WO2022135714A1

WO2022135714A1 - Apparatus for producing co2-enriched concrete

Info

Publication number: WO2022135714A1
Application number: PCT/EP2020/087798
Authority: WO
Inventors: Christian DÜMIG; Peter Brim; Georg Schneider; Steffen KÄMMERER; Florian Schmid; Wolfgang Seitz
Original assignee: Bhs-Sonthofen Gmbh; Wilhelm Geiger Gmbh & Co. Kg
Priority date: 2020-12-23
Filing date: 2020-12-23
Publication date: 2022-06-30

Abstract

The invention relates to an apparatus (100) for producing CO2-enriched concrete, which comprises a mixer (122) which is designed to mix the components of the concrete together, as well as a CO2 feed (112a). According to the invention the apparatus (100) further comprises a premixer (102), which is designed to mix cement and water to form a cement suspension, and also a pressurised container (108) to which the CO2 feed (112a) is connected and which is designed to enrich the cement suspension with the CO2 fed via the CO2 feed (112a). The mixer (122) according to the invention is also designed to mix the cement suspension enriched with CO2 with other components of the cement.

Description

Device for producing CO2-enriched concrete

description

The invention relates to a device for producing CO2-enriched concrete, comprising a mixer which is designed to mix the components of the concrete with one another, and a CO2 supply.

Such a device is known, for example, from US Pat. No. 10,654,191 B2.

The aim of enriching concrete with CO2 is that the concrete achieves the same compressive strength as conventional concrete with its higher cement content, despite a lower cement content.

This process is based on the fact that concrete absorbs CO2 from the ambient air continuously during its entire service life - albeit at a progressively decreasing absorption rate - and thus continues to harden. In this reaction, the so-called carbonation reaction,

the slaked lime, ie the calcium hydroxide (Ca(OH)2), of the cement reacts with carbon dioxide (CO2) from the air to form limestone, ie calcium carbonate (CaCOs) and water (H2O).

If you mix the concrete with an additional amount of CO2 when mixing (a small amount of CO2 is already present in concrete), i.e. enrich it with CO2, you make it easier, especially in the Initially, immediately after placing in the form, in the formwork or the like, the formation of calcium carbonate from the calcium hydroxide contained in the fresh concrete. As a result, the concrete achieves high strength more quickly.

Since in conventional concrete the proportion of cement is responsible for achieving a predetermined strength within a predetermined time, the proportion of cement in CO2-enriched concrete can therefore be reduced compared to conventional concrete. Since a great deal of energy is used in the production of cement and a great deal of CO2 is therefore released, concrete that has been enriched with CO2 performs better than conventional concrete in the ecological balance sheet.

However, the device known from US Pat. No. 10,654,191 B2 has the disadvantage that a great deal of CO2 has to be supplied to the concrete in order to be able to enrich it with CO2 to a small extent at all. The excess CO2 escapes into the environment.

In contrast, it is the object of the present invention to specify a device of the type mentioned at the outset, with which the concrete can be more effectively enriched with CO2.

This object is achieved according to the invention by a device of the type mentioned at the outset, which also includes a pre-mixer designed to mix cement and water to form a cement suspension, and a pressure vessel to which the CO2 supply is connected and which is designed for this to enrich the cement suspension with the CO2 supplied via the CO2 supply, and in which the mixer is designed to mix the cement suspension enriched with CO2 with other components of the concrete.

The cement suspension produced in the pre-mixer is moderately enriched with CO2 in the pressure vessel. The fact that it is a pressure vessel, i.e. a closed vessel, ensures that the CO2 cannot escape but is almost completely enriched in the cement suspension. In terms of process technology, this can also be supported by filling the pressure vessel as completely as possible with cement suspension, leaving at most a small headspace into which the CO2 can outgas. The other components of the concrete are then added to the cement suspension enriched with CO2 in the mixer. According to the above, the CO2 of the cement suspension does not have to be supplied in excess or only with a small excess, which significantly increases the effectiveness of the production of the CO2-enriched concrete.

An overpressure preferably prevails in the pressure vessel, with regard to the energy efficiency of the method preferably an overpressure of at most 20 bar, more preferably an overpressure of at most 10 bar.

Furthermore, it is advantageous if the CO2 enriched in the concrete accounts for a proportion by weight of between approximately 0.01% by weight and approximately 5% by weight of the cement contained in the ready-mixed concrete.

Furthermore, it can be provided that the pre-mixer is connected to at least one storage tank for cement and at least one storage tank for water. If the pre-mixer is only connected to at least one storage tank for cement and at least one storage tank for water, it can be ensured that there are no disruptive substances in the cement suspension, such as aggregate, additives, plastics or wire fibers, so that the CO2 is right there accumulates where it is later needed for hardening, namely on the cement or in the water surrounding it. Depending on the particular application can at best be thought of adding media to the cement suspension that increase the speed of the Set the carbonation reaction to a desired value.

The pre-mixer can be designed, for example, as a compulsory mixer, preferably as a twin-shaft batch mixer.

Furthermore, an intermediate store for cement suspension can be provided between the pre-mixer and the pressure vessel in order to be able to temporarily store the pre-mixed cement suspension before it is introduced into the pressure vessel. This can be advantageous in the event of a production delay, for example.

The provision of an intermediate store is of particular advantage when the mixer and the pre-mixer are formed by one and the same mixing device. This can be realized, for example, when the residence times of the product in the pre-mixer and mixer together are shorter than in the pressure vessel. In this case, the cement suspension can first be emptied into the intermediate reservoir after being mixed in the mixing device functioning as a pre-mixer. The contents of the pressure vessel, i.e. the cement suspension enriched with CO2, can then be discharged into the mixing device, which now functions as a mixer. After the content of the temporary store has been transferred to the pressure vessel, the mixing device first acts as the mixer in which the concrete is mixed and, after emptying, as a pre-mixer for the next batch of cement suspension.

In order to promote the most uniform possible distribution of the CO2 in the cement suspension, it is proposed in a further development of the invention that the CO2 supply is connected to distribution lines and/or outlet nozzles provided on the bottom of the pressure vessel. Additionally or alternatively, an agitator can also be provided in the pressure tank. The agitator can, for example, have at least one preferred wise, vertically arranged, include agitator shaft.

In a further development of the invention, the CO2 can preferably be supplied to the pressure vessel as a gas. In principle, supply in liquid form would also be conceivable, since the CO2 would evaporate immediately on contact with the cement suspension (possibly to a small extent via the detour to solid CO2). In this case, it could be necessary, at least in the range of higher weight percentages of CO2, to take into account the heat of vaporization extracted from the cement suspension when carrying out the process. On the other hand, with lower weight percentages of supplied CO2, there should be no or at most only a small temperature change. Nevertheless, the CO2 supply can be connected to a tank for liquid CO2 and/or a pressure vessel for gaseous CO2 and/or a storage vessel for solid CO2.

It may be advantageous if the CO2 supply has a heat exchanger. Such a heat exchanger can ensure that the CO2 has the optimum temperature for the process.

The amount of CO2 supplied to the pressure vessel can be changed, for example, via a pressure control valve assigned to the CO2 supply. Furthermore, the CO2 supply can have a volume flow measuring device and/or a mass flow measuring device, which records the quantity of CO2 supplied to the pressure vessel. Finally, the pressure control valve and the volume flow measuring device and/or mass flow measuring device can together form a control loop for the supply of CO2.

In a further development of the invention, it is proposed that the mixer be equipped with at least one further storage container for cement and/or with at least one storage container for additives and/or with at least one storage container for aggregates and/or with at least one storage container ter for additives.

The possibility of reintroducing cement is particularly advantageous when producing concrete with a low w/c ratio (water-cement ratio). In this case, the cement suspension produced in the pre-mixer can still have a higher w/c value, i.e. it can be more malleable than the finished concrete, which facilitates the enrichment with CO2. The desired w/c value can then be set in the mixer by adding more cement.

Additives are powdered substances that are added to the concrete. In connection with the present invention, it can be advantageous, for example with regard to the consistency of the concrete, if the amount of cement saved by the CO2 enrichment is substituted by an inert rock powder, i.e. a rock powder that does not take part in the carbonation reaction. for example limestone powder. However, the addition of other additives is also conceivable.

In contrast to additives, aggregates are granular solids that have a specified grading curve. For example, natural aggregates, such as sand or gravel, but also broken aggregates, such as chippings and gravel, can be used. However, artificially produced aggregates are also conceivable. Recently, recycled aggregates have also been increasingly used.

Finally, admixtures are liquid substances that can be added to the concrete, for example to influence its properties.

The mixer can also be designed as a compulsory mixer, for example as a twin-shaft batch mixer. In order to be able to combine all components according to a predetermined recipe, the at least one storage container for cement and/or the at least one storage container for water can have a weighing device. In addition, the at least one further storage container for cement and/or the at least one storage container for additives and/or the at least one storage container for aggregates and/or the at least one storage container for aggregate media can have a weighing device.

A cross-check can be made possible, for example, by the pre-mixer and/or the pressure vessel and/or the mixer having a weighing device.

The invention is described in more detail below using two embodiments with reference to the accompanying drawings. It shows:

FIG. 1 shows a schematic representation of a first device according to the invention for the production of concrete enriched with CO2; and

FIG. 2 shows a schematic representation of a second device according to the invention for the production of concrete enriched with CO2.

In FIG. 1, a device for the production of concrete enriched with CO 2 is denoted generally by 100 .

In the exemplary embodiment shown, the device 100 comprises a pre-mixer 102 designed as a compulsory mixer, for example as a twin-shaft batch mixer, in which cement and water are mixed to form a cement suspension. For this purpose, the pre-mixer 102 cement from a cement reservoir 104 and water from a Water tank 106 is supplied via supply lines 104a and 106a. In order to be able to mix the cement suspension according to a predetermined recipe, the cement storage container 104 and the water tank 106 are provided with weighing devices 104b and 106b, respectively.

After a sluice (not shown) has been opened, the cement suspension can be transferred from the pre-mixer 102 via a line 107 into a pressure vessel 108 . Optionally, the cement suspension can first be temporarily stored in an intermediate store 110 before it is then introduced into the pressure vessel 108 .

In the pressure vessel 108, the cement suspension is enriched with CO2, which is preferably fed to it in gaseous form from a tank 112 for liquid CO2 via a feed line 112a. In the pressure vessel 108, the CO2 is introduced into the cement suspension in a uniformly distributed manner via distributor lines 112b and nozzles 112c.

In order to be able to ensure that the initially liquid CO2 enters the pressure vessel 108 in gaseous form, a heat exchanger 114 can be provided in the feed line 112a.

Furthermore, a pressure control valve 116 and a mass flow measuring device 118 are provided in the supply line 112a in order to be able to control the quantity of CO2 supplied. Additionally or alternatively, the CO2 tank 112 could also be assigned a weighing device 112d (indicated by dashed lines).

In order to be able to evenly distribute the CO2 in the cement suspension, an agitator 120 can also be provided in the pressure vessel 108 .

If the cement suspension has been sufficiently enriched with CO2, it can, after opening a lock (not shown), via a Line 121 are transferred from the pressure vessel 108 in the actual mixer 122. When the cement suspension is ejected from the pressure vessel 108, the excess pressure that may be present in the head space 108a thereof can help. Once the pressure in the head space 108a has reached ambient pressure, a vent line 108b can be opened so that the cement suspension can flow out of the pressure vessel 108 by gravity.

In the mixer 122, the cement suspension can be mixed with the other components of the concrete. These further components can be further cement and/or additives and/or additives and/or aggregates. The device 100 therefore comprises at least one of the storage containers listed below, namely a cement storage container 124, which is connected to the mixer 122 via a feed line 124a, and/or an additive tank 126, which is connected to the mixer 122 via a feed line 126a and/or an additive reservoir 128, which is connected to the mixer 122 via a feed line 128a, and/or an aggregate reservoir 130, which is connected to the mixer 122 via a feed line 130a.

In order to be able to mix the concrete according to a predetermined recipe, the cement storage container 124 is provided with a weighing device 124b and/or the additive tank 126 is provided with a weighing device 126b and/or the additive storage container 128 is provided with a weighing device 128b and/or the aggregate storage container 130 is provided with a weighing device 130b.

As already mentioned, the possibility of re-feeding cement is particularly advantageous when producing concrete with a low w/c ratio (water-cement ratio).

Furthermore, additives are powdered substances that are added to the concrete will. In connection with the present invention, it can be advantageous, for example with regard to the consistency of the concrete, if the amount of cement saved by the CC enrichment is substituted by an inert rock dust, ie a rock dust that does not participate in the carbonation reaction. However, the addition of other additives is also conceivable.

In contrast to additives, aggregates are granular solids that have a specified grading curve. For example, natural aggregates, such as sand or gravel, but also broken aggregates, such as chippings and gravel, can be used. However, artificially produced aggregates or recycled aggregates are also conceivable.

At this point it should be noted that although four reservoirs 124, 126, 128 and 130 are provided in the exemplary embodiment of FIG. 1, any subgroup of these four types of reservoirs can also be provided. Furthermore, more than one storage container can also be provided for each of these four types, since, for example, several different types of additional media and/or several different types of aggregates can be added to the concrete.

Once the concrete has been mixed, a sluice (not shown) can be opened so that the concrete can exit the mixer 122 via a line 131 .

It should also be added that the mixer 122 can also be designed as a compulsory mixer, for example as a twin-shaft batch mixer. It should also be added that a weighing device 102a can be assigned to the pre-mixer 102, that a weighing device 108c can be assigned to the pressure vessel and that a weighing device 122a can be assigned to the mixer 122, in order to carry out a cross-check with the weighing results of the weighing devices of the other components of the device 100 to allow.

Finally, it should also be added that device 100 can include a central control unit (not shown) to which the output signals of all sensors are fed, in particular the output signals of all weighing devices 104b, 106b, 124b, 126b, 128b, 130b, 102a, 108c, 122a and optionally 112d and the mass flow meter 118, but also the output signal of at least one temperature sensor provided in the pre-mixer 102 and/or the pressure vessel 108 and/or the mixer 122 and/or the heat exchanger 114 and/or the CC tank 112 is. Furthermore, the central control unit can output control signals to the pressure control valve 116 and/or the locks (not shown) and/or valves and also the supply of cement from the storage container 104 and/or the supply of water from the tank 106 and/or the supply of further cement from the storage tank 124 and/or the supply of additional media from the storage tank 126 and/or the supply of additives from the storage tank 128 and/or the supply of additives from the storage tank 130.

FIG. 2 shows a second embodiment of a device according to the invention for producing concrete enriched with CO2, which corresponds to the embodiment of FIG. 1 apart from minor differences. Analogous parts in FIG. 2 are therefore provided with the same reference symbols as in FIG. 1, but with the number 100 added to them. In addition, the device 200 in FIG. 2 will only be described below to the extent that it differs from the device 100 in FIG , to the description of which reference is otherwise expressly made. The main difference between the device 200 and the device 100 is that the device 200 comprises only a single mixing device 240, which takes over the function of both the pre-mixer 102 and the mixer 122 of the device of FIG. This structure of the device 200 is particularly advantageous when the residence time of the cement suspension in the pre-mixer and of the concrete in the mixer together are shorter than the residence time of the cement suspension in the pressure vessel. In this case, after being mixed in the mixing device 240 functioning as a pre-mixer, the cement suspension can first be emptied into the intermediate reservoir 210 . The contents of the pressure vessel 208, ie the cement suspension enriched with CO2, can then be discharged via a line 242 into the mixing device 240, which now functions as a mixer. Finally, the contents of the buffer store 210 can be transferred to the pressure vessel 208, while the mixing device 240 now acts as the mixer in which the concrete is finished being mixed. Finally, after being emptied via a line 244, the mixing device can again serve as a pre-mixer for the next batch of cement suspension.

With regard to all other components, in particular the storage tank 204 for cement, the water tank 206, the tank 212 for liquid CO2, the additive tank 226, the additive storage tank 228 and the aggregate storage tank 230, as well as the supply lines connected to these and measuring and weighing devices, reference is made to the description of the device 100 in its entirety.

It is easy to see that the device 200 can dispense with an additional storage container for cement.

Claims

Claims Apparatus (100; 200) for producing CO2-enriched concrete, comprising:

• a mixer (122; 240) adapted to mix the components of the concrete together, and

• a CO2 supply (112a), characterized in that it further comprises a pre-mixer (102; 240) which is designed to mix cement and water into a cement suspension, and a pressure vessel (108; 208) to which the CO2 supply (112a) is connected and which is designed to enrich the cement suspension with the CO2 supply (112a) supplied CO2, and that the mixer (122; 240) is designed to enrich the cement suspension with CO2 with further Mixing components of the concrete. Device according to Claim 1, characterized in that the pre-mixer (102; 240) is connected to at least one storage tank (104; 204) for cement and at least one storage tank (106; 206) for water. Device according to Claim 1 or 2, characterized in that an intermediate store (110; 210) for cement suspension is provided between the pre-mixer (102; 202) and the pressure vessel (108; 208). Device according to Claim 3, characterized in that the mixer and the pre-mixer are formed by one and the same mixing device (240). Device according to one of Claims 1 to 4, characterized in that the CO2 supply (112a) is connected to distribution lines (112b) and/or outlet nozzles (112c) provided on the bottom of the pressure vessel (108; 208). Device according to one of Claims 1 to 5, characterized in that an agitator (120) is provided in the pressure vessel (108; 208). Device according to one of Claims 1 to 6, characterized in that the CO2 supply (112a) is connected to a tank (112; 212) for liquid CO2 and/or a pressurized container for gaseous CO2 and/or a storage container for solid CO2. Device according to one of Claims 1 to 7, characterized in that the CO2 supply (112a) has a heat exchanger (114). Device according to one of Claims 1 to 8, characterized in that the CO2 supply (112a) has a pressure control valve (116). Device according to one of Claims 1 to 9, characterized in that the CO2 supply (112a) has a volume flow measuring device and/or a mass flow measuring device (118). Device according to one of claims 1 to 10, characterized in that the mixer (122; 240) with at least one further storage container (124) for cement or / and with - 15 - connected to at least one storage tank for additives (128; 228) and/or to at least one storage tank (130; 230) for additives and/or to at least one storage tank for additives (126; 226). Device according to one of Claims 1 to 11, characterized in that the at least one storage container (104; 204) for cement and the at least one storage container (106; 206) for water have a weighing device (104b, 106b). Device according to one of Claims 1 to 12, characterized in that the at least one further storage container (124) for cement and/or the at least one storage container (128; 228) for additives and/or the at least one storage container (130; 230) for Additives and/or the at least one storage container (126; 226) for additional media has a weighing device (124b or 128b or 130b or 126b). Device according to one of Claims 1 to 13, characterized in that the pre-mixer (102; 240) and/or the pressure vessel (108; 208) and/or the mixer (122; 240) has a weighing device (102a or 108c or 122a ) having. Device according to one of Claims 1 to 14, characterized in that the mixer (122; 240) and/or the pre-mixer (102; 240) are designed as compulsory mixers, for example as double-shaft batch mixers.