Method for heating granular rock material, in particular for asphalt production

Abstract

The invention relates to a method for heating granular rock material (1a, 1b) in a dryer (2, 3) in which the rock material (1a, 1b) is heated using a hot gas flow (4a, 4b). The hot gas flow (4a, 4b) is generated using thermal energy (6) which has previously been stored in a heat accumulator (5). Using a heat accumulator for generating the hot gas flow makes it possible to heat the rock material with energy which could not be supplied to any other use at the time of its availability and which may otherwise have been wasted due to the lack of other storage possibilities. As a result, emissions from heating the rock material can be avoided, and the CO2 balance can be significantly improved.

Description

[0001] P192911PC00

[0002] Method for heating granular material

[0003] Rock material, especially for asphalt production

[0004] TECHNICAL AREA

[0005] The invention relates to a method for heating granular rock material, in particular for asphalt production, and to a plant for carrying out the method according to the preambles of the independent claims.

[0006] STATE OF THE ART

[0007] In asphalt production, the heating and drying of the aggregate material typically takes place in so-called drum dryers, in which the material is heated and dried by a stream of hot air. This hot air stream is typically generated by a burner powered by fossil or renewable fuels. The combustion of these fuels produces various undesirable emissions, such as CO, CO2, NOx, and hydrocarbons, and fossil-fueled burners also have a very poor CO2 balance.

[0008] PRESENTATION OF THE INVENTION

[0009] The task is to provide technical solutions that do not exhibit the aforementioned disadvantages of the state of the art, or at least partially avoid them.

[0010] This problem is solved by the subject matter of the independent patent claims.

[0011] According to this, a first aspect of the invention relates to a method for heating granular rock material (aggregates) in a dryer, preferably in a drum dryer, in which the P192911PC00

[0012] 2

[0013] Rock material is heated with a hot gas stream. If the rock material contains moisture, it is also dried in the process. The hot gas stream is generated using thermal energy that has previously been stored in a heat storage unit.

[0014] By using a thermal storage system to generate the hot gas stream, it becomes possible to heat the rock material with energy that, at the time of its availability, could not be used for any other purpose and, due to a lack of other storage options, might otherwise have been wasted. This avoids emissions for heating the rock material and significantly improves the CO2 balance.

[0015] In a preferred embodiment of the process, the hot gas stream is generated, at least temporarily, exclusively using the thermal energy previously stored in the heat storage tank. This offers the advantage that no additional thermal energy from other energy sources needs to be supplied for the generation of the hot gas stream. Such operation is particularly suitable for use with full heat storage tanks.

[0016] In another preferred embodiment of the method, the hot gas stream is generated, at least temporarily, with the additional use of one or more electric heating elements. This is achieved by further heating the hot gas stream coming from the heat storage unit with the heating element, in particular to a desired hot gas temperature, or by first heating the gas stream supplied to the heat storage unit for heating to the required hot gas stream with the heating element. Such operation is particularly intended for cases where the desired hot gas temperature cannot be reached, or can no longer be reached, with the heat storage unit. P192911PC00

[0017] 3

[0018] In yet another preferred embodiment of the process, a cooler gas stream is introduced, at least temporarily, into the hot gas stream coming from the heat storage unit before it is fed to the dryer, in order to reduce or adjust the temperature of the hot gas stream supplied to the dryer. Such operation is particularly suitable for cases where the temperature of the hot gas stream coming from the heat storage unit is significantly higher than the desired inlet temperature for the dryer.

[0019] It is preferred that the cooler gas stream consists of or includes recirculated exhaust gases from the dryer. This reduces the volume of exhaust gas and the dust load that burdens the exhaust gas filters.

[0020] The generated hot gas stream advantageously has a temperature greater than 500 °C, and in particular greater than 700 °C. Such temperatures are especially suitable for heating rock material for asphalt production.

[0021] In another preferred embodiment of the process, the dryer is heated exclusively with the hot gas stream, which is generated using the thermal energy previously stored in the heat storage unit and, if necessary, with the additional use of one or more electric heating elements. This variant of the process has the advantage that practically no emissions are produced at the site where the process is carried out.

[0022] In another preferred embodiment of the process, the dryer is heated, at least temporarily, by a burner in addition to the supply of the hot gas stream. This burner is advantageously operated with renewable fuels, preferably biogas, tall oil, or wood dust. The burner can heat one dryer or several dryers. This variant of the process is particularly suitable when P192911PC00

[0023] 4. No electric heating registers are present or are not used, e.g. because there is not enough electricity or no cheap electricity available, and the heat storage device(s) supply too little heat energy to ensure the desired hot gas temperature for the dryer.

[0024] In yet another preferred embodiment of the process, in addition to the hot gas stream, a further gas stream is supplied separately to the dryer, the temperature of which is lower than that of the supplied hot gas stream, in order to reduce or adjust the dryer's operating temperature to be lower than that of the supplied hot gas stream. Such operation is particularly suitable for cases where the temperature of the supplied hot gas stream is significantly higher than the desired operating temperature of the dryer.

[0025] It is preferred that the subsequent gas flow consists of or includes recirculated exhaust gases from the dryer. This reduces the volume of exhaust gas and the dust load that burdens the exhaust gas filters.

[0026] In particular, for the heating of rock material for asphalt production with recycled asphalt, it is preferred to carry out the process with two dryers in which different rock material is heated, namely so-called new mineral (fresh rock granulate) and recycled asphalt (granulated old asphalt).

[0027] It is preferred if the two dryers are operated at different temperatures, e.g. the new mineral dryer at 750 °C and the recycled asphalt dryer at 550 °C.

[0028] The dryer(s) used are preferably designed as counterflow drum dryers. Such dryers have proven particularly useful in heating rock material for asphalt production. P192911PC00

[0029] 5. Particularly proven. However, the use of DC drum dryers is also planned.

[0030] The thermal energy stored in the thermal storage system is preferably obtained from renewable energy sources, e.g., solar energy, wind energy, or hydropower; from waste heat, e.g., from waste heat from waste incineration or cement production; and / or from energy surpluses, e.g., from electricity production.

[0031] A second aspect of the invention relates to a plant for carrying out the method according to the first aspect of the invention.

[0032] The plant comprises a dryer for heating the rock material in a hot gas stream, a heat storage unit for generating a hot gas stream using heat energy previously stored in the heat storage unit, and a hot gas line arranged between the heat storage unit and the dryer for supplying a hot gas stream generated with the heat storage unit to the dryer.

[0033] Such systems make it possible to heat the rock material with energy that, at the time of its availability, could not be put to better use and would otherwise potentially be wasted due to a lack of other storage options. This avoids emissions from heating the rock material and significantly improves the CO2 balance.

[0034] In a preferred embodiment, the system comprises an electric heating element with which the hot gas stream coming from the heat storage unit can be further heated, in particular to a desired hot gas temperature, before it is fed to the dryer, or with which the gas stream fed to the heat storage unit for heating to the required hot gas stream can be preheated. This makes it possible to achieve the desired hot gas temperature even with an insufficient amount of heat in the heat storage unit.

[0035] 6

[0036] Storage to maintain operation at a desired hot gas temperature without generating additional emissions for heat generation at the point of process execution.

[0037] In another preferred embodiment, the system includes devices for supplying a gas stream into the hot gas line between the heat storage unit and the dryer, which is cooler than the hot gas stream coming from the heat storage unit, in order to reduce or adjust the temperature of the hot gas stream supplied to the dryer. This makes it possible to set the desired hot gas temperature for the dryer even if the temperature of the hot gas stream coming from the heat storage unit is significantly higher than the desired inlet temperature.

[0038] It is preferred that the equipment is designed to feed recirculated exhaust gases from the dryer into the hot gas line between the heat storage unit and the dryer. These exhaust gases are already significantly cooled, and their use allows for a reduction in the volume of exhaust gas and the dust load that burdens the exhaust gas filters.

[0039] In yet another preferred embodiment, the system includes a burner with which a hot gas stream can be generated for heating the dryer. This variant is particularly suitable when no electric heating elements are available or when they cannot be used at all times, e.g., because there is insufficient or no affordable electricity available, and the heat storage unit(s) temporarily supply too little or no heat energy to ensure the desired operating temperature in the dryer.

[0040] The burner can be designed to heat a single dryer or multiple dryers and is preferably designed with a capacity such that it can operate alone or at least together with any necessary P192911PC00

[0041] The plant's 7 electric heating registers ensure the plant's intended operation even with an empty heat storage tank.

[0042] It is preferred that the burner can be operated with renewable fuels, preferably biogas, tall oil or wood dust. This promotes a good CO2 balance.

[0043] In yet another preferred embodiment, the system is designed in such a way that, in addition to the hot gas stream supplied via the hot gas line, a further gas stream can be supplied separately to the dryer in order to set an operating temperature of the dryer which is lower than the temperature of a supplied hot gas stream.

[0044] This makes it possible to set the desired operating temperature of the dryer even if the temperature of the hot gas flow supplied via the hot gas line is significantly higher than the desired operating temperature of the dryer.

[0045] Advantageously, the system has a recirculation line by means of which exhaust gases from the gas outlet end of the dryer can be fed to the gas inlet end of the dryer as a required additional gas flow.

[0046] This can reduce the amount of exhaust gas and the dust load that burdens the exhaust gas filters.

[0047] Particularly in plants for heating rock material for asphalt production with recycled asphalt material, it is preferred that the plant includes two dryers in which different rock material can be heated, e.g. so-called new mineral (fresh rock granulate) and recycled asphalt (granulated old asphalt).

[0048] It is preferred if the two dryers are operated at different temperatures P192911PC00

[0049] 8 can be used, e.g. the new mineral dryer at 750 °C and the recycled asphalt dryer at 550 °C.

[0050] The dryer(s) of the inventive system are preferably designed as counter-current drum dryers. Such dryers have proven particularly effective in heating aggregate for asphalt production. However, it is also envisaged that co-current drum dryers may be used.

[0051] Although the terms "dryer", "drum dryer", "heat storage", "hot gas flow", "hot gas line", "burner", and "heating register" have been used essentially in the singular above and below, it should be clearly pointed out that several such elements can also be used in the inventive method and in the inventive plant. For example, it is provided that a single dryer is operated with one or more heat storage units, or that several dryers are operated with a common heat storage unit or with individual heat storage units assigned to the respective dryers.It is also provided that a single dryer is operated with one or more electric heating registers, or that in the case of several dryers, all are operated with a common heating register, or that all or some of the dryers are operated with individual heating registers assigned to the respective dryers.

[0052] BRIEF DESCRIPTION OF THE DRAWINGS

[0053] Further embodiments, advantages and applications of the invention will become apparent from the dependent claims and from the following description with reference to the figure.

[0054] This shows the system diagram of a system according to the invention with two drum dryers. P192911PC00

[0055] WAYS TO IMPLEMENT THE INVENTION

[0056] The single figure shows a highly abstracted plant diagram of a plant according to the invention with two counter-current drum dryers 2 , 3 for heating and drying granular rock material 1a, 1b for asphalt production .

[0057] The first drum dryer 2 is used for heating and drying recycled asphalt 1a, the second drum dryer 3 for heating and drying virgin mineral 1b.

[0058] As can be seen, the two material streams 1a, 1b pass through the drum dryers 2, 3 from right to left until they emerge from the dryers 2, 3 heated and dried. In the opposite direction, i.e., from left to right, hot gases flow through the drum dryers 2, 3, permeating the rock material 1a, 1b contained within. The gases exit the dryers 2, 3 as exhaust gas, which is then conveyed via an exhaust gas line 20 to a common filter system 21. In this system, the dust particles carried in the exhaust gas are separated as completely as possible. The filtered exhaust gas is then released into the atmosphere A.

[0059] The stream of hot gases, by means of which the rock material 1a, 1b is heated and dried in the drum dryers 2, 3, can be provided in different ways for each dryer. Each of the two drum dryers 2, 3 has its own burner 9a, 9b, with which a hot gas stream can be generated for heating the drum dryer 2, 3. The burners 9a, 9b are designed so that they can be operated with renewable fuels 10, specifically biogas 11. The burner capacities are designed such that, if necessary, operation using only burners 9a, 9b is possible. P192911PC00

[0060] 10

[0061] As an alternative to pure burner operation, it is also possible to provide the electricity from hot gases in the drum dryers 2, 3 completely or partially by supplying hot gas streams 4a, 4b to the dryers 2, 3 via associated hot gas lines 16a, 16b.

[0062] These hot gas streams 4a, 4b are generated by supplying a fresh air stream 17 to a heat storage tank 5, in which heat energy 6 has previously been stored. This fresh air stream is heated in the heat storage tank 5 and then exits it as two separate hot gas streams 4a, 4b, each of which is fed to one of the two drum dryers 2, 3. Before entering their respective drum dryers 2, 3, the hot gas streams 4a, 4b each flow through an electrically heated heating element 7a, 7b, which can be used to heat them further if required.

[0063] As can be seen from the symbols shown on the far left of the figure, the thermal energy 6 stored in the thermal storage unit 5 may have been obtained from renewable energy sources, such as solar energy 12, wind energy 13 or hydropower 22. However, it may also have been obtained from waste heat, such as high-temperature industrial waste heat 14, or from energy surpluses, such as from electricity production 15.

[0064] In the system shown here, the two hot gas streams 4a and 4b leave the heat storage tank 5 at approximately 750°C during pure heat storage operation. This hot gas temperature is well suited for operating the second drum dryer 3, in which the virgin mineral 1b is heated and dried. However, it is too high for operating the first drum dryer 2, in which the recycled asphalt 1a is heated and dried. This dryer 2 requires a gas stream temperature of approximately 550°C on the gas inlet side (left side).

[0065] To maintain this temperature in the first drum dryer 2 at a temperature of the supplied hot gas stream 4a P192911PC00

[0066] To enable 11 of 750 °C, the system has a recirculation line 19, by means of which a stream of recirculated filtered exhaust gas 8 from the drum dryers 2, 3 can be supplied to this drum dryer 2 in addition to the hot gas stream 4a, which has a temperature of approximately 100 °C.

[0067] Alternatively or additionally, the system is also provided for to include further lines 18 (shown as dashed lines) with which recirculated filtered exhaust gas 8 from the drum dryers 2, 3 can be fed into the hot gas lines 16a, 16b between the heat storage tank 5 and the drum dryers 2, 3, in order to reduce or adjust the temperatures of the hot gas streams 4a, 4b supplied to the drum dryers 2, 3.

[0068] While preferred embodiments of the invention are described in the present application, it should be clearly pointed out that the invention is not limited to these and can also be carried out in other ways within the scope of the following claims.

Claims

P192911PC00 12 PATENT CLAIMS 1. A method for heating granular rock material (1a, 1b), in particular for asphalt production, comprising the steps of: a) providing a dryer (2, 3) for heating the rock material (1a, 1b) with a hot gas stream (4a, 4b); b) providing a heat storage device (5); c) storing heat energy (6) in the heat storage device (5); d) generating a hot gas stream (4a, 4b) using the heat energy (6) previously stored in the heat storage device (5); e) supplying the hot gas stream (4a, 4b) to the dryer (2, 3); and f) heating the rock material (1a, 1b) in the dryer (2, 3) using the hot gas stream (4a, 4b).

2. Method according to claim 1, wherein the hot gas stream (4a, 4b) is generated exclusively using the heat energy (6) previously stored in the heat storage unit (5).

3. Method according to claim 1, wherein the hot gas stream (4a, 4b) is generated using an additional electric heating element (7a, 7b).

4. Method according to one of the preceding claims, wherein a cooler gas stream (8) is supplied to the hot gas stream (4a, 4b) coming from the heat storage (5) before it is supplied to the dryer (2, 3), in order to reduce or adjust the temperature of the hot gas stream (4a, 4b) supplied to the dryer (2, 3). P192911PC00 13 5. Method according to claim 4, wherein the cooler gas stream (8) consists of or comprises recirculated exhaust gases from the dryer (2, 3).

6. Method according to one of the preceding claims, wherein the generated hot gas stream (4a, 4b) has a temperature greater than 500°C, in particular greater than 700°C.

7. Method according to one of the preceding claims, wherein the dryer (2, 3) is heated exclusively with the hot gas stream (4a, 4b).

8. Method according to any one of claims 1 to 6, wherein the dryer (2, 3) is not heated exclusively with the hot gas stream (4a, 4b).

9. Method according to claim 8, wherein the dryer (2, 3) is additionally heated with a burner (9a, 9b).

10. Method according to claim 9, wherein the burner (9a, 9b) is operated with renewable fuels (10), in particular with biogas (11), tall oil or wood dust.

11. Method according to one of the preceding claims, wherein the dryer (2) is supplied with a hot gas stream in addition to the hot gas stream. (4a) a further gas stream (8) is supplied separately, the temperature of which is lower than the temperature of the supplied hot gas stream (4a) , to set an operating temperature of the dryer (2) which is lower than the temperature of the supplied hot gas stream (4a) .

12. Method according to claim 11, wherein the further gas stream (8) consists of or comprises recirculated exhaust gases from the dryer (2, 3). P192911PC00 14 13. Method according to one of the preceding claims, wherein two dryers (2, 3) are provided in which different rock material (1a, 1b) is heated, in particular virgin mineral (1b) and recycled asphalt (1a) .

14. Method according to claim 13, wherein the dryers (2, 3) are operated at different temperatures.

15. Method according to one of the preceding claims, wherein the dryer(s) (2, 3) are designed as drum dryers, in particular as counterflow drum dryers.

16. Method according to one of the preceding claims, wherein thermal energy is transferred into the heat storage device (5). (6) is stored, which was obtained from renewable energy sources, in particular solar energy (12), wind energy (13) or hydropower (22).

17. Method according to one of the preceding claims, wherein thermal energy is transferred into the heat storage device (5). (6) is stored which was obtained from waste heat, in particular waste heat from waste incineration, cement production or industry (14) .

18. Method according to one of the preceding claims, wherein thermal energy is transferred into the heat storage device (5). (6) is stored, which was obtained from energy surpluses, in particular from electricity production (15) .

19. Plant for carrying out the method according to one of the preceding claims, comprising a) a dryer (2, 3) for heating the rock material (1a, 1b) in a hot gas stream; P192911PC00 15 b) a heat storage unit (5) for generating a hot gas stream (4a, 4b) using heat energy (6) previously stored in the heat storage unit (5); and c) a hot gas line (16a, 16b) arranged between the heat storage unit (5) and the dryer (2, 3) , for supplying a hot gas stream (4a, 4b) generated with the heat storage unit (5) to the dryer (2, 3) .

20. System according to claim 19, further comprising an electric heating register (7a, 7b) with which the hot gas stream coming from the heat storage (5) can be further heated or a gas stream (17) supplied to the heat storage (5) for heating to the hot gas stream (4a, 4b) according to the claim can be preheated.

21. Plant according to one of claims 19 to 20, further comprising facilities (18) for supplying a gas stream (8) into the hot gas line (16a, 16b) between the heat storage unit (5) and the dryer (2, 3), which is cooler than the hot gas stream (4a, 4b) coming from the heat storage unit (5), for reducing or adjusting the temperature of the hot gas stream (4a, 4b) supplied to the dryer (2, 3).

22. Plant according to claim 21, wherein the devices (18) for supplying a gas flow into the hot gas line are designed for supplying exhaust gases (8) of the dryer (2, 3) into the hot gas line (16a, 16b).

23. System according to one of claims 19 to 22, further comprising a burner (9a, 9b) with which a hot gas stream can be generated for heating the dryer (2, 3) . P192911PC00 16 24. Plant according to claim 23, wherein the burner (9a, 9b) can be operated with renewable fuels (10), in particular with biogas (11), tall oil or wood dust.

25. Device according to one of claims 19 to 24, wherein the system is designed such that a further gas stream (8) can be supplied separately to the dryer (2) in addition to the hot gas stream (4a), in order to set an operating temperature of the dryer (2) which is lower than the temperature of a supplied hot gas stream (4a).

26. System according to claim 25, wherein the system has a recirculation line (19) by means of which exhaust gases from the dryer can be fed back to the dryer (2) as a further gas stream (8).

27. Device according to one of claims 19 to 25, comprising two dryers (2, 3) in which different rock material (1a, 1b) can be heated, in particular virgin mineral (1b) and recycled asphalt (da).

28. Plant according to one of claims 19 to 27, wherein the dryer(s) (2, 3) are designed as drum dryers, in particular as counterflow drum dryers.

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