Patent Application
20230286191
The invention relates to an apparatus, an arrangement and a method for cooling fresh concrete, in particular by means of a cryogenic liquid, such as liquid nitrogen or liquid carbon dioxide.
The curing of fresh concrete is an exothermic process. The resulting heat can lead to water in the fresh concrete evaporating at different rates in localized regions. This can in turn give rise to stresses in the cured concrete, which can lead to cracks. The larger a construction and the higher the exterior temperature, the more likely is crack formation to occur in the cured concrete. For this reason, the fresh concrete is normally cooled. Thus, cooling of the constituents of the fresh concrete before mixing, for example, is known. However, the known methods for cooling fresh concrete are inefficient in energy terms. In addition, the known methods are essentially manual and correspondingly laborious.
It is an object of the present invention to provide, proceeding from the prior art which has been described, a more efficient and automated method for cooling fresh concrete. In addition, a corresponding apparatus and arrangement are to be presented.
These objects are achieved by the apparatus, the arrangement and the method according to the independent claims. Further advantageous embodiments are indicated in the dependent claims. The features set forth in the claims and in the description can be combined with one another in any, technologically useful, way.
The invention provides an apparatus for cooling fresh concrete. The apparatus comprises a frame. The frame surrounds an open section through which the fresh concrete can flow. The apparatus further comprises an injection structure attached to the frame. Said injection structure extends inwardly from the frame. The injection structure has at least one nozzle for discharging a coolant into the fresh concrete, when said fresh concrete flows through the open section. For that purpose, each said nozzle is in fluid connection with a coolant inlet of the apparatus.
For the purposes of the present invention, fresh concrete is concrete before curing. As a result of curing, also referred to as “setting”, fresh concrete is converted into cured concrete. Fresh concrete can also be referred to as new concrete or wet concrete. Fresh concrete can be obtained by mixing the constituents of concrete, in particular cement, sand and water. As long as the mixture thus obtained can be shaped and/or compacted, it is referred to as fresh concrete.
To avoid crack formation in the cured concrete, the fresh concrete can be cooled by means of the apparatus described. This can be carried out at various stages in the process of processing the fresh concrete. Preference is given to the fresh concrete being cooled
The fresh concrete can be cooled at one or more of these places or other places. If the fresh concrete is cooled at a plurality of places, it is possible to use a plurality of the apparatuses described. The transport vehicle is preferably a vehicle for transporting ready-mixed concrete.
The apparatus is suitable for cooling fresh concrete. The apparatus is preferably used at a position in the processing process at which the fresh concrete is in any case in motion as a stream. In this case, the use of the apparatus described can be integrated into the processing process without further changes to the process. The cooling of the fresh concrete can therefore also proceed automatically when using the apparatus described. As soon as the apparatus described has been installed at the desired place, it is sufficient to switch on a coolant supply in order to cool the fresh concrete. This can be computer controlled and/or remotely controlled. The coolant supply can also be switched on automatically, for example, when a sensor detects that fresh concrete is flowing through the open section of the apparatus. When no more flowing fresh concrete is detected, the coolant supply can be switched off automatically. Apart from maintenance work, no handling by operating personnel is necessary for cooling the fresh concrete in this case.
The fresh concrete can thus be cooled by means of a coolant. The coolant is preferably a liquefied gas. The term liquefied gas refers to a liquefied substance which is gaseous under normal conditions (atmospheric pressure and ambient temperatures). The coolant is preferably a cryogenic material. In particular, it is possible to use nitrogen, helium, neon, argon, air, oxygen or carbon dioxide, especially in liquefied form, as coolant. A combination of these materials is also possible. The coolant is preferably an inert gas (i.e. gaseous under normal conditions), in particular, nitrogen. Preference is also given to carbon dioxide as the coolant.
The apparatus comprises a frame and an injection structure which is attached to the frame and which extends inwardly from the frame.
Due to the fact that the injection structure extends inwardly from the frame, the coolant is injected within the fresh concrete flowing through the open section, as opposed to towards a stream of flowing concrete. The contact between the coolant and the fresh concrete is therefore more intense and the cooling effect is thereby increased.
The injection structure may be entirely located within the open section which is surrounded by the frame, i.e. in the case of a planar frame: located within the plane of the frame. The injection structure may also extend inwardly and upstream of the frame or inwardly and downstream of the frame, whereby upstream and downstream refer to the flow direction of the fresh concrete through the open section of the frame.
It will be appreciated that, as the injection structure is generally a static injection structure, less maintenance will be required when compared with mechanically moving injection structures, such as agitators equipped with injection nozzles.
According to a preferred embodiment, the injection structure comprises at least one spoke which points inwardly from the frame. The at least one spoke is preferably attached directly to the frame. The frame and/or the injection structure/the spoke(s) are preferably made of hardened, in particular stainless, steel. When the apparatus is used as intended, fresh concrete flows through the open section surrounded by the frame. Preferably, all of the flowing fresh concrete flows through the open section surrounded by the frame. However, it is also possible for the frame to be completely enclosed in a stream of fresh concrete, so that part of the flowing fresh concrete flows through the open section surrounded by the frame and a further part of the fresh concrete flows along the outside of the frame. The fact that fresh concrete can flow through the open section of the frame is also reflected in the size of the frame, or rather the size of the open section thereof. The open section surrounded by the frame preferably has a dimension in the range from 20 to 100 cm, in particular in the range from 40 to 70 cm, in all directions. The frame is preferably configured as a ring or cylinder. In this case, the frame surrounds a circular open section. The diameter of the open section surrounded by the ring or cylinder is preferably in the range from 20 to 100 cm, in particular in the range from 40 to 70 cm. Particularly in the case of a ring, the spokes are preferably arranged radially with respect to the frame.
The frame provides rigidity. It serves, in particular, to hold the injection structure. Preference is given to an injection structure comprising a plurality of spokes with one or more injection nozzles. The following description generally relates to this case, but as far as possible also applies analogously to the case of a single spoke or to injection structures with a different configuration.
The coolant is introduced into the fresh concrete via the spokes when the fresh concrete flows through the frame and thus past the spokes. For this purpose, the spokes have at least one nozzle. The spokes preferably have a plurality of nozzles. The following description relates to this case, but as far as possible also applies analogously to the case of a single nozzle.
One or more nozzles can in each case be arranged on each of the spokes. However, it is not necessary for a nozzle to be arranged on each of the spokes. It is even conceivable that all nozzles are arranged on the same spoke.
The nozzles can be held within a stream of fresh concrete by means of the frame to which the spokes are attached. The coolant flowing out from the nozzles is then enclosed by the fresh concrete. The fresh concrete can be cooled particularly efficiently in this way because the coolant becomes distributed through the fresh concrete and is enclosed therein. The fresh concrete is therefore cooled not only by the enthalpy of vaporization but also by the gas formed on vaporization. The latter would be released unutilized into the surroundings if the coolant were not enclosed by the fresh concrete. This gives more efficient cooling compared to, in particular, cooling of the fresh concrete stream from the outside, i.e. with a coolant jet directed at the surface of the fresh concrete. Accordingly, the apparatus makes do with a particularly low coolant consumption.
In addition, the apparatus makes particularly uniform cooling of the fresh concrete possible. This has the advantage that fresh concrete can be cooled with great reproducibility. Furthermore, particularly cold places in the fresh concrete, known as “cold spots”, can be prevented by the uniform cooling. Such cold spots could, for example, damage a transport vehicle. Thus, for example, nitrogen has a boiling point of -196° C. Transport vehicles for fresh concrete are usually not suitable for such low temperatures. This has hitherto made the use of cryogenic materials for cooling fresh concrete difficult.
Furthermore, in the cooling of fresh concrete by means of cryogenic materials there is the fundamental problem that usually large amounts of these materials are released into the surroundings. Thus, a cloud of nitrogen can be liberated in the cooling of fresh concrete by means of liquid nitrogen. Although nitrogen as such is not hazardous to health, human beings can be injured by the low temperatures of nitrogen liberated. In addition, a nitrogen cloud can displace the surrounding air to such an extent that there is no longer sufficient oxygen available for breathing. The liberation of vaporized coolant can be prevented or in any case reduced or distributed over time by means of the apparatus described to such an extent that the problems described no longer occur or occur only to an acceptable extent. Particularly safe cooling of fresh concrete is thus possible by means of the apparatus described. In addition, the cooling of fresh concrete by means of the apparatus described is advantageous compared to known methods. Thus, the apparatus described is particularly cheap to procure, especially compared to cooling in a ready-mixed concrete vehicle.
In a preferred embodiment of the apparatus, the injection structure, such as the at least one spoke, is at least partly hollow so that the coolant can flow from a coolant inlet of the apparatus through the injection structure/one or more of the spokes to the nozzle.
In this embodiment, said hollow part of the injection structure/spokes serves as conduit(s) for the coolant. This assists construction because, apart from the injection structure/spokes, no separate conduits are required within the frame. In addition, the spokes are cooled by the coolant when the coolant flows through the spokes. The fresh concrete can in this way be additionally cooled by contact with the surfaces of the hollow part of the injection structure/spokes.
The statement that the injection structure/spokes are at least partly hollow means that at least a section of one of the spokes is hollow. It is sufficient for the injection structure/spokes to be hollow only in the sections via which the coolant can reach the nozzles. However, it is also possible for other parts of the injection structure or even the entire injection structure to be hollow. Thus, one, more than one or all of the spokes may be completely hollow. In particular, preference is given to the entire injection structure/all spokes being completely hollow. Here, the hollow parts/spokes are preferably connected to one another. The coolant can as a result spread from the one coolant inlet through the entire injection structure/all spokes. The nozzles are preferably formed as openings in the spokes.
If more than one nozzle is provided, preference is given to there being, for each of the nozzles, at least one flow path which leads from the coolant inlet via one or more of the spokes to the respective nozzle. Some of the flow paths can run jointly. A plurality of flow paths can lead to one nozzle.
In a further preferred embodiment of the apparatus, a plurality of the spokes come together radially in the center of the open section of the frame or on a frame axis through said center, with at least one of the nozzles being arranged in the center of the open section or on a frame axis through said center.
In this embodiment, the apparatus has a plurality of spokes attached toarranged in the frame. The spokes are preferably connected to one another in the center of the frame. In the case of hollow spokes, this is preferably realized in such a way that the coolant can flow from one of the spokes into one or more of the other spokes in the center of the frame. The coolant can therefore spread over the spokes as a result of the connection of the spokes in the center of the frame.
Preference is given to precisely one nozzle being arranged in the center of the frame. It is not necessary for this nozzle to be able to be assigned to one of the spokes. It is sufficient for the nozzles all to be able to be assigned to the spokes. Thus, one or more of the nozzles can be arranged exactly where the spokes come together.
The coolant can be introduced centrally into a stream of the fresh concrete by means of a nozzle arranged in the center of the frame. The advantages described for the apparatus can thus be achieved particularly well by means of this nozzle. The nozzle arranged in the center of the frame can be referred to as a central nozzle.
In a further preferred embodiment of the apparatus, a plurality of the spokes come together radially in the center of the frame, with at least one of the nozzles being arranged outside the center of the frame.
In this embodiment, at least one nozzle which, as a distinction from the above-described central nozzle, can be referred to as noncentral nozzle, is provided. The apparatus preferably has a plurality of nozzles for discharge of a coolant into the fresh concrete arranged outside the center of the frame.
Any combination of one or more central nozzles and one or more noncentral nozzles is possible. The apparatus preferably has one central nozzle and a plurality of noncentral nozzles.
In a further preferred embodiment of the apparatus, the at least one spoke has a droplet-shape cross section.
If the apparatus has more than one spoke, the spokes preferably all have a droplet-shape cross section. Preference is given to all spokes each having a droplet-shape cross section over their entire length.
For the purposes of the present invention, a droplet-shape cross section means that the cross section widens downward from a point at the top and finally goes over into a round section. The terms “top” and “below” are based on the fresh concrete flowing from the top downward through the apparatus described. This is preferred because the fresh concrete can be moved by the Earth’s gravity. However, the apparatus can also be used in any orientation as a result of the fresh concrete being driven by, for example, a pump. Instead of the description of the cross section as “droplet-shape”, the cross section can also be described as having a section which runs to a point in a direction opposite the flow direction of the fresh concrete. The shaping of the spokes as per this embodiment can prevent deposits of the fresh concrete on the spokes.
A further aspect of the invention is a use of the apparatus described for cooling fresh concrete.
The advantages and features described for the apparatus are applicable and transferable to the use.
A further aspect of the invention is an arrangement for filling a transport vehicle with cooled fresh concrete. The arrangement has a outlet element via which the fresh concrete can be introduced into the transport vehicle. The arrangement has an apparatus configured as described on the outlet element.
The advantages and features described for the apparatus are applicable and transferable to the arrangement, and vice versa. The apparatus is preferably suitable for the arrangement.
The arrangement preferably comprises a respective source for all constituents of the fresh concrete, for example a silo for cement, a sand store and a water connection. Furthermore, the arrangement preferably has a mixing device by means of which the constituents can be mixed in order to obtain the fresh concrete. The arrangement preferably has the outlet element directly adjoining the mixing device. The transfer element is preferably configured as a transfer funnel. As an alternative, the transfer element can be a pipe section. The transport vehicle, which is not part of the arrangement, can thus be driven under the transfer element so that the fresh concrete immediately after mixing of the constituents, i.e. immediately after formation of the fresh concrete, can be conveyed from the transfer element of the arrangement into an inlet funnel of the transport vehicle.
The apparatus described is provided on the transfer element. This means that the apparatus adjoins the transfer element upstream of the transfer element, adjoins the transfer element downstream of the transfer element or is integrated into the transfer element. As a result of this positioning of the apparatus, the fresh concrete is cooled directly on introduction into the transport vehicle. Cooling can thus be carried out in the concrete works. A coolant supply on a construction site is not necessary.
A further aspect of the invention is a method for cooling fresh concrete. The fresh concrete is conveyed through an apparatus which comprises a frame defining an open section through which the fresh concrete can flow and an injection structure, such as at least one spoke, attached to the frame and extending inwardly therefrom. A coolant is introduced into the fresh concrete via the injection structure.
The advantages and features described for the apparatus and the arrangement are applicable and transferable to the method, and vice versa. The apparatus and the arrangement are preferably each suitable for operation according to the method. The method is preferably carried out with the arrangement. The coolant can be introduced into the fresh concrete via the injection structure/spokes, in particular by the coolant being discharged from one or more nozzles on the injection structure/spokes.
In a preferred embodiment of the method, the coolant is nitrogen, carbon dioxide or a mixture of nitrogen and carbon dioxide.
The coolant is preferably liquid nitrogen, liquid carbon dioxide or a mixture of liquid nitrogen and liquid carbon dioxide.
Nitrogen is readily available and comparatively cheap. In addition, nitrogen is inert. Nitrogen therefore does not react with the fresh concrete. The fresh concrete is thus only cooled and not otherwise changed by nitrogen as coolant.
The fresh concrete can be partially carbonized by using carbon dioxide. Carbon dioxide which has, for example, been formed as offgas in an industrial production process can, in this manner, be bound in the fresh concrete. This carbon dioxide can thereby be prevented from getting into the atmosphere in order to protect the environment. In that case, the method described serves not only to cool the fresh concrete but also to protect the environment.
A chemical reaction can occur between the carbon dioxide and the fresh concrete. The carbon dioxide can thus be bound chemically into the fresh concrete. It is in this respect advantageous that the carbon dioxide can be distributed particularly uniformly in the fresh concrete by means of the method described. The chemical reaction between the carbon dioxide and the fresh concrete can thus proceed particularly efficiently, while ensuring sufficient homogeneity of the partially carbonated fresh concrete.
The above-described advantages can be combined with one another when using a mixture of nitrogen and carbon dioxide.
In a further preferred embodiment, the coolant comprises nitrogen, helium, neon, argon, air, oxygen and/or carbon dioxide.
The coolant can be any mixture of one or more of the abovementioned materials, optionally also with further materials. Depending on the choice of the coolant, the advantages of the various materials can be utilized individually or together.
In a further preferred embodiment of the method, the fresh concrete is cooled during filling of a transport vehicle. The coolant preferably comprises liquid nitrogen, liquid helium, liquid neon, liquid argon, liquid air, liquid oxygen and/or liquid carbon dioxide. The fresh concrete can similarly be cooled while it is being poured from the transport vehicle, in particular by having an apparatus mounted in or on a concrete outlet of the vehicle.
The invention will be illustrated in more detail below with the aid of the figures. The figures show a first particularly preferred working example and a second alternative working example, but the invention is not restricted to these. The figures and the size ratios depicted therein are purely schematic. The figures show:
The apparatus 1 has a coolant inlet 10. The spokes 3 are at least partly hollow so that the coolant can flow from the coolant inlet 10 through the spokes 3 to the nozzles 4, 5. The spokes 3 come together radially in the center 6 of the open section 2′ of frame 2. One of the nozzles 4 is arranged in the center 6 of the frame 2. Nozzle 4 will be referred to as the central nozzle. The three remaining nozzles 5 are arranged outside the center 6 of frame 2. As a distinction from the central nozzle 4, these nozzles 5 are referred to as noncentral nozzles.
A coolant such as liquid nitrogen or liquid carbon dioxide can be introduced into fresh concrete by means of apparatus 1 in such a way that the coolant is enclosed by the fresh concrete. In this way, the fresh concrete can be cooled particularly efficiently without large amounts of the coolant being released into the environment and without the fresh concrete becoming so cold in places that damage to, for example, a transport vehicle 8 can occur. The apparatus 1 can, in particular, be used during filling of the transport vehicle 8.
The apparatus shown in
1
2
2′
3
3′
4
5
6
7
8
9
10
11
12
13
14
15
It will be understood that many additional changes in the details, materials, steps and arrangement of parts, which have been herein described in order to explain the nature of the invention, may be made by those skilled in the art within the principle and scope of the invention as expressed in the appended claims. Thus, the present invention is not intended to be limited to the specific embodiments in the examples given above.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2020 117 592.2 | Jul 2020 | DE | national |
This application is a 371 of International Application No. PCT/EP2021/067464, filed Jun. 25, 2021, which claims priority to German Patent Application No. DE 102020117592, filed Jul. 3, 2020, the entire contents of which are incorporated herein by reference.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2021/067464 | 6/25/2021 | WO |
