Abstract:
One evaporator includes a housing defining a generally enclosed interior area and a stepped cascade separating the interior area into an upper chamber and a lower chamber. The stepped cascade includes sequential trays and risers. At least one tray has a hole connecting the upper chamber with the lower chamber, and at least one riser has a hole connecting the upper chamber with the lower chamber. An input device selectively introduces wastewater into the upper chamber, and a heat source selectively introduces heat into the lower chamber sufficient to evaporate water from the wastewater atop and passing through the stepped cascade. A gas exit provides a passage for gas from the interior area to outside the housing.

Description:
RELATED APPLICATIONS 
       [0001]    This application claims priority to provisional application 61/666,013 filed Jun. 29, 2012, the disclosure of which is incorporated herein in its entirety by reference. 
     
    
     BACKGROUND 
       [0002]    The prior art includes systems for heating wastewater to evaporate water from a slurry of sludge and water, and to collect the remaining solid particulate matter after the water has been evaporated. Yet such prior art systems are typically complicated and have limited capacity. A need exists for new systems having improved characteristics in these or other areas. 
       SUMMARY 
       [0003]    The following presents a simplified summary of the invention in order to provide a basic understanding of some aspects of the invention. This summary is not an extensive overview of the invention. It is not intended to identify critical elements of the invention or to delineate the scope of the invention. Its sole purpose is to present some concepts of the invention in a simplified form as a prelude to the more detailed description that is presented elsewhere. 
         [0004]    According to one embodiment, an evaporator includes a housing defining a generally enclosed interior area and a stepped cascade separating the interior area into an upper chamber and a lower chamber. The stepped cascade includes sequential trays and risers. At least one tray has a hole connecting the upper chamber with the lower chamber, and at least one riser has a hole connecting the upper chamber with the lower chamber. An input device selectively introduces wastewater into the upper chamber, and a heat source selectively introduces heat into the lower chamber sufficient to evaporate water from the wastewater atop and passing through the stepped cascade. A gas exit provides a passage for gas from the interior area to outside the housing. 
         [0005]    According to another embodiment, an evaporator includes a housing, a plurality of downwardly sloping sequential trays and risers, an input device, a heat source, and a gas exit. The housing defines a generally enclosed interior area, and the plurality of downwardly sloping sequential trays and risers divides the interior area into upper and lower chambers. The input device selectively introduces wastewater into the upper chamber for passing across at least a portion of the trays and risers. The heat source selectively introduces heat into the lower chamber sufficient to evaporate water from the wastewater atop the trays and risers. The gas exit provides a passage for gas from the interior area to outside the housing. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]      FIG. 1  is a side view of an evaporator according to one embodiment of the current invention, with a side wall removed for illustration. 
           [0007]      FIG. 2  is a section view taken from  FIG. 1  as illustrated. 
           [0008]      FIG. 3  is an end view of the evaporator of  FIG. 1 . 
           [0009]      FIG. 4  a bottom view of the evaporator of  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION 
       [0010]    Various evaporators/dryers of the current invention may be simple and economically built, and may efficiently evaporate water, dry solids, and leave oils and other liquids. As shown in  FIGS. 1-4 , one embodiment  1  of the evaporator/dryer includes a generally rectangular box-like metal housing  10 . An effective housing  10  can, for example, be modified from an ocean shipping container which has the approximate dimensions of twenty feet long by eight feet high by eight feet wide, and which has heavy gauge steel walls. Those skilled in the art will appreciate that the housing  10  can be made in many sizes and of various materials, however. 
         [0011]    The housing  10  according to one preferred embodiment includes a top  12 , a bottom  14 , a pair of opposed side walls  16 , an end wall  18 , and an opposite end  20  with a pair of doors  21 . Inner wall liners  22 ,  24  are spaced apart (e.g., approximately four inches) from the inside of the side walls  16  and the end wall  18 . The liners  22 ,  24  extend from the bottom  14  toward the top  12  of the housing  10 , and it may be desirable for the liners  22 ,  24  to be one unitary liner and to further cover the bottom  14 . At least one opening  26  in the bottom  14  of the housing  10  between the outer walls  16 ,  18  and inner liner  22 ,  24  may permit exterior air to be drawn into the gap (or “cooling passages”)  25  between the liners  22 ,  24  and walls  16 ,  18  to be used to cool ( FIG. 4 ). 
         [0012]    A high power gas burner  28  is mounted to the exterior surface of the end wall  18  as shown in  FIGS. 1 and 3 . In one preferred embodiment, the burner  28  is gas powered and creates approximately 5,000,000 BTU. Yet a wide range of acceptable fuel sources, burner efficiencies, and burner outputs may be used. The burner  28  may be mounted to the outside wall  18  so that heat is directed through a conduit  30  passing through the outer wall  18  and liner  22  into an interior  31  of the housing  10 . 
         [0013]    The burner  28  may be mounted to direct the air into the housing  10  under a collector pool  36  and a stepped cascade  37 . A flow control  29  may control the rate at which the liquid is introduced into the housing  10  as well as completely close entry of liquid for cleaning or other purposes. 
         [0014]    As shown in  FIG. 1 , a manifold  46  extends generally horizontally across the end liner  22  near the top  12  of the housing  10 . The manifold  46  has an elongated slit  50  extending generally horizontally. An intake pump  52  delivers wastewater to a passage  54  which extends generally horizontally through the manifold  46 . The wastewater flows out of the slit  50  to cascade downwardly to the collector pool  36  which bridges the side walls  16  beneath the manifold  46 . The pool  36  has a bottom formed of a heat conducting material such as galvanized steel, and in some embodiments the pool  36  has a depth of about five inches. Heat from the burner  28  heats the wastewater in the pool  36  before the wastewater cascades onto the stepped cascade  37 . 
         [0015]    The interior  31  of the housing  10  is divided into an upper chamber  32  and a lower chamber  34  by the collector pool  36  and the stepped cascade  37 , which includes an arrangement of grates (or “trays”)  38  and risers  40  which extend in a stepped down arrangement across the interior. The grates  38  extend at a slight angle to horizontal, allowing the wastewater to cascade down the grates  38 . Each grate  38  has a plurality of perforations  39  to permit a portion of the wastewater to drop into the lower chamber  34  where heat from the burner  28  vaporizes water from the slurry to leave solid matter. The remaining wastewater flows along the first grate  38  to the first steeply angled riser  40 . The risers  40  in the embodiment  1  are angled approximately sixty to seventy degrees to horizontal. And, like the grates  38 , the risers  40  may include a plurality of apertures  41 . Heat from the burner  28  passes through the apertures  41  to further heat wastewater passing over the risers  40  to assist in the vaporization process. 
         [0016]    As shown in  FIG. 1 , one or more misters  60  may be mounted to the top  12  of the housing  10 . The misters  60  may particularly be used to spray water onto the slurry flowing over the stepped cascade  37  to assist in moving the slurry down the stepped cascade  37 . 
         [0017]    An exhaust fan  62 , also shown in  FIG. 1 , is mounted to the housing top  12  in the embodiment  1 . The fan  62  may draw gas from the chambers  32 ,  34  and from the cooling passages  25  and expel the gas outside of the evaporator  1 . A control system  64  ( FIG. 3 ) may be positioned outside the housing  10  and receive data from various sensors monitoring, for example, flow rate of wastewater in various positions along the stepped cascade  37  and temperatures in the chambers  32 ,  34 . To effectively evaporate the wastewater, the control system  64  may control the rate of wastewater introduced into the manifold  46 , the operation of the burner  28 , the operation of the misters  60 , and the operation of the exhaust fan  62 . 
         [0018]    In using the evaporator  1 , the burner  28  is initiated to heat the interior  31  of the housing  10 . The air introduced by the burner  28  may be, for example, approximately 2700° F. at the flame&#39;s cone. Once the interior  31  of the housing  10  is heated, wastewater is introduced in the upper chamber  32  through the manifold  46  (e.g., at a rate of approximately 240-480 gallons per hour) and to the collector pool  36 . Wastewater is allowed to flow across a respective tray  38 , over the edge of the tray  38 , to and down a respective riser  40 , across the subsequent tray  38 , and so on. As the wastewater flows down the stepped cascade  37 , heat from the lower chamber  34  rises up through the perforations  39 ,  41  and because of the extreme temperature causes evaporation of the water from the wastewater. In some embodiments, a portion of the wastewater may pass through the perforations  39 ,  41  and be vaporized in the lower chamber  34 ; in such embodiments, it may be desirable to control the flow rates and temperatures for this vaporization to occur predominantly (or entirely) before the wastewater reaches a bottom of the lower chamber  34 . 
         [0019]    As the evaporation process proceeds, the remaining waste is collected on the stepped cascade  37  and because of the heat of the stepped cascade  37  may begin to evaporate and dry into the air. At the same time that the heated air is rising from the lower chamber  34  into the upper chamber  32 , cool ambient air may be drawn by the exhaust fan  62  from the exterior through the lower opening  26  into the gap  25  between the housing  10  and the liners  22 ,  24  to adjacent the housing top  12  where it mixes with the heated air and is carried to the rear of the housing  10  to exit carrying moisture and gases from the burned material. 
         [0020]    For most types of wastewater, this process may result in almost complete removal of all sludge either by drying or by evaporation, thus minimizing the need to remove the remaining solid material from the ramp. However, at such times as necessary to clean the stepped cascade  37 , the burner  28  is shut down and the housing  10  allowed to cool and introduction of the sludge water is stopped. The doors  21  are then opened and a long rake can be used to rake any particulate matter remaining from the stepped cascade  37  down to the end where it may be removed with a shovel or other implement. Once the particulate matter has been removed, the doors  21  are closed and the device  1  is ready again for use. 
         [0021]    Many different arrangements of the various components depicted, as well as components not shown, are possible without departing from the spirit and scope of the present invention. Embodiments of the present invention have been described with the intent to be illustrative rather than restrictive. Alternative embodiments will become apparent to those skilled in the art that do not depart from its scope. A skilled artisan may develop alternative means of implementing the aforementioned improvements without departing from the scope of the present invention. It will be understood that certain features and subcombinations are of utility and may be employed without reference to other features and subcombinations and are contemplated within the scope of the claims. The specific configurations and contours set forth in the accompanying drawings are illustrative and not limiting.