Concentric electrostatic filter

Abstract

An electrostatic filter, for filtering solid and liquid particles in gases composed of a case (3); concentric collectors (15), concentric diffusers (10); electrodes (2); insulated supports (7), distributor disc (8), thermal insulator (17), electrical resistors (4), main collector (9), filter cap (1); the concentric diffusers (10) host along their internal and external wall the electrodes (2); the insulated supports connect the filter cap (1) to the distributor disc (8) which in turn supports the concentric diffusers (10); the electrical resistors (4) are located around the case (3) as clamps and are covered by the thermal insulator (17); so that the gas flows through the filter from the filter inlet (14) located tangentially at the external face of the case (3), towards the insulated outlet (5) located in the central part between the distributor disc (8) and the filter cap (1), thus optimizing the space and surface of the constituent materials and a very high filtration efficiency of liquid and solid micron particles contained in gases at any temperature up to 900 C.

Claims

1. A concentric electrostatic filter for filtering solid and liquid particles in gases comprising: a case (3), which has an entrance or filter inlet (14) through which a gas is introduced tangentially; a distributor disc (8) that supports concentric diffusers (10), which house, along their walls, electrodes (2) which are in contact at their upper end with the distributor disc, spaced equidistantly from one another; and the distributor disc (8) is supported by the filter cap (1) through junction elements or pins between insulated supports (7) and disc connectors (16) through which high electric voltage is communicated to the distributor disc (8) by an insulated high-voltage electric conductor (11) inserted through an internal hole of the insulated supports (7) that contacts a head of the disc connectors (16); an insulated outlet (5) which extends from the top of the distributor disc (8) to a filter cap (1), said insulated outlet is configured to allow said gas to leave the electrostatic filter; a main collector (9) that is attached to a bottom of the case (3), which has slots (18) for filtering particles; concentric collectors (15) supported by the main collector (9), and electrically grounded, said concentric collectors are equally spaced from one another and from at least one of the concentric diffusers (10); a pressure insulating valve (6) located below the main collector (9) and the slots (18), which collects impurities; thermocouples (12) located in the filter cap (1); a thermal insulator (17) that covers the electrostatic filter, to avoid heat exchange with the environment; and electrical resistors (4) located around the case as clamps and covered by the thermal insulator (17).

Description

3 BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a cross sectional view of the filter

(2) FIG. 2 is cross sectional view of the concentric diffusers

(3) FIG. 3 is side view of the filter cap

(4) FIG. 4 is a horizontal cut, plant view of the filter

4 DESCRIPTION OF THE INVENTION

(5) The invention is an electrostatic filter which allows the filtration of solid and liquid particles in gases. It consists of a case (3), preferably cylindrical, with a filter inlet (14) through which the gas enters tangentially to the inner wall and subsequently leaves the filter through the insulated outlet (5) attached to the top of the distributor disc (8) and ends in the filter cap (1). The insulated outlet (5) is located in the central part of the filter cap (1) which is electrically insulated from the distributor disc despite contact. The bottom side of the distributor disc (8) is attached to several concentric diffusers (10), preferably cylindrical, which host along their inner and outer walls the electrodes (2), which are several rods of very thin diameter that contact at top the distributor disc (8) and are spaced equidistantly from one another. The distributor disc (8) is supported by the filter cap (1) through junction elements or pins between the insulated supports (7) and the disc connectors (16) through which the electric voltage is communicated to the distributor disc (8) thanks to an external insulated high-voltage electric conductor (11) inserted through the internal hole of the insulated supports (7) that contacts the head of the disc connectors (16).

(6) The case (3) is attached to the main collector (9) preferably conical with small slots (18) for liquid particle filtering applications, and with large and widely open slots for solid particle filtering applications. The main collector (9) is at zero or ground voltage and supports internally the concentric collectors (15), preferably cylindrical, equally spaced between them and the concentric diffusers (10). The space between the concentric collectors (15) and the main collector (9) at the startup, starts filled with solid or liquid particles up to a certain level which is slightly higher than the upper edge of the slots of the concentric collectors (15) and level remains constant thanks to the discharge star valve (6) referenced to a certain level by means of a level sensor not shown.

(7) The case (3), is attached to the filter cap (1) through anchoring bolts, and externally contacts the internal face of electrical resistors (4) that surround it and heat it when needed, to keep filter temperature, measured by the thermocouples (12), as desired. The filter is covered by a thermal insulator (17) to avoid heat exchange with the environment.

(8) Due to the filter configuration, explained in the previous paragraphs, it is achieved that the gas enters tangentially and then descends producing a cyclonic effect until a certain elevation, obtaining later a ring shaped profile of descent between the inner wall of the case (3) and the outer wall of the first concentric diffuser (10) where the charge and the expulsion of the particles to the concentric collectors happens. The gas then rises through the concentric ring between the inner wall of the first of the concentric diffusers (10) and the outer wall of the first of the concentric collectors (15) and the same happens for the next of the concentric diffusers and concentric collectors, following an upward and downward trajectory being subjected to the effect of electrostatic precipitation until reaching the insulated outlet (5). The solid and liquid particles precipitate down to the main collector (9).

4.1 Solution to the Current Problem

(9) After entering, the gas descends for a sufficient time as to uniform and occupy all the space between the concentric diffusers (10) and the concentric collectors (15), thus ensuring that the gas flow passes through the entire filtering field; not reducing efficiency.

(10) In the case that the flow is lower than that of the design, the gas will have a longer residence time, being this more advantageous, because the charged particle will be more likely to reach the concentric collectors (15) before leaving the filter.

(11) As collecting surface, the inner surface of the case (3) is used, plus the inner and outer surfaces of the concentric collectors (15), thus optimizing the material used and the volume of the filter too.

(12) The verticality of the electrodes (2) is ensured by the verticality of the concentric diffusers (10), thus achieving a uniform controlled electrons rain along the electrodes (2) and thereby along the single trajectory of the gas.

(13) The temperature of the filter is controlled by the electrical resistors (4) at a desired value higher than the dew point of the gas avoiding therefore unwanted condensable elements; incrustations and adhesions.

(14) For gases produced by high temperature reactors; the filter can be brought to a temperature higher than gas dew point, thus obtaining a dry filtration of the micron particles produced contained in the gas stream as soot for instance.

(15) The configuration of the filter allows easily the lifting of the internal parts, right after the filter cap (1) has been unmounted, making a quick and non-contact maintenance. It only requires pressurized water on the concentric diffusers (10) and collectors (15).

(16) Maintenance is low since configuration avoids the accumulation of solid or liquid due to their evacuation by the star valve (6)

5 DESCRIPTION OF ILLUSTRATIONS

5.1 Detail 1: Filter Cross Section

(17) 1. Filter Cap 2. Electrodes 3. Case 4. Electrical Resistors 5. Insulated Outlet 6. Star Valve 7. Insulated Supports 8. Distributor Disc 9. Main Collector 10. Concentric Diffusers 11. High voltage electric conductor 12. Thermocouple 13. Lifting lugs 14. Filter Inlet 15. Concentric Collectors 16. Disc Connectors 17. Thermal Insulator

5.2 Detail 2: Concentric Diffusers Cross Section

(18) 2. Electrodes 8. Distributor Disc 10. Concentric Diffusers 16. Disc Connectors

5.3 Detail 3: Filter Cap Details

(19) 1. Filter Cap 5. Insulated Outlet 7. Insulated Supports 11. High voltage electric conductor 12. Thermocouple 13. Lifting lugs

5.4 Detail 4: Horizontal Cut, Plant View

(20) 2. Electrodes 3. Case 6. Star valve 10. Concentric Diffusers 15. Concentric Collectors 17. Thermal insulator