JP5403795B2 - 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 that is a road pavement is composed of a dryer that is an aggregate heating and drying device, a plant body that includes a vibrating screen, a measuring tank, a mixer, and the like, and a vertical transfer device that connects the dryer and the plant body The main body is composed of, etc. The dryer includes a substantially cylindrical drum that is rotatable, supplies hot air from a burner provided at one end of the drum into the drum, and is provided at a downstream of an exhaust duct provided at the other end of the drum. A high-temperature gas flow is maintained by suction with a fan, and various aggregates are supplied into the drum in predetermined amounts to roll down, while the aggregate and hot air are brought into contact with each other to raise the aggregate to a desired temperature. It is warm.

  Then, the aggregate heated and dried by the dryer is sent to the vibrating sieve at the upper part of the plant body through the vertical conveying device, and the heated aggregate is sieved by the vibrating sieve and stored in the lower aggregate storage bin according to the particle size. A predetermined amount of heated aggregate is discharged from the aggregate storage bin, weighed in an aggregate measuring tank and discharged to a mixer, and an appropriate amount of molten asphalt is added and mixed to produce a desired asphalt mixture. .

  By the way, as described above, in an asphalt plant, since a large amount of heat energy is consumed when the aggregate is heated and dried, heat recovery is conventionally performed by various means from the viewpoint of energy saving. For example, as shown in Patent Document 1, a chimney downstream of a dryer is provided with a return flue, and the other end of the return flue is connected to a burner of the dryer to introduce exhaust gas as combustion air for the burner. In addition, there are those which deodorize by burning and decomposing odorous components in the exhaust gas, and at the same time, recovering heat by effectively utilizing the high temperature exhaust gas. Further, in Patent Document 2, the other end portion of the deaeration duct provided in the vertical conveyance device, the vibration sieve, the mixer, etc. is connected to the vicinity of the throat of the dryer burner, and is generated by the vertical conveyance device, the vibration sieve, the mixer, etc. Heat recovery is achieved by introducing deaeration (scavenging air) having a relatively high temperature and an oxygen concentration equivalent to that of outside air as secondary combustion air for the burner.

Japanese Patent Laid-Open No. 9-59913 Japanese Utility Model Publication No. 61-33044

  However, in the apparatus of Patent Document 1, since the combustion air of the burner is only the exhaust gas introduced from the return flue, it is considered that some outside air enters from the gap at the end of the drum. Over time, the oxygen concentration in the exhaust gas, which is the combustion air, gradually decreases, and there is a concern that proper combustion will no longer be possible. On the other hand, in the apparatus of Patent Document 2, outside air is introduced as the primary combustion air, and the deaeration from the deaeration duct introduced as the secondary combustion air has an oxygen concentration equivalent to that of the outside air. Therefore, although there is no risk of causing the above-mentioned combustion failure, the amount of heat possessed by the deaeration is very small compared to the amount of heat retained by the exhaust gas, so it is assumed that the heat recovery effect is not sufficient. The

  In view of the above points, the present invention is effective while maintaining proper combustion of the burner by suitably utilizing the degassing from the vertical conveying device, vibrating sieve, mixer, etc. as the combustion air of the burner together with the exhaust gas. It is an object of the present invention to provide an asphalt plant that can recover heat and save energy.

In order to solve the above-mentioned problem, the asphalt plant according to claim 1 sends the aggregate heated by the dryer to the vibration sieve in the upper part of the plant body through the vertical conveying device, and the heated aggregate is sieved by the vibration sieve. Assembling the asphalt mixture by storing it in the aggregate storage bin according to the particle size, discharging a predetermined amount of the heated aggregate from the aggregate storage bin, weighing it in the aggregate measuring tank and discharging it to the mixer, and adding and mixing molten asphalt In the asphalt plant for manufacturing the above, the circulation duct is branched downstream of the dust collector interposed in the exhaust duct for exhausting the exhaust gas of the dryer, and the combustion air introduction of the burner provided at the other end of the circulation duct in the dryer A part of the exhaust gas is introduced as primary combustion air by connecting to the mouth, and at least one of the vertical transfer device, the vibrating sieve, and the mixer The other end portion of the deaeration duct provided in the pipe is connected to the throat at the tip of the burner of the dryer so that a part of the deaeration is introduced as secondary combustion air. An air volume controller for controlling the rotational speed of the blower, and controlling the rotational speed of the exhaust fan with the air volume controller according to the combustion amount of the burner so as to introduce a deaeration amount to be introduced into the burner as secondary combustion air Adjusting and mixing the exhaust gas of the primary combustion air with the exhaust gas of the primary combustion air while adjusting the introduction amount of the deaeration having the oxygen concentration equivalent to the outside air as the secondary combustion air to the exhaust gas with reduced oxygen concentration circulated as the primary combustion air The oxygen concentration is increased to maintain proper combustion of the burner, and the circulation duct is provided with an open air supply valve that can be opened and closed, and the oxygen concentration becomes too low due to the exhaust gas circulation. Will maintain proper combustion. It is characterized by being configured so as to open the outside air supply valve to adjust the oxygen concentration in the exhaust gas to Itoki.

According to the asphalt plant of the first aspect of the present invention, the circulation duct is branched from the dust collector interposed in the exhaust duct for exhausting the exhaust gas from the dryer, and the other end of the circulation duct is provided in the dryer. In addition to a deaeration duct provided in at least one of the vertical transfer device, the vibrating sieve, and the mixer, the exhaust gas is connected to the combustion air inlet of the burner to introduce a part of the exhaust gas as primary combustion air. The end is connected to the throat of the burner tip of the dryer to introduce a part of the deaeration as secondary combustion air, and the deaeration duct has an air exhaust and an air volume control for controlling the rotational speed of the exhaust And adjusts the deaeration amount to be introduced into the burner as secondary combustion air by controlling the rotational speed of the exhaust fan according to the burner combustion amount, and circulates as primary combustion air Acid Proper combustion of the burner by increasing the oxygen concentration by agitating and mixing with the exhaust gas of the primary combustion air while adjusting the introduction amount of the deaeration having the same oxygen concentration as the external air to the exhaust gas with reduced concentration The circulation duct is provided with an open air supply valve that can be freely opened and closed. When the oxygen concentration becomes too low due to the exhaust gas circulation, the external air supply valve cannot be maintained when the amount of deaeration introduced cannot maintain proper combustion. Since it is configured to open and adjust the oxygen concentration in the exhaust gas, deaeration from the vertical conveying device, vibrating sieve, mixer, etc. can be used effectively as the combustion air of the burner together with the exhaust gas, Energy can be saved by effectively recovering heat while maintaining combustion.

It is a schematic explanatory drawing which shows one Example of the asphalt plant which concerns on this invention. It is the detailed explanatory view which omitted a part of burner part of the dryer of Drawing 1. It is XX sectional drawing which abbreviate | omitted a part of FIG.

  In the asphalt plant of the present invention, a circulation duct is branched downstream of the dust collector interposed in the exhaust duct of the dryer, and the other end of the circulation duct is provided in the combustion air inlet of the burner provided in the dryer. A part of the exhaust gas connected and cleaned by the dust collector is introduced as primary combustion air, while the other end of the vertical conveying device, the vibration sieve of the plant body, and the deaeration duct provided in the mixer is connected to the tip of the burner. It is connected to the throat so that part of the deaeration is introduced as secondary combustion air. In addition, the deaeration duct includes an exhaust fan and an air volume controller that controls the rotational speed of the exhaust fan, and controls the exhaust fan with the air volume controller according to the burner combustion amount, The amount of deaeration introduced as combustion air is adjusted.

  And when manufacturing an asphalt mixture in the said asphalt plant, predetermined amount of aggregate is supplied in the drum of a dryer, it exposes to the hot air from a burner, and is heated and dried to predetermined temperature. At this time, in the burner, the combustion amount of the burner is controlled by adjusting the fuel injection amount and the introduction amount of the primary combustion air so that suitable heating and drying can be performed according to the amount of aggregate to be supplied. In this case, not the outside air but high-temperature exhaust gas returned from the exhaust duct through the circulation duct is used, and the heat is effectively recovered from the high-temperature exhaust gas.

  On the other hand, the oxygen concentration in the exhaust gas is only about 13% of the amount of outside air entering from the gap at the end of the drum, etc. Even if only such exhaust gas having a low oxygen concentration is introduced into the burner as combustion air. Because proper combustion is difficult, the rotational speed of the exhaust fan is controlled by the air flow controller provided in the deaeration duct according to the combustion amount of the burner, and an appropriate amount of deaeration is used for secondary combustion from the deaeration duct. It is introduced as air. Deaeration derived from vertical conveyors, vibrating sieves, mixers, etc. contains a lot of dust and water vapor, but has a relatively high temperature and an oxygen concentration equivalent to that of the outside air, and burns as primary combustion air. However, if it is introduced into the throat part at the tip of the burner as secondary combustion air, there is no problem in the oxygen concentration in the combustion air. As a result, the burner can be maintained in proper combustion, and further heat recovery can be achieved, and energy saving can be expected.

  In this way, a part of the high-temperature exhaust gas is introduced as the primary combustion air for the burner, while a relatively high temperature derived from a vertical conveying device, a vibrating sieve, a mixer, etc. and having an oxygen concentration equivalent to that of the outside air. Part or all of the air is introduced into the burner as secondary combustion air, and the amount of deaeration introduced is adjusted according to the amount of burner burned, so it is effective while maintaining proper burner combustion. In addition, heat can be recovered, and energy saving can be suitably achieved. In addition, by introducing degassing containing odorous components into the burner as combustion air, the odorous components can be burned and decomposed for deodorization treatment, which is also preferable in terms of the environment.

  Embodiments of the present invention will be described below with reference to the drawings.

  Reference numeral 1 in the figure denotes an asphalt plant of the present invention, which connects a dryer 2 that is an aggregate heating and drying device, a plant main body 3 including a vibrating sieve, a measuring tank, a mixer, and the like, and the dryer 2 and the plant main body 3. The main body is constituted by the vertical transfer device 4 and the like. The dryer 2 supports a substantially cylindrical drum 5 having a large number of scraping blades (not shown) on its inner peripheral portion so as to be rotatable on a machine base 6, and is driven by a driving device (not shown). An exhaust duct 10 is connected to a cold hopper 9 on the other end side of the drum 5 while supplying hot air into the drum 5 from a burner 8 provided on the hot hopper 7 on one end side of the drum 5. The high-temperature gas flow which passes through the inside of the drum 5 is maintained by suction with the exhaust fan 11 provided downstream of the drum 5.

  Then, a predetermined amount of aggregate is discharged from an aggregate hopper (not shown) for storing the aggregate according to particle size, and the discharged aggregate is supplied into the drum 5 via the belt conveyor 12 and scraped with a scraping blade. While being raised, the drum 5 is brought into contact with a high-temperature gas flow while being tumbled down, heated to a desired temperature and discharged from the discharge portion 13 provided at the lower end portion of the hot hopper 7, and the discharge portion 13 The heated aggregate discharged from the plant is lifted up to the upper part of the plant main body 3 by the vertical conveying device 4 and is put into the vibrating sieve 15 provided at the uppermost part of the plant main body 3 through the discharge chute 14 at the upper part of the vertical conveying device 4. Yes.

  The heated aggregate put into the vibration sieve 15 is sieved according to particle size and stored in the compartments 16a to 16d of the lower aggregate storage bin 16, while the lower ends of the compartments 16a to 16d of the aggregate storage bin 16 are respectively A discharge gate (not shown) for discharging aggregate is provided so as to be openable and closable, and an aggregate measuring tank 18 supported by a load cell 17 serving as a measuring instrument is provided below the gate. Further, a stone powder measuring tank 21 for measuring the stone powder supplied by the screw feeder 20 at the lower end of the stone powder storage bin 19 and an asphalt measuring tank 22 for measuring the molten asphalt are provided, and the aggregate measuring tank 18 is included. A mixer 23 is provided in the lower part of each measuring tank, and a material measured by a predetermined amount in each measuring tank is put into the mixer 23 and mixed and adjusted to produce a desired asphalt mixture.

  Further, downstream of the exhaust duct 10, a dry cyclone 24 and a bag filter 25 are provided as a dust collector for collecting dust in the exhaust gas, and a downstream end of the chimney 27 is interposed via an air volume adjusting damper 26 and the exhaust fan 11. The exhaust gas purified by the dry cyclone 24 and the bag filter 25 is discharged from the chimney 27 into the atmosphere.

  Reference numeral 28 denotes a circulation duct that is branched from the downstream of the dry cyclone 24 and the bag filter 25 provided in the exhaust duct 10. The other end of the circulation duct 28 is connected to the combustion air inlet of the burner 8 of the dryer 2. 29, and a part of the high-temperature exhaust gas purified by the dry cyclone 24 and the bag filter 25 is introduced and used as the primary combustion air of the burner 8 by the combustion air introduction fan 30 of the burner 8. Therefore, the heat is effectively recovered from the high temperature exhaust gas.

  Further, since a large amount of dust is generated in the vertical transfer device 4, the vibration sieve 15 of the plant body 3, the mixer 23, etc., each of the devices is provided with a deaeration duct 31 for discharging dust, and the deaeration. The other end of the duct 31 is connected to the throat 32 at the tip of the burner 8 of the dryer 2, and part or all of the relatively high-temperature deaeration led out by the exhaust fan 33 interposed in the deaeration duct 31 is transferred to the burner 8. It is designed to be introduced and utilized as secondary combustion air, and is configured to effectively recover heat from relatively high-temperature deaeration. At this time, a large amount of dust, water vapor, and the like are contained in the deaeration, but this is introduced not from the combustion air inlet 29 on the burner 8 body side but from the throat 32 on the tip side of the burner 8. Therefore, there is no possibility that dust, water vapor, etc. during deaeration will adversely affect the burner 8.

  As shown in FIGS. 2 and 3, for example, the throat 32 of the burner 8 has a double structure comprising an inner cylinder 32a and an outer cylinder 32b, and the other end of the deaeration duct 31 is connected to the outer cylinder 32b. The cross-section tangential direction is connected, and the degassing of the secondary combustion air introduced from the degassing duct 31 is made along the gap space between the inner cylinder 32a and the outer cylinder 32b of the throat 32, and in the direction of arrow B1 in FIG. The primary combustion air and the secondary combustion air are effective in the throat 32 by reversing the exhaust gas flow direction A of the primary combustion air introduced from the combustion air introduction port 29 at the rear of the burner 8. It is possible to stir and mix. Further, a plurality of through holes 34 are formed at predetermined intervals on the peripheral wall of the inner cylinder 32a, and a part of the deaeration introduced as the secondary combustion air is indicated by an arrow B2 in FIG. Then, it is allowed to flow into the inner cylinder 32a and be more effectively stirred and mixed with the exhaust gas of the primary combustion air.

  A caster 35 having a predetermined thickness and excellent heat storage properties is attached to the inner peripheral surface of the inner cylinder 32a of the throat 32. Even when the burner 8 is in a low combustion state, the inside of the throat 32 is kept in a high temperature atmosphere. By maintaining and improving the combustibility of the fuel, unburned is prevented, and stable and good combustion is possible.

  Further, the burner 8 is provided with a combustion amount controller 36 for controlling the combustion amount by adjusting the fuel injection amount and the exhaust gas amount introduced as the primary combustion air, and the exhaust fan 33 of the deaeration duct 31. Is equipped with an air volume controller 37 for controlling the rotation speed, and the air volume controller 37 controls the rotation speed of the exhaust fan 33 in accordance with the combustion volume of the burner 8 controlled by the combustion volume controller 36. The amount of deaeration introduced into the burner 8 as secondary combustion air is adjusted.

  The above control will be described in detail. When adjusting the combustion amount of the burner 8, the combustion amount controller 36 controls the rotational speed of the combustion air introduction fan 30 together with the fuel injection amount and introduces it as primary combustion air. The amount of exhaust gas to be adjusted is appropriately adjusted to a desired combustion amount. Therefore, for example, when the combustion amount is increased, the rotational speed of the combustion air introduction fan 30 is increased and the amount of exhaust gas introduced is also increased. However, the oxygen concentration in the exhaust gas is slightly increased from the gap at the end of the drum 5 and the like. However, even if only such exhaust gas with a low oxygen concentration is introduced into the burner 8 as combustion air, proper combustion is difficult. The controller 37 controls the rotational speed of the exhaust fan 33 to increase the introduction amount of deaeration, which is the secondary combustion air. This deaeration has an oxygen concentration equivalent to that of the outside air (about 20.9%). By introducing this into the burner 8 as secondary combustion air, the deaeration is mixed with the exhaust gas of the primary combustion air and mixed with oxygen. The concentration is appropriately increased so that proper combustion of the burner 8 can be maintained.

  In addition, the circulation duct 28 is provided with an open air supply valve 38 that can be freely opened and closed. When the exhaust gas is circulated and used, the oxygen concentration becomes too low and proper combustion cannot be maintained only by increasing the introduction amount of deaeration. The outside air supply valve 41 is appropriately opened and closed to adjust the oxygen concentration in the exhaust gas.

  When producing an asphalt mixture in the asphalt plant 1 having the above-described configuration, first, a predetermined amount of aggregate is cut out from an aggregate hopper (not shown) and supplied to the drum 5 of the dryer 2 via the belt conveyor 12. Then, it is exposed to hot air from the burner 8, dried by heating to a predetermined temperature, and discharged from the hot hopper 7. The heated aggregate discharged from the hot hopper 7 is put into the vibration sieve 15 at the upper part of the plant body 3 through the vertical conveying device 4, and is sorted by the vibration sieve 15 and stored in the lower aggregate storage bins 16a to 16d according to the particle size. To do. Along with the shipment request of the asphalt mixture, a predetermined amount of heated aggregate is dispensed from the aggregate storage bins 16a to 16d, weighed in the aggregate measuring tank 18 and dispensed to the lower mixer 23, and an appropriate amount Stone powder and molten asphalt are added and mixed to produce a desired asphalt mixture.

  Further, the exhaust gas derived from the drum 5 is purified through a dust collector such as a dry cyclone 24 and a bag filter 25 via the downstream exhaust duct 10 and then discharged from the chimney 27 into the atmosphere. A part of the high-temperature exhaust gas is sucked by the combustion air introduction fan 30 of the burner 8 and introduced into the combustion air inlet 29 of the burner 8 through the circulation duct 28 to be effectively used as the primary combustion air. Perform heat recovery. In addition, relatively high-temperature deaeration led out by the exhaust fan 33 from the deaeration duct 31 for dust discharge provided in the vertical transfer device 4, the vibration sieve 15 of the plant body 3, and the mixer 23 is also at the tip of the burner 8. Heat is recovered by being introduced into the throat 32 and effectively used as secondary combustion air.

  At this time, the oxygen concentration in the exhaust gas is low, and even if only this is introduced into the burner 8 as combustion air, proper combustion is difficult, but the air volume control provided in the deaeration duct 31 according to the combustion amount of the burner 8 By controlling the number of rotations of the exhaust fan 33 with the ventilator 37 and introducing an appropriate amount of deaeration having an oxygen concentration equivalent to the outside air as secondary combustion air, the oxygen concentration of the combustion air is appropriately increased. Appropriate combustion of the burner 8 can be maintained.

  In this way, a part of the high-temperature exhaust gas is introduced as the primary combustion air for the burner, while a relatively high temperature derived from a vertical conveying device, a vibrating sieve, a mixer, etc. and having an oxygen concentration equivalent to that of the outside air. Part or all of the air is introduced into the burner as secondary combustion air, and the amount of deaeration introduced as secondary combustion air is adjusted according to the amount of combustion of the burner. Heat can be effectively recovered while maintaining stable combustion, and energy saving can be suitably achieved in an asphalt plant. In addition, by introducing deodorized gas containing odor components derived from vertical conveyors, vibrating screens, mixers, etc. into the burner as combustion air, the odor components can be burned and decomposed for deodorization treatment. Is preferred.

DESCRIPTION OF SYMBOLS 1 ... Asphalt plant 2 ... Dryer 3 ... Plant main body 4 ... Vertical conveyance apparatus 5 ... Drum 8 ... Burner 10 ... Exhaust duct 15 ... Vibrating sieve 23 ... Mixer 24 ... Dry-type cyclone (dust collector)
25 ... Bag filter (dust collector) 28 ... Circulation duct 29 ... Combustion air introduction port 30 ... Combustion air introduction fan 31 ... Deaeration duct 32 ... Throat 32a ... Inner cylinder (throat) 32b ... Outer cylinder (throat)
33 ... Air exhaust 36 ... Combustion amount controller 37 ... Air amount controller

Claims (1)

Aggregate heated by a dryer is sent to a vibrating sieve at the top of the plant body via a vertical conveying device, and the heated aggregate is sieved by the vibrating sieve and stored in an aggregate storage bin according to particle size. Dispose of a fixed amount of heated aggregate, weigh it in an aggregate measuring tank and dispense it to a mixer. In addition, in an asphalt plant where molten asphalt is added and mixed to produce an asphalt mixture, it is interposed in the exhaust duct for exhaust gas exhaust of the dryer. A circulation duct is branched downstream of the dust collector, and the other end of the circulation duct is connected to a combustion air inlet of a burner provided in the dryer to introduce a part of the exhaust gas as primary combustion air. The other end of the deaeration duct provided in at least one of the vertical conveying device, the vibrating sieve, and the mixer is connected to the throat at the tip of the dryer burner. Then, a part of the deaeration is introduced as secondary combustion air, and the deaeration duct is provided with an exhaust fan and an air volume controller for controlling the rotational speed of the exhaust fan, and according to the burner combustion amount. The air flow controller controls the rotational speed of the exhaust fan to adjust the deaeration amount introduced into the burner as secondary combustion air, and the secondary exhaust gas with reduced oxygen concentration is circulated as primary combustion air. The combustion air is stirred and mixed with the exhaust gas of the primary combustion air while adjusting the introduction amount of the deaeration having the oxygen concentration equivalent to the outside air so as to maintain the proper combustion of the burner by increasing the oxygen concentration, and The circulation duct is provided with an open air supply valve that can be freely opened and closed. When the oxygen concentration becomes too low due to the exhaust gas circulation, and the proper amount of degassing cannot be maintained, the open air supply valve is opened and the oxygen concentration in the exhaust gas is reduced. To adjust Configured asphalt plant, characterized in that the.

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