Method and plant for treating concrete powder and granular material

Abstract

The present invention is characterized in that it comprises a method and a plant (1) for treating concrete granules (2) and subsequently recycling the concrete granules. In the method, the concrete granules (2) are filled into an at least partially airtight container (4) of the plant (1). A CO2-containing gas is then continuously or discontinuously supplied depending on the measured value of the amount of CO2 absorbed by the concrete granules (2) in the container (4), determined via at least one sensor (8, 9, 19). After a predetermined CO2 saturation level of the concrete granules (2) has been determined, the CO2-absorbed concrete granules (2) are removed.

Description

Technical Field

[0001] The present invention relates to a treatment method and a plant for recycling concrete powder and granules later. The present invention particularly relates to a method and a plant for absorbing CO2 in concrete powder and granules. Furthermore, the present invention relates to concrete powder and granules that can be produced by the method of the present invention and to concrete.

[0002] In order to manufacture concrete, in addition to gravel and sand, cement in particular has an important meaning. However, the production of cement not only emits a large amount of greenhouse gases but also is a substantial cost factor in the production of concrete. Today, in order not to waste the resources of gravel and sand, the recycling of concrete already has important significance. However, in the conventional recycling method, it is not possible to obtain cement again, and it is not possible to suppress or avoid the emission of greenhouse gases. Conventional recycling is usually carried out by disassembling and removing demolished houses or other concrete structures. The demolished concrete is subsequently pulverized into concrete powder and can be used, for example, as a substitute for gravel when producing new concrete. By adding new cement, recycled concrete is produced. However, this conventional recycled concrete usually has degraded mechanical properties compared to primary concrete. Primary concrete is understood to be non-recycled concrete. Therefore, usually, in conventional recycled concrete, in order to obtain the same quality as primary concrete, the cement content is increased by about 10%. Furthermore, the concrete powder obtained from demolished concrete may be used, for example, as road construction materials in an unconsolidated state. However, its uses are severely limited. Because of the production, concrete contains harmful metals, and these harmful metals may dissolve in rainwater in the particularly unconsolidated (not hardened) state of concrete powder known from the prior art, and thus may contaminate groundwater. For the above reasons, today's concrete recycling can only be obtained as a low-value substitute for gravel at best, and it is not possible to reduce the greenhouse gas emissions of concrete or use the concrete powder without concern in an unconsolidated state through this recycling.

[0003] The object of the present invention is to provide an improved treatment method and a plant for recycling concrete powder and granules later. In particular, here, it is especially to at least partially solve the above-mentioned problems of known recycling methods.

[0004] Concrete powder and granules can be treated with carbon dioxide (hereinafter abbreviated as CO₂) for later recycling. When comparing recycled reference concrete (including cement, gravel, sand, and concrete powder and granules not absorbed by CO₂) with CO₂-absorbed concrete having substantially the same composition, the CO₂-absorbed concrete (including cement, gravel, sand, and concrete powder and granules absorbed by CO₂) can exhibit a higher compressive strength if the slump remains substantially unchanged. This compressive strength is a characteristic quantity regarding the hardness of fresh concrete. Similarly, even if the proportion of cement in the CO₂-absorbed concrete is correspondingly reduced, the same compressive strength can be achieved in comparison with reference concrete having an unchanged composition.

[0005] These correlations can also be understood from the following tables. These tables show the compositions (Table 1) and measurement results (Table 2) of reference concrete and various test concretes. Here, the reference concrete contains conventional concrete powder and granules not absorbed by CO₂. In contrast, the test concrete is absorbed by CO₂. The compressive strength was specified in accordance with the standard SN EN 206: 2013+A1:2016 and in accordance with the SIA data sheet "2030 Recyclingbeton". The slump was specified in accordance with the standard SN EN 12350-5:2019.

[0006]

Table 1

[0007]

Table 2

[0008] Therefore, in the CO2-absorbed concrete with a correspondingly reduced proportion of cement (for example, Test Concrete 3), greenhouse gas emissions are significantly reduced. For example, when cement is reduced by 10%, emissions during concrete production can be reduced by approximately 8.5%. On the other hand, existing CO2-emitted gas can be bound to the concrete powder particles in the process of this method, thereby reducing it. For example, when an average of 10 kg of CO2 is bound per 1000 kg of concrete powder particles, emissions can be further reduced by an average of 4%. Therefore, with this technology, under ideal conditions, the CO2 emissions from the production of recycled concrete can be reduced by approximately 12.5%.

[0009] Furthermore, it has been found that the CO2-absorbed concrete exhibits higher carbonation resistance. Here, carbonation resistance is an important factor for the corrosion of steel bars cast in the concrete and the damage occurring in concrete structures. Similarly, by absorbing CO2 into the concrete powder particles, the above-mentioned harmful metals can be better bound, reducing the unintentional leakage of the harmful metals into the surrounding environment. This expands the potential uses of the discrete concrete powder particles.

[0010] The method according to the claims for treating particulate concrete and subsequently recycling it, in particular for absorbing CO2, comprises the following method steps: filling a container that is at least partially airtight with particulate concrete; identifying the amount of CO2 absorbed by the particulate concrete in the container via at least one sensor and supplying a gas containing CO2 with a corresponding volumetric flow rate accordingly. Here, the gas supply may be continuous or discontinuous. Checking whether the particulate concrete has reached a predetermined saturated CO2, and if not, continuing the aforementioned method steps regarding the gas supply. If the particulate concrete has not yet reached the predetermined saturated CO2, the gas can be supplied continuously or discontinuously depending on the application until it reaches the predetermined saturated CO2. Furthermore, the method comprises removing the particulate concrete with absorbed CO2 from the container. After removing the particulate concrete, this particulate concrete can be used in further method steps for producing recycled (absorbed) concrete containing particulate concrete with absorbed CO2. For this purpose, the particulate concrete with absorbed CO2 can be processed into concrete with cement, water, sand and gravel.

[0011] The absorption of CO2 by particulate concrete is understood to mean that CO2 diffuses into the particulate concrete and undergoes a chemical reaction. For this absorption process, it is not necessary to add additional water, especially in liquid form, to the container. Particulate concrete contains pores through which CO2 can diffuse. Water (also called pore water) may be present in the pores, and this water reacts chemically with CO2. The pore water is in phase equilibrium with the cement phase of the particulate concrete and contains calcium ions. When CO2 is (chemically) absorbed, carbonate ions and bicarbonate ions are formed. That is, the resulting pore solution becomes supersaturated with respect to calcium carbonate (CaCO3), or its polymorphic minerals calcite, aragonite, vaterite, and the pores are filled.

[0012] However, depending on the composition, the concrete powder can only accept a specific amount of CO2. This maximum saturated CO2 is considered to be 30 kg to 45 kg of CO2 per 1000 kg of concrete powder, depending on the composition. In this method, it can be carried out until the maximum (at least almost maximum) saturated CO2 of the concrete powder in the container each time. For example, when the change in CO2 concentration and / or the change in pressure per initial volume of the gas can no longer be confirmed, the maximum saturated CO2 of the concrete powder has been reached. However, the method can also be terminated when a predetermined saturated CO2 lower than the maximum saturated CO2 is reached first. The predetermined saturated CO2 of the concrete powder may be between 5% and 100% of the maximum saturated CO2. However, a high saturation can only be achieved when CO2 is supplied as a gas for a sufficiently long time and requires a correspondingly large amount of CO2. Most preferably, good material properties can be achieved at a predetermined saturated CO2 between 5 kg of CO2 per 1000 kg and 15 kg of CO2 per 1000 kg. This corresponds to a predetermined saturated CO2 of about 10% to 50% of the maximum saturated CO2.

[0013] The amount of CO2 absorbed by the concrete powder usually decreases exponentially with time until the maximum saturated CO2 is reached. For example, if the change in CO2 absorption amount is smaller than a predetermined limit value within a predetermined period, it can be considered that the predetermined saturated CO2 has been reached. Alternatively or complementarily, in order to confirm the predetermined saturated CO2, for example, the CO2 absorption amount specified via at least one sensor can be plotted and extrapolated over time. Through this extrapolation, the (theoretical) limit value of the CO2 absorption amount corresponding to the maximum saturated CO2 of the concrete powder in the container can be determined. When this limit value (or the predetermined saturated CO2) reaches a predetermined percentage, the gas supply can be terminated.

[0014] The supply of gas to the container or the adjustment of the volume flow rate supplied to the container can be carried out via the adjustment of the inlet valve. The inlet valve may be arranged in the inflow line of the container. The adjustment of the inlet valve or the adjustment of the volume flow rate according to the amount of CO2 absorbed is carried out by at least one sensor and a control unit operatively connected to the inlet valve. Advantageously, the volume flow rate of the gas supplied (after the initial filling of the container) compensates for the CO2 already absorbed. In this way, a relatively constant CO2 concentration exists in the container as much as possible. This has the advantage that, on the one hand, the method can be carried out more quickly and, on the other hand, a uniform absorption of CO2 by the concrete powder can be achieved when the CO2 concentration is relatively high and the CO2 distribution in the container is uniform. Here, the control unit can determine the theoretically existing amount of CO2 in the container that would be present if no CO2 absorption took place, from the known composition of the gas or the CO2 content of the gas, and also from the known volume flow rate supplied via the inlet valve. Similarly, the theoretical pressure in the container can be determined. For this purpose, the inlet valve can include a flow sensor for determining the volume flow rate guided through the inlet valve, or the flow sensor can be connected upstream or downstream of the inlet valve. Alternatively or complementarily, in order to use the flow sensor, the volume flow rate guided according to the adjustment of the inlet valve can be stored in the control unit as a data set.

[0015] The supply of gas can be interrupted, at least temporarily (discontinuous supply of gas). This can be done by repeatedly performing the following series of steps: opening an inlet valve fluidly connected to the container, supplying a gas containing CO2 to the container, and closing the inlet valve. When the inlet valve is closed, the amount of CO2 absorbed can be determined particularly easily. The volumetric flow rate of the gas supplied while the inlet valve is open preferably compensates for the amount of CO2 absorbed in between (while the inlet valve is closed). This discontinuous gas supply can continue until the concrete powder reaches a predetermined CO2 saturation. The discontinuous gas supply is particularly suitable for containers that are partially open to the surrounding environment or ambient air during gas supply. Such containers may in particular be open towards the top.

[0016] Instead of a discontinuous gas supply, the volumetric flow rate can be supplied continuously according to the amount of CO2 absorbed over the period of gas supply (continuous supply of gas). Advantageously, the volumetric flow rate of the gas supplied compensates for the amount of CO2 already absorbed. If the absorption of CO2 decreases exponentially over time, the volumetric flow rate supplied can be adjusted such that it decreases exponentially accordingly.

[0017] The (initial) filling of the container with gas can be carried out until the desired filling level of the container with gas is reached. Alternatively or complementarily, the (initial) filling of the container can be carried out until a predetermined CO2 concentration, in particular a CO2 concentration of 95% or more in the container, is reached. After the initial filling, the volumetric flow rate may be reduced (further continuous supply) or interrupted in between (discontinuous supply). In this case, the further volumetric flow rate supplied can be controlled to compensate for the amount of CO2 absorbed in the container, as described above.

[0018] To determine the amount of CO2 absorbed by the concrete powder or granule, at least one sensor can be placed in the container or fluidly operatively connected to the container. The at least one sensor can be, for example, a CO2 concentration sensor for measuring the CO2 concentration in the container. From the amount of CO2 supplied (and optionally the measured amount of CO2 discharged), the theoretical amount of CO2 in the container (the amount if no absorption occurred) can be determined. Thus, the absorption amount can be determined from the difference between the theoretical amount of CO2 and the actual (measured) amount of CO2 via the concentration sensor in the container. As described above, for example, if the difference between the theoretical amount of CO2 and the actual amount of CO2 in the container is less than a predetermined limit value over a specific period, it can be assumed that a predetermined saturated CO2 has been reached. Alternatively, it can be assumed that a predetermined saturated CO2 has been reached or the gas supply can be stopped when the above difference reaches the limit value over the total process period up to that point. Further alternatively, it can be assumed that a predetermined saturated CO2 has been reached when the CO2 absorption amount determined by extrapolation reaches the theoretical limit value. Determining the amount of CO2 absorption performed via measurement of the CO2 concentration is particularly suitable when the container cannot be hermetically closed.

[0019] Instead of, or in addition to, a CO2 concentration sensor, the amount of CO2 absorbed by the concrete powder can be similarly determined by measuring the pressure. The pressure of a given volume of gas containing CO2 decreases when the CO2 comes into contact with the concrete powder and is absorbed. That is, the difference between the theoretical pressure that should be present in the container without absorption and the pressure actually measured in the container can be used as the CO2 absorption amount. The theoretical pressure can be determined at least approximately from the known container volume and the supplied (optionally discharged) volume flow rate. The determination of the CO2 absorption amount through pressure measurement is particularly suitable when the gas is supplied discontinuously to the container and the container can be closed airtight. As described above, for example, it can be assumed that a predetermined saturated CO2 has been reached when the pressure change is smaller than a predetermined limit value over a specific period, or when the performed CO2 absorption amount reaches a specific theoretical limit value.

[0020] Furthermore, the determination of the absorbed CO2 amount can additionally take into account the measured temperature. Since heat is released during the chemical reaction, this temperature change is also considered to affect the pressure in the same way. By complementary temperature measurement, the influence of the temperature change on the theoretical pressure can be taken into account. Similarly, complementary temperature measurement can be considered when determining the amount of CO2 absorbed through CO2 concentration measurement.

[0021] Alternatively or complementarily, the determination of the amount of CO2 absorbed can also additionally take into account the measured weight. For this purpose, at least one sensor may be a weighing scale or load cell operatively connected to the container and the control unit. For example, the volume available for gas supply in the container can be at least approximately determined via the weight of the concrete powder measured before the gas supply. This determination can be incorporated, for example, into the determination of the theoretical pressure. Furthermore, the difference between the weight of the concrete powder before the gas supply and the weight of the concrete powder after CO2 has been absorbed can be determined. Thereby, the amount of CO2 actually absorbed is inferred. This information can be used by companies for trading it, for example, with respect to a CO2 certificate, also referred to as an emission certificate.

[0022] Since gaseous water is released during the absorption of CO2, the relative humidity in the container can be complementarily measured depending on the implementation. While the supplied gas can exhibit a relative humidity of less than 1%, it is considered that there is a relative humidity of 50% to 95% in the container when the maximum saturated CO2 is reached. Therefore, the determination of the amount of CO2 absorbed can also additionally take into account the measured relative humidity.

[0023] As described above, the determination of the amount of CO2 absorbed by measuring the pressure and / or CO2 concentration can be performed more accurately by measuring the weight and / or temperature and / or relative humidity. For example, the measured values and / or known values can be related to each other via physical relationships such as the ideal gas state equation and the law of conservation of mass. Thereby, more accurate and comprehensive monitoring of the absorbed CO2 is realized.

[0024] Depending on the composition, the gas supplied into the container may contain, in addition to CO2, gaseous water and / or nitrogen and / or oxygen. The gas to be supplied to the container may be stored in a storage tank as a liquid and / or a gas before being supplied to the container. Advantageously, the gas contains 95% to 100% CO2. Depending on the application, the gas may contain renewable CO2. Renewable CO2 is understood to mean CO2 derived from organisms or obtained from the atmosphere. CO2 derived from organisms usually has the advantage that it can already be obtained in pure form and no longer needs to be processed. CO2 derived from organisms can be obtained, for example, as a by-product of biogas production or from the combustion of biomass (biological resources consisting of carbon, hydrogen and oxygen). Alternatively, the gas may likewise be an exhaust gas containing 10% to 25% CO2. For example, the exhaust gas from a cement factory can be used in the production of cement.

[0025] Primary concrete usually contains sand, gravel and cement. For example, the concrete powder obtained as demolished concrete may further contain mortar depending on the type of previous use. The concrete powder usually contains 4% to 10% by weight of calcium oxide. The concrete powder particularly contains hardened cement. Hardened cement is understood to mean cement that has reacted with water and the water has been absorbed by the cement. This reaction is called hydration and the reaction product is called hardened cement. During hydration, the cement can chemically bond with up to 25% of its mass of water and physically bond with up to 15% of its mass of water. For treatment, the demolished concrete can be pulverized into fine powder. Good results during treatment are obtained when the particles have a diameter of 0.05 mm to 50 mm. For treatment, usually the components of the concrete powder do not separate from each other.

[0026] After reaching a certain saturation of CO2, the excess gas present in the container can be discharged. This discharged gas can be processed for reuse and returned to the storage tank of the plant. Alternatively, the excess gas can also be introduced in the same way into a collection container that can be filled with concrete powder particles, and the method can be newly implemented in that collection container. For example, the method can be implemented alternately in the container and the collection container. Alternatively, a collection container filled with another concrete powder particle can be used as a passive filter, i.e., a filter that does not actively control the saturated CO2. The concrete powder particles arranged in this collection container can absorb the excess gas at least partially and particularly completely.

[0027] Before supplying the gas containing CO2, there may be air present in the container in addition to the concrete powder particles. When the inlet valve is opened for gas supply, a mixed gas containing CO2 and air is generated in the container. To increase the CO2 concentration in the container, especially during the initial filling of the container, in addition to supplying the gas containing CO2, the mixed gas can be discharged from the container continuously or discontinuously. In this process, advantageously, the proportion of CO2 in the container increases. The mixed gas discharged from the container can be processed in the same way as described for the excess gas or supplied to the collection container. After the container reaches a predetermined CO2 concentration, the discharge of the mixed gas can be stopped, and optionally, the supply of the gas can also be stopped at least temporarily in the same way.

[0028] The discharge of the gas from the container can be controlled via the outlet valve. The outlet valve can include a flow sensor for specifying the volumetric flow guided through the outlet valve, similar to the inlet valve, or the flow sensor can be connected upstream or downstream of the outlet valve. The flow sensor connected upstream or downstream is also operatively connected to the control unit. Alternatively or complementarily, for using the flow sensor, the volumetric flow guided according to the adjustment of the outlet valve can be stored in the control unit as a data set. Complementarily, a CO2 concentration sensor can also be connected upstream or downstream of the outlet valve.

[0029] The supply and / or discharge of the gas can be controlled by at least one pump operatively connected to the control unit. The supply of gas to the container and / or the discharge of the mixed gas from the container and / or the discharge of the excess gas from the container can be effected, for example, by a negative pressure (in relation to the ambient pressure). The negative pressure can be between 80,000 Pascal and 96,000 Pascal. However, the method can equally well be carried out at ambient pressure or at a pressure higher than that.

[0030] Furthermore, the invention relates to a plant for treating concrete powder and granules for later recycling, in particular for absorbing CO2. The plant includes a storage tank and at least a partially airtight container. The gas supplied to the container may be pre-stored in the storage tank in liquid form and / or in gaseous form, or may be temporarily stored. Here, the container can have at least one opening for receiving and / or removing the concrete powder and granules. The container includes an inlet for supplying gas to the container, and this inlet can be fluidly operatively connected to the storage tank via an inlet pipeline. Here, an inlet valve is used to control the volume flow rate of the gas supplied to the container. The inlet valve may be a proportional valve. The plant likewise includes at least one sensor and a control unit (as described above), and the control unit is operatively connected to at least one sensor and the inlet valve. The sensor is used to determine by the control unit the amount of CO2 absorbed by the concrete powder and granules in the container. The control unit is designed to control the volume flow rate of the gas passing through the inlet valve. Furthermore, the control unit can likewise be operatively connected to a pump. The pump can be arranged in the inlet pipeline or the outlet pipeline of the container. The pump may be a vacuum pump. This pump can be used to generate a negative pressure as described above.

[0031] The control of the volumetric flow is advantageously carried out automatically. According to the method described above, the control unit is designed to repeatedly perform the following steps: supplying a gas containing CO2 with a volumetric flow corresponding to the amount of CO2 absorbed by the concrete powder in the container, determined via at least one sensor, and checking whether the concrete powder has reached a predetermined saturated CO2. If the concrete powder has not yet reached the predetermined saturated CO2, the previous step of gas supply can be continued until the predetermined saturated CO2 is reached.

[0032] For efficient gas supply, the container is advantageously at least partially airtight. Depending on the configuration of the container, the container can include a container bottom and at least one circumferentially extending side wall. These surround the accommodation space of the container for accommodating the concrete powder. The at least one side wall can be, for example, tubular. The tubular side wall can have a circular or angular cross-section. Advantageously, the bottom and the at least one side wall are configured airtight. Depending on the application, the concrete powder can be filled and removed through a single opening. However, advantageously, the plant includes a first opening for filling the concrete powder and a second opening for removing the concrete powder. For example, a first (upper) opening and a second (lower) opening located on the opposite side of this first opening with respect to the direction of gravity can be provided. In this case, when the second (lower) opening is opened, the concrete powder can be automatically dropped from the container. In this embodiment, in particular, only the second (lower) opening can be configured to be airtight and closable, while the first (upper) opening can be left open. However, a configuration in which both openings can be airtight and closable is also conceivable. For this purpose, the plant can include at least one lid.

[0033] Advantageously, at least one sensor is arranged in the container. This includes embodiments in which the sensor is arranged on a protrusion on the side wall, a part of a pipe, etc., and is fluidly operatively connected to the accommodation space of the container. Different types of sensors (as described above) can be used to enable the determination of the amount of CO2 absorbed by the concrete powder. Similarly, any combination of one or more of those types of sensors is also conceivable. Since CO2 is heavier than air and thus basically tends to accumulate at the bottom of the container, for example, a plurality of concentration sensors can be arranged one above the other in the gravitational direction within the container.

[0034] To supply CO2 to the container uniformly and at high speed, the inflow part can include a plurality of gas inlet nozzles. Those gas inlet nozzles can be arranged on the bottom of the container and / or at least one side wall, and in particular can be arranged in a matrix. It is also conceivable to distribute a plurality of introduction nozzles in a matrix within the accommodation space of the container. Those plurality of introduction nozzles can be interconnected via an annular pipeline. Depending on the configuration of the container, the gas inlet nozzles can be arranged, for example, annularly dispersed around the accommodation space of the container. The container can further include an outflow part for allowing the gas to flow out of the container. Complementarily, an outlet valve and / or a flow sensor and / or another CO2 concentration sensor can be arranged in the outflow pipeline operatively connected to the outflow part.

[0035] Depending on the configuration of the plant, the plant can also include a plurality of containers. For example, the gas supply of the concrete powder to the plurality of containers can be carried out in parallel. Alternatively, the plurality of containers can also be connected in series one after another. The surplus gas from the first container is guided, for example, to the second container / collection container, and in the second container / collection container, the method can be repeated as described above. However, alternatively, it is also conceivable that the surplus gas from the first container is at least partially absorbed, especially completely absorbed, by the concrete powder placed in the collection container passively. Therefore, the second container / collection container may be fluidly operatively connected to the outflow pipeline of the first container. Alternatively or complementarily, the second container / collection container may be fluidly operatively connected to the storage tank via a separate inflow pipeline equipped with a (second) inlet valve.

[0036] The above-described embodiments of the plant may be used to implement the method according to the present invention. Also, the above-described embodiments of the method disclose corresponding configured embodiments of the plant for implementing the method, and this also applies vice versa.

[0037] Based on the examples illustrated in the accompanying drawings and the following description related to those examples, aspects of the present invention will be described in detail.

Brief Description of the Drawings

[0038]

Figure 1

Figure 2

Embodiments for Carrying Out the Invention

[0039] FIG. 1 shows a schematic view of a first variation of a plant 1 according to the present invention for treating concrete powder 2. The plant 1 includes a storage tank 3 for storing a gas containing CO2 and at least one, at least partially airtight container 4, 12. In the illustrated embodiment, a first container 4 and a second (collection) container 12 are provided. The two containers 4, 12 may be hermetically closable and each have at least one opening (not shown) for containing and / or removing the concrete powder 2 (in the open state). The first container 4 includes an inlet 5 for supplying gas into the container 4, and this inlet 5 is fluidically operatively connected to the storage tank 3 via an inlet pipeline 6. The second container 12 is operatively connected to an outlet 13 and is operatively connected to an outlet pipeline 14 of the first container. An inlet valve 7 used to control the volumetric flow of the gas supplied into the container 4 is arranged in the inlet pipeline 6 between the storage tank 3 and the first container 4. The inlet valve 7 may be a proportional valve. The inlet 5 may include a plurality of gas inlet nozzles. For high-speed filling, gas inlet nozzles may be arranged in a matrix on the accommodation space and / or bottom and / or at least one side wall (not shown) of the container 4. A pump 17 and an outlet valve 18 may be arranged in the pipeline between the first container 4 and the second container 12. The pump 17 may be designed to suck gas from the storage tank 3 into the first container 4 (when the inlet valve 7 is open and the outlet valve 18 is open). For this purpose, the pump 17 may be a vacuum pump. In addition, a CO2 concentration sensor 8 may be arranged in the outlet pipeline of the first container (or the pipeline between the two containers 4, 12). This CO2 concentration sensor 8 is used to monitor how much CO2 is released from the container 4.

[0040] In the first container 4, another sensors 8, 9, 10 are arranged. Based on the measured values of these sensors, the amount of CO2 absorbed by the concrete powder 2 can be specified as described above. The control unit 11 is used to control the supply of gas according to the amount of absorbed CO2. For this purpose, the sensors 8, 9, 10, the inlet valve 7, the outlet valve 18 and the pump 17 are operatively connected to the control unit 11. The inlet valve 7 and / or the outlet valve 18 may include a flow sensor. The control unit 11 may be designed to automatically control the gas supply and / or the gas discharge, particularly until the CO2 of the concrete powder 2 reaches a predetermined saturated CO2.

[0041] For the initial filling of the container 4 with the concrete powder granulate 2, first the inlet valve 7 and the outlet valve 18 can be opened. Subsequently, the pump 17 can suck gas from the storage tank 3 into the container 4. The concentration sensor 8 in the outflow line 14 of the container 4 can monitor the CO2 concentration. When the inside of the container 4 reaches the desired maximum CO2 concentration, the outlet valve 18 can be closed. The inlet valve 7 can similarly be closed at least temporarily. The sensors 8, 9, 10 in the container 4 can measure the pressure, CO2 concentration and temperature in the container 4. The measured values are used in the control unit to determine the amount of CO2 absorbed. Depending on the absorption amount, by additionally supplying the gas containing CO2 to the container, an optimal and as uniform as possible saturation of the concrete powder granulate 2 with CO2 (or absorption) is carried out. When a predetermined saturation with CO2 is reached, the excess gas can be discharged from the first container 4. Advantageously, as in the case shown, the excess gas is also sent to the collection container 12 filled with the concrete granulate 2. In the collection container 12, the excess gas is advantageously completely absorbed by the concrete powder granulate 2 in the collection container 12. This can be detected in particular by another CO2 concentration sensor 8 arranged in the outflow line of the collection container 12. Alternatively or complementarily, the weight difference between the concrete powder granulate 2 before the gas supply and the concrete powder granulate 2 with the absorbed CO2 after the gas supply can similarly be determined. A weighing scale 21 can be arranged on the container 4 to measure the weight or the weight difference.

[0042] Figure 2 shows a schematic view of a second variation of the plant according to the invention for treating the concrete powder 2. The plant 1 also includes a storage tank 3 for storing the gas containing CO2 and at least one, at least partially airtight container 4. In the illustrated example, the container 4 is configured to be open upward and includes an upper opening 19 for filling the concrete powder 2. A lower opening 20 for extracting the concrete powder is arranged in a first direction (the direction of gravity), which is the direction opposite to the side of the upper opening 19. The lower opening 20 is shown in a hermetically closed state. An annular side wall of the container is arranged between the upper opening 19 and the lower opening 20. This side wall is preferably also airtight. The annular side wall may be configured to have a circular cross-section or a rectangular cross-section. After the concrete powder 2 is filled, the inlet valve 7 is opened, and the container 4 is filled with the gas containing CO2 from below upward. For this purpose, in the illustrated case, a pump 17 is arranged in the inflow pipeline 6. However, other arrangements are also conceivable. In order to supply the gas at high speed, the container 4 preferably includes gas inlet nozzles 15 arranged in an annular shape. Those gas inlet nozzles 15 may be arranged in the accommodation space for the concrete powder 2 in the container 4, may be interconnected by an inflow pipeline, or may surround the accommodation space of the container. In the illustrated case, two groups of annularly arranged gas inlet nozzles 15 are arranged vertically in the first direction. At least one CO2 concentration sensor 8 can be arranged in the container 4. However, preferably, a plurality of CO2 concentration sensors 8 are dispersedly arranged in the first direction, and each is operatively connected to the control unit 11. Alternatively or complementarily, other sensors such as sensors for measuring temperature, pressure, or relative humidity can also be used. The CO2 concentration sensor 8 preferably continuously measures the CO2 concentration in the container 4. The control unit 11 controls the gas supply according to the amount of CO2 absorbed by the concrete powder 2. The amount of CO2 absorbed is determined by the control unit 11 through the measurement by the sensor(s) 8, as described in connection with the above method.Here, the amount of CO2 absorbed can be taken as the difference between the CO2 supplied to container 4 and the CO2 present in the measured container 4. Depending on the amount of CO2 already absorbed, a gas containing CO2 can be additionally supplied to container 4. This enables efficient and uniform saturation of the concrete powder particles 2 in container 4. The CO2 concentration sensor 8 located at the top in the gravitational direction can be used to ensure that the gas in container 4 does not exceed a predetermined filling level 16. That is, it is possible to prevent the gas from leaking out through the upper opening 19. Further, the process can be controlled so that a sufficiently thick layer of the non-carbonated concrete powder particles or the concrete granular particles 2 that are only partially carbonated always exists on the surface of container 4 (on the side of the first opening 19). This layer can be used as a filter layer for absorbing the inadvertently rising CO2. When the concrete powder particles 2 with absorbed CO2 are taken out of container 4 through the lower opening 20, this layer descends downward. For example, if another concrete powder particle 2 is replenished from above and the above method is repeatedly implemented, the predetermined saturated CO2 is correspondingly carried out.

Explanation of Signs

[0043] 1 Plant 2 Concrete Powder Particles 3 Storage Tank 4 Container 5 Inlet 6 Inflow Pipeline 7 Inlet Valve 8 Concentration Sensor 9 Pressure Sensor 10 Temperature Sensor 11 Control Unit 12 Collection Container 13 Outlet 14 Outflow Pipeline 15 Gas Inflow Nozzle 16 Filling Level 17 Pump 18 Outlet Valve 19 Upper Opening 20 Lower Opening 21 Weighing Scale

Claims

1. A method of treating concrete powder and granules for subsequent recycling, comprising: a. filling a container (4) that is at least partially airtight with the concrete powder and granules (2); b. Identifying, via at least one sensor (8, 9), the amount of CO absorbed by the concrete powder (2) in the container (4), and supplying, in response thereto, a gas containing CO at a volumetric flow rate to the container (4). ２ ２ ​​ c. Whether the concrete powder (2) has reached a predetermined saturation CO ２ that absorbs 5 kg to 15 kg of CO₂ per 1000 kg of the concrete powder (2), and if not, continuing step b; ２ ​ d. CO ２ The step of taking out the concrete powder particles (2) in which the above has been absorbed A method characterized by including the above.

2. The method according to claim 1, characterized in that the gas supplied to the container (4) contains 95% to 100% CO2.

3. Measuring the pressure and / or CO concentration by means of at least one sensor (8, 9, 10), and determining the amount of CO absorbed by the concrete powder (2). ２ The method according to claim 1 or 2, characterized in that the amount of CO absorbed by the concrete powder (2) is determined through measurement. ２ The method according to claim 1 or 2, characterized in that the amount of CO absorbed by the concrete powder (2) is determined through measurement.

4. The amount of CO absorbed by the concrete powder (2) ２ is further characterized by taking into account the measured temperature and / or the measured weight and / or the measured relative humidity in the container (4), according to the method of claim 3.

5. When the filling level of the gas into the container (4) reaches a desired level and / or when the CO2 concentration in the container (4) reaches a predetermined CO ２ concentration, the volumetric flow rate of the gas supplied is reduced or temporarily stopped. The method according to any one of claims 1 to 4, characterized in that.

6. CO ２ The volumetric flow rate of the gas containing ２ CO is reduced or temporarily stopped so as to compensate for the amount of CO already absorbed by the concrete powder (2) disposed in the container (4). The method according to claim 5, characterized in that.

7. After reaching the predetermined saturated CO ２ After reaching the above, the excess gas is guided from the container (4) to a collection container (12) filled with another concrete powder particle (2), and the another concrete powder particle (2) at least partially absorbs the excess gas. The method according to any one of claims 1 to 6, characterized in that.

8. The method according to claim 7, characterized in that steps b to d of the method according to claim 1 are repeated in the collection container (12).

9. A plant (1) for treating concrete powder and granules (2) for subsequent recycling, the plant (1) comprising: The plant (1) includes: a. a container (4) that is at least partially airtight; b. an inlet valve (7) for controlling the volume flow rate of the gas containing CO2 supplied to the container (4); c. At least one sensor (8, 9, 10) for specifying the amount of CO ２ absorbed by the concrete powder (2) in the container (4); d. at least one sensor (8, 9, 10) and a control unit (11) operatively connected to the inlet valve (7) and configured to control the volume flow rate of the gas supplied through the inlet valve (7); The container (4) includes: i. at least one opening (19, 20) for accommodating and / or removing the concrete powder and granules (2); ii. An inlet section (5) that can be fluidly and operatively connected to the storage tank (3) via the inlet pipe (6) and supplies a gas containing CO ２ to the container (4), and is provided with, The control unit (11) performs the following series of steps: a. identifying the amount of CO2 absorbed by the concrete powder and granules (2) in the container (4) via at least one sensor (8, 9), and supplying a gas containing CO2 with a corresponding volume flow rate to the container (4); b. checking whether the concrete powder and granules (2) have reached a predetermined CO2 saturation; A plant (1) characterized by being configured to automatically perform the above.

10. At least one sensor (8, 9) is arranged in the container (4) and is a pressure sensor (9) for measuring pressure and / or a concentration sensor (8) for measuring the CO ２ concentration, plant (1) according to claim 9, characterized in that it is such.

11. The plant (1) according to claim 10, characterized in that a plurality of concentration sensors (8) are arranged one above the other in the vertical direction within the container (4).

12. The plant (1) according to any one of claims 9 to 11, characterized in that the inlet part (5) includes a plurality of gas inlet nozzles (15) arranged in a matrix on the accommodation space of the container (4) and / or at least one side wall of the container (4) and / or the bottom of the container (4).

13. The plant (1) according to any one of claims 9 to 12, characterized in that it comprises a collection container (12) for containing another concrete powder or granular material (2), and the collection container (12) is fluidly operatively connectable to the container (4) via an outflow pipeline (14) of the container (4).

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