Abstract:
An improved vent ice prevention apparatus including a first conduit, a second conduit, and a third conduit, wherein the second conduit concentrically surrounds the first conduit thereby forming an annular region between the two conduits. The third conduit is in fluid communication with said annular region. The first conduit is configured to receive a cold vent stream, and the third conduit is configured to receive a dry purge stream and introduce the dry purge stream into the annular region in order to prevent ice formation.

Description:
BACKGROUND 
     Ice buildup on gaseous cryogenic vents, for example cold compressor seal gas discharge vents, is a problem in many cryogenic plants. The function of vent lines can be defeated by the formation of ice (from condensed moisture in the ambient air) in the vent line. This can also be a safety issue, if a large piece of ice should fall from an elevated vent stack. 
     For example,  FIG. 1  shows an example of the prior art. Cold vent conduit  12 , which is transporting a cryogenic vent gas (which can be around −300° F.) is usually insulated by insulating conduit  14  in order to prevent ice build up around cold vent conduit  12 . However, once the cryogenic gas exits cold vent conduit  12 , moisture in the surround air begins to condense and freeze, first on the surface of the exit, and then slowly begins to build on itself until it ultimately forms ice formation  16 . Eventually, ice formation  16  can close, thereby restricting the flow, which results in a large pressure drop and a less than efficient process. Operations personnel must then go outside to remove the ice, which takes time and subjects the personnel to possible harm. Therefore, a need exists in the industry for a simple and economical solution to this icing problem. 
     SUMMARY 
     An improved vent ice prevention apparatus including a cold vent stream disposed within a first conduit, wherein at least a portion of the first conduit is concentric with a second conduit, thereby producing an annular region, introducing a dry purge stream into a third conduit, wherein the third conduit is in fluid connection with the annular region, thereby preventing the first conduit from forming condensation or ice. In one embodiment, the cold vent stream is a cold stream originating from a compressor seal. In another embodiment, the dry purge stream is a dry stream originating from a warm compressor seal. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
       These and other features, aspects, and advantages of the present invention will become better understood with regard to the following description, claims, and accompanying drawings. It is to be noted, however, that the drawings illustrate only several embodiments of the invention and are therefore not to be considered limiting of the invention&#39;s scope as it can admit to other equally effective embodiments. 
         FIG. 1  illustrates an embodiment of the prior art. 
         FIG. 2  illustrates one embodiment of the present invention. 
         FIG. 3  illustrates another embodiment of the present invention. 
         FIG. 4  illustrates a cross sectional view of an embodiment of the present invention. 
     
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
     Illustrative embodiments of the invention are described below. While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof have been shown by way of example in the drawings and are herein described in detail. It should be understood, however, that the description herein of specific embodiments is not intended to limit the invention to the particular forms disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims. 
     It will of course be appreciated that in the development of any such actual embodiment, numerous implementation-specific decisions must be made to achieve the developer&#39;s specific goals, such as compliance with system-related and business-related constraints, which will vary from one implementation to another. Moreover, it will be appreciated that such a development effort might be complex and time-consuming, but would nevertheless be a routine undertaking for those of ordinary skill in the art having the benefit of this disclosure. 
     As used herein, the term “cold compressor” means a device for raising the pressure of a vapor in which both the inlet and discharge streams are below the freezing point of water. 
     As used herein, the term “warm compressor” means a device for raising the pressure of a vapor in which both the inlet and discharge streams are above the freezing point of water. 
     As used herein, the term “conduit” means any channel through which a fluid is conveyed. While the preferred embodiments show the conduits to be cylindrical in nature, it should be understood that the term conduit is not so limiting. Any shape that is suitable for conveying the fluid would be acceptable. As a non-limiting example, the first conduit can be a cylindrical pipe, while the second conduit could have a square cross section. 
     By inserting the first conduit inside a larger pipe (e.g., the second conduit) and discharging the dry, warm gas around the first conduit, the dry, warm gas displaces the wet atmospheric gas from the system and prevents the ice ball formation. Insulation is then only required from the cold vent stream&#39;s origin to the first conduit. 
     Other solutions have included a heating collar underneath installation but have not solved the problem effectively. As such, certain embodiments of the present invention can be practiced without the need for a heating collar. Therefore, the present solution is more effective and efficient than previous solutions, as it does not require a heating collar, which thereby saves energy costs and future maintenance. Embodiments of the present invention also provide a safety improvement as the vent is elevated (due to nitrogen purging) so the hazard of dropping ice onto personnel is eliminated. In the interest of clarity, element numbers are consistent between both figures. 
     Turning now to  FIGS. 2 and 3 , a cold vent stream  101  and a dry purge stream  105  are provided. Cold vent stream  101  may be the seal vent stream from a cold compressor  114 . In one embodiment, cold vent stream  101  may be any cold gas, for example: air or nitrogen. In one embodiment, dry purge stream  105  may be the seal vent stream from a warm compressor  115 . Dry purge stream  105  may be dry air, nitrogen, instrument air, or any other available dry vapor stream. In one embodiment, dry purge stream  105  is also warm (i.e., has a temperature over 32° F.) 
     Cold vent stream  101  may be directed through a first conduit  102 . At least part of first conduit  102  may be heat traced  104 , thermally insulated  103 , or both. In one embodiment, at least part of first conduit  102  is concentric with a second conduit  107 , thereby producing an annular region  112 . Dry purge stream  105  may be directed through a third conduit  106 , which intersects with second conduit  107 . This allows dry purge stream  105  to flow through annular region  112  and thereby displace wet gas that was previously surrounding part of the exterior of first conduit  102  thereby surrounding the exterior with dry gas, which prevents ice formation. Cold vent stream  101  then combines with dry purge stream  105  to produce combined vent stream  109 , which may be expelled into the atmosphere. 
     In one embodiment, combined vent stream  109  may have a mean temperature greater than 32° F. However, it is highly preferred that combined vent stream  109  be as dry as possible. The exit of the first conduit  102  may be recessed  110  from the exit of the second conduit  107 . In one embodiment, the exit of the first conduit  102  may be recessed from the exit of the second conduit  107  by at least half the difference between the outside diameter of the second conduit  107  and the first conduit  102  ((D 2 −D 1 )/2). In one embodiment, the exit of the first conduit  102  may be recessed from the exit of the second conduit  107  by about 1 to about 5 inches. In another embodiment, the exit of the first conduit  102  may be flush with the exit of the second conduit  107 . 
     Those of ordinary skill in the art will recognize that the appropriate amount of recess varies upon several factors, for example, flow rates of the cold vent gas and the dry purge gas, as well as overall humidity levels of the outside air, etc. . . . . As such, the optimum amount of recess cannot be specified as it would depend on these factors. Therefore, those of ordinary skill in the art will recognize that the distance of recess might need to be slightly adjusted depending on their own circumstances. Therefore, an effective amount of recess is any amount of recess that is effective in reducing or eliminating condensation or ice buildup on the device. 
       FIG. 4  represents a cross sectional view of an embodiment of the present invention. In this embodiment, an insulated donut  120  is disposed distal from opening  123  of second conduit  107  and behind the entry point of third conduit  106  in order to promote movement of the amount of dry purge stream  105  towards the exit. In this embodiment, an insulating sleeve  122  is also provided to provide additional insulation for second conduit  107 . A heating collar (not shown) can optionally be added; however, it is not necessary. 
     While the invention has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications, and variations will be apparent to those skilled in the art in light of the foregoing description. Accordingly, it is intended to embrace all such alternatives, modifications, and variations as fall within the spirit and broad scope of the appended claims. The present invention may suitably comprise, consist or consist essentially of the elements disclosed and may be practiced in the absence of an element not disclosed. Furthermore, if there is language referring to order, such as first and second, it should be understood in an exemplary sense and not in a limiting sense. For example, it can be recognized by those skilled in the art that certain steps can be combined into a single step. 
     The singular forms “a”, “an” and “the” include plural referents, unless the context clearly dictates otherwise. 
     “Comprising” in a claim is an open transitional term which means the subsequently identified claim elements are a nonexclusive listing i.e. anything else may be additionally included and remain within the scope of “comprising.” “Comprising” is defined herein as necessarily encompassing the more limited transitional terms “consisting essentially of” and “consisting of”; “comprising” may therefore be replaced by “consisting essentially of” or “consisting of” and remain within the expressly defined scope of “comprising”. 
     “Providing” in a claim is defined to mean furnishing, supplying, making available, or preparing something. The step may be performed by any actor in the absence of express language in the claim to the contrary. 
     Optional or optionally means that the subsequently described event or circumstances may or may not occur. The description includes instances where the event or circumstance occurs and instances where it does not occur. 
     Ranges may be expressed herein as from about one particular value, and/or to about another particular value. When such a range is expressed, it is to be understood that another embodiment is from the one particular value and/or to the other particular value, along with all combinations within said range. 
     All references identified herein are each hereby incorporated by reference into this application in their entireties, as well as for the specific information for which each is cited.