PROCESS AND PLANT FOR CONTINUOUSLY PRODUCING A BULK MATERIAL FROM TWO OR MORE DIFFERENT STARTING MATERIALS HAVING A HIGH LIQUID CONTENT

Abstract

 The present invention relates to a process for producing a bulk material from two or more different starting materials, wherein at least one of the starting materials has a vapor pressure between 0.1 to 1,000 hPa at 23°C, wherein the liquid content of the starting materials based on the sum of liquid and solid content is at least 5% by weight, wherein the process comprises the steps of i) continuously feeding the starting materials into a continuous dynamic mixer comprising at least one rotating shaft and preferably rotating screw shaft and mixing the starting materials therein, and of ii) continuously transferring the mixture obtained in step i) into a continuous evaporator and processing the mixture therein so as to obtain a bulk material having, at 23°C, a liquid content of less than 3% by weight.

Description

[0001] The present invention relates to a process and plant for continuously producing a homogenous bulk material from two or more different starting materials having a high liquid content.

[0002] The production of a homogenous bulk material having a low liquid content from two or more different starting materials, which in sum have a high liquid content, is typically performed in a batch process. Prominent examples of such liquids are water, an organic solvent, such as acetone, ethanol, benzene or the like, or an inorganic solvent, such as ammonia, carbon disulfide, hydrogen fluoride, sulfuric acid and the like. Such a batch processes typically uses a heatable static or dynamic mixer having a large heat exchange surface area, which allows to efficiently remove the liquid contained in the starting materials over the time. If all of the starting materials are already present in the powdery or granular form, such as in flaky form, and if the starting materials do not agglomerate in the mixer, for instance because the mixture is heated to a temperature, where the starting materials agglomerate, the deliquefied mixture obtained in the mixer is already a bulk material. Otherwise, i.e. when at least one of the starting materials is not in the powdery or granular form, such as flaky form, and/or if the starting agglomerates in the mixer during its operation to larger aggregates, the deliquefied mixture obtained in the mixer has to be crushed after its removal from the mixer in a crushing machine, such as in a pulverizer, to bulk material. However, such batch processes have the drawback of requiring significant dead times for emptying, cleaning and loading the mixer, which reduces the throughput of the respective machines. Furthermore, such batch processes do not lead reliably to a constant product quality. Another disadvantages of batch processes in comparison to continuous processes are that the batch processes usually require - for the same throughput - larger machines and such higher investment costs as well as higher operational costs.

[0003] Continuously working mixers are known but are not suitable to continuously producing a homogenous bulk material from two or more different starting materials having a high liquid content with an acceptable throughput and with acceptable machine investment costs as well as acceptable operational costs, especially when a very intense mixing of the components is required before the evaporation of the liquid and when the viscosity of the mixture is high. Typical examples are the fine dispersion of particles like a fine powder in a viscous phase, or when a low viscous liquid must be homogenized with a very high viscous phase. For instance, rotor and/or screw shaft-based mixers, such as single screw extruders, twin screw extruders or screw shaft-based mixers comprising a screw shaft rotating and simultaneously moving translationally back and forth in the axial direction during the operation, are used for continuously mixing different starting materials of solids, different starting materials of solids and melts or different starting materials of melts. Since the rotating screw shafts transport the material within the mixers in the axial direction, such screw shaft-based mixers are well suited for continuous mixing processes. They may be in particular used for two or more different starting materials leading upon mixing and homogenization to viscous mixtures, such as viscous melt mixtures, which are otherwise very difficult to mix and to homogenize. Often, heatable mixers are used, which allow to adjust a suitable temperature and in particular a suitable temperature profile over various sections of the mixers, and/or to generate the required temperature within the mixer by applying shear forces to the mixture. The rotor and/or screw shaft-based mixers are suited for mixing two or more different starting materials, which do not include any liquid or which only have a low liquid content, to a homogenous mixture. Since the aforementioned mixers are usually temperature controllable, they may remove in principle liquid from the mixture by evaporation, but only to a limited extent. This is, among others, due to an insufficient heat exchange surface area especially in larger machines, to a limited heat transfer coefficient and to the comparable short residence time in such rotor and/or mixers. Thus, they are not suitable to mix and process two or more different starting materials having a comparable high liquid content to a mixture having a comparable low liquid content. On the contrary, this would require that the throughput of the mixer is significantly reduced or that the respective rotor and/or screw shaft-based mixer is drastically oversized, in order to homogenously mix the different materials despite of the high liquid content and to form a homogenous mixture having a low liquid content. However, such a significant reduction of the throughput of the rotor and/or screw shaft-based mixer is not acceptable and the massive oversizing of the rotor and/or screw shaft-based mixer leads to inacceptable high costs, a high space footprint and consequently inacceptable high production costs. Therefore, rotor and/or screw shaft-based mixers are principally not suitable to produce a homogenous bulk material having a low or very low liquid content from two or more different starting materials, which in sum have a high liquid content.

[0004] In view of this, the object underlying the present invention is to provide a process for continuously producing a homogenous bulk material having a low liquid content from two or more different starting materials, which in sum have a high liquid content, wherein the process is able for starting materials and/or mixtures having a high viscosity as well as for starting materials and/or mixtures having a low viscosity, and wherein the process has comparable low capital expenses, low operational costs and a high throughput.

[0005] In accordance with the present invention this object is satisfied by providing a continuous process for producing a homogenous bulk material from two or more different starting materials, wherein at least one of the starting materials has a vapor pressure between 0.1 to 1,000 hPa at 23°C, wherein the liquid content of the starting materials based on the sum of liquid and solid content is at least 5% by weight, wherein the process comprises the steps of i) continuously feeding the starting materials into a continuous dynamic mixer comprising at least one rotating shaft and preferably rotating screw shaft and mixing the starting materials therein, and of ii) continuously transferring the mixture obtained in step i) into a continuous evaporator and processing the mixture therein so as to obtain a bulk material having, at 23°C, a liquid content of less than 3% by weight.

[0006] This solution bases on the finding that a continuous rotor and/or screw-based mixer may be used in a process for continuously producing a homogenous bulk material from two or more different starting materials having a high liquid content, wherein the process has comparable low capital expenses, low operational costs and a high throughput, when the continuous rotor and/or screw-based mixer is only used for the compounding or mixing, respectively, of the starting materials, wherein the evaporation and, if necessary, bulk material generation, for instance by pulverizing, is performed in a separate step in a continuous evaporator. Thus, independent from the form of the starting materials, a further crushing or pulverization step is not necessary. Advantageously, the process in accordance with the present invention may be not only used for starting materials and/or mixtures having a high viscosity, but also for starting materials and/or mixtures having a low viscosity. Continuous rotor and/or screw shaft-based mixers and in particular continuous screw shaft-based mixers comprising a screw shaft rotating and simultaneously moving translationally back and forth in the axial direction during the operation are suitable for processing and mixing mixtures having a high viscosity, in particular since these mixers allow to introduce high shear forces into a viscous mixture allowing to optimize the mixing effect and the evaporation extent. As set out above, such mixers may for low liquid contents effect an evaporation, but only to a limited extent. This is due to the heat, which may be introduced into the mixture by means of the heater in the wall of such mixers as well as by the introduction of shear forces. However, high shear forces cannot be introduced into low viscous mixture and also not into melt mixtures having a low melt strength. Therefore, these mixers are even less able to evaporate small amounts of liquid in low viscous mixtures. However, in the present invention the evaporation is effected in a downstream evaporator so that the process in accordance with the present invention does not need to rely on the anyway very limited evaporation effect of the continuous rotor and/or screw-based mixer. Since a drastic oversizing of the rotor and/or screw-based mixer as well as a drastic reduction of the throughput of the rotor and/or screw-based mixer is not at all required, the process in accordance with the present invention has comparable low capital expenses, low operational costs and a high throughput. Also in advantage to the known batch processes, the process in accordance with the present invention is characterized by significantly reduced capital expenses and operational costs, since much smaller mixers may be applied. Moreover, dead times, as required by batch processes for emptying, cleaning and loading the mixer, are not at all required in the process in accordance with the present invention.

[0007] In principle, the present invention is not particularly limited concerning the kind of continuous dynamic mixer comprising at least one rotating shaft and preferably rotating screw shaft, i.e. the continuous rotor and/or screw shaft-based continuous dynamic mixer. For instance, the continuous dynamic mixer may be a single-screw extruder or a twin-screw extruder. Alternatively, it may be a multi-screw extruder comprising more than 2 screws. An example therefore is a planetary screw extruder comprising a rotating central base screw shaft and 2 to 15 rotating planetary screws shafts being arranged around the central base screw shaft. Another example therefore is a ring extruder comprising a fixed central base screw shaft and 2 to 15 rotating planetary screws shafts being arranged around the central base screw shaft. Another example therefore is a continuous twin-rotor extruder.

[0008] In accordance with a particular preferred embodiment of the present invention, the continuous dynamic mixer contains one screw shaft, which comprises at least two blade elements extending radially outwards from the screw shaft, wherein the screw shaft rotates and simultaneously moves translationally back and forth in the axial direction of the continuous dynamic mixer during its operation. More specifically, the screw shaft comprises a shaft rod, onto the surface of which the blade elements are arranged so as to extending radially outwards from the shaft rod. The combination of the shaft rod and the blade elements is the screw shaft. However, for the ease of formulation, in the following it is also simplified referred to this as a screw shaft, which comprises at least two blade elements extending radially outwards from the screw shaft. Such a continuous dynamic mixer allows a particularly efficient homogenization of a mixture and even of a mixture having a particularly high viscosity or which is on account of other reasons very difficult to mix, since the oscillating screw shaft, i.e. the screw shaft rotating and simultaneously moving translationally back and forth in the axial direction of the continuous dynamic mixer, allows to incorporate high shear forces into the mixture and this homogenously over the whole surface of the screw shaft.

[0009] In a further development of the idea of this particularly preferred embodiment of the present invention, the continuous dynamic mixer comprises:

• a housing, in which a hollow interior being limited by the inner peripheral surface of the housing is designed,
• the aforementioned screw shaft extending in the axial direction through the interior, which rotates during operation in the interior and simultaneously moves translationally back and forth in the axial direction, and
• kneading elements fixed in receptacles provided in the housing, wherein the kneading elements extend from the inner peripheral surface of the housing into the housing, i.e. in direction of the screw shaft.

[0010] The presence of the kneading elements, which are for instance in the form of kneading bolts, allows to even improve the homogenization efficiency of the mixer, since the kneading elements also allow to incorporate high shear forces into the mixture and this homogenously over the whole hollow interior of the housing .

[0011] It is further preferred that the screw shaft, on which the blade elements are arranged, has a circular cross-section. Preferably, the blade elements are arranged to be spaced apart from one another on the surface of the screw shaft, wherein the blade elements are arranged on the circumferential surface of the screw shaft, at least in one section extending in the axial direction of the screw shaft, in two, three, four or six rows extending in the axial direction of the screw shaft, wherein preferably all of the at least two rows each comprise at least three, preferably at least ten and more preferably at least 20 blade elements.

[0012] It is preferred in the aforementioned embodiment that the receptacles and thus the kneading elements are arranged at least in one section extending in the axial direction of the of the inner peripheral surface of the housing in two, three, four or or six rows extending in the axial direction over at least one section of the inner peripheral surface of the housing, wherein preferably all of the at least two rows each comprise at least three, preferably at least ten and more preferably at least 20 receptacles, in which kneading elements are fixed. The number of rows of the receptacles in the housing preferably is the same as the number of rows of the blades on the screw shaft.

[0013] The blade elements of the screw shaft may have an elliptic, oval or biconvex outer peripheral surface in the top view.

[0014] For instance, each of the blade elements of the at least one section extending in the axial direction of the screw shaft may have a longitudinal extension L, which extends at an angle of 45° to 135°, preferably 60° to 120°, particularly preferably 80° to 100°, very particularly preferably from 85° to 95°, and most preferably of about 90° to the axial direction of the screw shaft.

[0015] Preferably, the at least one section extending in the axial direction of the screw shaft, in which the blade elements are arranged in two, three, four or six rows extending in the axial direction of the screw shaft as well as the at least one section extending in the axial direction of the inner peripheral surface of the housing, in which the receptables and the kneading elements are arranged in two, three, four or six rows extending in the axial direction of the inner peripheral surface of the housing, is at least 0.2 D, preferably at least 0.5 D, particularly preferably at least 1 D and very particularly preferably at least 5 D of the length of the screw shaft.

[0016] Good results are for instance obtained, when the blade elements are arranged on the surface of the screw shaft in the at least one section in two rows extending in the axial direction of the screw shaft, wherein each of the blade elements of the at least one section extends - as seen in the cross-section of the screw shaft - over an angular distance of at least 160°, preferably of at least 170°, further preferably of at least 175°, even further preferably of more than 180°, even further preferably of more than 180° to 270°, particularly preferably of 185° to 230°, particularly preferably of 185° to 210° and most preferably of 190° to 200° of the circumferential surface of the screw shaft. Alternatively, good results are obtained, when the blade elements are arranged on the surface of the screw shaft in the at least one section in two rows extending in the axial direction of the screw shaft, wherein each of the blade elements of the at least one section extends - as seen in the cross-section of the screw shaft - over an angular distance of 20° to less than 160°, preferably of 45° to 135°, particularly preferably of 60° to 120°, further preferably of 70° to 110°, very particularly preferably of 80° to 100°, and most preferably of 85° to 95° of the circumferential surface of the screw shaft. Preferably, each of the blade elements of the at least one section extending in the axial direction of the screw shaft - as seen in the cross-section of the screw shaft - extends over the same angular distance of the circumferential surface of the screw shaft.

[0017] According to an alternative embodiment, the blade elements are arranged on the surface of the screw shaft in the at least one section in three rows extending in the axial direction of the screw shaft, wherein each of the blade elements of the at least one section extends - as seen in the cross-section of the screw shaft - over an angular distance of 20° to 175° of the circumferential surface of the screw shaft. Preferably, each of the blade elements of the at least one section extending in the axial direction of the screw shaft - as seen in the cross-section of the screw shaft - extends over the same angular distance of the circumferential surface of the screw shaft.

[0018] According to still an alternative embodiment, the blade elements are arranged on the surface of the screw shaft in the at least one section in four rows extending in the axial direction of the screw shaft, wherein each of the blade elements of the at least one section extends - as seen in the cross-section of the screw shaft - over an angular distance of 10° to 125° and preferably of 20 to 80° of the circumferential surface of the screw shaft. Preferably, each of the blade elements of the at least one section extending in the axial direction of the screw shaft - as seen in the cross-section of the screw shaft - extends over the same angular distance of the circumferential surface of the screw shaft.

[0019] According to still an alternative embodiment, the blade elements are arranged on the surface of the screw shaft in the at least one section in six rows extending in the axial direction of the screw shaft, wherein each of the blade elements of the at least one section extends - as seen in the cross-section of the screw shaft - over an angular distance of 5° to 90° and preferably of 10 to 60° of the circumferential surface of the screw shaft. Preferably, each of the blade elements of the at least one section extending in the axial direction of the screw shaft - as seen in the cross-section of the screw shaft - extends over the same angular distance of the circumferential surface of the screw shaft.

[0020] In accordance with the present invention, the two or more different starting materials are continuously fed into the continuous dynamic mixer. Starting materials means in this context not necessarily educts to be reacted, but materials as they are provided at the beginning of the process. Thus, the starting materials may react during the mixing in step a), but must not. For most of the applications, the starting materials do not react during the mixing in step a). The different starting materials may be already fed into the continuous dynamic mixer as a pre-mixture. Preferably, however, the two or more different starting materials are fed separately from each other at different locations into the continuous dynamic mixer.

[0021] In accordance with the present invention, the liquid content of the starting materials, at 23°C, based on the sum of liquid and solid content is at least 5% by weight. This means that a mixture of the starting materials in the ratio as that with which the starting materials are continuously fed into the continuous dynamic mixer has a liquid content of at least 5% by weight. For example, if 4 kg/ hour of a starting material A and 8 kg/hour of a starting material B are fed into the continuous dynamic mixer, then the liquid content is that of a mixture of materials A and B in a weight ratio of 1 to 2. Preferably, the liquid content of the starting materials based on the sum of liquid and solid content is at least 6% by weight, more preferably at least 8% by weight, yet more preferably at least 10% by weight, still more preferably at least 15% by weight, still more preferably at least 20% by weight, still more preferably at least 25% by weight and most preferably at least 30% by weight. The liquid content of the starting material, at 23°C, may be for instance determined by vacuum distillation being performed with 10 grams of the mixture of the starting materials in the ratio as that with which the starting materials being continuously fed into the continuous dynamic mixer, wherein firstly at 23°C the pressure in the vacuum distillation vessel is decreased from atmospheric pressure to 100 Pa with a rate of 50 Pa/minute and secondly, when the pressure of 100 Pa is obtained and after one minute waiting, the temperature in the vacuum distillation vessel is increased, at 100 Pa, from 23°C to 120°C with a heating rate of 1°C/minute. For instance, the vacuum distillation is performed in a rotating evaporator. The weight difference between the mixture of the starting materials in the ratio as that with which the starting materials are continuously fed into the continuous dynamic mixer before starting the vacuum distillation and the weight of the solid residue being present after the vacuum distillation is the liquid content of the starting materials, at 23°C. The weight of the solid residue being present after the vacuum distillation is the solid content of the bulk material, at 23°C.

[0022] The vapor pressure of a liquid is preferably measured at 23°C according to DIN EN 13016-3.

[0023] Preferably, the starting materials comprise at least one starting material being liquid at the temperature at which the mixing is performed in step a) and/or being liquid at ambient temperature or 23°C, respectively. Examples for such a liquid starting material are the organic solvents acetone, alcohols, benzene, benzene derivates, N-methyl-2-pyrrolidone, dimethylformamide, dimethyl sulfoxide, water, ammonia and the like.

[0024] Preferably, the liquid has, at 23°C, a dynamic viscosity of at most 100 Pa·s, preferably of at most 10 Pa-s, more preferably of at most 1 Pa·s, even more preferably of at most 0,1 Pa·s and most preferably of at most 0,01 Pa·s, such as between 0.1 and 1,000 m Pa·s.

[0025] Since the process in accordance with the present invention is particularly suitable for processing starting materials with a high liquid content, it is suitable, if at least one of the starting materials is a liquid, a mixture of two or more liquids or a dispersion of solids in a liquid, preferably of solids in water, or in an organic solvent, such as acetone, ethanol, benzene, N-methyl-2-pyrrolidone or the like, or an inorganic solvent, such as ammonia, carbon disulfide, hydrogen fluoride, sulfuric acid and the like.

[0026] As set out above, the process in accordance with the present invention is also particularly suitable for starting materials with a comparable low viscosity. Preferably, at least one of the starting materials has, measured at 23°C, a dynamic viscosity of 0.01 to 100 mPa·s, preferably of 0.02 to 50 mPa·s and more preferably of 0.05 to 20 mPa·s.

[0027] Moreover, it is preferred that at least one of the starting materials is, at 23°C, a solid, such as a solid powder, a solid composed of granules or a solid composed of flakes.

[0028] Examples for solid starting materials are thermoplastic polymers or oligomers, such as polyolefins, copolymers, block-copolymers, polyamides, polycarbonates, grafted polymers and the like. Other suitable examples for solid starting materials are small organic molecules, inorganic Powders, such as hydrated minerals, calcium carbonate, carbon black and the like, natural fibers, such as those being made from HEMP, algae, cotton, cellulosic, silk, wool, hair and the like, synthetic fibers, such as those being made from glass, carbon and the like, inorganic solids , such as silica, glass, sand, minerals and the like and additives, such as UV stabilizers, dyes, antioxidants and the like.

[0029] Furthermore, it is preferred the starting materials comprise at least one of the starting material which is, at 23°C, a solid, and at least one of the starting material which is at the temperature at which the mixing is performed in step a) a liquid and/or which is, at 23°C, a liquid.

[0030] In a further development of the idea of the present invention, the starting materials are mixed in the continuous dynamic mixer at a temperature of 20 to 400°C, such as exemplarily of 150 to 300°C.

[0031] Good results are in particular achieved, when the starting materials are mixed in the continuous dynamic mixer at a pressure of 100 kPa to 20 MPa and preferably of 100 kPa to 5 MPa.

[0032] As set out above, the process in accordance with the present invention is also particularly suitable for mixtures with a comparable high viscosity. Preferably, the mixture has at the outlet of the dynamic mixer a dynamic viscosity of 1 to 50,000 Pa·s and more preferably of 10 to 15,000 Pa·s.

[0033] Concerning the type of the continuous evaporator, the process in accordance with the present invention is not particularly limited, as long as it is a continuously working evaporator being able to evaporate liquid in the required extent. Such a continuous evaporator may be also denoted as continuous dryer. The evaporator or dryer, respectively, transforms as much of the liquid contained in the mixture into its gaseous form. If the mixture transferred from the continuous dynamic mixer into the continuous evaporator is not already a bulk material, but for instance a viscous mass, the continuous evaporator also needs to be able to form bulk material thereof, i.e. to be able to pulverize the mixture or the like.

[0034] For instance, the continuous evaporator may be a shell and tube evaporator, in particular if the mixtures generated in the continuous dynamic mixer has a very high liquid content and is already present as bulk material. Suitable examples for a continuous evaporator are a falling film evaporator and a forced circulation evaporator.

[0035] Another example for a suitable continuous evaporator, in particular for mixtures generated in the continuous dynamic mixer having a very high liquid content and being already present as bulk material, is a short path evaporator, which is especially suitable for mixtures including high boiling compounds, since it is possible to be operated at a very low vacuum, and for mixtures including for sensitive materials.

[0036] Another example for a suitable continuous evaporator is an evaporator forming during its operation a hot mechanically fluidized bed, wherein the mixture obtained in the continuous dynamic mixer is continuously distributed into this fluidized bed. The fluidization of the bed may be achieved by a rotating paddle system. The mixture having a certain liquid content being continuously fed into the fluidized bed is evenly distributed throughout the fluidized bed so that the volatiles evaporate instantly.

[0037] In accordance with a particular preferred embodiment of the present invention, the continuous evaporator is a thin film evaporator. Thin film evaporators are also designated as scraped surface heat exchanger or swept surface evaporator.

[0038] The thin film evaporator may be a vertical thin film evaporator. Preferably, the vertical thin film evaporator comprises a hollow cylindrical, vertically arranged body including a heating jacket and inside its hollow interior a rotor being equipped with rows of blades all over the length of the rotor. The blades can be connected to the rotor with or without hinges. The blades spread the mixture to be dried in a thin layer over the heated wall, thereby evaporating the volatile components. The blades are designed with a minimum gap to prevent fouling of the heating surface by product, but is not in contact with the heated wall. Therefore, the blades breaks the dried mixture up to powder, i.e. a bulk material. The mixture to be dried is fed through an inlet located at the top into the vertical thin film evaporator, whereas the dried bulk material leaves the vertical thin film evaporator through an outlet at its bottom.

[0039] Most preferably, the continuous evaporator is a horizontal thin film evaporator. A horizontal thin film evaporator works essentially as the aforementioned vertical thin film evaporator, except that the body of the evaporator is arranged horizontally and that the inlet and outlet are on the same horizontal level on the opposite sites of the body of the evaporator. Thus, preferably the continuous evaporator comprises a housing, in which a hollow interior being limited by the inner peripheral surface of the housing is designed, wherein the housing comprises at its opposite sides an inlet and an outlet and further comprises a heated inner wall and in its hollow interior a rotating rotor comprising blades extending radially outwards from the rotor. During the operation, the mixture obtained in the continuous dynamic mixer is continuously fed through the inlet into the interior of the housing, picked up by the rotor blades and applied onto the heated inner wall and simultaneously conveyed towards and through the outlet. As in the vertical thin film evaporator, the blades of the horizontal thin film evaporator breaks the dried mixture up to powder, i.e. a bulk material, because the blades are designed with a minimum gap to prevent fouling of the heating surface by product, but is not in contact with the heated wall. The generated gas(es) are streaming counter-currently to the solid and dried mixture and leave the dryer at the side of the inlet for the mixture. The evaporation may be performed, as needed, at atmospheric pressure, under vacuum or at overpressure. The residence time of the mixture within the horizontal thin film evaporator may be between 10 seconds and 60 minutes and preferably between 20 seconds and 10 minutes.

[0040] As set out above, the process in accordance with the present invention leads to bulk material having, at 23°C, a liquid content of less than 3%. Preferably, the bulk material obtained in the continuous evaporator has, at 23°C, a liquid content of at most 2.5%, more preferably of at most 2.0%, even more preferably of at most 1.5%, yet more preferably of at most 1.0%, still more preferably of at most 0.5% and most preferably of at most 0.25% by weight. Likewise to the liquid content of the starting material, the liquid content of the bulk material, at 23°C, is determined by vacuum distillation being performed at 100 Pa with 10 grams of the bulk material being continuously fed into the continuous dynamic mixer, wherein firstly at 23°C the pressure in the vacuum distillation vessel is decreased from atmospheric pressure to 100 Pa with a rate of 50 Pa/minute and secondly, when the pressure of 100 Pa is obtained and after one minute waiting, the temperature in the vacuum distillation vessel is increased, at 100 Pa, from 23°C to 120°C with a heating rate of 1°C/minute. For instance, the vacuum distillation is performed in a rotating evaporator. The weight difference between the bulk material before starting the vacuum distillation and the weight of the solid residue being present after the vacuum distillation is the liquid content of the bulk material, at 23°C, whereas the weight of the solid residue being present after the vacuum distillation is the solid content of the bulk material, at 23°C.

[0041] Bulk material means in accordance with the present invention (dry) material, i.e. material having any of the above mentioned liquid contents, wherein the (dry) material has preferably an angle of repose of at most 75°, more preferably of at most 65°, yet more preferably of at most 60°, still more preferably of at most 55° and most preferably of at most 50°, such as of 25° to 40°. Preferably, the angle of repose of the (dry) material is measured in accordance with ISO 4324. Preferably, the bulk material is present in powdery or granular form, such as in flaky form.

[0042] The process in accordance with the present invention is in particular suitable to produce powdery or granular bulk material, which has preferably a dso-particle size of 0.1 µm to 10 mm, more preferably of 0.1 µm to 5 mm, even more preferably of 0.2 µm to 3 mm and most preferably of 0.5 µm to 1 mm. Powder and granular material comprises fine particles, which may have a spherical, ellipsoidal, cuboidal, flaky, similar and irregular form. Usually, the term powder is used for finer particles and the term granular material is used for larger particles. However, there is no clear distinction between both terms. Therefore, both terms are used here together to describe material in the above form with the above particle sizes. The dso-particle size is the corresponding particle size when the cumulative percentage reaches 50%, i.e. 50% of the particles of the powder are larger than the dso-particle size and 50%, of the particles of the powder are smaller than the d50-particle size. The d50-particle size may be measured - in particular, but not exclusively for very fine powders - by light scattering in accordance with ISO 22412:2017 or - in particular, but not exclusively for very fine powders - by laser diffraction in accordance with ISO 13320:2020 or - in particular, but not exclusively for very fine powders - by dynamic image analysis in accordance with ISO 13322:2021.

[0043] For instance, the process in accordance with the present invention is suitable to produce bulk material in form of flakes. Flakes means in this connection particles having an aspect ratio of the average particle length divided by the average particle thickness of at least 2, preferably of at least and more preferably of at least 10, wherein length means the longest extension of the particle surface and the thickness means the smallest extension of the particle surface. Preferably, the average length of the flaky particles is 100 µm to 20 mm and preferably 500 µm to 10 mm, whereas the average thickness of the particles is 10 µm to 2 mm and preferably 100 µm to 1 mm. For instance, the flakes may be plate-like particles, i.e. particles having a length, a width and a thickness. The length means the longest extension of the flaky particle surface, the width the largest extension of a line being oriented in a 90° angle to the length and the thickness means the extension of the particle in the plane being in a 90° angle to the plane spanned by the length and width of the particle.

[0044] Another aspect of the present invention is the use of the bulk material obtained with the aforementioned process in the food industry, as battery mass, or the chemical industry. Exemplarily, the bulk material obtained with the aforementioned process may be a heterogenous catalyst, which is prepared by mixing zeolite microspheres with a binder and a liquid containing the catalyst precursor. A very intense mixing is required to ensure a good contact of the microsphere with the catalyst precursor. After that, the liquid is evaporated and thereby the solid containing the catalyst precursor is pulverized to a powder. Another example is the use of the bulk material obtained with the aforementioned process for the electrode manufacturing such as for lithium-ion-batteries.

[0045] According to still another aspect the present invention relates to a plant for producing a bulk material from two or more different starting materials, wherein at least one of the starting materials has a vapor pressure between 0.1 to 1,000 hPa at 23°C, wherein the liquid content of the starting materials based on the sum of liquid and solid content is at least 5% by weight, comprising:

a) a continuous dynamic mixer comprising at least one inlet, an outlet and at least one rotatable shaft and preferably rotatable screw shaft and

b) a continuous evaporator comprising an inlet and an outlet, wherein the inlet of the continuous evaporator is connected with the outlet of the continuous dynamic mixer.

[0046] In accordance with one embodiment of the present invention, the continuous dynamic mixer is a single-screw extruder or a twin-screw extruder.

[0047] In accordance with an alternative, particular preferred embodiment of the present invention, the continuous dynamic mixer contains one screw shaft, which comprises at least two blade elements extending radially outwards from the screw shaft, wherein the screw shaft rotates and simultaneously moves translationally back and forth in the axial direction of the continuous dynamic mixer during its operation.

[0048] In a further development of the idea of the present invention it is proposed that the continuous dynamic mixer comprises:

• a housing, in which a hollow interior being limited by the inner peripheral surface of the housing is designed,
• the screw shaft extending in the axial direction through the interior, which rotates during operation in the interior and simultaneously moves translationally back and forth in the axial direction, and
• kneading elements fixed in receptacles provided in the housing, wherein the kneading elements extend from the inner peripheral surface of the housing into the housing, wherein the receptacles are arranged on the inner peripheral surface of the housing in at least two rows extending in the axial direction over at least one section of the inner peripheral surface of the housing, wherein at least two and preferably all of the at least two rows each comprise at least three receptacles, in which kneading elements are fixed.

[0049] Preferably, the screw shaft has a circular cross-section and the blade elements are arranged to be spaced apart from one another, wherein the blade elements are arranged on the circumferential surface of the screw shaft, at least in one section extending in the axial direction of the screw shaft, in two, three, four or six rows extending in the axial direction of the screw shaft.

[0050] It is further preferred that the continuous evaporator is i) a shell and tube evaporator, preferably a falling film evaporator or a forced circulation evaporator, or ii) a short path evaporator.

[0051] In accordance with an alternative, particular preferred embodiment of the present invention, the continuous evaporator is a thin film evaporator.

[0052] Good results are in particular obtained, when the continuous evaporator is a horizontal thin film evaporator, which comprises a housing, in which a hollow interior being limited by the inner peripheral surface of the housing is designed, wherein the housing comprises at its opposite sides an inlet and an outlet and further comprises a heated inner wall and in its hollow interior a rotating rotor comprising blades extending radially outwards from the rotor.

[0053] Subsequently, the present invention is explained in more detail with reference to the drawing, which is merely illustrative for an embodiment of the present invention and not at all limiting.

Fig. 1

shows a schematic plan view of a plant for producing a bulk material with a low liquid content from two or more different starting materials having a high liquid content according to one embodiment of the present invention.

Fig. 2

shows a schematic perspective view of the housing with a utilized screw shaft of the continuous dynamic mixer of the plant shown in Fig. 1.

Fig. 3a

shows a schematic perspective view of the continuous evaporator of the plant shown in Fig. 1.

Fig. 3b

shows a schematic perspective view of the rotor comprising blades extending radially outwards from the rotor of the continuous evaporator shown in Fig. 3a.

Fig. 4

shows a simplified schematic drawing illustrating the working principle of a continuous evaporator.

[0054] The plant 2 for producing a bulk material with a low liquid content from two or more different starting materials having a high liquid content according to one embodiment of the present invention shown in figure 1 as schematic plan view a continuous dynamic mixer 4 and downstream thereof a continuous evaporator 6. The continuous dynamic mixer 4 comprises a drive block, which in turn comprises a motor as well as a gearbox, a filling funnel 10 for introducing a solid into the continuous dynamic mixer 4 and a liquid inlet 12 for introducing a liquid or dispersion of a solid in a liquid into the continuous dynamic mixer 4. The continuous dynamic mixer 4 is connected with the continuous evaporator 6 via a connection line 14 functioning as outlet line for the continuous dynamic mixer 4 and as inlet line for the continuous evaporator 6. Moreover, the continuous evaporator 6 comprises an outlet line 16 for withdrawing the produced bulk material with low liquid content from the continuous evaporator 6.

[0055] As shown in more detail in figure 2, the continuous dynamic mixer 4 comprises a housing 18. The housing 18 comprises two housing halves 28, 28', which are clad inside with a so-called housing shell 30, which is composed of multiple housing shell parts 32, 32', 32" arranged in an axially adjoining manner. In the present patent application, the housing shell 30 is thereby considered to be part of the housing 18. When the two housing halves 28, 28' are closed, the inner circumferential surface of the housing 18 borders a cylindrical hollow interior, in which a rotating screw shaft 34 is arranged. The screw shaft 34 comprises a shaft rod 36, on whose circumferential surface blade elements 38 are arranged. Kneading elements 40, which are designed as kneading bolts 40, are provided on the inner circumferential surface of the two housing halves 28, 28'. Each of these kneading elements is arranged and fixed in a receptacle 42 provided in each case in the wall of the housing 18, said receptacle 42 extending from the inner circumferential surface of the housing shell 30 through the wall of the housing 18. The lower, radial inner end of each receptacle 42 can be designed having a square cross-section, wherein each kneading bolt 40 has an end fitting perfectly into the square-designed radial inner end of the receptacles 42 and is thereby fixed in the utilized state in a non-rotatable manner in the receptacle 42. Each of the kneading bolts 40 is evenly spaced apart from each other and extend into each of the two housing halves 28, 28', when viewed in the axial direction, in the form of three rows 44, 44', 44". The housing 18 is preferably temperature-controlled by means of one or more thermo-devices or heatable using electric heat cartridges or heating plates attached outside on the housing, and is water- or air-cooled, if necessary also cooled by a different fluid, such as an oil or another liquid or a special gas. The housing of the continuous dynamic mixer is subdivided in the axial direction into multiple process steps 46, 46', 46", wherein each process step 46, 46', 46" is adapted to the function of the individual process steps 46, 46', 46" in terms of the number of kneading bolts 40 as well as the number and dimension of the blade elements 38 on the shaft rod 34. In the left section 46 and in the right section 46" of the upper housing half 28, of the three rows 44, 44', 44" of receptacles 42 for kneading bolts 40, two rows, specifically the upper row 44 and the lower row 44", are furnished with kneading bolts 40, whereas the middle row 44' is not furnished with kneading bolts 40. In contrast, in the middle section 46' of the upper housing half 28, of the three rows 44, 44', 44" of receptacles 42 for kneading bolts 40, one row, specifically the middle row 44', is furnished with kneading bolts 40, whereas the upper row 44 and the lower row 44" are not furnished with kneading bolts 40.

[0056] As shown in figure 3a, the continuous evaporator 6 of the plant 2 of this embodiment is a horizontal thin film evaporator 6. The thin film evaporator 6 comprises a housing 48, in which a hollow interior being limited by the inner peripheral surface of the housing is designed, wherein the housing comprises at its opposite sides an inlet 50 and an outlet 52 and further comprises a heated inner wall 64 and in its hollow interior a rotating rotor 54 comprising blades 56 extending radially outwards from the rotor. The rotor and the rotor blades are in more detail shown in figure 3b. For heating the heated inner wall 64, the housing 48 is connected with a heating medium inlet 58 and a heating medium outlet 60. Moreover, the continuous evaporator 6 comprises at its upstream end a drive block 62.

[0057] During the operation of the plant 2, a solid starting material is continuously fed via the filling funnel 10 and a liquid starting material is continuously fed via the liquid inlet 12 into the continuous dynamic mixer 4, in which the starting materials are heated to an appropriate temperature and mixed with each other, wherein the so formed homogeneous mixture is continuously transported to and removed via the outlet into the connection line 14. From the connection line 14, the homogeneous mixture is continuously fed into the continuous evaporator 6, in which the homogeneous mixture is spread by the blades 56 in a thin layer over the heated inner wall 64 of the continuous evaporator 6, thereby evaporating the volatile components. This is in more detail schematically shown in figure 4, which does not correspond exactly to the design of the continuous evaporator 6 shown in figures 3a and 3b, but which is a simplified schematic drawing illustrating the working principle of a continuous evaporator. The blades 56 are designed with a minimum gap to prevent fouling of the heating surface of the heated inner wall 64 by the mixture, but is not in contact with the heated inner wall 64. Therefore, the blades 56 breaks the dried mixture up to powder, i.e. a bulk material.

Reference Numeral List

[0058] 

2

Plant

4

Continuous dynamic mixer

6

Continuous evaporator

8

Drive block of continuous dynamic mixer

10

Filling funnel

12

Liquid inlet

14

Connection line

16

Outlet line

18

Housing

28, 28'

Housing halves

30

Housing shell

32, 32', 32"

Housing shell part

34

Screw shaft

36

Shaft rod

38

Blade elements

40

Kneading elements / kneading bolts

42

Receptacle for kneading element

44, 44', 44"

Row of kneading elements

46, 46', 46"

Process sections

48

Housing of the evaporator

50

Inlet of the evaporator

52

Outlet of the evaporator

54

Rotor of the evaporator

56

Blades of the evaporator

58

Heating medium inlet

60

Heating medium outlet

62

Drive block of the continuous evaporator

64

Heated inner wall of the continuous evaporator

Claims

1. A continuous process for producing a bulk material from two or more different starting materials, wherein at least one of the starting materials has a vapor pressure between 0.1 to 1,000 hPa at 23°C, wherein the liquid content of the starting materials based on the sum of liquid and solid content is at least 5% by weight, wherein the process comprises the steps of i) continuously feeding the starting materials into a continuous dynamic mixer comprising at least one rotating shaft and preferably rotating screw shaft and mixing the starting materials therein, and of ii) continuously transferring the mixture obtained in step i) into a continuous evaporator and processing the mixture therein so as to obtain a bulk material having, at 23°C, a liquid content of less than 3% by weight.

2. The process in accordance with claim 1, wherein the continuous dynamic mixer is a single-screw extruder, a twin-screw extruder, a planetary extruder, a ring extruder or a continuous twin-rotor mixer.

3. The process in accordance with claim 1, wherein the continuous dynamic mixer contains one screw shaft, which comprises at least two blade elements extending radially outwards from the screw shaft, wherein the screw shaft rotates and simultaneously moves translationally back and forth in the axial direction of the continuous dynamic mixer during its operation.

4. The process in accordance with claim 3, wherein the continuous dynamic mixer comprises:

- a housing, in which a hollow interior being limited by the inner peripheral surface of the housing is designed,

- the screw shaft extending in the axial direction through the interior, which rotates during operation in the interior and simultaneously moves translationally back and forth in the axial direction, and

- kneading elements fixed in receptacles provided in the housing, wherein the kneading elements extend from the inner peripheral surface of the housing into the housing.

5. The process in accordance with any of the preceding claims, wherein the liquid content of the starting materials based on the sum of liquid and solid content is at least 6% by weight, preferably at least 8% by weight, more preferably at least 10% by weight, yet more preferably at least 15% by weight, still more preferably at least 20% by weight, still more preferably at least 25% by weight and most preferably at least 30% by weight.

6. The process in accordance with any of the preceding claims, wherein at least one of the starting materials is a liquid, a mixture of two or more liquids or a dispersion of solids in a liquid, preferably of solids in water, in an organic solvent or in an inorganic solvent, and/or, wherein at least one of the starting materials has, measured at 23°C, a dynamic viscosity of 0.01 to 100 mPa·s, preferably of 0.02 to 50 mPa·s and more preferably of 0.05 to 20 mPas.

7. The process in accordance with any of the preceding claims, wherein the starting materials are mixed in the continuous dynamic mixer at a temperature of 20 to 400°C and preferably of 50 to 300°C, wherein preferably the starting materials are mixed in the continuous dynamic mixer at a pressure of 100 kPa to 20 MPa and preferably 100 kPa to 5 MPa.

8. The process in accordance with any of the preceding claims, wherein the continuous evaporator is a thin film evaporator.

9. The process in accordance with claim 8, wherein the continuous evaporator is a horizontal thin film evaporator, which comprises a housing, in which a hollow interior being limited by the inner peripheral surface of the housing is designed, wherein the housing comprises at its opposite sides an inlet and an outlet and further comprises a heated inner wall and in its hollow interior a rotating rotor comprising blades extending radially outwards from the rotor, wherein the mixture is continuously fed through the inlet into the interior of the housing, picked up by the rotor blades and applied onto the heated inner wall wall and simultaneously conveyed towards and through the outlet.

10. The process in accordance with any of the preceding claims, wherein the bulk material obtained in the continuous evaporator has, at 23°C, a liquid content of at most 2.5%, preferably of at most 2.0%, even more preferably of at most 1.5%, yet more preferably of at most 1.0%, still more preferably of at most 0.5% and most preferably of at most 0.25% by weight.

11. Use of a bulk material obtained with the process of any of the preceding claims in the food industry, as battery mass or the chemical industry.

12. A plant for producing a bulk material from two or more different starting materials, wherein at least one of the starting materials has a vapor pressure between 0.1 to 1,000 hPa at 23°C, wherein the liquid content of the starting materials based on the sum of liquid and solid content is at least 5% by weight, comprising:

a) a continuous dynamic mixer comprising at least one inlet, an outlet and at least one rotatable shaft and preferably rotatable screw shaft and

b) a continuous evaporator comprising an inlet and an outlet, wherein the inlet of the continuous evaporator is connected with the outlet of the continuous dynamic mixer.

13. The plant in accordance with claim 12, wherein the continuous dynamic mixer contains one screw shaft, which comprises at least two blade elements extending radially outwards from the screw shaft, wherein the screw shaft rotates and simultaneously moves translationally back and forth in the axial direction of the continuous dynamic mixer during its operation, wherein the continuous dynamic mixer comprises:

- a housing, in which a hollow interior being limited by the inner peripheral surface of the housing is designed,

- the screw shaft extending in the axial direction through the interior, which rotates during operation in the interior and simultaneously moves translationally back and forth in the axial direction, and

- kneading elements fixed in receptacles provided in the housing, wherein the kneading elements extend from the inner peripheral surface of the housing into the housing.

14. The plant in accordance with claim 12 or 13, wherein the continuous evaporator is a thin film evaporator.

15. The plant in accordance with claim 14, wherein the continuous evaporator is a horizontal thin film evaporator, which comprises a housing, in which a hollow interior being limited by the inner peripheral surface of the housing is designed, wherein the housing comprises at its opposite sides an inlet and an outlet and further comprises a heated inner wall and in its hollow interior a rotating rotor comprising blades extending radially outwards from the rotor.

Drawing