Device for producing cooled fresh concrete

Abstract

According to the invention, for cooling cement during the production of fresh concrete, at least a partial stream of the cement or other additive supplied to the concrete mixer (4) is brought into contact with a liquefied cryogenic refrigerant in a conveying device (41). The conveying device (41) has a return line (44) through which at least a partial stream of the cooled additive is circulated until a predetermined temperature of the additive is reached. The refrigerant that evaporates in this process can then be used to cool the mixing water used in the production of the fresh concrete. The invention enables precise dosing and temperature control of the cooled additive, as well as very efficient use of the refrigerant.

Description

[0001] The invention relates to a device for producing cooled fresh concrete, comprising at least one storage container for an additive, a mixing device for mixing the additive from the storage container with further additives and with additive water to form fresh concrete, and a conveying line connecting the storage container to the mixing device, in which conveying line a cooling device for cooling and conveying the additive is integrated, wherein the cooling device comprises at least one coolant supply line for a liquefied cryogenic coolant, at least one gas discharge line for evaporated coolant, a feed opening for the additive to be cooled, and a discharge opening for the cooled additive, which is fluidly connected to the mixing device.

[0002] During the production of fresh concrete, a certain maximum temperature must be maintained to avoid thermal stresses in the solid concrete. This requires, especially at high ambient temperatures, cooling at least one of the solid raw materials, i.e., a binder such as cement, or another solid aggregate such as sand, gravel, chippings, fly ash, or blast furnace sand (binders and aggregates are referred to collectively as "additives" below), or the water used to produce the fresh concrete – referred to here as "mixture water." Various processes are currently used for this purpose, including cooling systems operated electrically or by means of a cooling base (hereinafter referred to as "conventional cooling processes"), or with the aid of cryogenic media, particularly liquid carbon dioxide or liquid nitrogen.

[0003] For example, various arrangements are known from EP 174 97 67 A2, EP 174 96 29 A2, DE 40 10 045 A1, or EP 0 436 140 A1, in which cement or another additive is cooled as it is fed into a storage silo. The cooled cement is then removed from the storage silo as needed and used to produce fresh concrete. Generally, such cooling processes, in which aggregates are cooled as they are fed into the storage silo, result in high consumption of coolant due to unavoidable losses. Furthermore, cooling of the entire stored supply is necessary even if only a small portion of the stored additive is actually required in cooled form.

[0004] DE 10 2007 008811 B3 discloses a device for producing cooled fresh concrete according to the preamble of claim 1.

[0005] EP 207 79 33 A1 discloses a device and method for producing fresh concrete. A second conveying line is arranged parallel to an existing conveying line between the storage silo and the scale or mixing device. A partial flow of the respective additive is branched off in this second conveying line and brought into thermal contact with a cryogenic refrigerant, such as nitrogen or carbon dioxide, in a cooling device. The cooling device is a vortex screw cooler or a fluidized-bed reactor. The invention enables precise dosing and temperature control of the additive as it is fed to the mixing device. However, even here, a significant portion of the refrigerant is lost unused.

[0006] The invention is therefore based on the object of specifying a device for producing cooled fresh concrete in which the efficiency of the cooling used is improved compared to methods or devices according to the prior art.

[0007] This object is achieved by a device having the features of patent claim 1. Advantageous embodiments of the invention are specified in the subclaims.

[0008] According to the invention, the cooling device is integrated into a cooling and conveying device, so that the additive is cooled and transported to the mixing device at the same time. For this purpose, the cooling and conveying device has a conveying tool arranged in a housing and extending between the feed opening and the discharge opening, which simultaneously functions as a tool for cooling the additive by ensuring thorough mixing of the additive and the coolant. The housing is equipped with one or more coolant supply lines, which are arranged, for example, at regular intervals on the housing. The coolant supply line(s) preferably opens into a lower region of the housing, preferably in a region in which the conveying tool is also located.

[0009] Furthermore, the cooling and conveying device has a return line through which at least a partial flow of the additive can be conveyed back towards the feed opening and thus circulated. In addition, the discharge opening is equipped with a closure means, for example a slide valve or a lock, by means of which the discharge opening is completely or partially closed and thus the size of the returned partial flow can be adjusted. Once the discharge opening is completely closed by the closure means, the entire conveyed flow enters the return line and is cooled again. Once a predetermined cooling temperature of the additive has been reached, the closure means opens the discharge opening. The cooled additive is then transported via the scale to the mixing device or directly to the mixing device, where it is mixed with the other additives and the mixing water.The sealing means also ensures that at least to a large extent no ambient moisture or added water from the mixing device gets into the cooling and conveying device.

[0010] It is also conceivable to design the opening cross-section of the discharge opening to be variable, so that a partial flow of variable size is continuously discharged through the discharge opening, while the remaining additive is returned via the return line and cooled again. In this case, the temperature of the discharged additive can be continuously controlled.

[0011] By recirculating at least a partial flow of the additive, a particularly intimate mixing of the cryogenic refrigerant with the additive can be achieved, thus achieving a particularly low temperature of the additive, for example (when choosing liquid nitrogen as the refrigerant) between -100°C and -170°C or below. The device according to the invention thus enables precise temperature control of the respective additive. This allows for very flexible response to the respective requirements and adjustment of the cooling accordingly. At the same time, the evaporated refrigerant, which is still at a very low temperature, is almost completely removed via the gas discharge line and can be used for further purposes.

[0012] Conveniently, a controlled temperature control of the additive is achieved by circulating the additive, or at least a partial flow thereof, in the cooling and conveying device until a certain cooling capacity has been achieved. In this embodiment, the cooling and conveying device is operatively connected to a control unit, by means of which the conveying of the additive in the cooling and conveying device and the actuation of the closure means in the discharge opening are controlled depending on a temperature determined by a measuring device. The measuring device can, for example, be arranged in the area of ​​the feed opening or the discharge opening of the cooling and conveying device or in the conveying line outside the cooling and conveying device in order to measure the temperature of the uncooled or cooled additive, or also in the area of ​​the mixing device in order to record the temperature of the finished fresh concrete.

[0013] A mechanical conveying device, such as a screw conveyor, is preferably used as the conveying tool in the cooling and conveying system. However, other conveying devices, such as a pneumatic conveying device or a fluidized-bed conveyor, are also conceivable. In the case of pneumatic or fluidized-bed conveying, the cryogenic refrigerant can also be fed in together with the propellant or fluidizing agent.

[0014] The housing is conveniently arranged at an angle, rising from the feed opening to the discharge opening. This allows the additive to overcome a height difference in the cooling and conveying device, for example, in cases where the mixing device is located at an elevated position so that the finished fresh concrete can be poured directly into a waiting transport vehicle.

[0015] In the simplest case, the return line is designed as a tubular line through which the returned partial flow of the additive reaches the area of ​​the feed opening under the effect of gravity. An advantageous embodiment of the invention, however, also provides for the provision of means for conveying and / or cooling the returned partial flow in the return line. Mechanical or pneumatic conveying means or a fluidized bed conveyor are conceivable here. One or more coolant supply lines can also be provided in the return line in order to maintain a cold atmosphere in the return line. In a preferred embodiment of the invention, the gas discharge line of the cooling device (or the cooling and conveying device) is connected to a device for cooling the mixing water used for the production of the fresh concrete.In this embodiment, after the aggregate has been cooled by the liquefied cryogenic refrigerant, the residual cold of the evaporated refrigerant is used to cool the mixing water. The invention thus overcomes the disadvantage of other cement cooling processes using cryogenic refrigerants, in which a significant portion of the cooling energy of the refrigerant is lost unused. Cooling of the mixing water is achieved, for example, by passing the evaporated refrigerant through a heat exchanger around which the mixing water flows, which is arranged in a container storing the mixing water, or by introducing the evaporated refrigerant into the mixing water, possibly after passing through such a heat exchanger.

[0016] The gas discharge line is expediently equipped with a filter device for separating solid particles from the evaporated cryogenic refrigerant. This prevents the accumulation of particles of the additive, for example, in the container storing the evaporated cryogenic refrigerant, particularly during subsequent use of the evaporated cryogenic refrigerant, for example, for cooling the additive water.

[0017] In a further advantageous embodiment of the device according to the invention, the cooling device comprises a twin-shaft mixer with two mixing shafts driven by at least one drive device, which are arranged in a housing which is essentially gas-tight and equipped with thermally insulating walls and which is equipped with a feed opening for the additive to be cooled, a discharge opening for cooled additive, with a plurality of refrigerant feed lines (injectors) opening into the housing and connected to a feed line for a liquefied cryogenic refrigerant, and with a gas discharge line for evaporated cryogenic medium.

[0018] The feed opening and the discharge opening of the twin-shaft mixer are arranged horizontally spaced from one another and each equipped with a closure unit, for example a lock or a slide valve, to enable a substantially gas-tight closure of the preferably pressure-resistant housing, with the exception of the gas discharge. The mixing shafts are typically equipped with mixing elements, such as mixing paddles or blades, which promote intensive mixing of the additive with the refrigerant. The mixing elements are preferably movably mounted on the respective shaft. The drive device comprises a motor for each of the mixing shafts or a motor for the entire device, which is equipped with a suitable gear for operating all mixing shafts.

[0019] When the cooling system is designed as a twin-shaft mixer, the additive is cooled batchwise. A predetermined amount of additive, e.g. cement, is fed to the twin-shaft mixer and the feed and discharge openings are sealed gas-tight. A liquefied cryogenic coolant, e.g. liquid nitrogen or liquid carbon dioxide, is fed in via the injectors. The movement of the mixing shafts constantly moves the additive from the feed opening to the discharge opening and back again, thereby achieving intensive cooling. As the additive absorbs heat, the cryogenic coolant evaporates and is discharged via the gas outlet. After a certain time, which can be set, for example, depending on the temperature of the fresh concrete or by continuously monitoring the temperature of the additive in the twin-shaft mixer, the discharge opening is opened.The now cooled additive is discharged through the discharge opening and transported to the mixing device, where it is mixed with other additives and mixing water to form fresh concrete.

[0020] The liquefied cryogenic refrigerant is supplied via a plurality of refrigerant supply lines, which can be arranged on all sides of the housing. Preferably, at least some of the injectors open into a lower section of the housing, i.e., the bottom of the housing or an area filled with the additive during operation of the twin-shaft mixer.

[0021] Since the additive in the cooling device (or in the cooling and conveying device) can be cooled to a temperature that is limited only by the temperature of the coolant, it is generally sufficient to cool a comparatively small first partial flow of the additive to achieve an efficient cooling result. Thus, an advantageous embodiment of the device according to the invention provides that a second partial flow of the additive stored in the storage silo is fed directly to the mixing device via a second conveying line past the cooling device, for example the twin-shaft mixer, wherein the ratio of the quantities of additive transported via the first conveying line and the second conveying line is preferably regulated as a function of a target temperature of the produced fresh concrete.The second partial flow thus contains either uncooled additive or additive that has been cooled, for example, using conventional cooling methods, to a higher temperature than the first partial flow cooled with the cryogenic refrigerant. The second feed line can also be used in particular when cooling of the additive is not required, for example, at low ambient temperatures. In this case, the additive is fed entirely via the second feed line, and the cooling device does not need to be started.

[0022] Advantageously, liquid nitrogen or liquid carbon dioxide is used as the cryogenic refrigerant in the cooling system (or the cooling and conveying system). The choice of cryogenic refrigerant depends on the specific circumstances: Nitrogen allows cooling of the additive to temperatures as low as -193°C. Carbon dioxide only allows cooling to approximately -78.5°C, but has the advantage of approximately twice the sublimation enthalpy compared to nitrogen. Furthermore, when carbon dioxide is supplied in liquid form, complex heat-insulated supply lines are not required.

[0023] The additive to be cooled in the device according to the invention is preferably cement, but it can also be sand or another free-flowing additive required for the production of fresh concrete.

[0024] An embodiment of the invention will be explained in more detail with reference to the drawing. The schematic views show: Fig. 1: A device according to the invention for producing cooled fresh concrete in a first embodiment Fig. 2a: the cooling device of the device from Fig. 1 in a side view, Fig. 2b: the cooling device from Fig. 1 in a sectional view from above, Fig. 3: A device according to the invention for producing cooled fresh concrete in a second embodiment, Fig. 4a: the cooling device from Fig. 3 in a sectional view from above and Fig. 4b: the cooling device from Fig. 3 in a lateral sectional view.

[0025] The device 1 typically comprises a storage silo 2 for an additive, in this embodiment cement. The storage silo 2 is connected via a conveyor line 3 to a scale 5, to which a mixing device 4 is connected, which is used to mix the fresh concrete and into which further feeds for other additives, such as sand, additives or mixing water, flow. The conveyor line 3 can be either a pneumatic conveyor line or a mechanical conveyor device, for example a conveyor belt. For dosing the additive, a dosing element 6, which is for example a slide valve or a dosing screw, is arranged in the conveyor line 3 in a manner known per se.

[0026] At the outlet of the storage silo 2, a conveying line 8 branches off, which is also fluidly connected to the scale 5 and in which cement is also transported pneumatically or mechanically from the storage silo 2. A valve 9 regulates the material flow through the conveying line 8. By actuating the dosing element 6 and the valve 9, the material flow can be directed entirely or partially through the conveying line 3 or through the conveying line 8.

[0027] The material flow conveyed through the conveying line 8 is cooled in the manner described below. The conveying line 8 flows into a cooling device 10 - described in more detail below - in which the cement is brought into direct thermal contact with a liquefied cryogenic coolant. In this exemplary embodiment, the coolant is liquid nitrogen, which is stored in a tank 11 and conveyed to the cooling device 10 via a thermally insulated coolant supply line 12. Due to the thorough mixing with the liquid nitrogen in the cooling device 10, the cement can be cooled to temperatures as low as -193°C. Instead of liquid nitrogen, another cryogenic coolant can also be used, for example liquid carbon dioxide. The nitrogen that evaporates during the cooling process is discharged from the cooling device 10 via a gas discharge line 13.

[0028] The cooled cement is then either fed directly to the scale 5 via a suitable dosing element (not shown here) or, as in the exemplary embodiment, temporarily stored in an insulated storage container 14. By means of a dosing element 15 arranged on the storage container 14, for example a slide valve, the cooled cement in the storage container 14 is fed entirely or in a predetermined amount to the scale 5. Cooled cement from the storage container 14 and uncooled cement from the delivery line 3 can be weighed either together or independently of one another in the scale 5 and then mixed into the mixing device 4.

[0029] The vaporized nitrogen discharged from the cooling device 10 via the gas discharge line 13, which still retains a considerable residual coldness, is subsequently used in the exemplary embodiments shown here to cool the mixing water used to produce the fresh concrete. The mixing water is stored in a closed container 16, which is fluidly connected to the mixing device 4 via a water line 17. The gas discharge line 13 runs through a passage in the wall of the container 16, passes through a heat exchanger 18, which, during operation of the device 1, is located below a water level 19 of the mixing water in the container 16, and finally discharges at an outlet opening 20 below the water level 19 in the container 16.In order to prevent the penetration of water into the gas discharge line 13 or the cooling device 10, particularly during breaks in operation, the gas discharge line 13 is equipped with a non-return valve 21, for example a non-return flap or a non-return valve, which only opens when a certain, predetermined overpressure in the gas discharge line 13 compared to the hydrostatic pressure of the water in the container 16 occurs.

[0030] Furthermore, it is also conceivable to dispense with a heat exchanger arranged in the container 16 and to feed the evaporated nitrogen from the cooling device directly into the addition water in the container 10 at an inlet device, or to carry out an exclusively indirect cooling of the addition water and to withdraw the evaporated nitrogen after passing through the heat exchanger 18 and not to introduce it into the addition water.

[0031] During operation of the device 1, liquid nitrogen from the tank 11 is brought into thermal contact with the cement from the delivery line 8 in the cooling device 10, cooling it and evaporating itself in the process. The evaporated nitrogen passes through a filter 22, in which any entrained cement powder is separated from the nitrogen. The nitrogen is then brought into indirect thermal contact with the mixing water in the tank 16 in the heat exchanger 18, where it heats up to such an extent that its outlet at the outlet opening 20 does not lead to ice formation at the outlet opening 20. The nitrogen gas accumulating above the water level in the tank 16 is discharged via an exhaust line 23.

[0032] The cement is fed via line 3 particularly when, for example, cooling of the cement is not required at low ambient temperatures. However, by varying the supply of cooled or uncooled cement by adjusting the partial flows conducted through lines 3, 8, the temperature of the total cement fed to the scale 5 can also be regulated. For this purpose, the dosing elements 6, 15 are connected to a control unit 24, by means of which the respective mass flows can be regulated depending on a temperature measured in the fresh concrete produced by a measuring device 25 arranged in the mixing device 4. Another possibility for tempering the cement is provided by the cooling device 10 described below.

[0033] In the Fig. 2a and 2bThe cooling device 10 shown in more detail is a twin-shaft mixer. This comprises, in a conventional manner, two mixing shafts 26a, 26b mounted for rotation about their longitudinal axes, each driven by a motor 27a, 27b. Reversing gears 28a, 28b enable the direction of rotation to be changed during operation. A plurality of blades 29, which are movably mounted on the mixing shaft 26a, 26b, are arranged on each of the mixing shafts 26a, 26b, in a likewise conventional manner. Furthermore, instead of the two motors 27a, 27b shown here, a common drive unit for both mixing shafts 26a, 26b can also be used.

[0034] The mixing shafts 26a, 26b are housed in a thermally well-insulated, pressure-resistant, and—with the exception of the openings described below—gas-tight housing 30. A feed unit 32 for supplying the cement opens into the housing 30 at a feed opening 31. A discharge opening 33 of the housing 30 is followed by a discharge unit 34, by means of which the cooled cement is transported to the storage container 14 or the scale 5 and the mixing device 4.

[0035] The refrigerant is supplied from the refrigerant supply line 12 via a plurality of injectors 35 into a (geodetically speaking) lower region of the housing 30. The housing 30 is designed such that the mixing shafts 26a, 26b are arranged horizontally or slightly ascending toward the discharge opening 33. The evaporated refrigerant is discharged via a gas outlet 36, which is connected to the gas discharge line 13 with filter 22.

[0036] During operation of the cooling device 10, cement is transported in a predetermined amount into the housing 30 via the feed unit 32 and the feed opening 31. The feed unit 32 is then sealed gas-tight by means of a slide valve 37. Another slide valve 38 is located in the discharge unit 34 and prevents the unwanted escape of cement and evaporated coolant via this route. Simultaneously with the cement supply, a liquefied cryogenic coolant, for example, liquid nitrogen, is introduced into the housing 30 via the injectors 35. By continuously actuating the mixing shafts 26a, 26b, the cement is continuously swirled and intimately mixed with the coolant, thereby cooling it. The mixing shaft 26a transports the cement from the feed opening 31 toward the discharge opening 33, which is horizontally spaced from the feed opening.If the slide valve 38 is closed, the mixing shaft 26b then transports the cement back to the discharge opening 31. The direction of rotation of the mixing shafts 26a, 26b can also be varied using the switching gears 28a, 28b. The coolant evaporates upon contact with the cement and creates an overpressure inside the housing 30, which reliably prevents the penetration of ambient air and the water vapor contained therein. The evaporated coolant, which is always at a relatively low temperature, for example, a temperature between -120°C and -170°C, is discharged via the gas vent 36 and the gas discharge line 13 and used to cool the added water in the manner described above. After a certain period of time, the slide valve 38 is opened. The cement transported toward the discharge opening 33 is no longer returned, but instead leaves the cooling device 10 via the discharge unit 34.The cooling device 10 is then available for cooling the next batch of cement.

[0037] The duration of the cement's residence in the device 1 is either determined by a predetermined period of time or is controlled by the control unit 24 as a function of a measured temperature, for example, the temperature of the fresh concrete measured by the measuring device 25. If, for example, the temperature of the fresh concrete measured by the measuring device 25 is greater than a predetermined maximum temperature of the fresh concrete, the slide valve 56 remains closed for a longer period. The cement is thus circulated for a correspondingly longer time by means of the mixing shafts 26a, 26b of the twin-shaft mixer and thus cools further before the slide valve 38 opens and the cement is discharged via the discharge opening 33.

[0038] The Fig. 3 and 4The device 40 shown differs from the device 1 only by a different cooling device 41, which in the device 40 replaces the cooling device 10 of the device 1. The remaining elements of the device 40 correspond in structure and function to those of the device 1 and are therefore identified by the same reference numerals.

[0039] The Fig. 4 a and Fig. 4bThe cooling device 41 shown in more detail comprises a housing 42, only partially shown here, which is divided longitudinally into two parallel conveying channels 43, 44 that are separated from one another by a wall 45. In the region of the end faces 46, 47 of the housing 42, the wall 45 is severed by an opening 48, 49, whereby the conveying channels 43, 44 are connected to one another. A conveying tool, in the embodiment shown here a conveyor screw 50, is arranged in the conveying channel 43 and extends over almost the entire length of the housing 42.

[0040] In the area of ​​the front side 46, a feed unit 52 for an additive to be cooled is arranged on the top side of the housing 42, said feed unit having a feed opening 53 which opens into the housing 42 above the conveyor screw 50. In the area of ​​the front side 47, a discharge unit 54 with a discharge opening 55 and slide 56 arranged below the conveyor screw 50 is provided on the bottom side of the housing 42. In the embodiment shown here, the housing 42 is arranged at an angle, rising from the feed opening 53 to the discharge opening 55, in order to overcome a height difference to the scale 5 and / or mixing device 4. This is particularly advantageous when the scale 5 and / or the mixing device is / are arranged in an elevated position, for example, to facilitate the loading of transport vehicles with the fresh concrete mixed in the mixing device 4.

[0041] Furthermore, a refrigerant supply line 58 is provided, which opens into the conveying channel 43 of the housing 42 at several outlet openings 59 on the bottom side, as well as a gas outlet 61, which serves to discharge evaporated refrigerant and is fluidly connected to the exhaust line 13 and the filter 22.

[0042] During operation of the cooling device 41, the additive to be cooled, for example, cement, is fed via the feed unit 52 and conveyed by the conveyor screw 50 in the conveying channel 43 toward the discharge opening 55. At the same time, a liquefied cryogenic coolant, for example, liquid nitrogen, is introduced via the coolant supply line 58. As the additive is conveyed by the conveyor screw 50, the coolant mixes thoroughly with the additive, cooling it. The coolant evaporates and is discharged via the gas outlet 61.

[0043] When the additive reaches the discharge opening 55, two possibilities exist: If the slide 56 is open, at least a partial flow of the additive falls through the discharge unit 54 to the scale 5, from which it is transported further to the mixing device 4. If, on the other hand, the slide 56 is closed, the additive passes through the opening 49 into the conveyor channel 44. In the conveyor channel 44, the already pre-cooled additive falls downwards under the effect of gravity due to the inclined arrangement of the housing 42 and passes through the opening 48 back into the conveyor channel 43, where it is again conveyed by the conveyor screw 50 and further cooled by the addition of coolant. In this way, the additive can pass through the conveyor channels 43, 44 several times and is constantly cooled further.After a certain time, for example as soon as a predetermined maximum temperature of the additive of, for example, a value between -100°C and -170°C is reached, the slide 56 is opened and the additive is discharged via discharge opening 55.

[0044] The duration of the additive's residence in the device 40 can also be regulated by the control unit 24 depending on a measured temperature, for example, the temperature of the additive measured in the cooling device 41 or the temperature of the fresh concrete measured by the measuring device 25. If the temperature measured by the measuring device 25 is greater than a predetermined maximum temperature of the fresh concrete, the slide valve 56 remains closed for a longer period. The additive is thus circulated in the conveying channels 43, 44 for a correspondingly longer time and thus cools further before being discharged via the discharge opening 54.

[0045] Furthermore, outlet openings for coolant can also be provided in the conveying channel 44 (not shown here). Furthermore, conveying means can also be provided in the conveying channel 44, for example, a screw conveyor, a conveyor belt, or means for pneumatic conveying or fluidized-bed conveying. Furthermore, instead of the screw conveyor 50 shown here in the conveying channel 43, another conveying means of the aforementioned type can also be provided. List of reference symbols 1 device 32 Task unit 2 storage silo 33 Dispensing opening 3 conveyor line 34 Output unit 4 Mixing device 35 Injector 5 Scale 36 Gas extractor 6 Dosing element 37 slider 7 - 38 slider 8 conveyor line 39 - 9 valve 40 device 10 Cooling device 41 Cooling device 11 tank 42 Housing 12 Refrigerant supply line 43 conveyor channel 13 Gas discharge 44 conveyor channel 14 storage container 45 Wall 15 Dosing element 46 front side 16 container 47 front side 17 water pipe 48 opening 18 heat exchanger 49 opening 19 water level 50 screw conveyor 20 muzzle opening 51 - 21 Check valve 52 Task unit 22 filter 53 Feed opening 23 exhaust pipe 54 Output unit 24 Control unit 55 Dispensing opening 26a, 26b Mixing shaft 56 slider 27a, 27b Motor 57 - 28a, 28b gearbox 58 Refrigerant supply line 29 shovel 59 Exit opening 30 Housing 60 - 31 Feed opening 61 Gas extractor

Claims

1. Apparatus for producing cooled fresh concrete, having at least one storage container (2) for an additive, having a mixing device (4) for mixing the additive from the storage container (2) with further additives and with mixing water to form fresh concrete, and having a conveying line (8) which connects the storage container (2) to the mixing device (4) and in which a cooling device (10, 41) for cooling and conveying the additive is integrated, wherein the cooling device (10, 41) is provided with at least one refrigerant supply line (12, 58) for a liquefied cryogenic refrigerant, with at least one gas discharge line (13) for evaporated refrigerant, with a feed opening (31, 53) for additive to be cooled and with a discharge opening (33, 55), connected in terms of flow to the mixing device (4), for cooled additive, wherein the cooling device (10, 41) is integrated in a cooling and conveying device having a conveying tool (26a, 26b, 50) which is arranged in a housing (30, 42) and which extends between the feed opening (31, 53) and the discharge opening (33, 55), said discharge opening being provided with a closure means (38, 56), wherein the conveying tool (26a, 26b, 50) simultaneously functions as a tool for cooling the additive, characterized in that the cooling and conveying device is provided with a return line (44) for returning at least a partial stream of the cooled additive into the region of the feed opening (31, 53), via which at least a partial stream of the additive can be conveyed back in the direction of the feed opening (31, 53) and thus conducted in a circuit.

2. Apparatus according to Claim 1, characterized in that, as conveying tool, use is made of a conveying screw (50), a pneumatic conveying means or a fluidized-bed conveyor.

3. Apparatus according to Claim 1 or 2, characterized in that the cooling and conveying device is operatively connected to a control unit (24), by means of which control unit the operation of the cooling and conveying device is able to be regulated according to a temperature which is determined by means of a measuring device (25).

4. Apparatus according to one of the preceding claims, characterized in that the housing (30, 42) is arranged in a manner ascending from the feed opening (31, 53) to the discharge opening (33, 55).

5. Apparatus according to one of the preceding claims, characterized in that, in the return line (44), means for conveying and / or cooling the returned partial stream are provided.

6. Apparatus according to one of the preceding claims, characterized in that the gas discharge line (13) is connected in terms of flow to a device for cooling mixing water stored in a container (16).

7. Apparatus according to one of the preceding claims, characterized in that the gas discharge line (13) is provided with a filter device (22) for separating solid particles from the evaporated cryogenic refrigerant.

8. Apparatus according to one of the preceding claims, characterized in that the cooling device (1, 41) comprises a double-shaft mixer having two mixing shafts (26a, 26b) which are driven by at least one drive device (27a, 27b) and which are arranged in a housing (30), said housing being closed off in a substantially gas-tight manner and being provided with thermally insulating walls, with a feed opening (31) for the additive to be cooled, with a discharge opening (33) for cooled additive, with a plurality of refrigerant lines (35) opening out into the housing (30) and connected to a supply line for a liquefied cryogenic refrigerant, and with a gas discharge line (13) for evaporated cryogenic medium.

9. Apparatus according to Claim 8, characterized in that at least some of the refrigerant lines (35) open out into a lower portion of the housing (30).

10. Apparatus according to one of the preceding claims, characterized in that the storage container (2) is connected to the mixing device (4) via a second conveying line (3), and, in the conveying lines (3, 8), there are provided means (6, 15) for regulating the flow-rate ratios of the partial streams, conducted via the two supply lines (3, 8), of the additive.

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