Abstract:
An exhaust treatment system and method for removing particulates and/or gases from exhaust gases and for cooling exhaust gases. The exhaust treatment system may include a venturi nozzle for injecting a mixture of water and air into the exhaust gases to cause particulate matter and/or certain gases present in the exhaust gases to adhere to water droplets in the mixture. The exhaust treatment system may further include a receptacle positioned in proximity to the exhaust outlet and adapted for collecting water and particulate matter exiting the exhaust outlet, a filter adapted to receive water from the receptacle and remove particulate matter from the water, and/or a heat transfer device adapted to receive water from the filter and remove heat from the water.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of U.S. Provisional Patent Application Ser. No. 60/777,612 filed on Feb. 28, 2006, the disclosure of which is incorporated herein by reference. 
    
    
     BACKGROUND 
     The present invention relates to exhaust treatment. More particularly, a system and method for removing particulate matter and certain gases from exhaust generated by combustion or other industrial processes, is described. 
     SUMMARY 
     In a first aspect, the present invention exhaust treatment system may include an exhaust duct adapted to receive exhaust gases from a source; an exhaust outlet joined to the exhaust duct in fluid communication with the exhaust duct, adapted to flow exhaust gases out from the exhaust duct and adapted to flow water and particulate matter out from the exhaust duct; and at least one venturi nozzle joined to the exhaust duct. The venturi nozzle may have a channel including a section of narrower width than the surrounding sections, an air inlet through which air can enter the channel, and an internal baffle in the channel around which water flowing through the channel can pass such that water entering the venturi nozzle is mixed with air and the mixture is injected into the exhaust duct where the mixture causes particulate matter suspended in the exhaust gases to adhere to water droplets in the mixture. The mixture may cause carbon dioxide and/or oxides of nitrogen present in the exhaust gases to adhere to water droplets in the mixture. The exhaust treatment system may further include a receptacle positioned in proximity to the exhaust outlet and adapted for collecting water and particulate matter exiting the exhaust outlet, a filter adapted to receive water from the receptacle and remove particulate matter from the water, and/or a heat transfer device adapted to receive water from the filter and remove heat from the water. 
     In a second aspect, the present invention method for exhaust treatment may include the steps of receiving exhaust gases, mixing a spray of water droplets with the exhaust gases by a venturi nozzle and collecting the water droplets. The venturi nozzle may include a channel having a section of narrower width than the surrounding sections; an air inlet through which air can enter the channel; and an internal baffle in the channel around which water flowing through the channel can pass such that particulate matter in the exhaust gases will adhere to the water droplets. Carbon dioxide and/or oxides of nitrogen present in the exhaust gases may adhere to water droplets in the mixture. The method for exhaust treatment may further include a step of filtering the collected water, cooling the collected water, and/or recirculating the cooled water by mixing the water as a spray of water droplets with the exhaust gases. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a diagram of an exhaust treatment system  10 , according to an exemplary embodiment of the present invention. 
         FIG. 2  is a cross-sectional view of the venturi nozzle, according to an exemplary embodiment of the present invention. 
         FIG. 3  is an exploded perspective view of the venturi nozzle, according to an exemplary embodiment of the present invention. 
         FIG. 4  shows a schematic diagram of a system for treating exhaust and filtering water, according to an exemplary embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  shows a schematic diagram of an exhaust treatment system  10  according to an exemplary embodiment of the present invention. Exhaust is produced by a source  12  and conveyed away by a duct  14  and a smokestack or exhaust outlet  16 , where the exhaust gases are emitted through opening  18 . The exhaust source  12  can be any source of exhaust gases containing particulate matter including, without limitation, industrial furnaces or boilers fired with coal, oil, or any other fuel; municipal solid waste incinerators; and glass crushing facilities, where small airborne glass particulates are trapped and removed from the air. For applications involving gases from combustion, the composition of the exhaust gases and particulate matter contained therein will depend on several variables, including the type of fuel burned, the combustion parameters (temperature, pressure, etc.), furnace volume, and airflow. Additionally, as discussed below, the system and method of the present invention can be used with any source of exhaust gases, regardless of the presence of particulate matter therein, to lower the temperature of the exhaust gases being released into the atmosphere. 
     As depicted in  FIG. 1 , the exhaust duct  14  and exhaust outlet  16  can be configured in such a way that an air/water mixture can be sprayed into the exhaust stream to remove particulate matter from the exhaust gases. The exhaust duct  14  can have one or more openings through which water can be sprayed using a venturi nozzle  50 . The venturi nozzle  50 , which is described in more detail below, receives water through input port  52  and mixes it with air drawn in through air port  54 . The water and air are mixed to form a finely dispersed water/air mixture, which is sprayed into the exhaust duct  14  in a direction toward the exhaust outlet  16 , as shown in  FIG. 1 . As this finely dispersed water/air mixture is sprayed into the exhaust duct  14 , fine particulates in the exhaust gases adhere to the water droplets. The exhaust outlet  16  can be adapted to have a lower opening  20  through which the water can pass as it falls downward from the junction point  22  where the exhaust duct  14  joins the exhaust outlet  16 . Meanwhile, the exhaust gases rise and are released through the opening  18  above the junction point  22 . The water, which now contains fine particulates that were trapped from the exhaust, can be collected in a receptacle  24  to be processed, filtered, or discarded. 
       FIG. 2  shows a side cutaway view of the venturi nozzle  50 , according to an exemplary embodiment of the present invention. Water is supplied to the venturi nozzle  50  through inlet  52 , and the water flow velocity is increased as the water passes through the channel  56 . The narrowed stream of water emerging from the channel  56  strikes the butt end  58  of the baffle  60 , which is held in place by radial stays  64 . Upon striking the butt end  58 , the water is dispersed into the annular region surrounding the baffle  60 . The dispersion of the water creates a partial vacuum in the region between the channel  56  and the baffle  60  and air is drawn in through port  54 . The water and air pass around the baffle  60  through the annular region and over the pointed end  62  of the baffle  60 . The turbulence resulting from the pass around the baffle  60  mixes the air with the water. The aerated water then exits the venturi nozzle  50  through opening  66 . In an exemplary embodiment, the overall diameter of the nozzle body is 40 mm (1.6 inches), the pointed end  62  of the baffle  60  is tapered with an angle of 30 degrees, the baffle  60  has an overall length of 76 mm (3 inches) with the tapered portion being 25 mm (1 inch) long, the butt end  58  of the baffle  60  is located 18 mm (0.7 inches) away from the end of the channel  56  from which water emerges, and the channel  56  and baffle  60  each have a diameter of 19 mm (0.75 inches). In an alternative embodiment, the overall diameter of the nozzle body is 51 mm (2.0 inches), the channel  56  and baffle  60  each have a diameter of 25 mm (1.0 inch), and the other measurements have the same values as in the first embodiment described above. In additional embodiments, other values for these parameters could be used to achieve the desired performance and mixing characteristics, as will be appreciated by persons skilled in the art. 
       FIG. 3  shows the venturi nozzle  50  equipped with a sprayer  70  to finely disperse the water/air mixture that exits the venturi nozzle, according to an exemplary embodiment of the present invention. The sprayer  70  includes a tapered disc having a maximum diameter that is approximately equal to the diameter of the exit orifice  66  of the nozzle body  68 . The disc of the sprayer  70  has a bolt  72  with a threaded end  74 . This threaded end  74  can be threaded into a hub  76  that is held in place along the longitudinal centerline of the nozzle body  68  by radial stays  78 . As water/air mixture exits the venturi nozzle  50  through the exit orifice  66 , it is deflected by the sprayer  70 , producing a relatively fine mist. 
     In addition to trapping and removing particulate matter from exhaust gases, the system and method described herein have the effect of lowering the temperature of the exhaust gases being released into the atmosphere. The fine water/air spray released by the venturi nozzle contains tiny air-entrained bubbles in a balance, which allow rapid heat transfer between the water droplets and the hot exhaust gases into which the water/air mixture is injected, thus cooling the exhaust gases. Accordingly, the system and method of the present invention can be used with any source of exhaust gases, regardless of the presence of particulate matter therein, to lower the temperature of the exhaust gases being released into the atmosphere. Additionally, the rapid cooling of the exhaust gas stream causes some of the gases, such as carbon dioxide and oxides of nitrogen, to adhere to the surfaces of the particulate matter and water droplets and become captured. The concentrations of these gases in the exhaust emissions is thus reduced. As will be appreciated by persons skilled in the art, various chemical additives can be added to the water supply for the venturi nozzle in order to assist in the capture of other specific gases and particulates that may be present, depending on the nature of the fuel and combustion. 
       FIG. 4  shows a schematic diagram of a system for treating exhaust and collecting and filtering the water containing the particulate matter removed from the exhaust, as discussed with respect to the exemplary embodiment depicted in  FIGS. 1 through 3 . Exhaust from the exhaust source  12  passes through the duct  14 , where water spray is injected by venturi nozzles  50  to capture particulates in the exhaust gases. The exhaust gases exit the exhaust opening  18  of the exhaust outlet  16  to atmosphere, and the water droplets, along with any particulates adhering to them, fall downward from the exhaust outlet, where the water can be collected in a receptacle  24 . The collected water can be run through a filter  90  to remove the particulate matter collected from the exhaust. 
     The filter  90  can be a ceramic filter using particles fabricated from refined porcelaneous clays, dry clays, sawdust, or other suitable material known to persons skilled in the art. In an exemplary embodiment, the filter medium is made from a mixture of 50% dry clay and 50% sawdust, screened between a 35 mesh and a 60 mesh screen The material that passes through the 35 mesh screen but does not pass through the 60 mesh screen is used for the filter medium and the material can then be soaked in a 32% colloidal silver solution. The filter medium can be contained in a clay or plastic container. This ceramic filter can have the advantage of cooling and condensing the steam as it passes through the filter, such that the water exits the filter in liquid form. Alternatively, the filter  90  can be implemented in other ways known to persons skilled in the art. 
     The filter  90  can be formed integrally with the receptacle  24  or the filter  90  can be contained in a separate unit. After filtering, the water can be passed through a heat transfer device or radiator  94 , which removes heat and lowers the water&#39;s temperature. From there, the water can be returned to a pump  98 , which can re-supply the water to the venturi nozzle  50  in the exhaust duct  14 . The pump  98  can also draw upon an external source of water to replenish water that is lost to evaporation or otherwise exits the system. Additionally, the pump  98  can supply a portion of the water to other uses  102 . 
     Following from the above description and invention summaries, it should be apparent to persons of ordinary skill in the art that, while the methods and apparatuses herein described constitute exemplary embodiments of the present invention, it is to be understood that the inventions contained herein are not limited to the above precise embodiments and that changes may be made without departing from the scope of the invention as defined by the following proposed points of novelty. Likewise, it is to be understood that it is not necessary to meet any or all of the identified advantages or objects of the invention disclosed herein in order to fall within the scope of the invention, since inherent and/or unforeseen advantages of the present invention may exist even though they may not have been explicitly discussed herein.