Spray dryer system and method

Abstract

This invention discloses a spray drying system for drying a liquid into a powder, comprising: an elongated body; and closed arrangements at opposite upper and lower ends of the elongated body for forming a drying chamber within the elongated body. One of the closed arrangements includes a drying gas inlet for guiding drying gas into the drying chamber. A nozzle assembly is supported in one of the closed arrangements. The lower closed arrangement includes a powder collection container for collecting the dried powder in the drying chamber. The powder collection container is configured such that a covering gas can be guided into the interior of the powder collection container to cover the powder in the powder collection chamber, thereby protecting the powder from exposure to the drying gas from the drying chamber.

Description

[0001] Cross-reference to related applications This application is a divisional application of Chinese Patent Application No. 201880083865.5. This patent application claims the benefit of U.S. Provisional Patent Application 62 / 578,009, filed October 27, 2017, and U.S. Provisional Patent Application 62 / 658,295, filed April 16, 2018. The entire contents of all the foregoing applications are incorporated herein by reference. Technical Field

[0002] The present invention relates generally to spray dryers, and more specifically, to apparatus and methods for spraying dry liquids into the form of dry powder. Background Technology

[0003] Spray drying is a well-known and widely used process in which a liquid slurry is sprayed into a drying chamber, and heated air is introduced into the chamber to dry the liquid into a powder. The slurry typically consists of a liquid (e.g., water), an ingredient (e.g., a food, flavoring, or pharmaceutical), and a carrier. During the drying process, the liquid is expelled, leaving the ingredient in powder form encapsulated in the carrier. Spray drying is also used to produce powders that do not require encapsulation, such as various foods, additives, and chemicals.

[0004] Spray drying systems are typically relatively large in structure, with drying towers reaching several stories in height. Not only is the instrument itself a significant capital investment, but the facilities using it must also be of sufficient size and design to accommodate such equipment. The heating requirements for the drying medium can also be expensive.

[0005] While it is desirable to use electrostatic nozzles to generate charged particles that would facilitate faster drying, the large steel structure of such spray dryer systems means that electrostatically charged liquid can somehow (especially in cases of accidental grounding) charge the system's components, hindering the operation of electrical controls and interrupting operation, resulting in the discharge of undried, uncharged liquid that has not been properly dried.

[0006] Although it is known that the drying chamber of an electrostatic spray dryer is formed from non-metallic materials to better insulate the system from charged liquids, particles can adhere to and accumulate on the walls of the drying chamber, requiring time-consuming cleaning work and disrupting the system's operation. Furthermore, the very fine drying powder in the heated air atmosphere inside the drying chamber can cause dangerous explosions due to accidental sparks, malfunctions of the electrostatic nozzles, or other components of the system.

[0007] This spray dryer system must also be operable to spray dry liquid slurries in different forms. For example, in the flavoring industry, it might be necessary to run the system using citrus flavoring ingredients in one run and coffee flavoring ingredients in the next. Residual flavoring material adhering to the walls of the drying chamber can contaminate the taste of subsequently processed products. Of course, in the pharmaceutical field, it is essential to ensure that drugs are not cross-contaminated during continuous operation.

[0008] Existing spray dryer systems also lack simplicity and versatility. Sometimes, it's necessary to run smaller batches of product for drying without using a large, integrated drying system. For specific applications, it may also be desirable to change the way material is sprayed into and dried within the system. In other processes, it may still be desirable for fine particles to agglomerate during drying for easier final use, such as dissolving more quickly in the liquid used with it. However, existing sprayers haven't yet been designed to be easily adaptable to accommodate these changing processing requirements.

[0009] Spray dryers also tend to produce very fine particles that can remain in the air as the dryer gas leaves the system and must be filtered out. These fine particles quickly clog filters, hindering the dryer's effective operation and requiring frequent filter cleaning. Existing spray dryers also typically use complex cyclone separators and filter arrangements to remove particulate matter from the air. Such equipment is expensive and requires costly maintenance and cleaning.

[0010] Another problem with spray dryer systems is the potential for damage to the finished product after the drying process. In particular, exposure to moisture-containing process gases, overheating, or oxygen can cause damage. For example, some spray-dried products are highly hygroscopic, and if exposed to moisture-containing dryer exhaust streams for extended periods, they may reabsorb moisture after the spray-drying process. Evaporative cooling protects spray-dried products from heat exposure during the drying process, but some spray-dried products can only withstand high temperatures for a short time before they begin to denature or otherwise degrade. Therefore, prolonged exposure to heated exhaust streams can lead to product damage. Furthermore, some products may oxidize if exposed to oxygen after the drying process.

[0011] Another problem with spray dryer systems is the potential for damage to the finished product after the drying process. In particular, exposure to moisture-containing process gases, overheating, or oxygen can cause damage. For example, some spray-dried products are highly hygroscopic, and if exposed to moisture-containing dryer exhaust streams for extended periods, they may reabsorb moisture after the spray-drying process. Evaporative cooling protects spray-dried products from heat exposure during the drying process, but some spray-dried products can only withstand high temperatures for a short time before they begin to denature or otherwise degrade. Therefore, prolonged exposure to heated exhaust streams can lead to product damage. Furthermore, some products may oxidize if exposed to oxygen after the drying process. Summary of the Invention

[0012] One object of the present invention is to provide a spray dryer system that is suitable for more efficient and versatile operation.

[0013] Another objective is to provide an electrostatic spray dryer system with the features described above, which is relatively small in size and more reliable in operation.

[0014] Another objective is to provide an electrostatic spray dryer system that is relatively short in height and can be installed and operated in locations without special building or ceiling requirements.

[0015] Another objective is to provide an electrostatic spray dryer system of the aforementioned type that can effectively spray dry different batches of products without cross-contamination.

[0016] Another objective is to provide the aforementioned electrostatic spray dryer systems that can be easily modified in terms of size and processing technology for specific drying applications.

[0017] Another objective is to provide an electrostatic spray dryer system operable to dry powder in such a way that fine particles are agglomerated into a form more readily available for subsequent use.

[0018] Another objective is to provide an electrostatic spray dryer system that operates efficiently with less heating required and is therefore more economical. A related objective is to provide this type of spray drying system that can operate to efficiently dry temperature-sensitive compounds.

[0019] Another objective is to provide a modular electrostatic spray dryer system in which modules can be selectively used for drying requirements of different capacities, and which can be maintained, serviced, and have modules replaced without shutting down the operation of the spray dryer system.

[0020] Another objective is to provide an electrostatic spray dryer system of the type described above, which is less susceptible to electrical faults and the hazardous explosion effects of fine powder and the heated atmosphere within the system's drying chamber. A related objective is to provide a control unit for such a spray dryer system, which is effectively used to monitor and control potential electrical faults in the system.

[0021] Another objective is to provide this type of spray dryer system with a filter system that removes particulate matter from the air more efficiently and effectively from the dried gas leaving the dryer, and requires less maintenance.

[0022] Another objective is to provide a spray dryer system with the features described above, wherein the dry gas filter system includes means for automatically and more effectively removing particulate matter accumulation on the filter.

[0023] Another objective is to provide an electrostatic spray dryer system that is relatively simple in structure and suitable for economical manufacturing.

[0024] Another objective is to provide a spray dryer system that protects the finished product from damage.

[0025] Other objects and advantages of the invention will become apparent from reading the following detailed description and referring to the accompanying drawings. Attached Figure Description

[0026] Figure 1 This is a side view of the powder processing tower of the spray dryer system shown. Figure 2 yes Figure 1 The diagram shows a vertical cross-sectional view of the powder processing tower. Figure 3 This is an exploded perspective view of the powder processing tower shown. Figure 3A This is a plan view of an unassembled, flexible, impermeable liner that can be used with the powder processing tower shown. Figure 3B This is a plan view of an alternative embodiment of the liner, which is similar to that shown in Figure A1 but is made of a permeable filter material; Figure 3C This is a plan view of another alternative embodiment of the liner, in which part of the liner is made of an impermeable material and part of a permeable filter material, which can be used in the powder processing tower shown. Figure 3D This is a plan view of another alternative embodiment of the liner, in which the liner is made of an impermeable, non-conductive rigid material, which can be used in the powder processing tower shown. Figure 4This is an enlarged top view of the top cap or cover of the powder processing tower shown, in which an electrostatic nozzle is centrally supported. Figure 5 yes Figure 4 Side view of the top cap and nozzle assembly shown; Figure 6 This is an enlarged vertical cross-section of the electrostatic nozzle assembly shown. Figure 7 This is an enlarged fracture cross-sectional view of the nozzle support head of the electrostatic nozzle assembly shown. Figure 8 This is an enlarged partial cross-sectional view of the discharge end of the electrostatic nozzle assembly shown. Figure 8A It is similar to Figure 8 A partial cross-sectional view showing the nozzle assembly, in which the exhaust spray tip is modified to spray more viscous liquid; Figure 9 It is along Figure 8 The cross-section of the electrostatic nozzle assembly shown is taken by line 9-9 in the figure; Figure 10 This is an enlarged partial cross-sectional view of the powder collecting cone and filter element housing of the powder processing tower shown. Figure 10A yes Figure 10 An exploded perspective view of the powder collecting cone and filter element housing shown; Figure 11 This is a partial cross-sectional side view of an alternative embodiment of the filter element housing used in the powder processing tower shown. Figure 11A yes Figure 11 The enlarged partial cross-sectional view of one of the filters in the filter housing shown indicates that its reverse gas pulse filter cleaning device is in a non-operating state. Figure 11B It is similar to Figure 11A An enlarged partial cross-sectional view shows its reverse gas pulse air filter cleaning device in operation; Figure 12 This is a side view of an alternative embodiment of the filter element housing and powder collection chamber; Figure 12A yes Figure 12 A top view of the filter element housing and powder collection chamber shown; Figure 12B yes Figure 12 The exploded view of a portion of the filter element housing and powder collection chamber is shown. Figure 12C yes Figure 12 An exploded perspective view of the filter element housing and the associated upstream air chamber shown; Figure 13It is a partial cross-sectional view showing the fastening arrangement for securing the top cover to the drying chamber with the associated upper liner support ring assembly. Figure 13A It is similar to Figure 12 A partial cross-sectional view, but showing the fastening arrangement for securing the drying chamber to the powder collection cone with the associated liner support ring assembly; Figure 14 This is a magnified partial view of one of the fasteners shown; Figure 15 This is a schematic diagram of the spray dryer system shown; Figure 15A This is a schematic diagram of an alternative embodiment of a spray dryer operable to cool a molten stream spray into solidified particles. Figure 16 This is a partial cross-sectional view showing the fluid supply pump used for the spray drying system shown and its associated drive motor; Figure 16A This is a vertical cross-sectional view of the fluid supply pump, which is supported within an external non-conductive housing; Figure 17 This is an enlarged top view of the insulating liner and its support ring assembly. Figure 18 It is similar to Figure 17 An enlarged top view, but showing the support ring assembly that supports the smaller diameter insulating liner; Figure 19 This is an enlarged side view of the top cap of the powder processing tower shown, which supports multiple electrostatic nozzle assemblies. Figure 20 yes Figure 19 The top view of the top cap shown; Figure 21 The diagram shows a vertical cross-sectional view of a powder processing tower, which has been modified to centrally support electrostatic nozzles near the bottom of its drying chamber for drying in the upward direction of the ejected liquid. Figure 22 yes Figure 21 A schematic side view of the bottom mounting support of the electrostatic nozzle assembly shown; Figure 23 yes Figure 22 Top view of the electrostatic nozzle assembly and bottom mounting support shown; Figure 24 yes Figure 22 and Figure 23 An enlarged cross-sectional view of one of the support rods used for mounting the support at the bottom of the nozzle; Figure 25 This is a diagram showing an alternative configuration of the powder drying system. Figure 25A This is a schematic diagram of an alternative embodiment of a spray dryer system, in which fresh nitrogen is introduced into the system's gas recirculation line; Figure 25B This is a schematic diagram of another alternative embodiment of a spray dryer system that utilizes a cyclone separator / filter bag assembly to filter particulate matter from a recirculated dry air stream; Figure 25C It is similar to Figure 25B An alternative embodiment, in which the dried fine particles separated in the cyclone separator are reintroduced into the drying chamber; Figure 25D This is another alternative embodiment of the spray dryer system, which has multiple fluidized bed filters for filtering particulate matter from the recirculated dry gas; Figure 26 This is a flowchart of a method for recovering from a fault in an operating voltage generator system according to the present disclosure; Figure 27 This is a flowchart of a method for modulating the pulse width in an electrostatic nozzle in an electrostatic spray dryer system according to the present disclosure; Figure 28 It is a top view illustration of a modular spray dryer system with multiple powder processing towers; Figure 29 yes Figure 28 The front plan view of the modular spray dryer system shown; and Figure 30 It is similar to Figure 28 A top view of a modular spray dryer system, but with an additional powder processing tower.

[0027] Figure 31 This is a side view of an alternative embodiment of the powder collection system.

[0028] Figure 32 yes Figure 31 An enlarged cross-sectional view of the collection container of the powder collection system.

[0029] Figure 33 It is used for Figure 31 and Figure 32 A schematic diagram of a blanket gas supply system for a powder collection system.

[0030] Figure 34 This is a schematic diagram of an alternative embodiment of a spray dryer operable to cool a molten stream spray into solidified particles. Figure 35 yes Figure 34 Enlarged cross-sectional view of the pulse nozzle assembly of the spray dryer system.

[0031] While various modifications and alternative constructions are possible with respect to the present invention, certain illustrative embodiments have been shown in the accompanying drawings and will be described in detail below. However, it should be understood that the invention is not intended to be limited to the specific forms disclosed, but rather, it is intended to cover all modifications, alternative constructions, and equivalents falling within the spirit and scope of the invention. Detailed Implementation

[0032] Referring now more specifically to the accompanying drawings, an exemplary spray drying system 10 according to the invention is shown, comprising a processing tower 11 including a drying chamber 12 in the form of an upright cylindrical structure; a top-closed arrangement for the drying chamber 12 in the form of a cover or cap 14 having a heated air inlet 15 and a liquid nozzle assembly 16; and a bottom-closed arrangement in the form of a powder collecting cone 18 supported at the bottom of the drying chamber 12; and a filter element housing 19 through which the powder collecting cone 18 extends, having a heated air outlet 20 and a bottom powder collecting chamber 21. The drying chamber 12, the collecting cone 18, the filter element housing 19, and the powder collecting chamber 21 are all preferably made of stainless steel. The top cover 14 is preferably made of plastic or other non-conductive material, and in this case, centrally supports the nozzle assembly 16. The heated air inlet 15 shown is oriented to guide heated air into the drying chamber 12 in a tangential rotational direction. A frame 24 supports the processing tower 11 in an upright position.

[0033] According to important aspects of this embodiment, such as Figures 6 to 9 In its best description, nozzle assembly 16 is a pressurized air-assisted electrostatic nozzle assembly used to guide a spray of electrostatically charged particles into drying chamber 12 to rapidly and efficiently dry a liquid slurry into the desired powder form. The nozzle assembly 16 shown (which may be of the type disclosed in International Application PCT / US2014 / 056728) includes a nozzle support head 31, an elongated nozzle barrel or body 32 extending downstream from the head 31, and an exhaust spray tip assembly 34 at the downstream end of the elongated nozzle body 32. In this case, the head 31 is made of plastic or other non-conductive material and has a radial liquid inlet channel 36 that receives and communicates with a liquid inlet fitting 38 to connect to a supply line 131, which is in communication with a liquid supply. It is understood that the supply liquid can be any of a variety of slurries or similar liquids that can be dried into powder form, including liquid slurries having a solvent (e.g., water), a desired ingredient (e.g., flavoring agent, food, pharmaceutical, etc.), and a carrier, such that after drying into powder form, the desired ingredient is encapsulated within the carrier, as is known in the art. Other forms of slurries may also be used, including liquids that do not contain a carrier or require encapsulation of the dried product.

[0034] In this configuration, the nozzle support head 31 also forms a radial pressurized air atomizing inlet channel 39 downstream of the liquid inlet channel 36. This radial pressurized air atomizing inlet channel 39 receives and communicates with an air inlet fitting 40, which is connected to a suitable pressurized gas supply source. The head 31 also has a radial channel 41 upstream of the liquid inlet channel 36. This radial channel 41 receives a fitting 42 for securing a high-voltage cable 44, which is connected to a high-voltage source. The high-voltage cable 44 has an end 44a that extends into the channel 41 in an abutment-to-electrode electrical contact with an electrode 48, which is axially supported within the head 31 and extends downstream of the liquid inlet channel 36.

[0035] To allow liquid to pass through the head 31, the electrode 48 has an internal axial channel 49 that communicates with the liquid inlet channel 36 and extends downstream through the electrode 48. The electrode 48 also has a plurality of radial channels 50 that communicate between the liquid inlet channel 36 and the internal axial channel 49. The electrode 48 shown has a radial hub 51 extending downstream and outward, which fits into a countersunk hole in the head 31, with a sealing O-ring 52 inserted therebetween.

[0036] The elongated body 32 takes the form of an outer cylindrical body member 55 made of plastic or other suitable non-conductive material, with its upstream end 55a threadedly engaged in a threaded hole in the head 31, having a sealing O-ring 56 inserted between the cylindrical body member 55 and the head 31. A liquid feed tube 58, made of stainless steel or other conductive metal, extends axially through the outer cylindrical body member 55 to define a liquid flow channel 59 for transferring liquid between the axial electrode liquid channel 49 and the discharge spray tip assembly 34, and defines an annular atomizing air channel 60 between the liquid feed tube 58 and the outer cylindrical body member 55. The upstream end of the liquid feed tube 58 protrudes above the threaded inlet end 55a of the outer cylindrical nozzle body 55, and is electrically fitted into a downwardly opening cylindrical hole 65 in the electrode hub 51. With electrode 48 charged by high-voltage cable 44, it can be seen that the liquid fed into inlet channel 36 will be energized as it travels along the entire length of the elongated nozzle body 32 through electrode channel 49 and liquid feed pipe 58. In this case, pressurized gas flows around the upstream end of liquid feed pipe 58, through radial air inlet channel 39, and then enters annular air channel 60 between liquid feed pipe 58 and outer cylindrical body member 55.

[0037] The liquid feed tube 58 is configured to be in electrical contact with the electrode 48 to effectively electrify the liquid throughout its passage from the head 31 through the elongated nozzle body 32 to the discharge spray tip assembly 34. For this purpose, the discharge spray tip assembly 34 includes a nozzle tip 70 having an upstream cylindrical portion 71 surrounding the downstream end of the liquid feed tube 58, with a sealing O-ring 72 inserted between them. The nozzle tip 70 includes an inwardly tapered or conical intermediate portion 74 and a downstream cylindrical nose portion 76 defining a cylindrical flow channel 75 and a liquid discharge orifice 78 of the nozzle tip 70. In this case, the nozzle tip 70 has segmented radially retaining flanges 78 extending outward from the upstream cylindrical portion 71, defining a plurality of air passages 77, which will become apparent.

[0038] To guide liquid from the feed pipe 58 into and through the nozzle tip 70, and to continue electrostatically charging the liquid as it passes through the nozzle tip 70, a conductive pin unit 80 is supported within the nozzle tip 70 in a conductive relationship adjacent to the downstream end of the feed pipe 58. In this configuration, the pin unit 80 includes an upstream cylindrical hub portion 81 forming a downstream conical wall portion 82, which is supported within a central conical portion 74 of the nozzle tip 70. The cylindrical hub portion 81 forms a plurality of radially spaced liquid flow channels 83 in the circumferential direction. Figure 8 It connects the liquid feed pipe 58 and the cylindrical nozzle tip channel portion 75. It can be seen that when the conductive pin unit 80 is placed inside the nozzle tip 70, the conductive pin unit 80 is physically supported in an adjacent relationship at the downstream end of the liquid feed pipe 58.

[0039] To concentrate the charge on the liquid exiting from the nozzle tip, pin unit 80 has a downwardly extending central electrode pin 84 supported concentrically with the nozzle tip channel 75, such that the liquid discharge orifice 78 is arranged annularly around the electrode pin 84. The electrode pin 84 has a tapering tip that extends beyond the annular nozzle tip discharge orifice 78 by a certain distance, for example, between approximately 1 / 4 inch and 1 / 2 inch. As the liquid exits the nozzle tip 70, the increased contact of the liquid with the protruding electrode pin 84 further enhances the concentration of charge on the exiting liquid, thereby enhancing the breakdown and distribution of liquid particles.

[0040] Alternatively, such as Figure 8AAs shown, when spraying more viscous liquid, the discharge spray tip assembly 34 may have a hub portion 81 (similar to the above), but without the downwardly extending central electrode pin 84. This arrangement allows the more viscous liquid to pass more freely through the nozzle tip, while the electrostatic charge on the discharged liquid still enhances liquid decomposition, thereby drying the viscous liquid more effectively.

[0041] The exhaust spray tip assembly 34 also includes an air cap or gas cap 90 disposed around the nozzle tip 70, which defines an annular atomizing air passage 91 around the nozzle tip 70 and keeps the nozzle tip 70, pin unit 80, and liquid feed tube 58 in an assembled, electrically conductive relationship. In this case, the gas cap 90 defines a tapered pressurized airflow passage portion 91a around the downstream end of the nozzle tip 70, which communicates with an annular air passage 60 between the liquid feed tube 58 and the outer cylindrical body member 55 via circumferentially spaced air passages 77 in the nozzle tip retaining flange 78, for guiding pressurized air or gas exhaust flow through an annular exhaust orifice 93 around the nozzle tip nose 76 and discharging liquid from the nozzle tip liquid exhaust orifice 78. To maintain the assembled relationship of the internal components of the nozzle, the gas cap 90 has an upstream cylindrical end 95 threadedly engaged around the downstream externally threaded end of the outer cylindrical member 55. The air cap 90 has a countersunk hole 96 that receives and supports the segmented radial flange 78 of the nozzle tip 70 to support the nozzle tip 70, and thus support the pin unit 80 and the liquid feed tube 58 which are in conductive relationship with the upstream electrode 48.

[0042] Nozzle assembly 16 is operable to discharge a spray of electrostatically charged liquid particles into drying chamber 12. Indeed, it has been found that the illustrated electrostatic nozzle assembly 16 can be operated to produce extremely fine particulate droplets, for example, droplet diameters on the order of approximately 70 micrometers. It is evident that the liquid particles are readily and efficiently dried into fine particulate form due to the decomposition and repulsion properties of the fine liquid spray particles introduced into the drying chamber from heated air inlet 15 and air-assisted nozzle assembly 16, and the drying gas. It should be understood that while the illustrated electrostatic nozzle assembly 16 has been found to have a specific use relevant to this invention, other electrostatic nozzles and systems can be used, including electrostatic hydraulic rotary nozzles of known types and high-volume low-pressure electrostatic sprays.

[0043] According to another important feature of this embodiment, the drying chamber 12 has an internal non-metallic insulating lining 100, which is concentrically spaced from the inner wall surface 12a of the drying chamber 12 into which electrostatically charged liquid spray particles from the nozzle assembly 16 are discharged. Figure 2As shown, the diameter d of the liner is smaller than the inner diameter d1 of the drying chamber 12 to provide an insulating air gap 101 with respect to the outer wall surface 12a of the drying chamber 12. The insulating air gap 101 is preferably at least about 2 inches (about 5 cm), but other sizes can be used. In this embodiment, the liner 100 is unstructured and preferably made of an impermeable flexible plastic material 100a. Figure 3 and Figure 3A Alternatively, as will be apparent, it can be made of a rigid, non-permeable, non-conductive material 100c ( Figure 3D ), permeable filter material 100b ( Figure 3B ), or partly composed of non-permeable material 100a and partly composed of permeable filter material 100b ( Figure 3C Made from ( ).

[0044] According to another aspect of this embodiment, the processing tower 11 has a quick-disconnect assembly structure that facilitates the assembly and installation of the annular liner 100 to the outer wall of the drying chamber 12 in an electrically insulating relationship. Therefore, the opposite ends of the annular insulating liner 100 are respectively supported by upper and lower support ring assemblies 104 (… Figure 1 , Figure 3 , Figure 13 , Figure 13A , Figure 14 and Figure 17 Support. In this case, each ring assembly 104 includes an inner cylindrical support ring 105, one end of the liner 100 is attached to the support ring 105, and a plurality of circumferentially spaced non-conductive polypropylene or other plastic support studs 106, which are fixed relative to the support ring 105 in a radially outward extending relationship. In the illustrated embodiment, the upper end of the liner 100 is folded over the top of the support ring 105 of the upper ring assembly 104 and is positioned between the liner 100 and the support ring 105. Figure 13 The lining 100 is secured to the folded end of the ring by a ring-shaped U-shaped rubber washer 108. The lower end of the lining 100 is similarly designed to surround the bottom of the support ring 105 of the lower ring assembly 104, and is secured by a similar rubber washer 108. Figure 13 A similar rubber gasket 108 is also supported on the opposite inner end of the cylindrical support ring 105 of the ring assembly 104 to protect the liner 100 from damage to the exposed edge of the support ring 105.

[0045] To secure each support ring assembly 104 within the drying chamber 12, a corresponding mounting ring 110 is fixed to the outside of the drying chamber 12, for example, by welding. Stainless steel mounting screws 111 extend through alignment holes in the mounting rings 110 and the outer wall of the drying chamber 12 for threaded engagement with insulated support studs 106. In this configuration, rubber O-rings 112 are disposed around the end of each support stud 106 to seal the inner wall of the drying chamber 12, and a neoprene-bonded sealing washer 114 is provided around the head of each retaining screw 111.

[0046] In order to secure the top cover 14 of the drying chamber to the drying chamber 12 in a sealing relationship with respect to the upper support ring assembly 104, the annular array 120 ( Figure 1 and Figure 2 The releasable latch assembly 121, separated by a spacer, is secured to the mounting ring 110. Figures 13 to 14 The circumferentially spaced position is located in the middle of the support stud 106 on the top cover 14. The latch assembly 121 can be of a known type, having an upwardly extending hook 122 that can be positioned at the top edge of the cover 14 and pulled into a locked position as the latch arm 124 pivots downward to the latched position, so that the top cover 14 is held on the U-shaped washer 108 around the upper edge of the support ring 105, and a similar large-diameter annular U-shaped washer 126 is held around the upper edge of the cylindrical drying chamber 12. The latch assembly 121 can be easily unlocked by the reverse pivoting movement of the latch hook 124, so that the hook 122 moves up and down to allow removal of the top cover 14 if necessary. A similar annular array 120a of latching assembly 121 is disposed around mounting ring 110 adjacent to the bottom of drying chamber 12, in this case having downwardly positioned hooks 124 that overlap with the outwardly extending flange 129 of collecting cone 18 to maintain the flange 129 of collecting cone 18 in a sealing relationship with rubber gaskets 108, 126 around the bottom edge of support ring 105 and the bottom cylindrical edge of drying chamber 12. Figure 13A It should be understood that, for a specific application, the liner 100, O-rings, and other sealing gaskets 108, 126 may or may not be made of FDA-compliant materials.

[0047] During the operation of the electrostatic nozzle assembly 16, liquid is supplied to the electrostatic nozzle assembly 16 from a liquid supply device (in this case, the liquid supply device is as follows). Figure 15The liquid reservoir 130 shown is guided by the electrostatic nozzle assembly 16 into the effective drying area 127 defined by the annular liner 100. Liquid is supplied from the liquid supply reservoir 130 via a liquid supply or delivery line 131 connected to the liquid inlet fitting 38 of the nozzle assembly 16 by a pump 132, preferably a peristaltic metering pump, which has a liquid guide roller system that can be operated in a conventional manner. Figure 16A As shown, in this configuration, the peristaltic metering pump 132 comprises three plastic electrically insulated pump rollers 33 within a plastic pump housing 37. In this configuration, the liquid supply or delivery line 131 is electrically shielded, and the stainless steel drying chamber 12 is preferably grounded via an approved grounding wire passing through the support frame 24, the stainless steel drying chamber 12 being secured to the support frame 24 by metal-to-metal contact.

[0048] Electronic controller 133 is operatively connected to various actuators and electrical or electronic devices of the electrostatic spray dryer system, such as motor 134, pump 132, liquid nozzle assembly 16, voltage generator supplying voltage to high-voltage cable 44, and others, and operates to control their operation. Although a single controller is shown, it should be understood that a distributed controller arrangement including more than one controller can be used. As shown, controller 133 is capable of operating in response to a program (e.g., a programmable logic controller). For clarity, in Figure 15 The various operable connections between the controller 133 and various other components of the system are omitted.

[0049] According to another aspect of this embodiment, pump 132 is powered by motor 134 ( Figure 16 In operation, the motor 134 is configured to be electrically insulated from the pump 132, and the liquid supply line 131 connects the pump 132 to the nozzle assembly 16 to prevent the motor 134 from becoming charged by the liquid charged by the nozzle assembly 16. For this purpose, the output shaft 135 of the drive motor 134 is connected to the pump head drive shaft 136 via a non-conductive drive portion 138 (e.g., made of rigid nylon), which insulates the pump 132 from the electrically driven motor 134. In the illustrated embodiment, the non-conductive drive portion 138 has a diameter of approximately 1.5 inches (approximately 3.8 cm) and an axial length of approximately 5 inches (approximately 12.7 cm). In this case, the motor drive shaft 135 carries an attachment plate 139 fixed to the non-conductive drive portion 138 by screws 141. The pump head drive shaft 136 similarly carries an attachment plate 140 fixed to the other end of the non-conductive drive portion 138 by screws 141.

[0050] An electrostatic voltage generator 222 is electrically connected to the nozzle assembly 16 via a wire 224 to provide a voltage that electrostatically charges the sprayed droplets. In the illustrated embodiment, the wire 224 includes a variable resistor element 226, which is optional and can be manually or automatically adjusted to control the voltage and current supplied to the nozzle assembly 16. An optional grounding wire 228 is also electrically connected between the liquid supply line 131 and ground 232. The grounding wire 228 includes a variable resistor 230, which can be manually or automatically adjusted to control the voltage present in the fluid. In the illustrated embodiment, the grounding wire is placed before the pump 132 to control the state of charge of the fluid supplied to the system. The system may also include a sensor that transmits the state of charge of the fluid to the controller 133, allowing the system to automatically monitor and selectively control the state of charge of the liquid by controlling the resistance of the variable grounding resistor 230 to drain charge from the liquid lines in the system.

[0051] In this configuration, the properly grounded drive motor 134 is supported within a non-conductive plastic motor mounting housing 144. The illustrated reservoir 130 is supported on a level gauge 145 to monitor the liquid level in the reservoir 130, and an electrical insulation barrier 146 is provided between the bottom of the reservoir 130 and the level gauge 145. It should be understood that, instead of the peristaltic pump 132, plastic pressure tanks and other types of pumps and liquid delivery systems that are electrically insulated from their electrical operating systems can be used.

[0052] In this configuration, the pressurized gas directed to the atomizing air inlet fitting 18 of the nozzle assembly 16 originates from a bulk nitrogen supply source 150, which is connected via a gas supply line 151. Figure 15 The nozzle assembly 16 is connected to the atomizing air inlet fitting 18. A gas heater 152 is disposed in the supply line 151 for supplying dry inert nitrogen gas to the nozzle assembly 16 at a controlled temperature and pressure. It should be understood that although nitrogen gas is described as an atomizing gas in this embodiment, other inert gases, or other gases containing air, can be used as long as the oxygen level in the drying chamber is maintained below a certain level that would create a combustion atmosphere for the dry powder particles in the drying chamber, which could be ignited by a spark or other electrical fault in the electrostatic nozzle assembly or other electronic control components of the drying system.

[0053] According to another important aspect of this embodiment, as an atomization event of the liquid sprayed into the drying chamber 12, heated nitrogen atomizing gas supplied to the nozzle assembly 16 and guided into the drying chamber 12 is continuously recirculated through the drying chamber 12 as a drying medium. Further reference will be made to... Figure 15As understood, the drying gas introduced into the drying chamber 12 from both the drying gas inlet 15 and the nozzle assembly 16 will circulate along the length of the drying chamber 12, thereby effectively drying the electrostatically charged liquid particles sprayed into the drying chamber 12 into powder form. The dried powder will migrate through the powder collection cone 18 to the powder collection chamber 21, where it can be removed by appropriate means (manually or by other automatic means).

[0054] As in Figure 10 and Figure 10A As best shown, the powder collecting cone 18 has an upper cylindrical portion 155, an inwardly tapering conical middle portion 156, and a lower cylindrical powder conveying portion 158 that extends centrally through the filter element housing 19 to guide dried powder into the powder collecting chamber 21. In this configuration, the filter element housing 19 has a pair of vertically stacked annular HEPA filters 160 mounted to the lower portion of the powder collecting cone 18 in a surrounding and outwardly spaced relationship. The powder collecting cone 18 has a radial flange 161 extending outwardly at the center of its end, positioned above the upper filter 160 within the filter element housing 19, and an annular seal 162 is inserted between the radial flange 161 and the filter element housing 19. Although most of the dry powder will fall downwards through the collecting cone 18 into the powder collecting chamber 19, only the finest particles will remain entrained in the dry gas as the dry gas migrates upwards around the bottom of the powder collecting cone 18 and then outwards through the HEPA filter 160, which restricts and filters out the fine powder before it is discharged through the exhaust outlet 20 of the filter housing 19.

[0055] Alternatively, such as Figure 11 , Figure 11A and Figure 11BAs described, a filter element housing 19a can be used, comprising a plurality of circumferentially spaced cylindrical filters 160a mounted vertically from a central transverse support plate 163 of the housing 19a. Potential gas carrying powder particles guided from the collection cone 18 into the lower collection chamber flows laterally through the filters 160a into a common exhaust chamber 164 in the filter element housing 19a above the transverse support plate 163, communicating with the particles through an outlet 20a, the particles being confined outside the airflow by the filters 160a. For periodic cleaning of the filters 160a, each of the filters 160a has a respective reverse pulse air filter cleaning device 167, the type of which is disclosed in U.S. Patent 8,876,928, assigned to the same applicant as this application, the disclosure of which is incorporated herein by reference. Each reverse pulse air filter cleaning device 167 has a corresponding gas supply line 167a for coupling to a pulse air supply source.

[0056] like Figure 11A and Figure 11B As shown, a reverse pulse air filter cleaning device 21 is illustrated, each comprising a reverse pulse nozzle 240 having a gas inlet 241 in the upper wall of an exhaust chamber 164, the gas inlet being secured by an annular retainer 242 for connection to a compressed gas supply line 167a connected to a pressurized gas source (e.g., nitrogen). The nozzle 240 has a cylindrical, closed bottom structure defining a hollow internal air passage 244 extending from the inlet 241 through the exhaust chamber 164 and substantially the length of the filter 160a. The nozzle 240 has a plurality of relatively large-diameter exhaust orifices 246 formed in a portion within the exhaust chamber 164, and a plurality of smaller-sized air exhaust orifices 248 along the length of the nozzle 240 within the filter 160a.

[0057] To interrupt the flow of process gas from the filter element housing 19a to the exhaust chamber 164 during operation of the reverse pulse nozzle 240, an annular exhaust port shut-off plunger 249 is provided above the reverse pulse nozzle 160a for axial movement within the exhaust chamber 164 between the exhaust port open and closed positions. To control the movement of the plunger 249, a bottom-opening plunger cylinder 250 is mounted in a sealing relationship with the upper wall of the exhaust chamber 164. The plunger 249 includes an annular sealing and guide flange 252 with a smaller upper diameter, having an outer periphery adapted for sliding sealing engagement with the interior of the cylinder 250; and a valve head 254 with a larger lower diameter, disposed below the lower end of the cylinder 250 for sealing engagement with the exhaust port 253 in the plate 163. The plunger 249 is preferably made of an elastic material: the upper sealing and guide flange 252 and the lower valve head 254 have a downwardly tapered or cup-shaped configuration.

[0058] like Figure 3 As shown, the plunger 249 is configured to make limited axial movement along the reverse pulse nozzle 240 and is biased to a normally open or retracted position by a helical spring 256 fixed around the outer periphery of the reverse pulse nozzle 240. With the valve plunger 249 biased to this position, process gas flows from the filter element housing 19a through the filter 160a and the exhaust port 253 into the exhaust chamber 164.

[0059] During the reverse pulse gas cleaning cycle, pulses of compressed gas are guided from inlet line 167a through reverse pulse nozzle 240. As the compressed gas travels through nozzle 160a, it first enters the plunger cylinder 250 above the plunger seal and guide flange 252 through the larger diameter or plunger actuation orifice 246, and then through the smaller reverse pulse nozzle orifice 248. Because the larger orifice 249 provides a path with less resistance, the gas first flows into the plunger cylinder 250, and as the pressure in the plunger cylinder 250 increases, it overcomes the bias force of spring 256 and pushes the plunger 249 downward. Eventually, the pressure increases to a point where it overcomes the force of spring 256 and forces the plunger 249 downward toward the exhaust port 253, thereby temporarily sealing it. After the plunger 249 seals the exhaust port 253, the compressed gas in the outer plunger cylinder 250 can no longer displace the plunger 249, and the gas pressure in the plunger cylinder 250 increases to a point where the compressed gas is forced through the smaller nozzle orifice 248 and close to the filter 160a to disperse the accumulated particulate matter around its outer surface.

[0060] After the reverse compressed air pulse and the removal of particles accumulated on filter 160a, the pressure will dissipate within plunger cylinder 250 to a point where it no longer counteracts spring 256. Then, plunger 249 will move upward under the force of spring 256 to its retracted or stationary position, opening exhaust port 253 to allow the dryer to continue operating.

[0061] Figures 12 to 12B Another alternative embodiment of the exhaust filter element housing 270 and the powder collection chamber 271 that can be mounted on the lower end of the drying chamber 12 is depicted. In this case, the upper powder orientation chamber 272 can be mounted on the lower side of the elongated drying chamber 12, the filter element housing 270 includes a plurality of vertically oriented cylindrical filters 274 and is disposed below the powder orientation chamber 272, the powder orientation cone 275 is coupled to the lower side of the filter element housing 270, and the powder collection chamber 271 is supported on the lower side of the powder orientation cone 275.

[0062] The powder orientation chamber 272 shown includes a cylindrical housing wall 289 that is hermetically mounted to the lower side of the drying chamber 12 and has an open upper end for receiving drying gas and powder from the drying chamber 12 and the drying zone 127. The powder orientation chamber 272 houses a downwardly opening, tapered exhaust chamber 281, which defines an exhaust cavity 282 on its lower side. Figure 12B Furthermore, on its upper side, the dry gas and powder from the drying chamber 12 are guided downward and outward around the outer periphery of the conical exhaust chamber 281.

[0063] The filter element housing 270 includes: an outer cylindrical housing wall 284, which is sealed to the bottom peripheral edge of the powder-oriented gas chamber 272 via an annular seal 285; and an inner cylindrical filter shroud 286, which is sealed to the bottom peripheral edge of the conical exhaust chamber 281 via an annular seal 288. The conical exhaust chamber 281 and the inner cylindrical filter shroud 286 are connected by a plurality of radial supports 290. Figure 12A The gas is supported within the outer cylindrical housing wall 289 of the gas guiding chamber 272 and the filter element housing 270, thereby defining an air passage 291 communicating around the bottom periphery of the conical exhaust chamber 281 and an annular gas passage 292 between the inner cylindrical filter shroud 286 and the outer cylindrical housing wall 284, such that the gas and powder passing through the powder direction chamber 272 are guided outward by the conical exhaust chamber 281 around the filter element shroud 281 to the lower powder direction cone 275 and the collection chamber 271.

[0064] In this configuration, the cylindrical filter 274 is supported in a dependent relationship to a circular support plate 295, which is fixedly disposed below the lower side of the downward-opening conical exhaust chamber 281. In this configuration, the circular filter support plate 295 is mounted to the upper periphery of the cylindrical shroud 286 in a slightly recessed relationship and defines the lower wall of the exhaust chamber 282. Each of the shown cylindrical filters 274 is in a cylindrical form, comprising a cylindrical filter element 296, an upper cylindrical retaining plate 298, a bottom cap, and a sealing plate 299 having inserted annular sealing elements 300, 301, and 302. To secure the filter cartridge in an assembled relationship, the upper cylindrical retaining plate 298 has a U-shaped support member 304, whose threaded lower end stud 305 can be positioned through a central hole in the bottom cap 299, secured by a nut 306, with an O-ring sealing ring 308 inserted between them. Each filter cartridge is secured in a sealed relationship with its upper retaining plate 298 around a corresponding circular opening 310 in the central support plate 295, wherein the filter element 296 is disposed in relation to the lower side of the support plate 295, and the central hole 311 in the retaining plate 298 communicates between the exhaust chamber 282 and the interior of the cylindrical filter element 296. In this case, the filter element cartridges are arranged with circumferential spacing around the center of the inner shroud 274.

[0065] In this configuration, the filter element housing 270 is secured to the powder-oriented air chamber 272 by a releasable clamp 315 or similar fastener for easy access to the filter cartridge. The internal filter shroud 286 is also releasably mounted around the cylindrical filter 274, for example, via pin and slot connection, to allow access to the filter for replacement.

[0066] During operation of the dryer system, it can be observed that the dry gas and powder guided into the powder direction chamber 272 are guided around the conical exhaust chamber 281 into the annular channels 291, 292 surrounding the internal filter shroud 274, and downwards into the powder direction cone 275 and collection chamber 271 for collection. While most of the dry powder remaining in the airflow will migrate to the powder collection chamber 271 (as previously described), it becomes apparent that fine airborne particulate matter will be separated and retained by the annular filter 274 as the dry gas passes through the filter into the dry gas exhaust chamber 282, for discharge through the dry gas exhaust port 320 and recirculated back into the drying chamber 12.

[0067] To clean the powder accumulated in the cylindrical filters 274 during use of the dryer system, each of the cylindrical filters 274 has a corresponding reverse gas pulse cleaning device 322. For this purpose, in this case, the gas directional chamber 272 has an external annular pressurized gas manifold passage 321 connected to a suitable pressurized air supply. Each reverse air pulse cleaning device 322 has a corresponding pressurized gas supply line 325 connected between the annular pressurized gas manifold passage 321 and a corresponding control valve 326, in this case mounted outside the air directional chamber 272. The gas pulse directional line or pipe 328 extends radially from the control valve 326 through the conical wall of the air directional chamber 272 and the exhaust chamber 329, and then the terminal discharge end 329 of the upper gas pulse guide line 328 rotates downward at a right angle and is aligned with the central hole 311 of the filter cartridge retaining plate 298 and the lower cylindrical filter element 296.

[0068] By appropriately selectively or automatically controlling the control valve 326, the control valve 26 can be cyclically operated to axially discharge pulses of compressed gas from the line 328 into the circulating filter 274, thereby removing powder accumulated on the outer wall of the cylindrical filter element 296. The discharge end 329 of the pulse gas guide line 328 is preferably arranged at an interval from the upper end of the periodic filter 274 to facilitate the guiding of compressed gas pulses to the filter element 296, while simultaneously drawing in gas from the exhaust chamber 282, which facilitates a reverse flow pulse that removes accumulated powder from the filter element 296. Preferably, the discharge end 329 of the air line 328 is spaced a certain distance from the upper end of the cylindrical filter element, thereby allowing the expanding airflow (such as...) Figure 12B As shown in Figure 330, upon reaching the filter cartridge, it has an outer perimeter that substantially corresponds to the diameter of the central hole 311 in the cartridge retainer plate 298. In an exemplary embodiment, the diameter of the air guide tube 28 is approximately one inch, and the distance between the discharge end 329 and the retainer plate 298 is approximately 2.5 inches.

[0069] In this case, the powder collection chamber 271 has a circular butterfly valve 340 (which separates the powder collection chamber 271 from the surrounding area). Figure 12B As shown in the diagram, the circular butterfly valve is mounted on the upper end of the collection chamber 271 and is operable by a suitable actuator 341 for rotatable movement between a vertical or open position and a horizontal closed position. In the vertical or open position, dry powder is allowed to be guided into the collection chamber 271; when removing powder, the horizontal closed position prevents dry powder from entering the collection chamber 271. Alternatively, it should be understood that the powder collection chamber 271 may allow powder to be deposited directly onto a movable conveyor from its open bottom end.

[0070] In order to recirculate and reuse the dry gas leaving the filter element housing 19a, the exhaust outlet 20 of the filter housing 19 is connected to the recirculation line 165, which in turn passes through the condenser 166, the blower 168, and the dry gas heater 169. Figure 15 The heating gas inlet port 15 is connected to the top cover 14 of the heating chamber 12. The condenser 170 removes any water vapor from the exhaust stream via a condenser coil 170a cooled by cold water supply and return lines 171, 172. The condensate from the condenser 170 is directed to a collection container 174 or to a drain. The dried nitrogen is then directed by a blower 168 through a gas heater 169, which reheats the dried gas cooled by the condenser 170 to a predetermined heating temperature for a specific powder drying operation, redirecting it back to the heating gas inlet port 15 and into the heating chamber 12. An exhaust control valve 175 is coupled to the recirculation line 165 between the blower 168 and the heater 169, allowing excess nitrogen introduced into the system from the electrostatic nozzle assembly 16 to be channeled to the appropriate exhaust duct system 176. The exhaust flow from the control valve 175 can be configured to match the excess nitrogen introduced into the drying chamber 12 through the electrostatic nozzle assembly 16. It should be understood that by selectively controlling the exhaust flow control valve 175 and the blower 168, the vacuum or pressure level in the drying chamber 12 can be selectively controlled for specific drying operations or for the purpose of controlling the evaporation and discharge of volatiles. Although a chilled water condenser 170 has been shown in the illustrated embodiment, it should be understood that other types of condensers or devices for removing moisture from the recirculated gas flow can be used.

[0071] It should be understood that the drying gas introduced from the electrostatic nozzle assembly 16 and the drying gas inlet port 15 into the effective drying area 127 defined by the flexible liner 100 is a dry inert gas (nitrogen in the illustrated embodiment), which facilitates the drying of liquid particles sprayed through the electrostatic nozzle assembly 16 into the drying chamber 12. As described above, the recirculation of the inert drying gas also removes oxygen from the drying gas, thereby preventing the possibility of a powder explosion hazard within the drying chamber in the event of an accidental spark generated by the electrostatic nozzle assembly 16 or other components of the system.

[0072] Furthermore, it has been found that recirculating inert drying gas through the spray drying system 10 enables the spray drying system 10 to operate efficiently and energy-savingly at significantly lower operating temperatures, resulting in substantial cost savings. As previously mentioned, the emulsion to be sprayed is typically made of three components, such as water (solvent), starch (carrier), and flavoring oil (core). In this case, the purpose of spray drying is to form starch around the oil and dry all the water with the drying gas. The starch is retained as a protective layer around the oil, preventing its oxidation. This desired result is found to be more easily achieved when a negative electrostatic charge is applied to the emulsion before and during atomization.

[0073] Although the operational theory is not yet fully understood, each of the three components of the spray emulsion possesses different electrical properties. Water is the most conductive component in the group, readily attracting the most electrons, followed by starch, and finally oil, which has the highest resistivity and attracts almost no electrons. It is known that opposite charges attract and like charges repel, and all water molecules with the largest similar charges exhibit the strongest repulsive force towards each other. This force guides the water molecules to the outer surface of the droplet, where they have the largest surface area available for the drying gas, thus improving the drying process. Oil molecules with smaller charges remain at the center of the droplet. This method is believed to contribute to faster drying, or drying with a lower heat source, and a more uniform coating. Testing of the spray-dried powder produced by the spray drying system of the present invention, operated at an inlet drying gas temperature of 90°C, revealed that the powder is comparable to that dried in a conventional spray drying process operating at 190°C. Furthermore, in certain cases, the spray drying system of this subject can operate efficiently without heating the drying gas.

[0074] Encapsulation efficiency (i.e., the uniformity of the coating on the dried powder) is also equivalent to the encapsulation efficiency achieved in spray drying at higher temperatures. Further findings revealed that low-temperature drying significantly reduced the emission of aromas, odors, and volatile components into the environment compared to conventional spray drying, further indicating a more uniform outer surface of the dried particles and complete starch formation. Reduced aroma and odor emissions further improve the working environment and eliminate the need for odor removal that could be irritating and / or harmful to operators. Lower-temperature processing also allows for the spray drying of temperature-sensitive components (organic or inorganic) without damaging or adversely affecting the compounds.

[0075] If any particles may adhere to or otherwise accumulate on the surface of liner 100 during the drying process, a liner agitation device is provided to periodically agitate liner 100 sufficiently to remove any accumulated powder. In the illustrated embodiment, drying chamber 12 has a side pneumatic liner agitation valve port 180 coupled to a pneumatic canister 181, which can be periodically actuated to direct compressed air through the pneumatic liner agitation valve port 180 and into the annular air space between liner 100 and the outer wall of drying chamber 12, which agitates the flexible liner 100 back and forth with sufficient force to remove any accumulated powder. The compressed air is preferably directed to the pneumatic liner agitation valve port 180 in a pulsating manner to enhance this agitation. Alternatively, it should be understood that mechanical devices can be used to agitate liner 100.

[0076] To ensure that cross-contamination is avoided between consecutive selective uses of the spray dryer system (e.g., between runs of different powders in drying chamber 12), the annular array 120, 120a of quick-disconnect fasteners 121 allows for removal of the cover 14 and collection cone 18 from drying chamber 12 for easy replacement of the liner 100. Since the liner 100 is made of relatively inexpensive materials, it is preferably disposable between runs of different powders, and replacement with a new liner is not subject to undue expense.

[0077] Consistent with another important feature of this embodiment, the drying chamber 12 can be easily modified to accommodate different spray drying requirements. For example, for smaller drying requirements, a smaller diameter liner 100a can be used to reduce the size of the effective drying area. For this purpose, a support ring assembly 104a (similar to the one described above, but with a smaller diameter inner support ring 105a) is used. Figure 18 The larger diameter support ring assembly 104 can be easily replaced. Replacement of the ring assembly can be achieved by unlocking the array 120, 120a of latches 121 for the circumferential spacing of the top cover 14 and the collecting cone 18, removing the larger diameter ring assembly 104 from the drying chamber 12, replacing it with the smaller diameter ring assembly 104a and liner 100a, and reassembling and relocking the top cover 14 and collecting cone 18 onto the drying chamber 12. The smaller diameter liner 100a effectively reduces the drying area in which heated drying gas and atomizing gas are introduced to achieve faster, more energy-efficient, and more effective small-batch drying.

[0078] To further achieve more efficient drying in smaller batches, the drying chamber 12 has a modular structure that allows for a reduction in the length of the drying chamber 12. In the illustrated embodiment, the drying chamber 12 comprises a plurality (in this case, two) vertically stacked cylindrical drying chamber modules or portions 185, 186. The lower chamber portion 186 is shorter than the upper chamber portion 185. The two cylindrical drying chamber portions 185, 186 are again releasably secured together by an array 102b of quick-release fasteners 121 spaced circumferentially as described above. Mounting rings 110 for the array 102b of fasteners 121 are welded to the upper cylindrical drying chamber portion 185 near their lower ends, and the fasteners 121 of the array 102b are oriented such that hooks 122 are positioned downwards to engage and retain the outer radial flange 188 at the top of the lower cylindrical drying chamber portion 186. Figure 1 and Figure 2 The lower cylindrical portion 186 is located on the lower side of the powder collection cone 18. When the two arrays 102a, 102b of fasteners 121 securing the lower cylindrical portion 186 to the upper cylindrical portion 185 and the collection cone 18 are released, the lower cylindrical portion 186 can be removed, the lower support ring assembly 104 is repositioned near the bottom of the upper chamber portion 185, and the liner 100 is replaced with a shorter liner. The upper cylindrical drying chamber portion 185 can then be directly secured to the powder collection cone 18 by the fasteners 121 of array 102b, with the lower support ring assembly 104 positioned therebetween and then engaging with the outer annular flange 129 of the collection cone 18. This improvement allows for the use of a significantly shorter effective drying zone to further reduce the heating requirements for drying smaller batches.

[0079] It should be understood that additional cylindrical drying chamber modules or sections 186 can be added to further increase the effective length of the drying chamber 12. To increase the amount of liquid sprayed into the drying chamber 12 (regardless of size increase), multiple electrostatic nozzle assemblies 16 can be provided in the top cover 14, such as... Figure 19 and Figure 20 As shown. Multiple nozzle assemblies 16 can be supplied by a common liquid and nitrogen supply source, and the multiple nozzle assemblies 16 are preferably located in corresponding, pre-covered metering orifices 190 in the top cover 14. Figure 4 They are supported by a circumferentially spaced relationship. Then, the unused center mounting hole 192 ( Figure 20 (Appropriately cover or otherwise close.)

[0080] According to another feature of this embodiment, the modular quick-disconnect component of the drying tower 11 also allows the electrostatic nozzle assembly 16 to be repositioned from its position on the top of the drying chamber 12 to spray downwards to a position adjacent to the bottom of the drying chamber 12, thereby guiding the electrostatically charged liquid spray upwards into the drying chamber 12. For this purpose, the nozzle assembly 16 can be removed from the top cover 14 and secured in the bottom nozzle mounting support 195. Figures 21 to 24 In this case, it is installed within the upper cylindrical wall portion 155 of the powder collecting cone 18, which is located immediately adjacent to the bottom of the drying chamber 12, to orient the electrostatic nozzle assembly 16 so as to spray a charged spray pattern upward into the drying chamber 12, as shown. Figure 21 As shown. Figures 22 to 24 As shown, the bottom nozzle mounting support 195 includes a central annular mounting hub 196 for supporting the nozzle assembly 16 near its upstream end. This upstream assembly is further supported by a plurality of radial mounting rods 198 within the upper cylindrical portion 155 of the powder collecting cone 18. The mounting rods 198 are made of a non-conductive material. Each radial mounting rod 198 is secured by its respective stainless steel screw 199. Figure 24 A rubber-bonded sealing gasket 200 is fixed to the cylindrical wall portion 155 and located between the head of the screw 199 and the outer wall surface of the powder collecting cone 18. A sealing O-ring 201 is clamped between the outer end of each mounting rod 198 and the inner wall surface of the powder collecting cone portion 18. Non-conductive PTFE or other plastic liquid and atomizing gas supply lines 205, 206 are radially connected to insulating fittings 208, 209 via the powder collecting cone 18, which in turn is connected to atomizing air and liquid supply lines 151, 131. The high-voltage cable 210 is also radially connected to the nozzle assembly via insulating fitting 211.

[0081] With the electrostatic nozzle assembly 16 installed on the lower side adjacent to the drying chamber 12, the central nozzle mounting hole 192 and the gas inlet port 15 in the cover 14 can be properly covered. The powder collecting cone 18 also has a tangentially oriented drying gas inlet 215, which can be left uncovered and connected to the drying gas recirculation line 165. In this case, the cover 14 has a pair of exhaust ports 216, which can also be left uncovered and connected to the heating gas return line.

[0082] With the nozzle assembly 16 installed on the lower side of the drying chamber 12, the electrostatically charged liquid spray particles guided upward into the drying chamber 12 are dried by drying gas. In this case, the gas is tangentially guided through the bottom heated gas inlet 215 by heating the atomized gas from the nozzle assembly 16. The atomized gas is a dry inert gas, namely nitrogen.

[0083] According to this embodiment, the annular lining 100 in the drying chamber 12 is preferably made of filter medium 100b ( Figure 3B The filter media 100 is designed to allow the dry gas to eventually migrate through the filter medium and exit from the upper exhaust port 216 in the cover 14 to the recirculation line 165 for recirculation, reheating, and redirection to the bottom gas inlet port 215, as described above. The powder dried by the upward-guided dry gas and atomizing gas will eventually float downwards into and through the powder collection cone 18 and into the collection chamber 19, where, as described above, only the finest particles are filtered by the filter medium liner 100. A pneumatic liner vibrator can be periodically actuated again to prevent powder accumulation on the liner 100.

[0084] As can be seen from the above, for specific spray applications, the treatment tower can be easily configured and operated in multiple treatment modes, such as... Figure 25 As shown in Table 220. By adding or removing the cylindrical drying chamber section 186, the length of the drying chamber can be selectively changed, the lining material (e.g., non-permeable or permeable) can be selectively determined, the orientation of the electrostatic nozzles can be changed between top-down spraying and bottom-up spraying, and the direction of the treated airflow can be changed between downward and upward directions as required.

[0085] While in the foregoing embodiments nitrogen or other inert dry gas is introduced into the system as the atomizing gas for the electrostatic nozzle assembly 16, alternatively, nitrogen may also be introduced into the recirculating gas. Figure 25A In the spray drying system shown, components similar to those described above are labeled with similar reference numerals. Nitrogen or other inert gases are introduced from the nitrogen injection line 169a into the gas heater 169, and guided to the drying chamber 100 via the gas delivery and supply line 169a, and recirculated from the drying chamber 100 through the condenser 170 and the blower 168 as previously described. In this embodiment, as described above, nitrogen can also be supplied as the atomizing gas to the electrostatic nozzle assembly 16, or air or a combination of inert gas and air can be supplied as the atomizing gas to the electrostatic nozzle assembly 16, as long as it does not create a combustion atmosphere in the drying chamber. Otherwise, Figure 25A The operation of the drying system described herein is the same as previously described.

[0086] Reference Figure 25BThis illustrates another alternative embodiment of a drying system similar to the one described above, except that the powder collection cone 18a guides the powder to a conventional cyclone separator / filter bag housing 19a, in which the dried product is discharged from the lower outlet 19b, and exhaust gas is guided from the upper exhaust port line 165 for recirculation through the condenser 170, blower 168, dry gas heater 169, and drying chamber 11. Figure 25C In, it shows something similar to Figure 25B An alternative embodiment of the drying system is shown, but with a fine powder recirculation line 19c between the cyclone separator and filter bag housing 19a and the upper end of the drying chamber 11. The dried fine particles separated in the cyclone separator 19a are recirculated back to the drying chamber 11 through the fine powder recirculation line 19c to produce a powder with fine particle agglomeration. Similarly, the system operates in the same manner as described above in other respects.

[0087] Now for reference Figure 25D This illustrates another alternative embodiment of a fluidized bed powder drying system. Again, the powder drying system has a cylindrical drying chamber 12 with an impermeable liner 100 concentrically disposed therein, and an electrostatic spray assembly 16 for guiding electrostatically charged liquid particles to an effective heating zone 127 defined by the liner 100, as described above. In this case, a conical collection container section 18b conveys the powder from the drying chamber 12 to the collection chamber 19b via a conventional type of fluidized bed sieve separator 19c. In this embodiment, similar to the combination... Figure 11A As described in the embodiments, multiple fluidized bed cylindrical filter elements 160b are supported by an upper transverse plate 163b, which defines an exhaust chamber 164b near the top of the drying chamber 12. In this configuration, a blower 168 draws air from the exhaust chamber 164b, from which powder and particulate matter have been filtered, to be directed via line 165 through a condenser 170 and a heater 169 for reintroduction into the bottom collection chamber 19 and recirculated upwards through the drying chamber 12. The filter 16b also has a reverse pulse air filter cleaning device 167b of the type disclosed in referenced U.S. Patent 8,876,928, which has a corresponding air control valve 167c for periodically directing pressurized air to and through the filter 16b to clean the powder accumulated in the filter 16b.

[0088] While the impermeable lining 100 of the foregoing embodiments is preferably made of a flexible, non-conductive material (e.g., plastic), it may alternatively be made of a rigid plastic material, such as... Figure 3DAs shown. In that case, a suitable non-conductive mounting bracket 100d can be provided to secure the lining concentrically within the drying chamber 12. Alternatively, as Figure 3C As shown, the permeable liner may be partially (e.g., on one side of the diameter) made of a permeable filter material 100b, which allows air to flow through the liner for exhaust, and partially (e.g., on the opposite side of the diameter) made of a non-permeable material 100a, which prevents dry particles from being drawn into the liner.

[0089] As another alternative embodiment, such as Figure 15A As shown, the spray dryer system illustrated can be readily modified to cool a spray of molten flow (e.g., wax, hard wax, and glycerides) into a cold gas stream to form solidified particles. Objects similar to those described above have been labeled with similar reference numerals. During spray cooling, the raw material, with a melting point slightly above ambient conditions, is heated and placed in a storage tank 130, which in this case is enclosed in an insulator 130a. Using a pump 132, the raw material is pumped through a feed line 131 to the atomizing nozzle 16. The molten raw material is atomized using a compressed gas (e.g., nitrogen 150). During spray cooling, the molten liquid raw material may be electrostatically charged or destatically charged. In the latter case, the electrodes of the electrostatic nozzle assembly are de-energized.

[0090] During spray cooling, the atomizing gas heater 152 is shut off to deliver cooled atomized gas to the atomizing nozzle 16. During spray cooling, the dry gas heater 169 is also shut off, delivering dry gas, already cooled by the dehumidifying coil 170a, through the dry gas line 165 to the drying chamber 12. As atomized droplets enter the dry gas zone 127, the droplets solidify into particles that fall into the collection cone 18, exit recirculation with the airflow, and are collected in the collection chamber 19. Again, the removable liner 100 facilitates cleaning of the drying chamber as it can be removed and discarded. The insulating air gap 101 prevents the drying chamber 12 from becoming cold enough to form condensation on its outer surface.

[0091] In another feature of this embodiment, the spray system 10 can be operated using an automatic fault recovery system that allows the system to continue operating in the event of a transient charge field failure within the drying chamber, while providing an alarm signal in the event of a persistent electrical fault. Figure 27 The diagram shows a method flowchart for a fault recovery method for operating a voltage generator used in spray system 10. The method shown can be implemented in controller 133 (…). Figure 15 It operates in the form of a program executed within a machine or a set of computer-executable instructions. According to the illustrated embodiment, Figure 26The method described includes activating or otherwise starting the liquid pump at 300 to provide a pressurized fluid supply source to the sprayer inlet. At 302, verification of the voltage supply's validity is performed. If the voltage supply is determined to be invalid at 302, an error message is provided at the machine interface at 304, and at 306, the voltage generator and liquid pump are disabled until any existing faults, such as those identified at 302, that may have caused the voltage supply to be invalid have been corrected.

[0092] When the voltage supply is confirmed to be valid at 302, a predetermined time (e.g., 5 seconds) is used before the liquid pump starts at 308, and after the delay, the liquid pump runs at 310. At 312, a short circuit or arc check is performed while the pump continues to run at 310. When a short circuit or arc is detected at 312, an event counter and timer are maintained to determine if more than a predetermined number (e.g., 5) of short circuits or arcs have been detected within a predetermined time period (e.g., 30 seconds). These checks are performed at 314 whenever a short circuit or arc is detected at 312. If fewer than the predetermined number of short circuits or arcs occur within the predetermined time period, or even if only a single short circuit or arc is detected, the liquid pump stops at 316, the voltage generator that generates the voltage is reset by disconnecting and restarting at 318, and after a delay at 308, the liquid pump restarts at 310. This allows the system to repair the fault causing the spark or arc, and the system can continue to operate. However, if more than a predetermined number of sparks or arcs occur at 314 within a predetermined time period, an error message is generated at the machine interface at 320, and at 306, the system is put into standby mode by disabling the voltage generator and liquid pump.

[0093] Therefore, in one aspect, methods for correcting faults in an electrostatic spray drying system include initiating a pump start-up sequence, which requires first determining the state of the voltage generator and prohibiting the liquid pump from starting while the voltage generator is not activated. To this end, in one embodiment, a time delay is used before starting the liquid pump to allow sufficient time for the voltage generator to activate. The liquid pump is then started, and while the pump is running, the system continuously monitors for the presence of sparks or arcs, for example, by monitoring the current consumed from the voltage generator. When a fault is detected, the voltage generator is disconnected, the liquid pump is also disconnected, and depending on the severity of the fault, the system automatically restarts or enters standby mode, requiring operator attention and action to restart the system.

[0094] Finally, in another aspect of this embodiment, the spray drying system 10 has a controller that periodically changes the charge of the liquid sprayed by the electrostatic nozzle assembly in such a way that, for a particular spray application and the final use of the dried product, it can induce controlled and selective agglomeration of spray particles. In one embodiment, selective or controlled agglomeration of spray particles is achieved by varying the timing and frequency of atomizer activation between high and low atomizer frequencies (e.g., by using a pulse width modulation (PWM) atomizer command signal) to produce spray particles of different sizes, resulting in varying degrees of agglomeration. In another embodiment, selective or controlled agglomeration of spray particles can be achieved by modulating the applied voltage level to electrostatically charge the spray fluid. For example, the voltage can be selectively varied in the range of 0 to 30 kV. It is conceivable that, with such voltage variation, a higher applied voltage that charges the fluid will generally reduce the droplet size, thereby reducing drying time, and may further induce carrier migration to the outer surface of the droplets, thereby improving encapsulation. Similarly, a decrease in the applied voltage may tend to increase the droplet size, which may contribute to agglomeration, especially in the presence of smaller droplets or particles.

[0095] Other embodiments that could selectively influence the agglomeration of the sprayed particles include selectively changing, or pulsating, between high and low predetermined values, various other operating parameters of the system. In one embodiment, the atomizing gas pressure, fluid delivery pressure, and atomizing gas temperature can be varied to control or generally influence the droplet size and drying time. Additional embodiments may further include varying other parameters of the atomizing gas and / or drying air, such as their respective absolute or relative water content, water activity, droplet or particle size, etc. In one conceivable specific embodiment, the dew point temperature of the atomizing gas and drying air is actively controlled, and in another embodiment, the volumetric or mass flow rate of the atomizing gas and / or drying air is also actively controlled.

[0096] Figure 27A flowchart of a method for modulating pulse width in an electrostatic nozzle to selectively control the agglomeration of spray particles is shown. According to one embodiment, at the initial stage of the process, a voltage generator is turned on at 322. At 324, a determination is made as to whether PWM control (which will selectively control agglomeration) is effective or required. When PWM is not required or is ineffective, the process controls the system by controlling the voltage generator to a voltage setpoint at 326, and the fluid injector operates normally. When PWM is required or is effective, the system alternates between a low PWM setpoint and a high PWM setpoint for a predetermined period and within one cycle. In the illustrated embodiment, this is achieved by controlling the low PWM setpoint at 328 with a low pulse duration at 330. When the low pulse duration has expired, the system switches to a high PWM setpoint at 332 until the high pulse duration has expired at 334, and then returns to 324 to determine if another PWM cycle is needed. Although the term is used herein in relation to... Figure 27 The flowchart shown illustrates the variation of the PWM setpoint; however, it should be understood that other parameters can be modulated in addition to or in place of the atomizer PWM. As mentioned above, other parameters that can be used include the voltage level applied to energize the liquid, the atomizing gas pressure, the liquid delivery rate and / or pressure, the atomizing gas temperature, the water content of the atomizing gas and / or the dry air, and / or the volumetric or mass flow rate of the atomizing gas and / or the dry air.

[0097] Therefore, on the one hand, the agglomeration of spray particles is controlled by varying the injection time of the atomizer. At high frequencies (i.e., under high PWM), the atomizer opens and closes more rapidly, resulting in smaller particles. At low frequencies (i.e., under low PWM), the atomizer opens and closes more slowly, resulting in larger particles. As larger and smaller particles pass through the dryer in alternating layers, some particles physically interact and aggregate, regardless of their mutual repulsive charges, to generate agglomerates through collision. The system can control the specific size of the larger and smaller particles, and the corresponding number of each particle size generated per unit time, by setting their respective high and low PWM setpoints and each duration to suit each specific application.

[0098] According to another feature, such as Figure 28 and Figure 29As shown, multiple powder processing towers 10 with drying chambers 11 and electrostatic nozzle assemblies 16 as described above can be provided in a modular design, with powder discharged onto a general-purpose conveyor system 340, etc. In this case, multiple processing towers 10 are arranged adjacent to each other around a general-purpose work platform 341, which is accessible from the top via stairs 342, and has a control panel and operator interface 344 located at its end. In this case, each of the processing towers 10 includes multiple electrostatic nozzle assemblies 16. Figure 28 As shown, eight substantially identical processing towers 10 are provided, in which powder is discharged onto a general-purpose powder conveyor 340 (e.g., a screw feeder, pneumatic or other powder conveying device) to be discharged into a collection container.

[0099] This modular processing system has been found to have many important advantages. First, it is a scalable system that can be customized to user requirements using common components (i.e., the essentially same powder processing tower 10). For example... Figure 30 As shown, the system can also be easily expanded using other modules. Compared to standard, larger production spray dryer systems that are 40 feet tall and require special building layouts for installation, the processing tower 10 using this modular arrangement can also process larger volumes of powder with smaller building height requirements (15 to 20 feet). The modular design also allows for the isolation and maintenance of the individual processing towers of the system without interrupting the operation of other modules during maintenance during processing. The modular arrangement also allows the system to be scaled for energy usage to meet the specific production needs of a user. For example, five modules can be used for one processing requirement, while only three modules are used for another batch.

[0100] refer to Figures 31 to 33 This illustrates an alternative embodiment of a powder collection system 350 configured to protect the finished product from damage caused by exposure to moisture, heat, and / or oxygen. More specifically, the powder collection system 350 is equipped with a gas covering system for protecting the finished powder from exposure to moisture-containing gases, heat, and oxygen associated with the drying process. Figure 31 As shown, and similar to, for example Figure 12 In one embodiment, the powder collection system 350 includes a collection container 352 having an open upper end disposed at the bottom of a powder collection cone 354, which is then located at the lower end of a separation chamber 356. The separation chamber 356 communicates with a drying chamber 358. Drying gas and powder (typically produced by...) Figure 31 (As indicated by arrow 359) gas flows from the drying chamber 358 into the separation chamber 356, as shown in the image. Figure 31As shown. The separation chamber 356 is also connected to the exhaust outlet 360. When the powder falls into the collecting cone 354, the dry gas containing moisture leaves the separation chamber 356 through the exhaust outlet 360. In this case, the collecting container 352 is configured as a movable container, which is detachably fixed to the lower end of the opening of the powder collecting cone 354 by a clamp 362.

[0101] To facilitate the introduction of blanketing gas into the collection container 352, an adapter 364 is provided at the upper end of the collection container 352. In the illustrated embodiment, as... Figure 32 As shown, adapter 364 includes a rubber seal 366 that engages with the upper edge 368 of collection container 352. Adapter 364 surrounds the upper end of collection container 352 and defines a central channel 370 through which dried product is transferred from powder collection cone 354 to collection container 352. In this case, adapter 364 also defines a flange 372 which is captured in a clamp 362 that secures collection container 352 to powder collection cone 354. A covering gas inlet 374 communicating with the interior of collection container 352 is located near the upper end of collection container 352 (in this case, in the sidewall of adapter 364). This inlet 374 can be connected to a covering gas supply source, allowing covering gas to be directed into the interior of collection container 352. The covering gas can be any suitable gas, and is preferably cold and does not contain a significant amount of moisture or oxygen. Nitrogen is an example of a suitable covering gas, although other gases or gas mixtures can be used.

[0102] exist Figure 33 An exemplary covering gas supply system 378 is shown, which can be used to direct covering gas to an inlet port 374, thereby entering a collection container 352. The illustrated covering gas supply system 378 includes a covering gas supply source 380, which may be a pressurized tank connected to the inlet port 374 via a gas feed line 382. To control the flow rate of the covering gas, an adjustable flow control device 384, such as a flow meter or rotameter, can be provided in the gas feed line 382. The flow control device 384 can be configured to be manually adjusted by an operator of the spray dryer system, or it can be automatically adjusted based on signals received, for example, from a controller. To prevent over-pressurization of the collection container 352 and / or the gas feed line 382, ​​a pressure reducing valve 386 can be arranged in the gas feed line between the flow control device 384 and the collection container 352.

[0103] In operation, the material is spray-dried in drying chamber 358 and falls downwards into separation chamber 356 by gravity and airflow, then into collection cone 354. The falling product is then collected in collection container 352. Covering gas is introduced into collection container 352 through inlet port 374 and covers the falling product (in... Figure 32 (referred to as 388 in the text) and the settled product in collection container 352 (in Figure 32 (Referring to 390 in the text). The covering gas slightly pressurizes the collection container 352 and adapter 364, which prevents the discharged dry gas from entering the collection container 352 and prevents the finished product from being exposed to the harmful effects of moisture, heat, and / or oxygen. Excess covering gas travels upward through the powder collection cone 354 and into the separation chamber 356, mixes with the dryer exhaust, and exits the drying chamber through the exhaust outlet 360. The flow control device 384 can be configured to direct a sufficient flow of covering gas into the collection container 352 to protect the finished powder from the heat, moisture, and oxygen originating from the drying chamber 358 and the separation chamber 356. However, the covering gas flow rate should be maintained below a level at which the finished powder would fluidize and become airborne. The covering gas flow rate should also be set so as not to pressurize the collection container 352 to a level that would prevent the dried product from falling down into the collection container 352. If necessary, the collection container 352 can be detached from the collection cone 354 to remove the finished product. When doing so, a closure device (such as a regular cap or lid) can be placed above the open upper end of the collection container 352 to prevent the product from being exposed to ambient air that may contain moisture and oxygen.

[0104] Figure 34 and Figure 35 Another embodiment of a spray dryer configured as a spray cooling system 400 is shown for performing spray cooling on molten streams, such as waxes and polymers that are solid under atmospheric or near-atmospheric conditions. Figure 34 and Figure 35 The spray cooling system 400 is configured to discharge molten raw materials into a cold or cooled airflow in the drying chamber 12 of the spray dryer to form solid particles. Figure 34 and Figure 35 The spray cooling system 400 has the same characteristics as... Figure 15A The embodiments have some similarities, and items similar to those described above are marked with similar reference numerals.

[0105] According to an important aspect of this embodiment, Figure 34 and Figure 35 The spray cooling system 400 uses a pulse nozzle assembly 402 to discharge molten material into the drying chamber 12. More specifically, the pulse nozzle assembly 402 is configured to generate pulsed flows alternating between an open flow state and a closed flow state. Figure 35A cross-sectional view of an exemplary embodiment of a suitable pulse nozzle assembly 402 is shown in the figure. Figure 35 The nozzle assembly 402 is electrically actuated and includes a nozzle body 404 having a nozzle tip 406 defining a discharge orifice 407 fixed at its downstream end, and a metal plunger 408 disposed in a solenoid coil 410. In this configuration, the solenoid coil 410 is suitably coupled to an external power source via electrical leads contained in a suitable conduit 412 extending from the nozzle body 404. In a known manner, the electrical actuation of the solenoid coil 410 is effective in overcoming the bias force of the closing spring 414 to move the valve plunger 408 to the nozzle tip open position. When in the open position, molten material entering through the inlet port 416 of the nozzle body 404 can pass through the nozzle body 404 and exit from the nozzle through the nozzle tip 406. When the solenoid coil 410 is deactivated, the closing spring 414 moves the valve plunger 408 to the nozzle tip closed position, which prevents molten material from flowing out of the nozzle tip 406. This electrically actuated nozzle assembly can cycle at high speed between open and closed positions to intermittently discharge the molten flow.

[0106] The illustrated nozzle assembly 402 is heated to help maintain the desired elevated temperature of the molten feed material until the material exits from the nozzle tip 406. Furthermore, the illustrated nozzle assembly 402 is configured such that the nozzle tip 406 is removable from the nozzle body 404 and interchangeable with another nozzle tip of similar or different configuration. The nozzle tip 406 of the nozzle assembly 402 is preferably configured to produce a fan-shaped discharge pattern, which helps prevent collisions as particles are cooled by the spray. However, full-cone or hollow-cone discharge methods can be used depending on the application, the physical properties of the raw material, and chemical or morphological requirements. If a fan-shaped pattern is used, multiple nozzles can be used, arranged such that the straight portions of the fan-shaped pattern are parallel to each other. With such an arrangement, the on / off function of each individual nozzle can be synchronized with adjacent nozzles to help prevent droplet collisions. The ability to interchange the nozzle tip 406 on the nozzle body 404 allows the nozzle assembly 402 to produce different spray angles and droplet sizes depending on, for example, the application and / or the raw material used. In the illustrated embodiment, the nozzle body 404 and nozzle tip 406 are configured to produce hydraulic atomization of the molten material. In other embodiments, the pulsed nozzle assembly 402 may be configured to provide air atomization of the molten flow.

[0107] The pulse nozzle assembly 402 may be of a commercially known type, such as the pulse nozzle assembly 402 under the trademark PulsaJet provided by the assignee of this application, SprayingSystems Co. The various components of the nozzle assembly 402 shown and their modes of operation are similar to those described in U.S. Patent No. 7,086,613, the disclosure of which is incorporated herein by reference. Alternatively, any nozzle assembly capable of producing a pulsed spray action and configured to stop the flow of liquid from the nozzle and then immediately transfer full pressure to the nozzle tip once the flow resumes.

[0108] As in Figure 15A As in the previous embodiment, during the spray cooling operation, the drying gas delivered to the drying chamber 12 is cooled by a cooler, for example, by a dehumidifying coil. When atomized droplets exiting from the pulse nozzle assembly 402 enter the drying gas region 127, they solidify into particles that fall into the collection cone 18 and are recirculated as the airflow exits, being collected in the collection chamber 19. The removable liner 100 again facilitates cleaning of the drying chamber, as it can be removed and discarded. An insulating air gap 101 may be provided to prevent the drying chamber 12 from becoming cold enough to cause condensation to form on its outer surface.

[0109] To ensure that the molten feed material is maintained at the desired temperature before being discharged into the spray dryer, the spray cooling system 400 can be configured with a heated recirculation loop, which, for example, can maintain the molten material supplied to the nozzle assembly 402 at the desired elevated temperature. Figure 34 An embodiment of this recirculation loop is shown in the figure. The illustrated recirculation loop includes a heated reservoir 420 for storing molten material. The reservoir 420 is connected to the nozzle assembly 402 via a supply line 422 communicating with an inlet port 416 of the nozzle assembly 402 and a recirculation line 424 communicating with a recirculation port 426 of the nozzle assembly. Figure 34 (Illustrated schematically). A temperature sensor 428, located in the supply line 422 near the nozzle assembly 402, communicates with and controls a heater 430 in the reservoir 420 to maintain the molten material at a desired temperature, for example, just above its melting point. Maintaining the molten material just above its melting point temperature reduces the heat transfer necessary to convert the droplets of molten material into particles in the drying chamber 12, thus helping to ensure that the droplets are solidified as quickly as possible.

[0110] High flow rates can overwhelm the heat-carrying capacity of the dry gas, leading to improper droplet formation. The pulsed action generated by the nozzle assembly 402 eliminates high flow rates and allows for full-pressure delivery of the molten material, which helps ensure proper droplet formation. Furthermore, the pulsed discharge of the nozzle assembly 402 prevents both over-discharge and under-discharge of the molten material, which can also deteriorate droplet formation.

[0111] To move molten material from tank 420 to nozzle assembly 402, a pump 432 is provided in supply line 422. In this case, pump 432 is driven by a variable speed drive 434, which allows the pressure delivered by pump 432 to be regulated. Other adjustable drive arrangements for pump 432 may also be used. Pressure sensor 436, arranged in supply line 422 near nozzle assembly 402, monitors the pressure of the molten material, and this information is transmitted to variable speed drive 434 and can be used to ensure that pump 432 supplies molten material to the nozzle assembly at a constant pressure. A heated recirculation loop allows precise control of the temperature of the molten material reaching the nozzle assembly, including ensuring that the molten material remains at the desired temperature even if spraying operation is interrupted. In this case, the heated recirculation loop ensures that the molten material is immediately at the desired temperature after spraying resumes for optimal system performance.

[0112] As can be seen from the foregoing, a spray dryer system is provided that is more efficient and versatile in operation. Due to the improved drying efficiency, the spray dryer system can be made smaller and used more economically. The electrostatic spray system can also effectively dry different batches of products without cross-contamination, and its size and processing technology can be easily modified for specific spray applications. The spray drying system is also less susceptible to electrical faults and dangerous explosions caused by fine powder in the drying chamber atmosphere. The system can also be selectively operated to form particles that are more readily available for subsequent use. The system also features an exhaust filtration system for more efficient and effective removal of airborne particulate matter from the dried gas leaving the dryer. This system includes an automated device for removing dried particulate matter accumulated on the filter, which can hinder operation and require costly maintenance. Additionally, the system can be equipped with a gas covering system to protect the collected finished product from exposure to moisture-containing gases, heat, and oxygen from the drying chamber. However, the system's structure is relatively simple, allowing for more economical manufacturing.

Claims

1. A spray drying system for drying a liquid into a powder, comprising: The processing tower has a slender body supported in an upright position; The elongated body forms a drying chamber within the elongated body; The upper closed arrangement is located at the upper end of the elongated body and the lower closed arrangement is located at the lower end of the elongated body. An electrostatic nozzle assembly, which is supported in the upper closed arrangement; The supply source of the liquid to be spray-dried; The electrostatic nozzle assembly includes a nozzle body having a liquid inlet; a liquid supply source is connected to the liquid inlet to supply liquid to be dried to the electrostatic nozzle assembly; and a discharge spray tip assembly at the downstream end of the nozzle body is used to guide the liquid to be dried into the drying chamber. And electrodes, which are connected to a power source for electrically discharging liquid through the nozzle assembly into the drying chamber; The upper closed arrangement has a dry gas inlet; The source of the heated drying gas; The supply source of the heated drying gas is connected to the drying gas inlet to introduce the heated drying gas into the drying chamber, thereby drying the liquid into powder; and The lower closed arrangement includes a powder separation chamber having multiple filters to separate the dried powder received from the drying chamber from the moisture-containing dry gas. The powder separation chamber includes a dry gas outlet through which the moisture-containing dry gas separated from the powder exits the powder separation chamber. A powder direction cone, which communicates with the powder separation chamber and tapers inward in a downstream direction to receive dry powder from the powder separation chamber; and a removable powder collection container, which is installed below the powder direction cone to receive dry powder separated by the filter element and guided through the powder direction cone. A supply source of a covering gas cooler than the heated drying gas is provided. The removable powder collection container has a covering gas inlet at its upper end. The supply source of the covering gas is coupled to the covering gas inlet to guide the covering gas, which is cooler than the heated drying gas, over the dry powder in the removable powder collection container and across its upper end to cover the powder in the removable powder collection container and prevent the drying gas from entering the removable powder collection container. This protects the powder in the removable powder collection container from exposure to heat, moisture, and oxygen from the heated drying gas in the drying chamber. The removable powder collection container is removable to allow for the dispensing of the powder collected in it.

2. The spray drying system according to claim 1 further includes a cover gas feeding system inserted between the cover gas inlet and the cover gas supply source.

3. The spray drying system of claim 2, wherein, The covering gas feeding system includes an adjustable flow control device configured to regulate the flow rate of covering gas from the covering gas supply source to the covering gas inlet.

4. The spray drying system of claim 3, wherein, The covering gas feeding system also includes a safety valve inserted between the flow control device and the covering gas inlet.

5. The spray drying system of claim 1, wherein, The covering gas does not contain a considerable amount of moisture or oxygen.

6. The spray drying system of claim 1, wherein, The covering gas is nitrogen.

7. The spray drying system of claim 1, wherein, The powder collection container includes an adapter disposed at the upper end of the powder collection container, and the covering gas inlet is disposed in the side wall of the adapter, the adapter being configured to removably attach the powder collection container to the elongated body.

8. The spray drying system of claim 1, wherein, All the powder dried in the drying chamber is guided through the powder separation chamber and the powder direction cone to the powder collection container.

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