Patent Publication Number: US-2005139073-A1

Title: Emission control device and method of operation thereof

Description:
Priority is claimed based upon U.S. Provisional Application Ser. No. 60/435,368 filed on Dec. 23, 2002. 
    
    
     BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      This invention relates to an emission control device to remove particulates from a gas and, more particularly to an emission control device that operates by adding moisture to the gas and subsequently removing moisture from the gas along with particulates. Still more particularly, this invention relates to a scrubber with a fan located therein.  
      2. Description of the Prior Art  
      Emission control devices are known. However, previous devices do not operate effectively to remove particulates from a gas, or, they are extremely expensive to operate or to construct, or, they are inefficient.  
      Settling tanks have been used previously to separate particulates from a gas. Further, it is known to have a wet scrubber that uses water to separate particulates from a gas, but previous scrubbers do not contain a fan.  
     SUMMARY OF THE INVENTION  
      It is an object of the present invention to provide an emission control device for removing particulates from a gas the device having an inlet and an outlet, the device containing a rotor and fan to separate moisture from the gas and to direct the gas to an outlet respectively.  
      An emission control device has an inlet and an outlet for gas containing particulates. The device has a housing with a passage extending between the inlet and outlet. A moisturizer is located at or near the inlet to moisturize the gas. A blower is located to cause the gas to flow through the device. A rotor is located in the housing across the passage, the rotor being rotatably mounted to remove moisture and particulates from the gas. The passage has a change in direction to assist in removing moisture and particulates from the gas, the device having a drain for moisture.  
      Preferably, the emission control device is a scrubber.  
      A method of operating an emission control device to remove particulates from a gas has an inlet and an outlet outlet with a passage therein to receive the gas and to direct the gas to the outlet. There is a moisturizer at or near the the inlet. The device has a blower that is located to cause the gas to flow through the device. A rotor is located in the housing across the passage, the rotor being rotatably mounted to remove moisture and particulates from the gas. The passage has a change of direction and the device has a drain for moisture, the method comprises adding moisture to the gas at the inlet, operating the blower to receive gas while simultaneously operating the rotor, removing particulars and moisture from the gas and directing the gas to the outlet, while draining moisture from the device through the drain. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a schematic side view of a scrubber;  
       FIG. 2  is a top view of the scrubber of  FIG. 1 ;  
       FIG. 3  is a schematic perspective view of a scrubber with a part of the housing partially cutaway; and  
       FIG. 4  is a schematic perspective view of the scrubber with the housing drawn with light lines. 
    
    
     DESCRIPTION OF A PREFERRED EMBODIMENT  
      In FIGS.  1  to  4 , an emission control device  2  has a housing  4  with an inlet  6  and an outlet  8 . Within the housing  4  there is a passage  10 , which extends in more than one direction to the outlet  8 . A cylindrical section  12  of the passage  10  is concentrically mounted in an upper portion  14  of the housing  4 . On a top  16  of the housing  4 , there is mounted a hood  18 . A shaft  20  extends vertically through the housing  4  from the hood  18  to a bottom  22 . The shaft  20  is rotatably mounted in bearings  24 ,  26 . A motor  28  is mounted in a bracket  30 . The motor has a shaft  32  that has a pulley  34  thereon. The shaft  20  that extends through the housing has a pulley  36  mounted thereon. Preferably, the motor  28  is an electrical motor (the electrical connections are not shown) and a belt  38  connects the pulleys  34 ,  36  so that the motor  28  can rotate the shaft  20 . Beneath a lower edge  40  of the cylindrical section  12 , there is a blower  42  mounted on the shaft  20 . The blower  42  is a fan. The fan  42  has outer blades  44  and inner vanes  46 . The inner vanes  46  form a rotor which is shown as being one component with the fan. The rotor and the fan could be separate components. The fan could be located outside of the device or elsewhere within the device. The purpose of the fan is to cause the gas to move through the device. The purpose of the rotor is to remove moisture and particulates from the gas. The inlet  6  is located near a top  16  of the housing  4 . The housing contains an annular baffle  48  that is located between the inlet  6  and the fan  42 . There is a lateral drain  50  located around a circumference of the housing  4  radially outward from the fan  42 . Additional drains  52  are located in a base  54  of the housing  4 .  
      A plurality of moisturizers  56  (only one of which is shown) is located outside the inlet  6 . The moisturizers  56  add a fine mist to a gas  58  just before the gas enters the inlet  6 . When the fan  42  is activated, gas containing particulates is drawn into the inlet  6  and is directed by the shape of the passage  10  and the annular baffle  48  downward and inward. Immediately after passing the baffle  48 , the gas strikes the outer blades  44  of the fan  42 . The outer blades  44  are generally flat and lie in a vertical plane and the blades direct the gas outward and downward. Since the gas contains moisture, the blades  44  remove some of the moisture from the gas  58  and force it by centrifugal force to the drain  50 . The particulates affix themselves to water droplets in the mist. Therefore, as the moisture is removed, some of the particulate matter is also removed through the lateral drain  50 . After passing downward through the fan  42 , the gas is forced inward and upward by the inner vanes  46  of the fan  42  into an interior of the cylindrical section  12 . The vanes  46  are angled to force the gas upward as the fan rotates. The abrupt change in direction causes the gas to lose more moisture and the gas moves upward through the hood  18  to the outlet  8 . The gas can then be further cleaned or it can be released to the atmosphere or recycled. The extra moisture is drained away through the drains  52  in the base  54 .  
      Preferably, the emission control device is a scrubber, the gas is air and the moisturizers are nozzles that are capable of creating a finely divided mist. The moisture is preferably water. Preferably, the fan has a disc  60  that extends beneath the outer blades  44 . For ease of illustration, not all of the blades and vanes are shown in  FIGS. 3 and 4 . Preferably, the blades and vanes are equally spaced around the circumference of the fan. Preferably, there is one blade for each vane. The inner vanes connect the outer blades and the disc to the shaft  20 . The fan is mounted across the passage  10  at a location where the air changes direction by 180° and the cross sectional area of the passage is substantially reduced. Further, the air direction changes from a downward direction to an upward direction. The amount of water injected into the gas stream is such that a wet environment is created with sufficient free water carried by the gas. Prior to entering the inlet  6 , the gas is transported in a duct  62  shown by dotted lines in  FIG. 1 .  
      The direction of flow of the gas is indicated by arrows in  FIGS. 1, 3  and  4 . As soon as the gas enters the housing  4  through the inlet  6 , it is directed inward and downward in a down-spiraled action. Partway down the housing, the gas is directed inwardly by the baffle  48  through a narrow annular opening  64  around the outside of the cylindrical section  12 . This forces the gas to rapidly increase in velocity and the moisture in the gas stream together with the free water will adhere to additional dust particles in the gas. After the gas has passed by the baffle  48 , the outer blades  44  of the fan  42  cause the gas to turn sharply outward while continuing to rotate the gas around an interior of the housing  4 . Since the water in the gas is heavier than the gas itself, the centrifugal effect caused by the outer blades  44  of the fan  42  effectively separates much of the water from the gas. The water, which has trapped the dust particles in the gas stream, swirls around within the housing and is forced against the inside wall of the housing  4 . The lateral drain  50  is a circumferential drain that extends around the housing  4  in a band  66  having an opening  68  located radially outward from the fan  42 . Since the water has trapped the dust particles in the gas stream, most of the dust particles and the water is forced out of the housing through the lateral drain  50 .  
      After passing by the blades  44  of the fan  42 , the gas contains virtually no free water, but only saturated moisture and little or no free water droplets. Additional water separation is achieved by the rapid change of direction in the gas stream as it makes a 180° turn upwards into the cylindrical section  12 . Moisture that separates from the gas and does not exit the housing through the lateral drain  50  falls to the base  54  and exits the housing through the additional drains  52 . The inner vanes  46  on the fan  42  force the gas upward through the cylindrical section  12 . The positive force exerted on the gas stream by the vanes  46  virtually eliminates any pressure drop in the gas as it passes through the emission control device  2 . When the gas reaches the hood  18  and the outlet  8 , it is preferably directed into a connecting duct (not shown) for further transport. All water is recovered in the scrubber, with the exception of the moisture absorbed by the saturated gas, and is collected in a container. From this container, the water is then piped for re-use to a pump, which increases the water pressure. The water is then piped back to the spray nozzles. The circulation and reuse of the water reduces the water consumption significantly.  
      By circulating and reusing the water, the concentration of suspended particles will increase. The device of the present invention can be operated continuously or, intermittently, as required. The water is independently pumped from the container by a second pump to a filter and then returned again.  
      The device of the present invention is efficient and cost effective to collect airborne dust particles from many sources of emissions. One source of these emissions is industrial boilers, including those that are burning waste wood and emit airborne ash particles (flyash) in the flue gas from their gas stacks.