spray dryer

Abstract

An electrostatic spray dryer for drying a liquid into a powder includes an elongated body defining a drying chamber, a spray nozzle assembly at one end of the drying chamber, and a filter element housing and a powder collection chamber at the opposite end. A non-structural, non-metallic liner is disposed within the elongated body in a relationship spaced apart from an inner wall surface to define an internal drying area. The liner is releasably supported within the body so as to be selectively removed and replaced after specific use. The elongated body shown has a modular structure comprising multiple modules, wherein at least one module is selectively removable and replaceable for changing the length of the drying chamber for a specific spray application. The liner can also be replaced with a liner whose length corresponds to the changed length of the drying chamber or a liner with a different diameter for a specific application.

Description

[0001] This application is a divisional application of patent application No. 201680077647.1, filed on November 3, 2016, entitled "Apparatus and Method for Spray Drying".

[0002] Cross-reference to related applications

[0003] This patent application claims priority to U.S. Patent Application No. 62 / 250,318, filed November 3, 2015, the entire contents of which are incorporated herein by reference. Technical Field

[0004] This invention generally relates to spray dryers, and more specifically to apparatus and methods for spray drying liquids into the form of dry powder. Background Technology

[0005] Spray drying is a well-known and widely used method in which a liquid slurry is sprayed into a drying chamber, and hot air is introduced to dry the liquid into a powder. The slurry typically consists of a liquid (such as water), an ingredient (such as food, flavoring, or pharmaceutical), and a carrier. During the drying process, the liquid is expelled, leaving the ingredient in powder form encapsulated within the carrier. Spray drying is also used to produce powders that do not require encapsulation, such as various foods, additives, and chemicals.

[0006] Spray drying systems are typically quite large in structure, with drying towers that can reach several stories in height. The equipment itself represents a significant capital investment, and the facilities used must be of sufficient size and design to accommodate such equipment. The heating requirements for the drying medium can also be expensive.

[0007] While it is desirable to use electrostatic spray nozzles to generate electrostatic particles that facilitate faster drying, the electrostatic liquid can charge the system's components in some way, especially if unintentionally grounded. This can impede the operation of electrical controls and interrupt operation, resulting in the discharge of non-electrostatic liquid that has not been dried as intended.

[0008] Although the drying chambers of electrostatic spray dryers for non-metallic materials are known to be formed to better isolate the system from the electrostatic liquid, particles can adhere to and accumulate on the walls of the drying chamber, requiring time-consuming cleaning and disrupting the use of the system. Furthermore, the very fine drying powder in the heated air environment within the drying chamber can create hazardous explosive conditions due to accidental sparks or malfunctions of the electrostatic spray nozzles or other components of the system.

[0009] This spray dryer system must also be operable for spray drying different forms of liquid slurry. For example, in the fragrance industry, it might be necessary to use 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, continuously running pharmaceuticals are protected from cross-contamination.

[0010] Existing spray dryer systems also lack simple versatility. Sometimes it's desirable to run smaller batches of product for drying without using an entire large drying system. It may also be desirable to change how material is sprayed and dried into the system for a specific application. In other processes, it may be desirable for fine particles to agglomerate during drying to better facilitate final use, such as dissolving more quickly into the liquid used with it. However, existing sprayers are not adapted for simple modifications to accommodate these changes in processing requirements.

[0011] Spray dryers also tend to produce very fine particles that can remain airborne in the dried gas leaving the dryer system and must be filtered out. These fine particles can quickly clog filters, hindering the dryer's effective operation and requiring frequent filter cleaning. Existing spray dryers also typically use complex cyclone separators and filtration systems to remove airborne particulate matter. This equipment is expensive and requires costly maintenance and cleaning. 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 as 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 low 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 is effective for spray drying different batches of products without cross-contamination.

[0016] Another objective is to provide an electrostatic spray dryer system of the type described above, which 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 for drying powders in a manner that allows fine particles to clump together in a form that is better suited for subsequent use.

[0018] Another objective is to provide an electrostatic spray dryer system that can operate with lower heating requirements and therefore more economically and efficiently. A related objective is to provide this type of spray dryer system that is operable for efficiently drying 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 is suitable for repair, maintenance, and module replacement without shutting down the spray dryer system.

[0020] Another objective is to provide an electrostatic spray dryer system of the type described above that is less susceptible to electrical faults and hazardous explosions caused by fine powder and the heated environment within the system's drying chamber. A related objective is to provide a control system for such a spray dryer system that is effective in monitoring and controlling potential electrical faults in the system.

[0021] Another objective is to provide this type of spray dryer system with a filtration system for more effectively and efficiently removing airborne particulate matter from the dried gas leaving the dryer, with fewer maintenance requirements.

[0022] Another objective is to provide a spray dryer system characterized as described above, wherein the drying gas filter system includes means for automatically and more effectively removing particulate matter buildup on the filter.

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

[0024] 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

[0025] Figure 1 This is a side view of the powder processing tower of the spray dryer system shown.

[0026] Figure 2 yes Figure 1 The vertical cross-section of the powder processing tower shown;

[0027] Figure 3 This is an exploded perspective view of the powder processing tower shown.

[0028] Figure 3A This is a plan view of an unassembled, flexible, non-permeable liner that can be used with the powder processing tower shown.

[0029] Figure 3B This is a plan view of an alternative embodiment of the liner, similar to that shown in Figure A1 but made of a permeable filter material;

[0030] Figure 3C This is a plan view of another alternative embodiment of the liner, wherein the liner is made of a partially non-permeable material and a partially permeable filter material, which can be used with the powder processing tower shown.

[0031] Figure 3D This is a plan view of another alternative embodiment of the liner, wherein the liner is made of a non-permeable, non-conductive rigid material, which can be used with the powder processing tower shown.

[0032] Figure 4 This is an enlarged top view of the top cover or lid of the powder processing tower shown, in which an electrostatic spray nozzle is centrally supported.

[0033] Figure 5 yes Figure 4 Side view of the top cover and spray nozzle assembly shown;

[0034] Figure 6 This is an enlarged vertical cross-section of the electrostatic spray nozzle assembly shown.

[0035] Figure 7 This is an enlarged partial cross-sectional view of the nozzle support head of the electrostatic spray nozzle assembly shown.

[0036] Figure 8 This is an enlarged partial cross-sectional view of the discharge end of the electrostatic spray nozzle assembly shown.

[0037] Figure 8A It is similar to Figure 8 The partial cross-sectional view of the spray nozzle assembly shown shows that its exhaust spray tip has been modified to spray more viscous liquid.

[0038] Figure 9 It is along Figure 8 The cross-section of the electrostatic spray nozzle assembly is shown in line 9-9.

[0039] Figure 10 This is a partially enlarged sectional view of the powder collecting cone and filter element housing of the powder processing tower shown.

[0040] Figure 10A yes Figure 10 An exploded perspective view of the powder collecting cone and filter element housing shown;

[0041] Figure 11 A partial cross-sectional side view of an alternative embodiment of a filter element housing for use with the powder processing tower shown;

[0042] Figure 11A yes Figure 11An enlarged partial cross-sectional view of one of the filters in the filter housing shown in the diagram, illustrating a reverse gas pulse filter cleaning device in a non-operating state;

[0043] Figure 11B It is similar to Figure 11A An enlarged partial cross-sectional view showing a reverse gas pulse air filter cleaning device in operation;

[0044] Figure 12 This is a side view of an alternative embodiment of the filter element housing and powder collection chamber;

[0045] Figure 12A yes Figure 12 The top plan view of the filter element housing and powder collection chamber shown;

[0046] Figure 12B yes Figure 12 An enlarged partial cross-sectional view of the filter element housing and powder collection chamber shown;

[0047] Figure 12C yes Figure 12 An exploded perspective view of the filter element housing and the associated upstream air intake chamber shown.

[0048] Figure 13 A partial cross-sectional view shows the fastening arrangement for securing the top cover and associated upper liner support ring assembly to the drying chamber;

[0049] Figure 13A It is similar to Figure 12 However, a partial cross-sectional view is shown of the fastening arrangement for securing the drying chamber to a powder collection cone having an associated bottom liner support ring assembly;

[0050] Figure 14 This is an enlarged partial view of one of the fasteners shown;

[0051] Figure 15 This is a schematic diagram of the spray dryer system shown.

[0052] Figure 15A This is a schematic diagram of an alternative embodiment of a spray dryer operable to cool a molten flow into solid particles;

[0053] Figure 16 A partial cross-sectional view of the fluid supply pump and its associated drive motor for the spray drying system shown is presented.

[0054] Figure 16A It is the vertical cross-section of the fluid supply pump shown, which is supported within an external non-conductive housing;

[0055] Figure 17This is an enlarged top view of the insulating liner and its support ring assembly.

[0056] Figure 18 It is similar to Figure 17 However, an enlarged top view of the support ring assembly supporting the smaller diameter insulating liner is shown;

[0057] Figure 19 This is an enlarged side view of the top cover of the powder processing tower shown, which supports multiple electrostatic spray nozzle assemblies.

[0058] Figure 20 yes Figure 19 Top view of the top cover shown;

[0059] Figure 21 The vertical cross-section of the powder processing tower shown is modified to support electrostatic spray nozzles near the center of the bottom of its drying chamber for spraying liquid in an upward direction for drying.

[0060] Figure 22 yes Figure 21 A schematic side view of the bottom mounting support of the electrostatic spray nozzle assembly shown;

[0061] Figure 23 yes Figure 22 A top view of the electrostatic spray nozzle assembly and bottom mounting support shown;

[0062] Figure 24 yes Figure 22 and Figure 23 An enlarged cross-sectional view of a support rod mounted on the bottom of the spray nozzle shown.

[0063] Figure 25 This is a diagram illustrating an alternative construction of an illustrative powder drying system;

[0064] Figure 25A This is a schematic diagram of an alternative embodiment of a spray dryer system in which fresh nitrogen is introduced into the gas recirculation line of the system.

[0065] Figure 25B This is a schematic diagram of another alternative embodiment of a spray dryer system that utilizes a cyclone separator / filter bag assembly for filtering particulate matter from a recirculated dry air stream.

[0066] Figure 25C It is similar to Figure 25B An alternative embodiment is provided, in which the dried fine particles separated in the cyclone separator are reintroduced into the drying chamber;

[0067] 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 drying gas;

[0068] Figure 26 This is a flowchart of a method for recovering from a voltage generator fault in an electrostatic spray dryer system, according to the present disclosure.

[0069] Figure 27 This is a flowchart of a method for modulating the pulse width in an electrostatic spray nozzle used in an electrostatic spray dryer system, according to the present disclosure;

[0070] Figure 28 This is a top view schematic diagram of a modular spray dryer system with multiple powder processing towers;

[0071] Figure 29 yes Figure 28 The front plan view of the modular spray dryer system shown; and

[0072] Figure 30 It is similar to Figure 28 However, this is a top view of a modular spray dryer system with an additional powder handling tower.

[0073] While the invention allows for various modifications and alternative constructions, 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, the invention covers all modifications, alternative constructions, and equivalents falling within the spirit and scope of the invention. Detailed Implementation

[0074] Referring now more specifically to the accompanying drawings, an illustrative spray drying system 10 according to the invention is shown, comprising a processing tower 11, the processing tower 11 including a drying chamber 12 in the form of an upright cylindrical structure, a top closure device in the form of a cover or lid 14 for the drying chamber 12 having a heated air inlet 15 and a liquid spray nozzle assembly 16, and a bottom closure device in the form of a powder collecting cone 18 supported at the bottom of the drying chamber 12, the powder collecting cone 18 extending through a filter element housing 19 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 spray nozzle assembly 16. The heated air inlet 15 shown is oriented to guide hot air into the drying chamber 12 in a tangential rotational direction. A frame 24 supports the processing tower 11 in an upright position.

[0075] According to an important aspect of this embodiment, such as Figures 6-9The illustrated spray nozzle assembly 16 is a pressurized air-assisted electrostatic spray nozzle assembly for introducing a spray of electrostatically charged particles into a drying chamber 12 to rapidly and efficiently dry a liquid slurry into the desired powder form. The illustrated spray nozzle assembly 16 may be of the type disclosed in International Application PCT / US2014 / 056728, comprising a nozzle support head 31, an elongated nozzle tube or body 32 extending downstream from the head 31, and a spray discharge 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 for connection to a supply line 131 communicating with a liquid supply. It should be 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 containing a solvent (e.g., water), desired ingredients (e.g., fragrances, food, pharmaceuticals, etc.), and a carrier such that, when dried into powder form, the desired ingredients are encapsulated within the carrier, as is known in the art. Other forms of slurry may also be used, including liquids that do not contain a carrier or require encapsulation to dry the product.

[0076] 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 channel 39 receives and communicates with an air inlet fitting 40 connected to a suitable pressurized gas supply. The head 31 also has a radial channel 41 upstream of the liquid inlet channel 36, which accommodates a fitting 42 for securing a high-voltage cable 44 to a high-voltage source, and has an end 44a extending into the channel 41, which is in electrical contact with an electrode 48 axially supported within the head 31 and extending downstream of the liquid inlet channel 36.

[0077] 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 has a downstream outwardly extending radial hub 51 that fits within a countersunk hole in the head 31, and a sealing O-ring 52 is inserted therebetween.

[0078] The elongated body 32 is in the form of an outer cylindrical body member 55 made of plastic or other suitable non-conductive material, having an upstream end 55a that is threadedly engaged in a threaded hole in the head 31, with a sealing O-ring 56 positioned between the cylindrical body member 55 and the head 31. A liquid supply 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 communicating liquid between the axial electrode liquid channel 49 and the discharge spray tip assembly 34, and to define an annular atomizing air channel 60 between the liquid supply tube 58 and the outer cylindrical body member 55. The upstream end of the liquid supply tube 58, protruding above the threaded inlet end 55a of the outer cylindrical nozzle body 55, fits within a downwardly opening cylindrical hole 65 in the electrode hub 51 and is electrically conductive. With electrode 48 charged by high-voltage cable 44, it can be seen that the liquid supply to inlet channel 36 is charged as it passes through electrode channel 49 and liquid supply pipe 58 along the entire length of elongated nozzle body 32. In this case, pressurized gas communicates around the upstream end of liquid supply pipe 58 through radial air inlet channel 39 and then enters annular air channel 60 between liquid supply pipe 58 and outer cylindrical body member 55.

[0079] The liquid supply tube 58 is configured to make electrical contact with the electrode 48 for effectively charging the liquid throughout the passage from the head 31 and the elongated nozzle body 32 to the discharge spray tip assembly 34. For this purpose, the discharge spray tip assembly 34 includes a spray tip 70 having an upstream cylindrical portion 71 surrounding the downstream end of the liquid supply tube 58, with a sealing O-ring 72 inserted therebetween. The spray tip 70 includes an inwardly tapered or conical intermediate portion 74 and a downstream cylindrical nose 76 defining a cylindrical flow channel 75 and a liquid discharge orifice 78. In this case, the spray tip 70 has a segmented radially retaining flange extending outward from the upstream cylindrical portion 71 defining a plurality of air channels 77, which will become apparent.

[0080] To introduce liquid from the feed pipe 58 and through the spray tip 70, while continuing electrostatic charging as the liquid is guided through the spray tip 70, a conductive pin unit 80 is supported within the spray tip 70 and is in electrical contact with the downstream end of the supply pipe 58. The pin unit 80 in this case includes an upstream cylindrical hub portion 81, which forms a downstream conical wall portion 82 supported within an intermediate conical portion 74 of the spray tip 70. The cylindrical hub portion 81 forms a plurality of radially spaced circumferentially spaced liquid flow passages 83. Figure 9It connects the liquid supply pipe 58 and the cylindrical spray tip channel portion 75. It can be seen that when the conductive pin unit 80 is placed inside the spray tip 70, it is physically supported by the downstream end of the liquid supply pipe 58.

[0081] To concentrate the charge on the liquid exiting from the spray tip, the pin unit 80 has a downwardly extending central electrode pin 84 supported concentrically with the spray 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 spray tip discharge orifice 78 by a distance, for example, between approximately 1 / 4 and 1 / 2 inch. As the protruding electrode pin 84 exits the spray tip 70, the contact of the liquid around it further enhances the charge concentration on the exiting liquid, thereby enhancing the breakdown and distribution of liquid particles.

[0082] Or, such as Figure 8A As shown, when spraying more viscous liquid, the discharge spray tip 34 may have a hub portion 81 similar to that described above, but without the downwardly extending central electrode pin 84. This arrangement allows the more viscous liquid to pass more freely through the spray tip, while electrostatic discharge of the liquid still enhances liquid decomposition to more effectively dry the viscous liquid.

[0083] The exhaust spray tip assembly 34 also includes an air or gas cap 90 disposed around the nozzle tip 70, which defines an annular atomizing air passage 91 around the nozzle tip 70 and holds the spray tip 70, pin unit 80, and liquid supply tube 58 in an electrically conductive assembly with each other. In this case, the gas cap 90 defines a tapered pressurized airflow passage portion 91a around the downstream end of the spray tip 70, which communicates via a circumferentially spaced air passage 77 in the spray tip retaining flange with an annular air passage 60 between the liquid supply tube 58 and the outer cylindrical body member 55, for guiding pressurized air or gas exhaust fluid around the nozzle tip nose 76 through an annular exhaust orifice 93 and out of the spray tip liquid exhaust orifice 78. To keep the internal components of the spray nozzle in an assembled relationship, the gas cap 90 has an upstream cylindrical end 95 that is threadedly engaged with a downstream externally threaded end of the outer cylindrical member 55. The gas cap 90 has a countersunk hole 96 that receives and supports the segmented radial flange of the spray tip 70 to support the spray tip 70, and thus the pin unit 80 and the liquid supply tube 58 are electrically connected to the upstream electrode 48.

[0084] The spray nozzle assembly 16 is operable to discharge a spray of electrostatically charged liquid particles into the drying chamber 12. Indeed, the illustrated electrostatic spray nozzle assembly 16 has been found to be operable to produce extremely fine liquid droplets, for example, approximately 70 micrometers in diameter. It is evident that the liquid particles are readily and efficiently dried into fine particulate form due to the breakdown and repulsive properties of the fine liquid spray particles introduced into the drying chamber from both the heated air inlet 15 and the air-assisted spray nozzle assembly 16, and the heated drying gas. It should be understood that although the illustrated electrostatic spray nozzle assembly 16 has been found to be particularly useful for the present invention, other electrostatic spray nozzles and systems can be used, including electrostatic hydraulic rotary spray nozzles of known types and high-capacity low-pressure electrostatic spray nozzles.

[0085] According to another important feature of this embodiment, the drying chamber 12 has an internal non-metallic insulating liner 100, which is coaxially spaced from the inner wall surface of the drying chamber 12, wherein electrostatically charged liquid spray particles from the spray nozzle assembly 16 are discharged. Figure 2 As shown, the diameter d of the liner is smaller than the inner diameter d1 of the drying chamber 12, thereby providing an insulating air gap 101, preferably at least about 2 inches (about 5 cm) from the outer wall surface of the drying chamber 12, but other sizes may also be used. In this embodiment, the liner 100 is non-structural and is preferably made of a non-permeable flexible plastic material 100a. Figure 3 and 3A Alternatively, as will become apparent, it can be made of a rigid, non-permeable, non-conductive material 100c ( Figure 3D ), Permeable filter material 100b ( Figure 3B ) or partially non-permeable material 100a and partially permeable filter material 100b ( Figure 3C Made from ( ).

[0086] According to another aspect of this embodiment, the processing tower 11 has a quick-assembly and disassembly structure, which facilitates the assembly and installation of the annular liner 100 and provides electrical insulation to the outer wall of the drying chamber 12. For this purpose, the annular insulating liner 100 is supported at opposite ends by corresponding upper and lower support ring assemblies 104. Figure 1 , Figure 3 , Figure 13 , Figure 13A , Figure 14 and Figure 17Support. In this case, each ring assembly 104 includes an inner cylindrical support ring 105, one end of a liner 100 is attached to the inner cylindrical support ring 105 and the inner cylindrical support ring 105, and a plurality of circumferentially spaced non-conductive polypropylene or other plastic support studs 106, which are secured in a radial relationship extending outward relative to the support ring 105. 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 positioned on the liner 100 and the support ring 105 ( Figure 13 The annular U-shaped rubber washer 108 is fixed to the folded end of the liner 100. Similarly, the lower end of the liner 100 is trained around 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 edges of the support ring 105.

[0087] To secure each bracket 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 aligned holes in the mounting rings 110 and the outer wall of the drying chamber 12 for threaded engagement of the insulating bracket studs 106. In this configuration, rubber O-rings 112 are arranged around the end of each bracket stud 106 to seal the inner wall of the drying chamber 12, and neoprene adhesive sealing washers 114 are arranged around the head of each retaining screw 111.

[0088] In order to securely fix the top cover 14 of the drying chamber to the drying chamber 12 on the upper support ring assembly 104, the annular array 120 ( Figure 1 and Figure 2 The spaced-apart releasable latch assemblies 121 are secured to the mounting ring 110 at circumferentially spaced positions between the spaced bracket studs 106. Figures 13-14The latch assembly 121 may be of a known type, having an upwardly extending pull hook 122 that is positioned on the top edge of the cover 14 and pulled downward into a locked position as the latch arm 124 pivots downward into a latched position, for holding the top cover 14 against a U-shaped washer 108 around the upper edge of the support ring 105, and holding a similarly larger diameter annular U-shaped washer 126 around the upper edge of the cylindrical drying chamber 12. The latch assembly 121 may be easily unlocked by a reverse pivoting movement of the latch hook 124, allowing the pull hook 122 to move upward and outward to allow removal of the top cover 14 if needed. A similar annular array 120a of latching assembly 121 is arranged around a mounting ring 110 adjacent to the bottom of the drying chamber 12, in this case having a traction hook 124 positioned downwards to overlap with the outwardly extending flange 129 of the collecting cone 18, for holding the flange 129 of the collecting cone 18 against the bottom edge of the support ring 105 and the bottom cylindrical edge of the drying chamber 12. Figure 13A The rubber gaskets 108 and 126 are sealed together. It should be understood that, for a particular application, the liner 100, O-rings, and other sealing gaskets 108 and 126 may or may not be made of FDA-compliant materials.

[0089] During the operation of the electrostatic spray nozzle assembly 16, from the liquid supply (such as...) Figure 15 As shown, the liquid supplied from the liquid storage tank 130 to the electrostatic spray nozzle assembly 16 is guided by the electrostatic spray nozzle assembly 16 into the effective drying area 127 defined by the annular liner 100. The liquid is supplied from the liquid supply holding tank 130 via a liquid supply or delivery line 131, which is connected via a pump 132 to the liquid inlet fitting 38 of the spray nozzle assembly 16. This pump 132 is preferably a peristaltic dosing pump with a liquid guide roller system that can operate in a conventional manner. Figure 16A As shown, in this configuration, the peristaltic metering pump 132 comprises three plastic electrically isolated 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 a recognized grounding wire through a support frame 24, which is secured to the machine via metal-to-metal contact.

[0090] The electronic controller 133 is operatively connected to and operated to control the operation of various actuators and electrical or electronic devices in the electrostatic spray dryer system, such as the electric motor 134, pump 132, liquid spray nozzle assembly 16, high-voltage generator supplying voltage to the high-voltage cable 44, etc. Although a single controller is shown, it should be understood that a distributed controller arrangement comprising more than one controller can be used. As shown, the controller 133 is capable of operating in response to a program, such as a programmable logic controller. For clarity, Figure 15 The various operable connections between the controller 133 and various other components of the system are omitted.

[0091] According to another aspect of this embodiment, pump 132 is provided by electric motor 134 which is electrically isolated from pump 132. Figure 16 The pump 132 is coupled to a liquid supply line 131 that connects to the spray nozzle assembly 16 to prevent electrostatically charged liquid from the spray nozzle assembly 16 from charging the electric motor 134. For this purpose, the drive motor 134 has an output shaft 135, which is coupled to a pump head drive shaft 136 via a non-conductive drive section 138, such as that made of rigid nylon, which isolates the pump 132 from the electric drive motor 134. In the illustrated embodiment, the non-conductive drive section 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 a connecting plate 139, which is fixed to the non-conductive drive section 138 by screws 141. The pump head drive shaft 136 similarly carries a connecting plate 140 fixed to the opposite end of the non-conductive drive section 138 by screws 141.

[0092] An electrostatic voltage generator 222 is electrically connected to the nozzle assembly 16 via a wire 224 to provide voltage for electrostatically charged spray droplets. In the illustrated embodiment, the wire 224 includes a variable resistance element 226, which is optional and can be manually or automatically adjusted to control the voltage and current supplied to the spray nozzle assembly 16. An optional grounding wire 228 is also electrically connected between the liquid supply line 131 and grounding 232. Grounding wire 228 includes a variable resistor 230 that is manually or automatically adjusted to control the voltage present in the fluid. In the illustrated embodiment, the grounding wire is positioned 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 line in the system.

[0093] In this configuration, the drive motor 134 is also properly grounded and is supported within a non-conductive plastic motor mounting housing 144. The illustrated liquid storage tank 130 is supported on a liquid gauge 145 to allow monitoring of the liquid level in the tank 130, and an electrical isolation barrier 146 is positioned between the underside of the liquid storage tank 130 and the 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 can be electrically insulated from their electrical operating systems can be used.

[0094] In this case, the pressurized gas directed to the atomizing air inlet fitting 18 of the spray nozzle assembly 16 originates from a large nitrogen supply 150, which is connected via a gas supply line 151. Figure 15 The atomizing air inlet fitting 18 is connected to the spray nozzle assembly 16. A gas heater 152 is provided in the supply line 151 to supply dry, inert nitrogen gas to the spray nozzle assembly 16 at controlled temperature and pressure. It should be understood that although nitrogen is described as an atomizing gas in connection with this embodiment, other inert gases, or other gases containing air, can be used, as long as the oxygen level in the drying chamber is kept below a certain level, which will create a combustible atmosphere in the drying chamber that can be ignited by sparks or other electrical faults of the electrostatic spray nozzle assembly or other electronic control components of the drying system.

[0095] According to another important aspect of this embodiment, heated nitrogen atomized gas supplied to the spray nozzle assembly 16 and incident into the drying chamber 12 is continuously circulated through the drying chamber 12 as a drying medium. See also... Figure 15 As understood, the drying gas introduced into the drying chamber 12 from the drying gas inlet 15 and the spray nozzle assembly 16 will circulate within the length of the drying chamber 12, thereby effectively drying the injected electrostatically charged liquid particles 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 manually or by other appropriate automated means.

[0096] like Figure 10 and Figure 10AThe powder collecting cone 18 shown 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 dry powder into the powder collecting chamber 21. In this case, the filter element housing 19 has a pair of vertically stacked annular FIEPA filters 160, which are spaced outwardly around the lower portion of the powder collecting cone 18. The powder collecting cone 18 shown has an outwardly extending radial flange 161, the middle end of which is located above the upper filter 160 in the filter element housing 19, and an annular seal 162 is located 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, only the finest particles will remain entrained in the dry gas as they migrate upwards around the bottom portion of the powder collecting cone 18 and then outwards through the FEPA filter 160, which restricts and filters the fine powder before it is discharged through the exhaust outlet 20 of the filter housing 19.

[0097] Or, such as Figure 11 , Figure 11A and Figure 11B As shown, a filter element housing 19a can be used, comprising a plurality of circumferentially spaced cylindrical filters 160a, the cylindrical filters 160a being mounted perpendicularly to a central transverse support panel 163 of the housing 19a. Particle-containing gas, guided from the collection cone 18 to the lower collection chamber, flows laterally through the filters 160a into a common exhaust chamber 164 above the transverse support panel 163 within the filter element housing 19a for communication via an outlet port 20a, wherein the filters 160a restrict the particles from being affected by the airflow. For periodic cleaning of the filters 160a, each filter 160a has a corresponding reverse pulse air filter cleaning device 167 of the type 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.

[0098] like Figure 11A and Figure 11BAs shown, each of the reverse pulse air filter cleaning devices 21 includes a reverse pulse nozzle 240, which has a gas inlet 241 in the upper wall of the exhaust chamber 164. The gas inlet 241, secured by an annular retainer 242, is used to connect 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 that defines a hollow internal air passage 244 extending from the inlet 241 through the exhaust chamber 164 and substantially defining the length of the filter 160a. The nozzle 240 has a plurality of relatively large-diameter exhaust holes 246 formed in the portion within the exhaust chamber 164, and a plurality of smaller-sized air exhaust holes 248 formed along the length of the nozzle 240 within the filter 160a.

[0099] 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 cut-off plunger 249 is provided above the reverse pulse nozzle 160a for axial movement within the exhaust chamber between an exhaust port open and closed position. 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 shown includes an upper annular seal of relatively small diameter and a guide flange 252 having an outer periphery adapted for sliding seal engagement with the interior of the cylinder 250, and a lower, larger-diameter valve head 254 disposed below the lower end of the cylinder 250 for sealing engagement with the exhaust port 253 in the panel 163. The plunger 249 is preferably made of an elastic material, and the upper seal and guide flange 252 and the lower valve head 254 have a downwardly tapering or cup-shaped construction.

[0100] The plunger 249 is configured for 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, such as Figure 11A As shown. When the valve plunger 249 is biased to this position, the process gas flows from the filter element housing 19a through the filter 160a, the exhaust port 253 and into the exhaust chamber 164.

[0101] 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 is first guided through a larger diameter or plunger actuation orifice 246 into plunger cylinder 250 above plunger seal and guide flange 252, and then through a smaller reverse pulse nozzle orifice 248. Because the larger orifice 249 provides a less resistant path, the gas initially flows into plunger cylinder 250, and as the pressure in plunger cylinder 250 increases, it overcomes the biasing force of spring 256, pushing plunger 249 downwards. Eventually, the pressure builds up to overcome the force of spring 256, pushing plunger 249 downwards towards exhaust port 253, thus temporarily sealing it. After the plunger 249 seals the exhaust port 253, the compressed gas in the external plunger cylinder 250 can no longer move the plunger 249, and the gas pressure in the plunger cylinder 250 increases to a point where the compressed gas is then forced through the smaller nozzle orifice 248 and against the filter 160a to remove particulate matter accumulated around its outer surface.

[0102] After the reverse compressed air pulse and the movement of accumulated particles on filter 160a, the pressure will dissipate within plunger cylinder 250 to the point where it no longer counteracts the 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 continue operating the dryer.

[0103] Figures 12-12B An alternative embodiment of an exhaust filter element housing 270 and a powder collection chamber 271, which can be mounted on the lower end of the drying chamber 12, is depicted. In this case, an upper powder guiding collection 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 disposed below the powder guiding collection chamber 272, a powder guiding 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 guiding cone 275.

[0104] The powder guiding gas collection chamber 272 shown includes an outer cylindrical housing wall 289, which is hermetically mounted on 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. A downwardly opening conical exhaust chamber 281 is provided within the powder guiding gas collection chamber 272, defining an exhaust chamber 282 on its lower side. Figure 12B And 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.

[0105] The filter element housing 270 includes an outer cylindrical housing wall 284 that is sealed to the bottom peripheral edge of the powder guiding gas collection chamber 272 via an annular seal 285, and an inner cylindrical filter shroud 286 that 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 powder is supported within the outer cylindrical housing wall 289 of the gas guiding collection chamber 272 and the filter element housing 270 to define an air passage 291 communicating around the bottom perimeter 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 gas and powder passing through the powder guiding collection chamber 272 are guided outward from the conical exhaust chamber 281 around the filter element shroud 281 to the powder guiding cone 275 and the collection chamber 271 below.

[0106] In this configuration, the cylindrical filter 274 is supported in relation to a circular support plate 295 fixedly disposed below the lower side of the downwardly opening conical exhaust chamber 281. In this configuration, the circular filter support plate 295 is mounted in a slightly recessed relationship to the circumferential boundary of the cylindrical cover 286 and defines the bottom wall of the exhaust chamber 282. The cylindrical filters 274 shown are all in box form, comprising a cylindrical filter element 296, an upper cylindrical box retaining plate 298, a bottom end cap, and a sealing plate 299 with inserted annular sealing elements 300, 301, and 302. To secure the filter box in an assembled relationship, the upper box retaining plate 298 has a suspended U-shaped support member 304 with a threaded lower end stud 305, which is positioned to pass through a central hole in the bottom end cap 299, secured by a nut 306 inserted therebetween via an O-ring sealing ring 308. Each filter cartridge has an upper retaining plate 298 that is sealed to a corresponding circular opening 310 in a central support plate 295. The filter element 296 is positioned relative to the lower side of the support plate 295, and the central opening 311 in the retaining plate 298 communicates between the exhaust chamber 282 and the interior of the cylindrical filter element 296. In this configuration, the filter element cartridges are arranged circumferentially spaced around the center of the inner shroud 274.

[0107] In this configuration, the filter element housing 270 is secured to the powder-guiding gas collection chamber 272 by a releasable clamp 315 or similar fastener to allow easy access to the filter cartridge. An internal filter shroud 286 may also be releasably mounted around the cylindrical filter 274, for example, via a pin and slot connection, to allow access to the filter for replacement.

[0108] During the operation of the dryer system, it will be observed that the dry gas and powder guided into the powder guiding collection chamber 272 will pass around the conical exhaust chamber 281 and enter the annular passages 291, 292 surrounding the internal filter element shroud 274, flowing downwards into the powder guiding cone 275 and the collection chamber 271 for collection within chamber 271. Although, as previously stated, most of the dry powder retained in the airflow will migrate to the powder collection chamber 271, it will become apparent that as the dry gas passes through the filter into the dry gas exhaust chamber 282 to be discharged through the dry gas exhaust port 320 and recirculated back to the drying chamber 12, the particulate matter carried by the fine gas will be separated and retained by the annular filter 274.

[0109] To clean the powder-accumulated cylindrical filters 274 during the use of the dryer system, each cylindrical filter 274 has a corresponding reverse gas pulse cleaning device 322. For this purpose, the gas guiding 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, which in this case is mounted on the outside of the air guiding chamber 272. The gas pulse guiding line or pipe 328 extends radially from the control valve 326 through the conical walls of the air guiding chamber 272 and the exhaust chamber 329, then turns downward at a right angle, and the end discharge end 329 of the gas pulse guiding line 328 is positioned above and aligned with the central opening 311 of the filter cartridge retaining plate 298, and located on the cylindrical filter element 296 below.

[0110] By appropriate selection or automatic control, control valve 26 can be cyclically operated to axially release pulses of compressed gas from line 328 into the circulating filter 274, thereby moving accumulated powder onto the outer wall 296 of the cylindrical filter element. The discharge end 329 of the pulsed gas guide line 328 is preferably spaced from the upper end of the circulating filter 274 to facilitate the guidance of compressed gas pulses into 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 from the upper end of the cylindrical filter element by a distance, such that the expanding airflow (e.g., Figure 12B (As shown in 330) it has an outer periphery that substantially corresponds to the diameter of the central opening 311 in the cartridge retainer plate 298 when it reaches the filter cartridge. In this exemplary embodiment, the air guide tube 28 has a diameter of about 1 inch, and the distance between the discharge end 329 and the retainer plate 298 is about 2.5 inches.

[0111] In this case, the powder collection chamber 271 has a circular butterfly valve installed at the upper end of the collection chamber 271 (shown separately within the powder collection chamber 271, as shown below). Figure 12B As shown, the collection chamber can be operated by a suitable actuating device 341 for rotatable movement between a vertical or open position that allows dry powder to be guided into the collection chamber 271 and a horizontal closed position that blocks dry powder from entering the collection chamber 271 when the powder is removed. Alternatively, it should be understood that the powder collection chamber 271 can deposit powder directly from its open bottom end onto a movable conveyor belt.

[0112] To recirculate and reuse the dry gas exiting from the filter element housing 19a, the outlet 20 of the filter housing 19a is connected to a recirculation line 165, which in turn passes through a condenser 166, a blower 168, and a dry gas heater 169. Figure 15 A 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 gas stream via a chilled water refrigeration coil 170a with corresponding chilled water supply and return lines 171, 172. The condensate from the condenser 170 is directed into a collection container 174 or a drain pipe. The dried nitrogen is then directed by a blower 168 through a gas heater 169, which reheats the dried gas to a predetermined heating temperature for specific powder drying after cooling in the condenser 170, and directs it back to the heating gas inlet port 15 and into the heating chamber 12. An exhaust control valve 175, connected to a recirculation line 165 between the blower 168 and the heater 169, allows excess nitrogen introduced into the system from the electrostatic spray nozzle assembly 16 to be discharged to the appropriate exhaust duct workpiece 176. The exhaust flow from the control valve 175 can be set to match the excess nitrogen introduced into the drying chamber 12 through the electrostatic spray 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 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 stream can be used.

[0113] It should be understood that the drying gas introduced into the effective drying zone 127 defined by the flexible liner 100 by both the electrostatic spray nozzle assembly 16 and the drying gas inlet 15 is a drying inert gas, i.e., nitrogen in the illustrated embodiment. This facilitates the drying of liquid particles sprayed into the drying chamber 12 by the electrostatic spray nozzle assembly 16. As mentioned above, the recirculation of the inert drying gas also removes oxygen from the drying gas to prevent the possibility of a dangerous explosion within the drying chamber in the event of an undesirable spark occurring in the electrostatic spray nozzle assembly 16 or other components of the system.

[0114] Furthermore, it has been found that the recirculation of the inert drying gas through the spray drying system 10 enables highly energy-efficient operation of the spray drying system 10 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 fragrance oil (core). In this case, the purpose of spray drying is to form starch around the oil and dry all moisture with the drying gas. The starch still acts as a protective layer around the oil layer, preventing its oxidation. This desired result has been found to be more easily achieved when a negative electrostatic charge is applied to the emulsion before and during atomization.

[0115] Although the operational theory is not fully understood, each of the three components of a spray emulsion possesses distinct electrical properties. Water, the most conductive in the group, readily attracts most electrons, followed by starch, and finally, the oil, which has the highest electrical resistance and attracts almost no electrons. Knowing that opposite charges attract and like charges repel, all water molecules with the highest charge exhibit the greatest repulsive force relative to each other. This force guides the water molecules to the outer surface of the droplet, where they have the largest surface area against the drying gas, which enhances the drying process. Oil molecules with smaller charges remain at the center of the droplet. It is this process that is thought to contribute to faster drying, or drying with a lower heat source, and more uniform coating. Tests of spray-dried powder produced by a spray drying system operating at an inlet drying gas temperature of 90 degrees Celsius found that the powder was comparable to that dried in a conventional spray drying process operable at 190 degrees Celsius. Furthermore, in some cases, spray drying systems can operate efficiently without heating the drying gas.

[0116] Encapsulation efficiency, i.e., the uniformity of the dried powder coating, is also equivalent to the effect achieved in higher-temperature spray drying. It was also found that lower-temperature drying significantly reduced the release of fragrance, odor, and volatile components into the environment compared to conventional spray drying, and also indicated that the outer surface of the dried particles was more uniform and entirely composed of starch. The reduction in released fragrance and odor also improved the working environment and eliminated the need for removal of such odors 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.

[0117] If any particles may adhere to or otherwise accumulate on the surface of the liner 100 during the drying process, a liner agitation device is provided to periodically apply a shaking motion to the liner 100 sufficient to remove any accumulated powder. In the illustrated embodiment, the 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 pressurized air through the pneumatic liner agitation valve port 180 and into the annular air space between the liner 100 and the outer wall of the drying chamber 12, which agitates the flexible liner 100 back and forth with sufficient force to remove any accumulated powder. The pressurized air is preferably directed to the pneumatic liner agitation valve port 180 in a pulsed manner to amplify this agitation motion. Alternatively, it will be understood that mechanical means can be used to agitate the liner 100.

[0118] To ensure protection against cross-contamination between successive selective uses of the spray dryer system (e.g., between runs of different powders in drying chamber 12), a ring array 120, 120a of quick-release fasteners 121 is provided, allowing the cover 14 and collecting cone 18 to be removed 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 batches of different powders, allowing for replacement with a fresh replacement liner without incurring unnecessary costs.

[0119] To maintain consistency with another important feature of this embodiment, the drying chamber 12 can be easily modified for 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. Similarly, the support ring assembly 104a, with a smaller diameter inner support ring 105a, is used for this purpose. Figure 18The larger diameter support ring assembly 104 can be easily replaced. Replacement of the ring assembly can be achieved by unlocking the circumferentially spaced arrays 120, 120a of the latches 121 for the top cover 14 and the collecting cone 18, removing the larger diameter ring assembly 104 from the drying chamber 12, replacing them with a smaller diameter ring assembly 104a and a liner 100a, and reassembling and re-engaging the top cover 14 and the collecting cone 18 to the drying chamber 12. The smaller diameter liner 100a effectively reduces the introduction of heated drying gas and atomizing gas into the drying zone, enabling faster and more energy-efficient small-batch drying.

[0120] To achieve more efficient drying for smaller batch operations, 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 multiple, 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 of circumferentially spaced quick-release fasteners 121, similar to those described above. Mounting rings 110 for this array of fasteners 121 are welded to the upper cylindrical drying chamber portion 185 adjacent to its lower end, and the fasteners 121 of this array are oriented with downwardly positioned traction hooks 122 for engaging and retaining the top outer radial flange 188 of the lower cylindrical drying chamber portion 186. Figure 1 and Figure 2 When the two arrays of fasteners 121 secure the lower cylindrical portion 186 to the upper cylindrical portion 185 and the collecting cone 18, the lower cylindrical portion 186 can be removed, the lower support ring assembly 104 is repositioned near the upper chamber portion 185, and the liner 100 is replaced with a shorter liner. The upper cylindrical dryer chamber portion 185 can then be directly secured to the powder collecting cone 18 by the array of fasteners 121, with the lower support ring assembly 104 secured therebetween by the array of fasteners 121, which engage the outer annular flange 129 of the collecting cone 18. This improvement allows for the use of a substantially shorter effective drying area, while also reducing the heating requirements for small-batch drying.

[0121] Understandably, 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 injected into the drying chamber 12, multiple electrostatic spray nozzle assemblies 16 can be disposed in the top cover 14, regardless of the size increase. Figure 19 and 20As shown. Multiple spray nozzle assemblies 16 can be supplied by a common liquid and nitrogen supply source, and are preferably supported in a circumferentially spaced relationship in corresponding previously covered mounting holes 190 in the top cover 14. Figure 4 The unused central mounting hole 192 at the time ( Figure 20 It can be properly covered or otherwise closed.

[0122] According to another feature of this embodiment, the modular quick-separation component of the drying tower 11 also allows the electrostatic spray nozzle assembly 16 to be repositioned from a position at the top of the drying chamber 12 for downward spraying to a position near the bottom of the drying chamber 12, for spraying electrostatically charged liquid upward into the drying chamber 12. For this purpose, the spray nozzle assembly 16 can be removed from the top cover 14 and secured to the bottom spray nozzle mounting support 195. Figures 21-24 In this case, the mounting support 195 is installed adjacent to the bottom of the drying chamber 12 within the upper cylindrical wall portion 155 of the powder collecting cone 18, for orienting the electrostatic spray nozzle assembly 16 to spray an upward electrostatic spray pattern into the drying chamber 12, such as... Figure 21 As shown. The bottom nozzle mounting support 195 is shown, as... Figures 22-24 As shown, it includes a central annular mounting hub 196 for supporting the spray nozzle assembly 16 adjacent to its upstream end, which in turn is supported in the upper cylindrical portion 155 of the powder collecting cone 18 by a plurality of radial mounting rods 198 made of non-conductive material. Each radial mounting rod 198 is secured by a corresponding stainless steel screw 199. Figure 24 The washing material 200 is secured to the cylindrical wall portion 155 by a rubber adhesive sealant between the head of the screw 199 and the outer wall surface of the powder collecting cone 18, and a sealing O-ring 201 is inserted 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 outward through the powder collecting cone 18 to insulating fittings 208, 209, respectively, which in turn are connected to atomizing air and liquid supply lines 151, 131. The high-voltage power cable 210 is also radially connected to the nozzle assembly via insulating fitting 211.

[0123] With the electrostatic spray nozzle assembly 16 installed near the lower side of the drying chamber 12, the central spray nozzle mounting hole 192 and the gas inlet 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, and the cover 14 in this case has a pair of exhaust ports 216, which can also be left uncovered and connected to the heating gas return line.

[0124] With the spray nozzle assembly 16 mounted on the lower side of the drying chamber 12, the electrostatic liquid spray particles introduced upward into the drying chamber 12 are dried by a drying gas. In this case, the gas passes tangentially through the bottom heated gas inlet 215 and the atomizing gas from the spray nozzle assembly 16 is heated. Both atomizing gases are dry inert gases, i.e., nitrogen.

[0125] According to this embodiment, the annular liner 100 in the drying chamber 12 is preferably made of filter medium 100b ( Figure 3B The filter media liner 100 is designed to allow the dry gas to ultimately 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. As described above, the powder dried by the upward-guided dry gas and atomizing gas will eventually float downwards and enter the collection chamber 19 through the powder collection cone 18, where only the finest particles are filtered by the filter medium liner 100. A pneumatic liner vibrator can be periodically actuated to prevent powder from accumulating on the liner 100.

[0126] As can be seen from the above, Figure 25 As shown in Table 220, the treatment tower can be easily configured and operated in various treatment modes for specific spray applications. The length of the drying chamber can be selectively changed by adding or removing cylindrical drying chamber sections 186, the lining material can be selectively determined, for example, non-permeable or permeable, the orientation of the electrostatic spray nozzles can be downward spraying from the top or upward spraying from the bottom, and the direction of the treated gas flow can be changed between downward or upward based on the desired configuration.

[0127] Although in the foregoing embodiments, nitrogen or other inert dry gases are introduced as atomizing gases into the electrostatic spray nozzle assembly 16, nitrogen may also be introduced into the circulating gas. Figure 25A In the spray drying system shown, components similar to those described above are given similar reference numerals. Nitrogen or other inert gas is introduced from nitrogen injection line 169a into gas heater 169 for recirculation from drying chamber 100 via gas delivery and supply line 169a to drying chamber 100, and from drying chamber 100 via condenser 170 and blower 168 as previously described. In this embodiment, nitrogen can also be supplied as an atomizing gas to electrostatic spray nozzle assembly 16. As described above, air or a combination of inert gas and air can also be supplied as an atomizing gas to electrostatic spray nozzle assembly 16, provided it does not create a combustion atmosphere within the drying chamber. Additionally, Figure 25A The operation of the drying system shown is the same as previously described.

[0128] Reference Figure 25BThis illustrates another alternative embodiment of a drying system similar to the one described above, except that the powder collecting cone 18a guides the powder to a conventional cyclone separator / filter bag housing 19a, the dried product is discharged from the lower outlet 19b, and exhaust gas is directed from the upper exhaust line 165 for recirculation through the condenser 170, blower 168, dry gas heater 169, and drying chamber 11. Figure 25C In the middle, a similar example is shown. Figure 25B An alternative embodiment of the drying system is shown, but with a fine powder recirculation line 19c between the cyclone separator and the filter bag housing 19a, and at the upper end of the drying chamber 11. The dried fine particles separated in the cyclone separator 19a are recirculated back into the drying chamber 11 via the fine powder recirculation line 19c to produce a powder with fine particle agglomeration. Furthermore, the system operates otherwise identically to that previously described.

[0129] Now for reference Figure 25D This illustrates another alternative embodiment of a fluidized bed powder drying system. The powder drying system again features a cylindrical drying chamber 12 with a non-permeable liner 100 coaxially disposed therein and an electrostatic spray nozzle assembly 16 for guiding electrostatic liquid particles to the 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 into the collection chamber 19b via a conventional type of fluidized bed screening separator 19c. In this embodiment, in conjunction with the above... Figure 11A The embodiments described herein depict multiple fluidized bed cylindrical filter elements 160b supported by an upper transverse plate 163b defining an exhaust chamber 164b adjacent to the top of the drying chamber 12. In this configuration, a blower 168 draws in air from the exhaust chamber 164b, through which powder and particulate matter are filtered out via a conduit 165, a condenser 170, and a heater 169, for reintroduction into the bottom collection chamber 19b and recirculation upwards through the drying chamber 12. Filter 16b also has a reverse pulse air filter cleaning device 167b of the type disclosed in cited U.S. Patent 8,876,928, which has a corresponding air control valve 167c for periodically directing pressurized air to and through filter 16b to clean the powder-accumulated powder.

[0130] Although the non-permeable liner 100 of the foregoing embodiments is preferably made of a flexible, non-conductive material such as plastic, it may optionally be made of a rigid plastic material, such as... Figure 3D As shown. In that case, a suitable non-conductive mounting bracket 100d can be provided to secure the liner coaxially within the drying chamber 12. Alternatively, as Figure 3CAs shown, the permeable liner can be partially formed, for example, on one diameter side of the permeable filter material 100b, which allows air to flow through the liner for exhaust and partially, for example, on the opposite diameter side, through the impermeable material 100a, which prevents dry particles from being drawn into the liner.

[0131] As an alternative embodiment, such as Figure 15A As shown, the spray dryer system can be readily modified to spray-cool a molten flow (e.g., wax, hard wax, and glycerides) into a cold stream to form solid particles. Similar items to those described above have been given similar reference numerals. During spray cooling, a raw material having a melting point slightly above ambient conditions is heated and placed in a storage tank 130, which is enclosed in an insulator 130a. The raw material is pumped through a feed line 131 to an atomizing nozzle 16 using a pump 132. The molten raw material is again atomized using a compressed gas such as nitrogen 150. During spray cooling, the molten liquid raw material may or may not be electrostatically charged. In the latter case, the electrodes of the electrostatic spray nozzle assembly are de-energized.

[0132] During spray cooling, the atomizing gas heater 152 is shut off, allowing cold atomized gas to be delivered to the atomizing nozzle 16. During spray cooling, the dry gas heater 169 is also shut off, allowing dry gas, already cooled by the dehumidifying coil 170a, to be delivered to the dry chamber 12 via the dry gas line 165. As atomized droplets enter the dry gas region 127, they condense to form particles that fall into the collection cone 18 and are carried away by the airflow for recirculation, thus collecting in the collection chamber 19. The removable liner 100 again facilitates cleaning of the dry chamber as it can be removed and disposed of. The insulating air gap 101 prevents the dry chamber 12 from becoming cold enough to form condensation on its outer surface.

[0133] In another feature of this embodiment, the injection system 10 can be operated using an automatic fault recovery system that allows the system to continue operating in the event of a momentary charging field failure in the drying chamber, while providing an alarm signal in the event of a persistent electrical fault. Figure 26 A flowchart of a method for recovering from a voltage generator failure used in the spray system 10 is shown. The method shown can be operated within the controller 133 as a program or a set of computer-executable instructions. Figure 15 According to the illustrated embodiment, Figure 26The method shown includes activating or otherwise starting the liquid pump at 300 to provide a pressurized fluid supply to the injector inlet. At 302, verification of whether the voltage supply is activated is performed. If it is determined at 302 that the voltage supply is not activated, an error message is provided at the machine interface at 304, and at 306 the voltage generator and liquid pump are deactivated until a condition arises that could cause the voltage supply deactivation determined at 302 to be corrected.

[0134] When voltage supply activation is confirmed at 302, a predetermined time (e.g., 5 seconds) is used before liquid pumping begins at 308, and liquid pumping starts at 310 after the delay has expired. A check is performed at 312 to detect short circuits or arcs, while the pump continues to run at 310. When a short circuit or arc is detected at 312, an event counter and a timer are maintained to determine if more than a predetermined number of short circuits or arcs, e.g., 5, are detected within a predefined time period, e.g., 30 seconds. These checks are confirmed at 314 whenever a short circuit or arc is detected at 312. When fewer than the predetermined number of short circuits or arcs occur within the predefined 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 at 318, for example, by shutting down and restarting, and the liquid pump is restarted at 310 after the delay at 308, allowing the system to remedy the fault causing the spark or arc and allowing the system to continue operating. However, if more than a predetermined number of sparks or arcs occur within a predefined time period at 314, an error message is generated at the machine interface at 320, and the system is put into standby mode at 306 by disabling the voltage generator and liquid pump.

[0135] Therefore, in one aspect, methods for troubleshooting faults in electrostatic spray drying systems include initiating a pump start-up sequence that requires first determining the state of the voltage generator and preventing the liquid pump from starting if the voltage generator is not activated. To achieve this, in one embodiment, a time delay is used before the liquid pump is turned on, allowing sufficient time for the voltage generator to activate. The liquid pump is then started, and the system continuously monitors for the presence of sparks or arcs while the pump is running by, for example, monitoring the current drawn from the voltage generator. When a fault is detected, the voltage generator shuts down like the liquid pump, 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.

[0136] Finally, in another aspect of this embodiment, the spray drying system 10 has a controller capable of periodically varying the charge of the liquid ejected by the electrostatic spray nozzle assembly, thereby inducing controlled and selective agglomeration of spray particles for specific spray applications and the final use of the dried product. In one embodiment, selective or controlled agglomeration of spray particles is achieved, for example, by altering the timing and frequency of injector activation using a pulse-width modulation (PWM) injector command signal between high and low activation frequencies to produce sprayed 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 voltage level applied to the electrostatic spray fluid. For example, the voltage can be selectively varied in a range such as 0-30 kV. It is conceivable that, with such voltage variations, applying a higher voltage for charging the fluid will generally have the effect of reducing droplet size, thereby reducing drying time, and may also induce carrier migration to the outer surface of the droplet, thereby improving encapsulation. Similarly, a decrease in the applied voltage may increase the droplet size, which may contribute to agglomeration, especially in the presence of smaller droplets or particles.

[0137] Other embodiments contemplated for selectively influencing the agglomeration of spray particles include selectively varying or pulsating these parameters between predetermined high and low values ​​over time, and 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 particle size and droplet drying time. Additional embodiments may also include varying other parameters of the atomizing gas and / or drying air, such as their respective absolute or relative humidity content, water activity, droplet or particle size, etc. In one particularly considered embodiment, the dew point temperature of the atomizing gas and drying air is actively controlled, and in another embodiment, the volumetric or mass airflow rate of the atomizing gas and / or drying air is also actively controlled.

[0138] exist Figure 27A flowchart of a method for modulating the pulse width in an electrostatic spray nozzle to selectively control the agglomeration of spray particles is shown. According to one embodiment, at the beginning of the process, a voltage generator is turned on at 322. At 324, it is determined whether selective control of agglomeration using PWM is effective or desired. When PWM is not needed or is activated, 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 needed or is activated, the system alternates between a low PWM setpoint and a high PWM setpoint for a predefined time period and cycle time. In the illustrated embodiment, this is achieved by controlling the low PWM setpoint at 330 to achieve 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 at 334 has expired, and then returns to 324 to determine whether another PWM cycle is needed. Although this is relative to... Figure 27 The flowchart shown illustrates the variation of the PWM setpoint. It should be understood that, in addition to or in place of the injector PWM, other parameters can be modulated. As mentioned above, other parameters that can be used include the level of the voltage applied to the liquid, the atomizing gas pressure, the liquid delivery rate and / or pressure, the atomizing gas temperature, the moisture content of the atomizing gas and / or dry air, and / or the volumetric or mass flow rate of the atomizing gas and / or dry air.

[0139] Therefore, in one aspect, the agglomeration of spray particles is controlled by varying the spraying time of the atomizer. At high frequencies, i.e., at high PWM, the atomizer will open and close more quickly, resulting in smaller particles. At low frequencies, i.e., at low PWM, the atomizer will open and close more slowly, resulting in larger particles. As increasingly smaller particles pass through the dryer in alternating layers, some particles will physically interact and agglomerate, regardless of their repulsive charges causing clumping. The system can control the specific size of the larger and smaller particles, as well as the corresponding number of each particle size per unit time, produced by setting their respective high and low PWM setpoints and the duration of each setpoint, to suit each specific application.

[0140] According to another feature, multiple powder processing towers 10, as described above, can be modularly designed and provided, having a drying chamber 11 and an electrostatic spray nozzle assembly 16, such as... Figure 28 and Figure 29As shown, powder is discharged onto a common conveyor system 340, etc. In this case, multiple processing towers 10 are arranged adjacent to each other around a common working platform 341, which is accessible to the top via an assembled ladder 342 and has a control panel and operator interface 344 located at its end. In this case, each processing tower 10 includes multiple electrostatic spray nozzle assemblies 16. Figure 28 As shown, eight essentially identical processing towers 10 are provided, in which powder is discharged onto a conventional powder conveyor 340, for example, by a screw feeder, pneumatic or other powder conveying device, to a collection container.

[0141] This modular processing system has been found to have many important advantages. First, it is a scalable processing system that can be customized to user requirements, using common components, namely, a substantially identical powder processing tower 10. For example... Figure 30 As shown, the system can also be easily expanded with additional modules. Using such a modular arrangement of processing tower 10 also enables the processing of larger volumes of powder with smaller building height requirements (15-20 feet), compared to standard large-scale production spray dryer systems that are 40 feet or more tall and require special building layouts for installation. The modular design also allows for the isolation and maintenance of individual processing towers without interrupting maintenance operations on other modules during processing. The modular layout also allows for scaling the system's energy consumption to meet specific user production needs. For example, five modules can be used for one processing requirement, and only three for another batch.

[0142] As can be seen from the above, a spray dryer system is provided that is more efficient and versatile in operation. Due to the improved drying efficiency, the spray dryer system is smaller in size and more economical to use. The electrostatic spray system is effective for drying batches of different products without cross-contamination, and it is easily modified in terms of size and processing technology for specific spray applications. The spray drying system is not susceptible to electrical faults or the dangerous explosive effects of fine powder in the drying chamber atmosphere. The system can also be selectively operated to form clumps into particles in a form better suited for subsequent use. The system also features an exhaust gas filtration system for more effectively and efficiently removing particulate matter from the dried gas exiting the dryer, and includes an automatic device for removing the accumulation of dried particulate matter on the filter, which hinders operation and requires costly maintenance. Furthermore, the system has a relatively simple structure, making it suitable for economical manufacturing.

Claims

1. An electrostatic spray drying system for drying a liquid into a powder, comprising: Drying chamber; An electrostatic spray nozzle having a spray tip assembly arranged to discharge a liquid supply into the drying chamber, the electrostatic spray nozzle being configured to discharge the liquid supply based on a duty cycle signal provided to the electrostatic spray nozzle, the duty cycle signal determining the period during which the electrostatic spray nozzle is open to inject the liquid supply; A controller, associated with and operated to provide the duty cycle signal to the electrostatic spray nozzle, is programmed and operated to perform a process including the following: Activate the PWM operation mode for the electrostatic spray nozzle; Start the first timer; When the first timer has not reached the first pulse duration, a first duty cycle signal at the first PWM activation frequency is first provided to the electrostatic spray nozzle; The second timer is started when the first timer has reached the duration of the first pulse. as well as When the second timer has not reached the second pulse duration, a second duty cycle signal at the second PWM activation frequency is provided to the second electrostatic spray nozzle. Since the first PWM activation frequency is different from the second PWM activation frequency, the first and second provisioning causes the electrostatic spray nozzle to produce spray particles of different sizes, resulting in varying degrees of agglomeration of the spray particles generated by the electrostatic spray drying system.

2. The electrostatic spray drying system of claim 1, further comprising a voltage source, wherein the electrostatic spray nozzle is connected to the voltage source and configured to apply electrostatic charge to the liquid supply discharged through the spray tip assembly into the drying chamber, and wherein, The controller is also associated with the voltage source and configured to control the voltage setpoint of the voltage source.

3. The electrostatic spray drying system as described in claim 2, characterized in that, The controller is programmed to activate the PWM operation mode when the voltage control operation mode is not activated.

4. The electrostatic spray drying system as described in claim 3, characterized in that, The controller is also programmed to activate the voltage control operation mode and control the voltage setpoint of the voltage source when the duty cycle signal is maintained at a predetermined PWM activation frequency.

5. The electrostatic spray drying system as described in claim 1, characterized in that, The activation frequency of the first PWM is lower than that of the second PWM.

6. The electrostatic spray drying system of claim 1, further comprising a pump configured to pressurize the liquid supply provided to the electrostatic spray nozzle to an injection pressure, wherein, The pump is associated with and operates to set the injection pressure in response to a pressure signal provided by the controller, wherein the controller is also programmed to selectively change the injection pressure over time.

7. The electrostatic spray drying system as described in claim 1, characterized in that, The electrostatic spray nozzle is configured to receive pressurized gas, which is combined with the liquid supply to atomize the liquid and discharge it into the drying chamber.

8. The electrostatic spray drying system of claim 7, further comprising a compressor configured to compress a gas supply at atomizing gas pressure to the pressurized gas supplied to the electrostatic spray nozzle, wherein, The compressor is associated with and operates to set the pressure of the atomizing gas in response to a gas pressure signal provided by the controller, wherein the controller is also programmed to selectively change the pressure of the atomizing gas.

9. The electrostatic spray drying system of claim 7, further comprising a gas heater associated with and configured to heat the pressurized gas to the atomizing gas temperature in response to a gas temperature command signal provided by the controller, wherein, The controller is also configured to selectively change the gas temperature command signal over time.

10. The electrostatic spray drying system of claim 1, further comprising a fan configured to provide a flow of drying gas through the drying chamber, the drying gas being provided with a moisture content and temperature selectively determined by a drying gas regulating module associated with the controller and responding to a signal provided from the controller to selectively set the moisture content and temperature of the drying gas flow, wherein... The controller is programmed to selectively change at least one of the moisture content and temperature of the drying gas stream.

11. The electrostatic spray drying system as described in claim 10, characterized in that, The fan is configured to selectively provide the dry gas flow at a mass airflow rate determined based on a control signal from the controller, wherein the controller is also programmed to selectively change the mass airflow rate over time.

12. A method for controlling the agglomeration of spray particles generated in an electrostatic spray drying system, the method comprising: Provides an electrostatic sprayer configured to discharge liquid into a drying chamber; The electrostatic sprayer is activated using a PWM signal; Alternating between a first PWM signal having a first duty cycle at a first activation frequency and a second PWM signal having a second duty cycle at a second activation frequency, wherein the first activation frequency is lower than the second activation frequency; The electrostatic sprayer is operated with the first PWM signal for a first time to cause the agglomerate to condense at a first size; and The electrostatic sprayer is operated with the second PWM signal for a second time to cause the agglomerates to condense at the second size. The first and second provisions cause the electrostatic sprayer to produce spray particles of different sizes, resulting in varying degrees of agglomeration. Wherein, the second dimension is smaller than the first dimension; and Controlling the average size of the agglomerate includes adjusting the first time and the second time during operation.

13. The method as described in claim 12, characterized in that, The electronic controller is used to provide the first PWM signal and the second PWM signal to the electrostatic sprayer.

14. The method of claim 12, further comprising selectively adjusting the voltage potential transmitted to the electrostatic sprayer.

15. The method of claim 12, further comprising pressurizing the liquid flow to an injection pressure, wherein, The method also includes selectively changing the injection pressure over time.

16. The method of claim 12, further comprising supplying pressurized gas to the electrostatic sprayer at atomizing gas pressure to atomize the liquid stream discharged into the drying chamber, wherein, The method also includes selectively changing the pressure of the atomizing gas.

17. The method of claim 16, further comprising supplying the pressurized gas to the electrostatic sprayer at an atomizing gas temperature, wherein, The method also includes selectively changing the temperature of the atomizing gas.

18. The method of claim 12, further comprising providing a stream of drying gas through the drying chamber, the drying gas being provided with a specific moisture content and temperature, wherein, The method also includes changing the moisture content of the drying gas stream.

19. The method of claim 18, further comprising changing the temperature of the dry gas stream.

20. The method as described in claim 18, characterized in that, The dry gas stream is provided at a mass air flow rate, and the method further includes selectively changing the mass air flow rate.

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