Abstract:
A flameless thermal oxidizer includes a container in which a ceramic matrix is contained, and a diptube having a passageway extending therethrough, the diptube positioned in and in communication with the ceramic matrix and in which a plurality of gaseous streams are present for combustion at the ceramic matrix, the plurality of gaseous streams including a vent stream and an oxygen stream. A related method is also provided.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The present embodiments relate to a flameless thermal oxidizer (FTO) used to oxidize gaseous waste streams. 
         [0002]    In order to reach a desired operating temperature in an FTO, the waste to be reacted in same must have a minimum calorific value. When a low energy content waste stream has to be completely combusted, but such stream includes therein a product of combustion temperature which is too low, a typical solution is to enrich the waste stream with a more valuable, higher calorific value gas as the fuel. This process requires an increase in air for combustion and as such, additional fuel is required as well as an increase in both the total combustion product volume and the size of the reaction chamber, all of which reduces cost effectiveness. 
         [0003]    In a conventional FTO shown generally at  10  in  FIG. 1 , air and a waste stream (a vent stream from another process) which may include organic and other particular material is introduced via a diptube into a preheated porous matrix. 
         [0004]    As the air and waste stream expands through a matrix it absorbs heat from the ceramic until the stream reaches its auto-ignition temperature, at which point it starts to react, liberate heat and deliver heat back to the ceramic matrix. Such delivered heat is then transferred back through the ceramic matrix, by a combination of conduction, convection and radiation, serving to preheat a fresh waste stream and air entering the matrix via the diptube. In such a process, a self-sustaining oxidation process is achieved, and high peak flame temperatures observed in conventional combustion systems are avoided by the transfer of heat rapidly to the ceramic matrix. 
         [0005]    In particular, the FTO includes a container  12  or vessel with internal space  14  in which a hot ceramic matrix  16  is disposed. A top of the container  12  is provided with an opening  18  through which a diptube  20  or inlet diptube is inserted. A lower end  22  of the diptube  20  opens into the ceramic matrix  16 . An upper end of the diptube above the opening  18  and external to the container  12  is provided with a plurality of inlets  24 ,  26 ,  28  (collectively “ 24 - 28 ”). The inlets  24 - 28  are connected to and in communication with an internal passage  30  extending through the diptube  20  to the lower end  22 . The inlet  24  is the vent or waste inlet for providing a waste stream from an upstream process (not shown) into the internal passage  30  of the diptube  20 . The inlet  26  is the air inlet introducing an air stream into the internal passage  30  of the diptube  20 . The inlet  28  is the fuel inlet for providing a fuel stream to the internal passage  30  of the diptube  20 . All of the streams provided by the inlets  24 - 28  are mixed in the internal passage  30  and are discharged from the lower end  22  of the diptube into the hot ceramic matrix  16  which provides an oxidation zone  32  extending from the lower end  22  outward and upward along the diptube. The oxidation zone  32  tapers to a reduced diameter and dissipates as it heats the ceramic matrix in the container, as shown by the arrows  34 . 
         [0006]    The container  12  is also provided with an outlet  36  or exhaust in which clean gas  38  is discharged from the ullage  40  in the container  12  above an upper surface  42  of the ceramic matrix  16 . That is, the outlet  36  is in fluid communication with the ullage  40  above the surface  42  of the ceramic matrix  16 , such that the latter will not be exhausted through the outlet with the clean gas  38 . In effect, the vent or waste stream being introduced at the inlet  24  may contain organic and/or particulate matter which is combusted and/or filtered in the hot ceramic matrix  16  and thereafter exhausted from the ullage  40  above the matrix and through the outlet  36  to be discharged as the clean gas stream  38 . 
         [0007]    The gaseous waste stream-air mixture  24 ,  26  has to be sufficiently reactive and have sufficient energy content to create products of combustion able to effectively heat the ceramic matrix and to preheat the incoming waste-air mixture. This is often accomplished by an adiabatic combustion temperature which can be readily calculated on a thermodynamic basis knowing the composition and temperature of the waste and air streams. 
         [0008]    If the waste stream-air mixture is not sufficiently reactive and the products of combustion cannot be raised to the required temperature using the inherent enthalpy of combustion of the waste stream, then supplemental fuel may be added. However, the added fuel increases operating costs, and also increases emissions and a requirement for a larger reaction vessel, due to the increased volume of combustion products. 
       SUMMARY OF THE INVENTION 
       [0009]    There is therefore provided herein to replace at least a portion of the air used in the FTO to combust the waste stream with an oxygen rich stream, such that the combustion product temperature is increased without the need to use additional fuel. The present embodiments therefore reduce the volume of combustion products which results in either a smaller volume FTO being used or a higher throughput through the existing FTO while avoiding the need for additional fuel. 
         [0010]    A flameless thermal oxidizer (FTO) provided herein includes a container in which a ceramic matrix is contained and a diptube having a passageway extending therethrough, the diptube inserted or positioned in the ceramic matrix and in which a plurality of gaseous streams are present for combustion at the ceramic matrix, the plurality of gaseous streams including at least a vent stream and an oxygen stream. 
         [0011]    A method of operating an FTO includes introducing a plurality of gaseous streams into a heated ceramic matrix contained within the FTO, the plurality of gaseous streams including at least a vent stream and an oxygen stream. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]    For a more complete understanding of the present inventive embodiments reference may be had to the following description of exemplary embodiments considered in connection with the accompanying drawing Figures, of which: 
           [0013]      FIG. 1  shows a side view in cross-section of a known flameless thermal oxidizer (FTO discussed above); 
           [0014]      FIG. 2  shows a side view in cross-section of a first embodiment of an FTO according to the present invention; 
           [0015]      FIG. 3  shows a side view in cross-section of another embodiment of an FTO according to the present invention; 
           [0016]      FIG. 4  shows a side view in cross-section of still another embodiment of an FTO according to the present invention; and 
           [0017]      FIG. 5  shows a side view in cross-section of still another embodiment of an FTO according to the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0018]    Before explaining the inventive embodiments in detail, it is to be understood that the invention is not limited in its application to the details of construction and arrangement of parts illustrated in the accompanying drawings, if any, since the invention is capable of other embodiments and being practiced or carried out in various ways. Also, it is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. 
         [0019]    In the following description, terms such as a horizontal, upright, vertical, above, below, beneath and the like, are to be used solely for the purpose of clarity illustrating the invention and should not be taken as words of limitation. The drawings are for the purpose of illustrating the invention and are not intended to be to scale. 
         [0020]    Referring to  FIGS. 2-5 , embodiments of an FTO are shown according to the present invention. Four exemplary embodiments of an FTO constructed in accordance with the present invention are illustrated in  FIGS. 2-5 , respectively. Elements illustrated in  FIGS. 2-5  which correspond with the elements described above with respect to  FIG. 1  have been designated by corresponding reference numerals increased by 100, 200, 300 and 400, respectively. The embodiments of  FIGS. 3-5  are designed for use in the same manner as the embodiment of  FIG. 2  unless otherwise stated. 
         [0021]    The present embodiments include a system where an increased oxygen concentration (greater than that found in air) is used to provide the desired combustion temperature without using additional fuel and air and, in fact, reduces the overall volume of the products of combustion. As such, either an increase in capacity for the same volume reactor or a smaller reactor is needed for the same throughput. This will result in capital cost savings. 
         [0022]    Referring to the embodiment shown at  FIG. 2 , a pure oxygen stream  11  is introduced into a separate inlet  13  which is connected to and in communication with the internal passage  130  of the diptube  120 . The oxygen stream  11  mixes with the inlet streams  124 - 128  in the internal passage  130 . 
         [0023]    Referring to  FIG. 3 , in this embodiment the FTO  210  is provided with a pure oxygen stream  15  introduced through an inlet pipe  17  which is sized and shaped for extending into and through a substantial length of the internal passage  230  of the diptube  220 . As shown in  FIG. 3 , a lower end  19  of the inlet pipe  17  opens at an outlet prior to or upstream of an opening at the lower end  222  of the diptube  220 . This provides for mixing of the oxygen stream  15  with the inlet streams  224 - 228  prior to being exhausted into the oxidation zone  232 . 
         [0024]    In the embodiment shown in  FIG. 4 , a pure oxygen stream  21  and the inlet stream  326  for the air are combined in a pipe  23  which has an outlet  25  for the combined oxygen-airstream  27  to be introduced at an inlet  29  in gaseous communication with the internal passage  330  of the diptube  320 . The oxygen-air stream  27  mixes with the vent stream  324  and the fuel stream  328  in the internal passage  330 . 
         [0025]    In the embodiment shown in  FIG. 5 , a pure oxygen stream  31  is mixed with the inlet streams  424 - 428  in a pipe  33  having an outlet  35  connected to and in communication with the internal passage  430  of the diptube  420 . The pipe  33  is external to the diptube  420 , wherein a construction of the pipe permits the pure oxygen stream  31  and the inlet streams  424 - 428  to be mixed together as shown generally at  37  whereupon said mixture  37  is introduced into the internal passage  430 . 
         [0026]    The oxygen concentration in the streams  11 ,  15 ,  21 ,  31  can be increased by using substantially pure oxygen introduced into air, using an oxygen rich stream mixed with air or, if in sufficient quantity, using only an oxygen rich stream. 
         [0027]    The oxygen rich streams of the embodiments in  FIGS. 2-5  may also be a by-product stream or vent stream from for example a nitrogen generator. 
         [0028]    As discussed above, the oxygen enriched stream may be mixed with the air prior to the diptube, mixed with the air-waste mixture prior to the diptube, or kept separate from the other streams until the discharge opening at the lower end of the diptube. 
         [0029]    The foregoing embodiments of  FIGS. 2-5  provide for: a reduction in reactor size for given capacity/throughput and therefore, capital cost savings occur; an increase in reactor throughput and therefore, increased productivity; a reduction in supplemental fuel and therefore, reduced operating costs; and allowance of processing of low CV/low BTU wastes that would not normally be used in an FTO and therefore, increased flexibility. 
         [0030]    The present embodiments may be used for example to process vent streams from processes such as for example a nitrogen generator. 
         [0031]    It will be understood that the embodiments described herein are merely exemplary, and that a person skilled in the art may make variations and modifications without departing from the spirit and scope of the invention. All such variations and modifications are intended to be included within the scope of the invention as provided and claimed herein. It should be understood that the embodiments described above are not only in the alternative, but can be combined.