1. Field of the Invention
The invention pertains to the field of separator apparatuses. More particularly, the invention pertains to an apparatus that can function as a filter unit as a precipitator or as a separator of materials that have different electrical properties.
2. Description of Related Art
U.S. Pat. No. 4,172,028 discloses an electrostatic sieve having parallel sieve electrodes that are either vertical or inclined. The particles are normally introduced into the electric sieve under the control of a feeder that is placed directly in front of the opposing screen electrode. The powder is attracted directly from the feeder tray to the opposing screen electrode by induced electric field that exists between the tray and the screen electrode. This system is a static air system.
Prior art precipitators have difficulty collecting highly conductive and very poorly conductive particulates.
The present invention includes an improved apparatus for collecting particulates using an aperture air flow control system and an inline series of alternating discharge and grid type electrodes each with a separate electrical circuit centrally located between either parallel grid electrodes and/or plate electrodes.
The present invention also includes a method for improving the rate of lateral movement and collection of particulates using the aperture air flow control system and an inline series of alternating discharge and grid type electrodes each with a separate electrical circuit centrally located between either parallel grid electrodes and/or plate electrodes.
In a preferred embodiment, the spacing between parallel grid and discharge electrodes varies between 0.50 and 1.50 inches with a narrow air stream being drawn between the electrodes.
The present invention also includes an improved method of charging particles using a pre-charger designed with a narrow air input channel. Using a narrow air input channel into the main air stream increases the probability that entrained particles and generated ions will come in contact, resulting in a high percentage of particles being charged.
In another embodiment, an external enclosed pre-discharger design and physical arrangement improves agglomeration of sub-micron particles. The present invention also includes an external opposing dual channel discharger design to improve agglomeration of particles. In one embodiment, two or more separate electrode arrangements are used within the collecting chamber to improve the operation and collection efficiency of the apparatus. In another embodiment, multiple collection chambers are placed in series, preferably with a discharge chamber placed in between each of the collection chambers to recharge the particles. Various designs recharge the particles, to increase collection efficiency.
A grid electrostatic precipitator (GEP) is a dynamic air system where a gradient air flow exists between the center air flow and collecting plate electrodes. External discharge electrodes are designed to charge and then agglomerate the fine particles into larger particles for ease of collection.
The present invention includes a grid type electrostatic precipitator/collector with a narrow air stream, various external pre-discharger designs with the ability to agglomerate sub-micron particles into larger particles and one or more collection chambers (fields). The pre-chargers preferably include a narrow air input channel. In one embodiment, the collection chamber includes both a recharging zone and a high voltage zone. In another embodiment, at least two collection chambers are placed in series and are separated by agglomerating recharging units. In yet another embodiment, one or more of the collection chambers placed in series includes a recharging zone and a high voltage zone. The present invention also addresses the differential flow pattern, illustrated in
In the embodiments of the present invention, the main air stream is preferably a single column of air flowing in a vertical direction or a single row of air flowing in a horizontal direction.
One problem with agglomeration is that, once two or more particles agglomerate into a larger, agglomerated particle, the agglomerated particle loses polarity. The present invention solves this problem by recharging these particles, permitting them to agglomerate further, which makes them even easier to collect. Recharging may be repeated over and over, to further increase the collection efficiency of the apparatus.
An electric field (24) is established between the alternating electrodes (5) and (6), (6) and (7), and (7) and (8). Generally the spacing between the last grid electrodes (7) and (8), and the plate electrode results in the absence of an electric field because of the distance between the plate and the grid electrodes. The charged particles move laterally (16), and gravitationally settle (18) in the open space (25).
When processing large, high-density particles, these particles may gravitate out of the process before the next grid electrode or the collection plate electrode (10). The collecting plate electrode (10) is used when collecting fine non-conductive particles or when there is a mixture of conducting and non-conducting particles. Deposited particles are removed by a tapping apparatus (32), or by a squeegee or other removal methods. The spacing between parallel grid electrodes preferably varies between ⅜ and 1.50 inches.
The spacing between electrodes, the electrical potential between electrodes and the number of grid electrodes are each a function of the concentration of solids in the air stream, the size of the particles, electrical and physical characteristics of the particles, and flow rate, as well as other process variables.
The grid supports (2) and (11) are preferably constructed from a dielectric material with openings (15) in the collection area. The dislodged powder falls by gravity or is tapped from the plate electrodes (10) and is collected (34) at the bottom of the precipitating chamber (33).
The polarities of the electrodes change when the apparatus processes clusters of powder that are lightly bonded and need more resident time to break down into smaller particles that respond to the electrical forces available.
The “modified U shaped” electrode assembly is a very efficient design and method for separating solids from an air stream. The major forces used to separate the particles from the air stream are the force of gravity that exerts a vertical downward force, the electrical inductive field force generated between the plate and grid electrodes and the angular, tangential force exerted on the particles as they traverse the angular section and around the radius of solid and grid electrodes.
The combination of the electrical field and the physical radius of the modified-U shaped electrode contribute to efficient separation by inducing turbulence and drag components to the air stream and particles.
The entrained air enters at (47) and is immediately subjected to the electrical lateral forces established between the modified U shaped plate electrode (48) and the wire grid electrodes (52) and (53). The entrained air (50) is drawn down the surface of the modified U shaped plate electrode (48) by the exhaust system located after the exit (1). As the air (50) flows down the angular section (56), the particulates (49) are laterally expelled (51) from the airflow. When the entrained air reaches the start of the radius (54) or tangent point, shown in
In one embodiment, a grid type electrostatic separator/collector (GES/C) includes alternating discharge and grid type electrodes. Using parallel and opposing grid electrodes achieves early lateral transfer of particles through the grid into an area where the airflow is at a lower velocity or static conditions.
The centrally located discharge corona electrode shown in
When a discharge electrode is placed between parallel grid electrodes and a voltage is applied, an electric field is established, generating flux lines that charged particles follow, ions, and an electric wind that introduces predictable turbulence.
At the surface of the grids, the air velocity develops turbulence or a shear factor associated with the boundary layer, generating unstable eddy or vortex rotation. The combination of the above factors also improves the separation and traverse of particles from the main air stream and into the lower air velocity collection area.
The particles then travel through the collector aperture (65) into the main part of the collector (80). The collector (80) includes a series of alternating central discharge electrodes (68) and central grid electrodes (67) centrally located between the parallel grid electrodes (61). Although three central discharge electrodes (68) and five central grid electrodes (67) are shown in
An example of a grid that may be used in the electrostatic precipitator/collector of the present invention is shown in
The electric field (84), established when central discharge electrodes (68) are placed between parallel grid electrodes (61), generates flux lines (66). Charged particles laterally move (89) in a direction following the flux lines (66) and an electric wind (63) introduces predictable turbulence. At the surface of the grids (61) and (67), the air velocity develops turbulence or a shear factor associated with the boundary layer generating unstable eddy or vortex (60) rotation. Particles are collected (64) on the plate electrodes (83).
In a preferred embodiment, the spacing (69) between central grid electrodes (67) and the parallel opposing grid electrodes (61) varies between 0.50 and 1.50 inches. The same distance variation preferably applies to the distance between the central discharge electrodes (68) and the parallel opposing grid electrodes (61).
The series of discharge and grid type electrodes preferably have different circuits that operate at different levels of current and voltage. As an example,
The present invention replaces the corona discharge electrodes (21) of
Some advantages of the embodiments employing a series of alternating discharge electrodes and grid electrodes include improved charging of particulates, faster removal of entrained particles from the main air stream and onto the collecting plates, which results in shorter and less expensive equipment, and the ability to have improved field effects by having both a high voltage-high current for the discharge-grid conditions and a higher voltage-low current condition for grid-grid conditions, resulting in more efficient lateral particle removal and collection.
The combination of electrodes also achieves a stable corona discharge by controlling both the voltage and the current. Drift velocity is not a major concern because the distance the particles have to travel before they are out of the main air stream is short. The distance between the discharge and extracting or grid electrodes is relatively close, preferably 0.50 to 1.50 inches.
During the early process of charging particulates, blinding or interference from other particles can occur prohibiting all particles from reaching the maximum charge and responding to the flux lines of the electric field. By alternating single or multiple groups of discharge and grid electrodes along the length of the collection chamber, the problem is substantially reduced.
In this embodiment, the present invention has dual channels (217) and (218) where the particles are charged with opposite polarities using a high voltage direct current. The particles then flow into a converging air zone (146) where the polarized particles mix and agglomerate (106) into larger particles. The agglomeration (106) continues as the particles flow into a narrow single channel (130) before entering the collection chamber (135). In a preferred embodiment, the width of the single channel (130) ranges from ¾ inches to 2½ inches. Using narrow airflow channels (217) and (218) in the discharger improves the probability of agglomerating the fine particles by exposing the particles to a high concentration of polarized particles. In a preferred embodiment, the width of each of the airflow channels (217) and (218) are the same, and ranges from ¾ inches to ½ inches such that the total width of both channels ranges from ½ inches to 3 inches.
In an example of the dual channel discharger (126), the dimensions include ⅜ of an inch between the plate electrodes (103) and discharge electrodes (105) such that each of the polarizing channels (217) and (218) are ¾ inches wide. In this example, the single channel (130) is preferably 1 inch wide.
In a preferred embodiment, the width of the main air stream, which is also the distance between the two chambers (102), is preferably in the range of ¾ to 2½ inches. In another preferred embodiment, the width of the output orifice (125) from the discharge chambers (102) into the main air stream preferably ranges from 10/1000 inch to 60/1000 inch.
Advantages of this system include the ability to adjust the ion input by varying either the orifice width (125) or the operating current. Another advantage is that the discharge electrodes are kept clean, resulting in maintaining a consistent ion input. Fine particle agglomeration is effective in this system because of the narrow air channel and the turbulent airflow created by the ions being drawn into the main air stream.
The discharge zone (131) is placed first because agglomerated particles will lose most of their charge and need to be recharged in order to continue to agglomerate. Particles that are not collected in zone (131) will be subjected to a higher voltage in zone (132), resulting in a stronger electrical field (104) that improves collection of sub-micron particles.
The collection process begins with particles entering at orifice (136) and being polarized by the corona from the discharge electrodes (105). The charged particles then respond to the opposite polarity of the grid electrode (107) and the electric field (104) and move laterally (109) or perpendicular to the airflow by following the flux lines of the electric field. Because of the momentum of the particles, the particles pass through the grid (107) into an area where there is a sharp drop in the air velocity (151) and decreases to near static conditions (115) at the collection plate surface (133) and (134). The sharp drop in flow immediately behind the grid electrode (151) is dependent on the porosity of the grid and airflow operating parameters. Due to the close proximity of the electrodes in the first zone (131), charging of the particles is aided by the turbulence created by the corona wind (127), movement of ions and the eddy currents (128) generated at the surface of the grid electrodes (107) and (138).
Sub-micron particles are collected when charged particles (124) follow the flux lines of the electrical field (104) and move laterally (109) through the grid electrode (107) into an area where there is a sharp drop in air movement and reaching near static conditions at the collecting plate surface (115).
In one example, the typical dimensions for one field include a distance between the discharge electrodes (105) and grid electrodes (107) that is preferably between ½ inches and 1.0 inch. The width of the collection chamber (135) is preferably 6.0 to 12.0 inches. The width of the grid electrodes can vary between 6 and 12 inches, depending on the structural size of equipment. There are preferably 3 to 6 discharge electrodes (105) per grid and 3 to 4 grid electrodes (107), (138). The length of the combined processing zones (131) and (132) is preferably 18 to 24 inches. The input (136) and exit (137) orifices are preferably each 1.0 to 2.0 inches wide.
The length of the processing zones, the number of electrodes, and the height will vary depending on the application. Another dimension that will vary based on the size and operating requirements is the aspect ratio of the width of the input and output orifice to the width of the field or collecting chamber. In preferred embodiments, aspect ratios of 10:1 or 3:1 may be used.
The external enclosed discharger shown in
Another method for improving the collection of fine and sub-micron particles is to recharge the particles more frequently. It is difficult to charge, agglomerate and collect ultra fine particles. The collection by the first field may be high but it is not 100 percent. Some of the particles will not be sufficiently charged to respond to the electrical field. By re-charging and then re-agglomerating these particles at frequent intervals, the process becomes more efficient.
Although two chambers are shown in
Collecting sub-micron particles is also tied into continuously collecting both inorganic and organic particles. The particles may be recharged by an energy source (113). One method for recharging the particles uses an ultraviolet energy source.
The pre-charger shown in
In other embodiments, other pre-charger designs may be used. One of the arrangements, shown in
On the left hand side of
The right hand side shows a slight modification where the input gases (150) are drawn through the air filter (111), but do not pass through controlling apertures (141). The input gases (150) only exit through the controlling apertures (125) near the attracting plate electrode (103). Selection of the location of the input orifice and the exit orifice is important because it permits the generated ions entering the main entrained air stream to exit the chamber before losing their charge to the attracting electrode. Other design and operating features of this apparatus include the ability to increase the distance between the corona (105) and attracting plate electrodes (103) so that a higher voltage is generated and maintained, resulting in the production of more ions.
The corona electrodes generate controlled amounts of electrically charged gases that are attracted to the opposing attracting electrode by the electrical field (104). These charged particles are preferably drawn into the main stream (100) by negative pressure of the precipitator, or forced into and mixed under low pressure with the main entrained airflow (100). Having the ability to protect the corona-generating electrode opens the door to extending the life of electrodes and generating higher ion counts using less energy.
In a preferred embodiment, the width of the main air stream (100) ranges from ¾ to 2½ inches. In one example, the width is 1 inch.
The high velocity gases and particulates in the main air stream (100) keep the attracting electrodes (145) clean. The charging corona electrodes (144) and (105) are kept clean by the positive constant flow of gases over the surface of the electrodes. Clearance between the electrode and sidewall of the orifice may vary and is based on operating parameters of the GEP. If the pre-charger design of
It should be noted that, in the case of designs shown in
The pre-charger arrangements shown in
Accordingly, it is to be understood that the embodiments of the invention herein described are merely illustrative of the application of the principles of the invention. The embodiments can also be used in combination with each other, within the spirit of the present invention. Reference herein to details of the illustrated embodiments is not intended to limit the scope of the claims, which themselves recite those features regarded as essential to the invention.
This application claims one or more inventions which were disclosed in Provisional Application No. 60/979,206, filed Oct. 11, 2007, entitled “GRID TYPE ELECTROSTATIC SEPARATOR/COLLECTOR AND METHOD OF USING SAME” and Provisional Application No. 61/086,274, filed Aug. 5, 2008, entitled “GRID TYPE ELECTROSTATIC SEPARATOR/COLLECTOR AND METHOD OF USING SAME”. The benefit under 35 USC § 119(e) of the United States provisional applications is hereby claimed, and the aforementioned applications are hereby incorporated herein by reference. This is also a continuation-in-part of co-pending patent application Ser. No. 11/380,714, filed Apr. 28, 2006, which is a continuation-in-part of patent application entitled “GRID TYPE ELECTROSTATIC SEPARATOR/COLLECTOR AND METHOD OF USING SAME”, Ser. No. 10/872,981, filed Jun. 21, 2004, now U.S. Pat. No. 7,105,041, which is a continuation-in-part of patent application entitled “GRID TYPE ELECTROSTATIC SEPARATOR/COLLECTOR AND METHOD OF USING SAME”, Ser. No. 10/225,523, filed Aug. 21, 2002, now U.S. Pat. No. 6,773,489, and claims one or more inventions which were disclosed in Provisional Application No. 60/675,575, filed Apr. 28, 2005, entitled “CORONA PARTICLE CHARGER”, Provisional Application No. 60/722,026, filed Sep. 29, 2005, entitled “CORONA PARTICLE CHARGER”, and Provisional Application No. 60/716,425, filed Sep. 13, 2005, entitled “GRID ELECTROSTATIC PRECIPITATOR/FILTER FOR DIESEL ENGINE EXHAUST REMOVAL”. The aforementioned applications are hereby incorporated herein by reference.
Number | Date | Country | |
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60979206 | Oct 2007 | US | |
61086274 | Aug 2008 | US | |
60675575 | Apr 2005 | US | |
60722026 | Sep 2005 | US | |
60716425 | Sep 2005 | US |
Number | Date | Country | |
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Parent | 11380714 | Apr 2006 | US |
Child | 12248942 | US | |
Parent | 10872981 | Jun 2004 | US |
Child | 11380714 | US | |
Parent | 10225523 | Aug 2002 | US |
Child | 10872981 | US |