Abstract:
The claimed invention teaches direct contact steam injection heater capable of handling steam pressure in excess of 300 psi. Specifically, the invention provides: a fixed upper seal assembly situated between the diffuser base and the diffuser which is designed to prevent the flow of steam around the regulating member into the diffuser.

Description:
FIELD OF THE INVENTION 
       [0001]    The claimed invention relates generally to direct contact steam injection heaters that are used for heating certain types of liquids and slurries. More specifically, it relates to a high pressure diffuser-type steam injection heater assembly. 
       BACKGROUND OF THE INVENTION 
       [0002]    In direct contact steam injection heaters, steam is directly mixed into a flowing fluid (e.g. liquid or slurry) to heat the flowing fluid. Direct contact steam injection heaters are well known in the art and are very effective at transferring heat energy to the flowing fluid. They provide rapid heat transfer with virtually no heat loss to the atmosphere, and also transfer both the latent and the available sensible heat of the steam to the liquid or slurry. 
         [0003]    A shortcoming of existing injection heater designs is that they are only operable at relatively low steam pressures. While adequate for most applications, existing diffuser style injection heater designs are unable to handle steam pressure in excess of approximately 300 psi. Generally speaking, power plants and other facilities with boiler operations have steam pressure in the 250-1200 psi range. 
         [0004]    Previous designs of diffuser-type steam injection heaters employ elastomeric, or otherwise pliant, seal elements between the regulating member and the diffuser. In such configurations, a lower seal is intended to prevent steam from leaking around the distal end of the regulating member and into the fluid chamber. An upper seal is intended to prevent steam from leaking between the diffuser and the regulating member. 
         [0005]    In the experience of this inventor, such seals can quickly wear out as they ride over the diffuser when the regulating member moves. Moreover, such pliant seals, which may be acceptable at lower pressures, are completely unsuitable for use at higher steam pressures. As a result, in prior heaters, it is difficult to prevent the flow of steam into the diffuser when, for example, it is desired to stop the flow of steam into the fluid to be heated. Therefore, what is needed is a new seal configuration to prevent steam from leaking past the upper seal so that steam can only enter the fluid to be heated through the regulating member. 
       SUMMARY OF THE INVENTION 
       [0006]    In view of the foregoing, what is needed is an improved injection heater assembly that is capable of handling higher pressure steam than existing heaters. Specifically, what is needed is a heater capable of handling steam pressure in excess of 300 psi. The claimed invention provides such a configuration. Generally speaking, the invention provides: a fixed upper seal assembly situated between the diffuser base and the diffuser which is designed to prevent the flow of steam into the diffuser. 
         [0007]    More specifically, the fixed upper seal assembly comprises an elastic member; a compression gland and a tacking seal, the upper seal assembly being fixed between the diffuser base and the diffuser. Even more specifically, the interior of the diffuser base is threaded as is the exterior of the diffuser such that when the diffuser is threaded into the diffuser base, the fixed upper seal is compressed between the diffuser base and the diffuser. That is, the fixed upper seal serves as a face seal to prevent flow into the diffuser and it also prevents flow between the steam regulating member and the diffuser. The foregoing and other features of the high pressure heating assembly of the claimed invention will be apparent from the detailed description that follows. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]      FIG. 1  is a section view of a diffuser style heater assembly that is constructed in accordance with the claimed invention. 
           [0009]      FIG. 2  is a section view of a diffuser showing a more detailed view of the fixed upper seal assembly of the claimed invention. 
           [0010]      FIG. 3  is a section view of an upper seal assembly constructed in accordance with the claimed invention and showing the securement means. 
           [0011]      FIG. 4  is an exploded view of a diffuser style heater constructed in accordance with the claimed invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0012]    Referring now to the drawings in detail, wherein like numbered elements correspond to like elements throughout,  FIG. 1  shows a diffuser style heater assembly  1  constructed in accordance with the claimed invention. Generally, the heater assembly  1  comprises a diffuser  11  in a fluid flow chamber  3  having an inlet  5  and an outlet  7 . 
         [0013]    The heater assembly  1  comprises a diffuser base  21 . The diffuser base  21  comprises a steam inlet  33  and a generally open cylindrical interior  35  through which steam is allowed to pass to the regulating member  41 . The interior lower portion  23  of the diffuser base  21  further comprises a first narrower portion  22  and a second wider portion  24 , the wider portion  24  further comprising a threaded cylindrical aperture  25  and a pair of peripheral threaded apertures  27 . The first narrower portion  22  and the second wider portion  24  of the diffuser base are separated by a shoulder  25 . The lower portion  23  of the diffuser base  21  further comprises a seal section  29  for accommodating a seal that terminated in a circumferential shoulder  25 , the purpose of which will be explained in more detail later in this description. 
         [0014]    The diffuser  11  of the claimed invention is generally cylindrical in shape and comprises a plurality of steam diffusion holes  17  such that steam can flow from the diffuser  11  into a fluid flow area such as fluid chamber  3  so as to heat the liquid within the fluid chamber  3 . The fluid chamber  3  has an inlet  5  to the fluid chamber  3  for the fluid to be heated and an outlet  7  from the fluid chamber  3  for the heated fluid and steam from the diffuser  11 . 
         [0015]    Referring again to  FIG. 2 , which shows a more detailed sectional view of the diffuser  11 , the diffuser  11  further comprises a proximal end  13  and a distal end  15 . The proximal end of the diffuser  13  is threaded so as to thread into the threaded cylindrical aperture  25  of the lower portion of the diffuser base  21  and further comprises a pair of set screw slots  19 . Once the diffuser  11  has been securely threaded into the threaded cylindrical aperture  25  of the diffuser base  21 , set screws  18  are threaded through the apertures  27  in the diffuser base into the set screw slots  19  to secure the diffuser base  21 . Additional means for attaching the diffuser base  21  to the diffuser  11  are also possible. For example, it is possible to press fit the diffuser  11  into the diffuser base  21  and to secure diffuser  11  within the diffuser base using snap rings (not shown). 
         [0016]    The distal end of the diffuser  15  is capped by an end cap  17 . Within the diffuser  11 , the regulating member  41  is operable by actuation of the modulating stem  43 , which is attached to the proximal end of the regulating member  41  to move the regulating member  41  upwardly and downwardly so as to release either more or less steam through the steam diffusion holes  17  in the diffuser  11 . 
         [0017]    A lower seal  47  is located at the distal end  45  of regulating member  41 . The lower seal  45  may be a piston ring type seal so as to provide a better seal to reduce the likelihood that steam will enter the diffuser  11  around the distal end  45  of the regulating member  41  and thus be unintentionally discharged into the fluid chamber  3 . 
         [0018]    The invention further provides a fixed upper seal assembly  51  within the interior of the diffuser base  21  and situated against the shoulder seal  25 . The upper seal assembly  51  is designed to prevent steam from escaping between the regulating member  41  and the diffuser  11 . In order to withstand higher steam pressures, the claimed invention provides a multi-layer upper seal assembly  51  situated between the regulating member  41  and the diffuser  11  in the seal section comprising an optional spring member  53 , a compression gland  55  and a packing seal  57 . As the diffuser  11  is threaded into the diffuser base  21 , the fixed upper seal assembly  51  is compressed between the regulating member, the diffuser  11 , and the seal section  29  of the diffuser base  21  so as to prevent steam leakage past the upper seal assembly  51 . 
         [0019]    When the diffuser  11  is threaded into the comprises threaded cylindrical aperture  25  of the diffuser base, the upward motion of the diffuser  11  applies a load to the spring member  53  which in turn compresses the compression gland  55  and tacking seal  57 . This fixed upper seal assembly  51  allows much higher steam pressures without steam leakage between the regulating member  41  and the diffuser base  21 , between the regulating member  41  and the diffuser  11  and between the diffuser  11  and the diffuser base  21 . All of this is accomplished while still permitting vertical movement of the regulating member  41  so as to modulate the flow of steam into the diffuser  11 . 
         [0020]    Additional advantages and modifications will readily occur to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details disclosed and described herein.