Equipment and methods for separating liquid droplets from an airflow using a centrifugal demister.

Abstract

This invention relates to a centrifugal demister for separating liquid droplets from a gas stream, comprising: a housing (1) having a circular cross-section and a vertical longitudinal axis (11); an upper cover (2) defining the top of the housing (1) and having a gas outlet connection (7) for the purified gas stream in the centrifugal demister; a drip plate (8) disposed below the gas outlet connection (7); and a lower cover (10) defining the bottom of the housing (1) and having a means for separating the liquid droplets. The invention comprises a liquid outlet connector (4) for discharging liquid droplets; and an inlet (3) for feeding airflow, the inlet being tangentially connected to the housing (1); the centrifugal demister is characterized by providing at least two nozzles (9) for feeding stabilizer liquid into the interior of the separator demister, each nozzle having a nozzle outlet (15) disposed between a tangential inlet (3) and a drip plate (8) in the vertical direction, and the main injection direction (12) of the nozzles (9) being an upward direction with an interior angle of 0 to 60° relative to the vertical longitudinal axis (11). The invention also relates to a method for separating liquid droplets from the airflow in such a centrifugal demister.

Description

Technical Field

[0001] The present invention relates to a centrifugal droplet separator for separating liquid droplets from a gas flow, comprising: a housing having a circular cross-section and a vertical longitudinal axis; an upper cover defining the top of the housing and having a gas outlet port for the purified gas flow in the centrifugal droplet separator; a drip plate disposed below the gas outlet port; a lower cover defining the bottom of the housing and having a liquid outlet port for removing deposited liquid droplets; and an inlet tangentially opening into the housing to supply the gas flow.

[0002] The present invention also relates to a method for separating liquid droplets from a gas stream in such a centrifugal droplet separator. Background Technology

[0003] In methods for producing acrylates from the acid-catalyzed esterification of (meth)acrylic acid with C4 to C10 alcohols, high-boiling-point process stabilizers, such as phenothiazine (PTZ), or other liquid solutions or mixtures containing process stabilizers, are conventionally used. These process stabilizers must be separated from the acrylate vapors produced in the process to ensure product quality. Depending on the alcohol used, these acrylate processes can also be used to produce acrylates including n-butyl acrylate (nBA), 2-ethylhexyl acrylate (2-EHA), isobutyl acrylate, 2-propylheptyl acrylate, or octyl acrylate.

[0004] These methods typically use droplet separators, such as sheet separators or demisters, which are also known as separators with braided wires. However, these droplet separators are prone to contamination or polymer formation caused by liquid droplets present in the airflow.

[0005] Therefore, over time, the resulting liquid droplets can clog the pores of sheets or braided fabrics. In such cases, the plant must be shut down to allow for cleaning or replacement. For example, document DE 19604253 A1 (BASF AG) describes this type of problem, disclosing a method for producing 2-ethylhexyl acrylate (2-EHA) using a demister. As another example, document DE 10063510 A1 (BASF AG) discloses a method for producing n-butyl acrylate (nBA), which also uses a demister to separate the liquid droplets.

[0006] In this context, the components present in the liquid droplets are refined using specific methods. For example, the liquid droplets may include high-boiling-point components derived from the reactor, or tangible value products such as nBA or 2-EHA.

[0007] A known alternative to a standalone droplet separator is the rising film evaporator (Ralf Goedecke, "Grundlagen, Methodik, Technik, Praxis" [Basic Knowledge, Methods, Techniques, Practical Applications], Fluidverfahrenstechnik [Fluid Engineering], WILEY-VCH Verlag, Weinheim, 2006), in which an integrated droplet separator is located in the upper region of the rising film evaporator.

[0008] Centrifugal droplet separators do not require porous structures, such as demisters. Therefore, compared to the braided wires described above, centrifugal droplet separators are less prone to clogging by polymers and impurities. Consequently, longer operating times, lower maintenance costs, and higher productivity can be expected.

[0009] In the prior art, general separators that utilize centrifugal force to deposit solid or liquid particles are also disclosed. Document EP 2 076 335 B1 (Vortex Ecological Technologies Ltd) describes how to remove impurities from flue gas. For example, document DE 2137128 A1 (Siemens AG) discloses another separator in which solid or liquid particles are removed from the crude gas.

[0010] However, this type of separator does not separate liquid droplets, or is only used for processing crude gaseous products. Furthermore, these separators are not used in chemical processes that aim to produce polymers as the target product.

[0011] Generally, centrifugal droplet separators offer separation performance comparable to that of braided yarn. Small droplets are largely separated from the vapor within the separator.

[0012] A drawback of centrifugal droplet separators is that their use in chemical processes often leads to polymer formation on the separator walls. Therefore, frequent cleaning is required. Typically, a spray device is used for this purpose. This spray device wets the walls with liquid, thus ensuring the centrifugal droplet separator remains functional for a certain period.

[0013] Public text EP 2512683 B1 (BASF SE) teaches the injection of cleaning liquid into a centrifugal droplet separator, which describes the injection in both tangential and circumferential directions relative to the wall of the gas discharge port.

[0014] The drawback of this method is that, in many applications or under certain operating conditions, cleaning cannot prevent polymer formation on the walls or internal components of the centrifugal droplet separator. The resulting deposits from polymer formation can impair the function of the centrifugal droplet separator.

[0015] Therefore, the centrifugal droplet separator used in this method must also be maintained and cleaned regularly. Summary of the Invention

[0016] The problem to be solved is to provide a centrifugal droplet separator for chemical methods in which polymer formation from liquid droplets does not occur on its walls and the walls of its internal components during operation, or at least significantly reduces polymer formation during operation, thereby achieving fewer maintenance intervals. In this case, small liquid droplets should be effectively separated from the gas stream even during operation.

[0017] Another problem to be solved is to provide a centrifugal droplet separator that can be used in chemical processes for the preparation of, in particular, n-butyl acrylate (nBA) or 2-ethylhexyl acrylate (2-EHA), and is particularly well suited for this purpose.

[0018] As disclosed, these problems have been solved according to the present invention.

[0019] The centrifugal droplet separator of the present invention for separating liquid droplets from a gas flow comprises: a housing having a circular cross-section and a vertical longitudinal axis; an upper cover defining the top of the housing and having a gas outlet port for the purified gas flow in the centrifugal droplet separator; a drip plate disposed below the gas outlet port; a lower cover defining the bottom of the housing and having a liquid outlet port for removing deposited liquid droplets; and an inlet tangentially opening into the housing for supplying the gas flow. According to the invention, at least two nozzles are provided for feeding stabilizer liquid into the interior of the centrifugal droplet separator, each nozzle having its nozzle outlet above the tangential inlet and below the drip plate, and the main jetting direction of each individual nozzle being an upward direction at an interior angle ranging from 0° to 60° relative to the vertical longitudinal axis, thus ensuring complete wetting of all walls within the interior of the centrifugal droplet separator.

[0020] Due to gravity, the stabilizer liquid, sprayed in the direction towards the upper cover, flows downwards, thereby also wetting other surface areas of the centrifugal droplet separator. The surfaces of the internal components within the jet flow range of the nozzle are also correspondingly wetted. Therefore, the arrangement of the present invention effectively prevents the formation of polymers on the surfaces of the centrifugal droplet separator and its internal components.

[0021] The nozzles of this invention are positioned below the drip plate, which allows the stabilizer liquid to thoroughly wet all walls of the housing and internal components of the centrifugal droplet separator. Even in dead zones known to those skilled in the art as reflux areas, the walls can be wetted, for example, in the edge regions of the upper centrifugal droplet separator area. The outer surfaces of the internal components (e.g., the drip plate) in the centrifugal droplet separator are also completely and sufficiently wetted.

[0022] Surprisingly, the airflow was not significantly disturbed by the jet in the opposite direction to gravity, so that the method of the present invention did not significantly reduce the separation performance of the centrifugal droplet separator.

[0023] In a preferred configuration of the centrifugal droplet separator, the length ratio between the axial distance of the nozzle outlet of the uppermost nozzle to the droplet plate and the height of the centrifugal droplet separator is in the range of 0.03 to 0.15. Therefore, considering that the usual height of the centrifugal droplet separator is in the range of 1 to 10 m, a suitable distance from the droplet plate is assumed, which means that a conventional nozzle can be used to ensure that the droplet plate is adequately wetted by the stabilizer liquid.

[0024] In another preferred configuration of the centrifugal droplet separator, the length ratio between the radial distance of the nozzle outlet to the inner surface of the housing and the height of the centrifugal droplet separator is no greater than 0.06. This ensures the injection of stabilizer liquid close to the wall, meaning the impact of the stabilizer liquid on the housing surface is at a sufficiently obtuse angle, thus only a small amount of stabilizer liquid splashes back from the housing surface.

[0025] In a preferred configuration of the centrifugal droplet separator, the inner angle of each nozzle is in the range of 0 to 50°, more preferably in the range of 0 to 40°, and most preferably in the range of 0 to 30°.

[0026] In another preferred configuration of the centrifugal droplet separator, the respective main jet direction of each nozzle is tilted away from the housing.

[0027] In another preferred configuration of the centrifugal droplet separator, an open top cone for stabilizing the airflow is mounted on a baffle in the liquid discharge port.

[0028] In another preferred configuration of the centrifugal droplet separator, the gas outlet port is at least partially above the housing, located on this side of the outer surface of the housing. Therefore, further reduced polymer formation or no polymer formation can occur at the gas outlet port, as this provides a smaller dead zone.

[0029] In a preferred configuration, the lower half of the centrifugal droplet separator has a temperature control device on the outer surface of the housing. This temperature control device is preferably a heater. In suitable chemical methods, heating of the housing can further reduce polymer formation.

[0030] In a preferred configuration of the centrifugal droplet separator, the nozzle is secured within the separator by at least one insertion element, each insertion element having a spray gun and at least one retaining element for at least one nozzle. This insertion element allows the nozzle to be introduced into the separator and can also be removed if necessary.

[0031] In another configuration of the centrifugal droplet separator, in each case at least one nozzle passes through an opening element in the housing, preferably through a port, wherein the opening element is sealed by an openable retaining element, preferably a flange. This port and flange can be readily and cost-effectively obtained.

[0032] In another configuration of the centrifugal droplet separator, at least one sealing element, preferably a rubber ring, is provided to seal the opening element. This reliably prevents leakage of airflow through the elastic element.

[0033] In another configuration of the centrifugal droplet separator, the lower and upper covers are achieved by installing a flange at each end of the centrifugal droplet separator. This method utilizes standard and readily available components.

[0034] The method of separating liquid droplets from a gas flow according to the present invention is carried out in a centrifugal droplet separator, the centrifugal droplet separator comprising: a housing having a circular cross-section and a vertical longitudinal axis; an upper cover defining the top of the housing and having a gas outlet port for the purified gas flow in the centrifugal droplet separator; a drip plate disposed below the gas outlet port; a lower cover defining the bottom of the housing and having a liquid outlet port for removing deposited liquid droplets; and an inlet tangentially opening into the housing through which the gas flow is fed. According to the invention, a stabilizer liquid is fed into the interior of the centrifugal droplet separator through at least two nozzles, each nozzle having its nozzle outlet above the tangential inlet and below the drip plate, the main injection direction of each nozzle being an upward direction with an interior angle ranging from 0° to 60° relative to the vertical longitudinal axis, resulting in all walls inside the centrifugal droplet separator being completely wetted with the stabilizer liquid.

[0035] Generally, stabilizers are substances that typically prevent the polymerization of chemical compounds. In particular, suitable stabilizers reduce the polymerization of chemical compounds in the 2-EHA or nBA processes.

[0036] In a preferred embodiment of the method, the stabilizer liquid is continuously fed into a centrifugal droplet separator. This ensures nearly uniform wetting of the wall.

[0037] In a preferred configuration of the method of the present invention, the stabilizer liquid comprises 4-methoxyphenol (MeHQ). In this case, polymer formation on the wall is very effectively prevented without any adverse effect on the subsequent quality of the target product. This is particularly true in the case of substances containing acrylates.

[0038] Other preferred stabilizers that may be present in the stabilizer liquid are, for example, 2,4-dimethyl-6-tert-butylphenol (Topanol A), hydroquinone, and / or butylated hydroxytoluene (2,6-di-tert-butyl-p-cresol). In principle, any amount of stabilizer may be present in the stabilizer liquid as a mixture.

[0039] The stabilizer liquid preferably contains not only the stabilizer but also the target product obtained from the method. In this document, the target product refers to the gas stream discharged from the centrifugal droplet separator. In the case of this stabilizer liquid, no impurities are added to the method. The target product may also suitably serve as a solvent and / or diluent for the stabilizer.

[0040] In a preferred configuration of the method, a substream of the target product is diverted, collected in a batch container, mixed with a stabilizer therein, and then fed to a nozzle to provide the stabilizer liquid to the nozzle.

[0041] In another preferred configuration of the method, the supplied gas flow contains droplets of substances that, due to their chemical properties, tend to polymerize on the walls of the centrifugal droplet separator. Complete and adequate wetting of the centrifugal droplet separator housing and its internal components prevents polymer formation on the walls, thereby extending the maintenance intervals of the centrifugal droplet separator.

[0042] In a particularly preferred configuration, the gas stream supplied to the centrifugal droplet separator comprises acrylates produced by the acid-catalyzed esterification of (meth)acrylic acid with C4 to C10 alcohols, particularly n-butyl acrylate produced by the esterification of acrylic acid with n-butanol, or 2-ethylhexyl acrylate produced by the esterification of acrylic acid with 2-ethylhexanol. In these methods, small amounts of unwanted components, such as phenothiazine (PTZ), are typically present due to the process. These unwanted components are primarily present in the liquid droplets of the gas stream and should be deposited in the centrifugal droplet separator to maintain the quality of the target product. Furthermore, the liquid droplets contain other components, preferably particularly from the target product.

[0043] In a preferred configuration of the method, the centrifugal droplet separator is designed such that the length ratio between the axial distance between the nozzle outlet of the uppermost nozzle and the droplet plate and the height of the centrifugal droplet separator is in the range of 0.03 to 0.15.

[0044] In a preferred configuration of the method, the centrifugal droplet separator is designed such that the length ratio between the radial distance between the nozzle outlet and the inner surface of the housing and the height of the centrifugal droplet separator is no greater than 0.06.

[0045] In a preferred configuration of the method, the centrifugal droplet separator is designed such that the inner angle of each nozzle is in the range of 0 to 50°, preferably in the range of 0 to 40°, and more preferably in the range of 0 to 30°.

[0046] In a preferred configuration of the method, the centrifugal droplet separator is designed such that an open top cone for stabilizing the airflow is mounted on a baffle in the liquid discharge port.

[0047] In a preferred configuration of the method, the centrifugal droplet separator is designed such that the gas discharge port in the centrifugal droplet separator is at least partially above the housing, on this side of the outer surface of the housing.

[0048] In a preferred configuration of the method, the centrifugal droplet separator is designed such that the lower half of the centrifugal droplet separator has a temperature control unit, particularly a heater, on the outer side of the housing.

[0049] In a preferred configuration of the method, the centrifugal droplet separator is designed such that the nozzle is secured in the centrifugal droplet separator by at least one insertion element, wherein each insertion element has a spray gun and at least one retaining element for at least one nozzle.

[0050] In a preferred configuration of the method, the centrifugal droplet separator is designed such that in each case at least one nozzle passes through an opening element in the housing, preferably through a port, wherein the opening element is sealed by an openable retaining element, preferably a flange. Attached Figure Description

[0051] The invention will now be described in detail with reference to the accompanying drawings. The drawings should be considered as schematic diagrams. They do not constitute a limitation on the invention, such as regarding specific dimensions or design variations. The drawings show:

[0052] Figure 1 Examples of embodiments of the centrifugal droplet separator of the present invention in longitudinal and transverse sections.

[0053] Figure 2 The main injection direction of the nozzle is perpendicular to the nozzle outlet.

[0054] Figure 3 : For the cross-sectional plane determined by the nozzle.

[0055] Figure 4 The interior angle between the main jet direction of the nozzle and the opposite gravity vector. In this case, the nozzle is tilted away from the housing surface.

[0056] Figure 5 The interior angle between the main jet direction of the nozzle and the opposite gravity vector. In this case, the nozzle is tilted towards the housing surface.

[0057] Figure 6 Insertion element used for each nozzle.

[0058] Figure 7 : Droplet separator with demister from existing technology.

[0059] List of reference numbers used:

[0060] 1. Shell

[0061] 2. Top Cover

[0062] 3 entrances

[0063] 4 Liquid discharge port

[0064] 5 Open-top cone

[0065] 6 baffles

[0066] 7 Gas exhaust port

[0067] 8 drip plates

[0068] 9 nozzles

[0069] 10 Lower Cover

[0070] 11. Vertical longitudinal axis

[0071] 12. Normal vector of the main injection direction or cross-section

[0072] 13. Gravity direction, gravity vector

[0073] 14 Vertical cross-section plane

[0074] 15. The nozzle outlet or cross-section of the nozzle from which liquid flows out.

[0075] 16 interior angles

[0076] 17 Inserting elements

[0077] 18 spray guns

[0078] 19 Holding element

[0079] 20 Opening elements

[0080] 23 Demister

[0081] 25. The opposite direction of gravity, the opposite direction of the gravity vector.

[0082] 26. Height of centrifugal droplet separator

[0083] 27. Diameter of centrifugal droplet separator

[0084] 28 Spraying equipment Detailed Implementation

[0085] Figure 1 This is a schematic diagram of one embodiment of the centrifugal droplet separator of the present invention. The left-hand side illustrates a longitudinal section of the centrifugal droplet separator along its vertical longitudinal axis. The right-hand side shows a cross-section perpendicular to the direction of gravity 13, from which the arrangement of the nozzle 9 relative to the housing 1 becomes apparent.

[0086] The centrifugal droplet separator is defined by its housing 1, its upper cover 2, its drop plate 8, its lower cover 10, and its dimensions, such as height 26 and diameter 27. Its housing 1 has a circular cross-section, its upper cover 2 forms a top boundary and has a gas discharge port 7 for the purified airflow in the centrifugal droplet separator, its drop plate 8 is arranged below the gas discharge port and is designed to capture relatively small liquid droplets, and its lower cover 10 defines the bottom of the housing 1 and has a liquid discharge port 4 for removing the separated liquid droplets.

[0087] A gas stream carrying liquid droplets is supplied to the centrifugal droplet separator through tangential inlet 3. This causes vortices to form along the housing 1. Under the influence of gravity 13, the liquid droplets move downwards along the direction of the liquid discharge port 4. To separate the droplets more efficiently, an open top cone 5 with baffles 6 is installed. The purified gas stream exits the separator through the gas discharge port 7.

[0088] In the illustrated embodiment, the stabilizer liquid is injected into the interior of the centrifugal droplet separator via six nozzles 9.

[0089] In the centrifugal droplet separator, the nozzle outlet of each nozzle 9 is above the tangential inlet 3 and below the droplet plate 8.

[0090] The main jet direction of each individual nozzle 9 is an upward direction with an interior angle 16 within the range of 0° to 60° relative to the vertical longitudinal axis, which means that all the walls inside the centrifugal droplet separator can be completely wetted.

[0091] Figure 2The main injection direction 12 of nozzle 9 is shown, which is defined as the normal vector of the cross section, i.e., nozzle outlet 15. Liquid is ejected through nozzle outlet 15 of nozzle 9.

[0092] Figure 3 The vertical cross-sectional plane 14 of each individual nozzle 9 is shown, the cross-sectional plane including the vertical longitudinal axis 11 of the housing 1 and the cross-section of the nozzle 9 (according to...). Figure 2 The geometric centroid of the nozzle outlet 15 is shown here. The gravity vector 13, the opposite direction of the gravity vector 25, and the main injection direction 12 of the nozzle 9, i.e., the normal vector, are also shown here.

[0093] Figure 4 The diagram shows an interior angle 16 that can be defined in the vertical cross-sectional plane 14 along the vertical longitudinal axis 11 between the vector (i.e., the normal vector) in the opposite direction 25 of the gravity vector and the vector (i.e., the vector of the main injection direction 12 of each nozzle 9). These two vectors are projected onto the vertical cross-sectional plane 14. In this case, the main injection direction 12 is inclined away from the housing surface 1.

[0094] Figure 5 This diagram illustrates a case in the vertical cross-sectional plane 14 along the vertical longitudinal axis 11, in which the main injection direction 12 (i.e., the normal vector) is inclined toward the housing surface 1. The interior angle 16 is defined as a vector between the opposite direction 25 of the gravity vector and the main injection direction 12 of each nozzle 9. These two vectors are projected onto the vertical cross-sectional plane 14.

[0095] Figure 6 A schematic diagram of the insertion element 17 for the nozzle 9 is shown. The nozzle 9 is here fixed to the spray gun 18. The spray gun 18 passes through an opening element 20 in the housing 1, wherein the opening element 20 is sealed by an openable retaining element 19. In this embodiment, the opening element is a port, and the openable retaining element 19 is a flange.

[0096] Figure 7 A droplet separator with a demister, from the prior art, is shown. An airflow carrying liquid droplets is fed into the separator through inlet 3 in housing 1. Under gravity, the liquid droplets move downwards along the direction of liquid outlet port 4 arranged in the lower shroud 10. The purified airflow exits the separator through gas outlet port 7, which is arranged on the upper shroud 2. Demister 23 ensures that relatively small liquid droplets are captured. A spray device 28 wets the demister to prevent rapid clogging due to droplet aggregation.

[0097] Example:

[0098] Comparative Example 1 of nBA Device:

[0099] n-Butyl acrylate (nBA) can be produced on an industrial scale via acid-catalyzed esterification of (meth)acrylic acid with n-butanol. A corresponding method is disclosed in document DE 10063510 A1 (BASF AG). The method involves separating liquid droplets from a gas stream, wherein the liquid droplets contain the phenothiazine (PTZ) component to be separated.

[0100] In Comparative Example 1 according to the prior art, the droplets are placed according to... Figure 7 The droplets are separated in a continuously operating droplet separator equipped with a demister 23.

[0101] The droplet separator has a height of 4 m and a diameter of 1.0 m. Neither the gas outlet port 7 nor the liquid outlet port 4 was considered when determining the height. The demister has a height of 1470 mm. The demister used is a "Euroform DV270" demister manufactured by Munters Euroform GmbH (Philipsstrasse 8, 52068 Aachen).

[0102] The product is fed at a rate of 10,000 kg / h. The pressure in the droplet separator is set to 420 mbar, which is higher than the standard pressure. The temperature is 118°C.

[0103] The composition of the product fed through inlet 3 of the droplet separator is as follows:

[0104] n-Butanol 0.04% by weight

[0105] 0.07% by weight of n-butyl acetate

[0106] 0.10% by weight of di-n-butyl ether

[0107] Isobutyl acrylate 0.07% by weight

[0108] 99.68% by weight of n-butyl acrylate

[0109] 10 ppm by weight of phenothiazine

[0110] 4-Methoxyphenol 0 ppm by weight

[0111] Nitrogen 0.04% by weight

[0112] A liquid with a flow rate of 400 kg / h is sprayed at 34°C onto the top side of the demister 23 via a spraying device 28. The liquid has the following composition:

[0113] n-Butanol 0.04% by weight

[0114] 0.07% by weight of n-butyl acetate

[0115] 0.10% by weight of di-n-butyl ether

[0116] Isobutyl acrylate 0.07% by weight

[0117] 99.72% by weight of n-butyl acrylate

[0118] Phenothiazine < 1 ppm by weight

[0119] 4-Methoxyphenol 15 ppm by weight

[0120] The 9657 kg / h gas flow discharged from gas outlet port 7 has the following composition:

[0121] n-Butanol 0.04% by weight

[0122] 0.07% by weight of n-butyl acetate

[0123] 0.10% by weight of di-n-butyl ether

[0124] Isobutyl acrylate 0.07% by weight

[0125] 99.68% by weight of n-butyl acrylate

[0126] phenothiazine 2 ppm by weight

[0127] 4-Methoxyphenol 1 ppm by weight

[0128] Nitrogen 0.04% by weight

[0129] The 743 kg / h liquid discharged from liquid discharge port 4 has the following composition:

[0130] n-Butanol 0.04% by weight

[0131] 0.07% by weight of n-butyl acetate

[0132] 0.10% by weight of di-n-butyl ether

[0133] Isobutyl acrylate 0.07% by weight

[0134] 99.71% by weight of n-butyl acrylate

[0135] Phenothiazine 110 ppm by weight

[0136] 4-Methoxyphenol 1 ppm by weight

[0137] After 120 days of operation, the droplet separator needed to be cleaned due to fouling. It was discovered that polymer had formed, contaminating the demister 23 and the inner walls of the droplet separator, necessitating the shutdown of the entire unit.

[0138] Example 1 of nBA device:

[0139] For Embodiment 1 of the present invention, the droplet separator of Comparative Embodiment 1 is replaced with... Figure 1 The present invention relates to a centrifugal droplet separator.

[0140] The dimensions of the centrifugal separator are:

[0141] - Diameter 27: 1500 mm

[0142] - Height 26: 3278 mm

[0143] - Height of the nozzle plane based on the lower shroud: 2039 mm

[0144] - Gas inlet 3: DN500

[0145] - Gas exhaust port 7: DN600

[0146] - Liquid discharge port 4: DN150

[0147] - Distance between nozzle and drip plate 8: 500 mm

[0148] - Distance between the external nozzle and the wall of the centrifugal droplet separator: 7.5 mm

[0149] - Top cone 5: Diameter: 1050 mm, Height: 300 mm

[0150] - Drip plate 8: Diameter: 1000 mm, Height: 300 mm

[0151] When determining the height, neither the gas discharge port 7 nor the liquid discharge port 4 are considered.

[0152] More specifically, six Lechler 490.404.1Y.CA.00.0 full-cone nozzles are installed in the centrifugal droplet separator. The inner angle of the main jet direction is 15° and it is tilted inward, i.e., in the direction away from the housing 1.

[0153] The stabilizer liquid is continuously metered and added through upward-facing nozzles. The total volumetric flow rate through all nozzles 9 is 200 to 600 l / h.

[0154] In this embodiment, the gas exhaust port 7 is located above the housing 1 on the outer surface of the housing 1, resulting in the centrifugal droplet separator providing less dead zone.

[0155] The feed rate of the gas stream carrying liquid droplets is 10,000 kg / h. The pressure in the centrifugal droplet separator is set to 420 mbar, which is higher than the standard pressure. The temperature is 118°C.

[0156] The composition of the product fed through inlet 3 of the centrifugal droplet separator is as follows:

[0157] n-Butanol 0.04% by weight

[0158] 0.07% by weight of n-butyl acetate

[0159] 0.10% by weight of di-n-butyl ether

[0160] Isobutyl acrylate 0.07% by weight

[0161] 99.68% by weight of n-butyl acrylate

[0162] 10 ppm by weight of phenothiazine

[0163] 4-Methoxyphenol 0 ppm by weight

[0164] Nitrogen 0.04% by weight

[0165] A liquid stream of stabilizer liquid with a total volume of 400 kg / h is sprayed onto the wall of a centrifugal droplet separator through nozzle 9 at a temperature of 34°C. The stabilizer liquid has the following composition:

[0166] n-Butanol 0.04% by weight

[0167] 0.07% by weight of n-butyl acetate

[0168] 0.10% by weight of di-n-butyl ether

[0169] Isobutyl acrylate 0.07% by weight

[0170] 99.72% by weight of n-butyl acrylate

[0171] Phenothiazine < 1 ppm by weight

[0172] 4-Methoxyphenol 15 ppm by weight

[0173] The 9657 kg / h gas flow discharged from gas outlet port 7 has the following composition:

[0174] n-Butanol 0.04% by weight

[0175] 0.07% by weight of n-butyl acetate

[0176] 0.10% by weight of di-n-butyl ether

[0177] Isobutyl acrylate 0.07% by weight

[0178] 99.68% by weight of n-butyl acrylate

[0179] Phenothiazine < 1 ppm by weight

[0180] 4-Methoxyphenol 1 ppm by weight

[0181] Nitrogen 0.04% by weight

[0182] The 743 kg / h liquid discharged from liquid discharge port 4 has the following composition:

[0183] n-Butanol 0.04% by weight

[0184] 0.07% by weight of n-butyl acetate

[0185] 0.10% by weight of di-n-butyl ether

[0186] Isobutyl acrylate 0.07% by weight

[0187] 99.71% by weight of n-butyl acrylate

[0188] Phenothiazine 130 ppm by weight

[0189] 4-Methoxyphenol 1 ppm by weight

[0190] In this embodiment, it is possible to achieve an operating time of over 180 days without downtime due to contamination in the centrifugal droplet separator. Even after 180 days of operation, no irreversible polymer coating or deposition on the centrifugal droplet separator was observed.

[0191] Furthermore, the centrifugal droplet separator, with its highly efficient deposition, achieved a reduction in the mass proportion of phenothiazine in the target product to less than 1 ppm by weight. The target product here refers to the gas stream exiting the centrifugal droplet separator. In the droplet separator with a demister according to Comparative Example 1, phenothiazine was reduced to only 2 ppm by weight.

[0192] Comparative Example 2 of 2-EHA Equipment:

[0193] 2-Ethylhexyl acrylate (2-EHA) can be produced on an industrial scale via acid-catalyzed esterification of (meth)acrylic acid with 2-ethylhexanol. A corresponding method is disclosed in document DE 19604253 A1 (BASF AG). The method involves separating liquid droplets from a gas stream, wherein the liquid droplets contain the phenothiazine (PTZ) component to be separated.

[0194] In Comparative Example 2 according to the prior art, the droplets are made to follow the... Figure 7 The droplets are separated in a continuously operating droplet separator equipped with a demister 23.

[0195] The droplet separator has a height of 4 m and a diameter of 1.2 m. The demister 23 has a height of 790 mm. The demister used is a "Euroform DV270" demister manufactured by Munters Euroform GmbH (Philipsstrasse 8, 52068 Aachen).

[0196] The product is fed at a rate of 10,000 kg / h. The pressure in the droplet separator is set to 140 mbar, which is higher than the standard pressure, and the temperature is 148°C.

[0197] The composition of the product fed through inlet 3 of the droplet separator is as follows:

[0198] 0.08% by weight of 2-ethylhexanol

[0199] 0.15% by weight of n-ethylhexyl acetate

[0200] diethylhexyl ether 0.01% by weight

[0201] 2-Ethylhexyl acrylate 99.71% by weight

[0202] 0.03% by weight of 2-(2-ethylhexyloxy)propionic acid ester

[0203] 10 ppm by weight of phenothiazine

[0204] 4-Methoxyphenol 0 ppm by weight

[0205] Nitrogen 0.02% by weight

[0206] A liquid stream of 490 kg / h is sprayed at 34°C onto the top side of the demister 23 via a spraying device 28. The liquid has the following composition:

[0207] 0.08% by weight of 2-ethylhexanol

[0208] 0.15% by weight of n-ethylhexyl acetate

[0209] diethylhexyl ether 0.01% by weight

[0210] 2-Ethylhexyl acrylate 99.73% by weight

[0211] 0.03% by weight of 2-(2-ethylhexyloxy)propionic acid ester

[0212] Phenothiazine < 1 ppm by weight

[0213] 4-Methoxyphenol 15 ppm by weight

[0214] The 9623 kg / h gas flow discharged from gas outlet port 7 has the following composition:

[0215] 0.08% by weight of 2-ethylhexanol

[0216] 0.15% by weight of n-ethylhexyl acetate

[0217] diethylhexyl ether 0.01% by weight

[0218] 2-Ethylhexyl acrylate 99.72% by weight

[0219] 0.02% by weight of 2-(2-ethylhexyloxy)propionic acid ester

[0220] phenothiazine 4 ppm by weight

[0221] 4-Methoxyphenol 1 ppm by weight

[0222] Nitrogen, 0.02% by weight

[0223] The 867 kg / h liquid discharged from liquid discharge port 4 has the following composition:

[0224] 0.03% by weight of 2-ethylhexanol

[0225] 0.09% by weight of ethylhexyl acetate

[0226] diethylhexyl ether 0.01% by weight

[0227] 2-Ethylhexyl acrylate 99.70% by weight

[0228] 0.16% by weight of 2-(2-ethylhexyloxy)propionic acid ester

[0229] Phenothiazine 70 ppm by weight

[0230] 4-Methoxyphenol 10 ppm by weight

[0231] After 80 days of operation, the droplet separator needed to be cleaned due to fouling. It was discovered that polymer had formed, contaminating the demister 23 and the inner walls of the droplet separator, necessitating the shutdown of the entire unit.

[0232] Example 2 of 2-EHA equipment:

[0233] For Embodiment 2 of the present invention, the droplet separator of Comparative Embodiment 2 is replaced with... Figure 1The present invention relates to a centrifugal droplet separator.

[0234] The dimensions of the centrifugal separator are:

[0235] - Diameter 27: 1800 mm

[0236] - Height 26: 3700 mm

[0237] - Height of the nozzle plane based on the lower shroud: 2370 mm

[0238] - Gas inlet 3: DN600

[0239] - Gas exhaust port 7: DN600

[0240] - Liquid discharge port (4): DN150

[0241] - Distance between nozzle and drip plate 8: 500 mm

[0242] - Distance between the external nozzle and the wall of the centrifugal droplet separator: 7.5 mm

[0243] - Top cone 5: Diameter: 1260 mm, Height: 360 mm

[0244] - Drip plate 8: Diameter: 1200 mm, Height: 400 mm

[0245] When determining the height, neither the gas discharge port 7 nor the liquid discharge port 4 are considered.

[0246] More specifically, the centrifugal droplet separator contains six nozzles. These nozzles are manufactured by Lechler. The nozzles used here are 490.404.1Y.CA.00.0 full-cone nozzles. The inner angle of the main jet direction is 15°, and it is inclined inward, i.e., in the direction away from the housing 1.

[0247] In this embodiment, the gas exhaust port 7 is located above the housing 1 on the outer surface of the housing 1, resulting in the centrifugal droplet separator providing less dead zone.

[0248] The feed rate of the gas stream carrying liquid droplets is 10,000 kg / h. The pressure in the centrifugal droplet separator is set to 140 mbar, which is higher than the standard pressure. The temperature is 148°C.

[0249] The composition of the product fed through inlet 3 of the centrifugal droplet separator is as follows:

[0250] 0.08% by weight of 2-ethylhexanol

[0251] 0.15% by weight of n-ethylhexyl acetate

[0252] diethylhexyl ether 0.01% by weight

[0253] 2-Ethylhexyl acrylate 99.71% by weight

[0254] 0.03% by weight of 2-(2-ethylhexyloxy)propionic acid ester

[0255] 10 ppm by weight of phenothiazine

[0256] 4-Methoxyphenol 0 ppm by weight

[0257] Nitrogen 0.02% by weight

[0258] A liquid stream of stabilizer liquid at a rate of 490 kg / h is sprayed onto the wall of a centrifugal droplet separator through nozzle 9 at a temperature of 34°C. The stabilizer liquid has the following composition:

[0259] 0.08% by weight of 2-ethylhexanol

[0260] 0.15% by weight of n-ethylhexyl acetate

[0261] diethylhexyl ether 0.01% by weight

[0262] 2-Ethylhexyl acrylate 99.73% by weight

[0263] 0.03% by weight of 2-(2-ethylhexyloxy)propionic acid ester

[0264] Phenothiazine < 1 ppm by weight

[0265] 4-Methoxyphenol 15 ppm by weight

[0266] The 9623 kg / h gas flow discharged from gas outlet port 7 has the following composition:

[0267] 0.08% by weight of 2-ethylhexanol

[0268] 0.15% by weight of n-ethylhexyl acetate

[0269] diethylhexyl ether 0.01% by weight

[0270] 2-Ethylhexyl acrylate 99.72% by weight

[0271] 0.02% by weight of 2-(2-ethylhexyloxy)propionic acid ester

[0272] Phenothiazine < 2 ppm by weight

[0273] 4-Methoxyphenol 1 ppm by weight

[0274] Nitrogen 0.02% by weight

[0275] The 867 kg / h liquid discharged from liquid discharge port 4 has the following composition:

[0276] 0.03% by weight of 2-ethylhexanol

[0277] 0.09% by weight of ethylhexyl acetate

[0278] diethylhexyl ether 0.01% by weight

[0279] 2-Ethylhexyl acrylate 99.70% by weight

[0280] 0.16% by weight of 2-(2-ethylhexyloxy)propionic acid ester

[0281] 100 ppm by weight of phenothiazine

[0282] 4-Methoxyphenol 10 ppm by weight

[0283] In this embodiment, it is possible to achieve an operating time of over 150 days without downtime due to contamination in the centrifugal droplet separator. Even after 150 days of operation, no irreversible polymer coating or deposition on the centrifugal droplet separator was observed.

[0284] Furthermore, the centrifugal droplet separator, with its ample deposition, achieved a reduction in the mass proportion of phenothiazine in the target product to less than 2 ppm by weight. The target product here refers to the gas stream exiting the centrifugal droplet separator. In a droplet separator with a demister (Comparative Example 2), phenothiazine was reduced to only 4 ppm by weight.

Claims

1. A centrifugal droplet separator for separating liquid droplets from a gas stream, comprising: The housing (1) has a circular cross-section and a vertical longitudinal axis (11). The upper cover (2) defines the top of the housing (1) and has a gas discharge port (7) for the gas stream purified in the centrifugal droplet separator. A drip plate (8) is arranged below the gas exhaust port (7). The lower cover (10) defines the bottom of the housing (1) and has a liquid discharge port (4) for removing deposited liquid droplets. Inlet (3), which is tangentially connected to the housing (1) to supply the airflow, It has at least two nozzles (9) for feeding stabilizer liquid into the interior of the centrifugal droplet separator. In the centrifugal droplet separator, the corresponding nozzle outlet (15) of the nozzle (9) is above the tangential inlet (3) and below the droplet plate (8). The main jet direction (12) of each individual nozzle (9) is an upward direction of the inner angle (16) in the range of 0 to 60° relative to the vertical longitudinal axis (11), thereby enabling all the walls inside the centrifugal droplet separator to be completely wetted.

2. The centrifugal droplet separator according to claim 1, wherein the length ratio between the axial distance between the nozzle outlet (15) of the uppermost nozzle and the drop plate (8) and the height (26) of the centrifugal droplet separator is in the range of 0.03 to 0.

15.

3. The centrifugal droplet separator according to claim 1 or 2, wherein the length ratio between the radial distance between the nozzle outlet (15) and the inner surface of the housing and the height (26) of the centrifugal droplet separator is not greater than 0.

06.

4. The centrifugal droplet separator according to claim 1 or 2, wherein the corresponding inner angle (16) of the nozzle (9) is in the range of 0 to 50°.

5. The centrifugal droplet separator according to claim 1 or 2, wherein the corresponding inner angle (16) of the nozzle (9) is in the range of 0 to 40°.

6. The centrifugal droplet separator according to claim 1 or 2, wherein the corresponding inner angle (16) of the nozzle (9) is in the range of 0 to 30°.

7. The centrifugal droplet separator according to claim 1 or 2, wherein an open top cone (5) for stabilizing the airflow is mounted on a baffle (6) of the liquid discharge port (4).

8. The centrifugal droplet separator according to claim 1 or 2, wherein the gas discharge port (7) in the centrifugal droplet separator is at least partially above the housing (1), located on this side of the outer surface of the housing (1).

9. The centrifugal droplet separator according to claim 1 or 2, wherein the lower half of the centrifugal droplet separator has a temperature control unit on the outer surface of the housing.

10. The centrifugal droplet separator according to claim 1 or 2, wherein the lower half of the centrifugal droplet separator has a heater on the outer side of the housing.

11. The centrifugal droplet separator according to claim 1 or 2, wherein the nozzle (9) is fixed in the centrifugal droplet separator by at least one insertion element (17), wherein each insertion element (17) has a spray gun (18) and at least one retaining element (19) for at least one nozzle (9).

12. The centrifugal droplet separator according to claim 1 or 2, wherein in each case at least one nozzle (9) passes through an opening element (20) in the housing (1), wherein the opening element is sealed by an openable retaining element (19).

13. The centrifugal droplet separator according to claim 12, wherein in each case at least one nozzle (9) passes through the port.

14. The centrifugal droplet separator according to claim 12, wherein the opening element is flange-sealed.

15. A method of separating liquid droplets from a gas stream in a centrifugal droplet separator, the centrifugal droplet separator comprising: The housing (1) has a circular cross-section and a vertical longitudinal axis (11). Upper cover (2), the upper cover defining the top of the housing (1) and having a gas outlet port (7) for the gas stream purified in the centrifugal droplet separator; drip plate (8), the drip plate being arranged below the gas outlet port (7); A lower cover (10) defines the bottom of the housing (1) and has a liquid discharge port (4) for removing deposited liquid droplets; and an inlet (3) tangentially opens into the housing (1) through which the airflow is fed. The stabilizer liquid is fed into the interior of the centrifugal droplet separator through at least two nozzles (9), with the respective nozzle outlets (15) of the nozzles (9) in the centrifugal droplet separator above the tangential inlet (3) and below the droplet plate (8). The respective main injection direction (12) of the nozzles (9) is an upward direction of the interior angle (16) in the range of 0 to 60° relative to the vertical longitudinal axis (11), thereby completely wetting all the walls inside the centrifugal droplet separator with the stabilizer liquid.

16. The method of claim 15, wherein the stabilizer liquid is continuously fed to the centrifugal droplet separator.

17. The method of claim 15 or 16, wherein the stabilizer liquid comprises 4-methoxyphenol (MeHQ).

18. The method according to claim 15 or 16, wherein the gas flow fed to the centrifugal droplet separator comprises droplets of a substance that, due to its chemical properties, has a tendency to aggregate on the wall of the centrifugal droplet separator.

19. The method of claim 18, wherein the gas flow fed to the centrifugal droplet separator comprises acrylates generated by acid-catalyzed esterification of (meth)acrylic acid with C4 to C10 alcohols.

20. The method of claim 18, wherein the gas flow fed to the centrifugal droplet separator comprises n-butyl acrylate or 2-ethylhexyl acrylate.

Images