CH615472A5 - Method and arrangement for the dust-free manufacture of coated chipping material for road surfacings - Google Patents

Description

The object of the present invention is to further improve this method. The invention further relates to a further development of the device for carrying out the method according to the main patent.

The method according to the invention is characterized in that the heating of the uncoated grit material and the bituminous binder begins simultaneously with the mixing without premixing the cold mix.

In order to achieve a thorough binding of the dust material by the evolving water vapor, it is recommended that the water content of the uncoated grit material be about 0.02 to 15% by weight, preferably 3% by weight or higher, based on the weight of the uncoated grit material.

During the hot mixing process, the mixer can be rotated about an approximately horizontal axis at a rotational speed advantageously between 50 and 90%, preferably at approximately 70% of the spin speed.

The subject of claim II of the main patent is a device for carrying out the method according to claim I of the main patent, which comprises a mixing drum which is rotatably mounted about an axis extending through the ends of the mixing drum and which has an opening at least at one end, and further a heater for the generation and subsequent introduction of a hot air stream into a line, and means for loading the drum with grit material and bituminous binder. It is characterized in that the mixing drum is tiltably mounted between at least one position, in which the axis of the mixing drum runs inclined, and a mixing position, in which an opening is aligned with an outlet opening of the line, and that means for moistening the grit material are present .

The device for carrying out the method according to the invention is characterized by a motor which is designed such that it can set the mixing drum in rotation at a speed which is at least 50% of the spin speed, so that the material in the drum forms a veil.

A loading device can be arranged in such a way that the mixer can be loaded in an inclined position which corresponds to the emptying position or in which the tilting angle of the mixer with respect to the horizontal is somewhat smaller than in the emptying position.

The binder can be introduced into the mixer in solid form. However, the binder can also be melted d. H. in liquid form through a nozzle into the mixer, at the latest when touching the cold,

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wet grit material becomes solid. In addition, it is possible to introduce a filler or a filler in powder form corresponding to the binder into the mixer via an insertion nozzle, an insertion nozzle or the like. Instead, the filler can also be introduced in the form of a slurry in which the powder is mixed with the water required to moisten the granular batch. The binder and the filler can be added to the mixer when the mixer is in an inclined position or when it is tilted. However, it is also possible to introduce the binder and the filler into the mixer after it has been returned to its horizontal working position. The filler can also be added to the granular batch located in a filling vessel or the like.

The device can also be designed so that the mixer can be loaded in its horizontal position. In this case, a movable, endless feed conveyor can be provided, which can be inserted with its discharge end into the feed opening of the mixer during the loading process. An outlet nozzle, an outlet connection or the like for the melted-on binder can be arranged on one side of the conveyor frame. The conveyor can be provided with a cover or a covering hood or the like, through which the outlet of a filling vessel, filling funnel or the like for the granular mixture can pass.

The mixer can be open at both ends so that the hot air flows through the mixer from one end to the other. On the other hand, the mixer can only be open at one end; in this case, the opening serves both for the introduction and removal of the hot air.

If cooling of the material to be mixed is required, a blower can be provided which guides unheated air through the mixer. In some cases, the arrangement of a blower can be dispensed with. Any cooling that may become necessary can be brought about by passing a secondary air flow through the mixer when the heater is set to a low flame.

It is advisable to carry out the heating of the granular additives and the binder in such a way that these mixtures are continuously circulated in a rotating mixing drum and thereby form a continuously falling veil of mix. Although protrusions, such as. B. Lifter u. Like., Can be arranged, which take the mix with the drum rotation in the upper drum area, it is preferable if the arrangement of such projections and entrainment elements to which the mix can bake is dispensed with and instead a drum is used which has an essentially smooth and flat inner wall. This drum can be driven at a rotational speed which is 50 to 90%, suitably 70%, of the centrifugal or centrifugal speed.

At the beginning of the heating of the mixed material, the amount of hot air flowing through the mixer can be adjusted depending on the tendency of the fine material to be entrained by the air flow. This means that the air flow rate is kept small at the beginning of the heating process if there is a risk that the fine material will be carried by the air. The amount of air is then correspondingly increased with increasing softening and liquefaction of the binder and accordingly with increasing binding of the fine material by the binder. This air volume setting can be carried out by the operator by observing the exhaust air leaving the exhaust air duct. However, there is also the possibility of automatically carrying out the air volume control as a function of the amount of dust emerging from the mixer, the air entrained

Amount of dust, e.g. B. is determined by means of a sensing or sensing device arranged on the exhaust air duct. The amount of air can be regulated by adjusting a throttle element arranged in the drainage channel, by changing the speed of a fan supplying the air to the heater or by changing the fuel supply to the heater, if appropriate also by combining these various measures.

The supply air duct, via which the air is fed to the mixer, can be connected to one end of a double-wall duct, which consists of an outer tube and an inner tube therein, both tubes being made of a refractory and non-heat-storing material, such as e.g. B. stainless steel. The arrangement is such that secondary air flows through the ring channel between the two tubes to the burner, which at the same time cools the inner tube in which the burner flame is located. If the mix is to be cooled, the burner can be set to a small flame. The secondary air then flows directly through the ring channel mentioned to the mixer. If necessary, a small amount of secondary air can still flow backwards in the direction of the mixer in order to prevent the inner tube from overheating due to the reset burner flame.

Exemplary embodiments of the invention are explained in more detail below with reference to the accompanying drawing. Show it:

Fig. 1 in side view of a device for coating granular materials, such as gravel material, stone chips and. Like. As they are used in road construction;

2 shows an axial section of a double jacket duct for supplying secondary air to the burner and hot or cold air to the mixer;

3 shows a side view of a second exemplary embodiment of the device, only its main parts being shown;

Fig. 4 also in side view of a third embodiment of the device in a partial view.

The device shown in Fig. 1 is used to coat grit, gravel or other granular material for road construction or for the production of road surfaces with a bituminous binder. The device has a frame 1, which can be driven by a truck or a towing vehicle to the respective place of use, at which the hot mix is discharged from the batch mixer. The mixer 2 is mounted on a lower stage 30 of the frame. It has a drum 3 which is frustoconical on both sides. The loading opening 4 is located at one end of the drum. The inside of the drum is smooth and flat and, with the exception of screws or rings which are located in the frustoconical part 7, has no lifters or other driving elements. The aforementioned screws prevent the mixed material from falling out of the emptying opening 5 of the drum when the drum is in the idle state and is thereby inclined or tilted. On the other hand, they support the emptying of the drum in its counterclockwise rotation. The drum is mounted in a frame 8 on idlers rotatable about its axis. It is driven by a hydraulic motor 9 via a gear. The frame 8 supporting the drum is pivotally or tiltably supported between supports 10. A hydraulic cylinder 11 engages on both sides of the frame 8. With the aid of the cylinders, the drum can therefore be tilted from a position in which the drum axis R runs horizontally to a loading position in which the drum axis is inclined, as indicated at R1. An air heater 12 is mounted on a stage 31 at one end of the frame. At

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In the preferred embodiment, the air heater is fired by means of an oil or gas burner 32, the burner flame of which can be varied in strength burns in a combustion chamber through which air is passed by a blower. The heated air flows into the mixer via a supply air duct 13.

The mouth of the supply air duct 13 is arranged such that it is aligned with the opening 5 of the drum when the axis of rotation of the drum is in a horizontal position. The supply air duct 13 is connected to a chimney or an exhaust pipe 14. A throttle valve 113 is arranged in the supply air duct and can be adjusted so that the hot air flows from the heater 12 via the supply air duct 13 to the drum 3 and is discharged via the exhaust pipe 14 in the other case. At the other end of the frame 1 there is an expansion space 17, the inlet opening of which is aligned with the drum opening 4 when the axis of rotation of the drum is in its horizontal position. The expansion space 17 also has an outlet opening, with which it is connected to a blower 18, which blows out into a shaft or an exhaust pipe 19. An adjustable throttle valve 119 or another throttle element is located in the exhaust pipe 19. The expansion space 17 has in its lower region an opening which can be closed by a door or the like in order to be able to remove solid particles which have collected here.

A conveyor (not shown in FIG. 1) serves for the batch-wise or batch-wise conveying of the undried granular batch into a weighing or filling vessel 22, which is provided with a discharge chute 221, the discharge opening of which can be closed by means of a hood-like closure member is. The chute 221 is arranged in such a way that the granular mixture located in the filling vessel 22 is introduced into the opening 4 of the drum via a pivotable feed channel 222.

Containers for holding the molten binder, a powdered filler and a flow or continuous oil are arranged on the upper stage. Pipelines connect the containers to outlet openings through which the substances mentioned are introduced into the drum. The outlet openings for the binder and the filler can be arranged in the interior of the feed trough 222, so that these substances are fed under gravity when the drum is in its tilted position. Instead, at least the outlet opening for the binder together with that for the flow-through oil can be arranged in the interior of the expansion space 17 in such a way that it opens out towards its inlet opening and a certain measured amount of binder emerges under the action of a pump or air pressure. Another outlet opening is connected to a water supply and arranged so that the granular mix (grit or other rock material) is sprayed with water before it reaches the drum 3.

The operation of the device described above is as follows:

The required types of a moist granular material are obtained from a storage location, e.g. B. is formed by a warehouse exposed to the weather, feeding tanks supplied from which the different grain types or grain classes are withdrawn on a conveyor belt. With the help of weighing devices such. B. belt weigher loading devices, or by means of volumetric measuring devices, the proportionate composition of the batch of the mixed material supplied via the conveyor belt can be determined. The water content of the individual grain classes is measured by means of moisture indicators, which, for. B. are arranged on the loading vessels, the water content being taken into account when weighing the proportions of the different grain classes to ensure that the dry weight of the granular batch complies with the respective regulations. It has been shown that in hot mixing the coating of the granular substances with the liquefied binder is promoted by the presence of the water, since the water improves the flowability and the flow rate of the liquid binder. In addition, the water promotes the adhesive effect of the binder with respect to the components of the granular mixture. The water content of the batch of the granular mixture can be adjusted according to the respective requirements with the aid of water spraying of the mixture so that it lies between 0.02 and 15% by weight, preferably at least 3% by weight. The moisture content of the granular batch has u. a. the purpose of preventing the dust or the fine material from the hot air flow from the mixing room. In view of this, it is advisable to soak the granular mixture as evenly as possible with the water so that there are no major deviations in the moisture content. Because the granular batch is moistened evenly before it reaches the mixer, it is not necessary to pre-mix it beforehand, which saves time.

The burner 32 is first set to a small flame. The throttle valve 113 is set in such a way that undesired warm air generated by the burner is discharged via the exhaust air duct 14. The fan 16 therefore works without load. The drum 3 is in its inclined loading position R1.

When the weighing vessel is filled, the hood closure and the feed trough 222 are pivoted into the open position so that the granular mixture is released into the drum 3. The monitoring system then closes the feed channel 222 and signals are delivered which request the next batch and pivot the mixer 2 into the horizontal mixing position with the aid of the cylinders 11. The binder can be added to the granular mixture when the drum 3 is in its tilted position or in the horizontal position, depending on where the outlet and the feed opening for the binder are located.

The motor 9 is started, whereby the drum 3 is rotated clockwise.

The control and monitoring system now sets the burner 32 to full flame; at the same time, the throttle valve 113 is switched over, so that hot air now flows from the air heater 12 through the rotating drum 3. After the drum 3, the air is discharged into the atmosphere via the exhaust duct 19. If the granular mixture has a uniform moisture level when the drum 3 is loaded, the cold premixing can be dispensed with and the hot mixing can be carried out immediately after the loading.

During the hot mixing, the drum 3 is expediently driven at a rotational speed which is approximately 70% of the spin speed. The spin speed is the speed of rotation of the drum at which the mixture in the drum remains in contact with the drum wall. The hot air flowing through the drum 3 drives the water out of the granular batch and at the same time liquefies the binder, so that the granular batch is coated and enveloped by the binder. The binder also binds the fine material and the dust contained in the granular mixture, so that the hot air stream cannot remove it from the mixing room. Coarser particles that escape from the drum 3 are in the expansion space 17

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collected. Until the binder softens and liquefies, the dust or the fine material is prevented from escaping from the mixing space by the water content of the mixed material. The drum 3 can be brought abruptly to a rotational speed which corresponds to approximately 70% of the spin speed. It is more expedient, however, if the drum 3 is continuously accelerated from standstill or slow running until it reaches this rotational speed. In addition, it is advisable to increase the amount of hot air steadily or step by step in accordance with the increase in the adhesive and adhesive properties of the binder as it heats up. If the operator determines that fines come out of the drain pipe 19, this is an indication that the water is being expelled more quickly than is appropriate in view of the increasing adhesive effect of the binder. The operator can then by adjusting the flap 119 and throttling the opening of the exhaust pipe 19, by reducing the fuel supply to the burner 32, which leads to a reduction in the amount of secondary air supplied, by reducing the speed of the air supplying the burner 32 or counteract the premature drying out of the mix by combining some of these measures. This setting can e.g. B. can be achieved by using a burner 32 that allows three settings, namely the setting of a pilot flame, a medium flame setting and a full flame setting. It goes without saying that other setting options can also be provided.

The above monitoring and setting can also be effected with the aid of an automatic monitoring system as a function of a signal which is supplied by a dust detector arranged in the exhaust pipe 19. Such a detector speaks z. B. on a radiation with a certain wavelength, which is sent through exhaust gas samples.

It may be necessary to cool the mix in order to bring it to a temperature corresponding to the respective mix recipe. The mixed material can also be cooled before the treatment with the flux. The cooling can be brought about by sending cold air through the drum 3. Flow and continuous oil can be introduced into the drum 3 during this stage. The cold air flow can be brought about by a blower which is provided with a throttling outlet which opens into the feed channel 13 in the flow direction behind the throttle valve 113. The cooling can also be brought about by setting the burner 32 for the air heater 12 on a low flame.

In order to obtain the desired quality of the mixture in certain cases, a further mixing stage may be required, in which the burner 32 works with a low flame and the throttle valve 113 is set in such a way that it supplies the air to the exhaust duct 14.

After the mixing process has ended, the mixer 2 is tilted into the position R2 and the motor 9 is driven at a lower speed in the opposite direction, so that the screws or spirals located in the conical drum part 7 discharge the hot mixture onto a trolley. The mixer 2 is then tilted slightly and brought into position R1 in order to be able to carry out the next mixing cycle. It is not necessary to cool the drum 3 before loading it with another batch of the granular mixture. Rather, it has been shown that it is expedient to insulate the drum 3 in order to avoid heat losses as far as possible. Correspondingly, insulation of the supply air duct 13 can also be provided.

Fig. 2 shows part of a modified device, which relates to the supply of air to the burner and to the drum 3, not shown in this figure.

According to FIG. 2, the burner is connected to the supply air duct 13 (FIG. 1) via a double-jacket tube, which consists of an inner tube 200 and a coaxial outer tube 201. The ring channel between the two cylindrical tubes is designated by 203, while the cylindrical inner channel of the inner tube 200 bears the reference number 202. The annular channel 203 is divided by an annular guide wall 204 into two sections, a front and a rear channel section. The two channel sections are each connected to the cylindrical inner channel 202. In the vicinity of a duct 206 connected to the outer tube, an adjustable flap 205 is arranged in the ring duct, which can be adjusted in such a way that the air flowing in via the duct 206 in the direction of the supply air duct 13 (FIG. 1) and in the other setting position flows backward as secondary air to the heater 12. This counter-flowing air cools the inner tube 200, which is made of a non-refractory and non-heat-storing material, such as. B. stainless steel or other material is made. Depending on the setting of the flap 205, a cold air flow or a hot air flow can be supplied to the supply air duct 13 and thus to the drum.

Fig. 3 shows a device in which the mixer performance can be increased by loading the drum 3 in a horizontal position. In this device, a feed conveyor 300 is provided, which preferably consists of a chain power conveyor or the like and which can be displaced in the longitudinal direction so that it can be brought into a loading position in which the discharge end of the conveyor lies inside the drum. The conveyor is provided with a jacket or cover 301 which has an opening for the discharge end of the conveyor. The arrangement can be such that the conveyor grips through the opening of a chimney or an exhaust duct 303 or the like. Since the drum only needs to be tilted for its emptying in this arrangement, the inside wall of the drum can be completely smooth and flat. Discharge screws or the like are not required. When emptying, the drum is rotated in the same direction as in the mixing process.

In the embodiment according to FIG. 4, the drum 3 has only a single drum opening, which is used both for loading and for emptying the drum when it is tilted into the positions R1 and R2. The drum opening also serves as an inlet and outlet for the hot air when the drum is in a horizontal position according to line R3. In Fig. 4, the filling vessel for the granular batch and the loading devices for the binder and the filler are not shown. The supply air duct 13 is enclosed by an outlet duct 117, to which a suction fan 16 for the air circulation is connected. In the channel 13 (not shown) inlet and outlet lines with adjustable throttle valves or the like. The drum can be supported on one side on a shaft which is arranged on a drive and tilting gear 9. This facility is of compact design. It therefore takes up little space, particularly when working with a binder in solid form, so that it can be used with particular advantage as a small-sized portable or mobile device. As mentioned, the arrangement of lifters, drivers, screws and the like. Like. Be disregarded on the inside wall of the drum. When emptying, the drum rotates in the same direction as in the mixing process. As in the exemplary embodiment according to FIG. 3, the drum can rotate continuously, whereby it is only tilted to a certain extent for loading and emptying. In both cases, the s

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Binder in solid form, instead of in liquid form, are introduced into the drum. It can therefore be added to the granular batch before it is introduced into the drum.

It can be seen that in all the exemplary embodiments described above, the complete process is carried out in a single mixer. Instead of continuously conveying the mixed material through a heater, the mixed material is mixed and heated in the form of a closed batch, the heat being supplied by an air heater arranged remote from the mixer. This results in the possibility of monitoring the temperature of the mixed material, so that good results can be achieved. The method according to the invention is particularly suitable for automatic control and monitoring based on temperature measurements.

2 sheets of drawings

Claims (12)

615472 PATENT CLAIM I Method according to claim I of the main patent, characterized in that the heating of the uncoated grit material and the bituminous binder begins simultaneously with the mixing without premixing the cold mix. SUB-CLAIMS 1. The method according to claim I, characterized in that the amount of hot air flowing through the mixer is set or regulated depending on the amount of dust material entrained in the hot air flow. 2. The method according to claim I, characterized in that the water content of the uncoated grit material to a value of 0.02 to 15 wt .-%, preferably 3. The method according to claim I, characterized in that during the hot mixing process the mixer is rotated about an approximately horizontal axis at a rotational speed which is between 50 to 90%, preferably about 70% of the spin speed. PATENT CLAIM II Device according to claim II of the main patent for carrying out the method according to claim I here-before, characterized by a motor (9) which is designed such that it can set the mixing drum (3) in rotation at a speed which is at least 50% the spin speed is such that the material in the drum forms a haze. SUB-CLAIMS 3 wt .-%, based on the weight of the uncoated grit material, is adjusted. 4. Device according to claim II, characterized in that an adjusting member (119) for adjusting the air throughput through the mixer (2) is arranged in an exhaust air duct (19). 5. Device according to claim II, characterized by a filling vessel (22) for loading the mixing drum (3) located in the inclined position with the moist grit material. 6. Device according to claim II, characterized by one of the mixing drum (3) in its horizontal position with the moist grit material loading conveyor (300). 7. Device according to claim II, characterized by a binder feed, with which the binder of the mixing drum (3) located in the horizontal position can be fed. 8. Device according to claim II, characterized in that the mixing drum (3) contains screws or rings inside. 9. Device according to claim II, characterized in that the mixing drum (3) for the supply and discharge of the hot air has a single opening. 10. Device according to claim II, characterized in that the hot air supply channel (13) is connected to one end of a double tube (200, 201), which consists of an outer tube (201) and an inner tube (200) located therein, wherein both tubes are made of a non-refractory and non-heat-storing material, and that the ring channel (203) between the two tubes serves for the passage of secondary burner air. 11. Device according to subclaim 10, characterized in that in the annular space (203) between the two pipes (200, 201) in the flow direction behind the supply air conclusion (206) an adjustable shut-off device (205) is arranged. 12. Device according to claim II, characterized in that there is an expansion space (17) between the mixing drum (3) and an exhaust air duct (19). The subject of claim I of the main patent is a method for the dust-free production of coated grit material for road surfaces, wherein cold, moist, non-earthy grit material and a bituminous binder are mixed and heated by a hot gas stream, so that the moisture is removed from the grit material and the binder liquefies and the grit material is coated, the moisture being sufficient to bind dust particles in the grit material until these dust particles are held in the mixture by the liquefied binder, and the entire dust-free mixing process takes place in only one mixing drum.