40 ... Blower 41 ... Supply duct

Claims (2)

  A chimney is connected to the dryer for heating the aggregate via an exhaust flue for exhaust gas exhaust, and a water storage tank having a heat retaining function is provided in the vicinity of the chimney, and the water in the tank is supplied to the water tank. Connected to the water circulation pipe that circulates to the water storage tank while raising the temperature by exchanging heat with the exhaust gas and heating the outside air using the hot water in the water storage tank heated to a predetermined temperature as a heat source An asphalt plant comprising a heat pump unit and a supply duct for supplying outside air heated by the heat pump unit to a dryer.   The vertical conveying device downstream of the dryer is provided with a branch chute provided with a path changing means, and a conveying device for returning the aggregate discharged to the branch chute side to the aggregate storage silo upstream of the dryer is provided below the branch chute. The asphalt plant according to claim 1.

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