Foam separation

Abstract

The invention relates to a device (1) for separating a foam floating on the surface of a liquid, comprising a container (100) with a first container wall which comprises an overflow (102); preferably a mixing device (101) for mixing the liquid; and a scraping device (120, 121) for scraping the foam from the liquid. The device (1) additionally comprises a scraping ramp (103), said scraping ramp (103) being arranged such that the scraping device (120, 121) can convey the foam from the liquid surface over the first container wall and out of the container (100) via the scraping ramp (103).

Description

[0001] Foam separation

[0002] Technical area

[0003] The invention relates to a device for separating foam floating on the surface of a liquid, comprising a container with a first container wall, the first container wall having an overflow, and a stripping device for stripping the foam from the liquid. Furthermore, the invention relates to a method for separating foam floating on the surface of a liquid.

[0004] State of the art

[0005] Devices for separating foam floating on a liquid surface are generally known. Such devices are used in processing and purification processes. Examples include purification devices for solids such as raw materials, rocks, ores, coal, etc., as well as processing devices in recycling plants, sewage treatment plants for contaminated water, etc., as well as the food industry and other areas of application. Further areas of application are known to those skilled in the art.

[0006] What these fields have in common is that a component of the substance to be cleaned or processed is separated in the process using foam or a floating fraction. This process is also known as flotation. It is a physico-chemical separation process in which, in a typically aqueous environment, a substance to be separated is transported to the surface of the liquid by means of gas bubbles. There, a foam containing the substance to be separated forms. The foam is finally separated from the liquid using a device for separating a foam floating on the surface of a liquid. Such processes are particularly suitable for the separation of hydrophobic particles or droplets. Gas bubbles, which are also hydrophobic, can attach themselves to the hydrophobic particles or droplets and transport them to the surface of the liquid.The deposition can also occur via electrostatic effects.

[0007] Various techniques are known for separating the floating fraction, or foam, from the liquid surface. One approach is to discharge the floating fraction, or foam, from the tank as a continuous overflow. This technique is well-known in the separation of bitumen from oil sands. However, such systems are inefficient because, on the one hand, a high liquid throughput is required, and, on the other hand, the floating foam only slowly reaches the overflow.

[0008] Alternatively, a mechanical scraper device can be provided to scrape the floating fraction or foam from the liquid. This creates a more efficient process for separating the floating fraction or foam from the liquid surface.

[0009] However, both processes are susceptible to wave motions in the liquid, which, on the one hand, complicates separation with the scraper device and, on the other hand, can cause large quantities of liquid to escape via the overflow. Such wave motions are generated by the agitators and mixers, which are intended to accelerate the separation process.

[0010] It is known that this effect can be reduced by providing a sufficiently high liquid column that absorbs the deep movements in the liquid. However, this has the disadvantage of requiring correspondingly large (especially high) reactors. Furthermore, a large amount of liquid is required. Especially if the liquid is to be heated, this requires a correspondingly large amount of energy, making the process expensive. Using a reagent to support the purification or separation process also requires a correspondingly larger amount of the reagent, which in turn makes the process more expensive.

[0011] Description of the invention

[0012] The object of the invention is to provide a device belonging to the technical field mentioned at the outset for separating foam floating on a liquid surface, which device can be operated particularly efficiently.

[0013] The solution to the problem is defined by the features of claim 1. According to the invention, the device comprises an overflow and a stripping device for stripping the foam from the liquid. The stripping device is designed and arranged such that the foam can be discharged from the container spatially separated from the overflow, in particular vertically above the overflow. The foam is thus not discharged via the overflow, but via a device separate from the overflow.

[0014] This ensures that the scraper device essentially removes the foam from the tank. In particular, the amount of liquid discharged with the foam can be significantly reduced. This, in turn, leads to a particularly efficient separation process. While wave motions from an agitator can lead to increased liquid discharge via the overflow, the arrangement and design of the scraper device can reduce or at least prevent this discharge along with the foam. This, in turn, allows for a smaller tank, which in turn can save costs, particularly energy costs for heating.

[0015] Furthermore, this allows the liquid in the tank to be efficiently circulated without negatively impacting foam separation. This, in turn, allows for a more efficient separation process. The scraper device is preferably positioned vertically spaced from the overflow, at least in some areas, so that the foam can be removed from the tank above the overflow. However, the scraper device does not necessarily have to be positioned exactly above the overflow; the overflow and the scraper device can also be located at different points on a tank rim.

[0016] The device preferably comprises a scraper ramp, the scraper ramp being arranged such that the scraper device can convey the foam from the liquid surface, in particular over the first container wall, out of the container via the scraper ramp. The scraper ramp is arranged in the region of the container edge, preferably vertically above the overflow, so that the foam is guided upwards from the liquid surface along the scraper ramp during the process. The highest point of the scraper ramp does not necessarily have to be above the container edge, but can also be arranged in front of or behind it. Preferably, a horizontal angle of the scraper ramp is adjustable, preferably automatically, in an angular range between preferably + / - 30°, in particular between + / - 15°, particularly preferably between + / - 5°.This allows the angle to be kept small at the beginning of the process, when the foam typically has a high density, and a larger angle to be set towards the end of the process, when the density of the foam is typically lower.

[0017] Instead of the scraper ramp, a different design of the scraper device can also be provided. In particular, for example, a conveyor belt can be provided that is partially immersed in the liquid, thus transporting the foam from the liquid surface upwards and can be discharged vertically from the container above the overflow.

[0018] By using a scraper ramp, the floating material or foam can be transported out of the container particularly efficiently and with minimal liquid loss. At the same time, the overflow ensures a constant liquid level in the container, so that the scraper device can be kept at a constant height throughout the process. This allows the water level to be kept constant regardless of waves caused, for example, by a mixing device or the like. Overall, this creates a device with which the floating material can be removed from the liquid particularly efficiently. It will be clear to those skilled in the art that for this purpose, the container can preferably be provided with a liquid supply to maintain the liquid level.

[0019] The device for separating foam floating on a liquid surface of a liquid comprises a container with a first container wall, wherein the first container wall comprises an overflow.

[0020] Preferably, the container has a cross-sectional area for the liquid surface in the region of the stripping device, in particular at a height of the overflow, wherein a ratio between a container volume of the container and the cross-sectional area is greater than 5 m 3 : 1 m 2 , preferably larger than 8 m 3 : 1 m 2 , particularly preferably larger than 10 m 3 : 1 m 2This keeps the cross-sectional area relatively small for a given tank volume. This allows the foam to be generated in a particularly concentrated form and removed from the surface. The cross-sectional area is preferably determined at the level of the overflow. In an exemplary dimensioning, the tank has a volume of 10 m up to the overflow. 3 where the cross-sectional area (surface at the level of the overflow) is 1 m 2 Experiments have shown that the combination of the relatively small cross-sectional area and the scraping device leads to particularly good results. This combination is particularly advantageous when the material to be separated has a relatively high density, which in turn results in a relatively high foam density.

[0021] In variants, the ratio between a container volume of the container and the cross-sectional area can be less than 5 m3 : 1 m 2 be.

[0022] Preferably, the container has a cross-sectional area for the liquid surface in the region of the stripping device, in particular at a height of the overflow, wherein a ratio between a container volume of the container and the cross-sectional area is less than 30 m 3 : 1 m 2 , preferably less than 20 m 3 : 1 m 2 , particularly preferably less than 15 m 3 : 1 m 2 Preferably, the ratio between the height of the container, in particular from the container bottom to the overflow, and the cross-sectional area of ​​the container is greater than 3 m : 1 m 2 , preferably larger than 5 m:1 m 2 , particularly preferably greater than 10 m : 1 m 2 In variants, the ratio between a tank height, in particular from the tank bottom to the overflow, to the cross-sectional area of ​​the tank can also be less than 3 m : 1 m 2Preferably, the container volume should be greater than 5 m 3 , especially larger than 10 m 3 . In variants, the container volume can also be less than 5 m 3 be.

[0023] Preferably, the container wall tapers towards the cross-sectional area at the level of the overflow. Particularly preferably, the cross-sectional area of ​​the container tapers towards the cross-sectional area at the level of the overflow in an upper fifth of the container, preferably in an upper third of the container. In variants, the container can also be cylindrical.

[0024] The overflow preferably has a rising zone that is separate from the liquid surface and, in particular, separated from the liquid surface by a partition. This prevents large quantities of liquid from escaping from the container via the overflow due to a wave movement. The structure of this rising zone can resemble a spout for the milk of a cream separator. An upper end of the partition is preferably located above the overflow so that the foam on the liquid surface cannot reach the rising zone and escape from the container via the overflow. The partition is therefore preferably designed such that a partition region that separates the rising zone from the liquid surface is higher than the overflow. The partition can, for example, comprise a channel that is connected to the inner wall of the container, with a channel inlet being arranged below the overflow and a channel outlet being fluidly connected to the overflow.The channel can be realized, for example, by a U-shaped profile that is connected, for example, welded, to the inner wall of the container. In some variants, the riser zone can also be omitted.

[0025] The overflow preferably comprises a deflection, whereby a flow direction of the liquid is deflected by an angle of at least 90° before reaching the overflow in order to prevent foam from escaping during the overflow. This can prevent the rising bubbles or nanobubbles (see below) and the foam formed thereby from escaping via the overflow. This achieves particularly efficient foam separation. The deflection can be part of the riser zone or formed as a separate element, preferably upstream of the riser zone and fluidically connected to the riser zone. The deflection is particularly preferably formed at the inlet region of the riser zone. A deflection of at least 90° means that an average flow direction differs in two different zones of the deflection by an angle of at least 90°.The diverter is preferably designed such that the liquid is directed downwards upon entering the diverter, thus away from the overflow, and then upwards again toward the overflow. Since bubbles or nanobubbles rise due to their low density, this ensures that the bubbles or nanobubbles do not reach the rising zone, or only reach it in small quantities. Many possible diverter designs are known to those skilled in the art.

[0026] In a simple case, the riser zone can be realized by a vertically arranged pipe section which is connected to a U-shaped pipe section at the pipe end located below the overflow, wherein the U-shaped pipe section forms the deflection. Other designs of the deflection are known to those skilled in the art. For example, the riser zone can also be equipped with a flow breaker such that the liquid is deflected by at least 90° along the riser zone. In principle, the deflection can also deflect the liquid by less than 90°, for example by 45° to 90°. In a further variant, particularly when large quantities of foam are produced, the riser zone can also have more than one deflection.In a particular embodiment, the rising zone can have a deflection at the liquid surface, which is open to the liquid surface, so that foam in the rising zone can be carried to the liquid surface and scraped off there. Thus, on its way to the overflow, the liquid first flows upwards toward the liquid surface, then downwards again, and is deflected upwards again toward the overflow. The rising zone can have several such regions, so that the liquid reaches the liquid surface several times on the way to the overflow. Those skilled in the art are aware of further variants for deflecting a liquid flow toward the overflow, which can prevent excessive foam from escaping from the overflow.

[0027] In some variants, the deflection can be omitted. The riser zone can thus be designed as a simple immersion tube.

[0028] Furthermore, the device preferably comprises a mixing device for mixing the liquid. The mixing device can comprise a mixer, for example a paddle mixer, a single-shaft mixer, an orbital mixer, a multi-shaft mixer, a fluidized bed mixer, a gas jet or liquid jet mixer, or the like. In principle, the mixing device can also comprise an agitator. The mixing device is preferably arranged in the container so that the liquid in the container can be thoroughly mixed.

[0029] In some variants, the mixing device can be omitted. In this case, the container can be used, for example, as a settling tank. The material to be cleaned or treated can be mixed with the liquid in a preliminary step and then transferred to the container.

[0030] In further variants, the container with the overflow and the scraper device can be arranged as the last container in a cascade, in which the foam in upstream containers is transferred to the next container via a scraper device. The upstream containers do not necessarily have to have an overflow, so that the next container in the cascade is fed with liquid from the previous container. On the other hand, several containers in the cascade (i.e. not just the last container) can be equipped with an overflow. Furthermore, several of the containers can be equipped with a mixing device (i.e. not just the first one). The cascade has the advantage that the foam can be cleaned of, for example, suspended matter which has a higher density than the liquid (sand and the like) by settling.When processing asphalt-containing material, where the asphalt is separated using foam, asphalt of particularly high purity can be achieved. It is generally possible to provide different liquids, different physical conditions (temperature, density) and / or chemical conditions (reagents, pH, surface tension, etc.) in the cascade tanks to ensure efficient foam separation.

[0031] The device further comprises a scraper device for scraping the foam from the liquid. The scraper device can be designed as a conveyor belt scraper, in which a conveyor belt is equipped with slats arranged transversely to the direction of movement, with slats on the underside of the conveyor belt scraping the foam from the liquid as the conveyor belt moves. Furthermore, the scraper device can also be designed as a rotating scraper arm. Further variants are known to those skilled in the art.

[0032] The foam is removed from the liquid via the scraper ramp using the scraper device. The scraper ramp is positioned in such a way that the scraper device can transport the foam from the liquid surface over the first container wall and out of the container.

[0033] The scraper ramp is preferably arranged such that a first end is located inside the container, below the overflow. This means that when the device is in operation, the first end is immersed in the liquid, allowing the foam to be removed from the liquid surface particularly effectively. Depending on the height of the waves caused by the mixing device, the immersion depth can be adjusted such that the first end of the scraper ramp is always inside the liquid. This can be achieved, for example, by inclining the ramp. The first end of the scraper ramp is preferably between 1 cm and 100 cm, more preferably between 2 cm and 50 cm, and most preferably between 5 cm and 25 cm below the overflow. In variants, the scraper ramp can also be arranged more than 100 cm below the overflow.

[0034] The scraper ramp is guided over the first container wall so that the foam can be discharged from the container. The maximum height of the scraper ramp can therefore basically be at the height of the overflow. Preferably, however, the scraper ramp is preferably higher than the overflow in the region of the container wall. This prevents excessive liquid from escaping via the scraper ramp. The scraper ramp is preferably arranged in the region of the container wall, in particular the overflow, between 1 cm and 100 cm, preferably between 10 cm and 50 cm above the overflow. The height above the overflow can also be greater than 100 cm. Particularly preferably, the height of the overflow is adapted depending on the waves caused by the mixing device such that the waves do not protrude above the highest point of the scraper ramp. This can prevent liquid from escaping from the container via the scraper ramp.

[0035] The device preferably further comprises a return device, in particular a fluid pump, with which liquid overflowing via the overflow can be returned, in particular continuously, to the container during operation. This keeps liquid loss to a minimum. As a result, less liquid needs to be replenished into the system during operation. This in turn means that energy is saved if the liquid is heated, and if reagents are used in the liquid, these reagents can also be saved. Overall, this enables an economical and ecological process for separating foam from a liquid surface. The return device preferably comprises a pump, in particular, for example, a submersible pump, with which the overflowing liquid can be pumped back into the container. In variants, the return device can also be omitted.

[0036] The container preferably comprises a sensor for determining a volume flow of the liquid overflowing over the overflow during operation, wherein the return device can be controlled by means of the sensor such that a level of the liquid surface can be kept constant. In variants, the sensor can also be omitted. The return device can also be operated continuously, preferably with an excess of liquid. This makes it simple to keep the level of the liquid surface constant. In variants, the return device can also be omitted. Alternatively or additionally, a device can be provided for supplying liquid to the container. Preferably, the container comprises a primary heating device for heating the liquid in the container.In variants or in addition, a peripheral heating device can also be provided instead of a primary heating device; in particular, the return device can comprise such a peripheral heating device.

[0037] The recirculation device preferably comprises a heating device with which the overflowed liquid can be heated. This allows the liquid temperature in the container to be maintained. The heating device preferably serves as a supplement to a primary heating device of the container. Furthermore, the recirculation device with the heating device can also assume the function of a continuous-flow heater, which heats the liquid in the container, so that the primary heating device of the container can be dispensed with. In variants, the heating device of the recirculation device can also be dispensed with.

[0038] The return device preferably comprises an introduction device for introducing a reagent into the overflowed liquid and, in particular, a mixing device arranged downstream of the introduction device with respect to a flow direction for mixing the overflowed liquid. This allows a reagent to be added simply and efficiently both initially and during ongoing operation. Various substances can be used as reagents, in particular, for example, oxidizing agents, acids, bases, precipitants or flocculants, foaming agents, etc. The list is not exhaustive. In particular, in conjunction with the mixing device, a reagent can thus be distributed particularly efficiently into the liquid in the container. In variants, the introduction device can also be designed independently of the return device. Furthermore, the introduction device can also be omitted.

[0039] Preferably, the height of the container overflow is adjustable, in particular automatically adjustable. This allows the overflow to be adapted to a wave movement caused by the mixing device. For example, if the liquid is mixed intensively, the overflow can be increased accordingly in order to reduce the outflow of the liquid. In variants, the adjustability of the overflow can also be omitted. Preferably, the container comprises a second container wall which is arranged outside the first container wall, wherein the scraper ramp is arranged such that the scraper device can convey the foam via the scraper ramp from the liquid surface over the first container wall and the second container wall out of the container. The second container wall preferably encloses the first container wall so that the first container wall comes to lie within the second container wall.The height of the first container wall is preferably higher than the height of the second container wall. On the other hand, the second container wall can, in principle, also be higher than the first container wall. The second container wall can also be arranged only in the overflow area. In some variants, the second container wall can be omitted. In this case, a separate container can be positioned in the overflow area, into which the overflowing liquid can flow.

[0040] Preferably, the overflow is arranged such that the overflowing liquid can flow over the first container wall between the first container wall and the second container wall. In variants, the overflow can also be arranged such that the overflowing liquid can flow into a separate container.

[0041] The mixing device preferably comprises a first agitator for mixing a lower region of the container, in particular for mixing a material to be separated, and preferably a second agitator, which is arranged above the first agitator, for mixing a doping region of the container.

[0042] The first agitator serves to mix the material to be separated. This allows the material to be circulated and, if necessary, crushed to increase the surface area. This allows the material to be separated to bind particularly efficiently to gas bubbles and be transported to the surface where the foam forms.

[0043] The second agitator is arranged above the first agitator and serves to circulate the liquid. This second agitator is particularly advantageous when the substance to be separated has a higher density than the liquid. In this case, the liquid can contain substances that are insoluble in the liquid but increase the density of the liquid. By circulating the liquid, the insoluble substances are kept in suspension and the density remains homogeneous so that the substance to be separated can be carried to the liquid surface with the bubbles. The circulation prevents or reduces the settling of the insoluble substances in the liquid. The liquid is particularly preferably homogenized in a laminar manner using the second agitator in order to prevent sedimentation and at the same time allow foam formation.

[0044] Preferably, the mass ratio between the material and the liquid in the process is between 1:1 and 1:2 (1 to 0.5), preferably between 4:5 and 3:5, in particular around 3:4. The mass ratio can also be less than 1:1 (e.g., 2:1) or greater than 1:2 (e.g., 1:3).

[0045] In a particular embodiment, the material to be separated is bituminous road demolition material. More preferably, the bituminous road demolition material is either unprocessed bituminous road demolition material, which is optionally crushed and thus fed into the process. In a further variant, the bituminous road demolition material is mechanically concentrated bituminous road demolition material, in which the bituminous portion has been concentrated through a friction process. In this case, the substance to be separated is bituminous material. During the process, the bituminous material is separated from the bituminous road demolition material and carried to the liquid surface by gas bubbles, in particular nanobubbles, where the foam is formed. The bituminous material typically comprises fillers, so that the density of the bituminous material is between 1.03 g / ml (density of bitumen) and 2.03 g / ml (density of bitumen).2 g / ml (density of filler). The density of the bituminous material is preferably between 1.5 and 2.1 g / ml, particularly preferably between 1.8 and 1.9 g / ml, but can also be below 1.5 g / ml or above 2.1 g / ml. The density of the liquid is increased by the presence of filler, which contains little or no bituminous material. This increases the buoyancy of the bituminous material with the gas bubbles / nanobubbles adhering to it, which in turn leads to more efficient foam formation. However, to keep the filler suspended, it is advantageous to circulate the liquid with the second agitator. This prevents the filler from settling or a density gradient (increasing density towards the bottom).The use of fillers to increase the density of the liquid is particularly advantageous in this process, as the filler is already contained in the material and is introduced into the liquid during the separation process without any special precautions. However, it is clear to those skilled in the art that other substances can also be added to the liquid to increase the density. In particular, fillers or similar mineral materials, as well as soluble materials such as salts, can be added separately and independently of the material to be separated to increase the density and thus increase the buoyancy of the material to be separated with the adhering bubbles / nanobubbles.

[0046] In some variants, one or both agitators can be omitted. The second agitator can be omitted if, for example, the first agitator already provides sufficient circulation of the liquid and thus a homogeneous density within the liquid. Furthermore, the second agitator can be omitted if the density of the substance to be separated is sufficiently low.

[0047] Preferably, an agitator shaft and / or agitator shaft bearing, in particular an agitator shaft and / or agitator shaft bearing of the mixing device, penetrates the first container wall. Thus, the mixing device preferably comprises a horizontally mounted agitator shaft. This achieves optimal circulation of solid material, allowing the solid to be processed, for example, cleaned, in a particularly optimal manner. Mounting the agitator shaft in the opening in the first container wall results in a particularly simply constructed reactor for foam separation and, in particular, for the processing of solids. In variants, the mixing device can also be designed and arranged such that no opening in the first container wall is necessary.The agitator shaft is preferably drivably coupled to a drive motor of the mixing device in a region between the first container wall and the second container wall. The drive motor is particularly preferably arranged vertically above the agitator shaft. The agitator shaft is preferably located entirely within the second container wall. Thus, the agitator shaft preferably does not penetrate the second container wall. This arrangement of the agitator shaft has the advantage that liquid escaping in the region of the agitator shaft, particularly at a bearing of the agitator shaft, can be collected in the space between the first container wall and the second container wall.Furthermore, in the process the space between the first container wall and the second container wall can be filled with the liquid, whereby a hydrostatic counterpressure can be generated in the area of ​​the agitator shaft bearing in order to prevent or at least reduce the escape of liquid from the agitator shaft. This reduces the load on the agitator shaft during operation caused by particles of the material to be processed, which in turn protects the agitator shaft bearings and the agitator shaft itself. The drive motor is preferably arranged essentially vertically above the agitator shaft. During operation, in particular when the liquid level between the first container wall and the second container wall is above the agitator shaft, the drive motor is therefore preferably above the liquid level. The drive motor is preferably coupled to the agitator shaft via coupling means.The coupling means are preferably designed as a gear, a drive belt, a drive chain, or the like. In variants, the drive motor can also be directly coupled to the agitator shaft, whereby the agitator shaft can be coaxially coupled to a drive shaft of the drive motor.

[0048] In a process for separating foam floating on the surface of a liquid, a solid and a liquid are typically filled into a container. The mixing device mixes the solid and the liquid, thereby producing a fraction floating on the liquid surface, in particular a foam. The scraping device then conveys the foam, preferably continuously, out of the container via the scraping ramp. For this purpose, the scraping ramp extends into the liquid with a first end. The scraping ramp extends over the first container wall and, if present, over the second container wall.

[0049] The liquid preferably comprises, in particular at least partially, nanobubbles having an average diameter of preferably less than 2000 nm, preferably less than 1000 nm, and particularly preferably less than 500 nm. Preferably, the diameter of at least 80%, preferably at least 90%, of the nanobubbles is between 200 nm and 500 nm. The nanobubbles can attach to the substance to be separated and thus transport it to the liquid surface to form a foam there comprising the substance to be separated.

[0050] Nanobubbles are generally known to those skilled in the art. They are gas bubbles in a liquid with an average diameter in the nanometer range. Nanobubbles can be held relatively stably in a liquid, in particular much more stably than macrobubbles, whose bubbles are in the millimeter range. Compared to macrobubbles, nanobubbles exhibit a significantly higher internal pressure. Furthermore, nanobubbles can achieve a particularly large increase in the volume of the liquid, up to a factor of 2.5 compared to "normal" gas bubbles. Furthermore, nanobubbles also achieve a particularly high specific surface area, which is a major advantage over micro- or macrobubbles, especially when interacting with substances to be separated (e.g., bituminous material from road demolition material).In addition, the nanobubbles exhibit particularly high coalescence stability, allowing their large specific surface area to be maintained for a relatively long time. Furthermore, they can form free radicals, as high amounts of energy can be generated when the nanobubbles collapse—both effects are particularly advantageous for the separation of the substance to be separated.

[0051] Various techniques are known for generating nanobubbles. Methods such as cavitation, electrolysis, nanopore deposition, membrane deposition, and sonochemistry using ultrasound are all known. However, a simple and cost-effective method for generating nanobubbles for industrial applications is currently lacking.

[0052] It has now surprisingly been shown that nanobubbles can be generated by the decomposition of peroxides, in particular hydrogen peroxide, a bicarbonate, a persulfate, or a mixture thereof, in the presence of dust or filler in an aqueous solution. The concentration of hydrogen peroxide relative to the liquid (typically relative to the water) is preferably between 0.01 wt.% and 1 wt.%, preferably between 0.03 wt.% and 0.3 wt.%. Particularly optimal results were achieved with these values. In variants, the concentration can be less than 0.01 wt.% or higher than 1 wt.%. Other reagents can also be used instead of peroxides, in particular, for example, bicarbonates or persulfates.

[0053] In the process, the nanobubbles are therefore preferably produced with a peroxide, in particular hydrogen peroxide, a bicarbonate, a persulfate, or a mixture thereof, preferably in the presence of mineral material, particularly preferably in the presence of mineral powder. This creates an efficient and cost-effective process for forming nanobubbles. As already mentioned above, however, other techniques for generating nanobubbles are also known to those skilled in the art. It should also be noted that the process for generating nanobubbles can also be carried out independently of the foam separation process and, if necessary, can be used in other applications.

[0054] The mineral powder preferably has an average grain diameter of less than 1 mm, preferably less than 0.5 mm, particularly preferably less than 0.1 mm, further preferably less than 0.07 mm. The average grain diameter is determined, for example, according to DIN 66165 (2016). It has been shown that with a small grain diameter, the density of the liquid can be increased, whereby the grains can be kept in suspension more easily due to their small size (e.g. supported by circulation with the second agitator). Furthermore, due to the high specific surface area, nanobubbles can be achieved particularly efficiently through the decomposition of peroxides. The average grain diameter is preferably greater than 0.01 mm, in particular greater than 0.04 mm. In variants, the average grain diameter can also be greater than 1 mm.

[0055] The mineral powder preferably comprises a proportion of more than 0.1 wt.%, preferably more than 0.5 wt.%, particularly preferably more than 1 wt.%, based on the liquid. Many experiments have shown that very good results in the generation of nanobubbles are achieved with a proportion of around 1 wt.%, while at the same time the density of the liquid is sufficiently high to achieve sufficient buoyancy of the substance to be separated with the adhering nanobubbles. The mineral powder preferably comprises a proportion of less than 10 wt.%, preferably less than 5 wt.%, particularly preferably less than 2 wt.%, based on the liquid. In variants, the proportion can also be less than 0.1 wt.% or greater than 10 wt.%.

[0056] Preferably, a liquid and a material contaminated with a substance to be separated are introduced into the container with a reagent to form a foam containing the substance to be separated, and the foam containing the substance to be separated is stripped off with the stripping device. This creates a process with which contaminated material can be cleaned. Instead of the contaminated material, the process can also be used to process a raw material or to separate raw materials or recycled products. The process can be used to purify raw materials such as rocks, ores, coal, etc. Furthermore, the process can be used in sewage treatment plants for the treatment of contaminated water, etc. Other areas of application are known to those skilled in the art, in particular in the food industry, pharmaceutical industry, etc.

[0057] The contaminated material preferably comprises soil material, slag from waste incineration, and / or recycled material, with the substance to be separated comprising, in particular, hydrocarbons, PAHs (polyaromatic hydrocarbons), PFAS (per- and polyfluorinated alkyl compounds), dioxin, furans, bituminous material, metals, especially heavy metals, metal oxides, or mixtures thereof. The substance to be separated may comprise other contaminant materials known to those skilled in the art, such as organometallic compounds such as organic mercury compounds. The contaminated soil material thus comprises, for example, humus, sand, rocks, mixtures thereof, etc.

[0058] The process can be used in particular to remove dioxin and furan from soil material.

[0059] The process is preferably carried out in such a way that a proportion of PFAS or PAH in the soil material is reduced by at least 60 wt.%, preferably at least 80 wt.%, particularly preferably by at least 95 wt.%.

[0060] In a further preferred variant, the device or method is used to process slag from waste incineration. The slag is typically demineralized in a first processing step. In a second step, the present method can be used to slurry the slag and add peroxide, in particular hydrogen peroxide, a bicarbonate, a persulfate, or a mixture thereof. This creates nanobubbles that attach to the metal oxides, allowing the metal oxides to be removed from the liquid surface in the form of a foam.

[0061] In the process, the contaminated soil material in the container is preferably mixed with water in order to remove the substance(s) to be separated from the water surface as foam using the scraping device. To assist in the separation of the substances, various reagents can be used, which are aimed on the one hand at separating the substance from the carrier material (e.g., PAH from rock) and on the other hand at flotation of the separated substance (gas-forming reagents). Such reagents can include, for example, acids, bases, salts, peroxides, organic solvents, etc. In particular, bicarbonates and / or hydrogen peroxide can be provided. However, other suitable reagents are also known to the person skilled in the art, which can be selected in particular depending on the substance to be separated and the carrier material.

[0062] The contaminated material preferably comprises road demolition material with a bitumen-containing portion, wherein the material to be separated comprises at least a portion of the bitumen-containing portion. The bituminous road surface typically consists of a top layer, which forms the road surface, a binder layer, a base layer, and a foundation layer. The bituminous road surface includes, among other things, bituminous material, chippings, sand, fillers, and binding agents.

[0063] In the process, the road demolition material in the container is preferably mixed with water in order to remove at least a portion of the bituminous material from the water surface as foam using the scraping device. To assist in the separation of the substances, various reagents can be used, which are aimed, on the one hand, at separating the bituminous material from the carrier material (in particular, chippings, sand, filler) and, on the other hand, at flotation of the separated bituminous material. Such reagents can include, for example, acids, bases, salts, peroxides, organic solvents, etc. In particular, bicarbonates and / or hydrogen peroxide can be used. The latter substances have led to particularly efficient and effective separation of the bituminous material in tests.However, other suitable reagents are also known to the person skilled in the art, which can be selected in particular depending on the substance to be separated and the carrier material.

[0064] In variants, however, the contaminated material can also comprise other materials, in particular all possible types of construction rubble, roofing felt, etc. Furthermore, the materials can also comprise secondary raw materials that can be processed, for example, cleaned or separated, for reuse using the device according to the invention. Those skilled in the art are familiar with a variety of materials that can be processed and / or cleaned using the device according to the invention.

[0065] The substance to be separated preferably comprises particles in the liquid which have a greatest diameter of less than 120 μm, preferably less than 60 μm, particularly preferably less than 40 μm, wherein the particles are present in particular as suspended particles or suspended matter in the liquid and the liquid in particular comprises water as its main component. Thus, the process can be used to free a liquid of suspended matter which is particularly difficult to settle. In the process, the suspended matter or suspended particles are transported to the liquid surface by means of gas bubbles, such that the suspended matter can be separated from the liquid in a material floating on the liquid surface, in particular a foam.

[0066] In a particularly preferred embodiment, the foam containing the suspended particles is generated using a peroxide and, if appropriate, heat. The foam can also be generated using a peroxide and FeCl3, bicarbonates, etc. Furthermore, the foam can be achieved by introducing gas bubbles, particularly air, CO2, oxygen, etc. Foam formation can be achieved, for example, by using surfactants (soap, particularly anionic, cationic, amphoteric, or nonionic surfactants). A mixer, particularly a pressure, gas, or water jet mixer, can be used for this purpose. The mixer can also be omitted.

[0067] By removing the foam generated on the liquid surface, the amount of suspended solids in the liquid can be reduced. The liquid, especially the water, can be circulated as described above to keep the water level at a constant level.

[0068] The container preferably includes an openable and closable bottom flap in the bottom area, which is particularly liquid-tight. This allows the material to be discharged downwards particularly efficiently by gravity after foam separation. In some variants, the bottom flap can be omitted.

[0069] The bottom flap preferably opens into an auxiliary container located below. This allows the material to be collected after the foam has been separated. The auxiliary container preferably comprises a discharge device with which the material can be discharged from the auxiliary container after the foam has been separated. The auxiliary container is preferably tightly connected to the container so that the liquid cannot escape from the auxiliary container. For this purpose, the discharge device is preferably designed such that the material is discharged above the overflow after the foam has been separated. This prevents the liquid from escaping from the discharge device due to hydrostatics when the bottom flap is opened. The discharge device can, for example, comprise a screw conveyor.Once the material has been collected in the auxiliary hopper following foam separation, the bottom flap can be closed, and the next batch can be run in the hopper while the material is still being discharged from the auxiliary hopper. This creates a particularly efficient foam separation device. In some variants, the auxiliary hopper can also be omitted.

[0070] Further advantageous embodiments and combinations of features of the invention emerge from the following detailed description and the entirety of the patent claims.

[0071] Short description of the drawings

[0072] The drawings used to explain the embodiment show:

[0073] Fig. 1 is a schematic representation of a side view of a first

[0074] Embodiment of a device for separating foam floating on a liquid;

[0075] Fig. 2 is a schematic representation of a side view of a second

[0076] Embodiment of a device for separating foam floating on a liquid;

[0077] Fig. 3 is a schematic representation of a side view of a third

[0078] Embodiment of a device for separating foam floating on a liquid;

[0079] Fig. 4 is a schematic representation of a side view of a container with a first container wall and a second container wall, as well as a mixing device;

[0080] Fig. 5 is a schematic representation of a side view of a fourth

[0081] Embodiment of a device for separating foam floating on a liquid; Fig. 6 shows a schematic representation according to Fig. 5 with an alternative design of the overflow;

[0082] Fig. 7 is a diagram illustrating the reduction of PAH content in contaminated soil; and

[0083] Fig. 8 is a diagram illustrating the reduction of PFAS in contaminated soil.

[0084] In principle, identical parts in the figures are provided with identical reference symbols.

[0085] Ways to implement the invention

[0086] Figure 1 shows a schematic representation of a side view of a first embodiment of a device 1 for separating foam floating on a liquid. The device comprises a container 100 in which two coaxially arranged mixers 101 are arranged as a mixing device. The container 100 comprises an overflow 102, above which a scraper ramp 103 is arranged. The scraper ramp 103 does not necessarily have to be arranged at the same location as the overflow 102. Below the overflow 102, a funnel 110 is provided, which receives the overflowing liquid and directs it via a line 111 into a collecting vessel 112. From this collecting vessel 112, a line 113 leads back into the container 100. The line 113 comprises a pump 114 (which can also be arranged as a submersible pump in the collecting vessel 112), which pumps the overflowed liquid back into the container 100.The container 100 further comprises a scraping device with a conveyor belt 120 and a scraping element 121 arranged thereon. This allows the floating foam to be removed from the liquid surface in the direction of the scraping ramp 103.

[0087] The scraping action and the mixing mechanisms 101 cause waves, which lead to the liquid spilling over the overflow. This essentially reduces the liquid level, which could interrupt the scraping process. By returning the overflowing liquid to the container 100, the liquid level can be kept constant, allowing the scraping device to effectively scrape the foam from the liquid surface.

[0088] The device 1 comprises a level sensor (not shown) in the container 100 and / or in the collecting vessel 112, with which a liquid level can be monitored. The pump 114 can be controlled based on the data from the level sensor. In a further embodiment, the overflow comprises a flow meter that measures the amount of overflowing liquid. The flow sensor can be arranged, for example, in the line 111. The pump 114 can be controlled based on the data from the flow meter.

[0089] Figure 2 shows a schematic representation of a side view of a second embodiment of a device 2 for separating foam floating on a liquid. This device 2 is designed as a cascade. An orbital agitator 201 is arranged in a first container 200. The first container 200 comprises a stripping ramp 203, via which a floating foam is stripped by the first stripping device, comprising a conveyor belt 220 and a stripping element 221 arranged thereon. The stripped foam and overflowing water enter a second container 230. In the present case, this does not comprise a mixing device, but functions as a settling tank to separate sand and the like from the foam. In a further variant, however, the second container 230 can also comprise a mixing device. The second container 230 comprises an overflow 232 and a stripping ramp 233.With the second stripping device, comprising a conveyor belt 260 and a stripping element 261 arranged thereon, the foam floating in the second container 230 is stripped off via the stripping ramp 233, while the overflowing liquid is collected via the overflow 232, a funnel 240, and a line 241 in a container 242. The overflowing liquid is transferred via line 243 and a pump 244 to a collection container 245; alternatively, the liquid can also be pumped directly into the first container. In the collection container 245, the liquid can be processed, for example, by adding a reagent, heating, filtering, or otherwise processing. From the collection container 245, the liquid is fed to the first container 200 to close the circuit.

[0090] The device 2 comprises a level sensor (not shown) in the container 200 and possibly also in the container 230, with which a liquid level can be monitored. Based on the data from the level sensors or the flow sensors, the pump 244, a liquid inlet valve on the collecting container 245, the first wiping device, and / or the second wiping device can be controlled. This ensures constant liquid levels in the first container 200 and the second container 230.

[0091] Figure 3 shows a schematic representation of a side view of a third embodiment of a device 3 for separating foam floating on a liquid. The device 3 is designed as a mobile device and, in this case, has the basic structure of a truck mixer 330. The container 300 is thus designed in the manner of a concrete mixer and rotates about its axis of rotation. A container extension 301 is arranged adjacent to the container 300, which does not rotate with the container 300. The container extension 301 comprises a scraper device with a conveyor belt 320 and a scraper element 321 arranged thereon, as well as an overflow 302 and a scraper ramp 303—analogous to the device 1 in Figure 1.

[0092] In variants, the container 300 can also be configured with a scraping device that is stationary relative to the vehicle and comprises a scraping arm, wherein the scraping arm extends horizontally into the container 300. The scraping arm can be positioned such that the floating foam is guided out of the container 300 due to the rotation of the container 300 along the scraping arm. The propulsion of the foam over the scraping ramp can be controlled by the inclination of the scraping ramp and the rotation speed of the container 300. The liquid exiting via the overflow is returned to the container 300 via a collecting device and a pump, analogous to device 1. Further variants are known to those skilled in the art. Finally, Figure 4 shows a schematic representation of a side view of a container 400 with a first container wall 401 and a second container wall 402, as well as a mixing device 403.The second container wall 402 completely surrounds the first container wall 401 at a distance. The mixing device 403 is mounted in the first container wall 401 via a horizontally arranged shaft, so that the shaft penetrates the first container wall 401. On one side, the shaft is connected via a drive belt 404 to a drive motor 405, which drives the mixing device 403. During operation of the mixing device 403, liquid penetrates between the shaft and the first container wall 401. This liquid enters the space between the first container wall 401 and the second container wall 402. The liquid is pumped from the space back into the container via a line 410 and a pump 411—although this recirculation can also be omitted.This design of the tank 400 and the mixing device 403 with the horizontal drive shaft reduces fluid loss during operation. Furthermore, the shaft bearings in the first tank wall 401 can be protected, since the hydrostatic counterpressure largely prevents fluid from flowing through the bearings, thus preventing abrasive particles from flowing through them.

[0093] Figure 5 shows a schematic representation of a side view of a fourth embodiment of a device 5 for separating foam floating on a liquid. The device comprises a first container 510, which has a capacity of 10 m 3 The container 510 includes an overflow

[0094] 514, which is designed as a dip tube with an opening in the container wall. The dip tube includes a deflection at the inlet end, ie below the liquid level.

[0095] 515, so that upwardly rising bubbles and nanobubbles cannot penetrate directly into the immersion channel. This prevents foam from escaping from the container 510 via the overflow 514. The deflection 515 is designed as a trough into which the immersion tube extends. The liquid escaping through the overflow 514 is collected via a funnel 516 to be fed back into the process. Beforehand, the liquid can be further processed (addition of reagents, tempering, filtering, etc.). The overflow 514 defines the level of the liquid surface 513. The liquid surface 513 has a surface area of ​​1 m 2The relatively small liquid surface 513 has the effect of concentrating rising foam, allowing the foam to be skimmed off more efficiently. Furthermore, the pressure of the nanobubbles is concentrated over a small area, allowing the heavy particles to be conveyed upwards more efficiently. The device 5 comprises a stripping ramp 532 above the level of the liquid surface 513, via which the foam can be stripped from the liquid surface 513 using stripping elements 531 attached to a conveyor belt 530. The movement of the conveyor belt 530 moves the stripping elements 531 over the liquid surface 513, allowing the foam to be removed from the liquid surface 513 via the ramp 532.

[0096] The container 510 is equipped with a first agitator 511, which is arranged in the bottom region of the container 5, above a bottom flap 517 (see below). This circulates the material to be separated. A second agitator 512 is arranged above the agitator 511, which mixes the liquid above the material to be separated in a laminar manner. This ensures a homogeneous density and, in particular, prevents suspended particles, especially fillers, from settling. This would reduce the density, which in turn would reduce the buoyancy of the material to be separated. The second agitator can thus increase the efficiency of the separation process and, under certain circumstances, even make it possible in the first place.

[0097] A bottom flap 517 is provided in the bottom region of the container 510. This flap opens into an underlying auxiliary container 518. The bottom flap 517 can be constructed in several parts, in particular in two parts. Preferably, the bottom flap 517 closes essentially watertight. After a batch has been processed and the foam has been separated, the bottom flap 517 can be opened, whereby the residue of the material to be separated flows downwards into the auxiliary container 518. The auxiliary container 518 comprises a screw conveyor 520, 521. The screw conveyor comprises a horizontal first region 520 and a vertical or obliquely upwardly extending second region 521 connected thereto in a fluid-tight manner. The second region 521 opens above the liquid surface 513, so that when the bottom flap 517 is opened, the liquid does not escape from the second region 521 for hydrostatic reasons.While the residue is being conveyed out of the auxiliary container 518 by the screw conveyor 520, 521, the next batch can be run simultaneously when the bottom flap 517 is closed again. This creates a particularly efficient device for batchwise foam separation. Figure 6 shows a schematic representation according to Figure 5 with an alternative design of the rising zone which leads to the overflow. The rising zone 600 comprises two deflections. The inlet is below the overflow and leads upwards to the level at the height of the overflow. In this area, the rising zone is open at the top so that foam can escape from the rising zone to the liquid surface. The liquid is then guided downwards to another deflection and finally back upwards to the overflow. This design of the rising zone ensures that the liquid fed to the overflow is as foam-free as possible.

[0098] Figure 7 shows a diagram illustrating the reduction of PAHs in contaminated soil. Specifically, this involves the cleaning of roadside verges containing fine asphalt particles that were eroded from the road and washed into the soil. These particles have a density of 1.8 kg / L and are therefore heavier than the process water. Because these particles are contaminated with polycyclic aromatic hydrocarbons, the concentration of pollutant molecules present in the soil before treatment is greatly reduced after treatment, while they are highly concentrated in the foam. Tests have shown that the device can reduce PAHs in contaminated soil surprisingly well, with a reduction of up to 95% by weight or more.

[0099] Similarly, Figure 8 shows a diagram illustrating the reduction in PFAS concentrations in contaminated soil. In the experiment, soil material containing per- and polyfluorinated alkyl compounds (PFAS) was cleaned. These molecules are hydrophobic and / or possess functional groups that allow them to bind to the nanobubbles through hydrophobic and / or electrostatic interactions, thereby carrying them to the liquid surface. The graph in Figure 8 shows that the concentration of pollutant molecules present in the soil before treatment decreased significantly after treatment. The experiments demonstrate a very effective reduction in PFAS concentrations of up to 95 wt% or more.

[0100] In summary, it can be stated that according to the invention a device for separating a foam floating on a liquid surface is created, with which a particularly efficient foam separation can be carried out.

Claims

Patent claims 1. Device (1) for separating foam floating on the surface of a liquid, comprising a container (100) with a first container wall, wherein the first container wall comprises an overflow (102), and preferably a mixing device (101) for mixing the liquid and a scraper device (120, 121) for scraping the foam from the liquid, in particular the liquid surface, characterized in that the scraper device is designed and arranged such that the foam can preferably be spatially separated from the overflow, in particular vertically above the overflow, and discharged from the container.

2. Device ( 1) according to claim 1 , characterized in that the scraper device ( 120, 121) comprises a scraper ramp ( 103) wherein the scraper ramp ( 103) is arranged such that the scraper device ( 120, 121) can convey the foam over the scraper ramp ( 103) from the liquid surface over the first container wall out of the container ( 100) and wherein in particular a horizontal angle of the scraper ramp is adjustable in an angular range between preferably + / - 30°, in particular between + / - 15°, in particular preferably between + / - 5°, preferably automatically.

3. Device ( 1) according to claim 1 or 2, characterized in that the container (100) has a cross-sectional area for the liquid surface in the area of ​​the scraper device (120, 121), wherein a ratio between a container volume of the container ( 100) and the cross-sectional area is greater than 5 m² 3 : 1 m 2, preferably larger than 8 m 3 : 1 m 2 , especially preferably larger than 10 m 3 : 1 m 2 is.

4. Device (1) according to one of claims 1 to 3, characterized in that the overflow has a rising zone separate from the liquid surface and in particular separated from the liquid surface by a partition wall.

5. Device (1) according to one of claims 1 to 4, characterized in that the overflow comprises a deflection whereby the flow direction of the liquid is deflected by an angle of at least 90° before reaching the overflow in order to prevent foam from escaping at the overflow.

6. Device ( 1) according to one of claims 1 to 5, characterized in that the device ( 1) further comprises a return device, in particular a fluid pump ( 1 14), with which, in operation, a liquid that has overflowed via the overflow ( 102) can be returned, in particular continuously, to the container ( 100).

7. Device (1) according to claim 6, characterized in that the container (100) comprises a sensor for determining a volume flow rate of the liquid overflowing during operation via the overflow (102), wherein the return device can be controlled by means of the sensor in such a way that a level of the liquid surface can be kept constant.

8. Device (1) according to claim 6 or 7, characterized in that the return device comprises a heating device with which the overflowing liquid can be heated.

9. Device ( 1) according to one of claims 6 to 8, characterized in that the return device comprises an injection device for introducing a reagent into the overflowed liquid and in particular a mixing device arranged with respect to a flow direction downstream of the injection device for mixing the overflowed liquid.

10. Device ( 1) according to one of claims 1 to 9, characterized in that a height of the overflow (102) of the container ( 100) and thus a level of the liquid surface is adjustable, in particular automatically, preferably in a range of + / - 40 cm, particularly preferably in a range of + / - 20 cm, particularly preferably in a range of + / - 5 cm. 1 1. Device (1) according to one of claims 1 to 10, characterized in that the container (100) comprises a second container wall which is located outside the first container wall is arranged, wherein the scraper ramp ( 103) is arranged such that the scraper device (120, 121) can convey the foam over the scraper ramp ( 103) from the liquid surface over the first container wall and the second container wall out of the container ( 100).

12. Device ( 1) according to claim 1 1 , characterized in that the overflow ( 102) is arranged such that the liquid can flow over the first container wall between the first container wall and the second container wall.

13. Device ( 1) according to one of claims 1 to 12, characterized in that the mixing device comprises a first agitator for mixing a lower region of the container, in particular for mixing a material to be separated, and preferably a second agitator which is arranged above the first agitator for mixing a doping region of the container.

14. Device (1) according to one of claims 1 to 13, characterized in that an agitator shaft and / or an agitator shaft bearing, in particular an agitator shaft and / or an agitator shaft bearing of the mixing device (101), penetrates the first container wall.

15. Device ( 1) according to claim 14, characterized in that the agitator shaft of the mixing device ( 101) penetrates the first container wall and wherein the agitator shaft is coupled to a drive motor of the mixing device ( 101) in a region between the first container wall and the second container wall, wherein the drive motor is arranged in particular vertically above the agitator shaft.

16. Method for separating a foam floating on the surface of a liquid, in particular using a device ( 1) according to claim 1.

17. Method according to claim 16, characterized in that the liquid, in particular at least partially, comprises nanobubbles which have an average The nanobubbles have a diameter of preferably less than 2000 nm, preferably less than 1000 nm, and particularly preferably less than 500 nm. The method according to claim 17, characterized in that the nanobubbles are produced with a peroxide, in particular hydrogen peroxide, a bicarbonate, a persulfate, or a mixture thereof, preferably in the presence of mineral material, and particularly preferably in the presence of mineral powder. The method according to claim 18, characterized in that the mineral powder has a mean particle diameter of less than 1 mm, preferably less than 0.5 mm, and particularly preferably less than 0.1 mm, and further preferably less than 0.07 mm. The method according to claim 18 or 19, characterized in that the mineral powder comprises a proportion of more than 0.1 wt.%, preferably more than 0.5 wt.%, and particularly preferably more than 1 wt.%, relative to the liquid.A method according to any one of claims 18 to 20, characterized in that the mineral powder comprises a proportion of less than 10 wt.%, preferably less than 5 wt.%, relative to the liquid. A method according to any one of claims 16 to 21, characterized in that the container (100) comprises a sensor for determining the volumetric flow rate of the liquid overflowing the overflow (102) during operation, wherein a return device for returning the overflowing liquid to the container (100) is controlled by the sensor such that the liquid surface level remains constant.Method according to one of claims 16 to 22, characterized in that the liquid and a material contaminated with a substance to be separated are placed in the container (100) together with a reagent to form a foam containing the substance to be separated, and wherein the foam containing the substance to be separated is scraped off with the scraping device (120, 121).

24. Method according to claim 23, characterized in that the contaminated material comprises soil material, slag from waste incineration and / or recycled material and wherein the substance to be separated comprises in particular hydrocarbons, PAHs, PFAS, dioxins, furans, bituminous material, heavy metals, organometallic compounds, in particular organic mercury compounds, or mixtures thereof.

25. Method according to claim 23 or 24, characterized in that the contaminated material comprises road demolition material with a bituminous component and wherein the substance to be separated comprises at least a part of the bituminous component.

26. Method, in particular according to one of claims 16 to 25, characterized in that the substance to be separated comprises particles in the liquid which have a maximum diameter of less than 120 ,m, preferably less than 60 ,m, and in particular preferably less than 40 ,m, wherein the particles are in particular suspended particles in the liquid and the liquid in particular comprises water as its main component.

27. Method for producing nanobubbles, characterized in that a peroxide, in particular hydrogen peroxide, a bicarbonate, a persulfate or a mixture thereof is mixed with a suspension of water and a mineral powder.

28. Method according to claim 27, characterized in that the mineral powder has a mean particle diameter of less than 1 mm, preferably less than 0.5 mm, particularly preferably less than 0.1 mm, more preferably less than 0.07 mm.

29. Method according to claim 27 or 28, characterized in that the mineral powder comprises a proportion of more than 0.1 wt.%, preferably more than 0.5 wt.%, and in particular preferably more than 1 wt.%, in relation to the liquid. Method according to one of claims 27 to 29, characterized in that the mineral powder comprises a proportion of less than 10 wt.%, preferably less than 5 wt.%, in relation to the liquid.

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