Device and method for producing solid particles

Abstract

The invention relates to a device for producing solid particles from liquid starting substances, the device comprising: at least two storage containers (3.1, 3.2) for the liquid starting substances; at least one reactor (13) in which a suspension containing solid particles is formed or solids are deposited on seeding surfaces or seeding bodies by reaction of the liquid starting substances; and, if a suspension is formed, at least one filtration apparatus (25) for separating the solid particles from the suspension. The storage containers (3.1, 3.2) are each connected to the reactor (13) via fluid connections, and pumps are accommodated in the fluid connections, by means of which pumps fluid can be pumped from the relevant storage container (3.1, 3.2) and into the reactor (13), and the reactor (13) is connected to the filtration apparatus (25) in such a way that the suspension formed in the reactor (13) can flow into the filtration apparatus (25). All system components of the device (1) are positioned in a closed housing (41). The invention also relates to a method for producing solid particles in a device of this type.

Description

[0001] Device and method for producing solid particles

[0002] Description

[0003] The invention relates to a device for producing solid particles from liquid starting substances, comprising at least storage containers for the liquid starting substances, a reactor in which a suspension containing solid particles is formed by reacting the liquid starting substances, and at least one filtration apparatus for separating the solid particles from the suspension. The invention further relates to a method for producing solid particles from liquid starting substances in such a device.

[0004] Solid particles are manufactured from various materials and with different particle sizes and, if necessary, after further processing steps, are transformed into flat or solid bodies and used. Typical applications of such bodies made from solid particles in chemical process engineering include catalysts for heterogeneous catalysis, solid electrolytes (solid oxide ceramics) for fuel cells or electrolyzers, functionalized filter materials, electrically active catalyst materials for electrochemistry or for energy storage, or pigment particle synthesis.

[0005] The solid particles are produced using various processes. Common methods for producing solid particles from solutions include precipitation reactions, spray drying, or crystallization. The composition of the solution used and the choice of process parameters, particularly temperature, pH, or conductivity, as well as suitable inline measurement methods, for example, for particle size distribution, offer a variety of options for influencing the properties of the solids.

[0006] The product yield, and thus the profitability of the process, depends significantly on the degree to which the solids content in the solution can be concentrated. Solids differ in their density from the density of the solution; this property is used for separation from the solution after the solids have been prepared in the solution. Solids with a lower density than the solution will float and can be separated from the solution by flotation; solids with a higher density can be separated by sedimentation, filtration, or centrifugation. Solids with a higher density can be forced into flotation by gassing due to bubble adhesion; however, this can also be an undesirable effect, for example, if bubbles form during the reaction. In the latter case, bubble separation is required prior to solids separation.

[0007] If the reaction is to be stopped at the same time as separating the solution, sedimentation alone followed by draining off the liquid is not sufficient, as parts of the solution still remain in the spaces between the solid and the reaction continues there. Solids with a high density or a high density difference to the solution tend to undergo undesirable sedimentation even before the actual filtration, particularly in areas where the flow of the solid-containing solution slows down or comes to a complete standstill. A settling sedimented solution requires high shear forces at the interface between the solid sediment and the solution, which can only be generated by active flow movement, for example through a nozzle or a stirrer. The required shear rates are not achieved in pipelines or valves, and particularly in container drain valves.

[0008] In the production of catalyst materials or storage materials, toxic solutions containing heavy metals are often processed into toxic solids containing heavy metals. In contrast to toxic solutions, solids cannot be simply cleaned off by rinsing, particularly after sedimentation or after drying on walls, for example, in empty pipelines or menisci above dry vessel interior walls. Deposits must generally be removed by operating personnel wearing protective equipment. This procedure is highly resource-intensive and time-consuming in both production and testing. After each new batch or each new test, the system must be completely cleaned of deposits to prevent carryover from the previous batch or test.

[0009] Standard laboratory containment equipment such as glove boxes is ill-suited for continuous production processes due to the airlock procedure and limited equipment accessibility. Complete clean rooms hamper system operation due to the requirement to wear full protective clothing.

[0010] Catalyst materials or storage materials produced from toxic solutions containing heavy metals, for example, are also powdered oxide materials, the production of which is of great economic and technical importance. The development and optimization of technical process conditions is of great interest, as the development and improvement of high-performance materials is seen as a solution to numerous current challenges and as a way to find new technologies that can conserve resources more effectively than existing technologies.

[0011] WO-A 2015 / 040005 discloses the production of electrode materials based on mixed metal oxides containing nickel, cobalt, manganese, and lithium. The materials also contain lithium and iron phosphate together with a divalent metal. To produce the electrode materials, the starting components are first combined in a precipitation reactor. The resulting suspension is then fed into a spray dryer, where the solid is separated from the suspension.

[0012] WO-A 2014 / 180743 and WO-A 2016 / 071219 disclose processes for the preparation of transition metal mixed oxides, in which spherical particles of transition metal hydroxides are first prepared as a precursor, in which at least one aqueous solution of an alkali metal (hydrogen)carbonate or alkali metal hydroxide and at least two aqueous solutions of transition metal salts are fed to a reactor in which mixed transition metal carbonates, transition metal hydroxides or transition metal carbonate hydroxides are precipitated and the precipitated particles are subsequently separated.

[0013] Further processes for producing particle-containing solutions are also known, for example, from WO-A 97 / 41954, WO-A 2017 / 045817, or US Pat. No. 3,124,418. WO-A 97 / 41954 describes a process for producing monodisperse silica sol from a geothermal brine, WO-A 2017 / 05817 describes a process for producing lithium-nickel-manganese-based transition metal oxide particles, and US Pat. No. 3,124,418 describes the production of an aluminum oxide-based catalyst material. A process for producing cobalt carbonate is known from CN-A 101376529, a process for producing hexaaluminate by a sol-gel process from EP-A 1 390 298, and a process for producing lithium carbonate from CN-A 106276988.

[0014] All processes involve the use of toxic solutions and / or the production of toxic solids with which contact must be avoided and which may also release toxic or corrosive fumes that must not be inhaled.

[0015] Therefore, it was an object of the present invention to provide a device and a method for producing solid particles from liquid starting substances, with which toxic starting substances can also be processed and / or toxic solids can be produced, which can also be operated continuously and in which contact with the substances used can be largely avoided during operation and also for cleaning.

[0016] This object is achieved with a device for producing solid particles from liquid starting substances, comprising: at least two storage containers for the liquid starting substances, at least one reactor in which a suspension containing solid particles is formed by reaction of the liquid starting substances or solids are deposited on seeding surfaces or seeding bodies and, upon formation of a suspension, at least one filtration apparatus for separating the solid particles from the suspension, wherein the storage containers are each connected to the reactor via fluid connections and pumps are accommodated in the fluid connections, with which liquid can be conveyed from the respective storage container into the reactor and the reactor is thus connected to the filtration apparatus,The suspension formed in the reactor can flow into the filtration apparatus, and all system components of the device are positioned in a sealed housing. Since particle growth depends significantly on the number of particles already formed, it may be useful to introduce particles into at least one of the storage tanks as so-called seeding agents (nucleating agents) on which the forming solid can grow. The seeding particles can consist of the growing solid or of another solid, which can then also be considered a carrier material for the growing material. This storage tank should also be equipped with devices to prevent particle sedimentation.

[0017] Alternatively, components can be inserted into the reactor as seeding surfaces or seeding bodies, allowing the desired growth of layer sequences. Bodies can be the size of conventional packing bodies, for example, with an average hydraulic diameter of 0.5 to 10 mm. If the bodies are to be removed as a filter cake, the size is limited to that which still allows hydraulic conveyance in pipelines.

[0018] Depending on the application of the device, seeding surfaces or seeding bodies can, for example, have dimensions comparable to those commonly used in laboratory-scale electrolysis cells or fuel cells for laboratory tests. Typical areas for such laboratory applications are, for example, 1 cm 2 up to 100 cm 2In addition to its use on a laboratory scale, the device according to the invention can also be used in industrial production. In this case, the seeding areas or surfaces of the seeding bodies can typically have a size of up to 1 m 2 , preferably up to 0.5 m 2 For use in even larger stacks, however, the surfaces can be even larger. Unlike a suspension, seeding surfaces or seeding bodies must be taken directly from the reactor. Conventional reactors can be equipped with baffles near the inner reactor wall. These can also be used in a modified form as seeding surfaces. Here, too, the size is limited by the inner reactor wall and the possibility of equipping it with surfaces. Filtration at the end of the process then only serves to remove any precipitated solids that have not settled from the discharged filtrate.

[0019] Growth can be electrochemically supported by applying a potential to the metal sheet acting as the cathode in a conductive electrolyte, similar to electroplating. The layer thickness can be estimated using Faraday's law and is proportional to the current. Here, too, growth begins at crystal nuclei on the surface. Particles can also be treated in this way. Suitable geometries for seeding surfaces or seeding bodies, on whose surface the crystal nuclei grow, correspond, for example, to the geometry of Berty reactors.

[0020] By positioning all plant components, i.e. the storage tanks, at least one reactor, at least one filtration apparatus as well as the fluid connections and the pumps in a closed housing, it is prevented that starting substances and products and by-products generated during the reaction can reach the environment during the process.

[0021] The object is further achieved by a method for producing solid particles from liquid starting substances in such a device, comprising:

[0022] (a) placing one liquid starting substance in each of the storage containers;

[0023] (b) continuous gravimetric dosing of the liquid starting substances into the at least one reactor;

[0024] (c) reaction of the liquid starting substances to form a suspension containing the solid particles as a product or to form solid particles which are deposited on a seeding surface or a seeding body;

[0025] (d) separating the solid particles from the suspension in the filtration apparatus and removing the filter basket with the solid particles contained therein or removing the seeding surface or the seeding body with solid particles deposited thereon.

[0026] In order to prevent contact with the starting substances used, the storage containers can preferably each be filled via an inlet, whereby each inlet has a suitable interface on the housing to which a storage container with the starting substance for the corresponding storage container can be connected.

[0027] To fill the storage tanks, they are preferably connected to a vacuum pump, so that liquid starting substance can be sucked into the storage tank via the inlet connected to the storage tank by applying a negative pressure. Since the storage tank is located within the sealed housing, this prevents any possible contact with the starting substances. Furthermore, by applying a negative pressure, it is not necessary to install a pump in the supply line through which the starting substances are conveyed. This pump must be opened at least for maintenance purposes, although contact with the starting substances conveyed by the pump cannot be prevented.

[0028] In order to be able to suck the starting substance into the storage container with the most constant negative pressure possible, it is also advantageous if the supply line opens into the storage container at the head. This way, it is not necessary to adapt the set negative pressure to the liquid column in the storage container. Instead, regardless of the liquid level in the storage container, further starting substance is sucked from the storage container through the supply line into the storage container at a constant negative pressure. The vacuum pump used to generate the negative pressure is preferably also located in the sealed housing and can be operated via a control unit outside the sealed housing. The individual starting substances are fed from the storage containers into at least one reactor. The dosing of the starting substances can be carried out, for example, volumetrically or gravimetrically.For volumetric dosing, for example, flow meters can be installed in the connecting line from the feed tank to the reactor. Alternatively or additionally, it is also possible to adjust the feed substances via the pump flow rate.

[0029] However, gravimetric dosing is preferred, with the feed tanks suspended from load cells. For dosing, the mass loss of the feed tank is recorded. As soon as the desired amount of starting substance has been introduced into the reactor, the withdrawal from the feed tank is stopped. Alternatively, continuous withdrawal is also possible, whereby the mass loss of the feed tank is continuously recorded and the pump flow rate into the reactor is controlled by the mass loss of the feed tank.

[0030] Particularly with gravimetric dosing of starting substances, these are preferably refilled when no starting substance is being removed from the storage container. For this reason, the storage containers are preferably dimensioned large enough to allow a desired batch of the product to be produced using the starting substances stored in the storage containers, and no starting substances need to be refilled during production.

[0031] The connecting lines from the feed tanks to the reactor are preferably hoses, each of which has a hose spiral at the connection point at the outlet of the feed tank in order to reduce the influence of vibrations on the weight measurement and thus increase the accuracy of the dosing.

[0032] In the at least one reactor, the liquid starting substances react to form the solid particles, creating a suspension containing the solid particles. The reaction can be carried out in just one reactor or in several reactors. If several reactors are used, they can be connected in parallel so that the reaction takes place in several reactors simultaneously, or alternatively as a reactor cascade so that the reaction starts in a first reactor and the reaction mixture produced is transferred to another reactor where the reaction continues. This is repeated until the reaction mixture has been introduced into the last reactor. The use of a reactor cascade also enables, for example, a targeted addition of the starting substances if it is desired to add different starting substances one after the other.A different starting substance or a different mixture of starting substances can be added to each reactor. This allows for continuous production of the solid particles. However, it is also possible to carry out such a staggered addition of the starting substances to only one reactor. In this case, the reaction takes place batchwise, since the solid particles can only be removed after the last starting substance has been added, making continuous operation impossible.

[0033] By staggered addition of the starting substances, it is possible, for example, to produce layered solid particles, as described in WO-A 2014 / 180743.

[0034] To prevent solid particles formed in the reactor from precipitating, it is preferred to use a stirred tank reactor. The reactor is particularly preferably a continuous stirred tank reactor (CSTR). If multiple reactors are used as a reactor cascade, it is preferred if all reactors in the reactor cascade are continuous stirred tank reactors. Using the stirred tank allows the suspension formed in the reactor to be continuously stirred, with the movement of the suspension preventing solid particles from precipitating and the formation of a coating on the reactor wall.

[0035] To increase the solids content and, if appropriate, to remove undesirable liquid by-products produced during the reaction, it may be advantageous to withdraw liquid from the reactor during the reaction, as described, for example, in WO-A 2014 / 180743.

[0036] To obtain the solid particles as a product, they must be separated from the suspension. Any solid-liquid separation method known to those skilled in the art can be used for this purpose, such as filtration or centrifugation. Filtration is preferably used for solid-liquid separation. For this purpose, the suspension is introduced into a filtration apparatus, where the solid particles collect as a filter cake on a filter, and the liquid from the suspension is drawn off through the filter.

[0037] To facilitate the removal of the filter cake containing the product, it is preferred if the filtration apparatus has a filter basket in which the solid particles collect as a filter cake and which can be removed from the sealed housing. The filter basket can be removed either manually via a lock in the sealed housing or automatically. For example, it is possible to design the filter basket in the form of a drawer that sits sealed in the housing during operation and can be pulled out of the housing for removal. The filter cake containing the solid particles can then be fed into further processing, for example drying. To ensure only a short interruption to production, it is preferred if the filter cake together with the filter basket is fed into further processing and a new, clean filter basket is inserted into the filtration apparatus.While the next batch is being filtered, the filter cake can be removed from the filter basket and the filter basket cleaned so that it can then be reinserted. Alternatively, it is also possible to use a sample changer that holds the filter basket. In order to be able to continue operating the process after a filter basket has been inserted into the sample changer, it is further preferred if the sample changer contains empty filter baskets so that an empty filter basket can be inserted into the filtration apparatus immediately after removing a filter basket containing the solid particles. This can then be repeated until all empty filter baskets have been used and the sample changer only contains full filter baskets.The filter baskets containing the solid particles or the entire sample changer can then be removed from the housing, for example via a lock, and the sample changer can be loaded with empty filter baskets.

[0038] If a sample changer is used, it can alternatively be designed to include a removal area outside the housing so that the filter baskets filled with solid particles are automatically transported through a suitable airlock to the removal area located outside the housing. Here, the filled filter baskets can be removed and replaced with empty filter baskets, which are then transported into the housing via the same airlock or another airlock. A suitable sample changer includes, for example, a carousel that holds the filter baskets. In this case, the entire carousel can be positioned inside the housing, with the carousel being removed each time it is filled with filter baskets filled with solid particles, the filled filter baskets being removed and replaced with empty filter baskets, and the carousel being reinserted.Alternatively and preferably, it is also possible to design the carousel in such a way that it comprises a removal area outside the housing, so that the filter baskets filled with solids can be transported out of the housing through a lock and removed from the carousel, empty filter baskets can be placed on the carousel outside the housing and moved back into the housing through a second lock so that they can then later be inserted into the filtration apparatus.

[0039] The filter basket is preferably constructed so that the bottom of the filter basket forms the filter and the side walls are impermeable. A sintered frit is particularly preferred as the filter.

[0040] In order to prevent contact with the filter cake contained therein when removing the filter basket, it is also advantageous if the filter basket has a lid that opens automatically when the filter basket is inserted into the filtration apparatus and closes automatically when the filter basket is removed from the filtration apparatus.

[0041] The pressure difference required for filtration is preferably generated by connecting the filtration apparatus to a vacuum pump. The vacuum pump is connected to the suction side of the filter basket so that the suspension is sucked towards the filter basket and the filtrate through the filter basket. It is particularly preferred if only one vacuum pump is used both to generate the pressure difference for filtration and to suck the starting substances from the storage containers into the feed containers. For this purpose, the vacuum pump is connected to the feed containers and the filtration apparatus via a multi-way valve, for example, and the multi-way valve is switched accordingly depending on the desired process, i.e., carrying out filtration or supplying starting substance. This has the advantage that only one pump needs to be used, thus reducing the number of system components requiring maintenance.Of course, it is also possible to use several vacuum pumps as an alternative, for example one to generate the pressure difference for filtration and one to suck the starting substances into the storage containers or even a separate one for each individual storage container.

[0042] The filter cake can be removed directly from the filtration apparatus or can be rinsed with a rinsing liquid before removal in order to remove any reactants still adhering to the solid particles, which could lead to undesired subsequent reactions, or other liquid contaminants. In order to reach all solid particles with the rinsing liquid, it is preferable to fluidise the filter cake for rinsing. For this purpose, a stirring element is preferably incorporated in the filtration apparatus. To achieve uniform mixing of the solid particles of the filter cake with the rinsing liquid, the stirring element preferably has an inclined blade stirrer positioned in the filter basket. It is particularly preferred if the stirrer blades of the inclined blade stirrer are only a very short distance from the bottom of the filter basket or even come into contact with the bottom of the filter basket.The distance between the stirrer blades and the pitched-blade stirrer is preferably in the range of 0 to 10 mm, more preferably in the range of 0.5 to 5 mm, and especially in the range of 1 to 2 mm. In addition to the pitched-blade stirrer in the region of the filter basket, the stirrer preferably has a further stirring element, for example in the form of an anchor stirrer, arranged above the pitched-blade stirrer.

[0043] To rinse the filter cake, the stirrer is set in motion, stirring the filter cake and bringing the solid particles into contact with the rinsing liquid. After a specified rinsing time, a pressure differential is again created, particularly by applying a negative pressure on the filtrate side, and the rinsing liquid is drawn through the filter. A new filter cake is formed from the cleaned solid particles, which can then be removed from the filtration apparatus as a product. If a single rinsing cycle is not sufficient, additional rinsing cycles can be performed before the filter cake is removed from the filtration apparatus.

[0044] Since the filter cake contains the product and must be regularly removed from the filtration apparatus, it is necessary to interrupt the filtration regularly to remove the filter cake and, if the filter cake is rinsed before removal, also for rinsing. Particularly in the case of a continuously conducted reaction, it is therefore preferred if a buffer tank is arranged between the at least one reactor and the filtration apparatus, so that the suspension is first passed from the reactor into the buffer tank and from the buffer tank into the filtration apparatus. If a reaction is carried out which requires a post-reaction or if the particles still need to age before being separated from the suspension, the buffer tank can also be used to carry out these processes.

[0045] To prevent the solid particles from precipitating out of the suspension and accumulating on the walls of the buffer tank, forming an undesirable coating, it is preferable for the buffer tank to include a stirrer that can keep the suspension moving. An axially conveying stirrer, such as a pitched-blade stirrer, is particularly preferred.

[0046] In order to save on pumps for conveying the suspension and in particular to prevent solid particles from being destroyed by shear forces occurring in the pump, it is preferred if the at least one reactor, the buffer tank and the filtration apparatus are arranged one above the other in such a way that the suspension can flow by gravity from the reactor into the buffer tank and further from the buffer tank into the filtration apparatus and thus no pumps are required to convey the suspension.

[0047] Since sedimentation of solid particles and the resulting formation of deposits cannot be completely avoided during operation, it is necessary to clean the device components where deposits can form after each batch. Cleaning after each batch also ensures that no residues from the production of the previous batch are carried over into a subsequent batch and thus contaminate the product. This is particularly necessary if the device is used to investigate reactions or if the device is intended to produce different solid particles in successive reactions.Since fine dust, in particular, can be inhaled during manual removal of deposits and thus pose a health risk to personnel tasked with cleaning, it is preferred if the at least one reactor, optionally the buffer vessel, and the filtration apparatus comprise rinsing nozzles to prevent drying on the interior walls. The rinsing nozzles can be used to spray a rinsing liquid onto the interior walls, which can be used to rinse off deposits. Furthermore, the use of rinsing nozzles also allows the walls of the apparatus to be kept moist during operation, for example by spraying solvent, which is also contained in the starting substances, against the walls. This prevents deposits from forming on the walls of the apparatus at the liquid meniscus at the liquid interface.

[0048] If the walls of the equipment are to be cleaned after a batch, it is advantageous if the rinsing fluid is sprayed against the walls under pressure from the rinsing nozzles. To reach all areas of the walls, it is also advantageous if the rinsing nozzles are axially movable and can thus be moved from top to bottom and back within the equipment to be cleaned. Furthermore, rotating nozzles are preferred. The entire rinsing process is preferably carried out fully automatically, eliminating the need for operating personnel to be present directly at the equipment.

[0049] To prevent the formation of deposits due to sedimentation of solid particles in the individual apparatuses, it is further preferred if vortex nozzles are arranged at the outlet of at least one reactor and, if appropriate, the buffer vessel, with which a shear force can be introduced into the suspension. The use of the vortex nozzles allows solid particles to sink downwards in the vessel, so that the suspension thickens in the region of the outlet, which is preferably arranged at the bottom of the vessel. However, the generated vortex keeps the particles in motion, preventing them from accumulating on the bottom and walls of the respective apparatus.

[0050] In addition to spraying the walls with a rinsing liquid, it is also possible to flood the containers with a rinsing liquid and agitate it within the containers, for example by stirring or using vortex nozzles. The rinsing liquid is then drawn through the filtration apparatus and can be analyzed to determine the cleaning progress. Drawing the rinsing liquid through the filtration apparatus offers the further advantage that rinsed-off solids are collected as a filter cake in the filter basket and, provided the cake is uncontaminated and meets the required specifications, can also be recovered as product. On the other hand, even if the cleaned-off solids are no longer usable, the rinsing liquid can be used for another rinsing cycle.

[0051] To continue to record the cleaning progress without looking directly into the system components, it is preferable to include sensors that can monitor the cleaning process. Suitable sensors for monitoring the cleaning process include, for example, measuring the conductivity of the effluent filtrate or using cameras that capture images of the cleaned surfaces, which are then evaluated using a suitable image capture system or, alternatively, monitored by operating personnel.

[0052] By using the rinsing nozzles and vortex nozzles in conjunction with the sensors for monitoring the cleaning process, it is possible to operate the system over a longer period of time and also to carry out several different reactions without having to open the housing, thus avoiding exposure of the operating personnel to the substances used or generated in the process.

[0053] To avoid the need for subsequent processes to increase the process yield and the associated additional interfaces with additional equipment that are prone to contamination, it is preferable to intensify the process control in the device for producing solid particles. This can be achieved, in particular, by specifically utilizing sedimentation in the vessels, for example, the reactor or the buffer tank, by adjusting the shear rate through active flow movement, for example, by stirring or the use of vortex nozzles, in such a way that solid sedimentation without particle movement is prevented while loose sedimentation with particle movement is possible.In this way, differential velocities can be created between the solution and the solid particles, keeping the solid particles suspended. This allows the residence time of the solid particles to be adjusted separately from the residence time of the solution in which the solid particles move. This also allows the structure of the solid particles to be specifically influenced, increasing the solids content in the solution and thus the process yield. Layer sequences on the solid particles are also possible by dosing the different starting substances in sections.

[0054] The particle size and particle size distribution, which can be characterized, for example, by a cumulative size distribution curve, can be adjusted in a feedback loop. For this purpose, the solid particles are measured directly in the reactor with a probe, for example, or in a flow cell in a reactor circuit or at a point downstream of the reactor, and the starting substances, pH value, temperature, and / or stirrer speed are adjusted accordingly.

[0055] To prevent the reactor contents from overheating due to stirring, it is also preferable to measure the torque at the stirrer drive. This provides an indication of the applied stirring energy, which must not be exceeded.

[0056] To record the progress of the reaction, it is preferable to take samples at regular intervals. For this purpose, it is possible, for example, to provide a valve at the reactor outlet and / or at the outlet of the buffer vessel. This valve can be switched so that an associated sample vessel is filled. The valve is then closed again. In the case of a continuously operating reactor, from which product is therefore also continuously withdrawn, the valve at the outlet is preferably designed so that it opens the connection to the buffer vessel or, if no buffer vessel is used, to the filtration apparatus during operation. For sampling, this connection is briefly closed with the valve and a connection to a sample vessel is opened. As soon as the desired amount of sample has been withdrawn, the valve is switched again so that the connection to the sample vessel is closed and the connection to the buffer vessel or to the filtration apparatus is opened.

[0057] Accordingly, a valve can also be provided at the outlet of the buffer container, with which either the connection to the filtration apparatus or the connection to a sample vessel can be opened.

[0058] In order to be able to take multiple samples without having to open the housing each time or insert the sample vessel through a lock for sample collection, it is preferred if a sample changer is used for sample collection. This is preferably constructed as described above for the sample changer for the filter baskets. Here, too, the sample changer is particularly preferably a carousel that can either be completely removed from the housing after all sample vessels have been filled or that in particular comprises a removal area outside the housing so that filled sample vessels are transported out of the housing with the carousel through a first lock and empty sample vessels can be transported back into the housing through a further lock, so that regular sampling is possible without opening the housing and more samples can be taken than the carousel has spaces for sample vessels.

[0059] Regardless of whether a sampling valve is provided on the reactor or on the filtration apparatus, it is preferably always switchable so that the outlet from the reactor or the buffer tank can be closed. Even if no sampling is provided, a valve or tap is preferably included with which the outlet from the reactor and the buffer tank can be closed.

[0060] To prevent the valve or tap used to close the outlet from the reactor or buffer tank from becoming clogged by sedimented solids, it is also advantageous to provide a flushing nozzle with which the valve or tap can be flushed. Flushing is performed each time the reactor or buffer tank is completely emptied to prevent the flushing solution used for flushing from entering the suspension. If the liquid phase of the suspension can be used as the flushing solution, it is also possible, if necessary, to flush even if the reactor or buffer tank is not completely emptied, since in this case, no undesirable components can enter the suspension.

[0061] To avoid contact with the samples, it is also preferable if they can be analyzed automatically, with the analysis preferably also taking place within the housing. Alternatively, the sampling process can be designed so that the sample containers are automatically closed after the sample has been collected and can then be removed from the housing for analysis via a suitable lock.

[0062] The device and method according to the invention are preferably used for the production of catalyst materials or electrode materials. These materials often use acids or alkalis as starting materials, and the resulting solid particles are often toxic.

[0063] Due to the aggressiveness of the acids or alkalis used, it is necessary to manufacture the plant components that come into contact with them from an inert material or to coat them with such a material. In particular, the storage tanks, the reactor, and connecting lines are manufactured from or coated with a material that is chemically inert to the liquid starting substances and the substances formed during the production of the solid particles.

[0064] In particular, when using strong alkalis such as alkali metal hydroxide or when using solutions of transition metal salts, such as in the production of spherical particles of transition metal carbonates, transition metal hydroxides or transition metal carbonate hydroxides as described in WO-A 2014 / 18743, no components made of a metal can be used, since this is decomposed by the starting substances and metals dissolved from the components can lead to undesirable contamination of the product.

[0065] To prevent such damage to the plant components, the storage vessels, the at least one reactor, and the buffer vessel are preferably made of glass. As an alternative to manufacturing them from glass, it is also possible to manufacture the vessels from a plastic that is inert towards the starting substances, or to manufacture them from steel or stainless steel and to coat them with a material that is inert towards the starting substances, for example a suitable plastic or enamel. However, it is preferred to manufacture the vessels from glass. The connecting lines are preferably pipes or hoses made of a plastic that is inert towards the starting substances used, for example polytetrafluoroethylene (PTFE), polyetheretherketone (PEEK), polypropylene (PP), polyethylene (PE), or mixtures thereof, and particularly preferably from PTFE.

[0066] Pumps used to convey the starting substances or the suspension containing the solid particles or intermediate products are preferably peristaltic pumps or diaphragm pumps. The hoses of the peristaltic pump or the diaphragm of the diaphragm pump are also made of polymers that are inert to the starting materials used. The same polymers can be used as described above for the connecting lines.

[0067] Embodiments of the invention are illustrated in the figures and are explained in more detail in the following description.

[0068] They show:

[0069] Figure 1 is a schematic representation of an apparatus according to the invention for producing solid particles;

[0070] Figure 2 shows a buffer container as used in the device for producing solid particles;

[0071] Figure 3 shows a filtration apparatus as used in the device for producing solid particles;

[0072] Figure 4 shows a stirrer used in the filtration apparatus.

[0073] A device 1 for producing solid particles from liquid starting substances comprises a plurality of storage containers 3.1, 3.2 into which the liquid starting substances are introduced, wherein a starting substance is kept in each storage container 3.1, 3.2, so that the number of storage containers 3.1, 3.2 depends on the number of liquid starting substances. The storage containers 3.1, 3.2 can each be connected via a connecting line 5.1, 5.2 to a storage container 7.1, 7.2 in which the respective starting substance is stored. For filling, a vacuum is applied to the storage containers 3.1, 3.2, through which vacuum the respective starting substance is conveyed from the storage container 7.1, 7.2 into the storage container 3.1, 3.2. To apply the negative pressure to the storage containers 7.1, 7.2, they are connected to a vacuum pump 9. For individual filling of the storage containers 3.1, 3.2, a valve 11 is provided that can be switched so that the vacuum is applied only to the storage container 3.1, 3.2 that is to be filled. If several storage containers 3.1, 3.2 are to be filled, this is preferably done sequentially so that only one storage container 3.1, 3.2 is filled at a time. This allows a vacuum pump 9 with a lower delivery rate to be used. Furthermore, this allows for more precise filling of the storage containers 3.1, 3.2.

[0074] In order to be able to suck the starting substance into the storage tank 3.1, 3.2 with a negative pressure that remains constant over the entire filling time and not to have to overcome the hydrostatic pressure built up by the liquid column as the filling level in the storage tank 3.1, 3.2 increases, the connecting lines 5.1, 5.2 each open into the upper area of ​​the storage tank 3.1, 3.2, preferably above the maximum specified filling level.

[0075] The starting substances are conveyed from the storage tanks 3.1 and 3.2 into a reactor 13. In reactor 13, the liquid starting substances react to form solid particles, so that a suspension forms in reactor 13.

[0076] For precise dosing of the starting substances, each storage container 3.1, 3.2 is suspended from a load cell 15.1, 15.2. The load cells 15.1, 15.2 allow gravimetric dosing of the liquid starting substances into the reactor 13. Depending on the reaction being carried out in the reactor and thus on the solid particles to be produced, the individual starting substances can be introduced into the reactor 13 in an individually controlled manner. Control is preferably automated using a suitable control device, for example, control software running on a computer 17.

[0077] To prevent solid particles from settling out of the suspension in reactor 13 and to simultaneously obtain a homogeneous mixture of the liquid starting substances, the reactor preferably comprises a mixing device, for example a stirrer 19. Particularly preferably, reactor 13 is a continuous stirred tank reactor (CSTR) or a reactor cascade comprising several reactors connected in series, wherein in this case, too, each reactor in the reactor cascade is preferably a CSTR.

[0078] During continuous operation of the reactor 13, the suspension produced in the reactor is continuously withdrawn via a drain line 21 and fed into a buffer tank 23. From the buffer tank 23, the suspension is then fed to a filtration apparatus 25, in which the solid particles are separated from the suspension. If the filtration is carried out batchwise, the buffer tank 23 also serves, in particular, as an intermediate storage facility for the continuously fed suspension, which is then withdrawn batchwise from the buffer tank 23 and fed to the filtration apparatus 25. Alternatively or additionally, the buffer tank 23 can also be used to give the solid particles sufficient time for a post-reaction, for example, if the reaction proceeds slowly and the residence time in the reactor 13 is insufficient to achieve complete conversion of the starting substances.

[0079] In order to prevent solid particles from sedimenting in the buffer tank 23 and forming an undesirable coating, the buffer tank 23 comprises a stirrer 27 with which the suspension is stirred and the solid particles are kept in motion in the liquid phase.

[0080] To monitor the reaction progress and analyze the solid particles produced, it is preferred if, as shown here, a sample line 29 branches off from the drain line 21. Samples can be taken via the sample line 29 and fed to an analysis unit 31. In this case, it is particularly preferred if the sample line 29 is connected to the drain line 21 by a valve, wherein the valve closes the sample line 29 and opens the drain line during normal operation and closes the drain line 21 and opens the sample line 29 to take a sample. A sample is taken in this valve position and the valve is then switched again so that the drain line 21 is open and the sample line 29 is closed. To take another sample, the valve is then switched again briefly.

[0081] The individual samples taken via the sample line 29 are preferably each introduced into a sample vessel 33, with a new sample vessel 33 being used for each sample. For this purpose, the sample vessels 33 are located, for example, on a carousel 35, which rotates one step further after taking a sample and positions the next, empty sample vessel 33 below the sample line 29.

[0082] The samples contained in the sample vessels 33 can either be analyzed automatically, or the holder containing the filled sample vessels 33 is removed and replaced with a new holder containing sample vessels 33 as soon as all sample vessels 33 are filled. In this case, the analysis of the samples contained in the sample vessels 33 can also be performed on a separate analysis unit.

[0083] In the filtration apparatus 25, the solid particles are separated from the suspension. For this purpose, a pressure difference is applied by connecting the filtrate side to a vacuum pump 37. It is particularly advantageous if the device 1 comprises only one vacuum pump, wherein the one vacuum pump is used both to generate the pressure difference for filtration and to generate the negative pressure in the storage containers 3.1, 3.2. For this purpose, the filtrate side of the filtration apparatus 25 is not connected to a separate vacuum pump 37 as shown here, but rather to the vacuum pump 9 via the valve 11. The valve 11 can then be switched so that a negative pressure is applied either to one of the storage containers 3.1, 3.2 or to the filtrate side of the filtration apparatus 25.Due to the applied negative pressure, the liquid phase of the suspension is drawn through a filter in the filtration apparatus 25, so that the solid particles collect as a filter cake on the filter, and the liquid phase can be removed as a filtrate. To remove the solid particles as a filter cake, it is preferred if the filter is designed as the bottom of a filter basket, and the filter basket can be removed from the filtration apparatus along with the filter cake.

[0084] To remove residual liquid phase from the solid particles, it is advantageous if the filter cake can be washed before removal from the filtration apparatus. For this purpose, the filter cake is mixed with a rinsing liquid, which can be removed again as filtrate after the rinsing process. To mix the solid particles of the filter cake with the rinsing liquid, the filtration apparatus preferably also has a stirrer 39. The rinsing liquid is preferably held in a storage container 40, as shown here.

[0085] In order to prevent operating personnel from coming into contact with toxic starting substances or toxic products, all components of the device 1 except for the storage containers 7.1, 7.2 and the computer 17 are arranged inside a closed housing 41.

[0086] In order to access the components arranged in the housing 41 when needed, for example when replacement or maintenance is required, the housing 41 preferably has an access that can be closed in a gas- and liquid-tight manner.

[0087] The gases removed from the process via the vacuum pumps 9, 37 and any further exhaust gases generated in the process can preferably be removed via an exhaust gas outlet 43 on the housing 41, wherein the exhaust gas outlet 43 is connected to an exhaust gas purification system in order to prevent gaseous hazardous substances extracted from the housing 41 from being released into the environment.

[0088] To prevent the formation of undesirable deposits in the containers containing the suspension, i.e., the reactor 13, the buffer tank 23, and the filtration apparatus 25, these containers preferably each have at least one rinsing nozzle arranged above the maximum liquid level, via which a rinsing liquid can be sprayed onto the walls of the containers to form a liquid film thereon and thus prevent solid particles from depositing at the interface of the liquid in the respective container. Furthermore, it is preferred if, in addition to the stirrers 19, 27, 39, vortex nozzles are also included, with which the liquid in the containers can be kept in motion to prevent deposits.

[0089] Once a batch is complete, it is further preferred if the system components can be cleaned automatically. For this purpose, for example, pressurized liquid can be sprayed onto the inner walls of the containers via the rinsing nozzles to remove any deposits. Furthermore, it is also possible to flood the containers with a rinsing liquid and agitate it, for example, using stirrers 19, 27, 39 or with the aid of vortex nozzles, thus rinsing away any deposits. The entire rinsing process is carried out fully automatically to prevent operating personnel from coming into contact with components used in the process.

[0090] Once the rinsing process is complete, a new batch can be started.

[0091] If the same rinsing liquid can be used for cleaning the system components as for cleaning the filter cake, this is preferably also taken from the storage container 40, which for this purpose is connected not only to the filter apparatus but also to the reactor 13.

[0092] Figure 2 shows a buffer container 23 as it can be used in the device shown in Figure 1.

[0093] The suspension from reactor 13 is introduced into buffer tank 23 via an inlet 43. In buffer tank 23, the suspension is kept in motion by stirrer 27 to prevent solid particles from precipitating from the suspension and forming an undesirable coating on the inner walls 45 of buffer tank 23. Any suitable stirrer can be used for this purpose, with the stirrer being particularly preferably an axially acting stirrer. Axial-acting inclined-blade stirrers are particularly suitable.

[0094] At the bottom of the buffer tank 23 is an outlet 47 through which the suspension can be removed from the buffer tank 23 and fed to the filtration apparatus 25. A rinsing line 49 preferably opens at the outlet 47, through which rinsing liquid can be introduced into the buffer tank 23 from below in order to rinse it after the end of a batch. Alternatively or in addition to the rinsing line 49, a sample line can also branch off from the outlet 47. Samples can be taken via the sample line in order to analyze the suspension removed from the buffer tank 23 before it is fed to the filtration apparatus 25.

[0095] Figure 3 shows a filtration apparatus 25 such as can be used in the device 1 according to the invention for producing solid particles.

[0096] The filtration apparatus 25 is filled with the suspension to be separated via an inlet line 51. The inlet line 51 is generally the line connected to the outlet 47 of the buffer tank 23, so that the suspension can be fed from the buffer tank 23 into the filtration apparatus 25. The filtration apparatus 25 can be operated continuously or batchwise, with batch operation being preferred. For this purpose, the filtration apparatus 25 is filled with the suspension, and a negative pressure is applied on the filtrate side, i.e., below a filter 53. For this purpose, the filtrate side is connected to the vacuum pump 37. By applying the negative pressure, a pressure difference is generated, which draws the liquid phase of the suspension through the filter 53. The solid particles contained in the suspension collect on the filter 53 and form a filter cake.The liquid phase is removed from the filtration apparatus as filtrate via outlet 55 and can be subjected to further processing if the filtrate can be processed appropriately. Alternatively, the filtrate can also be disposed of appropriately.

[0097] Once the liquid phase of the suspension has been removed as filtrate, a moist filter cake, which still contains residues of the liquid phase, remains on the filter 53. Since the liquid phase may still contain starting substances and in particular reactants, it is necessary to rinse the solid particles remaining as a filter cake in order to remove the residues of the liquid phase. For this purpose, the outlet 55 is closed with a valve 57 after the entire filtrate has been removed. A rinsing liquid is then introduced into the filtration apparatus 25 via a rinsing line 59. With the aid of the stirrer, the filter cake formed on the filter 53 is re-swirled so that all solid particles come into contact with the rinsing liquid and the remaining liquid phase of the suspension can be washed away.After a specified stirring time, stirring is stopped, and valve 57 is switched so that a vacuum can be applied to the filtrate side again. This removes the rinsing liquid as filtrate, leaving the rinsed solid particles as a purified filter cake on filter 53. If it is not possible to remove the solid particles from the entire liquid phase of the suspension in one rinse cycle, the rinsing process can be repeated one or more times.

[0098] To determine the rinsing progress and in particular to investigate whether starting substances are still being washed away with the rinsing liquid and thus whether starting substance still adheres to the solid particles, it is further preferred if the rinsing liquid is analyzed for residues of the starting substances after completion of a rinsing cycle. For this purpose, a probe is preferably placed at the outlet 55 of the rinsing liquid from the filtration apparatus 25, with which the rinsing liquid can be analyzed for residues. Suitable probes are, for example, probes for measuring conductivity in the rinsing liquid. A low conductivity is then an indication of a low loading with metal salts. As soon as no more residues are found, the solid particles have been sufficiently cleaned and can be removed from the filtration apparatus 25.For this purpose, it is particularly preferred if the filter 53 is the bottom of a filter basket 58, which can be removed together with the filter cake formed on the filter 53. The walls of the filter basket 58 are preferably impermeable, and only the bottom of the filter basket 58 acts as the filter 53.

[0099] Regardless of whether the filtration is carried out continuously or batchwise, it is still preferable if the filtration is repeated until the filter cake has reached a desired height. In continuous filtration, suspension is added until the filter cake has reached the desired height; in batchwise filtration, after the liquid phase of one batch has been removed, more suspension is added, the liquid phase is removed, and this process is repeated until the filter cake has reached the desired height. If the filter cake is to be rinsed, it is preferably not rinsed until the filter cake has reached the desired height, even in batchwise filtration, since otherwise the already cleaned solid particles from the previous filtrations will become contaminated again with the liquid phase.

[0100] To determine whether the filter cake has reached the desired height, a lower fill level sensor 61 is preferably provided, which is arranged so that the desired height of the filter cake can be detected. Furthermore, it is preferred if a second fill level sensor 63 is included, with which the desired fill level of the suspension or the rinsing liquid can be detected when the filtration apparatus 25 is filled with the suspension or the rinsing liquid. An upper fill level sensor 65 can detect the maximum permissible fill level in order to prevent the filtration apparatus from becoming overfilled. Optionally, the lower fill level sensor 61 can also be used to set a lower level of the suctioned-off cleaning liquid. This can prevent the filter cake from drying out too early between cleaning steps.

[0101] After completion of the filtration of a batch or if contaminants have formed on the filtration apparatus 25, the latter is preferably cleaned. For this purpose, a supply line 67 for a cleaning liquid is provided. This can be used to flood the filtration apparatus for cleaning. For cleaning, the filtration apparatus 67 is preferably filled to the maximum fill level, which is detected by the upper fill level sensor 65. The cleaning liquid is then set in motion in the filtration apparatus with the aid of the stirrer 39 and, if necessary, vortex nozzles (not shown here), so that the contaminants are washed off the walls of the filtration apparatus 25 with the generated shear forces. Solid contaminants are then collected in the filter basket and, provided they are still usable product, can be further processed and used as product. Alternatively, the solid contaminants are removed with the filter basket and disposed of.

[0102] To clean the filter cake, it is necessary to completely agitate the filter cake so that the rinsing liquid can flow around and rinse all the solid particles in the filter cake. For this purpose, a stirrer 39, as shown in Figure 4, is preferably used.

[0103] The stirrer 39 preferably has stirrer blades 69 at the lower end that are set at an angle to the horizontal, so that the lower part of the stirrer 39 is an inclined blade stirrer. When the stirrer is mounted in the filtration apparatus 25, the stirrer blades 69 are preferably located only a short distance above the filter 53 or even touch the filter 53. As a result, the solid particles that are directly on the filter 53 are scraped off the filter and can thus also be evenly washed with the rinsing liquid and cleaned. For even mixing of the solid particles with the rinsing liquid, a further stirring element 71 is located above the stirrer blades 69 forming the inclined blade stirrer, which stirrer element is preferably an anchor stirrer, as shown here. This achieves even mixing of the solid particles with the rinsing liquid.

[0104] After the rinsing step is complete, the stirrer is stopped again so that filtration can take place. Once the solid particles have been cleaned and the filter basket 58 with the filter cake is to be removed from the filtration apparatus 25, the stirrer is moved upwards if the filter basket 58 is to be removed from the side of the filtration apparatus 25. If the filter basket 58 is removed downwards from the filtration apparatus 25, it is not necessary to

[0105] To move the stirrer axially.

Claims

Patent claims 1. Device for producing solid particles from liquid starting materials, comprising: at least two feed containers (3.1, 3.2) for the liquid starting materials, at least one reactor (13) in which a suspension containing solid particles is formed by reaction of the liquid starting materials or solids are deposited on seeding surfaces or seeding bodies, and, in the case of formation of a suspension, at least one filtration apparatus (25) for separating the solid particles from the suspension, wherein the feed containers (3.1, 3.2) are each connected to the reactor (13) via fluid connections and pumps are included in the fluid connections with which liquid is drawn from the respective feed container (3.1, 3.2).2) can be conveyed into the reactor (13) and the reactor (13) is connected to the filtration apparatus (25) in such a way that the suspension formed in the reactor (13) can flow into the filtration apparatus (25) and wherein all system components of the device (1) are positioned in a closed housing (41).

2. Device according to claim 1, characterized in that the storage containers (3.1 , 3.2) are suspended from load cells (15.1 , 15.2).

3. Device according to claim 1 or 2, characterized in that the feed containers (3.1 , 3.2), the reactor (13) and connecting lines are made of or coated with a material that is chemically inert to the liquid starting materials and substances formed during the production of the solid particles.

4. Device according to one of claims 1 to 3, characterized in that the filtration apparatus (25) has a filter basket (58) in which the solid particles collect as a filter cake and which can be removed from the enclosed housing (41).

5. Device according to one of claims 1 to 4, characterized in that the storage containers (3.1 , 3.2) are connected to a vacuum pump (9) so that liquid starting substance can be drawn into each of the storage containers (3.1 , 3.2) via an inlet (5.1 , 5.2) connected to a storage container (7.1 , 7.2) by applying a vacuum.

6. Device according to one of claims 1 to 5, characterized in that the filtration apparatus (25) is connected to a vacuum pump (37) to generate the pressure difference necessary for filtration.

7. Device according to one of claims 1 to 6, characterized in that a buffer tank (23) is arranged between the reactor (13) and the filtration apparatus (25), so that the suspension from the reactor (13) is first directed into the buffer tank (23) and from the buffer tank (32) into the filtration apparatus (25).

8. Device according to one of claims 1 to 7, characterized in that the at least one reactor (13), optionally the buffer tank (23) and the filtration apparatus (25) comprise rinsing nozzles with which drying on inner walls can be prevented.

9. Device according to one of claims 1 to 8, characterized in that vortex nozzles are arranged at the outlet of the at least one reactor 813) and optionally the buffer tank (23) with which a shear force can be introduced into the suspension.

10. Device according to claim 8 or 9, characterized in that it includes sensors with which the cleaning can be monitored.

11. Method for producing solid particles from liquid starting materials in a device according to any one of claims 1 to 10, comprising (a) Place a liquid starting substance into each of the feed containers (3.1, 3.2); (b) continuous gravimetric dosing of the liquid starting materials into the at least one reactor (13); (c) Reaction of the liquid starting materials to form a suspension containing the solid particles as a product or to form solid particles which are deposited on a seeding surface or seeding body; (d) Separating the solid particles from the suspension in the filtration apparatus and removing the filter basket containing the solid particles or removing the seeding surface or seeding body containing the solid particles deposited thereon.

12. A method according to claim 11, characterized in that the liquid starting materials are drawn from storage containers (7.1, 7.2) into the feed containers (3.1, 3.2) by applying a vacuum.

13. A method according to claim 11 or 12, characterized in that the suspension is introduced into a buffer container (23) and from the buffer container (23) into the filtration apparatus (25).

14. Method according to one of claims 11 to 13, characterized in that liquid is withdrawn from the reactor (13) during the reaction.

15. Method according to one of claims 11 to 14, characterized in that a liquid is sprayed on the walls of the reactor (13) and / or the buffer container (23) above the liquid level of the suspension in order to form a liquid film on the walls.

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