Abstract:
A pipeline heater ( 20 ) for warming a fluid stream, such as a fluid being carried by a natural gas or petroleum pipeline includes a housing ( 22 ) having a plurality of IR heating elements ( 118 ) and coils ( 110 ) installed therein. Individual conduits ( 88, 90 ) direct the fluid stream into and out of the housing ( 22 ). Coils ( 110 ) direct portions of the fluid stream from the conduits ( 88, 90 ) past a plurality of IR heating elements ( 118 ).

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims the benefit of U.S. Provisional Application Ser. No. 62/120,733 filed Feb. 25, 2015, which is incorporated herein by reference in its entirety. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention generally pertains to a pipeline heating apparatus and methods of heating gas and liquid streams using the same. The preferred pipeline heaters employ flameless, catalytic infrared (IR) emitters positioned adjacent fluid-conveying coils in order to warm the fluids flowing therethrough. 
         [0004]    2. Description of the Prior Art 
         [0005]    Pipeline heaters are used to heat gas and liquids flowing through pipelines in order to prevent regulators and various sensing equipment from freezing up during pipeline operation. Traditionally, water bath indirect heaters have been used for this purpose. In water bath heaters, a vessel is filled with water or a mixture of water and ethylene glycol. A fire tube and process coil are submerged in the bath which transfers heat from the fire tube to the process stream in the coil. These types of heaters have the drawback in that the fire tubes produce significant amounts of noise and ethylene glycol presents health risks to people, pets, and property. In addition, water bath heaters tend to be less efficient because the heat transfer occurs through an intermediate medium, namely the water solution. 
         [0006]    Because of the undesirable attributes of conventional water bath heaters, there is a need for quiet and efficient apparatus and methods for heating pipeline fluids such as natural gas and other hydrocarbon streams. Furthermore, there is a particular need for environmentally friendly pipeline heater systems that generates virtually no nitrous oxide or volatile organic compounds. U.S. Pat. No. 7,066,730, which is incorporated by reference herein in its entirety, discloses one such pipeline heater. However, the normal draft induced through the heater housing results in reduced heater efficiency. Therefore, there is a need in the art for an improved heater apparatus that better controls the natural draft through the heater so that the heater operates more efficiently. 
       SUMMARY OF THE INVENTION 
       [0007]    According to one embodiment of the present invention there is provided a pipeline heater operable to warm a fluid, i.e., either liquids, gases, or mixtures thereof. The pipeline heater generally comprises a housing including a plurality of wall sections defining an enclosed space. At least one of the wall sections comprises at least one selectively controllable air flow damper installed therein to control the flow of air into the enclosed space. At least one other of the wall sections comprises a vent opening through which air and exhaust gases flow out of the enclosed space. The heater also comprises at least two conduit sections located within the housing. One of the conduit sections is configured to conduct a fluid stream into the housing, and one other of the conduit sections is configured to conduct the fluid stream out of the housing. There is at least one coil disposed within the housing having a coil inlet and a coil outlet. The coil inlet is fluidly coupled with the conduit section configured to conduct the fluid stream into the housing. The coil outlet is fluidly coupled with the conduit section configured to conduct the fluid stream out of the housing. There are a plurality of infrared catalytic heaters located adjacent to the at least one coil and configured to warm the fluid stream flowing within the coil. 
         [0008]    According to another embodiment of the present invention there is provided a pipeline heater operable to warm a fluid, i.e., either liquids, gases, or mixtures thereof. The pipeline heater generally comprises a housing including an upper housing portion and a lower housing portion, preferably in the form of a relatively large primary housing and a superposed, relatively small secondary housing in communication with the primary housing. At least two conduits or headers are located within the upper housing portion. One of the conduit is configured to conduct a fluid stream into the housing, and one other of the conduit is configured to conduct the fluid stream out of the housing. At least one coil is disposed within the housing having a coil inlet and a coil outlet. The coil inlet is fluidly coupled with the conduit configured to conduct the fluid stream into the housing, and the coil outlet is fluidly coupled with the conduit configured to conduct the fluid stream out of the housing. A plurality of infrared catalytic heaters are located adjacent to the at least one coil and configured to warm the fluid stream flowing within the coil. 
         [0009]    According to another embodiment of the present invention there is provided a method of warming a fluid stream comprising the steps of providing and operating a pipeline heater as described herein. Fluid is directed into the pipeline heater via one of the conduit sections. The fluid is then caused to enter the at least one coil of the pipeline heater. The plurality of heaters are operated so as to direct heat energy to the at least one coil for transfer to the fluid to form a warmed fluid. The warmed fluid is removed from the pipeline heater via one other of the conduit sections. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]      FIG. 1  is a top perspective view, with certain parts broken away, of an infrared pipeline heater in accordance with the invention, illustrated with the forward doors thereof in an opened condition; 
           [0011]      FIG. 2  is a side perspective view of the pipeline heater illustrated in  FIG. 1 ; 
           [0012]      FIG. 3  is a top perspective view of the pipeline heater illustrated in  FIGS. 1-2 , but depicting the rearward end of the heater and the sidewall thereof opposite that seen in  FIG. 1 ; 
           [0013]      FIG. 4  is a side perspective view of the pipeline heater of  FIG. 1 , with the sidewall structure removed to depict the inner heat insulating assembly of the heater; 
           [0014]      FIG. 5  is an enlarged, fragmentary, perspective view illustrating the forward end of the heater of  FIG. 1 , with parts broken away to illustrate the internal construction of the heater; 
           [0015]      FIG. 6  is a fragmentary, perspective view similar to that of  FIG. 4 , but with the heat insulating assembly removed to illustrate portions of the infrared heating assembly of the pipeline heater; 
           [0016]      FIG. 7  is another side perspective view similar to that of  FIG. 6 , but with the infrared heating assembly removed to illustrate the fluid-conveying coil assembly of the pipeline heater; 
           [0017]      FIG. 8  is a bottom perspective view of the fluid-conveying coil assembly of the pipeline heater; 
           [0018]      FIG. 9  is a top view with parts removed to illustrate the relationship of the fluid-conveying coil assembly, the infrared heating assembly, the insulating assembly, and the sidewalls of the housing of the pipeline heater; and 
           [0019]      FIG. 10  is a vertical sectional view of the pipeline heater, illustrating the pattern of induced cooling air flow developed in the heater by the air cooling assembly thereof 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0020]    Turning now to the drawings, a self-contained pipeline heater  20  is illustrated in  FIG. 1  and broadly includes a housing  22 , a fluid-conveying assembly  24  (see also,  FIGS. 7-8 ), an infrared heating assembly  26  (see  FIGS. 6 and 9-10 ), a heat insulating assembly  28  (see  FIGS. 4  and  9 ), an air-cooling assembly  30  (see  FIG. 10 ), and a power and control assembly  32  (see  FIG. 6 ). The purpose of heater  20  is to selectively and efficiently heat an incoming fluid (such as liquid or gaseous petroleum products) at an appropriate location along the length of a pipeline or the like. 
         [0021]    The housing  22  generally includes a lower, elongated, substantially rectangular in cross-section primary housing  34  as well as a smaller, upper housing  36  mounted atop the primary housing  34 , and defines an enclosed space therein. Although, this configuration presents certain advantages, the scope of the present invention is not limited to this particular design. The overall housing  22  accommodates all of the other assemblies  24 - 32 , as will be described. 
         [0022]    The primary housing  34  may be constructed using a standard metal shipping container, but this is not essential. In certain embodiments, the primary housing  34  has bottom wall  38 , a pair of laterally spaced apart, upright corrugated sidewalls  40  and  42 , as well as a corrugated top wall  44  having an elongated slot  46  formed therein. The forward end of the primary housing  34  has a pair of double doors  48  and, in like manner, the rearward end thereof has a rear wall  50  and a single, central door  52 . An intermediate upright wall  54  is provided toward the rearward end of the housing and serves to create a rearmost room  56 , which can be accessed via door  52 . The walls  40 - 44  and related structure of the primary housing  34  are supported by conventional frame structure  58 . Bottom wall  38  is supported by a series of laterally extending beams  60 . A pair of elongated, laterally spaced apart, somewhat L-shaped rails  62  are affixed to the upper surface of wall  38  and extend from the forward end of the housing  34  to intermediate wall  54 . Similarly, a pair of elongated tubular beams  64  are secured to the underside of top wall  44  directly above the rails  62  (see  FIG. 10 ). Beams  64  are electrical hazardous location glans and extend through wall  54 . The entire heater  20  is typically mounted above-grade on a series of cylindrical concrete footings  66 . If desired, front and rear concrete entry pads  68  and  70  are provided adjacent the front and rear doors  48 ,  52 , as illustrated. 
         [0023]    The elongated secondary housing  36  is positioned in spanning relationship to the slot  46  of top wall  44  and includes a pair of spaced apart side panels  72  and  74 , insulated top panel  76 , and insulated front and rear end panels  78  and  80 . The front panel  78  has an opening  82  formed therein, whereas top panel  76  has three vent openings  84 . An upright, gabled vent housing  86  is secured to top wall  76  in registry with each vent opening  84 . It will be appreciated that the secondary housing  36  is smaller in volume as compared with primary housing  34 , and has a lesser width, height, and length. Advantageously, the secondary housing  36  is smaller in at least one dimension as compared with the primary housing  34  (e.g., height), and preferably in at least two dimensions (e.g., height and length or length and width). Most preferably, the secondary housing  36  is smaller in all three dimensions of height, length, and width. 
         [0024]    The fluid-conveying assembly  24  (see  FIGS. 7-8 ) includes a substantially horizontally oriented fluid inlet conduit or header  88 , a juxtaposed fluid outlet conduit or header  90 , and a depending coil assembly  92 . The headers  88 ,  90  include connection flanges  94 ,  96  at the forward ends thereof, and are capped by end caps  98 ,  100  at their rearward ends. Conventional inlet and outlet pipe assemblies  102 ,  104  are secured to the headers  88  and  90  by connection to the associated flanges  94 ,  96 . The assemblies  102 ,  104  are typically capped for transport of the heater  20  to its intended use location by means of caps  106 ,  108 , but in use, fluid entry and exit pipelines (not shown) are operatively connected to the assemblies  102 ,  104 . In this way, the fluid(s) to be heated within heater  20  are conveyed to and from the assembly  24 . 
         [0025]    The coil assembly  92  is made up of a series of separate, elongated, vertically extending coils  110 , each having an inlet pipe  112  coupled with inlet header  88  and a corresponding outlet pipe  114  coupled with outlet header  90 . As illustrated, the piping of each coil  110  has a diameter substantially less than the diameter of the associated headers  88 ,  90 , to create a greater surface area for heat transfer. The coils  110  have multiple loops or convolutions  110   a  which are oblong in configuration and extend vertically beneath the headers  88 ,  90  as separate passes. The assembly  24  is centrally mounted within housing  22  by means of a plurality of support beam  115  ( FIG. 10 ) that span from sidewall  40  to sidewall  42 . Moreover, it will be seen that the headers  88 ,  90 , and the upper ends of the coil assembly  92  are situated within secondary housing  36 , whereas the main body of the coil assembly  92  is located within the confines of primary housing  34 . The forward ends of the headers  88  and  90  protrude through the opening  82 , as illustrated. The coils  110  may have a number of different configurations, such as those described in U.S. Patent Publication No. 2015/0020918, which is incorporated by reference herein in its entirety. 
         [0026]    The IR heating assembly  26  includes a plurality of vertically stacked, fore-and-aft extending, gas-fired infrared heating elements  118 , which extend the entire length of the coil assembly  92 ; the elements  118  are operable to emit IR energy through the flameless catalytic combustion of natural gas, and to direct such energy toward coils  110 . To this end, the elements  118  are positioned in two separate parallel banks or panels  120  and  122 , which are respectively astride the side margins of the coil assembly  92  and extend from a point adjacent bottom wall  38  into the secondary housing  36  to a point just beneath the headers  88 ,  90  (see  FIGS. 9-10 ). The banks  120 ,  122  are supported by a supporting frame  116  and upright frame elements  124 , and a gas line  125  is provided for delivery of natural gas to the elements  118 . The operation of the elements  118  is controlled by appropriate valve and sensor assemblies  126  located adjacent the forward end of housing  22 . Exemplary IR heating elements  118  include those available from Catalytic Industrial Group of Independence, Kansas, and are described in U.S. Pat. Nos. 5,557,858 and 6,003,244, both of which are incorporated by reference herein in their entireties. It is also within the scope of the present invention to use electrically powered IR heating elements. 
         [0027]    The heat insulating assembly  28  includes a series of upright heat insulating walls  128  positioned within primary housing  34  on opposite sides of the IR heater banks  120 ,  122 . As best illustrated in  FIG. 5 , walls  128  are mounted on lower grooved rollers  130 , whereas the upper ends of the walls are held captive by the rectangular beams  64 . Accordingly, the individual walls  128  are simply shifted along the lengths of the rails  62  to create essentially solid insulating walls  131  adjacent the outboard faces of the elements  118  making up the banks  120 ,  122 . As best seen in  FIG. 4 , the walls  131  extend from a point adjacent the forward end of primary housing  34  to the intermediate wall  54 . The spacing between the walls  40 ,  42  and the adjacent insulating walls  131  provide open passages or walkways  132  extending from the doors  48  to the intermediate wall  54  ( FIG. 9 ); this allows servicing and repair of the internal components of the heater  20 . 
         [0028]    The overall assembly  28  further includes insulating structure for the secondary housing  36 , namely side insulating panels  134  located inboard of the side panels  72 ,  74 , which extend the full length of the secondary housing. The panels  134 , together with insulated front and rear panels  78 ,  80 , thus provide the requisite degree of heat insulation for the secondary housing  36 . 
         [0029]    The air cooling assembly  30  includes a plurality of lower box-like air inlets  136  which are mounted to the sidewalls  40 ,  42  and communicate with the interior of heater  20  through ports  138  (see  FIG. 5 ). The inlets  136  are equipped with shiftable dampers or louvers  140  to facilitate control of air flow to the heater  20 , and thus serve as active air control assemblies. In certain embodiments, inlets  136  serve as the principal air inlet for the space enclosed by housing  22 . In addition, the assembly  30  includes a plurality of upright “mushroom” air outlets  142  secured to top wall  44  along the length of secondary housing  36 . Additionally, sidewall vents  144  are provided adjacent the upper ends of the sidewalls  40 ,  42  of primary housing  34 . 
         [0030]    Power and control assembly  32  includes a conventional electrical entrance panel  146  located within room  56  and adjacent intermediate wall  54 . Thus, the panel  146  may be accessed through door  52  as needed. The assembly also has a junction box  148  mounted adjacent the forward end of heater  20  between the valve/sensor assemblies  126 . The panel  146  houses the control elements and circuitry for the heater  20 , and has one or more programmable digital devices allowing control of the assemblies  24 - 30  during the operation of heater  20 . Box  148  can be readily accessed through forward doors  48 . The assembly  32  further has conventional temperature, pressure, and oxygen sensors  143  within the housing  22 , and a resistance temperature detector (RTD)  109  coupled with the forward-most coil  110 . 
         [0031]    In the operation of heater  20 , incoming fluid to be heated is conveyed through pipe assembly  102  to header  88  for passage through the coil inlet pipes  112  and ultimately through the individual coils  110 . To this end, the incoming fluid is delivered to the heater  20  by means of existing line pressure and the flow rate of which is generally uncontrolled. As the fluid passes through the coils  110 , the IR heaters  118  operate to heat the fluid before outward passage thereof from the pipes  114  and header  90 . From this point, the now-heated fluid is delivered to the desired use location for heating of the associated pipeline equipment or the like. Also during this heating operation, the air cooling assembly  30  comes into play. That is, operation of the heating elements  118 , which can achieve temperatures well above  500 F, induces air drafts within housing  22 . As best seen in  FIG. 10 , such induced air currents  150  are drawn through the inlets  136  and pass upwardly for exit through the vents  86 , mushroom outlets  142 , and side vents  144 . At least a portion of the draft is directed through a passage  145  defined between beams  64  and support frame  147  for insulating panels  134  and into a draft-conducting space  149  formed between heater arrays  120 ,  122  and insulated panels  128 . Shields  154  are positioned at the upper ends of space  149  to force the air draft to travel downwardly into space  149 . The air moving within space  149  is preheated by heater arrays  120 ,  122  prior to entering the heat exchange column  151  in which the coils  110  reside. The lower margin of insulated panels  128  is sealed from walkways  132  outboard of panels  128  causing the induced draft to overcome the natural buoyancy of the warming air in space  149  and pass through passageway  152  into the heat exchange column  151 . In certain embodiments, the air flowing within column  151  and past coils  110  flows in a direction that is opposite to that of the air flowing in draft-conducting space  149 . This air flow can create an environment of convective heat transfer from the fluid flowing through the coils  110  and, if the air flow is too strong, the efficiency of heater  20  is compromised. In order to control the air flow, the louvers  140 , operably coupled with control panel  146 , are adjusted to maintain the proper air flow through the heater  20 . Advantageously, the overall control system for the heater  20  comprises, in addition to the controller panel  146 , at least one member selected from the group consisting of an oxygen sensor  143 , carbon dioxide sensor, and a pressure transducer installed within the housing  22  and operable to determine a characteristic of the air draft within the housing  22 , in order to open or close the louvers  140  based upon determination of such characteristic(s). Hence, the heating/cooling operation of heater  20  may be precisely controlled to achieve optimum performance. 
         [0032]    In certain embodiments, it has been found that the pitch of the convolutions  110   a  of the coils  110  can be adjusted in order to further maximize the efficiency of heater  20 . The pitch of these convolutions refers to the lateral spacing between adjacent convolutions. For example, in certain cases, the pitch of the convolutions  110   a  is selected to keep all of the convolutions maximally “visible” to the opposed banks  120 ,  122  of the elements  118 .