Abstract:
A modular two-stage electrostatic precipitator for extracting airborne particles includes individual ionizer/collector cell modules having integrated power supplies and diagnostic systems. The cell modules are adapted to be joined blindly to one another in end-to-end nested relation through nestable end plates and in a series circuit utilizing floating electrical connectors. The module end plates provide self-correction in misalignment during a blind connection and provide sealed end plate cavities for the power supply and electrical connections. The diagnostic system provides detection for any open system circuit and/or short circuit condition and allows for trouble shooting on an individual cell module basis.

Description:
[0001]    This application claims priority to provisional application Serial No. 60/241,599, filed Oct. 19, 2000, which is incorporated herein by reference. 
     
    
     
       FIELD OF THE INVENTION  
         [0002]    The present invention relates generally to devices for removing smoke, dust and fumes from the air, and more particularly to a novel modular electrostatic precipitator (ESP) system having among its features the employment of modular ionizer/collector cells that facilitate mechanical nesting of individual cell modules, fault detection at the individual cell level, and a high voltage source for each modular ionizer/collector cell so as to enhance overall system air cleaning efficiency.  
         BACKGROUND OF THE INVENTION  
       DESCRIPTION OF RELATED ART  
         [0003]    Conventional two-stage ESPs are energized by a power supply source having a single, alternating current (AC) input voltage and a single or dual, direct current (DC) output voltage. Input voltages can range from 24v to 240v, and output voltages can range from 3 Kv to 15 Kv. A single output voltage power supply electrically connects the same high voltage potential to the ionization and collection section of an ESP. A dual output voltage power supply provides different levels of high voltage potential to the ionization and collection section, with the ionization section approximately twice the voltage level of the collection section. For example, a dual output voltage power supply that generates a high voltage level of 12 Kv to the ionization section will supply approximately 6 Kv to the collection section.  
           [0004]    Each power supply or combinations of power supplies in conventional ESP systems are located in an enclosure, separate from the ionization and collection section of the ESP. These enclosures can be in proximity to the ESP, for example, on the ESP access panel, or the enclosure can be remote mounted a distance from the ESP. High voltage electrical connections between power supply and ESP are made by an insulated cable or wire, sized to carry the maximum electrical load. Electrical conduit is required to shield and protect the high voltage cable or wire when the power supply enclosures are mounted in a remote location. Once connected to the ESP, various conductive devices such as springs, plungers, cables, wires, or buss bars transfer high voltage between multiple ionization/collection sections (known as a cell or module). Each device is isolated from ground by a non-conductive material such as a fiberglass reinforced plastic (FRP) or ceramic. The cell-to-cell high voltage connections are located at each end of the cell and are shielded or baffled from the air stream to prevent contamination or corrosion. A tie rod or expanded tube is conventionally used to transfer high voltage through an individual cell. A series of individual cells are trained together to form a tier of cells. Each cell on a tier slides on a rail. Multiple tiers can be stacked vertically to complete the final ESP configuration.  
           [0005]    The relationship between the current draw of a single cell, typically measured in milliamps, and the total current capacity of the power supply determines the number of cells that can be powered by one power supply. For example, a power supply rated for 10 milliamps can power 5 cells that draw 2 milliamps each. The number of cells or modules required for an ESP is dependent on the volume of air being moved in cubit feet per minute (CFM) and the desired efficiency (percentage of particles removed from air). After determining the number of cells required for an ESP based on this criteria and the total current draw for the cells, the number of power supplies required can be determined.  
           [0006]    There are several disadvantages to the aforedescribed prior ESP and power supply arrangement. For example, the larger the ESP, the more difficult and expensive the high voltage wiring becomes between the power supplies and the cells. Power supply enclosure quantity, size and expense increase with the increase in size of the ESP. High voltage connection points and transfer devices required increase in number with increasing size of the ESP, thereby adding additional expense. Each high voltage connection point or transfer device must be electrically sound. Weak high voltage connections result in decay and failure of surrounding materials caused by arcing or corona stress. On conventional ESP&#39;s, an operating status light is used as a diagnostic device. For example, an LED is frequently provided as part of the power supply circuitry. Under normal operating conditions the LED will illuminate, indicating that the ESP and power supply are functioning properly. In a fault condition, however the LED does not illuminate so that trouble-shooting and isolating individual component failure becomes more difficult because the only device used for detection is part of the power supply. For example, the LED, being connected in circuit with the failed power supply, will not indicate which cell, if any, has a problem. On a conventional electrostatic precipitator, one power supply energizes multiple ionizer/collector cells. Under this arrangement, a power supply failure would result in the loss of power to a group of cells and greatly reduce the air cleaning efficiency of the electrostatic precipitator. As an added expense, volt and amp meters can be provided in addition to the operating status light, for increased operational monitoring of the ESP. On ESP&#39;s that utilize a rail system configuration, clearance for sliding of the cell is provided between the sides of the rail and cell. This clearance, usually one sixteenth to one quarter inch, generally creates misalignment between cells in a tier. Any high voltage connections between cells must compensate for the misalignment.  
         BRIEF SUMMARY OF THE INVENTION  
         [0007]    One of the primary objects of the present invention is to overcome the aforementioned problems in known modular electrostatic precipitators (ESPs) by eliminating the high voltage components required for installation, and providing fault detection at the individual cell level in a cost-effective manner so as to enhance ESP performance.  
           [0008]    A more particular object of the present invention is to provide a system of modular ESP cells wherein the cells can be supported in tiers and a power supply is united into the body of each cell so that all high voltage components are contained and isolated within the cell, thereby eliminating high voltage connections between cells, high voltage cabling between the ESP and a remote mounted power supply, and power supply enclosures.  
           [0009]    Another object of the invention lies in providing each ESP cell with an alarm circuit and status indicator display for monitoring the normal operation of each cell, and wherein a tier of cells connects in series the alarm circuit from each cell, and a status indicator light monitors each tier of cells so that under normal operating conditions, a signal energizes each tier alarm circuit and illuminates the tier status indicator light.  
           [0010]    In accordance with one feature of the invention, the alarm circuit energizing signal is carried through the tier to each cell so that when a fault is detected in a cell or power supply, for example, if high voltage plates in the collector section of a cell are shorted to ground, the alarm circuit for that cell will open or become de-energized and the cell status indicator will not be illuminated. Such open circuit condition to a tier of ESP cells causes the status indicator light for the tier to become non-illuminated.  
           [0011]    In accordance with another feature of the invention, the status circuit also detects whether input power is connected to the cell power supply, and monitors cell arcing.  
           [0012]    In accordance with another feature of the invention, a tier auxiliary status port is provided whereby connection to external devices for monitoring tier status can be effected.  
           [0013]    Still another feature of the ESP modules in accordance with the invention lies in the provision of a low voltage (24v-240v) input power distribution network that utilizes a radial float “blind mate” connector (RFC) that is also used in the cell status circuit and is particularly suited for conventional ESP applications that require low voltage electrical connections between cells that may become misaligned in a support frame.  
           [0014]    In accordance with the invention, the ESP cell modules are adapted for mechanical nesting in a manner to correct misalignment for electrical connections between cells when placed in series on a support rack, and when nested provide sufficient air baffling between cells to protect exposed high and low voltage electrical components. To this end, end plates on the modular ESP cells are adapted for end-to-end nesting so as to form a sealed cavity in which electrical components such as power supplies can be enclosed. The sealed cavity also serves as a baffle, forcing air-borne particles through the ionization and collection sections of the cell and preventing bypass between cells. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]    [0015]FIG. 1 is a front elevational view of an electrostatic precipitator system constructed in accordance with the present invention and showing modular ionizer/collector cells supported on a support rack in nested relation, with other cells positioned for placement on the rack;  
         [0016]    [0016]FIG. 2 is a front elevational view showing two modular ESP cells being mechanically nested together, each cell having its pre-filter removed;  
         [0017]    [0017]FIG. 2A is a detail view, on an enlarged scale, of the portion of FIG. 2 encircled by line  2 A- 2 A,  
         [0018]    [0018]FIG. 3 is a fragmentary plan view taken along line  3 - 3  of FIG. 2, portions being broken away for clarity;  
         [0019]    [0019]FIG. 4 is a fragmentary elevation view of the discharge side of an ionizer/collector cell, the conductive perforated post filter being broken away for clarity;  
         [0020]    [0020]FIG. 5 is a plan sectional view of a representative electrostatic precipitator system illustrating the manner of mechanically and electrically connecting modular ionizer/collector cells together;  
         [0021]    [0021]FIG. 6 is a fragmentary detail view showing a typical radial float blind mate mechanical/electrical power connection between modular cells;  
         [0022]    [0022]FIG. 7 is a fragmentary exploded perspective view illustrating the plug portion of the blind mate connection of FIG. 6;  
         [0023]    [0023]FIG. 7A is a perspective view of the plug of FIG. 7 oriented with X, Y, Z coordinates;  
         [0024]    [0024]FIG. 8 is an elevational view of an ionizer/collector cell male end plate showing integrated power supply, cell status indicator, and low &amp; high voltage connections;  
         [0025]    [0025]FIG. 9 is an elevational view from the power distribution end of a representative electrostatic precipitation system, showing power distribution PCB modules and cable connections between tiers of ESP modules;  
         [0026]    [0026]FIG. 10 is a perspective view of a power distribution module as employed in the system of FIG. 9; and  
         [0027]    [0027]FIG. 11 is a schematic electrical diagram illustrating power distribution and operating status signals for the modular electrostatic precipitation cells as employed in the system of FIG. 1. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0028]    Referring now to the drawings, and in particular to FIG. 1, a representative electrostatic precipitator (ESP) system in accordance with the present invention is indicated generally at  10 . Briefly, the electrostatic precipitator system  10  includes an open framework rack  12  having horizontal rails  14  adapted to receive and support a plurality of modular two-stage ionizer/collector cells, indicated generally at  16 , in horizontal rows or tiers. As will be described, the modular two-stage ionizer/collector cells  16 , which may for simplicity be referred to hereinafter as modular cells, are generally rectangular and each includes a pair of substantially rectangular male and female end plates  18  and  20 , respectively, between which are disposed a plurality of parallel spaced high voltage charged collector plates  21  and grounded plates  23  supported in alternating sequence on suitable transverse tie rods or support rods, insulators and spacers so as to form the collection section of each cell with each plate in the sequence having opposite polarity to the next adjacent plates, as is known. Ionizing wires, indicated at  25  in FIG. 5, and extended ground plates,  23   a  are provided in a manner to generate corona current toward the extended ground plates  23   a  and thus form an ionization section of high concentration ion curtains in a conventional manner. Airborne particles passing into the ESP cell  16  must go through the high concentration ion curtains before entering the precipatory plate collection section of cells, and are charged as the particles pass through the ion curtains as disclosed in, for example, U.S. Pat. No. 6,096,119 which is incorporated herein by reference.  
         [0029]    The end plates  18  and  20  facilitate nesting relation between adjacent modular cells when supported in the rack  12 . As shown in FIG. 5, when the male and female end plates  18  and  20  of adjacent modular cells are disposed in nested relation, they form a sealed cavity  22  between the adjacent cells that houses a power supply  24 , radial float blind mate connectors  26  and  28  that facilitate distribution of control power and operating status signals through the nested cells, high voltage insulators  30 , a power supply connector  32 , a high voltage cable  34  and a low voltage cable  36 .  
         [0030]    As illustrated in FIGS. 2, 2A and  8 , the ionizer/collector cell male end plate  18  has a male flange  42  that extends about the full periphery of the rectangular end plate  18  and is tapered inwardly from its connection to the planar end plate, as shown in FIG. 2A. The female end plate  20  has a similar female flange  44  that extends about the full periphery of the planar end plate  20  but is normal to the end plate  20 . The flange  42  is tapered sufficiently to enable it to enter into and nest with the flange  44  of an adjacent cell  16  when the cells are positioned on and pushed together along a pair of laterally spaced parallel rails  14  on the rack  12  so that flanges  42  and  44  mate and form a sealed cavity  22  between the nested cells. The male flange  42  is tapered sufficiently to enter the female flange  44  and thereby accommodate initial mechanical misalignment between adjacent cells as they are positioned on and slid along rack rails.  
         [0031]    When the male flange  42  of end plate  18  of one ionizer collector cell  16  fully mates with the female flange  44  of end plate  20  of an adjacent ionizer/collector cell  16 , a complete air baffle between the adjacent cells is created, thus eliminating the requirement for external air baffles. As aforedescribed, with adjacent ionizer/collector cells  16  fully mated, a sealed cavity  22  is formed to house the integrated power supply  24 , radial float “blind mate” connectors  26  and  28 , high voltage insulators  30 , power supply connector  32 , high voltage cable  34 , and low voltage signal cable  36 . The sealed cavity thus provides a contaminate free environment for all housed electrical components.  
         [0032]    Each of the modular ionizer/collector cells  16  includes a perforated pre-filter  48  and a perforated post-filter  50 . As shown in FIG. 1, the pre-filter  48  is rectangular and mechanically attached to the air intake side or face of a modular cell  16  so as to cover the air intake side. The pre-filter  48  is made from a non-conductive material such as, for example, polyethylene plastic, that prohibits any corona field interruption between the ionizers (specially addressing spike blade ionizers) and ground. The perforated post-filters  50  are also rectangular and are mechanically attached to the air exiting or discharge faces of the ionizer/collector cells  16 . The post-filters  50  are made from conductive metal material, such as aluminum, and become grounded potential collector plates for attracting and collecting positive or negative charged air borne particulate, thus increasing the ionizer/collector cell air cleaning efficiency and loading capacity. Both the pre-filters  48  and post-filters  50  are attached to the frames of their respective ionizer/collector cell air intake and air discharge faces with conventional quick release hardware to facilitate removal for ionizer/collector cell cleaning. The pre-filters and post-filters eliminate the need for air-baffling components that are normally required on the air intake and air discharge faces of conventional electrostatic precipitators.  
         [0033]    [0033]FIG. 5 schematically illustrates the electrical connection technique and apparatus, alternatively termed the input power distribution network, for distributing low voltage (24V-240V) input power and operating status signals through two adjacent modular ionizer/collector cells  16  which is representative of the manner of distributing input power and operating status signals through a tier of cells. Each ionizer/collector cell  16  is equipped with radial float “blind mate” connector means in the form of a radial float plug connector  26  and a fixedly mounted receptacle connector  28 . Each cell has a plug connector  26  mounted on one of its end plates  18  and  20 , such as male end plate  18 , and has a receptacle connector  28  mounted on the opposite end plate, such as female end plate  20 . The plug connector  26  and receptacle connector  28  are mounted on their respective end plates  18  and  20 , such as at corner locations as the end plates are considered in elevational end views, so that when adjacent modular cells are brought into substantially axial alignment with the male end plate of one cell facing the female end plate of the next adjacent cell, the corresponding plug and receptacle connectors face each other in substantially aligned relation.  
         [0034]    As shown in FIG. 7, the radial float plug connector  26  includes a float plug  52  that may be made of molded plastic and has a pair of tubular guide sleeves  52   a  and  52   b  formed integral with or otherwise secured to a base  52   c  so as to facilitate mounting of the float plug on the cell end plate  18  through a pair of threaded stub shafts  54   a  and  54   b  fixed in normal relation to the cell male end plate  18 . A spacer plate  56  and compression springs  58  are mounted on the stub shafts  54   a,b  between end wall  18  and the float plug  52  so as to enable movement of the plug along the stub shafts, designated as the Z-axis in FIG. 7A, against the outward biasing of the springs  58 . Spacer sleeves  60 , washers  62  and nuts  64  maintain the float plug  52  on stub shafts  54   a,b  in a manner enabling movement of the float plug in the X and Y axis directions designated in FIG. 7A, thereby allowing the float plug to float in the X, Y and Z directions relative to end plate  18 .  
         [0035]    The float plug  52  includes a boss portion  52   d  having rounded comers  52   e  and  52   f  and tapered ends  52   g  and  52   h  that serve to slidingly guide the plug into a suitably configured recess or socket formed in a block  70  of the axially opposed receptacle connector  28  of the blind mate connector. The block  70  is fixed to the female end plate  20  of the associated modular cell  16  and carries a plurality of electrically conductive receptacle pins  72  (FIG. 6) that are connected to a low voltage (i.e., 24v-240v) input power distribution network, as will be described. The electrical receptacle pins  72  are pointed and guided into cylindrical plug socket contacts  74  formed in the boss portion  52   d  of float plug  52  as the plug connector  26  and receptacle connector  28  are mated. By mounting the float plug  52  for floating movement in the X, Y and Z axes, it will be appreciated that as the plug connector  26  and receptacle connector  28  are brought into mating relation, the float plug tapered lead ends  52   g, h  will enter the recess of the receptacle connector block  70  and orient or align the float plug with the connector block so that the receptacle pins  72  enter the plug socket contacts  74  and make electrical contact therewith even though the two adjacent modular cells  16  are not in exact alignment as they are initially brought into nested relation on the rack  12 .  
         [0036]    Referring to FIG. 5, a low voltage flexible wiring harness  76  having insulated electrical conductor cables connects and electrically unites the two float plug and receptacle connector halves  26  and  28  mounted on the opposite end plates  18  and  20  of each modular cell  16 . The low voltage harness  76  is protected from air borne particulate and shielded from the high voltage field by a barrier  78 . When adjacent modular cells  16  are fully nested together and plug sockets  74  mate with receptacle pins  72 , an additional contaminate free environment for cell-to-cell connections is created within the inner walls of the radial float “blind mate” connectors  26  and  28 , as shown in FIG. 6. When a plurality of modular ionizer/collector cells  16  are connected in a tier, such as on the rack  12 , an input power source is connected to the radial float connector means on the first cell in the tier. If multiple tiers of cells are supported on the rack, the first cells of the tiers are electrically connected together with flexible cables. The cells of each tier are electrically connected in a parallel circuit and joined end-to-end with the floating plug connector  26  of each cell mating into the receptacle connector  28  on the next adjacent cell.  
         [0037]    As shown in FIG. 5 and  8 , a power supply  24  is integrated into each ionizer/collector cell  16 . The power supply  24  is affixed to the outer face of the male flange end plate  18  with mounting hardware. The power supply  24  is enclosed and sealed to protect against moisture, dust and foreign matter. A free hanging power supply connector  32  is used to connect the low voltage cable  36  from the power supply  24  to the wiring harness  76 . The high voltage connection from power supply  24  can be made either from the back surface of the power supply  24  enclosure to an ionizer/collector cell insulator  82  (FIG. 8), or to a high voltage cable  34  which would be connected to the ionizer/collector cell insulator  82 . The power supply  24  of each individual ionizer/collector cell  16  includes a power status indicator in the form of a light, such as a light emitting diode indicated at  84  in FIG. 8, that is a sub-component of the power supply.  
         [0038]    Referring to FIG. 9, taken in conjunction with FIG. 10, each tier or row of ionizer/collector cells  16  on the rack  12  includes a power distribution module  88  adapted to plug into the receptacle half of the radial float “blind mate” connector  28  on the first ionizer/collector cell of a tier or row. That is, the first cell mounted on the rack to create a tier or row of cells. Each power distribution module  88  serves as a distribution point for electrically conducting power and signals to each tier of the ESP system  10 . Each power distribution module  88  has four primary components; a power input connector  90 , a tier-to-tier power distribution connector  92 , a tier status indicator  94 , and a tier status auxiliary connector  96 , as shown in FIG. 10. The power input connector  90  functions as a receptacle for the primary power cord plug. The tier power distribution connector  92  functions as a receptacle for a power jumper cable  98  and associated plug  98   a  that extend between tiers on the ESP system. The power distribution connector  92  is not used on single tier systems. The tier status indicator  94  functions as a operating status light. When the light is illuminated, all cells  16  on the associated tier are functioning properly. When the light is blinking, one or more cells  16  on the associated tier are arcing. When the light is not illuminated or blinking, one or more cells  16  on the associated tier will be shorted, or one or more cells may have a faulty connection, or one or more cells will have a faulty power supply  24 .  
         [0039]    [0039]FIG. 11 schematically illustrates an electrical circuit for effecting power distribution and operating status signals for a representative two tier system of electrostatic precipitating cells  16 . AC power is plugged into a power input connector  102  on a power distribution module  88 . If more than one tier of cells is employed, a tier-to-tier cable  106  is plugged into a tier-to-tier power distribution connector  108  on each tier. AC power is connected to the first cell on each tier through pins  110  and  112  to the radial float receptacle  26  which is accessible through a suitable opening in the end plate  18 . Power then is distributed to each cell on the associated tier through each radial float connector pair  26 ,  28 . Each cell power supply is connected to the AC power line  110  and  112 . The AC power on pins  110  is looped through a tier end plate  114  and back to power supply status control circuits  116 . If a power supply  118  is functioning properly, each power supply status control electronic switch  120  will close thus passing AC current to the power supply in the next adjacent ionizer/collector cell  16 .  
         [0040]    If all power supplies  118  are functioning properly, all power status control electronic switches  120  will be closed and AC current will pass through the radial float connector pin  122 , thus illuminating the tier status light  94  to indicate that all cells  16  on the associated tier are operating properly.  
         [0041]    Summarizing, the ESP system  10  of the present invention has a power supply  24  united or integrated into each ionizer/collector cell  16 , whereby the power supply and cell are one unit. A power status indicator display is built into each cell  16  so that each cell is provided with a visual display device, for example an LED  84 , that indicates normal operating condition when illuminated. An individual alarm system is also preferably provided on each cell connected in an input signal circuit that triggers an alarm during an open or short circuit condition. Each cell  16  has a sealed power supply  24  that protects the cell power supply components in a watertight enclosure that can withstand sub-mersion in a water-based cleaning solution during routine maintenance operations. Further, the ability to effect cell nesting (male and female end plates) creates a protective cavity for electrical components. Each cell module has two end plates, a plug (male)  18  and receptacle (female)  20 , which serve as a support platform for the cell structure. Each end plate  18 ,  20  has an outward-formed flange around its perimeter which forms a pocket or cavity. The plug or male end plate flange is preferably extended to approximately twice the depth of the female end plate flange. An offset has been added to the extended plug flange, which allows it to nest inside the female receptacle end plate. When connected end-to-end, the ionizer/collector cells  16  literally plug together (nest) forming a protective closed cavity. As a result of this arrangement, cell nesting corrects any misalignment between cells, and provides an air-stream baffle between end-to-end connected cells.  
         [0042]    A feature of the ESP system  10  is that each cell  16  has a radial float “blind mate” connector. Each connector has two components, a radial float plug  26  with socket contacts and a affixed mount receptacle  28  with pin contacts. The radial float plug  26  is mounted to one cell end plate and secured with hardware that allows limited  3 -dimensional movement of the plug on a generally flat surface. The fixed mount receptacle  28  is secured firmly with hardware to the opposite end plate of the same cell. When cells are pushed end-to-end in a tier arrangement, the plug from one cell end plate will self-align and fully engage with the receptacle of an adjacent cell. This radial float blind mate connector arrangement corrects for misalignment during cell-to-cell connection. Due to the unique floating design of the connector components  26  and  28 , misalignment up to three sixteenths of an inch can be overcome during connection of different ionizer/collector cells. Further, the radial float blind mate connector seals against air borne contaminates,  
         [0043]    By integrating a perforated non-metallic pre-filter and metallic post-filter  48  and  50 , respectively, into each ionizer/collector cells  16 , and mechanically affixing the post-filter to the grounded cell frame, an additional surface is created for attraction of opposite charged particles thereby improving efficiency. A further feature lies in the use of flexible cables with plugs (rated 24V-240V) as field connections, and the use of an integrated cable barrier to isolate the low voltage circuit from the high voltage circuit. The power cable is designed to place the fault system in series on an infinite number of cells.  
         [0044]    In accordance with the preferred embodiment, one or more ionizer/collector cells  16  may be connected end-to-end form a tier and a power distribution printed circuit board (PCB) module is incorporated into each tier. Each tier of cells has a built-in-visual display that illuminates under normal operating conditions. Further, each tier preferably has a connection port that is integrated into the tier status circuit to provide a means to connect external devices for monitoring tier status. When one or more ionizer/collector cell tiers are present in an ESP system, flexible cables with plugs at each end are preferably provided to transport power between each tier. Further, each cell  16  includes a status circuit that detects faulty electrical connection, monitors short circuit conditions in cells, monitors power supply failure, or monitors cell arcing. No low or high voltage hard wiring is necessary, nor are cell high voltage contacts necessary.  
         [0045]    While preferred embodiments of various components of a modular cell electrostatic precipitator system have been illustrated and described, it will be understood that changes and modifications may be made therein without departing from the invention in its broader aspects. Various features of the invention are defined in the following claims.