Abstract:
A pipeline heater comprising a plurality of flameless catalytic IR emitters positioned about a section of pipe in a substantially diamond-shaped configuration, the diameter of the pipe section being greater than the diameters of the heater inlet and outlet manifolds in order to increase the residence time of the fluid within the heater. The pipeline heater may comprise a single or multiple passes of the pipe section therethrough, each pass having a plurality of catalytic emitters positioned thereabout in a substantially diamond-shaped configuration.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention generally pertains to a pipeline heating apparatus and methods of heating gas and liquid streams using the same. The inventive pipeline heaters employ flameless, catalytic IR emitters positioned about a section of pipe which is in the form of a volume bottle for increasing the residence time of the fluid in the heater.  
         [0003]     2. Description of the Prior Art  
         [0004]     Pipeline heaters are used to heat gas and liquids flowing through a pipeline 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 filed 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 bath.  
         [0005]     Because of the undesirable attributes of conventional water bath heaters, there is a true 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 an environmentally friendly pipeline heater system that generates virtually no nitrous oxide or volatile organic compounds.  
       SUMMARY OF THE INVENTION  
       [0006]     The present invention generally pertains to a pipeline heater and a method of heating a fluid stream therewith. As used herein, the term “fluid” refers to compositions in either a liquid or gaseous state. The inventive pipeline heater generally comprises an inlet manifold presenting a diameter D 1 , a pipe section presenting a diameter D 2 , a plurality of flameless catalytic IR emitters positioned about the pipe section in a substantially diamond-shaped configuration, and an outlet manifold presenting a diameter D 3 . As used herein, the term “substantially diamond-shaped configuration” refers to the cross-sectional configuration of the catalytic emitter array taken along the plane that perpendicularly intersects the direction of fluid flow in the pipe. In preferred embodiments, the emitters are arranged at an approximately 90° incline relative to the emitters adjacent thereto and are in a surrounding relationship to the pipe carrying the fluid to be heated. It has been discovered that by positioning the catalytic emitters in such a manner that the quantity of heat transferred to the pipe (and ultimately to the fluid) can be significantly increased. Consequently, this arrangement is capable of heating the fluid stream to a temperature that is at least about 100° F. greater than a similarly sized, conventional heater.  
         [0007]     In another aspect, the inventive pipeline heater comprises an inlet manifold presenting a diameter D 1 , a pipe section presenting a diameter D 2 , a plurality of flameless catalytic IR emitters positioned about the pipe section, and an outlet manifold presenting a diameter D 3 , with D 2  being greater than each of D 1  and D 3 . Unless otherwise specified, the term “diameter” as used herein in relation to the manifolds and pipe section refer to the inner diameter of the structures through which the fluid stream flows. Preferably, D 2  is at least 50% greater, more preferably at least about 100% greater, even more preferably at least about 200% greater, and most preferably at least about 400% greater than each of D 1  and D 3 . In this manner, the pipe section forms a “volume bottle” which serves to slow the fluid flow rate through the heater thereby increasing the residence time of the fluid in the heater and allowing for greater heat transfer to occur. For example, in the instance where D 1  is about 2 inches, D 2  can be up to about 8 inches, or when D, is about 4 inches, D 2  can be about 10 inches.  
         [0008]     The pipes section used to conduct the pipeline fluid through the heater can be a relatively straight section thereby making a single pass through the heater, or the pipe section can be serpentine thereby making multiple passes through the heater. In the case of multiple passes, each pass has a plurality of flameless catalytic IR emitters positioned thereabout, and preferably in a substantially diamond-shaped configuration. Because the catalytic emitters do not produce a flame, the heaters operate much more quietly than conventional water bath-type heaters and can be safely used in virtually any location. Also, the use of automation equipment allows for remote operation of the heater.  
         [0009]     Pipeline heaters according to the present invention are generally environmentally safe and nuisance free. The pipeline heaters produce virtually no nitrous oxide or volatile organic compounds during operation thereof. Because there are no fluids, stacks, or containment rings, the pipeline heaters present few rust corrosion issues and present no chemical odor problems.  
         [0010]     Methods of using the inventive heaters are also provided herewith and generally comprise providing a heater such as those described above and passing a fluid stream therethrough for heating of the stream. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]      FIG. 1  is an end profile view of a multiple-pass heater according to the present invention.  
         [0012]      FIG. 2  is a side view depicting the volume bottle arrangement of the heater of  FIG. 1 .  
         [0013]      FIG. 3  is a side view of a modified version of the heater shown in  FIG. 2  with two banks of heating elements.  
         [0014]      FIG. 4  is an end profile view of a two-pass heater according to the present invention.  
         [0015]      FIG. 5  is a side view of the heater of  FIG. 4 .  
         [0016]      FIG. 6  is a side view of a modified version of the heater shown in  FIG. 5  with two banks of heating elements.  
         [0017]      FIG. 7  depicts a further modification to the heater of  FIG. 5  showing three banks of heating elements. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0018]     The following examples set forth preferred pipeline heaters in accordance with the present invention. It is to be understood, however, that these examples are provided by way of illustration and nothing therein should be taken as a limitation upon the overall scope of the invention.  
         [0019]     Turning now to the drawings, and in particular  FIGS. 1 and 2  which depict a four-pass pipeline heater  10 , heater  10  generally comprises a serpentine pipe  12  located within a heater housing  14 . Each pass of coil  12  is surrounded by a plurality of catalytic IR emitters  16  arranged in a diamond-shaped pattern. Emitters  16  are generally flameless, gas-fired elements that provide heat in the form of infrared energy. Exemplary emitters include those described in U.S. Pat. Nos. 5,557,858 and 6,003,244, both of which are incorporated by reference herein. Such catalytic emitters are also available from Catalytic Industrial Group, Inc. of Independence, KS.  
         [0020]     The diamond-shaped emitter arrangement allows more of the infrared energy to be concentrated over the entire circumference of the serpentine pipe  12 . This arrangement provides substantially increased pipe temperatures and improves efficiency by directing more of the infrared energy toward pipe  12 .  
         [0021]     In operation, the fluid to be heated enters heater  10  through inlet  18 . Heater  10  can be placed directly in-line with the pipeline system and is coupled thereto by flanges  20 . The fluid flows through an inlet manifold  22  to which a sensing and regulating equipment  24  that monitor various properties of the inlet fluid may be attached. In the embodiment shown in  FIG. 2 , inlet manifold  22  extends just inside housing  14  where it is coupled with serpentine pipe  12 . It is apparent that the diameter of pipe  12  is substantially greater than the diameter of manifold  22 . By employing a larger diameter, pipe  12  provides a greater surface area for heat transfer to occur and slows the fluid flow through heater  10  thereby maximizing fluid retention time.  
         [0022]     After the last pass of pipe  12 , the heated fluid flows through exit manifold  26  and is returned to the pipeline system at outlet  28 . The diameter of exit manifold  26  is also less than the diameter of pipe  12 , and preferably is approximately the same as inlet manifold  22 . Manifold  26  also is provided with a number of ports  30  to which sensing equipment capable of monitoring properties of the heated fluid stream can be attached.  
         [0023]     A venting hood  31  is provided proximate the top portion of housing  14  thereby permitting the escape of exhaust gases from catalytic emitters  16 . The top portion of housing  14  comprises a pair of upwardly converging sidewall sections  29  which direct the exhaust gases toward hood  31 . Side panels (not shown) can be placed around the outer periphery of housing  14  to further insulate heater  10 . Slats may be provided in the side panels to provide additional ventilation.  
         [0024]     Heater  10  is capable of being made fully automated thereby allowing for remote start, stop, and temperature control. For example, the operation of heater  10  can be automatically adjusted to achieve a desired fluid exit temperature by sensing the input temperature of the fluid in manifold  22  and controlling the output of emitters  16 . This automatic operation allows heater  10  to be placed in locations that are removed from populated areas without requiring an on-site human presence. Monitoring of the heater performance can occur at a more centralized and convenient location.  
         [0025]     Heater  10  can be modified to operate without a conventional electrical energy source. This modification is particularly useful in remote locations or in locations that are prone to power interruptions. During start up of the heater, a portable generator is used to preheat the catalyst. Operation of the heater is spontaneous from that point forward. A thermostat is then used to control the operating temperature by adjusting the fuel-gas flow rate between a preset minimum and maximum.  
         [0026]      FIG. 3  depicts a pipeline heater  10   a  that is similar to heater  10  shown in  FIG. 2 , however, heater  10   a  is an elongated version thereof and comprises two banks of catalytic emitters  32 ,  33 . This elongated heater  10   a  provides increased residence time for the fluid passing therethrough and is suitable for use in applications where greater heat transfer is required. In all other aspects, heater  10   a  is identical to heater  10  of  FIG. 2 .  
         [0027]     Turning now to  FIGS. 4 and 5 , these figures depict an alternate embodiment  10   b  of the inventive pipeline heater. As heater  10   b  shares many of the same parts as heater  10  shown in  FIGS. 1 and 2 , the same reference numerals will be used throughout. Heater  10   b  is a two-pass heater and is suitable for use in applications that do not require as significant heat transfer as heater  10  provides. The fluid stream to be heated enters heater  10   b  through inlet  18  which is secured to the pipeline system with flange  20 . The fluid stream continues along through inlet manifold  22  which has approximately the same diameter as the pipeline conduit. Once inside the housing  14  the manifold  22  is necked up into serpentine pipe  12  thereby decreasing the fluid stream flow rate and increasing the residence time of the fluid within heater  10   b.  The catalytic emitters  16  are arranged in a diamond-shaped pattern. The emitter arrangement generally comprises two pairs of emitters, each emitter pair comprising two parallel emitters  16  positioned facing each other on opposite sides of pipe  12 . The emitters  16  are positioned in a surrounding relationship to each pass of pipe  12  so that substantially the entire circumference of pipe  12  is exposed to the infrared energy from emitters  16 . After the second pass, pipe  12  containing the heated fluid stream is necked down and the fluid stream passes into exit manifold  26  and reenters the pipeline system at outlet  28 .  
         [0028]      FIGS. 6 and 7  depict yet additional embodiments derived from the embodiment shown in  FIGS. 4 and 5 .  FIG. 6  shows an elongated two-pass heater  10   c  comprising two emitter banks  32 ,  33 .  FIG. 7  is substantially identical to  FIG. 6  but includes an additional emitter bank  34 . It is clear that additional modifications to this design are possible in order to meet the needs of a particular application. For instance, if overhead clearance is an issue, a less tall but longer heater (i.e.,  10   d  of  FIG. 7 ) can be used instead of the four-pass heater  10  shown in  FIG. 2 . Heater  10   d  can be designed to achieve the same residence time and heat transfer as a four-pass heater  10 . Along the same lines, additional emitter banks may be added to any of the embodiments shown in order to achieve greater residence times and consequently effect a greater heat transfer to the fluid stream passing therethrough. It is also possible for the pipe  12  to comprise one or a plurality of passes through heater  10  depending upon a particular application.  
         [0029]     Preferably, pipe  12  has a dark finish in order to facilitate the maximum absorption of infrared energy from emitters  16 . Conversely, housing  14  and many of the other components comprising heater  10  comprise a lighter, reflective finish in order to retain as much infrared energy within heater  10  as possible. Insulation may also be added to heater  10  to assist in this goal and increase the overall efficiency of heater  10 . Preferably, housing  14 , in large part, is made from stainless steel.  
         [0030]     The inventive heaters  10  can be used in many different applications where cold operating conditions exist. The heaters are particularly useful in heating natural gas streams, but may also be used to heat high pressure gas from wellheads and distribution stations, natural gas at gate stations, and high pressure gas from oil fields. The heaters can also be used to heat liquid streams such as light hydrocarbons, viscous oils, and water or various aqueous streams in order to reduce pump pressures and improve pumping efficiencies.