AU2011362562B2

AU2011362562B2 - Method for operating an asphalt mixing plant, in particular a continuous asphalt mixing plant

Info

Publication number: AU2011362562B2
Application number: AU2011362562A
Authority: AU
Inventors: Jean-Luc DIDIER
Original assignee: Ammann Schweiz AG
Current assignee: Ammann Schweiz AG
Priority date: 2011-03-15
Filing date: 2011-03-15
Publication date: 2016-08-25
Anticipated expiration: 2031-03-15
Also published as: ES2551409T3; BR112013023235A2; EP2686485A1; AU2011362562A1; EP2686485B1; WO2012122659A1

Abstract

The invention relates to a method for operating an asphalt mixing plant, comprising a drum dryer (1) for drying and heating the mineral material and a mixer (2) for blending the heated mineral material with a binder. As the material flow starts to pass through the drum dryer (1) at the start of an operating phase the mineral material emerging from the drum dryer (1) is collected. In normal operation the emerging mineral material is blended in the mixer (2) with the binder to form asphalt. As the material flow moves down through the drum dryer (1) at the end of the operating phase the mineral material emerging from the drum dryer (1) is also collected. After the material flow has moved down through the drum dryer (1), the collected mineral material is blended in a mixer (2) with binder to form asphalt. Said method enables the amount of waste asphalt generated in continuous asphalt mixing plants to be appreciably reduced or eliminated, without compromising the formulation. In addition, even small amounts of quality asphalt having a formulation subject to strict tolerance requirements can be produced economically.

Description

Method for operating a in particular continuous asphalt mixing plant

The invention concerns a method for operating an asphalt mixing plant and a plant, in particular for conducting the method.

In the production of asphalt in a continuous process the mineral material which is to be processed first must be dried and heated, before it is mixed with at least one further component, in most cases bitumen, to become asphalt. This drying and heating typically takes place within in drum dryer, inside which the mineral material is fed through a hot gas stream generated therein, wherein it is repeatedly raised and in form of a dripping curtain is fed through the hot gas stream.

However, by doing so, for reasons that are inherent in the system, during the start-up and during the shut down of the material flow through the drum dryer it comes to a segregation of the mineral material.

During the start-up of the material flow through a counter flow drum dryer, initially merely coarse hot mineral material is discharged from the drum dryer. With increasing time of operation, increasingly also more fine material fractions come along, until finally a static operational state is reached, in which the material composition which is leaving the drum dryer, with the exception of fine material fractions which are carried by the hot gas stream into the filter system, corresponds to the material composition that is fed into the drum dryer.

During the shut down of the material flow through a counter flow drum dryer, the opposite effect occurs. In case starting from the before described static operational state no further mineral material is fed anymore into the drum dryer, increasingly more fine hot mineral material is discharged from the drum dryer until finally no hot mineral material is discharged from it anymore.

During the start-up and the shut down, respectively, of the material flow through a coflow drum dryer, the described effects correspondingly occur in opposi te manner.

Thus, during the start-up and the shut down of the material flow through the drum dryer it comes to a shifting in the composition of the hot mineral material, which is under today's requirements with regard to the quality of the asphalt not acceptable and results in corresponding amounts of waste asphalt per operating cycle. This cannot be sold and has to be dumped or has to be expensively recycled. Consequently, the production of small amounts of asphalt with such asphalt plants is quite uneconomical ,

In order to tackle this problem, in some plants the operation has been changed in such a manner that, during the start-up of the material flow through the drum dryer at the start of an operation cycle, the hot mineral material with a 'wrong composition which is discharged from the drum dryer is collected and is later, in the normal operation, continuously added to the hot mineral material which is discharged from the drum dryer in amounts which are agreeable with the composition. This method reduces the amount of waste asphalt per operation cycle, but has however the disadvantage that relative large amounts of asphalt need to be produced until the collected hot mineral material having a 'wrong composition is processed and that over a long time of operation a suboptimal composition has to be accepted.

Therefore it is desirable that embodiments of the present invention provide a method for operating an asphalt mixing plant and an asphalt mixing plant which do not show the disadvantages of the prior art or at least partially avoid them.

According to a first aspect of the present invention, there is provided a method for operating an asphalt mixing plant comprising a drum dryer for drying and heating the mineral material that is to be processed to become hot mineral material and comprising at least one mixer for mixing the hot mineral material with at least one further component to become asphalt, wherein during the start-up of the material flow through the drum dryer at the start of an operation cycle of the asphalt mixing plant the start-up hot mineral material which is discharged from the drum dryer is collected, wherein after the start-up of the material flow through the drum dryer in normal operation of the asphalt mixing plant the hot mineral material which is discharged from the drum dryer is mixed in the at least one mixer with the at least one further component to become asphalt, wherein during the shut down of the material flow through the drum dryer at the end of the operation cycle of the asphalt mixing plant the shut down hot mineral material which is discharged from the drum dryer is collected, and wherein during and/or after the shut down of the material flow through the drum dryer at least partial amounts of the collected start-up hot mineral material and of the collected shut down hot mineral material are jointly mixed in the at least one mixer with the at least one further component to become asphalt. • According to a second aspect of the present invention, there is provided a plant for conducting the method as described above.

According to an example of the invention there is provided a method for operating an asphalt mixing plant comprising a coflow or a counterflow drum dryer for drying and heating of the mineral material that is to be processed to become hot mineral material and comprising at least one mixer for mixing the hot mineral material with at least one further component, preferably with a binder material, like e.g. bitumen, to form asphalt. Furthermore it is for example envisaged, to mix the hot mineral material with other substances, e.g. with additives, fibres and/or with a granulate of recycling asphalt, namely with or without addition of binder material. The mineral material that is to be processed can be "new mineral material" as well as asphalt granulate/-recycling asphalt or also other recycled aggregates, or also compositions of such materials.

During the start-up of the material flow through the drum dryer at the start of an operating cycle of the asphalt mixing plant, the start-up hot mineral material which is discharged from the drum dryer is collected until the hot mineral material composition which is discharged is within a specific deviation from the mineral material composition which is fed or corresponds thereto.

Thereafter, the hot mineral material which is discharged from the drum dryer is mixed in the at least one mixer with the at least one further component to form asphalt. This operational state constitutes the normal operation of the operation cycle of the asphalt mixing plant.

During the shut down of the material flow through the drum dryer at the end of the operation cycle of the asphalt mixing plant, the shut down hot mineral material which is discharged from the drum dryer is collected .

During and/or after the. shut down of the material flow through the drum dryer, at least partial amounts of the collected start-up hot mineral material and of the collected shut down not mineral material are jointly mixed with the at least, one further component in the at least one mixer to form asphalt.

By means of this operation mode it becomes now possible to significantly reduce or eliminate in continuous asphalt mixing plants the amount of waste asphalt, or waste mineral material generated per operation, cycle, without having to accept the compromises with regard to the composition known from the prior art. Furthermore it. becomes now possible, to produce with continuous asphalt, mixing plants also small amounts of quality asphalt with a composition that is subject to strict tolerance requirements in an economic way.

In a preferred embodiment of the method, the hot mineral material which is discharged from the drum, dryer in the normal operation is continuously or batch-wise mixed in the at least one mixer with the at least one further component, in one or several continuous or batch mixers. Subsequently, the entire amount, of collected start-up hot mineral material and shut down hot mineral material is during and/or after the shutting down of the, material flow through the drum dryer at once or in several batches mixed, in one or several batch mixers with, the at least one further component to form asphalt.

By means of this operation mode it becomes possible to produce with continuous asphalt mixing plants quality asphalt with a composition that is subject to strict tolerance requirements in practically any desired amount without producing waste asphalt or waste mineral material.

In a further preferred embodiment of the method, the mixing of the collected start-up hot mineral material and of the collected shut down hot mineral material with the at least one further component takes place during and/or after the shutting down of the material flow through the drum dryer with the same mixer as the mixing of the hot mineral material that is discharged from the drum dryer with the at least one further component in the normal operation. By this it becomes possible to conduct the method with conventional plants which have only one mixer.

In still a further preferred embodiment of the method, the start-up hot mineral material and the shut down hot mineral material are collected in a common container. This container preferably is a silo having a quadrangular, preferably square cross section, since this cross section geometry promotes a mixing or merging, respectively, of the start-up hot mineral material and the shut down hot mineral material, which are deposed one above the other, during withdrawal, which is in particular of advantage or necessary, respectively, in case said collected hot mineral material is not at once as batch processed to asphalt. However, also all other cross section geometries and arrangements which promote a merging or mixing, respectively, of the start-up hot mineral material and the shut down hot mineral material during withdrawal are preferred.

In still a further preferred embodiment of the method, the entire amounts of the collected start-up hot mineral material and of the collected shut down hot mineral material are mixed at once in the mixer with the at least one further component. By this it becomes possible to produce asphalt from the collected start-up hot mineral material and shut down hot mineral material which has practically no shift in composition with respect to the asphalt produced in normal operation.

In still a further preferred embodiment of the method, during the start-up of the material flow through the drum dryer, the amount of mineral material that is fed into the drum dryer per time unit and the amount of hot mineral material which is discharged per time unit from the drum dryer are determined, preferably continuously. The hot mineral material which is discharged is collected as start-up hot mineral material until a specific ratio between the fed amount and the discharged amount is reached or the amounts are equal. As amount per time unit preferably the mass flow is determined. By this it becomes possible to keep possible shiftings in composition at the start of the normal operation within certain limits or practically eliminate them, respectively, in case the discharged hot mineral material is collected until the amounts are identical. A second example of the invention concerns an asphalt mixing plant, preferably for conduction the method according to the first aspect of the invention. The plant comprises a drum dryer for drying and heating the mineral material to become hot mineral material and at least one mixer for mixing the hot mineral material with at least one further component, in particular with a binder material like e.g. bitumen, to form asphalt. The plant also comprises a control unit. By means of the control unit, the plant can in an automated way be operated in such a manner, that during the start-up of the material flow through the drum dryer at the start of an operation cycle of the plant the start-up hot mineral material which is discharged from the drum dryer is collected, that after the start-up of the material flow through the drum dryer in normal operation of the plant the hot mineral material which is discharged from the drum dryer is mixed in said at least one mixer with said at least one further component to form asphalt, that during the shut down of the material flow through the drum dryer at the end of the operation cycle of the plant the shut down hot mineral material 'which is discharged from the drum dryer is collected, and that during and/or after the shut down of the material flow through the drum dryer at least partial amounts of the collected start-up hot mineral material and of the collected shut down hot mineral material are jointly mixed in said at least one mixer with said at least one further component to form asphalt.

By means of the, asphalt mixing plant according to the invention it is now possible, despite of a continuous normal operation, to significantly reduce or eliminate the amount of waste asphalt or waste mineral material generated per operation cycle, 'without, having to accept the compromises with regard to the composition known from the prior art, and also to produce small amounts of quality asphalt with a composition that is subject to strict, tolerance requirements in an economic 'way.

In a preferred embodiment of the plant, it is designed in such a manner that the hot mineral material 'which is discharged from the, drum dryer in the normal operation can continuously or batch-wise be mixed in the at least one mixer with the at least one further component, and during and/or after the shut down of the material flow through the drum dryer the entire amount of the collected start-up hot mineral material, and shut down hot mineral material can batch-wise be mixed in the at least one mixer 'with the at least one further component.

By means of such a plant it is possible to produce, despite of a continuous normal operation, quality asphalt with a composition that is subject to strict tolerance requirements in practically any desired amount without producing waste asphalt or waste mineral material .

In a further preferred embodiment, the plant is designed in such a manner that the mixing of the collected start-up hot mineral material and of the collected shut down hot mineral material with the at least one further component can take place during and/or after the shutting down of the material flow through the drum dryer with the same mixer as the mixing of the hot mineral material that is discharged from the drum dryer in the normal operation with the at least one further component. By this, the equipment costs for a plant according to an embodiment of the invention can be reduced.

In still a further preferred embodiment, the plant is designed in such a manner that the start-up hot mineral material and the shut down hot mineral material can be collected in a common container, in particular in a silo having a quadrangular, preferably square cross section, since this cross section geometry promotes a mixing or merging, respectively, of the start-up hot mineral material and the shut down hot mineral material, which are deposed one above the other, during withdrawal from the silo. This is in particular of advantage in case the collected hot mineral material is not at once processed to asphalt. However, also all other cross section geometries and arrangements which promote a merging or mixing, respectively, of the start-up hot mineral material and the shut down hot mineral material during withdrawal are preferred. Furthermore it is envisaged to provide in each case one container for collecting the start-up hot mineral material and the shut down hot mineral material and to process the respective partial amounts which are 'withdrawn from these containers commonly batch-wise in the mixer to form asphalt.

In still a further preferred embodiment, the plant is designed in such a manner that the collected start-up hot mineral material and the collected shut down hot. mineral material can batch-wise be mixed in a mixer with the at least one further component. This mixer and the drum dryer of the plant are dimensioned such that the mixer can at once receive an amount of hot mineral material and can mix it with at least, one further component, in particular with a. binder material like e.g. bitumen, which corresponds to twice the amount of mineral material which in the normal operation at nominal plant capacity is present in the drum dryer. By means of this it becomes possible to produce asphalt from, the collected start-up hot mineral material and shut down hot mineral material 'which has practically no shift in composition with respect to the asphalt produced in normal operation.

In still a further preferred embodiment, the plant comprises means for determining, in particular continuously, the amount of mineral material 'which is fed into the, drum dryer per time, unit and the amount of hot, mineral material which is discharged per time, unit from the drum dryer during the start-up of the material flow through the drum dryer. Preferably, in each case the mass flow is determined as amount per time unit.

Furthermore, the plant is designed in a way that it can in an automated, way be controlled by the control unit in such a manner that the hot mineral material 'which is discharged from the, drum dryer is collected as start-up hot mineral material until a specific ratio between the fed amount and the discharged amount is reached or until the amounts are equal, and that subsequently the hot mineral material which is discharged is processed in the normal operation to asphalt. By this it. becomes possible to keep possible shiftings in composition at the start of the normal operation 'within certain limits or to practically eliminate them, respectively, in case the discharged hot mineral material is collected until the fed and discharged amounts per time unit or the mass flows, respectively, are identical.

The present invention will now be described, by way of non-limiting example only, with reference to the accompanying drawing, in which Pig. 1 shows a diagrammatic plan of an asphalt mixing plant.

The asphalt mixing plant shown in Fig. 1 comprises a pre-dosing station A with a pre-dosing unit 4, a collating conveyor 5, a feeding conveyor 6 as well as an oversize particle precipitator 13, a drying arrangement В with a gas-fired counterflow drum dryer 1 and a drum feeding conveyor 7, a mixing arrangement C with a hot elevator 8, a mixer 2, a batcher 9 and a heated buffer silo 3 as well as an asphalt silo arrangement D with underpinned asphalt silos 10 and a movable hopper 11.

The mixer 2 is designed as twin shaft compulsory mixer and can be run in continuous operation mode, i.e. continuously, as well as in batch operation mode, i.e. non-continuously. It comprises a feeding 12 for binder material, in particular bitumen.

In operation, the pre-dosing station A serves for the provision of a desired mass flow of mineral material of a desired composition, which via the drum feeding conveyor 7 is fed into the drum dryer 1. Inside the drum dryer 1, the fed mineral material is fed in counterflow into a hot gas stream and by doing so is heated and dried. It leaves the dryer 1 as hot mineral material and is in the normal operation thereafter via the hot elevator 8 fed into the mixer 2, where it is mixed with binder material which is delivered via the feeding 12 to become asphalt. The ready mixed asphalt thereafter is discharged from the mixer 2 and drops into the batcher 9, where it is collected and is batch-wise discharged into the movable hopper 11, which then charges the individual asphalt silos 10. Inside the asphalt silos 10 the ready-made asphalt is stored for the hand over to the user.

The plant comprises a plant control unit (not shown) by which the plant in an automated manner can be operated as described in the following:

During the start-up of the material flow through the drum dryer I, the start-up hot mineral material which is discharged from the drum dryer 1 is fed into the buffer silo 8 via the hot elevator 8. While doing so, the mass flow of mineral material that is fed into the drum dryer 1 via the drum feeding conveyor 7 and the mass flow of hot mineral material that is discharged from the drum dryer are continuously monitored and compared.

As soon as a specific ratio between the fed mass flow and the discharged mass flow exists or these mass flows are practically identical, operation is switched to normal operation, i.e. the hot mineral material which is discharged from, the drum dryer 1 is fed via the hot elevator 8 into the mixer 2, which mixes this material in continuous operation mode with binder material that has been supplied to the mixer via the feeding 12 to form a spha11.

The ready-made asphalt drops after it has been discharged from the mixer 2 into the batcher 9, where it is collected and is batch-wise discharged into the movable hopper 11, which then charges the individual asphalt silos 10 with asphalt.

At the end of the operation cycle, during the shut down of the material flow through the drum dryer 1, the shut down hot mineral material that is discharged from the drum dryer 1 is fed via the hot elevator 8 into the buffer silo 3, which has already received the startup hot mineral material during the start-up of the material flow through the drum dryer 1.

As soon as no hot mineral material is discharged anymore from the drum dryer, the entire start-up hot mineral material and shut down hot mineral material which has been collected inside the silo 3 is via the hot elevator 8 fed into the mixer 2, which now mixes it in batch operation mode with binder material, which again is supplied via the feeding 12, to form asphalt.

The. ready-made asphalt which has been mixed as a batch is thereafter as well fed into the batcher 9, where it is collected and batch-wise is discharged into the movable hopper 11, which charges it then into one or several of the asphalt silos 10.

The before described way of operation, in which the entire amount of start-up hot mineral material and shut down hot mineral material which has been collected inside the buffer silo 3 at once is processed in batch operation to become asphalt, is possible since the mixer 2 and the drum dryer 2 of the plant are dimensioned in such a manner that the mixer 2 at once can receive an amount of hot mineral material and mix it with an amount of binding material which is necessary for the asphalt production, which corresponds to twice the amount of mineral material which in the normal operation at nominal plant capacity is present, in the drum dryer 1.

In a variant, of the plant, in which the mixer 2 can receive less than twice the amount of mineral material which in the normal operation at nominal plant capacity is present, in the drum dryer 1 plus binder material, the buffer silo 3 is designed in such a manner that, during the withdrawal of a partial amount of the amount of hot mineral material collected therein, the 'withdrawn partial amount consists of start-up hot mineral material as well as of shut down hot mineral material. For this, the silo 3 for example features a square cross section, which during the withdrawal promotes the merging or mixing, respectively, of the start-up hot mineral material and the shut down hot mineral material.

In this variant, as soon as during the shut down of the material flow through the drum dryer 1 no hot mineral material is discharged anymore from the drum dryer 1, the start-up hot mineral material and the shut down hot mineral material which has been collected in the silo 3 is fed in several partial amounts via the hot elevator 8 into the mixer 2, which mixes each of the partial amounts in batch operation mode with binding material that has bee supplied via the feeding 12 to become asphalt .

The ready-made asphalt which has been mixed as batch from the respective partial amount thereafter is, as has already been described, fed into the batcher 9, where it is collected and is batch-wise fed into the movable hopper 11, which then charges it to one or several of the asphalt silos 10.

While various embodiments of the present invention have been described above, it should be understood that they have been presented by way of example only, and not by way of limitation. It will be apparent to a person skilled in the relevant art that various changes in form and detail can be made therein without departing from the spirit and scope of the invention. Thus, the present invention should not be limited by any of the above described exemplary embodiments.

Throughout this specification and the claims which follow, unless the context requires otherwise, the word "comprise", and variations such as "comprises" and "comprising", will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps.

The reference in this specification to any prior publication {or information derived from it), or to any matter which is known, is not, and should not be taken as an acknowledgment or admission or any form of suggestion that that prior publication (or information derived from it) or known matter forms part of the common general knowledge in the field of endeavour to which this specification relates.

Claims

THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS:

1. Method for operating an asphalt mixing plant comprising a drum dryer for drying and heating the mineral material that is to be processed to become hot mineral material and comprising at least one mixer for mixing the hot mineral material with at least one further component to become asphalt, wherein during the start-up of the material flow through the drum dryer at the start of an operation cycle of the asphalt mixing plant the start-up hot mineral material which is discharged from the drum dryer is collected, wherein after the start-up of the material flow through the drum dryer in normal operation of the asphalt mixing plant the hot mineral material which is discharged from the drum dryer is mixed in the at least one mixer with the at least one further component to become asphalt, wherein during the shut down of the material flow through the drum dryer at the end of the operation cycle of the asphalt mixing plant the shut down hot mineral material which is discharged from the drum dryer is collected, and wherein during and/or after the shut down of the material flow through the drum dryer at least partial amounts of the collected start-up hot mineral material and of the collected shut down hot mineral material are jointly mixed in the at least one mixer with the at least one further component to become asphalt.
2. A method according to claim 1, wherein the at least one further component is a binder material.
3. A method according to claim 1 or claim 2, wherein the at least one further component is bitumen.
4. Method according to any one of the preceding claims, wherein the hot mineral material which is discharged from the drum dryer in normal operation is continuously or batch-wise mixed in the at least one mixer with the at least one further component and the collected start-up hot mineral material and the collected shut down hot mineral material during and/or after the shut down of the material flow through the drum dryer is batch-wise mixed in the at least one mixer with the at least one further component.
5. Method according to one of the preceding claims, wherein the mixing of the collected start-up hot mineral material and of the collected shut down hot mineral material with the at least one further component during and/or after the shut down of the material flow through the drum dryer is performed with the same mixer as the mixing of the hot mineral material which is discharged from the drum dryer with the at least one further component in normal operation.
6. Method according to one of the preceding claims, wherein the start-up hot mineral material and the shut down hot mineral material are collected in one common container, having a quadrangular or having another geometry or arrangement, which during withdrawal promotes a merging or mixing, respectively, of the start-up hot mineral material and the shut down hot mineral material.
7. A method according to claim 6, wherein the common container is a silo.
8. A method according to claim 6 or claim 7, wherein the common container has a square cross-section.
9. Method according to one of the preceding claims, wherein the entire amounts of the collected start-up hot mineral material and of the collected shut down hot mineral material at once or in several partial amounts are mixed in the mixer with the at least one further component.
10. Method according to one of the preceding claims, wherein at least during the start-up of the material flow through the drum dryer the amount of mineral material that is fed into the drum dryer per time unit and the amount of hot mineral material which is discharged per time unit from the drum dryer are determined and the hot mineral material which is discharged is collected as start-up hot mineral material until a specific ratio between the fed amount and the discharged amount is reached or until the amounts are equal.
11. A method according to claim 10, wherein the amount of hot mineral material which is discharged per time unit from the drum dryer is determined cont inuously.
12. Plant for conducting the method according to one of the preceding claims.
13. A plant according to claim 12, comprising a drum dryer for drying and heating the mineral material to become hot mineral material and comprising at least one mixer for mixing the hot mineral material with at least one further component to become asphalt, and further comprising a control unit by means of which the plant in an automated manner can be operated such, that during the start-up of the material flow through the drum dryer at the start of an operation cycle of the plant the start-up hot mineral material which is discharged from the drum dryer is collected, that after the start-up of the material flow through the drum dryer in normal operation of the plant the hot mineral material which is discharged from the drum dryer is mixed in the at least one mixer with the at least one further component to become asphalt, that during the shut down of the material flow through the drum dryer at the end of the operation cycle of the plant the shut down hot mineral material which is discharged from the drum dryer is collected, and that during and/or after the shut down of the material flow through the drum dryer at least partial amounts of the collected start-up hot mineral material and of the collected shut down hot mineral material are jointly mixed in the at least one mixer with the at least one further component to become asphalt.
14. A plant according to claim 12 or claim 13, wherein the at least one further component is bitumen.
15. Plant according to any one of claims 12 to 14, wherein the plant is designed in such a manner that the hot mineral material which is discharged from the drum dryer in normal operation can continuously be mixed in the at least one mixer with the at least one further component and during and/or after the shut down of the material flow through the drum dryer the collected start-up hot mineral material and the collected shut down hot mineral material can batch-wise be mixed in the at least one mixer with the at least one further component.
16. Plant according to one of the claims 12 to 15, wherein the plant is designed in such a manner that the mixing of the collected start-up hot mineral material and of the collected shut down hot mineral material with the at least one further component during and/or after the shut down of the material flow through the drum dryer can be performed with the same mixer as the mixing of the hot mineral material which is discharged in the normal operation from the drum dryer with the at least one further component.
17. Plant according to one of the claims 12 to 16, wherein the plant is designed in such a manner that the start-up hot mineral material and the shut down hot mineral material can be collected in a common container having a quadrangular, or having another geometry or arrangement, which during withdrawal promotes a merging or mixing, respectively, of the start-up hot mineral material and the shut down hot mineral material.
18. A plant according to claim 17, wherein the common container is a silo.
19. A plant according to claim 17 or claim 18, wherein the common container has a square crosssection .
20. Plant according to one of the claims 12 to 19, wherein the plant is designed in such a manner that the collected start-up hot mineral material and the collected shut down mineral material can batch-wise be mixed in a mixer with the at least one further component, and wherein this mixer and the drum dryer of the plant are dimensioned such that the mixer can at once receive an amount of hot mineral material and can mix it with at least one further component which corresponds to twice the amount of mineral material which in the normal operation at nominal plant capacity is present in the drum dryer.
21. Plant according to one of the claims 12 to 20, wherein the plant comprises means for determining the amount of mineral material that is fed into the drum dryer per time unit during the start-up of the material flow through the drum dryer and the amount of hot mineral material which is discharged from the drum dryer per time unit during the start-up of the material flow through the drum dryer, and wherein the plant is designed in such a way that it can be controlled by the control unit in an automated way in such a manner that the hot mineral material which is discharged from the drum dryer is collected as start-up hot mineral material until a specific ratio between the fed amount and the discharged amount is reached or until the amounts are equal, and subsequently the hot mineral material which is discharged is processed in the normal operation to become asphalt.
22. A plant according to claim 21, wherein the plant comprises means for determining continuously the amount of mineral material that is fed into the drum dryer per unit time during the start-up of the material flow through the drum dryer.