Abstract:
A flameless thermal oxidizer (FTO) includes at least one baffle constructed and arranged in a reaction chamber of the FTO to coact with a diptube of the FTO to radially expand a resulting “bubble” or reaction envelope from the diptube outward into a porous matrix of the FTO. A related method is also provided.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The present embodiments relate to baffles for a flameless thermal oxidizer (FTO), and a method of increasing capacity with the FTO. 
         [0002]    Known FTOs have been used to maintain an oxidation reaction of gaseous waste stream(s) within a matrix of the FTO. However, such arrangements result in a limited flow capacity and limited reaction stability within the FTO. This is because the overcapacity reaction envelope or “reaction bubble” produced from the FTO diptube permits the incomplete oxidation reaction products to flow rapidly upward to and break or pierce through the top surface of the FTO matrix. 
         [0003]    An example of a known FTO is shown in  FIG. 1  and referenced generally as  10 . The known FTO is a flameless matrix bed reactor which includes a vessel  12  or container in which a reaction chamber  14  is disposed. A porous matrix  16  is arranged in the reaction chamber  14 , but does not completely fill the chamber. A diptube  18  extends into the reaction chamber  14  and into the porous matrix  16  for providing a reactable process stream  20  into the porous matrix  16 . The oxidation product exhaust stack  22  is a continuation of the reaction space  14  above a surface  24  of the porous matrix  16 . 
         [0004]    In operation, the known FTO  10  receives the reactable process stream  20  in the diptube  18  whereupon the stream is exhausted from an outlet  26  of the diptube  18  into the porous matrix thereby creating a reaction bubble or reaction envelope  28 . 
         [0005]    However, the reaction bubble or reaction envelope  28  resulting from the stream will move vertically upward in the porous matrix  16  and along the diptube  18  and break or pierce the surface  24  of the matrix as turbulence shown generally at  30 . This vertical movement or “short circuiting” occurs because there is no structure or method to impede or prevent such vertical movement. 
         [0006]    What is therefore needed is an FTO that provides for a greater volume of the porous matrix  16  to be used which would result in a more stable reaction bubble or reaction envelope being created resulting in an increased capacity of the reactable process stream  20 . 
       SUMMARY OF INVENTION 
       [0007]    There is therefore provided a flameless thermal oxidizer (FTO) embodiment having at least one baffle constructed and arranged in the reactive chamber of the FTO to coact with a diptube of the FTO to radially expand the resulting reaction bubble or reaction envelope from the diptube into the porous matrix. 
         [0008]    A flameless thermal oxidizer (FTO) apparatus is provided and includes at least one baffle constructed and arranged in a reactive chamber of the FTO apparatus to coact with a diptube of the FTO apparatus to radially expand a resulting reaction envelope outward into a porous matrix of the FTO apparatus. 
         [0009]    A related method to radially expand the reaction bubble in the porous matrix is also provided. A method of controlling a reaction envelope or reaction bubble in a porous matrix of an FTO, includes positioning at least one baffle in the porous matrix coacting with a diptube of the FTO, and interrupting upward flow of the reaction envelope or reaction bubble with the at least one baffle for radially expanding said reaction envelope or reaction bubble in said porous matrix. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]    For a more complete understanding of the present invention, reference may be had to the following description of exemplary embodiments considered in connection with the accompanying drawing Figures, of which: 
           [0011]      FIG. 1  shows a portion of a known FTO and the disposition of the reaction envelope in same; 
           [0012]      FIG. 2  shows an embodiment of a reaction chamber of an FTO having a baffle of the present embodiments; 
           [0013]      FIG. 3  shows another embodiment of a baffle apparatus for an FTO; and 
           [0014]      FIG. 4  shows still another embodiment of a baffle apparatus for an FTO. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0015]    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. 
         [0016]    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. 
         [0017]    In general, and in an FTO of the present embodiments beginning at  FIG. 2 , the introduction of impermeable or semi-permeable baffles surrounding the diptube of the FTO between an upper surface of a porous matrix and a discharge of the diptube is shown. The baffles are arranged to inhibit or prevent a vertical movement (known as “short circuiting”) of gases exiting the diptube and subsequent reaction products around an exterior of the diptube. By “impermeable” it is meant that the material and construction of the baffle is such that no gas may pass through the baffle. The meaning of “semi-permeable” as used herein means that a portion of gas may pass through the baffle. The terms “reaction envelope” and “reaction bubble” can be used herein interchangeably. 
         [0018]    Referring to  FIG. 2 , a first embodiment of an FTO is shown generally at  100 , and includes a baffle  101  at or proximate a surface  124  of a porous matrix  116  disposed in a reaction chamber  114  of the FTO. As shown in the embodiment of  FIG. 2 , the baffle  101  can be constructed from impermeable or semi-permeable material. The baffle  101  substantially reduces if not eliminates short circuiting of the reaction bubble  128  so that same expands with an increased residence time within the porous matrix  116 . Disruptive turbulence at the surface  124  is avoided. Due to the perspective view of the embodiment in  FIG. 2 , approximately one-half of the baffle  101  is shown, but it is understood that a remaining portion of the baffle extends a corresponding amount at or proximate the surface of the porous matrix  116 . 
         [0019]    Two other exemplary embodiments of an FTO constructed in accordance with the present invention are illustrated in  FIGS. 3-4 , respectively. Elements illustrated in  FIGS. 3-4  which correspond to the elements described above with respect to  FIG. 2  had been designated by corresponding reference numerals increased by  200  and  300 , respectively. The embodiments of  FIGS. 3-4  are designed for use in this same manner as the embodiment of  FIG. 2  unless otherwise stated. 
         [0020]    Referring to  FIG. 3 , another embodiment of an FTO is shown generally at  200 , and includes a baffle  203  at or proximate an outlet  226  of a diptube  218  in a porous matrix  216  in the reaction chamber  214  of the FTO. As shown in the embodiment of  FIG. 3 , the baffle  203  can be constructed from impermeable or semi-permeable material. The baffle  203  substantially reduces if not eliminates short circuiting of the reaction bubble  228  so that same expands with an increased residence time within the porous matrix  216 . Disruptive turbulence at the surface  224  is avoided. Due to the perspective view of the embodiment in  FIG. 3 , approximately one-half of the baffle  203  is shown, but it is understood that a remaining portion of the baffle extends a corresponding amount at or through the porous matrix. 
         [0021]    Referring to  FIG. 4 , still another embodiment of an FTO is shown generally at  300 , and includes a baffle  301  at or proximate a surface  324  of a porous matrix  316  disposed in the reaction chamber  314  of the FTO. As also shown in  FIG. 4 , there is included a baffle  303  at or proximate an outlet  326  of a diptube  318  in a porous matrix  316  at the reaction chamber  314  of the FTO. As shown in  FIG. 4 , the baffles  301 , 303  can be constructed from impermeable or semi-permeable material. The baffles  301 ,  303  substantially reduce if not eliminate short circuiting of the reaction bubble  328  so that same expands with an increased residence time within the porous matrix  316 . The embodiment of  FIG. 4  may also includes a central baffle  305  positioned in the porous matrix  316  between the baffle  301  (upper) and the baffle  303  (lower). The central baffle  305  may also be constructed from impermeable or semi-permeable material. The use of the central baffle  305  provides for a more sinuous or circuitous path for constituents to travel through the porous matrix  316  from the reaction bubble  328 . Due to the perspective view of the embodiment in  FIG. 4 , approximately one-half of the baffles  301 ,  303  and  305  are shown, but it is understood that the remaining portions of these baffles extend a corresponding amount along the porous matrix. 
         [0022]    By inhibiting the immediate vertical movement of the gases and combustion products from the reaction bubbles  128 ,  228   328 , the flow from the diptubes  120 ,  220 ,  320  is forced to move radially outwards and expand, as well as move downward. Such an expanding flow field not only avoids the “short circuiting” discussed above, but also i) causes a greater volume of the porous matrix  116 ,  216 ,  316  to be utilized, and ii) provides a more stable reaction bubble  128 ,  228 ,  328  to form at higher flow capacities within the matrix. 
         [0023]      FIGS. 2-4  show internal baffle apparatus for the FTOs  100 ,  200  and  300  and related methods according to the present embodiments. Each one of the apparatus and method embodiments shown in  FIGS. 2-4  provide alternate ways in which baffles may be employed at an interior of an FTO to better control reaction within same and provide for a more efficient processing of the reactable process stream  120 ,  220 ,  320 . 
         [0024]    The justification for providing a more stable reaction bubble at higher volumes of reactable process streams being provided to the FTOs  100 ,  200 ,  300  is as follows. 
         [0025]    Referring to the embodiment of  FIG. 2  by way of example only, a surface of the reaction bubble is determined by “knitting together local locations”, wherein the combustion reaction takes place to form a combustion envelope or reaction bubble. Within the reaction envelope (or reaction bubble), there are predominantly reactants, while external or outside the envelope there are predominantly products. “Predominantly” herein means that while the combustion reactions are fast, such reactions do take a certain amount of time and therefore, external to and proximate the envelope there are varying degrees of combustion completeness. 
         [0026]    The local oxidation reaction occurs where the local reaction speed (the speed at which the reaction would propagate into a quiescent mixture of the same composition, pressure and temperature) matches the local flow velocities, i.e. the speed of the gas moving through the matrix. When these two speeds (the reaction speed and the gas velocity) match, the location of the combustion reaction is fixed in position and therefore, a stable reaction envelope or “reaction bubble” is formed. 
         [0027]    Forcing the flow from the diptube outlet (e.g.  226 ) outwards in a radial/downward direction causes the flow to decelerate in a direction away from the diptube, and the reaction envelope or reaction bubble will form at a certain distance from the diptube. Furthermore, with an increasing flow rate the “reaction bubble” may be expected to move radially outwards until the velocity is reduced to again match the reaction speed. 
         [0028]    The absence of a submerged baffle  203 ,  303  proximate an outlet of the submerged diptube  218 ,  318  results in the combustion gases being distributed into a flow path that minimizes the pressure drop through the porous matrix. A significant portion of the combustion gas therefore flows in the shortest path immediately up and around the diptube. This means that the gases do not all flow significantly radially/downward and accordingly, there is the propensity for the uncombusted gases to well-up around the diptube prior to the reaction bubble or reaction envelope growing to occupy a significant portion of the vessel or bed diameter. Use of the baffles  203 ,  303  prevents such occurrence. 
         [0029]    The placement of a baffle above and also surrounding the discharge outlet of the diptube forces the gases to move radially outwards, also to disperse downwards to form the three-dimensional (“3-D”) curved surface without moving vertically. This allows the reaction bubble to form at greater radii prior to breakthrough at the bed surface. The effect on stability and capacity is magnified as the local flow velocity will vary inversely proportionally to the square of the radial distance from the diptube. Thus, a change in overall flow or composition at high flow rates can be accommodated by only a small movement in the reaction bubble. 
         [0030]    In the current embodiments of  FIGS. 2-4 , the mixed gases exiting or being exhausted from the diptube outlet will distribute into the matrix  116 ,  216 ,  316  according to pressure drop. The lowest pressure path is along the circumference of the diptube. Because the reaction zone is defined as the point where the velocity of the gas is equal to the reverse velocity of the reaction, the controlling velocity is that of the gases along the diptube. The present embodiments provide that the shape of the reaction zone is an ellipsoid, when in fact it resembles a tear drop. The design flow rates provided by the present calculation based on the ellipsoid provide a breakthrough of partially combusted gases around the diptube that limits the capacity of the system. In an installation where the vessel  112  size is 22′ in diameter, a baffle was installed at the top of the bed to prevent the breakthrough. 
         [0031]    The impact on capacity was not a concern and therefore not quantified or accounted for. During CFD study examples to determine baffle placement in the reaction chamber, alternate baffle placement was considered only as related to minimizing breakthrough. Examples included a 12′ diameter FTO, with no baffle, an upper baffle (two different diameters) and a lower baffle. The upper baffle achieved the same results as with the current operating unit with respect to restricting the reaction within the matrix. The lower baffle also accomplished the same result, but provided an additional advantage of increasing the capacity on the order of 250% to 300%, ie. 6 MM Btu/hr as taught by the current embodiment to 15 MM Btu/hr. 
         [0032]    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.