Abstract:
Aspects of this disclosure enhance elimination problems that freezing sulfur creates with gas-liquid parallel plate separators by integrally heating the parallel plate gas-liquid separator assembly. Through integral heating the duration of time that the separator apparatus remains above the freezing temperature of elemental sulfur is prolonged, thereby, allowing the opportunity for residual liquid sulfur to drain from the parallel plate assembly during upsets in unit operations and after a sulfur recovery unit shutdown event, thereby reducing or eliminating the operation and maintenance problems that may occur with existing separator designs.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims the benefit of U.S. Provisional Application Ser. No. 61/832,181, filed by Matthew S. Hodson, et al., on Jun. 7, 2013, entitled “Heated Entrained Sulfur Removal Element” incorporated herein by reference. 
     
    
     TECHNICAL FIELD OF THE INVENTION 
       [0002]    The disclosure is directed to a heated entrained sulfur removal element. 
       BACKGROUND 
       [0003]    Entrained liquid elemental sulfur is detrimental to the performance and recovery efficiency of sulfur recovery process units utilized in the petroleum refining, natural gas processing, and petrochemical industries. The nature of the sulfur liquid formed in the sulfur condensing equipment of a sulfur recovery unit creates small-entrained liquid sulfur droplets, fog, or mist. Liquid mist eliminating pads are sometimes used in sulfur recovery unit condensers to remove the referenced entrained liquid sulfur but these devices are susceptible to high pressure drop, fouling, and plugging. 
         [0004]    Gas-liquid parallel plate or parallel vane separators can be used as an alternate to mist eliminating pads to recover these entrained particles of liquid sulfur and sulfur bearing compounds. Parallel plate separators are less susceptible to plugging than mist eliminating pads and have a lower pressure drop during normal operating conditions. 
         [0005]    Because elemental sulfur freezes at the relatively high temperature of approximately 239° F. when compared to the normal outlet operating temperature of the sulfur condensing equipment of approximately 300-350° F., upsets in the sulfur recover unit operation or unplanned shutdowns can cause any residual liquid sulfur that remains on the gas-liquid parallel plate separators to freeze causing a blockage in the gas flow path which requires significant maintenance to correct. 
       SUMMARY 
       [0006]    One embodiment of this disclosure provides a heated entrained sulfur removal element that comprises a support frame with opposing end plates. A thermally conductive plate is located between the opposing end plates and coupled to the support frame. At least one heating element extends through the thermally conductive plate and the opposing end plates. The heating element has connectors located on ends thereof configured to couple the ends of the heating element to a heating source. 
         [0007]    In another embodiment, there is provided a sulfur recovery system (SRS). The SRS system comprises a sulfur recovery unit combustion and thermal reactor couplable to a sulfur gas fee line. A waste heat recovery unit is coupled to the sulfur recovery unit combustion and thermal reactor. A first sulfur condenser heat exchanger is coupled to the waste heat recovery unit and further is coupled to a first heating media supply and a first heating media return, and a process gas heater is coupled to a catalytic reactor. A second sulfur condenser heat exchanger is coupled to the catalytic reactor and to a second heating media and a second heating return and is further coupled to a sulfur tail gas unit. A heated entrained sulfur removal element (HESRE) is coupled to at least one of the first sulfur condenser heat exchanger or the second sulfur condenser heat exchanger. In this embodiment, the HESRE comprises a support frame with opposing end plates. A thermally conductive plate is located between the opposing end plates and coupled to the support frame. At least one heating element extends through the thermally conductive plate and the opposing end plates. The heating element has connectors located on ends thereof configured to couple the ends of the heating element to a heating source. 
         [0008]    The foregoing has outlined some of the features provided by the embodiments of this disclosure. Those skilled in the art should appreciate that they can readily use the disclosed conception and the embodiments described herein as a basis for designing or modifying other structures for carrying out the same purposes of the present disclosure. Those skilled in the art should also realize that such equivalent constructions do not depart from the spirit and scope of this disclosure. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]    For a more complete understanding of the present invention, reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which: 
           [0010]      FIG. 1  illustrates a sulfur recovery system in which embodiments of the heated entrained sulfur removal element of this disclosure may be used; 
           [0011]      FIG. 2A  illustrates an embodiment of the heated entrained sulfur removal element having one or more heating elements extending through the heating plates and one or more tie rods extending through the heating plates and end plates; 
           [0012]      FIG. 2B  illustrates another embodiment of the heating element configured as a hollow heating tube through which heating fluid may flow; 
           [0013]      FIG. 2C  illustrates another embodiment of the heating element configured as a hollow tube through which an electrical heating element located within the heating tube; 
           [0014]      FIG. 3  illustrates one application of an embodiment of the heated entrained sulfur removal element as used in a sulfur condenser heat exchanger and an outlet piping section coupled to a downstream equipment of a sulfur recovery unit; 
           [0015]      FIG. 4A  illustrates one application of an embodiment of the heated entrained sulfur removal element as used in an outlet plenum of a sulfur condenser heat exchanger; 
           [0016]      FIG. 4B  illustrates a cross-sectional view taken through line  4 B- 4 B of the embodiment of  FIG. 4A  showing the entrained sulfur removal unit having opposing end plates and tie rods located within a sulfur condensing heat exchanger; 
           [0017]      FIG. 5A  illustrates one embodiment of the heated entrained sulfur removal element in which heating elements traverse the heated entrained sulfur removal element in a back and forth pattern; 
           [0018]      FIG. 5B  illustrates an embodiment where the parallel plate or parallel vane separator construction is heated by an electric heating media; 
           [0019]      FIG. 6  illustrates another embodiment of the heated entrained sulfur removal element that includes parallel plate or parallel vane separator assembly construction for use with multiple fluid heating media flow circuits connected through a fluid distribution manifold; and 
           [0020]      FIG. 7A  illustrates one embodiment of a heated parallel plate separator assembly with a liquid heating medium control system block diagram; and 
           [0021]      FIG. 7B  illustrates one embodiment of a heated parallel plate separator assembly with an electric heating media control system block diagram. 
       
    
    
     DETAILED DESCRIPTION 
       [0022]    This disclosure provides a means of preventing freezing of elemental sulfur on the surfaces of gas-liquid parallel plate or parallel vane separators used to remove entrained liquid elemental sulfur droplets, fog, or mist formed in the sulfur condensing equipment or liquid sulfur storage equipment of a sulfur recovery unit. 
         [0023]    In one embodiment, the parallel plate or parallel vane separator is installed in the process gas piping downstream or outlet plenum of a sulfur condensing heat exchanger which is an integral part of the sulfur recovery process unit. The separator assembly may also be installed in the piping or vessels used for storage of molten liquid sulfur. 
         [0024]    The process of removing heat from the sulfur recovery unit process gasses causes condensation of elemental sulfur. The condensed elemental sulfur naturally forms small droplets in the form of entrained liquid, liquid sulfur mist, or sulfur fog. The parallel vane separator removes these entrained droplets, mist, or fog through a means of direct impingement of the entrained liquid on the plates of the parallel vane separator. Once contacted with the separator plates the sulfur liquid adheres to the plate surface where it coagulates to form droplets large enough to drain from the parallel vane separator under the forces of gravity. 
         [0025]      FIG. 1  illustrates a sulfur recovery system (SRS)  100  in which embodiments of a heated entrained sulfur removal element (HESRE) of this disclosure may be used. Expect for the embodiments of the HESRE as covered by this disclosure, unless otherwise noted, the various components of the SRS  100  may be of conventional design. The SRS  100  receives a sulfur bearing gas feed from an upstream treating unit  102 . The sulfur bearing gas then passes to and through a sulfur recovery unit combustion and thermal reactor  104 , where the gas feed is partially combusted to form the sulfur compounds required to promote the reaction to form elemental sulfur. The heated gas feed then passes through a waste heat recovery boiler  106 , where partially combusted gas is partially cooled to remove excess heat from the reaction products and traverses connective pipe line to a first sulfur condensing heat exchanger  108 , where the gas feed is further cooled to below its dew point to form liquid elemental sulfur. The sulfur condensing heat exchangers  108  may include a heated entrained sulfur removal element (HESRE)  110 , which in turn is connected to a heating media supply  110   a  and a heating media return  110   b.  The heating media may be any type of heating medium sufficient to transfer heat to the heating elements of the HESRE  110 , such as heated liquid or an electrical current. The HESRE  110  is capable of providing heat to maintain liquid sulfur recovered from the sulfur-containing gas in a liquid state, and thereby, prevent it from freezing within the HESRE  110 . Then, in one embodiment, the gas proceeds to a process gas heater  112 , which may be a multiple pass unit or a single pass unit where the gas is reheated to a temperature sufficient to promote additional reaction of the sulfur bearing compounds to elemental sulfur in downstream catalytic reactors. 
         [0026]    The gas then passes on to a catalytic reactor  114 , which may also be a single or multiple pass unit where the gas is reacted to form additional elemental sulfur. In one embodiment, of the SRS  100 , the gas then passes to another or second sulfur condensing heat exchanger  116 , which may be a single pass or multiple pass unit, where the gas feed is cooled to below its dew point to form liquid elemental sulfur. As with the previous sulfur condensing heat exchanger unit  108 , the sulfur condensing heat exchanger unit  116  may optionally include an HESRE  110 , which is turn is connected to a heating media supply  118   a  and a heating media return  118   b.  The heating may be accomplished as noted above. The HESRE  110  is capable of providing heat to maintain liquid sulfur recovered from the sulfur-containing gas at this point in the SRS  100  to keep the sulfur in a liquid state, and thereby, prevent it from freezing within the HESRE  110 . 
         [0027]    In one alternative embodiment of the SRS  100 , the heat exchanger  116  may be further coupled to another of the HESRE  110  at the outlet piping  122 . In this embodiment the HERSU  110  includes a heating media supply  120   a  and heating media return  120   b.  Thus, as seen from the foregoing embodiments, the SRS  100  may include one or more of the HESREs  110  at various stages of the gas process flow. 
         [0028]      FIG. 2A  illustrates one embodiment of a HESRE  200 , as generally discussed above. In the embodiment of  FIG. 2A , the HESRE  200  includes a group  202  of thermally conductive plate(s)  204  that may comprise one or more sub-groups  206 . It should be understood that other embodiments may comprise only a single thermally conductive plate  204  or include multiples of groups  202  and sub-groups  206  of plates  204 . In one embodiment, the thermally conductive plate(s)  204  may be conventional parallel plates or parallel vane separators, which may be constructed of metal or some other type of known, thermally conductive material that has good thermal conductivity sufficient provide transmission of heat from a heat source, such as heated fluid or an electrical current. The thermally conductive plate(s)  204 , in one embodiment, may be a plurality of conventionally arranged vertical and parallel plates located at predetermined separations of distance along a direction perpendicular to the process gas flow to form one or more groups or sub-groups of vane assemblies. 
         [0029]    The thermally conductive plate(s)  204  of the vane assembly are held together by one or more tie rods  208  or alternatives thereof, as discussed below. The horizontal spacing between the thermally conductive plate(s)  204  may be maintained by the use of spacers or direct attachment of the vertical plate(s)  204  to the tie rods  208  through a conventional weld  210  or through a conventional press fit through sheet metal tabs or protrusions  212  stamped in the parallel plate sheet metal during fabrication, as shown in  FIG. 2B . 
         [0030]    The HESRE  200  further includes one or more heating elements  214 , as seen generally in  FIGS. 2B and 2C , which may be comprised of steel, such as stainless steel. In one embodiment, the heating elements  214  may be a solid, conductive heating element, while in other embodiments, it may be a hollow tube. Additionally, the heating elements  214  in certain embodiments may also serve as the tie rods  208 , so in some embodiments, the tie rods  208  and the heating elements  214  are the same component, while in other embodiments, they may be present as separate components with their separate, respective functions. In some embodiments, as illustrated in  FIG. 2B , the heating element  214  may be hollow tube  216 , which allows for the transmission of a heated liquid therethrough, or alternatively, as illustrated in  FIG. 2C , the hollow tube  216  may serve as a conduit for an electrical conductive wire  218 . In such embodiments, the wire  218  is surrounded by a thermally insulative material  220 , such as magnesium dioxide, within the hollow tube  216 . 
         [0031]    The tie rods  208  may serve as the heating elements  214  to integrally heat the plates  204  through thermal conduction at the attachment points between the individual plate  204  and the tie rod  208 . The heating element  214  has an appropriate fluid or electrical connector connected to the end of the tie rod  208  or heating element  214 , such that it may be connected to the appropriate heating source. For example, where the heat is achieved through a heated liquid, the end of the tie rod  208  or heating element  214  has a fluid tight connector located on an intake end that may be cooperatively connected to a tube (not shown) by which the heated liquid is transmitted to the tie rod  208  or heating element  214 . Alternatively, where the heating source is an electrical current, the tie rod  208  or heating element  214  has an electrical connector located on an end to which an electrical wire may be connected. 
         [0032]    The tie rod  208  or the heating element  214  are not necessarily of solid construction, but in one embodiment, is constructed of a hollow conduit, tubing, or piping, as seen in  FIGS. 2B and 2C , to carry the heating medium, such as condensing steam, hot water, heated glycol, hot oil, or other circulating fluids, or alternately electric resistive heating elements, required to enable thermal conduction heating of the plates  204 . 
         [0033]    Depending on the size and shape of the HERSE  200 , multiple tie-rods  208  or heating elements  214  may be utilized for mechanical integrity and to provide adequate distribution of the heating media to establish even temperature distribution through the parallel plate or parallel HESRE  200 , or vane separator assembly. 
         [0034]    In one embodiment, the group(s)  202  of thermally conductive plate(s)  204 , or vane assembly, may be installed in a metal support frame  222  to provide mechanical strength and ease of installation and removal of HESRE  200  assembly from a sulfur recovery condenser plenum, sulfur recovery unit process gas piping, or molten liquid sulfur storage equipment. In one configuration, the metal support frame  222  includes opposing end plates  222   a,    222   b,  and an optional capping plate  222   c.    
         [0035]      FIG. 3  illustrates an embodiment where the HESRE  200  is installed within the piping  300  of a sulfur condensing heat exchanger  301  as utilized in the SRS  100  and enclosed in a pressure containing housing  302  and attached in-line with the sulfur unit piping  300 . In this embodiment, the HESRE  200  is located downstream of a sulfur condenser heat exchanger outlet plenum  304 , or alternately, in the piping connecting any liquid sulfur containing equipment in the SRS  100 . Fluid or electric heating media is supplied to the HESRE  200  through external conduits  306 ,  308 . Entrained liquid elemental sulfur removed from process gas stream is collected and returned to the condenser, liquid sulfur storage equipment, or other suitable equipment located in the sulfur recovery unit through sulfur drain piping  310 ). 
         [0036]      FIGS. 4A and 4B  illustrate the application of the HESRE  200  installed at the condenser outlet tube sheet  312  within a sulfur condensing heat exchanger  400 . In this embodiment, the fluid or electric heating media is supplied to the heated parallel plate assembly through external conduits  402  and  404 . Entrained liquid elemental sulfur removed from the process gas stream is collected and drained from the condenser outlet plenum  304  through liquid sulfur drain nozzles  406  that are located in the sulfur condensing heat exchanger  400  outlet plenum  304 . After passing through the HESRE  200 , process gases exit the condensing heat exchanger  400  through piping  408 . As mentioned above, the HESRE  400  may be installed in a single pass or multiple pass sulfur condenser heat exchanger. The HESRE  200  may be located in the outlet plenum alone, or in addition, to the HESRE  200  attached in-line with the sulfur unit piping  300 , as discussed with respect to the embodiment of  FIG. 3 . 
         [0037]      FIGS. 5A and 5B  illustrate embodiments of the HESRE  200  that has multiple individual heating elements  214 , which may also serve as tie rods  208  and that have a serpentine configuration. In this embodiment, the heating elements  214  are hollow and are connected with a heating medium supply, as generally shown, by conventional liquid tight connectors  502  and  504 . The conduit connectors  502 ,  504  may be located at either end of the tie-rods. The flow path of the fluid conduit and heating elements  214  are configured to establish a fluid flow circuit to distribute the fluid heating media throughout the HESRES  200 . Multiple heating circuits can be included to provide additional heating capacity, as illustrated in  FIG. 4  and alternately  FIG. 4A . 
         [0038]      FIG. 5B  illustrates the HESRE  200  wherein the heating elements  214  are configured as heating elements. In one embodiment, the sheath of electric heating elements can be directly inserted into the heating elements  214 , as generally shown, with conventional electrical connectors  506 ,  508  located in the opposing end plate  222   b.  Alternately, the plates  204  can be attached directly to the metal sheath of an electric heating element using the same means of attachment shown in  FIG. 2B . The electric heating elements are connected to provide one or multiple electric circuits. The electric heater elements are interconnected to form a completed electrical circuit between the multiple rows of heating elements  214  with a connection wire protected in a suitable conduit, as discussed above regarding  FIG. 2C . The distribution of the electrical heating elements and heating elements  214  are configured to establish a single or multiple parallel circuits to distribute heating throughout the HESRE  200 . 
         [0039]    The conduit for transporting the heating media to and from the HESRE  200 , or alternately completing the electrical heating element circuit of the HESRE  200 , is connected to the fluid or electrical distribution conduit, not shown, by way of the fluid connections  502 ,  504 , or  506 ,  508 , respectively. Any of these elements can be routed outside the sulfur condensing heat exchangers of  FIG. 3  or  FIGS. 4A and 4B , or a separator assembly housing installed in the SRS  100 , or related molten liquid sulfur storage equipment through a pressure containing coupling or cable gland. 
         [0040]    In certain embodiments, the construction of the heating elements  214 , heating media fluid conduit or manifolds, or alternately electric resistance heating elements and associated wiring, are installed with expansion loops to provide adequate resistance to thermal expansion and to provide access to the unit for installation, maintenance, and removal. 
         [0041]      FIG. 6  illustrates another embodiment of the HESRE  200  that includes a manifold configuration of the heating elements  214 , which also may traverse the ERSE  200  in a back and forth configuration. 
         [0042]      FIGS. 7A and 7B  illustrate schematic diagram of the HESRE  200  as described above in a configuration where the heating elements  214  are heated by a fluid medium ( FIG. 7A ) and in a configuration where the heating elements  214  are heated by electrical current ( FIG. 7B ). The complete system for a fluid heated parallel plate separator assembly includes various embodiments of the HESRE  200 , as described above, that provides a means of supplying the heat and temperature that is required to prevent freezing of liquid elemental sulfur on the HESRE  200  assembly. In the embodiment where the heat source is a heated fluid medium, the HESRE  200  assembly includes a heater  700  and a supply conduit  702  and a return conduit  704  that connect to the heating elements  214 , as described above. The heated fluid is controlled by a temperature control loop  706  that includes a temperature controller  706   a  and a temperature measuring element  706   b.    
         [0043]    In the embodiment where the heat source is electrical, the HESRE  200  assembly includes a power panel  708  and a first conduit  710  and a second conduit  712  that connect to the heating elements  214 , as described above, to complete the electrical circuit. The current is controlled by a temperature control loop  714  that includes a temperature controller  714   a  and a temperature measuring element  714   b.  The temperature measuring element  714   b  can be mounted directly to the HESRE  200  to provide the feedback for the temperature control loop  714 . 
         [0044]    In one embodiment, these respective temperature control loops  706 ,  714  regulate the heat input to maintain the parallel plate element temperature between a minimum of approximately 239° F. to prevent freezing of elemental sulfur and not more than approximately 832° F. to prevent re-vaporization of the condensed and recovered elemental sulfur liquid. The temperature controller  706   a  and temperature sensing element  706   b  are not required if the fluid heating media is intrinsically maintained between the freezing and boiling temperature of elemental sulfur. 
         [0045]    Although the present invention has been described in detail, those skilled in the art should understand that they can make various changes, substitutions and alterations herein without departing from the spirit and scope of the invention in its broadest form.