Conversion of polyurethane in a tapered reactor
Patent Information
- Application Number
- EP2023727988
- Authority / Receiving Office
- EP · EP
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2022-05-26
- Filing Date
- 2023-05-19
- Publication Date
- 2025-04-09
Smart Images
Figure 1.1
Abstract
Description
[0001] Conversion of polyurethane in a tapered reactor
[0002] The invention relates to a process for converting a plastic material containing polyurethane and a corresponding device.
[0003] Due to their many adjustable properties, polyurethanes are widely used in industrial and household products. Examples of such products include foams, paints, adhesives, potting compounds, hoses, seals, flooring, mattresses, automotive parts, sports equipment parts, shoe parts, and the like.
[0004] Therefore, a high proportion of polyurethane waste is generated when the corresponding products are damaged or have reached the end of their service life.
[0005] In the past, attempts have therefore been made to recycle polyurethanes. European Patent 01976719 B1, for example, describes a process in which a polyurethane resin is hydrolyzed by contacting it with water at high temperatures.
[0006] The object of the invention is to provide an improved method.
[0007] The invention results from the features of the independent claims. Advantageous further developments and refinements are the subject of the dependent claims.
[0008] For the purposes of the invention, a plastic material is understood to mean a material comprising plastic, ranging from pure plastic to plastic-containing mixtures. The term "plastic" is used in the conventional sense and refers to a synthetically produced substance, for example, a substance produced as part of an organic synthesis, such as a polymer produced from one or more different monomers by polymerization, polyaddition, and / or polycondensation. Plastics are commonly classified into thermosets, thermoplastics, elastomers, and thermoplastic elastomers.Known examples of plastics are polyethylene, polycarbonate, polyacrylic, polymethacrylic, polyacrylamide, polystyrene, acrylonitrile-butadiene rubber, styrene-butadiene rubber, chloroprene rubber, butadiene rubber, and ethylene-propylene-diene rubber, as well as polyurethane. In particular embodiments, the plastic material comprises only hydrolyzable plastics, for example, in addition to polyurethanes, also polyesters, polyamides, and / or polycarbonates. Natural rubber previously used for a technical purpose, for example, obtained in the context of mattress production or chemically processed, such as vulcanized, is also considered a plastic within the scope of the invention. However, lignin, i.e., wood, is not.Depending on their original intended use, the plastics may contain other substances such as plasticizers, microbicidal substances, antioxidants, stabilizers (e.g., against UV light), flame retardants, dyes, or residues of polymerization initiators. Plastics also include those that are not based on petroleum-based starting materials, but rather are produced from renewable raw materials within the framework of a sustainability and renewability concept, either through chemical synthesis or through biotechnological or microbiological processes using appropriately designed enzymes or production organisms. The plastic-containing mixtures mentioned above are either mixtures of pure plastics or mixtures that also include one or more non-plastics, such as metal, ceramic, or glass.Preferably, the plastic(s) in such mixtures, which also comprise non-plastics, represent the relatively largest proportion, based on mass or volume, for example at least 67%, at least 75%, at least 80%, at least 90%, at least 95%, at least 98% or at least 99%. Preferably, there are no non-plastics in the plastic material, whereby methods for reducing these are known to the person skilled in the art and include, for example, manual removal of non-plastics, magnetic removal of magnetic metals or metal alloys, or the separation of plastics and optionally other materials of similar density due to density differences between materials of different densities, for example via air classification or shaking or vibrating devices.Within the plastic material, polyurethane makes up the largest mass fraction, preferably more than 60%, for example at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, or at least 95%, and therefore represents the predominant main component. For example, discarded polyurethane mattresses often contain correspondingly small amounts of polyethylene or polypropylene, which usually come from the cover materials.
[0009] The plastic material used in the process contains polyurethane and optionally further one or more hydrolyzable plastics selected from polyesters, polyamides, or polycarbonates, or consists of polyurethanes and optionally further polyesters, polyamides, or polycarbonates and / or a mixture thereof. According to a particular embodiment, the plastic material consists of polyurethane or a polyurethane mixture, or consists of polyurethane and polyester or a polyester mixture, for example, polyethylene terephthalate or a polyethylene terephthalate mixture, or consists of a polyurethane / polyolefin composite material, wherein the polyurethane in the composite preferably has a proportion of at least 50 percent by mass.Within the hydrolysable plastics, polyurethane accounts for the largest mass fraction, preferably more than 60%, for example at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, or at least 95%, and therefore represents the predominant main component. For example, the plastic material is mattresses or waste from mattress production, whereby the raw material contains polyurethane as a hydrolysable component.The polyurethane can be in the form of a foam, with the particular advantage of the process being that a high-volume starting material (namely, a foam that can be compressed to a certain extent but always tends to occupy a large volume and therefore requires appropriately dimensioned initial lines and reaction vessels) is reacted in the presence of a comparatively small volume of reaction medium, resulting in a significantly smaller volume after appropriate pressure and heat treatment. Essentially, a bulky solid, namely a foam, is converted into a more easily handled form with a significantly higher liquid content and a smaller volume, thus solving a major problem in polyurethane waste and recycling management.
[0010] One aspect of the invention relates to a continuous process for converting a plastic material containing at least one hydrolyzable plastic, comprising the following steps: providing a reaction mixture, wherein the reaction mixture comprises a plastic material present as a solid and containing a polyurethane and further an aqueous medium, wherein in the reaction mixture the mass ratio between the water of the aqueous medium and polyurethane is not more than 0.6 to 1; further transporting the reaction mixture by means of a first conveyor screw arranged in a first line to a filling opening designed as a pressure lock of a at least one end region, relative to the transport direction,tapered reactor; further transporting the reaction mixture by means of a reactor conveyor screw arranged in the reactor at a pressure of > 1 bar to 60 bar at a temperature of 180 °C to 270 °C to the end region of the reactor, further transferring the reaction mixture thus pressure- and heat-treated via a discharge opening designed as a pressure lock into a second line in the end region of the reactor, further transporting the pressure- and heat-treated reaction mixture by means of a second conveyor screw arranged in the second line, further providing a heating zone within the second line with a temperature which is higher than the temperature prevailing in the reactor,Further, in the evaporation zone, gaseous components are removed via at least one degassing point, and in or after the evaporation zone, the reaction mixture is recovered, which has been subjected to pressure and heat and freed of gaseous components. The reaction mixture may be partially or completely freed of the gaseous components.
[0011] The aqueous medium comprises or consists of water and may optionally contain a reaction additive.
[0012] From the resulting pressure and heat-treated reaction mixture, the liquid phase and the contained solids can optionally be separated, for example by centrifugation or filtration, and the resulting solids can optionally be dried.
[0013] The mass ratio between water in the aqueous medium and polyurethane in the plastic material is no more than 0.6 to 1, in particular no more than 0.5 to 1, for example 0.45 to 1, so that polyurethane is present in clear excess based on the mass ratios. Larger amounts of aqueous medium are possible, but it has surprisingly been found that good conversion rates can be achieved with the stated mass ratios. Accordingly, it is not necessary for the plastic material to be suspended in a coherent aqueous medium; it only needs to be moistened with it. With the goal of a resource-saving circular economy, reducing water consumption is a significant advantage. At the beginning of the process, the reaction mixture is transported by means of the first conveyor screw to the reactor's filler opening, which is designed as a pressure lock.One example of such pressure locks is the well-known double lock. Other examples include screw conveyors that convey material under material compaction, or screw conveyors that even have recirculation elements that lead to local compaction of the transported material, which in turn represents a pressure barrier and thus functions as a pressure lock. The volume of the reactor can range from the liter range through the cubic meter range to large-scale volumes of dozens of cubic meters or more.
[0014] After passing through the pressure lock, the polyurethane contained in the plastic material, initially present as a solid, as well as any other hydrolyzable plastics present therein, are converted into a liquid phase as the hydrolyzable plastics contained therein are increasingly converted due to the temperature and pressure conditions prevailing in the reactor in the presence of the aqueous medium, which optionally contains a reaction additive. Since the volume of the reaction mixture is primarily attributable to the plastic material due to the low water content, the volume of the plastic material decreases progressively as the mixture progresses toward the discharge opening.Consequently, a reactor tapered at least in one end region can be used, which advantageously requires less heating power and less space with increasing tapering and the associated smaller volume of the reaction mixture.
[0015] The process is carried out at a pressure in the range of >1 bar to 60 bar, i.e. at an overpressure, based on an atmospheric pressure of 1 bar, such as 5 to 50 bar, 10 to 40 bar, or 20 to 30 bar, for example at about 10, 15, 20, 25, 30, 35, 40, 45, 50, 55 or 60 bar. The temperature during the process is in a range of 180°C to 270°C, such as 180°C to 250°C, such as 190°C to 245°C, 200°C to 240°C, 210°C to 235, or 215°C to 230°C, such as 185, 190, 200, 210, 215, 220, 225, 230, 235, 240, or 250°C. Preferably, a target temperature and a target pressure are specified. However, it is understandable to those skilled in the art that during the execution of a process, the actual values may deviate from the target values or fluctuate around them, and can be controlled or adjusted accordingly if necessary. The temperature and pressure can be actively controlled.According to a particular development, only the temperature is actively regulated, with the pressure being passively established as the equilibrium pressure in a given reaction volume based on the existing temperature of the aqueous reaction mixture. The speed of transport from the filling opening to the removal opening can be adjusted depending on the achieved reduction in the solids content, for example reduced if an optionally possible sample removal shows an excessively high solids content in the pressure- and heat-treated reaction mixture. Non-limiting examples of the duration of the pressure and heat treatment are periods of, for example, 1 to 8 hours, for example 1.5 to 6 hours, such as 2 to 4 hours, for example 1, 2, 3, 4, 5, 6, 7, or 8 hours, + 0 to 59 minutes. For example, the duration of the pressure and heat treatment is 45 to 250 minutes, in particular 45 to 240 minutes.However, it is clear to the person skilled in the art that the times can be adjusted accordingly to suit particular reaction processes, for example they can be less than 1 hour if the reaction is very rapid, or more than 8 hours if the reaction is very slow. The process is carried out continuously, the degree of conversion being determined by taking samples from the reactor if necessary, and the time being adjusted accordingly. The reaction takes place in the absence of air. It can particularly take place under anaerobic conditions. Suitable measures for generating anaerobic conditions are known to the person skilled in the art, for example by expelling oxygen from the aqueous reaction mixture by heating, by generating steam and / or by purging with an inert gas such as nitrogen.
[0016] The taper of the reactor in the transport direction can be continuous, so that the cross-section between the feed opening and the discharge opening constantly decreases, for example decreases linearly. As a further alternative, the cross-section of the reactor after the feed opening can initially remain constant. This takes into account the fact that the conversion must first begin after the reaction mixture has been introduced into the reactor and thus a smaller reduction in volume of the solid can be expected in the feed opening. At a certain distance from the feed opening, the cross-section of the reactor can then be reduced. Surprisingly, it has actually been found that even with a small proportion of aqueous medium, the conversion of solids into liquids begins after just a short transport time in the reactor, and this is accompanied by a reduction in the volume of solids.Accordingly, it can be provided, for example, that the first 5 to 20% of the reactor's length, such as 10 to 15% of the length, have a constant cross-section, while the remaining portion has a taper, for example, a linear taper. According to one embodiment, the transport direction in the reactor follows gravity.
[0017] After passing through the reactor, the pressure- and heat-treated reaction mixture is transferred into a second line via the discharge opening designed as a pressure lock. At this point, the reaction mixture has a significantly lower volume fraction of solids compared to the initially used reaction mixture, and may even contain no solids at all. Instead, the pressure- and heat-treated reaction mixture is a liquid or a liquid with solids. One advantageous aim of the process is to reduce the volume of the solid used, consisting of the plastic material in solid form and, if appropriate, other solids.For example, a reduction of up to 95%, up to 90%, or 4 to 50%, such as 5 to 30%, for example 7 to 25% or 10 to 15% is possible, based on the volume of the solid used. A high reduction is possible in particular with foams.
[0018] Another optional objective of the process is the further use of the products obtained during the reaction. To provide a more uniform pressure- and heat-treated reaction mixture, an evaporation zone with a temperature higher than the temperature prevailing in the reactor is provided within the second line. The evaporation zone is therefore suitable for removing components whose boiling point is above the temperature prevailing in the reactor, but below the temperature prevailing in the evaporation zone. This is achieved via one or more degassing points, where gaseous components with a corresponding boiling point are removed. If necessary, known cold traps, vacuum traps, and / or valves or control devices for maintaining pressure drops can be used at the degassing points.The extracted gaseous components can be used separately. The pressure- and heat-treated reaction mixture, now freed of gaseous components with a boiling point above the temperature prevailing in the reactor, is recovered in or after the evaporation zone.
[0019] For improved implementation, the plastic material is preferably used in a comminuted state, especially if it comprises plastic that does not swell in water. Standard comminution methods can be used, for example, the plastic material can be cut, torn, grated into flakes, shredded, granulated, ground, or pulverized, optionally after a prior temperature reduction to increase brittleness. Non-limiting examples of the size of the plastic particles used are approximately 0.5 cm. 3 up to 10 cm 3 (0.5 ml to 10 ml), such as 1 cm 3 up to 5 cm3 , in particular for porous or large-surface-area plastic material, or plastic particles with a diameter, measured at the largest point, of a maximum of approximately 10, 5, 2, 1, 0.5, 0.1, 0.05 or 0.01 millimeters.
[0020] According to one embodiment, the temperature in the evaporation zone is greater than or equal to the boiling point of nitrogen-containing components and lower than the boiling point of high-boiling components. Such nitrogen-containing components occur in particular when nitrogen-containing plastics are present in the plastic material, i.e. also in the case of polyurethanes. The nitrogen-containing components are usually diamines or their degradation products or reaction products. By removing these nitrogen-containing components, on the one hand, they can be used separately and, on the other hand, a more uniform pressure- and heat-treated reaction mixture can be provided. In particular, a reaction mixture depleted of nitrogen-containing components or freed of these components is better suited for any subsequent processing steps, for example pyrolysis.
[0021] In one embodiment, the temperature of the evaporation zone is 265°C to 300°C, in particular 265°C to 280°C, such as 270°C to 280°C. At these temperature ranges, it has been determined that advantageously substantial proportions of nitrogen-containing constituents can be partially or completely removed from the pressure- and heat-treated reaction mixture via the at least one degassing point. In particular, it was found that at a temperature in the evaporation zone of 265°C to 280°C, diaminotoluenes could be withdrawn from the reaction mixture in gaseous form via the degassing point. Equally advantageously, the remaining pressure- and heat-treated reaction mixture, partially or completely freed of nitrogen-containing constituents in this way, contains constituents that boil at a higher temperature.Without wishing to be bound by any theory, it is assumed that, given the polyurethane present in the reaction mixture initially used, these are polyols and their degradation products and / or conversion products.
[0022] In one embodiment, a dewatering zone is arranged in the second line upstream of the evaporation zone, in which the temperature is above the boiling point of water and below the boiling point of nitrogen-containing components. Accordingly, gaseous water vapor can be removed via one or more water vapor removal points in the dewatering zone, thus reducing the water content of the pressure- and heat-treated reaction mixture. This enables the provision of a pressure- and heat-treated reaction mixture which is additionally partially or completely dewatered and thus advantageously in the more easily handled form of a solid. If necessary, known cold traps, vacuum traps, and / or valves or control devices for maintaining pressure drops can be used at the water vapor removal points.
[0023] The pressure in the second line can correspond to the pressure in the reactor or be atmospheric pressure. In the former case, an additional pressure lock can be provided at the end of the second line to convert the pressure to atmospheric pressure. In the latter case, the pressure is reduced to atmospheric pressure through the reactor's discharge opening, which is designed as a pressure lock. Another option is the use of one or more additional pressure locks between the discharge opening, which itself is designed as a pressure lock, and the end of the second line to gradually reduce the pressure.
[0024] According to one embodiment, in a second line in which atmospheric pressure prevails, the temperature prevailing in the second line corresponds at least to the boiling point of water at the corresponding atmospheric pressure. This advantageously enables the reduction of the water content if a dewatering zone with at least one degassing point is provided. In a further development, it is provided that the temperature in the dewatering zone is below the boiling point of nitrogen-containing components, wherein the dewatering zone is followed by an evaporation zone with a temperature above the boiling point of nitrogen-containing components, and wherein nitrogen-containing components can be removed from the pressure- and heat-treated reaction mixture from which water has been partially or completely freed via one or more corresponding degassing points in the evaporation zone.
[0025] According to one embodiment, in the reaction mixture with which the first line is fed, the volume ratio between solid and aqueous medium is 100:1 to 5:1, for example 75:1 to 10:1, 30:1 to 20:1, such as 25:1. In this respect, it is clear that an aqueous medium is not predominantly present in which the plastic material is suspended as a solid (and optionally other solids), but rather the predominant volume fraction is made up of the plastic material, which is merely moistened with a significantly smaller volume of aqueous medium. For example, it can be provided that 0.05 to 0.2 volume fractions of aqueous medium are provided per volume fraction of polyurethane foam or per volume fraction of solid.Accordingly, at the beginning of the reaction, only a plastic material moistened with an aqueous medium is present in the reaction mixture, i.e. essentially a solid moistened with the reaction medium, whereby as the transport progresses in the transport direction, the reaction converts solid with a high volume requirement into a liquid phase with a lower volume requirement.
[0026] According to special embodiments, the ratio of the cross-sectional area of the reactor before the taper to the cross-sectional area at maximum taper can be 10:1, in particular 5:1, in particular 2:1. This advantageously takes into account expected reductions in the volume of the solids.
[0027] According to one embodiment, the resulting pressure- and heat-treated reaction mixture is introduced directly or indirectly into a pyrolysis plant for pyrolysis. The principle of pyrolysis itself is known and is based on a thermochemical conversion of substances in the absence of external oxygen, typically in a temperature range of 150°C to 800°C. Within the scope of the process described herein, the highest temperature prevailing in the reactor or in the downstream second line is preferred as the lower limit of the temperature range, such as a temperature range of 265°C to 800°C. For example, this is a temperature range of 265°C to 500°C or 300°C to 500°C.Another example of a temperature range is the range from 700°C to 800°C, in particular from 750°C to 800°C, which is advantageously suitable for decomposing calcium carbonate present in the plastic material into calcium oxide and carbon dioxide and thus providing a calcium carbonate-poor or calcium carbonate-free pyrolysis coke as the pyrolysis product. The pyrolysis treatment is preferred over the use of the resulting pressure- and heat-treated reaction medium. Assuming that it essentially contains polyols and, if applicable, conversion products, additional purification or separation steps are required to ensure sufficient quality for their further use. On the other hand, pyrolysis can advantageously produce polyol monomers, which are assumed to have a higher qualitative purity compared to polyols.According to a preferred embodiment, the pressure- and heat-treated reaction mixture, which is introduced directly or indirectly into a pyrolysis plant, is a reaction mixture from which gaseous components with a boiling point below the temperature prevailing in an evaporation zone have previously been partially or completely removed. In particular, according to the embodiments described herein, it is possible to subject such a reaction mixture to pyrolysis which has a lower proportion of nitrogen-containing components or is free of such components. This makes it possible to provide pyrolysis products which, in turn, can be advantageously used further. In particular, liquid, gaseous, and solid pyrolysis products can be obtained during pyrolysis.The liquid products are pyrolysis oils, which can themselves be subjected to chemical cracking, although high levels of nitrogenous components would be detrimental. The resulting pyrolysis gas can be used to generate electricity, with low levels of nitrogenous components reducing the problem of nitrogen oxides. Solid pyrolysis products, which are a type of pyrolysis coke, can be used for various purposes, for example, as a substitute for carbon black or as petroleum coke, which can also be converted into electricity. Therefore, low or no levels of nitrogenous components are advantageous here as well.
[0028] According to a particularly preferred embodiment, the pressure- and heat-treated reaction mixture which is introduced directly or indirectly into a pyrolysis plant has a low water content or is free of water because, before passing through the evaporation zone, it was passed through a dewatering zone in which the water content was reduced.
[0029] The reaction additive optionally present in the aqueous medium is, according to one embodiment, selected from nitric acid, a carboxylic acid, urea, and / or a biological material. A good reaction can be achieved with nitric acid. However, if a pressure- and heat-treated reaction mixture with a low proportion of nitrogen-containing components is desired, other reaction additives are preferred, since nitric acid provides additional nitrogen input. In general, mineral acids such as hydrochloric acid or phosphoric acid, or mineral bases such as sodium hydroxide, are less preferred, since they would introduce chlorine, phosphorus, and sodium components into the pressure- and heat-treated reaction medium, which could have a detrimental effect in the case of downstream pyrolysis or in later uses of the resulting pyrolysis products.Alternative reaction additives with which a good conversion can be achieved are carboxylic acids, for example in particular linear, saturated monocarboxylic acids such as formic acid, acetic acid, propionic acid, butyric acid or pentanoic acid, hexanoic acid, heptanoic acid; dicarboxylic acids such as oxalic acid (ethanedioic acid), malonic acid (propanedioic acid), succinic acid (butanedioic acid), glutaric acid (pentanedioic acid), adipic acid (hexanedioic acid), malic acid.
[0030] (2-hydroxybutanedioic acid), tartaric acid (2,3-dihydroxybutanedioic acid); and tricarboxylic acids such as 3-carboxy-2-oxo-pentanedicarboxylic acid (oxalsuccinic acid), propane-1,2,3-tricarboxylic acid, citric acid (2-hydroxypropane-1,2,3-tricarboxylic acid) and isocitric acid (1-hydroxypropane-1,2,3-tricarboxylic acid). A further reaction additive is urea. Based on the total mass of the aqueous medium, the proportion of urea in the aqueous medium is, for example, 1 to 45 mass percent, in particular 1 to 20 mass percent, for example 1 to 10 mass percent, such as, for example, 1 to 7 mass percent, for example 1.5 to 5 mass percent, 1.5 to 4 mass percent, 2 to 4 mass percent, 2.5 to 3.5 mass percent, or 3 mass percent. Examples of further ranges or further concentrations are 5 to 10 mass percent, 1 mass percent, 5 mass percent, 7.5 mass percent and 10 mass percent.From the point of view of the relationship between the amount of urea to be used and the degree of degradation of polyurethane achieved, a range between 1 mass percent and 10 mass percent, for example 2.5 to 10 mass percent, 2 mass percent to 7.5 mass percent, such as 3 mass percent to 5 mass percent, is preferred.
[0031] According to a particular embodiment, the aqueous medium comprises 2.5 to 10 mass percent urea; the duration of the pressure and heat treatment is preferably 45 to 250 minutes, in particular 45 to 240 minutes. The ratio of urea-containing aqueous medium to polyurethane-containing plastic material can be, for example, 0.2 ml / g to 5 ml / g, in particular 0.4 ml / g to 5 ml / g.
[0032] The reaction additive can also be a biological material. In the context of the invention, biological material is understood to mean plant, animal, or microorganism material, for example entire plants or plant parts such as wood, leaves, stems, roots, or seeds, such as gardening waste or grass clippings. The biological material is preferably plant material. According to a particular embodiment, the biological material is wood, in particular comminuted wood, for example in the form of sawdust, wood chips, or shredded wood. It has been found that with plant material, for example with wood, after appropriate dewatering in a dewatering zone, a free-flowing solid can be obtained, which is well suited, for example, to be transported via screw conveyors.Subsequent use, for example, transport to and introduction into pyrolysis plants, is thereby made considerably easier. The presence of plant material in the reaction mixture accordingly leads to a significant improvement. The mass ratio of plastic material to biological material, in particular plant material, can be, for example, 3:1 to 1.5:1, such as 2:1. Particularly at mass proportions of one-third or more, based on the total mass of plastic material and biological material, for example 33 to 50 mass percent, in particular 33 to 45 mass percent, such as 34 to 40 mass percent, very free-flowing solids were obtained in the pressure- and heat-treated reaction medium after passage through the dewatering zone.
[0033] The above-mentioned reaction additives can be used individually or in any mixtures of two or more of the above-mentioned representatives.
[0034] Examples of mixing ratios of the plastic material with an aqueous medium containing a reaction additive are 2 to 25 liters of plastic material moistened with at least 0.08 to 1 liter of aqueous medium. The aqueous medium can contain 3 to 50 mass percent, in particular 4 to 40 mass percent, for example 4 to 20 mass percent, of nitric acid, carboxylic acid, a dicarboxylic acid, a tricarboxylic acid, and / or urea. In the case of the admixture of a biological material, it can be provided that the plastic material occupies 55 to 95 volume percent, in particular 67 to 95 volume percent, and the biological material correspondingly 5 to 45 volume percent, in particular 5 to 33 volume percent.The biological material can be mixed with the plastic material and then the aqueous medium added, or mixed first with the aqueous medium and then with the plastic material, or all three components can be mixed simultaneously.
[0035] If the plastic material and / or the hydrolyzable plastic contained therein is a compressible plastic, in particular a foam, the specified volumes refer to the uncompressed plastic.
[0036] According to one embodiment, one or more pressure barriers are arranged in the first line and / or the second line. These advantageously serve to prevent transport of the reaction mixture counter to the desired transport direction when a pressure gradient is created. According to one embodiment and with respect to the transport direction, the reactor conveyor screw in the reactor can extend only over a portion of the reactor, for example, over that portion of the reactor vessel in which a high proportion of solids is still present.
[0037] According to another embodiment, the reactor conveyor screw extends with a corresponding taper into the tapered end region of the reactor, thereby advantageously ensuring transport of the reaction medium to the discharge opening over the entire transport path.
[0038] The conveying speed of the reactor screw conveyor can be controlled. This advantageously opens up the possibility of influencing the residence time of the reaction mixture in the reactor. If the conversion is lower than originally expected, for example, the conveying speed can be reduced to achieve a longer residence time and thus a higher conversion. If the conversion occurs faster than originally expected, the conveying speed can be increased, thus increasing the reactor throughput.
[0039] According to one embodiment, water obtained after removing solids from the reaction mixture obtained after pressure and heat treatment and from which gaseous components have been removed, and / or water obtained from gaseous water extracted via a steam extraction point, is added to a reaction mixture to be prepared, optionally after adding a reaction additive. Advantageously, a recirculation process is thus carried out in which water from an already used aqueous medium is at least partially recycled into the continuous process, thus reducing resource consumption.
[0040] A further aspect of the invention relates to a device for carrying out a method as described herein. The device comprises a first line with a first conveyor screw arranged therein, wherein the first line opens into a reactor via a filling opening designed as a pressure lock, wherein a reactor conveyor screw is arranged in the reactor and the reactor, which is tapered at least in one end region, opens into a second line by means of a removal opening designed as an expression, in which a second conveyor screw is arranged, wherein an evaporation zone is provided in the second line, in which a higher temperature can be specified than in the reactor, and wherein the second line has a degassing point in the evaporation zone, via which gaseous components can be removed from the second line.Such a device is accordingly suitable for transporting a reaction mixture as described herein, namely a reaction mixture comprising a plastic material which contains polyurethane and is present as a solid, and further comprising an aqueous medium, optionally containing a reaction additive with which the plastic material is moistened, via the first conveyor screw of the first line to the filler opening, designed as a pressure lock, of the reactor which tapers at least in one end region. After entering the reactor via the filler opening, the reaction mixture is exposed to the pressure and temperature conditions prevailing there and reacted, and can be transferred into the second line via the discharge opening, designed as a pressure lock, in the end region of the reactor.By means of the second conveyor screw arranged in the second line, the pressure- and heat-treated reaction mixture can be transported to the evaporation zone, where gaseous components can be removed via at least one degassing point. The pressure- and heat-treated reaction mixture, thus depleted of gaseous components, can be removed after further transport in the second line, for example, for a pyrolysis treatment, or can be fed directly into a pyrolysis plant, which optionally represents an extension of the device described herein.
[0041] In a further embodiment of the device, a dewatering zone is arranged in the second line upstream of the evaporation zone, in which the temperature is above the boiling point of water and below the boiling point of nitrogen-containing components, and in which gaseous water can be removed via a steam removal point. The reaction mixture remaining in the second line after removal of steam, which has been pressure- and heat-treated and depleted of water or freed of water, is then partially or completely freed of remaining gaseous components in the evaporation zone, preferably from gaseous nitrogen-containing components. The reaction mixture then remaining, which has been pressure- and heat-treated, depleted of water or freed of water, and depleted of or freed from other gaseous components, can in turn be removed and, for example, fed directly or indirectly to pyrolysis.
[0042] Reference is made to implicit disclosures regarding the device made in connection with the method and vice versa.
[0043] Further advantages, features, and details will become apparent from the following description, in which at least one embodiment is described in detail—possibly with reference to the figures. Identical, similar, and / or functionally equivalent parts are provided with the same reference numerals.
[0044] They show:
[0045] Fig. 1 : a schematic sectional view of a reactor with an evaporation zone,
[0046] Fig. 2: a schematic representation of a reactor with an evaporation zone and a dewatering zone.
[0047] The representations in the figures are schematic, not necessarily to scale and show only essential components.
[0048] Examples
[0049] Example 1 : Preparation of a reaction mixture
[0050] In a pilot study, a polyurethane foam blend obtained from mattresses that had reached the end of their life cycle was used as the plastic material. The mattresses, which had a density of approximately 40 kg per cubic meter, were shredded, and the resulting material was a mixture of standard ether foams, HR foams, and viscoelastic foams. 400 g of the resulting material was placed in a 10 l bucket, which was thereby filled to approximately 85% capacity.
[0051] 100 g of fine sawdust and 100 g of shredded wood waste were added to the shredded material as biological material, assuming a density of approximately 700 kg per cubic meter. The plastic material was mixed with the biological material, leaving the bucket still approximately 85% full.
[0052] The aqueous medium used was 150 ml of the liquid phase of a pressure- and heat-treated reaction medium from a previous experiment, in which plant material had been added as a reaction additive and which had acquired a pH of 4 during the reaction. This aqueous medium was mixed with the mixture of plastic material and biological material, thereby moistening it. The volume of the resulting reaction mixture, i.e., a mixture of shredded mattress material and biological material moistened with reaction medium, was approximately 8.6 l.
[0053] Example 2: Feeding a reactor
[0054] A Büchi reactor pressure vessel with a volume of 10 l and a maximum pressure of 60 bar was used as the reactor. The prepared reaction mixture was placed in a stainless steel inner bucket (liner), which in turn was placed in the Büchi reactor pressure vessel. The Büchi reactor pressure vessel was then pressure-tightly sealed with a lid.
[0055] Example 3: Implementation
[0056] The objective of this experiment was to determine the reduction in the solids content during the reaction. The reactor was first heated to a jacket temperature of 260 °C, which was reached after approximately 10 minutes. It was then held at 260 °C for 1 hour and then at 240 °C for 2 hours, during which time equilibrium pressure was established in the reactor. The pressure vessel was then actively and rapidly cooled to ambient temperature.
[0057] Example 4: Determination of the remaining solid volume
[0058] After the reaction was complete, the liquid phase of the pressure- and heat-treated reaction medium was drained to determine the volume of the remaining solid. The original components were no longer recognizable in the remaining solid; instead, it was a brownish-black mass whose volume was determined to be 1.21. Accordingly, the reaction reduced the volume of the solid to approximately 14% of the initial volume.
[0059] In other experiments, in which urea solution was used as a reaction additive, complete liquefaction was partially observed. Accordingly, solid volume reductions of 90-95% ± 5% are realistically achievable.
[0060] Example 5: In another experiment, 500 g of shredded mattress material was added to the Büchi reactor pressure vessel with 150 mm of water containing 40 g of citric acid and 50 g of 96% acetic acid. The mattress material used essentially comprised polyurethane foam with portions of polyethylene and polypropylene.
[0061] This reaction mixture was heated to 260°C under equilibrium pressure for 60 minutes and then kept at 250°C for 120 minutes.
[0062] After cooling the reaction mixture subjected to pressure and heat treatment in this way, solid particles of polyethylene / polypropylene floated on the liquid phase due to their lower density and could be easily separated mechanically.
[0063] After separation of the liquid phase of the pressure and heat-treated reaction mixture, a blackish material remained, which was dried, resulting in a volume reduction of about 95% compared to the volume of the originally used plastic material.
[0064] Flfluren description
[0065] Fig. 1 shows a schematic representation of a reactor 16. A reaction mixture comprising a plastic material in solid form and containing at least one polyurethane and also an aqueous medium, optionally containing a reaction additive, is introduced into a first line 10 via a filling funnel (not further designated). In the line 10, the reaction mixture is transported by means of a first conveyor screw 12 to a filling opening 14 of a reactor 16, designed as a pressure lock, and is introduced into the reactor 16 via the filling opening. The pressure within the reactor 16 is > 1 bar to 60 bar at a temperature of 180 °C to 270 °C. The reaction mixture is transported towards an end region of the reactor 16 by means of a reactor conveyor screw 18 arranged in the reactor 16.The reaction of the polyurethane and any other hydrolyzable plastics contained in the plastic material in reactor 16 reduces the volume fraction of solids in the reaction mixture, which is why reactor 16 can taper towards the end region. The reaction mixture is introduced into a second line 22 via a discharge opening 20 of reactor 16 designed as a pressure lock and transported by a second conveyor screw 24 located therein. Located in second line 22 is an evaporation zone 26, in which the temperature is higher than that prevailing in reactor 16.At this temperature, gaseous components can be removed from the second line 22 via a degassing point 28, so that a pressure- and heat-treated reaction mixture, correspondingly depleted in gaseous components, is transported downstream of the removal opening within the second line 22 and can be recovered. Details such as motors for driving the first conveyor screw 12, the second conveyor screw 24, or the reactor conveyor screw 18, or heating devices for heating the reactor 16 or the evaporation zone 26 are not shown.
[0066] Fig. 2 shows a further schematic representation of a reactor 16, which corresponds to the reactor 16 shown in Figure 1, but additionally has a dewatering zone 30 in the second line 22. The dewatering zone 30 is located, with respect to the transport direction of the reaction mixture to be transported, upstream of the evaporation zone 26. The dewatering zone 30 is designed to assume a temperature that is above the temperature prevailing in the reactor 16, but below the temperature prevailing in the downstream evaporation zone 26. The temperature prevailing in the dewatering zone 30 is selected such that water evaporates under the corresponding pressure and temperature conditions.
[0067] The embodiments mentioned herein and / or individual elements thereof can be freely combined with one another. Although the invention has been illustrated and explained in detail using preferred embodiments, the invention is not limited by the disclosed examples, and other variations can be derived therefrom by those skilled in the art without departing from the scope of the invention. It is therefore clear that a multitude of possible variations exist. It is also clear that embodiments mentioned by way of example really only represent examples that are not to be construed in any way as limiting the scope, possible applications, or configuration of the invention.Rather, the preceding description and the description of the figures enable the person skilled in the art to implement the exemplary embodiments in concrete terms. With knowledge of the disclosed inventive concept, the person skilled in the art can make various changes, for example, with regard to the function or arrangement of individual elements mentioned in an exemplary embodiment, without departing from the scope of protection defined by the claims and their legal equivalents, such as further explanations in the description. List of reference symbols.
[0068] 10 first line
[0069] 12 first conveyor screw
[0070] 14 Filling opening
[0071] 16 reactor
[0072] 18 Reactor screw conveyor
[0073] 20 removal opening
[0074] 22 second line
[0075] 24 second conveyor screw
[0076] 26 Evaporation zone
[0077] 28 Degassing point
[0078] 30 Drainage zone
[0079] 32 steam extraction point
Claims
Patent claims Continuous process for the conversion of a plastic material containing a polyurethane, comprising the following steps: Providing a reaction mixture, wherein the reaction mixture - a plastic material in solid form containing polyurethane, and furthermore - comprising an aqueous medium, wherein the mass ratio between the water of the aqueous medium and polyurethane in the reaction mixture is not more than 0.6 to 1, transporting the reaction mixture by means of a first conveying screw arranged in a first line to a filling opening designed as a pressure lock of a reactor which tapers at least in one end region with respect to the direction of transport, Transporting the reaction mixture by means of a reactor conveyor screw arranged in the reactor vessel at a pressure of > 1 bar to 60 bar and a temperature of 180 °C to 270 °C to the end section of the reactor; in the end section of the reactor, transferring the pressure- and heat-treated reaction mixture via a discharge opening designed as a pressure lock into a second line. Transporting the pressure- and heat-treated reaction mixture by means of a second screw conveyor arranged in the second line, providing an evaporation zone within the second line with a temperature higher than the temperature prevailing in the reactor, extracting gaseous components in the evaporation zone via at least one degassing point and in or after the evaporation zone, obtaining the pressure- and heat-treated reaction mixture freed from gaseous components. A method according to claim 1, characterized in that the temperature in the evaporation zone is greater than or equal to the boiling point of nitrogenous components and less than the boiling point of high-boiling components. A method according to any of the preceding claims, characterized in that the temperature in the evaporation zone is between 265 °C and 300 °C. A method according to any of the preceding claims, characterized in that a dehydration zone is arranged in the second line upstream of the evaporation zone, in which the temperature is above the boiling point of water and below the boiling point of nitrogenous components, and in which gaseous water can be extracted via a steam extraction point.A method according to any one of the preceding claims, characterized in that atmospheric pressure prevails in the second line and the temperature corresponds at least to the boiling point of water at atmospheric pressure. A method according to any one of the preceding claims, characterized in that the volume ratio between solid and aqueous medium is 100:1 to 5:
1. A method according to any one of the preceding claims, characterized in that the ratio of the cross-sectional area of the reactor vessel before the narrowing to the cross-sectional area at maximum narrowing is 10:1, in particular 5:1, in particular 2:1.A process according to any of the preceding claims, characterized in that the resulting pressure- and heat-treated reaction mixture, optionally depleted of gaseous components with a boiling point below the temperature prevailing in the evaporation zone, is introduced directly or indirectly into a pyrolysis plant for the purpose of carrying out pyrolysis. A process according to any of the preceding claims, characterized in that the aqueous medium contains a selected reaction additive. under nitric acid, a carboxylic acid, a dicarboxylic acid, in particular adipic acid, a tricarboxylic acid, in particular citric acid, and / or urea and / or a biological material. Process according to claim 9, characterized in that the reaction additive is a plant material. Process according to any one of the preceding claims, characterized in that one or more pressure barriers are arranged in the first line and / or in the second line. Process according to any one of the preceding claims, characterized in that the reactor screw conveyor extends with a corresponding taper into the tapered end region of the reactor vessel. Process according to any one of the preceding claims, characterized in that water, - obtained after removal of solids from a recovered pressure- and heat-treated reaction mixture freed from gaseous components, and / or - Water obtained from gaseous water extracted via a steam extraction point, optionally added to a reaction mixture to be provided after the addition of a reaction additive.Apparatus for carrying out a method according to one of claims 1 to 13, comprising a first line (10) with a first screw conveyor (12) arranged therein, wherein the first line opens into a reactor (16) via a filling opening (14) designed as a pressure lock, wherein a reactor conveying screw conveyor (18) is arranged in the reactor (16) and the reactor (16), which is tapered at least in one end region, opens into a second line (22) by means of a discharge opening (20) designed as a pressure lock, in which a second screw conveyor (24) is arranged, wherein an evaporation zone (26) is provided in the second line (22) in which a higher temperature than in the reactor (16) can be specified, and wherein the second line (22) has a degassing point (28) in the evaporation zone (26) through which gaseous components can be removed from the second line (22). Device according to claim 14, characterized in that a drainage zone (30) is arranged in the second line (22) upstream of the evaporation zone (26), in which the temperature is above the boiling point of water and below the boiling point of nitrogenous components and in which gaseous water can be extracted via a steam extraction point (32).